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Sample records for isotope dilution thermal

  1. Isotope dilution mass spectrometry

    NASA Astrophysics Data System (ADS)

    Heumann, Klaus G.

    1992-09-01

    In the past isotope dilution mass spectrometry (IDMS) has usually been applied using the formation of positive thermal ions of metals. Especially in calibrating other analytical methods and for the certification of standard reference materials this type of IDMS became a routine method. Today, the progress in this field lies in the determination of ultra trace amounts of elements, e.g. of heavy metals in Antarctic ice and in aerosols in remote areas down to the sub-pg g-1 and sub-pg m-3 levels respectively, in the analysis of uranium and thorium at concentrations of a few pg g-1 in sputter targets for the production of micro- electronic devices or in the determination of sub-picogram amounts of230Th in corals for geochemical age determinations and of226Ra in rock samples. During the last few years negative thermal ionization IDMS has become a frequently used method. The determination of very small amounts of selenium and technetium as well as of other transition metals such as vanadium, chromium, molybdenum and tungsten are important examples in this field. Also the measurement of silicon in connection with a re-determination of Avogadro's number and osmium analyses for geological age determinations by the Re/Os method are of special interest. Inductively-coupled plasma mass spectrometry is increasingly being used for multi-element analyses by the isotope dilution technique. Determinations of heavy metals in samples of marine origin are representative examples for this type of multi-element analysis by IDMS. Gas chromatography-mass spectrometry systems have also been successfully applied after chelation of metals (for example Pt determination in clinical samples) or for the determination of volatile element species in the environment, e.g. dimethyl sulfide. However, IDMS--specially at low concentration levels in the environment--seems likely to be one of the most powerful analytical methods for speciation in the future. This has been shown, up to now, for species of

  2. Determination of trace iron in zirconium by isotope dilution-thermal ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Elliot, N. L.; Campbell, M. A.; Green, L. W.

    1995-08-01

    An isotope dilution-thermal ionization mass spectrometry method for the determination of parts-per-million levels of iron in zirconium is required for precise, accurate analyses in studies of the effects of iron on the irradiation deformation of nuclear alloys. A two-stage purification procedure was developed to avoid the signal suppression and interference caused by the zirconium matrix. After sample dissolution and spiking with 54Fe, the bulk of the zirconium is removed by ion exchange chromatography, and the eluted Fe(III) is further purified by micro-solvent extraction into tributyl phosphate-impregnated resin beads. The iron is back-extracted, submicrogram amounts are loaded onto previously outgassed zone-refined Re filaments, and 54/56 ratios are measured at 1170°C. A silica gel/boric acid ionization enhancer is used to obtain stable Fe+ currents as strong as 2 × 10-14. A from nanogram loadings of pure iron. The procedural blank of 20 ± 6 ng is sufficiently low to allow determination of ppm levels of iron in 0.1 g zirconium samples. The analyses of solution standards showed agreement within 2% between measured and expected values, and a good fit, r2 = 0.99997, to a linear regression. The analyses of metal standards exhibited a similar good fit to a linear regression of measured against expected values, and showed good agreement with other methods. The method meets the requirements for zirconium metallurgical studies, and may be extended to other applications.

  3. Simultaneous determination of the quantity and isotopic ratios of uranium in individual micro-particles by isotope dilution thermal ionization mass spectrometry (ID-TIMS).

    PubMed

    Park, Jong-Ho; Choi, Eun-Ju

    2016-11-01

    A method to determine the quantity and isotopic ratios of uranium in individual micro-particles simultaneously by isotope dilution thermal ionization mass spectrometry (ID-TIMS) has been developed. This method consists of sequential sample and spike loading, ID-TIMS for isotopic measurement, and application of a series of mathematical procedures to remove the contribution of uranium in the spike. The homogeneity of evaporation and ionization of uranium content was confirmed by the consistent ratio of n((233)U)/n((238)U) determined by TIMS measurements. Verification of the method was performed using U030 solution droplets and U030 particles. Good agreements of resulting uranium quantity, n((235)U)/n((238)U), and n((236)U)/n((238)U) with the estimated or certified values showed the validity of this newly developed method for particle analysis when simultaneous determination of the quantity and isotopic ratios of uranium is required. PMID:27591656

  4. Gluconeogenesis from labeled carbon: estimating isotope dilution

    SciTech Connect

    Kelleher, J.K.

    1986-03-01

    To estimate the rate of gluconeogenesis from steady-state incorporation of labeled 3-carbon precursors into glucose, isotope dilution must be considered so that the rate of labeling of glucose can be quantitatively converted to the rate of gluconeogenesis. An expression for the value of this isotope dilution can be derived using mathematical techniques and a model of the tricarboxylic acid (TCA) cycle. The present investigation employs a more complex model than that used in previous studies. This model includes the following pathways that may affect the correction for isotope dilution: 1) flux of 3-carbon precursor to the oxaloacetate pool via acetyl-CoA and the TCA cycle; 2) flux of 4- or 5-carbon compounds into the TCA cycle; 3) reversible flux between oxaloacetate (OAA) and pyruvate and between OAA and fumarate; 4) incomplete equilibrium between OAA pools; and 5) isotope dilution of 3-carbon tracers between the experimentally measured pool and the precursor for the TCA-cycle OAA pool. Experimental tests are outlined which investigators can use to determine whether these pathways are significant in a specific steady-state system. The study indicated that flux through these five pathways can significantly affect the correction for isotope dilution. To correct for the effects of these pathways an alternative method for calculating isotope dilution is proposed using citrate to relate the specific activities of acetyl-CoA and OAA.

  5. STABLE ISOTOPE DILUTION FOR HAZARDOUS WASTE INCINERATION

    EPA Science Inventory

    The report gives results of a project to determine if a proposed catalytic exchange procedure could be adapted to produce the labeled analog materials necessary for isotope dilution gas chromatography/mass spectrometry (GC/MS) analysis. It is related to a general evaluation of th...

  6. Measurement of attogram quantities of 231Pa in dissolved and particulate fractions of seawater by isotope dilution thermal ionization mass spectroscopy.

    PubMed

    Shen, Chuan-Chou; Cheng, Hai; Edwards, R Lawrence; Moran, S Bradley; Edmonds, Henrietta N; Hoff, John A; Thomas, Rebecca B

    2003-03-01

    A technique has been developed to quantify ultratrace 231Pa (50-2000 ag; 1 ag = 10(-18) g) concentrations in seawater using isotope-dilution thermal ionization mass spectrometry (TIMS). The method is a modification of a process developed by Pickett et al. (Pickett, D. A.; Murrell, M. T.; Williams, R. W. Anal. Chem. 1994, 66, 1044-1049) and extends the technique to very low levels of protactinium. The procedural blank is 16 +/- 15 ag (2sigma), and the ionization efficiency (ions generated/atom loaded) approaches 0.5%. Measurement time is <1 h. The amount of 231Pa needed to produce 231Pa data with an uncertainty of +/-4-12% is 100-1000 ag (approximately 3 x 10(5) to 3 x 10(6) atoms). Replicate measurements made on known standards and seawater samples demonstrate that the analytical precision approximates that expected from counting statistics and that, based on detection limits of 38 and 49 ag, protactinium can be detected in a minimum sample size of surface seawater of approximately 2 L for suspended particulate matter and <0.1 L for filtered (<0.4 microm) seawater, respectively. The concentration of 231Pa (tens of attograms per liter) can be determined with an uncertainty of +/-5-10% (2sigma) for suspended particulate matter filtered from 5 to 10 L of seawater. For the dissolved fraction, 0.5-1 L of seawater yields 231Pa measurements with a precision of 1-10%. Sample size requirements are orders of magnitude less than traditional decay-counting techniques and significantly less than previously reported ICP-MS techniques. Our technique can also be applied to other environmental samples, including cave waters, rivers, and igneous rocks. PMID:12641225

  7. Isotope dilution study of exchangeable oxygen in premium coal samples

    SciTech Connect

    Finseth, D.

    1987-01-01

    A difficulty with improving the ability to quantitate water in coal is that truly independent methods do not always exist. The true value of any analytical parameter is always easier to determine if totally independent methods exist to determine that parameter. This paper describes the possibility of using a simple isotope dilution technique to determine the water content of coal and presents a comparison of these isotope dilution measurements with classical results for the set of Argonne coals from the premium coal sample program. Isotope dilution is a widely used analytical method and has been applied to the analysis of water in matrices as diverse as chicken fat, living humans, and coal. Virtually all of these applications involved the use of deuterium as the diluted isotope. This poses some problems if the sample contains a significant amount of exchangeable organic hydrogen and one is interested in discriminating exchangeable organic hydrogen from water. This is a potential problem in the coal system. To avoid this potential problem /sup 18/O was used as the diluted isotope in this work.

  8. Consequences of Accounting for Isotopic Dilution in Thymidine Incorporation Assays

    PubMed Central

    Chrzanowski, Thomas H.

    1988-01-01

    Rates of thymidine incorporation into DNA were corrected for isotope dilution by internal nucleotide pools and were compared with rates obtained from uncorrected data. Differences as large as 109% were observed between corrected and uncorrected estimates of thymidine incorporation. The degree of underestimation varied seasonally and, to a lesser extent, spatially. PMID:16347698

  9. Determination of lead, cadmium, indium, thallium and silver in ancient ices from Antarctica by isotope dilution-thermal ionization mass spectrometry

    USGS Publications Warehouse

    Matsumoto, A.; Hinkley, T.K.

    1997-01-01

    The concentrations of five chalcophile elements (Pb, Cd, In, Tl and Ag) and the lead isotope rarios in ancient ices from the Taylor Dome near coastal Antarctica, have been determined by the isotope dilutionthermal ionization mass spectrometry (ID-TIMS), with ultra-clean laboratory techniques. The samples were selected from segments of cores, one of which included a visible ash layer. Electric conductivity measurement (ECM) or dielectric properties (DEP) gave distinctive sharp peaks for some of the samples c hosen. Exterior portions of the sample segments were trimmed away by methods described here. Samples w ere evaporated to dryness and later separated into fractions for the five elements using an HBr-HNO3 a nion exchange column method. The concentrations are in the range 2.62-36.7 pg Pb/g of ice, 0.413-2.83 pg Cd/g, 0.081-0.34 pg In/g, 0.096-2.8 pg Tl/g and 0.15-0.84 pg Ag/g. respectively. The dispersions in duplicate analyses are about ??1% for lead and cadmium, ??2% for indium. ??4% for thallium and ??6% for silver, respectively. The concentrations of lead obtained are commonly higher than those in the present-day Antarctic surface snows, but the isotope ratios are distinctively higher than those of the present-day snows and close to those of the other ancient ice collected from a different Antarctic area.

  10. Short course on St-02 applications of isotope dilutions and isotopic measurements

    SciTech Connect

    Miller, P.

    1998-01-05

    This short course includes information on these topics and subtopics: (I) Nuclear Properties: (A) Historic roots; (B) Nomenclature; (C) Nuclear Stability and abundance; (D) Uses of isotopic techniques; (II) Instrumentation: (A) Sources; (B) Mass resolving elements; (C) Detectors; (III) Making Isotopic Measurements by ICP-MS: (A) Deadtime Correction; (B) Mass Discrimination; (C) Signal /Noise considerations; (IV) Applications and examples: (A) Isotope dilution; (B) Double Spike; (C) Biological Application; (D) Environmental Application; (E) Geological.

  11. Using isotope dilution mass spectrometry to determine aqueous trichloroacetic acid

    SciTech Connect

    Norwood, D.L.; Christman, R.F.; Johnson, J.D.; Hass, J.R.

    1986-01-01

    The development, verification, and application of a method based on isotope-dilution gas chromatography-mass spectrometry to determine aqueous trichloroacetic acid (TCAA) at the micrograms per litre level are described. The simultaneous determination of aqueous chloroform is also demonstrated. Trichloroacetic acid is shown to be a significant by-product of the chlorination of raw waters in the laboratory and to constitute a large fraction of the total organic halide (TOX) formed. Analysis of finished-water samples indicated that TCAA, like trihalomethanes is ubiquitous. Positive correlations exist between the levels of TCAA in laboratory-chlorinated raw waters and in finished waters and measured TOX.

  12. Trace determination of zinc by substoichiometric isotope dilution analysis

    SciTech Connect

    Sandhya, D.; Priya, S.; Subramanian, M.O.S.

    1996-09-01

    A radiometric method based on substoichiometric isotope dilution analysis using 1,10-phenanthroline and a substoichiometric amount of eosin was developed for determining trace amounts of zinc. Evaluation of various metal ion interferences shows that as little as 0.2 {mu}g Zn could be determined in an aqueous-phase volume of 60 mL. The method has been successfully applied to the determination of Zn in city waste incineration ash, cadmium metal, Fourts-B tablets, Boro-plus ointment, and magnesium alloy samples. 12 refs., 3 figs., 3 tabs.

  13. Thermal diffusion in dilute nanofluids investigated by photothermal interferometry

    NASA Astrophysics Data System (ADS)

    Philip, J.; Nisha, M. R.

    2010-03-01

    We have carried out a theoretical analysis of the dependence of the particle mass fraction on the thermal diffusivity of dilute suspensions of nanoparticles in liquids (dilute nanofluids). The analysis takes in to account adsorption of an ordered layer of solvent molecules around the nanoparticles. It is found that thermal diffusivity decreases with mass fraction for sufficiently small particle sizes. Beyond a critical particle size thermal diffusivity begins to increase with mass fraction for the same system. The results have been verified experimentally by measuring the thermal diffusivity of dilute suspensions of TiO2 nanoparticles dispersed in polyvinyl alcohol (PVA) medium. The effect is attributed to Kapitza resistance of thermal waves in the medium.

  14. Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

    NASA Astrophysics Data System (ADS)

    Shetaya, Waleed; Huang, Jen-How; Osterwalder, Stefan; Alewell, Christine

    2016-04-01

    Mercury (Hg) is a toxic element that can cause severe health problems to humans. Mercury is emitted to the atmosphere from both natural and anthropogenic sources and can be transported over long distances before it is deposited to aquatic and terrestrial environments. Aside from accumulation in soil solid phases, Hg deposited in soils may migrate to surface- and ground-water or enter the food chain, depending on its lability. There are many operationally-defined extraction methods proposed to quantify soil labile metals. However, these methods are by definition prone to inaccuracies such as non-selectivity, underestimation or overestimation of the labile metal pool. The isotopic dilution technique (ID) is currently the most promising method for discrimination between labile and non-labile metal fractions in soil with a minimum disturbance to soil-solid phases. ID assesses the reactive metal pool in soil by defining the fraction of metal both in solid and solution phases that is isotopically-exchangeable known as the 'E-value'. The 'E-value' represents the metal fraction in a dynamic equilibrium with the solution phase and is potentially accessible to plants. This is carried out by addition of an enriched metal isotope to soil suspensions and quantifying the fraction of metal that is able to freely exchange with the added isotope by measuring the equilibrium isotopic ratio by ICP-MS. E-value (mg kg‑1) is then calculated as follows: E-Value = (Msoil/ W) (CspikeVspike/ Mspike) (Iso1IAspike ‑Iso2IAspikeRss / Iso2IAsoil Rss - Iso1IAsoil) where M is the average atomic mass of the metal in the soil or the spike, W is the mass of soil (kg), Cspike is the concentration of the metal in the spike (mg L‑1), Vspike is the volume of spike (L), IA is isotopic abundance, and Rss is the equilibrium ratio of isotopic abundances (Iso1:Iso2). Isotopic dilution has been successfully applied to determine E-values for several elements. However, to our knowledge, this method has not

  15. Nutritional assessment by isotope dilution analysis of body composition

    SciTech Connect

    Szeluga, D.J.; Stuart, R.K.; Utermohlen, V.; Santos, G.W.

    1984-10-01

    The three components of body mass, body cell mass (BCM), extracellular fluid (ECF), and fat + extracellular solids (ECS: bone, tendon, etc) can be quantified using established isotope dilution techniques. With these techniques, total body water (TBW) and ECF are measured using 3H/sub 2/O and /sup 82/Bromine, respectively, as tracers. BCM is calculated from intracellular fluid (ICF) where ICF . TBW - ECF. Fat + ECS is estimated as: body weight - (BCM + ECF). TBW and ECF can be determined by either of two calculation methods, one requiring several timed plasma samples (extrapolation method) and one requiring a single plasma sample and a 4-h urine collection (urine-corrected method). The comparability of the two calculation methods was evaluated in 20 studies in 12 bone marrow transplant recipients. We found that for determination of TBW and ECF there was a very strong linear relationship (r2 greater than 0.98) between the calculation methods. Further comparisons (by t test, 2-sided) indicated that for the determination of ECF, the methods were not significantly (p greater than 0.90) different; however, TBW determined by the urine-corrected method was slightly (0.1 to 6%), but significantly (p less than 0.01) greater than that determined by the extrapolation method. Therefore, relative to the extrapolation method, the urine-corrected method ''over-estimates'' BCM and ''under-estimates'' fat + ECS since determination of these compartment sizes depends on measurement of TBW. We currently use serial isotope dilution studies to monitor the body composition changes of patients receiving therapeutic nutritional support.

  16. Bioavailability of soilborne lead in adults, by stable isotope dilution.

    PubMed Central

    Maddaloni, M; Lolacono, N; Manton, W; Blum, C; Drexler, J; Graziano, J

    1998-01-01

    Using stable isotope dilution, we determined the bioavailability of soilborne lead (Pb) in human adult volunteers. Soil from a residential yard at a mining-impacted federal Superfund site that had negligible amounts of other priority pollutants was dried and screened through a 25-micron mesh sieve. The < 250-micron fraction, which likely represents that ingested via hand-to-mouth activity, was then sterilized by exposure to radiation. Ten replicate samples yielded a mean (SD) soil Pb concentration of 2924 +/- 36 ppm, and a mean 206Pb/207Pb ratio of 1.1083 +/- 0.0002, indicating remarkable soil homogeneity. Six adults with 206Pb/207Pb ratios of > 1.190 were admitted to the clinical research center and fasted overnight prior to dosing with 250 micrograms Pb/70 kg bw (i.e., 85.5 mg soil/70 kg) in a gelatin capsule. Blood for Pb and 206Pb/207Pb ratios was obtained at 14 time points through 30 hr. Results of the isotopic analyses from these subjects indicate that on average 26.2% +/- 8.1 of the administered dose was absorbed. Six additional subjects were subsequently studied but ingested soil immediately after a standardized breakfast. Bioavailability in this group was only 2.52% +/- 1.7. Collectively, this study provides the first experimental estimates of soil Pb absorption in humans, and should allow for more precise estimates of health risks due to Pb-contaminated soil. Images Figure 1 Figure 2 Figure 3 PMID:9860919

  17. Application of Uranium Isotope Dilution Mass Spectrometry in the preparation of New Certified Reference Materials

    NASA Astrophysics Data System (ADS)

    Hasözbek, A.; Mathew, K. J.; Orlowicz, G.; Srinivasan, B.; Narayanan, U.

    2012-04-01

    Proven measurement techniques play a critical role in the preparation of Certified Reference Materials (CRMs) - those requiring high accuracy and precision in the measurement results. Isotope Dilution Mass Spectrometry (IDMS) is one such measurement method commonly used in the quantitative analysis of uranium in nuclear safeguards and isotope geology applications. In this project, we evaluated the possibility of using some of the uranium isotopic and assay CRMs made earlier by the New Brunswick laboratory as IDMS spikes to define the uranium mass fraction in future preparations of CRMs. Uranium solutions prepared from CRM 112-A (a highly pure uranium metal assay standard) and CRM 115 (a highly pure uranium oxide isotopic and assay standard) were used as spikes in the determination of uranium. Two different thermal ionization mass spectrometer instruments (MAT 261 and TRITON) were used for the isotopic measurements. Standard IDMS equation was used for data reduction to yield results for uranium mass fraction along with uncertainties, the latter calculated according to GUM. The results show that uranium mass fraction measurements can be made with the required accuracy and precision for defining the uranium concentration in new CRMs as well as in routine samples analyses.

  18. Oxygen and hydrogen isotopes in thermal waters at Zunil, Guatemala

    SciTech Connect

    Fournier, R.O.; Hanshaw, B.B.; Urrutia Sole, J.F.

    1982-10-01

    Enthalpy-chloride relations suggest that a deep reservoir exists at Zunil with a temperature near 300/sup 0/C. Water from that reservoir moves to shallower and cooler local reservoirs, where it mixes with diluted water and then attains a new water-rock chemical equilibrium. This mixed water, in turn, generally is further diluted before being discharged from thermal springs. The stable-isotopic composition of the thermal water indicates that recharge for the deep water at Zunil comes mainly from local sources. The presence of measurable tritium, which suggests that the deep water has been underground about 20 to 30 years, also indicates a local source for the recharge.

  19. Quantification of ferritin-bound iron in plant samples by isotope tagging and species-specific isotope dilution mass spectrometry.

    PubMed

    Hoppler, Matthias; Zeder, Christophe; Walczyk, Thomas

    2009-09-01

    Ferritin is nature's predominant iron storage protein. The molecule consists of a hollow protein shell composed of 24 subunits which is capable of storing up to 4500 iron atoms per molecule. Recently, this protein has been identified as a target molecule for increasing iron content in plant staple foods in order to combat dietary iron deficiency, a major public health problem in developing countries. Here, we present a novel technique for quantification of ferritin-bound iron in edible plant seeds using species-specific isotope dilution mass spectrometry (IDMS) by means of a biosynthetically produced (57)Fe-labeled ferritin spike and negative thermal ionization mass spectrometry (NTIMS). Native plant ferritin and added spike ferritin were extracted in 20 mM Tris buffer (pH 7.4) and separated by anion exchange chromatography (DEAE Sepharose), followed by isotopic analysis by thermal ionization mass spectrometry. The chosen IDMS approach was critically evaluated by assessing the (i) efficiency of analyte extraction, (ii) identical behavior of spike and analyte, and (iii) potential iron isotope exchange with natural iron. Repeatabilities that can be achieved are on the order of <5% RSD for quintuplicate analyses at an absolute detection limit of 60 ng of ferritin-bound iron for plant seeds. Studies in six different legumes revealed ferritin-iron contents ranging from 15% of total iron in red kidney beans up to 69% in lentils. PMID:19653660

  20. Quantitation of DNA adducts by stable isotope dilution mass spectrometry

    PubMed Central

    Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

    2012-01-01

    Exposure to endogenous and exogenous chemicals can lead to the formation of structurally modified DNA bases (DNA adducts). If not repaired, these nucleobase lesions can cause polymerase errors during DNA replication, leading to heritable mutations potentially contributing to the development of cancer. Due to their critical role in cancer initiation, DNA adducts represent mechanism-based biomarkers of carcinogen exposure, and their quantitation is particularly useful for cancer risk assessment. DNA adducts are also valuable in mechanistic studies linking tumorigenic effects of environmental and industrial carcinogens to specific electrophilic species generated from their metabolism. While multiple experimental methodologies have been developed for DNA adduct analysis in biological samples – including immunoassay, HPLC, and 32P-postlabeling – isotope dilution high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) generally has superior selectivity, sensitivity, accuracy, and reproducibility. As typical DNA adducts concentrations in biological samples are between 0.01 – 10 adducts per 108 normal nucleotides, ultrasensitive HPLC-ESI-MS/MS methodologies are required for their analysis. Recent developments in analytical separations and biological mass spectrometry – especially nanoflow HPLC, nanospray ionization MS, chip-MS, and high resolution MS – have pushed the limits of analytical HPLC-ESI-MS/MS methodologies for DNA adducts, allowing researchers to accurately measure their concentrations in biological samples from patients treated with DNA alkylating drugs and in populations exposed to carcinogens from urban air, drinking water, cooked food, alcohol, and cigarette smoke. PMID:22827593

  1. Development of a stable isotope dilution assay for tenuazonic acid.

    PubMed

    Asam, Stefan; Liu, Yang; Konitzer, Katharina; Rychlik, Michael

    2011-04-13

    A stable isotope dilution assay (SIDA) for the Alternaria mycotoxin tenuazonic acid was developed. Therefore, [(13)C(6),(15)N]-tenuazonic acid was synthesized from [(13)C(6),(15)N]-isoleucine by Dieckmann intramolecular cyclization after acetoacetylation with diketene. The synthesized [(13)C(6),(15)N]-tenuazonic acid was used as the internal standard for determination of tenuazonic acid in tomato products by liquid chromatography tandem mass spectrometry after derivatization with 2,4-dinitrophenylhydrazine. Method validation revealed a limit of detection of 0.1 μg/kg and a limit of quantitation of 0.3 μg/kg. Recovery was close to 100% in the range of 3-300 μg/kg. Determination of tenuazonic acid in two samples of different tomato ketchups (naturally contaminated) was achieved with a coefficient of variation of 2.3% and 4.7%. Different tomato products (n = 16) were analyzed for their content of tenuazonic acid using the developed SIDA. Values were between 15 and 195 μg/kg (tomato ketchup, n = 9), 363 and 909 μg/kg (tomato paste, n = 2), and 8 and 247 μg/kg (pureed tomatoes and comparable products, n = 5). PMID:21370870

  2. Reducing the matrix effects in chemical analysis: fusion of isotope dilution and standard addition methods

    NASA Astrophysics Data System (ADS)

    Pagliano, Enea; Meija, Juris

    2016-04-01

    The combination of isotope dilution and mass spectrometry has become an ubiquitous tool of chemical analysis. Often perceived as one of the most accurate methods of chemical analysis, it is not without shortcomings. Current isotope dilution equations are not capable of fully addressing one of the key problems encountered in chemical analysis: the possible effect of sample matrix on measured isotope ratios. The method of standard addition does compensate for the effect of sample matrix by making sure that all measured solutions have identical composition. While it is impossible to attain such condition in traditional isotope dilution, we present equations which allow for matrix-matching between all measured solutions by fusion of isotope dilution and standard addition methods.

  3. Quantitative Analysis by Isotopic Dilution Using Mass Spectroscopy: The Determination of Caffeine by GC-MS.

    ERIC Educational Resources Information Center

    Hill, Devon W.; And Others

    1988-01-01

    Describes a laboratory technique for quantitative analysis of caffeine by an isotopic dilution method for coupled gas chromatography-mass spectroscopy. Discusses caffeine analysis and experimental methodology. Lists sample caffeine concentrations found in common products. (MVL)

  4. Thermal conductivity and sound attenuation in dilute atomic Fermi gases

    SciTech Connect

    Braby, Matt; Chao Jingyi; Schaefer, Thomas

    2010-09-15

    We compute the thermal conductivity and sound attenuation length of a dilute atomic Fermi gas in the framework of kinetic theory. Above the critical temperature for superfluidity, T{sub c}, the quasiparticles are fermions, whereas below T{sub c}, the dominant excitations are phonons. We calculate the thermal conductivity in both cases. We find that at unitarity the thermal conductivity {kappa} in the normal phase scales as {kappa}{proportional_to}T{sup 3/2}. In the superfluid phase we find {kappa}{proportional_to}T{sup 2}. At high temperature the Prandtl number, the ratio of the momentum and thermal diffusion constants, is 2/3. The ratio increases as the temperature is lowered. As a consequence we expect sound attenuation in the normal phase just above T{sub c} to be dominated by shear viscosity. We comment on the possibility of extracting the shear viscosity of the dilute Fermi gas at unitarity using measurements of the sound absorption length.

  5. Stable isotope dilution analysis of hydrologic samples by inductively coupled plasma mass spectrometry

    USGS Publications Warehouse

    Garbarino, J.R.; Taylor, H.E.

    1987-01-01

    Inductively coupled plasma mass spectrometry is employed in the determination of Ni, Cu, Sr, Cd, Ba, Ti, and Pb in nonsaline, natural water samples by stable isotope dilution analysis. Hydrologic samples were directly analyzed without any unusual pretreatment. Interference effects related to overlapping isobars, formation of metal oxide and multiply charged ions, and matrix composition were identified and suitable methods of correction evaluated. A comparability study snowed that single-element isotope dilution analysis was only marginally better than sequential multielement isotope dilution analysis. Accuracy and precision of the single-element method were determined on the basis of results obtained for standard reference materials. The instrumental technique was shown to be ideally suited for programs associated with certification of standard reference materials.

  6. Dry Blending to Achieve Isotopic Dilution of Highly Enriched Uranium Oxide Materials

    SciTech Connect

    Henry, Roger Neil; Chipman, Nathan Alan; Rajamani, R. K.

    2001-04-01

    The end of the cold war produced large amounts of excess fissile materials in the United States and Russia. The Department of Energy has initiated numerous activities to focus on identifying material management strategies for disposition of these excess materials. To date, many of these planning strategies have included isotopic dilution of highly enriched uranium as a means of reducing the proliferation and safety risks. Isotopic dilution by dry blending highly enriched uranium with natural and/or depleted uranium has been identified as one non-aqueous method to achieve these risk (proliferation and criticality safety) reductions. This paper reviews the technology of dry blending as applied to free flowing oxide materials.

  7. Scattering of dilute thermal atom clouds on optical Weber beams

    NASA Astrophysics Data System (ADS)

    Hernández-Cedillo, C. L.; Bernon, S.; Hattermann, H.; Fortágh, J.; Jáuregui, R.

    2013-02-01

    We report the experimental observation and a theoretical description of the scattering of free falling dilute thermal clouds of 87Rb atoms by microscopically structured light beams with parabolic-cylindrical symmetry. These structured beams are known in the literature as Weber beams. High-fidelity Weber beams are generated by means of a spatial light modulator and an annular spatial filtering process, which yields a quasipropagation-invariant electromagnetic field in the region of interaction with the atom cloud. The dynamics of the atomic density profile and the phase space distribution of the scattered atoms is explored. A natural dynamical variable of Weber modes is the product of the angular momentum along the axis of propagation of the beam with a component of linear momentum perpendicular to that axis. To pave the way of the understanding about the transfer of this variable, we study the evolution of the analogous atomic variable.

  8. Isotopic Dilution Analysis and Secular Equilibrium Study: Two Complementary Radiochemistry Experiments.

    ERIC Educational Resources Information Center

    Williams, Kathryn R.; Lipford, Levin C.

    1985-01-01

    Describes a complementary pair of radiochemistry experiments for instruction of isotopic dilution analysis and secular equilibrium. Both experiments use the readily available cesium-137 nuclide and the simple precipitation technique for cesium with the tetraphenylborate anion. Procedures used and typical results obtained are provided and…

  9. Direct determination of halogens in powdered geological and environmental samples using isotope dilution laser ablation ICP-MS

    NASA Astrophysics Data System (ADS)

    Boulyga, Sergei F.; Heumann, Klaus G.

    2005-04-01

    Laser ablation inductively coupled plasma isotope dilution mass spectrometry (LA-ICP-IDMS) with a special laser ablation system for bulk analyses (LINA-Spark(TM)-Atomiser) was applied for direct determinations of chlorine, bromine, and iodine in rock and sediment samples. Special attention was focused on possible inter-halogen fractionations and analyte/spike isotope fractionations by using LA-ICP-MS and LA-ICP-IDMS, respectively. A variation of Br/Cl and I/Cl element intensity ratios by a factor of 1.3-3 was observed when changing the nebulizer gas flow rate in the range of 0.84-1.0 L min-1 and the laser power density in the range of 2-10 GW cm-2, respectively. When using an internal standard for halogen quantification in LA-ICP-MS, this inter-element fractionation can cause systematic errors, which can be avoided by applying the isotope dilution technique. However, at high laser power densities (>5.7 GW cm-2 for iodine and >4.0 GW cm-2 for bromine and chlorine) the corresponding measured isotope ratio of the isotope-diluted sample deviates significantly from the target value. Under optimised conditions concentrations in the range of 30 [mu]g g-1-16 × 103 [mu]g g-1 for chlorine, <2-140 [mu]g g-1 for bromine, and <0.1-31 [mu]g g-1 for iodine were determined by LA-ICP-IDMS in two sediment reference materials (SRM 1646, SRM 2704) and three rock reference samples (GS-N, Granite; BX-N, Bauxite; DT-N, Disthene), which have not been certified for these halogens. The sediment results agree well within the given uncertainties with indicative values by different methods and the results of the rock samples with those obtained by negative thermal ionisation isotope dilution mass spectrometry. The detection limits of LA-ICP-IDMS are 8 [mu]g g-1 for chlorine, 1.7 [mu]g g-1 for bromine, and 0.1 [mu]g g-1 for iodine.

  10. Determination of iodine in oyster tissue by isotope dilution laser resonance ionization mass spectrometry

    SciTech Connect

    Fassett, J.D.; Murphy, T.J. )

    1990-02-15

    The technique of laser resonance ionization mass spectrometry has been combined with isotope dilution analysis to determine iodine in oyster tissue. The long-lived radioisotope, 129I, was used to spike the samples. Samples were equilibrated with the 129I, wet ashed under controlled conditions, and iodine separated by coprecipitation with silver chloride. The analyte was dried as silver ammonium iodide upon a tantalum filament from which iodine was thermally desorbed in the resonance ionization mass spectrometry instrument. A single-color, two-photon resonant plus one-photon ionization scheme was used to form positive iodine ions. Long-lived iodine signals were achieved from 100 ng of iodine. The precision of 127I/129I measurement has been evaluated by replicate determinations of the spike, the spike calibration samples, and the oyster tissue samples and was 1.0%. Measurement precision among samples was 1.9% for the spike calibration and 1.4% for the oyster tissue. The concentration of iodine determined in SRM 1566a, Oyster Tissue, was 4.44 micrograms/g with an estimate of the overall uncertainty for the analysis of +/- 0.12 microgram/g.

  11. An isotopic dilution approach for 1,3-butadiene tailpipe emissions and ambient air monitoring.

    PubMed

    Riservato, Manuela; Rolla, Antonio; Davoli, Enrico

    2004-01-01

    An isotopic dilution approach for 1,3-butadiene analysis in gaseous samples is presented. The methodology is based on active sampling on sorbent tubes and subsequent analysis by thermal desorption into a gas chromatography/mass spectrometry system. By adding a perdeuterated internal standard onto the sorbent tubes before sampling, and using mass spectrometric detection, the methodology gives high accuracy for this unstable analyte. The method has been used to monitor 1,3-butadiene ambient air concentrations in a residential area in proximity to a heavy-traffic roadway over a one-week period, for comparison with other traffic-related pollutants analysed by standard procedures. It has also been used to determine tailpipe emissions of two vehicles by standard emission testing procedures in a dynamometer. These vehicles were chosen as examples of low- and high-end emission rate vehicles, i.e., an old no-catalytic converter Otto engine and a new direct-injection diesel engine with catalytic converter. Exhaust gas emissions were 0.052 and 35.85 mg/km, reflecting differences in fuel, engine design, age, and presence (or not) of a catalytic abatement system. The ambient air results showed a weekly average concentration of 1,3-butadiene of 0.53 microg/m(3). PMID:14966846

  12. Quantification of ferritin bound iron in human serum using species-specific isotope dilution mass spectrometry.

    PubMed

    Ren, Yao; Walczyk, Thomas

    2014-09-01

    Ferritin is a hollow sphere protein composed of 24 subunits that can store up to 4500 iron atoms in its inner cavity. It is mainly found in the liver and spleen but also in serum at trace levels. Serum ferritin is considered as the best single indicator in assessing body iron stores except liver or bone marrow biopsy. However, it is confounded by other disease conditions. Ferritin bound iron (FBI) and ferritin saturation have been suggested as more robust biomarkers. The current techniques for FBI determination are limited by low antibody specificity, low instrument sensitivity and possible analyte losses during sample preparation. The need for a highly sensitive and reliable method is widely recognized. Here we describe a novel technique to detect serum FBI using species-specific isotope dilution mass spectrometry (SS-IDMS). [(57)Fe]-ferritin was produced by biosynthesis and in vitro labeling with the (57)Fe spike in the form of [(57)Fe]-citrate after cell lysis and heat treatment. [(57)Fe]-ferritin for sample spiking was further purified by fast liquid protein chromatography. Serum ferritin and added [(57)Fe]-ferritin were separated from other iron species by ultrafiltration followed by isotopic analysis of FBI using negative thermal ionization mass spectrometry. Repeatability of our assay is 8% with an absolute detection limit of 18 ng FBI in the sample. As compared to other speciation techniques, SS-IDMS offers maximum control over sample losses and species conversion during analysis. The described technique may therefore serve as a reference technique for clinical applications of FBI as a new biomarker for assessing body iron status. PMID:25008269

  13. Cadmium fixation in soils measured by isotopic dilution

    SciTech Connect

    Smolders, E.; Brans, K.; Foeldi, A.; Merckx, R.

    1999-01-01

    There is conflicting evidence on the effect of time of contact between soil and Cd on Cd availability to plants. If Cd can be fixed in soil by aging, higher soil contamination may be tolerated. Fixation of Cd by soil can be studied by adding small quantities of {sup 109}Cd to the indigenous soil Cd. The ratio of {sup 109}Cd to indigenous Cd in soil extracts or in plants gives information on the lability of Cd in soil. This isotope exchange technique was used to measure the labile and fixed Cd fractions in 10 Belgian agricultural soils (Soils A--I) with both background and elevated Cd content. The isotopically exchangeable Cd pool (E value) was measured after equilibrating {sup 109}Cd spiked soil suspensions in CaCl{sub 2} 0.01 M for 7 d. The %E values (the E value relative to aqua regia soluble Cd) ranged from 62 to 90% in the eight soils where %E values could be detected. The plant labile Cd pool, relative to aqua regia soluble Cd (%L value) was measured from the specific activities in wheat (Triticum aestivum L.) seedlings grown for 16 to 21 d on soils spiked with {sup 109}Cd. The Cd %L value varied from 55 to 109% (mean: 82%) with five soils having a significant (P < 0.05) fixed Cd fraction. Varying the soil incubation procedure after soil spiking and before plant growth marginally affected the specific activity of Cd in plants. The %L values always exceeded the respective %E value between 1.05- and 1.4-fold. It is concluded that Cd fixation, where found, is not very pronounced.

  14. Chemically selective polymer substrate based direct isotope dilution alpha spectrometry of Pu.

    PubMed

    Paul, Sumana; Pandey, Ashok K; Shah, R V; Aggarwal, S K

    2015-06-01

    Quantification of actinides in the complex environmental, biological, process and waste streams samples requires multiple steps like selective preconcentration and matrix elimination, solid source preparations generally by evaporation or electrodeposition, and finally alpha spectrometry. To minimize the sample manipulation steps, a membrane based isotope dilution alpha spectrometry method was developed for the determination of plutonium concentrations in the complex aqueous solutions. The advantages of this method are that it is Pu(IV) selective at 3M HNO3, high preconcentration factor can be achieved, and obviates the need of solid source preparation. For this, a thin phosphate-sulfate bifunctional polymer layer was anchored on the surface of microporous poly(ethersulfone) membrane by UV induced surface grafting. The thickness of the bifunctional layer on one surface of the poly(ethersulfone) membrane was optimized. The thickness, physical and chemical structures of the bifunctional layer were studied by secondary ionization mass spectrometry (SIMS), scanning electron microscopy (SEM) and SEM-EDS (energy-dispersive spectroscopy). The optimized membrane was used for preconcentration of Pu(IV) from aqueous solutions having 3-4M HNO3, followed by direct quantification of the preconcentrated Pu(IV) by isotope dilution alpha spectrometry using (238)Pu spike. The chemical recovery efficiency of Pu(IV) was found to be 86±3% below Pu(IV) loading capacity (1.08 μg in 2×1 cm(2)) of the membrane sample. The experiments with single representative actinides indicated that Am(III) did not sorb to significant extent (7%) but U(VI) sorbed with 78±3% efficiency from the solutions having 3M HNO3 concentration. However, Pu(IV) chemical recovery in the membrane remained unaffected from the solution containing 1:1000 wt. proportion of Pu(IV) to U(VI). Pu concentrations in the (U, Pu)C samples and in the irradiated fuel dissolver solutions were determined. The results thus obtained

  15. Development of stable isotope dilution assays for the quantitation of Amadori compounds in foods.

    PubMed

    Meitinger, Michael; Hartmann, Sandra; Schieberle, Peter

    2014-06-01

    During thermal processing of foods, reducing carbohydrates and amino acids may form 1-amino-1-desoxyketoses named Amadori rearrangement products after the Italian chemist Mario Amadori. Although these compounds are transient intermediates of the Maillard reaction, they are often used as suitable markers to measure the extent of a thermal food processing, such as for spray-dried milk or dried fruits. Several methods are already available in the literature for their quantitation, but measurements are often done with external calibration without addressing losses during the workup procedure. To cope with this challenge, stable isotope dilution assays in combination with LC-MS/MS were developed for the glucose-derived Amadori products of the seven amino acids valine, leucine, isoleucine, phenylalanine, tyrosine, methionine, and histidine using the respective synthesized [(13)C6]-labeled isotopologues as internal standards. The quantitation of the analytes added to a model matrix showed a very good sensitivity with the lowest limits of detection for the Amadori compound of phenylalanine of 0.1 μg/kg starch and 0.2 μg/kg oil, respectively. Also, the standard deviation measured in, for example, wheat beer was only ±2% for this analyte. Application of the method to several foods showed the highest concentrations of the Amadori product of valine in unroasted cocoa (342 mg/kg) as well as in dried bell pepper (3460 mg/kg). In agreement with literature data, drying of foods led to the formation of Amadori products, whereas they were degraded during roasting of, for example, coffee or cocoa. The study presents for the first time results on concentrations of the Amadori compounds of tyrosine and histidine in foods. PMID:24865106

  16. Optimization in multidimensional gas chromatography applying quantitative analysis via a stable isotope dilution assay.

    PubMed

    Schmarr, Hans-Georg; Slabizki, Petra; Legrum, Charlotte

    2013-08-01

    Trace level analyses in complex matrices benefit from heart-cut multidimensional gas chromatographic (MDGC) separations and quantification via a stable isotope dilution assay. Minimization of the potential transfer of co-eluting matrix compounds from the first dimension ((1)D) separation into the second dimension separation requests narrow cut-windows. Knowledge about the nature of the isotope effect in the separation of labeled and unlabeled compounds allows choosing conditions resulting in at best a co-elution situation in the (1)D separation. Since the isotope effect strongly depends on the interactions of the analytes with the stationary phase, an appropriate separation column polarity is mandatory for an isotopic co-elution. With 3-alkyl-2-methoxypyrazines and an ionic liquid stationary phase as an example, optimization of the MDGC method is demonstrated and critical aspects of narrow cut-window definition are discussed. PMID:23732869

  17. Spectrophotometric-isotope dilution determination of arsenic in soils and rock

    USGS Publications Warehouse

    Brown, F.W.; Simon, F.O.; Greenland, L.P.

    1975-01-01

    Arsenic in soil and rock samples may be determined in part-per-million concentrations using a radiochemical-isotope dilution method. Arsenic in the sample plus added As76 tracer is separated as arsine and determined spectrophotometrically as a molybdenum blue complex. The As76 activity in the absorbing solution allows corrections for chemical losses. A lower limit of 1 ppm is determinate in a 0.5-g sample.

  18. Comparison of bile acid synthesis determined by isotope dilution versus fecal acidic sterol output in human subjects

    SciTech Connect

    Duane, W.C.; Holloway, D.E.; Hutton, S.W.; Corcoran, P.J.; Haas, N.A.

    1982-05-01

    Fecal acidic sterol output has been found to be much lower than bile acid synthesis determined by isotope dilution. Because of this confusing discrepancy, we compared these 2 measurements done simultaneously on 13 occasions in 5 normal volunteers. In contrast to previous findings, bile acid synthesis by the Lindstedt isotope dilution method averaged 16.3% lower than synthesis simultaneously determined by fecal acidic sterol output (95% confidence limit for the difference - 22.2 to -10.4%). When one-sample determinations of bile acid pools were substituted for Lindstedt pools, bile acid synthesis by isotope dilution averaged 5.6% higher than synthesis by fecal acidic sterol output (95% confidence limits -4.9 to 16.1%). These data indicate that the 2 methods yield values in reasonably close agreement with one another. If anything, fecal acidic sterol outputs are slightly higher than synthesis by isotope dilution.

  19. Determination of perchlorate in infant formula by isotope dilution ion chromatography/tandem mass spectrometry

    PubMed Central

    Wang, Z.; Lau, B.P.-Y.; Tague, B.; Sparling, M.; Forsyth, D.

    2011-01-01

    A sensitive and selective isotope dilution ion chromatography/tandem mass spectrometry (ID IC-MS/MS) method was developed and validated for the determination of perchlorate in infant formula. The perchlorate was extracted from infant formula by using 20 ml of methanol and 5 ml of 1% acetic acid. All samples were spiked with 18O4 isotope-labelled perchlorate internal standard prior to extraction. After purification on a graphitised carbon solid-phase extraction column, the extracts were injected into an ion chromatography system equipped with an Ionpac AS20 column for separation of perchlorate from other anions. The presence of perchlorate in samples was quantified by isotope dilution mass spectrometry. Analysis of both perchlorate and its isotope-labelled internal standard was carried out on a Waters Quattro Ultima triple quadrupole mass spectrometer operating in a multiple reaction monitoring (MRM) negative ionisation mode. The method was validated for linearity and range, accuracy, precision, sensitivity, and matrix effects. The limit of quantification (LOQ) was 0.4 μg 1−1 for liquid infant formula and 0.95 μg kg−1 for powdered infant formula. The recovery ranged from 94% to 110% with an average of 98%. This method was used to analyse 39 infant formula, and perchlorate concentrations ranging from

  20. A stable isotope dilution method for measuring bioavailability of organic contaminants

    PubMed Central

    Delgado-Moreno, Laura; Gan, Jay

    2014-01-01

    Methods for determining bioavailability of organic contaminants suffer various operational limitations. We explored the use of stable isotope labeled references in developing an isotope dilution method (IDM) to measure the exchangeable pool (E) of pyrene and bifenthrin as an approximation of their bioavailability in sediments. The exchange of deuterated bifenthrin or pyrene with its native counterpart was completed within 48 h. The derived E was 38–82% for pyrene and 28–59% for bifenthrin. Regression between E and the sum of rapid and slow desorption fractions obtained from sequential desorption showed a slope close to 1.0. The ability of IDM to predict bioavailability was further shown from a strong relationship (r2 > 0.93) between E and bioaccumulation into Chironomus tentans. Given the abundance of stable isotope labeled references and their relatively easy analysis, the IDM has the potential to become a readily adoptable tool for estimating organic contaminants bioaccessibility in various matrices. PMID:23434573

  1. Total synthesis of isotopically enriched Si-29 silica NPs as potential spikes for isotope dilution quantification of natural silica NPs.

    PubMed

    Pálmai, Marcell; Szalay, Roland; Bartczak, Dorota; Varga, Zoltán; Nagy, Lívia Naszályi; Gollwitzer, Christian; Krumrey, Michael; Goenaga-Infante, Heidi

    2015-05-01

    A new method was developed for the preparation of highly monodisperse isotopically enriched Si-29 silica nanoparticles ((29)Si-silica NPs) with the purpose of using them as spikes for isotope dilution mass spectrometry (IDMS) quantification of silica NPs with natural isotopic distribution. Si-29 tetraethyl orthosilicate ((29)Si-TEOS), the silica precursor was prepared in two steps starting from elementary silicon-29 pellets. In the first step Si-29 silicon tetrachloride ((29)SiCl4) was prepared by heating elementary silicon-29 in chlorine gas stream. By using a multistep cooling system and the dilution of the volatile and moisture-sensitive (29)SiCl4 in carbon tetrachloride as inert medium we managed to reduce product loss caused by evaporation. (29)Si-TEOS was obtained by treating (29)SiCl4 with absolute ethanol. Structural characterisation of (29)Si-TEOS was performed by using (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. For the NP preparation, a basic amino acid catalysis route was used and the resulting NPs were analysed using transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), dynamic light scattering (DLS) and zeta potential measurements. Finally, the feasibility of using enriched NPs for on-line field-flow fractionation coupled with multi-angle light scattering and inductively coupled plasma mass spectrometry (FFF/MALS/ICP-MS) has been demonstrated. PMID:25617615

  2. Assessment of vitamin A status in rats by isotope dilution: A simplified model

    SciTech Connect

    Furr, H.C.; Cooper, D.A.; Olson, J.A. )

    1990-02-26

    Isotope-dilution analysis of vitamin A status requires giving a known quantity of labeled vitamin A to the subject and measuring the ratio of labeled to unlabeled retinol in the blood after a period for equilibration. To calculate total body stores from the isotopic ratio of plasma retinol, several assumptions must be made. In considering new ways of better calculating liver vitamin A stores from isotope-dilution data, the authors used the data of Green et al. to estimate loss of vitamin A tracer as a function of time and of vitamin A status. This correction markedly improves the correlation between calculated and analyzed liver vitamin A stores and also quantitively explains the hyperbolic relationship between fraction of tracer dose recovered in liver and mass of liver vitamin A stores. Agreement of this model with experimental data suggests that efficiency of absorption and storage of vitamin A is not affected by vitamin A status. This model can be used to estimate both the amount of tracer needed for a given lower limit of detection and an optimum sampling time.

  3. Use of Isotope Dilution Method To Predict Bioavailability of Organic Pollutants in Historically Contaminated Sediments

    PubMed Central

    2015-01-01

    Many cases of severe environmental contamination arise from historical episodes, where recalcitrant contaminants have resided in the environment for a prolonged time, leading to potentially decreased bioavailability. Use of bioavailable concentrations over bulk chemical levels improves risk assessment and may play a critical role in determining the need for remediation or assessing the effectiveness of risk mitigation operations. In this study, we applied the principle of isotope dilution to quantify bioaccessibility of legacy contaminants DDT and PCBs in marine sediments from a Superfund site. After addition of 13C or deuterated analogues to a sediment sample, the isotope dilution reached a steady state within 24 h of mixing. At the steady state, the accessible fraction (E) derived by the isotope dilution method (IDM) ranged from 0.28 to 0.89 and was substantially smaller than 1 for most compounds, indicating reduced availability of the extensively aged residues. A strong linear relationship (R2 = 0.86) was found between E and the sum of rapid (Fr) and slow (Fs) desorption fractions determined by sequential Tenax desorption. The IDM-derived accessible concentration (Ce) was further shown to correlate closely with tissue residue in the marine benthic polychaete Neanthes arenaceodentata exposed in the same sediments. As shown in this study, the IDM approach involves only a few simple steps and may be readily adopted in laboratories equipped with mass spectrometers. This novel method is expected to be especially useful for historically contaminated sediments or soils, for which contaminant bioavailability may have changed significantly due to aging and other sequestration processes. PMID:24946234

  4. Use of isotope dilution method to predict bioavailability of organic pollutants in historically contaminated sediments.

    PubMed

    Jia, Fang; Bao, Lian-Jun; Crago, Jordan; Schlenk, Daniel; Gan, Jay

    2014-07-15

    Many cases of severe environmental contamination arise from historical episodes, where recalcitrant contaminants have resided in the environment for a prolonged time, leading to potentially decreased bioavailability. Use of bioavailable concentrations over bulk chemical levels improves risk assessment and may play a critical role in determining the need for remediation or assessing the effectiveness of risk mitigation operations. In this study, we applied the principle of isotope dilution to quantify bioaccessibility of legacy contaminants DDT and PCBs in marine sediments from a Superfund site. After addition of 13C or deuterated analogues to a sediment sample, the isotope dilution reached a steady state within 24 h of mixing. At the steady state, the accessible fraction (E) derived by the isotope dilution method (IDM) ranged from 0.28 to 0.89 and was substantially smaller than 1 for most compounds, indicating reduced availability of the extensively aged residues. A strong linear relationship (R2=0.86) was found between E and the sum of rapid (Fr) and slow (Fs) desorption fractions determined by sequential Tenax desorption. The IDM-derived accessible concentration (Ce) was further shown to correlate closely with tissue residue in the marine benthic polychaete Neanthes arenaceodentata exposed in the same sediments. As shown in this study, the IDM approach involves only a few simple steps and may be readily adopted in laboratories equipped with mass spectrometers. This novel method is expected to be especially useful for historically contaminated sediments or soils, for which contaminant bioavailability may have changed significantly due to aging and other sequestration processes. PMID:24946234

  5. Stable-isotope dilution LC–MS for quantitative biomarker analysis

    PubMed Central

    Ciccimaro, Eugene; Blair, Ian A

    2010-01-01

    The ability to conduct validated analyses of biomarkers is critically important in order to establish the sensitivity and selectivity of the biomarker in identifying a particular disease. The use of stable-isotope dilution (SID) methodology in combination with LC–MS/MS provides the highest possible analytical specificity for quantitative determinations. This methodology is now widely used in the discovery and validation of putative exposure and disease biomarkers. This review will describe the application of SID LC–MS methodology for the analysis of small-molecule and protein biomarkers. It will also discuss potential future directions for the use of this methodology for rigorous biomarker analysis. PMID:20352077

  6. Isotopic Dilution GC/MS Method for Methionine Determination in Biological Media

    NASA Astrophysics Data System (ADS)

    Horj, Elena; Iordache, Andreea; Culea, Monica

    2011-10-01

    The isotopic dilution mass spectrometry technique is the method of choice for sensitive and accurate determination of analytes in biological samples. The aim of this work was to establish a sensitive analytical method for the determination of methionine in different biological media. Quantitation of methionine from the resultant tracer spectrum requires deconvolution of the enrichment of the isotopomers. Deconvolution of the ion abundance ratios to yield tracer-to-tracee ratio for the isotopomer was done using Brauman's least squares approach. Comparison with regression curve calculation method is presented. The method was applied for amino-acids determination in beef, pork and fish meat.

  7. Thermal dilution measurement of cardiac output in dogs using an analog computer.

    PubMed

    Hendriks, F F; Schipperheyn, J J; Quanjer, P H

    1978-01-01

    Thermal dilution cardiac output determinations in dogs were compared to simultaneously performed Fick oxygen measurements. The purpose of this study was to validate in dog experiments a method for thermal dilution measurement which employs a double-thermistor catheter combined with an automatic computer as described by Olsson et al. Dilution and injectate temperature are entered directly into the calculation. The method does not employ logarithmic extrapolation, integration of the dilution signal being terminated when a preset cut-off level is reached. Errors due to recirculation, thermal capacitance of the right heart and heat exchange with the catheter's dead space require the use of an empirically derived correction factor, which in dogs was found to be significantly different from the factor used for human thermal dilution curves. With the appropriate cut-off level and correction factor a good agreement was found between the results of the thermal dilution and the Fick method. The regression equation for 47 experiments was found to be COtd = 0.95 COFick + 0.08; the correlation coefficient was 0.94. PMID:728031

  8. Determination of total cholesterol in serum by liquid chromatography-isotope dilution mass spectrometry.

    PubMed

    Kock, R; Delvoux, B; Greiling, H

    1997-10-01

    We have developed a liquid chromatography-isotope dilution mass spectrometry procedure to quantify total cholesterol in serum. A particle-beam interface was used for coupling the liquid chromatograph and the mass spectrometer. After electron impact ionization the ions m/z = 386 and m/z = 389 were used for selective ion monitoring of cholesterol and the internal standard [25,26,27-(13)C]cholesterol. The sample preparation steps required for serum materials are alkaline hydrolysis and an extraction of the cholesterol into the cyclohexane phase. Imprecision for the determination of cholesterol in control materials is typically <1.0%. The deviation from the certified reference values was <0.75% for all control materials tested. A method comparison of the results obtained by this method with those obtained by gas chromatography-isotope dilution mass spectrometry for n = 28 pooled human sera derived from samples analyzed in our routine laboratory did not show differences >2.5%. PMID:9342010

  9. Column chromatographic boron isotope separation at 5 and 17 MPa with diluted boric acid solution.

    PubMed

    Musashi, Masaaki; Oi, Takao; Matsuo, Motoyuki; Nomura, Masao

    2008-08-01

    Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25 degrees C, using 0.1 mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at the atmospheric pressure at 25 degrees C with the boron concentration of 10mM, but were larger than the values under the same condition with much higher concentration of 100 and 501 mM. Calculations based on the theory of isotope distribution between two phases estimated that 21% (5 MPa) and 47% (17 MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)(3)-form, instead of in the four-coordinated B(OH)(4)-form, at high pressures even with a very diluted boric acid solution. We discussed the present results by introducing (1) hydration and (2) a partial molar volume difference between isotopic molecules. Borate may have been partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Instead, it may be possible that the difference in the isotopic partial molar volume difference between B(OH)(3) and B(OH)(4)(-) caused the S value to decrease with increasing pressure. PMID:18585727

  10. Quantification of four artificial sweeteners in Finnish surface waters with isotope-dilution mass spectrometry.

    PubMed

    Perkola, Noora; Sainio, Pirjo

    2014-01-01

    The artificial sweeteners sucralose (SCL), acesulfame (ACS), saccharin (SAC), and cyclamate (CYC) have been detected in environmental waters in Europe and North America. Higher environmental levels are expected in view of the increasing consumption of these food additives. In this study, an isotope-dilution mass spectrometry (IDMS) LC-MS/MS method was developed and validated for quantifying the four artificial sweeteners in boreal lakes (n = 3) and rivers (n = 12). The highest concentrations of ACS, SAC, CYC and SCL were 9,600, 490, 210 and 1000 ng/L, respectively. ACS and SAC were detected in all studied samples, and CYC and SCL in 98% and 56% of the samples. Seasonal trends of ACS and SAC were observed in some rivers. ACS and SCL concentrations in rivers correlated linearly with population equivalents of the wastewater treatment plants in the catchment areas, whereas SAC and CYC concentrations depend more on the source. PMID:24100049

  11. Adenosine 3',5'-monophosphate waves in dictyostelium discoideum: a demonstration by isotope dilution-fluorography

    SciTech Connect

    Tomchik, K.J.; Devreotes, P.N.

    1981-04-24

    The distribution of adenosine 3',5'-monophosphate (cyclic AMP) in fields of aggregating amoebae of Dictyostelium discoidenum was examined by a novel isotope dilution-fluorographic technique. Cellular cyclic AMP was visualized by its competition with exogenous /sup 3/H-labeled cyclic AMP for high-affinity binding sites on protein kinase immobilized on a Millipore filter used to blot the monolayer. The cyclic AMP was distributed in spiral or concentric circular wave patterns which centered on the foci of the aggregations. These patterns were correlated with those of cell shape change that propagate through the monolayers. These observations support the hypothesis that the aggregation process in Dictyostelium is mediated by the periodic relay of cyclic AMP signals and suggest a simple scheme for the dynamics of the aggregation process.

  12. Determination of lead in rocks by radiometric isotope dilution and substoichiometric extraction

    USGS Publications Warehouse

    Aruscavage, P.

    1976-01-01

    A rapid procedure is described for the determination of lead in rocks by an isotope-dilution substoichiometric method. After the sample has been digested with acid in the presence of 210Pb tracer, the lead is separated by dithizone extractions. After the lead has been back-extracted into aqueous solution, it is reacted with a substoichiometric amount of EDTA. Excess of unreacted lead is removed by extraction with dithizone in carbon tetrachloride, and the specific activity of the aqueous complex is determined by counting 210Pb. The standard deviation of the method is less than 10 % for replicate determinations of lead in several U.S. Geological Survey standard rocks. The agreement with literature values indicates that the method is accurate. ?? 1976.

  13. Quantitation of vitamin B6 in biological samples by isotope dilution mass spectrometry

    SciTech Connect

    Hachey, D.L.; Coburn, S.P.; Brown, L.T.; Erbelding, W.F.; DeMark, B.; Klein, P.D.

    1985-11-15

    Methods have been developed for the simultaneous quantitative analysis of vitamin B6 forms in biological samples by isotope dilution mass spectrometry using deuterated forms of pyridoxine, pyridoxal, pyridoxamine, and pyridoxic acid. The biological fluid or tissue sample was homogenized and then treated with a cocktail containing appropriate amounts of each deuterated vitamer, as well as the deuterated, phosphorylated vitamer forms. The individual vitamers were isolated from the homogenate by a complex high-performance liquid chromatographic procedure that provided separate fractions for each of the six vitamers found in biological samples. Aldehydic B6 vitamers were reduced to the alcohol form prior to acetylation and analysis by gas chromatography/mass spectrometry (GC/MS). The three resulting vitamers were analyzed by electron ionization GC/MS using a silicone capillary column. The methods have been applied to analysis of vitamin B6 in liver, milk, urine, and feces at levels as low as 0.02 nmol/ml.

  14. An isotope-dilution standard GC/MS/MS method for steroid hormones in water

    USGS Publications Warehouse

    Foreman, William T.; Gray, James L.; ReVello, Rhiannon C.; Lindley, Chris E.; Losche, Scott A.

    2013-01-01

    An isotope-dilution quantification method was developed for 20 natural and synthetic steroid hormones and additional compounds in filtered and unfiltered water. Deuterium- or carbon-13-labeled isotope-dilution standards (IDSs) are added to the water sample, which is passed through an octadecylsilyl solid-phase extraction (SPE) disk. Following extract cleanup using Florisil SPE, method compounds are converted to trimethylsilyl derivatives and analyzed by gas chromatography with tandem mass spectrometry. Validation matrices included reagent water, wastewater-affected surface water, and primary (no biological treatment) and secondary wastewater effluent. Overall method recovery for all analytes in these matrices averaged 100%; with overall relative standard deviation of 28%. Mean recoveries of the 20 individual analytes for spiked reagent-water samples prepared along with field samples analyzed in 2009–2010 ranged from 84–104%, with relative standard deviations of 6–36%. Detection levels estimated using ASTM International’s D6091–07 procedure range from 0.4 to 4 ng/L for 17 analytes. Higher censoring levels of 100 ng/L for bisphenol A and 200 ng/L for cholesterol and 3-beta-coprostanol are used to prevent bias and false positives associated with the presence of these analytes in blanks. Absolute method recoveries of the IDSs provide sample-specific performance information and guide data reporting. Careful selection of labeled compounds for use as IDSs is important because both inexact IDS-analyte matches and deuterium label loss affect an IDS’s ability to emulate analyte performance. Six IDS compounds initially tested and applied in this method exhibited deuterium loss and are not used in the final method.

  15. Validity of the tritiated thymidine method for estimating bacterial growth rates: measurement of isotope dilution during DNA synthesis

    SciTech Connect

    Pollard, P.C.; Moriarty, D.J.W.

    1984-12-01

    The rate of tritiated thymidine incorporation into DNA was used to estimate bacterial growth rates in aquatic environments. To be accurate, the calculation of growth rates has to include a factor for the dilution of isotope before incorporation. The validity of an isotope dilution analysis to determine this factor was verified in experiments reported here with cultures of a marine bacterium growing in a chemostat. Growth rates calculated from data on chemostat dilution rates and cell density agreed well with rates calculated by tritiated thymidine incorporation into DNA and isotope dilution analysis. With sufficiently high concentrations of exogenous thymidine, de novo synthesis of deoxythymidine monophosphate was inhibited, thereby preventing the endogenous dilution of isoope. The thymidine technique was also shown to be useful for measuring growth rates of mixed suspensions of bacteria growing anaerobically. Thymidine was incorporated into the DNA of a range of marine pseudomonads that were investigated. Three species did not take up thymidine. The common marine cyanobacterium Synechococcus species did not incorporate thymidine into DNA.

  16. Validation of New Instrumentation for Isotope Dilution Mass Spectrometric Determination of Organic Serum Analytes

    PubMed Central

    Ellerbe, P.; Phinney, C. S.; Sniegoski, L. T.; Welch, M. J.

    1999-01-01

    A major activity in the 20 year collaboration between the Analytical Chemistry Division at NIST and the College of American Pathologists (CAP) has been the development of highly accurate and precise “definitive” methods for important clinical analytes in human serum. Definitive methods for organic analytes use isotope dilution/gas chromatography/mass spectrometry and require a mass spectrometer capable of making highly precise measurements of the ratio between the ion intensities of a characteristic ion from the analyte of interest and its stable-isotope-labeled analog. Recently, the mass spectrometer used for 20 years for definitive method development and measurements was replaced with a modern instrument capable of automated operation, with accompanying gains in convenience and sample throughput. Switching to the new instrument required modifications of measurement protocols, acceptance criteria, and ratio calculations with background corrections to go along with automated instrument operation. Results demonstrated that the two instruments gave comparable results for measurements of both urea and cholesterol in samples from various serum-based Standard Reference Materials [SRMs] and College of American Pathologists materials.

  17. A practical method for cell-free protein synthesis to avoid stable isotope scrambling and dilution.

    PubMed

    Yokoyama, Jun; Matsuda, Takayoshi; Koshiba, Seizo; Tochio, Naoya; Kigawa, Takanori

    2011-04-15

    During recent years, the targets of protein structure analysis using nuclear magnetic resonance spectroscopy have become larger and more complicated. As a result, a complete and precise stable isotope labeling technique has been desired. A cell-free protein synthesis system is appropriate for this purpose. In the current study, we achieved precise and complete (15)N and (2)H labeling using an Escherichia coli cell extract-based cell-free protein synthesis system by controlling the metabolic reactions in the system with their chemical inhibitors. The addition of aminooxyacetate, d-malate, l-methionine sulfoximine, S-methyl-l-cysteine sulfoximine, 6-diazo-5-oxo-l-norleucine, and 5-diazo-4-oxo-l-norvaline was quite effective for precise amino acid-selective (15)N labeling even for aspartic acid, asparagine, glutamic acid, and glutamine, which generally suffer from severe isotope scrambling and dilution when using the conventional cell-free system. For (2)H labeling, the back-protonation of the H(α) and H(β) positions, which commonly occurred in the conventional system, was dramatically suppressed by simply adding aminooxyacetate and d-malate to the cell-free system except for the H(α) positions in methionine and cysteine. PMID:21256106

  18. Determination of Selected B-complex Vitamins in the NIST Multivitamin Reference Standard Material by Stable Isotope Dilution Mass Spectrometry (Experimental Biology, April, 2007, Washington, D.C.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is increased interest in accurately assessing the total dietary intake of vitamins from all sources, including foods and dietary supplements. Isotope dilution can be a definitive analytical method for very accurate concentration determinations. Thus, a liquid chromatographic (LC) isotope dilut...

  19. STATISTICAL ESTIMATES OF VARIANCE FOR 15N ISOTOPE DILUTION MEASUREMENTS OF GROSS RATES OF NITROGEN CYCLE PROCESSES

    EPA Science Inventory

    It has been fifty years since Kirkham and Bartholmew (1954) presented the conceptual framework and derived the mathematical equations that formed the basis of the now commonly employed method of 15N isotope dilution. Although many advances in methodology and analysis have been ma...

  20. Quantitation of 5-Methyltetrahydrofolic Acid in Dried Blood Spots and Dried Plasma Spots by Stable Isotope Dilution Assays

    PubMed Central

    Kopp, Markus; Rychlik, Michael

    2015-01-01

    Because of minimal data available on folate analysis in dried matrix spots (DMSs), we combined the advantages of stable isotope dilution assays followed by LC-MS/MS analysis with DMS sampling to develop a reliable method for the quantitation of plasma 5-methyltetrahydrofolic acid in dried blood spots (DBSs) and dried plasma spots (DPSs) as well as for the quantitation of whole blood 5-methyltetrahydrofolic acid in DBSs. We focused on two diagnostically conclusive parameters exhibited by the plasma and whole blood 5-methyltetrahydrofolic acid levels that reflect both temporary and long-term folate status. The method is performed using the [2H4]-labeled isotopologue of the vitamin as the internal standard, and three steps are required for the extraction procedure. Elution of the punched out matrix spots was performed using stabilization buffer including Triton X-100 in a standardized ultrasonication treatment followed by enzymatic digestion (whole blood only) and solid-phase extraction with SAX cartridges. This method is sensitive enough to quantify 27 nmol/L whole blood 5-methyltetrahydrofolic acid in DBSs and 6.3 and 4.4 nmol/L plasma 5-methyltetrahydrofolic acid in DBSs and DPSs, respectively. The unprecedented accurate quantification of plasma 5-methyltetrahydrofolic acid in DBSs was achieved by thermal treatment prior to ultrasonication, inhibiting plasma conjugase activity. Mass screenings are more feasible and easier to facilitate for this method in terms of sample collection and storage compared with conventional clinical sampling for the assessment of folate status. PMID:26605791

  1. Determination of Mercury Content in a Shallow Firn Core from Summit, Greenland by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Mann, Jacqueline L.; Long, Stephen E.; Shuman, Christopher A.; Kelly, W. Robert

    2003-01-01

    The total mercury Hg content was determined in 6 cm sections of a near-surface 7 m firn core and in surrounding surface snow from Summit, Greenland (elevation: 3238 m, 72.58 N, 38.53 W) in May 2001 by isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS). The focus of this research was to evaluate the capability of the ID-CV-ICPMS technique for measuring trace levels of Hg typical of polar snow and firn. Highly enriched Hg-201 isotopic spike is added to approximately 10 ml melted core and thoroughly mixed. The Hg(+2) in the sample is reduced on line with tin (II) chloride (SnCl2) and the elemental Hg (Hg(0)) vapor pre-concentrated on to gold gauze using a commercial amalgam system. The Hg is then thermally desorbed and introduced into a quadrupole ICP-MS. The blank corrected Hg concentrations determined for all samples ranged from 0.25 ng/L to 1.74 ng/L (ppt) (average 0.59 ng/L plus or minus 0.28 ng/L) and fall within the range of those previously determined by Boutron et al., 1998 (less than or equal to 0.05 ng/L to 2.0 ng/L) for the Summit site. The average blank value was 0.19 ng/L plus or minus 0.045 ng/L (n=6). The Hg values specifically for the firn core range from 0.25 ng/L to 0.87 ng/L (average 0.51 ng/L plus or minus 0.13 ng/L) and show both values declining with time and larger variability in concentration in the top 1.8 m.

  2. Direct quantitative determination of cyanamide by stable isotope dilution gas chromatography-mass spectrometry.

    PubMed

    Hiradate, Syuntaro; Kamo, Tsunashi; Nakajima, Eri; Kato, Kenji; Fujii, Yoshiharu

    2005-12-01

    Cyanamide is a multifunctional agrochemical used, for example, as a pesticide, herbicide, and fertilizer. Recent research has revealed that cyanamide is a natural product biosynthesized in a leguminous plant, hairy vetch (Vicia villosa). In the present study, gas chromatography-mass spectrometry (GC-MS) equipped with a capillary column for amines was used for direct quantitative determination of cyanamide. Quantitative signals for ((14)N(2))cyanamide, ((15)N(2))cyanamide (internal standard for stable isotope dilution method), and m-(trifluoromethyl)benzonitrile (internal standard for correcting errors in GC-MS analysis) were recorded as peak areas on mass chromatograms at m/z 42 (A(42)), 44 (A(44)), and 171 (A(IS)), respectively. Total cyanamide content, ((14)N(2))cyanamide plus ((15)N(2))cyanamide, was determined as a function of (A(42)+A(44))/A(IS). Contents of ((14)N(2))cyanamide and ((15)N(2))cyanamide were then calculated by multiplying the total cyanamide content by A(42)/(A(42)+A(44)) and A(44)/(A(42)+A(44)), respectively. The limit of detection for the total cyanamide content by the GC-MS analysis was around 1ng. The molar ratio of ((14)N(2))cyanamide to ((15)N(2))cyanamide in the injected sample was equal to the observed A(42)/A(44) value in the range from 0.1 to 5. It was, therefore, possible to use the stable isotope dilution method to quantify the natural cyanamide content in samples; i.e., the natural cyanamide content was derived by subtracting the A(42)/A(44) ratio of the internal standard from the A(42)/A(44) ratio of sample spiked with internal standard, and then multiplying the resulting difference by the amount of added ((15)N(2))cyanamide (SID-GC-MS method). This method successfully gave a reasonable value for the natural cyanamide content in hairy vetch, concurring with the value obtained by a conventional method in which cyanamide was derivatized to a photometrically active compound 4-cyanimido-1,2-naphthoquinone and analyzed with reversed

  3. Convenient synthesis of stable deuterium-labeled alkylpyrazines for use in stable isotope dilution assays.

    PubMed

    Fang, Mingchih; Cadwallader, Keith R

    2013-04-17

    Stable isotope dilution assays (SIDA) provide for accurate and precise quantitation of aroma components, such as alkylpyrazines, which are often present in low concentrations in complex food matrices. The unavailability of labeled standards is the main limitation to the widespread use of SIDA. This study describes the chlorination of several alkylpyrazines to form the corresponding chloroalkylpyrazine compounds, which are efficient starting materials for the synthesis of deuterium-labeled alkylpyrazines, namely [²H₃]-2-methylpyrazine (d-1), [²H₅]-2-ethylpyrazine (d-2), [²H₃]-2,3(or 6)-dimethylpyrazine (d-3A, d-3B), [²H₃]-2,[²H₃]-6-dimethylpyrazine (d-3C), [²H₅]-2,[²H₅]-6-diethylpyrazine (d-4), [²H₅]-2-ethyl-3(or 6)-methylpyrazine (d-5A, d-5B), 2,[²H₃]-3,5-trimethylpyrazine (d-6), [²H₅]-2-ethyl-3,6-dimethylpyrazine (d-7), [²H₅]-2-ethyl-3,5-dimethylpyrazine (d-8), and 2,3-diethyl-[²H₃]-5-methylpyrazine (d-9), which were obtained in good yields (57-100%) and high purities (86-98%). These stable isotopes were used as internal standards in SIDA to accurately and precisely determine selected alkylpyrazines in commercial peanut butter, cocoa powder, and instant coffee. 2,3-Diethyl-5-methylpyrazine (p-9) and 2-ethyl-3,5-dimethylpyrazine (p-8), despite their low abundance, had the highest odor-active values among the 13 pyrazines quantified in all products due to their very low odor thresholds. PMID:23528050

  4. Stable isotope dilution method for the determination of guanidinoacetic acid by gas chromatography/mass spectrometry.

    PubMed

    Fingerhut, Ralph

    2003-01-01

    For more than 30 years, guanidinoacetic acid (GAA), together with other guanidino compounds, has been proposed as an important marker for renal failure, in kidney transplantation, and for renal metabolism, especially for the metabolic activity of the renal proximal tubules. Since the discovery of the first patient with guanidinoacetic acid methyltransferase deficiency in 1994 by Stöckler et al. (Pediatr. Res. 1994; 36: 409), GAA has become of great interest for all laboratories involved in the diagnosis of metabolic diseases. In the literature there are several methods described for the determination of GAA, ranging from ion-exchange chromatography with post-column derivatisation, enzymatic methods, gas chromatography/mass spectrometry (GC/MS), to liquid chromatography/atmospheric pressure chemical ionisation mass spectrometry (LC/APCI-MS). Here a stable isotope dilution method for quantitative and accurate determination of GAA in urine, plasma, and cerebrospinal fluid is described. GAA is converted to the bis(trifluoromethyl)pyrimidine di(tert-butyldimethylsilyl) derivative by stepwise derivatisation with hexafluoroacetylacetone and N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA). Analysis can be performed using a standard benchtop GC/MS system. For quantitative GAA determination with 1,2-(13)C-GAA as internal standard, selected ion monitoring is performed using m/z 460/462, with m/z 432/433 and 375/376 as qualifiers. PMID:12661026

  5. Sulfur-based absolute quantification of proteins using isotope dilution inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Lee, Hyun-Seok; Heun Kim, Sook; Jeong, Ji-Seon; Lee, Yong-Moon; Yim, Yong-Hyeon

    2015-10-01

    An element-based reductive approach provides an effective means of realizing International System of Units (SI) traceability for high-purity biological standards. Here, we develop an absolute protein quantification method using double isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS) combined with microwave-assisted acid digestion for the first time. We validated the method and applied it to certify the candidate protein certified reference material (CRM) of human growth hormone (hGH). The concentration of hGH was determined by analysing the total amount of sulfur in hGH. Next, the size-exclusion chromatography method was used with ICP-MS to characterize and quantify sulfur-containing impurities. By subtracting the contribution of sulfur-containing impurities from the total sulfur content in the hGH CRM, we obtained a SI-traceable certification value. The quantification result obtained with the present method based on sulfur analysis was in excellent agreement with the result determined via a well-established protein quantification method based on amino acid analysis using conventional acid hydrolysis combined with an ID liquid chromatography-tandem mass spectrometry. The element-based protein quantification method developed here can be generally used for SI-traceable absolute quantification of proteins, especially pure-protein standards.

  6. Assessing the labile arsenic pool in contaminated paddy soils by isotopic dilution techniques and simple extractions.

    PubMed

    Stroud, Jacqueline L; Khan, M Asaduzzman; Norton, Gareth J; Islam, M Rafiqul; Dasgupta, Tapash; Zhu, Yong-Guan; Price, Adam H; Meharg, Andrew A; McGrath, Steve P; Zhao, Fang-Jie

    2011-05-15

    Arsenic (As) contamination of paddy soils threatens rice cultivation and the health of populations relying on rice as a staple crop. In the present study, isotopic dilution techniques were used to determine the chemically labile (E value) and phytoavailable (L value) pools of As in a range of paddy soils from Bangladesh, India, and China and two arable soils from the UK varying in the degree and sources of As contamination. The E value accounted for 6.2-21.4% of the total As, suggesting that a large proportion of soil As is chemically nonlabile. L values measured with rice grown under anaerobic conditions were generally larger than those under aerobic conditions, indicating increased potentially phytoavailable pool of As in flooded soils. In an incubation study, As was mobilized into soil pore water mainly as arsenite under flooded conditions, with Bangladeshi soils contaminated by irrigation of groundwater showing a greater potential of As mobilization than other soils. Arsenic mobilization was best predicted by phosphate-extractable As in the soils. PMID:21504212

  7. Determination of total mercury in biological tissue by isotope dilution ICPMS after UV photochemical vapor generation.

    PubMed

    Liu, Rui; Xu, Mo; Shi, Zeming; Zhang, Jiayun; Gao, Ying; Yang, Lu

    2013-12-15

    A method is developed for the determination of trace mercury in biological samples using photo chemical vapor generation (PVG) and isotope dilution inductively coupled plasma mass spectrometry (ID ICPMS) detection. Biological tissues were solubilized in formic acid. Subsequently, the sample solutions were exposed to an ultraviolet (UV) source for the reduction of mercury into vapor species prior to ICPMS measurements. The formic acid served not only as a tissue solubilizer in the sample preparation procedure, but also as a photochemical reductant for mercury in the PVG process. The problem arising from the opaque formic acid digested solution was efficiently solved by using ID method. The optimum conditions for sample treatment and PVG were investigated. A limit of detection (LOD) of 0.5 pg g(-1), based on an external calibration, provided 350-fold improvement over that obtained by utilizing conventional pneumatic nebulization sample introduction. Method validation was demonstrated by the determination of total mercury in several biological tissue certified reference materials (CRMs). The results were in good agreement with the certified values. PMID:24209355

  8. Daily cortisol production rate in man determined by stable isotope dilution/mass spectrometry

    SciTech Connect

    Esteban, N.V.; Loughlin, T.; Yergey, A.L.; Zawadzki, J.K.; Booth, J.D.; Winterer, J.C.; Loriaux, D.L. )

    1991-01-01

    Growth retardation as well as the development of Cushingoid features in adrenally insufficient patients treated with the currently accepted replacement dose of cortisol (33-41 mumol/day.m2; 12-15 mg/m2.day) prompted us to reevaluate the cortisol production rate (FPR) in normal subjects and patients with Cushing's syndrome, using a recently developed thermospray liquid chromatography-mass spectrometry method. The stable isotope (9,12,12-2H3)cortisol was infused continuously for 31 h at about 5% of the anticipated FPR. Blood samples were obtained at 20-min intervals for 24 h, spun, and pooled in 4-h groups. Tracer dilution in plasma was determined by liquid chromatography/mass spectrometry. The method was validated with controlled infusions in 6 patients with adrenal insufficiency. Results from 12 normal volunteers revealed a FPR of 27.3 +/- 7.5 mumol/day (9.9 +/- 2.7 mg/day) or 15.7 mumol/day.m2; 5.7 mg/m2. day. A previously unreported circadian variation in FPR was observed. Patients with Cushing's syndrome demonstrated unequivocal elevation of FPR and cortisol concentration correlated during each sample period in normal volunteers, indicating that cortisol secretion, rather than metabolism, is mainly responsible for changes in plasma cortisol. Our data suggest that the FPR in normal subjects may be lower than previously believed.

  9. Analysis of acrylamide in coffee and cocoa by isotope dilution liquid chromatography-tandem mass spectrometry.

    PubMed

    Aguas, Patricia C; Fitzhenry, Matthew J; Giannikopoulos, Georgina; Varelis, Peter

    2006-08-01

    An accurate and precise method for the quantification of acrylamide using stable isotope dilution liquid chromatography-tandem mass spectrometry was developed and used to measure acrylamide in coffee and cocoa samples. The sample preparation involved extraction of the analyte and its internal standard, 13C3-acrylamide, into water and subsequent defatting of the aqueous extract with dichloromethane. An aliquot of the resulting aqueous extract was then azeotropically dried under reduced pressure and subsequently purified using an aminopropyl-bonded silica cartridge. The purified extracts were then chromatographed on a 5-microm 2.1 x 150 mm Hypercarb column, the effluent of which was monitored for the analyte and its internal standard using positive-ion APCI-selected reaction monitoring. The intra-laboratory reproducibility of the method, expressed as a relative coefficient of variation (%, n=5), was determined at four levels of concentration (12.3, 42.3, 139.3 and 464.8 microg kg(-1)) and was found to vary between 0.6-2.5%. The accuracy of the method was assessed using a reference sample of coffee. The average result obtained using our method differed from the assigned value of the reference material by less than 1%. An analysis of a cocoa sample revealed that the method is capable of precisely estimating acrylamide in challenging matrices down to a level of at least 12.3 microg kg(-1). PMID:16819634

  10. A novel method for the quantification of quinic acid in food using stable isotope dilution analysis.

    PubMed

    Erk, Thomas; Bergmann, Hannah; Richling, Elke

    2009-01-01

    Organic acids play an important role in the flavor and taste of plant-derived foods. Quinic acid (QA) is one of the major acids. In the past, several methods like HPLC/UV, GC, and capillary electrophoresis were used for identification and quantification of QA. For the first time, a novel, sensitive, and selective method for the quantification of QA in food using stable isotope dilution analysis with HPLC/MS/MS has been established. Uniformly labeled 13C-QA was used as a standard to reduce sample preparations and to overcome matrix and ionization effects. The method was used to determine the QA content of red wines, instant coffees, and cloudy apple juices. QA contents of instant coffees were 64.4 and 63.6 g/kg powder. The concentrations in red wines were 24.0 and 25.1 mg/L, and 1493.3 and 1705.2 mg/L in cloudy apple juices. PMID:19610361

  11. [Determination of trace organochlorine pesticides in soil using isotope dilution-high resolution gas chromatography].

    PubMed

    Huang, Wenjun; Gao, Lirong; Gong, Aijun; Li, Cheng; Wang, Pu; Fu, Shan; Xiao, Ke; Zhang, Bing; Liu, Wenbin

    2010-05-01

    A method for the determination of trace organochlorine pesticides (OCPs) in soil using isotope dilution and high resolution gas chromatography-high resolution mass spectrometry (ID-HRGC-HRMS) was developed. The sample was extracted by accelerated solvent extractor (ASE) and cleaned-up by a Florisil solid phase extraction (SPE) cartridge. The analytes were separated by HRGC on a DB-5MS column (30 mx 0.25 mm x 0.25 microm) and determined by HRMS. The identifications of OCPs were based on the retention time of 13C-labelled standard and the abundance ratio of the two exact mass-to-charge ratios. The quantitative analysis was performed using the ratios of the integrated areas of the 13C-labelled standards. This method has the recoveries ranging from 77.3% to 114.5% and the relative standard deviations (RSD) less than 10.81% (n=5). The limits of detection (LODs) of this method for all OCPs were lower than 0.04 pg/g. The results indicated that the method is rapid, selective and sensitive for precise determination requirements of organochlorine pesticides at trace level in soil. PMID:20812621

  12. Multi-mycotoxin stable isotope dilution LC-MS/MS method for Fusarium toxins in cereals.

    PubMed

    Habler, Katharina; Rychlik, Michael

    2016-01-01

    A multi-mycotoxin stable isotope dilution LC-MS/MS method was developed for 14 Fusarium toxins including modified mycotoxins in cereals (deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, HT2-toxin, T2-toxin, enniatin B, enniatin B1, enniatin A1, enniatin A, beauvericin, fusarenone X, nivalenol, deoxynivalenol-3-glucoside, and zearalenone). The chromatographic separation of the toxins with particular focus on deoxynivalenol and deoxynivalenol-3-glucoside was achieved using a C18-hydrosphere column. An expedient sample preparation method was developed that uses solid-phase extraction for the purification of trichothecenes combined with zearalenone, enniatins, and beauvericin and provides excellent validation data. Linearity, intra-day precision, inter-day precision, and recoveries were ≥0.9982, 1-6%, 5-12%, and 79-117%, respectively. Method accuracy was verified by analyzing certified reference materials for deoxynivalenol, HT2-toxin, and T2-toxin with deviations below 7%. The results of this method found barley malt samples from 2012, 2013, and 2014 frequently contaminated with high concentrations of enniatin B, deoxynivalenol, and its modified mycotoxin deoxynivalenol-3-glucoside. Samples from 2012 were especially contaminated. Fusarenone X was not detected in any of the analyzed samples. PMID:26514672

  13. Thermal unfolding and refolding of lysozyme in deep eutectic solvents and their aqueous dilutions.

    PubMed

    Esquembre, Rocio; Sanz, Jesus M; Wall, J Gerard; del Monte, Francisco; Mateo, C Reyes; Ferrer, M Luisa

    2013-07-21

    The stability of hen's egg white lysozyme in different choline chloride-based pseudo-concentrated and neat deep eutectic solvents (DESs) has been studied by means of intrinsic fluorescence and CD spectroscopy. Thermal unfolding experiments carried out in non-diluted urea:choline chloride and glycerol:choline chloride eutectic solvents (UCCl-DES and GCCl-DES, respectively) showed the accumulation at certain temperatures of discrete, partially folded intermediates that displayed a high content of secondary structure and a disrupted tertiary structure. Reversibility of the unfolding process was incomplete in these circumstances, with the urea-based DES showing higher protein structure destabilization upon thermal treatment. On the other hand, aqueous dilution of the eutectic mixtures allowed the recovery of a reversible, two-state denaturation process. Lysozyme activity was also affected in neat and pseudo-concentrated GCCl-DES, with an increasing recovery of activity upon aqueous dilution, and full restoration after DES removal through extensive dialysis. These results suggest that protein interactions at room temperature are reversible and depend on the DES components and on the aqueous content of the original DES dilution. PMID:23722327

  14. Comparison of isotope dilution and excretion methods for determining the half-life of ascorbic acid in the guinea pig

    SciTech Connect

    Kipp, D.E.; Rivers, J.M.

    1984-08-01

    The half-life of ascorbic acid (AA) in guinea pigs was investigated by the isotope dilution and excretion methods. The dilution method measures (1-14C)AA disappearance from the plasma, whereas the excretion method measures the elimination of (1-14C)AA and the metabolites from the body. Two groups of animals underwent both isotope studies in reverse order. Animals were conditioned to the experimental procedures and fed 2.5 mg AA/100 g body weight orally to maintain a daily intake of the vitamin independent of food consumption. The two isotope procedures imposed similar stress on the animals, as determined by plasma cortisol levels and body weight changes. The AA half-life calculations of the rapidly exchangeable pool by the isotope dilution method yielded values of 1.23 and 0.34 hours for the two groups, respectively. The half-life of the slowly exchangeable pool for the two groups was 60.2 and 65.8 hours, respectively. The half-life of AA in the rapidly exchangeable pool, as measured by the excretion studies, was 4.57-8.75 hours. For the slowly exchangeable pool, it was 146-149 hours. The longer half-life of both pools obtained with the excretion method indicates that the isotope is disappearing from the plasma more rapidly than it is being excreted. This suggests that a portion of the (1-14C)AA leaving the plasma is removed to a body pool that is not sampled by the isotope excretion method.

  15. Odorant Screening and Quantitation of Thiols in Carmenere Red Wine by Gas Chromatography-Olfactometry and Stable Isotope Dilution Assays.

    PubMed

    Pavez, Carolina; Agosin, Eduardo; Steinhaus, Martin

    2016-05-01

    The sensory impact of thiols in Vitis vinifera 'Carmenere' red wines was evaluated. For this purpose, aroma extract dilution analysis was applied to the thiols isolated from a Carmenere red wine by affinity chromatography with a mercurated agarose gel. Results revealed the presence of four odorants, identified as 2-furanylmethanethiol, 3-sulfanylhexyl acetate, 3-sulfanyl-1-hexanol, and 2-methyl-3-sulfanyl-1-butanol, with the latter being described here for the first time in Carmenere red wines. Quantitation of the four thiols in the Carmenere wine screened by aroma extract dilution analysis and in three additional Carmenere wines by stable isotope dilution assays resulted in concentrations above the respective orthonasal odor detection threshold values. Triangle tests applied to wine model solutions with and without the addition of the four thiols showed significant differences, thus suggesting that the compounds do have the potential to influence the overall aroma of red wine. PMID:27070203

  16. Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

    DOE PAGESBeta

    Horkley, J. J.; Carney, K. P.; Gantz, E. M.; Davies, J. E.; Lewis, R. R.; Crow, J. P.; Poole, C. A.; Grimes, T. S.; Giglio, J. J.

    2015-03-17

    Isotope dilution mass spectrometry (IDMS) is an analytical technique capable of providing accurate and precise quantitation of trace isotope abundance and assay providing measurement uncertainties below 1 %. To achieve these low uncertainties, the IDMS method ideally utilizes chemically pure “spike” solutions that consist of a single highly enriched isotope that is well-characterized relating to the abundance of companion isotopes and concentration in solution. To address a current demand for accurate 137Cs/137Ba ratio measurements for “age” determination of radioactive 137Cs sources, Idaho National Laboratory (INL) is producing enriched 134Ba isotopes that are tobe used for IDMS spikes to accurately determinemore » 137Ba accumulation from the decay of 137Cs. The final objective of this work it to provide a homogenous set of reference materials that the National Institute of Standards and Technology can certify as standard reference materials used for IDMS. The process that was developed at INL for the separation and isolation of Ba isotopes, chemical purification of the isotopes in solution, and the encapsulation of the materials will be described.« less

  17. Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

    SciTech Connect

    J.J. Horkley; K.P E.M. Gantz; J.E. Davis; R.R. Lewis; J.P. Crow; C.A. Poole; T.S. Grimes; J.J. Giglio

    2015-03-01

    t Isotope dilution mass spectrometry (IDMS) is an analytical technique capable of providing accurate and precise quantitation of trace isotope abundance and assay providing measurement uncertainties below 1 %. To achieve these low uncertainties, the IDMS method ideally utilizes chemically pure ‘‘spike’’ solutions that consist of a single highly enriched isotope that is well-characterized relating to the abundance of companion isotopes and concentration in solution. To address a current demand for accurate 137Cs/137Ba ratio measurements for ‘‘age’’ determination of radioactive 137Cs sources, Idaho National Laboratory (INL) is producing enriched 134Ba isotopes that are tobe used for IDMS spikes to accurately determine 137Ba accumulation from the decay of 137Cs. The final objective of this work it to provide a homogenous set of reference materials that the National Institute of Standards and Technology can certify as standard reference materials used for IDMS. The process that was developed at INL for the separation and isolation of Ba isotopes, chemical purification of the isotopes in solution,

  18. Production of highly-enriched 134Ba for a reference material for isotope dilution mass spectrometry measurements

    SciTech Connect

    Horkley, J. J.; Carney, K. P.; Gantz, E. M.; Davies, J. E.; Lewis, R. R.; Crow, J. P.; Poole, C. A.; Grimes, T. S.; Giglio, J. J.

    2015-03-17

    Isotope dilution mass spectrometry (IDMS) is an analytical technique capable of providing accurate and precise quantitation of trace isotope abundance and assay providing measurement uncertainties below 1 %. To achieve these low uncertainties, the IDMS method ideally utilizes chemically pure “spike” solutions that consist of a single highly enriched isotope that is well-characterized relating to the abundance of companion isotopes and concentration in solution. To address a current demand for accurate 137Cs/137Ba ratio measurements for “age” determination of radioactive 137Cs sources, Idaho National Laboratory (INL) is producing enriched 134Ba isotopes that are tobe used for IDMS spikes to accurately determine 137Ba accumulation from the decay of 137Cs. The final objective of this work it to provide a homogenous set of reference materials that the National Institute of Standards and Technology can certify as standard reference materials used for IDMS. The process that was developed at INL for the separation and isolation of Ba isotopes, chemical purification of the isotopes in solution, and the encapsulation of the materials will be described.

  19. The geochemical behaviour of W in subduction zones: constraints from high precision isotope dilution measurements

    NASA Astrophysics Data System (ADS)

    Konig, S.; Munker, C.; Schuth, S.

    2007-12-01

    Assessing the behaviour of W during silicate Earth's differentiation is hampered by low abundances of W in terrestrial reservoirs, making sufficiently precise and accurate measurements difficult. Previous results (e.g., Newsom et al. 1996) indicate a lower W/Th of the mantle (ca. 0.19) compared to the Earth's crust, (ca. 0.26), suggesting that W appears to be more incompatible than Th. New data for MORB (Munker et al. 2007), however, demonstrate that W/Th is not significantly fractionated during dry peridotite melting, tentatively suggesting a fractionation of the two elements during crust formation by subduction related processes. We present high precision W and Nb-Ta, Zr-Hf data obtained by isotope dilution, using a mixed 183W-180Ta- 94Zr-180Hf-176Lu tracer and multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS). This enables the direct determination of W and HFSE from one sample digestion. For some samples, a "nugget effect" as previously reported for PGE was observed, reflecting sample heterogeneity. Measured Ta and W abundances determined in basaltic glasses and whole rock powders from various island arc settings yield Ta/W ratios of 0.6 to 1.7, significantly lower than the values reported for MORB (4-6). In contrast, Nb/Ta for the samples overlap with MORB values, suggesting that Nb and Ta were not mobile in the magma sources. These systematic differences indicate that W does not behave as other HFSE (Nb-Ta, Zr-Hf) in subduction zones but rather displays a higher mobility in slab components. Intra-oceanic arc suites involving subducted pelagic sediment in their sources generally display higher W/Th compared to magmas without sediment-derived components in their sources, reflecting the higher initial W abundances in subducted pelagic sediments. A fractionation of W/Th during crust formation could consequently be explained by a selective W enrichment relative to Th during subduction processes.

  20. Quantitative determination of free and total bisphenol A in human urine using labeled BPA glucuronide and isotope dilution mass spectrometry.

    PubMed

    Kubwabo, Cariton; Kosarac, Ivana; Lalonde, Kaela; Foster, Warren G

    2014-07-01

    Bisphenol A (BPA) is a widely used industrial chemical in the manufacturing of polycarbonate plastic bottles, food and beverage can linings, thermal receipts, and dental sealants. Animal and human studies suggest that BPA may disrupt normal hormonal function and hence, potentially, have negative effects on the human health. While total BPA is frequently reported, it is recognized that free BPA is the biologically active form and is rarely reported in the literature. The objective of this study was to develop a sensitive and improved method for the measurement of free and total BPA in human urine. Use of a labeled conjugated BPA (bisphenol A-d6 β-D-glucuronide) allowed for the optimization of the enzymatic reaction and permitted an accurate determination of the conjugated BPA concentration in urine samples. In addition, a (13)C12-BPA internal standard was used to account for the analytical recoveries and performance of the isotope dilution method. Solid-phase extraction (SPE) combined with derivatization and analysis using a triple quadrupole GC-EI/MS/MS system achieved very low method detection limit of 0.027 ng/mL. BPA concentrations were measured in urine samples collected during the second and third trimesters of pregnancy in 36 Canadian women. Total maternal BPA concentrations in urine samples ranged from not detected to 9.40 ng/mL (median, 1.21 ng/mL), and free BPA concentrations ranged from not detected to 0.950 ng/mL (median, 0.185 ng/mL). Eighty-six percent of the women had detectable levels of conjugated BPA, whereas only 22 % had detectable levels of free BPA in their urine. BPA levels measured in this study agreed well with data reported internationally. PMID:24817354

  1. Simultaneous Determination of Selected B Vitamins in the NIST SRM 3280 Multivitamin/Multielement Tablets by Liquid Chromatography Isotope Dilution Mass Spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is increased interest in accurately assessing the total dietary intake of vitamins from all sources, including foods and dietary supplements. Isotope dilution mass spectrometry (IDMS) can be a definitive analytical method for very accurate concentration determinations. A liquid chromatographic...

  2. Determination of Polychlorinated Biphenyls in Solid Samples by Isotope Dilution Mass Spectrometry Using ³⁷Cl-Labeled Analogues.

    PubMed

    Somoano-Blanco, Lourdes; Rodriguez-Gonzalez, Pablo; García Fonseca, Sergio; Alonso, J Ignacio Garcia

    2015-08-01

    This work describes the first application of (37)Cl-labeled compounds to isotope dilution mass spectrometry (IDMS). The synthesis of 12 (37)Cl-labeled polychlorinated biphenyls (PCBs) was carried out by the chlorination of biphenyl with isotopically enriched chlorine gas, generated by the direct oxidation of Na(37)Cl with potassium peroxymonosulfate. After an exhaustive purification due to the presence of other congeners, the concentration and the isotopic enrichment of all (37)Cl-labeled PCBs in the mixture was determined. The proposed procedure allows the simultaneous quantification of every isotope diluted PCB congener in a single gas chromatography-tandem mass spectrometry (GC-MS/MS) injection without resorting to a methodological calibration graph. The results obtained here demonstrate that the use of (37)Cl-labeled analogues provides results in agreement with the certified values of three different Certified Reference Materials (marine sediment SRM 1944, fish tissue 1947, and loamy soil CRM 962-50) and analytical figures of merit comparable to those obtained using regular IDMS procedures based on the use of commercially available (13)C-labeled analogues. PMID:26165349

  3. Determination of Sb(III) and Sb(V) by HPLC-Online isotopic dilution-ICP MS.

    PubMed

    Fontanella, Maria Chiara; Beone, Gian Maria

    2016-01-01

    This work provides a method with application of valid techniques to extract and determinate inorganic species of antimony (Sb) for water. The procedure involves•the simultaneous accumulation of Sb(III) and Sb(V) on passive samplers like Diffusive Gradient in Thin Films (DGT) with iron (Fe) oxide gel, eliminating the risk of speciation changes due to transport and storage;•application of less concentrated acid (50 mM Na2EDTA) for elution and preservation of Sb species from DGT resin;•subsequent analytical determination of inorganic species with High Performance Liquid Chromatography-Isotopic Dilution-Inductively Coupled Plasma Mass Spectrometer (HPLC-ID-ICP MS) based on determination of the isotope ratio ((123)Sb/(121)Sb) of isotopes in the samples after spiking with 123Sb enriched standard solution, reducing the effect of signal drift and matrix effect on the final value. PMID:27408828

  4. High-Precision Th-Pb Dating by Isotope-Dilution TIMS+MC-ICPMS - Preliminary Results

    NASA Astrophysics Data System (ADS)

    Ickert, R. B.; Mundil, R.; Sharp, W. D.

    2014-12-01

    Relative to the U-Pb decay series, the Th-Pb decay series has received relatively little attention for geochronology although it offers promising applications in both high-resolution geochronology as well as thermochronology. The limitations are partly because Th measurements by thermal ionization have proven notoriously difficult, and for many geochronological applications, the additional information provided by Th-Pb has not been worth the effort required. However, the current generation of MC-ICPMS instruments provides nearly two orders of magnitude better sensitivity of Th than TIMS, eliminating this barrier to measurement and opening up this chronometer for new use. We have developed a method to measure relative abundances of Th, U and Pb by isotope dilution for high-precision geochronology. This method leverages the strengths of two instruments, the high sensitivity and stable mass fractionation of MC-ICPMS instruments for Th and U, and the low background, lack of isobaric interference, and signal stability of TIMS instruments for Pb. To make these measurements, we have calibrated a new synthetic isotope tracer that comprises a mixture of 229Th-233U-236U-202Pb-205Pb. The analytical strategy developed for accessory minerals is a hybrid of techniques previously developed for U-Pb ID-TIMS and U/230Th ID-MC-ICPMS, with a two-column HCl-HNO3 anion exchange procedure (one to separate U and Pb from matrix+Th, and the other to separate Th from matrix), followed by a recombination of the U and Th fractions for MC-ICPMS analysis while the Pb fraction is measured by TIMS. Th-Pb measurements are complementary to, and potentially as precise as the U-Pb gold standard, and the method will find application in certain geological problems, including (1) precisely determining the relative decay rates of 232Th and 238U, (2) dating materials that are young enough to be substantially affected by 230Th or 231Pa disequilibria, and (3) dating small quantities of high-Th minerals like

  5. Further verification of the isotope dilution approach for estimating the degree of participation of (/sup 3/H)thymidine in DNA synthesis in studies of aquatic bacterial production

    SciTech Connect

    Bell, R.T.

    1986-11-01

    The optimal concentration of (/sup 3/H)thymidine (i.e., the maximal degree of participation in DNA synthesis) as determined by adding increasing amounts of labeled thymidine at the same specific activity was similar to the concentration of thymidine inhibiting the de novo pathway as determined by isotope dilution plots. These experiments provide further verification of the isotope dilution approach for determining the degree of participation of (/sup 3/H)thymidine in DNA synthesis.

  6. NUCLEAR ISOTOPIC DILUTION OF HIGHLY ENRICHED URANIUM BY DRY BLENDING VIA THE RM-2 MILL TECHNOLOGY

    SciTech Connect

    Raj K. Rajamani; Sanjeeva Latchireddi; Vikas Devrani; Harappan Sethi; Roger Henry; Nate Chipman

    2003-08-01

    DOE has initiated numerous activities to focus on identifying material management strategies to disposition various excess fissile materials. In particular the INEEL has stored 1,700 Kg of offspec HEU at INTEC in CPP-651 vault facility. Currently, the proposed strategies for dispositioning are (a) aqueous dissolution and down blending to LEU via facilities at SRS followed by shipment of the liquid LEU to NFS for fabrication into LWR fuel for the TVA reactors and (b) dilution of the HEU to 0.9% for discard as a waste stream that would no longer have a criticality or proliferation risk without being processed through some type of enrichment system. Dispositioning this inventory as a waste stream via aqueous processing at SRS has been determined to be too costly. Thus, dry blending is the only proposed disposal process for the uranium oxide materials in the CPP-651 vault. Isotopic dilution of HEU to typically less than 20% by dry blending is the key to solving the dispositioning issue (i.e., proliferation) posed by HEU stored at INEEL. RM-2 mill is a technology developed and successfully tested for producing ultra-fine particles by dry grinding. Grinding action in RM-2 mill produces a two million-fold increase in the number of particles being blended in a centrifugal field. In a previous study, the concept of achieving complete and adequate blending and mixing (i.e., no methods were identified to easily separate and concentrate one titanium compound from the other) in remarkably short processing times was successfully tested with surrogate materials (titanium dioxide and titanium mono-oxide) with different particle sizes, hardness and densities. In the current project, the RM-2 milling technology was thoroughly tested with mixtures of natural uranium oxide (NU) and depleted uranium oxide (DU) stock to prove its performance. The effects of mill operating and design variables on the blending of NU/DU oxides were evaluated. First, NU and DU both made of the same oxide

  7. Chemical and isotopic composition of water from thermal and mineral springs of Washington

    SciTech Connect

    Mariner, R.H.; Presser, T.S.; Evans, W.C.

    1982-02-01

    Waters from the thermal springs of Washington range in chemical composition from dilute Na-HCO/sub 3/ to moderately saline CO/sub 2/-charged Na-HCO/sub 3/-Cl type waters. St. Martin's Hot Spring which discharges a slightly saline Na-Cl water, is the notable exception. The dilute Na-HCO/sub 3/ waters are generally associated with granitic intrusions; the warm to hot CO/sub 2/-charged waters issue on or near the large stratovolcanoes. The dilute waters have oxygen-isotopic compositions that indicate relatively little water-rock exchange. The CO/sub 2/-charged waters are usually more enriched in oxygen-18 due to more extensive water-rock reaction. The carbon-13 in the CO/sub 2/-charged thermal waters is more depleted (-10 to -12 %) than in the cold CO/sub 2/-charged soda springs (-2 to -8%) which are also scattered throughout the Cascades. The hot and cold CO/sub 2/-charged waters are supersaturated with respect to CaCO/sub 3/, but only the hot springs are actively depositing CaCO/sub 3/. Baker, Gamma, Sulphur, and Ohanapecosh hot springs seem to be associated with thermal aquifers of more than 100/sup 0/C. As these springs occur as individual springs or in small clusters, the respective aquifers are probably of restricted size.

  8. Chemical and isotopic composition of water from thermal springs and mineral springs of Washington

    USGS Publications Warehouse

    Mariner, R.H.; Presser, T.S.; Evans, William C.

    1982-01-01

    Water from thermal springs of Washington range in chemical composition from dilute NaHC03, to moderately saline C02-charged NaHC03-Cl waters. St. Martin 's Hot Spring which discharges a slightly saline NaCl water, is the notable exception. Mineral springs generally discharge a moderately saline C02-charged NaHC03-Cl water. The dilute Na-HC03 waters are generally associated with granite. The warm to hot waters charged with C02 issue on or near the large stratovolcanoes and many of the mineral springs also occur near the large volcanoes. The dilute waters have oxygen isotopic compositions which indicate relatively little water-rock exchange. The C02-charged waters are usually more enriched in oxygen-18 due to more extensive water-rock reaction. Carbon-13 in the C02-charged thermal waters is more depleted (-10 to -12 permil) than in the cold C02-charged soda springs (-2 to -8 permil) which are also scattered throughout the Cascades. The hot and cold C02-charged waters are supersaturated with respect to CaC03, but only the hot springs are actively depositing CaC03. Baker, Gamma, Sulphur , and Ohanapecosh seem to be associated with thermal aquifers of more than 100C. (USGS)

  9. Stable isotope dilution assays of alternariol and alternariol monomethyl ether in beverages.

    PubMed

    Asam, Stefan; Konitzer, Katharina; Schieberle, Peter; Rychlik, Michael

    2009-06-24

    Stable isotope dilution assays (SIDAs) for the determination of the most important mycotoxins of the black mold Alternaria, namely, alternariol and alternariol monomethyl ether, have been developed. For this purpose, deuterated alternariol and alternariol methyl ether were synthesized by palladium catalyzed protium-deuterium exchange from the unlabeled toxins. Reaction conditions were chosen in such a manner that the formation of the [(2)H(4)]-isotopologues was favored. The synthesized products were characterized by LC-MS, NMR, and UV-spectroscopy. On the basis of the use of [(2)H(4)]-alternariol and [(2)H(4)]-alternariol methyl ether as internal standards, SIDAs were developed and applied to the determination of alternariol and alternariol methyl ether in beverages using LC-MS/MS. Method validation revealed a high sensitivity, i.e., low limits of detection (alternariol, 0.03 microg/kg; alternariol methyl ether, 0.01 microg/kg) and limits of quantitation (alternariol, 0.09 microg/kg; alternariol methyl ether, 0.03 microg/kg), respectively. Recovery from spiked apple juice was 100.5 +/- 3.4% for alternariol (range 0.1-1 microg/kg) and 107.3 +/- 1.6% for alternariol methyl ether (range 0.05-0.5 microg/kg). Interassay precision (expressed as coefficient of variation, CEV) for alternariol was 4.0% (7.82 +/- 0.31 microg/kg; vegetable juice, naturally contaminated) and 4.6% (1.04 +/- 0.05 microg/kg; grape juice, naturally contaminated). For alternariol methyl ether, a CEV of 2.3% (0.79 +/- 0.02 microg/kg; vegetable juice, naturally contaminated) was obtained. Analysis of fruit juices showed low contamination with alternariol and alternariol methyl ether in general, but higher values of both toxins were found in wine and vegetable juices. The values for alternariol were higher than those for alternariol methyl ether in nearly any case. However, the developed SIDA has proven to be optimally suited for further studies on alternariol and alternariol methyl ether content in

  10. Chemical Synthesis of Deoxynivalenol-3-β-d-[(13)C₆]-glucoside and Application in Stable Isotope Dilution Assays.

    PubMed

    Habler, Katharina; Frank, Oliver; Rychlik, Michael

    2016-01-01

    Modified mycotoxins have been gaining importance in recent years and present a certain challenge in LC-MS/MS analysis. Due to the previous lack of a labeled isotopologue of the modified mycotoxin deoxynivalenol-3-glucoside, in our study we synthesized the first (13)C-labeled internal standard. Therefore, we used the Königs-Knorr method to synthesize deoxynivalenol-3-β-d-[(13)C₆]-glucoside originated from unlabeled deoxynivalenol and [(13)C₆]-labeled glucose. Using the synthesized isotopically-labeled standard deoxynivalenol-3-β-d-[(13)C₆]-glucoside and the purchased labeled standard [(13)C15]-deoxynivalenol, a stable isotope dilution LC-MS/MS method was firstly developed for deoxynivalenol-3-glucoside and deoxynivalenol in beer. The preparation and purification of beer samples was based on a solid phase extraction. The validation data of the newly developed method gave satisfying results. Intra- and interday precision studies revealed relative standard deviations below 0.5% and 7%, respectively. The recoveries ranged for both analytes between 97% and 112%. The stable isotope dilution assay was applied to various beer samples from four different countries. In summary, deoxynivalenol-3-glucoside and deoxynivalenol mostly appeared together in varying molar ratios but were quantified in rather low contents in the investigated beers. PMID:27355938

  11. Determination of lead, uranium, thorium, and thallium in silicate glass standard materials by isotope dilution mass spectrometry

    USGS Publications Warehouse

    Barnes, I.L.; Garner, E.L.; Gramlich, J.W.; Moore, L.J.; Murphy, T.J.; Machlan, L.A.; Shields, W.R.; Tatsumoto, M.; Knight, R.J.

    1973-01-01

    A set of four standard glasses has been prepared which have been doped with 61 different elements at the 500-, 50-, 1-, and 0.02-ppm level. The concentrations of lead, uranium, thorium, and thallium have been determined by isotope dilution mass spectrometry at a number of points in each of the glasses. The results obtained from independent determinations in two laboratories demonstrate the homogeneity of the samples and that precision of the order of 0.5% (95% L.E.) may be obtained by the method even at the 20-ppb level for these elements. The chemical and mass spectrometric procedures necessary are presented.

  12. An Isotope-Powered Thermal Storage unit for space applications

    NASA Technical Reports Server (NTRS)

    Lisano, Michael E.; Rose, M. F.

    1991-01-01

    An Isotope-Powered Thermal Storage Unit (ITSU), that would store and utilize heat energy in a 'pulsed' fashion in space operations, is described. Properties of various radioisotopes are considered in conjunction with characteristics of thermal energy storage materials, to evaluate possible implementation of such a device. The utility of the unit is discussed in light of various space applications, including rocket propulsion, power generation, and spacecraft thermal management.

  13. Simultaneous sample preparation and species-specific isotope dilution mass spectrometry analysis of monomethylmercury and tributyltin in a certified oyster tissue.

    PubMed

    Monperrus, M; Rodriguez Martin-Doimeadios, R C; Scancar, J; Amouroux, D; Donard, O F X

    2003-08-15

    A rapid, accurate, sensitive, and simple method for simultaneous speciation analysis of mercury and tin in biological samples has been developed. Integrated simultaneous sample preparation for tin and mercury species includes open focused microwave extraction and derivatization via ethylation. Capillary gas chromatography-inductively plasma mass spectrometry (CGC-ICPMS) conditions and parameters affecting the analytical performance were carefully optimized both for species-specific isotope dilution analysis of MMHg and TBT and for conventional analysis of MBT and DBT201Hg-enriched monomethylmercury and 117Sn-enriched tributyltin were used for species-specific isotope dilution mass spectrometry (SIDMS) analysis. As important, accurate isotope dilution analysis requires equilibration between the spike and the analyte to achieve successful analytical procedures. Since the spike stabilization and solubilization are the most critical and time-consuming steps in isotope dilution analysis, different spiking procedures were tested. Simultaneous microwave-assisted spike stabilization and solubilization can be achieved within less than 5 min. This study originally introduces a method for the simultaneous speciation and isotope dilution of mercury and tin in biological tissues. The sample throughput of the procedure was drastically reduced by fastening sample preparation and GC separation steps. The accuracy of the method was tested by both external calibration analysis and species-specific isotope dilution analysis using the first biological reference material certified for multielemental speciation (oyster tissue, CRM 710, IRMM). The results obtained demonstrate that isotope dilution analysis is a powerful method allowing the simultaneous speciation of TBT and MMHg with high precision and excellent accuracy. Analytical problems related to low recovery during sample preparation are thus minimized by SIDMS. In addition, a rapid procedure allows us to establish a performant

  14. On-line double isotope dilution laser ablation inductively coupled plasma mass spectrometry for the quantitative analysis of solid materials.

    PubMed

    Fernández, Beatriz; Rodríguez-González, Pablo; García Alonso, J Ignacio; Malherbe, Julien; García-Fonseca, Sergio; Pereiro, Rosario; Sanz-Medel, Alfredo

    2014-12-01

    We report on the determination of trace elements in solid samples by the combination of on-line double isotope dilution and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The proposed method requires the sequential analysis of the sample and a certified natural abundance standard by on-line IDMS using the same isotopically-enriched spike solution. In this way, the mass fraction of the analyte in the sample can be directly referred to the certified standard so the previous characterization of the spike solution is not required. To validate the procedure, Sr, Rb and Pb were determined in certified reference materials with different matrices, including silicate glasses (SRM 610, 612 and 614) and powdered samples (PACS-2, SRM 2710a, SRM 1944, SRM 2702 and SRM 2780). The analysis of powdered samples was carried out both by the preparation of pressed pellets and by lithium borate fusion. Experimental results for the analysis of powdered samples were in agreement with the certified values for all materials. Relative standard deviations in the range of 6-21% for pressed pellets and 3-21% for fused solids were obtained from n=3 independent measurements. Minimal sample preparation, data treatment and consumption of the isotopically-enriched isotopes are the main advantages of the method over previously reported approaches. PMID:25440666

  15. Pantothenic acid quantification by a stable isotope dilution assay based on liquid chromatography-tandem mass spectrometry.

    PubMed

    Rychlik, Michael

    2003-07-01

    A stable isotope dilution assay for the quantification of free and total pantothenic acid has been developed by using [13C3,15N]-pantothenic acid as the internal standard. The three-dimensional specificity of liquid chromatography-tandem mass spectrometry enabled unequivocal determination of the vitamin. Due to the very simple extraction and clean-up procedure, free pantothenic acid could be analysed within 2 h, which is much faster than by microbiological or gas chromatographic assays. For quantification of total pantothenic acid, the vitamin was liberated from its conjugates by an overnight incubation with pigeon liver pantetheinase and alkaline phosphatase. In analyses of corn flour, the intra-assay coefficient of variation was 8.5% (n = 5) and 15.3% (n = 4) for free and total pantothenic acid, respectively. When pantothenic acid was added to corn starch at a level of 6 mg kg(-1), a recovery of 97.5% was found. Application of the stable isotope dilution assay to whole egg powder, hazel nuts and corn revealed similar data compared to those listed in nutrition data bases, whereas the content in mushrooms and porcine liver determined by the newly developed assay appeared to be lower and that of cocoa higher than reported in the literature. PMID:12894818

  16. Quantification of nerve agent adducts with albumin in rat plasma using liquid chromatography-isotope dilution tandem mass spectrometry.

    PubMed

    Bao, Yi; Liu, Qin; Chen, Jia; Lin, Ying; Wu, Bidong; Xie, Jianwei

    2012-03-16

    A sensitive method for the determination of the organophosphorus nerve agents sarin, soman and VX adducts with tyrosine residue of albumin in rat plasma has been developed and validated using liquid chromatography-isotope dilution tandem mass spectrometry (LC-IDMS/MS). O-(O-Alkyl methylphosphonyl) tyrosine adducts and their deuterated products that were used as the internal standards were synthesised to establish the quantitative isotope-dilution method. Protein purification and solid-phase extraction (SPE) were applied to improve the recovery efficiency, reduce interference and achieve high sensitivity. The method provided a detection limit of 0.01 ng/mL for sarin and soman adducts and 0.05 ng/mL for the VX adduct. The value of the intra-day relative standard deviation over the calibration range was less than 6.16% (n=6), and that of the inter-day was less than 12.7% (n=6). The recovery varied from 86% to 111%. This sensitive method was successfully applied to the analysis of adducts in rat plasma after nerve agent exposure, and the results demonstrated the dose-effect relationships. PMID:22305360

  17. Determination of 4(5)-methylimidazole in carbonated beverages by isotope-dilution liquid chromatography-tandem mass spectrometry.

    PubMed

    Ratnayake, Geemitha; Halldorson, Thor; Bestvater, Lianna; Tomy, Gregg T

    2015-01-01

    The purpose of this study was to develop a method to quantify 4(5)-methylimidazole (4-MEI), a suspected carcinogen, in carbonated beverages by simple sample dilution and isotope-dilution reverse-phase LC-MS/MS. Isotope dilution using hexa-deuterated methylimidazole (d6-4-MEI) was used to quantify native 4-MEI and to assess matrix effects quantitatively. The accuracy of the method was assessed by intentionally fortifying a negative control sample at three doses: low, medium and high (replicates of n = 5 each) with a known amount of 4-MEI. The respective absolute error in each case was 18.7 ± 0.7%, 14.6 ± 2.8% and 21.1 ± 9.7%. Within-day (intra-) and day-to-day (inter-) repeatability, determined as the relative standard deviation by fortifying a negative control sample (n = 5), were 9.5% and 15.4%, respectively. Average ion suppression of d6-4-MEI in beer was 63.9 ± 3.2%, while no suppression or enhancement was seen in non-alcoholic samples. The instrument and method limit of detection were calculated as 0.6 and 5.8 ng ml(-1), respectively. 4(5)-Methylimidazole was quantified in a variety of store-bought consumer beverages and it was found that in many of the samples tested consuming a single can of beer would result in intake levels of 4-MEI that exceed the no significant risk guideline of 29 µg day(-1). Conversely, 4-MEI in the samples was orders of magnitude smaller than the European Food Safety Authority acceptable daily intake threshold value of 100 mg kg(-1) bw day(-1). PMID:25994392

  18. Existing and emerging technologies for measuring stable isotope labelled retinol in biological samples: isotope dilution analysis of body retinol stores.

    PubMed

    Preston, Tom

    2014-01-01

    This paper discusses some of the recent improvements in instrumentation used for stable isotope tracer measurements in the context of measuring retinol stores, in vivo. Tracer costs, together with concerns that larger tracer doses may perturb the parameter under study, demand that ever more sensitive mass spectrometric techniques are developed. GCMS is the most widely used technique. It has high sensitivity in terms of sample amount and uses high resolution GC, yet its ability to detect low isotope ratios is limited by background noise. LCMSMS may become more accessible for tracer studies. Its ability to measure low level stable isotope tracers may prove superior to GCMS, but it is isotope ratio MS (IRMS) that has been designed specifically for low level stable isotope analysis through accurate analysis of tracer:tracee ratios (the tracee being the unlabelled species). Compound-specific isotope analysis, where GC is interfaced to IRMS, is gaining popularity. Here, individual 13C-labelled compounds are separated by GC, combusted to CO2 and transferred on-line for ratiometric analysis by IRMS at the ppm level. However, commercially-available 13C-labelled retinol tracers are 2 - 4 times more expensive than deuterated tracers. For 2H-labelled compounds, GC-pyrolysis-IRMS has now become more generally available as an operating mode on the same IRMS instrument. Here, individual compounds are separated by GC and pyrolysed to H2 at high temperature for analysis by IRMS. It is predicted that GC-pyrolysis-IRMS will facilitate low level tracer procedures to measure body retinol stores, as has been accomplished in the case of fatty acids and amino acids. Sample size requirements for GC-P-IRMS may exceed those of GCMS, but this paper discusses sample preparation procedures and predicts improvements, particularly in the efficiency of sample introduction. PMID:25537104

  19. An Isotopic Dilution Experiment Using Liquid Scintillation: A Simple Two-System, Two-Phase Analysis.

    ERIC Educational Resources Information Center

    Moehs, Peter J.; Levine, Samuel

    1982-01-01

    A simple isotonic, dilution analysis whose principles apply to methods of more complex radioanalyses is described. Suitable for clinical and instrumental analysis chemistry students, experimental manipulations are kept to a minimum involving only aqueous extraction before counting. Background information, procedures, and results are discussed.…

  20. Uranium disequilibrium in groundwater: An isotope dilution approach in hydrologic investigations

    USGS Publications Warehouse

    Osmond, J.K.; Rydell, H.S.; Kaufman, M.I.

    1968-01-01

    The distribution and environmental disequilibrium patterns of naturally occurring uranium isotopes (U234 and U238) in waters of the Floridan aquifer suggest that variations in the ratios of isotopic activity and concentrations can be used quantitatively to evaluate mixing proportions of waters from differing sources. Uranium is probably unique in its potential for this approach, which seems to have general usefulness in hydrologic investigations.

  1. Uranium disequilibrium in groundwater: an isotope dilution approach in hydrologic investigations.

    PubMed

    Osmond, J K; Rydell, H S; Kaufman, M I

    1968-11-29

    The distribution and environmental disequilibrium patterns of naturally occurring uranium isotopes (U(234) and U(238)) in waters of the Floridan aquifer suggest that variations in the ratios of isotopic activity and concentrations can be used quantitatively to evaluate mixing proportions of waters from differing sources. Uranium is probably unique in its potential for this approach, which seems to have general usefulness in hydrologic investigations. PMID:4880720

  2. Comparisons among Equations Used for Retinol Isotope Dilution in the Assessment of Total Body Stores and Total Liver Reserves.

    PubMed

    Gannon, Bryan M; Tanumihardjo, Sherry A

    2015-05-01

    Vitamin A plays an essential role in animal biology and has negative effects associated with both hypo- and hypervitaminosis A. Many notable interventions are being done globally to eliminate vitamin A deficiency, including supplementation, fortification, and biofortification. At the same time, it is important to monitor vitamin A status in nations where preformed vitamin A intake is high because of consumption of animal source foods (e.g., liver, dairy, eggs), fortified foods (e.g., milk, cereals, oil, sugar, margarine), or vitamin supplements (e.g., one-a-day multivitamins) to ensure the population does not reach hypervitaminosis A. To accurately assess population status and evaluate interventions aimed at improving vitamin A status, accurate assessment methods are needed. The primary storage site of vitamin A is the liver; however, routinely obtaining liver samples from humans is impractical and unethical. Isotope dilution using deuterium- or (13)C-labeled retinol is currently the most sensitive indirect biomarker of vitamin A status across a wide range of liver reserves. The major drawback to its application is the increased technicality in sample analysis and data calculations when compared to less sensitive methodology, such as serum retinol concentrations and dose response tests. Two main equations have emerged for calculating vitamin A body pool size or liver concentrations from isotope dilution data: the "Olson equation" and the "mass balance equation." Different applications of these equations can lead to confusion and lack of consistency if the underlying principles and assumptions used are not clarified. The purpose of this focused review is to describe the evolution of the equations used in retinol stable-isotope work and the assumptions appropriate to different applications of the test. Ultimately, the 2 main equations are shown to be fundamentally the same and differ only in assumptions made for each specific research application. PMID:25809683

  3. A novel quantification strategy of transferrin and albumin in human serum by species-unspecific isotope dilution laser ablation inductively coupled plasma mass spectrometry (ICP-MS).

    PubMed

    Feng, Liuxing; Zhang, Dan; Wang, Jun; Shen, Dairui; Li, Hongmei

    2015-07-16

    Species-specific (SS) isotope dilution analysis with gel electrophoresis (GE)-laser ablation (LA)-ICP-MS is a promising technique for the quantification of particular metal-binding proteins in biological samples. However, unavailable isotopically enriched spike and metal losses in GE separation are main limitations for SS-isotope dilution PAGE-LA-ICP-MS. In this study, we report for the first time the absolute quantification of transferrin (Tf) and albumin (Alb) in human serum by non-denaturing (native) GE combined with species-unspecific isotope dilution mass spectrometry (IDMS). In order to achieve a homogeneous distribution of both protein and isotope-enriched spike (simulated isotope equilibration), immersing the protein strips with (34)S spike solution after gel electrophoresis was demonstrated to be an effective way of spike addition. Furthermore, effects of immersion time and (34)S spike concentration were investigated to obtain optimal conditions of the post-electrophoresis isotope dilution method. The relative mass of spike and ablated sample (m(sp)/m(sam)) in IDMS equation was calculated by standard Tf and Alb proteins, which could be applied to the quantification of Tf and Alb in ERM-DA470k/IFCC for method confirmation. The results were in agreement with the certified value with good precision and small uncertainty (1.5-3%). In this method, species-specific spike protein is not necessary and the integrity of the heteroatom-protein could be maintained in sample preparation process. Moreover, the application of species-unspecific isotope dilution GE-LA-ICP-MS has the potential to offer reliable, direct and simultaneous quantification of proteins after conventional 1D and 2D gel electrophoretic separations. PMID:26073803

  4. Chaotic dynamics of dilute thermal atom clouds on stationary optical Bessel beams

    NASA Astrophysics Data System (ADS)

    Castañeda, J. A.; Pérez-Pascual, R.; Jáuregui, R.

    2013-07-01

    We characterize the semiclassical dynamics of dilute thermal atom clouds located in three-dimensional optical lattices generated by stationary optical Bessel beams. The dynamics of the cold atoms is explored in the quasi-Hamiltonian regime that arises using laser beams with far-off resonance detuning. Although the transverse structure of Bessel beams exhibits a complex topological structure, it is found that the longitudinal motion along the main propagation axis of the beam is the detonator of a high sensitivity of the atoms' motion to the initial conditions. This effect would not be properly described by bidimensional models. We show that an experimental implementation can be highly simplified by an analysis of the behaviour of the dynamical system under scale transformations. Experimentally feasible signatures of the chaotic dynamics of the atom clouds are also identified.

  5. Examining the stability of thermally fissile Th and U isotopes

    NASA Astrophysics Data System (ADS)

    Kumar, Bharat; Biswal, S. K.; Singh, S. K.; Patra, S. K.

    2015-11-01

    The properties of recently predicted thermally fissile Th and U isotopes are studied within the framework of the relativistic mean-field approach using the axially deformed basis. We calculate the ground, first intrinsic excited state for highly neutron-rich thorium and uranium isotopes. The possible modes of decay such as α decay and β decay are analyzed. We found that neutron-rich isotopes are stable against α decay, however, they are very unstable against β decay. The lifetime of these nuclei is predicted to be tens of seconds against β decay. If these nuclei are utilized before their decay time, a lot of energy can be produced with the help of multifragmentation fission. Also, these nuclei have great implications from the astrophysical point of view. In some cases, we found that the isomeric states with energy range from 2 to 3 MeV and three maxima in the potential energy surface of Th-230228 and U-234228 isotopes.

  6. The longevity of the South Pacific isotopic and thermal anomaly

    USGS Publications Warehouse

    Staudigel, H.; Park, K.-H.; Pringle, M.; Rubenstone, J.L.; Smith, W.H.F.; Zindler, A.

    1991-01-01

    The South Pacific is anomalous in terms of the Sr, Nd, and Pb isotope ratios of its hot spot basalts, a thermally enhanced lithosphere, and possibly a hotter mantle. We have studied the Sr, Nd, and Pb isotope characteristics of 12 Cretaceous seamounts in the Magellans, Marshall and Wake seamount groups (western Pacific Ocean) that originated in this South Pacific Isotopic and Thermal Anomaly (SOPITA). The range and values of isotope ratios of the Cretaceous seamount data are similar to those of the island chains of Samoa, Tahiti, Marquesas and Cook/Austral in the SOPITA. These define two major mantle components suggesting that isotopically extreme lavas have been produced at SOPITA for at least 120 Ma. Shallow bathymetry, and weakened lithosphere beneath some of the seamounts studied suggests that at least some of the thermal effects prevailed during the Cretaceous as well. These data, in the context of published data, suggest: 1. (1)|SOPITA is a long-lived feature, and enhanced heat transfer into the lithosphere and isotopically anomalous mantle appear to be an intrinsic characteristic of the anomaly. 2. (2)|The less pronounced depth anomaly during northwesterly plate motion suggests that some of the expressions of SOPITA may be controlled by the direction of plate motion. Motion parallel to the alignment of SOPITA hot spots focusses the heat (and chemical input into the lithosphere) on a smaller cross section than oblique motion. 3. (3)|The lithosphere in the eastern and central SOPITA appears to have lost its original depleted mantle characteristics, probably due to enhanced plume/lithosphere interaction, and it is dominated by isotopic compositions derived from plume materials. 4. (4)|We speculate (following D.L. Anderson) that the origin of the SOPITA, and possibly the DUPAL anomaly is largely due to focussed subduction through long periods of the geological history of the earth, creating a heterogeneous distribution of recycled components in the lower mantle

  7. Separation of Hydrogen Isotopes by Thermal Diffusion

    SciTech Connect

    Rutherford, W. M.; Lindsay, C. N.

    1985-09-01

    At high hot wall temperatures the gas phase thermal diffusion column acts as an atomic rather than a molecular separator. A modified theory was developed to describe the process. Equivalent transport equations were derived for the two nuclides in a binary atomic mixture. The equations are identical in form to those normally encountered in thermal diffusion column theory. Experiments to test the theory were carried out with two 3-meter columns. Experimental results with deuterium-tritium mixtures were found to be in satisfactory agreement with theory, and it was concluded that the theory was sufficiently accurate for design purposes.

  8. Determination of 241Am in sediments by isotope dilution high resolution inductively coupled plasma mass spectrometry (ID HR ICP-MS).

    PubMed

    Agarande, M; Benzoubir, S; Bouisset, P; Calmet, D

    2001-08-01

    Trace levels (pg kg(-1)) of 241Am in sediments were determined by isotope dilution high resolution inductively coupled plasma mass spectrometry (ID HR ICP-MS) using a microconcentric nebulizer. 241Am was isolated from major elements like Ca and Fe by different selective precipitations. In further steps. Am was first separated from other transuranic elements and purified by anion exchange and extraction chromatography prior to the mass spectrometric measurements. The ID HR ICP-MS results are compared with isotope dilution alpha spectrometry. PMID:11393755

  9. Simultaneous determination of alachlor, metolachlor, atrazine, and simazine in water and soil by isotope dilution gas chromatography/mass spectrometry

    SciTech Connect

    Huang, L.Q.

    1989-03-01

    A multiresidue method was developed for the simultaneous determination of low parts per billion (ppb) concentrations of the herbicides alachlor, metolachlor, atrazine, and simazine in water and soil using isotope dilution gas chromatography/mass spectrometry (GC/MS). Known amounts of /sup 15/N,/sup 13/C-alachlor and /sup 2/H/sub 5/-atrazine were added to each sample as internal standards. The samples were then prepared by a solid phase extraction with no further cleanup. A high resolution GC/low resolution MS system with data acquisition in selected ion monitoring mode was used to quantitate herbicides in the extract. The limit of detection was 0.05 ppb for water and 0.5 ppb for soil. Accuracy greater than 80% and precision better than 4% was demonstrated with spiked samples.

  10. Accuracy of some routine method used in clinical chemistry as judged by isotope dilution-mass spectrometry

    SciTech Connect

    Bjoerkhem, I.; Bergman, A.; Falk, O.; Kallner, A.; Lantto, O.; Svensson, L.; Akerloef, E.; Blomstrand, R.

    1981-05-01

    Serum from patients was pooled, filtered, dispensed, and frozen. This pooled specimen was used for accuracy control in 64 participating laboratories in Sweden. Mean values (state-of-the-art values) were obtained for creatinine, cholesterol, glucose, urea, uric acid, and cortisol. These values were compared with values obtained with highly accurate reference methods based on isotope dilution-mass spectrometry. Differences were marked in the case of determination of creatinine and cortisol. Concerning the other components, the differences between the state-of-the-art value and the values obtained with the reference methods were negligible. Moreover, the glucose oxidase and the oxime methods for determination of glucose and urea were found to give significantly lower values than the hexokinase and urease methods, respectively. Researchers conclude that methods with a higher degree of accuracy are required for routine determination of creatinine and cortisol.

  11. Short communication: milk output in llamas (Lama glama) in relation to energy intake and water turnover measured by an isotope dilution technique.

    PubMed

    Riek, A; Klinkert, A; Gerken, M; Hummel, J; Moors, E; Südekum, K-H

    2013-03-01

    Despite the fact that llamas have become increasingly popular as companion and farm animals in both Europe and North America, scientific knowledge on their nutrient requirements is scarce. Compared with other livestock species, relatively little is known especially about the nutrient and energy requirements for lactating llamas. Therefore, we aimed to measure milk output in llama dams using an isotope dilution technique and relate it to energy intakes at different stages of lactation. We also validated the dilution technique by measuring total water turnover (TWT) directly and comparing it with values estimated by the isotope dilution technique. Our study involved 5 lactating llama dams and their suckling young. Milk output and TWT were measured at 4 stages of lactation (wk 3, 10, 18, and 26 postpartum). The method involved the application of the stable hydrogen isotope deuterium ((2)H) to the lactating dam. Drinking water intake and TWT decreased significantly with lactation stage, whether estimated by the isotope dilution technique or calculated from drinking water and water ingested from feeds. In contrast, lactation stage had no effect on dry matter intake, metabolizable energy (ME) intake, or the milk water fraction (i.e., the ratio between milk water excreted and TWT). The ratios between TWT measured and TWT estimated (by isotope dilution) did not differ with lactation stage and were close to 100% in all measurement weeks, indicating that the D(2)O dilution technique estimated TWT with high accuracy and only small variations. Calculating the required ME intakes for lactation from milk output data and gross energy content of milk revealed that, with increasing lactation stage, ME requirements per day for lactation decreased but remained constant per kilogram of milk output. Total measured ME intakes at different stages of lactation were similar to calculated ME intakes from published recommendation models for llamas. PMID:23332845

  12. Body water measurement in growth disorders: a comparison of bioelectrical impedance and skinfold thickness techniques with isotope dilution.

    PubMed Central

    Gregory, J W; Greene, S A; Scrimgeour, C M; Rennie, M J

    1991-01-01

    Total body water was estimated as part of the assessment of body composition in children with growth disorders, using the newly commercially available method of bioelectrical impedance. This was undertaken to compare the precision and accuracy of the results with those derived from skinfold thickness against measurement of stable isotopically labelled water (H2(18)O) dilution as a standard. The comparisons were carried out to see to what extent the impedance method could be applied with confidence to assessment of children with growth disorders. Total body water was derived from impedance (I) using an association with height (Ht2/I). Impedance and skinfold thickness estimates of total body water were equally precise when compared with values obtained from H2(18)O dilution (limits of agreement -1.9 to +1.3 and -1.7 to +2.0 kg respectively). The mean intraobserver coefficient of variation for repeat measurements of impedance was 0.9% compared with 4.6% for skinfold thickness with an interobserver coefficient of variation for impedance of 2.8%. Bioelectrical impedance estimation of body composition is likely to be of value in the growth clinic when expertise in measurement of skinfold thickness is limited or repeated measurements are to be undertaken by different observers. PMID:2001107

  13. Measurement of the body composition of living gray seals by hydrogen isotope dilution

    SciTech Connect

    Reilly, J.J.; Fedak, M.A. )

    1990-09-01

    The body composition of living gray seals (Halichoerus grypus) can be accurately predicted from a two-step model that involves measurement of total body water (TBW) by {sup 2}H or {sup 3}H dilution and application of predictive relationships between body components and TBW that were derived empirically by slaughter chemical analysis. TBW was overestimated by both {sup 2}HHO and {sup 3}HHO dilution; mean overestimates were 2.8 +/- 0.9% (SE) with 2H and 4.0 +/- 0.6% with {sup 3}H. The relationships for prediction of total body fat (TBF), protein (TBP), gross energy (TBGE), and ash (TBA) were as follows: %TBF = 105.1 - 1.47 (%TBW); %TBP = 0.42 (%TBW) - 4.75; TBGE (MJ) = 40.8 (mass in kg) - 48.5 (TBW in kg) - 0.4; and TBA (kg) = 0.1 - 0.008 (mass in kg) + 0.05 (TBW in kg). These relationships are applicable to gray seals of both sexes over a wide range of age and body conditions, and they predict the body composition of gray seals more accurately than the predictive equations derived from ringed seals (Pusa hispida) and from the equation of Pace and Rathbun, which has been reported to be generally applicable to mammals.

  14. Oxygen and hydrogen isotopes in deep thermal waters from the South Meager Creek geothermal area, British Columbia, Canada

    SciTech Connect

    Ghomshei, M.M. ); Clark, I.D. )

    1993-04-01

    Deuterium and oxygen-18 ([sup 18]O) have been measured in deep thermal, shallow thermal and non-thermal water samples collected at various times between 1982 and 1989 from the Meager Creek area, with the aim of assessing the origin of the thermal waters. The isotopic composition of the reservoir waters ([delta][sup 18]O = [minus]13[per thousand] and [delta]D= [minus]114.8[per thousand]) was calculated from data on post-flash deep thermal waters, using a two-stage steam loss model. The reservoir composition shows an oxygen shift of 2.4[per thousand] relative to the local meteoric water line. The composition of the recharge, obtained by removing the oxygen shift, is isotopically heavier than the average local meteoric waters, suggesting that the recharge may be from an area to the west of Mt Meager where isotopically heavier ground-waters are likely to be found. The small [delta][sup 18]O shift of the deep high-temperature waters is indicative of dominance of fracture-related permeability in the reservoir. Analyses of the chemistry and the temperature of the waters from hot springs and shallow thermal wells suggests that these waters have evolved from the deep geothermal waters through dilution by meteoric waters and about 40C adiabatic cooling (steam loss).

  15. Determination of atrazine, lindane, pentachlorophenol, and diazinon in water and soil by isotope dilution gas chromatography/mass spectrometry

    SciTech Connect

    Lopez-Avila, V.; Hirata, P.; Kraska, S.; Flanagan, M.; Taylor, J.H. Jr.; Hern, S.C.

    1985-12-01

    This paper describes an isotope dilution GC/MS technique for the analysis of low-parts-per-billion concentrations of atrazine, lindane, pentachlorophenol, and diazinon in water and soil. Known amounts of stable-labeled isotopes such as atrazine-d/sub 5/, lindane-d/sub 6/, pentachlorophenol-/sup 13/C/sub 6/, and diazinon-d/sub 10/ are spiked into each sample prior to extraction. Water samples are extracted with methylene chloride; soil samples are extracted with acetone/hexane. Analysis is performed by high-resolution GC/MS with the mass spectrometer operated in the selected ion monitoring mode. Accuracy greater than 86% and precision better than 8% were demonstrated by use of spiked samples. This technique has been used successfully in the analysis of over 300 water and 300 soil samples. Detection limits of 0.1-1.0 ppb were achieved for the test compounds by selected ion monitoring GC/MS. 8 references, 2 figures, 4 tables.

  16. Mercury speciation analysis in human hair by species-specific isotope-dilution using GC-ICP-MS.

    PubMed

    Laffont, Laure; Maurice, Laurence; Amouroux, David; Navarro, Patricia; Monperrus, Mathilde; Sonke, Jeroen E; Behra, Philippe

    2013-03-01

    We optimized a mercury (Hg) speciation extraction method for human hair in combination with species-specific isotope-dilution analysis by gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS). The method was validated on human hair reference material RM (IAEA-086), which is recommended for analysis of monomethylmercury (MMHg) and inorganic mercury (IHg). Three reagents, hydrochloric acid (HCl), nitric acid (HNO3), and tetramethylammonium hydroxide (TMAH), and three extraction procedures, at ambient temperature for 12 h, microwave-assisted at 75 °C for 6 min, and oven heated at 80 °C for 2 h were tested. Extraction efficiency, recovery, and potential species transformations were evaluated for each method. The most efficient procedures, with recovery of ~90 % for each species with limited demethylation (<5 %) and methylation (0 %), were HNO3 digestion, irrespective of temperature, and microwave-assisted TMAH extraction. Acidic extraction with HCl induces significant demethylation, with production of artifacts. To correct for potential demethylation artifacts we recommend spiking with isotopically enriched standards before the extraction step. PMID:22669307

  17. Quantification of Cr(VI) in soil samples from a contaminated area in northern Italy by isotope dilution mass spectrometry.

    PubMed

    Guidotti, Laura; Queipo Abad, Silvia; Rodríguez-González, Pablo; García Alonso, J Ignacio; Beone, Gian Maria

    2015-11-01

    The aims of the work were to detect and quantify hexavalent chromium in 14 soil samples from an area in Lombardia (northern Italy) contaminated by two polluted water plumes. Cr(VI) was extracted from the solid samples by applying focused microwaves in an alkaline medium after Cr(III) complexation with EDTA. Cr(VI) was reduced to Cr(III) when previously reported extraction conditions for the analysis of certified reference materials were used, and Cr(VI) could not be reliably quantified in the soil samples. The influence of organic matter and iron contents in the samples on the reduction of Cr(VI) was subsequently studied using a new set of soil samples with different iron and organic matter concentrations. Isotope dilution mass spectrometry (IDMS) measured two different enriched stable isotopes of Cr (54 and 53) to evaluate the reduction extent of hexavalent chromium during the analytical procedure. The extraction conditions were optimized to obtain the lowest amount of Cr(VI) reduction and quantify Cr(VI) in the polluted soil samples from Lombardia. PMID:26141979

  18. Analysis of organophosphate flame retardants and plasticisers in water by isotope dilution gas chromatography-electron ionisation tandem mass spectrometry.

    PubMed

    Teo, Tiffany L L; McDonald, James A; Coleman, Heather M; Khan, Stuart J

    2015-10-01

    The widespread use of organophosphate flame retardants (PFRs) in commercial products have led to their increased presence in the environment. In this study, a rapid and reliable analytical method was developed for the analysis of five PFRs in water using gas chromatography tandem mass spectrometry (GC-MS/MS) with electron ionisation (EI) and a run time of 13 min. The PFRs investigated were tributyl phosphate (TBP), tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), tris(1,3-dichloro-2-propyl) phosphate (TDCP) and triphenyl phosphate (TPP). Solid phase extraction (SPE) was undertaken to extract and concentrate target analytes from aqueous matrices. All water samples were extracted from a volume of 500 mL. Isotopically labelled compounds were used to account for analytical variability and for accurate quantification by isotope dilution. Method recoveries for all compounds were above 80% in all tested water samples. Method detection limits for all target analytes ranged from 0.3 to 24 ng/L in ultrapure water, tap water, seawater, surface water, secondary effluent and swimming pool water. Validation of this method confirmed satisfactory method stability with less than 1% coefficients of variation, verifying that this approach produced good reproducibility. PMID:26078137

  19. Measurement of Niacin in a Variety of Food Samples by High Performance Liquid Chromatography-Stable Isotope Dilution Mass Spectrometry (AOAC Annual Meeting, Minneapolis, MN, Sept. 2006)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The availability of deuterium-labeled nicotinic acid makes stable isotope dilution mass spectrometry (SIDMS) coupled with liquid chromatography (LC) an attractive option for the determination of the water-soluble B-vitamin, niacin, in food samples. We have developed a method based on AOAC Peer-Verif...

  20. Measurement of Niacin in a Variety of Food Samples by High Performance Liquid Chromatography-Stable Isotope Dilution Mass Spectrometry (Experimental Biology, April, 2007, Washington, D.C.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The availability of deuterium-labeled nicotinic acid makes stable isotope dilution mass spectrometry (SIDMS) coupled with liquid chromatography (LC) an attractive option for the determination of the water-soluble B-vitamin, niacin, in food samples. We have developed a method based on AOAC Peer-Verif...

  1. Alternative Filament Loading Solution for Accurate Analysis of Boron Isotopes by Negative Thermal Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Dwyer, G. S.; Vengosh, A.

    2008-12-01

    The negative thermal ionization mass spectrometry technique has become the major tool for investigating boron isotopes in the environment. The high sensitivity of BO2- ionization enables measurements of ng levels of boron. However, B isotope measurement by this technique suffers from two fundamental problems (1) fractionation induced by selective ionization of B isotopes in the mass spectrometer; and (2) CNO- interference on mass 42 that is often present in some load solutions (such as B-free seawater processed through ion-exchange resin). Here we report a potentially improved methodology using an alternative filament loading solution with a recently-installed Thermo Scientific TRITON thermal ionization mass spectrometer. Our initial results suggest that this solution -- prepared by combining high-purity single- element standard solutions of Ca, Mg, Na, and K in proportions similar to those in seawater in a 5% HCl matrix -- may offer significant improvement over some other commonly used load solutions. Total loading blank is around 15pg as determined by isotope dilution (NIST952). Replicate analyses of NIST SRM951 and modern seawater thus far have yielded 11B/10B ratios of 4.0057 (±0.0008, n=14) and 4.1645 (±0.0017, n=7; δ11B=39.6 permil), respectively. Replicate analyses of samples and SRM951 yield an average standard deviation (1 σ) of approximately 0.001 (0.25 permil). Fractionation during analysis (60-90 minutes) has thus far typically been less than 0.002 (0.5 permil). The load solution delivers ionization efficiency similar to directly-loaded seawater and has negligible signal at mass 26 (CN-), a proxy for the common interfering molecular ion (CNO-) on mass 42. Standards and samples loaded with the solution behave fairly predictably during filament heating and analysis, thus allowing for the possibility of fully automated data collection.

  2. Development and validation of a liquid chromatography isotope dilution mass spectrometry method for the reliable quantification of alkylphenols in environmental water samples by isotope pattern deconvolution.

    PubMed

    Fabregat-Cabello, Neus; Sancho, Juan V; Vidal, Andreu; González, Florenci V; Roig-Navarro, Antoni Francesc

    2014-02-01

    We present here a new measurement method for the rapid extraction and accurate quantification of technical nonylphenol (NP) and 4-t-octylphenol (OP) in complex matrix water samples by UHPLC-ESI-MS/MS. The extraction of both compounds is achieved in 30min by means of hollow fiber liquid phase microextraction (HF-LPME) using 1-octanol as acceptor phase, which provides an enrichment (preconcentration) factor of 800. On the other hand we have developed a quantification method based on isotope dilution mass spectrometry (IDMS) and singly (13)C1-labeled compounds. To this end the minimal labeled (13)C1-4-(3,6-dimethyl-3-heptyl)-phenol and (13)C1-t-octylphenol isomers were synthesized, which coelute with the natural compounds and allows the compensation of the matrix effect. The quantification was carried out by using isotope pattern deconvolution (IPD), which permits to obtain the concentration of both compounds without the need to build any calibration graph, reducing the total analysis time. The combination of both extraction and determination techniques have allowed to validate for the first time a HF-LPME methodology at the required levels by legislation achieving limits of quantification of 0.1ngmL(-1) and recoveries within 97-109%. Due to the low cost of HF-LPME and total time consumption, this methodology is ready for implementation in routine analytical laboratories. PMID:24423386

  3. Use of a {sup 15}N isotope dilution method to assess contaminant effects on soil nitrification

    SciTech Connect

    Nason, G.E.; Dinwoodie, G.D.

    1995-12-31

    Ecologically relevant bioassays are needed to assess effects of contaminants on soil processes such as decomposition and nutrient cycling. This study was conducted to assess the potential of a soil-based nitrification bioassay. Soil samples adjusted to 0.03 MPa moisture content were amended with 0.1, 1.0, 10 and 100 mg kg{sup {minus}1} PCP or PCB, and 0.05, 0.5, 5 and 50 mg kg{sup {minus}1} Hg and preincubated for 7 days. A 2-d incubation was then started by addition of 10 mg kg{sup {minus}1} {sup 15}NO{sub 3}-N. Diethyl ether used as a carrier for PCP addition had little effect on inorganic nitrogen concentrations during the incubation. Net nitrogen mineralization and nitrification were unaffected by PCB. Higher amendment levels of both PCP and Hg resulted in increases in ammonium concentrations and decreases in net nitrification. {sup 15}N-nitrate pool dilution was sensitive to contamination and showed some gross nitrification was occurring even when net nitrification had ceased. Recoveries of Hg and PCB at the end of the study were greater than 90%. Recovery of PCP was 5%. Incubations carried out under sterile and non-sterile conditions indicated that both sorption and biological degradation were factors in the low PCP recovery.

  4. Phonon-isotope scattering and thermal conductivity in materials with a large isotope effect: A first-principles study

    NASA Astrophysics Data System (ADS)

    Lindsay, L.; Broido, D. A.; Reinecke, T. L.

    2013-10-01

    The interplay between phonon-isotope and phonon-phonon scattering in determining lattice thermal conductivities in semiconductors and insulators is examined using an ab initio Boltzmann transport equation approach. We identify materials with large enhancements to their thermal conductivities with isotopic purification, known as the isotope effect, and we focus in particular on results for beryllium-VI compounds and cubic germanium carbide. We find that germanium carbide and beryllium selenide have very large room temperature isotope effects of 450%, far larger than in any other material. Thus, isotopic purification in these materials gives surprisingly high intrinsic room temperature thermal conductivities, over 1500 Wm-1 K-1 for germanium carbide and over 600 Wm-1 K-1 for beryllium selenide, well above those of the best metals. In compound semiconductors, a large mass ratio of the constituent atoms and large isotope mixture for the heavier atom gives enhanced isotope scattering. A frequency gap between acoustic and optic phonons (also due to a large mass ratio) and bunching of the acoustic phonon branches give weak anharmonic scattering. Combined, weak anharmonic phonon scattering and strong isotope scattering give a large isotope effect in the materials examined here. The physical insights discussed in this work will help guide the efficient manipulation of thermal transport properties of compound semiconductors through isotopic modification.

  5. Application of isotope dilution mass spectrometry: determination of ochratoxin A in the Canadian Total Diet Study

    PubMed Central

    Tam, J.; Pantazopoulos, P.; Scott, P.M.; Moisey, J.; Dabeka, R.W.; Richard, I.D.K.

    2011-01-01

    Analytical methods are generally developed and optimized for specific commodities. Total Diet Studies, representing typical food products ‘as consumed’, pose an analytical challenge since every food product is different. In order to address this technical challenge, a selective and sensitive analytical method was developed suitable for the quantitation of ochratoxin A (OTA) in Canadian Total Diet Study composites. The method uses an acidified solvent extraction, an immunoaffinity column (IAC) for clean-up, liquid chromatography-tandem mass spectrometry (LC-MS/MS) for identification and quantification, and a uniformly stable isotope-labelled OTA (U-[13C20]-OTA) as an internal recovery standard. Results are corrected for this standard. The method is accurate (101% average recovery) and precise (5.5% relative standard deviation (RSD)) based on 17 duplicate analysis of various food products over 2 years. A total of 140 diet composites were analysed for OTA as part of the Canadian Total Diet Study. Samples were collected at retail level from two Canadian cities, Quebec City and Calgary, in 2008 and 2009, respectively. The results indicate that 73% (102/140) of the samples had detectable levels of OTA, with some of the highest levels of OTA contamination found in the Canadian bread supply. PMID:21623499

  6. Determination of ultratrace levels of tributyltin in waters by isotope dilution and gas chromatography coupled to tandem mass spectrometry.

    PubMed

    Rodríguez-Cea, Andrés; Rodríguez-González, Pablo; Font Cardona, Nuria; Aranda Mares, José Luís; Ballester Nebot, Salomé; García Alonso, J Ignacio

    2015-12-18

    The current EU legislation lays down the Environmental Quality Standards (EQS) of 45 priority substances in surface water bodies. In particular, the concentration of tributyltin (TBT) must not exceed 0.2ngL(-1) and analytical methodologies with a Limit of Quantification (LOQ) equal or below 0.06ngL(-1) are urged to be developed. This work presents a procedure for the determination of ultratrace levels of TBT in water samples by Isotope Dilution and GC-MS/MS operating in Selected Reaction Monitoring (SRM) mode which meets current EU requirements. The method requires the monitorization of five consecutive transitions (287>175 to 291>179) for the sensitive and selective detection of TBT. The measured isotopic distribution of TBT fragment ions was in agreement with the theoretical values computed by a polynomial expansion algorithm. The combined use of Tandem Mass Spectrometry, a sample volume of 250mL, the preconcentration of 1mL of organic phase to 30μL and an injection volume of 25μL by Programmed Temperature Vaporization provided a LOQ of 0.0426ngL(-1) for TBT (calculated as ten times the standard deviation of nine independent blanks). The recovery for TBT calculated in Milli-Q water at the EQS level was 106.3±4%. A similar procedure was also developed for the quantification of dibutyltin (DBT) and monobutyltin (MBT) in water samples showing satisfactory results. The method was finally implemented in a routine testing laboratory to demonstrate its applicability to real samples obtaining quantitative recoveries for TBT at the EQS level in mineral water, river water and seawater. PMID:26614170

  7. Thermal Neutron Capture Cross Sections of the PalladiumIsotopes

    SciTech Connect

    Firestone, R.B.; Krticka, M.; McNabb, D.P.; Sleaford, B.; Agvaanluvsan, U.; Belgya, T.; Revay, Zs.

    2006-07-17

    Precise gamma-ray thermal neutron capture cross sectionshave been measured at the Budapest Reactor for all elements withZ=1-83,92 except for He and Pm. These measurements and additional datafrom the literature been compiled to generate the Evaluated Gamma-rayActivation File (EGAF), which is disseminated by LBNL and the IAEA. Thesedata are nearly complete for most isotopes with Z<20 so the totalradiative thermal neutron capture cross sections can be determineddirectly from the decay scheme. For light isotopes agreement with therecommended values is generally satisfactory although large discrepanciesexist for 11B, 12,13C, 15N, 28,30Si, 34S, 37Cl, and 40,41K. Neutroncapture decay data for heavier isotopes are typically incomplete due tothe contribution of unresolved continuum transitions so only partialradiative thermal neutron capture cross sections can be determined. Thecontribution of the continuum to theneutron capture decay scheme arisesfrom a large number of unresolved levels and transitions and can becalculated by assuming that the fluctuations in level densities andtransition probabilities are statistical. We have calculated thecontinuum contribution to neutron capture decay for the palladiumisotopes with the Monte Carlo code DICEBOX. These calculations werenormalized to the experimental cross sections deexciting low excitationlevels to determine the total radiative thermal neutron capture crosssection. The resulting palladium cross sections values were determinedwith a precision comparable to the recommended values even when only onegamma-ray cross section was measured. The calculated and experimentallevel feedings could also be compared to determine spin and parityassignments for low-lying levels.

  8. Comparison of thermal ionization mass spectrometry and Multiple Collector Inductively Coupled Plasma Mass Spectrometry for cesium isotope ratio measurements

    NASA Astrophysics Data System (ADS)

    Isnard, H.; Granet, M.; Caussignac, C.; Ducarme, E.; Nonell, A.; Tran, B.; Chartier, F.

    2009-11-01

    In the nuclear domain, precise and accurate isotopic composition determination of elements in spent nuclear fuels is mandatory to validate neutron calculation codes and for nuclear waste disposal. The present study presents the results obtained on Cs isotope ratio by mass spectrometric measurements. Natural cesium is monoisotopic ( 133Cs) whereas cesium in spent fuels has 4 isotopes ( 133Cs, 134Cs, 135Cs, and 137Cs). As no standard reference material is available to evaluate the accuracy of Cs isotopic measurements, a comparison of cesium isotopic composition in spent nuclear fuels has been performed between Thermal Ionization Mass Spectrometry (TIMS) and a new method involving Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) measurements. For TIMS measurements, isotopic fractionation has been evaluated by studying the behavior of cesium isotope ratios ( 133Cs/ 137Cs and 135Cs/ 137Cs) during the analyses. For MC-ICPMS measurements, the mass bias effects have been corrected with an external mass bias correction using elements (Eu and Sb) close to cesium masses. The results obtained by the two techniques show good agreement: relative difference on 133Cs/ 137Cs and 135Cs/ 137Cs ratios for two nuclear samples, analyzed after chemical separation, ranges from 0.2% to 0.5% depending on the choice of reference value for mass bias correction by MC-ICPMS. Finally the quantification of the 135Cs/ 238U ratio by the isotope dilution technique is presented in the case of a MOx (mixed oxide) spent fuel sample. Evaluation of the global uncertainties shows that this ratio could be defined at an uncertainty of 0.5% ( k = 2). The intercomparison between two independent mass spectrometric techniques is fundamental for the evaluation of uncertainty when no isotopic standard is available.

  9. Quantitative determination of sodium monofluoroacetate "1080" in infant formulas and dairy products by isotope dilution LC-MS/MS.

    PubMed

    Bessaire, Thomas; Tarres, Adrienne; Goyon, Alexandre; Mottier, Pascal; Dubois, Mathieu; Tan, Wan Ping; Delatour, Thierry

    2015-01-01

    A fast and easy-to-use confirmatory liquid-chromatography tandem mass-spectrometry (LC-MS/MS) based-method was developed for the analysis of the pesticide sodium monofluoroacetate (MFA, also called "1080") in infant formulas and related dairy products. Extraction of the compound encompassed sample reconstitution and liquid-liquid extraction under acidic conditions. Time-consuming solid-phase extraction steps for clean-up and enrichment and tedious derivatisation were thus avoided. Resulting sample extracts were analysed by electrospray ionisation (ESI) in negative mode. Quantification was performed by the isotopic dilution approach using (13)C-labelled MFA as internal standard. The procedure was validated according to the European document SANCO/12571/2013 and performance parameters such as linearity (r(2) > 0.99), precision (RSD(r) ≤ 9%, RSD(iR) ≤ 11%) and recovery (96-117%) fulfilled its requirements. Limit of quantifications (LOQ) was 1 µg kg(-1) for infant formulas and related dairy products except for whey proteins powders with a LOQ of 5 µg kg(-1). Method ruggedness was further assessed in another laboratory devoted to routine testing for quality control. PMID:26366530

  10. Accurate determination of ochratoxin A in Korean fermented soybean paste by isotope dilution-liquid chromatography tandem mass spectrometry.

    PubMed

    Ahn, Seonghee; Lee, Suyoung; Lee, Joonhee; Kim, Byungjoo

    2016-01-01

    Ochratoxin A (OTA), a naturally occurring mycotoxin, has been frequently detected in doenjang, a traditional fermented soybean paste, when it is fermented under improper conditions. Reliable screening of OTA in traditional fermented soybean paste (doenjang) is a special food-safety issue in Korea. Our laboratory, the National Metrology Institute of Korea, established an isotope dilution-liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) method as a higher-order reference method to be used for SI-traceable value-assignment of OTA in certified reference materials (CRMs). (13)C20-OTA was used as an internal standard. Sample preparation conditions and LC/MS measurement parameters were optimised for this purpose. The analytical method was validated by measuring samples fortified with OTA at various levels. Repeatability and reproducibility studies showed that the ID-LC/MS/MS method is reliable and reproducible within 2% relative standard deviation. The analytical method was applied to determine OTA in various commercial doenjang products and home-made doenjang products. PMID:26212984

  11. Sensitive isotope dilution liquid chromatography/electrospray ionization tandem mass spectrometry method for the determination of acrylamide in chocolate.

    PubMed

    Ren, Yiping; Zhang, Yu; Jiao, Jingjing; Cai, Zengxuan; Zhang, Ying

    2006-03-01

    Isotope dilution liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was applied to the quantification of acrylamide in chocolate matrixes (dark chocolate, milk chocolate, chocolate with nuts, chocolate with almonds, and chocolate with wheat best element). The method included defatting with petroleum ether, extracting with aqueous solution of 2 mol l(-1) sodium chloride and clean-up by solid-phase (SPE) with OASIS HLB 6 cm3 cartridges. Acrylamide was detected with an Atlantis dC18 5 microm 210 x 1.5 mm column using 10% methanol/0.1% formic acid in water as the mobile phase. The analytical method was in-house validated and good results were obtained with respect to repeatability (RSD < 3.5%) and recovery (86-93%), which fulfilled the requirements defined by European Union legislation. The acrylamide levels in chocolate were 23-537 microg kg(-1). Therefore, the method was successfully used for the quantitative analysis of acrlyamide in various chocolate products. PMID:16517524

  12. Quantitation of Gingerols in Human Plasma by Newly Developed Stable Isotope Dilution Assays and Assessment of Their Immunomodulatory Potential.

    PubMed

    Schoenknecht, Carola; Andersen, Gaby; Schmidts, Ines; Schieberle, Peter

    2016-03-23

    In a pilot study with two volunteers, the main pungent and bioactive ginger (Zingiber officinale Roscoe) compounds, the gingerols, were quantitated in human plasma after ginger tea consumption using a newly established HPLC-MS/MS(ESI) method on the basis of stable isotope dilution assays. Limits of quantitation for [6]-, [8]-, and [10]-gingerols were determined as 7.6, 3.1, and 4.0 nmol/L, respectively. The highest plasma concentrations of [6]-, [8]-, and [10]-gingerols (42.0, 5.3, and 4.8 nmol/L, respectively) were reached 30-60 min after ginger tea intake. Incubation of activated human T lymphocytes with gingerols increased the intracellular Ca(2+) concentration as well as the IFN-γ secretion by about 20-30%. This gingerol-induced increase of IFN-γ secretion could be blocked by the specific TRPV1 antagonist SB-366791. The results of the present study point to an interaction of gingerols with TRPV1 in activated T lymphocytes leading to an augmentation of IFN-γ secretion. PMID:26939769

  13. [Determination of polychlorinated naphthalenes in environmental samples by isotope dilution gas chromatography-triple quadrupole mass spectrometry].

    PubMed

    Liu, Zhitong; Zhang, Bing; Wang, Wenwen; Liu, Guorui; Gao, Lirong; Zheng, Minghui

    2013-09-01

    An isotope dilution gas chromatography combined with triple quadrupole mass spectrometry (GC-MS/MS) method was established for the analysis of twenty polychlorinated naphthalenes (PCNs) congeners in environmental samples. The linear correlation coefficients (R2) of calibration curves were greater than 0.99 in the concentration range of 0.5 - 200 microg/L for all the twenty PCN congeners. The average relative response factors (RRF) were calculated based on a seven-point calibration for the twenty PCN congeners. The relative standard deviations (RSDs) of all the congeners were below 15% (n = 7). The limits of detection (LOD) of the established method ranged from 0.04 to 0.48 microg/L for the twenty PCN congeners. The recoveries of matrix spiked samples ranged from 45.2% to 87.9%, and the RSDs ranged from 0.4% to 21.2%. The sediment samples and stack gas samples collected from secondary aluminum smelting were analyzed by the established method. The obtained results were also compared with the data analyzed by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) method. The comparison indicated that the data of the established method was in good agreement with those of HRGC/HRMS method with the RSDs of 0.5% - 41.4%. Consequently, the established GC-MS/MS method can be applied to the determination of PCNs in environmental samples. PMID:24392626

  14. Parkinson-dementia complex and development of a new stable isotope dilution assay for BMAA detection in tissue

    SciTech Connect

    Snyder, Laura R.; Cruz-Aguado, Reyniel; Sadilek, Martin; Galasko, Douglas; Shaw, Christopher A.; Montine, Thomas J.

    2009-10-15

    {beta}-Methylamino-L-alanine (BMAA) has been proposed as a global contributor to neurodegenerative diseases, including Parkinson-dementia complex (PDC) of Guam and Alzheimer's disease (AD). The literature on the effects of BMAA is conflicting with some but not all in vitro data supporting a neurotoxic action, and experimental animal data failing to replicate the pattern of neurodegeneration of these human diseases, even at very high exposures. Recently, BMAA has been reported in human brain from individuals afflicted with PDC or AD. Some of the BMAA in human tissue reportedly is freely extractable (free) while some is protein-associated and liberated by techniques that hydrolyze the peptide bond. The latter is especially intriguing since BMAA is a non-proteinogenic amino acid that has no known tRNA. We attempted to replicate these findings with techniques similar to those used by others; despite more than adequate sensitivity, we were unable to detect free BMAA. Recently, using a novel stable isotope dilution assay, we again were unable to detect free or protein-associated BMAA in human cerebrum. Here we review the development of our new assay for tissue detection of BMAA and show that we are able to detect free BMAA in liver but not cerebrum, nor do we detect any protein-associated BMAA in mice fed this amino acid. These studies demonstrate the importance of a sensitive and specific assay for tissue BMAA and seriously challenge the proposal that BMAA is accumulating in human brain.

  15. Development of a stable isotope dilution LC-MS/MS method for the Alternaria toxins tentoxin, dihydrotentoxin, and isotentoxin.

    PubMed

    Liu, Yang; Rychlik, Michael

    2013-03-27

    For the Alternaria toxins tentoxin, dihydrotentoxin, and isotentoxin, a stable isotope dilution LC-MS/MS method was first developed. Triply deuterated internal standards were prepared via total synthesis and introducing the labels in the last step before cyclization. Method validation was carried out by using potato starch, tomato puree, and white pepper powder as blank matrices. For the three toxins the limits of detection ranged from 0.10 to 0.99 μg/kg. The inter-/intraday relative standard deviations of the method were below 8.8%, and the recoveries ranged between 98 and 115%. Although cyclic peptides are known to show only negligible fragmentation, a low limit of detection was achieved with the optimization of mass spectrometry parameters and cleanup on C18-phenyl SPE columns providing a more selective binding of these phenyl-containing cyclic peptides. The method was applied to 103 food samples including bread, cereals, chips, juice, nuts, oil, sauce, seeds, and spices. Of these, 85% were contaminated with tentoxin and 55% were contaminated with dihydrotentoxin, whereas isotentoxin was not quantifiable. Maximal concentrations of tentoxin and dihydrotentoxin were 52.4 and 36.3 μg/kg, respectively, and were both detected in paprika powder. PMID:23432357

  16. Detection of 1,N(2)-propano-2'-deoxyguanosine in human urine by stable isotope dilution UHPLC-MS/MS analysis.

    PubMed

    Zhang, Ning; Song, Yuanyuan; Zhang, Weibing; Wang, Hailin

    2016-06-15

    A sensitive and accurate stable isotope dilution UHPLC-MS/MS method was developed and validated for the detection and quantification of ProdG adducts in human urine, a surrogate for the ProdG adducts in genomic DNA of human. A specific solid phase extraction (SPE) approach was established for selective enrichment of urinary ProdG adducts and elimination of urinary matrix facilitating the coupled MS/MS detection. The recovery of the method is estimated about 84.8-107.2%, and the precision are about 0.8-3.6% for intraday and 2.8-10.0% for interday. Due to that the matrix effect is efficiently eliminated by SPE pretreatment, the limits of detection (LODs, S/N=3) and quantification (LOQs, S/N=10) are decreased to 100 and 300 amol for urinary ProdG adducts, respectively. By coupling the developed SPE pretreatment with the UHPLC-MS/MS analysis, ProdG adducts were accurately quantified in healthy human urine. PMID:27158096

  17. Human hepatic N-acetylglutamate content and N-acetylglutamate synthase activity. Determination by stable isotope dilution.

    PubMed Central

    Tuchman, M; Holzknecht, R A

    1990-01-01

    N-Acetyl-L-glutamate (N-acetylglutamate) content and N-acetylglutamate synthase activity ranges were established in human liver tissue homogenates by stable isotope dilution. The methods employ N-[methyl-2H3]acetyl[15N]glutamate as internal standard, extraction of N-acetylglutamate by anion-exchange technique and its determination by g.l.c.-mass spectrometry by using selected ion monitoring. Hepatic N-acetylglutamate content in 16 different human livers, normal in structure and function, ranged from 6.8 to 59.7 nmol/g wet wt. (25.0 +/- 13.4 mean +/- S.D.) or from 64.6 to 497.6 nmol/g of protein (223.2 +/- 104.2 mean +/- S.D.). In vitro, N-acetylglutamate synthase activity in liver tissue homogenate ranged from 44.5 to 374.5 (132.0 +/- 90.6 mean +/- S.D.) nmol/min per g wet wt. or from 491.7 to 3416.9 (1159.6 +/- 751.1 mean +/- S.D.) nmol/min per g of protein. No correlation was found between hepatic N-acetylglutamate concentrations and the respective maximal enzymic activities in vitro of N-acetylglutamate synthase. The marked variability in this system among individual livers may reflect its regulatory role in ureagenesis. PMID:2241918

  18. Parkinson’s-Dementia Complex and Development of a New Stable Isotope Dilution Assay for BMAA Detection in Tissue

    PubMed Central

    Snyder, Laura R.; Cruz-Aguado, Reyniel; Sadilek, Martin; Galasko, Douglas; Shaw, Christopher A.; Montine, Thomas J.

    2009-01-01

    β-Methylamino-L-alanine (BMAA) has been proposed as a global contributor to neurodegenerative diseases, including Parkinson-dementia complex (PDC) of Guam and Alzheimer’s disease (AD). The literature on the effects of BMAA is conflicting with some but not all in vitro data supporting a neurotoxic action, and experimental animal data failing to replicate the pattern of neurodegeneration of these human diseases, even at very high exposures. Recently, BMAA has been reported in human brain from individuals afflicted with PDC or AD. Some of the BMAA in human tissue reportedly is freely extractable (free) while some is protein-associated and liberated by techniques that hydrolyze the peptide bond. The latter is especially intriguing since BMAA is a non-proteinogenic amino acid that has no known tRNA. We attempted to replicate these findings with techniques similar to those used by others; despite more than adequate sensitivity, we were unable to detect free BMAA. Recently, using a novel stable isotope dilution assay we again were unable to detect free or protein-associated BMAA in human cerebrum. Here we review the development of our new assay for tissue detection of BMAA and show that we are able to detect free BMAA in liver but not cerebrum, nor do we detect any protein-associated BMAA in mice fed this amino acid. These studies demonstrate the importance of a sensitive and specific assay for tissue BMAA and seriously challenge the proposal that BMAA is accumulating in human brain. PMID:19716838

  19. Determination of epoxidized soybean oil by gas chromatography/single quadrupole and tandem mass spectrometry stable isotope dilution assay.

    PubMed

    Rothenbacher, Thorsten; Schwack, Wolfgang

    2007-01-01

    PVC lids of glass jars often contain epoxidized soybean oil (ESBO), able to migrate and contaminate food. To establish a stable isotope dilution assay (SIDA), the 13C18-labelled internal standard ethyl 9,10,12,13-diepoxyoctadecanoate (13C(18:2E)Et) was synthesized, providing after sample preparation the same retention time as methyl 9,10,12,13-diepoxyoctadecanoate ((18:2E)Me), commonly used as a marker for ESBO in gas chromatographic (GC) analysis. For eleven different food matrices, the GC capillary columns VF-17ms, DB1701 and DB1 were tested with single quadrupole (GC/MS) as well as tandem mass spectrometric detection (GC/MS/MS). Overall, the VF-17ms column coupled with MS/MS detection showed the best results in terms of separation and sensitivity. The method validation for the matrix spiked olive oil resulted in a limit of detection (LOD) of 5 mg kg-1, a limit of quantification (LOQ) of 11 mg kg-1, a mean recovery (n=5, c=106.5 mg kg-1) of 99.7+/-5.5%, with a repeatability (within-run precision) of 6.0%. By means of GC/MS an LOQ of 21 mg kg-1 and a mean recovery (n=5, c=106.5 mg kg-1) of 103.3+/-0.8% with a repeatability of 0.9% were determined. PMID:17510930

  20. Determination of six sulfonamide antibiotics, two metabolites and trimethoprim in wastewater by isotope dilution liquid chromatography/tandem mass spectrometry.

    PubMed

    Le-Minh, Nhat; Stuetz, Richard M; Khan, Stuart J

    2012-01-30

    A highly sensitive method for the analysis of six sulfonamide antibiotics (sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethazine and sulfamethoxazole), two sulfonamide metabolites (N(4)-acetyl sulfamethazine and N(4)-acetyl sulfamethoxazole) and the commonly co-applied antibiotic trimethoprim was developed for the analysis of complex wastewater samples. The method involves solid phase extraction of filtered wastewater samples followed by liquid chromatography-tandem mass spectral detection. Method detection limits were shown to be matrix-dependent but ranged between 0.2 and 0.4 ng/mL for ultrapure water, 0.4 and 0.7 ng/mL for tap water, 1.4 and 5.9 ng/mL for a laboratory-scale membrane bioreactor (MBR) mixed liquor, 0.7 and 1.7 ng/mL for biologically treated effluent and 0.5 and 1.5 ng/g dry weight for MBR activated sludge. An investigation of analytical matrix effects was undertaken, demonstrating the significant and largely unpredictable nature of signal suppression observed for variably complex matrices compared to an ultrapure water matrix. The results demonstrate the importance of accounting for such matrix effects for accurate quantitation, as done in the presented method by isotope dilution. Comprehensive validation of calibration linearity, reproducibility, extraction recovery, limits of detection and quantification are also presented. Finally, wastewater samples from a variety of treatment stages in a full-scale wastewater treatment plant were analysed to illustrate the effectiveness of the method. PMID:22284510

  1. Determining mycotoxins in baby foods and animal feeds using stable isotope dilution and liquid chromatography tandem mass spectrometry.

    PubMed

    Zhang, Kai; Wong, Jon W; Krynitsky, Alexander J; Trucksess, Mary W

    2014-09-10

    We developed a stable isotope dilution assay with liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine multiple mycotoxins in baby foods and animal feeds. Samples were fortified with [(13)C]-uniformly labeled mycotoxins as internal standards ([(13)C]-IS) and prepared by solvent extraction (50% acetonitrile in water) and filtration, followed by LC-MS/MS analysis. Mycotoxins in each sample were quantitated with the corresponding [(13)C]-IS. In general, recoveries of aflatoxins (2-100 ng/g), deoxynivalenol, fumonisins (50-2000 ng/g), ochratoxin A (20-1000 ng/kg), T-2 toxin, and zearalenone (40-2000 ng/g) in tested matrices (grain/rice/oatmeal-based formula, animal feed, dry cat/dog food) ranged from 70 to 120% with relative standard deviations (RSDs) <20%. The method provides sufficient selectivity, sensitivity, accuracy, and reproducibility to screen for aflatoxins at ng/g concentrations and deoxynivalenol and fumonisins at low μg/g concentrations in baby foods and animal feeds, without using conventional standard addition or matrix-matched calibration standards to correct for matrix effects. PMID:25153173

  2. Isotope dilution gas chromatographic-mass spectrometric method for the determination of isoflavonoids, coumestrol, and lignans in food samples.

    PubMed

    Mazur, W; Fotsis, T; Wähälä, K; Ojala, S; Salakka, A; Adlercreutz, H

    1996-01-15

    We present a method for the quantitative determination of the phytoestrogens formononetin, biochanin A, daidzein, genistein, and coumestrol and simultaneously the lignans secoisolariciresinol (SECO) and matairesinol in plant-derived foods. These compounds are measured by isotope dilution gas chromatography-mass spectrometry in the selected ion monitoring mode (ID/GC/MS/SIM) using synthesized deuterated internal standards for the correction of losses during the procedure. A three-step hydrolysis--a rehydration with distilled H2O, followed by enzymatic and acid hydrolysis--has been applied in order to convert the diphenolic glycosides into their respective aglycones. Purification and separation are carried out in two ion-exchange chromatographic steps followed by derivatization and GC-MS. The within-assay imprecision values vary 3.1-9.6% and the between-assay imprecision 7.0-21.2%. The mean recovery of authentic standards processed through the whole procedure varied from 95.5 to 105.5%. Values for some different food samples are presented. The simultaneous determination of the biologically most interesting phytoestrogens and lignans in foods has not been carried out previously and the method will be useful for screening of important foods in populations with different risk of cancer and coronary heart disease, and for metabolic studies. PMID:8789715

  3. Simultaneous detection of multiple hydroxylated polychlorinated biphenyls from a complex tissue matrix using gas chromatography/isotope dilution mass spectrometry.

    PubMed

    Eguchi, Akifumi; Nomiyama, Kei; Ochiai, Mari; Mizukawa, Hazuki; Nagano, Yasuko; Nakagawa, Katsuhiro; Tanaka, Kouki; Miyagawa, Haruhiko; Tanabe, Shinsuke

    2014-01-01

    In this study, we developed a comprehensive, highly sensitive, and robust method for determining 53 congeners of three to eight chlorinated OH-PCBs in liver and brain samples by using isotope dilution gas chromatography (GC) coupled with electron capture negative ionization mass spectrometry (ECNI-MS). These results were compared with those from GC coupled with electron ionization high-resolution mass spectrometry (EI-HRMS). Clean-up procedures for analysis of OH-PCBs homologs in liver and brain samples involve a pretreatment step consisting of acetonitrile partition and 5% hydrated silica-gel chromatography before derivatization. Recovery rates of tri- and tetra-chlorinated OH-PCBs in the acetonitrile partition method followed by the 5% hydrated silica-gel column (82% and 91%) were higher than conventional sulfuric acid treatment (2.0% and 3.5%). The method detection limits of OH-PCBs for each matrix obtained by GC/ECNI-MS and GC/EI-HRMS were 0.58-2.6 pg g(-1) and 0.36-1.6 pg g(-1) wet wt, respectively. Recovery rates of OH-PCB congeners in spike tests using sample matrices (10 and 50 pg) were 64.7-117% (CV: 4.7-14%) and 70.4-120% (CV: 2.3-12%), respectively. This analytical method may enable the simultaneous detection of various OH-PCBs from complex tissue matrices. Furthermore, this method allows more comprehensive assessment of the biological effects of OH-PCB exposure on critical organs. PMID:24274296

  4. Sulphur Speciation and Turnover in Soils: Evidence from Sulphur K-Edge XANES Spectroscopy and Isotope Dilution Studies

    SciTech Connect

    Zhao,F.; Lehmann, J.; Solomon, D.; Fox, M.; McGrath, S.

    2005-01-01

    Sulphur K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to quantify S species in humic substance extracts from ten soils from the UK, China and New Zealand, which differ in land use and agricultural management. XANES spectroscopy showed the presence of most reduced (sulphides, disulphides, thiols and thiophenes), intermediate (sulphoxides and sulphonates) and highly oxidised S (ester sulphates) forms, with the three groups representing 14-32%, 33-50% and 22-53% of the organic S in the humic substance extracts, respectively. Land use had a profound influence on the relative proportions of S species. Well-drained arable soils generally had a higher proportion of organic S present in the most oxidised form than the grassland soils collected nearby, whereas paddy soils showed a more reduced profile due to episodic flooding. In the Broadbalk Classical Experiment at Rothamsted, reversion of an arable system to grassland or woodland in the 1880s resulted in an increase of the most reduced and intermediate S species at the expense of the most oxidised S species. Long-term applications of farmyard manure to an arable plot also shifted S species from the most oxidised to the intermediate and the most reduced species. Sulphur immobilization and gross mineralization were determined in seven soils using the {sup 35}S isotope dilution method. Gross mineralization during a 53-day incubation correlated more closely with the amounts of the most reduced and intermediate S species than with the most oxidised S species, suggesting that the former (C-bonded S) were the main source of organic S for mineralization in the short-term.

  5. Sulphur Speciation and Turnover in Soils: Evidence from Sulfur K-Edge XANES Spectroscopy and Isotope Dilution Studies

    SciTech Connect

    Zhao,F.; Lehmann, J.; Solomon, D.; Fox, M.; McGrath, S.

    2006-01-01

    Sulphur K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to quantify S species in humic substance extracts from ten soils from the UK, China and New Zealand, which differ in land use and agricultural management. XANES spectroscopy showed the presence of most reduced (sulphides, disulphides, thiols and thiophenes), intermediate (sulphoxides and sulphonates) and highly oxidised S (ester sulphates) forms, with the three groups representing 14-32%, 33-50% and 22-53% of the organic S in the humic substance extracts, respectively. Land use had a profound influence on the relative proportions of S species. Well-drained arable soils generally had a higher proportion of organic S present in the most oxidised form than the grassland soils collected nearby, whereas paddy soils showed a more reduced profile due to episodic flooding. In the Broadbalk Classical Experiment at Rothamsted, reversion of an arable system to grassland or woodland in the 1880s resulted in an increase of the most reduced and intermediate S species at the expense of the most oxidised S species. Long-term applications of farmyard manure to an arable plot also shifted S species from the most oxidised to the intermediate and the most reduced species. Sulphur immobilisation and gross mineralisation were determined in seven soils using the {sup 35}S isotope dilution method. Gross mineralisation during a 53-day incubation correlated more closely with the amounts of the most reduced and intermediate S species than with the most oxidised S species, suggesting that the former (C-bonded S) were the main source of organic S for mineralisation in the short-term.

  6. Simultaneous analysis of urinary phthalate metabolites of residents in Korea using isotope dilution gas chromatography-mass spectrometry.

    PubMed

    Kim, Miok; Song, Na Rae; Choi, Jong-Ho; Lee, Jeongae; Pyo, Heesoo

    2014-02-01

    Phthalates are used in industry products, household items, and medical tools as plasticizers. Human exposure to phthalates has raised concern about its toxicity. In the present study, optimization was conducted for the simultaneous analysis of eight kinds of phthalate metabolites using gas chromatography-mass spectrometry (GC-MS): MEP, MiBP, MnBP, MBzP, MiNP, MEHP, MEOHP, and MEHHP. In order to minimize the matrix effect and to do quantitative analysis, isotope dilution and LLE-GC-MS methods were performed. Urine samples were enzymatically hydrolyzed, extracted with a mixture of n-hexane and ethyl ether (8:2; v:v), and subsequently derivatized with trimethylsilylation. All eight kinds of analytes showed clear resolution and high reproducibility in GC-MS results. The method detection limit ranged from 0.05 ng/mL to 0.2 ng/mL. Calibration curves were found to be linear from 0.2 to 100 ng/mL with -(2)>0.992. The relative standard deviation of the intraday precision using water and urine ranged from 2.1% to 16.3%. The analysis was performed with urine samples that were collected from adults residing in the Republic of Korea. The analyzed concentration results were compared according to gender and region. As a result, DEHP metabolites showed the highest detected concentration (75.92 μg/g creatinine, 100%), and MiNP, a metabolite of DiNP, showed the lowest detected concentration (0.42 μg/g creatinine, 22.5%). On average, female urine (200.76 μg/g creatinine) had a higher detected concentration of ∑8 phthalate metabolites than male urine. Samples from rural regions (211.96 μg/g creatinine) had higher levels than samples from urban regions. PMID:23928369

  7. Profiles of Steroid Hormones in Canine X-Linked Muscular Dystrophy via Stable Isotope Dilution LC-MS/MS

    PubMed Central

    Martins-Júnior, Helio A.; Simas, Rosineide C.; Brolio, Marina P.; Ferreira, Christina R.; Perecin, Felipe; Nogueira, Guilherme de P.; Miglino, Maria A.; Martins, Daniele S.; Eberlin, Marcos N.; Ambrósio, Carlos E.

    2015-01-01

    Golden retriever muscular dystrophy (GRMD) provides the best animal model for characterizing the disease progress of the human disorder, Duchenne muscular dystrophy (DMD). The purpose of this study was to determine steroid hormone concentration profiles in healthy golden retriever dogs (control group - CtGR) versus GRMD-gene carrier (CaGR) and affected female dogs (AfCR). Therefore, a sensitive and specific analytical method was developed and validated to determine the estradiol, progesterone, cortisol, and testosterone levels in the canine serum by isotope dilution liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). To more accurately understand the dynamic nature of the serum steroid profile, the fluctuating levels of these four steroid hormones over the estrous cycle were compared across the three experimental groups using a multivariate statistical analysis. The concentration profiles of estradiol, cortisol, progesterone, and testosterone revealed a characteristic pattern for each studied group at each specific estrous phase. Additionally, several important changes in the serum concentrations of cortisol and estradiol in the CaGR and AfCR groups seem to be correlated with the status and progression of the muscular dystrophy. A comprehensive and quantitative monitoring of steroid profiles throughout the estrous cycle of normal and GRMD dogs were achieved. Significant differences in these profiles were observed between GRMD and healthy animals, most notably for estradiol. These findings contribute to a better understanding of both dog reproduction and the muscular dystrophy pathology. Our data open new venues for hormonal behavior studies in dystrophinopathies and that may affect the quality of life of DMD patients. PMID:26010907

  8. International experiences in assessing vitamin A status and applying the vitamin A-labeled isotope dilution method.

    PubMed

    Lopez-Teros, Veronica; Chileshe, Justin; Idohou-Dossou, Nicole; Fajarwati, Tetra; Medoua Nama, Gabriel; Newton, Sam; Vinod Kumar, Malavika; Wang, Zhixu; Wasantwisut, Emorn; Hunt, Janet R

    2014-01-01

    Inadequate vitamin A (VA) nutrition continues to be a major problem worldwide, and many interventions being implemented to improve VA status in various populations need to be evaluated. The interpretation of results after an intervention depends greatly on the method selected to assess VA status. To evaluate the effect of an intervention on VA status, researchers in Cameroon, India, Indonesia, Mexico, Senegal and Zambia have used serum retinol as an indicator, and have not always found improvement in response to supplementation. One problem is that homeostatic control of serum retinol may mask positive effects of treatment in that changes in concentration are observed only when status is either moderately to severely depleted or excessive. Because VA is stored mainly in the liver, measurements of hepatic VA stores are the “gold standard” for assessing VA status. Dose response tests such as the relative dose response (RDR) and the modified relative dose response (MRDR), allow a qualitative assessment of VA liver stores. On the other hand, the use of the vitamin A-labeled isotope dilution (VALID) technique, (using 13C or 2H-labeled retinyl acetate) serves as an indirect method to quantitatively estimate total body and liver VA stores. Countries including Cameroon, China, Ghana, Mexico, Thailand and Zambia are now applying the VALID method to sensitively assess changes in VA status during interventions, or to estimate a population’s dietary requirement for VA. Transition to the use of more sensitive biochemical indicators of VA status such as the VALID technique is needed to effectively assess interventions in populations where mild to moderate VA deficiency is more prevalent than severe deficiency. PMID:25537105

  9. Measurement of mercury species in human blood using triple spike isotope dilution with SPME-GC-ICP-DRC-MS.

    PubMed

    Sommer, Yuliya L; Verdon, Carl P; Fresquez, Mark R; Ward, Cynthia D; Wood, Elliott B; Pan, Yi; Caldwell, Kathleen L; Jones, Robert L

    2014-08-01

    The measurement of different mercury compounds in human blood can provide valuable information about the type of mercury exposure. To this end, our laboratory developed a biomonitoring method for the quantification of inorganic (iHg), methyl (MeHg), and ethyl (EtHg) mercury in whole blood using a triple-spike isotope dilution (TSID) quantification method employing capillary gas chromatography (GC) and inductively coupled dynamic reaction cell mass spectrometry (ICP-DRC-MS). We used a robotic CombiPAL(®) sample handling station featuring twin fiber-based solid-phase microextraction (SPME) injector heads. The use of two SPME fibers significantly reduces sample analysis cycle times making this method very suitable for high sample throughput, which is a requirement for large public health biomonitoring studies. Our sample preparation procedure involved solubilization of blood samples with tetramethylammonium hydroxide (TMAH) followed by the derivatization with sodium tetra(n-propyl)borate (NaBPr(4)) to promote volatility of mercury species. We thoroughly investigated mercury species stability in the blood matrix during the course of sample treatment and analysis. The method accuracy for quantifying iHg, MeHg, and EtHg was validated using NIST standard reference materials (SRM 955c level 3) and the Centre de Toxicologie du Québec (CTQ) proficiency testing (PT) samples. The limit of detection (LOD) for iHg, MeHg, and EtHg in human blood was determined to be 0.27, 0.12, and 0.16 μg/L, respectively. PMID:24948088

  10. Quantification of Polybrominated and Polychlorinated Biphenyls in Human Matrices by Isotope-Dilution Gas Chromatography-Tandem Mass Spectrometry.

    PubMed

    Marder, M Elizabeth; Panuwet, Parinya; Hunter, Ronald E; Ryan, P Barry; Marcus, Michele; Barr, Dana Boyd

    2016-09-01

    We have developed a highly sensitive and selective analytical method capable of quantifying a total of 15 polybrominated and polychlorinated biphenyls (11 PBBs and 4 PCBs) in human serum. Samples were subjected to liquid-liquid extraction followed by solid-phase extraction prior to measurement using gas chromatography-tandem mass spectrometry in multiple reaction monitoring mode. Quantification was performed using isotope-dilution calibration covering a concentration range of 0.005-12.5 ng/mL. Limits of detection for all target compounds were in the low range (0.7-6.5 pg/mL). The method was validated using in-house pooled human serum fortified at two concentrations (0.5 ng/mL and 1.0 ng/mL), whole semen fortified at one concentration (0.25 ng/mL), and NIST Standard Reference Material (SRM) 1958, which includes five of the target compounds. Method accuracies for all target compounds ranged from 84 to 119% with relative standard deviations (RSDs) of <19%. The measured values for the five target compounds present in the SRM agreed with the certified reference values (89-119% accuracy with RSDs <9%). As this method was developed to support ongoing epidemiologic investigations, we evaluated its suitability by analyzing subsets of serum and whole semen samples from the Michigan PBB Registry cohort. PBB-153, PCB-118, PCB-138, PCB-153 and PCB-180 were detected in all serum samples analyzed, with PBB-77 and PBB-101 detected less frequently in serum. PBB-153, PCB-118, PCB-138, PCB-153 and PCB-180 were detected in at least one whole semen sample. PMID:27445313

  11. Measurement of Mercury Species in Human Blood using Triple Spike Isotope Dilution with SPME-GC-ICP-DRC-MS

    PubMed Central

    Sommer, Yuliya L.; Verdon, Carl P.; Fresquez, Mark R.; Ward, Cynthia D.; Wood, Elliott B.; Pan, Yi; Caldwell, Kathleen L.; Jones, Robert L.

    2015-01-01

    The measurement of different mercury compounds in human blood can provide valuable information about the type of mercury exposure. To this end, our laboratory developed a biomonitoring method for the quantification of inorganic (iHg), methyl (MeHg) and ethyl (EtHg) mercury in whole blood using a triple spike isotope dilution (TSID) quantification method employing capillary gas chromatography (GC) and inductively coupled dynamic reaction cell mass spectrometry (ICP-DRC-MS). We used a robotic CombiPAL® sample handling station featuring twin fiber-based solid phase microextraction (SPME) injector heads. The use of two SPME fibers significantly reduces sample analysis cycle times making this method very suitable for high sample throughput, which is a requirement for large public health biomonitoring studies. Our sample preparation procedure involved solubilization of blood samples with tetramethylammonium hydroxide (TMAH) followed by the derivatization with sodium tetra(n-propyl)borate (NaBPr4) to promote volatility of mercury species. We thoroughly investigated mercury species stability in the blood matrix during the course of sample treatment and analysis. The method accuracy for quantifying iHg, MeHg and EtHg was validated using NIST standard reference materials (SRM 955c Level 3) and the Centre de Toxicologie du Québec (CTQ) proficiency testing (PT) samples. The limit of detection (LOD) for iHg, MeHg and EtHg in human blood was determined to be 0.27, 0.12, and 0.16 μg/L, respectively. PMID:24948088

  12. Folate bioavailability from foods rich in folates assessed in a short term human study using stable isotope dilution assays.

    PubMed

    Mönch, Sabine; Netzel, Michael; Netzel, Gabriele; Ott, Undine; Frank, Thomas; Rychlik, Michael

    2015-01-01

    Different sources of folate may have different bioavailability and hence may impact the standard definition of folate equivalents. In order to examine this, a short term human study was undertaken to evaluate the relative native folate bioavailabilities from spinach, Camembert cheese and wheat germs compared to pteroylmonoglutamic acid as the reference dose. The study had a single-centre, randomised, four-treatment, four-period, four-sequence, cross-over design, i.e. the four (food) items to be tested (referred to as treatments) were administered in sequences according to the Latin square, so that each experimental treatment occurred only once within each sequence and once within each study period. Each of the 24 subjects received the four experimental items separated by a 14-day equilibrium phase and received a pteroylmonoglutamic acid supplement for 14 days before the first testing and between the testings for saturation of body pools. Folates in test foods, plasma and urine samples were determined by stable isotope dilution assays, and in urine and plasma, the concentrations of 5-methyltetrahydrofolate were evaluated. Standard non-compartmental methods were applied to determine the biokinetic parameters C(max), t(max) and AUC from baseline corrected 5-methyltetrahydrofolate concentrations within the interval from 0 to 12 hours. The variability of AUC and C(max) was moderate for spinach and oral solution of pteroylmonoglutamic acid but high for Camembert cheese and very high for wheat germs. The median t(max) was lowest for spinach, though t(max) showed a high variability among all treatments. When comparing the ratio estimates of AUC and C(max) for the different test foods, highest bioavailability was found for spinach followed by that for wheat germs and Camembert cheese. The results underline the dependence of folate bioavailability on the type of food ingested. Therefore, the general assumption of 50% bioavailability as the rationale behind the definition of

  13. Synthesis of deuterium-labeled 17-hydroxyprogesterone suitable as an internal standard for isotope dilution mass spectrometry

    SciTech Connect

    Shimizu, K.; Yamaga, N.; Kohara, H.

    1988-03-01

    A synthesis is reported of 17-hydroxyprogesterone, labeled with four atoms of deuterium at ring C and suitable for use as an internal standard for isotope dilution mass spectrometry. Base-catalyzed equilibration of methyl 3 alpha-acetoxy-12-oxo-cholanate (III) with /sup 2/H/sub 2/O, followed by reduction of the 12-oxo group by the modified Wolff-Kisher method using (/sup 2/H)diethylene glycol and (/sup 2/H)hydrazine hydrate afforded (11,11,12,12,23,23(-2)H)lithocholic acid (V). The Meystre-Miescher degradation of the side chain of V yielded 3 alpha-hydroxy-5 beta-(11,11,12,12(-2)H)pregnan-20-one (X). Oxidation of the 3,20-enol-diacetate of X with perbenzoic acid followed by saponification afforded 3 alpha,17-dihydroxy-5 beta-(11,11,12,12(-2)H)pregnan-20-one (XI). Oxidation of XI with N-bromoacetamide yielded 17-hydroxy-5 beta-(11,11,12,12(-2)H)pregnane-3,20-dione (XII). Bromination of XII followed by dehydrobromination yielded 17-hydroxy-(11,11,12,12(-2)H) progesterone (XIV), consisting of 0.3% /sup 2/H0-, 1.1% /sup 2/H/sub 1/-, 8.6% /sup 2/H/sub 2/-, 37.1% /sup 2/H/sub 3/-, 52.1% /sup 2/H/sub 4/-, and 0.8% /sup 2/H/sub 5/-species.

  14. An Isotope Dilution Method for High-frequency Measurements of Dissolved Inorganic Carbon concentration in the Surface Ocean

    NASA Astrophysics Data System (ADS)

    Huang, K.; Bender, M. L.; Wanninkhof, R. H.; Cassar, N.

    2013-12-01

    Dissolved inorganic carbon (DIC) is one of the most important species in the ocean carbon system. An autonomous system using isotope dilution as its core method has been developed to obtain high-frequency measurements of dissolved inorganic carbon (DIC) concentrations in the surface ocean. This system accurately mixes a seawater sample and a 13C-labeled sodium bicarbonate solution (spike). The mixed solution is then acidified and sent through a gas permeable membrane contactor. CO2 derived from DIC in the mixture is extracted by a CO2-free gas stream, and is sent to a cavity ring-down spectrometer to analyze its 13C/12C ratio. [DIC] of the seawater can then be derived from the measured 13C/12C, the known mixing ratio and the [DI13C] of the spike. The method has been tested under a wide [DIC] range (1800-2800 μmol/kg) in the laboratory. It has also been deployed on a cruise that surveyed ocean waters to the south of Florida. At a sampling resolution of 4 minutes (15 samples per hour), the relative standard deviation of DIC determined from the laboratory tests and the field deployment is ×0.07% and ×0.09%, respectively. The accuracy of the method is better than 0.1% except where [DIC] varies faster than 5 μmol/kg per minute. Based on the laboratory and field evaluations, we conclude that this method can provide accurate underway [DIC] measurements at high resolution in most oceanic regions. Schematic illustration of the work flow.

  15. A method for the routine determination of methylmercury in marine tissue by GC isotope dilution-ICP-MS.

    PubMed

    Valdersnes, Stig; Maage, Amund; Fliegel, Daniel; Julshamn, Kåre

    2012-01-01

    Currently, there is no legal limit for methyl mercury (MeHg) in food; thus, no standardized method for the determination of MeHg in seafood exists within the European jurisdiction. In anticipation of a future legislative limit an inductively coupled plasma isotope dilution mass spectrometry (GC-ICP-ID-MS) method was developed in collaboration with the European Standardization Organization (CEN). The method comprises spiking the tissue sample with Me201Hg, followed by decomposition with tetramethylammonium hydroxide, pH adjustment and derivatization with sodium tetraethylborate, and finally organic extraction of the derivatized MeHg in a hexane phase. Subsequently, the sample is analyzed via GC-ICP-MS and the result calculated using the ID equation. The working range of the method was 0.0005-1.321 mg/kg MeHg in marine tissue, with an internal reproducibility (RSD) of 12-1%. The method was validated based on statistical measures, such as the z-scores, using the commercially available reference materials from National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1566b, NIST SRM 2977 and National Research Council of Canada (NRCC) TORT 2, NRCC, DORM 3, NRCC DOLT 4, and European Reference Material (ERM) CE 464. Z-scores for all standard reference materials, except for NIST SRM 1566b, were better than 11.51. The wide range of marine tissues used during the validation ensures that the method will be applicable for measuring of MeHg in seafood matrixes of all kinds. PMID:22970590

  16. Characterization of candidate reference materials for bone lead via interlaboratory study and double isotope dilution mass spectrometry

    PubMed Central

    Bellis, David J.; Hetter, Katherine M.; Verostek, Mary Frances; Parsons, Patrick J.

    2012-01-01

    Summary Four candidate ground bone reference materials (NYS RMs 05-01 through 04), were produced from lead-dosed bovine and caprine sources, and characterized by interlaboratory study. The consensus value ( X ) and expanded standard uncertainty (UX ) were determined from the robust average and standard deviation of the participants’ data for each NYS RM 05-01 through 04. The values were 1.08 ±0.04, 15.3 ±0.5, 12.4 ±0.5, and 29.9 ±1.1 μg g−1 Pb, respectively. Youden plots of z-scores showed a statistically significant correlation between the results for pairs of NYS RM 05-02 through 04, indicating common sources of between-laboratory variation affecting reproducibility. NYS RM 05-01 exhibited more random variability affecting repeatability at low concentration. Some participants using electrothermal atomic absorption spectrometry (ETAAS) exhibited a negative bias compared to the all-method consensus value. Other methods used included inductively coupled plasma mass spectrometry (ICP-MS), isotope dilution (ID-) ICP-MS, and ICP atomic (optical) emission spectroscopy (-OES). The NYS RMs 05-01 through 04 were subsequently re-analyzed in house using double ID-ICP-MS to assign certified reference values (C ) and expanded uncertainty (UC ) of 1.09 ± 0.03, 16.1 ± 0.3, 13.2 ± 0.3 and 31.5 ± 0.7, respectively, indicating a low bias in the interlaboratory data. SRM 1486 Bone Meal was analyzed for measurement quality assessment obtaining results in agreement with the certified values within the stated uncertainty. Analysis using a primary reference method based on ID-ICP-MS with full quantification of uncertainty calculated according to ISO guidelines provided traceability to SI units. PMID:23087531

  17. Profiles of Steroid Hormones in Canine X-Linked Muscular Dystrophy via Stable Isotope Dilution LC-MS/MS.

    PubMed

    Martins-Júnior, Helio A; Simas, Rosineide C; Brolio, Marina P; Ferreira, Christina R; Perecin, Felipe; Nogueira, Guilherme de P; Miglino, Maria A; Martins, Daniele S; Eberlin, Marcos N; Ambrósio, Carlos E

    2015-01-01

    Golden retriever muscular dystrophy (GRMD) provides the best animal model for characterizing the disease progress of the human disorder, Duchenne muscular dystrophy (DMD). The purpose of this study was to determine steroid hormone concentration profiles in healthy golden retriever dogs (control group - CtGR) versus GRMD-gene carrier (CaGR) and affected female dogs (AfCR). Therefore, a sensitive and specific analytical method was developed and validated to determine the estradiol, progesterone, cortisol, and testosterone levels in the canine serum by isotope dilution liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). To more accurately understand the dynamic nature of the serum steroid profile, the fluctuating levels of these four steroid hormones over the estrous cycle were compared across the three experimental groups using a multivariate statistical analysis. The concentration profiles of estradiol, cortisol, progesterone, and testosterone revealed a characteristic pattern for each studied group at each specific estrous phase. Additionally, several important changes in the serum concentrations of cortisol and estradiol in the CaGR and AfCR groups seem to be correlated with the status and progression of the muscular dystrophy. A comprehensive and quantitative monitoring of steroid profiles throughout the estrous cycle of normal and GRMD dogs were achieved. Significant differences in these profiles were observed between GRMD and healthy animals, most notably for estradiol. These findings contribute to a better understanding of both dog reproduction and the muscular dystrophy pathology. Our data open new venues for hormonal behavior studies in dystrophinopathies and that may affect the quality of life of DMD patients. PMID:26010907

  18. Determination of Glyphosate, its Degradation Product Aminomethylphosphonic Acid, and Glufosinate, in Water by Isotope Dilution and Online Solid-Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry

    USGS Publications Warehouse

    Meyer, Michael T.; Loftin, Keith A.; Lee, Edward A.; Hinshaw, Gary H.; Dietze, Julie E.; Scribner, Elisabeth A.

    2009-01-01

    The U.S. Geological Survey method (0-2141-09) presented is approved for the determination of glyphosate, its degradation product aminomethylphosphonic acid (AMPA), and glufosinate in water. It was was validated to demonstrate the method detection levels (MDL), compare isotope dilution to standard addition, and evaluate method and compound stability. The original method USGS analytical method 0-2136-01 was developed using liquid chromatography/mass spectrometry and quantitation by standard addition. Lower method detection levels and increased specificity were achieved in the modified method, 0-2141-09, by using liquid chromatography/tandem mass spectrometry (LC/MS/MS). The use of isotope dilution for glyphosate and AMPA and pseudo isotope dilution of glufosinate in place of standard addition was evaluated. Stable-isotope labeled AMPA and glyphosate were used as the isotope dilution standards. In addition, the stability of glyphosate and AMPA was studied in raw filtered and derivatized water samples. The stable-isotope labeled glyphosate and AMPA standards were added to each water sample and the samples then derivatized with 9-fluorenylmethylchloroformate. After derivatization, samples were concentrated using automated online solid-phase extraction (SPE) followed by elution in-line with the LC mobile phase; the compounds separated and then were analyzed by LC/MS/MS using electrospray ionization in negative-ion mode with multiple-reaction monitoring. The deprotonated derivatized parent molecule and two daughter-ion transition pairs were identified and optimized for glyphosate, AMPA, glufosinate, and the glyphosate and AMPA stable-isotope labeled internal standards. Quantitative comparison between standard addition and isotope dilution was conducted using 473 samples analyzed between April 2004 and June 2006. The mean percent difference and relative standard deviation between the two quantitation methods was 7.6 plus or minus 6.30 (n = 179), AMPA 9.6 plus or minus 8

  19. Multiple spiking species-specific isotope dilution analysis by molecular mass spectrometry: simultaneous determination of inorganic mercury and methylmercury in fish tissues.

    PubMed

    Castillo, Angel; Rodríguez-González, Pablo; Centineo, Giuseppe; Roig-Navarro, Antoni Francesc; García Alonso, J Ignacio

    2010-04-01

    This work demonstrates, for the first time, the applicability of multiple spiking isotope dilution analysis to molecular mass spectrometry exemplified by the speciation analysis of mercury using GC(EI)MS instrumentation. A double spike isotope dilution approach using isotopically enriched mercury isotopes has been applied for the determination of inorganic mercury Hg(II) and methylmercury (MeHg) in fish reference materials. The method is based on the application of isotope pattern deconvolution for the simultaneous determination of degradation-corrected concentrations of methylmercury and inorganic mercury. Mass isotopomer distributions are employed instead of isotope ratios to calculate the corrected concentrations of the Hg species as well as the extent of species degradation reactions. The isotope pattern deconvolution equations developed here allow the calculation of the different molar fractions directly from the GC(EI)MS mass isotopomer distribution pattern and take into account possible impurities present in the spike solutions employed. The procedure has been successfully validated with the analysis of two different certified reference materials (BCR-464 and DOLT-4) and with the comparison of the results obtained by GC(ICP)MS. For the tuna fish matrix (BCR-464), no interconversion reactions were observed at the optimized conditions of open focused microwave extraction at 70 degrees C during 8 min. However, significant demethylation was found under the same conditions in the case of the certified dogfish liver DOLT-4. Methylation and demethylation factors were confirmed by GC(ICP)MS. Transformation reactions have been found to depend on the sample matrix and on the derivatization reagent employed. Thus, it is not possible to recommend optimum extraction conditions suitable for all types of matrices demonstrating the need to apply multiple spiking methodologies for the determination of MeHg and Hg(II) in biological samples. Double spike isotope dilution

  20. Measurement of mercury species in whole blood using speciated isotope dilution methodology integrated with microwave-enhanced solubilization and spike equilibration, headspace-solid-phase microextraction, and GC-ICP-MS analysis.

    PubMed

    Rahman, G M Mizanur; Wolle, Mesay Mulugeta; Fahrenholz, Timothy; Kingston, H M Skip; Pamuku, Matt

    2014-06-17

    A biomonitoring method was developed for the determination of inorganic-, methyl-, and ethylmercury (Hg(2+), CH3Hg(+), and C2H5Hg(+), respectively) in whole blood by triple-spiking speciated isotope dilution mass spectrometry (SIDMS) using headspace (HS) solid-phase microextraction (SPME) in combination with gas chromatographic (GC) separation and inductively coupled plasma mass spectrometric (ICP-MS) detection. After spiking the blood sample with isotopically enriched analogues of the analytes ((199)Hg(2+), CH3(200)Hg(+) and C2H5(201)Hg(+)), the endogenous Hg species were solubilized in 2.0 mol L(-1) HNO3 and equilibrated with the spikes using a microwave-enhanced protocol. The microwaved sample was treated with a 1% (w/v) aqueous solution of sodium tetrapropylborate (buffered to pH 5.2), and the propylated Hg species were sampled in the HS using a Carboxen/polydimethylsiloxane-coated SPME fiber. The extracted species were thermally desorbed from the fiber in the GC injection port and determined by GC-ICP-MS. The analytes were quantified, with simultaneous correction for their method-induced transformation, on the basis of the mathematical relationship in triple-spiking SIDMS. The method was validated using a bovine blood standard reference material (SRM 966, Level 2). Analysis of human blood samples demonstrated the accuracy and reproducibility of the method, which can detect the Hg species down to 30 pg g(-1) in blood. The validity of the analytical results found for the blood samples was demonstrated using mass balance by comparing the sum of the concentrations of the individual Hg species with the total Hg in the corresponding samples; the latter was determined by isotope dilution mass spectrometry (IDMS) after decomposing the blood using EPA Method 3052 with single-spiking. PMID:24845130

  1. Quantification of Nε-(2-Furoylmethyl)-L-lysine (furosine), Nε-(Carboxymethyl)-L-lysine (CML), Nε-(Carboxyethyl)-L-lysine (CEL) and total lysine through stable isotope dilution assay and tandem mass spectrometry.

    PubMed

    Troise, Antonio Dario; Fiore, Alberto; Wiltafsky, Markus; Fogliano, Vincenzo

    2015-12-01

    The control of Maillard reaction (MR) is a key point to ensure processed foods quality. Due to the presence of a primary amino group on its side chain, lysine is particularly prone to chemical modifications with the formation of Amadori products (AP), Nε-(Carboxymethyl)-L-lysine (CML), Nε-(Carboxyethyl)-L-lysine (CEL). A new analytical strategy was proposed which allowed to simultaneously quantify lysine, CML, CEL and the Nε-(2-Furoylmethyl)-L-lysine (furosine), the indirect marker of AP. The procedure is based on stable isotope dilution assay followed by liquid chromatography tandem mass spectrometry. It showed high sensitivity and good reproducibility and repeatability in different foods. The limit of detection and the RSD% were lower than 5 ppb and below 8%, respectively. Results obtained with the new procedure not only improved the knowledge about the reliability of thermal treatment markers, but also defined new insights in the relationship between Maillard reaction products and their precursors. PMID:26041204

  2. New method for caffeine quantification by planar chromatography coupled with electropray ionization mass spectrometry using stable isotope dilution analysis.

    PubMed

    Aranda, Mario; Morlock, Gertrud

    2007-01-01

    A new high-performance thin-layer chromatography/electrospray ionization mass spectrometry (HPTLC/ESI-MS) method for the quantification of caffeine in pharmaceutical and energy drink samples was developed using stable isotope dilution analysis (SIDA). After sample preparation, samples and caffeine standard were applied on silica gel 60 F254 HPTLC plates and over-spotted with caffeine-d3 used for correction of the plunger positioning. After chromatography, densitometric detection was performed by UV absorption at 274 nm. The bands were then eluted by means of a plunger-based extractor into the ESI interface of a single-quadrupole mass spectrometer. For quantification by MS the [M+H]+ ions of caffeine and caffeine-d3 were recorded in the positive ion single ion monitoring (SIM) mode at m/z 195 and 198, respectively. The calibration showed a linear regression with a determination coefficient (R2) of 0.9998. The repeatability (RSD, n=6) in matrix was

  3. Determination of Ag, Tl, and Pb in few milligrams of platinum nanoclusters by on-line isotope dilution in laser ablation inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Becker, J. Sabine; Pickhardt, Carola; Pompe, W.

    2004-09-01

    A new analysis procedure for determination of trace impurities in a few milligram noble metal nanoclusters, using on-line isotope dilution in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was developed. During the laser ablation of investigated sample simultaneous the dry aerosol of nebulized enriched isotope spike solution was added and mixed in the laser ablation chamber. The capability of solution-based calibration by a modified isotope dilution analysis in LA-ICP-MS for the determination of selected elements was tested, using platinum reference material NIST SRM 681. A good agreement of measured with certified concentration for Ag and Pb was found. The detection limits for trace element determination of the developed analytical technique, using LA-ICP-MS with quadrupole analyzer varied between 6 ng g-1 for Ag and 90 ng g-1 for Pb. The analytical technique was applied for the determination of Ag, Tl, and Pb in a few milligram of platinum nanoclusters.

  4. On-line isotope dilution in laser ablation inductively coupled plasma mass spectrometry using a microflow nebulizer inserted in the laser ablation chamber

    NASA Astrophysics Data System (ADS)

    Pickhardt, Carola; Izmer, Andrej V.; Zoriy, Miroslav V.; Schaumlöffel, D.; Sabine Becker, J.

    2006-02-01

    Laser ablation ICP-MS (inductively coupled plasma mass spectrometry) is becoming one of the most important analytical techniques for fast determination of trace impurities in solid samples. Quantification of analytical results requires matrix-matched standards, which are in some cases (e.g., high-purity metals, proteins separated by 2D gel electrophoresis) difficult to obtain or prepare. In order to overcome the quantification problem a special arrangement for on-line solution-based calibration has been proposed in laser ablation ICP-MS by the insertion of a microflow nebulizer in the laser ablation chamber. This arrangement allows an easy, accurate and precise quantification by on-line isotope dilution using a defined standard solution with an isotope enriched tracer nebulized to the laser-ablated sample material. An ideal matrix matching in LA-ICP-MS is therefore obtained during the measurement. The figures of merit of this arrangement with a microflow nebulizer inserted in the laser ablation chamber and applications of on-line isotope dilution in LA-ICP-MS on two different types of sample material (NIST glass SRM 612 and NIST apple leaves SRM 1515) will be described.

  5. Isotope dilution analysis of Se in human blood serum by using high-power nitrogen microwave-induced plasma mass spectrometry coupled with a hydride generation technique.

    PubMed

    Ohata, M; Ichinose, T; Furuta, N; Shinohara, A; Chiba, M

    1998-07-01

    To establish a method for sensitive, accurate, and precise determination of Se in real samples, isotope dilution analysis using high-power nitrogen microwave-induced plasma mass spectrometry (N2 MIP-IDMS) was conducted. In this study, freeze-dried human blood serum (Standard Reference Material, NIES No. 4) provided by NIES (National Institute for Environmental Studies) was used as a real sample. The measured isotopes of Se were 78Se and 80Se which are the major isotopes of Se. The appropriate amount of a Se spike solution was theoretically calculated by using an error multiplication factor (F) and was confirmed experimentally for the isotope dilution analysis. The mass discrimination effect was corrected for by using a standard Se solution for the measurement of Se isotope ratios in the spiked sample. However, the sensitivity for the detection of Se was not so good and the precision of the determination was not improved (2-3%) by N2 MIP-IDMS with use of the conventional nebulizer. Therefore, a hydride generation system was connected to N2 MIP-IDMS as a sample introduction system (HG-N2 MIP-IDMS) in order to establish a more sensitive detection and a more precise determination of Se. A detection limit (3 sigma) of 10 pg mL-1 could be achieved, and the RSD was less than 1% at the concentration level of 5.0-10.0 ng mL-1 by HG-N2 MIP-IDMS. The analytical results were found to be in a good agreement with those obtained by the standard addition method using conventional Ar ICPMS. PMID:9666737

  6. Reference measurements for total mercury and methyl mercury content in marine biota samples using direct or species-specific isotope dilution inductively coupled plasma mass spectrometry.

    PubMed

    Krata, Agnieszka; Vassileva, Emilia; Bulska, Ewa

    2016-11-01

    The analytical procedures for reference measurements of the total Hg and methyl mercury (MeHg) mass fractions at various concentration levels in marine biota samples, candidates for certified reference materials (oyster and clam Gafrarium tumidum), were evaluated. Two modes of application of isotope dilution inductively coupled plasma mass spectrometry method (ID ICP-MS), namely direct isotope dilution and species-specific isotope dilution analysis with the use of two different quantification mass spectrometry techniques were compared. The entire ID ICP-MS measurement procedure was described by mathematical modelling and the combined uncertainty of measurement results was estimated. All factors influencing the final results as well as isotopic equilibrium were systematically investigated. This included the procedural blank, the moisture content in the biota samples and all factors affecting the blend ratio measurements (instrumental background, spectral interferences, dead time and mass discrimination effects as well as the repeatability of measured isotopic ratios). Modelling of the entire measurement procedures and the use of appropriate certified reference materials enable to assure the traceability of obtained values to the International System of Units (SI): the mole or the kilogram. The total mass fraction of mercury in oyster and clam biota samples, after correction for moisture contents, was found to be: 21.1 (1.1) 10(-9) kg kg(-1) (U =5.1% relative, k=2) and 390.0 (9.4) 10(-9) kg kg(-1) (U=2.4% relative, k=2), respectively. For the determination of mercury being present as methyl mercury, the non-chromatographic separation on anion-exchange resin AG1-X8 of the blended samples was applied. The content of MeHg (as Hg) in oyster sample was found: 4.81 (24) 10(-9)kgkg(-1) (U=5.0%, k=2) and 4.84 (21) 10(-9)kgkg(-1) (U=4.3%, k=2) with the use of quadrupole (ICP QMS) or sector field (ICP SFMS) inductively coupled plasma mass spectrometers, respectively. In the

  7. Molecular speciated isotope dilution mass spectrometric methods for accurate, reproducible and direct quantification of reduced, oxidized and total glutathione in biological samples.

    PubMed

    Fahrenholz, Timothy; Wolle, Mesay Mulugeta; Kingston, H M Skip; Faber, Scott; Kern, John C; Pamuku, Matt; Miller, Logan; Chatragadda, Hemasudha; Kogelnik, Andreas

    2015-01-20

    Novel protocols were developed to accurately quantify reduced (GSH), oxidized (GSSG) and total (tGSH) glutathione in biological samples using molecular speciated isotope dilution mass spectrometry (SIDMS). For GSH and GSSG measurement, the sample was spiked with isotopically enriched analogues of the analytes ((310)GSH and (616)GSSG), along with N-ethylmaleimide (NEM), and treated with acetonitrile to solubilize the endogenous analytes via protein precipitation and equilibrate them with the spikes. The supernatant was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the analytes were quantified with simultaneous tracking and correction for auto-oxidation of GSH to GSSG. For tGSH assay, a (310)GSH-spiked sample was treated with dithiothreitol (DTT) to convert disulfide-bonded glutathione to GSH. After removing the protein, the supernatant was analyzed by LC-MS/MS and the analyte was quantified by single-spiking isotope dilution mass spectrometry (IDMS). The mathematical relationships in IDMS and SIDMS quantifications are based on isotopic ratios and do not involve calibration curves. The protocols were validated using spike recovery tests and by analyzing synthetic standard solutions. Red blood cell (RBC) and saliva samples obtained from healthy subjects, and whole blood samples collected and shipped from a remote location were analyzed. The concentrations of tGSH in the RBC and whole blood samples were 2 orders of magnitude higher than those found in saliva. The fractions of GSSG were 0.2-2.2% (RBC and blood) and 15-47% (saliva) of the free glutathione (GSH + 2xGSSG) in the corresponding samples. Up to 3% GSH was auto-oxidized to GSSG during sample workup; the highest oxidations (>1%) were in the saliva samples. PMID:25519489

  8. Determination of the alkylpyrazine composition of coffee using stable isotope dilution-gas chromatography-mass spectrometry (SIDA-GC-MS).

    PubMed

    Pickard, Stephanie; Becker, Irina; Merz, Karl-Heinz; Richling, Elke

    2013-07-01

    A stable isotope dilution analysis based on gas chromatography-mass spectrometry analysis (SIDA-GC-MS) was developed for the quantitative analysis of 12 alkylpyrazines found in commercially available coffee samples. These compounds contribute to coffee flavor. The accuracy of this method was tested by analyzing model mixtures of alkylpyrazines. Comparisons of alkylpyrazine-concentrations suggested that water as extraction solvent was superior to dichloromethane. The distribution patterns of alkylpyrazines in different roasted coffees were quite similar. The most abundant alkylpyrazine in each coffee sample was 2-methylpyrazine, followed by 2,6-dimethylpyrazine, 2,5-dimethylpyrazine, 2-ethylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-5-methylpyrazine, and 2,3,5-trimethylpyrazine, respectively. Among the alkylpyrazines tested, 2,3-dimethylpyrazine, 2-ethyl-3-methylpyrazine, 2-ethyl-3,6-dimethylpyrazine, and 2-ethyl-3,5-dimethylpyrazine revealed the lowest concentrations in roasted coffee. By the use of isotope dilution analysis, the total concentrations of alkylpyrazines in commercially available ground coffee ranged between 82.1 and 211.6 mg/kg, respectively. Decaffeinated coffee samples were found to contain lower amounts of alkylpyrazines than regular coffee samples by a factor of 0.3-0.7, which might be a result of the decaffeination procedure. PMID:23745606

  9. Determination of trace sulfur in biodiesel and diesel standard reference materials by isotope dilution sector field inductively coupled plasma mass spectrometry.

    PubMed

    Amais, Renata S; Long, Stephen E; Nóbrega, Joaquim A; Christopher, Steven J

    2014-01-01

    A method is described for quantification of sulfur at low concentrations on the order of mgkg(-1) in biodiesel and diesel fuels using isotope dilution and sector field inductively coupled plasma mass spectrometry (ID-SF-ICP-MS). Closed vessel microwave-assisted digestion was employed using a diluted nitric acid and hydrogen peroxide decomposition medium to reduce sample dilution volumes. Medium resolution mode was employed to eliminate isobaric interferences at (32)S and (34)S related to polyatomic phosphorus and oxygen species, and sulfur hydride species. The method outlined yielded respective limits of detection (LOD) and limits of quantification (LOQ) of 0.7 mg kg(-1) S and 2.5 mg kg(-1) S (in the sample). The LOD was constrained by instrument background counts at (32)S but was sufficient to facilitate value assignment of total S mass fraction in NIST SRM 2723b Sulfur in Diesel Fuel Oil at 9.06±0.13 mg kg(-1). No statistically significant difference at a 95% confidence level was observed between the measured and certified values for certified reference materials NIST SRM 2773 B100 Biodiesel (Animal-Based), CENAM DRM 272b and NIST SRM 2723a Sulfur in Diesel Fuel Oil, validating method accuracy. PMID:24331043

  10. Determination of 90Sr / 238U ratio by double isotope dilution inductively coupled plasma mass spectrometer with multiple collection in spent nuclear fuel samples with in situ 90Sr / 90Zr separation in a collision-reaction cell

    NASA Astrophysics Data System (ADS)

    Isnard, H.; Aubert, M.; Blanchet, P.; Brennetot, R.; Chartier, F.; Geertsen, V.; Manuguerra, F.

    2006-02-01

    Strontium-90 is one of the most important fission products generated in nuclear industry. In the research field concerning nuclear waste disposal in deep geological environment, it is necessary to quantify accurately and precisely its concentration (or the 90Sr / 238U atomic ratio) in irradiated fuels. To obtain accurate analysis of radioactive 90Sr, mass spectrometry associated with isotope dilution is the most appropriated method. But, in nuclear fuel samples the interference with 90Zr must be previously eliminated. An inductively coupled plasma mass spectrometer with multiple collection, equipped with an hexapole collision cell, has been used to eliminate the 90Sr / 90Zr interference by addition of oxygen in the collision cell as a reactant gas. Zr + ions are converted into ZrO +, whereas Sr + ions are not reactive. A mixed solution, prepared from a solution of enriched 84Sr and a solution of enriched 235U was then used to quantify the 90Sr / 238U ratio in spent fuel sample solutions using the double isotope dilution method. This paper shows the results, the reproducibility and the uncertainties that can be obtained with this method to quantify the 90Sr / 238U atomic ratio in an UOX (uranium oxide) and a MOX (mixed oxide) spent fuel samples using the collision cell of an inductively coupled plasma mass spectrometer with multiple collection to perform the 90Sr / 90Zr separation. A comparison with the results obtained by inductively coupled plasma mass spectrometer with multiple collection after a chemical separation of strontium from zirconium using a Sr spec resin (Eichrom) has been performed. Finally, to validate the analytical procedure developed, measurements of the same samples have been performed by thermal ionization mass spectrometry, used as an independent technique, after chemical separation of Sr.

  11. CARDIO--a Lotus 1-2-3 based computer program for rapid calculation of cardiac output from dye or thermal dilution curves.

    PubMed

    Brill, R W; Bushnell, P G

    1989-01-01

    We have developed a menu-driven computer program (CARDIO), based on a Lotus 1-2-3 template and a series of macrocommands, that rapidly and semiautomatically calculates cardiac output from dye or thermal dilution curves. CARDIO works with any dye or thermal dilution recorder with an analog output, any analog to digital (A-to-D) conversion system, and any computer capable of running Lotus 1-2-3 version 2. No prior experience with Lotus 1-2-3 is needed to operate CARDIO, but experienced users can take full advantage of Lotus 1-2-3's graphics, data manipulation, and data retrieval capabilities. PMID:2689079

  12. Liquid-phase thermal diffusion isotope separation apparatus and method having tapered column

    DOEpatents

    Rutherford, William M.

    1988-05-24

    A thermal diffusion counterflow method and apparatus for separating isotopes in solution in which the solution is confined in a long, narrow, vertical slit which tapers from bottom to top. The variation in the width of the slit permits maintenance of a stable concentration distribution with relatively long columns, thus permitting isotopic separation superior to that obtainable in the prior art.

  13. Liquid-phase thermal diffusion isotope separation apparatus and method having tapered column

    DOEpatents

    Rutherford, W.M.

    1985-12-04

    A thermal diffusion counterflow method and apparatus for separating isotopes in solution in which the solution is confined in a long, narrow, vertical slit which tapers from bottom to top. The variation in the width of the slit permits maintenance of a stable concentration distribution with relatively long columns, thus permitting isotopic separation superior to that obtained in the prior art.

  14. Unusual isotope effect on thermal transport of single layer molybdenum disulphide

    SciTech Connect

    Wu, Xufei; Yang, Nuo; Luo, Tengfei

    2015-11-09

    Thermal transport in single layer molybdenum disulfide (MoS{sub 2}) is critical to advancing its applications. In this paper, we use molecular dynamics simulations with first-principles force constants to study the isotope effect on the thermal transport of single layer MoS{sub 2}. Through phonon modal analysis, we found that isotopes can strongly scatter phonons with intermediate frequencies, and the scattering behavior can be radically different from that predicted by conventional scattering model based on perturbation theory, where Tamura's formula is combined with Matthiessen's rule to include isotope effects. Such a discrepancy becomes smaller for low isotope concentrations. Natural isotopes can lead to a 30% reduction in thermal conductivity for large size samples. However, for small samples where boundary scattering becomes significant, the isotope effect can be greatly suppressed. It was also found that the Mo isotopes, which contribute more to the phonon eigenvectors in the intermediate frequency range, have stronger impact on thermal conductivity than S isotopes.

  15. Isotope Production Facility Conceptual Thermal-Hydraulic Design Review and Scoping Calculations

    SciTech Connect

    Pasamehmetoglu, K.O.; Shelton, J.D.

    1998-08-01

    The thermal-hydraulic design of the target for the Isotope Production Facility (IPF) is reviewed. In support of the technical review, scoping calculations are performed. The results of the review and scoping calculations are presented in this report.

  16. Analysis of trace metals (Cu, Cd, Pb, and Fe) in seawater using single batch nitrilotriacetate resin extraction and isotope dilution inductively coupled plasma mass spectrometry.

    PubMed

    Lee, Jong-Mi; Boyle, Edward A; Echegoyen-Sanz, Yolanda; Fitzsimmons, Jessica N; Zhang, Ruifeng; Kayser, Richard A

    2011-02-01

    A simple and accurate low-blank method has been developed for the analysis of total dissolved copper, cadmium, lead, and iron in a small volume (1.3-1.5 mL per element) of seawater. Pre-concentration and salt-separation of a stable isotope spiked sample are achieved by single batch extraction onto nitrilotriacetate (NTA)-type Superflow(®) chelating resin beads (100-2400 beads depending on the element). Metals are released into 0.1-0.5 M HNO(3), and trace metal isotope ratios are determined by ICPMS. The benefit of this method compared to our previous Mg(OH)(2) coprecipitation method is that the final matrix is very dilute so cone-clogging and matrix sensitivity suppression are minimal, while still retaining the high accuracy of the isotope dilution technique. Recovery efficiencies are sensitive to sample pH, number of resin beads added, and the length of time allowed for sample-resin binding and elution; these factors are optimized for each element to yield the highest recovery. The method has a low procedural blank and high sensitivity sufficient for the analysis of pM-nM open-ocean trace metal concentrations. Application of this method to samples from the Bermuda Atlantic Time-Series Study station provides oceanographically consistent Cu, Cd, Pb, and Fe profiles that are in good agreement with other reliable data for this site. In addition, the method can potentially be modified for the simultaneous analysis of multiple elements, which will be beneficial for the analysis of large number of samples. PMID:21237313

  17. Thermal neutron capture cross sections of the potassium isotopes

    NASA Astrophysics Data System (ADS)

    Firestone, R. B.; Krtička, M.; Révay, Zs.; Szentmiklosi, L.; Belgya, T.

    2013-02-01

    Precise thermal neutron capture γ-ray cross sections σγ for 39,40,41K were measured on a natural potassium target with the guided neutron beam at the Budapest Reactor. The cross sections were internally standardized using a stoichiometric KCl target with well-known 35Cl(n,γ) γ-ray cross sections [Révay and Molnár, Radiochimica ActaRAACAP0033-823010.1524/ract.91.6.361.20027 91, 361 (2003); Molnár, Révay, and Belgya, Nucl. Instrum. Meth. Phys. Res. BNIMBEU0168-583X10.1016/S0168-583X(03)01529-5 213, 32 (2004)]. These data were combined with γ-ray intensities from von Egidy [von Egidy, Daniel, Hungerford, Schmidt, Lieb, Krusche, Kerr, Barreau, Borner, Brissot , J. Phys. G. Nucl. Phys.JPHGBM0305-461610.1088/0305-4616/10/2/013 10, 221 (1984)] and Krusche [Krusche, Lieb, Ziegler, Daniel, von Egidy, Rascher, Barreau, Borner, and Warner, Nucl. Phys. ANUPABL0375-947410.1016/0375-9474(84)90506-2 417, 231 (1984); Krusche, Winter, Lieb, Hungerford, Schmidt, von Egidy, Scheerer, Kerr, and Borner, Nucl. Phys. ANUPABL0375-947410.1016/0375-9474(85)90429-4 439, 219 (1985)] to generate nearly complete capture γ-ray level schemes. Total radiative neutron cross sections were deduced from the total γ-ray cross section feeding the ground state, σ0=Σσγ(GS) after correction for unobserved statistical γ-ray feeding from levels near the neutron capture energy. The corrections were performed with Monte Carlo simulations of the potassium thermal neutron capture decay schemes using the computer code dicebox where the simulated populations of low-lying levels are normalized to the measured cross section depopulating those levels. Comparisons of the simulated and experimental level feeding intensities have led to proposed new spins and parities for selected levels in the potassium isotopes where direct reactions are not a significant contribution. We determined the total radiative neutron cross sections σ0(39K)=2.28±0.04 b, σ0(40K)=90±7 b, and σ0(41K)=1.62±0.03 b from the

  18. First principles study of lattice thermal conductivity and large isotope effect in materials

    NASA Astrophysics Data System (ADS)

    Broido, David; Lindsay, Lucas; Reinecke, Tom

    2014-03-01

    The isotope effect--the percent enhancement to a material's lattice thermal conductivity, k, with isotopic purification--depends on the interplay between phonon-isotope and phonon-phonon scattering. Diamond is known to have the largest measured room temperature (RT) isotope effect of any bulk crystal, achieving a k enhancement of 50%. Using an ab initioBoltzmann transport equation approach, we have identified several other materials with far larger RT isotope effects. In particular, we find that germanium carbide (GeC) and beryllium selenide (BeSe) have RT isotope effects of 450%, almost an order of magnitude higher than that in diamond. Isotopic purification in these materials gives surprisingly high intrinsic RT k values, over 1500 Wm-1K-1 for GeC and over 600 Wm-1 K-1 for BeSe, well above those of the best metals. These large values stem from fundamental material properties that give both enhanced phonon scattering by isotopes and weak anharmonic phonon-phonon scattering. The physical insights discussed in this work provide guidance for efficient manipulation of thermal transport properties of compound semiconductors through isotopic modification. This work was supported by ONR, DARPA and NSF.

  19. Assessment of the amount of body water in the Red Knot (Calidris canutus): an evaluation of the principle of isotope dilution with 2H, (17)O, and (18)O as measured with laser spectrometry and isotope ratio mass spectrometry.

    PubMed

    Kerstel, Erik R T; Piersma, Theunis; Piersma, Theunis A J; Gessaman, James A; Gessaman, G Jim; Dekinga, Anne; Meijer, Harro A J; Visser, G Henk

    2006-03-01

    We have used the isotope dilution technique to study changes in the body composition of a migratory shorebird species (Red Knot, Calidris canutus) through an assessment of the amount of body water in it. Birds were quantitatively injected with a dose of water with elevated concentrations of 2H, (17)O, and (18)O. Thereafter, blood samples were taken and distilled. The resulting water samples were analysed using an isotope ratio mass spectrometry (for 2H and (18)O only) and a stable isotope ratio infrared laser spectrometry (2H, (17)O, and (18)O) to yield estimates of the amount of body water in the birds, which in turn could be correlated to the amount of body fat. Here, we validate laser spectrometry against mass spectrometry and show that all three isotopes may be used for body water determinations. This opens the way to the extension of the doubly labelled water method, used for the determination of energy expenditure, to a triply labelled water method, incorporating an evaporative water loss correction on a subject-by-subject basis or, alternatively, the reduction of the analytical errors by statistically combining the (17)O and (18)O measurements. PMID:16500750

  20. Isotope dilution mass spectrometry for quantitative elemental analysis of powdered samples by radiofrequency pulsed glow discharge time of flight mass spectrometry.

    PubMed

    Alvarez-Toral, Aitor; Fernandez, Beatriz; Malherbe, Julien; Claverie, Fanny; Molloy, John L; Pereiro, Rosario; Sanz-Medel, Alfredo

    2013-10-15

    In recent years particular effort is being devoted to the development of pulsed glow discharges (PGDs) for mass spectrometry because this powering operation mode could offer important ionization analytical advantages. However, the capabilities of radiofrequency (RF) PGD coupled to a time of flight mass spectrometry (ToFMS) for accurate isotope ratio measurements have not been demonstrated yet. This work is focused on investigating different time positions along the pulse profile for the accurate measurement of isotope ratios. As a result, a method has been developed for the direct and simultaneous multielement determination of trace elements in powdered geological samples by RF-PGD-ToFMS in combination with isotope dilution mass spectrometry (IDMS) as an absolute measurement method directly traceable to the International System of Units. Optimized operating conditions were 70 W of applied radiofrequency power, 250 Pa of pressure, 2 ms of pulse width and 4 ms of pulse period, being argon the plasma gas used. To homogeneously distribute the added isotopically-enriched standards, lithium borate fusion of powdered solid samples was used as sample preparation approach. In this way, Cu, Zn, Ba and Pb were successfully determined by RF-PGD-ToF(IDMS) in two NIST Standard Reference Materials (SRM 2586 and SRM 2780) representing two different matrices of geological interest (soil and rock samples). Cu, Zn, Ba and Pb concentrations determined by RF-PGD-ToF(IDMS) were well in agreement with the certified values at 95% confidence interval and precisions below 12% relative standard deviation were observed for three independent analyses. Elemental concentrations investigated were in the range of 81-5770 mg/kg, demonstrating the potential of RF-PGD-ToF(IDMS) for a sensitive, accurate and robust analysis of powdered samples. PMID:24054645

  1. Quantification of cysteine S-conjugate of 3-sulfanylhexan-1-ol in must and wine of petite arvine vine by stable isotope dilution analysis.

    PubMed

    Luisier, Jean-Luc; Buettner, Hermann; Völker, Sebastian; Rausis, Thierry; Frey, Urban

    2008-05-14

    Making use of a convenient synthetic approach to prepare the deuterated S-3-(hexan-1-ol)-cysteine by a Michael addition reaction, an analytical method was developed to measure the presence of the cysteine S-conjugate, precursor of 3-sulfanylhexan-1-ol (3-mercaptohexan-1-ol), in must and wine from Petite Arvine vine. The method uses a stable isotope dilution assay with a suitable one-step sample preparation and HPLC-MS detection. The method has limits of detection and quantification of 3 and 10 microg/L, respectively. A correlation between the increase of the precursor concentration and the increase of the degree of rot has been established. PMID:18416552

  2. Assessing the 210At impurity in the production of 211At for radiotherapy by 210Po analysis via isotope dilution alpha spectrometry.

    PubMed

    Schultz, Michael K; Hammond, Michelle; Cessna, Jeffrey T; Plascjak, Paul; Norman, Bruce; Szajek, Lawrence; Garmestani, Kayhan; Zimmerman, Brian E; Unterweger, Michael

    2006-01-01

    A method for assessing the impurity 210At in cyclotron-produced 211At via isotope dilution alpha spectrometry is presented. The activity of 210At is quantified by measuring the activity of daughter nuclide 210Po. Counting sources are prepared by spontaneous deposition of Po on a silver disc. Activity of 210At (at the time of 210Po maximum activity) is found to be 83.5+/-9.0 Bq, corresponding to an atom ratio (210At:211At at the time of distillation) of 0.010+/-0.007% (k=2). The method produces high-quality alpha spectra, with baseline alpha-peak resolution and chemical yields of greater than 85%. PMID:16563782

  3. A stable-isotope dilution GC-MS approach for the analysis of DFRC (derivatization followed by reductive cleavage) monomers from low-lignin plant materials.

    PubMed

    Schäfer, Judith; Urbat, Felix; Rund, Katharina; Bunzel, Mirko

    2015-03-18

    The derivatization followed by reductive cleavage (DFRC) method is a well-established tool to characterize the lignin composition of plant materials. However, the application of the original procedure, especially the chromatographic determination of the DFRC monomers, is problematic for low-lignin foods. To overcome these problems a modified sample cleanup and a stable-isotope dilution approach were developed and validated. To quantitate the diacetylated DFRC monomers, their corresponding hexadeuterated analogs were synthesized and used as internal standards. By using the selected-ion monitoring mode, matrix-associated interferences can be minimized resulting in higher selectivity and sensitivity. The modified method was applied to four low-lignin samples. Lignin from carrot fibers was classified as guaiacyl-rich whereas the lignins from radish, pear, and asparagus fibers where classified as balanced lignins (guaiacyl/syringyl ratio=1-2). PMID:25727138

  4. Quantification by solid phase micro extraction and stable isotope dilution assay of norisoprenoid compounds in red wines obtained from Piedmont rare varieties.

    PubMed

    Petrozziello, Maurizio; Borsa, Daniela; Guaita, Massimo; Gerbi, Vincenzo; Bosso, Antonella

    2012-12-15

    A method to identify and quantify megastigmane norisoprenoid compounds in wines was developed using headspace solid phase micro extraction (SPME) coupled with gas-chromatography/mass-spectrometry (GC-MS). Three different compounds were quantified by stable isotope dilution assay (SIDA): β-damascenone, β-ionone and α-ionone. Particular attention was paid to maximising the method's sensitivity while reducing the extraction time. To optimise the extraction conditions, a statistically designed experiment was performed using extraction time, extraction temperature and ethanol content as operating variables. Five different SPME fibres suitable for the analysis of volatile compounds were compared. This study confirmed that the PDMS/DVB coating performs best for the quantification of β-damascenone and β-ionone, and the crucial influence of ethanol content of the sample on extraction effectiveness. Finally, the optimised method was applied to the study of various wines derived from rare and autochthonous grape varieties of north-western Italy. PMID:22980832

  5. Impact of isotopic disorders on thermal transport properties of nanotubes and nanowires

    SciTech Connect

    Sun, Tao; Kang, Wei; Wang, Jianxiang

    2015-01-21

    We present a one-dimensional lattice model to describe thermal transport in isotopically doped nanotubes and nanowires. The thermal conductivities thus predicted, as a function of isotopic concentration, agree well with recent experiments and other simulations. Our results display that for any given concentration of isotopic atoms in a lattice without sharp atomic interfaces, the maximum thermal conductivity is attained when isotopic atoms are placed regularly with an equal space, whereas the minimum is achieved when they are randomly inserted with a uniform distribution. Non-uniformity of disorder can further tune the thermal conductivity between the two values. Moreover, the dependence of the thermal conductivity on the nanoscale feature size becomes weak at low temperature when disorder exists. In addition, when self-consistent thermal reservoirs are included to describe diffusive nanomaterials, the thermal conductivities predicted by our model are in line with the results of macroscopic theories with an interfacial effect. Our results suggest that the disorder provides an additional freedom to tune the thermal properties of nanomaterials in many technological applications including nanoelectronics, solid-state lighting, energy conservation, and conversion.

  6. Light stable isotope study of the Roosevelt Hot Springs thermal area, Southwestern Utah

    SciTech Connect

    Rohrs D.T.; Bowman, J.R.

    1980-05-01

    The isotopic composition of hydrogen, oxygen, and carbon has been determined for regional cold springs, thermal fluids, and rocks and minerals from the Roosevelt Hot Springs thermal area. The geothermal system has developed within plutonic granitic rocks and amphibolite facies gneiss, relying upon fracture-controlled permeability for the migration of the thermal fluids. Probably originating as meteoric waters in the upper elevations of the Mineral Mountains, the thermal waters sampled in the production wells display an oxygen isotopic shift of at least +1.2. Depletions of delta /sup 18/O in wole rock, K-feldspar, and biotite have a positive correlation with alteration intensity. W/R mass ratios, calculated from the isotopic shifts of rock and water, range up to 3.0 in a producing horizon of one well, although the K-feldspar has experienced only 30% exchange with the thermal waters. While veinlet quartz has equilibrated with the thermal waters, the /sup 18/O values of K-mica clay, an alteration product of plagioclase, mimic the isotopic composition of K-feldspar and whole rock. This suggests that locally small W/R ratios enable plagioclase to influence its alteration products by isotopic exchange.

  7. Validation of an isotope dilution gas chromatography-mass spectrometry method for combined analysis of oxysterols and oxyphytosterols in serum samples.

    PubMed

    Schött, Hans-Frieder; Lütjohann, Dieter

    2015-07-01

    We describe the validation of a method for the analysis of oxysterols, i.e. oxycholesterols and oxyphytosterols, in human serum using gas chromatography-mass spectrometry selected ion monitoring (GC-MS-SIM). Concentrations of 7α- and 7β-hydroxy-, and 7oxo-cholesterol, -campesterol, and -sitosterol as well as 4β-hydroxycholesterol and side-chain oxygenated 24S-, 25-, and 27-hydroxycholesterol were determined by isotope dilution methodology. After saponification at room temperature the oxysterols were extracted, separated from their substrates, cholesterol, campesterol, and sitosterol, by solid phase extraction, and subsequently derivatised to their corresponding trimethylsilyl-ethers prior to GC-MS-SIM. In order to prevent artificial autoxidation butylated hydroxytoluene and ethylenediaminetetraacetic acid were added. The validation of the method was performed according to the International Conference on Harmonisation guidance, including limits of detection and quantification, ranges, recovery and precision. Due to improved instrumental settings and work-up procedure, limits of detection and quantification ranged between 8.0-202.0pg/mL and 28.0-674pg/mL, respectively. Recovery data in five calibration points varied between 91.9% and 116.8% and in serum samples between 93.1% and 118.1%. The mean coefficient of variation (CV) for the recovery of all compounds was <10%. Well satisfying CVs for within-day precision (2.1-10.8%) and for between-day precision (2.3-12.1%) were obtained. More than 20 samples could be processed in a single routine day and test series of about 300 samples can be realised without impairment of the validation parameters during a sequence. Comparison of oxysterol and oxyphytosterol content in serum and plasma revealed no difference. A fully validated isotope dilution methodology for the quantification of oxycholesterols and oxyphytosterols from human serum or plasma is presented. PMID:25701095

  8. Quantification of carcinogenic 4- to 6-ring polycyclic aromatic hydrocarbons in human urine by solid-phase microextraction gas chromatography-isotope dilution mass spectrometry.

    PubMed

    Campo, Laura; Fustinoni, Silvia; Bertazzi, Pieralberto

    2011-08-01

    Polycyclic aromatic hydrocarbons (PAHs) are pollutants found in living and working environments. The aim of this study was to develop a solid-phase microextraction (SPME) gas chromatography (GC)-isotope dilution mass spectrometry method for the quantification of 10 four- to six-ring PAHs in urine samples. Seven of the selected PAHs have been classified as carcinogenic. Under the final conditions, analytes were sampled with a 100-μm polydimethylsiloxane SPME fibre for 60 min at 80 °C and desorbed in the injection port of the GC at 270 °C. Fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene were separated using a highly arylene-modified phase capillary column and quantified by MS using eight deuterated PAHs as surrogate internal standards. Limits of quantification (LOQ) were in the 0.5- to 2.2-ng/L range. Validation showed linear dynamic ranges up to 340 ng/L, inter- and intra-run precisions <20%, and accuracies within 20% of spiked concentrations. Matrix effect evaluation and the use of control charts to monitor process performances showed that the isotope dilution approach allowed for the control of bias sources. Urinary PAHs were above or equal to LOQ, depending on different compounds, in 58-100% (min-max), 40-100% and 5-39% of samples from coke oven workers (n = 12), asphalt workers (n = 10) and individuals not occupationally exposed to PAHs (n = 18), respectively. Chrysene was the most abundant PAH determined with median levels of 62.6, 6.9 and <0.6 ng/L, respectively. These results show that the method is suitable for quantifying carcinogenic PAHs in specimens from individuals with different levels of PAH exposure. PMID:21626187

  9. Inoculation of Bacillus sphaericus UPMB-10 to Young Oil Palm and Measurement of Its Uptake of Fixed Nitrogen Using the 15N Isotope Dilution Technique

    PubMed Central

    Zakry, Fitri Abdul Aziz; Shamsuddin, Zulkifli H.; Rahim, Khairuddin Abdul; Zakaria, Zin Zawawi; Rahim, Anuar Abdul

    2012-01-01

    There are increasing applications of diazotrophic rhizobacteria in the sustainable agriculture system. A field experiment on young immature oil palm was conducted to quantify the uptake of N derived from N2 fixation by the diazotroph Bacillus sphaericus strain UPMB-10, using the 15N isotope dilution method. Eight months after 15N application, young immature oil palms that received 67% of standard N fertilizer application together with B. sphaericus inoculation had significantly lower 15N enrichment than uninoculated palms that received similar N fertilizers. The dilution of labeled N served as a marker for the occurrence of biological N2 fixation. The proportion of N uptake that was derived from the atmosphere was estimated as 63% on the whole plant basis. The inoculation process increased the N and dry matter yields of the palm leaflets and rachis significantly. Field planting of young, immature oil palm in soil inoculated with B. sphaericus UPMB-10 might mitigate inorganic fertilizer-N application through supplementation by biological nitrogen fixation. This could be a new and important source of nitrogen biofertilizer in the early phase of oil palm cultivation in the field. PMID:22446306

  10. Geochemistry and isotope geochemistry of the Monfalcone thermal waters (northern Italy): inference on the deep geothermal reservoir

    NASA Astrophysics Data System (ADS)

    Petrini, R.; Italiano, F.; Ponton, M.; Slejko, F. F.; Aviani, U.; Zini, L.

    2013-09-01

    Geochemical investigations were carried out to define the origin of the low- to moderate-temperature thermal waters feeding the Monfalcone springs in northern Italy. Chemical data indicate that waters approach the composition of seawater. Mixing processes with cold low-salinity waters are highlighted. The δ18O and δD values are in the range -5.0 to -6.4 ‰, and -33 to -40 ‰, respectively, suggesting the dilution of the saline reservoir by karst-type freshwaters. A surplus of Ca2+ and Sr2+ ions with respect to a conservative mixing is ascribed to diagenetic reactions of the thermal waters with Cretaceous carbonates at depth. The measured Sr isotopic composition (87Sr/86Sr ratio) ranges between 0.70803 and 0.70814; after correction for the surplus Sr, a 87Sr/86Sr ratio indicating Miocene paleo-seawater is obtained. The dissolved gases indicate long-lasting gas-water interactions with a deep-originated gas phase of crustal origin, dominated by CO2 and marked by a water TDIC isotopic composition in the range -5.9 to-8.8 and helium signature with 0.08 < R/Ra < 0.27, which is a typical range for the crust. A possible scenario for the Monfalcone thermal reservoir consists of Miocene marine paleowaters which infiltrated through the karstic voids formed within the prevalently Cretaceous carbonates during the upper Eocene emersion of the platform, and which were entrapped by the progressive burial by terrigenous sediments.

  11. Ultra-trace level speciated isotope dilution measurement of Cr(VI) using ion chromatography tandem mass spectrometry in environmental waters.

    PubMed

    Mädler, Stefanie; Todd, Aaron; Skip Kingston, H M; Pamuku, Matt; Sun, Fengrong; Tat, Cindy; Tooley, Robert J; Switzer, Teresa A; Furdui, Vasile I

    2016-08-15

    The reliable analysis of highly toxic hexavalent chromium, Cr(VI), at ultra-trace levels remains challenging, given its easy conversion to non-toxic trivalent chromium. This work demonstrates a novel analytical method to quantify Cr(VI) at low ngL(-1) concentration levels in environmental water samples by using speciated isotope dilution (SID) analysis and double-spiking with Cr(III) and Cr(VI) enriched for different isotopes. Ion chromatography tandem mass spectrometry (IC-MS/MS) was used for the analysis of Cr(VI) as HCrO4(-) → CrO3(-). Whereas the classical linear multipoint calibration (MPC) curve approach obtained a method detection limit (MDL) of 7ngL(-1) Cr(VI), the modified SID-MS method adapted from U. S. EPA 6800 allowed for the quantification of Cr(VI) with an MDL of 2ngL(-1) and provided results corrected for Cr(VI) loss occurred after sample collection. The adapted SID-MS approach proved to yield more accurate and precise results than the MPC method, allowed for compensation of Cr(VI) reduction during sample transportation and storage while eliminating the need for frequent external calibration. The developed method is a complementary tool to routinely used inductively-coupled plasma (ICP) MS and circumvents typically experienced interferences. PMID:27260441

  12. Application of Microwave-Induced Combustion and Isotope Dilution Strategies for Quantification of Sulfur in Coals via Sector-Field Inductively Coupled Plasma Mass Spectrometry.

    PubMed

    Christopher, Steven J; Vetter, Thomas W

    2016-05-01

    In recent years, microwave-induced combustion (MIC) has proved to be a robust sample preparation technique for difficult-to-digest samples containing high carbon content, especially for determination of halogens and sulfur. National Institute of Standards and Technology (NIST) has applied the MIC methodology in combination with isotope dilution analysis for sulfur determinations, representing the first-reported combination of this robust sample preparation methodology and high-accuracy quantification approach. Medium-resolution mode sector-field inductively coupled plasma mass spectrometry was invoked to avoid spectral interferences on the sulfur isotopes. The sample preparation and instrumental analysis scheme was used for the value assignment of total sulfur in Standard Reference Material (SRM) 2682c Subbituminous Coal (nominal mass fraction 0.5% sulfur). A description of the analytical procedures required is provided, along with metrological results, including an estimation of the overall method uncertainty (<1.5% relative expanded uncertainty) calculated using the IDMS measurement function and a Kragten spreadsheet approach. PMID:27032706

  13. Simultaneous determination of PPCPs, EDCs, and artificial sweeteners in environmental water samples using a single-step SPE coupled with HPLC-MS/MS and isotope dilution.

    PubMed

    Tran, Ngoc Han; Hu, Jiangyong; Ong, Say Leong

    2013-09-15

    A high-throughput method for the simultaneous determination of 24 pharmaceuticals and personal care products (PPCPs), endocrine disrupting chemicals (EDCs) and artificial sweeteners (ASs) was developed. The method was based on a single-step solid phase extraction (SPE) coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and isotope dilution. In this study, a single-step SPE procedure was optimized for simultaneous extraction of all target analytes. Good recoveries (≥ 70%) were observed for all target analytes when extraction was performed using Chromabond(®) HR-X (500 mg, 6 mL) cartridges under acidic condition (pH 2). HPLC-MS/MS parameters were optimized for the simultaneous analysis of 24 PPCPs, EDCs and ASs in a single injection. Quantification was performed by using 13 isotopically labeled internal standards (ILIS), which allows correcting efficiently the loss of the analytes during SPE procedure, matrix effects during HPLC-MS/MS and fluctuation in MS/MS signal intensity due to instrument. Method quantification limit (MQL) for most of the target analytes was below 10 ng/L in all water samples. The method was successfully applied for the simultaneous determination of PPCPs, EDCs and ASs in raw wastewater, surface water and groundwater samples collected in a local catchment area in Singapore. In conclusion, the developed method provided a valuable tool for investigating the occurrence, behavior, transport, and the fate of PPCPs, EDCs and ASs in the aquatic environment. PMID:23708627

  14. Stable isotope dilution HILIC-MS/MS method for accurate quantification of glutamic acid, glutamine, pyroglutamic acid, GABA and theanine in mouse brain tissues.

    PubMed

    Inoue, Koichi; Miyazaki, Yasuto; Unno, Keiko; Min, Jun Zhe; Todoroki, Kenichiro; Toyo'oka, Toshimasa

    2016-01-01

    In this study, we developed the stable isotope dilution hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC-MS/MS) technique for the accurate, reasonable and simultaneous quantification of glutamic acid (Glu), glutamine (Gln), pyroglutamic acid (pGlu), γ-aminobutyric acid (GABA) and theanine in mouse brain tissues. The quantification of these analytes was accomplished using stable isotope internal standards and the HILIC separating mode to fully correct the intramolecular cyclization during the electrospray ionization. It was shown that linear calibrations were available with high coefficients of correlation (r(2)  > 0.999, range from 10 pmol/mL to 50 mol/mL). For application of the theanine intake, the determination of Glu, Gln, pGlu, GABA and theanine in the hippocampus and central cortex tissues was performed based on our developed method. In the region of the hippocampus, the concentration levels of Glu and pGlu were significantly reduced during reality-based theanine intake. Conversely, the concentration level of GABA increased. This result showed that transited theanine has an effect on the metabolic balance of Glu analogs in the hippocampus. PMID:26033549

  15. Measurement of intact sulfate and glucuronide phytoestrogen conjugates in human urine using isotope dilution liquid chromatography-tandem mass spectrometry with [13C(3)]isoflavone internal standards.

    PubMed

    Clarke, Don B; Lloyd, Antony S; Botting, Nigel P; Oldfield, Mark F; Needs, Paul W; Wiseman, Helen

    2002-10-01

    A method has been developed for the analysis of phytoestrogens and their conjugates in human urine using liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Stable isotopically labeled [13C(3)]daidzein and [13C(3)]genistein were synthesized and used as internal standards for isotope dilution mass spectrometry. Free aglycons and intact glucuronide, sulfate, diglucuronide, disulfate, and mixed sulfoglucuronide conjugates of isoflavones and lignans were observed in naturally incurred urine samples. Sample pretreatment was not necessary, other than addition of internal standards and pH adjustment. Urine was injected directly onto the analytical column. The limits of detection were generally <50ng/ml, precision was generally <10% CV for conjugates. Total hydrolyzed daidzein and genistein were measured against quality assurance urine sample and were accurate to within 12%. The accuracy of conjugate measurement can not be ascertained, as no reference samples are available. The mean sum of daidzein and its conjugates was within 20% of the hydrolyzed value. Concentrations of the free aglycons of up to 22% of genistein and 18% of daidzein were observed. The average pattern was ca. 54% 7-glucuronide, 25% 4(')-glucuronide, 13% monosulfates, 7% free daidzein, 0.9% sulfoglucuronides, 0.4% diglucuronide, and <0.1% disulfate. Selective enzymatic deconjugation with glucuronidase and mixed glucuronidase/sulfatase were used to validate the accuracy of the quantitation of the intact daidzein conjugates. There were no apparent sex differences, or conditioning effects on the conjugation profile of isoflavones after chronic dosing. PMID:12381375

  16. Measurement of methyl tert-butyl ether and tert-butyl alcohol in human blood by purge-and-trap gas chromatography-mass spectrometry using an isotope-dilution method.

    PubMed

    Bonin, M A; Ashley, D L; Cardinali, F L; McCraw, J M; Wooten, J V

    1995-01-01

    We developed an isotope-dilution method for measuring methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) in whole human blood using a purge-and-trap gas chromatographic-mass spectrometric method. The labeled analogues for MTBE and TBA were [2H12]methyl tert-butyl ether and [2H9]-tert-butyl alcohol, respectively. Volatiles were removed from the blood by direct helium purging of the liquid; were trapped on a Tenax trap; and were desorbed, cryofocused, and chromatographed on a DB-624 capillary column that was connected directly to the ion source of a mass spectrometer. Detection was by mass analysis using a double-focusing magnetic-sector mass spectrometer operating in the full-scan mode at the medium mass resolution of 3000. For the isotope-dilution method, the minimum detection limits in blood (5-10 mL) are 0.01 microgram/L for MTBE and 0.06 microgram/L for TBA. The isotope-dilution method proved to be a big improvement in recovery, reproducibility, and sensitivity over our previous analytical method, which used the labeled ketone, [4-2H3]-2-butanone, as the internal standard for both MTBE and TBA. The isotope-dilution method has sufficient sensitivity for monitoring blood levels of MTBE and TBA in populations exposed to oxygenated fuels containing MTBE. PMID:7564298

  17. Cadmium determination in natural waters at the limit imposed by European legislation by isotope dilution and TiO2 solid-phase extraction.

    PubMed

    García-Ruiz, Silvia; Petrov, Ivan; Vassileva, Emilia; Quétel, Christophe R

    2011-11-01

    The cadmium content in surface water is regulated by the last European Water Framework Directive to a maximum between 0.08 and 0.25 μg L(-1) depending on the water type and hardness. Direct measurement of cadmium at this low level is not straightforward in real samples, and we hereby propose a validated method capable of addressing cadmium content below μg L(-1) level in natural water. It is based on solid-phase extraction using TiO(2) nanoparticles as solid sorbent (0.05 g packed in mini-columns) to allow the separation and preconcentration of cadmium from the sample, combined to direct isotope dilution and detection by inductively coupled plasma mass spectrometry (ID-ICP-MS). The extraction setup is miniaturised and semi-automated to reduce risks of sample contamination and improve reproducibility. Procedural blanks for the whole measurement process were 5.3 ± 2.8 ng kg(-1) (1 s) for 50 g of ultrapure water preconcentrated ten times. Experimental conditions influencing the separation (including loading pH, sample flow rates, and acid concentration in the eluent) were evaluated. With isotope dilution the Cd recovery rate does not have to be evaluated carefully. Moreover, the mathematical model associated to IDMS is known, and provides transparency for the uncertainty propagation. Our validation protocol was in agreement with guidelines of the ISO/IEC 17025 standard (chapter 5.4.5). Firstly, we assessed the experimental factors influencing the final result. Secondly, we compared the isotope ratios measured after our separation procedure to the reference values obtained with a different protocol for the digested test material IMEP-111 (mineral feed). Thirdly, we analysed the certified reference material BCR-609 (groundwater). Finally, combined uncertainties associated to our results were estimated according to ISO-GUM guidelines (typically, 3-4% k = 2 for a cadmium content of around 100 ng kg(-1)). We applied the developed method to the groundwater and wastewater

  18. Isotope dilution quantification of ultratrace gamma-glutamyl-Se-methylselenocysteine species using HPLC with enhanced ICP-MS detection by ultrasonic nebulisation or carbon-loaded plasma.

    PubMed

    Goenaga Infante, Heidi; Ovejero Bendito, María del Carmen; Cámara, Carmen; Evans, Linda; Hearn, Ruth; Moesgaard, Sven

    2008-04-01

    A method for the accurate determination of ultratrace selenium species of relevance to cancer research, such as gamma-glutamyl-Se-methylselenocysteine (gamma-glutamyl-SeMC), using species-specific double isotope dilution analysis (IDA) with HPLC-ICP-MS is reported for the first time. The (77)Se-enriched gamma-glutamyl-SeMC spike was produced in-house by collecting the fraction at the retention time of the gamma-glutamyl-SeMC peak from a chromatographed aqueous extract of (77)Se-enriched yeast, pooling the collected fractions and freeze-drying the homogenate. The Se content of this spike was characterised using reverse isotope dilution mass spectrometry (IDMS) and the isotopic composition of this spike was checked prior to quantification of the natural abundance dipeptide species in garlic using speciated IDA. The extraction of the gamma-glutamyl-SeMC species in water was performed in a sonication bath for 2 h after adding an appropriate quantity of (77)Se-enriched gamma-glutamyl-SeMC to 50 mg of garlic to give optimal (78)Se/(77)Se and (82)Se/(77)Se ratios of 1.5 and 0.6, respectively. The effect of ultrasonic nebulisation, in comparison with the loading of the ICP with carbon (through the addition of methane gas on-line), on the detection of Se associated with gamma-glutamyl-SeMC using collision/reaction cell ICP-MS with hydrogen as collision gas was investigated. Sensitivity enhancements of approximately fourfold and twofold were achieved using USN and methane mixed plasma, respectively, in comparison with conventional nebulisation and conventional Ar ICP-MS. However, an approximately twofold improvement in the detection limit was achieved using both approaches (42 ng kg(-1) for (78)Se using peak height measurements). The use of species-specific IDMS enabled quantification of the dipeptide species at ng g(-1) levels (603 ng g(-1) Se) in the complex food matrix with a relative standard deviation (RSD, n = 4) of 4.5%, which was approximately half that obtained

  19. Significance of Isotopically Labile Organic Hydrogen in Thermal Maturation of Organic Matter

    SciTech Connect

    Arndt Schimmelmann; Maria Mastalerz

    2010-03-30

    Isotopically labile organic hydrogen in fossil fuels occupies chemical positions that participate in isotopic exchange and in chemical reactions during thermal maturation from kerogen to bitumen, oil and gas. Carbon-bound organic hydrogen is isotopically far less exchangeable than hydrogen bound to nitrogen, oxygen, or sulfur. We explore why organic hydrogen isotope ratios express a relationship with organic nitrogen isotope ratios in kerogen at low to moderate maturity. We develop and apply new techniques to utilize organic D/H ratios in organic matter fractions and on a molecular level as tools for exploration for fossil fuels and for paleoenvironmental research. The scope of our samples includes naturally and artificially matured substrates, such as coal, shale, oil and gas.

  20. Quantitation of S-methylmethionine in raw vegetables and green malt by a stable isotope dilution assay using LC-MS/MS: comparison with dimethyl sulfide formation after heat treatment.

    PubMed

    Scherb, Julia; Kreissl, Johanna; Haupt, Sonja; Schieberle, Peter

    2009-10-14

    The potent odorant dimethyl sulfide (1), showing a low odor threshold of 0.12 microg/L in water, is known to contribute to the aromas of various foods. Its cabbage-like odor plays an important role, particularly, in cooked vegetables, such as cabbage, celery, or asparagus. On the other hand, in fruit juices or beer, 1 may generate off-flavors. S-Methylmethionine (2) has previously been characterized as precursor of 1 during thermal processing, and several methods for its quantitation have been proposed. Using deuterium-labeled 2 as the internal standard, a stable isotope dilution assay (SIDA) using LC-MS/MS was developed for the fast quantitation of 2 in vegetables and malt. Application of the method to different foods revealed amounts between 2.8 mg (fresh tomatoes) and 176 mg (celery) of 2 per kilogram. To correlate the amount of 1 formed upon processing with the amounts of 2 present in the raw material, 1 was quantified before and after a thermal treatment of the same raw materials by a SIDA. Concentrations between 1.1 mg/kg (fresh tomatoes) and 26 mg/kg (celery) were determined in the processed samples. The quantitation of 2 during steeping, germination, and malting of barley, and a correlation of the data with the amounts of 1 formed after thermal treatment of the malt, resulted in yields between 24 and 27 mol % calculated on the basis of the amounts of 2. The results suggested that the extent of the formation of 1 can be predicted, for example, in plant materials, from the amount of 2 present in the raw foods. PMID:19754146

  1. Thermal Conductivity and Large Isotope Effect in GaN from First Principles

    SciTech Connect

    Lindsay, L.; Broido, D. A.; Reinecke, T. L.

    2012-08-28

    We present atomistic first principles results for the lattice thermal conductivity of GaN and compare them to those for GaP, GaAs, and GaSb. In GaN we find a large increase to the thermal conductivity with isotopic enrichment, ~65% at room temperature. We show that both the high thermal conductivity and its enhancement with isotopic enrichment in GaN arise from the weak coupling of heat-carrying acoustic phonons with optic phonons. This weak scattering results from stiff atomic bonds and the large Ga to N mass ratio, which give phonons high frequencies and also a pronounced energy gap between acoustic and optic phonons compared to other materials. Rigorous understanding of these features in GaN gives important insights into the interplay between intrinsic phonon-phonon scattering and isotopic scattering in a range of materials.

  2. Accurate determination of selected pesticides in soya beans by liquid chromatography coupled to isotope dilution mass spectrometry.

    PubMed

    Huertas Pérez, J F; Sejerøe-Olsen, B; Fernández Alba, A R; Schimmel, H; Dabrio, M

    2015-05-01

    A sensitive, accurate and simple liquid chromatography coupled with mass spectrometry method for the determination of 10 selected pesticides in soya beans has been developed and validated. The method is intended for use during the characterization of selected pesticides in a reference material. In this process, high accuracy and appropriate uncertainty levels associated to the analytical measurements are of utmost importance. The analytical procedure is based on sample extraction by the use of a modified QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction and subsequent clean-up of the extract with C18, PSA and Florisil. Analytes were separated on a C18 column using gradient elution with water-methanol/2.5 mM ammonium acetate mobile phase, and finally identified and quantified by triple quadrupole mass spectrometry in the multiple reaction monitoring mode (MRM). Reliable and accurate quantification of the analytes was achieved by means of stable isotope-labelled analogues employed as internal standards (IS) and calibration with pure substance solutions containing both, the isotopically labelled and native compounds. Exceptions were made for thiodicarb and malaoxon where the isotopically labelled congeners were not commercially available at the time of analysis. For the quantification of those compounds methomyl-(13)C2(15)N and malathion-D10 were used respectively. The method was validated according to the general principles covered by DG SANCO guidelines. However, validation criteria were set more stringently. Mean recoveries were in the range of 86-103% with RSDs lower than 8.1%. Repeatability and intermediate precision were in the range of 3.9-7.6% and 1.9-8.7% respectively. LODs were theoretically estimated and experimentally confirmed to be in the range 0.001-0.005 mg kg(-1) in the matrix, while LOQs established as the lowest spiking mass fractionation level were in the range 0.01-0.05 mg kg(-1). The method reliably identifies and quantifies the

  3. Chemical and isotopic data for water from thermal springs and wells of Oregon

    SciTech Connect

    Mariner, R.H.; Swanson, J.R.; Orris, G.J.; Presser, T.S.; Evans, W.C.

    1981-01-01

    The thermal springs of Oregon range in composition from dilute NaHCO/sub 3/ waters to moderately saline CO/sub 2/-charged NaCl-NaHCO/sub 3/ waters. Most of the thermal springs are located in southeastern or southcentral Oregon, with a few in northeastern Oregon and near the contact of the Western Cascades with the High Cascades. Thermal springs in the central and northern parts of the Cascades generally issue moderately saline NaCl waters. Farther south in the Cascades, the thermal waters are high in CO/sub 2/ as well as chloride. Most thermal springs in northeastern Oregon issue dilute NaHCO/sub 3/ waters of high pH (>8.5). These waters are similar to the thermal waters which issue from the Idaho batholith, farther east. Most of the remaining thermal waters are Na mixed-anion waters. Based on the chemical geothermometers, Mickey Srpings, Hot Borax Lake, Alvord Hot Springs, Neal Hot Springs, Vale Hot Springs, Crump Well, Hunters (Lakeview) Hot Springs, and perhaps some of the springs in the Cascades are associated with the highest temperature systems (>150/sup 0/C).

  4. Airborne measurements of sulfur dioxide, dimethyl sulfide, carbon disulfide, and carbonyl sulfide by isotope dilution gas chromatography/mass spectrometry

    NASA Technical Reports Server (NTRS)

    Bandy, Alan R.; Thornton, Donald C.; Driedger, Arthur R., III

    1993-01-01

    A gas chromatograph/mass spectrometer is described for determining atmospheric sulfur dioxide, carbon disulfide, dimethyl sulfide, and carbonyl sulfide from aircraft and ship platforms. Isotopically labelled variants of each analyte were used as internal standards to achieve high precision. The lower limit of detection for each species for an integration time of 3 min was 1 pptv for sulfur dioxide and dimethyl sulfide and 0.2 pptv for carbon disulfide and carbonyl sulfide. All four species were simultaneously determined with a sample frequency of one sample per 6 min or greater. When only one or two species were determined, a frequency of one sample per 4 min was achieved. Because a calibration is included in each sample, no separate calibration sequence was needed. Instrument warmup was only a few minutes. The instrument was very robust in field deployments, requiring little maintenance.

  5. Using isotopic dilution to assess chemical extraction of labile Ni, Cu, Zn, Cd and Pb in soils.

    PubMed

    Garforth, J M; Bailey, E H; Tye, A M; Young, S D; Lofts, S

    2016-07-01

    Chemical extractants used to measure labile soil metal must ideally select for and solubilise the labile fraction, with minimal solubilisation of non-labile metal. We assessed four extractants (0.43 M HNO3, 0.43 M CH3COOH, 0.05 M Na2H2EDTA and 1 M CaCl2) against these requirements. For soils contaminated by contrasting sources, we compared isotopically exchangeable Ni, Cu, Zn, Cd and Pb (EValue, mg kg(-1)), with the concentrations of metal solubilised by the chemical extractants (MExt, mg kg(-1)). Crucially, we also determined isotopically exchangeable metal in the soil-extractant systems (EExt, mg kg(-1)). Thus 'EExt - EValue' quantifies the concentration of mobilised non-labile metal, while 'EExt - MExt' represents adsorbed labile metal in the presence of the extractant. Extraction with CaCl2 consistently underestimated EValue for Ni, Cu, Zn and Pb, while providing a reasonable estimate of EValue for Cd. In contrast, extraction with HNO3 both consistently mobilised non-labile metal and overestimated the EValue. Extraction with CH3COOH appeared to provide a good estimate of EValue for Cd; however, this was the net outcome of incomplete solubilisation of labile metal, and concurrent mobilisation of non-labile metal by the extractant (MExtEValue). The Na2H2EDTA extractant mobilised some non-labile metal in three of the four soils, but consistently solubilised the entire labile fraction for all soil-metal combinations (MExt ≈ EExt). Comparison of EValue, MExt and EExt provides a rigorous means of assessing the underlying action of soil chemical extraction methods and could be used to refine long-standing soil extraction methodologies. PMID:27153236

  6. A universal SI-traceable isotope dilution mass spectrometry method for protein quantitation in a matrix by tandem mass tag technology.

    PubMed

    Li, Jiale; Wu, Liqing; Jin, Youxun; Su, Ping; Yang, Bin; Yang, Yi

    2016-05-01

    Isotope dilution mass spectrometry (IDMS), an important metrological method, is widely used for absolute quantification of peptides and proteins. IDMS employs an isotope-labeled peptide or protein as an internal standard although the use of a protein provides improved accuracy. Generally, the isotope-labeled protein is obtained by stable isotope labeling by amino acids in cell culture (SILAC) technology. However, SILAC is expensive, laborious, and time-consuming. To overcome these drawbacks, a novel universal SI-traceable IDMS method for absolute quantification of proteins in a matrix is described with human transferrin (hTRF). The hTRF and a human serum sample were labeled with different tandem mass tags (TMTs). After mixing the TMT-labeled hTRF and serum sample together followed by digestion, the peptides were separated by nano-liquid chromatography and analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Using the signature peptides, we calculated the ratios of reporter ions from the TMT-labeled peptides which, in turn, allowed determination of the mass fraction of hTRF. The recovery ranged from 97% to 105% with a CV of 3.9%. The LOD and LOQ were 1.71 × 10(-5) g/g and 5.69 × 10(-5) g/g of hTRF in human serum, respectively, and the relative expanded uncertainty was 4.7% with a mass fraction of 2.08 mg/g. For comparison, an enzyme-linked immunosorbent assay (ELISA) method for hTRF yielded a mass fraction of 2.03 mg/g. This method provides a starting point for establishing IDMS technology to accurately determine the mass fractions of protein biomarkers in a matrix with traceability to SI units. This technology should support the development of a metrological method useful for quantification of a wide variety of proteins. PMID:26942737

  7. Thermal property characterization of single crystal diamond with varying isotopic composition

    SciTech Connect

    Wei, L.

    1993-01-01

    The mirage-effect/thermal wave technique as a modern technique for thermal property characterization is described. The thermal diffusivity of a material is determined by measuring the time and space varying temperature distribution (thermal wave) in the material generated by an intensity modulated heating laser beam. These thermal waves are detected through the deflection of a probe laser beam due to modulation of gradient of the index of refraction (mirage effect) either in the air above the specimens (the in-air technique) or in the specimen itself (the in-solid technique). Three-dimensional theories, for both in-air and in-solid mirage techniques, are represented. In order to extract the material parameters by comparing the theory with experimental data, an extensive data analysis procedure based on multiparameter-least-squares has been developed. The experimental and data analysis details are discussed. Topics concerns with the quality and reliability of the measurements are addressed. This technique has been successfully applied to the thermal property characterization of single crystal diamond with varying isotope contents. The results showed a 50% enhancement in the thermal conductivity by removal of C[sup 13] content from 1.1% to 0.1% in diamond at room temperature. The technique has also been adapted to function in cryogenic temperatures. The temperature dependence of thermal conductivity in the temperature range 80-378K for natural IIA specimen and 187-375K for isotopically enriched specimen are obtained, the former results agree with previous works and the latter results demonstrate the isotope effect on the thermal conductivity of single crystal diamond consistently in a large temperature range. The physical source of this enhancement in diffusivity due to the isotope effect in diamond is discussed. The discussion is based on the full Callaway's theory with emphasizing the role of N-processes in the phonon scattering mechanism.

  8. Isotopic Fractionation of 20Ne, 21Ne, and 22Ne in a Simulated Thermal Gradient

    NASA Astrophysics Data System (ADS)

    Jester, B.; Dominguez, G.

    2014-12-01

    Computer simulations allow for the analysis of the thermodynamic properties of systems which are difficult or impossible to do experimentally. Isotopic fractionation in thermal gradients is an example of a system which is not fully understood but could provide background for understanding variations in fractionations like those observed for noble gases in terrestrial and extraterrestrial material. Using a recently developed molecular dynamics simulation focused on the accuracy of the simulated physics, the isotopic fractionation of Neon in a thermal gradient was analyzed in order to provide a correlation between the fractionation and the experimental system's properties. Various ratios of isotopes 20Ne, 21Ne, and 22Ne were simulated in a thermal gradient ranging from 218 K to 233 K for a variety of time scales. Data was collected for various configurations including box sizes on the order of 1 nm to 100 μm. The simulated thermal conductivity was determined and compared with known values. The analysis indicates that the dimensions of the box heavily influence the magnitude of the isotopic fractionation in the thermal gradient.

  9. [International comparison APMP. QM-S6: determination of clenbuterol in porcine meat by isotopic dilution mass spectrometry].

    PubMed

    Xu, Sen; Li, Xiuqin; Luo, Ximing; Zhang, Qinghe

    2014-10-01

    A method was developed for the determination of clenbuterol in porcine meat by iso- topic dilution mass spectrometry (IDMS). National Institute of Metrology of China (NIM) par- ticipated in the international comparison activity organized by Asia Pacific Metrology (APMP) and got an international mutual recognition result using this method. The important factors of the method, such as the spray voltage, mobile phase, chromatographic column, extraction, purification and filtration conditions were investigated to acquire optimum conditions. The opti- mization results showed that the composition and pH value of the mobile phase had effects on the response of the mass spectrum of clenbuterol and the optimal value of the spray voltage. The solvent of sample had influences on the chromatographic retention behavior of clenbuterol. It was found that methanol caused a serious solvent effect, even made chromatographic peak split. Since clenbuterol was easily adsorbed on hydrophilic filter membranes and solid phase extraction columns, there were interference suppressions for the quantification of clenbuterol because of the eluate of the solid phase extraction columns. The homogenate method with extraction solvent of 0.1% (v/v) formic acid in acetonitrile had the highest extraction efficiency. The limit of the detection (LOD, S/N > 3) of the method was 0.2 μg/kg. The determination results of clenbuterol in the porcine meat by this method were 5.18 μg/kg ± 0.50 μg/kg (k = 2). This method is accurate, reliable, reproducible, and suitable for the determination of clenbuterol with trace quantity in porcine meat. PMID:25739271

  10. Simultaneous analysis of polychlorinated biphenyls and polychlorinated naphthalenes by isotope dilution comprehensive two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry.

    PubMed

    Xia, Dan; Gao, Lirong; Zheng, Minghui; Wang, Shasha; Liu, Guorui

    2016-09-21

    Polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) are listed as persistent organic pollutants (POPs) under the Stockholm Convention. Because they have similar physical and chemical properties, they are coeluted and are usually analyzed separately by different gas chromatography high-resolution mass spectrometry (GC-HRMS) methods. In this study, a novel method was developed for simultaneous analysis of six indicator PCBs, 12 dioxin-like PCBs, and 16 PCNs using isotope dilution comprehensive two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry (GC × GC-HRTOF-MS). The method parameters, including the type of GC column, oven temperature program, and modulation period, were systematically optimized. Complete separation of all target analytes and the matrix was achieved with a DB-XLB column in the first dimension and a BPX-70 column in the second dimension. The isotope dilution method was used for quantification of the PCBs and PCNs by GC × GC-HRTOF-MS. The method showed good linearity from 5 to 500 pg μL(-1) for all the target compounds. The instrumental limit of detection ranged from 0.03 to 0.3 pg μL(-1) for the 18 PCB congeners and from 0.09 to 0.6 pg μL(-1) for the 16 PCN congeners. Repeatability for triplicate injections was always lower than 20%. The method was successfully applied to the determination of 18 PCBs present at 0.9-2054 pg g(-1) and 16 PCNs present at 0.2-15.7 pg g(-1) in three species of fish. The GC × GC-HRTOF-MS results agreed with those obtained by GC-HRMS. The GC × GC-HRTOF-MS method proved to be a sensitive and accurate technique for simultaneous analysis of the selected PCBs and PCNs. With the excellent chromatographic separation offered by GC × GC and accurate mass measurements offered by HRTOF-MS, this method allowed identification of non-target contaminants in the fish samples, including organochlorine pesticides and polycyclic aromatic hydrocarbons. PMID

  11. Thin-layer chromatography/direct analysis in real time time-of-flight mass spectrometry and isotope dilution to analyze organophosphorus insecticides in fatty foods.

    PubMed

    Kiguchi, Osamu; Oka, Kazuko; Tamada, Masafumi; Kobayashi, Takashi; Onodera, Jun

    2014-11-28

    To assess food safety emergencies caused by highly hazardous chemical-tainted foods, simultaneous analysis of organophosphorus insecticides in fatty foods such as precooked foods was conducted using thin-layer chromatography/direct analysis in real time time-of-flight mass spectrometry (TLC/DART-TOFMS) and isotope dilution technique. Polar (methamidophos and acephate) and nonpolar organophosphorus insecticides (fenitrothion, diazinon, and EPN) were studied. Experiments to ascertain chromatographic patterns using TLC/DART-TOFMS reveal that it was more useful than GC/MS or GC/MS/MS for the simultaneous analyses of polar and nonpolar pesticides, while obviating the addition of a protective agent for tailing effects of polar pesticides. Lower helium gas temperature (260°C) for DART-TOFMS was suitable for the simultaneous analysis of target pesticides. Linearities were achieved respectively at a lower standard concentration range (0.05-5 μg) for diazinon and EPN and at a higher standard concentration range (2.5-25 μg) for methamidophos, acephate, and fenitrothion. Their respective coefficients of determination were ≥ 0.9989 and ≥ 0.9959. A few higher repeatabilities (RSDs) for diazinon and EPN were found (>20%), although isotope dilution technique was used. Application to the HPTLC plate without an automatic TLC sampler might be inferred as a cause of their higher RSDs. Detection limits were estimated in the higher picogram range for diazinon and EPN, and in the lower nanogram range for methamidophos, acephate, and fenitrothion. Aside from methamidophos, recovery results (n=3) obtained using a highly insecticide-tainted fatty food (dumpling) and raw food (grapefruit) samples (10mg/kg) using TLC/DART-TOFMS with both complex and simpler cleanups were not as susceptible to matrix effects (95-121%; RSD, 1.3-14%) as those using GC/MS/MS (102-117%; RSD, 0.4-8.5%), although dumpling samples using GC/MS were remarkably susceptible to matrix effects. The coupled method of

  12. Lead and strontium isotope data for thermal waters of the regional geothermal system in the Twin Falls and Oakley areas, South-Central Idaho

    SciTech Connect

    Mariner, R.H.; Young, H.W.

    1995-12-31

    Thermal fluids obviously related to aquifers in both rhyolite and limestone occur in the Twin Falls-Oakley area of south-central Idaho. Limestone-related waters (high calcium with low silica and fluoride) occur in the middle and upper (southern) parts of the area. Rhyolite-related waters (low calcium but high in silica and fluoride) occur in the lower (northern) part of the area. The relation of thermal fluids in Paleozoic limestone to thermal fluids in Tertiary rhyolite is unknown. Thermal fluids from limestone are dilute, so water-rock reaction in rhyolite could obliterate chemical evidence of fluid residence in a limestone. However, isotopic tracers such as {sup 206}Pb/{sup 204}Pb, {sup 207}Pb/{sup 204}Pb, {sup 208}Pb/{sup 204}Pb, and {sup 87}Sr/{sup 86}Sr might preserve evidence of fluid residence in limestone. Systematic relations between these isotopes and dissolved constituents in the water demonstrate the presence of limestone beneath most if not all of the study area and that aquifers in the limestone and rhyolite are hydrologically connected.

  13. Liquid chromatography with isotope-dilution mass spectrometry for determination of water-soluble vitamins in foods.

    PubMed

    Phillips, Melissa M

    2015-04-01

    Vitamins are essential for improving and maintaining human health, and the main source of vitamins is the diet. Measurement of the quantities of water-soluble vitamins in common food materials is important to understand the impact of vitamin intake on human health, and also to provide necessary information for regulators to determine adequate intakes. Liquid chromatography (LC) and mass spectrometry (MS) based methods for water-soluble vitamin analysis are abundant in the literature, but most focus on only fortified foods or dietary supplements or allow determination of only a single vitamin. In this work, a method based on LC/MS and LC/MS/MS has been developed to allow simultaneous quantitation of eight water-soluble vitamins, including multiple forms of vitamins B3 and B6, in a variety of fortified and unfortified food-matrix Standard Reference Materials (SRMs). Optimization of extraction of unbound vitamin forms and confirmation using data from external laboratories ensured accuracy in the assigned values, and addition of stable isotope labeled internal standards for each of the vitamins allowed for increased precision. PMID:25433686

  14. Analysis of nitromethane from samples exposed in vitro to chloropicrin by stable isotope dilution headspace gas chromatography with mass spectrometry.

    PubMed

    Halme, Mia; Pesonen, Maija; Grandell, Toni; Kuula, Matti; Pasanen, Markku; Vähäkangas, Kirsi; Vanninen, Paula

    2015-10-01

    Chloropicrin (trichloronitromethane) is a widely used soil fumigant and an old chemical warfare agent. The metabolism of chloropicrin is not well known in mammals but nitromethane has been shown to be one of its main metabolites. Here, a fast and simple headspace gas chromatography with mass spectrometry method was applied for the measurement of nitromethane from aqueous samples. The analytical method was validated using stable isotope labeled internal standard and a small sample volume of 260 μL. No conventional sample preparation steps were needed. The method was accurate (relative standard deviations ≤1.5%) and linear (R(2) = 0.9996) within the concentration range of 0.1-6.0 μg/mL. This method was used to measure nitromethane in in vitro incubations with human and pig liver cell fractions containing enzymes for xenobiotic metabolism, exposed to chloropicrin. The results indicate that the presence of glutathione is necessary for the formation of nitromethane from chloropicrin. Also, nitromethane was formed mostly in liver cytosol fractions, but not in microsomal fractions after the incubation with chloropicrin. Our results suggest that although nitromethane is not the unequivocal biomarker of chloropicrin exposure, this method could be applied for screening the elevated levels in humans after chloropicrin exposure. PMID:26255649

  15. An Ultrahigh Precision, High-Frequency Dissolved Inorganic Carbon Analyzer Based on Dual Isotope Dilution and Cavity Ring-Down Spectroscopy.

    PubMed

    Huang, Kuan; Cassar, Nicolas; Jonsson, Bror; Cai, Wei-jun; Bender, Michael L

    2015-07-21

    We present a novel method for continuous and automated shipboard measurements of dissolved inorganic carbon concentration ([DIC]) in surface water. The method is based on dual isotope dilution and cavity ring-down spectroscopy (DID-CRDS). In this method, seawater is continuously sampled and mixed with a flow of NaH(13)CO3 solution that is also enriched in deuterated water (the spike). The isotopic composition of CO2 (δ(13)C(spiked_sample)) derived from the DIC in the mixture, and the D/H ratio of the mixed water (δD(spiked_sample)), are measured by CRDS analyzers. The D/H of the water in the mixture allows accurate estimates of the mixing ratio of the sample and the spike. [DIC] of the sample is then calculated from the mixing ratio, [DI(13)C] of the spike, and δ(13)C(spiked_sample). In the laboratory, the precision of the method is <0.02% (±0.4 μmol kg(-1) when [DIC] = 2000 μmol kg(-1)). A shipboard test was conducted in the Delaware Bay and Estuary. For 2 min average [DIC], a precision of <0.03% was achieved. Measurements from the DID-CRDS showed good agreement with independent measurements of discrete samples using the well-established coulometric method (mean difference = -1.14 ± 1.68 μmol kg(-1)), and the nondispersive infrared(NDIR)-based methods (mean difference = -0.9 ± 4.73 μmol kg(-1)). PMID:26119512

  16. Quantification of 11 thyroid hormones and associated metabolites in blood using isotope-dilution liquid chromatography tandem mass spectrometry.

    PubMed

    Hansen, Martin; Luong, Xuan; Sedlak, David L; Helbing, Caren C; Hayes, Tyrone

    2016-08-01

    This paper describes a novel analytical methodology for the simultaneous determination of absolute and total concentrations of 11 native thyroid hormones and associated metabolites, viz. thyroxine (T4), 3,3', 5-triiodothyronine (T3), 3,3', 5'-triiodothyronine (rT3), 3,5-diiodothyronine (3,5-T2), 3,3'- diiodothyronine (3,3'-T2), 3-iodothyronine (T1), thyronine (T0), 3-iodothyronamine (T1AM), tetraiodothyroacetic acid (Tetrac), triiodothyroacetic acid (Triac), and diiodothyroacetic acid (Diac), in 50-μL of plasma or serum. The method was optimized using four isotopic labeled surrogate and internal standards in combination with solid-phase extraction and LC-MS/MS. The methodology was further evaluated using amphibian plasma and serum with matrix-matched calibration applied for quantification. Method detection limits are 3.5 pg T4, 1.5 pg T3, 2.9 pg rT3, 1.7 pg 3,3'-T2, 2.3 pg 3,5-T2, and between 0.3 and 7.5 pg for the remaining six metabolites in 50 μL aliquots of blood sera or plasma. Accuracies and repeatabilities for all analytes were between 88 and 103 % and 1.31 and 17.2 %, respectively. Finally, we applied the method on adult frog (Xenopus laevis) plasma and tadpole (Rana (Lithobates) catesbeiana) serum. We observed up to seven different thyroid hormones and associated metabolites in tadpole serum. This method will enable researchers to improve the assessment of thyroid homeostasis and endocrine disruption in animals and humans. Graphical Abstract Quantification of 11 thyroid hormones and metabolites from 50 μL plasma or serum using protein denaturation in combination with solid-phase extraction followed by LC-MS/MS. PMID:27215639

  17. Separation and Analysis of Boron Isotope in High Plant by Thermal Ionization Mass Spectrometry

    PubMed Central

    Xu, Qingcai; Dong, Yuliang; Zhu, Huayu; Sun, Aide

    2015-01-01

    Knowledge of boron and its isotope in plants is useful to better understand the transposition and translocation of boron within plant, the geochemical behavior in the interface between soil and plant, and the biogeochemical cycle of boron. It is critical to develop a useful method to separate boron from the plant for the geochemical application of boron and its isotope. A method was developed for the extraction of boron in plant sample, whose isotope was determined by thermal ionization mass spectrometry. The results indicated that this method of dry ashing coupled with two-step ion-exchange chromatography is powerful for the separation of boron in plant sample with large amounts of organic matters completely. The ratios of boron isotope composition in those plant tissue samples ranged from −19.45‰ to +28.13‰ (total range: 47.58‰) with a mean value of 2.61 ± 11.76‰ SD. The stem and root isotopic compositions were lower than those in flower and leaf. The molecular mechanism of boron isotope may be responsible for the observed variation of boron isotopic composition and are considered as a useful tool for the better understanding of boron cycling process in the environment and for the signature of living systems. PMID:26819618

  18. Separation and Analysis of Boron Isotope in High Plant by Thermal Ionization Mass Spectrometry.

    PubMed

    Xu, Qingcai; Dong, Yuliang; Zhu, Huayu; Sun, Aide

    2015-01-01

    Knowledge of boron and its isotope in plants is useful to better understand the transposition and translocation of boron within plant, the geochemical behavior in the interface between soil and plant, and the biogeochemical cycle of boron. It is critical to develop a useful method to separate boron from the plant for the geochemical application of boron and its isotope. A method was developed for the extraction of boron in plant sample, whose isotope was determined by thermal ionization mass spectrometry. The results indicated that this method of dry ashing coupled with two-step ion-exchange chromatography is powerful for the separation of boron in plant sample with large amounts of organic matters completely. The ratios of boron isotope composition in those plant tissue samples ranged from -19.45‰ to +28.13‰ (total range: 47.58‰) with a mean value of 2.61 ± 11.76‰ SD. The stem and root isotopic compositions were lower than those in flower and leaf. The molecular mechanism of boron isotope may be responsible for the observed variation of boron isotopic composition and are considered as a useful tool for the better understanding of boron cycling process in the environment and for the signature of living systems. PMID:26819618

  19. Constraining the Thermal History of the Midcontinent Rift System with Clumped Isotopes and Organic Thermal Maturity Indices

    NASA Astrophysics Data System (ADS)

    Gallagher, T. M.; Sheldon, N. D.; Mauk, J. L.; Gueneli, N.; Brocks, J. J.

    2015-12-01

    The Mesoproterozoic (~1.1 Ga) North American Midcontinent Rift System (MRS) has been of widespread interest to researchers studying its economic mineral deposits, continental rifting processes, and the evolution of early terrestrial life and environments. For their age, the MRS rocks are well preserved and have not been deeply buried, yet a thorough understanding of the regional thermal history is necessary to constrain the processes that emplaced the mineral deposits and how post-burial alteration may have affected various paleo-records. To understand the thermal history of the MRS better, this study presents carbonate clumped isotope (Δ47) temperatures from deposits on the north and south sides of the rift. Due to the age of these deposits and known post-depositional processes, uncertainties exist about whether the clumped isotope signature has been reset. To test this, three generations of calcite were analyzed from the Nonesuch Fm. from the White Pine mine in Michigan including: sedimentary limestone beds, early diagenetic carbonate nodules, and hydrothermal calcite veins associated with the emplacement of copper mineralization. Clumped isotope temperatures from the White Pine mine range from 84 to 131°C, with a hydrothermal vein producing the hottest temperature. The clumped isotope temperature range for samples throughout the rift expands to 41-134°C. The hottest temperatures are associated with areas of known copper mineralization, whereas the coolest temperatures are found on the northern arm of the rift in Minnesota, far from known basin-bounding faults. Our hottest temperatures are broadly consistent with preexisting maximum thermal temperature estimates based on clay mineralogy, fluid inclusions, and organic geochemistry data. Clumped isotope results will also be compared to new hydrocarbon maturity data from the Nonesuch Fm., which suggest that bitumen maturities consistently fall within the early oil window across Michigan and Wisconsin.

  20. Measurement of (5'R)- and (5'S)-8,5'-cyclo-2'-deoxyadenosines in DNA in vivo by liquid chromatography/isotope-dilution tandem mass spectrometry

    SciTech Connect

    Jaruga, Pawel; Xiao, Yan; Nelson, Bryant C.; Dizdaroglu, Miral

    2009-09-04

    Oxidatively induced DNA lesions (5'R)- and (5'S)-8,5'-cyclo-2'-deoxyadenosines (R-cdA and S-cdA) are detectable and accumulate in vivo due to disease states and defects in DNA repair. They block transcription and inhibit gene expression, and may play a role in disease processes. Accurate measurement of these lesions in DNA in vivo is necessary to understand their biological effects. We report on a methodology using liquid chromatography/isotope-dilution tandem mass spectrometry to measure R-cdA and S-cdA in DNA. This methodology permitted the detection of these compounds at a level of 0.1 fmol on-column. Levels of R-cdA and S-cdA in mouse liver DNA amounted to 0.133 {+-} 0.024 and 0.498 {+-} 0.065 molecules/10{sup 7} DNA 2'-deoxynucleosides, respectively. The successful measurement of R-cdA and S-cdA in DNA in vivo suggests that this methodology will be used for understanding of their repair and biological consequences, and that these compounds may be used as putative biomarkers for disease states.

  1. A Simplified Method for Quantifying Sulfur Mustard Adducts to Blood Proteins by Ultra-High Pressure Liquid Chromatography-Isotope Dilution Tandem Mass Spectrometry

    PubMed Central

    Pantazides, Brooke G.; Crow, Brian S.; Garton, Joshua W.; Quiñones-González, Jennifer A.; Blake, Thomas A.; Thomas, Jerry D.; Johnson, Rudolph C.

    2016-01-01

    Sulfur mustard binds to reactive cysteine residues, forming a stable sulfur-hydroxyethylthioethyl [S-HETE] adduct that can be used as a long-term biomarker of sulfur mustard exposure in humans. The digestion of sulfur mustard-exposed blood samples with proteinase K following total protein precipitation with acetone produces the tripeptide biomarker [S-HETE]-Cys-Pro-Phe. The adducted tripeptide is purified by solid phase extraction, separated by ultra-high pressure liquid chromatography, and detected by isotope dilution tandem mass spectrometry. This approach was thoroughly validated and characterized in our laboratory. The average interday relative standard deviation was ≤ 9.49%, and the range of accuracy was between 96.1-109% over a concentration range of 3.00 to 250. ng/mL with a calculated limit of detection of 1.74 ng/mL. A full 96-well plate can be processed and analyzed in 8 h which is five times faster than our previous 96-well plate method and only requires 50 µL of serum, plasma, or whole blood. Extensive ruggedness and stability studies and matrix comparisons were conducted to create a robust, easily transferrable method. As a result, a simple and high-throughput method has been developed and validated for the quantitation of sulfur mustard blood protein adducts in low volume blood specimens which should be readily adaptable for quantifying human exposures to other alkylating agents. PMID:25622494

  2. Comparison of digestion procedures and methods for quantification of trace lead in breast milk by isotope dilution inductively coupled plasma mass spectrometry

    PubMed Central

    Amarasiriwardena, Chitra J.; Jayawardene, Innocent; Lupoli, Nicola; Barnes, Ramon M.; Hernandez-Avila, Mauricio; Hu, Howard

    2014-01-01

    Measurement of lead in breast milk is an important public health consideration and can be technically quite challenging. The reliable and accurate determination of trace lead in human breast milk is difficult for several reasons including: potential for contamination during sample collection, storage, and analysis; complexities related to the high fat content of human milk; and poor analytic sensitivity at low concentrations. Breast milk lead levels from previous published studies should therefore be reviewed with caution. Due to the difficulty in identifying a method that would successfully digest samples with 100% efficiency, we evaluated three different digestion procedures including: (1) dry ashing in a muffle furnace, (2) microwave oven digestion, and (3) digestion in high pressure asher. High temperature, high pressure asher digestion was selected as the procedure of choice for the breast milk samples. Trace lead analysis was performed using isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS). Measured lead concentrations in breast milk samples (n = 200) from Mexico ranged from 0.2 to 6.7 ng ml−1. The precision for these measurements ranged from 0.27–7.8% RSD. Use of strict contamination control techniques and of a very powerful digestion procedure, along with an ID-ICP-MS method for lead determination, enables us to measure trace lead levels as low as 0.2 ng ml−1 in milk (instrument detection limit = 0.01 ng ml−1). PMID:24808927

  3. Analysis of permethrin isomers in composite diet samples by molecularly imprinted solid-phase extraction and isotope dilution gas chromatography-ion trap mass spectrometry.

    PubMed

    Vonderheide, Anne P; Boyd, Brian; Ryberg, Anna; Yilmaz, Ecevit; Hieber, Thomas E; Kauffman, Peter E; Garris, Sherry T; Morgan, Jeffrey N

    2009-05-29

    Determination of an individual's aggregate dietary ingestion of pesticides entails analysis of a difficult sample matrix. Permethrin-specific molecularly imprinted polymer (MIP) solid-phase extraction cartridges were developed for use as a sample preparation technique for a composite food matrix. Vortexing with acetonitrile and centrifugation were found to provide optimal extraction of the permethrin isomers from the composite foods. The acetonitrile (with 1% acetic acid) was mostly evaporated and the analytes reconstituted in 90:10 water/acetonitrile in preparation for molecularly imprinted solid-phase extraction. Permethrin elution was accomplished with acetonitrile and sample extracts were analyzed by isotope dilution gas chromatography-ion trap mass spectrometry. Quantitation of product ions provided definitive identification of the pesticide isomers. The final method parameters were tested with fortified composite food samples of varying fat content (1%, 5%, and 10%) and recoveries ranged from 99.3% to 126%. Vegetable samples with incurred pesticide levels were also analyzed with the given method and recoveries were acceptable (81.0-95.7%). Method detection limits were demonstrated in the low ppb range. Finally, the applicability of the MIP stationary phase to extract other pyrethroids, specifically cyfluthrin and cypermethrin, was also investigated. PMID:19393156

  4. Isotope dilution gas chromatography with mass spectrometry for the analysis of 4-octyl phenol, 4-nonylphenol, and bisphenol A in vegetable oils.

    PubMed

    Wu, Pinggu; Zhang, Liqun; Yang, Dajin; Zhang, Jing; Hu, Zhengyan; Wang, Liyuan; Ma, Bingjie

    2016-03-01

    By the combination of solid-phase extraction as well as isotope dilution gas chromatography with mass spectrometry, a sensitive and reliable method for the determination of endocrine-disrupting chemicals including bisphenol A, 4-octylphenol, and 4-nonylphenol in vegetable oils was established. The application of a silica/N-(n-propyl)ethylenediamine mixed solid-phase extraction cartridge achieved relatively low matrix effects for bisphenol A, 4-octylphenol, and 4-nonylphenol in vegetable oils. Experiments were designed to evaluate the effects of derivatization, and the extraction parameters were optimized. The estimated limits of detection and quantification for bisphenol A, 4-octylphenol, and 4-nonylphenol were 0.83 and 2.5 μg/kg, respectively. In a spiked experiment in vegetable oils, the recovery of the added bisphenol A was 97.5-110.3%, recovery of the added 4-octylphenol was 64.4-87.4%, and that of 4-nonylphenol was 68.2-89.3%. This sensitive method was then applied to real vegetable oil samples from Zhejiang Province of China, and none of the target compounds were detected. PMID:26698324

  5. Simplified method for the determination of Ru, Pd, Re, Os, Ir and Pt in chromitites and other geological materials by isotope dilution ICP-MS and acid digestion.

    PubMed

    Meisel, T; Moser, J; Fellner, N; Wegscheider, W; Schoenberg, R

    2001-03-01

    A method for the determination of low Ru, Pd, Re, Os, Ir and Pt abundances in geological reference materials by isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) after acid digestion in a high pressure asher (HPA-S) is presented. The digestion technique is similar to that using Carius tubes but easier to handle and reaches higher temperatures. Osmium can be determined as OsO4 with ICP-MS directly after digestion through a sparging technique. The remaining elements are preconcentrated by means of anion column chromatography. The resin is digested directly without elution leading to high yields but this causes problems if Zr is present at higher levels in the silicate rich materials. The analytical results for international platinum group element (PGE) reference materials, chromitite CHR-Bkg, basalt TDB-1 and gabbro WGB-1, are presented and compared with literature data, demonstrating the validity of the described method. Although higher in concentration, PGEs determined for reference material WGB-1 were worse than for TDB-1 indicating a more inhomogeneous distribution of the platinum group mineral phases. The low PGE abundance chromitite standard, CHR-Bkg, is likely to be homogeneous for Ru, Re, Os and Ir and is recommended as a reference material for the study of chromitites. Detection limits (3s x total procedure blank) range from 0.012 ng (Re and Os) to 0.77 ng (Pt), which could be further improved by applying higher quality acids. PMID:11284333

  6. Determination of Os by isotope dilution-inductively coupled plasma-mass spectrometry with the combination of laser ablation to introduce chemically separated geological samples

    NASA Astrophysics Data System (ADS)

    Sun, Yali; Ren, Minghao; Xia, Xiaoping; Li, Congying; Sun, Weidong

    2015-11-01

    A method was developed for the determination of trace Os in geological samples by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) with the combination of chemical separation and preconcentration. Samples are digested using aqua regia in Carius tubes, and the Os analyte is converted into volatile OsO4, which is distilled and absorbed with HBr. The HBr solution is concentrated for further Os purification using the microdistillation technique. The purified Os is dissolved in 10 μl of 0.02% sucrose-0.005% H3PO4 solution and then evaporated on pieces of perfluoroalkoxy (PFA) film, resulting in the formation of a tiny object (< 3 × 104 μm2 superficial area). Using LA-ICP-MS measurements, the object can give Os signals at least 100 times higher than those provided by routine solution-ICP-MS while successfully avoiding the memory effect. The procedural blank and detection limit in the developed technique are 3.0 pg and 1.8 pg for Os, respectively when 1 g of samples is taken. Reference materials (RM) are analyzed, and their Os concentrations obtained by isotope dilution are comparable to reference or literature values. Based on the individual RM results, the precision is estimated within the range of 0.6 to 9.4% relative standard deviation (RSD), revealing that this method is applicable to the determination of trace Os in geological samples.

  7. Regional water-quality analysis of 2,4-D and dicamba in river water using gas chromatography-isotope dilution mass spectrometry

    USGS Publications Warehouse

    Thurman, E.M.; Zimmerman, L.R.; Aga, D.S.; Gilliom, R.J.

    2001-01-01

    Gas chromatography with isotope dilution mass spectrometry (GC-MS) and enzyme-linked immunosorbent assay (ELISA) were used in regional National Water Quality Assessment studies of the herbicides, 2,4-D and dicamba, in river water across the United States. The GC-MS method involved solid-phase extraction, derivatized with deutemted 2,4-D, and analysis by selected ion monitoring. The ELISA method was applied after preconcentration with solid-phase extraction. The ELISA method was unreliable because of interference from humic substances that were also isolated by solid-phase extraction. Therefore, GC-MS was used to analyzed 80 samples from river water from 14 basins. The frequency of detection of dicamba (28%) was higher than that for 2,4-D (16%). Concentrations were higher for dicamba than for 2,4-D, ranging from less than the detection limit (<0.05 ??g/L) to 3.77 ??g/L, in spite of 5 times more annual use of 2,4-D as compared to dicamba. These results suggest that 2,4-D degrades more rapidly in the environment than dicamba.

  8. Elevated urinary levels of carcinogenic N-nitrosamines in patients with urinary tract infections measured by isotope dilution online SPE LC-MS/MS.

    PubMed

    Hu, Chiung-Wen; Shih, Ying-Ming; Liu, Hung-Hsin; Chiang, Yi-Chen; Chen, Chih-Ming; Chao, Mu-Rong

    2016-06-01

    N-nitrosamines (NAms) are well-documented for their carcinogenic potential. Human exposure to NAms may arise from the daily environment and endogenous formation via the reaction of secondary amines with nitrites or from bacteria infection. We describe the use of isotope dilution online solid-phase extraction (SPE) LC-MS/MS to quantify nine NAms in human urine. This method was validated and further applied to healthy subjects and patients with urinary tract infection (UTI). N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA), N-nitrosopyrrolidine (NPYR) and N-nitrosomorpholine (NMOR) were analyzed with an APCI source, while N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPIP), N-nitrosodi-n-propylamine (NDPA), N-nitrosodibutylamine (NDBA) and N-nitrosodiphenylamine (NDPhA) were quantified with an ESI source, due to their effect on the sensitivity and chromatography. NDMA was the most abundant N-nitrosamine, while NDPhA was firstly identified in human. UTI patients had three to twelve-fold higher concentrations for NDMA, NPIP, NDEA, NMOR and NDBA in urine than healthy subjects, and the NAms were significantly decreased after antibiotics treatment. NDMA concentrations were also significantly correlated with the pH value, leukocyte esterase activity or nitrite in urines of UTI patients. Our findings by online SPE LC-MS/MS method evidenced that UTI patients experienced various NAms exposures, especially the potent carcinogen NDMA, which was likely induced by bacteria infection. PMID:26937867

  9. [Preparation and certification of mussel reference material for organochlorine pesticides and polychlorinated biphenyls using isotope dilution-high resolution mass spectrometry].

    PubMed

    Lu, Xianbo; Chen, Jiping; Wang, Shuqiu; Zou, Lili; Tian, Yuzeng; Ni, Yuwen; Su, Fan

    2012-09-01

    A method for the preparation and certification of the reference material of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in mussel tissue is described. The mussel tissue from Dalian Bay was frozen-dried, comminuted, sieved, homogenized, packaged, and sterilized by 60Co radiation sterilization in turn. The certified values for 18 OCPs and 16 PCBs were determined by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) using isotope dilution and internal standard quantitation techniques. The certified values were validated and given based on seven accredited laboratories, and these values are traceable to the SI (international system of units) through gravimetrically prepared standards of established purity and measurement intercomparisons. The certified values of PCBs and OCPs in mussel span 4 orders of magnitude with a relative uncertainty of about 10%. This material is a natural biological material with confirmed good homogeneity and stability, and it was approved as the grade "primary reference material" (GBW10069) in June 2012 in China. This reference material provided necessary quality control products for our country to implement the Stockholm Treaty on the monitoring of persistent organic pollutants (POPs). The material is intended to be used for the method validation and quality control in the determination of OCPs and PCBs in biota samples. PMID:23285973

  10. Phenylboronic Acid Solid Phase Extraction Cleanup and Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry for the Determination of Florfenicol Amine in Fish Muscles.

    PubMed

    Sin, Della Wai-Mei; Ho, Clare; Wong, Yiu-Tung

    2015-01-01

    Florfenicol (FFC) residues in foods are regulated as the sum of florfenicol and its metabolites measured as florfenicol amine (FFA). An isotope dilution LC-MS/MS method utilizing phenylboronic acid (PBA) SPE cleanup is established for the accurate determination of FFA in fish muscles (i.e., salmon and tilapia) after acid catalyzed hydrolysis. Comparisons of the PBA SPE cleanup procedure with other cleanup procedures such as mixed-mode cationic (MCX) SPE and solid supported liquid-liquid extraction were performed. Quantification of FFA in fish muscles was accomplished by using matrix-matched calibration with FFA-D3 as the internal standard. The method was validated with FFA fortified fish muscles at three different levels (50, 100, and 200 μg/kg). Conversion of FFC to FFA by acid catalyzed hydrolysis was evaluated and found to be ≥88%. The recoveries of FFA in fish muscles at the three fortification levels ranged from 89 to 106%, and RSDs were ≤9% in all cases. The LOD values in salmon and tilapia muscles were 0.13 and 1.64 μg/kg, respectively. The LOQ values in salmon and tilapia muscles were 0.29 and 4.13 μg/kg, respectively. This method is suitable for the application in routine control of FFC in fishes according to its residue definition. PMID:26025252

  11. Quantification of 2-acetyl-1-pyrroline in rice by stable isotope dilution assay through headspace solid-phase microextraction coupled to gas chromatography-tandem mass spectrometry.

    PubMed

    Maraval, Isabelle; Sen, Kemal; Agrebi, Abdelhamid; Menut, Chantal; Morere, Alain; Boulanger, Renaud; Gay, Frédéric; Mestres, Christian; Gunata, Ziya

    2010-08-24

    A new and convenient synthesis of 2-acetyl-1-pyrroline (2AP), a potent flavor compound in rice, and its ring-deuterated analog, 2-acetyl-1-d(2)-pyrroline (2AP-d(2)), was reported. A stable isotope dilution assay (SIDA), involving headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-positive chemical ionization-ion trap-tandem mass spectrometry (GC-PCI-IT-MS-MS), was developed for 2AP quantification. A divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was used for HS-SPME procedure and parameters affecting analytes recovery, such as extraction time and temperature, pH and salt, were studied. The repeatability of the method (n=10) expressed as relative standard deviation (RSD) was 11.6%. A good linearity was observed from 5.9 to 779 ng of 2AP (r(2)=0.9989). Limits of detection (LOD) and quantification (LOQ) for 2AP were 0.1 and 0.4 ng g(-1) of rice, respectively. The recovery of spiked 2AP from rice matrix was almost complete. The developed method was applied to the quantification of 2AP in aerial parts and grains of scented and non-scented rice cultivars. PMID:20800726

  12. Quantification of DNA damage products resulting from deamination, oxidation and reaction with products of lipid peroxidation by liquid chromatography isotope dilution tandem mass spectrometry

    PubMed Central

    Taghizadeh, Koli; McFaline, Jose L.; Pang, Bo; Sullivan, Matthew; Dong, Min; Plummer, Elaine; Dedon, Peter C.

    2009-01-01

    The analysis of damage products as biomarkers of inflammation has been hampered by a poor understanding of the chemical biology of inflammation, the lack of sensitive analytical methods, and a focus on single chemicals as surrogates for inflammation. To overcome these problems, we developed a general and sensitive liquid chromatographic tandem mass spectrometry (LC/MS-MS) method to quantify, in a single DNA sample, the nucleoside forms of seven DNA lesions reflecting the range of chemistries associated with inflammation: 2′-deoxyuridine, 2′-deoxyxanthosine, and 2′-deoxyinosine from nitrosative deamination; 8-oxo-2′-deoxyguanosine from oxidation; and 1,N2-etheno-2′-deoxyguanosine, 1,N6-etheno-2′-deoxyadenosine, and 3,N4-etheno-2′-deoxycytidine arising from reaction of DNA with lipid peroxidation products. Using DNA purified from cells or tissues under conditions that minimize artifacts, individual nucleosides are purified by HPLC and quantified by isotope-dilution, electrospray ionization LC/MS-MS. The method can be applied to other DNA damage products and requires 4-6 days to complete depending upon the number of samples. PMID:18714297

  13. Comparison of digestion procedures and methods for quantification of trace lead in breast milk by isotope dilution inductively coupled plasma mass spectrometry.

    PubMed

    Amarasiriwardena, Chitra J; Jayawardene, Innocent; Lupoli, Nicola; Barnes, Ramon M; Hernandez-Avila, Mauricio; Hu, Howard; Ettinger, Adrienne S

    2013-01-01

    Measurement of lead in breast milk is an important public health consideration and can be technically quite challenging. The reliable and accurate determination of trace lead in human breast milk is difficult for several reasons including: potential for contamination during sample collection, storage, and analysis; complexities related to the high fat content of human milk; and poor analytic sensitivity at low concentrations. Breast milk lead levels from previous published studies should therefore be reviewed with caution. Due to the difficulty in identifying a method that would successfully digest samples with 100% efficiency, we evaluated three different digestion procedures including: (1) dry ashing in a muffle furnace, (2) microwave oven digestion, and (3) digestion in high pressure asher. High temperature, high pressure asher digestion was selected as the procedure of choice for the breast milk samples. Trace lead analysis was performed using isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS). Measured lead concentrations in breast milk samples (n = 200) from Mexico ranged from 0.2 to 6.7 ng ml(-1). The precision for these measurements ranged from 0.27-7.8% RSD. Use of strict contamination control techniques and of a very powerful digestion procedure, along with an ID-ICP-MS method for lead determination, enables us to measure trace lead levels as low as 0.2 ng ml(-1) in milk (instrument detection limit = 0.01 ng ml(-1)). PMID:24808927

  14. Determination of ochratoxin A in food: comparison of a stable isotope dilution assay, liquid chromatography-fluorescence detection and an enzyme-linked immunosorbent assay.

    PubMed

    Lindenmeier, Michael; Schieberle, Peter; Rychlik, Michael

    2011-05-01

    Quantitative results for the mycotoxin ochratoxin A (OTA), obtained by a stable isotope dilution assay (SIDA) were compared with two commonly used analytical methods for OTA quantitation. For this, different types of food, such as wheat, coffee, sultanas, and blood sausages, were analyzed. Because results obtained by the SIDA method were closest to the certified contents of an OTA reference material, data obtained by this method were considered as reference data. For liquid chromatography-fluorescence detection, a clean-up by solid phase extraction on silica was found to be necessary, and a correction for recovery had to be performed to match the data from the SIDA experiments. The enzyme-linked immunosorbent assay (ELISA) strongly overestimated the OTA content in coffee and nutmeg therefore an extract clean-up by immunoaffinity chromatography had to be used to match the SIDA results. Following this sample preparation, ELISA gave correct qualitative and semiquantitative results, and proved to be a suitable screening method. SIDA was also established as a valuable tool to quantify OTA in meat products, when using a clean-up procedure developed recently for blood samples. PMID:23605702

  15. A novel approach for high sensitive determination of sulfur mustard by derivatization and isotope-dilution LC-MS/MS analysis.

    PubMed

    Xu, Bin; Zong, Cheng; Nie, Zhiyong; Guo, Lei; Xie, Jianwei

    2015-01-01

    A new isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of sulfur mustard (SM) has been developed using a direct chemical derivatization method by nucleophile potassium thioacetate (PTA) in aqueous solution. The reaction conditions for derivatization, such as reaction temperature, time, solvent and concentration of PTA, were optimized for high performance. Reversed phase liquid chromatography was suitable for analysis of such a PTA derivatized SM in complex environmental samples. Compared with other conventional gas chromatography or gas chromatography-mass spectrometry methods for direct detection on SM, better sensitivity and selectivity were achieved by this direct derivatization and LC-MS/MS method, where SM can be detected as low as 0.05 ng/mL in acetonitrile. The linear range was from 0.1 to 1000 ng/mL. The relative standard deviation (RSD) of the intra-day precision was less than 11.8%, and RSD of the inter-day precision was less than 12.3%. The whole procedure for both derivatization and analysis was quick and simple, and the total time was less than 1h. This established method has been successfully employed for determination of spiking samples both in water and soil. A detection limit of 0.1 ng/mL was achieved for river water, while the SM in soil sample could be detected at 0.1 ng/g. PMID:25476305

  16. Detection and Quantitative Analysis of the Non-cytotoxic allo-Tenuazonic Acid in Tomato Products by Stable Isotope Dilution HPLC-MS/MS.

    PubMed

    Hickert, Sebastian; Krug, Isabel; Cramer, Benedikt; Humpf, Hans-Ulrich

    2015-12-23

    Tenuazonic acid (1) is a mycotoxin produced mainly by fungi of the genus Alternaria. It occurs in a variety of agricultural products. allo-Tenuazonic acid (2) is an isomer of 1 that is not chromatographically separated from 1 in most analytical methods. Therefore, both isomers are quantitated as a sum parameter. In this study a QuEChERS (quick, easy, cheap, effective, rugged and safe) based stable isotope dilution HPLC-MS/MS method including the chromatographic separation of both isomers was developed and applied to 20 tomato products from the German market. All products showed contamination with both toxins. 1 was found in a range from 5.3 ± 0.1 to 550 ± 15 μg/kg (average = 120 μg/kg) and 2 in a range from 1.5 ± 0.4- to 270 ± 0.8 μg/kg (average = 58 μg/kg). 2 represents 7.0-44% of the sum of both isomers (average = 29%). This is the first reported occurrence of 2 in food samples. To evaluate and compare the cytotoxicities of 1 and 2, both compounds were isolated from a synthetic racemic mixture. 1 showed moderate cytotoxic effects on HT-29 cells starting at 100 μM, whereas 2 exhibited no activity. 2 was not produced in liquid cultures of Alternaria alternata in yeast extract sucrose (YES) medium, but could be detected in small amounts in tomato puree inoculated with the fungus. PMID:26633086

  17. Isotope dilution high-resolution gas chromatography/high-resolution mass spectrometry method for analysis of selected acidic herbicides in surface water.

    PubMed

    Woudneh, Million B; Sekela, Mark; Tuominen, Taina; Gledhill, Melissa

    2006-11-10

    In this work, an isotope dilution method for determination of selected acidic herbicides by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) was developed for surface water samples. Average percent recoveries of native analytes were observed to be between 70.8 and 93.5% and average recoveries of labeled quantification standards [(13)C(6)]2,4-D and [(13)C(6)]2,4,5-T were 85.5 and 101%, respectively. Using this method, detection limits of 0.05 ng/L for dicamba, MCPA, MCPP, and triclopyr, and 0.5 ng/L for 2,4-D were routinely achieved. The method was applied to measuring the concentration of these analytes in surface water samples collected from five sampling locations in the Lower Fraser Valley region of British Columbia, Canada. All of the herbicides monitored were detected at varying levels in the surface water samples collected. The highest concentrations detected for each analyte were 345 ng/L for 2,4-D, 317 ng/L for MCPA, 271 ng/L for MCPP, 15.7 ng/L for dicamba, and 2.18 ng/L for triclopyr. Average detection frequencies of the herbicides were 95% for MCPA, 80% for MCPP, 70% for dicamba, 65% for 2,4-D, and 46% for triclopyr. Seasonal variations of herbicide levels are also discussed. PMID:16956613

  18. Determination of nerve agent metabolites in human urine by isotope-dilution gas chromatography-tandem mass spectrometry after solid phase supported derivatization.

    PubMed

    Lin, Ying; Chen, Jia; Yan, Long; Guo, Lei; Wu, Bidong; Li, Chunzheng; Feng, Jianlin; Liu, Qin; Xie, Jianwei

    2014-08-01

    A simple and sensitive method has been developed and validated for determining ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA), isobutyl methylphosphonic acid (iBuMPA), and pinacolyl methylphosphonic acid (PMPA) in human urine using gas chromatography-tandem mass spectrometry (GC-MS/MS) coupled with solid phase derivatization (SPD). These four alkyl methylphosphonic acids (AMPAs) are specific hydrolysis products and biomarkers of exposure to classic organophosphorus (OP) nerve agents VX, sarin, RVX, and soman. The AMPAs in urine samples were directly derivatized with pentafluorobenzyl bromide on a solid support and then extracted by liquid-liquid extraction. The analytes were quantified with isotope-dilution by negative chemical ionization (NCI) GC-MS/MS in a selected reaction monitoring (SRM) mode. This method is highly sensitive, with the limits of detection of 0.02 ng/mL for each compound in a 0.2 mL sample of human urine, and an excellent linearity from 0.1 to 50 ng/mL. It is proven to be very suitable for the qualitative and quantitative analyses of degradation markers of OP nerve agents in biomedical samples. PMID:24633564

  19. Measurement of 2-carboxyarabinitol 1-phosphate in plant leaves by isotope dilution. [Spinacea oleracea; Triticum aestivum; Arabidopsis thaliana; Maize; Phaseolus vulgaris; Petunia hybrida

    SciTech Connect

    Moore, B.D.; Kobza, J.; Seemann, J.R. )

    1991-05-01

    The level of 2-carboxyarabinitol 1-phosphate (CA1P) in leaves of 12 species was determined by an isotope dilution assay. {sup 14}C-labeled standard was synthesized from (2-{sup 14}C)carboxyarabinitol 1,5-bisphosphate using acid phosphatase, and was added at the initial point of leaf extraction. Leaf CA1P was purified and its specific activity determined. CA1P was found in dark-treated leaves of all species examined, including spinach (Spinacea oleracea), wheat (Triticum aestivum), Arabidopsis thaliana, and maize (Zea mays). The highest amounts were found in bean (Phaseolus vulgaris) and petunia (Petunia hybrida), which had 1.5 to 1.8 moles CA1P per mole ribulose 1,5-bisphosphate carboxylase catalytic sites. Most species had intermediate amounts of CA1P (0.2 to 0.8 mole CA1P per mole catalytic sites). Such intermediate to high levels of CA1P support the hypothesis that CA1P functions in many species as a light-dependent regulator of ribulose 1,5-bisphosphate carboxylase activity and whole leaf photosynthetic CO{sub 2} assimilation. However, CA1P levels in spinach, wheat, and A. thaliana were particularly low (less than 0.09 mole CA1P per mole catalytic sites). In such species, CA1P does not likely have a significant role in regulating ribulose 1,5-bisphosphate carboxylase activity, but could have a different physiological role.

  20. Precision of glucose measurements in control sera by isotope dilution/mass spectrometry: proposed definitive method compared with a reference method

    SciTech Connect

    Pelletier, O.; Arratoon, C.

    1987-08-01

    This improved isotope-dilution gas chromatographic/mass spectrometric (GC/MS) method, in which (/sup 13/C)glucose is the internal standard, meets the requirements of a Definitive Method. In a first study with five reconstituted lyophilized sera, a nested analysis of variance of GC/MS values indicated considerable among-vial variation. The CV for 32 measurements per serum ranged from 0.5 to 0.9%. However, concentration and uncertainty values (mmol/L per gram of serum) assigned to one serum by the NBS Definitive Method (7.56 +/- 0.28) were practically identical to those obtained with the proposed method (7.57 +/- 0.20). In the second study, we used twice more (/sup 13/C)glucose diluent to assay four serum pools and two lyophilized sera. The CV ranged from 0.26 to 0.5% for the serum pools and from 0.28 to 0.59% for the lyophilized sera. In comparison, results by the hexokinase/glucose-6-phosphate dehydrogenase reference method agreed within acceptable limits with those by the Definitive Method but tended to be slightly higher (up to 3%) for lyophilized serum samples or slightly lower (up to 2.5%) for serum pools.

  1. On-line species-unspecific isotope dilution analysis in the picomolar range reveals the time- and species-depending mercury uptake in human astrocytes.

    PubMed

    Wehe, Christoph A; Pieper, Imke; Holtkamp, Michael; Thyssen, Georgina M; Sperling, Michael; Schwerdtle, Tanja; Karst, Uwe

    2014-03-01

    In order to reveal the time-depending mercury species uptake by human astrocytes, a novel approach for total mercury analysis is presented, which uses an accelerated sample introduction system combined on-line with an inductively coupled plasma mass spectrometer equipped with a collision/reaction cell. Human astrocyte samples were incubated with inorganic mercury (HgCl2), methylmercury chloride (MeHgCl), and thimerosal. After 1-h incubation with Hg(2+), cellular concentrations of 3 μM were obtained, whereas for organic species, concentrations of 14-18 μM could be found. After 24 h, a cellular accumulation factor of 0.3 was observed for the cells incubated with Hg(2+), whereas the organic species both showed values of about 5. Due to the obtained steady-state signals, reliable results with relative standard deviations of well below 5 % and limits of detection in the concentration range of 1 ng L(-1) were obtained using external calibration and species-unspecific isotope dilution analysis approaches. The results were further validated using atomic fluorescence spectrometry. PMID:24442014

  2. [Determination of atmospheric polybrominated diphenyl ethers and polybrominated biphenyl 153 using isotope dilution-high resolution gas chromatography/high resolution mass spectrometry].

    PubMed

    Zheng, Xiaoyan; Yu, Jianzhao; Xu, Xiuyan; Yu, Haibin; Chen, Ye; Tan, Li; Lü, Yibing

    2015-10-01

    Considering the features and demands of the environmental monitoring, an isotope dilution-high resolution gas chromatography/high resolution mass spectrometry method was developed for the determination of polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls 153 (BB153) in the ambient air. PBDEs and BB153 were extracted using an accelerated solvent extraction apparatus with a mixture of hexane-dichloromethane (v/v, 1:1) and hexane, respectively. The concentrated extracts were loaded on the composite silica gel column for cleanup. The mean recoveries of native compounds at 10% and 90% of the highest levels of calibration curves were 100% and 104% with 5% and 6% of the mean relative standard deviations (n = 7), respectively. The recoveries of 13C labeled surrogates for di- to deca-brominated diphenyl ethers and BB153 were in the range of 36.5%-133%. However, the recoveries of 13C-monobrominated diphenyl ethers were relatively low, maybe due to the different physicochemical properties compared with the other homologues. No breakthrough of pollutants was estimated under real sampling volume of 300 m3. The limits of detection were lower than 2 x 10(-4) ng/Nm3. The recoveries of 13C labeled surrogates were between 56% and 126%, except monoBDEs. The results demonstrated that the method is suitable for the analysis of di- to decabrominated diphenyl ethers and BB153 in the ambient air with precise quantification. PMID:26930965

  3. Direct determination of fatty acid esters of 3-chloro-1, 2-propanediol in edible vegetable oils by isotope dilution - ultra high performance liquid chromatography - triple quadrupole mass spectrometry.

    PubMed

    Li, Heli; Chen, Dawei; Miao, Hong; Zhao, Yunfeng; Shen, Jianzhong; Wu, Yongning

    2015-09-01

    A selective and sensitive ultra-high performance liquid chromatography - triple quadrupole mass spectrometry (UHPLC-MS/MS) method coupled with matrix solid phase dispersion (MSPD) extraction was developed for the direct determination of fatty acid esters of 3-chloro-1,2-propanediol (3-MCPD esters) in edible vegetable oils. The method integrated the isotope dilution technique, MSPD extraction and UHPLC - MS/MS analysis with multi-reaction monitoring mode (MRM). Matrix-matched calibration curves showed good linearity within the range of 0.01-10mgL(-1) with the correlation coefficient not less than 0.999. Limits of detection (LODs) and limit of quantification (LOQs) of the 3-MCPD esters fell into the range of 0.0001-0.02mgkg(-1) and 0.0004-0.05mgkg(-1), respectively. The recoveries for the spiked extra virgin olive oils ranged from 94.4% to 108.3%, with the relative standard deviations (RSD) ranging from 0.6% to 10.5%. The method was applied for the oil sample (T2642) of the official Food Analysis Performance Assessment Scheme (FAPAS) in 2014 and other real samples from supermarket, and the results showed that the present method was comparative to the gas chromatography-mass spectrometry (GC-MS) method based on the improved German Society for Fat Science (DGF) standard method C-III 18 (09) except for palm oil. PMID:26239698

  4. Determination of bisphenol A, triclosan and their metabolites in human urine using isotope-dilution liquid chromatography-tandem mass spectrometry.

    PubMed

    Provencher, Gilles; Bérubé, René; Dumas, Pierre; Bienvenu, Jean-François; Gaudreau, Eric; Bélanger, Patrick; Ayotte, Pierre

    2014-06-27

    Bisphenol A (BPA) and triclosan (TCS) are ubiquitous environmental phenols exhibiting endocrine disrupting activities that may be involved in various health disorders in humans. There is a need to measure separately free forms and conjugated metabolites because only the former are biologically active. We have developed sensitive methods using isotope-dilution liquid chromatography-tandem mass spectrometry for individual measurements of free BPA and TCS as well as their metabolites, BPA glucuronide (BPAG), BPA monosulfate (BPAS), BPA disulfate (BPADS), TCS glucuronide (TCSG) and TCS sulfate (TCSS) in urine. Comparative analyses of urine samples from 46 volunteers living in the Quebec City area using the new methods and a GC-MS/MS method previously used in our laboratory revealed very strong correlations for total BPA (Spearman's rs=0.862, p<0.0001) and total TCS concentrations (rs=0.942, p<0.0001). Glucuronide metabolites were the most abundant BPA and TCS species in urine samples (>94% of total urinary concentrations). Unconjugated TCS concentrations represented a small proportion of total TCS species (median=1.6%) but its concentration was likely underestimated due to losses by adsorption to the surface of polypropylene tubes used for sample storage. To our knowledge, we are the first to report levels of free, sulfated and glucuronidated TCS levels in human urine. PMID:24835763

  5. Isotope Dilution and LA ICPMS Study of Trace Elements in Garnets: Implications for Sm-Nd and Lu-Hf Dating.

    NASA Astrophysics Data System (ADS)

    Anczkiewicz, R.; Platt, J. P.; Thirlwall, M. F.; Alard, O.

    2003-12-01

    One of the main advantages of garnet geochronology is a possibility of establishing a direct link between isotopic ages and PT conditions. However, both Lu-Hf and Sm-Nd garnet dating can strongly be affected by submicroscopic inclusions capable of dominating the Sm-Nd and Lu-Hf budget. We investigated possible effects of various inclusions on Sm-Nd and Lu-Hf systems by combined isotope dilution and LA ICPMS studies. Internal isochrons obtained for 6 high-grade blocks of metabasites from the Franciscan complex yielded highly precise Lu-Hf ages ranging from 114 to 170 Ma, but failed to provide Sm-Nd dates. The main reason for failure of the Sm-Nd dating was a rather large amount of matrix silicate inclusions, which contained > 100 times more Nd than analyzed "impure" garnet fractions. The same inclusions had very limited influence on the Lu-Hf budget. This is mainly due to strong enrichment of garnets in heavy REE and due to much lower Hf concentrations in rock forming silicates. The 176Lu/177Hf ratios obtained for the analyzed garnets are typically between 1.5 and 8, but for two samples with spessartine-rich garnets, values range between 21 and 28 and are the highest yet reported. Small amount of zircon and rutile inclusions did not notably suppress 176Lu/177Hf ratios. This is mainly due to their small size (<10 μ m) and low abundance, but also because of their limited dissolution during sample digestion on a hotplate. Our results demonstrate that even samples with significant amounts of inclusions can yield precise and accurate Lu-Hf dates. For upper amphibolite facies metapelites from Vietnam, we obtained well defined Sm-Nd ages of 52.1+/-2.5 and 31.4+/-1.0 Ma, which are grossly discordant with the corresponding Lu-Hf dates of 84.1+/-1.6 Ma and 77.9+/-1.6 Ma, respectively. We therefore conducted LA ICP MS measurements on 4 selected samples. Sm/Nd ratios show rather flat zonation profiles throughout most of the crystal, with an up to 30% increase in the rims. The

  6. Thermal conductivity reduction in analogous 2D nanomaterials with isotope substitution: Graphene and silicene

    NASA Astrophysics Data System (ADS)

    Srinivasan, Srilok; Ray, Upamanyu; Balasubramanian, Ganesh

    2016-04-01

    We employ molecular dynamics simulations to understand how the presence of isotopes influences thermal transport across silicene, and compare the findings with that in structurally analogous graphene. The simulated structures are about 140 nm long and around 4 nm wide. The phonon spectra along with the variation of thermal conductivity reveal that out-of-plane modes are delocalized relative to the in-plane counterparts. The absolute thermal conductivity reductions are more pronounced in graphene than in silicene. Our computational findings agree with results of an analytical model based on mean-field approximation with appropriate corrections for the lattice anharmonicity.

  7. An Update on the Non-Mass-Dependent Isotope Fractionation under Thermal Gradient

    NASA Technical Reports Server (NTRS)

    Sun, Tao; Niles, Paul; Bao, Huiming; Socki, Richard; Liu, Yun

    2013-01-01

    Mass flow and compositional gradient (elemental and isotope separation) occurs when flu-id(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been theoretically and experimentally studied for more than a century, although there has not been a satisfactory theory to date. Nevertheless, for isotopic system, the Chapman-Enskog theory predicts that the mass difference is the only term in the thermal diffusion separation factors that differs one isotope pair to another,with the assumptions that the molecules are spherical and systematic (monoatomic-like structure) and the particle collision is elastic. Our previous report indicates factors may be playing a role because the Non-Mass Dependent (NMD) effect is found for both symmetric and asymmetric, linear and spherical polyatomic molecules over a wide range of temperature (-196C to +237C). The observed NMD phenomenon in the simple thermal-diffusion experiments demands quantitative validation and theoretical explanation. Besides the pressure and temperature dependency illustrated in our previous reports, efforts are made in this study to address issues such as the role of convection or molecular structure and whether it is a transient, non-equilibrium effect only.

  8. Mass-independent fractionation of oxygen isotopes during thermal decomposition of carbonates

    PubMed Central

    Miller, Martin F.; Franchi, Ian A.; Thiemens, Mark H.; Jackson, Teresa L.; Brack, André; Kurat, Gero; Pillinger, Colin T.

    2002-01-01

    Nearly all chemical processes fractionate 17O and 18O in a mass-dependent way relative to 16O, a major exception being the formation of ozone from diatomic oxygen in the presence of UV radiation or electrical discharge. Investigation of oxygen three-isotope behavior during thermal decomposition of naturally occurring carbonates of calcium and magnesium in vacuo has revealed that, surprisingly, anomalous isotopic compositions are also generated during this process. High-precision measurements of the attendant three-isotope fractionation line, and consequently the magnitude of the isotopic anomaly (Δ17O), demonstrate that the slope of the line is independent of the nature of the carbonate but is controlled by empirical factors relating to the decomposition procedure. For a slope identical to that describing terrestrial silicates and waters (0.5247 ± 0.0007 at the 95% confidence level), solid oxides formed during carbonate pyrolysis fit a parallel line offset by −0.241 ± 0.042‰. The corresponding CO2 is characterized by a positive offset of half this magnitude, confirming the mass-independent nature of the fractionation. Slow, protracted thermolysis produces a fractionation line of shallower slope (0.5198 ± 0.0007). These findings of a 17O anomaly being generated from a solid, and solely by thermal means, provide a further challenge to current understanding of the nature of mass-independent isotopic fractionation. PMID:12167677

  9. Chlorine isotope geochemistry of Icelandic thermal fluids: Implications for geothermal system behavior at divergent plate boundaries

    NASA Astrophysics Data System (ADS)

    Stefánsson, Andri; Barnes, Jaime D.

    2016-09-01

    The chlorine isotope composition of thermal fluids from Iceland were measured in order to evaluate the source of chlorine and possible chlorine isotope fractionation in geothermal systems at divergent plate boundaries. The geothermal systems studied have a wide range of reservoir temperatures from 40 to 437 °C and in-situ pH of 6.15 to 7.15. Chlorine concentrations range from 5.2 to 171 ppm and δ37 Cl values are -0.3 to + 2.1 ‰ (n = 38). The δ37 Cl values of the thermal fluids are interpreted to reflect the source of the chlorine in the fluids. Geothermal processes such as secondary mineral formation, aqueous and vapor speciation and boiling were found to have minimal effects on the δ37 Cl values. However, further work is needed on incorporation of Cl into secondary minerals and its effect on Cl isotope fractionation. Results of isotope geochemical modeling demonstrate that the range of δ37 Cl values documented in the natural thermal fluids can be explained by leaching of the basaltic rocks by meteoric source water under geothermal conditions. Magmatic gas partitioning may also contribute to the source of Cl in some cases. The range of δ37 Cl values of the fluids result mainly from the large range of δ37 Cl values observed for Icelandic basalts, which range from -0.6 to + 1.2 ‰.

  10. Helium and Carbon isotopes of thermal springs hosted by deep faults in South China

    NASA Astrophysics Data System (ADS)

    Mao, X.; Wang, Y.; Yuan, J.

    2012-12-01

    Helium and carbon isotopes were important indicators to identify the origin of volatile dissolved in groundwater. Four thermal springs were sampled and discussed by helium and carbon isotopes for they were hosted by local deep faults and had significant connection to deep geothermal activity in Guangdong, China. 4He content of four thermal springs varied greatly from 3.72×10-8 to 199.54×10-8 cm3STP/mL, and 20Ne content varied greatly from 0.21×10-8 to 2.96×10-8 cm3STP/mL. While 3He/4He varied slightly from 0.36 to 0.57Ra (atmosphere 3He/4He ratio Ra=1.4×10-6). It indicated that the mixing of a lot of noble gases from other sources besides atmosphere not only changed the content of noble gases in groundwater, but also changed the isotopic compositions of noble gases, during the runoff process of groundwater. Because 22Ne was almost derived from atmosphere, an improved method of 4He/22Ne - 3He/4He was used to identify the origin of helium. 4% to 6% mantle He in thermal springs revealed that significant mantle He migrating in deep faults can bring a certain amount of energy along with thermal volatile and contribute to thermal spring formation. The δ13C value of four thermal springs was -3.79‰ to -2.17‰. Then dissolved inorganic carbon in thermal springs was speculated from rock metamorphism, it indicated geothermal activity. The four thermal springs were illustrated in the zone of crustal CO2 of rock inorganic chemistry, near to that of crust-mantle mixing CO2. It seemed that negligible or a small amount of volcanic mantle CO2 mixed with crustal CO2, and dissolved in thermal groundwater. So, δ13C revealed that dissolved inorganic carbon in thermal springs was from rock metamorphism occurred in certain deep crust as geothermal activity, which maybe the main energy source of thermal springs. Fig. 1. AIR (ASW)-MORB-CRUST mixing model of He and Ne isotopes. Fig. 2. CO2 origin identified by the relationship of δ13C and 3He/ 4He.

  11. Diagnosis of medium chain acyl-CoA dehydrogenase deficiency by stable isotope dilution analysis of urinary acylglycines: Retrospective and prospective studies, and comparison of its accuracy to acylcarnitine identification by FAB/mass spectrometry

    SciTech Connect

    Rinaldo, P.; O'Shea, J.J.; Welch, R.D.; Tanaka, K. )

    1990-01-01

    In summary, we have demonstrated that the accurate quantitation of urinary HG and PPG by stable isotope dilution analysis is currently the most reliable method for the diagnosis of MCAD deficiency. This method is particularly useful for testing random samples from asymptomatic patients without any provocative test, and it is suitable to widely survey a fairly large population, such as patients with episodic manifestations and families with a history of SIDS.

  12. Determination of mycotoxins in milk-based products and infant formula using stable isotope dilution assay and liquid chromatography tandem mass spectrometry.

    PubMed

    Zhang, Kai; Wong, Jon W; Hayward, Douglas G; Vaclavikova, Marta; Liao, Chia-Ding; Trucksess, Mary W

    2013-07-01

    A stable isotope dilution assay and liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of 12 mycotoxins, aflatoxins B₁, B₂, G₁, G₂, and M₁, deoxynivalenol, fumonisins B₁, B₂, and B₃, ochratoxin A, T-2 toxin, and zearalenone, in milk-based infant formula and foods. Samples were fortified with 12 ¹³C uniformly labeled mycotoxins ([¹³C]-mycotoxins) that correspond to the 12 target mycotoxins and prepared by dilution and filtration, followed by LC-MS/MS analysis. Quantitation was achieved using the relative response factors of [¹³C]-mycotoxins and target mycotoxins. The average recoveries in fortified milk, milk-based infant formula, milk powder, and baby yogurt of aflatoxins B₁, B₂, G₁, and G₂ (2, 10, and 50 μg/kg), aflatoxin M₁ (0.5, 2.5, and 12.5 μg/kg), deoxynivalenol, fumonisins B₁, B₂, and B₃ (40, 200, and 1000 μg/kg), ochratoxin A, T-2 toxin, and zearalenone (20, 100, and 500 μg/kg), range from 89 to 126% with RSDs of <20%. The individual recoveries in the four fortified matrices range from 72% (fumonisin B₃, 20 μg/kg, milk-based infant formula) to 136% (T-2 toxin, 20 μg/kg, milk powder), with RSDs ranging from 2 to 25%. The limits of quantitation (LOQs) were from 0.01 μg/kg (aflatoxin M₁) to 2 (fumonisin B₁) μg/kg. Aflatoxin M₁ was detected in two European Reference materials at 0.127 ± 0.013 μg/kg (certified value = 0.111 ± 0.018 μg/kg) and 0.46 ± 0.04 μg/kg (certified value = 0.44 ± 0.06 μg/kg), respectively. In 60 local market samples, aflatoxins B₁ (1.14 ± 0.10 μg/kg) and B₂ (0.20 ± 0.03 μg/kg) were detected in one milk powder sample. Aflatoxin M₁ was detected in three imported samples (condensed milk, milk-based infant formula, and table cream), ranging from 0.10 to 0.40 μg/kg. The validated method provides sufficient selectivity, sensitivity, accuracy, and reproducibility to screen for aflatoxin M₁ at nanograms per

  13. Quantification of activated NF-kappaB/RelA complexes using ssDNA aptamer affinity-stable isotope dilution-selected reaction monitoring-mass spectrometry.

    PubMed

    Zhao, Yingxin; Widen, Steven G; Jamaluddin, Mohammad; Tian, Bing; Wood, Thomas G; Edeh, Chukwudi B; Brasier, Allan R

    2011-06-01

    Nuclear Factor-κB (NF-κB) is a family of inducible transcription factors regulated by stimulus-induced protein interactions. In the cytoplasm, the NF-κB member RelA transactivator is inactivated by binding inhibitory IκBs, whereas in its activated state, the serine-phosphorylated protein binds the p300 histone acetyltransferase. Here we describe the isolation of a ssDNA aptamer (termed P028F4) that binds to the activated (IκBα-dissociated) form of RelA with a K(D) of 6.4 × 10(-10), and its application in an enrichment-mass spectrometric quantification assay. ssDNA P028F4 competes with cognate duplex high affinity NF-κB binding sites for RelA binding in vitro, binds activated RelA in eukaryotic nuclei and reduces TNFα-stimulated endogenous NF-κB dependent gene expression. Incorporation of P028F4 as an affinity isolation step enriches for serine 536 phosphorylated and p300 coactivator complexed RelA, simultaneously depleting IκBα·RelA complexes. A stable isotope dilution (SID)-selected reaction monitoring (SRM)- mass spectrometry (MS) assay for RelA was developed that produced a linear response over 1,000 fold dilution range of input protein and had a 200 amol lower limit of quantification. This multiplex SID-SRM-MS RelA assay was used to quantify activated endogenous RelA in cytokine-stimulated eukaryotic cells isolated by single-step P028F4 enrichment. The aptamer-SID-SRM-MS assay quantified the fraction of activated RelA in subcellular extracts, detecting the presence of a cytoplasmic RelA reservoir unresponsive to TNFα stimulation. We conclude that aptamer-SID-SRM-MS is a versatile tool for quantification of activated NF-κB/RelA and its associated complexes in response to pathway activation. PMID:21502374

  14. A Sr-isotopic comparison between thermal waters, rocks, and hydrothermal calcites, Long Valley caldera, California

    USGS Publications Warehouse

    Goff, F.; Wollenberg, H.A.; Brookins, D.C.; Kistler, R.W.

    1991-01-01

    The 87Sr/86Sr values of thermal waters and hydrothermal calcites of the Long Valley caldera geothermal system are more radiogenic than those of young intracaldera volcanic rocks. Five thermal waters display 87Sr/86Sr of 0.7081-0.7078 but show systematically lighter values from west to east in the direction of lateral flow. We believe the decrease in ratio from west to east signifies increased interaction of deeply circulating thermal water with relatively fresh volcanic rocks filling the caldera depression. All types of pre-, syn-, and post-caldera volcanic rocks in the west and central caldera have (87Sr/86Sr)m between about 0.7060 and 0.7072 and values for Sierra Nevada granodiorites adjacent to the caldera are similar. Sierran pre-intrusive metavolcanic and metasedimentary rocks can have considerably higher Sr-isotope ratios (0.7061-0.7246 and 0.7090-0.7250, respectively). Hydrothermally altered volcanic rocks inside the caldera have (87Sr/86Sr)m slightly heavier than their fresh volcanic equivalents and hydrothermal calcites (0.7068-0.7105) occupy a midrange of values between the volcanic/plutonic rocks and the Sierran metamorphic rocks. These data indicate that the Long Valley geothermal reservoir is first equilibrated in a basement complex that contains at least some metasedimentary rocks. Reequilibration of Sr-isotope ratios to lower values occurs in thermal waters as convecting geothermal fluids flow through the isotopically lighter volcanic rocks of the caldera fill. ?? 1991.

  15. A novel strategy for Cr(III) and Cr(VI) analysis in dietary supplements by speciated isotope dilution mass spectrometry.

    PubMed

    Unceta, Nora; Astorkia, Maider; Abrego, Zuriñe; Gómez-Caballero, Alberto; Goicolea, M Aránzazu; Barrio, Ramón J

    2016-07-01

    In recent years, Cr speciation in dietary supplements has become decisive in the evaluation of their health risks. Despite being an beneficial micronutrient, Cr(III) can be toxic at living organisms at high concentrations, while Cr(VI) is known to be highly toxic and carcinogenic. The main objective of this work was to optimize an analytical methodology for the extraction and accurate quantification of Cr(III) and Cr(VI) in dietary supplements. The extraction of Cr species was carried out with 50mM EDTA solution on a hotplate under optimized conditions. Special attention was paid to bidirectional species transformations. No noticeable oxidation of Cr(III) into Cr(VI) was observed and the reduction to Cr(III) only occurred at very high Cr(VI) concentrations. Cr(III) as Cr(EDTA)(-) complex was chromatographically separated from Cr(VI), retained as CrO4(2-), on an anion exchange column coupled to inductively coupled plasma mass spectrometry (LC-ICP-MS). The limit of quantification (0.08µgg(-1)) was below the limit established for Cr enriched yeasts by the European Union. Eleven dietary supplements were analyzed and Cr(III) and Cr(VI) quantification was carried out by external calibration monitoring (52)Cr isotope and by speciated isotope dilution mass spectrometry (SIDMS) adding (50)Cr(III) and (53)Cr(VI) spikes. Total Cr was also quantified by ICP-MS and mass balance between total Cr and the sum of Cr(III) and Cr(VI) was achieved. In eight of the eleven tested supplements Cr(III) calculated amounts were higher than those indicated by the manufacturer, but only one of them exceeded the 250µgday(-1) recommended by World Health Organization (WHO). In contrast, it is worth noting that Cr(VI) amounts beyond the recommendations of the European Union for Cr enriched yeasts were found in five supplements. These results revealed that more accurate and rigorous quality assurance protocols should be applied to the testing of the final products, including the analysis of both

  16. Stable Isotope Dilution Assays for Clinical Analyses of Folates and Other One-Carbon Metabolites: Application to Folate-Deficiency Studies

    PubMed Central

    Kopp, Markus; Morisset, Rosalie; Koehler, Peter

    2016-01-01

    Folate deficiency is generally accepted as a potential direct or indirect risk factor for diseases including spina bifida, coronary heart diseases, malfunctions of the central nervous system, and cancer. The direct inclusion of folates in the methylation cycle, including the remethylation of homocysteine and regeneration of S-adenosylmethionine, underlines the importance of these vitamins and other components of one-carbon metabolism. Therefore, the aim of the present study was to develop a multiple stable isotope dilution assay (SIDA) for the respective analytes in plasma and tissue samples to allow for a closer look at the interaction between a severe folate deficiency and local folate status, as well as further interactions with circulating S-adenosylmethionine, S-adenosylhomocysteine, and homocysteine. The analytical methods were based on SIDAs coupled with liquid chromatography—tandem mass spectrometry (LC-MS/MS) analysis using the deuterated folates [2H4]-5-methyltetrahydrofolic acid, [2H4]-5-formyltetrahydrofolic acid, [2H4]-tetrahydrofolic acid, [2H4]-10-formylfolic acid, and [2H4]-folic acid and the deuterated one-carbon metabolites [2H4]-homocysteine, [2H4]-S-adenosylhomocysteine, and [2H3]-S-adenosylmethionine as internal standards. Three analytical methods have been developed for the analysis of homocysteine, S-adenosylmethionine, S-adenosylhomocysteine, and six folate vitamers. Validation data for the analysis of C1-metabolites in plasma and tissue samples or folate analysis in tissue samples revealed excellent sensitivity, precision, and recovery for all analytes studied. The miniaturized methods using sample volumes as low as 50 μL and weighed portions of 5–25 mg will allow the assessment of the status of folates and additional biomarkers of impaired one-carbon metabolism during folate deficiency. PMID:27276031

  17. Addiction to MTH1 protein results in intense expression in human breast cancer tissue as measured by liquid chromatography-isotope-dilution tandem mass spectrometry.

    PubMed

    Coskun, Erdem; Jaruga, Pawel; Jemth, Ann-Sofie; Loseva, Olga; Scanlan, Leona D; Tona, Alessandro; Lowenthal, Mark S; Helleday, Thomas; Dizdaroglu, Miral

    2015-09-01

    MTH1 protein sanitizes the nucleotide pool so that oxidized 2'-deoxynucleoside triphosphates (dNTPs) cannot be used in DNA replication. Cancer cells require MTH1 to avoid incorporation of oxidized dNTPs into DNA that results in mutations and cell death. Inhibition of MTH1 eradicates cancer, validating MTH1 as an anticancer target. By overexpressing MTH1, cancer cells may mediate cancer growth and resist therapy. To date, there is unreliable evidence suggesting that MTH1 is increased in cancer cells, and available methods to measure MTH1 levels are indirect and semi-quantitative. Accurate measurement of MTH1 in disease-free tissues and malignant tumors of patients may be essential for determining if the protein is truly upregulated in cancers, and for the development and use of MTH1 inhibitors in cancer therapy. Here, we present a novel approach involving liquid chromatography-isotope-dilution tandem mass spectrometry to positively identify and accurately quantify MTH1 in human tissues. We produced full length (15)N-labeled MTH1 and used it as an internal standard for the measurements. Following trypsin digestion, seven tryptic peptides of both MTH1 and (15)N-MTH1 were identified by their full scan and product ion spectra. These peptides provided a statistically significant protein score that would unequivocally identify MTH1. Next, we identified and quantified MTH1 in human disease-free breast tissues and malignant breast tumors, and in four human cultured cell lines, three of which were cancer cells. Extreme expression of MTH1 in malignant breast tumors was observed, suggesting that cancer cells are addicted to MTH1 for their survival. The approach described is expected to be applicable to the measurement of MTH1 levels in malignant tumors vs. surrounding disease-free tissues in cancer patients. This attribute may help develop novel treatment strategies and MTH1 inhibitors as potential drugs, and guide therapies. PMID:26202347

  18. Development of three stable isotope dilution assays for the quantitation of (E)-2-butenal (crotonaldehyde) in heat-processed edible fats and oils as well as in food.

    PubMed

    Granvogl, Michael

    2014-02-12

    Three stable isotope dilution assays (SIDAs) were developed for the quantitation of (E)-2-butenal (crotonaldehyde) in heat-processed edible fats and oils as well as in food using synthesized [¹³C₄]-crotonaldehyde as internal standard. First, a direct headspace GC-MS method, followed by two indirect methods on the basis of derivatization with either pentafluorophenylhydrazine (GC-MS) or 2,4-dinitrophenylhydrazine (LC-MS/MS), was developed. All methods are also suitable for the quantitation of acrolein using the standard [¹³C₃]-acrolein. Applying these three methods on five different types of fats and oils varying in their fatty acid compositions revealed significantly varying crotonaldehyde concentrations for the different samples, but nearly identical quantitative data for all methods. Formed amounts of crotonaldehyde were dependent not only on the type of oil, e.g., 0.29-0.32 mg/kg of coconut oil or 33.9-34.4 mg/kg of linseed oil after heat-processing for 24 h at 180 °C, but also on the applied temperature and time. The results indicated that the concentration of formed crotonaldehyde seemed to be correlated with the amount of linolenic acid in the oils. Furthermore, the formation of crotonaldehyde was compared to that of its homologue acrolein, demonstrating that acrolein was always present in higher amounts in heat-processed oils, e.g., 12.3 mg of crotonaldehyde/kg of rapeseed oil in comparison to 23.4 mg of acrolein/kg after 24 h at 180 °C. Finally, crotonaldehyde was also quantitated in fried food, revealing concentrations from 12 to 25 μg/kg for potato chips and from 8 to 19 μg/kg for donuts, depending on the oil used. PMID:24428123

  19. Stable Isotope Dilution Assays for Clinical Analyses of Folates and Other One-Carbon Metabolites: Application to Folate-Deficiency Studies.

    PubMed

    Kopp, Markus; Morisset, Rosalie; Koehler, Peter; Rychlik, Michael

    2016-01-01

    Folate deficiency is generally accepted as a potential direct or indirect risk factor for diseases including spina bifida, coronary heart diseases, malfunctions of the central nervous system, and cancer. The direct inclusion of folates in the methylation cycle, including the remethylation of homocysteine and regeneration of S-adenosylmethionine, underlines the importance of these vitamins and other components of one-carbon metabolism. Therefore, the aim of the present study was to develop a multiple stable isotope dilution assay (SIDA) for the respective analytes in plasma and tissue samples to allow for a closer look at the interaction between a severe folate deficiency and local folate status, as well as further interactions with circulating S-adenosylmethionine, S-adenosylhomocysteine, and homocysteine. The analytical methods were based on SIDAs coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis using the deuterated folates [2H4]-5-methyltetrahydrofolic acid, [2H4]-5-formyltetrahydrofolic acid, [2H4]-tetrahydrofolic acid, [2H4]-10-formylfolic acid, and [2H4]-folic acid and the deuterated one-carbon metabolites [2H4]-homocysteine, [2H4]-S-adenosylhomocysteine, and [2H3]-S-adenosylmethionine as internal standards. Three analytical methods have been developed for the analysis of homocysteine, S-adenosylmethionine, S-adenosylhomocysteine, and six folate vitamers. Validation data for the analysis of C1-metabolites in plasma and tissue samples or folate analysis in tissue samples revealed excellent sensitivity, precision, and recovery for all analytes studied. The miniaturized methods using sample volumes as low as 50 μL and weighed portions of 5-25 mg will allow the assessment of the status of folates and additional biomarkers of impaired one-carbon metabolism during folate deficiency. PMID:27276031

  20. Determination of agmatine using isotope dilution UPLC-tandem mass spectrometry: application to the characterization of the arginine decarboxylase pathway in Pseudomonas aeruginosa.

    PubMed

    Dalluge, Joseph J; McCurtain, Jennifer L; Gilbertsen, Adam J; Kalstabakken, Kyle A; Williams, Bryan J

    2015-07-01

    A method has been developed for the direct determination of agmatine in bacterial culture supernatants using isotope dilution ultra performance liquid chromatography (UPLC)-tandem mass spectrometry (UPLC-MS/MS). Agmatine determination in bacterial supernatants is comprised of spiking culture or isolate supernatants with a fixed concentration of uniformly labeled (13)C5,(15)N4-agmatine (synthesized by decarboxylation of uniformly labeled (13)C6,(15)N4-arginine using arginine decarboxylase from Pseudomonas aeruginosa) as an internal standard, followed by derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBDF) to improve the reversed-phase chromatographic retention characteristics of agmatine, as well as the selectivity and sensitivity of UPLC-MS/MS detection of this amine in complex biologically derived mixtures. Intrasample precisions for measurement of agmatine in culture supernatants average 4.1% (relative standard deviation). Calibration curves are linear over the range 5 nM to 10 μM, and the detection limit is estimated at 1.5 nM. To demonstrate the utility of the method, agmatine levels in supernatants of overnight cultures of wild-type (UCBPP-PA14), as well as arginine decarboxylase and agmatine deiminase mutant strains of P. aeruginosa strain UCBPP-PA14 were measured. This method verified that the mutant strains are lacking the specific metabolic capabilities to produce and metabolize agmatine. In addition, measurement of agmatine in supernatants of a panel of clinical isolates from patients with cystic fibrosis revealed that three of the P. aeruginosa isolates hyper-secreted agmatine into the supernatant, hypothesized to be a result of a mutation in the aguA gene. Because agmatine has potential inflammatory activities in the lung, this phenotype may be a virulence factor for P. aeruginosa in the lung environment of cystic fibrosis patients. PMID:25957842

  1. Validation and uncertainties evaluation of an isotope dilution-SPE-LC-MS/MS for the quantification of drug residues in surface waters.

    PubMed

    Brieudes, V; Lardy-Fontan, S; Lalere, B; Vaslin-Reimann, S; Budzinski, H

    2016-01-01

    The present work describes the development and validation of a reference method conducted at the French National Institute of Metrology (LNE) for the quantitative determination of psychoactive compounds in the dissolved fraction of surface waters. More specifically an isotope dilution-SPE-LC-MS/MS based method has been implemented for the characterization of a broad range of analytes belonging to different classes of psychotropic drugs such as benzodiazepines, antidepressants, stimulants, opiates and opioids, anticonvulsants, anti-dementia drugs, analgesics as well as the anti-inflammatory drug diclofenac in the low ng L(-1) range of concentration. Full validation of the method was performed following procedures described by the French standard NF T90-210. Limits of quantification between 0.14 and 3.54 ng L(-1) were obtained. Method recoveries from 71 to 123% were observed with standard deviation below 10% in intermediate precision conditions. Accuracy was determined for every compound: measurement errors were between -4 and +1% and standard deviations in intermediate precision conditions were included within a 1-9% interval. Finally, measurement uncertainties were evaluated following the Guide to the expression of uncertainty in measurement (GUM). Expanded uncertainties (k=2) ranged from 2% for carbamazepine, EDDP (2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine) and venlafaxine to 17% for diazepam. The validated method was implemented to Seine river surface waters demonstrating its fitness for purpose. All compounds were detected and 22 out of 25 analytes were quantified. More specifically, measured concentration ranged from 0.39 ng L(-1) for MDMA (3,4-methylene-dioxy-N-methylamphetamine) to 182 ng L(-1) for gabapentine. PMID:26695245

  2. An optimized method for the accurate determination of patulin in apple products by isotope dilution-liquid chromatography/mass spectrometry.

    PubMed

    Seo, Miyeong; Kim, Byungjoo; Baek, Song-Yee

    2015-07-01

    Patulin, a mycotoxin produced by several molds in fruits, has been frequently detected in apple products. Therefore, regulatory bodies have established recommended maximum permitted patulin concentrations for each type of apple product. Although several analytical methods have been adopted to determine patulin in food, quality control of patulin analysis is not easy, as reliable certified reference materials (CRMs) are not available. In this study, as a part of a project for developing CRMs for patulin analysis, we developed isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC/MS/MS) as a higher-order reference method for the accurate value-assignment of CRMs. (13)C7-patulin was used as internal standard. Samples were extracted with ethyl acetate to improve recovery. For further sample cleanup with solid-phase extraction (SPE), the HLB SPE cartridge was chosen after comparing with several other types of SPE cartridges. High-performance liquid chromatography was performed on a multimode column for proper retention and separation of highly polar and water-soluble patulin from sample interferences. Sample extracts were analyzed by LC/MS/MS with electrospray ionization in negative ion mode with selected reaction monitoring of patulin and (13)C7-patulin at m/z 153→m/z 109 and m/z 160→m/z 115, respectively. The validity of the method was tested by measuring gravimetrically fortified samples of various apple products. In addition, the repeatability and the reproducibility of the method were tested to evaluate the performance of the method. The method was shown to provide accurate measurements in the 3-40 μg/kg range with a relative expanded uncertainty of around 1%. PMID:25925860

  3. Detection of triclocarban and two co-contaminating chlorocarbanilides in US aquatic environments using isotope dilution liquid chromatography tandem mass spectrometry

    SciTech Connect

    Sapkota, Amir; Heidler, Jochen; Halden, Rolf U. . E-mail: rhalden@jhsph.edu

    2007-01-15

    The antimicrobial compound triclocarban (TCC; 3,4,4'-trichlorocarbanilide; CAS-bar 101-20-2) is a high-production-volume chemical, recently suggested to cause widespread contamination of US water resources. To test this hypothesis, we developed an isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry method for ultratrace analysis of TCC (0.9ng/L detection limit) and analyzed low-volume water samples (200mL) along with primary sludge samples from across the United States. All river water samples (100%) collected downstream of wastewater treatment plants had detectable levels of TCC, as compared to 56% of those taken upstream. Concentrations of TCC (mean+/-standard deviation) downstream of sewage treatment plants (84+/-110ng/L) were significantly higher (P<0.05; Wilcoxon rank sum test) than those of samples taken upstream (12+/-15ng/L). Compared to surface water, mean TCC concentrations found in dried, primary sludge obtained from municipal sewage treatment plants in five states were six orders of magnitude greater (19,300+/-7100{mu}g/kg). Several river samples contained a co-contaminant, identified based on its chromatographic retention time, molecular base ion, and MS/MS fragmentation behavior as 4,4'-dichlorocarbanilide (DCC; CAS-bar 1219-99-4). In addition to TCC and DCC, municipal sludge contained a second co-contaminant, 3,3',4,4'-tetrachlorocarbanilide (TetraCC; CAS-bar 4300-43-0). Both newly detected compounds were present as impurities (0.2%{sub w/w} each) in technical grade TCC (99%). Application of the new method for chlorocarbanilide analysis yielded TCC occurrence data for 13 US states, confirmed the role of sewage treatment plants as environmental inputs of TCC, and identified DCC and TetraCC as previously unrecognized pollutants released into the environment alongside TCC.

  4. Simultaneous Measurement of Tabun, Sarin, Soman, Cyclosarin, VR, VX, and VM Adducts to Tyrosine in Blood Products by Isotope Dilution UHPLC-MS/MS

    PubMed Central

    Crow, Brian S.; Pantazides, Brooke G.; Quiñones-González, Jennifer; Garton, Joshua W.; Carter, Melissa D.; Perez, Jonas W.; Watson, Caroline M.; Tomcik, Dennis J.; Crenshaw, Michael D.; Brewer, Bobby N.; Riches, James R.; Stubbs, Sarah J.; Read, Robert W.; Evans, Ronald A.; Thomas, Jerry D.; Blake, Thomas A.; Johnson, Rudolph C.

    2015-01-01

    This work describes a new specific, sensitive, and rapid stable isotope dilution method for the simultaneous detection of the organophosphorus nerve agents (OPNAs) tabun (GA), sarin (GB), soman (GD), cyclosarin (GF), VR, VX, and VM adducts to tyrosine (Tyr). Serum, plasma, and lysed whole blood samples (50 µL) were prepared by protein precipitation followed by digestion with Pronase. Specific Tyr adducts were isolated from the digest by a single solid phase extraction (SPE) step, and the analytes were separated by reversed-phase ultra high performance liquid chromatography (UHPLC) gradient elution in less than 2 min. Detection was performed on a triple quadrupole tandem mass spectrometer using time-triggered selected reaction monitoring (SRM) in positive electrospray ionization (ESI) mode. The calibration range was characterized from 0.100–50.0 ng/mL for GB– and VR– Tyr and 0.250–50.0 ng/mL for GA–, GD–, GF–, and VX/VM–Tyr (R2 ≥ 0.995). Inter- and intra-assay precision had coefficients of variation of ≤17 and ≤10%, respectively, and the measured concentration accuracies of spiked samples were within 15% of the targeted value for multiple spiking levels. The limit of detection was calculated to be 0.097, 0.027, 0.018, 0.074, 0.023, and 0.083 ng/mL for GA–, GB–, GD–, GF–, VR–, and VX/VM–Tyr, respectively. A convenience set of 96 serum samples with no known nerve agent exposure was screened and revealed no baseline values or potential interferences. This method provides a simple and highly specific diagnostic tool that may extend the time postevent that a confirmation of nerve agent exposure can be made with confidence. PMID:25286390

  5. Development and validation of a stable-isotope dilution liquid chromatography-tandem mass spectrometry method for the determination of bisphenols in ready-made meals.

    PubMed

    Regueiro, Jorge; Wenzl, Thomas

    2015-10-01

    Due to their growing consumption, ready-made meals are a major dietary component for many people in today's society, representing an important potential route of human exposure to several food contaminants. The recent restrictions in the use of bisphenol A have led the plastic industry to look for alternative chemicals, most of them belonging to the same family of p,p'-bisphenols. The aim of the current work was to develop and validate a method based on stable-isotope dilution liquid chromatography-tandem mass spectrometry for the analysis of bisphenol A and its main analogs - bisphenol S, 4,4'-sulfonylbis(2-methylphenol), bisphenol F, bisphenol E, bisphenol B, bisphenol Z, bisphenol AF, bisphenol AP, tetrabromobisphenol A and bisphenol P - in solid foodstuffs, and particularly in ready-made meals. Extraction was carried out by ultrasound-assisted extraction after sample disruption with sand. A selective solid-phase extraction procedure was then applied to reduce potential matrix interferences. Derivatization of bisphenols with pyridine-3-sulfonyl chloride increased their ionization efficiency by electrospray ionization. Validation of the proposed method was performed in terms of selectivity, matrix effects, linearity, precision, measurement uncertainty, trueness and limits of detection. Satisfactory repeatability and intermediate precision were obtained; the related relative standard deviations were ≤7.8% and ≤10%, respectively. The relative expanded uncertainty (k=2) was below 17% for all bisphenol analogs and the trueness of the method was demonstrated by spike recovery experiments. Low limits of detection, in the range from 0.025μgkg(-1) to 0.140μgkg(-1), were obtained for all compounds. To demonstrate the applicability of the proposed method, it was eventually applied to several ready-made meals purchased from different supermarkets in Belgium. PMID:26456223

  6. Quantification of key red blood cell folates from subjects with defined MTHFR 677C>T genotypes using stable isotope dilution liquid chromatography/mass spectrometry

    PubMed Central

    Huang, Yuehua; Khartulyari, Stefanie; Morales, Megan E.; Stanislawska-Sachadyn, Anna; Von Feldt, Joan M.; Whitehead, Alexander S.; Blair, Ian A.

    2014-01-01

    Red blood cell (RBC) folate levels are established at the time of erythropoiesis and therefore provide a surrogate biomarker for the average folate status of an individual over the preceding four months. Folates are present as folylpolyglutamates, highly polar molecules that cannot be secreted from the RBCs, and must be converted into their monoglutamate forms prior to analysis. This was accomplished using an individual’s plasma pteroylpolyglutamate hydrolase by lysing the RBCs in whole blood at pH 5 in the presence of ascorbic acid. Quantitative conversion of formylated tetrahydrofolate derivatives into the stable 5,10-methenyltetrahydrofolate (5,10-MTHF) form was conducted at pH 1.5 in the presence of [13C5]-5-formyltetrahydrofolate. The resulting [13C5]-5,10-MTHF was then used as an internal standard for the formylated forms of tetrahydrofolate that had been converted into 5,10-MTHF as well any 5,10-MTHF that had been present in the original sample. A stable isotope dilution liquid chromatography-multiple reaction monitoring/mass spectrometry method was validated and then used for the accurate and precise quantification of RBC folic acid, 5-methyltetrahydrofolate (5-MTHF), tetrahydrofolate (THF), and 5,10-MTHF. The method was sensitive and robust and was used to assess the relationship between different methylenetetrahydrofolate reductase (MTHFR) 677C>T genotypes and RBC folate phenotypes. Four distinct RBC folate phenotypes could be identified. These were classified according to the relative amounts of individual RBC folates as type I (5-MTHF >95%; THF <5%; 5,10-MTHF <5%), type II (5-MTHF <95%; THF 5% to 20%; 5,10-MTHF <5%), type III (5-MTHF >55%; THF >20%; 5,10-MTHF >5%), and type IV (5-MTHF <55%; THF >20%; 5,10-MTHF >5%). PMID:18634122

  7. Stable isotope dilution ultra-high performance liquid chromatography-tandem mass spectrometry quantitative profiling of tryptophan-related neuroactive substances in human serum and cerebrospinal fluid.

    PubMed

    Hényková, Eva; Vránová, Hana Přikrylová; Amakorová, Petra; Pospíšil, Tomáš; Žukauskaitė, Asta; Vlčková, Magdaléna; Urbánek, Lubor; Novák, Ondřej; Mareš, Jan; Kaňovský, Petr; Strnad, Miroslav

    2016-03-11

    Many compounds related to L-tryptophan (L-TRP) have interesting biological or pharmacological activity, and their abnormal neurotransmission seems to be linked to a wide range of neurodegenerative and psychiatric diseases. A high-throughput method based on ultra-high performance liquid chromatography connected to electrospray tandem mass spectrometry (UHPLC-ESI-MS/MS) was developed for the quantitative analysis of L-TRP and 16 of its metabolites in human serum and cerebrospinal fluid (CSF), representing both major and minor routes of L-TRP catabolism. The combination of a fast LC gradient with selective tandem mass spectrometry enabled accurate analysis of almost 100 samples in 24h. The standard isotope dilution method was used for quantitative determination. The method's lower limits of quantification for serum and cerebrospinal fluid ranged from 0.05 to 15nmol/L and 0.3 to 45nmol/L, respectively. Analytical recoveries ranged from 10.4 to 218.1% for serum and 22.1 to 370.0% for CSF. The method's accuracy ranged from 82.4 to 128.5% for serum matrix and 90.7 to 127.7% for CSF matrix. All intra- and inter-day coefficients of variation were below 15%. These results demonstrate that the new method is capable of quantifying endogenous serum and CSF levels of a heterogeneous group of compounds spanning a wide range of concentrations. The method was used to determine the physiological levels of target analytes in serum and CSF samples from 18 individuals, demonstrating its reliability and potential usefulness in large-scale epidemiological studies. PMID:26879452

  8. Determination of the maleic acid in rat urine and serum samples by isotope dilution-liquid chromatography-tandem mass spectrometry with on-line solid phase extraction.

    PubMed

    Chen, Hsin-Chang; Wu, Charlene; Wu, Kuen-Yuh

    2015-05-01

    A rapid and simple on-line solid-phase extraction coupled with isotope dilution-liquid chromatography-tandem mass spectrometry (SPE-ID-LC-MS/MS) method was developed to quantitate maleic acid in serum and urine of SpragueDawley (SD) rats. The aforementioned biological samples were spiked with (13)C2-maleic acid, vigorously vortexed, added with acetonitrile to precipitate proteins, and then injected into the on-line SPE-LC-MS/MS system for quantification. Upon validation, this method demonstrated excellent feasibility and sensitivity: calibration curves for maleic acid in serum and urine display excellent linearity with the coefficient of determination (R(2)) greater than 0.999; the limits of detection and quantitation (LOD and LOQ) for maleic acid were determined at 0.2 and 0.5μg L(-1), respectively. Additionally, intra-day accuracy for maleic acid in serum and urine samples ranged from 94.0% to 100.2% and 101.3% to 104.4%, respectively. Furthermore, inter-day accuracy ranged from 93.6% to 101.0% and from 102.3% to 111.4% in serum and urine samples, respectively. Intra-day precision %RSD of maleic acid in serum and urine samples was 13.8% or less, whereas the inter-day precision was 6.1% or less. The matrix effects were not found to be statistically significant (p=0.9145 and p=0.5378, correspondingly) based on the calculations of recovery functions. The collected serum and urine samples were analyzed using SPE-ID-LC-MS/MS. Our results reveal trace levels of maleic acid in the control rats, demonstrating that this method is capable of analyzing background levels of contaminants in biofluids with excellent sensitivity and specificity at part-per-billion levels concentrations in complex matrices. PMID:25702978

  9. Lewisite Metabolites in Urine by Solid Phase Extraction-Dual Column Reversed-Phase Liquid Chromatography-Isotope Dilution Tandem Mass Spectrometry.

    PubMed

    Palcic, Jason D; Donovan, Stephen F; Jones, Janet S; Flagg, E Lindsay; Salonga, Redentor A; Mock, Walter E; Asirvatham, Victor S

    2016-07-01

    Lewisite (2-chlorovinyldichloroarsine) is a chemical warfare agent developed during World War I. A quantitative method using solid phase extraction (SPE) followed by dual column liquid chromatography (LC)-isotope dilution tandem mass spectrometry (MS-MS) was developed for the determination of (2-chlorovinyl)arsonic acid (CVAOA), a metabolite of Lewisite, in human urine. The sample was treated with hydrogen peroxide to oxidize any (2-chlorovinyl)arsonous acid (CVAA) that remained in the trivalent arsenic oxidation state. There was 1.19% (arsenic purity) of bis-(2-chlorovinyl)arsinic acid (BCVAOA), a minor Lewisite metabolite, in the stock CVAA material. The high-throughput method qualitatively assessed BCVAOA simultaneously utilizing normal-phase silica SPE followed by reversed-phase C18 LC for an orthogonal separation. The chromatographic method results in a 5.8-min cycle time with adequate retention (k' = 2.4) of CVAOA. The mass spectrometer was operated in positive electrospray ionization mode with quantitative m/z 186.9→61.0 and confirmation 186.9→91.0 mass transitions. This selective method demonstrated linearity, accuracy and reproducibility for the clinically relevant calibration range (25-3,200 µg/L as CVAA). The method detection limit was 3.3 µg/L as CVAA from a 10 µL injection. This LC-MS-MS emergency response method has a throughput of >240 samples (2.5 extracted 96-well plates) per day. PMID:27339483

  10. Simultaneous measurement of tabun, sarin, soman, cyclosarin, VR, VX, and VM adducts to tyrosine in blood products by isotope dilution UHPLC-MS/MS.

    PubMed

    Crow, Brian S; Pantazides, Brooke G; Quiñones-González, Jennifer; Garton, Joshua W; Carter, Melissa D; Perez, Jonas W; Watson, Caroline M; Tomcik, Dennis J; Crenshaw, Michael D; Brewer, Bobby N; Riches, James R; Stubbs, Sarah J; Read, Robert W; Evans, Ronald A; Thomas, Jerry D; Blake, Thomas A; Johnson, Rudolph C

    2014-10-21

    This work describes a new specific, sensitive, and rapid stable isotope dilution method for the simultaneous detection of the organophosphorus nerve agents (OPNAs) tabun (GA), sarin (GB), soman (GD), cyclosarin (GF), VR, VX, and VM adducts to tyrosine (Tyr). Serum, plasma, and lysed whole blood samples (50 μL) were prepared by protein precipitation followed by digestion with Pronase. Specific Tyr adducts were isolated from the digest by a single solid phase extraction (SPE) step, and the analytes were separated by reversed-phase ultra high performance liquid chromatography (UHPLC) gradient elution in less than 2 min. Detection was performed on a triple quadrupole tandem mass spectrometer using time-triggered selected reaction monitoring (SRM) in positive electrospray ionization (ESI) mode. The calibration range was characterized from 0.100-50.0 ng/mL for GB- and VR-Tyr and 0.250-50.0 ng/mL for GA-, GD-, GF-, and VX/VM-Tyr (R(2) ≥ 0.995). Inter- and intra-assay precision had coefficients of variation of ≤17 and ≤10%, respectively, and the measured concentration accuracies of spiked samples were within 15% of the targeted value for multiple spiking levels. The limit of detection was calculated to be 0.097, 0.027, 0.018, 0.074, 0.023, and 0.083 ng/mL for GA-, GB-, GD-, GF-, VR-, and VX/VM-Tyr, respectively. A convenience set of 96 serum samples with no known nerve agent exposure was screened and revealed no baseline values or potential interferences. This method provides a simple and highly specific diagnostic tool that may extend the time postevent that a confirmation of nerve agent exposure can be made with confidence. PMID:25286390

  11. Application of the Reference Method Isotope Dilution Gas Chromatography Mass Spectrometry (ID/GC/MS) to Establish Metrological Traceability for Calibration and Control of Blood Glucose Test Systems

    PubMed Central

    Andreis, Elisabeth; Küllmer, Kai

    2014-01-01

    Self-monitoring of blood glucose (BG) by means of handheld BG systems is a cornerstone in diabetes therapy. The aim of this article is to describe a procedure with proven traceability for calibration and evaluation of BG systems to guarantee reliable BG measurements. Isotope dilution gas chromatography mass spectrometry (ID/GC/MS) is a method that fulfills all requirements to be used in a higher-order reference measurement procedure. However, this method is not applicable for routine measurements because of the time-consuming sample preparation. A hexokinase method with perchloric acid (PCA) sample pretreatment is used in a measurement procedure for such purposes. This method is directly linked to the ID/GC/MS method by calibration with a glucose solution that has an ID/GC/MS-determined target value. BG systems are calibrated with whole blood samples. The glucose levels in such samples are analyzed by this ID/GC/MS-linked hexokinase method to establish traceability to higher-order reference material. For method comparison, the glucose concentrations in 577 whole blood samples were measured using the PCA-hexokinase method and the ID/GC/MS method; this resulted in a mean deviation of 0.1%. The mean deviation between BG levels measured in >500 valid whole blood samples with BG systems and the ID/GC/MS was 1.1%. BG systems allow a reliable glucose measurement if a true reference measurement procedure, with a noninterrupted traceability chain using ID/GC/MS linked hexokinase method for calibration of BG systems, is implemented. Systems should be calibrated by means of a traceable and defined measurement procedure to avoid bias. PMID:24876614

  12. Determination of 43 polycyclic aromatic hydrocarbons in air particulate matter by use of direct elution and isotope dilution gas chromatography/mass spectrometry.

    PubMed

    Li, Zheng; Pittman, Erin N; Trinidad, Debra A; Romanoff, Lovisa C; Mulholland, James; Sjödin, Andreas

    2010-02-01

    We are reporting a method for measuring 43 polycyclic aromatic hydrocarbons (PAH) and their methylated derivatives (Me-PAHs) in air particulate matter (PM) samples using isotope dilution gas chromatography/high-resolution mass spectrometry (GC/HRMS). In this method, PM samples were spiked with internal standards, loaded into solid phase extraction cartridges, and eluted by dichloromethane. The extracts were concentrated, spiked with a recovery standard, and analyzed by GC/HRMS at 10,000 resolution. Sixteen (13)C-labeled PAHs and two deuterated Me-PAHs were used as internal standards to account for instrument variability and losses during sample preparation. Recovery of labeled internal standards was in the range of 86-115%. The proposed method is less time-consuming than commonly used extraction methods, such as sonication and accelerated solvent extraction (ASE), and it eliminates the need for a filtration step required after the sonication extraction method. Limits of detection ranged from 41 to 332 pg/sample for the 43 analytes. This method was used to analyze reference materials from the National Institute of Standards and Technology. The results were consistent with those from ASE and sonication extraction, and these results were also in good agreement with the certified or reference concentrations. The proposed method was then used to measure PAHs on PM(2.5) samples collected at three sites (urban, suburban, and rural) in Atlanta, GA. The results showed distinct seasonal and spatial variation and were consistent with an earlier study measuring PM(2.5) samples using an ASE method, further demonstrating the compatibility of this method and the commonly used ASE method. PMID:19936717

  13. Rapid and sensitive method for the determination of four EU marker polycyclic aromatic hydrocarbons in cereal-based foods using isotope-dilution GC/MS.

    PubMed

    Kacmaz, Sibel; Zelinkova, Zuzana; Wenzl, Thomas

    2016-04-01

    A rapid and sensitive method has been developed for the determination of the four European Union marker polycyclic aromatic hydrocarbons (PAHs; benz[a]anthracene, chrysene, benzo[b]fluoranthene and benzo[a]pyrene) in some cereal-based foods. The method is based on pressurised liquid extraction (PLE), solid-phase extraction clean-up (SPE) and isotope-dilution gas chromatography with mass-spectrometric detection (GC/MS). The developed method was calibrated for the content range of 0.05-12.5 µg kg(-1) (expressed on a product basis). Recoveries of PAH were monitored in each sample via the recovery of (13)C-labelled PAHs. Recovery values were in the range between 86% and 91%, with relative standard deviations (RSDs) between 5% and 9%. The achieved limits of detection for all analytes were below 0.05 µg kg(-1). The applicability of the method for the analysis of routine samples was studied by the analysis of a set of commercial bread and breakfast cereal samples. In all analysed samples, benzo[a]pyrene (BAP) was the most prevalent PAH with the content between 0.09 and 0.30 µg kg(-1). On average, samples showed low levels of the sum of the four EU marker PAHs (ΣPAH4) that ranged between 0.11 and 0.22 µg kg(-1) for bread samples and between 0.23 and 0.87 µg kg(-1) for breakfast cereal samples. The developed method was found suitable for the determination of PAHs in cereal-based foods like cornflakes and breads with total relative fat contents below 3.5%. PMID:26950570

  14. Isotope dilution-GC-MS/MS analysis of 16 polycyclic aromatic hydrocarbons in selected medicinal herbs used as health food additives.

    PubMed

    Yu, L; Cao, Y; Zhang, J; Cui, Z; Sun, H

    2012-01-01

    Medicinal herbs have a very important role in health protection and disease control, and have been used in health foods. Polycyclic aromatic hydrocarbons (PAHs) have carcinogenic, biological and mutagenic effects. In this paper, the content of 16 PAHs as representative contaminants in nine Chinese medicinal herbs, as additives for health foods, was investigated in order to ensure food safety from this source. A highly sensitive isotope dilution-gas chromatography-tandem mass spectrometry (ID-GC-MS/MS) method combined with gel permeation chromatography (GPC) and solid-phase extraction (SPE) was developed. Calibration curves showed good linearity for all PAHs (R² > 0.999), and the limit of quantification (LOQ) ranged from 0.42 to 2.7 µg kg⁻¹. Average recoveries for these compounds were in the range of 52.5-117%, 52.6-119% and 81.4-108% at the concentrations of 10, 50 and 250 µg kg⁻¹ with RSD of 1.8-15%, 0.9-15% and 1.0-15%, respectively. The proposed method was used for the analysis of nine Chinese medicinal herbs. Total levels of PAHs varied from 98.2 µg kg⁻¹ (cassia seed) to 2245 µg kg⁻¹ (eucommia bark). The highest level was found for phenanthrene (Phe) in liquorice root (631.3 µg kg⁻¹), indigowoad leaf (551.0 µg kg⁻¹), rose flower (435.2 µg kg⁻¹) and eucommia bark (432.3 µg kg⁻¹). The proposed method could provide a useful basis for safety monitoring of herbs and risk management for PAHs in the health food industry. PMID:22870881

  15. Studies on the analysis of 25-hydroxyvitamin D{sub 3} by isotope-dilution liquid chromatography–tandem mass spectrometry using enzyme-assisted derivatisation

    SciTech Connect

    Abdel-Khalik, Jonas; Crick, Peter J.; Carter, Graham D.; Makin, Hugh L.; Wang, Yuqin; Griffiths, William J.

    2014-04-11

    Highlights: • New method for the analysis of 25-hydroxyvitamin D{sub 3} exploiting Girard P derivatisation. • Method also applicable to vitamin D{sub 3}, 1α,25- and 24,25-dihydroxyvitamin D{sub 3}. • By modification of the method 3-epi-25-hydroxyvitamin D{sub 3} can also be analysed. - Abstract: The total serum concentration of 25-hydroxyvitamins D (25-hydroxyvitamin D{sub 3} and 25-hydroxyvitamin D{sub 2}) is currently used as an indicator of vitamins D status. Vitamins D insufficiency is claimed to be associated with multiple diseases, thus accurate and precise reference methods for the quantification of 25-hydroxyvitamins D are needed. Here we present a novel enzyme-assisted derivatisation method for the analysis of vitamins D metabolites in adult serum utilising 25-[26,26,26,27,27,27-{sup 2}H{sub 6}]hydroxyvitamin D{sub 3} as the internal standard. Extraction of 25-hydroxyvitamins D from serum is performed with acetonitrile, which is shown to be more efficient than ethanol. Cholesterol oxidase is used to oxidize the 3β-hydroxy group in the vitamins D metabolites followed by derivatisation of the newly formed 3-oxo group with Girard P reagent. 17β-Hydroxysteroid dehydrogenase type 10 is shown to oxidize selectively the 3α-hydroxy group in the 3α-hydroxy epimer of 25-hydroxyvitamin D{sub 3}. Quantification is achieved by isotope-dilution liquid chromatography–tandem mass spectrometry. Recovery experiments for 25-hydroxyvitamin D{sub 3} performed on adult human serum give recovery of 102–106%. Furthermore in addition to 25-hydroxyvitamin D{sub 3}, 24,25-dihydroxyvitamin D{sub 3} and other uncharacterised dihydroxy metabolites, were detected in adult human serum.

  16. Route of tracer administration does not affect ileal endogenous nitrogen recovery measured with the 15N-isotope dilution technique in pigs fed rapidly digestible diets.

    PubMed

    Steendam, C A Carina; Verstegen, Martin W A; Tamminga, Seerp; Boer, Huug; van 't End, Marianne; Verstappen, Berthe; Caine, William R; Visser, G Henk

    2004-11-01

    The (15)N-isotope dilution technique ((15)N-IDT), with either pulse-dose oral administration or continuous i.v. administration of [(15)N]-l-leucine (carotid artery), both at 5 mg/(kg body weight . d), was used to measure ileal (postvalve T-cecum cannula) endogenous nitrogen recovery (ENR) in pigs (9 +/- 0.6 kg). Diets were cornstarch, enzyme-hydrolyzed casein with no (control) or high (4%) content of quebracho extract (Schinopsis spp.) rich in condensed tannins. Blood was sampled from a catheter in the external jugular vein. Mean plasma (15)N-enrichment at d 8-10 was higher (P = 0.0009) after i.v. than after oral administration [0.0356 vs. 0.0379 atom% excess (APE)]. Plasma (15)N-enrichment for i.v. infused pigs was 0.01117 APE higher (P < 0.0001) and for orally dosed pigs 0.0081 APE lower (P < 0.0001) at 11 h postprandial compared with 1 h postprandial. Apparent ileal N digestibility was higher (P < 0.0001) for the control (85.5%) than for the quebracho diet (69.5%). ENR was calculated from the ratio of (15)N-enrichment of plasma and digesta. The ENR for the quebracho diet was approximately 300% higher than for the control diet (6.03 vs. 1.94 g/kg dry matter intake, P < 0.001). The real N digestibility (92.2 +/- 0.4%) was equal for both diets (P = 0.1030) and both tracer methods (P = 0.9730). We concluded that oral administration of [(15)N]leucine provides reasonable estimates of ENR in pigs fed semipurified diets with high or low content of tannins; however, one must be careful in extrapolating this conclusion to studies with other protein sources or feeding frequencies. PMID:15514277

  17. Two high performance liquid chromatographic methods for the determination of alpha-tocopherol in serum compared to isotope dilution-gas chromatography-mass spectrometry.

    PubMed

    Kock, R; Seitz, S; Delvoux, B; Greiling, H

    1997-05-01

    Two high performance liquid chromatographic methods (HPLC) with isocratic reversed-phase separation are presented for the determination of alpha-tocopherol (vitamin E) in serum. In the first method alpha-tocopherol acetate is used as internal standard, detection of absorbance is performed at 284 nm. In the second method tocol is used as internal standard, detection of fluorescence is performed with an excitation wavelength of 292 nm and emission wavelength of 325 nm. Both methods require a liquid-liquid extraction as sample preparation. The results of both HPLC methods have been tested by method comparison for n = 25 serum samples versus an isotope dilution-gas chromatography-mass spectrometry (ID-GC-MS) method using alpha-tocopherol-d6 as internal standard. The imprecision within-run was lower than 2.5% for the UV method and lower than 1% for the fluorescence method for both standards and serum pools. The between-run imprecision, obtained for serum pools, was below 5% for the UV method and not higher than 1.5% for the fluorescence method and not higher 1.8% for the ID-GC-MS. Recovery experiments performed by spiking pool sera with alpha-tocopherol showed recoveries between 98.5% and 100.6% for all methods studied. The result of the method comparison was a coefficient of correlation of r = 0.998 for the HPLC method with fluorescence detection to the ID-GC-MS reference method and a coefficient of correlation of r = 0.981 for the HPLC method with UV detection to the ID-GC-MS reference method. Both methods presented are useful for the analysis of alpha-tocopherol in patient samples. If detection of fluorescence is used, imprecision and inaccuracy of the HPLC method are comparable to the ID-GC-MS chosen as reference method. PMID:9189742

  18. Simultaneous determination of sulfur mustard and related oxidation products by isotope-dilution LC-MS/MS method coupled with a chemical conversion.

    PubMed

    Qi, Meiling; Xu, Bin; Wu, Jianfeng; Zhang, Yajiao; Zong, Cheng; Chen, Jia; Guo, Lei; Xie, Jianwei

    2016-08-15

    Sulfur mustard (SM) is a highly reactive alkylating vesicant with high toxicity and complicated metabolism, the in vivo profile of its oxidation metabolism is not still fully known and urgently needs to be clarified well. In this work, an isotope-dilution high performance liquid chromatography-tandem mass spectrometric method coupled with chemical conversion was developed for the simultaneous quantification of SM and its oxidation products, i.e., mustard sulfoxide (SMO) and mustard sulfone (SMO2). The accurate measurement of SM and its oxidation products with high reaction activity was achived via the method of chemical conversion of 2-(3,5-bis(mercaptomethyl)phenoxy) acetic acid into stable derivative products. Method validation was performed in whole blood matrix, the linear range of the method was between 0.2 and 1000μg/L with correlation coefficients (r(2))>0.99, and the lower limits of quantification for SM, SMO and SMO2 were 1, 1, 0.2μg/L, respectively. The validated method was successfully applied to a toxicokinetics research of SM and its oxidation products after SM dermal exposed rats in a single dose. All three target analytes were found in whole blood samples from poisoned rats, and significant time-dependent responses were also observed. Among them, SMO2 with relatively high toxicity was identified and quantified in vivo for the first time, while SMO was the major product in whole blood and some of them continued to be oxidized to SMO2in vivo. These results give a direct experimental evidence to support that a large amount of SM is converted into the corresponding SMO and SMO2, and these oxidation products might cause potential combined toxic effects. PMID:27322628

  19. Accurate Quantification of Selenoprotein P (SEPP1) in Plasma Using Isotopically Enriched Seleno-peptides and Species-Specific Isotope Dilution with HPLC Coupled to ICP-MS/MS.

    PubMed

    Deitrich, Christian L; Cuello-Nuñez, Susana; Kmiotek, Diana; Torma, Frank Attila; Del Castillo Busto, Maria Estela; Fisicaro, Paola; Goenaga-Infante, Heidi

    2016-06-21

    A novel strategy for the absolute quantification of selenium (Se) included in selenoprotein P (SEPP1), an important biomarker for human nutrition and disease, including diabetes and cancer, is presented here for the first time. It is based on the use of species-specific double isotope dilution mass spectrometry (SSIDA) in combination with HPLC-ICP-MS/MS for the determination of protein bound Se down to the peptide level in a complex plasma matrix with a total content of Se of 105.5 μg kg(-1). The method enabled the selective Se speciation analysis of human plasma samples without the need of extensive cleanup or preconcentration steps as required for traditional protein mass spectrometric approaches. To assess the method accuracy, two plasma reference materials, namely, BCR-637 and SRM1950, for which literature data and a reference value for SEPP1 have been reported, were analyzed using complementary hyphenated methods and the species-specific approach developed in this work. The Se mass fractions obtained via the isotopic ratios (78)Se/(76)Se and (82)Se/(76)Se for each of the Se-peptides, namely, ENLPSLCSUQGLR (ENL) and AEENITESCQUR (AEE) (where U is SeCys), were found to agree within 2.4%. A relative expanded combined uncertainty (k = 2) of 5.4% was achieved for a Se (as SEPP1) mass fraction of approximately 60 μg kg(-1). This work represents a systematic approach to the accurate quantitation of plasma SEPP1 at clinical levels using SSIDA quantification. Such methodology will be invaluable for the certification of reference materials and the provision of reference values to clinical measurements and clinical trials. PMID:27108743

  20. Correction of NPL-2013 estimate of the Boltzmann constant for argon isotopic composition and thermal conductivity

    NASA Astrophysics Data System (ADS)

    de Podesta, Michael; Yang, Inseok; Mark, Darren F.; Underwood, Robin; Sutton, Gavin; Machin, Graham

    2015-10-01

    In 2013, a team from NPL, Cranfield University and SUERC published an estimate of the Boltzmann constant based on precision measurements of the speed of sound in argon. A key component of our results was an estimate of the molar mass of the argon gas used in our measurements. To achieve this we made precision comparison measurements of the isotope ratios found in our experimental argon against the ratios of argon isotopes found in atmospheric air. We then used a previous measurement of the atmospheric argon isotope ratios to calibrate the relative sensitivity of the mass spectrometer to different argon isotopes. The previous measurement of the atmospheric argon isotope ratios was carried out at KRISS using a mass spectrometer calibrated using argon samples of known isotopic composition, which had been prepared gravimetrically. We report here a new measurement made at KRISS in October 2014, which directly compared a sample of our experimental gas against the same gravimetrically-prepared argon samples. We consider that this direct comparison has to take precedence over our previous more indirect comparison. This measurement implies a molar mass which is 2.73(60) parts in 106 lighter than our 2013 estimate, a shift which is seven times our 2013 estimate of the uncertainty in the molar mass. In this paper we review the procedures used in our 2013 estimate of molar mass; describe the 2014 measurement; highlight some questions raised by the large change in our estimate of molar mass; and describe how we intend to address the inconsistencies between them. We also consider the effect of a new estimate of the low pressure thermal conductivity of argon at 273.16 K. Finally we report our new best estimate of the Boltzmann constant with revised uncertainty, taking account of the new estimates for the molar mass and the thermal conductivity of the argon.

  1. Hydrogeochemical and isotopic tracers for identification of seasonal and long-term over-exploitation of the Pleistocene thermal waters.

    PubMed

    Rman, Nina

    2016-04-01

    The aim of the study was to develop and test an optimal and cost-effective regional quality monitoring system in depleted transboundary low-temperature Neogene geothermal aquifers in the west Pannonian basin. Potential tracers for identification of seasonal and long-term quality changes of the Pleistocene thermal waters were investigated at four multiple-screened wells some 720 to 1570 m deep in Slovenia. These thermal waters are of great balneological value owing to their curative effects and were sampled monthly between February 2014 and January 2015. Linear correlation and regression analyses, ANOVA and Kolmogorov-Smirnov two-sample test for two independent samples were used to determine their seasonal and long-term differences. Temperature, pH, electrical conductivity, redox potential and dissolved oxygen did not identify varying inflow conditions; however, they provided sufficient information to distinguish between the four end-members. Characteristic (sodium) and conservative (chloride) tracers outlined long-term trends in changes in quality but could not differentiate between the seasons. Stable isotopes of δ (18)O and δ (2)H were used to identify sequential monthly and long-term trends, and origin and mixing of waters, but failed to distinguish the difference between the seasons. A new local paleo-meteoric water line (δ (2)H = 9.2*δ (18)O + 26.3) was outlined for the active regional groundwater flow system in the Pannonian to Pliocene loose sandstone and gravel. A new regression line (δ (2)H = 2.3*δ (18)O-45.2) was calculated for thermomineral water from the more isolated Badenian to Lower Pannonian turbiditic sandstone, indicating dilution of formation water. Water composition was generally stable over the 1-year period, but long-term trends indicate that changes in quality occur, implying deterioration of the aquifers status. PMID:27007290

  2. Constraints on ocean circulation at the Paleocene-Eocene Thermal Maximum from neodymium isotopes

    NASA Astrophysics Data System (ADS)

    Abbott, April N.; Haley, Brian A.; Tripati, Aradhna K.; Frank, Martin

    2016-04-01

    Global warming during the Paleocene-Eocene Thermal Maximum (PETM) ˜ 55 million years ago (Ma) coincided with a massive release of carbon to the ocean-atmosphere system, as indicated by carbon isotopic data. Previous studies have argued for a role of changing ocean circulation, possibly as a trigger or response to climatic changes. We use neodymium (Nd) isotopic data to reconstruct short high-resolution records of deep-water circulation across the PETM. These records are derived by reductively leaching sediments from seven globally distributed sites to reconstruct past deep-ocean circulation across the PETM. The Nd data for the leachates are interpreted to be consistent with previous studies that have used fish teeth Nd isotopes and benthic foraminiferal δ13C to constrain regions of convection. There is some evidence from combining Nd isotope and δ13C records that the three major ocean basins may not have had substantial exchanges of deep waters. If the isotopic data are interpreted within this framework, then the observed pattern may be explained if the strength of overturning in each basin varied distinctly over the PETM, resulting in differences in deep-water aging gradients between basins. Results are consistent with published interpretations from proxy data and model simulations that suggest modulation of overturning circulation had an important role for initiation and recovery of the ocean-atmosphere system associated with the PETM.

  3. Impact of dilution of deuterium on ion thermal diffusivity and turbulence in C-Mod Ohmic plasmas

    NASA Astrophysics Data System (ADS)

    Porkolab, Miklos; Ennever, P.; Edlund, E.; Rice, J.; Rost, J. C.; Ernst, D.; Fiore, C.; Hubbard, A.; Hughes, J.; Terry, J.; Reinke, M. L.; Staebler, G.; Candy, J.; Alcator C-Mod Team

    2015-11-01

    Past experiments on C-Mod and gyrokinetic studies indicated that dilution of the deuterium ion species decreases the ion diffusivity in Ohmically heated deuterium plasmas. Comparison of recent controlled seeding experiments to TGLF and GYRO simulations shows that main ion dilution reduces the ion transport in low density (LOC) plasmas by increasing the critical gradient, while in high density (SOC) plasmas ion dilution primarily decreased the stiffness (1). Meanwhile, there is still a deficit in the predicted electron transport in simulations that are restricted to wavenumbers kρs <= 1 . Importantly, measurements of the turbulent spectrum were also carried out with a Phase Contrast Imaging (PCI) diagnostic with a new detector array with an improved frequency response (now up to 1 MHz), and the results are in good agreement with synthetic diagnostic predictions. References: (1) Paul Ennever, Invited Talk at this meeting. Work supported by US DOE awards DE-FG02-94-ER54235 and DE-FC02-99-ER54512.

  4. Essentials of iron, chromium, and calcium isotope analysis of natural materials by thermal ionization mass spectrometry

    USGS Publications Warehouse

    Fantle, M.S.; Bullen, T.D.

    2009-01-01

    The use of isotopes to understand the behavior of metals in geological, hydrological, and biological systems has rapidly expanded in recent years. One of the mass spectrometric techniques used to analyze metal isotopes is thermal ionization mass spectrometry, or TIMS. While TIMS has been a useful analytical technique for the measurement of isotopic composition for decades and TIMS instruments are widely distributed, there are significant difficulties associated with using TIMS to analyze isotopes of the lighter alkaline earth elements and transition metals. Overcoming these difficulties to produce relatively long-lived and stable ion beams from microgram-sized samples is a non-trivial task. We focus here on TIMS analysis of three geologically and environmentally important elements (Fe, Cr, and Ca) and present an in-depth look at several key aspects that we feel have the greatest potential to trouble new users. Our discussion includes accessible descriptions of different analytical approaches and issues, including filament loading procedures, collector cup configurations, peak shapes and interferences, and the use of isotopic double spikes and related error estimation. Building on previous work, we present quantitative simulations, applied specifically in this study to Fe and Ca, that explore the effects of (1) time-variable evaporation of isotopically homogeneous spots from a filament and (2) interferences on the isotope ratios derived from a double spike subtraction routine. We discuss how and to what extent interferences at spike masses, as well as at other measured masses, affect the double spike-subtracted isotope ratio of interest (44Ca/40Ca in the case presented, though a similar analysis can be used to evaluate 56Fe/54Fe and 53Cr/52Cr). The conclusions of these simulations are neither intuitive nor immediately obvious, making this examination useful for those who are developing new methodologies. While all simulations are carried out in the context of a

  5. Isotopic geochemistry of acid thermal waters and volcanic gases from Zaō volcano in Japan

    NASA Astrophysics Data System (ADS)

    Kiyosu, Yasuhiro; Kurahashi, Makoto

    1984-08-01

    The chemical composition and D/H, {18O }/{16O } and {34S }/{32S } ratios have been determined for the acid hot waters and volcanic gases discharging from Zaō volcano in Japan. The thermal springs in Zaō volcano issue acid sulfate-chloride type waters (Zaō) and acid sulfate type waters (Kamoshika). Gases emitted at Kamoshika fumaroles are rich in CO 2, SO 2 and N 2, exclusive of H 2O. Chloride concentrations and oxygen isotope data indicate that the Zaō thermal waters issue a fluid mixture from an acid thermal reservoir and meteoric waters from shallow aquifers. The waters in the Zaō volcanic system have slight isotopic shifts from the respective local meteoric values. The isotopic evidence indicates that most of the water in the system is meteoric in origin. Sulfates in Zaō acid sulfate-chloride waters with δ34S values of around +15‰, are enriched in 34S compared to Zaō H 2S, while the acid sulfate waters at Kamoshika contain supergene light sulfate ( δ 34S = ˜ + 4‰ ) derived from volcanic sulfur dioxide from the volcanic exhalations. The sulfur species in Zaō acid waters are lighter in δ34S than those of other volcanic areas, reflecting the difference in total pressure.

  6. OXYGEN ISOTOPIC COMPOSITIONS OF THE ALLENDE TYPE C CAIs: EVIDENCE FOR ISOTOPIC EXCHANGE DURING NEBULAR MELTING AND ASTEROIDAL THERMAL METAMORPHISM

    SciTech Connect

    Krot, A N; Chaussidon, M; Yurimoto, H; Sakamoto, N; Nagashima, K; Hutcheon, I D; MacPherson, G J

    2008-02-21

    that CAIs 100, 160 and CG5 experienced melting in an {sup 16}O-rich ({Delta}{sup 17}O < -20{per_thousand}) nebular gas in the CAI-forming region. The Type C and Type-B-like portions of CAI 6-1-72 experienced melting in an {sup 16}O-depleted ({Delta}{sup 17}O {ge} -13{per_thousand}) nebular gas. CAIs ABC, TS26 and 93 experienced isotopic exchange during re-melting in the presence of an {sup 16}O-poor ({Delta}{sup 17}O {ge} -10{per_thousand}) nebular gas in the chondrule-forming region(s). Subsequently, Allende Type C CAIs experienced post-crystallization isotopic exchange with an {sup 16}O-poor reservoir that affected largely melilite and anorthite. Because pseudomorphic replacement of lacy melilite by grossular, monticellite and forsterite occurred during thermal metamorphism, some oxygen isotopic exchange of melilite and anorthite must have continued after formation of these secondary minerals. We suggest that some or all oxygen isotopic exchange in melilite and anorthite occurred during fluid-assisted thermal metamorphism on the CV parent asteroid. Similar processes may have also affected melilite and anorthite of CAIs in metamorphosed CO chondrites.

  7. In vivo prediction of goat kids body composition from the deuterium oxide dilution space determined by isotope-ratio mass spectrometry.

    PubMed

    Lerch, S; Lastel, M L; Grandclaudon, C; Brechet, C; Rychen, G; Feidt, C

    2015-09-01

    Deuterium oxide dilution space (DOS) determination is one of the most accurate methods for in vivo estimation of ruminant body composition. However, the time-consuming vacuum sublimation of blood preceding infrared spectroscopy analysis, which is traditionally used to determine deuterium oxide (DO) concentration, limits its current use. The use of isotope-ratio mass spectrometry (IRMS) to determine the deuterium enrichment and thus quantify DO in plasma could counteract this limitation by reducing the sample preparation for plasma deproteinisation through centrifugal filters. The aim of this study was to validate the DOS technique using IRMS in growing goat kids to establish in vivo prediction equations of body composition. Seventeen weaned male Alpine goat kids (8.6 wk old) received a hay-based diet supplemented with 2 types of concentrates providing medium ( = 9) or high ( = 8) energy levels. Kids were slaughtered at 14.0 ( = 1, medium-energy diet), 17.2 ( = 4, medium-energy diet, and = 4, high-energy diet), or 21.2 wk of age ( = 4, medium-energy diet, and = 4, high-energy diet). Two days before slaughter, DOS was determined after an intravenous injection of 0.2 g DO/kg body mass (BM) and the resulting study of DO dilution kinetics from 4 plasma samples (+5, +7, +29, and +31 h after injection). The deuterium enrichment was analyzed by IRMS. After slaughter, the gut contents were discarded, the empty body (EB) was minced, and EB water, lipid, protein, ash, and energy contents were measured by chemical analyses. Prediction equations for body components measured postmortem were computed from in vivo BM and DOS. The lack of postmortem variation of fat-free EB composition was confirmed (mean of 75.3% [SD 0.6] of water), and the proportion of lipids in the EB tended ( = 0.06) to be greater for the high-energy diet (13.1%) than for the medium-energy diet (11.1%). There was a close negative relationship (residual CV [rCV] = 3.9%, = 0.957) between EB water and lipid

  8. Chemical and stable-radiogenic isotope compositions of Polatlı-Haymana thermal waters (Ankara, Turkey)

    NASA Astrophysics Data System (ADS)

    Akilli, Hafize; Mutlu, Halim

    2016-04-01

    Complex tectono-magmatic evolution of the Anatolian land resulted in development of numerous geothermal areas through Turkey. The Ankara region in central Anatolia is surrounded by several basins which are filled with upper Cretaceous-Tertiary sediments. Overlying Miocene volcanics and step faulting along the margins of these basins played a significant role in formation of a number of low-enthalpy thermal waters. In this study, chemical and isotopic compositions of Polatlı and Haymana geothermal waters in the Ankara region are investigated. The Polatlı-Haymana waters with a temperature range of 24 to 43 °C are represented by Ca-(Na)-HCO3 composition implying derivation from carbonate type reservoir rocks. Oxygen-hydrogen isotope values of the waters are conformable with the Global Meteoric Water Line and point to a meteoric origin. The carbon isotopic composition in dissolved inorganic carbon (DIC) of the studied waters is between -21.8 and -1.34 permil (vs. VPDB). Marine carbonates and organic rocks are the main sources of carbon. There is a high correlation between oxygen (3.7 to 15.0 permil; VSMOW) and sulfur (-9.2 to 19.5 permil; VCDT) isotope compositions of sulfate in waters. The mixing of sulfate from dissolution of marine carbonates and terrestrial evaporite units is the chief process behind the observed sulfate isotope systematics of the samples. 87Sr/86Sr ratios of waters varying from 0.705883 to 0.707827 are consistent with those of reservoir rocks. The temperatures calculated by SO4-H2O isotope geothermometry are between 81 and 138 °C nearly doubling the estimates from chemical geothermometers.

  9. Thermal conduction mechanisms in isotope-disordered boron nitride and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Savic, Ivana; Mingo, Natalio; Stewart, Derek

    2009-03-01

    We present first principles studies which determine dominant effects limiting the heat conduction in isotope-disordered boron nitride and carbon nanotubes [1]. Using an ab initio atomistic Green's function approach, we demonstrate that localization cannot be observed in the thermal conductivity measurements [1], and that diffusive scattering is the dominant mechanism which reduces the thermal conductivity [2]. We also give concrete predictions of the magnitude of the isotope effect on the thermal conductivities of carbon and boron nitride single-walled nanotubes [2]. We furthermore show that intershell scattering is not the main limiting mechanism for the heat flow through multi-walled boron nitride nanotubes [1], and that heat conduction restricted to a few shells leads to the low thermal conductivities experimentally measured [1]. We consequently successfully compare the results of our calculations [3] with the experimental measurements [1]. [1] C. W. Chang, A. M. Fennimore, A. Afanasiev, D. Okawa, T. Ikuno, H. Garcia, D. Li, A. Majumdar, A. Zettl, Phys. Rev. Lett. 2006, 97, 085901. [2] I. Savic, N. Mingo, D. A. Stewart, Phys. Rev. Lett. 2008, 101, 165502. [3] I. Savic, D. A. Stewart, N. Mingo, to be published.

  10. Quantification of benzo[a]pyrene diol epoxide DNA-adducts by stable isotope dilution liquid chromatography/tandem mass spectrometry.

    PubMed

    Ruan, Qian; Kim, Hye-Young H; Jiang, Hao; Penning, Trevor M; Harvey, Ronald G; Blair, Ian A

    2006-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants found in car exhausts, charbroiled food, and tobacco smoke. Three pathways for the metabolic activation of B[a]P to ultimate carcinogens have been proposed. The most widely accepted pathway involves cytochrome-P450 (CYP) 1A1- and/or 1B1-mediated formation of B[a]P-7,8-oxide, which undergoes epoxide hydrolase-mediated metabolism to the proximate carcinogen B[a]P-7,8-dihydro-7,8-diol. Further CYP1A1- and/or CYP1B1-mediated activation of the dihydrodiol results in the formation of 7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (B[a]PDE), the ultimate carcinogen. In previous studies, it was demonstrated that (+)-anti-B[a]PDE was the most potent tumorigen of the CYP-derived B[a]PDE diastereomers. We have developed a stable isotope dilution, liquid chromatography multiple reaction monitoring/mass spectrometry (LC-MRM/MS) assay for all eight (+/-)-anti-B[a]PDE-derived dGuo and dAdo DNA-adducts. The LC-MRM/MS assay was rigorously validated and used to show that (+)-anti-trans-B[a]PDE-dGuo was the major adduct formed when naked DNA and human bronchoalveolar adenocarcinoma H358 cells were treated with (+/-)-anti-B[a]PDE. The preference for DNA-adducts derived from (+)-anti-B[a]PDE was even more apparent in cellular DNA. Thus, the increased potency of (+)-anti-B[a]PDE as a tumorigen is most likely due its ability to preferentially form DNA-adducts when compared with (-)-anti-B[a]PDE. Also, the adduct profile suggests that this occurs by binding of (+)-anti-B[a]PDE to DNA in a manner that facilitates covalent binding to dGuo rather than dAdo residues. PMID:16557497

  11. Endogenous N-losses in broilers estimated by a [15N]-isotope dilution technique: effect of dietary fat type and xylanase addition.

    PubMed

    Dänicke, S; Jeroch, H; Simon, O

    2000-01-01

    Male broilers were given a low protein diet (15.5% CP) spiked with [15N]H4HCO3 from day 12 to day 18 of age to label the endogenous N-constituents. Experimental diets were subsequently fed from day 19 to day 24 of age and consisted of a rye based diet (56% dietary inclusion) which contained either 10% soya oil (S) or 10% beef tallow (T), each of which was either unsupplemented (-) or supplemented (+) with a xylanase containing enzyme preparation (2700 IU/kg at pH 5.3). [15N]-atom percent excess (APE) of excreta, faeces and urine were monitored on a daily basis during both experimental periods. Furthermore, APE was measured in various tissues at the end of the experiment. The APE of urine on the last day of the experiment was between the APE of the pancreas and that of the jejunal tissue, an observation which supported the usefulness of using urinary APE as an indicator for the endogenous N-pool. Endogenous N-proportions were estimated by an isotope dilution technique at the end of the experiment by examination of the ratio of APE in faeces and urine. The endogenous N-proportion in the faeces was greatest in birds receiving the T(-) diet. The proportions were 0.321, 0.319, 0.451 and 0.289 in S(-), S(+), T(-) and T(+) fed groups, respectively. Xylanase addition reduced endogenous N-proportion, a factor which was used to correct apparent crude protein digestibility (85.6, 86.2, 84.3 and 88.5% in S(-), S(+), T(-) and T(+) fed birds, respectively) for endogenous losses resulting in almost equal true digestibilities of crude protein for all treatments (90.3, 90.6, 90.4 and 91.5%). The amounts of endogenous N in faces were estimated to be 87, 69, 244 and 81 mg per day per kg0.67 body weight in S(-), S(+), T(-) and T(+) fed birds, respectively. It was concluded that xylanase supplementation of a rye based broiler diet does not change endogenous N-secretions when the supplemental fat is soya oil. However, addition of tallow rather than soya oil increased these N

  12. A candidate reference measurement procedure for quantifying serum concentrations of 25-hydroxyvitamin D₃ and 25-hydroxyvitamin D₂ using isotope-dilution liquid chromatography-tandem mass spectrometry.

    PubMed

    Mineva, Ekaterina M; Schleicher, Rosemary L; Chaudhary-Webb, Madhulika; Maw, Khin L; Botelho, Julianne C; Vesper, Hubert W; Pfeiffer, Christine M

    2015-07-01

    The inaccuracy of routine serum 25-hydroxyvitamin D measurements hampers the interpretation of data in patient care and public health research. We developed and validated a candidate reference measurement procedure (RMP) for highly accurate quantitation of two clinically important 25-hydroxyvitamin D metabolites in serum, 25-hydroxyvitamin D2 [25(OH)D2] and 25-hydroxyvitamin D3 [25(OH)D3]. The two compounds of interest together with spiked deuterium-labeled internal standards [d 3-25(OH)D2 and d 6-25(OH)D3] were extracted from serum via liquid-liquid extraction. The featured isotope-dilution LC-MS/MS method used reversed-phase chromatography and atmospheric pressure chemical ionization in positive ion mode. A pentafluorophenylpropyl-packed UHPLC column together with isocratic elution allowed for complete baseline resolution of 25(OH)D2 and 25(OH)D3 from their structural C-3 isomers within 12 min. We evaluated method trueness, precision, potential interferences, matrix effects, limits of quantitation, and measurement uncertainty. Calibration materials were, or were traceable to, NIST Standard Reference Materials 2972. Within-day and total imprecision (CV) averaged 1.9 and 2.0% for 25(OH)D3, respectively, and 2.4 and 3.5% for 25(OH)D2, respectively. Mean trueness was 100.3% for 25(OH)D3 and 25(OH)D2. The limits of quantitation/limits of detection were 4.61/1.38 nmol/L for 25(OH)D3 and 1.46/0.13 nmol/L for 25(OH)D2. When we compared our RMP results to an established RMP using 40 serum samples, we found a nonsignificant mean bias of 0.2% for total 25(OH)D. This candidate RMP for 25(OH)D metabolites meets predefined method performance specifications (≤5% total CV and ≤1.7% bias) and provides sufficient sample throughput to meet the needs of the Centers for Disease Control and Prevention Vitamin D Standardization Certification Program. Graphical abstract Bias assessment using NIST standard reference materials. Legend CDC mean mass fractions (ng/g) ± U 95 (6

  13. Selenium and Tellurium concentrations of ultradepleted peridotites determined by isotope dilution ICPMS: implications for Se-Te systematics of the Earth's mantle

    NASA Astrophysics Data System (ADS)

    König, S.; Luguet, A.; Lorand, J.-P.; Wombacher, F.; Lissner, M.

    2012-04-01

    As for highly siderophile elements, selenium and tellurium may constitute key tracers for planetary processes such as formation of the Earth's core and the Late Veneer composition, provided that their geochemical behaviour and abundances in the primitive upper mantle (PUM) are constrained. Within this scope, we have developed a high precision analytical method for the simultaneous determination of selenium and tellurium concentrations from a single sample aliquot and various rock matrices, including ultradepleted peridotites. The technique employs isotope dilution, thiol cotton fiber (TCF) separation and hydride generation MC-ICP-MS. A selection of international mafic and ultramafic rock reference materials BIR-1, BE-N, TDB-1, UB-N, FON B 93, BIR-1 and BHVO-2 with a range of 30 to 350 ppb Se and 0.7 to 12 ppb Te show external reproducibilities of 3 to 8% for Se and 0.4 to 11% for Te (2 relative standard deviations (r.s.d.)). We have applied this method to a suite of refractory mantle peridotites (Al2O3 <1.5 wt. %) from Lherz, previously shown to be strongly and uniformly depleted in Se, Te and incompatible elements by high degree of partial melting (20 ± 5%). In contrast to fertile lherzolites which remain at broadly chondritic values (Se/Te = 9), the ultradepleted harzburgites show highly fractionated and up to suprachondritic Se/Te (< 35) that correlate with decreasing Te concentrations. The fractionation is displayed by the depleted peridotites as well as multiple analysis of a single Lherz harzburgite sample (64-3). This shows 1) a strong sample heterogeneity effect for Te and 2) a more incompatible behaviour of Te compared to Se on the whole rock scale, once base metal sulfides are highly depleted and in some cases entirely consumed by partial melting. The marked differences in Se-Te systematics observed between fertile lherzolites and depleted harzburgites can be explained by the combined effect of i) different abundances and proportions of residual and

  14. Determination of Exposure to the Alternaria Mycotoxin Tenuazonic Acid and Its Isomer allo-Tenuazonic Acid in a German Population by Stable Isotope Dilution HPLC-MS(3).

    PubMed

    Hövelmann, Yannick; Hickert, Sebastian; Cramer, Benedikt; Humpf, Hans-Ulrich

    2016-08-31

    The content of the Alternaria toxin tenuazonic acid and its isomer allo-tenuazonic acid was quantitated in urine of a German cohort (n = 48) using a newly developed and successfully validated solid phase extraction based stable isotope dilution HPLC-MS(3) method. Tenuazonic acid was detected in all of the samples and quantifiable in 97.9% of these samples in a range of 0.16-44.4 ng/mL (average = 6.58 ng/mL) or 0.07-63.8 ng/mg creatinine (average = 8.13 ng/mg creatinine). allo-Tenuazonic acid was for the first time detected in human urine (95.8% of the samples positive) and quantitated in 68.8% of the samples in a range of 0.11-5.72 ng/mL (average = 1.25 ng/mL) or 0.08-10.1 ng/mg creatinine (average = 1.52 ng/mg creatinine), representing 3.40-25.0% of the sum of both isomers (average = 12.4%). Food-frequency questionnaires were used to document food consumption of study participants to correlate mycotoxin exposure to nutritional habits. Although no statistically significant correlation between consumption of a specific food and urinary excretion of tenuazonic acid could be determined, a trend regarding elevated intake of cereal products and higher excretion of tenuazonic acid was evident. On the basis of these results, a provisional mean daily intake (PDI) for both tenuazonic acid and allo-tenuazonic acid was calculated, being 0.183 and 0.025 μg/kg body weight, respectively. A combined mean PDI for both isomers amounts to 0.208 μg/kg body weight with the highest individual PDI for one of the participants (1.582 μg/kg body weight) slightly exceeding the threshold of toxicological concern assumed for tenuazonic acid by the European Food Safety Authority of 1.500 μg/kg body weight. This is the first study to investigate the tenuazonic acid content in human urine of a larger sample cohort enabling the calculation of PDIs for tenuazonic acid and allo-tenuazonic acid. PMID:27452834

  15. Monitoring urinary metabolites resulting from sulfur mustard exposure in rabbits, using highly sensitive isotope-dilution gas chromatography-mass spectrometry.

    PubMed

    Nie, Zhiyong; Zhang, Yajiao; Chen, Jia; Lin, Ying; Wu, Bidong; Dong, Yuan; Feng, Jianlin; Liu, Qin; Xie, Jianwei

    2014-08-01

    A highly sensitive method for the determination of sulfur mustard (SM) metabolites thiodiglycol (TDG) and thiodiglycol sulfoxide (TDGO) in urine was established and validated using isotope-dilution negative-ion chemical ionization (NICI) gas chromatography-mass spectrometry (GC-MS). TDGO in the samples was reduced with TiCl3, and then determined together with TDG as a single analyte. The sample preparation procedures, including two solid-phase-extraction (SPE) clean-up steps, were optimized to improve the sensitivity of the method. The limits of detection (LOD) for both TDG and TDG plus TDGO (TDG + TDGO) were 0.1 ng mL(-1), and the limits of quantitation (LOQ) for both were 0.3 ng mL(-1). The method was used in a rabbit cutaneous SM exposure model. Domestic rabbits were exposed to neat liquid SM at three dosage levels (0.02, 0.05, and 0.15 LD50), and the urinary excretion of four species of hydrolysis metabolites, namely free TDG, free plus conjugated TDG (total TDG), free TDG + TDGO, and free plus conjugated TDG + TDGO (total TDG + TDGO), was evaluated to investigate the metabolic processes. The total urinary excretion profiles of the metabolites, including the peak time, time window, and dose-response and time-response relationships, were clarified. The results revealed that the concentrations of TDG and TDG + TDGO in the urine increased quickly and then decreased rapidly in the first two days after SM exposure. The cumulative amount of total TDG + TDGO excreted in urine during the first five days accounted for 0.5-1% of the applied dose of SM. It is also concluded that TDG and TDGO in urine existed mainly in free form, the levels of glucuronide and of sulfate conjugates of TDG or TDGO were very low, and most hydrolysis metabolites were present in the oxidized form (TDGO). The study indicates that the abnormal increase of TDG and TDGO excretion levels can be used as a diagnostic indicator and establishes a reference time-window for retrospective analysis and

  16. Simultaneous Measurement of 3-Chlorotyrosine and 3,5-Dichlorotyrosine in Whole Blood, Serum and Plasma by Isotope Dilution HPLC-MS-MS.

    PubMed

    Crow, Brian S; Quiñones-González, Jennifer; Pantazides, Brooke G; Perez, Jonas W; Winkeljohn, W Rucks; Garton, Joshua W; Thomas, Jerry D; Blake, Thomas A; Johnson, Rudolph C

    2016-05-01

    Chlorine is a public health concern and potential threat due to its high reactivity, ease and scale of production, widespread industrial use, bulk transportation, massive stockpiles and history as a chemical weapon. This work describes a new, sensitive and rapid stable isotope dilution method for the retrospective detection and quantitation of two chlorine adducts. The biomarkers 3-chlorotyrosine (Cl-Tyr) and 3,5-dichlorotyrosine (Cl2-Tyr) were isolated from the pronase digest of chlorine exposed whole blood, serum or plasma by solid-phase extraction (SPE), separated by reversed-phase HPLC and detected by tandem mass spectrometry (MS-MS). The calibration range is 2.50-1,000 ng/mL (R(2)≥ 0.998) with a lowest reportable limit (LRL) of 2.50 ng/mL for both analytes, an accuracy of ≥93% and an LOD of 0.443 ng/mL for Cl-Tyr and 0.396 ng/mL for Cl2-Tyr. Inter- and intra-day precision of quality control samples had coefficients of variation of ≤10% and ≤7.0%, respectively. Blood and serum samples from 200 healthy individuals and 175 individuals with chronic inflammatory disease were analyzed using this method to assess background levels of chlorinated tyrosine adducts. Results from patients with no known inflammatory disease history (healthy) showed baseline levels of

  17. Quantitation of Benzo[a]pyrene Metabolic Profiles in Human Bronchoalveolar H358) Cells by Stable Isotope Dilution Liquid Chromatography-Atmospheric Chemical Ionization Mass Spectrometry

    PubMed Central

    Lu, Ding; Harvey, Ronald G.; Blair, Ian A.; Penning, Trevor M.

    2013-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants and are carcinogenic in multiple organs and species. Benzo[a]pyrene (B[a]P) is a representative PAH and has been studied extensively for its carcinogenicity and toxicity. B[a]P itself is chemically inert and requires metabolic activation to exhibit its toxicity and carcinogenicity. Three major metabolic pathways have been well documented. The signature metabolites generated from the radical cation (peroxidase or monooxygenase mediated) pathway are B[a]P-1,6-dione and B[a]P-3,6-dione, the signature metabolite generated from the diol-epoxide (P450 mediated) pathway is B[a]P-r-7,t-8,t-9,c-10-tetrahydrotetrol (B[a]P-tetrol-1) and the signature metabolite generated from the o-quinone (aldo-keto reductase mediated) pathway is B[a]P-7,8-dione. The contributions of these different metabolic pathways to cancer initiation and the exploitation of this information for cancer prevention are still under debate. With the availability of a library of [13C4]-labeled B[a]P metabolite internal standards, we developed a sensitive stable isotope dilution atmospheric pressure chemical ionization tandem mass spectrometry method to address this issue by quantitating B[a]P metabolites from each metabolic pathway in human lung cells. This analytical method represents a 500 fold increased sensitivity compared with a method using HPLC-radiometric detection. The limit of quantitation (LOQ) was determined to be 6 fmol on column for 3-hydroxybenzo[a]pyrene (3-OH-B[a]P), the generally accepted biomarker for B[a]P exposure. This high level of sensitivity and robustness of the method was demonstrated in a study of B[a]P metabolic profiles in human bronchoalveolar H358 cells induced or uninduced with the AhR ligand, 2,3,7,8-tetrachlorodibenzodioxin (TCDD). All the signature metabolites were detected and successfully quantitated. Our results suggest that all three metabolic pathways contribute equally in the overall

  18. An update on the Thermal Gradient Induced Non -Mass-Dependent Isotope Fractionation

    NASA Astrophysics Data System (ADS)

    Sun, T.; Niles, P. B.; Bao, H.; Socki, R. A.

    2012-12-01

    Mass flow and compositional gradient (elemental and isotope separation) occur when fluid(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been experimentally and theoretically investigated for more than a century, although there has not been a satisfactory theory to date. Nevertheless, theories predict that when dealing with a multi-isotope system, such as O16-O17-O18, S32-S33-S34-S36, or Ne20-Ne21-Ne22, the mass difference is the only term in the thermal diffusion separation factors that distinguish one isotope pair from another. Thus a mass dependent relationship is expected. For O-bearing molecules the α17O/ α 18O is expected to be at 0.5 to 0.515, and for S-bearing molecules the α33S/ α 34S at 0.5 to 0.508, where α is isotope fractionation factor between cold and warm reservoirs. We recently reported that thermal diffusion generates non-mass dependent (NMD) isotope fractionation for low-pressure O2 and SF6 gases. The observed NMD phenomenon in the simple thermal-diffusion experiments demands quantitative validation and theoretical explanation. It was suggested that additional (not mass related) terms need to be theoretically considered in the order to account for the observations. In addition to the pressure and temperature dependency illustrated in our earlier report, the role of turbulence, batch gas effects, and whether it is only a transient, non-equilibrium effect have been examined in this study. We report here new results on low-pressure O2 gas thermal diffusion. (1) In a purely diffusive vertical two-bulb setting with colder reservoir at lower position, time course experiments showed that the NMD effect persists after the system reaches isotopic steady state between warmer and colder compartments, suggesting that the effect is not a transient one. (2) When the average temperature approaching condensation point for O2, the 17O switches to migrating

  19. Two-dimensional heart-cut LC-LC improves accuracy of exact-matching double isotope dilution mass spectrometry measurements of aflatoxin B1 in cereal-based baby food, maize, and maize-based feed.

    PubMed

    Breidbach, Andreas; Ulberth, Franz

    2015-04-01

    Aflatoxins, mycotoxins of fungi of the Aspergillus sp., pose a risk to consumer health and are, therefore, regulated by more than 100 countries. To facilitate method development and validation as well as assessment of measurement capabilities, availability of certified reference materials and proficiency testing schemes is important. For these purposes, highly accurate determinations of the aflatoxin content in the materials used are necessary. We describe here the use of two-dimensional heart-cut LC-LC in combination with exact-matching double isotope dilution mass spectrometry to determine the content of aflatoxin B1 in three materials used in a proficiency testing scheme. The serious reduction in ionization suppression afforded by the two-dimensional heart-cut LC-LC had a positive effect on the precision of the measured isotope ratios of the exact-matching double isotope dilution mass spectrometry. This is evidenced by the expanded measurement uncertainty (k=2) of 0.017 μg/kg or 8.9 % relative to a mass fraction of aflatoxin B1 in a cereal-based baby food of 0.197 μg/kg. This value is in perfect agreement with the consensus value of this material from a proficiency test (PT) scheme for National Reference Laboratories executed by the European Reference Laboratory for Mycotoxins. The effort necessary to perform the described methodology precludes its frequent use but for specific applications we see it as a valuable tool. PMID:25015044

  20. Nuclear Isotopic Dilution of Highly-Enriched Uranium-235 and Uranium-233 by Dry Blending via the RM-2 Mill Technology

    SciTech Connect

    N. A. Chipman; R. N. Henry; R. K. Rajamani; S. Latchireddi; V. Devrani; H. Sethi; J. L. Malhotra

    2004-02-01

    The United States Department of Energy has initiated numerous activities to identify strategies to disposition various excess fissile materials. Two such materials are the off-specification highly enriched uranium-235 oxide powder and the uranium-233 contained in unirradiated nuclear fuel both currently stored at the Idaho National Engineering and Environmental Laboratory. This report describes the development of a technology that could dilute these materials to levels categorized as low-enriched uranium, or further dilute the materials to a level categorized as waste. This dilution technology opens additional pathways for the disposition of these excess fissile materials as existing processing infrastructure continues to be retired.

  1. Influence of thermal maturity on the hydrogen isotope content of extractable hydrocarbons

    NASA Astrophysics Data System (ADS)

    Radke, J.; Bechtel, A.; Püttmann, W.; Gleixner, G.

    2003-04-01

    Based on hydrogen isotope analysis of hydrocarbons from recent sediments it is suggested that compound specific hydrogen isotope ratios are a new proxy to reconstruct the palaeoclimate (Sauer et al., 2001). However, it remains unclear if transformation of carbon bound hydrogen with environmental water during maturation or thermal methanogenesis might influence the observed values. Short-term experiments excluded exchange reactions of deuterium from alkanes (Schimmelmann et al., 1999), however, thermally stressed kerogens are enriched in deuterium (Schoell, 1984). Therefore, we investigated the influence of maturity on the deltaD-values of alkanes and acyclic isoprenoids. In the Kupferschiefer horizon from the Polish Zechstein Basin thermal maturity of organic matter is correlated to burial depth yielding a natural long-term exchange experiment. The deltaD-values of extracted hydrocarbons linearly correlated with thermal maturity. These results enable the correction of deltaD values from biomarkers with known maturity and therefore expanding palaeoclimatic reconstructions using deltaD values to the geological past. References: SAUER, P.E., EGLINTON, T.I., HAYES, J.M., SCHIMMELMANN, A. &SESSIONS, A.L. (2001) Compound specific D/H ratios of lipid biomarkers from sediments as a proxy for environmental and climatic conditions. Geochimica et Cosmochimica Acta, 65(2), 213-222. SCHIMMELMANN, A., LEWAN, M.D. &WINTSCH, R.P. (1999) D/H isotope ratios of kerogen, bitumen, oil, and water in hydrous pyrolysis of source rocks containing kerogen types I, II, IIS, and III. Geochimica et Cosmochimica Acta, 63(22), 3751-3766. SCHOELL, M. (1984) Wasserstoff- und Kohlenstoffisotope in organischen Substanzen, Erdölen und Erdgasen. Schweitzerbart'sche Verlagsbuchhandlung, Stuttgart. Reihe D (67), 161pp.

  2. Deuterium isotopic exchangeability of resin and amber at low thermal stress under hydrous conditions

    NASA Astrophysics Data System (ADS)

    Gonzalez, G.; Tappert, R.; Wolfe, A. P.; Muehlenbachs, K.

    2012-04-01

    Hydrous deuterium-exchange experiments have shown that a significant fraction of the original D/H composition of bulk kerogens, bitumens and expelled oils may participate in isotopic exchange reactions during burial diagenesis. However, it is unknown to what extent plant-derived secondary metabolites, namely resins and their fossil counterpart amber, exchange hydrogen isotopes following their biosynthesis. This situation hinders the application of resin D/H measurements in paleoenvironmental reconstruction. Here, we assess explicitly hydrogen exchange in resins and ambers using a series of immersion experiments in deuterated (D-enriched) waters over a period of several months at several temperatures. We are especially interested in assessing whether significant H-isotopic exchange occurs between resins and meteoric waters during early thermal maturation and polymerization. At 90°C, equivalent to ~3km of burial in most diagenetic regimes, modern conifer and angiosperm resins have an average post-metabolic H exchange of 4.6%, compared to only 1.1% for mature, polymerized ambers. At 55°C the degree of exchange is considerably lower: 1.9% for resins and 0.6% for ambers. These results indicate that most D/H isotopic exchange occurs prior to polymerization reactions, thereby confirming that D/H measurements from amber constitute a potentially sensitive proxy for environmental change.

  3. Constraints on ocean circulation at the Paleocene-Eocene Thermal Maximum from neodymium isotopes

    NASA Astrophysics Data System (ADS)

    Abbott, A. N.; Haley, B. A.; Tripati, A. K.; Frank, M.

    2015-06-01

    Global warming during the Paleocene Eocene Thermal Maximum (PETM) ~55 million years ago (Ma) coincided with a massive release of carbon to the ocean-atmosphere system, as indicated by carbon isotopic data. Previous studies have argued for a role for changing ocean circulation, possibly as a trigger or response to climatic changes. We use neodymium (Nd) isotopic data to reconstruct short high-resolution records of deep-water circulation across the PETM. These records are derived by reductively leaching sediments from seven globally distributed sites and comparing data with published data from fossil fish debris to reconstruct past deep ocean circulation across the PETM. The Nd data for the leachates are interpreted to be consistent with previous studies that have used fish teeth and benthic foraminiferal δ13C to constrain regions of convection. There is some evidence from combining Nd isotope and δ13C records that the three major ocean basins may not have had substantial exchanges of deep waters. If the isotopic data are interpreted within this framework, then the observed pattern may be explained if the strength of overturning in each basin varied distinctly over the PETM, resulting in differences in deep-water aging gradients between basins. Results are consistent with published interpretations from proxy data and model simulations that suggest modulation of overturning circulation had an important role for global recovery of the ocean-atmosphere system after the PETM.

  4. Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology

    SciTech Connect

    Gaffney, A M; Borg, L E; Asmerom, Y

    2008-12-10

    Shock and thermal metamorphism of meteorites from differentiated bodies such as the Moon and Mars have the potential to disturb chronometric information contained in these meteorites. In order to understand the impact-related mechanisms and extent of disturbance to isochrons, we undertook experiments to shock and heat samples of 10017, a 3.6 billion year old lunar basalt. One sub-sample was shocked to 55 GPa, a second subsample was heated to 1000 C for one week, and a third sub-sample was maintained as a control sample. Of the isotope systems analyzed, the Sm-Nd system was the least disturbed by shock or heat, followed by the Rb-Sr system. Ages represented by the {sup 238}U-{sup 206}Pb isotope system were degraded by shock and destroyed with heating. In no case did either shock or heating alone result in rotated or reset isochrons that represent a spurious age. In some cases the true crystallization age of the sample was preserved, and in other cases age information was degraded or destroyed. Although our results show that neither shock nor thermal metamorphism alone can account for the discordant ages represented by different isotope systems in martian meteorites, we postulate that shock metamorphism may render a meteorite more susceptible than unshocked material to subsequent disturbance during impact-related heating or aqueous alteration on Mars or Earth. The combination of these processes may result in the disparate chronometric information preserved in some meteorites.

  5. An experimental and numerical investigation on the influence of external gas recirculation on the HCCI autoignition process in an engine: Thermal, diluting, and chemical effects

    SciTech Connect

    Machrafi, Hatim; Cavadias, Simeon; Guibert, Philippe

    2008-11-15

    In order to contribute to the solution of controlling the autoignition in a homogeneous charge compression ignition (HCCI) engine, parameters linked to external gas recirculation (EGR) seem to be of particular interest. Experiments performed with EGR present some difficulties in interpreting results using only the diluting and thermal aspect of EGR. Lately, the chemical aspect of EGR is taken more into consideration, because this aspect causes a complex interaction with the dilution and thermal aspects of EGR. This paper studies the influence of EGR on the autoignition process and particularly the chemical aspect of EGR. The diluents present in EGR are simulated by N{sub 2} and CO{sub 2}, with dilution factors going from 0 to 46 vol%. For the chemically active species that could be present in EGR, the species CO, NO, and CH{sub 2}O are used. The initial concentration in the inlet mixture of CO and NO is varied between 0 and 170 ppm, while that of CH{sub 2}O alters between 0 and 1400 ppm. For the investigation of the effect of the chemical species on the autoignition, a fixed dilution factor of 23 vol% and a fixed EGR temperature of 70 C are maintained. The inlet temperature is held at 70 C, the equivalence ratios between 0.29 and 0.41, and the compression ratio at 10.2. The fuels used for the autoignition are n-heptane and PRF40. It appeared that CO, in the investigated domain, did not influence the ignition delays, while NO had two different effects. At concentrations up until 45 ppm, NO advanced the ignition delays for the PRF40 and at higher concentrations, the ignition delayed. The influence of NO on the autoignition of n-heptane seemed to be insignificant, probably due to the higher burn rate of n-heptane. CH{sub 2}O seemed to delay the ignition. The results suggested that especially the formation of OH radicals or their consumption by the chemical additives determines how the reactivity of the autoignition changed. (author)

  6. A Transient Model of Induced Natural Circulation Thermal Cycling for Hydrogen Isotope Separation

    SciTech Connect

    SHADDAY, MARTIN

    2005-07-12

    The property of selective temperature dependence of adsorption and desorption of hydrogen isotopes by palladium is used for isotope separation. A proposal to use natural circulation of nitrogen to alternately heat and cool a packed bed of palladium coated beads is under active investigation, and a device consisting of two interlocking natural convection loops is being designed. A transient numerical model of the device has been developed to aid the design process. It is a one-dimensional finite-difference model, using the Boussinesq approximation. The thermal inertia of the pipe walls and other heat structures as well as the heater control logic is included in the model. Two system configurations were modeled and results are compared.

  7. Gas and isotope chemistry of thermal features in Yellowstone National Park, Wyoming

    USGS Publications Warehouse

    Bergfeld, D.; Lowenstern, Jacob B.; Hunt, Andrew G.; Shanks, W.C. Pat, III; Evans, William

    2011-01-01

    This report presents 130 gas analyses and 31 related water analyses on samples collected from thermal features at Yellowstone between 2003 and 2009. An overview of previous studies of gas emissions at Yellowstone is also given. The analytical results from the present study include bulk chemistry of gases and waters and isotope values for water and steam (delta18O, dealtaD), carbon dioxide (delta13C only), methane (delta13C only), helium, neon, and argon. We include appendixes containing photos of sample sites, geographic information system (GIS) files including shape and kml formats, and analytical results in spreadsheets. In addition, we provide a lengthy discussion of previous work on gas chemistry at Yellowstone and a general discussion of the implications of our results. We demonstrate that gases collected from different thermal areas often have distinct chemical signatures, and that differences across the thermal areas are not a simple function of surface temperatures or the type of feature. Instead, gas chemistry and isotopic composition are linked to subsurface lithologies and varying contributions from magmatic, crustal, and meteoric sources.

  8. Ammonium in thermal waters of Yellowstone National Park: processes affecting speciation and isotope fractionation

    USGS Publications Warehouse

    Holloway, J.M.; Nordstrom, D.K.; Böhlke, J.K.; McCleskey, R.B.; Ball, J.W.

    2011-01-01

    Dissolved inorganic nitrogen, largely in reduced form (NH4(T)≈NH4(aq)++NH3(aq)o), has been documented in thermal waters throughout Yellowstone National Park, with concentrations ranging from a few micromolar along the Firehole River to millimolar concentrations at Washburn Hot Springs. Indirect evidence from rock nitrogen analyses and previous work on organic compounds associated with Washburn Hot Springs and the Mirror Plateau indicate multiple sources for thermal water NH4(T), including Mesozoic marine sedimentary rocks, Eocene lacustrine deposits, and glacial deposits. A positive correlation between NH4(T) concentration and δ18O of thermal water indicates that boiling is an important mechanism for increasing concentrations of NH4(T) and other solutes in some areas. The isotopic composition of dissolved NH4(T) is highly variable (δ15N = −6‰ to +30‰) and is positively correlated with pH values. In comparison to likely δ15N values of nitrogen source materials (+1‰ to +7‰), high δ15N values in hot springs with pH >5 are attributed to isotope fractionation associated with NH3(aq)o loss by volatilization. NH4(T) in springs with low pH typically is relatively unfractionated, except for some acid springs with negative δ15N values that are attributed to NH3(g)o condensation. NH4(T) concentration and isotopic variations were evident spatially (between springs) and temporally (in individual springs). These variations are likely to be reflected in biomass and sediments associated with the hot springs and outflows. Elevated NH4(T) concentrations can persist for 10s to 1000s of meters in surface waters draining hot spring areas before being completely assimilated or oxidized.

  9. METHOD OF AND APPARATUS FOR WITHDRAWING LIGHT ISOTOPIC PRODUCT FROM A LIQUID THERMAL DIFFUSION PLANT

    DOEpatents

    Dole, M.

    1959-09-22

    An improved process and apparatus are described for removing enriched product from the columns of a thermal diffusion plant for separation of isotopes. In the removal cycle, light product at the top cf the diffusion columns is circulated through the column tops and a shipping cylinder connected thereto unttl the concertation of enriched product in the cylinder reaches the desired point. During the removal, circulation through the bottoms is blocked bv freezing. in the diffusion cycle, the bottom portion is unfrozen, fresh feed is distributed to the bottoms of the columns, ard heavy product is withdrawn from the bottoms, while the tops of the columns are blocked by freezing.

  10. Recent Advances in SRS on Hydrogen Isotope Separation Using Thermal Cycling Absorption Process

    DOE PAGESBeta

    Xiao, Xin; Sessions, Henry T.; Heung, L. Kit

    2015-02-01

    The recent Thermal Cycling Absorption Process (TCAP) advances at Savannah River Site (SRS) include compressor-free concept for heating/cooling, push and pull separation using an active inverse column, and compact column design. The new developments allow significantly higher throughput and better reliability from 1/10th of the current production system’s footprint while consuming 60% less energy. Various versions are derived in the meantime for external customers to be used in fusion energy projects and medical isotope production.

  11. Chemical and isotope compositions of nitric thermal water of Baikal rift zone

    NASA Astrophysics Data System (ADS)

    Plyusnin, A. M.; Chernyavsky, M. K.; Peryazeva, E. G.

    2010-05-01

    Three types of hydrotherms (nitric, carbonaceous and methane) are distinguished within the Baikal Rift Zone. The unloading sites of nitric therms are mostly located in the central and north-eastern parts of the Rift. Several chemical types are found among nitric therms (Pinneker, Pisarsky, Lomonosov, 1968; Lomonosov, 1974, etc.). The formation of terms being various in chemical compositions is associated with effect of several factors, i.e. various chemical, mineralogical compositions of rocks, various temperatures, extent of interaction in water-rock system, etc. The ratio data of water oxygen and hydrogen isotopes of the studied thermal springs indicate that water is largely of meteoric origin. All established ratios of oxygen (δ18OSMOW = -19.5‰ - -17.5‰) and hydrogen (δDSMOW = -155‰ - - 130‰) isotopes are along the line of meteoric waters. Oxygen values from -20‰ to -5‰ are characteristic of the current meteoric and surface waters in the region. The average value equals -16.5‰ in Lake Baikal. By our data, a large group with oxygen lighter isotope composition that corresponds to isotope ratio being specific for glaciers is revealed in fissure-vein waters. Significant shift toward the oxygen getting heavier is observed in some springs. It is mostly observed in the springs that form chemical composition within the area of the intrusive and metamorphic rock distribution. As a result of hydrolysis reaction of alumosilicates, heavy isotope passes from rocks into water molecule, whereas oxygen heavy isotope passes from rocks into solutes during decomposition of carbonates. High contents of fluoride and sulfate-ions are specific feature of the Baikal Rift Zone most nitric therms. Water is tapped in one of the drill holes, where fluoride-ion dominates in its anion composition (46.7 mg/dm3) and pH reaches 10, 12. The sulphate sulphur isotope composition studies carried out allow to conclude that its heavy isotope (δ34SCDT = +25‰ - +30‰) prevails in

  12. Zn isotope compositions of the thermal spring waters of La Soufrière volcano, Guadeloupe Island

    NASA Astrophysics Data System (ADS)

    Chen, Jiu-Bin; Gaillardet, Jérôme; Dessert, Céline; Villemant, Benoit; Louvat, Pascale; Crispi, Olivier; Birck, Jean-Louis; Wang, Yi-Na

    2014-02-01

    To trace the sources and pathways of Zn in hydrothermal systems, the Zn isotope compositions of seventeen water samples from eight thermal springs and six gas samples from two fumaroles from La Soufrière, an active volcano on Guadeloupe Island (French West Indies, FWI), were analyzed using a method adapted for purifying Zn from Fe- and SO4-enriched thermal solutions. The fumaroles are enriched in Zn 100 to 8000 times compared to the local bedrock and have isotopic compositions (δ66Zn values from +0.21‰ to +0.35‰) similar to or slightly higher than fresh andesite (+0.21‰). The enrichment of Zn in the thermal springs compared with the surface waters shows that Zn behaves as a soluble element during hydrothermal alteration but is significantly less mobile than Na. The δ66Zn values of most of the spring waters are relatively constant (approximately 0.70‰), indicating that the thermal springs from La Soufrière are enriched in heavy isotopes (i.e., 66Zn) compared to the host rocks (from -0.14‰ to +0.42‰). Only three thermal springs have lower δ66Zn values (as low as -0.43%). While the Zn in the fumaroles is essentially derived from magma degassing, which is consistent with a previous study on Merapi volcano (Toutain et al., 2008), we show that the Zn in the thermal springs is mainly derived from water-rock interactions. The 66Zn-enriched isotopic signature in most of the spring waters can be explained qualitatively by the precipitation at depth of sulfide minerals that preferentially incorporate the light isotopes. This agrees with the isotopic fractionation that was recently calculated for aqueous complexes of Zn. The few thermal springs with lower δ66Zn values also have low Zn concentrations, indicating the preferential scavenging of heavy Zn isotopes in the hydrothermal conduits. This study shows that unlike chemical weathering under surface conditions, hydrothermal alteration at high temperatures significantly fractionates Zn isotopes and enriches

  13. Determination of six thyroid hormones in the brain and thyroid gland using isotope-dilution liquid chromatography/tandem mass spectrometry.

    PubMed

    Kunisue, Tatsuya; Fisher, Jeffrey W; Kannan, Kurunthachalam

    2011-01-01

    Thyroid hormones (THs) play critical roles in the regulation of growth and development, including brain development, in both humans and animals. Until recently, TH levels were assayed with measurements in serum, using immunoassay (IA)-based methods. IA methods are sensitive but are compromised by the lack of adequate specificity. Furthermore, measurements of TH levels in blood do not necessarily reflect the levels and profiles found in critical organs such as the brain. Measurement of TH levels in the brain is critical for studies that assess the effects of environmental contaminants on TH homeostasis. In this study, we developed a selective and sensitive method for the analysis of six THs, l-thyroxine (T(4)), 3,3',5-triiodo-l-thyronine (T(3)), 3,3',5'-triiodo-l-thyronine (rT(3)), 3,5-diiodo-l-thyronine (3,5-T(2)), 3,3'-diiodo-l-thyronine (3,3'-T(2)), and 3-iodo-l-thyronine (3-T(1)), in the brain and thyroid gland (TG) using isotope ([(13)C]T(4))-dilution liquid chromatography (LC)/tandem mass spectrometry (MS/MS). Proteins in the (rat) brain and TG were digested by pronase, and THs were extracted with a solid-phase extraction method and analyzed by LC/MS/MS. The instrumental calibration range for each TH ranged from 0.5 to 200 ng/mL and showed excellent linearity (r > 0.9995). The instrumental detection limits for THs were in the range of 7.5-13.5 pg, in positive ion mode, and 13.5-16.5 pg, in negative ion mode. The optimized procedural recoveries for THs (except for 3-T(1)), spiked into a pig-brain matrix, were between 97.6% and 109%, with a coefficient of variation (CV) of 1.2-8.2%, for the brain, and between 96.4% and 101%, with a CV of 1.8-8.6%, for the TG. Concentrations of THs in the brain and TG of the five rats were 2.20-3.65 ng/g T(4), 1.56-2.20 ng/g T(3), and below the limit of detection (

  14. Dilution Confusion: Conventions for Defining a Dilution

    ERIC Educational Resources Information Center

    Fishel, Laurence A.

    2010-01-01

    Two conventions for preparing dilutions are used in clinical laboratories. The first convention defines an "a:b" dilution as "a" volumes of solution A plus "b" volumes of solution B. The second convention defines an "a:b" dilution as "a" volumes of solution A diluted into a final volume of "b". Use of the incorrect dilution convention could affect…

  15. On a thermal analysis of a second stripper for rare isotope accelerator.

    SciTech Connect

    Momozaki, Y.; Nolen, J.; Nuclear Engineering Division

    2008-08-04

    This memo summarizes simple calculations and results of the thermal analysis on the second stripper to be used in the driver linac of Rare Isotope Accelerator (RIA). Both liquid (Sodium) and solid (Titanium and Vanadium) stripper concepts were considered. These calculations were intended to provide basic information to evaluate the feasibility of liquid (thick film) and solid (rotating wheel) second strippers. Nuclear physics calculations to estimate the volumetric heat generation in the stripper material were performed by 'LISE for Excel'. In the thermal calculations, the strippers were modeled as a thin 2D plate with uniform heat generation within the beam spot. Then, temperature distributions were computed by assuming that the heat spreads conductively in the plate in radial direction without radiative heat losses to surroundings.

  16. Cold source moderator vessel development for the High Flux Isotope Reactor: Thermal-hydraulic studies

    SciTech Connect

    Williams, P.T.; Lucas, A.T.; Wendel, M.W.

    1998-07-01

    A project is underway at Oak Ridge National Laboratory (ORNL) to design, test, and install a cold neutron source facility in the High Flux Isotope Reactor (HFIR). This new cold source employs supercritical hydrogen at cryogenic temperatures both as the medium for neutron moderation and as the working fluid for removal of internally-generated nuclear heating. The competing design goals of minimizing moderator vessel mass and providing adequate structural integrity for the vessel motivated the requirement of detailed multidimensional thermal-hydraulic analyses of the moderator vessel as a critical design subtask. This paper provides a summary review of the HFIR cold source moderator vessel design and a description of the thermal-hydraulic studies that were carried out to support the vessel development.

  17. Estimation of the isotope effect on the lattice thermal conductivity of group IV and group III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Morelli, D. T.; Heremans, J. P.; Slack, G. A.

    2002-11-01

    The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and transverse phonon Grüneisen constants and the effective sample diameter. The model can quantitatively account for the observed isotope effect in diamond and germanium but not in silicon. The magnitude of the isotope effect is predicted for silicon carbide, boron nitride, and gallium nitride. In the case of boron nitride the predicted increase in the room-temperature thermal conductivity with isotopic enrichment is in excess of 100%. Finally, a more general method of estimating normal phonon-scattering rate coefficients for other types of solids is presented.

  18. Characterization of Key Aroma Compounds in Raw and Thermally Processed Prawns and Thermally Processed Lobsters by Application of Aroma Extract Dilution Analysis.

    PubMed

    Mall, Veronika; Schieberle, Peter

    2016-08-24

    Application of aroma extract dilution analysis (AEDA) to an aroma distillate of blanched prawn meat (Litopenaeus vannamei) (BPM) revealed 40 odorants in the flavor dilution (FD) factor range from 4 to 1024. The highest FD factors were assigned to 2-acetyl-1-pyrroline, 3-(methylthio)propanal, (Z)-1,5-octadien-3-one, trans-4,5-epoxy-(E)-2-decenal, (E)-3-heptenoic acid, and 2-aminoacetophenone. To understand the influence of different processing conditions on odorant formation, fried prawn meat was investigated by means of AEDA in the same way, revealing 31 odorants with FD factors between 4 and 2048. Also, the highest FD factors were determined for 2-acetyl-1-pyrroline, 3-(methylthio)propanal, and (Z)-1,5-octadien-3-one, followed by 4-hydroxy-2,5-dimethyl-3(2H)-furanone, (E)-3-heptenoic acid, and 2-aminoacetophenone. As a source of the typical marine, sea breeze-like odor attribute of the seafood, 2,4,6-tribromoanisole was identified in raw prawn meat as one of the contributors. Additionally, the aroma of blanched prawn meat was compared to that of blanched Norway and American lobster meat, respectively (Nephrops norvegicus and Homarus americanus). Identification experiments revealed the same set of odorants, however, with differing FD factors. In particular, 3-hydroxy-4,5-dimethyl-2(5H)-furanone was found as the key aroma compound in blanched Norway lobster, whereas American lobster contained 3-methylindole with a high FD factor. PMID:27486834

  19. Noble gas isotopic signatures in thermal waters of the Dead Sea Transform

    NASA Astrophysics Data System (ADS)

    Tsur, Neta; Kaudse, Tillmann; Aeschbach-Hertig, Werner

    2014-05-01

    Noble gas isotope composition in thermal groundwater provides information about crust-mantle interactions, in form of geotectonic activity, volcanism and advective heat transfer. The knowledge of the geothermal state of the crust is useful for the indication of thermal energy resources, which are of significant environmental and economic importance. In this study, groundwater samples were collected in Israel and Jordan in 2012, along the east and west sides of the central Dead Sea Transform. The helium isotope ratio, 3He/4He, is a well-established marker to discriminate three different geochemical reservoirs: Atmosphere, crust and mantle. The distinct isotope ratios in each reservoir make it possible to separate the total helium concentration in groundwater into mantle, crustal (radiogenic) and atmospheric components. The 3He/4He ratios of all sampled waters exceed the typical crustal ratio, indicating contributions of mantle-derived helium to the total helium concentration. Most of the samples contain less than 3% atmospheric helium, whereas the mantle-derived helium component ranges from 1% to 61%. In Israel, a clear trend is observed. Samples from the northern parts of the sampling area show higher 3He/4He ratios than samples from southern parts. These findings confirm Torfstein et al. [1], who analyzed thermal groundwaters from Israel. In our data from Jordan, however, no north-south trend is seen, but a local anomaly is observed in the area between the Dead Sea and the Sea of Galilee, with a 3He/4He ratio that is 5 times higher than the atmospheric 3He/4He ratio. Moreover, some samples from North Jordan exhibit only minor mantle contributions, compared to the samples from the north of Israel. Our results emphasize the importance of local faulting patterns, which enable a better transfer of mantle derived helium into the shallow crust. In addition to helium, the origin of CO2 in the water was examined. Measurements of δ13C suggest that CO2 originates from

  20. Comparison between GC-MS and GC-ICPMS using isotope dilution for the simultaneous monitoring of inorganic and methyl mercury, butyl and phenyl tin compounds in biological tissues.

    PubMed

    Cavalheiro, J; Preud'homme, H; Amouroux, D; Tessier, E; Monperrus, M

    2014-02-01

    The aim of this work is to compare simultaneous isotope dilution analysis of organotin and organomercury compounds by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP/MS) on certified bivalve samples. These samples were extracted by microwave with tetramethylammonium hydroxide (TMAH). Derivatization with both NaBEt4 and NaBPr4 was evaluated, and analytical performances were compared. Two CRM materials, BCR-710 and CRM-477, were analyzed by both techniques to verify accuracy. A mixed spike containing (201)Hg-enriched methylmercury (MeHg), (199)Hg-enriched inorganic mercury (iHg), (119)Sn-enriched monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) as well as homemade (116)Sn-enriched monophenyltin (MPT), diphenyltin (DPT), and triphenyltin (TPT) was used for the isotope dilution analysis of samples. The two techniques studied were compared in terms of classic analytical parameters: linearity, precision or repeatability (i.e., percent relative standard deviation, RSD%), limit of detection (LOD), and limit of quantification (LOQ), showing excellent linearity, precision below 12% for all analytes, and LOQs of 0.06-1.45 pg for GC-MS and 0.02-0.27 pg for GC-ICP/MS. PMID:24136249

  1. METHOD FOR REMOVAL OF LIGHT ISOTOPE PRODUCT FROM LIQUID THERMAL DIFFUSION UNITS

    DOEpatents

    Hoffman, J.D.; Ballou, J.K.

    1957-11-19

    A method and apparatus are described for removing the lighter isotope of a gaseous-liquid product from a number of diffusion columns of a liquid thermal diffusion system in two stages by the use of freeze valves. The subject liquid flows from the diffusion columns into a heated sloping capsule where the liquid is vaporized by the action of steam in a heated jacket surrounding the capsule. When the capsule is filled the gas flows into a collector. Flow between the various stages is controlled by freeze valves which are opened and closed by the passage of gas and cool water respectively through coils surrounding portions of the pipes through which the process liquid is passed. The use of the dual stage remover-collector and the freeze valves is an improvement on the thermal diffusion separation process whereby the fraction containing the lighter isotope many be removed from the tops of the diffusion columns without intercolumn flow, or prior stage flow while the contents of the capsule is removed to the final receiver.

  2. Radium isotope geochemistry of thermal waters, Yellowstone National Park, Wyoming, USA

    SciTech Connect

    Sturchio, N.C.; Bohlke, J.K.; Markun, F.J. )

    1993-03-01

    Radium isotope activities ([sup 226]Ra, [sup 228]Ra, and [sup 224]Ra), chemical compositions, and sulfur isotope ratios in sulfate were determined for water samples from thermal areas in Yellowstone National Park, Wyoming. Activities of [sup 226]Ra in these waters range from <0.2 to 37.9 dpm/kg. Activity ratios of [sup 228]Ra/[sup 226]Ra range from 0.26 to 14.2, and those of [sup 224]Ra/[sup 228]Ra range from 0.73 to 3.1. Radium concentrations are inversely correlated with aquifer equilibration temperatures (estimated from dissolved silica concentrations), while [Ra/Ba][sub aq] and [sup 228]Ra/[sup 226]Ra activity ratios depend upon U/Ba and Th/U ratios in aquifer rocks. Major controls on Ra concentration in Yellowstone thermal waters are inferred to be (1) barite saturation (at Norris Geyser Basin, Mammoth Hot Springs, and other northern areas) and (2) zeolite-water ion exchange (at Upper Geyser Basin). The data are consistent with a model in which (1) radium and barium are supplied to water by bulk dissolution of aquifer rock, and (2) chemical equilibration of water with rock is rapid relative to the 1602 year half-life of [sup 226]Ra. The [sup 228]Ra/[sup 226]Ra activity ratios of the waters may in some cases reflect surface enrichments of [sup 232]Th and/or may indicate that [alpha]-recoil input of [sup 228]Ra is rapid relative to water-rock chemical equilibration. Activity ratios of [sup 224]Ra/[sup 228]Ra indicate a nearly ubiquitous [sup 224]Ra excess that generally increases with decreasing pH. Near-surface ([le]100 m) thermal water flow velocities at Mammoth Hot Springs are estimated from [sup 224]Ra/[sup 228]Ra variation to be [ge]1 m h[sup [minus]1]. 73 refs., 4 figs., 4 tabs.

  3. Simultaneous determination of 19 triazine pesticides and degradation products in processed cereal samples from Chinese total diet study by isotope dilution-high performance liquid chromatography-linear ion trap mass spectrometry.

    PubMed

    Li, Peng; Yang, Xin; Miao, Hong; Zhao, Yunfeng; Liu, Wei; Wu, Yongning

    2013-06-01

    A selective and sensitive isotope dilution-high performance liquid chromatography-linear ion trap mass spectrometry (Isotope Dilution-HPLC-LIT-MS(3)) method was developed for the simultaneous determination of 19 triazine pesticides and their degradation products in processed cereal samples from Chinese total diet study (TDS). The method integrated the addition of isotope internal standards, liquid-liquid extraction (LLE), clean-up with MCX solid-phase extraction (SPE) cartridges and HPLC-LIT-MS(3) analysis with selected reaction monitoring (SRM) mode. Matrix-matched calibration curves showed good linearity (R(2)≥0.9940) verified by applying the Mandel's fitting test (p>0.087) performed at the 95% confidence level. Decision limits (CCαs) and detection capabilities (CCβs) of the 19 triazine pesticides and their degradation products fell in the ranges of 0.0020-0.4200 μg kg(-1) and 0.0024-0.4500 μg kg(-1), respectively. Recoveries ranged from 70.1% to 112.8%, with the relative standard deviations (RSDs) ranging from 1.5% to 13.5%. Furthermore, the proposed method was applied to analyzing the proposed cereal samples from the fourth Chinese TDS. Eleven triazines were detected in six cereal samples with the concentrations ranging from 0.013 to 0.987 μg kg(-1). This method can also be used for the further determination of the triazines in other food group composites, and ultimately served as a methodological foundation for assessing the triazines in the average Chinese diet in the general population. PMID:23684466

  4. Isotope Geochemistry of Calcite Coatings and the Thermal History of the Unsaturated Zone at Yucca Mountain, Nevada

    SciTech Connect

    B.D. Marshall; J.F. Whelan

    2000-07-27

    Calcite and opal coatings found on fracture footwalls and lithophysal cavity bottoms in the volcanic section at Yucca Mountain (exposed in a tunnel) contain a record of gradual chemical and isotopic changes that have occurred in the unsaturated zone. The thin (less than 6 cm) coatings are composed primarily of calcite, opal, chalcedony, and quartz. Fluid inclusions in calcite that homogenize at greater than ambient temperatures provide impetus for geochronologic studies in order to determine the thermal history. In the welded Topopah Spring Tuff (12.7 Ma), U-Pb ages of opal and chalcedony layers provide evidence of a long history of deposition throughout the past 10 m.y. However, these ages can constrain the ages of associated calcite layers only in samples with an easily interpretable microstratigraphy. Strontium isotope ratios in calcite increase with microstratigraphic position from the base up to the outermost surface of the coatings. The strontium incorporated in these coatings records the systematic change in pore-water isotopic composition due to water-rock interaction primarily in the overlying nonwelded tuffs. A one-dimensional advection-reaction model simulates strontium isotope ratios measured in pore water extracted from core in three vertical boreholes adjacent to the tunnel. By calculating the strontium isotope compositions of the rocks at various past times, the model predicts a history of the strontium isotope ratios in the water that matches the record in the calcite and therefore provides approximate ages. Oxygen isotope ratios measured in calcite gradually increase with decreasing model strontium age. Assuming that the oxygen isotope ratio of the percolating water was relatively constant, this trend indicates a gradual cooling of the rocks over millions of years, in agreement with thermal modeling of magma beneath the 12-Ma Timber Mountain caldera just north of Yucca Mountain. This model predicts that temperatures significantly exceeding current

  5. Chlorine isotopes of thermal springs in arc volcanoes for tracing shallow magmatic activity

    NASA Astrophysics Data System (ADS)

    Li, Long; Bonifacie, Magali; Aubaud, Cyril; Crispi, Olivier; Dessert, Céline; Agrinier, Pierre

    2015-03-01

    The evaluation of the status of shallow magma body (i.e., from the final intrusion stage, to quiescence, and back to activity), one of the key parameters that trigger and sustain volcanic eruptions, has been challenging in modern volcanology. Among volatile tracers, chlorine (Cl) uniquely exsolves at shallow depths and is highly hydrophilic. Consequently, Cl enrichment in volcanic gases and thermal springs has been proposed as a sign for shallow magmatic activities. However, such enrichment could also result from numerous other processes (e.g., water evaporation, dissolution of old chloride mineral deposits, seawater contamination) that are unrelated to magmatic activity. Here, based on stable isotope compositions of chloride and dissolved inorganic carbon, as well as previous published 3He/4He data obtained in thermal springs from two recently erupted volcanoes (La Soufrière in Guadeloupe and Montagne Pelée in Martinique) in the Lesser Antilles Arc, we show that the magmatic Cl efficiently trapped in thermal springs displays negative δ37Cl values (≤ - 0.65 ‰), consistent with a slab-derived origin but distinct from the isotope compositions of chloride in surface reservoirs (e.g. seawater, local meteoric waters, rivers and cold springs) displaying common δ37Cl values of around 0‰. Using this δ37Cl difference as an index of magmatic Cl, we further examined thermal spring samples including a 30-year archive from two thermal springs in Guadeloupe covering samples from its last eruption in 1976-1977 to 2008 and an island-wide sampling event in Martinique in 2008 to trace the evolution of magmatic Cl in the volcanic hydrothermal systems over time. The results show that magmatic Cl can be rapidly flushed out of the hydrothermal systems within <30 to 80 years after the eruption, much quicker than other volatile tracers such as CO2 and noble gases, which can exsolve at greater depths and constantly migrate to the surface. Because arc volcanoes often have well

  6. Detection of 1,N(2)-propano-2'-deoxyguanosine adducts in genomic DNA by ultrahigh performance liquid chromatography-electrospray ionization-tandem mass spectrometry in combination with stable isotope dilution.

    PubMed

    Zhang, Ning; Song, Yuanyuan; Wu, Danni; Xu, Tian; Lu, Meiling; Zhang, Weibing; Wang, Hailin

    2016-06-10

    Crotonaldehyde (Cro) is one of widespread and genotoxic α,β-unsaturated aldehydes and can react with the exocyclic amino group of 2'-deoxyguanosine (dG) in genomic DNA to form 1,N(2)-propano-2'-deoxyguanosine (ProdG) adducts. In this study, two diastereomers of high purity were prepared, including non-isotope and stable isotope labeled ProdG adducts, and exploited stable isotope dilution-based calibration method. By taking advantage of synthesized ProdG standards, we developed a sensitive ultrahigh performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UHPLC-ESI-MS/MS) method for accurate quantification of two diastereomers of ProdG adducts. In addition to optimization of the UHPLC separation, ammonium bicarbonate (NH4HCO3) was used as additive in the mobile phase for enhancing the ionization efficiency to ProdG adducts and facilitating MS detection. The limits of detection (LODs, S/N=3) and the limits of quantification (LOQs, S/N=10) are estimated about 50 amol and 150 amol, respectively. By the use of the developed method, both diastereomers of ProdG adducts can be detected in untreated human MRC5 cells with a frequency of 2.4-3.5 adducts per 10(8) nucleotides. Crotonaldehyde treatment dramatically increases the levels of ProdG adducts in human MRC5 in a concentration-dependent manner. PMID:27179676

  7. Enhanced thermal conductivity and isotope effect in single-layer hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Broido, David; Lindsay, Lucas

    2012-02-01

    We have calculated the lattice thermal conductivity, k, of both naturally occurring and isotopically enriched single layers of hexagonal boron nitride (h-BN) as well as bulk h-BN using an exact numerical solution of the Boltzmann transport equation for phonons [1]. Good agreement is obtained with measured bulk h-BN data [2], and the stronger phonon-phonon scattering identified in these systems explains why their k values are significantly lower than those in graphene and graphite. A reduction in such scattering in the single layer arising mainly from a symmetry-based selection rule leads to a substantial increase in k, with calculated room temperature values of more than 600 W/m-K. Additional enhancement is obtained from isotopic enrichment, which exhibits a strong peak as a function of temperature, with magnitude growing rapidly with crystallite size. [1] L. Lindsay and D. A. Broido, Phys. Rev. B 84, 155421 (2011). [2] E. K. Sichel, R. E. Miller, M. S. Abrahams, and C. J. Buiocchi, Phys. Rev. B 13, 4607 (1976).

  8. Isotope geochemistry of thermal and nonthermal waters in the Valles caldera, Jemez Mountains, northern New Mexico

    SciTech Connect

    Vuataz, F.D.; Goff, F.

    1986-02-10

    Over 100 stable isotope and 45 tritium analyses from thermal and nonthermal waters of the Jemez Mountains region, New Mexico, have been used to define the hydrodynamics of the Valles caldera (Baca) geothermal system and related geothermal fluids of the region. Evaluation of 36 cold meteoric waters yields an equation for the Jemez Mountains meteoric water line of deltaD = 8delta/sup 18/O+12, while further evaluation of nine cold meteoric waters yields an equation relating recharge elevation to deuterium content of E(meters) = -44.9 (deltaD)-1154. Based on the deuterium content of five Baca well waters (223/sup 0/--294/sup 0/C), the average recharge elevation of the Valles geothermal system ranges from 2530 to 2890 m. This range of elevations falls between the elevations of the lowest point of the caldera floor (2400 m) and the summit of the resurgent dome inside the caldera (3430 m). Thus stable isotopes indicate that the caldera depression probably serves as a recharge basin for the deep geothermal system. Although cold spring waters of the Jemez Mountains region consist of meteoric water, tritium analyses show that most of them contain water between 20 and 75 years old.

  9. Advanced Multiphysics Thermal-Hydraulics Models for the High Flux Isotope Reactor

    SciTech Connect

    Jain, Prashant K; Freels, James D

    2015-01-01

    Engineering design studies to determine the feasibility of converting the High Flux Isotope Reactor (HFIR) from using highly enriched uranium (HEU) to low-enriched uranium (LEU) fuel are ongoing at Oak Ridge National Laboratory (ORNL). This work is part of an effort sponsored by the US Department of Energy (DOE) Reactor Conversion Program. HFIR is a very high flux pressurized light-water-cooled and moderated flux-trap type research reactor. HFIR s current missions are to support neutron scattering experiments, isotope production, and materials irradiation, including neutron activation analysis. Advanced three-dimensional multiphysics models of HFIR fuel were developed in COMSOL software for safety basis (worst case) operating conditions. Several types of physics including multilayer heat conduction, conjugate heat transfer, turbulent flows (RANS model) and structural mechanics were combined and solved for HFIR s inner and outer fuel elements. Alternate design features of the new LEU fuel were evaluated using these multiphysics models. This work led to a new, preliminary reference LEU design that combines a permanent absorber in the lower unfueled region of all of the fuel plates, a burnable absorber in the inner element side plates, and a relocated and reshaped (but still radially contoured) fuel zone. Preliminary results of estimated thermal safety margins are presented. Fuel design studies and model enhancement continue.

  10. Enhanced thermal conductivity and isotope effect in single-layer hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Lindsay, L.; Broido, D. A.

    2011-10-01

    The thermal conductivity, κ, of single layers of hexagonal boron nitride (h-BN), as well as that of bulk h-BN have been calculated utilizing an exact numerical solution of the phonon Boltzmann transport equation. The stronger phonon-phonon scattering in h-BN is revealed as the cause for its lower κ compared with graphite. A reduction in such scattering in the single layer arising mainly from a symmetry-based selection rule leads to a substantial increase in κ, with calculated room temperature values of more than 600 Wm-1K-1. Isotopic enrichment further increases κ, with the calculated enhancement exhibiting a peak with temperature, whose magnitude shows a dramatic sensitivity to crystallite size.

  11. Recent advances in SRS on hydrogen isotope separation using thermal cycling absorption process

    SciTech Connect

    Xiao, X.; Kit Heung, L.; Sessions, H.T.

    2015-03-15

    TCAP (Thermal Cycling Absorption Process) is a gas chromatograph in principle using palladium in the column packing, but it is unique in the fact that the carrier gas, hydrogen, is being isotopically separated and the system is operated in a semi-continuous manner. TCAP units are used to purify tritium. The recent TCAP advances at Savannah River Site (SRS) include compressor-free concept for heating/cooling, push and pull separation using an active inverse column, and compact column design. The new developments allow significantly higher throughput and better reliability from 1/10 of the current production system's footprint while consuming 60% less energy. Various versions are derived in the meantime for external customers to be used in fusion energy projects.

  12. Isotopically exchangeable organic hydrogen in coal relates to thermal maturity and maceral composition

    USGS Publications Warehouse

    Mastalerz, Maria; Schimmelmann, A.

    2002-01-01

    Hydrogen isotopic exchangeability (Hex) and ??Dn values of non-exchangeable organic hydrogen were investigated in coal kerogens ranging in rank from lignite to graphite. The relative abundance of Hex is highest in lignite with about 18% of total hydrogen being exchangeable, and decreases to around 2.5% in coals with Ro of 1.7 to ca. 5.7%. At Still higher rank (Ro > 6%), Hex increases slightly, although the abundance of total hydrogen decreases. ??Dn is influenced by original biochemical D/H ratios and by thermal maturation in contact with water. Therefore, ??Dn does not show an overall consistent trend with maturity. ?? 2002 Elsevier Science Ltd. All rights reserved.

  13. COMSOL Simulations for Steady State Thermal Hydraulics Analyses of ORNL s High Flux Isotope Reactor

    SciTech Connect

    Khane, Vaibhav B; Jain, Prashant K; Freels, James D

    2012-01-01

    Simulation models for steady state thermal hydraulics analyses of Oak Ridge National Laboratory s High Flux Isotope Reactor (HFIR) have been developed using the COMSOL Multiphysics simulation software. A single fuel plate and coolant channel of each type of HFIR fuel element was modeled in three dimensions; coupling to adjacent plates and channels was accounted for by using periodic boundary conditions. The standard k- turbulence model was used in simulating turbulent flow with conjugate heat transfer. The COMSOL models were developed to be fully parameterized to allow assessing impacts of fuel fabrication tolerances and uncertainties related to low enriched uranium (LEU) fuel design and reactor operating parameters. Heat source input for the simulations was obtained from separate Monte Carlo N Particle calculations for the axially non-contoured LEU fuel designs at the beginning of the reactor cycle. Mesh refinement studies have been performed to calibrate the models against the pressure drop measured across the HFIR core.

  14. Mass-47 clumped isotope thermal history reordering: Example from the Greater Green River basin

    NASA Astrophysics Data System (ADS)

    Lacroix, B.; Niemi, N. A.

    2015-12-01

    During the last several years, many studies have tried to reconstruct the paleoelevations of sedimentary basins and paleosol sequences using the mass-47 clumped isotope thermometer. Ideally, this technique directly preserves the temperature of carbonate formation, avoiding any speculation on the composition of surface or water from which the carbonate precipitated. Recently, however, concerns about post-depositional alteration of the mass-47 isotope signature, due to the effects of burial, O and C volume diffusion, and/or diagenetic alteration have arisen, potentially complicating the application of the clumped thermometer for determining paleo-surface conditions. Here we investigate the effect of burial depth on mass-47 bond reordering. To this purpose we collected samples, from the surface and from drill cores, in two different areas of the Greater Green River basin: the Washakie Basin near Rock Springs, Wyoming and Green River basin near Pinedale, Wyoming. Both basins are filled with a thick Eocene lacustrine series that include numerous limestone beds. The thermal histories of the basins are well documented from petroleum prospecting studies. The Δ47 composition of lacustrine limestones with peak burial depths ranging from 1 to 6 km have been measured and compared to values derived from temperature history reordering models (THRMs). These results show that the THRMs does not predict the observed clumped isotope composition, suggesting than parameters other than temperature are controlling the Δ47 reordering. In order to refine the predictive model, we propose to independently model the best k0 factor of each analyzed sample starting from their final measured Δ47 values and implementing the thermal history from current depth to the period of deposition. Resulting k0 values are surprisingly well correlated with depth, suggesting that pressure and/or depth have a strong influence on the k0factor, and consequently on Δ47 bond reordering. These results suggest

  15. Hydrogeochemical and isotopic study of thermal and mineralized waters from the Nevşehir (Kozakli) area, Central Turkey

    NASA Astrophysics Data System (ADS)

    Pasvanoğlu, S.; Chandrasekharam, D.

    2011-05-01

    In the Kozakli geothermal province, thermal waters are manifested along a valley 1.5 km long and 200 m in width. Thermal waters utilised by the resort and some other hotels are mostly discharged from bore wells. The issuing temperatures of the thermal waters vary from 40-50 °C in thermal springs and 45-96 °C in bores and open wells. The geochemical and isotopic signatures of the thermal water suggest mixing of thermal waters with formation waters and cold near-surface groundwaters before emerging to the surface, and hence geochemical indicators fail to indicate the near true reservoir temperatures. However, the oxygen and hydrogen isotopic signatures strongly suggest a high temperature reservoir (> 220 °C) in the crystalline basement rocks. Long circulation of meteoric waters within the basement rocks is indicated by low tritium values in the thermal waters. Major involvement of Miocene Marls in modifying the chemical signatures of the thermal waters is inferred from the trace element concentrations.

  16. Distribution of the hallucinogens N,N-dimethyltryptamine and 5-methoxy-N,N-dimethyltryptamine in rat brain following intraperitoneal injection: application of a new solid-phase extraction LC-APcI-MS-MS-isotope dilution method.

    PubMed

    Barker, S A; Littlefield-Chabaud, M A; David, C

    2001-02-10

    A method for the solid-phase extraction (SPE) and liquid chromatographic-atmospheric pressure chemical ionization-mass spectrometric-mass spectrometric-isotope dilution (LC-APcI-MS-MS-ID) analysis of the indole hallucinogens N,N-dimethyltryptamine (DMT) and 5-methoxy DMT (or O-methyl bufotenin, OMB) from rat brain tissue is reported. Rats were administered DMT or OMB by the intraperitoneal route at a dose of 5 mg/kg and sacrificed 15 min post treatment. Brains were dissected into discrete areas and analyzed by the methods described as a demonstration of the procedure's applicability. The synthesis and use of two new deuterated internal standards for these purposes are also reported. PMID:11232854

  17. Isotope source apportionment of carbonaceous aerosol as a function of particle size and thermal refractiveness

    NASA Astrophysics Data System (ADS)

    Masalaite, Agne; Holzinger, Rupert; Remeikis, Vidmantas; Röckmann, Thomas; Dusek, Ulrike

    2016-04-01

    The stable carbon isotopes can be used to get information about sources and processing of carbonaceous aerosol. We will present results from source apportionment of carbonaceous aerosol as a function of particle size thermal refractiveness. Separate source apportionment for particles smaller than 200 nm and for different carbon volatility classes are rarely reported and give new insights into aerosol sources in the urban environment. Stable carbon isotope ratios were measured for the organic carbon (OC) fraction and total carbon (TC) of MOUDI impactor samples that were collected on a coastal site (Lithuania) during the winter 2012 and in the city of Vilnius (Lithuania) during the winter of 2009. The 11 impactor stages spanned a size range from 0.056 to 18 μm, but only the 6 stages in the submicron range were analysed. The δ13C values of bulk total carbon (δ13CTC) were determined with an elemental analyser (Flash EA 1112) coupled with an isotope ratio mass spectrometer (Thermo Finnigan Delta Plus Advantage) (EA - IRMS). Meanwhile δ13COC was measured using thermal-desorption isotope ratio mass spectrometry (IRMS) system. This allows a rough separation of the more volatile OC fraction (desorbed in the oven of IRMS up to 250 0C) from the more refractory fraction (desorbed up to 400 0C). In this study we investigated the composition of organic aerosol desorbed from filter samples at different temperatures using the thermal-desorption proton-transfer-reaction mass spectrometry (TD-PTR-MS) technique. During winter-time in Lithuania we expect photochemistry and biogenic emissions to be of minor importance. The main sources of aerosol carbon should be fossil fuel and biomass combustion. In both sites, the coastal and the urban site, δ13C measurements give a clear indication that the source contributions differ for small and large particles. Small particles < 200 nm are depleted in 13C with respect to larger particles by 1 - 2 ‰Ṫhis shows that OC in small particle

  18. Analysis of dibenzo[def,p]chrysene-deoxyadenosine adducts in wild-type and cytochrome P450 1b1 knockout mice using stable-isotope dilution UHPLC-MS/MS.

    PubMed

    Harper, Tod A; Morré, Jeff; Lauer, Fredine T; McQuistan, Tammie J; Hummel, Jessica M; Burchiel, Scott W; Williams, David E

    2015-04-01

    The polycyclic aromatic hydrocarbon (PAH), dibenzo[def,p]chrysene (DBC; also known as dibenzo[a,l]pyrene), is a potent carcinogen in animal models and a class 2A human carcinogen. Recent investigations into DBC-mediated toxicity identified DBC as a potent immunosuppressive agent similar to the well-studied immunotoxicant 7,12-dimethylbenz[a]anthracene (DMBA). DBC, like DMBA, is bioactivated by cytochrome P450 (CYP) 1B1 and forms the reactive metabolite DBC-11,12-diol-13,14-epoxide (DBCDE). DBCDE is largely responsible for the genotoxicity associated with DBC exposure. The immunosuppressive properties of several PAHs are also linked to genotoxic mechanisms. Therefore, this study was designed to identify DBCDE-DNA adduct formation in the spleen and thymus of wild-type and cytochrome P450 1b1 (Cyp1b1) knockout (KO) mice using a highly sensitive stable-isotope dilution UHPLC-MS/MS method. Stable-isotope dilution UHPLC-MS/MS identified the major DBC adducts (±)-anti-cis-DBCDE-dA and (±)-anti-trans-DBCDE-dA in the lung, liver, and spleen of both WT and Cyp1b1 KO mice. However, adduct formation in the thymus was below the level of quantitation for our method. Additionally, adduct formation in Cyp1b1 KO mice was significantly reduced compared to wild-type (WT) mice receiving DBC via oral gavage. In conclusion, the current study identifies for the first time DBCDE-dA adducts in the spleen of mice supporting the link between genotoxicity and immunosuppression, in addition to supporting previous studies identifying Cyp1b1 as the primary CYP involved in DBC bioactivation to DBCDE. The high levels of DBC-DNA adducts identified in the spleen, along with the known high levels of Cyp1b1 expression in this organ, supports further investigation into DBC-mediated immunotoxicity. PMID:25868132

  19. Analysis of Dibenzo[def,p]chrysene-Deoxyadenosine Adducts in Wild-Type and Cytochrome P450 1b1 Knockout Mice using Stable-Isotope Dilution UHPLC-MS/MS

    PubMed Central

    Harper, Tod A.; Morré, Jeff; Lauer, Fredine T.; McQuistan, Tammie J.; Hummel, Jessica M.; Burchiel, Scott W.; Williams, David E.

    2015-01-01

    The polycyclic aromatic hydrocarbon (PAH), dibenzo[def,p]chrysene (DBC; also known as dibenzo[a,l]pyrene), is a potent carcinogen in animal models and a class 2A human carcinogen. Recent investigations into DBC-mediated toxicity identified DBC as a potent immunosuppressive agent similar to the well-studied immunotoxicant 7,12-dimethylbenz[a]anthracene (DMBA). DBC, like DMBA, is bioactivated by cytochrome P450 (CYP) 1B1 and forms the reactive metabolite DBC-11,12-diol-13,14-epoxide (DBCDE). DBCDE is largely responsible for the genotoxicity associated with DBC exposure. The immunosuppressive properties of several PAHs are also linked to genotoxic mechanisms. Therefore, this study was designed to identify DBCDE-DNA adduct formation in the spleen and thymus of wild-type and cytochrome P450 1b1 (Cyp1b1) knockout (KO) mice using a highly sensitive stable-isotope dilution UHPLC-MS/MS method. Stable-isotope dilution UHPLC-MS/MS identified the major DBC adducts (±)-anti-cis-DBCDE-dA and (±)-anti-trans-DBCDE-dA in the lung, liver, and spleen of both WT and Cyp1b1 KO mice. However, adduct formation in the thymus was below the level of quantitation for our method. Additionally, adduct formation in Cyp1b1 KO mice was significantly reduced compared to wild-type (WT) mice receiving DBC via oral gavage. In conclusion, the current study identifies for the first time DBCDE-dA adducts in the spleen of mice supporting the link between genotoxicity and immunosuppression, in addition to supporting previous studies identifying Cyp1b1 as the primary CYP involved in DBC bioactivation to DBCDE. The high levels of DBC-DNA adducts identified in the spleen, along with the known high levels of Cyp1b1 expression in this organ, supports further investigation into DBC-mediated immunotoxicity. PMID:25868132

  20. Determination of 1-methyl-1H-1,2,4-triazole in soils contaminated by rocket fuel using solid-phase microextraction, isotope dilution and gas chromatography-mass spectrometry.

    PubMed

    Yegemova, Saltanat; Bakaikina, Nadezhda V; Kenessov, Bulat; Koziel, Jacek A; Nauryzbayev, Mikhail

    2015-10-01

    Environmental monitoring of Central Kazakhstan territories where heavy space booster rockets land requires fast, efficient, and inexpensive analytical methods. The goal of this study was to develop a method for quantitation of the most stable transformation product of rocket fuel, i.e., highly toxic unsymmetrical dimethylhydrazine - 1-methyl-1H-1,2,4-triazole (MTA) in soils using solid-phase microextraction (SPME) in combination with gas chromatography-mass spectrometry. Quantitation of organic compounds in soil samples by SPME is complicated by a matrix effect. Thus, an isotope dilution method was chosen using deuterated analyte (1-(trideuteromethyl)-1H-1,2,4-triazole; MTA-d3) for matrix effect control. The work included study of the matrix effect, optimization of a sample equilibration stage (time and temperature) after spiking MTA-d3 and validation of the developed method. Soils of different type and water content showed an order of magnitude difference in SPME effectiveness of the analyte. Isotope dilution minimized matrix effects. However, proper equilibration of MTA-d3 in soil was required. Complete MTA-d3 equilibration at temperatures below 40°C was not observed. Increase of temperature to 60°C and 80°C enhanced equilibration reaching theoretical MTA/MTA-d3 response ratios after 13 and 3h, respectively. Recoveries of MTA depended on concentrations of spiked MTA-d3 during method validation. Lowest spiked MTA-d3 concentration (0.24 mg kg(-1)) provided best MTA recoveries (91-121%). Addition of excess water to soil sample prior to SPME increased equilibration rate, but it also decreased method sensitivity. Method detection limit depended on soil type, water content, and was always below 1 mg kg(-1). The newly developed method is fully automated, and requires much lower time, labor and financial resources compared to known methods. PMID:26078153

  1. Thermal neutron capture cross section of the radioactive isotope 60Fe

    NASA Astrophysics Data System (ADS)

    Heftrich, T.; Bichler, M.; Dressler, R.; Eberhardt, K.; Endres, A.; Glorius, J.; Göbel, K.; Hampel, G.; Heftrich, M.; Käppeler, F.; Lederer, C.; Mikorski, M.; Plag, R.; Reifarth, R.; Stieghorst, C.; Schmidt, S.; Schumann, D.; Slavkovská, Z.; Sonnabend, K.; Wallner, A.; Weigand, M.; Wiehl, N.; Zauner, S.

    2015-07-01

    Background: Fifty percent of the heavy element abundances are produced via slow neutron capture reactions in different stellar scenarios. The underlying nucleosynthesis models need the input of neutron capture cross sections. Purpose: One of the fundamental signatures for active nucleosynthesis in our galaxy is the observation of long-lived radioactive isotopes, such as 60Fe with a half-life of 2.60 ×106 yr. To reproduce this γ activity in the universe, the nucleosynthesis of 60Fe has to be understood reliably. Methods: An 60Fe sample produced at the Paul Scherrer Institut (Villigen, Switzerland) was activated with thermal and epithermal neutrons at the research reactor at the Johannes Gutenberg-Universität Mainz (Mainz, Germany). Results: The thermal neutron capture cross section has been measured for the first time to σth=0.226 (-0.049+0.044) b . An upper limit of σRI<0.50 b could be determined for the resonance integral. Conclusions: An extrapolation towards the astrophysically interesting energy regime between k T =10 and 100 keV illustrates that the s -wave part of the direct capture component can be neglected.

  2. Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization.

    PubMed

    Salim, Michael A; Willow, Soohaeng Yoo; Hirata, So

    2016-05-28

    Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of

  3. Ice Ih anomalies: Thermal contraction, anomalous volume isotope effect, and pressure-induced amorphization

    NASA Astrophysics Data System (ADS)

    Salim, Michael A.; Willow, Soohaeng Yoo; Hirata, So

    2016-05-01

    Ice Ih displays several anomalous thermodynamic properties such as thermal contraction at low temperatures, an anomalous volume isotope effect (VIE) rendering the volume of D2O ice greater than that of H2O ice, and a pressure-induced transition to the high-density amorphous (HDA) phase. Furthermore, the anomalous VIE increases with temperature, despite its quantum-mechanical origin. Here, embedded-fragment ab initio second-order many-body perturbation (MP2) theory in the quasiharmonic approximation (QHA) is applied to the Gibbs energy of an infinite, proton-disordered crystal of ice Ih at wide ranges of temperatures and pressures. The quantum effect of nuclei moving in anharmonic potentials is taken into account from first principles without any empirical or nonsystematic approximation to either the electronic or vibrational Hamiltonian. MP2 predicts quantitatively correctly the thermal contraction at low temperatures, which is confirmed to originate from the volume-contracting hydrogen-bond bending modes (acoustic phonons). It qualitatively reproduces (but underestimates) the thermal expansion at higher temperatures, caused by the volume-expanding hydrogen-bond stretching (and to a lesser extent librational) modes. The anomalous VIE is found to be the result of subtle cancellations among closely competing isotope effects on volume from all modes. Consequently, even ab initio MP2 with the aug-cc-pVDZ and aug-cc-pVTZ basis sets has difficulty reproducing this anomaly, yielding qualitatively varied predictions of the sign of the VIE depending on such computational details as the choice of the embedding field. However, the temperature growth of the anomalous VIE is reproduced robustly and is ascribed to the librational modes. These solid-state MP2 calculations, as well as MP2 Born-Oppenheimer molecular dynamics, find a volume collapse and a loss of symmetry and long-range order in ice Ih upon pressure loading of 2.35 GPa or higher. Concomitantly, rapid softening of

  4. Insights into the Key Aroma Compounds in Mango (Mangifera indica L. 'Haden') Fruits by Stable Isotope Dilution Quantitation and Aroma Simulation Experiments.

    PubMed

    Munafo, John P; Didzbalis, John; Schnell, Raymond J; Steinhaus, Martin

    2016-06-01

    Thirty-four aroma-active compounds, previously identified with high flavor dilution factors by application of an aroma extract dilution analysis, were quantified in tree-ripened fruits of mango (Mangifera indica L. 'Haden'). From the results, the odor activity value (OAV) was calculated for each compound as the ratio of its concentration in the mangoes to its odor threshold in water. OAVs > 1 were obtained for 24 compounds, among which ethyl 2-methylbutanoate (fruity; OAV 2100), (3E,5Z)-undeca-1,3,5-triene (pineapple-like; OAV 1900), ethyl 3-methylbutanoate (fruity; OAV 1600), and ethyl butanoate (fruity; OAV 980) were the most potent, followed by (2E,6Z)-nona-2,6-dienal (cucumber-like), ethyl 2-methylpropanoate (fruity), (E)-β-damascenone (cooked apple-like), ethyl hexanoate (fruity), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like), 3-methylbut-2-ene-1-thiol (sulfurous), γ-decalactone (peach-like), β-myrcene (terpeny), (3Z)-hex-3-enal (green), 4-methyl-4-sulfanylpentan-2-one (tropical fruit-like), and ethyl octanoate (fruity). Aroma simulation and omission experiments revealed that these 15 compounds, when combined in a model mixture in their natural concentrations, were able to mimic the aroma of the fruits. PMID:27167034

  5. Mass Dependency of Isotope Fractionation of Gases Under Thermal Gradient and Its Possible Implications for Planetary Atmosphere Escaping Process

    NASA Technical Reports Server (NTRS)

    Sun, Tao; Niles, Paul; Bao, Huiming; Socki, Richard

    2014-01-01

    Physical processes that unmix elements/isotopes of gas molecules involve phase changes, diffusion (chemical or thermal), effusion and gravitational settling. Some of those play significant roles for the evolution of chemical and isotopic compositions of gases in planetary bodies which lead to better understanding of surface paleoclimatic conditions, e.g. gas bubbles in Antarctic ice, and planetary evolution, e.g. the solar-wind erosion induced gas escaping from exosphere on terrestrial planets.. A mass dependent relationship is always expected for the kinetic isotope fractionations during these simple physical processes, according to the kinetic theory of gases by Chapman, Enskog and others [3-5]. For O-bearing (O16, -O17, -O18) molecules the alpha O-17/ alpha O-18 is expected at 0.5 to 0.515, and for S-bearing (S32,-S33. -S34, -S36) molecules, the alpha S-33/ alpha S-34 is expected at 0.5 to 0.508, where alpha is the isotope fractionation factor associated with unmixing processes. Thus, one isotope pair is generally proxied to yield all the information for the physical history of the gases. However, we recently] reported the violation of mass law for isotope fractionation among isotope pairs of multiple isotope system during gas diffusion or convection under thermal gradient (Thermal Gradient Induced Non-Mass Dependent effect, TGI-NMD). The mechanism(s) that is responsible to such striking observation remains unanswered. In our past studies, we investigated polyatomic molecules, O2 and SF6, and we suggested that nuclear spin effect could be responsible to the observed NMD effect in a way of changing diffusion coefficients of certain molecules, owing to the fact of negligible delta S-36 anomaly for SF6.. On the other hand, our results also showed that for both diffusion and convection under thermal gradient, this NMD effect is increased by lower gas pressure, bigger temperature gradient and lower average temperature, which indicate that the nuclear spin effect may

  6. Analysis of natural-occurring and synthetic sexual hormones in sludge-amended soils by matrix solid-phase dispersion and isotope dilution gas chromatography-tandem mass spectrometry.

    PubMed

    Albero, Beatriz; Sánchez-Brunete, Consuelo; Miguel, Esther; Pérez, Rosa A; Tadeo, José L

    2013-03-29

    A sensitive analytical method is presented for the simultaneous determination of four synthetic estrogens and six steroid hormones in sludge-amended soil. The method employs matrix solid-phase dispersion (MSPD) followed by isotope dilution gas chromatography-tandem mass spectrometry injecting a large volume sample (10μL) after trimethylsilyl derivatization, using the solvent vent mode. It affords good resolution, high sensitivity and reproducibility and freedom from interferences even from complex matrices as soil amended with sewage sludge. The limits of detection (LODs) ranged from 10 to 300pgg(-1) with testosterone and progesterone having the highest limits. Soil amended with sewage sludge was spiked at 2, 10, 25 and 50ngg(-1) and the recoveries after MSPD with acetonitrile:methanol (90:10, v/v), ranged from 80 to 110% with relative standard deviations ≤9%. The method was applied to the analysis of six soil samples collected from agricultural plots and forested fields that had been amended with sewage sludge using isotopically labeled surrogates. Three of the synthetic estrogens studied were found at least in one of the six samples analyzed and trans-androsterone and estrone were the only natural hormones detected, although at very low levels (≤0.4ngg(-1)). PMID:23465128

  7. Development and validation of a new analytical method for the determination of 1,4-dichlorobenzene in honey by gas chromatography-isotope dilution mass spectrometry after steam-distillation.

    PubMed

    Botitsi, E V; Kormali, P N; Kontou, S N; Economou, A; Tsipi, D F

    2006-10-01

    A simple, fast, sensitive and robust analytical method using gas chromatography (GC)-isotope dilution mass spectrometry (MS) was developed and validated for the identification and quantification of 1,4-dichlorobenzene (p-DCB) residues in honey samples. The proposed methodology is based on steam-distillation using a Clevenger-type apparatus followed by gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring (SIM) mode employing the isotopically labeled analogue d4-1,4-dichlorobenzene (d4-p-DCB) as internal standard (IS). Validation of the method was performed in two different GC-MS systems, using quadrupole MS (QMS) and ion-trap MS (ITMS) detectors, with no statistically significant differences between two. Recoveries were better than 91% with percent relative standard deviations lower than 12%. The instrumental limits of detection were 1 microg kg(-1) in the GC-ITMS system and 0.6 microg kg(-1) in the GC-QMS system. The expanded uncertainty was estimated as 17% at the currently accepted "action level" of 10 microg kg(-1). The method was applied to the analysis of 310 honey samples in an extensive national monitoring study. A quality control (QC) system applied during the assays has demonstrated a good performance and long-term stability over a period of more than 8 months of continuous operation. PMID:17723727

  8. Nitrogen Isotope Composition of Thermally Produced NOx from Various Fossil-Fuel Combustion Sources.

    PubMed

    Walters, Wendell W; Tharp, Bruce D; Fang, Huan; Kozak, Brian J; Michalski, Greg

    2015-10-01

    The nitrogen stable isotope composition of NOx (δ(15)N-NOx) may be a useful indicator for NOx source partitioning, which would help constrain NOx source contributions in nitrogen deposition studies. However, there is large uncertainty in the δ(15)N-NOx values for anthropogenic sources other than on-road vehicles and coal-fired energy generating units. To this end, this study presents a broad analysis of δ(15)N-NOx from several fossil-fuel combustion sources that includes: airplanes, gasoline-powered vehicles not equipped with a three-way catalytic converter, lawn equipment, utility vehicles, urban buses, semitrucks, residential gas furnaces, and natural-gas-fired power plants. A relatively large range of δ(15)N-NOx values was measured from -28.1‰ to 8.5‰ for individual exhaust/flue samples that generally tended to be negative due to the kinetic isotope effect associated with thermal NOx production. A negative correlation between NOx concentrations and δ(15)N-NOx for fossil-fuel combustion sources equipped with selective catalytic reducers was observed, suggesting that the catalytic reduction of NOx increases δ(15)N-NOx values relative to the NOx produced through fossil-fuel combustion processes. Combining the δ(15)N-NOx measured in this study with previous published values, a δ(15)N-NOx regional and seasonal isoscape was constructed for the contiguous U.S., which demonstrates seasonal and regional importance of various NOx sources. PMID:26332865

  9. U-Pb dating of Plinian-eruption ashfalls by the isotope dilution method: A reliable and precise tool for time-scale calibration and biostratigraphic correlation

    SciTech Connect

    Tucker, R.D. . Dept. of Earth and Planetary Sciences)

    1992-01-01

    Through a combination of low analytical blanks, clean Pb-205 enriched tracer-solution, and refined procedures of sample preparation, it is possible to isolate and measure minute quantities of radiogenic Pb in concordant zircon, thereby permitting accurate isotopic age determinations of small multigrain samples of Paleozoic zircon with 7--20 ppm radiogenic Pb. Refinement of these procedures, including reduction of laboratory blank, allows for analysis of single grains of Paleozoic zircon with greater than 25 ppm radiogenic Pb with an age precision of better than 1%. Mass spectrometric measurement of all Pb and U isotopes allows for the calculation of three isotopic ages from a single sample. Concordant multigrain and single-grain U-Pb zircon analyses from 13 biostratigraphically dated K-bentonites in Europe and North America define an internally consistent, absolute chronostratigraphy of Middle ordovician to Upper silurian stratotypes. As a test of trans-Atlantic stratigraphic correlation, a volcanic ash from Middle Ordovician (Rocklandian) strata of North America was found to be in excellent age agreement with Caradocian K-bentonites in Britain and Sweden, demonstrating age equivalence of sedimentary sequences lacking directly comparable fauna. In other case, precise dating of single zircons from three Caradocian K-bentonite in Sweden and Virginia was performed to test a hypothesis that a single ultraplinian volcanic eruption deposited airborne debris on both Larentia and Baltica. The ages of these presumed correlative ashes will be shown to provide quantitative information about the depositional rates of their enclosing strata, as well as tectonic events affecting the margins of Iapetus in Ordovician time.

  10. Simultaneous determination of seven β2-agonists in human and bovine urine by isotope dilution liquid chromatography-tandem mass spectrometry using compound-specific minimally (13)C-labelled analogues.

    PubMed

    González-Antuña, Ana; Rodríguez-González, Pablo; Centineo, Giuseppe; García Alonso, J Ignacio

    2014-10-29

    Seven β2-agonist (clenproperol, clenbuterol, salbutamol, bronbuterol, ractopamine, clenpenterol and clencyclohexerol) were determined simultaneously in human and bovine urine by isotope dilution LC-ESI-MS/MS in a triple quadrupole instrument. The method is based on the application of multiple linear regression in combination with compound-specific minimally (13)C-labelled analogues. Additionally, the increase of the bandpass of the first quadrupole during the selected reaction monitoring (SRM) measurement procedure allowed the simultaneous quantification of the seven compounds at sub ngg(-1) levels in a single chromatogram without resorting to a methodological calibration graph. Recovery values at concentration levels between 5.0 and 0.05ngg(-1) ranged from 95 to 110% in fortified bovine urine and from 91 to 108% in human urine, with relative standard deviations lower than 5% except for salbutamol and ractopamine. The proposed methodology was validated by analyzing the certified reference material BCR-503 (lyophilized bovine urine) certified for clenbuterol and salbutamol. The limits of detection (LOD) for a sample volume of 10mL of both human and bovine urine was found to be lower than 0.012ngg(-1) for all compounds, except to salbutamol in bovine urine which was of 0.029ngg(-1). The use of compound-specific isotopically labelled analogues minimally labelled in (13)C minimized the occurrence of isotope effects and corrected for matrix effects during ESI ionization and can be efficiently applied for the quantification of ultra-trace concentrations of β2-agonists in human and bovine urine. PMID:25468499

  11. [The measurement of extra vascular lung water using a thermal-sodium double indicator dilution technique in patients undergoing surgery for esophageal cancer].

    PubMed

    Watanabe, A; Kusajima, K; Kawaharada, N; Komatsu, K; Sugimoto, S; Doi, H; Tanaka, A; Takeda, H; Mishina, H; Komatsu, S

    1990-11-01

    The Extra Vascular Lung Water (EVLW) was measured using the thermal sodium double indicator dilution technique in 21 patients undergoing surgery for esophageal cancer. This measurement is an important parameter in the control of the respiratory function. In the 16 cases without pulmonary complications, the preoperative EVLW was 5.3 +/- 0.2 (mean +/- SEM) ml/kg and the immediate postoperative EVLW was 4.8 +/- 0.4 ml/kg. This change was significant (p less than 0.05), but within 24 hours the EVLW returned to almost the same levels as those recorded before surgery. In only 3 cases, the EVLW were elevated beyond 7.5 ml/kg, but these high EVLW levels did not continue for more than 12 hours. Of the 5 patients with pulmonary complications, only two experienced pulmonary edema. Their preoperative EVLW levels were normal, but the immediate postoperative EVLW levels were significantly elevated beyond 10 ml/kg. These elevated levels were observed before the PaO2, the portable chest roentgenograms and the other test results changed following surgery. The high EVLW levels beyond 7.5 ml/kg continued for 72 hours after surgery. We found no correlation between the EVLW and measureable hemodynamic parameters (Cardiac Index, Pulmonary Wedge Pressure, Colloid Osmotic Pressure-Pulmonary Wedge Pressure gradient) during the observation period. In the other cases with pulmonary complications (2 cases were pneumonia, one was atelectasis with pneumonia), the changes in the EVLW levels were the same as for the cases without pulmonary complications. These results indicate that the EVLW is the optimum parameter for the control of the respiratory function and early diagnosis of pulmonary edema after surgery for esophageal cancer. PMID:2280095

  12. Isotope and chemical compositions of meteoric and thermal waters and snow from the greater Yellowstone National Park region

    USGS Publications Warehouse

    Kharaka, Yousif K.; Thordsen, James J.; White, Lloyd D.

    2002-01-01

    An intensive hydrogeologic investigation, mandated by U.S. Congress and centered on the Norris-Mammoth corridor was conducted by USGS and other scientists during 1988-90 to determine the effects of using thermal water from a private well located in the Corwin Springs Known Geothermal Resources Area, Montana, on the thermal springs of Yellowstone National Park (YNP), especially Mammoth Hot Springs. As part of this investigation, we carried out a detailed study of the isotopic and chemical compositions of meteoric water from cold springs and wells, of thermal water, especially from the Norris-Mammoth corridor and of snow. Additional sampling of meteoric and thermal waters from YNP and surrounding region in northwest Wyoming, southwest Montana and southeast Idaho was carried out in 1991-92 to characterize the distribution of water isotopes in this mountainous region and to determine the origin and possible recharge locations of thermal waters in and adjacent to the Park. The D and 18O values for 40 snow samples range from ?88 to ?178? and ?12.5 to ?23.9?, respectively, and define a well constrained line given by D = 8.2 18O + 14.7 (r2 = 0.99) that is nearly identical to the Global Meteoric Water Line. The D and 18O values of 173 cold water samples range from ?115 to ?153? and ?15.2 to ?20.2?, respectively, and exhibit a similar relationship although with more scatter and with some shift to heavier isotopes, most likely due to evaporation effects. The spatial distribution of cold-water isotopes shows a roughly circular pattern with isotopically lightest waters centered on the mountains and high plateau in the northwest corner of Yellowstone National Park and becoming heavier in all directions. The temperature effect due to altitude is the dominant control on stable water isotopes throughout the region; however, this effect is obscured in narrow 'canyons' and areas of high topographic relief. The effects due to distance (i.e. 'continental') and latitude on water

  13. Mercury (Hg) in meteorites: Variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M. M.; Cloquet, Christophe; Marty, Bernard

    2016-06-01

    We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ppb to 14,000 ppb), with the highest concentration orders of magnitude above the expected bulk solar system silicates value. From the presence of several different Hg carrier phases in thermal release profiles (150-650 °C), we argue that these variations are unlikely to be mainly due to terrestrial contamination. The Hg abundance of meteorites shows no correlation with petrographic type, or mass-dependent fractionation of Hg isotopes. Most carbonaceous chondrites show mass-independent enrichments in the odd-numbered isotopes 199Hg and 201Hg. We show that the enrichments are not nucleosynthetic, as we do not find corresponding nucleosynthetic deficits of 196Hg. Instead, they can partially be explained by Hg evaporation and redeposition during heating of asteroids from primordial radionuclides and late-stage impact heating. Non-carbonaceous chondrites, most achondrites and the Earth do not show these enrichments in vapor-phase Hg. All meteorites studied here have however isotopically light Hg (δ202Hg = ∼-7 to -1) relative to the Earth's average crustal values, which could suggest that the Earth has lost a significant fraction of its primordial Hg. However, the late accretion of carbonaceous chondritic material on the order of ∼2%, which has been suggested to account for the water, carbon, nitrogen and noble gas inventories of the Earth, can also contribute most or all of the Earth's current Hg budget. In this case, the isotopically heavy Hg of the Earth's crust would have to be the result of isotopic fractionation between surface and deep-Earth reservoirs.

  14. Measurement of the stable carbon isotope ratio of atmospheric volatile organic compounds using chromatography, combustion, and isotope ratio mass spectrometry coupled with thermal desorption

    NASA Astrophysics Data System (ADS)

    Kawashima, Hiroto; Murakami, Mai

    2014-06-01

    The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular of their stable carbon isotope ratio (δ13C), could potentially be used as an effective tool for identifying the sources of VOCs. However, to date, there have been very few such analyses. In this work, we analyze the δ13C values of VOCs using thermal desorption coupled with chromatography, combustion, and isotope ratio mass spectrometry (TD-GC/C/IRMS). The measured peak shapes were of high quality and 36 compounds in a standard gas containing 58 VOCs (C5-C11) were detected. The measured δ13C varied widely, from -49.7‰ to -22.9‰, while the standard deviation of the δ13C values varied from 0.07‰ to 0.85‰ (n = 5). We then measured samples from two passenger cars in hot and cold modes, three gas stations, roadside air, and ambient air. In comparison with existing studies, the analytical precision for the 36 compounds in this study was reasonable. By comparing the δ13C values obtained from the cars and gas stations, we could identify some degree of the sources of VOCs in the roadside and ambient air samples.

  15. The Precambrian Biogeochemical Carbon Isotopic Record: Contributions of Thermal Versus Biological Processes

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Superplumes offer a new approach for understanding global C cycles. Isotopes help to discern the impacts of geological, environmental and biological processes ujpun the evolution of these cycles. For example, C-13/C-12 values of coeval sedimentary organics and carbonates give global estimates of the fraction of C buried as organics (Forg), which today lies near 0.2. Before Oxygenic photosynthesis arose, our biosphere obtained reducing power for biosynthesis solely from thermal volatiles and rock alteration. Thus Forg was dominated by the mantle redox state, which has remained remarkably constant for greater than Gy. Recent data confirm that the long-term change in Forg had been small, indicating that the mantle redox buffer remains important even today. Oxygenic photosynthesis enabled life to obtain additional reducing power by splitting the water molecule. Accordingly, biological organic production rose above the level constrained by the mantle-derived flux of reduced species. For example, today, chemoautotrophs harvesting energy from hydrothermal emanations can synthesize at most between 0.2 x 10(exp 12) and 2x 10(exp 12) mol C yr-1 of organic C globally. In contrast, global photosynthetic productivity is estimated at 9000 x 10(exp 12) mol C yr-1. Occasionally photosynthetic productivity did contribute to dramatically -elevated Forg values (to 0.4 or more) as evidenced by very high carbonate C-13/C-12. The interplay between biological, tectonic and other environmental factors is illustrated by the mid-Archean to mid-Proterozoic isotopic record. The relatively constant C-13/C-12 values of Archean carbonates support the view that photosynthetically-driven Forg increases were not yet possible. In contrast, major excursions in C-13/C-12, and thus also in Forg, during the early Proterozoic confirmed the global importance of oxygenic photosynthesis by that time. Remarkably, the superplume event at 1.9 Ga did not trigger another major Forg increase, despite the

  16. Lattice thermal conductivity of crystalline and amorphous silicon with and without isotopic effects from the ballistic to diffusive thermal transport regime

    SciTech Connect

    Park, Minkyu; Lee, In-Ho; Kim, Yong-Sung

    2014-07-28

    Thermal conductivity of a material is an important physical parameter in electronic and thermal devices, and as the device size shrinks down, its length-dependence becomes unable to be neglected. Even in micrometer scale devices, materials having a long mean free path of phonons, such as crystalline silicon (Si), exhibit a strong length dependence of the thermal conductivities that spans from the ballistic to diffusive thermal transport regime. In this work, through non-equilibrium molecular-dynamics (NEMD) simulations up to 17 μm in length, the lattice thermal conductivities are explicitly calculated for crystalline Si and up to 2 μm for amorphous Si. The Boltzmann transport equation (BTE) is solved within a frequency-dependent relaxation time approximation, and the calculated lattice thermal conductivities in the BTE are found to be in good agreement with the values obtained in the NEMD. The isotopic effects on the length-dependent lattice thermal conductivities are also investigated both in the crystalline and amorphous Si.

  17. Optimisation of sample preparation protocols for measurement of PGE and Re-Os in organic-rich shales by isotope dilution ICP-MS

    NASA Astrophysics Data System (ADS)

    Rammensee, Philipp; Aulbach, Sonja; Gudelius, Dominik; Brey, Gerhard

    2013-04-01

    Platinum-group elements (PGE) and Re-Os isotopes, which are variably redox-sensitive and fluid-soluble, have potential as proxies for the oxygenation of the atmosphere and oceans (e.g. [1]). However, analysis of these elements in organic rich shales (ORS) is challenging due to abundances of <1 ng/g and the presence of interfering isotopes or molecules of matrix elements. Furthermore, PGE-ReOs systematics in detrital and hydrogenous components may vary, and the choice of digestion parameters (reagents, temperature and pressure) during decomposition of rock powder affects the ratio of digested components [2,3]. Additional treatment to remove the matrix and pre-concentrate PGE-Re by column chromatography is necessary to minimise the effects of interfering elements, but presents its own challenges. We are in the process of conducting variations of acid digestion and column chromatographic protocols on reference sample SDO-1 (Devonian Ohio Shale, USGS). We aim to identify the optimum protocol to investigate PGE-Re-Os systematics of ORS that were sampled as part of the Barberton Drilling Project BARB5 drill core, in order to constrain the changes in detrital and hydrogenous contributions to the sediment with time, to assess the extent of euxinity in the sedimentary basin and to look for evidence of transient "whiffs of oxygen" [1]. The following digestion methods were tested: (1) 4h acid digestion in High Pressure Asher (HPA) apparatus with reverse aqua regia at 300°C and 130 bar (only this digestion allows extraction of volatilised Os in CHCl3 followed by HBr); (2) 3h reverse aqua regia digestion in centrifuge vials on hotplate at 80°C; (3) 48h reverse aqua regia digestion in closed Teflon beakers on hotplate at 140°C followed by a HF/HNO3 digestion step; (4) 48h HF/HNO3 digestion of ashed sample powder in closed Teflon beaker at 140°C on hotplate followed by an aqua regia digestion step. Column chromatographic approaches to decrease the concentrations of

  18. Thermodynamics of Dilute Solutions.

    ERIC Educational Resources Information Center

    Jancso, Gabor; Fenby, David V.

    1983-01-01

    Discusses principles and definitions related to the thermodynamics of dilute solutions. Topics considered include dilute solution, Gibbs-Duhem equation, reference systems (pure gases and gaseous mixtures, liquid mixtures, dilute solutions), real dilute solutions (focusing on solute and solvent), terminology, standard states, and reference systems.…

  19. Influence of longitudinal isotope substitution on the thermal conductivity of carbon nanotubes: Results of nonequilibrium molecular dynamics and local density functional calculations

    SciTech Connect

    Leroy, Frédéric Böhm, Michael C.; Schulte, Joachim; Balasubramanian, Ganesh

    2014-04-14

    We report reverse nonequilibrium molecular dynamics calculations of the thermal conductivity of isotope substituted (10,10) carbon nanotubes (CNTs) at 300 K. {sup 12}C and {sup 14}C isotopes both at 50% content were arranged either randomly, in bands running parallel to the main axis of the CNTs or in bands perpendicular to this axis. It is found that the systems with randomly distributed isotopes yield significantly reduced thermal conductivity. In contrast, the systems where the isotopes are organized in patterns parallel to the CNTs axis feature no reduction in thermal conductivity when compared with the pure {sup 14}C system. Moreover, a reduction of approximately 30% is observed in the system with the bands of isotopes running perpendicular to the CNT axis. The computation of phonon dispersion curves in the local density approximation and classical densities of vibrational states reveal that the phonon structure of carbon nanotubes is conserved in the isotope substituted systems with the ordered patterns, yielding high thermal conductivities in spite of the mass heterogeneity. In order to complement our conclusions on the {sup 12}C-{sup 14}C mixtures, we computed the thermal conductivity of systems where the {sup 14}C isotope was turned into pseudo-atoms of 20 and 40 atomic mass units.

  20. Quantitation of fluoride ion released sarin in red blood cell samples by gas chromatography-chemical ionization mass spectrometry using isotope dilution and large-volume injection.

    PubMed

    Jakubowski, E M; McGuire, J M; Evans, R A; Edwards, J L; Hulet, S W; Benton, B J; Forster, J S; Burnett, D C; Muse, W T; Matson, K; Crouse, C L; Mioduszewski, R J; Thomson, S A

    2004-01-01

    A new method for measuring fluoride ion released isopropyl methylphosphonofluoridate (sarin, GB) in the red blood cell fraction was developed that utilizes an autoinjector, a large-volume injector port (LVI), positive ion ammonia chemical ionization detection in the SIM mode, and a deuterated stable isotope internal standard. This method was applied to red blood cell (RBC) and plasma ethyl acetate extracts from spiked human and animal whole blood samples and from whole blood of minipigs, guinea pigs, and rats exposed by whole-body sarin inhalation. Evidence of nerve agent exposure was detected in plasma and red blood cells at low levels of exposure. The linear method range of quantitation was 10-1000 pg on-column with a detection limit of approximately 2-pg on-column. In the course of method development, several conditions were optimized for the LVI, including type of injector insert, injection volume, initial temperature, pressure, and flow rate. RBC fractions had advantages over the plasma with respect to assessing nerve agent exposure using the fluoride ion method especially in samples with low serum butyrylcholinesterase activity. PMID:15239856

  1. Simultaneous analysis of multiple classes of antimicrobials in environmental water samples using SPE coupled with UHPLC-ESI-MS/MS and isotope dilution.

    PubMed

    Tran, Ngoc Han; Chen, Hongjie; Do, Thanh Van; Reinhard, Martin; Ngo, Huu Hao; He, Yiliang; Gin, Karina Yew-Hoong

    2016-10-01

    A robust and sensitive analytical method was developed for the simultaneous analysis of 21 target antimicrobials in different environmental water samples. Both single SPE and tandem SPE cartridge systems were investigated to simultaneously extract multiple classes of antimicrobials. Experimental results showed that good extraction efficiencies (84.5-105.6%) were observed for the vast majority of the target analytes when extraction was performed using the tandem SPE cartridge (SB+HR-X) system under an extraction pH of 3.0. HPLC-MS/MS parameters were optimized for simultaneous analysis of all the target analytes in a single injection. Quantification of target antimicrobials in water samples was accomplished using 15 isotopically labeled internal standards (ILISs), which allowed the efficient compensation of the losses of target analytes during sample preparation and correction of matrix effects during UHPLC-MS/MS as well as instrument fluctuations in MS/MS signal intensity. Method quantification limit (MQL) for most target analytes based on SPE was below 5ng/L for surface waters, 10ng/L for treated wastewater effluents, and 15ng/L for raw wastewater. The method was successfully applied to detect and quantify the occurrence of the target analytes in raw influent, treated effluent and surface water samples. PMID:27474294

  2. Simultaneous determination of asymmetric and symmetric dimethylarginine, L-monomethylarginine, L-arginine, and L-homoarginine in biological samples using stable isotope dilution liquid chromatography tandem mass spectrometry.

    PubMed

    Davids, Mariska; Swieringa, Eliane; Palm, Fredrik; Smith, Desirée E C; Smulders, Yvo M; Scheffer, Peter G; Blom, Henk J; Teerlink, Tom

    2012-07-01

    Production of the endogenous vasodilator nitric oxide (NO) from L-arginine by NO synthase is modulated by L-homoarginine, l-monomethylargine (MMA), asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). Here we report on a stable isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of these metabolites in plasma, cells and tissues. After addition of the internal standards (D(7)-ADMA, D(4)-L-homoarginine and (13)C(6)-L-arginine), analytes were extracted from the samples using Waters Oasis MCX solid phase extraction cartridges. Butylated analytes were separated isocratically on a Waters XTerra MS C18 column (3.5 μm, 3.9 mm × 100 mm) using 600 mg/L ammonium formate in water - acetonitrile (95.5:4.5, v/v) containing 0.1 vol% formic acid, and subsequently measured on an AB Sciex API 3000 triple quadrupole mass spectrometer. Multiple reaction monitoring in positive mode was used for analyte quantification. Validation was performed in plasma. Calibration lines were linear (r(2)≥0.9979) and lower limits of quantification in plasma were 0.4 nM for ADMA and SDMA and 0.8 nM for the other analytes. Accuracy (% bias) was <3% except for MMA (<7%), intra-assay precision (expressed as CV) was <3.5%, inter-assay precision <9.6%, and recovery 92.9-103.2% for all analytes. The method showed good correlation (r(2)≥0.9125) with our previously validated HPLC-fluorescence method for measurement in plasma, and was implemented with good performance for measurement of tissue samples. Application of the method revealed the remarkably fast (i.e. within 60 min) appearance in plasma of stable isotope-labeled ADMA, SDMA, and MMA during infusion of D(3)-methyl-1-(13)C-methionine in healthy volunteers. PMID:22682940

  3. Measurement of urinary desmosine by isotope dilution and high performance liquid chromatography. Correlation between elastase-induced air-space enlargement in the hamster and elevation of urinary desmosine

    SciTech Connect

    Stone, P.J.; Bryan-Rhadfi, J.; Lucey, E.C.; Ciccolella, D.E.; Crombie, G.; Faris, B.; Snider, G.L.; Franzblau, C. )

    1991-08-01

    The accuracy of methods employed to measure the elastin-specific crosslinks, desmosine (DES) and isodesmosine (IDES), has been called into question because contaminants in the urine may cause elevated values. In the present study urine samples were spiked with a known amount of (14C)DES and refluxed in 6 N HCl. Sephadex G-15 chromatography of the hydrolyzed urine employed to remove contaminants. DES and IDES were quantified by high performance liquid chromatography (HPLC) as well as by amino acid analysis. The amount of isotope recovered was used to determine losses during the overall procedure and the isotope dilution to calculate the amounts of endogenous DES and IDES originally present in the urine. Because similar values were obtained by both methods, the more rapid HPLC method was used for all succeeding analyses. In one experiment, the DES amounts in urine collected from hamsters for 3 days after intratracheal treatment with human neutrophil elastase (300 micrograms) or porcine pancreatic elastase (300 micrograms) were 0.212 {plus minus} 0.012 (mean {plus minus} SEM, two measurements on a single pool) and 0.816 {plus minus} 0.005 (two measurements) microgram per hamster per day, respectively. Urine from control hamsters had a mean value of 0.074 {plus minus} 0.008 (eight measurements) microgram per hamster per day. The HNE- and PPE-treated hamsters had mean linear intercept values of 119 and 159% of control values, respectively, giving a positive correlation between increase in airspace size and elevation of urinary DES.

  4. Development and Validation of a Rapid 13C6-Glucose Isotope Dilution UPLC-MRM Mass Spectrometry Method for Use in Determining System Accuracy and Performance of Blood Glucose Monitoring Devices

    PubMed Central

    Matsunami, Risë K.; Angelides, Kimon; Engler, David A.

    2015-01-01

    Background: There is currently considerable discussion about the accuracy of blood glucose concentrations determined by personal blood glucose monitoring systems (BGMS). To date, the FDA has allowed new BGMS to demonstrate accuracy in reference to other glucose measurement systems that use the same or similar enzymatic-based methods to determine glucose concentration. These types of reference measurement procedures are only comparative in nature and are subject to the same potential sources of error in measurement and system perturbations as the device under evaluation. It would be ideal to have a completely orthogonal primary method that could serve as a true standard reference measurement procedure for establishing the accuracy of new BGMS. Methods: An isotope-dilution liquid chromatography/mass spectrometry (ID-UPLC-MRM) assay was developed using 13C6-glucose as a stable isotope analogue to specifically measure glucose concentration in human plasma, and validated for use against NIST standard reference materials, and against fresh isolates of whole blood and plasma into which exogenous glucose had been spiked. Assay performance was quantified to NIST-traceable dry weight measures for both glucose and 13C6-glucose. Results: The newly developed assay method was shown to be rapid, highly specific, sensitive, accurate, and precise for measuring plasma glucose levels. The assay displayed sufficient dynamic range and linearity to measure across the range of both normal and diabetic blood glucose levels. Assay performance was measured to within the same uncertainty levels (<1%) as the NIST definitive method for glucose measurement in human serum. Conclusions: The newly developed ID UPLC-MRM assay can serve as a validated reference measurement procedure to which new BGMS can be assessed for glucose measurement performance. PMID:25986627

  5. Simulating High Flux Isotope Reactor Core Thermal-Hydraulics via Interdimensional Model Coupling

    SciTech Connect

    Travis, Adam R

    2014-05-01

    A coupled interdimensional model is presented for the simulation of the thermal-hydraulic characteristics of the High Flux Isotope Reactor core at Oak Ridge National Laboratory. The model consists of two domains a solid involute fuel plate and the surrounding liquid coolant channel. The fuel plate is modeled explicitly in three-dimensions. The coolant channel is approximated as a twodimensional slice oriented perpendicular to the fuel plate s surface. The two dimensionally-inconsistent domains are linked to one another via interdimensional model coupling mechanisms. The coupled model is presented as a simplified alternative to a fully explicit, fully three-dimensional model. Involute geometries were constructed in SolidWorks. Derivations of the involute construction equations are presented. Geometries were then imported into COMSOL Multiphysics for simulation and modeling. Both models are described in detail so as to highlight their respective attributes in the 3D model, the pursuit of an accurate, reliable, and complete solution; in the coupled model, the intent to simplify the modeling domain as much as possible without affecting significant alterations to the solution. The coupled model was created with the goal of permitting larger portions of the reactor core to be modeled at once without a significant sacrifice to solution integrity. As such, particular care is given to validating incorporated model simplifications. To the greatest extent possible, the decrease in solution time as well as computational cost are quantified versus the effects such gains have on the solution quality. A variant of the coupled model which sufficiently balances these three solution characteristics is presented alongside the more comprehensive 3D model for comparison and validation.

  6. H-isotope retention and thermal/ion-induced release in boronized films

    SciTech Connect

    Walsh, D.S. ); Doyle, B.L.; Wampler, W.R.; Hays, A.K. )

    1990-01-01

    Over the past decade, it has been clearly demonstrated that the composition of the very near surface ({approximately}100nm) of plasma-interactive components plays a determinant role in most processes which occur in the plasma-edge of Tokamaks. Two very successful techniques to effect control of the plasma-wall interaction are (1) in-situ deposition of amorphous carbon or boron-carbon films and (2) the use of He/C conditioning discharges or He glow discharge cleaning to modify the near surface of bulk graphite components. We have deposited boronized layers into Si using plasma-assisted CVD and sputter deposition. The PCVD deposition conditions were as close as possible to those used in TFTR, and some films deposited in TFTR have also been studied. Using these two deposition techniques, B{sub x}CH{sub y} films have been produced with x varying from 1/2 -- 4, and y from {approximately}1 (sputtered) to {approximately}3 (PCVD). Most films also contained significant amounts of 0. Thermal and ion-induced release of H-isotopes from BC films is qualitatively similar to that measured for graphite. Implanted H saturates in these films at a H/host atom ratio of 0.7 which is considerably higher than that of graphite({approximately}0.4). As-deposited PCVD films are already saturated with H, while sputtered films are not. Sputtered BC films therefore possess an inherent H-pumping capability which could prove to be extremely beneficial to TFTR. 16 refs., 5 figs., 1 tab.

  7. Multiplexed Immunoaffinity Enrichment of Peptides with Anti-peptide Antibodies and Quantification by Stable Isotope Dilution Multiple Reaction Monitoring Mass Spectrometry.

    PubMed

    Kuhn, Eric; Carr, Steven A

    2016-01-01

    Immunoaffinity enrichment of peptides using anti-peptide antibodies and their subsequent analysis by targeted mass spectrometry using stable isotope-labeled peptide standards is a sensitive and relatively high-throughput assay technology for unmodified and modified peptides in cells, tissues, and biofluids. Suppliers of antibodies and peptides are increasingly aware of this technique and have started incorporating customized quality measures and production protocols to increase the success rate, performance, and supply of the necessary reagents. Over the past decade, analytical biochemists, clinical diagnosticians, antibody experts, and mass spectrometry specialists have shared ideas, instrumentation, reagents, and protocols, to demonstrate that immuno-MRM-MS is reproducible across laboratories. Assay performance is now suitable for verification of candidate biomarkers from large scale discovery "omics" studies, measuring diagnostic proteins in plasma in the clinical laboratory, and for developing a companion assay for preclinical drug studies. Here we illustrate the process for developing these assays with a step-by-step guide for a 20-plex immuno-MRM-MS assay. We emphasize the need for analytical validation of the assay to insure that antibodies, peptides, and mass spectrometer are working as intended, in a multiplexed manner, with suitable assay performance (median values for 20 peptides: CV = 12.4 % at 740 amol/μL, LOD = 310 amol/μL) for applications in quantitative biology and candidate biomarker verification. The assays described conform to Tier 2 (of 3) level of analytical assay validation (1), meaning that the assays are capable of repeatedly measuring sets of analytes of interest within and across samples/experiments and employ internal standards for each analyte for confident detection and precise quantification. PMID:26867743

  8. Simultaneous determination of albendazole and its metabolites in fish muscle tissue by stable isotope dilution ultra-performance liquid chromatography tandem mass spectrometry.

    PubMed

    Zhang, Xiaojun; Xu, Hanxiang; Zhang, Hong; Guo, Yuanming; Dai, Zhiyuan; Chen, Xuechang

    2011-08-01

    A rapid, specific, and sensitive method utilizing ultra-performance liquid chromatography tandem mass spectrometry was developed and validated to determine albendazole, albendazole sulfoxide, albendazole sulfone, and albendazole 2-aminosulfone in fish muscle tissue. The fish samples were extracted with ethyl acetate, then the organic phase was evaporated to dryness, and the residue was reconstituted in methanol-water solution and cleaned up by n-hexane. Reversed-phase separation of target compounds was achieved using a BEH C18 column and a gradient consisting of 0.2% (v/v) formic acid and methanol. Tandem mass spectrometry analyses were performed on a triple-quadrupole tandem mass spectrometer. In the whole procedure, the isotope-labeled internal standards were used to correct the matrix effect and variations associated with the analysis. The method was validated with respect to linearity, specificity, accuracy, and precision. The method exhibited a linear response from 0.1 to 20 ng mL(-1) (r(2) > 0.9985). The limit of quantitation for albendazole (ABZ), albendazole sulfoxide (ABZSO), albendazole sulfone (ABZSO(2)), and albendazole 2-aminosulfone (ABZ-2-NH(2)SO(2)) was 0.1, 0.1, 0.1, and 0.2 ng g(-1), respectively. The mean recoveries of ABZ, ABZSO, ABZSO(2), and ABZ-2-NH(2)SO(2) spiked at a level of 0.2-5.0 ng g(-1) were 95.3-113.7%, and the relative standard deviations of intra- and inter-day measurements were less than 6.38%. The method was later successfully applied to the determination of albendazole and its three metabolites in 60 fish samples collected from local markets. PMID:21633840

  9. Determination of the antihypertensive drug 1-[2-ethoxy-2-(3'-pyridyl)ethyl]-4-(2'-methoxyphenyl) piperazine (IP/66) in rat and human plasma by high-performance liquid chromatography and isotope dilution mass spectrometry.

    PubMed

    Agostini, O; Moneti, G; Bonacchi, G; Fedi, M; Manzini, S

    1989-02-24

    In connection with pharmacokinetic studies on the antihypertensive drug 1-[2-ethoxy-2-(3'-pyridyl)ethyl]-4-(2'-methoxyphenyl)piperazine (IP/66) (I), appropriate high-performance liquid chromatographic (HPLC) and gas chromatographic-mass spectrometric isotope dilution (GC-MS-ID) methods for its determination in rat and human plasma, respectively, were developed. In both techniques, deproteinized and basified plasma samples were extracted and purified by adsorption on an Extrelut-1 column, then the drug was eluted with dichloromethane. Quantitative HPLC analysis was performed on a C8 reversed-phase column. The mobile phase was phosphate buffer (0.02 M, pH 2.8)-acetonitrile (65:35), with UV detection at 208 nm. The internal standard was 1-[2-butoxy-2-(3'-pyridyl)ethyl]-4-(2'-methoxyphenyl)piperazine, a homologue of I. The inter-assay coefficient of variation (C.V.) was 9.9% for a drug level of 2 micrograms/ml. Quantitative GC-MS-ID analysis was performed with a DB-17 fused-silica capillary column using the selected-ion monitoring technique. The deuterated form of I, 1-[2-ethoxy-2-(3'-pyridyl)ethyl]-4-2'-trideuteromethoxyphenyl)pipe razine, utilized as internal standard, was synthesized. The inter-assay C.V. was 7.36% for a drug level of 1 ng/ml. PMID:2723000

  10. Determination of 2-Methylimidazole, 4-Methylimidazole, and 2-Acetyl-4-(1,2,3,4-tetrahydroxybutyl)imidazole in Licorice Using High-Performance Liquid Chromatography-Tandem Mass Spectrometry Stable-Isotope Dilution Analysis.

    PubMed

    Raters, Marion; Elsinghorst, Paul W; Goetze, Stephanie; Dingel, Anna; Matissek, Reinhard

    2015-07-01

    A quick and selective analytical method was developed for the simultaneous quantitation of 2-methylimidazole, 4-methylimidazole, and 2-acetyl-4-(1,2,3,4-tetrahydroxybutyl)imidazole, which are known to be formed by Maillard reactions. The methodology reported here employs stable-isotope dilution analysis (SIDA) using 4-methylimidazole-d6 and [(13)C6]-2-acetyl-4-(1,2,3,4-tetrahydroxybutyl)imidazole as internal standards. It was successfully applied in a model assay to show that the addition of ammonium chloride during the manufacture of licorice promotes imidazole formation depending on the added amount of ammonium chloride without the well-known impact of present caramel food colorings. Furthermore, a monitoring assay of 29 caramel coloring-free licorice products showed that both 4-methylimidazole and 2-acetyl-4-(1,2,3,4-tetrahydroxybutyl)imidazole are endogenously generated in detectable quantities. None of the samples showed 2-methylimidazole levels above the limit of detection, 50 μg/kg. PMID:26073294

  11. Simultaneous Quantification of Methylated Cytidine and Adenosine in Cellular and Tissue RNA by Nano-Flow Liquid Chromatography-Tandem Mass Spectrometry Coupled with the Stable Isotope-dilution Method

    PubMed Central

    Fu, Lijuan; Amato, Nicolas J.; Wang, Pengcheng; McGowan, Sara J.; Niedernhofer, Laura J.; Wang, Yinsheng

    2016-01-01

    The rising interest in understanding the functions, regulation and maintenance of the epitranscriptome calls for robust and accurate analytical methods for the identification and quantification of post-transcriptionally modified nucleosides in RNA. Mono-methylations of cytidine and adenosine are common post-transcriptional modifications in RNA. Herein, we developed an LC-MS/MS/MS coupled with the stable isotope-dilution method for the sensitive and accurate quantifications of 5-methylcytidine (m5C), 2′-O-methylcytidine (Cm), N6-methyladenosine (m6A) and 2′-O-methyladenosine (Am) in RNA isolated from mammalian cells and tissues. Our results showed that the distributions of the four methylated nucleosides are tissue-specific. In addition, the 2′-O-methylated ribonucleosides (Cm and Am) are present at higher levels than the corresponding methylated nucleobase products (m5C and m6A) in total RNA isolated from mouse brain, pancreas and spleen, but not mouse heart. We also found that the levels of m5C, Cm and Am are significantly lower (by 6.5-43 fold) in mRNA than in total RNA isolated from HEK293T cells, whereas the level of m6A was slightly higher (by 1.6 fold) in mRNA than in total RNA. The availability of this analytical method, in combination with genetic manipulation, may facilitate the future discovery of proteins involved in the maintenance and regulation of these RNA modifications. PMID:26158405

  12. Preparation, certification and validation of a stable solid spike of uranium and plutonium coated with a cellulose derivative for the measurement of uranium and plutonium content in dissolved nuclear fuel by isotope dilution mass spectrometry.

    PubMed

    Surugaya, Naoki; Hiyama, Toshiaki; Verbruggen, André; Wellum, Roger

    2008-02-01

    A stable solid spike for the measurement of uranium and plutonium content in nitric acid solutions of spent nuclear fuel by isotope dilution mass spectrometry has been prepared at the European Commission Institute for Reference Materials and Measurements in Belgium. The spike contains about 50 mg of uranium with a 19.838% (235)U enrichment and 2 mg of plutonium with a 97.766% (239)Pu abundance in each individual ampoule. The dried materials were covered with a thin film of cellulose acetate butyrate as a protective organic stabilizer to resist shocks encountered during transportation and to eliminate flaking-off during long-term storage. It was found that the cellulose acetate butyrate has good characteristics, maintaining a thin film for a long time, but readily dissolving on heating with nitric acid solution. The solid spike containing cellulose acetate butyrate was certified as a reference material with certified quantities: (235)U and (239)Pu amounts and uranium and plutonium amount ratios, and was validated by analyzing spent fuel dissolver solutions of the Tokai reprocessing plant in Japan. This paper describes the preparation, certification and validation of the solid spike coated with a cellulose derivative. PMID:18270417

  13. Effects of processing and of storage on the stability of pantothenic acid in sea buckthorn products (Hippophaë rhamnoides L. ssp. rhamnoides) assessed by stable isotope dilution assay.

    PubMed

    Gutzeit, Derek; Klaubert, Bernd; Rychlik, Michael; Winterhalter, Peter; Jerz, Gerold

    2007-05-16

    A stable isotope dilution assay for quantification of pantothenic acid in sea buckthorn berries, juice, and concentrate using a four-fold labeled isotopologue of vitamin B5 as the internal standard was adopted using reversed phase liquid chromatography-mass spectrometry with electrospray ionization. Because of a rapid sample clean up procedure without the necessity of external calibration, this methodology permits the accurate analysis of a high number of samples within a short time. Sea buckthorn juice was stored at 25 and 40 degrees C for up to 7 days to determine the effects of storage temperature on the stability of pantothenic acid. Analysis of kinetic data suggested that the degradation follows a first-order model. The results of the experiments showed that storage of sea buckthorn juice for 7 days at ambient temperature (25 degrees C) already resulted in a significant degradation of pantothenic acid of about 18%. The processing effects of juice production and subsequent concentration revealed a decrease of about 6-7% in the juice and of 23% in the juice concentrate. PMID:17447792

  14. Quantification of oxidative DNA lesions in tissues of Long-Evans Cinnamon rats by capillary high-performance liquid chromatography-tandem mass spectrometry coupled with stable isotope-dilution method.

    PubMed

    Wang, Jin; Yuan, Bifeng; Guerrero, Candace; Bahde, Ralf; Gupta, Sanjeev; Wang, Yinsheng

    2011-03-15

    The purpose of our study was to develop suitable methods to quantify oxidative DNA lesions in the setting of transition metal-related diseases. Transition metal-driven Fenton reactions constitute an important endogenous source of reactive oxygen species (ROS). In genetic diseases with accumulation of transition metal ions, excessive ROS production causes pathophysiological changes, including DNA damage. Wilson's disease is an autosomal recessive disorder with copper toxicosis due to deficiency of ATP7B protein needed for excreting copper into bile. The Long-Evans Cinnamon (LEC) rat bears a deletion in Atp7b gene and serves as an excellent model for hepatic Wilson's disease. We used a sensitive capillary liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS/MS) method in conjunction with the stable isotope-dilution technique to quantify several types of oxidative DNA lesions in the liver and brain of LEC rats. These lesions included 5-formyl-2'-deoxyuridine, 5-hydroxymethyl-2'-deoxyuridine, and the 5'R and 5'S diastereomers of 8,5'-cyclo-2'-deoxyguanosine and 8,5'-cyclo-2'-deoxyadenosine. Moreover, the levels of these DNA lesions in the liver and brain increased with age and correlated with age-dependent regulation of the expression of DNA repair genes in LEC rats. These results provide significant new knowledge for better understanding the implications of oxidative DNA lesions in transition metal-induced diseases, such as Wilson's disease, as well as in aging and aging-related pathological conditions. PMID:21323344

  15. Can Edman degradation be used for quantification? Isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry and the long-term stability of 20 phenylthiohydantoin-amino acids.

    PubMed

    Satoh, Ryo; Goto, Takaaki; Lee, Seon Hwa; Oe, Tomoyuki

    2013-10-01

    Edman degradation is a well-known method for obtaining amino acid (AA) sequences from a peptide by means of sequential reactions that release the N-terminal AAs from the peptide as a phenylthiohydantoin (PTH) derivative. Because of unexpected loss during the reaction and handling, there are few reports of use of this reaction for quantification. This manuscript describes the development of isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry for 20 PTH-AA derivatives, and long-term stability testing of PTH-AAs to ensure quantitative quality in the reaction. The 20 corresponding [(13)C6]-PTH-AAs were prepared by use of a one-pot reaction involving a mixture of [(13)C6]-Edman reagent and 20 AAs. Good linearity was observed for standard curves for the PTH-AAs, using the corresponding [(13)C6]-PTH-AAs as internal standards (1-100 pmol per injection, r(2) = 0.989-1.000). Serum albumin (human), pepsin (porcine stomach mucosa), α-casein (bovine milk), ribonuclease A (bovine), lysozyme (chicken egg white), and insulin (bovine) subjected to Edman degradation were examined as model proteins and peptides for N-terminal AA analysis. The results of the impurity test were satisfactory. Yield from the entire reaction with human serum albumin was estimated to be at least 75%, indicating great potential for absolute quantification of proteins without protein standards. PMID:23545858

  16. A candidate reference method for the determination of uric acid in serum based on high performance liquid chromatography, compared with an isotope dilution-gas chromatography-mass spectrometer method.

    PubMed

    Kock, R; Delvoux, B; Tillmanns, U; Greiling, H

    1989-03-01

    A method based on isocratic high performance liquid chromatography (HPLC) with UV detection at 292 nm is proposed as a candidate reference method for the determination of uric acid. Data obtained by this method are compared with those from an isotope dilution-gas chromatography-mass spectrometric method (ID-GC-MS), using [1,3-15N2]uric acid as internal standard and selected mass detection at m/z = 456 and m/z = 458. The inaccuracy of the ID-GC-MS method is maximally 0.4% for NBS-SRM-909 control sera with a concentration of 483 mumol/l. The coefficient of variation between days is 0.26%-0.80% and 0.37-0.90% for 14 control sera from other suppliers. The maximum bias of the HPLC method is 0.6%, and the coefficient of variation between days is 0.31%-0.65% for NBS-SRM-909 control sera. The coefficient of variation between days for the other 14 control sera tested is 0.35%-0.66%. Comparison of the HPLC method with the reference ID-GC-MS method resulted in a coefficient of correlation of r = 0.9998 (n = 14). The concentration of uric acid in the tested control sera ranged from 160 to 624 mumol/l. PMID:2651552

  17. On-line monitoring of benzene air concentrations while driving in traffic by means of isotopic dilution gas chromatography/mass spectrometry.

    PubMed

    Davoli, E; Cappellini, L; Moggi, M; Ferrari, S; Fanelli, R

    1996-01-01

    There is no shortage of information about the average benzene concentrations in urban air, but there is very little about microenvironmental exposure, such as in-vehicle concentrations while driving in various traffic conditions, while refuelling, or while in a parking garage. The main reason for this lack of data is that no analytical instrumentation has been available to measure on-line trace amounts of benzene in such situations. We have recently proposed a highly accurate, high-speed cryofocusing gas chromatography/mass spectrometry (GC/MS) system for monitoring benzene concentrations in air. Accuracy of the analytical data is achieved by enrichment of the air sample before trapping, with a stable isotope permeation tube system. The same principles have been applied to a new instrument, specifically designed for operation on an electric vehicle (Ducato Elettra, Fiat). The zero emission vehicle and the fully transportable, battery-operated GC/MS system provide a unique possibility of monitoring benzene exposure in real everyday situations such as while driving, refuelling, or repairing a car. All power consumptions have been reduced so as to achieve a battery-operated GC/MS system. Liquid nitrogen cryofocusing has been replaced by a packed, inductively heated, graphitized charcoal microtrap. The instrument has been mounted on shock absorbers and installed in the van. The whole system has been tested in both fixed and mobile conditions. The maximum monitoring period without external power supply is 6 h. The full analytical cycle is 4 min, allowing close to real-time monitoring, and the minimum detectable level is 1 microgram/m3 for benzene. In-vehicle monitoring showed that, when recirculation was off and ventilation on, i.e., air from outside the vehicle was blown inside, concentrations varied widely in different driving conditions: moving from a parking lot into normal traffic on an urban traffic condition roadway yielded an increase in benzene concentration

  18. Structural, Thermal, and Safety Analysis of Isotope Heat Source and Integrated Heat Exchangers for 6-kWe Dynamic Isotope Power System (DIPS)

    SciTech Connect

    Schock, Alfred

    1989-01-01

    The design of the 30-kWt isotope heat source integrated with a Rankine boiler and a Brayton gas heater, which was described in the preceding paper in these proceedings, was subjected to structural, thermal, and safety analyses. The present paper describes and discusses the results of these analyses. Detailed structural analyses of the heat source integrated with the boiler and gas heater showed positive safety margins at all locations during the launch. Detailed thermal analyses showed acceptable temperatures at all locations, during assembly, transfer and orbital operations. Reentry thermal analyses showed that the clads have acceptable peak and impact temperatures. Loss-of-cooling analyses indicated the feasibility of a passive safety concept for preventing over temperatures. Static structural analysis showed positive safety margins at all locations, and dynamic analysis showed that there were no low-frequency resources. Continuum-mechanics code analyses of the effects of the impact of Solid Rocket Booster (SRB) fragments on the heat source and of the very unlikely impact of the full heat source on concrete indicated relatively modest fuel clad deformations and little or no fuel release.

  19. Calculation of the transport and relaxation properties of dilute water vapor.

    PubMed

    Hellmann, Robert; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S; Vesovic, Velisa

    2009-07-01

    Transport properties of dilute water vapor have been calculated in the rigid-rotor approximation using four different potential energy hypersurfaces and the classical-trajectory method. Results are reported for shear viscosity, self-diffusion, thermal conductivity, and volume viscosity in the dilute-gas limit for the temperature range of 250-2500 K. Of these four surfaces the CC-pol surface of Bukowski et al. [J. Chem. Phys. 128, 094314 (2008)] is in best accord with the available measurements. Very good agreement is found with the most accurate results for viscosity in the whole temperature range of the experiments. For thermal conductivity the deviations of the calculated values from the experimental data increase systematically with increasing temperature to around 5% at 1100 K. For both self-diffusion and volume viscosity, the much more limited number of available measurements are generally consistent with the calculated values, apart from the lower temperature isotopically labeled diffusion measurements. PMID:19586101

  20. Isotope Variations in Terrestrial Carbonates and Thermal Springs as Biomarkers: Analogs for Martian Processes

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Gibson, Everett K., Jr.; Bissada, K. K.

    2006-01-01

    Stable isotope measurements of carbonate minerals contained within ALH84001 [1] suggest that fluids were present at 3.9 Gy on Mars [2, 3, 4, 5]. Both oxygen and carbon isotopes provide independent means of deciphering paleoenvironmental conditions at the time of carbonate mineral precipitation. In terrestrial carbonate rocks oxygen isotopes not only indicate the paleotemperature of the precipitating fluid, but also provide clues to environmental conditions that affected the fluid chemistry. Carbon isotopes, on the other hand, can indicate the presence or absence of organic compounds during precipitation (i.e. biogenically vs. thermogenically-generated methane), thus serving as a potential biomarker. We have undertaken a study of micro scale stable isotope variations measured in some terrestrial carbonates and the influence of organic compounds associated with the formation of these carbonates. Preliminary results indicate that isotope variations occur within narrow and discrete intervals, providing clues to paleoenvironmental conditions that include both biological and non-biological activity. These results carry implications for deciphering Martian isotope data and therefore potential biological prospecting on the planet Mars. Recently, Fourier Transform Spectrometer observations have detected methane occurring in the Martian atmosphere [6] that could be attributed to a possible biogenic source. Indeed, Mars Express has detected the presence of methane in the Martian atmosphere [7], with evidence indicating that methane abundances are greatest above those basins with high water concentrations.

  1. Dilutions Made Easy.

    ERIC Educational Resources Information Center

    Kamin, Lawrence

    1996-01-01

    Presents problems appropriate for high school and college students that highlight dilution methods. Promotes an understanding of dilution methods in order to prevent the unnecessary waste of chemicals and glassware in biology laboratories. (JRH)

  2. Chitin: 'Forgotten' Source of Nitrogen: From Modern Chitin to Thermally Mature Kerogen: Lessons from Nitrogen Isotope Ratios

    USGS Publications Warehouse

    Schimmelmann, A.; Wintsch, R.P.; Lewan, M.D.; DeNiro, M.J.

    1998-01-01

    Chitinous biomass represents a major pool of organic nitrogen in living biota and is likely to have contributed some of the fossil organic nitrogen in kerogen. We review the nitrogen isotope biogeochemistry of chitin and present preliminary results suggesting interaction between kerogen and ammonium during thermal maturation. Modern arthropod chitin may shift its nitrogen isotope ratio by a few per mil depending on the chemical method of chitin preparation, mostly because N-containing non-amino-sugar components in chemically complex chitin cannot be removed quantitatively. Acid hydrolysis of chemically complex chitin and subsequent ion-chromatographic purification of the "deacetylated chitin-monomer" D-glucosamine (in hydrochloride form) provides a chemically well-defined, pure amino-sugar substrate for reproducible, high-precision determination of ??15N values in chitin. ??15N values of chitin exhibited a variability of about one per mil within an individual's exoskeleton. The nitrogen isotope ratio differed between old and new exoskeletons by up to 4 per mil. A strong dietary influence on the ??15N value of chitin is indicated by the observation of increasing ??15N values of chitin from marine crustaceans with increasing trophic level. Partial biodegradation of exoskeletons does not significantly influence ??15N values of remaining, chemically preserved amino sugar in chitin. Diagenesis and increasing thermal maturity of sedimentary organic matter, including chitin-derived nitrogen-rich moieties, result in humic compounds much different from chitin and may significantly change bulk ??15N values. Hydrous pyrolysis of immature source rocks at 330??C in contact with 15N-enriched NH4Cl, under conditions of artificial oil generation, demonstrates the abiogenic incorporation of inorganic nitrogen into carbon-bound nitrogen in kerogen. Not all organic nitrogen in natural, thermally mature kerogen is therefore necessarily derived from original organic matter, but may

  3. Separation processes using expulsion from dilute supercritical solutions

    DOEpatents

    Cochran, Jr., Henry D.

    1993-01-01

    A process for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached.

  4. Separation processes using expulsion from dilute supercritical solutions

    DOEpatents

    Cochran, H.D. Jr.

    1993-04-20

    A process is described for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached.

  5. Serial Dilution Simulation Lab

    ERIC Educational Resources Information Center

    Keler, Cynthia; Balutis, Tabitha; Bergen, Kim; Laudenslager, Bryanna; Rubino, Deanna

    2010-01-01

    Serial dilution is often a difficult concept for students to understand. In this short dry lab exercise, students perform serial dilutions using seed beads. This exercise helps students gain skill at performing dilutions without using reagents, bacterial cultures, or viral cultures, while being able to visualize the process.

  6. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer. (c) Flow conditioning... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Dilution air and diluted exhaust flow...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Flow-Related...

  7. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer. (c) Flow conditioning... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Dilution air and diluted exhaust flow...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Flow-Related...

  8. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer. (c) Flow conditioning... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Dilution air and diluted exhaust flow...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Flow-Related...

  9. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer. (c) Flow conditioning... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Dilution air and diluted exhaust flow...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Flow-Related...

  10. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer. (c) Flow conditioning... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Dilution air and diluted exhaust flow...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Flow-Related...

  11. Effects of high-temperature diluted-H2 annealing on effective mobility of 4H-SiC MOSFETs with thermally-grown SiO2

    NASA Astrophysics Data System (ADS)

    Hirai, Hirohisa; Kita, Koji

    2016-04-01

    The impact of post-oxidation annealing (POA) in diluted-H2 ambient on a 4H-SiC/SiO2 interface was investigated with a cold wall furnace. Effective mobility (μeff) was extracted from lateral metal-oxide-semiconductor field-effect transistors (MOSFETs) by applying the split capacitance-voltage (C-V) technique to the determination of charge density and a calibration technique using two MOSFETs with different gate lengths to minimize the contribution of parasitic components. POA at 1150 °C in diluted-H2 ambient resulted in an enhancement of μeff compared with that for POA in N2 ambient. It was indicated that the effects of POA in diluted H2 should be attributed to the reduction in the density of near interface traps, which disturb the electron transportation in the inversion channel, from the measurement temperature dependence of μeff as well as from the C-V curves of MOS capacitors fabricated on n-type SiC.

  12. Performance and System Validation of a New Cellular-Enabled Blood Glucose Monitoring System Using a New Standard Reference Measurement Procedure of Isotope Dilution UPLC-MRM Mass Spectrometry

    PubMed Central

    Angelides, Kimon; Matsunami, Risë K.; Engler, David A.

    2015-01-01

    Background: We evaluated the accuracy, precision, and linearity of the In Touch® blood glucose monitoring system (BGMS), a new color touch screen and cellular-enabled blood glucose meter, using a new rapid, highly precise and accurate 13C6 isotope-dilution liquid chromatography-mass spectrometry method (IDLC-MS). Methods: Blood glucose measurements from the In Touch® BGMS were referenced to a validated UPLC-MRM standard reference measurement procedure previously shown to be highly accurate and precise. Readings from the In Touch® BGMS were taken over the blood glucose range of 24-640 mg/dL using 12 concentrations of blood glucose. Ten In Touch® BGMS and 3 lots of test strips were used with 10 replicates at each concentration. A lay user study was also performed to assess the ease of use. Results: At blood glucose concentrations <75 mg/dL 100% of the measurements are within ±8 mg/dL from the true reference standard; at blood glucose levels >75 mg/dL 100% of the measurements are within ±15% of the true reference standard. 100% of the results are within category A of the consensus grid. Within-run precision show CV < 3.72% between 24-50 mg/dL and CV<2.22% between 500 and 600 mg/dL. The results show that the In Touch® meter exceeds the minimum criteria of both the ISO 15197:2003 and ISO 15197:2013 standards. The results from a user panel show that 100% of the respondents reported that the color touch screen, with its graphic user interface (GUI), is well labeled and easy to navigate. Conclusions: To our knowledge this is the first touch screen glucose meter and the first study where accuracy of a new BGMS has been measured against a true primary reference standard, namely IDLC-MS. PMID:26002836

  13. Highly sensitive isotope-dilution liquid-chromatography-electrospray ionization-tandem-mass spectrometry approach to study the drug-mediated modulation of dopamine and serotonin levels in Caenorhabditis elegans.

    PubMed

    Schumacher, Fabian; Chakraborty, Sudipta; Kleuser, Burkhard; Gulbins, Erich; Schwerdtle, Tanja; Aschner, Michael; Bornhorst, Julia

    2015-11-01

    Dopamine (DA) and serotonin (SRT) are monoamine neurotransmitters that play a key role in regulating the central and peripheral nervous system. Their impaired metabolism has been implicated in several neurological disorders, such as Parkinson's disease and depression. Consequently, it is imperative to monitor changes in levels of these low-abundant neurotransmitters and their role in mediating disease. For the first time, a rapid, specific and sensitive isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of DA and SRT in the nematode Caenorhabditis elegans (C. elegans). This model organism offers a unique approach for studying the effect of various drugs and environmental conditions on neurotransmitter levels, given by the conserved DA and SRT biology, including synaptic release, trafficking and formation. We introduce a novel sample preparation protocol incorporating the usage of sodium thiosulfate in perchloric acid as extraction medium that assures high recovery of the relatively unstable neurotransmitters monitored. Moreover, the use of both deuterated internal standards and the multiple reaction monitoring (MRM) technique allows for unequivocal quantification. Thereby, to the best of our knowledge, we achieve a detection sensitivity that clearly exceeds those of published DA and SRT quantification methods in various matrices. We are the first to show that exposure of C. elegans to the monoamine oxidase B (MAO-B) inhibitor selegiline or the catechol-O-methyltransferase (COMT) inhibitor tolcapone, in order to block DA and SRT degradation, resulted in accumulation of the respective neurotransmitter. Assessment of a behavioral output of the dopaminergic system (basal slowing response) corroborated the analytical LC-MS/MS data. Thus, utilization of the C. elegans model system in conjunction with our analytical method is well-suited to investigate drug-mediated modulation of the DA and

  14. On-line solid phase extraction-high performance liquid chromatography-isotope dilution-tandem mass spectrometry approach to quantify N,N-diethyl-m-toluamide and oxidative metabolites in urine.

    PubMed

    Kuklenyik, Peter; Baker, Samuel E; Bishop, Amanda M; Morales-A, Pilar; Calafat, Antonia M

    2013-07-17

    Human exposure to N,N-diethyl-m-toluamide (DEET) occurs because of the widespread use of DEET as an active ingredient in insect repellents. However, information on the extent of such exposure is rather limited. Therefore, we developed a fast on-line solid phase extraction-high performance liquid chromatography-isotope dilution tandem mass spectrometry (HPLC-MS/MS) method to measure in urine the concentrations of DEET and two of its oxidative metabolites: N,N-diethyl-3-(hydroxymethyl)benzamide and 3-(diethylcarbamoyl)benzoic acid (DCBA). To the best of our knowledge, this is the first HPLC-MS/MS method for the simultaneous quantification of DEET and its select metabolites in human urine. After enzymatic hydrolysis of the conjugated species in 0.1 mL of urine, the target analytes were retained and pre-concentrated on a monolithic column, separated from each other and from other urinary biomolecules on a reversed-phase analytical column, and detected by atmospheric pressure chemical ionization in positive ion mode. The limits of detection ranged from 0.1 ng mL(-1) to 1.0 ng mL(-1), depending on the analyte. Accuracy ranged between 90.4 and 104.9%, and precision ranged between 5.5 and 13.1% RSD, depending on the analyte and the concentration. We tested the usefulness of this method by analyzing 75 urine samples collected anonymously in the Southeastern United States in June 2012 from adults with no known exposure to DEET. Thirty eight samples (51%) tested positive for at least one of the analytes. We detected DCBA most frequently and at the highest concentrations. Our results suggest that this method can be used for the analysis of a large number of samples for epidemiological studies to assess human exposure to DEET. PMID:23830449

  15. Combining the quick, easy, cheap, effective, rugged and safe approach and clean-up by immunoaffinity column for the analysis of 15 mycotoxins by isotope dilution liquid chromatography tandem mass spectrometry.

    PubMed

    Desmarchelier, Aurélien; Tessiot, Sabine; Bessaire, Thomas; Racault, Lucie; Fiorese, Elisa; Urbani, Alessandro; Chan, Wai-Chinn; Cheng, Pearly; Mottier, Pascal

    2014-04-11

    Optimization and validation of a multi-mycotoxin method by LC-MS/MS is presented. The method covers the EU-regulated mycotoxins (aflatoxins, fumonisins, ochratoxin A, deoxynivalenol, zearalenone, T-2 and HT-2), as well as nivalenol and 3- and 15-acetyldeoxynivalenol for analysis of cereals, cocoa, oil, spices, infant formula, coffee and nuts. The proposed procedure combines two clean-up strategies: First, a generic preparation suitable for all mycotoxins based on the QuEChERS (for quick, easy, cheap, effective, rugged and safe) protocol. Second, a specific clean-up devoted to aflatoxins and ochratoxin A using immunoaffinity column (IAC) clean-up. Positive identification of mycotoxins in matrix was conducted according to the confirmation criteria defined in EU Commission Decision 2002/657/EC while quantification was performed by isotopic dilution using (13)C-labeled mycotoxins as internal standards. Limits of quantification were at or below the maximum levels set in the EC/1886/2006 document for all mycotoxin/matrix combinations under regulation. In particular, the inclusion of an IAC step allowed achieving LOQs as low as 0.05 and 0.25μg/kg in cereals for aflatoxins and ochratoxin A, respectively. Other performance parameters like linearity [(r)(2)>0.99], recovery [71-118%], precision [(RSDr and RSDiR)<33%], and trueness [78-117%] were all compliant with the analytical requirements stipulated in the CEN/TR/16059 document. Method ruggedness was proved by a verification process conducted by another laboratory. PMID:24636559

  16. Effects of thermal maturation on stable organic carbon isotopes as determined by hydrous pyrolysis of Woodford Shale

    NASA Astrophysics Data System (ADS)

    Lewan, M. D.

    1983-08-01

    Acquiring crude oils that have been expelled from the same rock unit at different levels of thermal maturation is currently not feasible in the natural system. This prevents direct correlation of compositional changes between the organic matter retained in a source rock and its expelled crude oil at different levels of thermal maturation. Alleviation of this deficiency in studying the natural system requires the use of laboratory experiments. Natural generation of petroleum from amorphous type-II kerogen in the Woodford Shale may be simulated by hydrous pyrolysis, which involves heating crushed rock in contact with water at subcritical temperatures (<374°C). Four distinct stages of petroleum generation are observed from this type of pyrolysis; (1) pre-oil generation, (2) incipient-oil generation, (3) primary-oil generation, and (4) post-oil generation. The effects of thermal maturation on the δ 13C values of kerogen, bitumen, and expelled oil-like pyrolysate from the Woodford Shale have been studied through these four stages of petroleum generation. Similar to the natural system, the kerogens isolated from the pyrolyzed rock showed no significant change in δ 13C. This suggests that the δ 13C value of kerogens may be useful in kerogen typing and oil-to-source rock correlations. δ 13C values of bitumens extracted from the pyrolyzed rock showed an initial decrease during the incipient-oil generation stage, followed by depletion during the primary- and post-oil generation stages. This reversal is not favorable for geochemical correlation or maturity evaluation. Saturated and polar components of the bitumen show the greatest δ 13C variations with increasing thermal maturation. The difference between the δ 13C of these two components gives a unidirectional trend that serves as a general indicator of thermal maturation and is referred to as the bitumen isotope index (BII). δ 13C values of the expelled pyrolysates show a unidirectional increase with increasing

  17. A comparison of lead-isotope measurements on exploration-type samples using inductively coupled plasma and thermal ionization mass spectrometry

    USGS Publications Warehouse

    Gulson, B.L.; Meier, A.L.; Church, S.E.; Mizon, K.J.

    1989-01-01

    Thermal ionization mass spectrometry (TI-MS) has long been the method of choice for Pb-isotope determinations. More recently, however, inductively coupled plasma mass spectrometry (ICP-MS) has been used to determine Pb-isotope ratios for mineral exploration. The ICP-MS technique, although not as precise as TI-MS, may promote a wider application of Ph-isotope ratio methods because it allows individual isotopes to be determined more rapidly, generally without need for chemical separation (e.g., Smith et al., 1984; Hinners et al., 1987). To demonstrate the utility of the ICP-MS method, we have conducted a series of Pb-isotope measurements on several suites of samples using both TI-MS and ICP-MS. ?? 1989.

  18. Alternative Methodology for Boron Isotopic Analysis of CaCO3 by Negative Thermal Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Dwyer, G. S.; Vengosh, A.

    2012-12-01

    Negative thermal ionization mass spectrometry (NTIMS) has been a common tool for investigating boron isotopes in CaCO3 and other environmental samples, the high sensitivity of BO2- ionization enabling measurements of ng levels of boron. However, B isotope measurement by this technique suffers from a number of problems, including: (1) fractionation induced by selective ionization of B isotopes in the mass spectrometer; (2) CNO- interference on mass 42 ([10BO2]-) that may be present in some filament load solutions (such as B-free seawater processed through ion-exchange resin), and (3) potential matrix effects due to widely differing chemistry of samples and standards. Here we examine a potentially improved NTIMS methodology that incudes removal of sample-related calcium (and other cations) by ion exchange and uses an alternative filament loading solution prepared from high-purity single-element solutions of Ca, Mg, Na, and K. Initial results suggest that this new method may offer significant improvement over the more traditional NTIMS approach in which digested CaCO3 samples are directly loaded onto filaments in B-free seawater. Replicate analyses of standards and samples yield a typical standard deviation of approximately 0.3‰ δ11B and boron isotopic compositions comparable to reported or consensus values. Fractionation during analysis has thus far typically been less than 0.5‰ δ11B. The method delivers boron ionization efficiency similar to directly-loaded seawater, and negligible signal at mass 26 (CN-), a proxy for the possible interfering molecular CNO- ion. Standards and samples behave similarly and predictably during filament heating and analysis, thus allowing for fully automated data acquisition, which in turn may increase sample throughput and reduce potential analytical inconsistencies associated with operator-controlled heating and analysis.

  19. ISOTOPE CONVERSION DEVICE

    DOEpatents

    Wigner, E.P.; Young, G.J.; Ohlinger, L.A.

    1957-12-01

    This patent relates to nuclear reactors of tbe type utilizing a liquid fuel and designed to convert a non-thermally fissionable isotope to a thermally fissionable isotope by neutron absorption. A tank containing a reactive composition of a thermally fissionable isotope dispersed in a liquid moderator is disposed within an outer tank containing a slurry of a non-thermally fissionable isotope convertible to a thermally fissionable isotope by neutron absorption. A control rod is used to control the chain reaction in the reactive composition and means are provided for circulating and cooling the reactive composition and slurry in separate circuits.

  20. Relative humidity across the Paleocene-Eocene Thermal Maximum via combined hydrogen-oxygen isotope paleohygrometry (Invited)

    NASA Astrophysics Data System (ADS)

    McInerney, F. A.; Bloch, J. I.; Secord, R.; Wing, S. L.; Kraus, M. J.; Boyer, D. M.

    2009-12-01

    The Paleocene-Eocene Thermal Maximum (PETM) presents an opportunity to characterize continental hydrologic changes during rapid and extreme global warming. The Bighorn Basin, Wyoming, USA, has long been recognized for the PETM sequences preserved there and sits in an ideal location for recording hydrologic changes in the interior of North America. The southeast Bighorn Basin is of particular interest because it contains not only alluvial paleosols and vertebrate fossils, but also macrofloral remains from the PETM. The carbon isotope excursion associated with this event is preserved in this part of the Basin in leaf wax lipids, tooth enamel, and bulk organic matter. To characterize the hydrologic changes that occurred during the PETM we are applying a suite of isotopic, paleobotanical and paleopedological approaches to sections in the southeast Bighorn Basin. Reported here are results from the combined hydrogen and oxygen isotope analysis aimed at reconstructing relative humidity. Oxygen isotope ratios (δ18O) of biogenic apatite from mammalian tooth enamel and fish scales vary with environment, physiology and diet. Because mammals are homeothermic, they primarily track surface water values with predictable physiological offsets. Hydrogen isotope ratios (δD) of leaf-wax lipids (long-chain n-alkanes) reflect both meteoric water δD values and additional D-enrichment caused by evapotranspiration. The enrichment factor between water δD and n-alkane δD can therefore be used as a proxy for relative humidity (RH). In this study, δ18O of surface water is estimated using the δ18O of Coryphodon tooth enamel. We use these δ18O values to estimate surface water δD values using the Global Meteoric Water Line (δD = 8δ18O + 10). We then calculate relative humidity from n-alkane δD values using a Craig-Gordon type isotopic model for D-enrichment caused by transpiration from leaves. Results of the combined hydrogen-oxygen isotope paleohygrometer indicate a general rise in

  1. Design and construction of the RPI enhanced thermal neutron target and thermal cross-section measurements of rare earth isotopes

    SciTech Connect

    Danon, Y.

    1993-12-31

    In order to perform thermal cross section measurements the neutron flux in the RPI linac facility had to be increased. A new Enhanced Thermal Target (ETT) was designed, constructed and used. The thermal flux of the new target was up to six times higher than the previous RPI Bounce Target (BT). The ETT was also designed to be coupled to a cold moderator that will give an additional flux increase in the MeV energy region. Design calculations for the cold moderator including neutronics and cryogenics are also presented. The ETT was used for transmission measurements of rare earth metal samples of Ho, Er and Tm and enriched oxide samples of {sup 166}Er{sub 2}O{sub 3} and {sup 167}Er{sub 2}O{sub 3} in the energy range from 0.001 eV to 20 eV. The measurements were done with a 15 meter time-of-flight spectrometer and provide high quality data in the thermal and subthermal region as well as in the low energy resonance region. These measurements allowed a systematic study of paramagnetic scattering for the materials with Z = 67, 68 and 69 for which the paramagnetic scattering has the strongest effect. The paramagnetic scattering was inferred from the total cross section and compared to theoretical results and other experiments.

  2. Microfluidic serial dilution ladder.

    PubMed

    Ahrar, Siavash; Hwang, Michelle; Duncan, Philip N; Hui, Elliot E

    2014-01-01

    Serial dilution is a fundamental procedure that is common to a large number of laboratory protocols. Automation of serial dilution is thus a valuable component for lab-on-a-chip systems. While a handful of different microfluidic strategies for serial dilution have been reported, approaches based on continuous flow mixing inherently consume larger amounts of sample volume and chip real estate. We employ valve-driven circulatory mixing to address these issues and also introduce a novel device structure to store each stage of the dilution process. The dilution strategy is based on sequentially mixing the rungs of a ladder structure. We demonstrate a 7-stage series of 1 : 1 dilutions with R(2) equal to 0.995 in an active device area of 1 cm(2). PMID:24231765

  3. Tracing chlorine sources of thermal and mineral springs along and across the Cascade Range using halogen and chlorine isotope compositions

    USGS Publications Warehouse

    Cullen, Jeffrey T.; Barnes, Jaime D.; Hurwitz, Shaul; Leeman, William P.

    2015-01-01

    In order to provide constraints on the sources of chlorine in spring waters associated with arc volcanism, the major/minor element concentrations and stable isotope compositions of chlorine, oxygen, and hydrogen were measured in 28 thermal and mineral springs along the Cascade Range in northwestern USA. Chloride concentrations in the springs range from 64 to 19,000 mg/L and View the MathML source values range from +0.2‰ to +1.9‰ (average=+1.0±0.4‰), with no systematic variation along or across the arc, nor correlations with their presumed underlying basement lithologies. Additionally, nine geochemically well-characterized lavas from across the Mt. St. Helens/Mt. Adams region of the Cascade Range (Leeman et al., 2004 and Leeman et al., 2005) were analyzed for their halogen concentrations and Cl isotope compositions. In the arc lavas, Cl and Br concentrations from the volcanic front are higher than in lavas from the forearc and backarc. F and I concentrations progressively decrease from forearc to backarc, similar to the trend documented for B in most arcs. View the MathML source values of the lavas range from −0.1 to +0.8‰ (average = +0.4±0.3‰). Our results suggest that the predominantly positive View the MathML source values observed in the springs are consistent with water interaction with underlying 37Cl-enriched basalt and/or altered oceanic crust, thereby making thermal spring waters a reasonable proxy for the Cl isotope compositions of associated volcanic rocks in the Cascades. However, waters with View the MathML source values >+1.0‰ also suggest additional contributions of chlorine degassed from cooling magmas due to subsurface vapor–liquid HCl fractionation in which Cl is lost to the aqueous fluid phase and 37Cl is concentrated in the ascending magmatic HCl vapor. Future work is necessary to better constrain Cl isotope behavior during volcanic degassing and fluid–rock interaction in order to improve volatile flux estimates through

  4. The thermal desorption of CO2 from amine carbamate solutions for the 13C isotope enrichment

    NASA Astrophysics Data System (ADS)

    Dronca, S.; Varodi, C.; Gligan, M.; Stoia, V.; Baldea, A.; Hodor, I.

    2012-02-01

    The CO2 desorption from amine carbamate in non-aqueous solvents is of major importance for isotopic enrichment of 13C. A series of experiments were carried out in order to set up the conditions for the CO2 desorption. For this purpose, a laboratory- scale plant for 13C isotope separation by chemical exchange between CO2 and amine carbamate was designed and used. The decomposition of the carbamate solution was mostly produced in the desorber and completed in the boiler. Two different-length desorbers were used, at different temperatures and liquid flow rates of the amine-non-aqueous solvent solutions. The residual CO2 was determined by using volumetric and gaschromatographic methods. These results can be used for enrichment of 13C by chemical exchange between CO2 and amine carbamate in nonaqueous solvents.

  5. Comprehensive profiling of mercapturic acid metabolites from dietary acrylamide as short-term exposure biomarkers for evaluation of toxicokinetics in rats and daily internal exposure in humans using isotope dilution ultra-high performance liquid chromatography tandem mass spectrometry.

    PubMed

    Zhang, Yu; Wang, Qiao; Cheng, Jun; Zhang, Jingshun; Xu, Jiaojiao; Ren, Yiping

    2015-09-24

    Mercapturic acid metabolites from dietary acrylamide are important short-term exposure biomarkers for evaluating the in vivo toxicity of acrylamide. Most of studies have focused on the measurement of two metabolites, N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA). Thus, the comprehensive profile of acrylamide urinary metabolites cannot be fully understood. We developed an isotope dilution ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for the simultaneous determination of all four mercapturic acid adducts of acrylamide and its primary metabolite glycidamide under the electroscopy ionization negative (ESI-) mode in the present study. The limit of detection (LOD) and limit of quantification (LOQ) of the analytes ranged 0.1-0.3 ng/mL and 0.4-1.0 ng/mL, respectively. The recovery rates with low, intermediate and high spiking levels were calculated as 95.5%-105.4%, 98.2%-114.0% and 92.2%-108.9%, respectively. Acceptable within-laboratory reproducibility (RSD<7.0%) substantially supported the use of current method for robust analysis. Rapid pretreatment procedures and short run time (8 min per sample) ensured good efficiency of metabolism profiling, indicating a wide application for investigating short-term internal exposure of dietary acrylamide. Our proposed UHPLC-MS/MS method was successfully applied to the toxicokinetic study of acrylamide in rats. Meanwhile, results of human urine analysis indicated that the levels of N-acetyl-S-(2-carbamoylethyl)-L-cysteine-sulfoxide (AAMA-sul), which did not appear in the mercapturic acid metabolites in rodents, were more than the sum of GAMA and N-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-L-cysteine (iso-GAMA). Thus, AAMA-sul may alternatively become a specific biomarker for investigating the acrylamide exposure in humans. Current proposed method provides a substantial methodology support for comprehensive profiling of

  6. Certification of butyltins and phenyltins in marine sediment certified reference material by species-specific isotope-dilution mass spectrometric analysis using synthesized 118Sn-enriched organotin compounds

    PubMed Central

    Takatsu, Akiko; Watanabe, Takuro; Aoyagi, Yoshie; Yarita, Takashi; Okamoto, Kensaku; Chiba, Koichi

    2006-01-01

    A new marine sediment certified reference material, NMIJ CRM 7306-a, for butyltin and phenyltin analysis has been prepared and certified by the National Metrological Institute of Japan at the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Candidate sediment material was collected at a bay near industrial activity in Japan. After air-drying, sieving, and mixing the material was sterilized with γ-ray irradiation. The material was re-mixed and packaged into 250 glass bottles (15 g each) and these were stored in a freezer at −30 °C. Certification was performed by use of three different types of species-specific isotope-dilution mass spectrometry (SSID–MS)—SSID–GC–ICP–MS, SSID–GC–MS, and SSID–LC–ICP–MS, with 118Sn-enriched organotin compounds synthesized from 118Sn-enriched metal used as a spike. The 118Sn-enriched mono-butyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) were synthesized as a mixture whereas the 118Sn-enriched di-phenyltin (DPhT) and triphenyltin (TPhT) were synthesized individually. Four different extraction methods, mechanical shaking, ultrasonic, microwave-assisted, and pressurized liquid extraction, were adopted to avoid possible analytical bias caused by non-quantitative extraction and degradation or inter-conversion of analytes in sample preparations. Tropolone was used as chelating agent in all the extraction methods. Certified values are given for TBT 44±3 μg kg−1 as Sn, DBT 51 ± 2 μg kg−1 as Sn, MBT 67 ± 3 μg kg−1 as Sn, TPhT 6.9 ± 1.2 μg kg−1 as Sn, and DPhT 3.4 ± 1.2 μg kg−1 as Sn. These levels are lower than in other sediment CRMs currently available for analysis of organotin compounds. PMID:16874473

  7. Method to simultaneously determine the sphingosine 1-phosphate breakdown product (2E)-hexadecenal and its fatty acid derivatives using isotope-dilution HPLC-electrospray ionization-quadrupole/time-of-flight mass spectrometry.

    PubMed

    Neuber, Corinna; Schumacher, Fabian; Gulbins, Erich; Kleuser, Burkhard

    2014-09-16

    Sphingosine 1-phosphate (S1P), a bioactive lipid involved in various physiological processes, can be irreversibly degraded by the membrane-bound S1P lyase (S1PL) yielding (2E)-hexadecenal and phosphoethanolamine. It is discussed that (2E)-hexadecenal is further oxidized to (2E)-hexadecenoic acid by the long-chain fatty aldehyde dehydrogenase ALDH3A2 (also known as FALDH) prior to activation via coupling to coenzyme A (CoA). Inhibition or defects in these enzymes, S1PL or FALDH, result in severe immunological disorders or the Sjögren-Larsson syndrome, respectively. Hence, it is of enormous importance to simultaneously determine the S1P breakdown product (2E)-hexadecenal and its fatty acid metabolites in biological samples. However, no method is available so far. Here, we present a sensitive and selective isotope-dilution high performance liquid chromatography-electrospray ionization-quadrupole/time-of-flight mass spectrometry method for simultaneous quantification of (2E)-hexadecenal and its fatty acid metabolites following derivatization with 2-diphenylacetyl-1,3-indandione-1-hydrazone and 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide. Optimized conditions for sample derivatization, chromatographic separation, and MS/MS detection are presented as well as an extensive method validation. Finally, our method was successfully applied to biological samples. We found that (2E)-hexadecenal is almost quantitatively oxidized to (2E)-hexadecenoic acid, that is further activated as verified by cotreatment of HepG2 cell lysates with (2E)-hexadecenal and the acyl-CoA synthetase inhibitor triacsin C. Moreover, incubations of cell lysates with deuterated (2E)-hexadecenal revealed that no hexadecanoic acid is formed from the aldehyde. Thus, our method provides new insights into the sphingolipid metabolism and will be useful to investigate diseases known for abnormalities in long-chain fatty acid metabolism, e.g., the Sjögren-Larsson syndrome, in more detail. PMID:25137547

  8. Abundance of four sulfur mustard-DNA adducts ex vivo and in vivo revealed by simultaneous quantification in stable isotope dilution-ultrahigh performance liquid chromatography-tandem mass spectrometry.

    PubMed

    Yue, Lijun; Wei, Yuxia; Chen, Jia; Shi, Huiqin; Liu, Qin; Zhang, Yajiao; He, Jun; Guo, Lei; Zhang, Tingfen; Xie, Jianwei; Peng, Shuangqing

    2014-04-21

    Sulfur mustard (SM) is a highly reactive alkylating vesicant and causes blisters upon contact with skin, eyes, and respiratory organs. It covalently links with DNAs by forming four mono- or cross-link adducts. In this article, the reference standards of SM-DNA adducts and deuterated analogues were first synthesized with simplified procedures containing only one or two steps and using less toxic chemical 2-(2-chloroethylthio)ethanol or nontoxic chemical thiodiglycol as starting materials. A sensitive and high-throughput simultaneous quantification method of N(7)-[2-[(2-hydroxyethyl)thio]-ethyl]guanine (N(7)-HETEG), O(6)-[2-[(2-hydroxyethyl)thio]-ethyl]guanine (O(6)-HETEG), N(3)-[2-[(2-hydroxyethyl)thio]-ethyl]adenine (N(3)-HETEA), and bis[2-(guanin-7-yl)ethyl]sulfide (Bis-G) in the Sprague-Dawley rat derma samples was developed by stable isotope dilution-ultrahigh performance liquid chromatography-tandem mass spectrometry (ID-UPLC-MS/MS) with the aim of revealing the real metabolic behaviors of four adducts. The method was validated, the limit of detection (S/N ratio greater than 10) was 0.01, 0.002, 0.04, and 0.11 fmol on column for N(7)-HETEG, O(6)-HETEG, Bis-G, and N(3)-HETEA, respectively, and the lower limit of quantification (S/N ratio greater than 20) was 0.04, 0.01, 0.12, and 0.33 fmol on column for N(7)-HETEG, O(6)-HETEG, Bis-G, and N(3)-HETEA, respectively. The accuracy of this method was determined to be 76% to 129% (n = 3), and both the interday (n = 6) and intraday (n = 7) precisions were less than 10%. The method was further applied for the quantifications of four adducts in the derma of adult male Sprague-Dawley rats exposed to SM ex vivo and in vivo, and all adducts had time- and dose-effect relationships. To the best of our knowledge, this is the first time that the real presented status of four DNA adducts was simultaneously revealed by the MS-based method, in which Bis-G showed much higher abundance than the result previously reported and N(3

  9. Quantification of N2-Carboxymethyl-2’-deoxyguanosine in Calf-thymus DNA and Cultured Human Kidney Epithelial Cells by Capillary HPLC-Tandem Mass Spectrometry Coupled with Stable Isotope-dilution Method

    PubMed Central

    Wang, Hongxia; Cao, Huachuan; Wang, Yinsheng

    2009-01-01

    Glyoxal is generated endogenously from the degradation of glucose and the oxidation of carbohydrates, lipids as well as the 2-deoxyribose moieties of DNA. Glyoxal is also widely used in industry and is present cigarette smoke and food. Glyoxal can conjugate with nucleobases and proteins to give advanced glycation end products. N2-carboxymethyl-2’-deoxyguanosine (N2-CMdG) and the cyclic 1,N2-glyoxal-dG are the major glyoxal adducts formed in DNA. In this study, we first assessed the stabilities of these two adducts. It turned out that 1,N2-glyoxal-dG was very unstable, with more than 70% of the adduct being decomposed to dG upon a 24-hr incubation at 37°C in phosphate buffered saline. However, N2-CMdG was very stable, less than 0.5% of the lesion was degraded to dG after a 7-day incubation under the same conditions. We further developed a sensitive capillary LC-ESI-MS/MS/MS coupled with stable isotope dilution method and quantified the formation of N2-CMdG in calf thymus DNA and 293T human kidney epithelial cells that were exposed to glyoxal and in calf thymus DNA treated with D-glucose. Our results showed that N2-CMdG was produced at 2–134 lesions per 106 nucleosides in calf thymus DNA when the surrounding glyoxal concentration was increased from 10 to 500 µM and approximately 3–27 lesions per 107 nucleosides while the D-glucose concentration changed from 2 to 50 mM. Furthermore, N2-CMdG was induced endogenously in 293T human kidney epithelial cells and exposure to glyoxal further stimulated the formation of this lesion; the level of this adduct ranged from 7 to 15 lesions per 108 nucleosides while the glyoxal concentration increased from 10 µM to 1.25 mM. Collectively, our results suggested that N2-CMdG might serve as a biomarker for glyoxal exposure. PMID:19968260

  10. An Ocean Acidification Pulse in the Pre-onset Carbon Isotope Excursion Preceding the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Robinson, M. M.; Self-Trail, J. M.; Willard, D. A.; Stassen, P.; Spivey, W.

    2015-12-01

    The Paleocene-Eocene Thermal Maximum (PETM; ~55.5 Ma) is recognized globally in marine sediments by a carbonate dissolution zone, the extinction or turnover of benthic taxa, and a radiation of planktic excursion taxa, all accompanied by a rapid-onset, negative carbon isotope excursion (CIE). The cause and nature of the massive carbon release leading to this extreme climate event remains under debate. Regardless of cause, the environmental and ecosystem changes centered on the PETM are the subject of much study because they provide an analog to modern deteriorating conditions associated with the ongoing rise in atmospheric carbon dioxide. We present evidence from sediments of the South Dover Bridge core, deposited on the U.S. mid-Atlantic shelf, for an ocean acidification event in the latest Paleocene that coincides with a relatively small (-2‰) negative carbon isotope excursion (CIE) that precedes the larger (-4‰) Paleocene-Eocene CIE onset. Planktic foraminifers during this pre-onset event (POE) show post-deposition dissolution in which the coarsely cancellate and muricate wall textures characteristic of many Late Paleocene species have been dissolved away, leaving smooth, thin-walled specimens often with collapsed chambers. In addition, we document biotic responses in benthic, planktic, and terrestrial communities to the POE, including shifts in foraminifer and pollen assemblages and adaptations in calcareous nannofossil species in response to environmental perturbations. A complete recovery is evident between the POE and CIE in both the carbon isotopic signal and in the biotic response, providing additional evidence not only for a pulsed carbon release, but also for a more rapid rate of carbon release than is suggested by a single pulse over a longer period of time. The timing, nature and magnitude of ecological changes during the less extreme POE shallow water acidification event may help to define the ecological tipping point of shallow marine ecosystems.

  11. Thermal, chemical and isotopic homogenization of syn-extensional I-type plutons and mafic microgranular enclaves

    NASA Astrophysics Data System (ADS)

    Tatar Erkül, Sibel; Erkül, Fuat; Uysal, İbrahim

    2015-04-01

    Magma mixing and mingling processes are common phenomenon in the evolution of granitoid magmas. This study deals with examination of mineral chemical, geochemical and isotopic characteristics of enclaves and enclosing syn-extensional granite bodies in western Turkey to make an attempt to solve problems regarding their origin. Mafic microgranular enclaves have granodiorite, quartz monzonite, monzonite and monzodiorite compositions, are subalkaline/calc-alkaline and high-K in character and display typical mixing/mingling textures. Mafic enclaves have partially overlapping geochemical characteristics onto their host rocks in terms of mobile elements and their isotopes while distinct immobile element patterns occur within host rocks and enclaves. Contrasting geochemistry of enclaves is mainly defined by their low SiO2 and high MgO, Mg# and high Fe2O3 contents. Chondrite-normalized spidergrams of enclaves also reveal two contrasting patterns. One is relatively enriched in rare earth element content and the other is slightly enriched and displays relatively flat pattern. 87Sr/86Sr and 143Nd/144Nd contents of enclaves imply considerable amount of crustal input. Crustally derived felsic magma coeval with mafic magma have been chemically, thermally and mechanically exchanged with each other and resulting homogenization led to compositional and isotopic equilibration of mafic and felsic magmas. Fractional crystallization, mixing and the following crustal contamination were responsible for the final composition of syn-extensional granitoids. Such processes appear to have been widely occurred in continental extensional regime that caused melting and mixing of crustal and mantle sources at MOHO depth.

  12. Effects of ocean acidification on the marine calcium isotope record at the Paleocene-Eocene Thermal Maximum

    NASA Astrophysics Data System (ADS)

    Griffith, Elizabeth M.; Fantle, Matthew S.; Eisenhauer, Anton; Paytan, Adina; Bullen, Thomas D.

    2015-06-01

    Carbonates are used extensively to reconstruct paleoclimate and paleoceanographic conditions over geologic time scales. However, these archives are susceptible to diagenetic alteration via dissolution, recrystallization and secondary precipitation, particularly during ocean acidification events when intense dissolution can occur. Despite the possible effects of diagenesis on proxy fidelity, the impacts of diagenesis on the calcium isotopic composition (δ44Ca) of carbonates are unclear. To shed light on this issue, bulk carbonate δ44Ca was measured at high resolution in two Pacific deep sea sediment cores (ODP Sites 1212 and 1221) with considerably different dissolution histories over the Paleocene-Eocene Thermal Maximum (PETM, ∼ 55 Ma). The δ44Ca of marine barite was also measured at the deeper Site 1221, which experienced severe carbonate dissolution during the PETM. Large variations (∼ 0.8 ‰) in bulk carbonate δ44Ca occur in the deeper of the two sites at depths corresponding to the peak carbon isotope excursion, which correlate with a large drop in carbonate weight percent. Such an effect is not observed in either the 1221 barite record or the bulk carbonate record at the shallower Site 1212, which is also less affected by dissolution. We contend that ocean chemical changes associated with abrupt and massive carbon release into the ocean-atmosphere system and subsequent ocean acidification at the PETM affected the bulk carbonate δ44Ca record via diagenesis in the sedimentary column. Such effects are considerable, and need to be taken into account when interpreting Ca isotope data and, potentially, other geochemical proxies over extreme climatic events that drive sediment dissolution.

  13. Quantification of the 2-deoxyribonolactone and nucleoside 5’-aldehyde products of 2-deoxyribose oxidation in DNA and cells by isotope-dilution gas chromatography mass spectrometry: Differential effects of γ-radiation and Fe2+-EDTA

    PubMed Central

    Chan, Wan; Chen, Bingzi; Wang, Lianrong; Taghizadeh, Koli; Demott, Michael S.; Dedon, Peter C.

    2010-01-01

    The oxidation of 2-deoxyribose in DNA has emerged as a critical determinant of the cellular toxicity of oxidative damage to DNA, with oxidation of each carbon producing a unique spectrum of electrophilic products. We have developed and validated an isotope-dilution gas chromatography-coupled mass spectrometry (GC-MS) method for the rigorous quantification of two major 2-deoxyribose oxidation products: the 2-deoxyribonolactone abasic site of 1’-oxidation and the nucleoside 5’-aldehyde of 5’-oxidation chemistry. The method entails elimination of these products as 5-methylene-2(5H)-furanone (5MF) and furfural, respectively, followed by derivatization with pentafluorophenylhydrazine (PFPH), addition of isotopically labeled PFPH derivatives as internal standards, extraction of the derivatives, and quantification by GC-MS analysis. The precision and accuracy of the method were validated with oligodeoxynucleotides containing the 2-deoxyribonolactone and nucleoside 5’-aldehyde lesions. Further, the well defined 2-deoxyribose oxidation chemistry of the enediyne antibiotics, neocarzinostatin and calicheamicin γ1I, was exploited in control studies, with neocarzinostatin producing 10 2-deoxyribonolactone and 300 nucleoside 5’-aldehyde per 106 nt per µM in accord with its established minor 1’- and major 5’-oxidation chemistry. Calicheamicin unexpectedly caused 1’-oxidation at a low level of 10 2-deoxyribonolactone per 106 nt per µM in addition to the expected predominance of 5’-oxidation at 560 nucleoside 5’-aldehyde per 106 nt per µM. The two hydroxyl radical-mediated DNA oxidants, γ-radiation and Fe2+-EDTA, produced nucleoside 5’-aldehyde at a frequency of 57 per 106 nt per Gy (G-value 74 nmol/J) and 3.5 per 106 nt per µM, respectively, which amounted to 40% and 35%, respectively, of total 2-deoxyribose oxidation as measured by a plasmid nicking assay. However, γ-radiation and Fe2+-EDTA produced different proportions of 2-deoxyribonolactone at 7

  14. Quantification of the 2-deoxyribonolactone and nucleoside 5'-aldehyde products of 2-deoxyribose oxidation in DNA and cells by isotope-dilution gas chromatography mass spectrometry: differential effects of gamma-radiation and Fe2+-EDTA.

    PubMed

    Chan, Wan; Chen, Bingzi; Wang, Lianrong; Taghizadeh, Koli; Demott, Michael S; Dedon, Peter C

    2010-05-01

    The oxidation of 2-deoxyribose in DNA has emerged as a critical determinant of the cellular toxicity of oxidative damage to DNA, with oxidation of each carbon producing a unique spectrum of electrophilic products. We have developed and validated an isotope-dilution gas chromatography-coupled mass spectrometry (GC-MS) method for the rigorous quantification of two major 2-deoxyribose oxidation products: the 2-deoxyribonolactone abasic site of 1'-oxidation and the nucleoside 5'-aldehyde of 5'-oxidation chemistry. The method entails elimination of these products as 5-methylene-2(5H)-furanone (5MF) and furfural, respectively, followed by derivatization with pentafluorophenylhydrazine (PFPH), addition of isotopically labeled PFPH derivatives as internal standards, extraction of the derivatives, and quantification by GC-MS analysis. The precision and accuracy of the method were validated with oligodeoxynucleotides containing the 2-deoxyribonolactone and nucleoside 5'-aldehyde lesions. Further, the well-defined 2-deoxyribose oxidation chemistry of the enediyne antibiotics, neocarzinostatin and calicheamicin gamma(1)(I), was exploited in control studies, with neocarzinostatin producing 10 2-deoxyribonolactone and 300 nucleoside 5'-aldehyde per 10(6) nt per microM in accord with its established minor 1'- and major 5'-oxidation chemistry. Calicheamicin unexpectedly caused 1'-oxidation at a low level of 10 2-deoxyribonolactone per 10(6) nt per microM in addition to the expected predominance of 5'-oxidation at 560 nucleoside 5'-aldehyde per 10(6) nt per microM. The two hydroxyl radical-mediated DNA oxidants, gamma-radiation and Fe(2+)-EDTA, produced nucleoside 5'-aldehyde at a frequency of 57 per 10(6) nt per Gy (G-value 74 nmol/J) and 3.5 per 10(6) nt per microM, respectively, which amounted to 40% and 35%, respectively, of total 2-deoxyribose oxidation as measured by a plasmid nicking assay. However, gamma-radiation and Fe(2+)-EDTA produced different proportions of 2

  15. Isotope ratio analysis of actinides, fission products, and geolocators by high-efficiency multi-collector thermal ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Bürger, S.; Riciputi, L. R.; Bostick, D. A.; Turgeon, S.; McBay, E. H.; Lavelle, M.

    2009-09-01

    A ThermoFisher "Triton" multi-collector thermal ionization mass spectrometer (MC-TIMS) was evaluated for trace and ultra-trace level isotope ratio analysis of actinides (uranium, plutonium, and americium), fission products and geolocators (strontium, cesium, and neodymium). Total efficiencies (atoms loaded to ions detected) of up to 0.5-2% for U, Pu, and Am, and 1-30% for Sr, Cs, and Nd can be reported employing resin bead load techniques onto flat ribbon Re filaments or resin beads loaded into a millimeter-sized cavity drilled into a Re rod. This results in detection limits of <0.1 fg (104 atoms to 105 atoms) for 239-242+244Pu, 233+236U, 241-243Am, 89,90Sr, and 134,135,137Cs, and <=1 pg for natural Nd isotopes (limited by the chemical processing blank) using a secondary electron multiplier (SEM) or multiple-ion counters (MICs). Relative standard deviations (RSD) as small as 0.1% and abundance sensitivities of 1 × 106 or better using a SEM are reported here. Precisions of RSD [approximate]0.01-0.001% using a multi-collector Faraday cup array can be achieved at sub-nanogram concentrations for strontium and neodymium and are suitable to gain crucial geolocation information. The analytical protocols reported herein are of particular value for nuclear forensic and nuclear safeguard applications.

  16. Helium isotope systematics of volcanic gases and thermal waters of Guadeloupe Island, Lesser Antilles

    NASA Astrophysics Data System (ADS)

    Jean-Baptiste, P.; Allard, P.; Fourré, E.; Parello, F.; Aiuppa, A.

    2014-08-01

    The island of Guadeloupe is located in the middle of the 850 km long Lesser Antilles island arc. Present-day volcanic and geothermal activity is concentrated in two systems both located in the southwestern part of the island (Basse Terre): the La Soufrière volcanic complex and the Bouillante hydrothermal system, some 20 km to the northwest of the volcano. We report here the largest isotopic data set for helium isotopes in hydrothermal gases and waters from both systems, acquired between 1980 and 2012. 3He/4He ratios in the fumarolic gases of La Soufrière volcano have been quite homogeneous and stable over the last thirty years. The average ratio of 8.2 ± 0.2 Ra confirms that the volcano is tapping a MORB-like mantle source. In contrast, the nearby Bouillante geothermal system displays a much lower 3He/4He ratio (4.5 ± 0.1 Ra). He-C elemental and isotopic relationships show that both systems are actually fed by the same magmatic source, and that their marked difference in 3He/4He results from the 4He contamination of the Bouillante deep aquifer by the surrounding wallrock. This conclusion is strengthened by the spatial distribution of 3He/4He ratios which shows that La Soufrière fumaroles and the Bouillante geothermal system are the two end-members of a spatial trend of decreasing 3He/4He ratio with distance from La Soufrière summit dome, implying an increasing addition of radiogenic 4He from the host rocks away from the present-day active volcanic edifice.

  17. Chemical and isotopic composition of the Monfortinho thermal water (Portugal): contribution to the aquifer conceptual model and resource evaluation

    NASA Astrophysics Data System (ADS)

    do Rosário Carvalho, Maria; Martins Carvalho, José

    2015-04-01

    Groundwaters from quartzite aquifers are usually cold waters with very low mineralization as consequence of circulation in fractured aquifers and rocks with very low solubility. In the Monfortinho, Beira Baixa region in Portugal, a thermal water occurs associated to a Ordovician quartzite syncline, the Penha Garcia syncline (Sequeira et al., 1999). The thermal water is used for balneology and supplies a thermal Spa trough boreholes discharging about 36 l/s. The syncline of Penha Garcia has NW-SE axis and is fractured by a NE-SW fault, where the valley of Ponsul river is developed. The natural discharge of the thermal aquifer occur at the SE edge of the syncline. The Monfortinho thermal water has temperature around 30 °C, pH of 5.45, very low mineralization, with electric conductivity about 35 uS/cm; the main dissolved specie is the SiO2 that reaches 24 mg/L, corresponding to 53% of the total dissolved solids. The chemical facies is of Na-HCO3 type. The d18O and d2H diagram indicates that Monfortinho water is derived from the local meteoric waters. The δ18O and δ2H content also pointed out a recharge area of the thermal aquifer above 400 m of elevation, with a isotopic gradient value of -0.15‰ d18O/100m. This elevation corresponds to the top of the eastern block of the syncline, suggesting that Ponsul fault is a negative barrier to groundwater flow and the thermal aquifer is developed only in eastern block of the syncline. The groundwater flows at about 600-700 m depth along the syncline base toward SE. The average rainfall in the region is 790 mm/year and the estimated recharge is about 17% (Carvalho, 2001) of the precipitation, corresponding to 134 mm/year and 4x105 m3/ano of hydrothermal resource. References: Carvalho, JM (2001). A Hidrogeologia das águas minerais naturais de Monfortinho. Geonovas, Rev. Assoc. Portg. Geólogos, Lisboa, v15, pp. 61-70 (in portuguese). Sequeira, AF, Cunha, PP, Ribeiro, ML (1999). Notícia Explicativa da Folha 25-B Salvaterra

  18. Magnitude of the carbon isotope excursion at the Paleocene Eocene thermal maximum: The role of plant community change

    NASA Astrophysics Data System (ADS)

    Smith, Francesca A.; Wing, Scott L.; Freeman, Katherine H.

    2007-10-01

    Carbon-isotope measurements ( δ13C) of leaf-wax n-alkanes from the Paleocene-Eocene Thermal Maximum (PETM) in the Bighorn Basin, Wyoming, reveal a negative carbon isotope excursion (CIE) of 4-5‰, which is 1-2‰ larger than that observed in marine carbonate δ13C records. Reconciling these records requires either that marine carbonates fail to record the full magnitude of the CIE or that the CIE in plants has been amplified relative to the marine. Amplification of the CIE has been proposed to result from an increase in available moisture that allowed terrestrial plants to increase 13C-discrimination during the PETM. Leaf physiognomy, paleopedology and hydrogen isotope ratios of leaf-wax lipids from the Bighorn Basin, however, all suggest that rather than a simple increase in available moisture, climate alternated between wet and dry during the PETM. Here we consider two other explanations and test them quantitatively with the carbon isotopic record of plant lipids. The "marine modification" hypothesis is that the marine carbonate record was modified by chemical changes at the PETM and that plant lipids record the true magnitude of the CIE. Using atmospheric CO 2δ13C values estimated from the lipid record, and equilibrium fractionation between CO 2 and carbonate, we estimate the expected CIE for planktonic foraminifera to be 6‰. Instead, the largest excursion observed is about 4‰. No mechanism for altering marine carbonate by 2‰ has been identified and we thus reject this explanation. The "plant community change" hypothesis is that major changes in floral composition during the PETM amplified the CIE observed in n-alkanes by 1-2‰ relative to marine carbonate. This effect could have been caused by a rapid transition from a mixed angiosperm/conifer flora to a purely angiosperm flora. The plant community change hypothesis is consistent with both the magnitude and pattern of CIE amplification among the different n-alkanes, and with data from fossil plants

  19. High-Precision Tungsten Isotopic Analysis by Multicollection Negative Thermal Ionization Mass Spectrometry Based on Simultaneous Measurement of W and (18)O/(16)O Isotope Ratios for Accurate Fractionation Correction.

    PubMed

    Trinquier, Anne; Touboul, Mathieu; Walker, Richard J

    2016-02-01

    Determination of the (182)W/(184)W ratio to a precision of ± 5 ppm (2σ) is desirable for constraining the timing of core formation and other early planetary differentiation processes. However, WO3(-) analysis by negative thermal ionization mass spectrometry normally results in a residual correlation between the instrumental-mass-fractionation-corrected (182)W/(184)W and (183)W/(184)W ratios that is attributed to mass-dependent variability of O isotopes over the course of an analysis and between different analyses. A second-order correction using the (183)W/(184)W ratio relies on the assumption that this ratio is constant in nature. This may prove invalid, as has already been realized for other isotope systems. The present study utilizes simultaneous monitoring of the (18)O/(16)O and W isotope ratios to correct oxide interferences on a per-integration basis and thus avoid the need for a double normalization of W isotopes. After normalization of W isotope ratios to a pair of W isotopes, following the exponential law, no residual W-O isotope correlation is observed. However, there is a nonideal mass bias residual correlation between (182)W/(i)W and (183)W/(i)W with time. Without double normalization of W isotopes and on the basis of three or four duplicate analyses, the external reproducibility per session of (182)W/(184)W and (183)W/(184)W normalized to (186)W/(183)W is 5-6 ppm (2σ, 1-3 μg loads). The combined uncertainty per session is less than 4 ppm for (183)W/(184)W and less than 6 ppm for (182)W/(184)W (2σm) for loads between 3000 and 50 ng. PMID:26751903

  20. Thermal history of the Mississippian-Pennsylvanian boundary at Arrow Canyon, NV, USA: Insights from carbonate clumped isotopes and fluid inclusion microthermometry

    NASA Astrophysics Data System (ADS)

    Shenton, B.; Grossman, E. L.; Passey, B. H.; Henkes, G. A.; Becker, S. P.; Pottorf, R. J.

    2013-12-01

    Constraining the temperature-time history of sedimentary basins is critical for understanding basin evolution and related problems, such as petroleum systems analysis and genesis of metallic ore deposits. The importance of burial history studies is confirmed by the abundance and diversity of techniques aimed at acquiring thermal history information. Often, multiple techniques are required to fully characterize sediment thermal histories because each tool targets different burial temperatures (e.g., maximum burial temperature, T-t points, or cooling rates) and different indicators may be limited by suitable study material or geologic setting. Therefore it is important to test new techniques, such as clumped isotopes, that may aid in reconstructing basin thermal histories. The potential utility of clumped isotopes as a thermal history tool is suggested by the observation of elevated clumped isotope temperatures in nominally well-preserved fossils, and also from recent laboratory heating experiments showing that C-O bonds can reorder in the solid-state during heating. While this phenomenon conceals primary paleoclimate information, it may record burial temperatures useful for constraining basin thermal histories. Here we present clumped isotope measurements from brachiopods, crinoids, diagenetic cements, and bulk matrix material collected from within ~ 50 m of the global stratotype section and point (GSSP) for the Mississippian-Pennsylvanian boundary along with new fluid inclusion microthermometry data. Preliminary clumped isotope temperatures range from ~100-165 °C and generally cluster based on component type. Secondary fluid inclusion assemblages in blocky calcite cement indicate that strata surrounding the GSSP experienced at least 175-180 °C during burial in the Antler foreland basin. The fact that clumped isotope temperatures in all carbonate components are lower than independently constrained peak temperature estimates from fluid inclusions suggests that

  1. Thermal stratification of Dilute Lakes. Evaluation of regulatory processes and biological effects before and after base addition: Effects on brook trout habitat and growth. Technical report series

    SciTech Connect

    Schofield, C.L.; Josephson, D.; Keleher, C.; Gloss, S.P.

    1993-04-01

    The authors address the significance of changes in summer thermal stratification patterns of Adirondack lakes affected by acidification to cold-water fish populations inhabiting these sensitive lakes. The brook trout (Salvelinus fontinalis) is the primary cold-water fish species indigenous to acid-sensitive lakes in the Adirondack region of northern New York State; the ability of these lakes to sustain this important sport species is highly dependent on the availability of adequate summer habitat, consisting of cool, well-oxygenated water. The authors hypothesized that acidification-induced reductions in the thermal stability of sensitive Adirondack lakes could lead to degradation of potential brook trout habitat. These hypotheses were addressed in the study by utilizing data available from previous lake liming studies in the Adirondack region, brook trout growth data from management studies in the region, and the extensive Adirondack Lake Survey Corporation (ALSC) data base. More than 70% of the small, shallow ALSC lakes were classified as predominantly weakly stratified systems that would be potentially sensitive to changes in thermal stratification status resulting from relatively small changes in color and transparency.

  2. Determination of oxygen self-diffusion in akermanite, anorthite, diopside, and spinel: Implications for oxygen isotopic anomalies and the thermal histories of Ca-Al-rich inclusions

    SciTech Connect

    Ryerson, F.J. ); McKeegan, K.D. )

    1994-09-01

    Oxygen self-diffusion coefficients have been measured for three natural diopsidic clinopyroxenes, a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic akermanite for oxygen fugacities ranging from the NNO to IW buffers. The oxygen diffusion data are used to evaluate the effects of three different types of thermal histories upon the oxygen isotopic compositions of minerals found in Type B Ca-Al-rich inclusions (CAIBs) in carbonaceous chondrites: (1) gas-solid exchange during isothermal heating, (2) gas-solid exchange as a function of cooling rate subsequent to instantaneous heating, and (3) isotopic exchange with a gaseous reservoir during partial melting and recrystallization. With the assumptions that the mineral compositions within a CAIB were uniformly enriched in [sup 16]O prior to any thermal processing, that effective diffusion dimensions may be estimated from observed grain sizes, and that diffusion in diopside is similar to that in fassaitic clinopyroxene, none of the above scenarios can reproduce the relative oxygen isotopic anomalies observed in CAIBs without improbably long or unrealistically intense thermal histories relative to current theoretical models of nebular evolution. The failure of these simple models, coupled with recent observations of disturbed magnesium isotopic abundances and correlated petrographic features in anorthite and melilite indicative of alteration and recrystallization, suggests that the oxygen isotopic compositions of these phases may have also been modified by alteration and recrystallization possibly interspersed with multiple melting events. Because the modal abundance of spinel remains relatively constant for plausible melting scenarios, and its relatively sluggish diffusion kinetics prevent substantial equilibration, Mg-Al spinel is the most reliable indicator of the oxygen isotopic composition of precursor material which formed Type B CAIs.

  3. Stable Chlorine Isotopes and Elemental Chlorine by Thermal Ionization Mass Spectrometry and Ion Chromatography; Martian Meteorites, Carbonaceous Chondrites and Standard Rocks

    NASA Technical Reports Server (NTRS)

    Nakamura, N.; Nyquist, L. E.; Reese, Y.; Shih, C.-Y.; Fujitani, T.; Okano, O.

    2011-01-01

    Recently significantly large mass fractionation of stable chlorine isotopes has been reported for terrestrial and lunar samples [1,2]. In addition, in view of possible early solar system processes [3] and also potential perchlorate-related fluid/microbial activities on the Martian surface [4,5], a large chlorine isotopic fractionation might be expected for some types of planetary materials. Due to analytical difficulties of isotopic and elemental analyses, however, current chlorine analyses for planetary materials are controversial among different laboratories, particularly between IRMS (gas source mass spectrometry) and TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1,6,7] for isotopic analyses, as well as between those doing pyrohydrolysis and other groups [i.e. 6,8]. Additional careful investigations of Cl isotope and elemental abundances are required to confirm real chlorine isotope and elemental variations for planetary materials. We have developed a TIMS technique combined with HF-leaching/ion chromatography at NASA JSC that is applicable to analysis of small amounts of meteoritic and planetary materials. We present here results for several standard rocks and meteorites, including Martian meteorites.

  4. MECHANICAL ALLOYING AND THERMAL TREATMENT FOR PRODUCTION OF ZIRCONIUM IRON HYDROGEN ISOTOPE GETTERS

    SciTech Connect

    Fox, K.

    2008-02-20

    The objective of this task was to demonstrate that metal hydrides could be produced by mechanical alloying in the quantities needed to support production-scale hydrogen isotope separations. Three starting compositions (ratios of elemental Zr and Fe powders) were selected and attritor milled under argon for times of 8 to 60 hours. In general, milling times of at least 24 hours were required to form the desired Zr{sub 2}Fe and Zr{sub 3}Fe phases, although a considerable amount of unalloyed Zr and Fe remained. Milling in liquid nitrogen does not appear to provide any advantages over milling in hexane, particularly due to the formation of ZrN after longer milling times. Carbides of Zr formed during some of the milling experiments in hexane. Elemental Zr was present in the as-milled material but not detected after annealing for milling times of 48 and 60 hours. It may be that after intimate mixing of the powders in the attritor mill the annealing temperature was sufficient to allow for the formation of a Zr-Fe alloy. Further investigation of this conversion is necessary, and could provide an opportunity for reducing the amount of unreacted metal powder after milling.

  5. Isotopic yield measurement in the heavy mass region for 239Pu thermal neutron induced fission

    NASA Astrophysics Data System (ADS)

    Bail, A.; Serot, O.; Mathieu, L.; Litaize, O.; Materna, T.; Köster, U.; Faust, H.; Letourneau, A.; Panebianco, S.

    2011-09-01

    Despite the huge number of fission yield data available in the different evaluated nuclear data libraries, such as JEFF-3.1.1, ENDF/B-VII.0, and JENDL-4.0, more accurate data are still needed both for nuclear energy applications and for our understanding of the fission process itself. It is within the framework of this that measurements on the recoil mass spectrometer Lohengrin (at the Institut Laue-Langevin, Grenoble, France) was undertaken, to determine isotopic yields for the heavy fission products from the 239Pu(nth,f) reaction. In order to do this, a new experimental method based on γ-ray spectrometry was developed and validated by comparing our results with those performed in the light mass region with completely different setups. Hence, about 65 fission product yields were measured with an uncertainty that has been reduced on average by a factor of 2 compared to that previously available in the nuclear data libraries. In addition, for some fission products, a strongly deformed ionic charge distribution compared to a normal Gaussian shape was found, which was interpreted as being caused by the presence of a nanosecond isomeric state. Finally, a nuclear charge polarization has been observed in agreement, with the one described on other close fissioning systems.

  6. Determination of the hydrogen isotopic compositions of organic materials and hydrous minerals using thermal combustion laser spectroscopy.

    PubMed

    Koehler, Geoff; Wassenaar, Leonard I

    2012-04-17

    Hydrogen isotopic compositions of hydrous minerals and organic materials were measured by combustion to water, followed by optical isotopic analysis of the water vapor by off-axis integrated cavity output spectroscopy. Hydrogen and oxygen isotopic compositions were calculated by numerical integration of the individual isotopologue concentrations measured by the optical spectrometer. Rapid oxygen isotope exchange occurs within the combustion reactor between water vapor and molecular oxygen so that only hydrogen isotope compositions may be determined. Over a wide range in sample sizes, precisions were ±3-4 per mil. This is comparable but worse than continuous flow-isotope ratio mass spectroscopy (CF-IRMS) methods owing to memory effects inherent in water vapor transfer. Nevertheless, the simplicity and reduced cost of this analysis compared to classical IRMS or CF-IRMS methods make this an attractive option to determine the hydrogen isotopic composition of organic materials where the utmost precision or small sample sizes are not needed. PMID:22432837

  7. Trapping state of hydrogen isotopes in carbon and graphite investigated by thermal desorption spectrometry

    SciTech Connect

    Atsumi, H.; Tanabe, T.; Shikama, T.

    2015-03-15

    Thermal desorption spectrometry (TDS) has been investigated to obtain fundamental information of tritium behavior in graphite and carbon materials especially at high temperatures. 29 brands of graphite, HOPG, glassy carbon and CFC materials charged with deuterium gas are tested up to the temperature of 1735 K with a heating rate of 0.1 K/s. TDS spectra have five peaks at 600-700 K, around 900 K, 1200 K, 1300-1450 K and 1600-1650 K. The amounts of released deuterium have been compared with crystallographic parameters derived from XRD analysis. The results can be summarized as follows. First, TDS spectra of deuterium were quite varied among the samples tested, such as existence of peaks, peak temperatures and release amounts of deuterium. Secondly, TDS spectra may consist of five peaks, which are peak 1 (600-700 K), peak 2 (around 900 K), peak 3 (around 1200 K), peak 4 (1300-1450 K) and peak 5 (1600-1650 K). Thirdly, the correlations between the estimated surface area of edge surface and the total amount of released deuterium could be observed for peaks 4 and 5. Fourthly, high energy trapping site (peak 5) may exist even at edge surface or a near surface region, not only for intercalary. And fifth, in order to obtain the lower tritium retention for graphite and CFC materials, the material should be composed of a filler grain with a smaller crystallite size or having the smaller net edge surface in its structure. It is shown that heat treatment does not reduce originally existing trapping sites but trapping sites generated by neutron irradiation for instance can be reduced in some degree.

  8. Rhenium-osmium isotope systematics of ordinary chondrites and iron meteorites

    NASA Technical Reports Server (NTRS)

    Walker, R. J.; Morgan, J. W.; Horan, M. F.; Grossman, J. N.

    1993-01-01

    Using negative thermal ionization mass spectrometry, Re and Os abundances were determined by isotope dilution and Os-187/Os-186 measured in 11 ordinary chondrites, and also in 1 IIB and 3 IIIB irons. In addition, Os-186/Os-188 and Os-189/Os-188 ratios were precisely determined for 3 unspiked ordinary chondrites as a means of constraining the intensity of any neutron irradiation these meteorites may have experienced.

  9. Dilution, Concentration, and Flotation

    ERIC Educational Resources Information Center

    Liang, Ling; Schmuckler, Joseph S.

    2004-01-01

    As both classroom teaching practice and literature show, many students have difficulties learning science concepts such as density. Here are some investigations that identify the relationship between density and floating through experimenting with successive dilution of a liquid, or the systematic change of concentration of a saltwater solution.…

  10. Helium dilution refrigeration system

    DOEpatents

    Roach, P.R.; Gray, K.E.

    1988-09-13

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation is disclosed. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains [sup 3]He and [sup 4]He liquids which are precooled by a coupled container containing [sup 3]He liquid, enabling the phase separation of a [sup 3]He rich liquid phase from a dilute [sup 3]He-[sup 4]He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the [sup 3]He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute [sup 3]He-[sup 4]He liquid phase. 2 figs.

  11. Helium dilution refrigeration system

    DOEpatents

    Roach, Patrick R.; Gray, Kenneth E.

    1988-01-01

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains .sup.3 He and .sup.4 He liquids which are precooled by a coupled container containing .sup.3 He liquid, enabling the phase separation of a .sup.3 He rich liquid phase from a dilute .sup.3 He-.sup.4 He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the .sup.3 He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute .sup.3 He-.sup.4 He liquid phase.

  12. Coupled variations in helium isotopes and fluid chemistry: Shoshone Geyser Basin, Yellowstone National Park

    SciTech Connect

    Hearn, E.H.; Kennedy, B.M. ); Truesdell, A.H. )

    1990-11-01

    Early studies of {sup 3}He/{sup 4}He variations in geothermal systems have generally attributed these fluctuations to either differences in the source of the magmatic {sup 3}He-rich helium or to local differences in the deep flux of magmatic {sup 3}He-rich helium. Kennedy et al, however, show that near-surface processes such as boiling and dilution may also drastically affect {sup 3}He/{sup 4}He ratios of geothermal vapors. Helium isotope ratios were determined for several hot springs at Shoshone Geyser Basin of Yellowstone National Park for this study, along with other noble gas data. Stable isotope data and water and gas chemistry data for each spring were also compiled. The water chemistry indicates that there is one deep, hot thermal water in the area which is mixing with dilute meteoric water that has entered the system at depth. Spring HCO{sub 3}{sup {minus}} concentrations correlate with {sup 3}He/{sup 4}He values, as in nearby Lower Geyser Basin. This correlation is attributed to variable amounts of deep dilution of thermal waters with a relatively cool water that inhibits boiling at depth, thus preventing the loss of CO{sub 2} and magmatic He in the most diluted samples. Oxygen and hydrogen isotope data also support a boiling and dilution model, but to produce the observed fractionations, the boiling event would have to be extensive, with steam loss at the surface, whereas the boiling that affected the helium isotope ratios was probably a small scale event with steam loss at depth. It is possible that deep boiling occurred in the basin and that small amounts of steam escaped along fractures at about 500 m below the surface while all subsequently produced steam was lost near or at the surface.

  13. Coupled variations in helium isotopes and fluid chemistry: Shoshone Geyser Basin, Yellowstone National Park

    USGS Publications Warehouse

    Hearn, E.H.; Kennedy, B.M.; Truesdell, A.H.

    1990-01-01

    Early studies of 3He/4He variations in geothermal systems have generally attributed these fluctuations to either differences in the source of the magmatic 3He-rich helium or to local differences in the deep flux of magmatic 3He-rich helium. Kennedy et al. (1987), however, show that near-surface processes such as boiling and dilution may also drastically affect 3He 4He ratios of geothermal vapors. Helium isotope ratios were determined for several hot springs at Shoshone Geyser Basin of Yellowstone National Park for this study, along with other noble gas data. Stable isotope data and water and gas chemistry data for each spring were also compiled. The water chemistry indicates that there is one deep, hot thermal water in the area which is mixing with dilute meteoric water that has entered the system at depth. Spring HCO3- concentrations correlate with 3He 4He values, as in nearby Lower Geyser Basin. This correlation is attributed to variable amounts of deep dilution of thermal waters with a relatively cool water that inhibits boiling at depth, thus preventing the loss of CO2 (and therefore HCO3-) and magmatic He in the most diluted samples. Oxygen and hydrogen isotope data also support a boiling and dilution model, but to produce the observed fractionations, the boiling event would have to be extensive, with steam loss at the surface, whereas the boiling that affected the helium isotope ratios was probably a small scale event with steam loss at depth. It is possible that deep boiling occurred in the basin and that small amounts of steam escaped along fractures at about 500 m below the surface while all subsequently produced steam was lost near or at the surface. ?? 1990.

  14. Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

    NASA Astrophysics Data System (ADS)

    Badin, Alice; Broholm, Mette M.; Jacobsen, Carsten S.; Palau, Jordi; Dennis, Philip; Hunkeler, Daniel

    2016-09-01

    Thermal tetrachloroethene (PCE) remediation by steam injection in a sandy aquifer led to the release of dissolved organic carbon (DOC) from aquifer sediments resulting in more reduced redox conditions, accelerated PCE biodegradation, and changes in microbial populations. These changes were documented by comparing data collected prior to the remediation event and eight years later. Based on the premise that dual C-Cl isotope slopes reflect ongoing degradation pathways, the slopes associated with PCE and TCE suggest the predominance of biotic reductive dechlorination near the source area. PCE was the predominant chlorinated ethene near the source area prior to thermal treatment. After thermal treatment, cDCE became predominant. The biotic contribution to these changes was supported by the presence of Dehalococcoides sp. DNA (Dhc) and Dhc targeted rRNA close to the source area. In contrast, dual C-Cl isotope analysis together with the almost absent VC 13C depletion in comparison to cDCE 13C depletion suggested that cDCE was subject to abiotic degradation due to the presence of pyrite, possible surface-bound iron (II) or reduced iron sulphides in the downgradient part of the plume. This interpretation is supported by the relative lack of Dhc in the downgradient part of the plume. The results of this study show that thermal remediation can enhance the biodegradation of chlorinated ethenes, and that this effect can be traced to the mobilisation of DOC due to steam injection. This, in turn, results in more reduced redox conditions which favor active reductive dechlorination and/or may lead to a series of redox reactions which may consecutively trigger biotically induced abiotic degradation. Finally, this study illustrates the valuable complementary application of compound-specific isotopic analysis combined with molecular biology tools to evaluate which biogeochemical processes are taking place in an aquifer contaminated with chlorinated ethenes.

  15. Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools.

    PubMed

    Badin, Alice; Broholm, Mette M; Jacobsen, Carsten S; Palau, Jordi; Dennis, Philip; Hunkeler, Daniel

    2016-09-01

    Thermal tetrachloroethene (PCE) remediation by steam injection in a sandy aquifer led to the release of dissolved organic carbon (DOC) from aquifer sediments resulting in more reduced redox conditions, accelerated PCE biodegradation, and changes in microbial populations. These changes were documented by comparing data collected prior to the remediation event and eight years later. Based on the premise that dual C-Cl isotope slopes reflect ongoing degradation pathways, the slopes associated with PCE and TCE suggest the predominance of biotic reductive dechlorination near the source area. PCE was the predominant chlorinated ethene near the source area prior to thermal treatment. After thermal treatment, cDCE became predominant. The biotic contribution to these changes was supported by the presence of Dehalococcoides sp. DNA (Dhc) and Dhc targeted rRNA close to the source area. In contrast, dual C-Cl isotope analysis together with the almost absent VC (13)C depletion in comparison to cDCE (13)C depletion suggested that cDCE was subject to abiotic degradation due to the presence of pyrite, possible surface-bound iron (II) or reduced iron sulphides in the downgradient part of the plume. This interpretation is supported by the relative lack of Dhc in the downgradient part of the plume. The results of this study show that thermal remediation can enhance the biodegradation of chlorinated ethenes, and that this effect can be traced to the mobilisation of DOC due to steam injection. This, in turn, results in more reduced redox conditions which favor active reductive dechlorination and/or may lead to a series of redox reactions which may consecutively trigger biotically induced abiotic degradation. Finally, this study illustrates the valuable complementary application of compound-specific isotopic analysis combined with molecular biology tools to evaluate which biogeochemical processes are taking place in an aquifer contaminated with chlorinated ethenes. PMID:27318432

  16. Assessment of groundwater pollution from ash ponds using stable and unstable isotopes around the Koradi and Khaperkheda thermal power plants (Maharashtra, India).

    PubMed

    Voltaggio, M; Spadoni, M; Sacchi, E; Sanam, R; Pujari, P R; Labhasetwar, P K

    2015-06-15

    The impact on local water resources due to fly ash produced in the Koradi and Khaperkheda thermal power plants (district of Nagpur, Maharashtra - India) and disposed in large ponds at the surface was assessed through the study of environmental variation of ratios of stable and unstable isotopes. Analyses of oxygen and hydrogen isotopes suggest scarce interaction between the water temporarily stored in the ponds and the groundwater in the study area. Data also highlight that the high salinity of groundwater measured in the polluted wells is not due to evaporation, but to subsequent infiltration of stream waters draining from the ponds to the local aquifer. (87)Sr/(86)Sr values, when associated with Sr/Ca ratios, demonstrate the dominant role of waste waters coming from tens of brick kilns surrounding the pond sulfate pollution. Uranium isotopic analyses clearly show evidence of the interaction between groundwater and aquifer rocks, and confirm again the low influence of ash ponds. A new conceptual model based on the study of the isotopes of radium is also proposed and used to estimate residence times of groundwater in the area. This model highlights that high salinity cannot be in any case attributed to a prolonged water-rock interaction, but is due to the influence of untreated waste water of domestic or brick kiln origin on the shallow and vulnerable aquifers. PMID:25783943

  17. Characterization of Volatile Nylon 6.6 Thermal-Oxidative Degradation Products by Selective Isotopic Labeling and Cryo-GC/MS

    NASA Astrophysics Data System (ADS)

    Smith, Jonell N.; V. White, Gregory; White, Michael I.; Bernstein, Robert; Hochrein, James M.

    2012-09-01

    Aged materials, such as polymers, can exhibit modifications to their chemical structure and physical properties, which may render the material ineffective for its intended purpose. Isotopic labeling was used to characterize low-molecular weight volatile thermal-oxidative degradation products of nylon 6.6 in an effort to better understand and predict changes in the aged polymer. Headspace gas from aged (up to 243 d at 138 °C) nylon 6.6 monomers (adipic acid and 1,6-hexanediamine) and polymer were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). Observations regarding the relative concentrations observed in each chromatographic peak with respect to aging time were used in conjunction with mass spectra for samples aged under ambient air to determine the presence and identity of 18 degradation products. A comparison of the National Institute of Standards and Technology (NIST) library, unlabeled, and isotopically labeled mass spectra (C-13 or N-15) and expected fragmentation pathways of each degradation product were used to identify the location of isotopically labeled atoms within the product's chemical structure, which can later be used to determine the exact origin of the species. In addition, observations for unlabeled nylon 6.6 aged in an O-18 enriched atmosphere were used to determine if the source of oxygen in the applicable degradation products was from the gaseous environment or the polymer. Approximations for relative isotopic ratios of unlabeled to labeled products are reported, where appropriate.

  18. Direct isotope ratio analysis of individual uranium-plutonium mixed particles with various U/Pu ratios by thermal ionization mass spectrometry.

    PubMed

    Suzuki, Daisuke; Esaka, Fumitaka; Miyamoto, Yutaka; Magara, Masaaki

    2015-02-01

    Uranium and plutonium isotope ratios in individual uranium-plutonium (U-Pu) mixed particles with various U/Pu atomic ratios were analyzed without prior chemical separation by thermal ionization mass spectrometry (TIMS). Prior to measurement, micron-sized particles with U/Pu ratios of 1, 5, 10, 18, and 70 were produced from uranium and plutonium certified reference materials. In the TIMS analysis, the peaks of americium, plutonium, and uranium ion signals were successfully separated by continuously increasing the evaporation filament current. Consequently, the uranium and plutonium isotope ratios, except the (238)Pu/(239)Pu ratio, were successfully determined for the particles at all U/Pu ratios. This indicates that TIMS direct analysis allows for the measurement of individual U-Pu mixed particles without prior chemical separation. PMID:25479434

  19. Determination of Oxygen Self-Diffusion in Akermanite, Anorthite, Diopside, and Spinel: Implications for Oxygen Isotopic Anomalies and the Thermal Histories of Ca-Al-rich Inclusions

    NASA Astrophysics Data System (ADS)

    Ryerson, F. J.; McKeegan, K. D.

    1993-07-01

    Oxygen self-diffusion coefficients have been measured for three natural clinopyroxenes (diopside end member), a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic akermanite over oxygen fugacities ranging from the NNO to IW buffers. The experiments employed a gas-solid isotopic exchange technique utilizing 99% ^18O-enriched COCO2 gas mixtures to control both the oxygen fugacity and the isotopic composition of the exchange reservoir. Diffusion profiles of the ^18O tracer were obtained by in-depth analysis with an ion microprobe. The experimental results yield Arrhenius relations that appear here in the hard copy. At a given temperature, oxygen diffuses about 100 times more slowly in diopside than indicated by previous bulk-exchange experiments [1]. Our data for anorthite, spinel, and akermanite agree well with prior results obtained by gas-solid isotopic exchange and depth profiling methods [2-4]. Since these other experiments were conducted at different oxygen fugacities, this agreement indicates that diffusion of oxygen in these nominally iron-free minerals is not greatly affected by fO2 in the range between pure oxygen and the iron-wustite buffer. The oxygen diffusion data are used to evaluate the effects of three different types of therrnal histories upon the oxygen isotopic compositions of minerals found in Type B calciumaluminum-rich inclusions (CAIBs): (1) gas-solid exchange during isothermal heating, (2) gassolid exchange due to instantaneous heating followed by cooling at different rates, and (3) isotopic exchange with a gaseous reservoir during partial melting and recrystallization. With the assumptions that the mineral compositions within a CAIB were uniformly enriched in ^16O prior to any thermal processing, that effective diffusion dimensions may be estimated from observed grain sizes, and that diffusion in diopside is similar to that in fassaite, all the above scenarios fail to reproduce either the relative oxygen isotopic

  20. Automatic diluter for bacteriological samples.

    PubMed

    Trinel, P A; Bleuze, P; Leroy, G; Moschetto, Y; Leclerc, H

    1983-02-01

    The described apparatus, carrying 190 tubes, allows automatic and aseptic dilution of liquid or suspended-solid samples. Serial 10-fold dilutions are programmable from 10(-1) to 10(-9) and are carried out in glass tubes with screw caps and split silicone septa. Dilution assays performed with strains of Escherichia coli and Bacillus stearothermophilus permitted efficient conditions for sterilization of the needle to be defined and showed that the automatic dilutions were as accurate and as reproducible as the most rigorous conventional dilutions. PMID:6338826

  1. Automatic diluter for bacteriological samples.

    PubMed Central

    Trinel, P A; Bleuze, P; Leroy, G; Moschetto, Y; Leclerc, H

    1983-01-01

    The described apparatus, carrying 190 tubes, allows automatic and aseptic dilution of liquid or suspended-solid samples. Serial 10-fold dilutions are programmable from 10(-1) to 10(-9) and are carried out in glass tubes with screw caps and split silicone septa. Dilution assays performed with strains of Escherichia coli and Bacillus stearothermophilus permitted efficient conditions for sterilization of the needle to be defined and showed that the automatic dilutions were as accurate and as reproducible as the most rigorous conventional dilutions. Images PMID:6338826

  2. Phonon coherence in isotopic silicon superlattices

    SciTech Connect

    Frieling, R.; Radek, M.; Eon, S.; Bracht, H.; Wolf, D. E.

    2014-09-29

    Recent experimental and theoretical investigations have confirmed that a reduction in thermal conductivity of silicon is achieved by isotopic silicon superlattices. In the present study, non-equilibrium molecular dynamics simulations are performed to identify the isotope doping and isotope layer ordering with minimum thermal conductivity. Furthermore, the impact of isotopic intermixing at the superlattice interfaces on phonon transport is investigated. Our results reveal that the coherence of phonons in isotopic Si superlattices is prevented if interfacial mixing of isotopes is considered.

  3. Isotopic and Symmetry Effects in the Collision of Atomic Helium

    NASA Astrophysics Data System (ADS)

    Bouledroua, Moncef; Bouchelaghem, Fouzia; Tahar Bouazza, M.; Reggami, Lamia

    2006-11-01

    The thermophysical properties of a helium dilute gas at low and high temperatures are revisited with new and recent potential data points. The second virial coefficients are computed in order to assess the accuracy of the constructed He-He potentials. The results, mainly at high temperatures, are in a good agreement with the published values. The isotopic effects due to the presence of ^4He and ^3He atoms are also examined and the calculations of various transport parameters, namely diffusion, viscosity, and thermal conductivity, are extended to include the nuclear spins and the symmetry effects, which arise from the identity and indistinguishability of the colliding atoms.

  4. Neutron scattering study of dilute supercritical solutions

    SciTech Connect

    Cochran, H.D.; Wignall, G.D.; Shah, V.M.; Londono, J.D.; Bienkowski, P.R.

    1994-10-01

    Dilute solutions in supercritical solvents exhibit interesting microstructures that are related to their dramatic macroscopic behavior. In typical attractive solutions, solutes are believed to be surrounded by clusters of solvent molecules, and solute molecules are believed to congregate in the vicinity of one another. Repulsive solutions, on the other hand, exhibit a local region of reduced solvent density around the solute with solute-solute congregation. Such microstructures influence solubility, partial molar volume, reaction kinetics, and many other properties. We have undertaken to observe these interesting microstructures directly by neutron scattering experiments on dilute noble gas systems including Ar. The three partial structure factors for such systems and the corresponding pair correlation functions can be determined by using the isotope substitution technique. The systems studied are uniquely suited for our objectives because of the large coherent neutron scattering length of the isotope {sup 36}Ar and because of the accurate potential energy functions that are available for use in molecular simulations and theoretical calculations to be compared with the scattering results. We will describe our experiment, the unique apparatus we have built for it, and the neutron scattering results from our initial allocations of beam time. We will also describe planned scattering experiments to follow those with noble gases, including study of long-chain molecules in supercritical solvents. Such studies will involve hydrocarbon mixtures with and without deuteration to provide contrast.

  5. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2001-12-21

    Semiconductor bulk crystals and multilayer structures with controlled isotopic composition have attracted much scientific and technical interest in the past few years. Isotopic composition affects a large number of physical properties, including phonon energies and lifetimes, bandgaps, the thermal conductivity and expansion coefficient and spin-related effects. Isotope superlattices are ideal media for self-diffusion studies. In combination with neutron transmutation doping, isotope control offers a novel approach to metal-insulator transition studies. Spintronics, quantum computing and nanoparticle science are emerging fields using isotope control.

  6. Dilution jet mixing program

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; Coleman, E.; Johnson, K.

    1984-01-01

    Parametric tests were conducted to quantify the mixing of opposed rows of jets (two-sided injection) in a confined cross flow. Results show that jet penetrations for two sided injections are less than that for single-sided injections, but the jet spreading rates are faster for a given momentum ratio and orifice plate. Flow area convergence generally enhances mixing. Mixing characteristics with asymmetric and symmetric convergence are similar. For constant momentum ratio, the optimum S/H(0) with in-line injections is one half the optimum value for single sided injections. For staggered injections, the optimum S/H(0) is twice the optimum value for single-sided injection. The correlations developed predicted the temperature distributions within first order accuracy and provide a useful tool for predicting jet trajectory and temperature profiles in the dilution zone with two-sided injections.

  7. Standard dilution analysis.

    PubMed

    Jones, Willis B; Donati, George L; Calloway, Clifton P; Jones, Bradley T

    2015-02-17

    Standard dilution analysis (SDA) is a novel calibration method that may be applied to most instrumental techniques that will accept liquid samples and are capable of monitoring two wavelengths simultaneously. It combines the traditional methods of standard additions and internal standards. Therefore, it simultaneously corrects for matrix effects and for fluctuations due to changes in sample size, orientation, or instrumental parameters. SDA requires only 200 s per sample with inductively coupled plasma optical emission spectrometry (ICP OES). Neither the preparation of a series of standard solutions nor the construction of a universal calibration graph is required. The analysis is performed by combining two solutions in a single container: the first containing 50% sample and 50% standard mixture; the second containing 50% sample and 50% solvent. Data are collected in real time as the first solution is diluted by the second one. The results are used to prepare a plot of the analyte-to-internal standard signal ratio on the y-axis versus the inverse of the internal standard concentration on the x-axis. The analyte concentration in the sample is determined from the ratio of the slope and intercept of that plot. The method has been applied to the determination of FD&C dye Blue No. 1 in mouthwash by molecular absorption spectrometry and to the determination of eight metals in mouthwash, wine, cola, nitric acid, and water by ICP OES. Both the accuracy and precision for SDA are better than those observed for the external calibration, standard additions, and internal standard methods using ICP OES. PMID:25599250

  8. Springtime carbon emission episodes at the Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles

    NASA Astrophysics Data System (ADS)

    Jung, J.; Kawamura, K.

    2011-11-01

    In order to investigate the emission of carbonaceous aerosols at the Gosan background super-site (33.17° N, 126.10° E) in East Asia, total suspended particles (TSP) were collected during spring of 2007 and 2008 and analyzed for particulate organic carbon, elemental carbon, total carbon (TC), total nitrogen (TN), and stable carbon isotopic composition (δ13C) of TC. The stable carbon isotopic composition of TC (δ13CTC) was found to be lowest during pollen emission episodes (range: -26.2‰ to -23.5‰, avg. -25.2 ± 0.9‰), approaching those of the airborne pollen (-28.0‰) collected at the Gosan site. Based on a carbon isotope mass balance equation, we found that ~42% of TC in the TSP samples during the pollen episodes was attributed to airborne pollen from Japanese cedar trees planted around tangerine farms in Jeju Island. A negative correlation between the citric acid-carbon/TC ratios and δ13CTC was obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollen and then transported to the Gosan site. Thermal evolution patterns of organic carbon during the pollen episodes were characterized by high OC evolution in the OC2 temperature step (450 °C). Since thermal evolution patterns of organic aerosols are highly influenced by their molecular weight, they can be used as additional information on the formation of secondary organic aerosols and the effect of aging of organic aerosols during the long-range atmospheric transport and sources of organic aerosols.

  9. Mass-dependent and Mass-independent Sulphur Isotope Fractionation Accompanying Thermal- and Photo-chemical Decomposition of Sulphur Bearing Organic Compounds

    NASA Astrophysics Data System (ADS)

    Oduro, Harry; Izon, Gareth; Ono, Shuhei

    2014-05-01

    The bimodal S-isotope record, specifically the transition from mass independent (MIF) to mass dependent fractionation (MDF), is perhaps the most widely cited line of evidence for an irreversible rise in atmospheric oxygen at ca. 2.4Ga. The production and preservation of S-MIF, manifested in both Δ33S and Δ36S, within the geological record are linked to atmospheric O2 via a number of arguments. However, to date, the only mechanism capable of generating S-MIF consistent with the Archaean sedimentary records involves gas-phase ultraviolet irradiation of SO21 photolysis. More recently, Δ33S S-MIF trends have been reported from en vitro thermochemical sulphate reduction (TSR) experiments, prompting authors to question the importance of S-MIF as a proxy for Earth oxidation2. Importantly, whilst emerging TSR experiments3,4 affirm the reported Δ33S trends2, these experiments fail to identify correlated S-MIF between Δ33S and Δ36S values3,4. Realization that S-MIF is confined to Δ33S during TSR, precludes TSR as a mechanism responsible for the origin of the Archaean S-MIF record but strongly suggests the effect originating from a magnetic isotope effect (MIE) associated with 33S nucleus3,4. Clearly, photochemical and thermochemical processes impart different Δ36S/Δ33S trends with significant variation in δ34S; however, a complete experimental elucidation of mechanisms responsible for the S-MIF and S-MIE signatures is lacking. Interestingly, a complete understanding of the S-isotope chemistry during thermal- and photo-chemical decomposition may reveal wavelength and thermal dependence archived in the sedimentary record. Here we extend the experimental database to explore the magnitude and sign of Δ36S/Δ33S and δ34S produced during both photo- and thermochemical processes. Here the organic sulphur compounds (OSC) utilized in these experiments carries diagnostic Δ36S/Δ33S patterns that differ from those reported from photolysis experiment SO2 and from the

  10. Evaluation of two gas-dilution methods for instrument calibration

    NASA Technical Reports Server (NTRS)

    Evans, A., Jr.

    1977-01-01

    Two gas dilution methods were evaluated for use in the calibration of analytical instruments used in air pollution studies. A dual isotope fluorescence carbon monoxide analyzer was used as the transfer standard. The methods are not new but some modifications are described. The rotary injection gas dilution method was found to be more accurate than the closed loop method. Results by the two methods differed by 5 percent. This could not be accounted for by the random errors in the measurements. The methods avoid the problems associated with pressurized cylinders. Both methods have merit and have found a place in instrument calibration work.

  11. Stress in dilute suspensions

    NASA Technical Reports Server (NTRS)

    Passman, Stephen L.

    1989-01-01

    Generally, two types of theory are used to describe the field equations for suspensions. The so-called postulated equations are based on the kinetic theory of mixtures, which logically should give reasonable equations for solutions. The basis for the use of such theory for suspensions is tenuous, though it at least gives a logical path for mathematical arguments. It has the disadvantage that it leads to a system of equations which is underdetermined, in a sense that can be made precise. On the other hand, the so-called averaging theory starts with a determined system, but the very process of averaging renders the resulting system underdetermined. A third type of theory is proposed in which the kinetic theory of gases is used to motivate continuum equations for the suspended particles. This entails an interpretation of the stress in the particles that is different from the usual one. Classical theory is used to describe the motion of the suspending medium. The result is a determined system for a dilute suspension. Extension of the theory to more concentrated systems is discussed.

  12. Tracing chlorine sources of thermal and mineral springs along and across the Cascade Range using halogen concentrations and chlorine isotope compositions

    NASA Astrophysics Data System (ADS)

    Cullen, Jeffrey T.; Barnes, Jaime D.; Hurwitz, Shaul; Leeman, William P.

    2015-09-01

    In order to provide constraints on the sources of chlorine in spring waters associated with arc volcanism, the major/minor element concentrations and stable isotope compositions of chlorine, oxygen, and hydrogen were measured in 28 thermal and mineral springs along the Cascade Range in northwestern USA. Chloride concentrations in the springs range from 64 to 19,000 mg/L and δ37Cl values range from + 0.2 ‰ to + 1.9 ‰ (average = + 1.0 ± 0.4 ‰), with no systematic variation along or across the arc, nor correlations with their presumed underlying basement lithologies. Additionally, nine geochemically well-characterized lavas from across the Mt. St. Helens/Mt. Adams region of the Cascade Range (Leeman et al., 2004, 2005) were analyzed for their halogen concentrations and Cl isotope compositions. In the arc lavas, Cl and Br concentrations from the volcanic front are higher than in lavas from the forearc and backarc. F and I concentrations progressively decrease from forearc to backarc, similar to the trend documented for B in most arcs. δ37Cl values of the lavas range from -0.1 to + 0.8 ‰ (average = + 0.4 ± 0.3 ‰). Our results suggest that the predominantly positive δ37Cl values observed in the springs are consistent with water interaction with underlying 37Cl-enriched basalt and/or altered oceanic crust, thereby making thermal spring waters a reasonable proxy for the Cl isotope compositions of associated volcanic rocks in the Cascades. However, waters with δ37Cl values > + 1.0 ‰ also suggest additional contributions of chlorine degassed from cooling magmas due to subsurface vapor-liquid HCl fractionation in which Cl is lost to the aqueous fluid phase and 37Cl is concentrated in the ascending magmatic HCl vapor. Future work is necessary to better constrain Cl isotope behavior during volcanic degassing and fluid-rock interaction in order to improve volatile flux estimates through subduction zones.

  13. Quantification of thiazolidine-4-carboxylic acid in toxicant-exposed cells by isotope-dilution liquid chromatography-mass spectrometry reveals an intrinsic antagonistic response to oxidative stress-induced toxicity.

    PubMed

    Liu, Jingjing; Chan, Wan

    2015-03-16

    Carcinogenic formaldehyde is produced by endogenous protein oxidation and various exogenous sources. With formaldehyde being both ubiquitous in the ambient environment and one of the most common reactive carbonyls produced from endogenous metabolism, quantifying formaldehyde exposure is an essential step in risk assessments. We present in this study an approach to assess the risk of exposure to oxidative stress by quantifying thiazolidine-4-carboxylic acid (TA), a cysteine-conjugated metabolite of formaldehyde in toxicant-exposed Escherichia coli. The method entails TA derivatization with ethyl chloroformate, addition of isotope-labeled TA derivatives as internal standards, solid-phase extraction of the derivatives, and quantification by liquid chromatography-mass spectrometry (LC-MS). After validating for accuracy and precision, the developed method was used to detect TA in oxidizing agent-exposed E. coli samples. Dose-dependent TA formation was observed in E. coli exposed to hydroxyl radical mediators Fe(2+)-EDTA, H2O2, and NaOCl, indicating the potential use of TA as a biomarker of exposure to oxidative stress and disease risk. PMID:25325739

  14. Lowering detection limits for 1,2,3-trichloropropane in water using solid phase extraction coupled to purge and trap sample introduction in an isotope dilution GC-MS method.

    PubMed

    Liao, Wenta; Ghabour, Miriam; Draper, William M; Chandrasena, Esala

    2016-09-01

    Purge and trap sample introduction (PTI) has been the premier sampling and preconcentration technique for gas chromatographic determination of volatile organic compounds (VOCs) in drinking water for almost 50 years. PTI affords sub parts-per-billion (ppb) detection limits for purgeable VOCs including fixed gases and higher boiling hydrocarbons and halocarbons. In this study the coupling of solid phase extraction (SPE) to PTI was investigated as a means to substantially increase enrichment and lower detection limits for the emerging contaminant, 1,2,3-trichloropropane (TCP). Water samples (500 mL) were dechlorinated, preserved with a biocide, and spiked with the isotope labeled internal standard, d5-TCP. The entire 500 mL sample was extracted with activated carbon or carbon molecular sieve SPE cartridges, and then eluted with dichloromethane -- excess solvent was removed in a nitrogen evaporator and diethylene glycol "keeper" remaining was dispersed in 5 mL of water for PTI GC-MS analysis. The experimental Method Detection Limit (MDL) for TCP was 0.11 ng/L (ppt) and accuracy was 95-103% in sub-ppt determinations. Groundwater samples including impaired California sources and treated water (n = 21) were analyzed with results ranging from below the method reporting limit (0.30 ng/L) to > 250 ng/L. Coupling of SPE with PTI may provide similar reductions in detection limits for other VOCs with appropriate physical-chemical properties. PMID:27262687

  15. Vibrational and thermal properties of ternary semiconductors and their isotopic dependence: chalcopyrite CuGaS2

    NASA Astrophysics Data System (ADS)

    Romero, Aldo; Cardona, M.; Kremer, R.; Lauck, R.; Muñoz, A.

    2011-03-01

    The availability of ab initio electronic calculations and the concomitant techniques for deriving the corresponding lattice dynamics have been profusely used in the past decade for calculating thermodynamic and vibrational properties of semiconductors, as well as their dependence on isotopic masses. The latter have been compared with experimental data for elemental and binary semiconductors with different isotopic compositions. Here we present theoretical and experimental data for several vibronic and thermodynamic properties of a canonical ternary semiconductor of the chalcopyrite family: CuGaS2. Among these properties are the lattice parameters, the phonon dispersion relations and densities of states (projected on the Cu, Ga, and S constituents), the specific heat and the volume expansion coefficient. The calculations were performed with the ABINIT and VASP codes within the LDA approximation for exchange and correlation. Supported by CONACYT under projects J-59853-F and J-83247-F.

  16. Chemical and isotopic compositions of thermal waters in Anatolia, Turkey: A link to fluid-mineral equilibria

    NASA Astrophysics Data System (ADS)

    Mutlu, Halim; Gülec, Nilgün; Hilton, David R.

    2015-04-01

    The complex magmato-tectonic setting of Turkey has resulted in the occurrence of numerous geothermal fields with distinct chemical and isotopic fluid compositions. We evaluate the data on these fluids in terms of water-rock interaction, mineral equilibrium conditions and reservoir temperatures of each geothermal field. The Ca-HCO3 rich nature of most waters is ascribed to derivation from carbonate-type reservoir rocks. SO4-type waters are found in areas where the reservoir is partly comprised of evaporite units. Na-Cl type waters are characteristic for the coastal areas of west Anatolia. Chemical geothermometer applications estimate average reservoir temperatures of 180 °C for the western Anatolian region, 120 °C for the Balıkesir region, 130 °C for the eastern Anatolian region, 140 °C for the North Anatolian Fault Zone and 70 °C for the Eskişehir region. For most of the waters, chalcedony controls the silica solubility and the majority of waters are equilibrated with calcite and chalcedony minerals. Oxygen and hydrogen isotope compositions (-13.5 to -4 permil (VSMOW) and -95.4 to -23 permil (VSMOW), respectively) are generally conformable with Global Meteoric Water Line (GMWL); however, stable isotope systematics of geothermal waters close to the coast are consistent with the Mediterranean Meteoric Water Line (MMWL). Carbon and sulfur isotope compositions (δ13C (VPDB): -17.7 to +5.6 permil and δ34S (VCDT): -5.5 to +45.7 permil) suggest marine carbonates and terrestrial evaporite units as the main source of dissolved carbon and sulfate in the waters.

  17. Uniform deposition of uranium hexafluoride (UF6): Standardized mass deposits and controlled isotopic ratios using a thermal fluorination method.

    PubMed

    McNamara, Bruce K; O'Hara, Matthew J; Casella, Andrew M; Carter, Jennifer C; Addleman, R Shane; MacFarlan, Paul J

    2016-07-01

    We report a convenient method for the generation of volatile uranium hexafluoride (UF6) from solid uranium oxides and other U compounds, followed by uniform deposition of low levels of UF6 onto sampling coupons. Under laminar flow conditions, UF6 is shown to interact with surfaces within a fixed reactor geometry to a highly predictable degree. We demonstrate the preparation of U deposits that range between approximately 0.01 and 500ngcm(-2). The data suggest the method can be extended to creating depositions at the sub-picogramcm(-2) level. The isotopic composition of the deposits can be customized by selection of the U source materials and we demonstrate a layering technique whereby two U solids, each with a different isotopic composition, are employed to form successive layers of UF6 on a surface. The result is an ultra-thin deposit that bears an isotopic signature that is a composite of the two U sources. The reported deposition method has direct application to the development of unique analytical standards for nuclear safeguards and forensics. Further, the method allows access to very low atomic or molecular coverages of surfaces. PMID:27154668

  18. Thermal history and origin of the Tanzanian Craton from Pb isotope thermochronology of feldspars from lower crustal xenoliths

    NASA Astrophysics Data System (ADS)

    Bellucci, Jeremy J.; McDonough, William F.; Rudnick, Roberta L.

    2011-01-01

    Common and radiogenic Pb isotopic compositions of plagioclase and anti-perthitic feldspars from granulite-facies lower crustal xenoliths from the Labait Volcano on the eastern margin of the Tanzanian Craton have been measured via laser ablation MC-ICP-MS. Common Pb in plagioclase and a single stage Pb evolution model indicate that the lower crust of the Tanzanian Craton was extracted from mantle having a 238U/ 204Pb of 8.1 ± 0.3 and a 232Th/ 238U of 4.3 ± 0.1 at 2.71 ± 0.09 Ga (all uncertainties are 2σ). Since 2.4 Ga, some orthoclase domains within anti-perthites have evolved with a maximum 238U/ 204Pb of 6 and 232Th/ 238U of 4.3. The spread in Pb isotopic composition in the anti-perthitic feldspars yields single crystal Pb-Pb isochrons of ˜ 2.4 Ga, within uncertainty of U-Pb zircon ages from the same sample suite. The Pb isotopic heterogeneities imply that these granulites resided at temperatures < 600 °C in the lower crust of the Tanzanian Craton from ca. 2.4 Ga to the present. In concert with the chemistry of surface samples, mantle xenoliths, and lower crustal xenoliths, our data imply that the cratonic lithosphere in Tanzania formed ca. ˜ 2.7 Ga, in a convergent margin setting, and has remained undisturbed since 2.7 Ga.

  19. Considerations in the Application of Multiple Ion Counting for the Trace Analysis of Plutonium and Uranium Isotope Ratios Using Thermal Ionization and Inductively-Coupled Plasma Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Riciputi, L. R.

    2008-12-01

    The use of simultaneous multiple-ion counting for the analysis of small samples of plutonium and uranium has been investigated using three different instruments, the ThermoElectron Neptune inductively-coupled plasma mass spectrometer, the ThermoElectron Triton thermal ionization mass spectrometer, and the Isotopex Iso-T thermal ionization mass spectrometer. The Neptune and Triton instruments utilize identical multiple ion counter arrays, with ions impinging directly on the channeltron surface. The Isotopex instruments utilize a different style of channeltron detector. The most significant difference in the Isotopex detectors is the presence of a conversion dynode at the entrance to the channeltron. Results suggest that the performance of the ThermoElectron MIC system varies between the Neptune and Triton instruments, which probably reflects both differences in the inherent characteristics of plasma and thermal sources and the performance of the MICS themselves. Differences in performance and stability between the '"naked"' and conversion dynode equipped channeltrons on the two thermal ionization instruments support these observations. These differences suggest that different analytical approaches to calibration of the multiple-ion counters may be required. Differences in potential analytical strategies employing multiple ion counters on the different instruments, including calibration schemes, precision and accuracy limits, and analytical strategies that can be employed, will be discussed. Results from both thermal ionization and inductively-coupled plasma sources suggest that the dominant source of uncertainty in isotope ratio measurement using multiple ion counting shifts from counting limitations for very small signals to uncertainties in gain calibration and detector drift among the ion counters at higher count rates. These characteristics place limits on the applicability of multiple ion counters; results from mixed Faraday/multiple ion counting analysis will

  20. Simultaneous determination of N7-alkylguanines in DNA by isotope-dilution LC-tandem MS coupled with automated solid-phase extraction and its application to a small fish model

    PubMed Central

    Chao, Mu-Rong; Wang, Chien-Jen; Yen, Cheng-Chieh; Yang, Hsi-Hsien; Lu, Yao-Cheng; Chang, Louis W.; Hu, Chiung-Wen

    2006-01-01

    In the present study, we report the development of a sensitive and selective assay based on LC (liquid chromatography)–MS/MS (tandem MS) to simultaneously measure N7-MeG (N7-methylguanine) and N7-EtG (N7-ethylguanine) in DNA hydrolysates. With the use of isotope internal standards (15N5-N7-MeG and 15N5-N7-EtG) and on-line SPE (solid-phase extraction), the detection limit of this method was estimated as 0.42 fmol and 0.17 fmol for N7-MeG and N7-EtG respectively. The high sensitivity achieved here makes this method applicable to small experimental animals. This method was applied to measure N7-alkylguanines in liver DNA from mosquito fish (Gambusia affinis) that were exposed to NDMA (N-nitrosodimethylamine) and NDEA (N-nitrosodiethylamine) alone or their combination over a wide range of concentrations (1–100 mg/l). Results showed that the background level of N7-MeG in liver of control fish was 7.89±1.38 μmol/mol of guanine, while N7-EtG was detectable in most of the control fish with a range of 0.05–0.19 μmol/mol of guanine. N7-MeG and N7-EtG were significantly induced by NDMA and NDEA respectively, at a concentration as low as 1 mg/l and increased in a dose-dependent manner. Taken together, this LC-MS/MS assay provides the sensitivity and high throughput required to evaluate the extent of alkylated DNA lesions in small animal models of cancer induced by alkylating agents. PMID:17134374

  1. A new series of uranium isotope reference materials for investigating the linearity of secondary electron multipliers in isotope mass spectrometry

    NASA Astrophysics Data System (ADS)

    Richter, S.; Alonso, A.; Aregbe, Y.; Eykens, R.; Kehoe, F.; Kühn, He; Kivel, N.; Verbruggen, A.; Wellum, R.; Taylor, P. D. P.

    2009-04-01

    A new series of gravimetrically prepared uranium isotope reference materials, the so-called IRMM-074 series, with the n(235U)/n(238U) isotope ratio held constant at unity and the n(233U)/n(238U) isotope ratios varying from 1.0 to 10-6 has been prepared and certified. This series is suited for calibration of secondary electron multipliers used widely in isotope mass spectrometry, in particular for techniques such as thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICPMS), accelerator mass spectrometry (AMS) and resonance ionization mass spectrometry (RIMS). The new IRMM-074 was prepared as a replacement for the already exhausted IRMM-072 predecessor series. Uranium materials with high isotopic enrichments of 233U, 235U and 238U were purified using identical methods involving separation on anion and cation column followed by a precipitation as peroxide. The oxides were calcined to convert them to U3O8 simultaneously, in an oven installed in a glove-box that provided a controlled low-humidity environment. The oxides of 235U and 238U were weighed and mixed with a mole ratio n(235U)/n(238U) = 1.0 and then dissolved. The 233U oxide was dissolved to form a separate solution with the same concentration and 6rom this primary solution three dilutions were made by weighing. A weighed amount of the n(235U)/n(238U) solution and weighed amounts of the 233U solutions were mixed in various proportions in order to achieve n(233U)/n(238U) isotope ratios varying from 1.0 to 10-6. The methods for the preparation, the mixing and the mixing calculations are described. The expanded uncertainties (coverage factor k = 2) of the certified isotope ratios for the IRMM-074 series are 0.015% for the n(235U)/n(238U) ratio and 0.025% for the n(233U)/n(238U) ratios, which constitutes an improvement compared to those of the predecessor IRMM-072 series. In addition, recent observations regarding the linearity response of secondary electron multipliers (SEMs

  2. Dilution physics modeling: Dissolution/precipitation chemistry

    SciTech Connect

    Onishi, Y.; Reid, H.C.; Trent, D.S.

    1995-09-01

    This report documents progress made to date on integrating dilution/precipitation chemistry and new physical models into the TEMPEST thermal-hydraulics computer code. Implementation of dissolution/precipitation chemistry models is necessary for predicting nonhomogeneous, time-dependent, physical/chemical behavior of tank wastes with and without a variety of possible engineered remediation and mitigation activities. Such behavior includes chemical reactions, gas retention, solids resuspension, solids dissolution and generation, solids settling/rising, and convective motion of physical and chemical species. Thus this model development is important from the standpoint of predicting the consequences of various engineered activities, such as mitigation by dilution, retrieval, or pretreatment, that can affect safe operations. The integration of a dissolution/precipitation chemistry module allows the various phase species concentrations to enter into the physical calculations that affect the TEMPEST hydrodynamic flow calculations. The yield strength model of non-Newtonian sludge correlates yield to a power function of solids concentration. Likewise, shear stress is concentration-dependent, and the dissolution/precipitation chemistry calculations develop the species concentration evolution that produces fluid flow resistance changes. Dilution of waste with pure water, molar concentrations of sodium hydroxide, and other chemical streams can be analyzed for the reactive species changes and hydrodynamic flow characteristics.

  3. THE ANISOTROPIC TRANSPORT EFFECTS ON DILUTE PLASMAS

    SciTech Connect

    Devlen, Ebru

    2011-04-20

    We examine the linear stability analysis of a hot, dilute, and differentially rotating plasma by considering anisotropic transport effects. In dilute plasmas, the ion Larmor radius is small compared with its collisional mean free path. In this case, the transport of heat and momentum along the magnetic field lines becomes important. This paper presents a novel linear instability that may be more powerful and greater than ideal magnetothermal instability and ideal magnetorotational instability in the dilute astrophysical plasmas. This type of plasma is believed to be found in the intracluster medium (ICM) of galaxy clusters and radiatively ineffective accretion flows around black holes. We derive the dispersion relation of this instability and obtain the instability condition. There is at least one unstable mode that is independent of the temperature gradient direction for a helical magnetic field geometry. This novel instability is driven by the gyroviscosity coupled with differential rotation. Therefore, we call it gyroviscous-modified magnetorotational instability (GvMRI). We examine how the instability depends on signs of the temperature gradient and the gyroviscosity and also on the magnitude of the thermal frequency and on the values of the pitch angle. We provide a detailed physical interpretation of the obtained results. The GvMRI is applicable not only to the accretion flows and ICM but also to the transition region between cool dense gas and the hot low-density plasma in stellar coronae, accretion disks, and the multiphase interstellar medium because it is independent of the temperature gradient direction.

  4. Structure of the carbon isotope excursion in a high-resolution lacustrine Paleocene-Eocene Thermal Maximum record from central China

    NASA Astrophysics Data System (ADS)

    Chen, Zuoling; Wang, Xu; Hu, Jianfang; Yang, Shiling; Zhu, Min; Dong, Xinxin; Tang, Zihua; Peng, Ping'an; Ding, Zhongli

    2014-12-01

    The carbon isotope excursion (CIE) associated with the Paleocene-Eocene Thermal Maximum (PETM) has been recognized for the first time in the micritic carbonate, total organic carbon (TOC) and black carbon (BC) contained within the lacustrine sediments from the Nanyang Basin, central China. The remarkably large excursion (∼ - 6 ‰) in the δ13CTOC and δ13CBC values is possibly attributable to increased humidity and elevated pCO2 concentration. The ∼ - 4 ‰ CIE recorded in the δ13Ccalcite, reflecting the average isotope change of the watershed system, is consistent with that observed in planktonic foraminifera. This correspondence suggests that the true magnitude of the carbon isotope excursion in the ocean-atmosphere system is likely close to - 4 ‰. The ∼10 m excursion onset in our multi-proxy δ13C records demonstrates that the large input of 13C-depleted carbon into the ocean-atmosphere system was not geologically instantaneous. Despite difference and somewhat smoothness in detailed pattern of the CIE due to localized controls on different substrates, inorganic and organic δ13C data generally depict a gradual excursion onset at least over timescales of thousands of years. In addition, continental temperature reconstruction, based on the distribution of membrane lipids of bacteria, suggests a warming of ∼4 °C prior to the PETM and ∼7 °C increase in temperature during the PETM. The temperature data are overall similar in pattern and trend to the δ13C change across the PETM. These observations, combined with pre-CIE warming, are in line with the idea that 13C-depleted carbon release operated as a positive feedback to temperature, suggesting supply from one or more large organic carbon reservoirs on Earth's surface.

  5. Geothermal reservoir temperatures estimated from the oxygen isotope compositions of dissolved sulfate and water from hot springs and shallow drillholes

    USGS Publications Warehouse

    McKenzie, W.F.; Truesdell, A.H.

    1977-01-01

    The oxygen isotope compositions of dissolved sulfate and water from hot springs and shallow drillholes have been tested as a geothermometer in three areas of the western United States. Limited analyses of spring and borehole fluids and existing experimental rate studies suggest that dissolved sulfate and water are probably in isotopic equilibrium in all reservoirs of significant size with temperatures above ca. 140??C and that little re-equilibration occurs during ascent to the surface. The geothermometer is, however, affected by changes in ??18O of water due to subsurface boiling and dilution and by addition of sulfate of nearsurface origin. Methods are described to calculate the effects of boiling and dilution. The geothermometer, is applied to thermal systems of Yellowstone Park, Wyoming, Long Valley, California, and Raft River, Idaho to estimate deep reservoir temperatures of 360, 240, and 142??C, respectively. ?? 1976.

  6. Determination of femtogram quantities of protactinium in geologic samples by thermal ionization mass spectrometry

    SciTech Connect

    Pickett, D.A.; Murrell, M.T.; Williams, R.W. )

    1994-04-01

    We describe a procedure for measurement of [sup 231]Pa in geologic samples by isotope dilution thermal ionization mass spectrometry, using [sup 233]Pa as a spike isotope, which provides marked improvements in precision and sample size relative to established decay counting techniques. This method allows determination of as little as a few tens of femtograms of [sup 231]Pa (approximately 10[sup 3] atoms) with a conservative estimated uncertainty of [+-]1% (95% confidence level). Applications of [sup 231]Pa-[sup 235]U systematics to uranium-series geochemistry and geochronology should be greatly enhanced by this approach. 31 refs., 4 figs., 1 tab.

  7. Dilution refrigeration for space applications

    NASA Technical Reports Server (NTRS)

    Israelsson, U. E.; Petrac, D.

    1990-01-01

    Dilution refrigerators are presently used routinely in ground based applications where temperatures below 0.3 K are required. The operation of a conventional dilution refrigerator depends critically on the presence of gravity. To operate a dilution refrigerator in space many technical difficulties must be overcome. Some of the anticipated difficulties are identified in this paper and possible solutions are described. A single cycle refrigerator is described conceptually that uses forces other than gravity to function and the stringent constraints imposed on the design by requiring the refrigerator to function on the earth without using gravity are elaborated upon.

  8. Geothermal investigations in Idaho. Part 12. Stable isotopic evaluation of thermal water occurrences in the Weiser and Little Salmon River drainage basins and adjacent areas, west-central Idaho with attendant gravity and magnetic data on the Weiser area

    SciTech Connect

    Mitchell, J.C.; Bideganeta, K.; Palmer, M.A.

    1984-12-01

    Fifteen thermal springs, two thermal wells, and eight cold springs in the Weiser and Little Salmon river drainages were sampled for deuterium and oxygen-18 analysis during the fall of 1981. The straight-line fit of delta D and delta /sup 18/O versus latitude and longitude observed in the data is what would be expected if the recharge areas for the thermal and non-thermal waters were in close proximity to their respective discharge points. The discrete values of delta D and delta /sup 18/O for each thermal discharge suggest that none of the sampled thermal systems have common sources. The depleted deuterium and oxygen-18 contents of most thermal relative to non-thermal waters sampled suggests that the thermal waters might be Pleistocene age precipitation. The isotopic data suggest little or no evidence for mixing of thermal and non-thermal water for the sampled discharges. Thermal waters from Weiser, Crane Creek, Cove Creek, and White Licks hot springs show enrichment in oxygen-18 suggesting that these waters have been at elevated temperatures relative to other sampled thermal discharges in the area. Gravity and magnetic data gathered by the Idaho State University Geology Department in the Weiser Hot Springs area suggest that southeastward plunging synclinal-anticlinal couples, which underlie the hot springs, are cut south of the springs by a northeast trending boundary fault.

  9. Uranium-lead Isotope Evidence in the Shelyabinsk LL5 Chondrite Meteorite for Ancient and Recent Thermal Events

    NASA Technical Reports Server (NTRS)

    Lapen, T. J.; Kring, D. A.; Zolensky, M. E.; Andreasen, R.; Righter, M.; Swindle, T. D.; Beard, S. P.; Swindle, T. D.

    2014-01-01

    The impact histories on chondrite parent bodies can be deduced from thermochronologic analyses of materials and isotope systems with distinct apparent closure temperatures. It is especially critical to better understand the geological histories and physical properties of potenally hazardous near-Earth asteroids. Chelyabinsk is an LL5 chondrite meteorite that was dispersed over a wide area tens of kilometers south of the town of Chelyabinsk, Russia by an explosion at an altitude of 27 km at 3:22 UT on 15 Feb 2013 [1,2]. The explosion resulted in significant damage to surrounding areas and over 1500 injuries along with meteorite fragments being spread over a wide area [1].

  10. Determination of the concentration and isotopic composition of uranium in environmental air filters

    SciTech Connect

    Russ, G.P. III; Bazan, J.M.

    1994-08-26

    For many years, Lawrence Livermore National Laboratory has collected monthly air-particulate filter samples from a variety of environmental monitoring stations on and off site. Historically the concentration and isotopic composition of uranium collected on these filters was determined by isotope dilution using a {sup 233}U spike and thermal ionization mass spectrometry (TIMS). For samples containing as little as 10 nanograms of uranium, ICP-MS is now used to make these measurements to the required level of precision, about 5% in the measured 235/238 and 233/238. Unless particular care is taken to control bias in the mass filter, variable mass bias limits accuracy to a few percent. Measurements of the minor isotopes 236 (if present) and 234 are also possible and provide useful information for identifying the source of the uranium. The advantage of ICP-MS is in rapid analysis, {approximately}12 minutes of instrument time per sample.

  11. Method for ultra-trace cesium isotope ratio measurements from environmental samples using thermal ionization mass spectrometry

    SciTech Connect

    Snow, Mathew S.; Snyder, Darin C.; Mann, Nick R.; White, Byron M.

    2015-05-01

    135Cs/137Cs isotope ratios can provide the age, origin and history of environmental Cs contamination. Relatively high precision 135Cs/137Cs isotope ratio measurements from samples containing femtogram quantities of 137Cs are needed to accurately track contamination resuspension and redistribution following environmental 137Cs releases; however, mass spectrometric analyses of environmental samples are limited by the large quantities of ionization inhibitors and isobaric interferences which are present at relatively high concentrations in the environment. We report a new approach for Cs purification from environmental samples. An initial ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) column provides a robust method for extracting Cs under a wide variety of sample matrices and mass loads. Cation exchange separations using a second AMP-PAN column result in more than two orders of magnitude greater Cs/Rb separation factors than commercially available strong cation exchangers. Coupling an AMP-PAN cation exchanging step to a microcation column (AG50W resin) enables consistent 2-4% (2σ) measurement e