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1

Isotope dilution mass spectrometry  

NASA Astrophysics Data System (ADS)

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 iodine, selenium and some heavy metals in aquatic systems.

Heumann, Klaus G.

1992-09-01

2

An algorithm for U-Pb isotope dilution data reduction and uncertainty propagation  

E-print Network

High-precision U-Pb geochronology by isotope dilution-thermal ionization mass spectrometry is integral to a variety of Earth science disciplines, but its ultimate resolving power is quantified by the uncertainties of ...

McLean, Noah Morgan

3

Isotopic dilution and solvent effect studies using raman difference spectroscopy  

E-print Network

ISOTOPIC DILUTION AND SOLVENT EFFECT STUDIES USING RAMAN DIFFERENCE SPECTROSCOPY A Thesis by ANDREW NORMAN JOHNSON Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE August 1984 Major Subject: Chemistry ISOTOPIC DILUTION AND SOLVENT EFFECT STUDIES USING RAMAN DIFFERENCE SPECTROSCOPY A Thesis by ANDREW NORMAN JOHNSON Approved as to style and content by: Jaan Laane (Chairman of Committee) J. . Bevan...

Johnson, Andrew Norman

2012-06-07

4

Further development of IDGS: Isotope dilution gamma-ray spectrometry  

NASA Astrophysics Data System (ADS)

The isotope dilution gamma-ray spectrometry (IDGS) technique for determining the plutonium concentration and isotopic composition of highly radioactive spent-fuel dissolver solutions has been further developed. Both the sample preparation and the analysis have been improved. The plutonium isotopic analysis is based on high-resolution, low-energy gamma-ray spectrometry. The plutonium concentration in the dissolver solutions then is calculated from the measured isotopic differences among the spike, the dissolver solution, and the spiked dissolver solution. Plutonium concentrations and isotopic compositions of dissolver solutions analyzed from this study agree well with those obtained by traditional isotope dilution mass spectrometry (IDMS) and are consistent with the first IDGS experimental result. With the current detector efficiency, sample size, and a 100-min count time, the estimated precision is approximately 0.5 percent for Pu-239 and Pu-240 isotopic analyses and approximately 1 percent for the plutonium concentration analysis.

Li, T. K.; Parker, J. L.; Kuno, Y.; Sato, S.; Kamata, M.; Akiyama, T.

5

DETERMINATION OF BORON TRACES BY MASS SPECTROMETRIC ISOTOPIC DILUTION  

Microsoft Academic Search

Traces of boron contained in some acids and reagents, as well as in some ; soft steels, were determined by isotopic dilution with B¹°. The boron is ; extracted in the form of methyl borate, saponified, and analyzed in the form of ; borax. Concentrations of 150 to 0.0005 mu g were measured with a precision of ; 10 to

M. Perie; M. Chemla

1962-01-01

6

How to correct for blanks in isotope dilution mass spectrometry  

NASA Astrophysics Data System (ADS)

A general equation for isotope delution mass spectrometry (IDMS) has been developed which considers the correction for blanks from labware and reagents used to dissolve, purify and transform samples in a form suitable for (thermal ionization) mass spectrometric measurement. The equation takes into account that sample, spike and blank may have three diffirent isotopic compositions. It is further shown that the isotopic composition of non-natural unknown samples must be determined independently on a sample of known chemical concentration, or, if this is not possible, on an aliquot of the unknown sample to be determined by IDMS.

Lamberty, A.; Pauwels, J.

1991-01-01

7

Isotopic Fractionation and Dilution of CO on Titan  

NASA Astrophysics Data System (ADS)

There are theoretical and observational reasons for believing that the atmosphere of Titan has evolved extensively. We expect the heavy isotopomers of CO, 13CO and C18O, to be enriched relative to CO. However, the isotopic signature resulting from atmospheric evolution may be altered by photochemical reactions in the atmosphere of Titan. We investigate the possibility of isotopic fractionation and dilution using the Caltech/JPL one-dimensional kinetics model of Titan. In the upper atmosphere of Titan there are energetic processes initiated by solar EUV radiation, precipitation of magnetospheric particles and photoelectrons. As a result of the interaction with the energetic particles, CO is readily dissociated into C and O. Some of the energetic C and O can escape to space. The fates of C and O in CO that remain in the atmosphere are quite different with respect to exchange with other reservoirs. The most important reaction for O is insertion into CH3 and C2H4 to form H2CO, but all eventually recycle back to CO. The C atom in the reformed CO comes from CH3 and C2H4, which in turn are derived from CH4 photolysis. However, the most rapid exchange for C atoms between the CH4 and CO reservoirs is mediated by the exchange reaction 1CH2 + C*O -> 1C*H2 + CO, where C* is an isotopically heavy carbon atom. Based on recent laboratory measurements, we estimate the rate coefficient for this reaction to be 2.3 x 10-11 cm3 s-1 at the temperature appropriate for the upper atmosphere of Titan. The time constants for the isotopic exchange processes will be estimated by our model.

Wong, A. S.; Morgan, C. G.; Yung, Y. L.; Owen, T.

2000-10-01

8

Oxygen and hydrogen isotopes in thermal waters at Zunil, Guatemala  

SciTech Connect

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.

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

1982-10-01

9

Quality criteria for the isotope dilution method with HRGC\\/MS  

Microsoft Academic Search

The isotope dilution method is characterized by the use of appropiately labelled standard compounds in conjunction with mass spectrometry coupled to chromatographic systems. Although the isotope dilution method seems to be a simple procedure, some quality criteria for sample preparation, measurement and quantification have to be considered. Furthermore, archiving and documentation of analysis data as well as the use of

B. Henkelmann; K.-W. Schramm; C. Klimm; A. Kettrup

1996-01-01

10

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

11

Quantitation of DNA adducts by stable isotope dilution mass spectrometry  

PubMed Central

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

Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

2012-01-01

12

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

ERIC Educational Resources Information Center

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)

Hill, Devon W.; And Others

1988-01-01

13

Characterizing uranium oxide reference particles for isotopic abundances and uranium mass by single particle isotope dilution mass spectrometry.  

PubMed

Uranium and plutonium particulate test materials are becoming increasingly important as the reliability of measurement results has to be demonstrated to regulatory bodies responsible for maintaining effective nuclear safeguards. In order to address this issue, the Institute for Reference Materials and Measurements (IRMM) in collaboration with the Institute for Transuranium Elements (ITU) has initiated a study to investigate the feasibility of preparing and characterizing a uranium particle reference material for nuclear safeguards, which is finally certified for isotopic abundances and for the uranium mass per particle. Such control particles are specifically required to evaluate responses of instruments based on mass spectrometric detection (e.g. SIMS, TIMS, LA-ICPMS) and to help ensuring the reliability and comparability of measurement results worldwide. In this paper, a methodology is described which allows quantifying the uranium mass in single micron particles by isotope dilution thermal ionization mass spectrometry (ID-TIMS). This methodology is characterized by substantial improvements recently achieved at IRMM in terms of sensitivity and measurement accuracy in the field of uranium particle analysis by TIMS. The use of monodisperse uranium oxide particles prepared using an aerosol generation technique developed at ITU, which is capable of producing particles of well-characterized size and isotopic composition was exploited. The evidence of a straightforward correlation between the particle volume and the mass of uranium was demonstrated in this study. Experimental results have shown that the uranium mass per particle can be measured via the ID-TIMS method to a relative expanded uncertainty of about 10% (coverage factor k=2). The availability of reliable and validated methods for the characterization of uranium particles is considered to be essential for the establishment of SI-traceable measurement results. It is therefore expected that the method developed in this study is valuable for the certification of particulate materials in which the isotopic composition and the content of uranium must be accurately known. PMID:23021805

Kraiem, M; Richter, S; Erdmann, N; Khn, H; Hedberg, M; Aregbe, Y

2012-10-20

14

Determination of plutonium isotopes in seawater reference materials using isotope-dilution ICP-MS.  

PubMed

We analyzed the activities of (239)Pu, (240)Pu, (239+240)Pu, (241)Pu, the ratio of number of atoms (atom ratio) for (240)Pu/(239)Pu, and the activity ratio of (241)Pu/(239+240)Pu in seawater reference materials, IAEA-443 and IAEA-381, using a highly sensitive isotope dilution sector field inductively coupled plasma mass spectrometry method. With a mean chemical yield of 65% determined with (242)Pu as a tracer, we found that the experimentally established values in IAEA-443 for (239)Pu, (240)Pu, (241)Pu and (239+240)Pu activities are almost the same as those in IAEA-381. Regarding the (239+240)Pu activity, we provided the most precise and accurate result among the twelve laboratories, which participated in the interlaboratory comparison. In addition, for the (240)Pu/(239)Pu atom ratio, our results for IAEA-381 (0.23150.0008) and IAEA-443 (0.23250.0008) are in good agreement with the IAEA information value (0.2290.006), but have much smaller uncertainty. Since the new seawater reference material, IAEA-443, is commercially available, it can be used not only for method validation for seawater plutonium isotope ratio and activity analysis, but also for more general use as a plutonium isotope standard for mass discrimination correction for other environmental samples. PMID:22386661

Zheng, Jian; Yamada, Masatoshi

2012-09-01

15

Isotopic dilution of {sup 233}U with depleted uranium for criticality safety in processing and disposal  

SciTech Connect

The disposal of excess {sup 233}U as waste is being considered. Because {sup 233}U is a fissile material, a key requirement for processing {sup 233}U to a final waste form and disposing of it is the avoidance of nuclear criticality. For many processing and disposal options, isotopic dilution is the most feasible and preferred option to avoid nuclear criticality. Isotopic dilution is dilution of fissile {sup 233}U with nonfissile {sup 238}U. The use of isotopic dilution removes any need to control nuclear criticality in process or disposal facilities through geometry or chemical composition. Isotopic dilution allows the use of existing waste management facilities that are not designed for significant quantities of fissile materials to be used for processing and disposing of {sup 233}U. The amount of isotopic dilution required to reduce criticality concerns to reasonable levels was determined in this study to be approximately 0.53 wt % {sup 233}U. The numerical calculations used to define this limit consisted of a homogeneous system of silicon dioxide (SiO{sub 2}), water (H{sub 2}O), {sup 233}U and depleted uranium (DU) in which the ratio of each component was varied to learn the conditions of maximum nuclear reactivity. About 188 parts of DU (0.2 wt % {sup 235}U) are required to dilute 1 part of {sup 233}U to this limit in a water-moderated system with no SiO{sub 2} present. Thus for the U.S. inventory of {sup 233}U, several hundred metric tons of DU would be required for isotopic dilution.

Hopper, C.M.; Wright, R.Q.; Elam, K.R.; Forsberg, C.W.

1997-07-01

16

Thermal conductivity and sound attenuation in dilute atomic Fermi gases  

SciTech Connect

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.

Braby, Matt; Chao Jingyi; Schaefer, Thomas [Physics Department, North Carolina State University, Raleigh, North Carolina 27695 (United States)

2010-09-15

17

Thermally induced rotons in two-dimensional dilute Bose gases  

SciTech Connect

We show that rotonlike excitations are thermally induced in a two-dimensional dilute Bose gas as a consequence of the strong phase fluctuations in two dimensions. At low momentum, the rotonlike excitations lead for small enough temperatures to an anomalous phonon spectrum with a temperature-dependent exponent reminiscent of the Kosterlitz-Thouless transition. Despite the anomalous form of the energy spectrum, it is shown that the corresponding effective theory of vortices describes the usual Kosterlitz-Thouless transition. The possible existence of an anomalous normal state in a small temperature interval is also discussed.

Nogueira, Flavio S.; Kleinert, Hagen [Institut fuer Theoretische Physik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin (Germany)

2006-03-01

18

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

USGS Publications Warehouse

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.

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

1987-01-01

19

Describing chemical transformations in multiple spiking isotope dilution: fundamental aspects and definitions.  

PubMed

Currently, several mathematical methods exist to address simultaneous species formation and degradation using multiple spiking isotope dilution mass spectrometry. While all of these strategies have been compared numerically, comparison of the underlying principles is lacking. Owing to recent interest in using the species inter-conversion factors, mainly to study the quality of analytical methods, this manuscript reviews the mathematical logic and inconsistencies of the existing double or triple spiking isotope dilution models. Systematic terminology is also introduced to clarify the species inter-conversion coefficient definitions. PMID:19238281

Meija, Juris; Ouerdane, Laurent; Mester, Zoltn

2009-03-01

20

On the capabilities of isotope dilution alpha spectrometry in the determination of plutonium concentration  

NASA Astrophysics Data System (ADS)

The determination of plutonium in spent fuel solution by isotope dilution alpha spectrometry (IDAS) is described. Two aliquots of spent fuel solution were separately spiked with well characterized solutions of 238Pu and 239Pu. The pure spiked and unspiked plutonium solutions were obtained using a partition chromatographic technique. The alpha activity ratios of {238Pu}/{(239Pu+240Pu)} have been measured by alpha spectrometry and the concentration of plutonium calculated using isotopic composition data from mass spectrometry measurements. In parallel, the plutonium concentration was also determined by isotope dilution mass spectrometry (IDMS). The main aim of this experiment was to show the capability of IDAS compared to IDMS. Therefore the factors affecting the precision and accuracy of the IDAS method are discussed in detail. Also the outline of IDAS based exclusively on radiometric measurements (isotopic composition of plutonium by gamma spectrometry) is presented and its capabilities discussed.

Parus, J.; Raab, W.; Swietly, H.; Cappis, J.; Deron, S.

1992-02-01

21

Determination of boron in nuclear materials by isotope dilution technique. Part I  

Microsoft Academic Search

Summary The application of the mass-spectrometric stable-isotope dilution technique for the determination of microgram and submicrogram quantities of boron in nuclear materials is described. An adequate amount of spike solution (enriched in10B) is added to the sample and the mixture is treated chemically to ensure isotopic equilibration. Boron is then separated as methyl borate by distillation from phosphoric acid and

J. Marsel; D. Milivojevi?

1971-01-01

22

Candidate processes for diluting the {sup 235}U isotope in weapons-capable highly enriched uranium  

SciTech Connect

The United States Department of Energy (DOE) is evaluating options for rendering its surplus inventories of highly enriched uranium (HEU) incapable of being used to produce nuclear weapons. Weapons-capable HEU was earlier produced by enriching uranium in the fissile {sup 235}U isotope from its natural occurring 0.71 percent isotopic concentration to at least 20 percent isotopic concentration. Now, by diluting its concentration of the fissile {sup 235}U isotope in a uranium blending process, the weapons capability of HEU can be eliminated in a manner that is reversible only through isotope enrichment, and therefore, highly resistant to proliferation. To the extent that can be economically and technically justified, the down-blended uranium product will be made suitable for use as commercial reactor fuel. Such down-blended uranium product can also be disposed of as waste if chemical or isotopic impurities preclude its use as reactor fuel.

Snider, J.D.

1996-02-01

23

Natural variability of coral Cd\\/Ca using a novel isotope dilution ICP-MS method  

Microsoft Academic Search

Here we present a new method for the rapid and precise determination of Cd\\/Ca in coral skeleton using inductively coupled mass spectrometry (ICP-MS). This ratio has been shown to be a promising proxy for oceanic upwelling. This method uses isotope dilution for Cd determination and gravimetric standards with internal standardization for Ca determination. In addition, an ion exchange resin is

K. A. Matthews; W. F. McDonough; A. G. Grottoli

2005-01-01

24

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

NASA Astrophysics Data System (ADS)

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.

Boulyga, Sergei F.; Heumann, Klaus G.

2005-04-01

25

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

PubMed

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

Ren, Yao; Walczyk, Thomas

2014-09-01

26

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

SciTech Connect

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.

Fassett, J.D.; Murphy, T.J. (National Institute of Standards and Technology, Gaithersburg, MD (USA))

1990-02-15

27

Cadmium fixation in soils measured by isotopic dilution  

SciTech Connect

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.

Smolders, E.; Brans, K.; Foeldi, A.; Merckx, R. [K.U. Leuven, Heverlee (Belgium). Lab. of Soil Fertility and Soil Biology

1999-01-01

28

Determination of iodide amounts in urine and water by isotope dilution analysis  

Microsoft Academic Search

Urinary iodide and iodine in drinking water were determined in 318 healthy children aged 0 to 18 yr living in Izmir and environmental\\u000a rural and urban areas in the western part of Turkey. The method is based on substochiometric isotope dilution analysis. Iodide\\u000a was precipitated by substoichiometric amounts of AgNO3. Iodide-131 was used as a tracer. Electrophoresis was performed to

P. Unak; ?. Darcan; F. Yurt; Z. Biber; M. oker

1999-01-01

29

Quantification of Pantothenic Acid and Folates by Stable Isotope Dilution Assays  

Microsoft Academic Search

Stable isotope dilution assays for the quantification of pantothenic acid and folates in foods by using four-fold labeled isotopomers of the vitamins as internal standards (IS) were developed. The use of labeled IS enabled to exactly correct losses during cleanup and derivatization.Pantothenic acid and its labeled isotopomer were detected as trimethylsilyl derivatives by gas chromatographymass spectrometry. In starch a detection

Michael Rychlik; Achim Freisleben

2002-01-01

30

Evidence for dilution of deep, confined ground water by vertical recharge of isotopically heavy Pleistocene water  

Microsoft Academic Search

New analyses of the isotopic composition of water, 14-dating of dissolved inorganic carbon, and order-of-magnitude Darcy calculations suggest that a dilute body of water, trending north-south in the Cambrian-Ordovician aquifer of Iowa, was emplaced as vertical recharge of Pleistocene-age water from the base of the Des Moines lobe of late Wisconsin time. The recharge occurred through more than 300 m

D. I. Siegel

1991-01-01

31

Quantification of Orotic Acid in Dried Filter-Paper Urine Samples by Stable Isotope Dilution  

Microsoft Academic Search

A rapid, sensitive, and specific method for quantification of orotic acid from dried filter-paper urine samples is described. The method involves stable isotope dilution with 1,3-(15N2)orotic acid and analysis by gas chroma- tography-mass spectrometry. The assay is sufficiently sensitive to be used with solvent extraction techniques commonly used for urinary organic acid analysis. Extrac- tion efficiencies of both native and

Mark T. McCann; Mark M. Thompson; Joni C. Gueron; Mendel Tuchman

32

Determination of total chromium in seawater by isotope dilution sector field ICPMS using GC sample introduction  

Microsoft Academic Search

A method for the accurate determination of total Cr in seawater by isotope dilution (ID) sector field inductively coupled plasma mass spectrometry (SF-ICPMS) using GC as a means of sample introduction is described. Chromium was reduced to CrIII by addition of SO2-saturated water and derivatized with trifluoroacetylacetonate (TFA) to form volatile Cr(TFA) 3. Derivatized analyte was either extracted into hexane

L. a Yang; Zoltn Mester; Laszlo Abranko; Ralph E. Sturgeon

2004-01-01

33

Analysis of acrylamide in coffee and cocoa by isotope dilution liquid chromatographytandem mass spectrometry  

Microsoft Academic Search

An accurate and precise method for the quantification of acrylamide using stable isotope dilution liquid chromatographytandem\\u000a mass spectrometry was developed and used to measure acrylamide in coffee and cocoa samples. The sample preparation involved\\u000a 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\\u000a aqueous

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

2006-01-01

34

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

PubMed Central

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 ?g 1?1 for liquid infant formula and 0.95 ?g 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

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

2011-01-01

35

A stable isotope dilution method for measuring bioavailability of organic contaminants  

PubMed Central

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 3882% for pyrene and 2859% 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

Delgado-Moreno, Laura; Gan, Jay

2014-01-01

36

Automated isotope dilution liquid chromatography-tandem mass spectrometry with on-line dilution and solid phase extraction for the measurement of cortisol in human serum sample.  

PubMed

A candidate reference measurement procedure involving automated isotope dilution coupled with liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) with on-line dilution and solid phase extraction (SPE) has been developed and critically evaluated. We constructed the LC-MS/MS with on-line dilution and SPE system. An isotopically labelled internal standard, cortisol-d4, was added to serum sample. After equilibration, the methanol was added to the sample, and deproteination was performed. Then, the sample was applied to the LC-MS/MS system. The limit of detection (LOD) and limit of quantification (LOQ) were 0.2 and 1ngg(-1), respectively. Excellent precision was obtained with within-day variation (RSD) of 1.9% for ID-LC-MS/MS analysis (n=6). This method, which demonstrates simple, easy, good accuracy, high precision, and is free from interferences from structural analogues, qualifies as a reference measurement procedure. PMID:24769301

Kawaguchi, Migaku; Eyama, Sakae; Takatsu, Akiko

2014-08-01

37

Apparatus for Isotope Separation by Thermal Diffusion  

Microsoft Academic Search

A compact, all-metal, multi-stage thermal diffusion apparatus for the separation of isotopes in quantity in non-corrosive gases at any pressure up to 175 lb\\/in.2 is described. For a particular gas the proper pressure may be well-enough calculated in advance as that giving maximum separation factor in the last column only. Operating with neon at 3 atmos. pressure, and using 12

W. W. Watson; L. Onsager; A. Zucker

1949-01-01

38

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

SciTech Connect

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.

Furr, H.C.; Cooper, D.A.; Olson, J.A. (Iowa State Univ., Ames (United States))

1990-02-26

39

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

PubMed

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

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

2014-07-15

40

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

NASA Astrophysics Data System (ADS)

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.

Horj, Elena; Iordache, Andreea; Culea, Monica

2011-10-01

41

CBNM certification of Cd in polyethylene by isotope dilution mass spectrometry  

NASA Astrophysics Data System (ADS)

Four polyethylene materials have been certified for their cadmium content by isotope dilution mass spectrometry. To do so, a spike (enriched 111Cd) was characterized by reverse IDMS using high purity cadmium metal. The cadmium concentration certified in the polyethylene is 0.363, 0.676, 1.760 and 3.62 mmol kg-1 respectively (40.9, 75.9 197.9 and 407 mg kg-1 respectively). These certified materials can be used in calibrating routine methods and measurements.

Gtz, A.; Lamberty, A.; de Bivre, P.

1993-01-01

42

Towards compound-independent calibration for organic compounds using online isotope dilution mass spectrometry.  

PubMed

Isotope dilution mass spectrometry (IDMS) can be considered a primary measurement method directly traceable to the International System of Units (SI). This measurement technique is increasingly employed in routine laboratories, owing to its unequalled analytical performance, precision and ease of accreditation. Unfortunately, for the adequate application of IDMS, several isotopically labelled standards, corresponding to the compounds of interest, are required. Additionally, when the enriched isotope is continuously added after a chromatographic separation, and an elemental ion source is used, it allows quantification of the different analytes being eluted from the column without requiring specific standards for each compound (online IDMS). In this article, we discuss how the traditional applicability of online IDMS for elemental speciation can be dramatically expanded by using carbon isotope tracers, oxidation or combustion reactions and a conventional molecular ion source. With such a strategy every carbon-containing compound being eluted from a chromatography system can be quantified without the need for specific standards as long as quantitative combustion/oxidation and complete elution occur. So far, only gas chromatography-combustion-mass spectrometry applications have been described, but recent results indicate the great possibilities of extending this novel approach to the quantification of organic compounds after separation by liquid chromatography. PMID:22009048

Daz, Sergio Cueto; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo; Alonso, Jos Ignacio Garca

2012-01-01

43

Accuracy in the isotope dilution mass spectrometry of uranium in rubidium uranium sulphate Rb[sub 2]U(SO[sub 4])[sub 3  

SciTech Connect

Problems encountered in the determination of uranium in rubidium uranium sulphate (Rb[sub 2]U(SO[sub 4])[sub 3]) employing isotope dilution thermal ionization mass spectrometry (ID-TIMS) are discussed. The positive bias of 0.2 to 0.3% in the determination of uranium in Rb[sub 2]U(SO[sub 4])[sub 3] by ID-TIMS with respect to the stoichiometric composition has been resolved by modifying the chemical exchange procedures. The concentration of uranium in Rb[sub 2]U(SO[sub 4])[sub 3] could be determined with an accuracy better than 0.1% employing the HClO[sub 4] treatment for proper isotopic exchange between the spike and sample isotopes. 12 refs., 1 fig., 5 tabs.

Ramakumar, K.L.; Jeyakumar, S.; Raman, V.A.; Gnanayyan, L.; Rao, R.; Saxena, M.K.; Kavimandan, V.D.; Jain, H.C. (Bhabha Atomic Research Centre, Bombay (India))

1993-05-01

44

An isotope dilution-precipitation process for removing radioactive cesium from wastewater.  

PubMed

A novel isotope dilution-precipitation method has been developed to remove cesium-137 from radioactive wastewater. The process involves adding stable cesium chloride to wastewater in order to raise the total cesium concentration, which then allows both the stable and radioactive cesium ions to be precipitated together using sodium tetraphenylborate. This process was investigated utilizing laboratory solutions to determine stable cesium dose rates, mixing times, effects of pH, and filtration requirements. Once optimized, the process was then tested on synthetic wastewater and aqueous low-level waste. Experiments showed the reaction to be very quick and stable in the pH range tested, 2.5-11.5. The wastewater may need to be filtered using a 0.45-?m filter, though ferric sulfate has been shown to promote coagulation and settling, thereby eliminating the necessity for filtration. This investigation showed that this isotope dilution-precipitation process can remove Cs-37 levels below the U.S. Department of Energy's (DOE) Derived Concentration Standard (DCS) of 3.0 10(-6) ?Ci/mL using a single dosage, potentially allowing the wastewater to be discharged directly to sanitary sewers. PMID:23116720

Rogers, Harold; Bowers, John; Gates-Anderson, Dianne

2012-12-01

45

Steroid hormone levels in pregnancy and 1 year postpartum using isotope dilution tandem mass spectrometry  

PubMed Central

Objective To establish normal, trimester-specific reference intervals for serum 17?-estradiol, progesterone (P), 17?-hydroxyprogesterone, cortisol, 11-deoxycortisol, androstenedione, DHEA, and DHEAS, measured simultaneously using isotope dilution tandem mass spectrometry. Design Sequential cohort study. Patient(s) Healthy women undergoing a normal pregnancy (age, 2538 years; mean, 30 years) attending a prenatal well clinic at gestation weeks 12, 22, and 32 and approximately 1 year postpartum. Main Outcome Measure(s) Trimester-specific reference intervals of endogenous steroid hormones analyzed using an isotope dilution tandem mass spectrometer equipped with an atmospheric pressure photoionization source with deuterium-labeled internal standards. Result(s) Serum estradiol, P, 17?-hydroxyprogesterone, and 11-deoxycortisol increased throughout pregnancy; cortisol increased up to the second trimester and then remained steady, while androstenedione increased by 80 percent by gestation week 12, then remained constant. Serum DHEA-S decreased by 50% by the third trimester. Conclusion(s) Trimester-specific reference intervals are reported for eight serum steroids. The ratios of individual serum hormone concentrations during pregnancy relative to their 1-year postpartum concentrations illustrate the expected normal trends of changes in hormone concentrations during pregnancy. PMID:16169406

Soldin, Offie P.; Guo, Tiedong; Weiderpass, Elisabete; Tractenberg, Rochelle E.; Hilakivi-Clarke, Leena; Soldin, Steven J.

2013-01-01

46

Investigation of matrix effects and isotope dilution in SIMS measurement of uranium in soils  

NASA Astrophysics Data System (ADS)

The characteristics of sputter-initiated resonance ionization spectroscopy (SIRIS) for determining trace uranium concentrations in soils are investigated. Although, presently, the most formidable problem in the assay of environmental materials with SIRIS is the low sensitivity of the system, we have chosen to focus on matrix effects as possible limiting factors in this paper. Separate active efforts are being made to improve sensitivity and isotopic selectivity in RIS systems. Electrically conducting solid samples compatible with high vacuum are made by compacting soil with 15% or greater graphite binder. It is found that matrix effects on the absolute uranium SIRIS signals can be as large as two orders of magnitude, precluding a direct comparison of uranium concentrations through uranium SIRIS signal levels. The method of isotope dilution is also explored. Systematic errors caused by different molecular forms or different microscopic physical locations of the two isotopes are less than 30% in this method. It is found that for samples in which these effects are minimized, the capability of the instrument is such that uranium concentrations can be determined successfully to better than 10% accuracy.

Hutchinson, J. M. R.; Inn, K. G. W.; Parks, J. E.; Beekman, D. W.; Spaar, M. T.; Fairbank, W. M.

1987-06-01

47

Preparation of a 238Pu standard source . I. Isotope dilution alpha-ray spectrometry used for standardization  

NASA Astrophysics Data System (ADS)

A 238Pu source was prepared by electrodeposition method. For the standardization of the source, isotope dilution alpha-ray spectrometry (IDAS) was investigated: The content of 238Pu in a sample solution was determined both by IDAS and by isotope dilution mass spectrometry (IDMS) using a standard reference material of 239Pu as a spike. The estimated uncertainty in the determination of 238Pu is 0.13% for IDAS, and the factor of IDAS/IDMS is calculated to be 1.00000.0015.

Nobuo, Shinohara; Nobuaki, Kohno

1988-07-01

48

Isotope dilution assay in peptide quantification: the challenge of microheterogeneity of internal standard.  

PubMed

Isotope dilution analysis allows quantitation of elements and different compounds in complex mixtures. The quantitation is based on a known amount of reference material (internal standard, IS) added to a sample that makes the result critically dependent on the value assigned to the standard. In the case of peptides, IS concentration is determined by nitrogen and amino acid analysis while purity is normally assessed by methods such as chromatography or electrophoresis that might not be able to detect many possible amino acid modifications, either naturally occurring or chemically induced. Microheterogeneity of the IS, if it is not accounted for when assigning a reference value to the standard, results in highly overestimated values in target analyte quantitation. In this viewpoint article, we illustrate the problem of internal standard microheterogeneity by analyzing synthetic human C-peptide labeled analogs. PMID:23983084

Stoyanov, Alexander V; Rogatsky, Eduard; Stein, Daniel; Connolly, Shawn; Rohlfing, Curt L; Little, Randie R

2013-12-01

49

A rapid isotope dilution procedure for estimating the relative proportion of mitochondrial DNA in yeast.  

PubMed

A method is described for estimating rapidly the relative proportion of total DNA that is of mitochondrial origin in small quantities of the yeast, Saccharomyces cerevisiae. This procedure involves the mechanical disruption of cells followed by the addition of small amounts of radioactively labeled yeast nuclear and mitochondrial DNA to the lysate. Both labeled and unlabeled DNAs are then co-extracted from the mixture and separated into nuclear and mitochondrial DNA components by poly(L-lysine) Kieselguhr column chromatography. The resulting specific radioactivities of each species of DNA, when compared to the amount of labeled DNA initially added, or related to the relative proportion of unlabeled nuclear and mitochondrial DNA in the original cell sample. The isotope dilution procedure reported here is shown to be both reproducible and to reflect the true relative concentration of each species of DNA in this yeast. PMID:7025913

Cottrell, S F

1981-10-27

50

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

USGS Publications Warehouse

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 20092010 ranged from 84104%, with relative standard deviations of 636%. Detection levels estimated using ASTM Internationals D609107 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 IDSs 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.

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

2013-01-01

51

Determination of vertical fluxes of sulfur dioxide and dimethyl sulfide in the remote marine atmosphere by eddy correlation and an airborne isotopic dilution atmospheric pressure ionization mass spectrometer  

Microsoft Academic Search

Vertical fluxes of dimethyl sulfide (DMS) and sulfur dioxide (SO 2) were determined by eddy correlation and an isotopic dilution atmospheric pressure ionization mass spectrometer (APIMS) on an aircraft platform. The sampling frequency of the isotopic dilution APIMS ranged from 1 Hz to 25 Hz for real-time measurements. Measurements were made near the surface in the marine boundary layer to

Glenn M. Mitchell

2001-01-01

52

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...

53

Thermal degradation of polyacrylic acid in dilute aqueous solution  

Microsoft Academic Search

The thermal degradation of polyacrylic acid of molecular weight (Mw) 5660 (PAA 5K) has been studied between 180 and 260C, representing the heat conditions prevailing at the high pressure heaters (185C) and steam generators (260C) of the steam-condensate cycle of CANDU nuclear power plants. The degradation does not follow a simple first-order kinetics but probably a rather complex mechanism that

Louis Lpine; Roland Gilbert

2002-01-01

54

Quantitative analysis of WRN exonuclease activity by isotope dilution mass spectrometry.  

PubMed

Werner syndrome is a disorder characterized by a premature aging phenotype. The disease is caused by mutations in the WRN gene which encodes a DNA helicase/exonuclease which is involved in multiple aspects of DNA metabolism. Current methods mostly rely on radiometric techniques to assess WRN exonuclease activity. Here we present an alternative, quantitative approach based on non-radioactive isotope dilution mass spectrometry (LC-MS/MS). A oligoduplex substrate mimicking the telomeric sequence was used for method development. Released nucleotides, which correlate with the degree of oligoduplex degradation, were dephosphorylated, purified, and quantified by LC-MS/MS. Heavy-isotope-labeled internal standards were used to account for technical variability. The method was validated in terms of reproducibility, time-course and concentration-dependency of the reaction. As shown in this study, the LC-MS/MS method can assess exonuclease activity of WRN mutants, WRN's substrate and strand specificity, and modulatory effects of WRN interaction partners and posttranslational modifications. Moreover, it can be used to analyze the selectivity and processivity of WRN exonuclease and allows the screening of small molecules for WRN exonuclease inhibitors. Importantly, this approach can easily be adapted to study nucleases other than WRN. This is of general interest, because exonucleases are key players in DNA metabolism and aging mechanisms. PMID:22766507

Mangerich, Aswin; Veith, Sebastian; Popp, Oliver; Fahrer, Jrg; Martello, Rita; Bohr, Vilhelm A; Brkle, Alexander

2012-08-01

55

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)

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.

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

2003-01-01

56

Lambda genomic DNA quantification using ultrasonic treatment followed by liquid chromatography-isotope dilution mass spectrometry.  

PubMed

Quantification of genomic DNA that is traceable to the SI was performed successfully by measuring the individual nucleotides. Specifically, ultrasound was used to shear lambda genomic DNA into fragments of less than 200 base pairs, followed by deoxyribonuclease ? and phosphodiesterase ? digestion and liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) quantification to estimate the mass fraction of the lambda DNA, based on the constituent deoxynucleotide monophosphates (dNMPs) within the molecule. Digital PCR (dPCR) was employed to quantify the same lambda DNA solution to provide independent data for comparing the performance of two quantitative methods. On the basis of the LC-IDMS measurement after ultrasonic treatment of the sample, the concentration of lambda DNA was 273.1 9.8 ?g/g (expanded uncertainty at the 95% confidence interval). This shows good agreement with the data from dPCR. Additionally, the result calculated on the basis of the sum of the concentrations of the four dNMPs is the same as that calculated on the basis of the sequence, which indicates that knowledge of the DNA sequence and length is unnecessary to measure the total DNA concentration when applying ultrasonic treatment-LC-IDMS. PMID:22218463

Dong, Lianhua; Zang, Chao; Wang, Jing; Li, Liang; Gao, Yunhua; Wu, Liqing; Li, Peng

2012-02-01

57

Development of hemoglobin A1c certified reference material by liquid chromatography isotope dilution mass spectrometry.  

PubMed

We report the development of a National Institute of Metrology (NIM) hemoglobin A(1c) (HbA(1c)) certified reference material (CRM). Each CRM unit contains about 10 ?L of hemoglobin. Both hemoglobin and glycated hemoglobin were quantitatively determined by high-performance liquid chromatography (HPLC)-isotope dilution mass spectrometry (IDMS) with synthesized VHLTPE and glycated VHLTPE as standards. The mass fraction of synthesized VHLTPE or glycated VHLTPE was also quantitatively determined by HPLC-IDMS with NIM amino acid CRMs as standards. The homogeneity and stability of the CRMs were examined with a commercial HbA(1c) analyzer based on the HPLC principle. Fifteen units were randomly selected for homogeneity examination, and statistical analysis showed there was no inhomogeneity. Examination of the stability showed that the CRM was stable for at least 6 months at -80 C. Uncertainty components of the balance, amino acid purity, hydrolysis and proteolysis efficiency, method reproducibility, homogeneity, and stability were taken into consideration for uncertainty evaluation. The certified value of NIM HbA(1c) CRM was expressed as the ratio of HbA(1c) to total hemoglobin in moles, and was (9.6 1.9)%. The CRM can be used as a calibration or validation standard for clinical diagnostics. It is expected to improve the comparability for HbA(1c) measurement in China. PMID:22349405

Bi, Jiaming; Wu, Liqing; Yang, Bin; Yang, Yi; Wang, Jing

2012-04-01

58

Isotope dilution LC/MS/MS for the detection of nerve agent exposure in urine.  

PubMed

Organophosphorus nerve agents (OPNA), chemically related to and derived from organophosphate insecticides, constitute a clear and present threat to both military and civilian targets. Military regimes and terrorist organizations have demonstrated the will and ability to produce mass casualties by dispersing organophosphorus nerve agents, which, in turn could terrorize populations and overwhelm healthcare systems. A high throughput, robust and sensitive analytical protocol has been developed for the quantitation of the urinary metabolites of sarin (GB), soman (GD), VX, Russian VX (RVX) and cyclohexylsarin (GF) utilizing solid phase extraction (SPE) followed by High Performance Liquid Chromatography (HPLC)-isotope dilution tandem mass spectrometry (LC/MS/MS). The method has demonstrated linearity and reproducibility (1-200 ng/mL) for all analytes and has a Limit of Quantitation (LOQ)< or =0.5 ng/mL for all analytes (S/N> or =10/1). The method was validated by performing 20 individual analyses over 10 days by five scientists with all values falling within two standard deviations of the mean. PMID:16935039

Ciner, Frederic L; McCord, Carla E; Plunkett, Roy W; Martin, Michael F; Croley, Timothy R

2007-02-01

59

Precise determination of seawater calcium using isotope dilution inductively coupled plasma mass spectrometry.  

PubMed

We describe a method for rapid, precise and accurate determination of calcium ion (Ca(2+)) concentration in seawater using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). A 10 ?L aliquot of seawater was spiked with an appropriate (43)Ca enriched solution for (44)Ca/(43)Ca ID-ICP-MS analyses, using an Element XR (Thermo Fisher Scientific), operated at low resolution in E-scan acquisition mode. A standard-sample bracketing technique was applied to correct for potential mass discrimination and ratio drift at every 5 samples. A precision of better than 0.05% for within-run and 0.10% for duplicate measurements of the IAPSO seawater standard was achieved using 10 ?L solutions with a measuring time less than 3 minutes. Depth profiles of seawater samples collected from the Arctic Ocean basin were processed and compared with results obtained by the classic ethylene glycol tetra-acetic acid (EGTA) titration. Our new ID-ICP-MS data agreed closely with the conventional EGTA data, with the latter consistently displaying 1.5% excess Ca(2+) values, possibly due to a contribution of interference from Mg(2+) and Sr(2+) in the EGTA titration. The newly obtained Sr/Ca profiles reveal sensitive water mass mixing in the upper oceanic column to reflect ice melting in the Arctic region. This novel technique provides a tool for seawater Ca(2+) determination with small sample size, high throughput, excellent internal precision and external reproducibility. PMID:24434804

Liu, Hou-Chun; You, Chen-Feng; Cai, Wei-Jun; Chung, Chuan-Hsiung; Huang, Kuo-Fang; Chen, Bao-Shan; Li, Yen

2014-02-21

60

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

SciTech Connect

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.

Esteban, N.V.; Loughlin, T.; Yergey, A.L.; Zawadzki, J.K.; Booth, J.D.; Winterer, J.C.; Loriaux, D.L. (National Institute of Child Health and Human Development, Bethesda, MD (USA))

1991-01-01

61

Boundary-layer isotope dilution/mass balance methods for measurement of nocturnal methane emissions from grazing sheep  

NASA Astrophysics Data System (ADS)

Following advances with methods for 13C/ 12C isotopic analysis of methane in small (?4 L) air samples, new isotope dilution techniques are proposed for measurement of methane emissions at the paddock scale from grazing ruminant animals. These techniques combine measurement of the isotopic ?13CH 4 composition of air samples with a non-intrusive mass balance method applied in the nocturnal boundary layer. Flux estimates from trials using the isotope dilution techniques are compared with estimates based on scaling up individual animal emission measurements using a rumen gas tracer technique. The methane flux assessed by the latter technique ranged from 35 to 70 mg (CH 4) m -2 d -1 with a stocking density between 10 and 20 sheep ha -1. The isotope dilution based nocturnal boundary-layer estimates generally agreed to better than a factor of 2 and usually to within 20% of the average of individual animal emission rate per unit area of paddock. Both static and advecting mass balance methods are developed. In the advecting case, the upwind/downwind contrast in ?13C was typically 0.2-0.5. Care was necessary with air sampling to avoid error in this small contrast contributing to error in the flux. Agreement between concentration- and isotope-based nocturnal boundary layer methods and the sheep breath measurements indicated that sample representativeness was generally good. Factors which affect the accuracy of the method are examined and include variability in nocturnal mixing height, the assumed ?13CH 4 composition of the source sheep breath and diurnal patterns in sheep emission. This paper establishes new techniques useful in the paddock to landscape scale although widespread application awaits further development of technology for rapid and repeatable field analysis of ?13CH 4 in small samples.

Harvey, M. J.; Brailsford, G. W.; Bromley, A. M.; Lassey, K. R.; Mei, Z.; Kristament, I. S.; Reisinger, A. R.; Walker, C. F.; Kelliher, F. M.

62

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

SciTech Connect

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.

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

1984-08-01

63

Quantification of human growth hormone by amino acid composition analysis using isotope dilution liquid-chromatography tandem mass spectrometry  

Microsoft Academic Search

We describe an accurate method for protein quantification based on conventional acid hydrolysis and an isotope dilutionHPLCmass spectrometry (IDHPLCMS) method. Sample purity was confirmed using capillary zone electrophoresis, HPLC and MS. The analyte protein, human growth hormone (hGH), was effectively hydrolyzed by incubation with 8M hydrochloric acid at 130C for 48h, where at least 1?M of hGH was treated to

Ji-Seon Jeong; Hyuk-Min Lim; Sook-Kyung Kim; Hyung-Keun Ku; Kyung-Hwa Oh; Sang-Ryoul Park

2011-01-01

64

Application of stable isotope dilution assays based on liquid chromatographytandem mass spectrometry for the assessment of folate bioavailability  

Microsoft Academic Search

A pilot study was performed to prove the suitability of stable isotope dilution assays for assessing the bioavailability of endogenous folates in foods. By using [2H4]folic acid, [2H4]tetrahydrofolate, [2H4]5-methyltetrahydrofolate, [2H4]5-formyltetrahydrofolate and [2H4]10-formylfolic acid as internal standards, folates in spinach, apple juice and blood plasma were quantified by liquid chromatography coupled to tandem mass spectrometry. To liberate the pteroyl monoglutamates, sample

Michael Rychlik; Michael Netzel; Inga Pfannebecker; Thomas Frank; Irmgard Bitsch

2003-01-01

65

Suitability and use of the 15N-isotope dilution method to estimate nitrogen fixation by actinorhizal shrubs  

Microsoft Academic Search

Nitrogen fixation rates were estimated by the 15N-isotope dilution method for Ceanothusvelutinus and Purshia tridentata in the understory of central Oregon ponderosa pine forests. Field rates were measured in small pole-, large pole-, and sawtimber-sized pine stands using two shrubs (Arctostaphylos patula, Ribes cereum) and one graminoid (Carex rossii) as non-fixing reference species. Shrub cover ranged from 23 to 59%

Matt D. Busse

2000-01-01

66

Testosterone Measurement by Isotope-Dilution Liquid Chromatography-Tandem Mass Spectrometry: Validation of a Method for Routine Clinical Practice  

Microsoft Academic Search

Background: Immunoassay is unsatisfactory for mea- suring the testosterone concentrations typically found in women. Bench-top tandem mass spectrometers are a viable alternative technology for measurements in the clinical laboratory. Methods: We used stable-isotope dilution liquid chro- matography-tandem mass spectrometry (ID\\/LC-MS\\/ MS) to measure testosterone in plasma and serum. The sample volume was 50 L in duplicate; preparation and analysis were

Marion L. Cawood; Helen P. Field; Clive G. Ford; Scott Gillingwater; Andrew Kicman; David Cowan; Julian H. Barth

67

State-of-the-Art of Serum Testosterone Measurement by Isotope Dilution Liquid Chromatography Tandem Mass Spectrometry  

Microsoft Academic Search

BACKGROUND: The recent interest of clinical laborato- ries in developing serum testosterone assays based on isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS\\/MS) stems from the lack of accuracy of direct immunoassays. In this study, we assessed the accuracy and state of standardization (traceability) of 4 published ID-LC-MS\\/MS proce- dures in a method comparison with an ID-gas chro- matography (GC)-MS reference measurement

Linda M. Thienpont; Katleen Van Uytfanghe; Stuart Blincko; Carol S. Ramsay; Hui Xie; Robert C. Doss; Brian G. Keevil; Laura J. Owen; Alan L. Rockwood; Mark M. Kushnir; Kelly Y. Chun; Donald W. Chandler; Helen P. Field; Patrick M. Sluss

68

Extended Gross-Pitaevskii description for the dynamics of thermal dilute Bose gases  

NASA Astrophysics Data System (ADS)

We introduce a technique to simulate the dynamics of a thermal dilute Bose gas. With the method of the nonequilibrium statistical operator, a correction to the Gross-Pitaevskii equation (GPE) is derived. This modification of the GPE describes spontaneous scattering processes. It regularizes the ultraviolet catastrophe and captures the dynamics of the particles at all energies, including the tail of the momentum distribution. We apply our model to the simulation of an evaporative cooling quench of a two-dimensional Bose gas.

Wouters, Michiel

2014-09-01

69

Assessment of body composition in Indian adults: comparison between dual-energy X-ray absorptiometry and isotope dilution technique.  

PubMed

Dual-energy X-ray absorptiometry (DXA) and isotope dilution technique have been used as reference methods to validate the estimates of body composition by simple field techniques; however, very few studies have compared these two methods. We compared the estimates of body composition by DXA and isotope dilution (18O) technique in apparently healthy Indian men and women (aged 19-70 years, n 152, 48% men) with a wide range of BMI (14-40kg/m2). Isotopic enrichment was assessed by isotope ratio mass spectroscopy. The agreement between the estimates of body composition measured by the two techniques was assessed by the Bland-Altman method. The mean age and BMI were 37 (sd 15) years and 233 (sd 51)kg/m2, respectively, for men and 37 (sd 14) years and 241 (sd 58)kg/m2, respectively, for women. The estimates of fat-free mass were higher by about 7 (95% CI 6, 9)%, those of fat mass were lower by about 21 (95% CI -18, -23)%, and those of body fat percentage (BF%) were lower by about 74 (95% CI -82, -66)% as obtained by DXA compared with the isotope dilution technique. The Bland-Altman analysis showed wide limits of agreement that indicated poor agreement between the methods. The bias in the estimates of BF% was higher at the lower values of BF%. Thus, the two commonly used reference methods showed substantial differences in the estimates of body composition with wide limits of agreement. As the estimates of body composition are method-dependent, the two methods cannot be used interchangeably. PMID:25111193

Kulkarni, Bharati; Kuper, Hannah; Taylor, Amy; Wells, Jonathan C; Radhakrishna, K V; Kinra, Sanjay; Ben-Shlomo, Yoav; Smith, George Davey; Ebrahim, Shah; Kurpad, A V; Byrne, Nuala M; Hills, Andrew P

2014-10-01

70

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

USGS Publications Warehouse

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)

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

1982-01-01

71

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

PubMed

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 ?-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

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

2014-07-01

72

Accurate determination of mean cell volume by isotope dilution in erythrocyte populations with variable deformability.  

PubMed

Variations in erythrocyte deformability and morphology lead to artifacts in electronic determinations of mean cellular volume (MCV) by the aperture-impedance method. The micropipette-aspiration technique loses accuracy when applied to severely aberrant cells such as dense sickle cells. A new light-scattering technique requires that the cells be capable of undergoing isovolumetric sphering. In contrast, the isotope-dilution (ID) method measures absolute mean volume and is free of artifacts associated with abnormal deformability or morphology. It does not depend on any algorithms or correction factors and does not subject the cells to any stringent processing, not even centrifugation. The ID method can be used to determine the mean volume of red cells in hypo- or hypertonic media or in the presence of pharmacologic agents. It requires no more than a 1-ml aliquot of suspended cells at a hematocrit of at least 30%. The cells can be readily recovered, washed, and reused. Using EDTA labeled with 57Co as an extracellular space marker we have used ID to determine the MCV of fractionated normal human red blood cells (RBC), unfractionated RBC containing SS hemoglobin, and RBC from four other mammalian species. In the case of human RBC obtained from eight normal donors, we obtained mean MCV values (+/- SD) of 83.6 +/- 3.0, 87.5 +/- 3.9, and 76.5 +/- 5.3 fl for unfractionated and top and bottom 10% density fractions, respectively. The value 83.6 is significantly lower than the generally accepted range of 89-91 indicated by electronic analyzers calibrated against spun microhematocrits. The discrepancy of about 7% can account for the difference between mean cell hemoglobin concentration (MCHC) data determined by a calibrated Coulter Counter and corresponding data obtained with paired samples using a cyanmethemoglobin procedure specified in NCCLS Standard H15-A and corrected for trapped plasma. PMID:1760558

Marvel, J S; Sutera, S P; Krogstad, D J; Zarkowsky, H S; Williamson, J R

1991-01-01

73

Determination of total chromium in seawater by isotope dilution sector field ICPMS using GC sample introduction.  

PubMed

A method for the accurate determination of total Cr in seawater by isotope dilution (ID) sector field inductively coupled plasma mass spectrometry (SF-ICPMS) using GC as a means of sample introduction is described. Chromium was reduced to Cr(III) by addition of SO(2)-saturated water and derivatized with trifluoroacetylacetonate (TFA) to form volatile Cr(TFA)(3). Derivatized analyte was either extracted into hexane or directly sampled by solid-phase microextraction (SPME) using a poly(dimethylsiloxane)-coated fused-silica fiber for GC/SF-ICPMS analysis. With medium resolution required to efficiently separate argide, argon chloride and oxide interferences, a concentration of 0.154 +/- 0.013 ng mL(-1) (1 SD, n = 4) was obtained for Cr in NRCC seawater CRM CASS-4 using a 1-microL hexane extract, in agreement with the certified value of 0.144 +/- 0.029 ng mL(-1) (95% confidence interval). A detection limit of 20 pg mL(-1) was achieved. Low-resolution GC/SF-ICPMS in combination with solvent-free SPME sampling effectively eliminated spectroscopic interferences, yielding a concentration of 0.132 +/- 0.004 ng mL(-1) (1 SD, n = 4) for Cr in CASS-4 with a method detection limit of 3.9 pg mL(-1). By comparison, SPME sampling with GC/SF-ICPMS in medium-resolution mode provided a concentration of 0.146 +/- 0.013 ng mL(-1) (1 SD, n = 4) and a method detection limit of 9.1 pg mL(-1). PMID:15228318

Yang, Lu; Mester, Zoltn; Abranko, Laszlo; Sturgeon, Ralph E

2004-07-01

74

Speciation and isotope dilution analysis of gadolinium-based contrast agents in wastewater.  

PubMed

The fate of Gadolinium (Gd)-based contrast agents for magnetic resonance imaging (MRI) during sewage treatment was investigated. The total concentration of Gd in influent and effluent 2 and 24 h composite samples was determined by means of isotope dilution analysis. The balancing of Gd input and output of a sewage plant over seven days indicated that approximately 10% of the Gd is removed during treatment. Batch experiments simulating the aeration tank of a sewage treatment plant confirmed the Gd complex removal during activated sludge treatment. For speciation analysis of the Gd complexes in wastewater samples, high performance liquid chromatography (HPLC) was hyphenated to inductively coupled plasma sector field mass spectrometry (ICP-SFMS). Separation of the five predominantly used contrast agents was carried out on a new hydrophilic interaction liquid chromatography stationary phase in less than 15 min. A limit of detection (LOD) of 0.13 ?g/L and a limit of quantification of 0.43 ?g/L could be achieved for the Gd chelates without having to apply enrichment techniques. Speciation analysis of the 24 h composite samples revealed that 80% of the Gd complexes are present as Gd-BT-DO3A in the sampled treatment plant. The day-of-week dependent variation of the complex load followed the variation of the total Gd load, indicating a similar behavior. The analysis of sewage sludge did not prove the presence of anthropogenic Gd. However, in the effluent of the chamber filter press, which was used for sludge dewatering, two of the contrast agents and three other unknown Gd species were observed. This indicates that species transformation took place during anaerobic sludge treatment. PMID:23062026

Telgmann, Lena; Wehe, Christoph A; Birka, Marvin; Knnemeyer, Jens; Nowak, Sascha; Sperling, Michael; Karst, Uwe

2012-11-01

75

Simultaneous Quantification of Steroids in Rat Intratesticular Fluid by HPLC-Isotope Dilution Tandem Mass Spectrometry  

PubMed Central

An isotope dilution mass spectrometry method has been developed for the simultaneous measurement of picolinoyl derivatives of testosterone (T), dihydrotestosterone (DHT), 17?-estradiol (E2), and 5?-androstan-3?,17?-diol (3?-diol) in rat intratesticular fluid. The method uses reversed-phase high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry. Following derivatization of 10-?L samples of testicular fluid with picolinoyl chloride hydrochloride, the samples were purified by solid phase extraction before analysis. The accuracy of the method was satisfactory for the 4 analytes at 3 concentrations, and both inter- and intraday reproducibility were satisfactory for T, DHT, and E2. Measurements of intratesticular T concentrations in a group of 8 untreated adult rats by this method correlated well with measurements of the same samples by radioimmunoassay. As in men, there was considerable rat-to-rat variability in T concentration, despite the fact that the rats were inbred. Although its levels were more than an order of magnitude lower than those of T, DHT was measured reliably in all 8 intratesticular fluid samples. DHT concentration also varied from rat to rat and was highly correlated with T levels. The levels of E2 and 3?-diol also were measurable. The availability of a sensitive method by which to measure steroids accurately and rapidly in the small volumes of intratesticular fluid obtainable from individual rats will make it possible to examine the effects, over time, of such perturbations as hormone and drug administration and environmental toxicant exposures on the intratesticular hormonal environment of exposed individual males and thereby to begin to understand differences in response between individuals. PMID:22016356

RENNE, ALISSA; LUO, LINDI; JAROW, JONATHAN; WRIGHT, WILLIAM W.; BROWN, TERRY R.; CHEN, HAOLIN; ZIRKIN, BARRY R.; FRIESEN, MARLIN D.

2014-01-01

76

Accurate determination of sulfur in gasoline and related fuel samples using isotope dilution ICPMS with direct sample injection and microwave-assisted digestion  

Microsoft Academic Search

Inductively coupled plasma isotope-dilution mass spectrometry (ICPIDMS) with direct injection of isotope-diluted samples into the plasma, using a direct injection high-efficiency nebulizer (DIHEN), was applied for accurate sulfur determinations in sulfur-free premium gasoline, gas oil, diesel fuel, and heating oil. For direct injection a micro-emulsion consisting of the corresponding organic sample and an aqueous 34S-enriched spike solution with additions of

Jens Heilmann; Sergei F. Boulyga; Klaus G. Heumann

2004-01-01

77

Determination of trace level cadmium in SRM 3280 Multivitamin/Multielement Tablets via isotope dilution inductively coupled plasma mass spectrometry.  

PubMed

Cadmium was quantified at 80.150.86 ng/g (mean95% expanded uncertainty) in NIST SRM 3280 Multivitamin/Multielement Tablets, using isotope dilution mass spectrometry. The method described utilized various precipitation and solid-phase extraction separation methodologies to isolate Cd from Sn and Mo, present respectively, at 11.10.9 mg/kg and 70.74.5 mg/kg in the tablet matrix. This allowed for measurement of (111)Cd/(113)Cd and (111)Cd/(114)Cd isotope ratios using both quadrupole collision cell technology inductively coupled plasma mass spectrometry (Q-CCT-ICP-MS) and sector field (SF)-ICP-MS equipped with a desolvating nebulizer system to mitigate the MoO(+) and MoOH(+) molecular ion interferences that typically affect the envelope of Cd isotopes. PMID:24148367

Christopher, Steven J; Thompson, Robert Q

2013-11-15

78

Analysis of ochratoxin A in grapes, musts and wines by LC-MS/MS: first comparison of stable isotope dilution assay and diastereomeric dilution assay methods.  

PubMed

Ochratoxin A (OTA) exhibits potent nephrotoxic, carcinogenic and teratogenic effects and its maximum level in wines has been set to 2 ?g L(-1) by regulation. Consequently, the analytical procedures for OTA determination in wines have to be both very sensitive and reliable. In this paper, we compared two quantification methods: the stable isotope dilution assay (SIDA) and the diastereomeric dilution assay (DIDA). For this purpose, non-natural analogues of OTA were synthesized: the labeled OTA (OTA-d4) as a diastereomeric mixture for the SIDA and one non-natural OTA's diastereomer (OTA-dia) for the DIDA. To quantify OTA in red grapes, musts or wines, the sample preparation was optimized using immunoaffinity column extraction and the analysis was performed by LC-MS/MS in Multiple Reaction Monitoring mode. A validation procedure in agreement with the International Organization of Vine and Wine recommendations was conducted. It appeared that SIDA quantification exhibited excellent sensitivity (LOD<1 ng L(-1)), accuracy (recovery=98%), repeatability (RSD<3%) and intermediate reproducibility (RSD<4%) compared to quantification by DIDA. Indeed, DIDA method did not provide satisfactory results demonstrating that immunoaffinity extraction is exclusively selective for the natural OTA and not for its diastereomer, which therefore cannot be considered as a good internal standard for this particular method. PMID:24626401

Roland, Aurlie; Bros, Pauline; Bouisseau, Anas; Cavelier, Florine; Schneider, Rmi

2014-03-25

79

An Isotope-Powered Thermal Storage unit for space applications  

NASA Astrophysics Data System (ADS)

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.

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

80

Osmium isotope ratio determinations by negative thermal ionization mass spectrometry  

Microsoft Academic Search

A new technique for osmium isotope ratio determinations by negative thermal ionization mass spectrometry using the formation of OsO-3 ions is presented. Different filament materials and chemicals to reduce the electron work function are investigated. With Ba(OH)2 and platinum as filament material an ionization efficiency of more than 1% is obtained for nanogram sample amounts. The isotopic abundances of a

Joachim Vlkening; Thomas Walczyk; Klaus G. Heumann

1991-01-01

81

Potential for using isotopically altered metalloproteins in species-specific isotope dilution analysis of proteins by HPLC coupled to inductively coupled plasma mass spectrometry.  

PubMed

The production and evaluation of an isotopically enriched metalloprotein standard for use as a calibrant in species-specific isotope dilution analysis by HPLC coupled to inductively coupled plasma mass spectrometry is described. Using a model system involving the copper-containing protein rusticyanin (Rc) from the bacterium Acido-thiobacillus ferrooxidans, it was possible to demonstrate the analytical conditions that could be used for the measurement of metalloproteins by on-line IDMS analysis. Rc was chosen because it is a well-characterized protein with an established amino acid sequence and can be produced in suitable quantities using a bacterial recombinant system. Three different forms of the protein were studied by organic and inorganic mass spectrometry: the native form of the protein containing a natural isotopic profile for copper, an isotopically enriched species containing virtually all of its copper as the 65Cu isotope, and the nonmetalated apo form. Incorporation of the copper isotopes into the apo form of the protein was determined using a UV-vis spectrophotometric assay and shown to be complete for each of the copper-containing species. The experimental conditions required to maintain the conformational form of the protein with a nonexchangeable copper center were established using +ve electrospray mass spectrometry. A pH 7.0 buffer was found to afford the most appropriate conditions, and this was then used with HPLC-ICP-MS to verify the stability of the copper center by analysis of mixtures of different isotopic solutions. No exchange of the enriched copper isotope from Rc with an added naturally abundant inorganic copper cation was observed under a neutral pH environment, indicating that species-specific ID-MS analysis of metalloproteins is possible. PMID:15987108

Harrington, Chris F; Vidler, Daniel S; Watts, Michael J; Hall, John F

2005-07-01

82

Simplified absolute metabolite quantification by gas chromatography-isotope dilution mass spectrometry on the basis of commercially available source material.  

PubMed

In the field of metabolomics, GC-MS has rather established itself as a tool for semi-quantitative strategies like metabolic fingerprinting or metabolic profiling. Absolute quantification of intra- or extracellular metabolites is nowadays mostly accomplished by application of diverse LC-MS techniques. Only few groups have so far adopted GC-MS technology for this exceptionally challenging task. Besides numerous and deeply investigated problems related to sample generation, the pronounced matrix effects in biological samples have led to the almost mandatory application of isotope dilution mass spectrometry (IDMS) for the accurate determination of absolute metabolite concentrations. Nevertheless, access to stable isotope labeled internal standards (ILIS), which are in many cases commercially unavailable, is quite laborious and very expensive. Here we present an improved and simplified gas chromatography-isotope dilution mass spectrometry (GC-IDMS) protocol for the absolute determination of intra- and extracellular metabolite levels. Commercially available (13)C-labeled algal cells were used as a convenient source for the preparation of internal standards. Advantages as well as limitations of the described method are discussed. PMID:22100557

Vielhauer, Oliver; Zakhartsev, Maksim; Horn, Thomas; Takors, Ralf; Reuss, Matthias

2011-12-15

83

Kinetic study on thermal decomposition of chlorobenzene diluted in H sub 2  

SciTech Connect

Thermal reaction studies of dilute mixtures (0.37%) of chlorobenzene in hydrogen have been performed in tubular flow reactors at various surface to volume ratios and 1 atm total pressure. Residence times range from 0.02 to 2.5 s with temperatures between 1,050 and 1,275 K. HCl, benzene, and C (solids) are observed as the major products; minor products include methane, cyclopentadiene, toluene, naphthalene, and biphenyls. Chlorobenzene pyrolysis in helium yields significantly less conversion but more C (solids) for similar residence times. A detailed chemical mechanism is developed to describe this reaction system.

Ritter, E.R.; Bozzelli, J.W. (New Jersey Institute of Technology, Newark (USA)); Dean, A.M. (Exxon Research and Engineering Co., Annandale, NJ (USA))

1990-03-22

84

Chemical and isotopic characteristics of thermal fluids in the Long Valley caldera lateral flow system, California  

SciTech Connect

Chemical and isotopic data of thermal waters in Long Valley caldera have been used to identify both the origins and characteristics of the fluids and to evaluate mixing and boiling processes occurring within the lateral flow system of the caldera. Recharge to the Long Valley geothermal system occurs in the western part of the caldera with the water being heated at depth and flowing laterally eastward in the subsurface. The lateral flow system was recently intersected by the Shady Rest Continental Scientific Drilling Program (CSDP) corehole at 335 m (1100 ft) with fluids in this 202/sup 0/C zone being more concentrated than non-boiled fluids to the east. As the Na-K-HCO/sub 3/-Cl thermal fluids flow eastward, they are increasingly mixed with isotopically depleted, dilute groundwaters similar to cold waters east of Lake Crowley. Near surface boiling of Casa Diablo well fluids at 100/sup 0/C forms waters with the compositions of Colton and Casa Diablo hot springs. Waters to the east of the Casa Diablo area are mixtures of meteoric water and boiled thermal fluids with a composition close to that of Colton Hot Spring. There is no correlation between /sup 3/H and /sup 36/Cl in thermal fluids or between these components and conservative species, and it appears that cold fluids involved in mixing must be relatively old waters, low in both meteoric /sup 3/H and /sup 36/Cl.

Shevenell, L.; Goff, F.; Grigsby, C.O.; Janik, C.J.; Trujillo, P.E. Jr.; Counce, D.

1987-01-01

85

High flux isotope reactor redesigned beryllium reflector thermal stress calculations  

SciTech Connect

The Beryllium reflector of the High Flux Isotope Reactor is currently redesigned for upgrading the capability of the reactor. The original design criteria are adopted in the redesign analysis. Both nuclear heating and thermal stress calculations are revised. The results show that more margin of safety have been achieved and the updated design assures more precise design estimates for the reflector thermal stress conditions. 1 ref., 2 figs., 2 tabs.

Chang, S.J.

1996-06-01

86

Stable isotope fractionation by thermal diffusion through partially molten wet and dry silicate rocks  

E-print Network

Stable isotope fractionation by thermal diffusion through partially molten wet and dry silicate 2012 Editor: T.M. Harrison Keywords: thermal diffusion hydrogen isotope separation oxygen isotopes lithium isotopes 17-O meteoric hydrothermal systems a b s t r a c t Water plays a fundamental role

Bindeman, Ilya N.

87

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

PubMed

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

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

2012-03-16

88

Fast and accurate procedure for the determination of Cr(VI) in solid samples by isotope dilution mass spectrometry.  

PubMed

We present here a new environmental measurement method for the rapid extraction and accurate quantification of Cr(VI) in solid samples. The quantitative extraction of Cr(VI) is achieved in 10 minutes by means of focused microwave assisted extraction using 50 mmol/L Ethylendiamintetraacetic acid (EDTA) at pH 10 as extractant. In addition, it enables the separation of Cr species by anion exchange chromatography using a mobile phase which is a 1:10 dilution of the extracting solution. Thus, neutralization or acidification steps which are prone to cause interconversion of Cr species are not needed. Another benefit of using EDTA is that it allows to measure Cr(III)-EDTA complex and Cr(VI) simultaneously in an alkaline extraction solution. The application of a 10 minutes focused microwave assisted extraction (5 min at 90 C plus 5 min at 110 C) has been shown to quantitatively extract all forms of hexavalent chromium from the standard reference materials (SRM) candidate NIST 2700 and NIST 2701. A double spike isotope dilution mass spectrometry (IDMS) procedure was employed to study chromium interconversion reactions. It was observed that the formation of a Cr(III)-EDTA complex avoided Cr(III) oxidation for these two reference materials. Thus, the use of a double spiking strategy for quantification is not required and a single spike IDMS procedure using isotopically enriched Cr(VI) provided accurate results. PMID:23092182

Fabregat-Cabello, Neus; Rodrguez-Gonzlez, Pablo; Castillo, ngel; Malherbe, Julien; Roig-Navarro, Antoni F; Long, Stephen E; Garca Alonso, J Ignacio

2012-11-20

89

Stable isotope dilution gas chromatography-mass spectrometry for quantification of thymoquinone in black cumin seed oil.  

PubMed

Black cumin seed (Nigella sativa L.) is a widely used spice and herb, where thymoquinone (2-isopropyl-5-methyl-1,4-benzoquinone) is the major bioactive compound. Here, a stable isotope dilution (SID) gas chromatography-mass spectrometry (GC-MS) technique was developed for the quantification of thymoquinone. A doubly deuterated thymoquinone ([(2)H2]-thymoquinone) was synthesized for the first time with more than 93% deuteration degree shown by mass spectrometry and proton nuclear magnetic resonance ((1)H NMR). This compound was used as an internal standard for the quantification of thymoquinone using a SID GC-MS method. The validation experiment showed a recovery rate of 99.1 1.1% relative standard deviation (RSD). Standard addition and external calibration methods have also been used to quantify thymoquinone, which cross-validated the developed stable isotope dilution assay (SIDA). In comparison to external calibration and standard addition methods, the SIDA method is robust and accurate. The concentration of thymoquinone in five marketed black cumin seed oils ranged between 3.34 and 10.8 mg/mL by use of SID GC-MS. PMID:24871868

Johnson-Ajinwo, Okiemute Rosa; Li, Wen-Wu

2014-06-18

90

Direct ?-flow injection isotope dilution ICP-MS for the determination of heavy metals in oil samples.  

PubMed

The determination of trace elements in oil samples and their products is of high interest as their presence significantly affects refinery processes and the environment by possible impact of their combustion products. In this context, inductively coupled plasma mass spectrometry (ICP-MS) plays an important role due to its outstanding analytical properties in the quantification of trace elements. In this work, we present the accurate and precise determination of selected heavy metals in oil samples by making use of the combination of ?-flow direct injection and isotope dilution ICP-MS (ICP-IDMS). Spike solutions of (62)Ni, (97)Mo, (117)Sn and (206)Pb were prepared in an organic solvent, mixed directly with the diluted oil samples and tested to be fit for purpose for the intended ID approach. The analysis of real samples revealed strong matrix effects affecting the ICP-MS sensitivity, but not the isotope ratio measurements, so that accurate results are obtained by ICP-IDMS. Typical relative standard deviations were about 15% for peak area and peak height measurements, whereas the isotope ratios were not significantly affected (RSD < 2%). The developed method was validated by the analysis of a metallo-organic multi-element standard (SCP-21, typically applied as a calibration standard) and the standard reference material SRM1084a (wear metals in lubricating oil). The obtained results were in excellent agreement with the certified values (recoveries between 98% and 102%), so the proposed methodology of combining ?-flow direct injection and ICP-IDMS can be regarded as a new tool for the matrix-independent, multi-element and reliable determination of trace elements in oil and related organic liquids. PMID:21983977

Bettmer, Jrg; Heilmann, Jens; Kutscher, Daniel J; Sanz-Medel, Alfredo; Heumann, Klaus G

2012-01-01

91

Peptide production and decay rates affect the quantitative accuracy of protein cleavage isotope dilution mass spectrometry (PC-IDMS).  

PubMed

No consensus has been reached on the proper time to add stable-isotope labeled (SIL) peptides in protein cleavage isotope dilution mass spectrometry workflows. While quantifying 24 monolignol pathway enzymes in the xylem tissue of Populus trichocarpa, we compared the protein concentrations obtained when adding the SIL standard peptides concurrently with the enzyme or after quenching of the digestion (i.e. postdigestion) and observed discrepancies for nearly all tryptic peptides investigated. In some cases, greater than 30-fold differences were observed. To explain these differences and potentially correct for them, we developed a mathematical model based on pseudo-first-order kinetics to account for the dynamic production and decay (e.g. degradation and precipitation) of the native peptide targets in conjunction with the decay of the SIL peptide standards. A time course study of the digests confirmed the results predicted by the proposed model and revealed that the discrepancy between concurrent and postdigestion introduction of the SIL standards was related to differential decay experienced by the SIL peptide and the native peptide in each method. Given these results, we propose concurrent introduction of the SIL peptide is most appropriate, though not free from bias. Mathematical modeling of this method reveals that overestimation of protein quantities would still result when rapid peptide decay occurs and that this bias would be further exaggerated by slow proteolysis. We derive a simple equation to estimate the bias for each peptide based on the relative rates of production and decay. According to this equation, nearly half of the peptides evaluated here were estimated to have quantitative errors greater than 10% and in a few cases over 100%. We conclude that the instability of peptides can often significantly bias the protein quantities measured in protein cleavage isotope dilution mass spectrometry-based assays and suggest peptide stability be made a priority when selecting peptides to use for quantification. PMID:22595788

Shuford, Christopher M; Sederoff, Ronald R; Chiang, Vincent L; Muddiman, David C

2012-09-01

92

Fast methodology for the reliable determination of nonylphenol in water samples by minimal labeling isotope dilution mass spectrometry.  

PubMed

In this work we have developed and validated an accurate and fast methodology for the determination of 4-nonylphenol (technical mixture) in complex matrix water samples by UHPLC-ESI-MS/MS. The procedure is based on isotope dilution mass spectrometry (IDMS) in combination with isotope pattern deconvolution (IPD), which provides the concentration of the analyte directly from the spiked sample without requiring any methodological calibration graph. To avoid any possible isotopic effect during the analytical procedure the in-house synthesized (13)C1-4-(3,6-dimethyl-3-heptyl)phenol was used as labeled compound. This proposed surrogate was able to compensate the matrix effect even from wastewater samples. A SPE pre-concentration step together with exhaustive efforts to avoid contamination were included to reach the signal-to-noise ratio necessary to detect the endogenous concentrations present in environmental samples. Calculations were performed acquiring only three transitions, achieving limits of detection lower than 100ng/g for all water matrix assayed. Recoveries within 83-108% and coefficients of variation ranging from 1.5% to 9% were obtained. On the contrary a considerable overestimation was obtained with the most usual classical calibration procedure using 4-n-nonylphenol as internal standard, demonstrating the suitability of the minimal labeling approach. PMID:23746647

Fabregat-Cabello, Neus; Castillo, ngel; Sancho, Juan V; Gonzlez, Florenci V; Roig-Navarro, Antoni Francesc

2013-08-01

93

Isotope dilution analysis of polychlorinated biphenyls (PCBs) in transformer oil and global commercial PCB formulations by high resolution gas chromatographyhigh resolution mass spectrometry  

Microsoft Academic Search

Special polychlorinated biphenyls (PCBs) standards (native and isotope labeled) were analyzed by isotope dilution method using HRGCHRMS. Multiple analysis of special PCBs standards by three different laboratories produced the relative response factors (RRFs) and relative standard deviations (RSDs %) was in the average of 0.979 and 3.86, respectively. Additionally, inter-laboratory analysis of various forms of transformer oil revealed the PCBs

Takumi Takasuga; Kurunthachalam Senthilkumar; Tohru Matsumura; Ken Shiozaki; Shin-ichi Sakai

2006-01-01

94

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

PubMed

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

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

2013-03-01

95

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

SciTech Connect

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.

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

1981-05-01

96

Burnup Determination of High Burnup and Dry Processed Fuels Based on Isotope Dilution Mass Spectrometric Measurements  

Microsoft Academic Search

Destructive methods were used for the burnup determination of a PWR nuclear fuel irradiated to a high burnup in power reactors, and of a dry processed fuel fabricated from a spent PWR fuel and irradiated in the Hanaro research reactor. The total burnup was determined from a measurement of the Nd and Cs isotope burnup monitors. The methods included U,

Jung Suk KIM; Young Shin JEON; Soon Dal PARK; Sun Ho HAN; Jong Goo KIM

2007-01-01

97

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

PubMed

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

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

1991-02-01

98

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

PubMed Central

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

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

1991-01-01

99

Achieving traceable chemical measurements: inter-laboratory evaluation of a simplified technique for isotope dilution mass spectrometry (IDMS). Part 1: Methodology for high accuracy analysis of trace metals  

Microsoft Academic Search

A high accuracy measurement procedure developed and validated at the Laboratory of the Government Chemist (LGC) has been transferred to a number of expert United Kingdom laboratories and their experience in applying the technique has been evaluated by inter-laboratory comparisons. It is an approximate matching calibration procedure for analysis of trace metals using isotope dilution mass spectrometry (IDMS). Use of

Rita Harte; Gerry Newman; Mike Sargent

2004-01-01

100

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

Microsoft Academic Search

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

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

1991-01-01

101

Determination of zinc in plant samples by isotope dilution inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Determination of zinc involved spiking with 68Zn enriched solution, digestion by HNO3+H2O2 in microwave decomposition unit, off-line separation of zinc on Chelex-100 column and measurement of (64Zn+66Zn)\\/68Zn isotope ratio on ICP-MS spectrometer with a quadrupole mass filter. After optimization of standard operation procedure (details are given) the method was validated. LOD was found to be 0.3 ?g g?1 for the

Oto Mestek; Jana Kom??nkov; Richard Kopl??k; Miloslav Suchnek

2001-01-01

102

Hydrophobic hydration processes. General thermodynamic model by thermal equivalent dilution determinations.  

PubMed

The "hydrophobic hydration processes" can be satisfactorily interpreted on the basis of a common molecular model for water, consisting of two types of clusters, namely W(I) and W(II) accompanied by free molecules W(III). The principle of thermal equivalent dilution (TED) is the potent tool (Ergodic Hypothesis) employed to monitor the water equilibrium and to determine the number xi(w) of water molecules W(III) involved in each process. The hydrophobic hydration processes can be subdivided into two Classes: Class A includes those processes for which the transformation A(-xi(w)W(I)-->xi(w)W(II)+xi(w)W(III)+cavity) takes place with the formation of a cavity, by expulsion of xi(w) water molecules W(III) whereas Class B includes those processes for which the opposite transformation B(-xi(w)W(II)-xi(w)W(III)-->xi(w)W(I)-cavity) takes place with reduction of the cavity, by condensation of xi(w) water molecules W(III). The number xi(w) depends on the size of the reactants and measures the extent of the change in volume of the cavity. Disaggregating the thermodynamic functions DeltaH(app) and DeltaS(app) as the functions of T (or lnT) and xi(w) has enabled the separation of the thermodynamic functions into work and thermal components. The work functions DeltaG(Work), DeltaH(Work) and DeltaS(Work) only refer specifically to the hydrophobic effects of cavity formation or cavity reduction, respectively. The constant self-consistent unitary (xi(w)=1) work functions obtained from both large and small molecules indicate that the same unitary reaction is taking place, independent from the reactant size. The thermal functions DeltaH(Th) and DeltaS(Th) refer exclusively to the passage of state of water W(III). Essential mathematical algorithms are presented in the appendices. PMID:20656401

Fisicaro, E; Compari, C; Braibanti, A

2010-10-01

103

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

PubMed

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 12h, microwave-assisted at 75C for 6min, and oven heated at 80C for 2h 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

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

2013-03-01

104

Evaluation of matrix effect in isotope dilution mass spectrometry based on quantitative analysis of chloramphenicol residues in milk powder.  

PubMed

In the present study, we developed a comprehensive strategy to evaluate matrix effect (ME) and its impact on the results of isotope dilution mass spectrometry (IDMS) in analysis of chloramphenicol (CAP) residues in milk powder. Stable isotope-labeled internal standards do not always compensate ME, which brings the variation of the ratio (the peak area of analyte/the peak area of isotope). In our investigation, impact factors of this variation were studied in the extraction solution of milk powder using three mass spectrometers coupled with different ion source designs, and deuterium-labeled chloramphenicol (D5-CAP) was used as the internal standard. ME from mobile phases, sample solvents, pre-treatment methods, sample origins and instruments was evaluated, and its impact on the results of IDMS was assessed using the IDMS correction factor (?). Our data showed that the impact of ME of mobile phase on the correction factor was significantly greater than that of sample solvent. Significant ion suppression and enhancement effects were observed in different pre-treated sample solutions. The IDMS correction factor in liquid-liquid extraction (LLE) and molecular imprinted polymer (MIP) extract with different instruments was greater or less 1.0, and the IDMS correction factor in hydrophilic lipophilic balance (HLB) and mix-mode cation exchange (MCX) extract with different instruments was all close to 1.0. To the instrument coupled with different ion source design, the impact of ME on IDMS quantitative results was significantly different, exhibiting a large deviation of 11.5%. Taken together, appropriate chromatographic conditions, pre-treatment methods and instruments were crucial to overcome ME and obtain reliable results, when IDMS methods were used in the quantitative analysis of trace target in complex sample matrix. PMID:24356223

Li, Xiu Qin; Yang, Zong; Zhang, Qing He; Li, Hong Mei

2014-01-01

105

Some Physics Aspects of Isotope Scaling of Ion Thermal Transport  

NASA Astrophysics Data System (ADS)

We have already reported results of isotopic scaling experiments in the Columbia Linear Machine which indicate inverse dependence of ion thermal conductivity due to ITG modes on the isotopic mass close to K_bot A_i-0.5[1]. This is similar to the tokamak results, but in stark contrast to most present theoretical models. We now experimentally study some of the possible physics basis of this result using the following possible causal chain for transport: (i) Linear instability drive (?) causes fluctuation => (ii) Saturated fluctuation level (tilden) via nonlinear coupling => (iii) Statistical mechanics of scattering of energy and particles. The isotopic scaling of linear growth rate is measured via a feedback diagnostic for two gases, Hydrogen and Deuterium. Our preliminary experiments indicated that linear growth rate is mass dependent and lower for Deuterium. Secondly, we will report on the isotopic effect on the nonlinear dynamics, say 3-wave coupling, via changes in the bi-coherence between the two gases. *The research is supported by U.S. DOE grant DE - FG02-98ER54464. [1] V.Sokolov and A.K.Sen, Bull. Am. Phys. Soc., DPP, 46 (8), p. 243 (2001).

Sokolov, Vladimir; Sen, Amiya K.; Fan, Wenli

2002-11-01

106

Thermal Neutron Capture Cross Sections of the PalladiumIsotopes  

SciTech Connect

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.

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

2006-07-17

107

Determination of zinc in plant samples by isotope dilution inductively coupled plasma mass spectrometry.  

PubMed

Determination of zinc involved spiking with (68)Zn enriched solution, digestion by HNO(3)+H(2)O(2) in microwave decomposition unit, off-line separation of zinc on Chelex-100 column and measurement of ((64)Zn+(66)Zn)/(68)Zn isotope ratio on ICP-MS spectrometer with a quadrupole mass filter. After optimization of standard operation procedure (details are given) the method was validated. LOD was found to be 0.3 mug g(-1) for the procedure without zinc separation and 3.6 mug g(-1) for the procedure involving zinc separation, respectively. The accuracy of results was proved by analyses of several CRM and a primary solution of zinc, the concentration of which was verified by gravimetry and complexometric titration. Barium is the only element causing serious interferences and it must be removed from samples. The uncertainty budget is given together with the scheme of combined uncertainty calculation. The main uncertainty components are contamination during zinc separation and uncertainty of isotopic composition of natural zinc. PMID:18968316

Mestek, O; Komnkov, J; Koplk, R; Suchnek, M

2001-06-21

108

Measurement uncertainty in single, double and triple isotope dilution mass spectrometry.  

PubMed

Triple IDMS has been applied for the first time to the quantification of element concentrations. It has been compared with single and double IDMS obtained on the same sample set in order to evaluate the advantages and disadvantages of triple IDMS over single and double IDMS as an analytical reference procedure. The measurement results of single, double and triple IDMS are indistinguishable, considering rounding due to the individual measurement uncertainties. As expected, the relative expanded uncertainties (k?=?2) achieved with double IDMS (0.08%) are dramatically smaller than those obtained with single IDMS (1.4%). Triple IDMS yields the smallest relative expanded uncertainties (k?=?2, 0.077%) unfortunately at the expense of a much higher workload. Nevertheless triple IDMS has the huge advantage that the isotope ratio of the spike does not need to be determined. Elements with high memory effects, highly enriched spikes or highest metrological requirements may be typical applications for triple IDMS. PMID:22223313

Vogl, Jochen

2012-02-15

109

Transient Thermal Performance of a Radially Diluted and Centrally Cooled Nuclear Fuel Cell  

Microsoft Academic Search

Steady and unsteady heat transfer in a radially diluted and centrally cooled nuclear fuel rod are investigated numerically. The nuclear fuel cell is radially diluted by the addition of a non-heat-generating material of high melting point, high specific heat, and high resistance to oxidation and ignition, with the intention of increasing its time delay before melting, when convection is totally

F. Moukalled; R. Nuwayhid; I. Lakkis

1995-01-01

110

An accurate and transferable protocol for reproducible quantification of organic pollutants in human serum using direct isotope dilution mass spectrometry.  

PubMed

A robust method has been developed for easy transfer between analytical laboratories to obtain highly accurate and reproducible quantification of persistent organic pollutants (POPs) in micro-volumes of serum. This method is suited for analysts researching the impact of environmental exposure on human health. When performed by highly trained analysts, existing methods can produce high quality data; however, complex sample preparation steps often cannot be consistently replicated by laboratories, leading to variance in extraction recovery and quantitation. By combining stir-bar sorptive extraction (SBSE) with direct isotope dilution (D-ID) mass spectrometry quantification, a new analytical method was developed. The D-ID quantification significantly improved accuracy, corrected sample-to-sample irreproducibility, and reduced sample preparation time. Independent production of statistically identical data then confirmed transfer of the validated operating protocol to an off-site laboratory with different instrument models. SBSE performance was compared with industry-accepted extraction techniques. D-ID quantification was compared with peer-reviewed relative isotopic response factor (RF) quantification methods. Holding other variables constant, D-ID improved accuracy by 250% and precision by 300% compared with RF; SBSE improved accuracy by 37% compared to industry-accepted extraction methods. Limits of quantification of the analytes ranged from 60 pg g(-1) to 1 ?g g(-1). Protocol transfer exhibited <7% mean between-laboratory error and <2% mean within-laboratory RSD. These results indicate that a transferable method has been developed for academic, government, commercial, and clinical laboratories seeking to maximize throughput and improve quantitative validity. This validated method was applied in a recent clinical study to assess non-communicable disease in children in Pennsylvania, USA. PMID:25302342

Boggess, Andrew J; Rahman, G M Mizanur; Pamukcu, Matt; Faber, Scott; Kingston, H M Skip

2014-10-27

111

Development of a simple, fast, and accurate method for the direct quantification of selective estrogen receptor modulators using stable isotope dilution mass spectrometry.  

PubMed

A rapid analytical procedure was developed to quantify major selective estrogen receptor modulators (SERMs) simultaneously using stable isotope dilution mass spectrometry (SID-LCMS). Two novel isotopically labeled (SIL) analogues of natural SERMs, genistein and daidzein, were synthesized using a H/D exchange reaction mechanism. Computational chemistry coupled with MS and NMR data confirmed the site and mechanism of deuteration. The SIL analogues, which were mono- and dideutero substituted at the ortho positions, exhibited minimal deuterium isotope effects and were stable under the employed sample preparation protocol and MS analysis. An isotopic overlap correction was successfully employed to improve the accuracy and precision of the analytical method. The developed method, which was found to be sensitive, selective, precise and accurate, could be a valuable tool for research focused on determining the bioavailability of individual SERMs. PMID:23805827

Yerramsetty, Vamsidhar; Roe, Mikel; Cohen, Jerry; Hegeman, Adrian; Ismail, Baraem

2013-07-24

112

Quantitative determination of four nitrofuran metabolites in meat by isotope dilution liquid chromatography-electrospray ionisation-tandem mass spectrometry.  

PubMed

A confirmatory method based on isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the low-level determination of residues of four nitrofuran veterinary drugs in meat, e.g., furazolidone, furaltadone, nitrofurantoin, and nitrofurazone. The procedure entails an acid-catalysed release of protein-bound metabolites, followed by their in situ conversion into the 2-nitrobenzaldehyde (NBA) imine-type derivatives. Liquid-liquid extraction and clean-up on a polymeric solid phase extraction cartridge are then performed before LC-MS/MS analysis by positive electrospray ionisation (ESI) applying multiple reaction monitoring of three transition reactions for each compound. Reliable quantitation is obtained by using one deuterated analogue per analyte (d4-NBA derivative) as internal standard (IS). Validation of the method in chicken meat was conducted following the European Union (EU) criteria for the analysis of veterinary drug residues in foods. The decision limits (CCalpha) were 0.11-0.21 microg/kg, and the detection capabilities (CCbeta) 0.19-0.36 microg/kg, thus below the minimum required performance limit (MRPL) set at 1 microg/kg by the EU. The method is robust and suitable for routine quality control operations, and more than 200 sample injections were performed without excessive pollution of the mass spectrometer or loss of LC column performance. PMID:15844512

Mottier, Pascal; Khong, Seu-Ping; Gremaud, Eric; Richoz, Janique; Delatour, Thierry; Goldmann, Till; Guy, Philippe A

2005-03-01

113

Comprehensive quantification of monolignol-pathway enzymes in populus trichocarpa by protein cleavage isotope dilution mass spectrometry.  

PubMed

The economic value of wood/pulp from many tree species is largely dictated by the quantity and chemical properties of lignin, which is directly related to the composition and linkages of monolignols comprising the polymer. Although much is known regarding the monolignol biosynthetic pathway, our understanding is still deficient due to the lack of quantitative information at the proteomic level. We developed an assay based on protein cleavage isotope dilution mass spectrometry (PC-IDMS) for the determination of all potential, primary enzymes involved in the biosynthesis of monolignols and the peroxidases responsible for their polymerization to form lignin in the model tree species, Populus trichocarpa. Described is the identification of quantitative surrogate peptides through shotgun analysis of native and recombinant proteins, optimization of trypsin proteolysis using fractional factorial design of experiments, and development of a liquid chromatography-selected reaction monitoring method for specific detection of all targeted peptides. Of the 25 targeted enzymes, three were undetected in the normal xylem tissues, and all but two of the detectable species showed good day-to-day precision (CV < 10%). This represents the most comprehensive assay for quantification of proteins regulating monolignol biosynthesis and will lead to a better understanding of lignin formation at a systems level. PMID:22524869

Shuford, Christopher M; Li, Quanzi; Sun, Ying-Hsuan; Chen, Hsi-Chuan; Wang, Jack; Shi, Rui; Sederoff, Ronald R; Chiang, Vincent L; Muddiman, David C

2012-06-01

114

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

PubMed

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 ?g/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

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

2014-09-10

115

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

SciTech Connect

{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.

Snyder, Laura R. [Department of Chemistry, University of Washington, Seattle, WA (United States); Cruz-Aguado, Reyniel [Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC (Canada); Sadilek, Martin [Department of Chemistry, University of Washington, Seattle, WA (United States); Galasko, Douglas [Department of Neurosciences, University of California at San Diego, San Diego, CA (United States); Shaw, Christopher A. [Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC (Canada); Montine, Thomas J. [Department of Pathology, University of Washington, Seattle, WA 98104 (United States)], E-mail: tmontine@u.washington.edu

2009-10-15

116

Radioimmunoassay and liquid-chromatographic analysis for free cortisol in urine compared with isotope dilution-mass spectrometry  

SciTech Connect

Three different routine methods for analysis for urinary cortisol with those by a highly specific reference method based on isotope dilution-mass spectrometry (I) were compared. A ''high-performance'' liquid-chromatographic method (II) gave the most comparable results (regression coefficient 0.86, intercept 9 nmol/L). For some urines much lower values were obtained by I than by II. Two radioimmunoassay (III) methods, one involving direct assay and one involving extraction, gave less-accurate results (regression coefficients of 1.87 and 1.52 and intercepts of 86 and 12 nmol/L, respectively), although values obtained by III and by I correlated well (r = 0.95-0.99), indicating a relation between the free cortisol and the compounds interfering in III. The apparent accuracy for the extraction method was improved by using as calibration standards urine samples previously assayed by I (regression coefficient 0.90, intercept 6 nmol/L). All four methods investigated showed a statistically significant sex-related difference in 24-h urinary cortisol excretion; evidently such a finding should be a prerequisite in any such method proposed for routine use.

Lantto, O.

1982-05-01

117

Investigation of isotope dilution mass spectrometric (ID-MS) method to determine niacin in infant formula, breakfast cereals and multivitamins.  

PubMed

An isotope dilution LC/mass spectrometric (ID-LC/MS) method was developed as a candidate reference method for the accurate determination of niacin in infant formula, breakfast cereals and multivitamin. After spiking nicotinamide-d(4) as an internal standard, infant formula and breakfast cereal samples were hydrolysed under alkaline condition. Samples were then analysed in SRM mode to detect nicotinic acid and nicotinic acid-d(4) at m/z 124?80 and 127?84, respectively. In the case of multivitamin sample that contains mainly free nicotinamide, LC/MS monitored nicotinamide and nicotinamide-d(4) at their SRM channels of m/z 123?80 and m/z 127?84, respectively, after simple extraction. The repeatability and reproducibility were tested for the validation of the developed ID/LC-MS method. Additionally, the developed analytical method was applied to determine total niacin contents in homogenised infant formula, homogenised multivitamin, and commercially available products including different types of infant formula, breakfast cereals, and multivitamin tablets. PMID:23411221

Shin, Hyunju; Kim, Byungjoo; Lee, Joonhee

2013-06-01

118

Development of an isotope dilution GC-MS procedure for the routine determination of creatinine in complex serum samples.  

PubMed

The accurate determination of creatinine in serum is essential for the diagnosis and treatment of kidney diseases. The determination of serum creatinine in clinical laboratories is routinely carried out by the Jaffe method or by enzymatic methods that may suffer from interferences. So, the development of reliable, fast and interference-free routine methods for complex serum samples is required. A fast method using isotope dilution mass spectrometry (IDMS) and gas chromatography mass spectrometry (GC-MS) was developed using minimally (13)C labeled creatinine analogs, multiple linear regression and rapid derivatization of creatinine with acetylacetone in 2 min by using focused microwave technology. The proposed method was validated with the analyses of two Certified Reference Materials (ERM-DA252a and ERM-DA253a) and compared with the Jaffe and enzymatic methods when analyzing real serum samples containing variable levels of bilirubin The proposed method is capable of providing accurate serum creatinine concentrations in less than 45 min from sample arrival to full data treatment and can be an alternative routine procedure for creatinine determinations in complex serum samples. PMID:24508629

Fernndez-Fernndez, Mario; Gonzlez-Antua, Ana; Rodrguez-Gonzlez, Pablo; An lvarez, M Elena; lvarez, Francisco V; Garca Alonso, J Ignacio

2014-04-20

119

Detection of allantoin in clinical samples using hydrophilic liquid chromatography with stable isotope dilution negative ion tandem mass spectrometry.  

PubMed

Allantoin is the major oxidation product of urate in humans and is a potential biomarker of oxidative stress. Several methods are used to measure allantoin in biological samples but they have inherent issues that can include lack of specificity and sensitivity, difficulty in sample preparation, or artefactual generation of allantoin. We have developed a method for measuring allantoin using hydrophilic liquid chromatography with stable isotope dilution tandem mass spectrometry (HILIC-MS/MS). It was validated for measuring allantoin in plasma, synovial fluid and urine from human subjects. The limit of quantification was determined to be 10 fmol and the assay displayed excellent linearity for the wide range of concentrations found in clinical samples. Relative standard deviations were <5% for between-day and <7% for within-day variation. Accuracy was between 100% and 104%. Concentrations of allantoin in plasma of healthy controls (2.0 ?M; interquartile range 1.4-3.6 ?M, n=35) was significantly lower (p<0.001) than that in plasma from patients with rheumatoid arthritis (3.7 ?M; IQR 3.0-5.6 ?M, n=43) and in synovial fluid of patients with gout (3.3 ?M; IQR 2.8-5.8 ?M, n=10). This newer HILIC-MS/MS method is a simple and highly sensitive assay for detection of allantoin. It can be used to assess the level of oxidative stress in human pathologies. PMID:22398212

Turner, Rufus; Stamp, Lisa K; Kettle, Anthony J

2012-04-01

120

Precise determination of dissolved silica in seawater by ion-exclusion chromatography isotope dilution inductively coupled plasma mass spectrometry.  

PubMed

Ion exclusion chromatograph (IEC) isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS) (IEC-ID-ICP-MS) was developed for measurement of dissolved silica in seawater, which was applied to production of certified reference materials (CRMs) of three concentration levels of nutrients (high, medium and low levels). IEC-ICP-MS has been employed to separate dissolved silica from seawater matrix. In the present study, in order to solve substantial problems due to spectral interference in ICP-MS and to improve the accuracy of IEC-ICP-MS beyond standard addition or conventional calibration methods, ID method was coupled with ICP-sector field mass spectrometry (operated under medium resolution,i.e., m/?m=4000). In addition, effects of various operating parameters in ICP-MS on a silicon background level were also investigated to obtain lower background equivalent concentration (BEC). As a result, 3 ng g(-1) of the BEC and 0.5 % of relative standard uncertainties were achieved in the analyses of dissolved silica in seawater samples at concentration levels from 4.0 mg kg (-1) to 0.8 mg kg(-1) as silicon. The developed method was successfully validated by analyses of an artificial seawater containing a known amount of silicate and the seawater certified reference material MOOS-2 produced by the National Research Council Canada. PMID:25086888

Nonose, Naoko; Cheong, Chikako; Ishizawa, Yukari; Miura, Tsutomu; Hioki, Akiharu

2014-08-20

121

Four frequently used test systems for serum cholesterol evaluated by isotope dilution gas chromatography-mass spectrometry candidate reference method.  

PubMed

We evaluated the performance of four frequently used cholesterol test systems, using split-sample measurements with a panel of 79 patients' specimens and isotope dilution gas chromatography-mass spectrometry (ID GS-MS) as a comparison method. The test systems were from Beckman, a Boehringer Mannheim, Merck, and Johnson & Johnson Clinical Diagnostics, performed on the Synchron CX7, Hitachi 717, Mega, and Ektachem 250 analyzers, respectively. The liner regression data for the method comparison [ID GS-MS as independent variable (x)] were for Beckman: slope = 1.012, intercept = 0.0243 mmol/L, dispersion (S(y/x)) = 0.1303 mmol/l, and correlation coefficient (r) = 0.9867; for Boehringer Mannheim: slope = 1.002, intercept = 0.114 mmol/L, Sy/x = 0.0759 mmol/L, r = 0.9954; for Merck: slope = 1.034, intercept = -0.0613 mmol/L, Sy/x = 0.0886 mmol/L, r = 0.9941; and for Johnson & Johnson Clinical Diagnostics: slope = 1.007, intercept = 0.01 mmol/L, Sy/x = 0.15 mmol/L, and r = 0.9811. These data demonstrate excellent state-of-the-art cholesterol measurement for some of the most widely used test systems. PMID:8605669

Thienpont, L M; Van Landuyt, K G; Stckl, D; De Leenheer, A P

1996-04-01

122

Survey of Natural Cadmium Isotope Fractionation by Double Spike Thermal Ionisation Mass Spectrometry  

Microsoft Academic Search

Wombacher et al. (2003) have shown recently that natural Cd isotope fractionations in terrestrial materials are extremely limited (~100 ppm\\/amu or less). Thus, excellent external precision is absolutely paramount if Cd isotope fractionations are to be adequately quantified. Here we present a new high-precision double spike (DS) technique for Cd isotopes in which the Cd is measured by thermal ionisation

A. Schmitt; S. J. Galer; W. Abouchami

2006-01-01

123

A HEAVY ISOTOPE IN A SOLID DRIFTS DOWN A THERMAL ENERGY GRADIENT  

E-print Network

183 A HEAVY ISOTOPE IN A SOLID DRIFTS DOWN A THERMAL ENERGY GRADIENT R. V. HESKETH CEGB Berkeley théories couramment admises. Ici, on présente une autre possibilité. Abstract. 2014 Isotopic substitution, the sign of isotopic thermomigration is significant. The observed sign is a severe embarrassment

Paris-Sud XI, Université de

124

Simultaneous detection and quantification of 3-nitrotyrosine and 3-bromotyrosine in human urine by stable isotope dilution liquid chromatography tandem mass spectrometry  

Microsoft Academic Search

Nitration and bromination of proteins, giving rise to the respective 3-nitrotyrosine (3NT) and 3-bromotyrosine (3BT), are implicated in asthma, allergic inflammatory disorders, and cancer. We have developed an isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry (LC\\/MS\\/MS) assay for simultaneous analysis of protein-bound 3NT and 3BT in human urine. The detection limits (S\\/N=3) were 10pg (44fmol) for 3NT and

Hauh-Jyun Candy Chen; Wei-Loong Chiu

2008-01-01

125

Determination of neptunium in plutonium and mixed uranium-plutonium samples by isotope dilution gamma-spectrometry with 243 Am as a spike  

Microsoft Academic Search

A method was developed for isolating neptunium from Pu, U or mixed oxide (MOX) samples and its determination by isotope dilution -spectrometry (IDGS) using239Np (243Am) as a spike. Extraction chromatography with trilaurylamine fixed on a SGX-C18 support was used for the isolation of Np. The decontamination factors for U, Pu, Am and Pa vary between 10002000 and 100, respectively. The

F. Sus; J. L. Parus; W. Raab

1996-01-01

126

Determination of cadmium in oyster tissue using isotope dilution inductively coupled plasma mass spectrometry: comparison of results obtained in the standard and He\\/H 2 cell modes  

Microsoft Academic Search

An inductively coupled plasma quadrupole mass spectrometer equipped with an octopole collision\\/reaction cell was used for\\u000a the determination of cadmium in oyster tissue samples using isotope dilution inductively coupled plasma mass spectrometry.\\u000a The oyster samples in question were found to contain Mo and Zr. In our feasibility study on a Cd standard solution (10?g\\u000a L?1) containing a matrix of Mo

Yiu-chung Yip; Hei-shing Chu; Kwok-chu Chan; Kam-kit Chan; Ping-yuk Cheung; Wing-cheong Sham

2006-01-01

127

Simultaneous supercritical fluid extraction and chemical derivatization for the gas chromatographicisotope dilution mass spectrometric determination of amphetamine and methamphetamine in urine  

Microsoft Academic Search

An in-situ supercritical fluid extraction (SFE) and chemical derivatization (ChD) procedure followed by gas chromatographyisotope dilution mass spectrometry (GCMS) for the determination of amphetamines in urine is described and evaluated. While using celite as the SFE wet-support, the one-pot sample pretreatment procedure also employs ammonium water to alkalize the urine matrix that contains protonated amphetamine (AP) and methamphetamine (MA). The

Sheng-Meng Wang; Yun-Seng Giang; Yong-Chien Ling

2001-01-01

128

The role of root-associated Klebsiella pneumoniae in the nitrogen nutrition of Poa pratensis and Triticum aestivum as estimated by the method of 15 N isotope dilution  

Microsoft Academic Search

SummaryThe technique of15N isotope dilution was used to verify that nitrogen was fixed and transferred to the plant byKlebsiella pneumoniae strain Pp in association withPoa pratensis orTriticum aestivum. Surface sterilized, sprouting seeds were inoculated withK. pneumoniae and grown in sand in modified Leonard jars. Potassium nitrate enriched with15N was used to provide N concentrations ranging from 1040 mg Nl1 nutrient

Kielo Haahtela; Kirsti Kari

1986-01-01

129

Simultaneous determination of reduced glutathione, glutathione disulphide and glutathione sulphonamide in cells and physiological fluids by isotope dilution liquid chromatographytandem mass spectrometry  

Microsoft Academic Search

A stable isotope dilution liquid chromatography tandem mass spectrometry (LCMS\\/MS) method was developed and validated for simultaneously quantifying glutathione (GSH), glutathione disulphide (GSSG) and glutathione sulphonamide (GSA) from biological samples. GSA is a selective product of the reaction of GSH with hypochlorous acid and a potential biomarker of myeloperoxidase activity. GSH was detected as the N-ethylmaleimide alkylated adduct, as formation

D. Tim Harwood; Anthony J. Kettle; Siobhain Brennan; Christine C. Winterbourn

2009-01-01

130

Determination of vertical fluxes of sulfur dioxide and dimethyl sulfide in the remote marine atmosphere by eddy correlation and an airborne isotopic dilution atmospheric pressure ionization mass spectrometer  

NASA Astrophysics Data System (ADS)

Vertical fluxes of dimethyl sulfide (DMS) and sulfur dioxide (SO 2) were determined by eddy correlation and an isotopic dilution atmospheric pressure ionization mass spectrometer (APIMS) on an aircraft platform. The sampling frequency of the isotopic dilution APIMS ranged from 1 Hz to 25 Hz for real-time measurements. Measurements were made near the surface in the marine boundary layer to over 6 km in the free troposphere. The APIMS demonstrated an average sensitivity of 80 cps/pptv for DMS and SO2 with a signal-to-noise (S/N) ratio > 5. A lower limit of detection of 0.1 pptv in a one second integration period was also determined for DMS and SO2 in airborne atmospheric measurements. Use of the isotopic dilution technique provided an internal calibration of every ambient sample along with manifold conditioning for rapid and efficient transport of the ambient species through the manifold. As a result the eddy correlation flux determinations were accurate, precise, and reproducible. Laboratory results suggest the addition of ozone in excess of 45 ppbv to the APIMS sampling manifold to ensure unaltered formation of SO5 - ion (the ion detected for SO2). Use of a Nafion dryer was warranted for sensitive APIMS detection of SO2 in humid air. A Nafion dryer along with an air temperature of 400C was required for sensitive APIMS detection of DMS in humid air. Results from an initial airborne test deployment in continental air include a successful SO2 intercomparison between the APIMS and a GC/MS/ILS (isotopically labeled standard-gas chromatography/mass spectrometer). Fast SO2 measurements in thin moist layers and pollution plumes demonstrated the utility of the fast isotopic dilution APIMS technique. Results from a second airborne test deployment in the remote marine boundary layer include a successful DMS intercomparison and eddy correlation fluxes of DMS and SO2 from isotopic dilution APIMS measurements. The average DMS flux near the surface was (1.7 +/- 0.2) 1013 molecules m-2 s-1. A flux gradient for DMS generated a DMS surface flux of (2.3 +/- 0.7) 10 13 molecules in m-2 s-1 and a DMS entrainment flux of (7.5 +/- 4.4) 1012 molecules m-2 s-1. High resolution altitude profiles of DMS allowed for the determination of the DMS entrainment velocity (1.9 +/- 1.1 cm/s). A SO2 flux of (4.3 +/- 1.9) 1012 molecules m-2 s-1 and a deposition velocity of 2.4 +/- 1.1 mm/s also was determined. All values reported are in good agreement with the literature.

Mitchell, Glenn M.

2001-08-01

131

Development of isotope dilution-liquid chromatography/mass spectrometry combined with standard addition techniques for the accurate determination of tocopherols in infant formula.  

PubMed

During the development of isotope dilution-liquid chromatography/mass spectrometry (ID-LC/MS) for tocopherol analysis in infant formula, biased measurement results were observed when deuterium-labeled tocopherols were used as internal standards. It turned out that the biases came from intermolecular H/D exchange and intramolecular H/D scrambling of internal standards in sample preparation processes. Degrees of H/D exchange and scrambling showed considerable dependence on sample matrix. Standard addition-isotope dilution mass spectrometry (SA-IDMS) based on LC/MS was developed in this study to overcome the shortcomings of using deuterium-labeled internal standards while the inherent advantage of isotope dilution techniques is utilized for the accurate recovery correction in sample preparation processes. Details of experimental scheme, calculation equation, and uncertainty evaluation scheme are described in this article. The proposed SA-IDMS method was applied to several infant formula samples to test its validity. The method was proven to have a higher-order metrological quality with providing very accurate and precise measurement results. PMID:23830431

Lee, Joonhee; Jang, Eun-Sil; Kim, Byungjoo

2013-07-17

132

Application of stable isotope dilution assays based on liquid chromatography-tandem mass spectrometry for the assessment of folate bioavailability.  

PubMed

A pilot study was performed to prove the suitability of stable isotope dilution assays for assessing the bioavailability of endogenous folates in foods. By using [2H(4)]folic acid, [2H(4)]tetrahydrofolate, [2H(4)]5-methyltetrahydrofolate, [2H(4)]5-formyltetrahydrofolate and [2H(4)]10-formylfolic acid as internal standards, folates in spinach, apple juice and blood plasma were quantified by liquid chromatography coupled to tandem mass spectrometry. To liberate the pteroyl monoglutamates, sample extracts of foods were treated by rat plasma. Sample clean-up was achieved by solid-phase extraction on anion-exchange cartridges, which proved to be sufficient to obtain mass chromatograms devoid of matrix interferences. The bioavailability study was designed as a short-time protocol with three meals, the first consisting of 600 g spinach (meal A), the second consisting of 600 g apple sauce with additionally 400 microg synthetic folic acid (meal B) and the third consisting solely of 600 g apple sauce (meal C). Prior to the meals, the participating volunteer's tissue was saturated with folates to achieve a significant response of plasma folate to the meals. After consumption of meals A and B a significant rise in folate plasma level compared to meal C (mean level at 28 microg/ml) was observed. The relative bioavailability of folate following meal A exceeded significantly the suggested value of 50% for food folates by taking the dose-normalized area under the curve (AUC) following ingestion of meal B as reference. PMID:12860024

Rychlik, Michael; Netzel, Michael; Pfannebecker, Inga; Frank, Thomas; Bitsch, Irmgard

2003-07-25

133

Quantification of the H7N7 Influenza Hemagglutinin and Neuraminidase by Isotope-Dilution Mass Spectrometry  

PubMed Central

Influenza vaccination is the primary method for preventing influenza and its severe complications. Government agencies dedicate much time and resources to surveillance of circulating influenza strains and try to predict which strains would be most likely to be transmitted among humans in order to develop a safe and effective influenza vaccine each year. Influenza viral strains undergo rapid mutations and may experience an abrupt change in the surface proteins hemagglutinin (HA) and neuraminidase (NA), which can result in a virus that is radically different from those previously circulating in human populations. This is the reason that seasonal vaccines must be annually updated. The mutations and their effects on the virus and its subsequent transmissibility to or between humans cannot be adequately foreseen. Thus, the strategy of predicting which strain of influenza may cause the next worldwide pandemic so that vaccines can be manufactured and stockpiled prior to the emergence of an influenza pandemic may not be successful. It is instead, imperative that the process of producing a vaccine that will protect the public in the face of an unpredicted virus strain be streamlined and as swift as possible. We have developed an isotope dilution mass spectrometry method to quantify HA and NA in H7N7 influenza samples. The IDMS method involves enzymatic digestion of viral proteins and the specific detection of target peptides. Four HA peptides and two NA peptides of the H7N7 influenza strain were used in the analysis to ensure complete digestion of the protein, verify accuracy of the measurement, and provide flexibility in the case of amino acid changes among H7N7 strains. The IDMS method is an accurate, precise, sensitive, and selective method to quantify the amount of HA and NA antigens in crude allantoic fluid, purified virus samples, and final vaccine presentations.

Williams, T.; Pirkle, J.; Barr, J.; Santana, Wanda

2013-01-01

134

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

SciTech Connect

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.

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

2006-01-01

135

Studies of transport and collection characteristics of gaseous mercury in natural gases using amalgamation and isotope dilution analysis.  

PubMed

Transport and collection characteristics were studied for gaseous elemental mercury (Hg(0)(g)) in natural gases using newly developed methodology based on amalgamation, isotope dilution with permeation tubes and inductively coupled plasma mass spectrometry. The study involved different Au-Pt collection tube designs, tubing materials and gaseous matrices, including air, natural and sales gas, as well as methane and sales gas to which hydrogen sulfide (H(2)S) had been added. The Hg(0)(g) capacity of the Au-Pt tubes was determined to 3.5 +/- 0.1 microg. Blanks and detection limits of gaseous mercury (Hg(g)) were 58 +/- 17 pg m(-3) and 50 pg m(-3), respectively, for a 60 L sample volume. For the gases tested, added Hg(0)(g) tracers could be collected with 90% or higher efficiency at flow rates and volumes of up to 10 L min(-1) and 100 L, respectively. The collection efficiency was found to be independent of the type of gas tested, even in the presence of H(2)S. However, for the gases containing H(2)S, the apparent transport efficiency of added Hg(0)(g) tracers through stainless steel tubing varied from 50 to 150% upon changing the temperature from 25 to 100 degrees C. The interaction of stainless steel with Hg(0)(g) leading to either a sink, or source of Hg, was not observed in the absence of H(2)S, nor was it observed for PTFE tubing in the presence of H(2)S. These observations raise questions about the applicability of currently used sampling procedures for determination of Hg(g) in H(2)S rich natural gases, including the 6978-2 ISO standard method, in which stainless steel is a prescribed material for tubing and valves of the sampling apparatus. PMID:17525816

Larsson, Tom; Frech, Wolfgang; Bjrn, Erik; Dybdahl, Bjrn

2007-06-01

136

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

SciTech Connect

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.

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

2005-01-01

137

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

PubMed Central

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 ?g 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

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

2012-01-01

138

Identification and quantification of human DNA repair protein NEIL1 by liquid chromatography/isotope-dilution tandem mass spectrometry.  

PubMed

Accumulated evidence points to DNA repair capacity as an important factor in cancer and other diseases. DNA repair proteins are promising drug targets and are emerging as prognostic and therapeutic biomarkers. Thus, the knowledge of the overexpression or underexpression levels of DNA repair proteins in tissues will be of fundamental importance. In this work, mass spectrometric assays were developed for the measurement in tissues of the human DNA repair protein NEIL1 (hNEIL1), which is involved in base excision and nucleotide excision repair pathways of oxidatively induced DNA damage. Liquid chromatography/isotope-dilution tandem mass spectrometry (LC-MS/MS), in combination with a purified and fully characterized recombinant (15)N-labeled analogue of hNEIL1 ((15)N-hNEIL1) as an internal standard, was utilized to develop an accurate method for the quantification of hNEIL1. Both hNEIL1 and (15)N-hNEIL1 were hydrolyzed with trypsin, and 18 tryptic peptides from each protein were identified by LC-MS/MS on the basis of their full-scan mass spectra. These peptides matched the theoretical peptides expected from trypsin hydrolysis of hNEIL1 and provided a statistically significant protein score that would unequivocally identify hNEIL1. The product ion spectra of the tryptic peptides from both proteins were recorded, and the characteristic product ions were defined. Selected-reaction monitoring was used to analyze mixtures of hNEIL1 and (15)N-hNEIL1 on the basis of product ions. Additional confirmation of positive identification was demonstrated via separation of the proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and in-gel tryptic digestion followed by LC-MS/MS analysis. These results suggest that the developed assays would be highly suitable for the in vivo positive identification and accurate quantification of hNEIL1 in tissues. PMID:23268652

Reddy, Prasad T; Jaruga, Pawel; Kirkali, Gldal; Tuna, Gamze; Nelson, Bryant C; Dizdaroglu, Miral

2013-02-01

139

Some aspects of the thermal conductivity of isotopically enriched diamond single crystals  

NASA Astrophysics Data System (ADS)

New data on the thermal-conductivity temperature dependence k(T) of both natural abundance and isotopically enriched synthetic diamond gems are presented. The existing data on the thermal-conductivity temperature dependence k(T) of natural type-IIa diamond have been reanalyzed using a comprehensive Klemens-Callaway model. The high thermal conductivity of isotopically pure diamond is shown to be consistent with the model.

Onn, D. G.; Witek, A.; Qiu, Y. Z.; Anthony, T. R.; Banholzer, W. F.

1992-05-01

140

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

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

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

2014-06-17

141

Structure and saccharification of rice straw pretreated with sulfur trioxide micro-thermal explosion collaborative dilutes alkali.  

PubMed

In this paper, a sulfur trioxide collaborative dilutes alkali method has been developed to pre-treat rice straw and it has been studied that the pre-treated rice straw structure affected the saccharification of the rice straw hydrolyzed by cellulose enzymatic hydrolysis. The results show that the reaction of the sulfur trioxide with rice straw resulted in the internal micro-thermal explosion, and the saccharification rate was 91% based on the pretreated rice straw with sulfur trioxide for 4h following 1% w/v NaOH treatment for 7h at 50C. PMID:21392977

Yao, Ri-sheng; Hu, Hua-jia; Deng, Sheng-song; Wang, Huai; Zhu, Hui-xia

2011-05-01

142

Isotope and strain effects on thermal conductivity of silicon thin film  

NASA Astrophysics Data System (ADS)

In this paper, non-equilibrium molecular dynamics simulations (NEMD) are employed to study the effects of isotope and in-plane strain on the thermal conductivity of silicon thin film. The results show that the thermal conductivity of silicon thin film decreases with the isotope concentration at the lower concentration and increases with the isotope concentration at the higher concentration, respectively. In addition, simulations on the strained film indicate that the thermal conductivity decreases monotonously with the applied strain. To achieve a fundamental understanding of the physical mechanisms, phonon density of states (DOS) and phonon dispersion are analyzed in details. High frequency phonons are found to be sensitive to the impurity, which leads to the reduction of phonon group velocity. For the strained thin film, high frequency phonons, especially of transverse optical (TO) phonon branch, play an important role in the change of thermal conductivity. Our findings suggest the great potential of tailoring the thermal properties by isotope and mechanical strain.

Yang, Zhenyu; Feng, Rui; Su, Fei; Hu, Dayong; Ma, Xiaobing

2014-11-01

143

Investigation of the tungsten isotopes via thermal neutron capture  

NASA Astrophysics Data System (ADS)

Total radiative thermal neutron-capture ?-ray cross sections for the 182,183,184,186W isotopes were measured using guided neutron beams from the Budapest Research Reactor to induce prompt and delayed ? rays from natural and isotopically-enriched tungsten targets. These cross sections were determined from the sum of measured ?-ray cross sections feeding the ground state from low-lying levels below a cutoff energy, Ecrit, where the level scheme is completely known, and continuum ? rays from levels above Ecrit, calculated using the Monte Carlo statistical-decay code dicebox. The new cross sections determined in this work for the tungsten nuclides are ?0(182W)=20.5(14) b and ?11/2+(183Wm,5.2s )=0.177(18) b; ?0(183W)=9.37(38) b and ?5-(184Wm,8.33?s )=0.0247(55) b; ?0(184W)=1.43(10) b and ?11/2+(185Wm,1.67min)=0.0062(16) b; and, ?0(186W)=33.33(62) b and ?9/2+(187Wm,1.38?s)=0.400(16) b. These results are consistent with earlier measurements in the literature. The 186W cross section was also independently confirmed from an activation measurement, following the decay of 187W, yielding values for ?0(186W) that are consistent with our prompt ?-ray measurement. The cross-section measurements were found to be insensitive to choice of level density or photon strength model and only weakly dependent on Ecrit. Total radiative-capture widths calculated with dicebox showed much greater model dependence; however, the recommended values could be reproduced with selected model choices. The decay schemes for all tungsten isotopes were improved in these analyses. We were also able to determine new neutron-separation energies from our primary ?-ray measurements for the respective (n ,?) compounds: 183W [Sn=6190.88(6) keV]; 184W [Sn=7411.11(13) keV]; 185W [Sn=5753.74(5) keV]; and, 187W [Sn=5466.62(7) keV].

Hurst, A. M.; Firestone, R. B.; Sleaford, B. W.; Summers, N. C.; Rvay, Zs.; Szentmiklsi, L.; Basunia, M. S.; Belgya, T.; Escher, J. E.; Krti?ka, M.

2014-01-01

144

Effect of isotopic purity on thermal conductivity of boron nitride: A theoretical study  

NASA Astrophysics Data System (ADS)

In this letter we report the theoretical study of the effect of isotopic purity on the temperature dependence of the lattice thermal conductivity of cubic BN single crystals. The maximum thermal conductivity of pure BN is very high (~105 W/m/K) and it is comparable to the thermal conductivity of the carbon nanotube. It is two orders of magnitude higher than that of BN with 50%10B. We find that the very high contribution (~ 95%) of the usually neglected N-drift scattering at the thermal conductivity peak is the reason for such an increase in thermal conductivity of pure BN, compared to that of natural BN. The thermal conductivity is nearly symmetric with respect to the isotopic composition of boron and it is minimum for 50%10B and 50%11B. The role of phonon scattering by boron isotopes present in BN, in controlling the temperature dependence of thermal conductivity has been accurately quantified.

Barman, Saswati

2011-10-01

145

Accurate determination of element species by on-line coupling of chromatographic systems with ICP-MS using isotope dilution technique  

NASA Astrophysics Data System (ADS)

The instrumental design for coupling different liquid chromatographic systems such as ion, reversed phase, and size exclusion chromatography as well as capillary gas chromatography, with ICP-MS for the determination of element species is described. For accurate analyses obtaining 'real time' concentrations of chromatographic peaks, the isotope dilution mass spectrometric (IDMS) technique is applied. Two different spiking modes are possible, one using species-specific and another one using species-unspecific spike solutions of isotope-enriched labelled compounds. The species-specific mode is only possible for element species well defined in their structure and composition, for example iodate or selenite, whereas the species-unspecific mode must be applied in all cases where the structure and composition of the species is unknown, for example, for metal complexes with humic substances. For accurate determinations by the isotope dilution technique the mass discrimination effect must also be taken into account. Iodate, iodide and organoiodine species, including those of humic substances, have been analysed in mineral, drinking and environmental water samples by coupling different liquid chromatographic methods with ICP-IDMS. Heavy metal complexes with humic substances in water samples of different origin have been characterized by size exclusion/ICP-IDMS. The possibilities of determining different environmental selenium species are discussed and the results for the analysis of selenite and selenate, which has been carried out by GC/ICP-IDMS after converting these species into a volatile piazselenol compound, are presented.

Heumann, Klaus G.; Gallus, Stefan M.; Rdlinger, Gunther; Vogl, Jochen

1998-02-01

146

Origin of isotopic heterogeneity in the solar nebula by thermal processing and mixing of nebular dust  

NASA Astrophysics Data System (ADS)

We have investigated Mo and W isotope compositions in acid leachates and an insoluble residue from the Murchison carbonaceous chondrite. The new data reveal variable enrichments of s- and r-process isotopes and demonstrate that several isotopically diverse presolar components are present in Murchison. The insoluble residue is enriched in s-process Mo and W, evidently due to the enrichment of presolar SiC grains. In contrast, Mo and W released by leaching with weak acids are depleted in s-process isotopes, most likely reflecting the isotope composition of the homogenized portion of the protosolar nebula. The Mo and W isotope compositions of the different leach steps are broadly correlated as expected from s-process nucleosynthesis theory, indicating that Mo and W are presumably hosted in the same carriers. However, at the bulk meteorite scale, no nucleosynthetic W isotope anomalies have been identified (except for IVB iron meteorites) in spite of large Mo isotope heterogeneities among the same samples. This decoupling of Mo and W isotopes in bulk meteorites may reflect physical mixing of varying proportions of isotopically diverse presolar components with a "normal" solar nebula component. Due to the high W/Mo ratio and near-terrestrial W isotope composition of the latter, such mixing has no measurable effect on W isotopes, but results in large Mo isotope variations. Alternatively, thermal processes within the solar nebula imparted Mo isotope heterogeneity on an initially homogeneous mixture of presolar dust, while W was not affected. Removal of volatile Mo oxides during the thermal destruction of fragile presolar components would have created isotopically heterogeneous reservoirs of nebular dust. Accretion of meteorite parent bodies from such variably processed dust would thus result in Mo isotope heterogeneities at the bulk meteorite scale. Other elements such as Os and W were not or only slightly affected because they were more refractory during thermal processing and, therefore, remained isotopically homogeneous. Thermal processing of presolar dust within the solar nebula can thus account for both isotope heterogeneities observed for some elements and the lack of such isotopic heterogeneity for other elements.

Burkhardt, Christoph; Kleine, Thorsten; Dauphas, Nicolas; Wieler, Rainer

2012-12-01

147

Heavy stable isotope measurements with thermal ionization mass spectrometry : non mass-dependent fractionation effects between even and uneven isotopes.  

NASA Astrophysics Data System (ADS)

The isotopic composition of elements such as Zn, Cd, Pb can be precisely measured by thermal ionization mass spectrometry technique (TIMS) using the silicagel method [1]. Advantages of TIMS are: 1)- low instrumental isotope fractionation (from percent/amu down to permil/amu) and 2)- high ionization yields. The mass-dependent instrumental fractionation for elements characterized by more than 2 isotopes is generally corrected by employing the multispike method [?]. We will show that non mass-dependent fractionation effects are detected during the ionic thermal emission of Zn, Cd, Pb. In the case of Cd the even isotopes (110Cd, 112Cd, 114Cd) show a << normal >> (mass-dependent) fractionation whereas non mass-dependent fractionation effects are clearly resolved for the uneven isotopes (111Cd, 113Cd) relative to the even isotopes. The deviation from the mass-dependent evolution increases with time and reaches up to 0,1 %. A similar behavior is stated during the thermal emission of Zn. Mass-dependent fractionation occurs between the even isotopes (64Zn, {66}Zn, 68Zn), whereas the fractionation of 67Zn deviates from the mass-dependent evolution of the even isotopes by several permils. (amu??) << Abnormal fractionation >> of 207Pb during thermal emission of Pb in the order of a few 10{-4} relatively to the mass-dependent fractionation between 204Pb, 206Pb, 208Pb was described [2,3]. We consider that the non mass-dependent discrimination effects of the uneven compared to the even isotopes set in evidence for a variety of elements has a common origin. We attribute this effect to the hyperfine interaction between apparied electron and the nucleus of the uneven isotopes, that carries a nuclear magnetic moment. The coupling between electronic spin and nuclear spin occurs inside the silica-glass bead. This non mass-dependent fractionation probably may also be found for other elements when the silicagel loading technique is employed. [1] Akishin P.A. et al. 1957, Geokhimya 5, 425. - [2] Thirwall M.F. 2000, Chem. Geol. 163, 299-322. - [3] Doucelance R. and Manhs G. 2001, Chem. Geol. 176, 361-377.

Manhs, G.; Gpel, C.

2003-04-01

148

PUBLISHED ONLINE: 10 JANUARY 2012 | DOI: 10.1038/NMAT3207 Thermal conductivity of isotopically  

E-print Network

Ri is the average radius, is the Gruneisen parameter, which characterizes the anharmonicity of the lattice to ensure uniformity in material parameters. The thermal conductivity, K, of isotopically pure 12 C (0, and is a phenomenological parameter. The mass of a foreign atom (impurity, vacancy, defect or isotope) is known well whereas

149

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

DOEpatents

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.

Rutherford, William M. (Dayton, OH)

1988-05-24

150

Elemental analyses of soil and sediment fused with lithium borate using isotope dilution laser ablation-inductively coupled plasma-mass spectrometry.  

PubMed

Quantitative analysis using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) remains challenging primarily due to the lack of appropriate reference materials available for the wide variety of samples of interest and to elemental fractionation effects. Isotopic dilution mass spectrometry (IDMS) is becoming the methodology of choice to address these issues because the different isotopes of an element represent near-perfect internal standards. In this work, we investigated the lithium borate fusion of powdered solid samples, including soils, sediments, rock mine waste and a meteorite, as a strategy to homogenously distribute, i.e. equilibrate the elements and the added isotopically enriched standards. A comparison of this methodology using two pulsed laser ablation systems (ArF* excimer and Nd:YAG) with different wavelengths as well as two ICP-MS instruments (quadrupole and double-focusing sector field) was performed. Emphasis was put on using standard equipment to show the potential of the proposed strategy for its application in routine laboratories. Cr, Zn, Ba, Sr and Pb were successfully determined by LA-ICP-IDMS in six Standard Reference Materials (SRMs) representing different matrices of environmental interest. Experimental results showed the SRM fused glasses exhibited a low level of heterogeneity (intra- and inter-sample) for both natural abundance and isotopically enriched samples (RSD <3%, n=3, 1?). A good agreement between experimental results and the certified values was also observed. PMID:23953208

Malherbe, Julien; Claverie, Fanny; Alvarez, Aitor; Fernandez, Beatriz; Pereiro, Rosario; Molloy, John L

2013-09-01

151

Non-thermal plasma processing for environmental protection: decomposition of dilute VOCs in air  

Microsoft Academic Search

Non-thermal plasma processing is one of the most hopeful air-cleaning technologies to remove toxic gas contaminants in air. The historical background of the non-thermal plasma related with the electrostatics is described and the fundamental experimental system including the reactor designs and their power supplies is introduced. Some experimental results suggested the high potential of the plasma processing to decompose those

T. Oda

2003-01-01

152

Detection and quantification of 1,N6-ethenoadenine in human urine by stable isotope dilution capillary gas chromatography/negative ion chemical ionization/mass spectrometry.  

PubMed

1,N(6)-Ethenoadenine (epsilonAde) is a promutagenic lesion detected in tissue DNA; it has been shown that epsilonAde can be repaired by human DNA glycosylases, and it is expected to be excreted in urine. In this paper, we present for the first time detection and accurate quantification of epsilonAde in human urine samples by a highly sensitive and specific stable isotope dilution gas chromatography/negative ion chemical ionization/mass spectrometric assay (GC/NICI/MS). Analysis by GC/NICI/MS includes adduct enrichment by a solid phase extraction column, followed by electrophore labeling and postderivatization cleanup. Using selective ion monitoring mode, the assay allows quantification of 0.5 pg of epsilonAde in as little as 0.1 mL of the urine sample, which is equivalent to corresponding concentration quantification limit of 31 pM. Using this assay, concentrations of epsilonAde in the 24 h urine samples of 23 healthy individuals were determined, which ranged from 0 to 124 pg/mL. After we adjusted for creatinine, a statistically significant correlation was found between epsilonAde excretion and cigarette smoking in males (p = 0.03). Thus, this stable isotope dilution GC/NICI/MS assay offers a sensitive and accurate quantification of urinary epsilonAde as a potential biomarker for oxidative damage of DNA and repair. PMID:12971797

Chen, Hauh-Jyun Candy; Chiu, Wei-Loong

2003-09-01

153

Thermal neutron capture cross sections of the potassium isotopes  

NASA Astrophysics Data System (ADS)

Precise thermal neutron capture ?-ray cross sections ?? 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,?) ?-ray cross sections [Rvay and Molnr, Radiochimica ActaRAACAP0033-823010.1524/ract.91.6.361.20027 91, 361 (2003); Molnr, Rvay, and Belgya, Nucl. Instrum. Meth. Phys. Res. BNIMBEU0168-583X10.1016/S0168-583X(03)01529-5 213, 32 (2004)]. These data were combined with ?-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 ?-ray level schemes. Total radiative neutron cross sections were deduced from the total ?-ray cross section feeding the ground state, ?0=???(GS) after correction for unobserved statistical ?-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 ?0(39K)=2.280.04 b, ?0(40K)=907 b, and ?0(41K)=1.620.03 b from the prompt ?-ray data and the ?-ray transition probability P?(1524.66)=0.164(4) in the ?- decay of 42K in a low-background counting experiment.

Firestone, R. B.; Krti?ka, M.; Rvay, Zs.; Szentmiklosi, L.; Belgya, T.

2013-02-01

154

Thermal and Optical Properties of Zn1- x Mn x Te Diluted Magnetic Semiconductor Studied by Photoacoustic Spectroscopic Method  

NASA Astrophysics Data System (ADS)

Using photoacoustic spectroscopy, the composition-dependent absorption coefficient ( ?), thermal diffusivity ( ?), and optical bandgap ( E g) of Zn1- x Mn x Te diluted magnetic semiconductor have been measured. For higher Mn compositions, the absorption spectrum of the Zn-Mn-Te system consists of three regions, viz., the high absorption region, the exponential region, and the weak absorption tail. The bandgap follows a nonlinear variation with composition, showing a downward bowing with a minimum around x = 0.31 as a consequence of the electro-negativity difference between the substituted atoms. The composition-dependent band-edge effective mass of the carriers does not show the bowing behavior indicating that the momentum matrix is not the same for all the Zn1- x Mn x Te alloys due to different lattice constants. The absorption spectra show that the transition is allowed and direct.

Sarkar, B. K.; Verma, A. S.; Gupta, R. C.; Singh, K.

2010-03-01

155

Reversed-phase liquid chromatography/electrospray ionization/mass spectrometry with isotope dilution for the analysis of nitrate and nitrite in water.  

PubMed

A new method was developed for the analysis of nitrate and nitrite in a variety of water matrices by using reversed-phase liquid chromatography/electrospray ionization/mass spectrometry in the negative ion mode. For this direct analysis method, nitrate and nitrite anions were well separated under the optimized LC conditions, detected by monitoring m/z 62 and m/z 46 ions, and quantitated by using an isotope dilution technique that utilized the isotopically labeled analogs. The method sensitivity, accuracy, and precision were investigated, along with matrix effects resulting from common inorganic matrix anions. The isotope dilution technique, along with sample pretreatment using barium, silver, and hydrogen cartridges, effectively compensated for the ionization suppression caused by the major water matrix anions, including chloride, sulfate, phosphate, and carbonate. The method detection limits, based on seven reagent water replicates fortified at 0.01 mg N/L nitrate and 0.1 mg N/L nitrite, were 0.001 mg N/L for nitrate and 0.012-0.014 mg N/L for nitrite. The mean recoveries from the replicate fortified reagent water and lab water samples containing the major water matrix anions, were 92-103% for nitrate with an imprecision (relative standard deviation, RSD) of 0.4-2.1% and 92-110% for nitrite with an RSD of 1.1-4.4%. For the analysis of nitrate and nitrite in drinking water, surface water, and groundwater samples, the obtained results were generally consistent with those obtained from the reference methods. The mean recoveries from the replicate matrix spikes were 92-123% for nitrate with an RSD of 0.6-7.7% and 105-113% for nitrite with an RSD of 0.3-1.8%. PMID:21168849

Li, Yongtao; Whitaker, Joshua S; McCarty, Christina L

2011-01-21

156

The 2H thermal diffusion isotope effect in benzene and methanol  

NASA Astrophysics Data System (ADS)

The 2H thermal diffusion isotope effect is investigated for mixtures benzene-benzeed benzene-o dideuterobenzene, benzene-p didouterobenzen, mathanol d-methanold4, methanol-melhanol d. The thermal diffusion measurements wre made using a cylindrical thermo gravitational diffusion apparatus. (AIP)

Ma, Ning-Yuan Richard; Beyerlein, Adolph L.

1983-06-01

157

First-principles calculation of the isotope effect on boron nitride nanotube thermal conductivity.  

PubMed

Isotopic composition can dramatically affect thermal transport in nanoscale heat conduits such as nanotubes and nanowires. A 50% increase in thermal conductivity for isotopically pure boron ((11)B) nitride nanotubes was recently measured, but the reason for this enhancement remains unclear. To address this issue, we examine thermal transport through boron nitride nanotubes using an atomistic Green's function transport formalism coupled with phonon properties calculated from density functional theory. We develop an independent scatterer model for (10)B defects to account for phonon isotope scattering found in natural boron nitride nanotubes. Phonon scattering from (10)B dramatically reduces phonon transport at higher frequencies and our model accounts for the experimentally observed enhancement in thermal conductivity. PMID:19090747

Stewart, Derek A; Savi?, Ivana; Mingo, Natalio

2009-01-01

158

Overcoming matrix effects in electrospray: quantitation of ?-agonists in complex matrices by isotope dilution liquid chromatography-mass spectrometry using singly (13)C-labeled analogues.  

PubMed

In this work, the implementation of isotope dilution mass spectrometry (IDMS) using minimal labeling and isotope pattern deconvolution (IPD) is evaluated as a strategy for the minimization of matrix effects during trace determination of ?2-agonists in complex matrices by liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS). First, the parameters affecting the measurement of isotopic composition of organic compounds by liquid chromatography electrospray ionization high resolution mass spectrometry with a time-of-flight analyzer were evaluated using as a case of study three different ?2-agonists: clenbuterol, clenproperol and brombuterol. Then, a calibration graph-free IDMS methodology was evaluated in order to overcome matrix effects in LC-ESI-MS in complex samples. In this procedure singly (13)C-labeled analogues of clenbuterol, clenproperol and brombuterol were employed in combination with IPD. Using this approach accurate and precise results were obtained in the simultaneous quantification of ?2-agonists in human urine and bovine liver, even at the sub ngg(-1) and particularly in spite of the previously reported matrix effects. Recovery rates in the range of 97-114% in fortified human urine and from 95% to 111% in fortified bovine liver were obtained with RSD (%) of independent recovery experiments always lower than 6%. These results demonstrate that the proposed methodology based on the use of (13)C1-labeled standards and IPD is a reliable approach for accurate LC-MS quantitation of small molecules and compatible with full-scan high-resolution mass spectrometry. PMID:23523066

Gonzlez-Antua, Ana; Domnguez-Romero, Juan C; Garca-Reyes, Juan F; Rodrguez-Gonzlez, Pablo; Centineo, Giuseppe; Garca Alonso, J Ignacio; Molina-Daz, Antonio

2013-05-01

159

Hydrochemical and isotopic evidence of origin of thermal karst water at Taiyuan, northern China  

Microsoft Academic Search

Thermal karst groundwaters with temperatures ranging from 32.8 to 62.5 C were found at Taiyuan (??) City, the capital of\\u000a Shanxi (??) Province. To identify the origin of the thermal groundwater, the following tracers were used in this study: ?D, ?\\u000a 18O, 4He, 3He\\/4He, and major chemical constituents in water. Hydrochemical and isotopic data indicate that the thermal groundwaters in

Teng Ma; Yanxin Wang; Qinghai Guo; Chunmiao Yan; Rui Ma; Zheng Huang

2009-01-01

160

Development and validation of a new analytical method for the determination of 1,4-dichlorobenzene in honey by gas chromatographyisotope dilution mass spectrometry after steam-distillation  

Microsoft Academic Search

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 chromatographymass spectrometry (GCMS) in the selected ion monitoring (SIM) mode employing the isotopically labeled

E. V. Botitsi; P. N. Kormali; S. N. Kontou; A. Economou; D. F. Tsipi

2006-01-01

161

Validation of a simplified field-adapted procedure for routine determinations of methyl mercury at trace levels in natural water samples using species-specific isotope dilution mass spectrometry  

Microsoft Academic Search

A field-adapted procedure based on species-specific isotope dilution (SSID) methodology for trace-level determinations of methyl mercury (CH 3Hg +) in mire, fresh and sea water samples was developed, validated and applied in a field study. In the field study, mire water samples were filtered, standardised volumetrically with isotopically enriched CH 3 200Hg +, and frozen on dry ice. The samples

Lars Lambertsson; Erik Bjrn

2004-01-01

162

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

PubMed

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

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

2013-10-15

163

Solution to data integration problems during isotope ratio measurements by magnetic sector inductively coupled plasma mass spectrometer at medium mass resolution: application to the certification of an enriched 53Cr material by isotope dilution  

NASA Astrophysics Data System (ADS)

The suitability of a single-detector magnetic sector inductively coupled plasma mass spectrometer for low uncertainty Cr isotope ratio measurements was evaluated. Operation at medium mass resolution ( m/? m?4000) was required to eliminate the interferences from polyatomic ions commonly observed on Cr isotope masses. However, the repeatability of the ratios appeared to be far worse than expected and extremely unstable. The mass calibration was found to drift by up to 0.0016 amu on peak center (i.e. 12.5% of the peak width) for the duration of a measurement (i.e. 675 s). Moreover, for individual peak signals (0.12-0.36 s duration depending on isotopes) the instabilities observed, particularly for low abundant isotopes, lead to multiple maxima that could potentially complicate the data integration step. However, the major problem turned out to be the instrument software, failing to integrate the data in a reproducible and predictable manner. An 'off line' method of data integration was developed to overcome these problems that led to a nearly tenfold improvement in the repeatability of natural n( 52Cr)/ n( 50Cr) isotope ratio measurements. The stability of the repeatability over 45 min improved by a factor of 2.6, the reproducibility of the ratios improved by more than a factor of 4 and the average ratio changed by 0.75% (and by up to 1.5% in the worst case). Under these stabilized conditions, direct isotope dilution could be applied as a primary method of measurement for the certification of the Cr amount content in a 53Cr enriched material. The isotope ratio measurements, whose repeatability varied from 0.1 to 0.7% depending on the value of the ratio, were calibrated (corrected for mass discrimination effects) using the IRMM-625 certified isotopic reference material. Combined uncertainties were estimated for all results following the ISO guide to the expression of uncertainty in measurements. A combined uncertainty (expanded, with k=2) on the Cr amount content of less than 0.6% relative was achieved, where the repeatability of the isotope ratio measurements accounted for less than 1% of this value.

Trel, I.; Qutel, C. R.; Taylor, P. D. P.

2003-03-01

164

Radium isotope geochemistry of thermal waters, Yellowstone National Park, Wyoming, USA  

Microsoft Academic Search

Radium isotope activities ( 226 Ra, 228 Ra, and 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 226 Ra in these waters range from <0.2 to 37.9 dpm\\/kg. Activity ratios of 228 Ra \\/ 226 Ra range from 0.26 to 14.2, and those

N. C. Sturchio; J. K. Bohlke; F. J. Markun

1993-01-01

165

Radium isotope geochemistry of thermal waters, Yellowstone National Park, Wyoming, USA  

Microsoft Academic Search

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

N. C. Sturchio; J. K. Bohlke; F. J. Markun

1993-01-01

166

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

PubMed

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): ?-damascenone, ?-ionone and ?-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 ?-damascenone and ?-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

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

2012-12-15

167

The measurement of theophylline in human serum or plasma using gas chromatography and isotope dilution-mass spectrometry (GC-IDMS) taking other substituted xanthines into consideration.  

PubMed

A method is described which uses a combination of gas chromatography and isotope dilution-mass spectrometry (GC-IDMS) to determine the concentration of theophylline (1,3-dimethyl xanthine) in human plasma or serum samples. The effects of similar substituted xanthines - namely theobromine (3,7-dimethyl xanthine), paraxanthine (1,7-dimethyl xanthine) 1,3-dimethyl-7-(2-hydroxyethyl) xanthine (internal standard HPLC) and caffeine (1,3,7-trimethyl xanthine) were tested to confirm the specificity of the method. The derivatisation of all xanthines was performed with N-methyl-N-trimethylsilyl trifluroacetamide (MSTFA). The internal standard used was 2-(13)C ,1,3-(15)N2-theophylline. The extraction and derivatisation procedures were examined in detail and optimised stepwise during the development of the method. High-performance liquid chromatography (HPLC) was used for comparison. PMID:12389715

Kress, Michael; Meissner, Dieane; Kaiser, Patricia; Hanke, Rainer; Wood, William Graham

2002-01-01

168

Determination of picomolar levels of platinum in estuarine waters: a comparison of cathodic stripping voltammetry and isotope dilution-inductively coupled plasma mass spectrometry.  

PubMed

A comparative study to determine picomolar concentrations of platinum in natural waters was performed using two different analytical techniques. Results obtained by cathodic stripping voltammetry (CSV) were compared with those obtained by isotope dilution-inductively coupled plasma mass spectrometry (ID-ICPMS) combined with anion exchange resin column extraction method. Using successive UV irradiations with low-pressure mercury (L-Hg) lamp for 4h prior to CSV analysis, the results of both methods were comparable. Without adequate photolytic decomposition, the results obtained using CSV were generally lower than those obtained using ID-ICPMS in the estuarine waters around Tokyo Bay. This difference implies the presence of organically complexed Pt species in the estuarine waters. The Pt enrichment in the middle of the Tokyo Bay estuaries probably reflects the anthropogenic release of Pt from highly populated areas in Tokyo. PMID:17723753

Obata, Hajime; Yoshida, Tetsuaki; Ogawa, Hiroshi

2006-10-27

169

Tracing the flow rate and mixing ratio of the Changjiang diluted water in the northwestern Pacific marginal seas using radium isotopes  

NASA Astrophysics Data System (ADS)

measured Ra isotopes (223Ra and 228Ra) in surface seawater of the northwestern Pacific marginal seas to trace the flow rate and mixing of the Changjiang diluted water (CDW) in the summer of 2012. Based on the horizontal distribution of 223Ra activities, the arrival time of CDW from the river mouth to 450 km offshore northeast was estimated to be 20-35 days, which is similar to that determined in previous studies. Moreover, we successfully calculated the relative contribution of CDW at each sampling station using a salinity and 228Ra diagram. Using this unique method, we found that the relative contribution of CDW was more than 30% in most surface seawaters of the northern East China Sea, the Yellow Sea, and the southern sea off Korea. Our results suggest that CDW is of high significance in the biogeochemistry of surface seawater of these northwestern Pacific marginal seas during the summer monsoon period.

Lee, Hojun; Kim, Guebuem; Kim, Jeonghyun; Park, Gwanserk; Song, Ki-Hoon

2014-07-01

170

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

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

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

2012-01-01

171

Burning transuranium isotopes in thermal and fast reactors  

Microsoft Academic Search

Energy production in nuclear power plants on the basis of fission processes lead inevitably to fission products and to the generation of new actinide isotopes. Most of these fission products are rather shortlived and decay within less than about 500 years to stable nuclides. However, a few of them, e.g. 99Tc and 129I, are longlived and may contribute to the

C. H. M. Broeders; E. Kiefhaber; H. W. Wiese

2000-01-01

172

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

SciTech Connect

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).

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

1981-01-01

173

Quantitation of Red Blood Cell Folates by Stable Isotope Dilution Gas Chromatography-Mass Spectrometry Utilizing a Folate Internal Standard  

Microsoft Academic Search

We report a new gas chromatography-mass spectrometry (GC-MS) method of measurement of red blood cell folates utilizing a stable isotope-labeled bacterial synthesized folate internal standard. The GC-MS method exploits the fact that the common feature of all folate molecules is a p-aminobenzoic acid moiety sandwiched between a pteridine ring and a polyglutamate chain of varying length. In this method, red

C. R. Santhoshkumar; J. C. Deutsch; K. L. Hassell; N. M. Kolhouse; J. F. Kolhouse

1995-01-01

174

Rapid and Precise Measurement of Serum Branched-Chain and Aromatic Amino Acids by Isotope Dilution Liquid Chromatography Tandem Mass Spectrometry  

PubMed Central

Background Serum branched-chain and aromatic amino acids (BCAAs and AAAs) have emerged as predictors for the future development of diabetes and may aid in diabetes risk assessment. However, the current methods for the analysis of such amino acids in biological samples are time consuming. Methods An isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) method for serum BCAAs and AAAs was developed. The serum was mixed with isotope-labeled BCAA and AAA internal standards and the amino acids were extracted with acetonitrile, followed by analysis using LC/MS/MS. The LC separation was performed on a reversed-phase C18 column, and the MS/MS detection was performed via the positive electronic spray ionization in multiple reaction monitoring mode. Results Specific analysis of the amino acids was achieved within 2 min. Intra-run and total CVs for the amino acids were less than 2% and 4%, respectively, and the analytical recoveries ranged from 99.6 to 103.6%. Conclusion A rapid and precise method for the measurement of serum BCAAs and AAAs was developed and may serve as a quick tool for screening serum BCAAs and AAAs in studies assessing diabetes risk. PMID:24339906

Yang, Ruiyue; Dong, Jun; Guo, Hanbang; Li, Hongxia; Wang, Shu; Zhao, Haijian; Zhou, Weiyan; Yu, Songlin; Wang, Mo; Chen, Wenxiang

2013-01-01

175

Determination of steroid hormones in a human-serum reference material by isotope dilution--mass spectrometry: A candidate definitive method for cortisol  

SciTech Connect

We report a method, based on isotope dilution--mass spectrometry, for determining cortisol in a pooled specimen of human serum. Isotopically labeled cortisol is added to 5.0 mL of serum so that the molar concentrations of labeled cortisol and unlabeled cortisol are approximately equal. The specimen and two calibration standards are extracted with dichloromethane, and the extracted cortisol is converted to the methoxime-trimethylsilyl ether derivative. Samples and standards are analyzed by gas chromatography--mass spectrometry by monitoring the peak areas for m/z 605 and 608. The cortisol concentration is calculated by linear interpolation between the two bracketing standards. Variances of data collected during six weeks showed that the overall coefficient of variation (CV) was 0.69% (n . 32); the within-vial CV, 0.63%; the among-vial CV, 0.22%; and the among-day CV, 0.15% (means . 3.973 nmol/vial). Method specificity was demonstrated by liquid chromatographic as well as C/sub 8/ mini-column cleanup of samples before derivation, by alternative ion monitoring at m/z 636 and 639, and by negative-ion chemical ionization at m/z 459 and 462. Derivatives of all observed degradation products of cortisol under basic, neutral, and acidic conditions did not interfere.

Patterson, D.G.; Patterson, M.B.; Culbreth, P.H.; Fast, D.M.; Holler, J.S.; Sampson, E.J.; Bayse, D.D.

1984-05-01

176

[Determination of urinary cotinine of children exposed to passive smoking by stable isotope dilution gas chromatography-triple quadrupole mass spectrometry].  

PubMed

An analytical method for the determination of urinary cotinine of children exposed to passive smoking was established based on stable isotope dilution by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS). The samples were extracted and purified with chloroform. The extracts were determined by GC-MS/MS in multiple reaction monitoring (MRM) mode. The cotinine-d3 as an isotope internal standard was applied to quantify and confirm the urinary cotinine of children exposed to passive smoking. The method had a good linearity from 0.1 microg/L to 10 microg/L with the correlation coefficient (r) > 0.998. The recoveries of the cotinine in blank urine were from 79.2% to 112.8% at spiked levels of 0.1, 1.0 and 10 microg/ L, with relative standard deviations (RSDs) from 2.1% to 5. 8%. The limit of quantification ( LOQ) of the method was 0.1 microg/L. The developed method is accurate, sensitive, rapid and can be applied to detect urinary cotinine of children exposed to passive smoking at home. PMID:25269267

Wang, Yun; Huang, Zhiqiang; Ye, Ying; Zhang, Ying; Xiao, Shuiyuan

2014-06-01

177

Quantification of Cry1Ab in genetically modified maize leaves by liquid chromatography multiple reaction monitoring tandem mass spectrometry using 18O stable isotope dilution.  

PubMed

Cry1Ab is one of the most common Bacillus thuringiensis (Bt) proteins in genetically modified crops, which exhibits strong resistance against insect pests. In the present study, a sensitive and precise liquid chromatography stable isotope dilution multiple reaction monitoring tandem mass spectrometry (LC-SID-MRM-MS) assay was developed and validated to quantify the amount of Cry1Ab expression in transgenic maize leaves. The measurement of protein was converted to measurement of unique peptides to Cry1Ab protein. Two peptides unique to Cry1Ab were synthesized and labeled in H(2)(18)O to generate (18)O stable isotope peptides as internal standards. The validated method obtained superior specificity and good linearity. And the inter- and intra-day precision and accuracy for all samples were satisfactory. The results demonstrated Cry1Ab protein was 31.7 4.1 ?g g(-1) dry weight in Bt-176 transgenic maize leaves. It proved that the novel LC-SID-MRM-MS method was sensitive and selective to quantify Cry1Ab in the crude extract without time-consuming pre-separation or purification procedures. PMID:22543512

Zhang, Yongqian; Lai, Chengjun; Su, Rui; Zhang, Mei; Xiong, Yan; Qing, Hong; Deng, Yulin

2012-06-01

178

Accurate quantification of polycyclic aromatic hydrocarbons in dust samples using microwave-assisted solvent extraction combined with isotope-dilution mass spectrometry.  

PubMed

For accurate quantification of polycyclic aromatic hydrocarbons (PAHs) in dust samples, we investigated the use of microwave-assisted solvent extraction (MAE) combined with isotope-dilution mass spectrometry (IDMS) using deuterium-labelled PAHs (D-PAHs). Although MAE with a methanol/toluene mixture (1:3 by volume) at 160C for 40 min was best for extracting PAHs from tunnel dust among examined, the recovery yields of D-PAHs decreased with increasing molecular weight (<40% for MW?264; that of deuterium-labelled indeno[123-cd]pyrene (D-IcdP) was only 7.1%). Although the residues were extracted a second time, the observed concentrations did not change dramatically (<5%), and the recovery yields of heavier D-PAHs (i.e., MW?264) were approximately half of those of the first extract, including D-IcdP (3.4%). These results suggest that both partitioning and isotopic equilibria of PAHs and D-PAHs between sample and solvent were achieved for extractable heavier PAHs under the condition. Thus, the observed concentrations of PAHs obtained by MAE-IDMS were reasonable, even though recovery yields of D-PAHs were <50%. From the results of carbon analyses and extractable contents, lower recovery yields of D-PAHs from the tunnel dust were due to a large content of char with low extractable contents. PMID:21704757

Itoh, Nobuyasu; Fushimi, Akihiro; Yarita, Takashi; Aoyagi, Yoshie; Numata, Masahiko

2011-08-01

179

Isotope Dilution High-Performance Liquid ChromatographyTandem Mass Spectrometry Method for Quantifying Urinary Metabolites of Synthetic Pyrethroid Insecticides  

Microsoft Academic Search

This paper describes a method for measuring cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acids (cis-DCCA and trans-DCCA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DBCA), 3-phenoxybenzoic acid (3PBA), and 4-fluoro-3-phenoxybenzoic acid (4F3PBA) in human urine. These compounds are considered to be reliable biomarkers of exposure for many pyrethroid insecticides used in the United States. In this method, stable isotopically labeled analogues of trans-DCCA and 3PBA were spiked into

Samuel E. Baker; Anders O. Olsson; Dana B. Barr

2004-01-01

180

Thermal hydraulics of PWRS with respect to boron dilution phenomena. Experimental results from the test facilities PKL and UPTF  

Microsoft Academic Search

Within the PWR safety analyses, attention has increasingly focused in recent years on boron dilution events which could potentially lead to reactivity transients. In Germany, the current discussion concerning boron dilution events is focused on small break loss of coolant accident (SB-LOCA) scenarios with reflux-condenser mode and restart of natural circulation (NC). The investigation of this topic was the subject

K Umminger; W Kastner; J Liebert; T Mull

2001-01-01

181

Fast and sample cleanup-free measurement of nicotine and cotinine by stable isotope dilution ultra-performance liquid chromatography-tandem mass spectrometry.  

PubMed

We developed a stable isotope dilution ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry assay to measure nicotine and cotinine, the major oxidative and pharmacologically less active metabolite of nicotine, in human urine. A simple dilution step was used as sample preparation and the measurement of nicotine and cotinine was performed during a 1.5-min run-time using nicotine-D? and cotinine-D? as internal standards. Multiple calibration curves for the analysis of both nicotine and cotinine exhibited a consistent excellent linearity and reproducibility in the range of 5-35,000 ?g/L (r>0.999). Limits of Detection were 0.7 ?g/L for nicotine and 0.4 ?g/L for cotinine, and Lower Limits of Quantification were 1.7 ?g/L for nicotine and 1.1 ?g/L for cotinine. The intraassay coefficients of variation (CVs) for nicotine and cotinine were <4% and <2%, respectively, the interassay CVs were <6% for nicotine and <4% for cotinine. The inaccuracy was <6% for both substances. The mean recovery was 103.2% (range 96.8-105.1%) for nicotine and 97.4% (range 94.3-99.2%) for cotinine. A method comparison showed that the values of nicotine metabolites in human urine samples (n=98) measured by a commercially available chemiluminescent immunoassay tested on analyzer IMMULITE 2000 were much higher than the cotinine concentration in the same urine samples measured by our UPLC-MS/MS assay. The Passing-Bablok regression line was: immunoassay=4.62 (UPLC-MS/MS)+3.64 [?g/L]; r=0.75. This robust, sensitive and interference-free UPLC-MS/MS assay permits rapid and accurate determination of nicotine and cotinine in human urine. PMID:22608097

Kuhn, Joachim; Vollmer, Tanja; Martin, Claudia; Hendig, Doris; Knabbe, Cornelius

2012-01-01

182

On the Theory of Isotope Separation by Thermal Diffusion  

Microsoft Academic Search

We here develop the theory of the processes in an apparatus with two concentric tubes, such as that used by Brewer and Bramley. In the first section we describe the process of thermal diffusion in general, and review the theoretical information on the subject. In Section II we set up the equations for the convection and diffusion processes, and obtain

W. H. Furry; R. Clark Jones; L. Onsager

1939-01-01

183

An LC/MS/MS method for stable isotope dilution studies of ?-carotene bioavailability, bioconversion, and vitamin A status in humans.  

PubMed

Isotope dilution is currently the most accurate technique in humans to determine vitamin A status and bioavailability/bioconversion of provitamin A carotenoids such as ?-carotene. However, limits of MS detection, coupled with extensive isolation procedures, have hindered investigations of physiologically-relevant doses of stable isotopes in large intervention trials. Here, a sensitive liquid chromatography-tandem mass spectrometry (LC/MS/MS) analytical method was developed to study the plasma response from coadministered oral doses of 2 mg [(13)C10]?-carotene and 1 mg [(13)C10]retinyl acetate in human subjects over a 2 week period. A reverse phase C18 column and binary mobile phase solvent system separated ?-carotene, retinol, retinyl acetate, retinyl linoleate, retinyl palmitate/retinyl oleate, and retinyl stearate within a 7 min run time. Selected reaction monitoring of analytes was performed under atmospheric pressure chemical ionization in positive mode at m/z 537?321 and m/z 269?93 for respective [(12)C]?-carotene and [(12)C] retinoids; m/z 547?330 and m/z 274?98 for [(13)C10]?-carotene and [(13)C5] cleavage products; and m/z 279?100 for metabolites of [(13)C10]retinyl acetate. A single one-phase solvent extraction, with no saponification or purification steps, left retinyl esters intact for determination of intestinally-derived retinol in chylomicrons versus retinol from the liver bound to retinol binding protein. Coadministration of [(13)C10]retinyl acetate with [(13)C10]?-carotene not only acts as a reference dose for inter-individual variations in absorption and chylomicron clearance rates, but also allows for simultaneous determination of an individual's vitamin A status. PMID:24158962

Oxley, Anthony; Berry, Philip; Taylor, Gordon A; Cowell, Joseph; Hall, Michael J; Hesketh, John; Lietz, Georg; Boddy, Alan V

2014-02-01

184

Isotope dilution high-performance liquid chromatography-tandem mass spectrometry method for quantifying urinary metabolites of synthetic pyrethroid insecticides.  

PubMed

This paper describes a method for measuring cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acids (cis-DCCA and trans-DCCA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DBCA), 3-phenoxybenzoic acid (3PBA), and 4-fluoro-3-phenoxybenzoic acid (4F3PBA) in human urine. These compounds are considered to be reliable biomarkers of exposure for many pyrethroid insecticides used in the United States. In this method, stable isotopically labeled analogues of trans-DCCA and 3PBA were spiked into urine as internal standards. After solid-phase extraction, the extracts were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry using turbo ion-spray atmospheric pressure ionization. The limits of detection (LODs) ranged from 0.1 to 0.5 microg/L. Within-day relative standard deviations ranged from 1.8 to 13% and between-day relative standard deviations ranged from 0.5 to 18%. Absolute analyte recoveries ranged from 72 to 93%. Chromatographic retention times were less than 8 min. This method was used to measure urinary concentrations of these metabolites in persons with no known exposure to pyrethroids and some with suspected residential exposure. Metabolites of synthetic pyrethroids were detected in 74% of the samples analyzed. cis-DCCA, trans-DCCA, DBCA, 4F3PBA, and 3PBA were detected in 36, 50, 3, 9, and 64% of the samples analyzed, respectively. PMID:15195798

Baker, Samuel E; Olsson, Anders O; Barr, Dana B

2004-04-01

185

Seasonal changes of total body water and water intake in Shetland ponies measured by an isotope dilution technique.  

PubMed

Water is an essential nutrient necessary to support life, and adequate water supply is crucial for animal survival and productivity. The present study was designed to determine seasonal changes in the water metabolism of horses under outdoor conditions. Total body water (TBW) and total water intake (TWI) of 10 adult Shetland pony mares were estimated at monthly intervals for 14 mo by using the deuterium dilution technique. During the last 4 mo, 5 ponies were fed restrictively to simulate natural feed shortage in winter, and 5 ponies served as controls. The TBW (kg) was closely related to body mass [TBW (kg) = -2.86 + 0.67 body mass (kg); P < 0.001; n = 105] explaining 86% of the variation. In contrast to TBW (kg), TBW (%) remained relatively stable across all measurements (57.8 to 71.2%). The TWI showed an increase in summer and a decrease in winter [TWI (mLkg(-1)d(-1)) = 15.07 + 23.69 month - 1.45 month(2) (R(2) = 0.64, P < 0.01)]. However, TWI measured at ambient temperatures (Ta) < 0C did not follow the same trend as TWI at Ta > 0C. Therefore, removing TWI values measured at Ta < 0C from the analysis resulted in high correlations with locomotor activity (r = 0.87), Ta (r = 0.86), and resting heart rate (r = 0.88). The multiple regression among TWI, Ta, and heart rate explained 84% of the variation in TWI [TWI (mLkg(-1)d(-1)) = -13.38 + 1.77 heart rate (beats/min) + 2.11 Ta (C); P < 0.001]. Feed restriction had no effect on TWI and TBW. The TBW content was unaffected by season and physical activity. The established regression equation for TBW and body mass can be used to predict TBW from body mass in ponies under field conditions. The comparison of TWI with published data on drinking water intake revealed that ponies had 1.7 to 5.1 times greater total water intakes when other sources of water such as feed and metabolic water were included. The TWI was highly influenced by environmental conditions and metabolic rate. Contrary to expectation, water supply during the cold seasons might be more critical than under summer conditions when water content of grass is high to allow for the compensation of limited availability of drinking water. PMID:23736044

Brinkmann, L; Gerken, M; Riek, A

2013-08-01

186

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

PubMed

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 0.02ng/mL for each compound in a 0.2mL sample of human urine, and an excellent linearity from 0.1 to 50ng/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

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

2014-08-01

187

Analysis of matrix-bound nitrofuran residues in worldwide-originated honeys by isotope dilution high-performance liquid chromatography-tandem mass spectrometry.  

PubMed

A sensitive and selective isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) method is presented for the simultaneous analysis of the metabolites of four nitrofuran veterinary drugs, that is, furazolidone, furaltadone, nitrofurantoin, and nitrofurazone, in honey samples. The method entails a combined hydrolysis of protein-bound drug metabolites and derivatization of the resulting metabolites with 2-nitrobenzaldehyde (NBA) during an overnight incubation, followed by a liquid-liquid extraction and a cleanup on a polymeric solid-phase extraction cartridge. Mass spectral acquisition is carried out in the positive ion mode by applying multiple reaction monitoring (MRM) of three diagnostic transition reactions for each analyte under survey. A reliable quantification is obtained by the use of one deuterated analogue per analyte (NBA-d(4) derivative). The method has been validated in honey according to the European Union criteria for the analysis of veterinary drug residues in food. Expressed in underivatized nitrofuran metabolite concentrations, the decision limits (CCalpha) ranged within 0.07-0.46 microg/kg, and the detection capabilities (CCbeta) were within 0.12-0.56 microg/kg. The method has been successfully applied in a survey of honeys of various geographical origins, showing that furazolidone is the main nitrofuran antibiotic administered to treat bacterial diseases of bees. PMID:15315362

Khong, Seu-Ping; Gremaud, Eric; Richoz, Janique; Delatour, Thierry; Guy, Philippe A; Stadler, Richard H; Mottier, Pascal

2004-08-25

188

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

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.

Moore, B.D.; Kobza, J.; Seemann, J.R. (Univ. of Nevada, Reno (United States))

1991-05-01

189

Isotope dilution mass spectrometry of 10B and 6LiF reference deposits used for the determination of the neutron lifetime  

NASA Astrophysics Data System (ADS)

The accurate characterization of 10B and 6LiF reference deposits is of the highest importance in absolute neutron counting e.g. for the determination of the lifetime of the free neutron [J. Byrne , Phys. Rev. Lett., 65 (1990) 289]. A series of 10B and 6LiF deposits, with different surface densities, were prepared on silicon substrates by vacuum deposition and analyzed by isotope dilution mass spectrometry (IDMS), subsequent to their relative characterization by neutron induced charged particle counting and determination of their surface area. The IDMS results were performed to calibrate the (n,[alpha]) measurements. They carry a total uncertainty (ls equivalent) on the number of 10B atoms in the deposit of 0.48% on Series I (without chemical purification) and 0.58% on Series II (with chemical purification). The corresponding uncertainty on the number of 6Li atoms in the deposit is 0.25%. The systematic components of these uncertainties are 0.12% on the 10B content and 0.21% on the 6Li content. An intercomparison on the basis of the count rates of the (n,[alpha]) measurements, the surface areas and the IDMS results shows an excellent agreement between the results for 10B and 6Li.

Lamberty, A.; de Bivre, P.

1991-10-01

190

Rapid determination of trace dicyandiamide in mussels from Zhejiang coast by ultra-fast liquid chromatography-tandem mass spectrometry with isotope internal standard dilution technique.  

PubMed

In this study, a rapid and accurate ultra-fast liquid chromatography-tandem quadrupole mass spectrometry (UFLC-MS/MS) method coupled with the isotope internal standard dilution technique was established and validated to determine trace dicyandiamide (DCD) in mussels. The sample was extracted by acetonitrile, and chromatographic separations were performed on an Acquity UPLC BEH Amide column by using water-acetonitrile (9:91, v/v) as the mobile phase within 3min. DCD was determined by using DCD-(15)N4 as an internal standard. The results showed that the recoveries were between 96.2 and 103% with relative standard deviations (RSDs) in the range of 0.6-6.0%. The limit of quantification (LOQ) was 0.05?g/kg. This method can be applied to the routine analysis for the rapid and sensitive determination of trace DCD in mussels. Overall, the data reiterate the importance of investigating the presence of DCD in marine biological samples, which can act as food quality controls for human health. PMID:25035051

Zhang, Yun; Gong, Wen-Jie; Zhao, Yong-Gang; Zhou, Hua

2014-12-01

191

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

PubMed Central

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 0.277.8% 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

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

2014-01-01

192

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

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

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

2001-03-01

193

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

PubMed

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?M were obtained, whereas for organic species, concentrations of 14-18?M could be found. After 24h, 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 1ngL(-1) were obtained using external calibration and species-unspecific isotope dilution analysis approaches. The results were further validated using atomic fluorescence spectrometry. PMID:24442014

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

2014-03-01

194

Effective elimination of isobaric ions interference and precise thermal ionization mass spectrometer analysis for boron isotope  

NASA Astrophysics Data System (ADS)

An ionization depressor, 1% H3PO4 was used to eliminate the isobaric interference that has been of a great concern during the procedure of boron isotopic ratio analysis by thermal ionization mass spectrometer (TIMS). Our experiments have shown that it appears to be an effective method to completely restrain the formation of isobaric ions of CNO- and Cs2CNO+ in the ionization source of mass spectrometer. We have also discussed the optimum proportion of depressor to nitrite for precise analysis of boron isotopes in natural samples based on a conditional experiment. In this case, the pretreatment of boron extraction from natural samples is greatly simplified since it is not necessary to remove nitrite and organic matter completely. In virtue of the method, we determined boron isotope in different types of natural samples, and our results are consistent with previous reports.

Wei, Haizhen; Xiao, Yingkai; Sun, Aide; Zhang, Chonggeng; Li, Shizhen

2004-07-01

195

Magnesium isotope fractionation in silicate melts by chemical and thermal diffusion  

NASA Astrophysics Data System (ADS)

Two types of laboratory experiments were used to quantify magnesium isotopic fractionations associated with chemical and thermal (Soret) diffusion in silicate liquids. Chemical diffusion couples juxtaposing a molten natural basalt (SUNY MORB) and a molten natural rhyolite (Lake County Obsidian) were run in a piston cylinder apparatus and used to determine the isotopic fractionation of magnesium as it diffused from molten basalt to molten rhyolite. The thermal diffusion experiments were also run in a piston cylinder apparatus but with a sample made entirely of molten SUNY MORB displaced from the hotspot of the assembly furnace so that the sample would have a temperature difference of about 100-200 C from one end to the other. The chemical diffusion experiments showed fractionations of 26Mg/ 24Mg by as much as 7, which resulted in an estimate for the mass dependence of the self-diffusion coefficients of the magnesium isotopes corresponding to D/D=(24/26)? with ? = 0.05. The thermal diffusion experiments showed that a temperature difference of about 100 C resulted in the MgO, CaO, and FeO components of the basalt becoming slightly enriched by about 1 wt% in the colder end while SiO 2 was enriched by several wt% in the hotter end. The temperature gradient also fractionated the magnesium isotopes. A temperature difference of about 150 C produced an 8 enrichment of 26Mg/ 24Mg at the colder end relative to the hotter end. The magnesium isotopic fractionation as a function of temperature in molten basalt corresponds to 3.6 10 -2/C/amu.

Richter, Frank M.; Watson, E. Bruce; Mendybaev, Ruslan A.; Teng, Fang-Zhen; Janney, Philip E.

2008-01-01

196

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  

Microsoft Academic Search

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

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

2006-01-01

197

Folate content in sea buckthorn berries and related products ( Hippopha rhamnoides L. ssp. rhamnoides ): LCMS\\/MS determination of folate vitamer stability influenced by processing and storage assessed by stable isotope dilution assay  

Microsoft Academic Search

A stable isotope dilution assay was adopted for quantitation of folate vitamers in sea buckthorn berries, juice, and concentrate\\u000a using fourfold labeled folate isotopologues of the folate derivatives as the internal standards and reversed-phase liquid\\u000a chromatographytandem mass spectrometry with electrospray ionization (LC-ESI-MS\\/MS). Processing effects and storage stability\\u000a were investigated during juice and concentrate production from sea buckthorn berries (Hippopha rhamnoides).

Derek Gutzeit; Sabine Mnch; Gerold Jerz; Peter Winterhalter; Michael Rychlik

2008-01-01

198

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

USGS Publications Warehouse

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 specific isotope system, it should be noted that the same methods can be used to evaluate any isotope system of interest. ?? 2008 Elsevier B.V.

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

2009-01-01

199

New Measurement of the Thermal-capture Cross Section for the Minor Isotope 180W  

NASA Astrophysics Data System (ADS)

Tungsten occurs naturally in five isotopic forms; four of them, 182,183,184,186W, contribute significantly to the overall elemental abundance (with each contribution between 14 and 30 %), whereas 180W only occurs at the 0.12 % level and is a minor isotope. Given its very low abundance, a precise measurement of the thermal neutron-capture cross section is extremely challenging. This work reports a new value of the thermal neutron-capture cross section from a direct 180W(n,?) measurement using a guided-thermal beam at the Budapest Research Reactor, incident upon an 11.35 % enriched sample to induce prompt ?-ray activation within the sample. The thermal-capture cross section was determined as the sum of experimentally observed partial neutron-capture ?-ray cross sections feeding the ground state directly, and, the modeled contribution from the (unobserved) ground-state feeding predicted from statistical-model calculations using the Monte Carlo program DICEBOX. The preliminary value of the 180W(n,?) thermal neutron-capture cross section is 20.5(42) b.

Hurst, A. M.; Firestone, R. B.; Szentmiklsi, L.; Rvay, Zs.; Basunia, M. S.; Belgya, T.; Escher, J. E.; Krti?ka, M.; Summers, N. C.; Sleaford, B. W.

2014-05-01

200

Fission yields in the symmetric region: Yields of the stable isotopes of tin and cadmium in the thermal neutron fission of 235U and 239Pu  

Microsoft Academic Search

The relative isotopic abundances of five isotopes of cadmium (111, 112, 113, 114, and 116) and eight isotopes of tin (117, 118, 119, 120, 21, 122, 124, and 126) have been measured in the thermal neutron fission of 235U and 239Pu. Samples of 235U and 239Pu were irradiated in a reactor; the elements were chemically separated and the isotopic abundances

C. K. Mathews

1977-01-01

201

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

PubMed

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 ?L) 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

Crow, Brian S; Pantazides, Brooke G; Quiones-Gonzlez, 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

202

Identification and quantification of DNA repair protein apurinic/apyrimidinic endonuclease 1 (APE1) in human cells by liquid chromatography/isotope-dilution tandem mass spectrometry.  

PubMed

Unless repaired, DNA damage can drive mutagenesis or cell death. DNA repair proteins may therefore be used as biomarkers in disease etiology or therapeutic response prediction. Thus, the accurate determination of DNA repair protein expression and genotype is of fundamental importance. Among DNA repair proteins involved in base excision repair, apurinic/apyrimidinic endonuclease 1 (APE1) is the major endonuclease in mammals and plays important roles in transcriptional regulation and modulating stress responses. Here, we present a novel approach involving LC-MS/MS with isotope-dilution to positively identify and accurately quantify APE1 in human cells and mouse tissue. A completely (15)N-labeled full-length human APE1 was produced and used as an internal standard. Fourteen tryptic peptides of both human APE1 (hAPE1) and (15)N-labeled hAPE1 were identified following trypsin digestion. These peptides matched the theoretical peptides expected from trypsin digestion and provided a statistically significant protein score that would unequivocally identify hAPE1. Using the developed methodology, APE1 was positively identified and quantified in nuclear and cytoplasmic extracts of multiple human cell lines and mouse liver using selected-reaction monitoring of typical mass transitions of the tryptic peptides. We also show that the methodology can be applied to the identification of hAPE1 variants found in the human population. The results describe a novel approach for the accurate measurement of wild-type and variant forms of hAPE1 in vivo, and ultimately for defining the role of this protein in disease development and treatment responses. PMID:23922845

Kirkali, Gldal; Jaruga, Pawel; Reddy, Prasad T; Tona, Alessandro; Nelson, Bryant C; Li, Mengxia; Wilson, David M; Dizdaroglu, Miral

2013-01-01

203

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

PubMed

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 (R > 0.999), and the limit of quantification (LOQ) ranged from 0.42 to 2.7?g?kg?. 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?g?kg? 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?g?kg? (cassia seed) to 2245?g?kg? (eucommia bark). The highest level was found for phenanthrene (Phe) in liquorice root (631.3?g?kg?), indigowoad leaf (551.0?g?kg?), rose flower (435.2?g?kg?) and eucommia bark (432.3?g?kg?). 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

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

2012-01-01

204

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

SciTech Connect

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.

Sapkota, Amir [Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Johns Hopkins University Center for Water and Health, Baltimore, MD 21205-2103 (United States); Heidler, Jochen [Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Johns Hopkins University Center for Water and Health, Baltimore, MD 21205-2103 (United States); Halden, Rolf U. [Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Johns Hopkins University Center for Water and Health, Baltimore, MD 21205-2103 (United States)]. E-mail: rhalden@jhsph.edu

2007-01-15

205

Simultaneous determination of four sulfur mustard-DNA adducts in rabbit urine after dermal exposure by isotope-dilution liquid chromatography-tandem mass spectrometry.  

PubMed

Sulfur mustard (SM) is a classic vesicant agent, which has been greatly employed in several wars or military conflicts. The most lesion mechanism is its strong alkylation of DNAs in vivo. Until now there are four specific DNA adducts of SM identified for further retrospective detection, i.e., N(7)-(2-hydroxyethylthioethyl)-2'-guanine (N(7)-HETEG), bis(2-ethyl-N(7)-guanine)thioether (Bis-G), N(3)-(2-hydroxyethylthioethyl)-2'-adenine (N(3)-HETEA) and O(6)-(2-hydroxyethylthioethyl)-2'-guanine (O(6)-HETEG), respectively. Here, a novel and sensitive method of isotope-dilution ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combining with solid phase extraction was reported for the simultaneous determination of four SM-DNA adducts. A lower limit of detection of 2-5ngL(-1), and a lower limit of quantitation of 5-10ngL(-1) were achieved, respectively, and the recoveries ranged from 87% to 116%. We applied this method in the determination of four SM-DNA adducts in rabbit urine after dermal exposure by SM in three dose levels (2, 5, 15mgkg(-1)), so as to investigate the related metabolic behavior in vivo. For the first time, in SM exposed rabbit urine, our results revealed the relative accumulation abundance of four SM-DNA adducts, i.e., 67.4% for N(7)-HETEG, 22.7% for Bis-G, 9.8% for N(3)-HETEA, 0.1% for O(6)-HETEG, and significant dose and time dependent responses of these SM-DNA adducts. The four adducts were detectable after 8h, afterwards, their contents continuously increased, achieved maximum in the first two or three days and then gradually decreased till the end of one month. Meanwhile, the amounts of SM-DNA adducts were positively correlated with the exposure doses. PMID:24858262

Zhang, Yajiao; Yue, Lijun; Nie, Zhiyong; Chen, Jia; Guo, Lei; Wu, Bidong; Feng, Jianlin; Liu, Qin; Xie, Jianwei

2014-06-15

206

Development of SI-traceable C-peptide certified reference material NMIJ CRM 6901-a using isotope-dilution mass spectrometry-based amino acid analyses.  

PubMed

A certified reference material (CRM) is a higher-order calibration material used to enable a traceable analysis. This paper describes the development of a C-peptide CRM (NMIJ CRM 6901-a) by the National Metrology Institute of Japan using two independent methods for amino acid analysis based on isotope-dilution mass spectrometry. C-peptide is a 31-mer peptide that is utilized for the evaluation of ?-cell function in the pancreas in clinical testing. This CRM is a lyophilized synthetic peptide having the human C-peptide sequence, and contains deamidated and pyroglutamylated forms of C-peptide. By adding water (1.00 0.01) g into the vial containing the CRM, the C-peptide solution in 10 mM phosphate buffer saline (pH 6.6) is reconstituted. We assigned two certified values that represent the concentrations of total C-peptide (mixture of C-peptide, deamidated C-peptide, and pyroglutamylated C-peptide) and C-peptide. The certified concentration of total C-peptide was determined by two amino acid analyses using pre-column derivatization liquid chromatography-mass spectrometry and hydrophilic chromatography-mass spectrometry following acid hydrolysis. The certified concentration of C-peptide was determined by multiplying the concentration of total C-peptide by the ratio of the relative area of C-peptide to that of the total C-peptide measured by liquid chromatography. The certified value of C-peptide (80.7 5.0) mg/L represents the concentration of the specific entity of C-peptide; on the other hand, the certified value of total C-peptide, (81.7 5.1) mg/L can be used for analyses that does not differentiate deamidated and pyroglutamylated C-peptide from C-peptide itself, such as amino acid analyses and immunochemical assays. PMID:22610603

Kinumi, Tomoya; Goto, Mari; Eyama, Sakae; Kato, Megumi; Kasama, Takeshi; Takatsu, Akiko

2012-07-01

207

Association between cigarette smoking and urinary excretion of 1,N2-ethenoguanine measured by isotope dilution liquid chromatography-electrospray ionization/tandem mass spectrometry.  

PubMed

Levels of the promutagenic 1,N2-ethenoguanine (1,N2-epsilonGua), an etheno DNA adduct derived mainly from lipid peroxidation, in experimental animals are associated with risk of cancer formation. Since 1,N2-epsilonGua can be repaired by human glycosylases, it is possible to use it as a biomarker for cancer risk assessment in humans. In the present study, a highly sensitive and specific stable isotope dilution liquid chromatography-electrospray ionization/tandem mass spectrometry (LC-ESI/MS/MS) was developed for accurate quantification of 1,N2-epsilonGua in human urine. The sample pretreatment involved a consecutive strong cation exchange solid-phase extraction (SPE) and reversed phase SPE chromatography. The pretreated sample was analyzed by LC-ESI/MS/MS under multiple reaction monitoring mode (MRM) using a triple quadrupole mass spectrometer. The detection limit of 1,N2-epsilonGua using this LC-ESI/MS/MS assay was 1.0 pg (5.8 fmol) injected on-column. Levels of urine samples collected from healthy volunteers were found to range from 0 to 199 pg/mL, and levels as low as 5.0 pg/mL (29 pM) could be accurately quantified. After adjusting for creatinine levels and body weight, an statistically significant association was observed between urinary levels of 1,N2-epsilonGua and cigarette smoking (p = 0.0006). This highly specific and sensitive assay should be valuable in measuring urinary 1,N2-epsilonGua as a potential noninvasive biomarker for oxidative DNA damage. PMID:16533024

Chen, Hauh-Jyun Candy; Chiu, Wei-Loong

2005-10-01

208

Simultaneous supercritical fluid extraction and chemical derivatization for the gas chromatographic-isotope dilution mass spectrometric determination of amphetamine and methamphetamine in urine.  

PubMed

An in-situ supercritical fluid extraction (SFE) and chemical derivatization (ChD) procedure followed by gas chromatography-isotope dilution mass spectrometry (GC-MS) for the determination of amphetamines in urine is described and evaluated. While using celite as the SFE wet-support, the one-pot sample pretreatment procedure also employs ammonium water to alkalize the urine matrix that contains protonated amphetamine (AP) and methamphetamine (MA). The mean recoveries achieved by simultaneous SFE-ChD, i.e., 95% (RSD=3.8%) for AP and 89% (RSD=4.0%) for MA, are significantly better than the corresponding overall recoveries obtained upon stepwise SFE-ChD, suggesting the unreacted trifluoroacetic anhydride (TFA) in the former procedure has strengthened the extracting power of CO, fluid as has been evidenced by a control test. As to GC-MS analysis, the optimal qualitative ions and quantitative ions of the respective analytes were determined via a rigorous evaluation process. Thus, the regression calibration curves for AP and MA in urine are linear within 100 approximately 50,000 ng/ml, with correlation coefficients typically exceeding 0.999. The limits of detection determined by two methods for AP and MA vary from 19 to 50 ng/ml, and limits of quantitation from 21 to 100 ng/ml. Precisions calculated for the triplicate analyses of AP and MA in a 500-ng/ml spiked control, two real-case samples and two quasi real-case samples, respectively, using regression calibration are typically below 10%. The method is simple and reliable. It may serve as an alternative to the existing confirmatory protocol for forensic urine drug testing. PMID:11499622

Wang, S M; Giang, Y S; Ling, Y C

2001-08-01

209

Simultaneous measurement of amiodarone and desethylamiodarone in human plasma and serum by stable isotope dilution liquid chromatography-tandem mass spectrometry assay.  

PubMed

A stable isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) assay to measure amiodarone, the most frequently used agent for maintaining sinus rhythm in patients with atrial fibrillation, and its major metabolite desethylamiodarone in human plasma and serum was developed. Measurement of amiodarone and desethylamiodarone was performed during a 4.0-min run-time using amiodarone-D(4) and desethylamiodarone-D(4) as internal standards. Calibration curves covering 12 calibrators measured in four replicates each for the analysis of both amiodarone and desethylamiodarone were linear and reproducible in the range of 0.01-40.0 mg/L (r>0.999). Limits of detection in plasma matrix were 2.7 microg/L for amiodarone and 1.9 microg/L for desethylamiodarone, and lower limits of quantification in plasma matrix were 7.5 microg/L for amiodarone and 2.5 microg/L for desethylamiodarone. Interassay imprecision and inaccuracy were <8% and <9% for both substances. Mean extraction yield was 99.6% (range 92.6-107.7%) for amiodarone and 90.2% (range 80.0-94.7%) for desethylamiodarone. Agreement was moderate for amiodarone (n=162) and desethylamiodarone (n=117), respectively, between the present method and a HPLC method with UV detection using a commercially available reagent set for the HPLC analysis of these drugs. The Passing-Bablok regression line was HPLC=0.98 (LC-MS/MS)+0.10 [mg/L]; r=0.94 for amiodarone and HPLC=1.05 (LC-MS/MS)+0.02 [mg/L]; r=0.90 for desethylamiodarone. This sensitive and interference-free LC-MS/MS assay permits rapid and accurate determination of amiodarone and desethylamiodarone in human plasma and other body fluids. PMID:19720490

Kuhn, Joachim; Gtting, Christian; Kleesiek, Knut

2010-01-01

210

Identification and quantification of DNA repair proteins by liquid chromatography/isotope-dilution tandem mass spectrometry using their fully 15N-labeled analogues as internal standards.  

PubMed

Oxidatively induced DNA damage is implicated in disease, unless it is repaired by DNA repair. Defects in DNA repair capacity may be a risk factor for various disease processes. Thus, DNA repair proteins may be used as early detection and therapeutic biomarkers in cancer and other diseases. For this purpose, the measurement of the expression level of these proteins in vivo will be necessary. We applied liquid chromatography/isotope-dilution tandem mass spectrometry (LC-MS/MS) for the identification and quantification of DNA repair proteins human 8-hydroxyguanine-DNA glycosylase (hOGG1) and Escherichia coli formamidopyrimidine DNA glycosylase (Fpg), which are involved in base-excision repair of oxidatively induced DNA damage. We overproduced and purified (15)N-labeled analogues of these proteins to be used as suitable internal standards to ensure the accuracy of quantification. Unlabeled and (15)N-labeled proteins were digested with trypsin and analyzed by LC-MS/MS. Numerous tryptic peptides of both proteins were identified on the basis of their full-scan mass spectra. These peptides matched the theoretical peptide fragments expected from trypsin digestion and provided statistically significant protein scores that would unequivocally identify these proteins. We also recorded the product ion spectra of the tryptic peptides and defined the characteristic product ions. Mixtures of the analyte proteins and their (15)N-labeled analogues were analyzed by selected-reaction monitoring on the basis of product ions. The results obtained suggest that the methodology developed would be highly suitable for the positive identification and accurate quantification of DNA repair proteins in vivo as potential biomarkers for cancer and other diseases. PMID:21619077

Dizdaroglu, Miral; Reddy, Prasad T; Jaruga, Pawel

2011-08-01

211

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

NASA Astrophysics Data System (ADS)

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.

Savic, Ivana; Mingo, Natalio; Stewart, Derek

2009-03-01

212

Effect of the detector dead-time uncertainty on the analytical result of minor elements in low-alloy steel by isotope dilution/ICP sector field mass spectrometry.  

PubMed

In the present study the effects of the detector dead-time and its uncertainties on the accuracy and uncertainty of isotope dilution mass spectrometry (IDMS) were considered through an interlaboratory study on the analysis of low-alloy steel by using an ICP-sector field mass spectrometer. Also, an optimized mixing ratio of the sample and the spike to obtain highly precise results was theoretically and experimentally investigated. The detector dead-time used in the interlaboratory study showed a negative value. However, it less affected the trueness of the analytical result if the dead-time correction for the measured isotope ratio was done properly. As many researchers have pointed out, the detector dead-time showed a clear mass dependence. Therefore, it is desirable to check the dead-time in every target element by using assay standards or isotopic standards, which would lead to an accurate result even if the detector dead-time is a negative value. On the other hand, the effect of the uncertainty of the detector dead-time can be minimized when both isotope ratios and ICP-MS signals of the [sample + spike] blend in IDMS are equal to those of [spike + assay standard] in reverse IDMS. From standpoints of error magnification theory and the precision of the isotope ratio measurement, an optimized isotope ratio of the sample-spike blend would be 1.0 for an element with a large difference in ten times and more between the atomic fractions of two isotopes used for IDMS. In the case of an element with no significant difference between the atomic fractions of two isotopes, an optimized isotope ratio can be calculated by a formula expressed as a function of the atomic fractions of the sample and the spike as well as the signal of ICP-MS. PMID:25213815

Nonose, Naoko; Hioki, Akiharu; Chiba, Koichi

2014-01-01

213

A Transient Model of Induced Natural Circulation Thermal Cycling for Hydrogen Isotope Separation  

SciTech Connect

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.

SHADDAY, MARTIN

2005-07-12

214

Effect of thermal decarbonation on the stable isotope composition of carbonates  

SciTech Connect

The unusual texture and stable isotope variability of carbonates in AH84001 have been used as evidence for early life on Mars (Romanek et al., 1994; McKay et al., 1996). Oxygen and carbon isotope variability is most commonly attributed to low-temperature processes, including Rayleigh-like fractionation associated with biological activity. Another possible explanation for the isotopic variability in meteoritic samples is thermal decarbonation. In this report, different carbonates were heated in a He-stream until decomposition temperatures were reached. The oxygen and carbon isotope ratios ({delta}{sup 18}O and {delta}{sup 13}C values) of the resulting gas were measured on a continuous flow isotope ratio mass spectrometer. The aim of this work is to evaluate the possibility that large isotopic variations can be generated on a small scale abiogenically, by the process of thermal decarbonation. Oxygen isotope fractionations of >4{per_thousand} have been measured during decarbonation of calcite at high temperatures (McCrea, 1950), and in excess of 6{per_thousand} for dolomite decarbonated between 500 and 600 C (Sharma and Clayton, 1965). Isotopic fractionations of this magnitude, coupled with Rayleigh-like distillation behavior could result in very large isotopic variations on a small scale. To test the idea, calcite, dolomite and siderite were heated in a quartz tube in a He-stream in excess of 1 atmosphere. Simultaneous determinations of {delta}{sup 13}C and {Delta}{sup 18}O values were obtained on 250 {micro}l aliquots of the CO{sub 2}-bearing He gas using an automated 6-way switching valve system (Finnigan MAT GasBench II) and a Finnigan MAT Delta Plus mass spectrometer. It was found that decarbonation of calcite in a He atmosphere begins at 720 C, but the rate significantly increases at temperatures of 820 C. After an initial light {delta}{sup 18}O value of -14.1{per_thousand} at 720 C associated with very early decarbonation, {delta}{sup 18}0 values increase to a constant -11.8{per_thousand}, close to the accepted value of -12.09{per_thousand} (PDB). After 10 minutes at 820 C, the {delta}{sup 18}O values and signal strength both begin to decrease linearly to a {delta}{sup 18}O value of -14.75 and very low amounts of CO{sub 2} (Fig. 1). In contrast, the {delta}{sup 13}C values are extremely constant (0.12 {+-} 0.25{per_thousand}) for all measurements, in very good agreement with accepted values of 0.33{per_thousand} (PDB). There is much less isotopic variability during dolomite decarbonation. CO{sub 2} is first detected at 600 C. The signal strength increases by an order of magnitude between 670 and 700 C and again at 760 C. Both {delta}{sup 13}C and {delta}{sup 18}O values are nearly constant over the entire temperature range and sample size. For oxygen, the measured {delta}{sup 18}O values averaged -20.9 {+-} 0.7{per_thousand} (n = 30). Including only samples over 700 C, the average is -21.2 {+-} 0.2{per_thousand} compared to the accepted value of -21{per_thousand}. Carbon is similarly constant. The average {delta}{sup 13}C value is -2.50{per_thousand} compared to the accepted value of -2.62{per_thousand}. Far more variability is seen during the decomposition of siderite. Two samples were analyzed. In both samples, the initial {delta}{sup 18}O values were far lower than expected.

Durakiewicz, T. (Tomasz); Sharp, Z. D. (Zachary D.); Papike, J. J. (James Joseph),

2001-01-01

215

Ammonium in thermal waters of Yellowstone National Park: processes affecting speciation and isotope fractionation  

USGS Publications Warehouse

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 ?18O 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 (?15N = ?6 to +30) and is positively correlated with pH values. In comparison to likely ?15N values of nitrogen source materials (+1 to +7), high ?15N 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 ?15N 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.

Holloway, J.M.; Nordstrom, D.K.; Bhlke, J.K.; McCleskey, R.B.; Ball, J.W.

2011-01-01

216

Isotope dilution inductively coupled plasma quadrupole mass spectrometry in connection with a chromatographic separation for ultra trace determinations of platinum group elements (Pt, Pd, Ru, Ir) in environmental samples.  

PubMed

An isotope dilution inductively coupled plasma quadrupole mass spectrometric (ID-ICP-QMS) method was developed for the simultaneous determination of the platinum group elements Pt, Pd, Ru, and Ir in environmental samples. Spike solutions, enriched with the isotopes 194Pt, 108Pd, 99Ru, and 191Ir, were used for the isotope dilution step. Interfering elements were eliminated by chromatographic separation using an anion-exchange resin. Samples were dissolved with aqua regia in a high pressure asher. Additional dissolution of possible silicate portions by hydrofluoric acid was usually not necessary. Detection limits of 0.15 ng x g(-1), 0.075 ng x g(-1), and 0.015 ng x g(-1) were achieved for Pt, Pd, Ru, and Ir, respectively, using sample weights of only 0.2 g. The reliability of the ID-ICP-QMS method was demonstrated by analyzing a Canadian geological reference material and by participating in an interlaboratory study for the determination of platinum and palladium in a homogenized road dust sample. Surface soil, sampled at different distances from a highway, showed concentrations in the range of 0.1-87 ng x g(-1). An exponential decrease of the platinum and palladium concentration with increasing distance and a small anthropogenic contribution to the natural background concentration of ruthenium and iridium was found in these samples. PMID:11220823

Mller, M; Heumann, K G

2000-09-01

217

Isotope dilution liquid chromatography-tandem mass spectrometry for simultaneous identification and quantification of beta-casomorphin 5 and beta-casomorphin 7 in yoghurt.  

PubMed

A highly selective and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous identification and quantification of beta-casomorphin 5 (BCM5) and beta-casomorphin 7 (BCM7) in yoghurt. The method used deuterium labelled BCM5-d10 and BCM7-d10 as surrogate standards for confident identification and accurate and quantification of these analytes in yoghurt. Linear responses for BCM5 and BCM7 (R(2)=0.9985 and 0.9986, respectively) was observed in the range 0.01-10ng/?L. The method limits of detection (MLDs) in yoghurt extracts were found to be 0.5 and 0.25ng/g for BCM5 and BCM7, respectively. Analyses of spiked samples were used to provide confirmation of accuracy and precision of the analytical method. Recoveries relative to the surrogate standards of these spikes were in the range of 95-106% for BCM5 and 103-109% for BCM7. Precision from analysis of spiked samples was expressed as relative standard deviation (%RSD) and values were in the range 1-16% for BCM5 and 1-6% for BCM7. Inter-day reproducibility was between 2.0-6.4% for BCM5 and between 3.2-6.1% for BCM7. The validated isotope dilution LC-MS/MS method was used to measure BCM5 and BCM7 in ten commercial and laboratory prepared samples of yoghurt and milk. Neither BCM5 nor BCM7 was detected in commercial yoghurts. However, they were observed in milk and laboratory prepared yoghurts and interestingly their levels decreased during processing. BCM5 decreased from 1.3ng/g in milk to 1.1ng/g in yoghurt made from that milk at 0day storage and

Nguyen, D D; Solah, V A; Johnson, S K; Charrois, J W A; Busetti, F

2014-03-01

218

Chemical and isotope compositions of nitric thermal water of Baikal rift zone  

NASA Astrophysics Data System (ADS)

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 (?18OSMOW = -19.5 - -17.5) and hydrogen (?DSMOW = -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 (?34SCDT = +25 - +30) prevails in the therms. Sulphate-ion enters solution not as a result of sulfide oxidation, but dissolution of sulphate minerals of may be originally sedimentary and magmatic rocks. Microelement contents in waters depend on total mineralization. In particular, this regulation is clearly observed for rare alkaline and alkaline-earth elements. We established dependence of one microelement concentrations on temperature of solutions (Sc, Al, W) and that of the other ones - on extent of water - rock (Sr, Ba) interaction. Active use of thermal water for purposes of thermal energetic can contribute to inflow of highly mineralized solutions into water collecting reservoir and result in breakdowns of heat-net work. The study has been carried out with financial support of RFBR. Grant N09-05-00726, Integration Project N87 of SB RAS.

Plyusnin, A. M.; Chernyavsky, M. K.; Peryazeva, E. G.

2010-05-01

219

Nuclear Isotopic Dilution of Highly-Enriched Uranium-235 and Uranium-233 by Dry Blending via the RM-2 Mill Technology  

SciTech Connect

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.

N. A. Chipman; R. N. Henry; R. K. Rajamani; S. Latchireddi; V. Devrani; H. Sethi; J. L. Malhotra

2004-02-01

220

Cold source moderator vessel development for the High Flux Isotope Reactor: Thermal-hydraulic studies  

SciTech Connect

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.

Williams, P.T.; Lucas, A.T.; Wendel, M.W.

1998-07-01

221

Radium isotope geochemistry of thermal waters, Yellowstone National Park, Wyoming, USA  

NASA Astrophysics Data System (ADS)

Radium isotope activities ( 226Ra, 228Ra, and 224Ra), chemical compositions, and sulfur isotope ratios in sulfate were determined for water samples from thermal areas in Yellowstone National Park, Wyoming. Activities of 226Ra in these waters range from <0.2 to 37.9 dpm/kg. Activity ratios of 228Ra /226Ra range from 0.26 to 14.2, and those of 224Ra /228Ra range from 0.73 to 3.1. Radium concentrations are inversely correlated with aquifer equilibration temperatures (estimated from dissolved silica concentrations), while[ Ra/Ba] aq and 228Ra /226Ra 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 Morris Geyser Basin, Mammoth Hot Springs, and other northern areas) and (2) zeolitewater 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 226Ra. The 228Ra /226Ra activity ratios of the waters may in some cases reflect surface enrichments of 232Th and/or may indicate that ?-recoil input of 228Ra is rapid relative to water-rock chemical equilibration. Activity ratios of 224Ra /228Ra indicate a nearly ubiquitous 224Ra excess that generally increases with decreasing pH. Near-surface (?100 m) thermal water flow velocities at Mammoth Hot Springs are estimated from 224Ra /228Ra variation to be ? 1 m h -1.

Sturchio, N. C.; Bohlke, J. K.; Markun, F. J.

1993-03-01

222

Radium isotope geochemistry of thermal waters, Yellowstone National Park, Wyoming, USA  

SciTech Connect

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.

Sturchio, N.C.; Bohlke, J.K.; Markun, F.J. (Argonne National Lab., IL (United States))

1993-03-01

223

High Precision Osmium Isotope Measurements Using New Generation Thermal Ionization Mass Spectrometry  

NASA Astrophysics Data System (ADS)

The technique for measuring Os isotopes to high precision (e.g. +/-30-50 ppm on the 186/188 ratio, 2 sigma) via negative thermal ionization mass spectrometry (NTIMS) was established a decade ago at the University of Maryland. Recent technical advances have resulted in the production of a new generation of TIMS that allows isotopic measurements with substantial improvement in accuracy and precision. Because of the improved capability, the new generation TIMS holds great potential to examine a variety of problems in geochemistry and cosmochemistry. Over the past 5 years, I have refined the technique for higher precision measurements of Os isotopes using the Triton TIMS from Thermo Electron. The measurements are made in static mode using 7 Faraday collectors. 70 or more nanograms of Os is loaded onto a Pt filament with barium hydroxide, the latter is an electron emitter that promotes efficient production of Os trioxide. Oxygen is bled into the source at constant pressures. Signal intensities of 120-180 mV 186Os trioxide are generated and measured as negative ions. Oxygen corrections to the raw data are made using the oxygen isotopic composition obtained for 2 ng loads of Re tetroxide measured on the Faraday cups. Multiple runs over the course of 3 years for the same lecture bottle used to bleed in oxygen to the source showed no change in the oxygen isotopic composition. Oxygen corrections are followed by instrumental mass fractionation corrections using 189/188, 192/189, or 192/188 using the exponential law. Both the internal and external precision for standard and unknown data are best when using 192/188, by a factor of 1.4 over 189/188, and 1.8 over 192/189. Replicate runs on 100 ng standard loads of a single filament shows no change in corrected values within external precision for all Os isotopic ratios over a wide range of fractionation, confirming adherence to the exponential law during emission. 39 runs for a standard solution gave +/-14 ppm (2 sigma) on the 186/188 ratio when using 192/188 of 3.083 for normalization. Technique development continues, with a goal of reducing the amount of Os measured to generate these precisions. Applications of this technique to ongoing studies include further examination of 186/188-187/188 variations in mantle-derived materials. Samples studied include Archean and Proteozoic komatiites, abyssal peridotites, plume-derived basalts, and Os-rich alloys from ultramafic portions of ophiolites. The origin of nucleosynthetic Os isotopic anomalies in meteorites, and the cosmic ray exposure effects to the Os isotopic composition of extra-terrestrial materials, are being investigated to evaluate the variation identified in a preliminary set of chondrites using the Triton.

Brandon, A.

2006-12-01

224

Chemical, isotopic, and gas compositions of selected thermal springs in Arizona, New Mexico, and Utah  

USGS Publications Warehouse

Twenty-seven thermal springs in Arizona, New Mexico, and Utah were sampled for detailed chemical and isotopic analysis. The springs issue sodium chloride, sodium bicarbonate, or sodium mixed-anion waters of near neutral (6.2) to alkaline (9.2) pH. High concentrations of fluoride, more than 8 milligrams per liter, occur in Arizona in waters from Gillard Hot Springs, Castle Hot Springs, and the unnamed spring of Eagle Creek, and in New Mexico from springs along the Gila River. Deuterium compositions of the thermal waters cover the same range as those expected for meteoric waters in the respective areas. The chemical compositions of the thermal waters indicate that Thermo Hot Springs in Utah and Gillard Hot Springs in Arizona represent hydrothermal systems which are at temperatures higher than 125 deg C. Estimates of subsurface temperature based on the quartz and Na-K-Ca geothermometer differ by up to 60 deg C for Monroe, Joseph, Red Hill, and Crater hot springs in Utah. Similar conflicting estimates of aquifer temperature occur for Verde Hot Springs, the springs near Clifton and Coolidge Dam, in Arizona; and the warm springs near San Ysidro, Radium Hot Springs, and San Francisco Hot Springs, in New Mexico. Such disparities could result from mixing, precipitation of calcium carbonate, or perhaps appreciable concentrations of magnesium. (Woodard-USGS)

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

1977-01-01

225

Dilution Confusion: Conventions for Defining a Dilution  

ERIC Educational Resources Information Center

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

Fishel, Laurence A.

2010-01-01

226

Enhanced thermal conductivity and isotope effect in single-layer hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

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).

Broido, David; Lindsay, Lucas

2012-02-01

227

Isotopically exchangeable organic hydrogen in coal relates to thermal maturity and maceral composition  

USGS Publications Warehouse

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.

Mastalerz, M.; Schimmelmann, A.

2002-01-01

228

COMSOL Simulations for Steady State Thermal Hydraulics Analyses of ORNL s High Flux Isotope Reactor  

SciTech Connect

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.

Khane, Vaibhav B [ORNL] [ORNL; Jain, Prashant K [ORNL] [ORNL; Freels, James D [ORNL] [ORNL

2012-01-01

229

Enhanced thermal conductivity and isotope effect in single-layer hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

The thermal conductivity, ?, 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 ? 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 ?, with calculated room temperature values of more than 600 Wm-1K-1. Isotopic enrichment further increases ?, with the calculated enhancement exhibiting a peak with temperature, whose magnitude shows a dramatic sensitivity to crystallite size.

Lindsay, L.; Broido, D. A.

2011-10-01

230

Use of stable sulphur isotopes to monitor directly the behaviour of sulphur in coal during thermal desulphurization  

USGS Publications Warehouse

A method has been developed using stable sulphur isotope analyses to monitor the behaviour of sulphur forms in a coal during thermal desulphurization. In this method, the natural stable isotopic composition of the pyritic and organic sulphur in coal is used as a tracer to follow their mobility during the desulphurization process. This tracer method is based on the fact that the isotopic compositions of pyritic and organic sulphur are significantly different in some coals. Isotopic results of pyrolysis experiments at temperatures ranging from 350 to 750 ??C indicate that the sulphur released with the volatiles is predominantly organic sulphur. The pyritic sulphur is evolved in significant quantities only when pyrolysis temperatures exceed 500 ??C. The presence of pyrite seems to have no effect on the amount of organic sulphur evolved during pyrolysis. The chemical and isotopic mass balances achieved from three different samples of the Herrin (No. 6) coal of the Illinois Basin demonstrate that this stable isotope tracer method is quantitative. The main disadvantage of this tracing technique is that not all coals contain isotopically distinct organic and pyritic sulphur. ?? 1987.

Liu, C.-L.; Hackley, K.C.; Coleman, D.D.

1987-01-01

231

Solar Carbon Monoxide, Thermal Profiling, and the Abundances of C, O, and their Isotopes  

E-print Network

A solar photospheric "thermal profiling" analysis is presented, exploiting the infrared rovibrational bands of carbon monoxide (CO) as observed with the McMath-Pierce Fourier transform spectrometer (FTS) at Kitt Peak, and from above the Earth's atmosphere by the Shuttle-borne ATMOS experiment. Visible continuum intensities and center-limb behavior constrained the temperature profile of the deep photosphere, while CO center-limb behavior defined the thermal structure at higher altitudes. The oxygen abundance was self consistently determined from weak CO absorptions. Our analysis was meant to complement recent studies based on 3-D convection models which, among other things, have revised the historical solar oxygen (and carbon) abundance downward by a factor of nearly two; although in fact our conclusions do not support such a revision. Based on various considerations, an oxygen abundance of 700+/-100 ppm (parts per million relative to hydrogen) is recommended; the large uncertainty reflects the model sensitivity of CO. New solar isotopic ratios also are reported for 13C, 17O, and 18O.

Thomas R. Ayres; Claude Plymate; Christoph U. Keller

2006-06-07

232

Drinking behaviour and water turnover rates of Antarctic fur seal pups: implications for the estimation of milk intake by isotopic dilution  

Microsoft Academic Search

The estimation of milk consumption in free-ranging seals using tritium dilution techniques makes the key assumption that the animals drink no pre-formed water during the experimental period. However, frequent observations of unweaned Antarctic fur seal pups drinking water at Iles Kerguelen necessitated the testing of this assumption. We estimated water flux rates of 30 pups (10.70.3 kg) in four experimental

Mary-Anne Lea; Francesco Bonadonna; Mark A. Hindell; Christophe Guinet; Simon D. Goldsworthy

2002-01-01

233

Mass Dependency of Isotope Fractionation of Gases Under Thermal Gradient and Its Possible Implications for Planetary Atmosphere Escaping Process  

NASA Technical Reports Server (NTRS)

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 not be the significant contributor as the energies involved in the hyperfine effect are much smaller than those with molecular collisions, especially under convective conditions.

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

2014-01-01

234

Halogen Chemistry and Stable Cl Isotope Composition of Thermal Springs in the Cascade Arc  

NASA Astrophysics Data System (ADS)

The Cascade volcanic arc is located above a young (~6Ma) and slowly subducting (~4 cm/y) Juan de Fuca plate. Because of the high temperatures in the subduction slab, dehydration reactions are thought to occur at shallow depth to the west of the Cascade volcanic front. Spatial devolatization trends may be observed at the surface by examining geochemical trends from along and across the volcanic front. We have measured the concentration of halogens (F, Cl, Br, I) and the stable Cl isotope compositions of thermal spring waters and primitive basalts along and across the Cascade arc in order to further quantify the extent of halogen cycling through the Cascadia subduction system. Thermal springs from 13 localities, between north-central Washington to Lassen, Northern California with Cl concentrations ranging from 250 to 180,000 ppm (Bergfeld et al., 2008, Hurwitz et al., 2005) were analyzed for their Cl isotope composition. The ?37Cl values range from -2.1 to +1.3 (n=17), and show no correlation with Cl concentrations and sample location along the arc. The majority of samples are characterized by slightly positive values, whereas only three have negative values (-0.9, -1.6, -2.1). Given the upper mantle has a ?37Cl value near 0, the variation in the Cl isotope data suggests either that the chloride isotope compositions of these spring waters were modified upon ascent to the surface by the interaction of underlying sediment and/or contain a subducted slab derived component. Nine well characterized basalt samples from across the southern Washington Cascades, (Leeman et al., 2005) were analyzed for their bulk halogen concentrations. Cl concentrations are highest at the volcanic front (140-157 ppm Mt. St. Helens and Mt. Adams) compared to the forearc (17-82 ppm) and in the backarc (19-65 ppm). Br shows a similar trend to Cl with the highest concentrations at the volcanic front (0.22-0.31 ppm) compared to the forearc (0.08-0.13 ppm) and in the backarc (<0.06 ppm). In contrast, F and I show decreasing concentrations from the forearc to the backarc. F concentrations are highest in the forearc (144-600 ppm) decreasing to 120-197 ppm at the volcanic front and 75-164 ppm in the backarc. Iodine concentrations are highest in the forearc (0.09 to 0.10 ppm) to <0.03 ppm in the volcanic front and backarc. Like F and I, B concentrations decrease steadily toward the backarc (Leeman et al., 2004). Bergfeld et al., 2008, USGS Prof. Paper 1750, chap. 25, 523-542. Hurwitz et al., 2005,EPSL., 235, 700-71. Leeman et al., 2004, ChemGeol. 212, 101-124. Leeman et al., 2005, JVGR. 140, 67-105.

Cullen, J.; Barnes, J.; Hurwitz, S.; Leeman, W. P.

2012-12-01

235

Inorganic origin of carbon dioxide during low temperature thermal recovery of bitumen: Chemical and isotopic evidence  

NASA Astrophysics Data System (ADS)

Carbon dioxide, produced at low temperatures, is the dominant gaseous species evolved during steam-assisted thermal recovery of bitumen at the Tucker Lake pilot, Cold Lake, Alberta. Two possible sources for the produced CO 2 are considered: pyrolysis of bitumen and dissolution of carbonate minerals. Data from natural systems and experiments by other authors suggest that clay-carbonate reactions are the dominant source of CO 2. Carbon isotope and chemical analyses of produced gas and water reveal that CO 2 and HCO 3- become more enriched in 13C, and concentrations of Ca 2+ and HCO 3- rise during production. Temperatures in the producing zone are estimated to be between 70 and 220C using the Na/K and chalcedony chemical geothermometers, and show that production of 13C-enriched CO 2 and HCO 3- occurs as temperature decreases during production. This extends the temperature range at which CO 2 is known to be produced from carbonates to lower levels than previously noted. The ? 13C of calcite in the reservoir is enriched in ? 13C, giving values as high as + 17.4%. When the calcite isotopic compositions are combined with temperature data and temperature fractionation equations for calcite, CO 2, and HCO 3-, they show calcite to be the only viable source of CO 2. Bitumen pyrolysis may contribute small amounts of CO 2, probably by decarboxylation, early in the production cycle but cannot contribute significant volumes. The recognition of production of CO 2 by reactive calcite destruction at temperatures between 70 and 220C suggests that this process may be responsible for the production of large quantities of CO 2 in natural systems, particularly in lithofeldspathic sands and shales with high carbonate content and abundant clays. Organic acids have been suggested to be the source of CO 2 in diagenetic fluids, but the results presented here suggest that this hypothesis requires more complete investigation.

Hutcheon, Ian; Abercrombie, Hugh J.; Krouse, H. R.

1990-01-01

236

A structural evaluation of the tungsten isotopes via thermal neutron capture  

E-print Network

Total radiative thermal neutron-capture $\\gamma$-ray cross sections for the $^{182,183,184,186}$W isotopes were measured using guided neutron beams from the Budapest Research Reactor to induce prompt and delayed $\\gamma$ rays from elemental and isotopically-enriched tungsten targets. These cross sections were determined from the sum of measured $\\gamma$-ray cross sections feeding the ground state from low-lying levels below a cutoff energy, E$_{\\rm crit}$, where the level scheme is completely known, and continuum $\\gamma$ rays from levels above E$_{\\rm crit}$, calculated using the Monte Carlo statistical-decay code DICEBOX. The new cross sections determined in this work for the tungsten nuclides are: $\\sigma_{0}(^{182}{\\rm W}) = 20.5(14)$ b and $\\sigma_{11/2^{+}}(^{183}{\\rm W}^{m}, 5.2 {\\rm s}) = 0.177(18)$ b; $\\sigma_{0}(^{183}{\\rm W}) = 9.37(38)$ b and $\\sigma_{5^{-}}(^{184}{\\rm W}^{m}, 8.33 \\mu{\\rm s}) = 0.0247(55)$ b; $\\sigma_{0}(^{184}{\\rm W}) = 1.43(10)$ b and $\\sigma_{11/2^{+}}(^{185}{\\rm W}^{m}, 1.67 {\\rm min}) = 0.0062(16)$ b; and, $\\sigma_{0}(^{186}{\\rm W}) = 33.33(62)$ b and $\\sigma_{9/2^{+}}(^{187}{\\rm W}^{m}, 1.38 \\mu{\\rm s}) = 0.400(16)$ b. These results are consistent with earlier measurements in the literature. The $^{186}$W cross section was also independently confirmed from an activation measurement, following the decay of $^{187}$W, yielding values for $\\sigma_{0}(^{186}{\\rm W})$ that are consistent with our prompt $\\gamma$-ray measurement. The cross-section measurements were found to be insensitive to choice of level density or photon strength model, and only weakly dependent on E$_{\\rm crit}$. Total radiative-capture widths calculated with DICEBOX showed much greater model dependence, however, the recommended values could be reproduced with selected model choices. The decay schemes for all tungsten isotopes were improved in these analyses.

A. M. Hurst; R. B. Firestone; B. W. Sleaford; N. C. Summers; Zs. Revay; L. Szentmiklosi; M. S. Basunia; T. Belgya; J. E. Escher; M. Krticka

2013-11-06

237

Limited range of interspecific vital effects in coccolith stable isotopic records during the Paleocene-Eocene thermal maximum  

NASA Astrophysics Data System (ADS)

Small but significant differences exist among stable carbon and oxygen isotopic excursions measured in coccolith-dominated bulk carbonate and planktic foraminifera during the Paleocene-Eocene thermal maximum (PETM). One hypothesis suggests that the bulk carbonate isotopic record is compromised by changing nannofossil assemblages, since modern nannofossils show a large (5 permil) range of interspecific vital effects. New techniques are employed here to separate different size fractions of coccoliths from PETM sediments at ODP Site 690 for isotopic analysis, removing a major portion of the variation in nannofossil assemblages. Isotopic compositions of coarse and fine coccolith fractions dominated by coccoliths of genus Chiasmolithus and Toweius, respectively, differ by less than 0.5 permil for both oxygen and carbon. The near-monogeneric Toweius record closely parallels the main trends in the bulk carbonate isotope records, including multiple steps in the negative carbon isotopic excursion, suggesting that the trends in the bulk carbonate record are not artifacts of changing species assemblages. Because both coccolithophorids and symbiont-bearing foraminifera like Acarinina must inhabit the photic zone, it is unlikely that the 103 year lags in isotope event onset between coccoliths and Acarinina reflect true time-transgressive invasion of isotopically depleted CO2 into the water column. The small range of vital effects among Paleocene coccoliths is unlikely to result from diagenetic homogenization, and instead may reflect more similar carbon acquisition strategies of Paleocene coccolithophorid algae due to larger and/or more similar cell sizes and higher atmospheric carbon dioxide. The small range of vital effects suggests that bulk carbonate records are likely reliable for other early and pre-Cenozoic sediments where foraminifera are often scarce.

Stoll, Heather M.

2005-03-01

238

Synthesis of (13) C2 (15) N2 -labeled anti-inflammatory and cytoprotective tricyclic bis(cyanoenone) ([(13) C2 (15) N2 ]-TBE-31) as an internal standard for quantification by stable isotope dilution LC-MS method.  

PubMed

Tricyclic bis(cyanoenone), TBE-31, one of the most potent activators of the Keap1/Nrf2/antioxidant response element pathway, has been developed as a new anti-inflammatory and cytoprotective agent. (13) C2 (15) N2 -labeled TBE-31 ([(13) C2 (15) N2 ]-TBE-31), which has two (13) C and two (15) N atoms in two cyano groups, was designed to develop a method for quantification of cell, tissue, and plasma levels of TBE-31 that involves chromatography/mass spectrometry coupled with the use of a stable isotope-labeled internal standard. [(13) C2 (15) N2 ]-TBE-31 was successfully synthesized in four steps from a previously reported intermediate, which is prepared in 11 steps from cyclohexanone, by introduction of two (13) C atoms with ethyl [(13) C]formate and two (15) N atoms with hydroxyl[(15) N]amine. The stable isotope dilution liquid chromatography-mass spectrometry method for quantification of TBE-31 was successfully developed using [(13) C2 (15) N2 ]-TBE-31 to compensate for any variables encountered during sample processing and analysis. PMID:25196444

Zheng, Suqing; Huang, Jeffrey T-J; Knatko, Elena V; Sharp, Sheila; Higgins, Maureen; Ojima, Iwao; Dinkova-Kostova, Albena T; Honda, Tadashi

2014-08-01

239

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

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 (10?L) 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

Albero, Beatriz; Snchez-Brunete, Consuelo; Miguel, Esther; Prez, Rosa A; Tadeo, Jos L

2013-03-29

240

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

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

Botitsi, E V; Kormali, P N; Kontou, S N; Economou, A; Tsipi, D F

2006-10-01

241

Dynamics calculations for the Cl+C2H6 abstraction reaction: Thermal rate constants and kinetic isotope effects  

Microsoft Academic Search

Thermal rate constants and H\\/D kinetic isotope effects for the Cl+C2H6-->HCl+C2H5 reaction were computed by microcanonical variational transition state theory on a high-level ab initio potential energy surface (PES). The calculations show that the reaction proceeds through a ``loose'' transition state, and so the consideration of variational effects is important. The PES presents a van der Waals minimum in the

A. Fernndez-Ramos; E. Martnez-Nez; J. M. C. Marques; S. A. Vzquez

2003-01-01

242

Dynamics calculations for the Cl+C2H6 abstraction reaction: Thermal rate constants and kinetic isotope effects  

Microsoft Academic Search

Thermal rate constants and H\\/D kinetic isotope effects for the Cl+C2H6?HCl+C2H5 reaction were computed by microcanonical variational transition state theory on a high-level ab initio potential energy surface (PES). The calculations show that the reaction proceeds through a loose transition state, and so the consideration of variational effects is important. The PES presents a van der Waals minimum in the

A. Fernandez-Ramos; J. M. C. Marques; S. A. Vazquez

2003-01-01

243

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)

The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular of their stable carbon isotope ratio (?13C), 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 ?13C 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 ?13C varied widely, from-49.7 to-22.9, while the standard deviation of the ?13C 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 ?13C 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.

Kawashima, Hiroto; Murakami, Mai

2014-06-01

244

The Precambrian Biogeochemical Carbon Isotopic Record: Contributions of Thermal Versus Biological Processes  

NASA Technical Reports Server (NTRS)

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 favorable conditions for organic burial that were evidenced by elevated sea levels and higher black shale abundances. Perhaps those superplume-rated processes that favored enhanced organic burial were offset by the ability of mantle-derived redox buffering, which was enhanced during the superplume event, to limit excursions in Forg.

DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

245

Vitamin A concentrations in liver determined by isotope dilution assay with tetradeuterated vitamin A and by biopsy in generally healthy adult humans  

SciTech Connect

The vitamin A status in 11 generally healthy surgical patients was estimated by measuring the dilution of a 45-mg oral dose of tetradeuterated retinyl acetate (99% pure). After purification of retinol by high-performance liquid chromatography, the ratio of /sup 2/H/sub 4/-retinol:/sup 1/H-retinol in plasma was measured by gas chromatography-mass spectrometry. On the basis of the observed ratios of (/sup 2/H/sub 4/)retinol:(/sup 1/H)retinol over 19-47 d, the total body reserves and liver concentrations of vitamin A were calculated. Liver biopsy samples taken at surgery were directly analyzed for vitamin A. The correlation coefficient between calculated and measured liver vitamin A concentrations for 10 of the subjects was 0.88, and the Spearman's rank correlation coefficient was 0.95 (p less than 0.002). Thus, total body reserves of vitamin A in humans can be estimated validly in the marginal and satisfactory ranges by a benign, relatively noninvasive procedure.

Furr, H.C.; Amedee-Manesme, O.; Clifford, A.J.; Bergen, H.R. 3d.; Jones, A.D.; Anderson, D.P.; Olson, J.A.

1989-04-01

246

Simple and sensitive analysis of histamine and tyramine in Japanese soy sauces and their intermediates using the stable isotope dilution HILIC-MS/MS method.  

PubMed

We established a simple, sensitive, and reproducible method to analyze the histamine and tyramine levels in Japanese soy sauce and its mash (called moromi) using hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC-MS/MS). Histamine and tyramine quantification was performed using their stable isotopes for electrospray ionization-tandem mass spectrometry in the selected reaction monitoring mode. The sample pretreatment process was a simple, one-step liquid-liquid extraction. HILIC separation was performed with a gradient elution of aqueous ammonium formate and acetonitrile. Because of validation tests, the linearity, the accuracies, and precisions were sufficient. The limit of detection and the limit of quantification were 0.09 and 0.29 ppm for histamine and 0.13 and 0.42 ppm for tyramine, respectively. We successfully applied this method to histamine and tyramine determination in four kinds of commercial Japanese soy sauces and also in moromi samples during soy sauce production. PMID:24901408

Todoroki, Kenichiro; Ishii, Yasuhiro; Miyauchi, Chiemi; Kitagawa, Sachiyo; Min, Jun Zhe; Inoue, Koichi; Yamanaka, Tomoyuki; Suzuki, Kuniaki; Yoshikawa, Yuko; Ohashi, Norio; Toyo'oka, Toshimasa

2014-07-01

247

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)

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 300C 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 80C; (3) 48h reverse aqua regia digestion in closed Teflon beakers on hotplate at 140C followed by a HF/HNO3 digestion step; (4) 48h HF/HNO3 digestion of ashed sample powder in closed Teflon beaker at 140C on hotplate followed by an aqua regia digestion step. Column chromatographic approaches to decrease the concentrations of interfering elements (Y, Zr, Mo, Cd, Hf, Hg) include the use of cation- and anion resins, and variations of the molarity and composition of the eluent. Preliminary results show that digestion method (1) leaves behind small amounts of presumably PGE-free silica gel; (2) yields consistently higher Re concentrations with an expectedly large amount of solid residue; (3) produces an insoluble sludge; (4) allows complete digestion, but precludes the collection of Os. Column calibrations show the best recovery of PGE-Re in cation resin using 0.2 mol/l HCl as eluent, but intolerably high ratios of interfering over elements of interest, whereas the best matrix separation is achieved using 0.05 mol/l HCl as eluent, but is accompanied by low PGE-Re yields presumably due to the instability of Cl complexes in this medium. They also show that U elutes separately from PGE-Re in 6 mol/l HCl and could be collected with a view to analysing U isotopes as an additional redox proxy. Further tests will be carried out using alternative high-pressure digestion systems. [1] Anbar, et al. (2007) Science 317:1903-1906; [2] Meisel et al. (2003) JAAS 18:720-726; [3] Xu et al. (2012) CG 324:132-147

Rammensee, Philipp; Aulbach, Sonja; Gudelius, Dominik; Brey, Gerhard

2013-04-01

248

High precision uranium, thorium and radium isotope ratio measurements by high dynamic range thermal ionisation mass spectrometry  

NASA Astrophysics Data System (ADS)

Mass spectrometric methods are presented for the precise determination of the isotopic compositions of uranium, thorium and radium. M+ ions were produced by thermal ionisation. Analysis involved either a dynamic routine using the Daly detector or a static routine employing both the Daly detector and off-axis Faraday detectors. Instrument performance was assessed using a set of uranium standards, CBNM IRM 072. The response of the Daly detector was linear up to ratios of at least 5 104 and when operated dynamically it is ideally suited to the measurement of ion beams in the range 5-1 105 cps. The static mode of analysis was employed successfully for the measurement of isotope ratios up to 5 105.

Cohen, Anthony S.; Belshaw, Nicholas S.; O'Nions, R. Keith

1992-07-01

249

Determination of pharmaceuticals and antiseptics in water by solid-phase extraction and gas chromatography/mass spectrometry: analysis via pentafluorobenzylation and stable isotope dilution.  

PubMed

A sensitive yet robust analytical method is presented for the simultaneous determination of 12 human pharmaceuticals (valproic acid, phenytoin, ibuprofen, gabapentin, acetaminophen, gemfibrozil, naproxen, ketoprofen, secobarbital, phenobarbital, 5-fluorouracil, and diclofenac) and 6 antiseptics (biosol, biphenylol, p-chloro-m-cresol, p-chloro-m-xylenol, chlorophene, and triclosan). The method employs solid-phase extraction (SPE) followed by a novel pentafluorobenzylation using a mixture of acetontrile/water (1/1, v/v). The method is simple to perform (derivatization can be completed in a single test tube) and eliminates the need for any solvent/SPE cartridge drying or blow-down. It affords excellent resolution, high sensitivity and reproducibility, and freedom from interference even for matrices as complex as untreated sewage. The method was applied to the analysis of sewage samples using 15 isotopically labeled surrogates, which resulted in the detection of 10 of the 12 pharmaceuticals and all of the antiseptics sought. Ten of 15 surrogates were synthesized from pure analytes by a simple H-D exchange reaction employing D(2)O and D(2)SO(4). Measured recoveries were sensitive to matrix effects and varied substantially among analytes, indicative of the limitations associated with using a single surrogate standard. PMID:22367332

Yu, Jim T; Bisceglia, Kevin J; Bouwer, Edward J; Roberts, A Lynn; Coelhan, Mehmet

2012-04-01

250

The determination of carbon dioxide concentration using atmospheric pressure ionization mass spectrometry/isotopic dilution and errors in concentration measurements caused by dryers.  

PubMed

An atmospheric pressure ionization mass spectrometry/isotopically labeled standard (APIMS/ILS) method has been developed for the determination of carbon dioxide (CO(2)) concentration. Descriptions of the instrumental components, the ionization chemistry, and the statistics associated with the analytical method are provided. This method represents an alternative to the nondispersive infrared (NDIR) technique, which is currently used in the atmospheric community to determine atmospheric CO(2) concentrations. The APIMS/ILS and NDIR methods exhibit a decreased sensitivity for CO(2) in the presence of water vapor. Therefore, dryers such as a nafion dryer are used to remove water before detection. The APIMS/ILS method measures mixing ratios and demonstrates linearity and range in the presence or absence of a dryer. The NDIR technique, on the other hand, measures molar concentrations. The second half of this paper describes errors in molar concentration measurements that are caused by drying. An equation describing the errors was derived from the ideal gas law, the conservation of mass, and Dalton's Law. The purpose of this derivation was to quantify errors in the NDIR technique that are caused by drying. Laboratory experiments were conducted to verify the errors created solely by the dryer in CO(2) concentration measurements post-dryer. The laboratory experiments verified the theoretically predicted errors in the derived equations. There are numerous references in the literature that describe the use of a dryer in conjunction with the NDIR technique. However, these references do not address the errors that are caused by drying. PMID:18574165

DeLacy, Brendan G; Bandy, Alan R

2008-01-01

251

Thermodynamics of Dilute Solutions.  

ERIC Educational Resources Information Center

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.

Jancso, Gabor; Fenby, David V.

1983-01-01

252

A novel reversed-phase HPLC method for the determination of urinary creatinine by pre-column derivatization with ethyl chloroformate: comparative studies with the standard Jaff and isotope-dilution mass spectrometric assays.  

PubMed

Creatinine is an important biomarker for renal function diagnosis and normalizing variations in urinary drug/metabolites concentration. Quantification of creatinine in biological fluids such as urine and plasma is important for clinical diagnosis as well as in biomonitoring programs and urinary metabolomics/metabonomics research. Current methods for creatinine determination either are nonselective or involve the use of expensive mass spectrometers. In this paper, a novel reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of creatinine of high hydrophilicity by pre-column derivatization with ethyl chloroformate is presented. N-Ethyloxycarbonylation of creatinine significantly enhanced the hydrophobicity of creatinine, facilitating its chromatographic retention as well as quantification by HPLC. Factors governing the derivatization reaction were studied and optimized. The developed method was validated and applied for the determination of creatinine in rat urine samples. Comparative studies with isotope-dilution mass spectrometric method revealed that the two methods do not yield systematic differences in creatinine concentrations, indicating the HPLC method is suitable for the determination of creatinine in urine samples. PMID:24408302

Leung, Elvis M K; Chan, Wan

2014-02-01

253

Speciation analysis of bromine-containing drug metabolites in feces samples from a human in vivo study by means of HPLC/ICP-MS combined with on-line isotope dilution.  

PubMed

The aim of this work was speciation analysis of metabolites in feces samples collected within a clinical study during which a bromine-containing anti-tuberculosis drug (TMC207) was administered to patients with multi-drug resistant tuberculosis infection. Owing to slow elimination of the drug, no (14)C label was used within this study. Quantification of the bromine species was accomplished using high performance liquid chromatography coupled to inductively coupled plasma-mass spectrometry (HPLC/ICP-MS) in combination with on-line isotope dilution (on-line ID), while structural elucidation of the species was performed using HPLC coupled to electrospray ionization-mass spectrometry. The ICP-MS-based method developed shows a good intra- and inter-day reproducibility (relative standard deviation = 3.5%, N = 9); the limit of detection (1.5 mg TMC207 L(-1)) is of the same order of magnitude as that for HPLC/radiodetection; the dynamic range of the method covers more than two orders of magnitude. Furthermore, the column recovery was demonstrated to be quantitative (recoveries between 90.6% and 99.5%). Based on the excellent figures of merit, the "cold" HPLC/ICP-MS approach could be deployed for the actual human in vivo metabolism study, such that exposure of the human volunteers to the (14)C radiolabel was avoided. PMID:21877185

Meermann, Bjrn; Bockx, Marc; Laenen, Aline; Van Looveren, Cis; Cuyckens, Filip; Vanhaecke, Frank

2012-01-01

254

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 Central

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. Wilsons 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 Wilsons disease. We used a sensitive capillary LC-ESI-MS/MS/MS method in conjunction with stable-isotope dilution technique to quantify several types of oxidative DNA lesions in 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 Wilsons disease, as well as in ageing and ageing-related pathological conditions. PMID:21323344

Wang, Jin; Yuan, Bifeng; Guerrero, Candace; Bahde, Ralf; Gupta, Sanjeev; Wang, Yinsheng

2011-01-01

255

High-precision simultaneous determination of 147Sm/144Nd and 143Nd/144Nd ratios in Sm-Nd mixtures using multi-collector inductively coupled plasma mass spectrometry and its comparison to isotope dilution analysis  

NASA Astrophysics Data System (ADS)

This work demonstrates, for the first time, the feasibility and capability of the high-precision simultaneous determination of 147Sm/144Nd and 143Nd/144Nd ratios in Sm-Nd mixtures using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) without Nd and Sm separation and without the use of costly enriched spikes. Mass discrimination was exponentially corrected by applying the natural constant of 146Nd/144Nd ratio as an internal standard, after correction of the isobaric interference of 144Sm on 144Nd using interference-free 147Sm/149Sm ratio for Sm mass fractionation, without assuming identical mass bias of Nd and Sm. The accuracy and precision of the present protocol, obtained from replicate analyses of various types of Sm-Nd mixtures encompassing a wide range of Sm/Nd (ca. 0.1-1.0) or 147Sm/144Nd ratios (ca. 0.06-0.62) was found to be comparable to the classic isotope dilution (ID) method. The present method is characterized by a higher sample throughput compared to the ID method, and shows great potential for the simultaneous determination of 147Sm/144Nd and 143Nd/144Nd ratios in real geological samples.

Yang, Yue-Heng; Wu, Fu-Yuan; Chu, Zhu-Yin; Xie, Lie-Wen; Yang, Jin-Hui

2013-01-01

256

Click chemistry mediated Eu-tagging: activity-based specific quantification and simultaneous activity evaluation of CYP3A4 using 153Eu species-unspecific isotope dilution inductively coupled plasma mass spectrometry.  

PubMed

P450 3A4 (CYP3A4) is one of the most important isoforms in the human cytochrome P450 superfamily. It was used as an example in this proof-of-concept study in order to demonstrate an activity-based labeling and then click chemistry (CC) mediated element-tagging strategy for simultaneously specific quantification and activity measurement of an enzyme using species-unspecific isotope dilution inductively coupled plasma mass spectrometry (SUID ICPMS). A dual functional hexynylated 17?-ethynylestradiol activity-based probe was synthesized for specifically labeling CYP3A4 and then CC-mediated Eu-tagging with an azido-DOTA-Eu complex for CYP3A4 quantification and activity measurement in human liver microsome and serum samples using (153)Eu SUID ICPMS. The LOD (3?) of CYP3A4 reached 20.3 fmol when monitoring (151/153)Eu ICPMS signals, in addition to the merits of specificity and simultaneous activity measurement achieved. We believe that this activity-based CC-mediated element-tagging strategy will liberate more potential advantages of ICPMS in bioanalysis. PMID:24654690

Liang, Yong; Yan, Xiaowen; Li, Zhaoxin; Yang, Limin; Zhang, Bo; Wang, Qiuquan

2014-04-15

257

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

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

Wang, Jin; Yuan, Bifeng; Guerrero, Candace; Bahde, Ralf; Gupta, Sanjeev; Wang, Yinsheng

2011-03-15

258

Isotopic dilution, self-association, and Raman non-coincidence in the binary system (CH 3) 2C?O+(CD 3) 2C?O reinvestigated by polarized Raman measurement and ab initio calculations  

NASA Astrophysics Data System (ADS)

Raman spectra of the binary system (CH 3) 2C?O (acetone)+(CD 3) 2C?O (acetone-d 6) were reinvestigated employing a more precise and sensitive scanning multichannel detection scheme. The I? and I? components of the Raman scattered radiation were recorded in the C?O stretching region, 1600-1800 cm -1 as well as in the C-D and C-H stretching regions, 2000-2300 and 2800-3100 cm -1, respectively, in different mixtures with the varying mole fractions of the reference system. A careful Raman line shape analysis yielded after fit ? ?nc due to Raman non-coincidence effect (NCE) in acetone and acetone-d 6 as 4.870.01 and 4.490.01 cm -1, respectively. The optimized geometries and wavenumbers of the neat acetone molecule and its self-associated structure were calculated using ab initio method at the MP2 level using 6-31++G(d,p) basis set. The influence of self-association and NCE together were examined. A systematic study of Raman line shape analysis led to a hitherto unexplored aspect, the wavenumber shift and linewidth variation of the ?1(C-H) stretching mode of acetone upon isotopic dilution. The linewidth variation with the mole fraction of the reference system shows an excellent agreement with the corresponding linewidths derived from the T 2 values obtained by three color fs-CARS study reported earlier.

Srivastava, Sunil K.; Ojha, Animesh K.; Koster, J.; Shukla, M. K.; Leszczynski, J.; Asthana, B. P.; Kiefer, W.

2003-12-01

259

Determination of the carbon isotopic composition of whole/intact biological specimens using at-line direct thermal desorption to effect thermally assisted hydrolysis/methylation.  

PubMed

In this paper, we discuss the use of a direct thermal desorption (DTD) interface as an alternative to Curie-point flash pyrolysis system as an inlet technique in gas chromatography-combustion isotope-ratio mass spectrometry (GC/C-IRMS) analysis of whole/intact phytoplankton and zooplankton specimens. The DTD in combination with a combipal auto-injector is programmed to perform the injection, evaporation of solvents, transport of capped programmed-temperature vaporizer (PTV) liners to the PTV injector and chemical derivatisation (thermally assisted hydrolysis/methylation; THM) such that a profile of a cellular fatty acids is obtained. Flow-cytometric sorted microalgae and handpicked zooplankton are used as samples with trimethylsulfonium hydroxide (TMSH) as methylating reagent. A major advantage of this novel approach over the Curie-point technique is the automation of the total procedure, which allows unattended analysis of large sample series. The profiles and delta(13)C carbon isotopic signatures of the fatty acid methyl esters (FAMEs) produced are very similar to those obtained using the Curie-point flash pyrolysis method. It is shown that algal samples must be kept no longer than 48 h in the DTD sample tray prior to the THM-analysis in order to maintain the integrity of their FAME profile. PMID:17897655

Akoto, Lawrence; Vreuls, Ren J J; Irth, Hubertus; Floris, Virgilio; Hoogveld, Hans; Pel, Roel

2008-04-01

260

Stable-isotope dilution LC-MS/MS measurement of nitrite in human plasma after its conversion to S-nitrosoglutathione.  

PubMed

A specific, sensitive and fast LC-MS/MS method with positive electrospray ionization for the quantitative determination of nitrite in human plasma is reported. Added [(15)N]nitrite served as the internal standard (IS). Endogenous nitrite and IS were converted to their S-nitrosoglutathione (GSNO) derivatives, i.e., GS(14)NO and GS(15)NO, respectively, by using excess glutathione (GSH) and HCl. For plasmatic nitrite, fresh plasma (0.5mL) was spiked with the IS (1000nM) and ultrafiltered (cut-off 10kDa). Ultrafiltrate aliquots (100?L) were treated with aqueous GSH at a final concentration of 1mM and 1?L of 5M HCl for 5min. After final sample dilution (1:1, v/v) with acetonitrile-water (70:30, v/v), 2?L aliquots were injected via a thermostated (4C) autosampler. The mobile phase was acetonitrile-water (70:30, v/v), contained 20mM ammonium formate, had a pH value of 7, and was pumped isocratically at 0.5mL/min. A Nucleoshell column was used for LC separation. The retention time of GSNO was about 0.8min and the total analysis time 5min. Quantification was performed by selected-reaction monitoring the specific mass transition m/z337([M+H](+))?m/z 307([M+H-(14)NO](+)) for GS(14)NO (i.e., for endogenous nitrite) and m/z338([M+H](+))?m/z307([M+H-(15)NO](+)) for GS(15)NO (i.e., for the IS). The method was thoroughly validated in human plasma (range, 0-2000nM). The LOD and LOQ values of the LC-MS/MS method were determined to be 1fmol and 5nM [(15)N]nitrite, respectively. The relative matrix-effect of about 21% was outweighed entirely by the IS. In freshly prepared plasma samples from heparinized blood donated by three healthy subjects, nitrite concentration was determined by LC-MS/MS to be 516, 199 and 369nM. These concentrations were confirmed by using a previously reported GC-MS method and agree with those measured previously by HPLC-UV (334nm) after nitrite conversion to S-nitroso-N-acetylcysteine (SNAC) by N-acetylcysteine (NAC). Measurement of nitrite by LC-MS/MS as GSNO is about 1000 times more sensitive than by HPLC-UV as SNAC. The applicability of the method to microdialysate, urine, and saliva samples from humans was demonstrated. The agreement of two orthogonal MS-based methods indicates that the concentration of nitrite in freshly prepared, non-frozen plasma from heparinized blood of fasted healthy humans is of the order of 400nM. PMID:25237784

Hanff, Erik; Bhmer, Anke; Jordan, Jens; Tsikas, Dimitrios

2014-11-01

261

On-line monitoring of benzene air concentrations while driving in traffic by means of isotopic dilution gas chromatography/mass spectrometry.  

PubMed

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 from 17 to 62.3 micrograms/m3 even if the actual distance was small. A larger increase was observed when a car was left with the engine running at a distance 2 m from the zero emission vehicle: We measured an increment of benzene concentrations from 15.2 to 174.4 micrograms/m3 with a car equipped with a catalytic converter, and from 19.1 to 386.3 micrograms/m3 with a car without such a converter. PMID:8738357

Davoli, E; Cappellini, L; Moggi, M; Ferrari, S; Fanelli, R

1996-01-01

262

Carbon addition during the Paleocene-Eocene Thermal Maximum: Model inversion of a new, high-resolution carbon isotope record from Svalbard  

Microsoft Academic Search

Newly analyzed core material from Svalbard presents the most expanded sedimentary section spanning the Paleocene Eocene Thermal Maximum (PETM) studied to date. Carbon isotopic analysis of the bulk organic matter extracted from core BH9-05 details the onset of the negative carbon isotope excursion (CIE) of approximately 4.20\\/00 over 19,000 years (8 m of section, sampled every 30 cm) and its

Y. Cui; L. Kump; A. Ridgwell; C. Junium; A. F. Diefendorf; K. H. Freeman; N. Urban

2010-01-01

263

A comparison of lead-isotope measurements on exploration-type samples using inductively coupled plasma and thermal ionization mass spectrometry  

USGS Publications Warehouse

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.

Gulson, B. L.; Meier, A. L.; Church, S. E.; Mizon, K. J.

1989-01-01

264

Unusually large secondary deuterium isotope effect. Thermal trans-cis isomerization of trans-1-phenylcyclohexene  

SciTech Connect

The magnitudes of secondary deuterium isotope effects (SDIE) are generally in the range of 0.9 < k/sub H//k/sub D/ < 1.25, and are often satisfactorily rationalized by the zero-point energy (ZPE) change on going from reactant to transition state due to C-H rehybridization. They now report a far larger SDIE for the title reaction. Its rationalization on the basis of transition state theory suggests that it more closely resembles a primary isotope effect.

Caldwell, R.A.; Misawa, H.; Healy, E.F.; Dewar, M.J.S.

1987-10-28

265

Determination of bisphenol A in water by isotope dilution headspace solid-phase microextraction and gas chromatography/mass spectrometry without derivatization.  

PubMed

The original solid-phase microextraction (SPME) fibers use an epoxy resin adhesive that releases bisphenol A (BPA) during thermal desorption of the fiber. This adversely affects the method detection limit and accuracy when these products are used for the determination of BPA. In this work, 5 new metal alloy SPME fibers that do not use epoxy resins were compared for the extraction of BPA in water. The performance of the optimum SPME fiber with 60 microm carbowax-polyethylene glycol coating for the headspace SPME of BPA in water was investigated systematically under different extraction conditions. Salt was found to increase the partitioning of BPA from water into the headspace until saturation was reached. Partitioning of BPA from water into the headspace also increased at higher extraction temperatures, as did longer extraction times. However, extraction of BPA from water onto the SPME fiber was not improved for solutions adjusted to pH 2 compared to the unadjusted neutral solutions. The new BPA method showed good linearity over the concentration range of 2.5 to 40 microg/L [correlation coefficient (r2) = 0.995] . The method detection limit for BPA was 0.5 microg/L, while the instrument detection limit was as low as 0.05 microg/L. Good repeatability was observed for BPA at levels of 5 and 20 microg/L with relative standard deviation values < 10%. The automated headspace SPME method developed in this work was used to investigate migration of BPA from polycarbonate bottles into water, and levels of BPA in water ranged from 1.7 to 4.1 microg/L. PMID:18567309

Cao, Xu-Liang; Corriveau, Jeannette

2008-01-01

266

Relative humidity across the Paleocene-Eocene Thermal Maximum via combined hydrogen-oxygen isotope paleohygrometry (Invited)  

NASA Astrophysics Data System (ADS)

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 (?18O) 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 (?D) of leaf-wax lipids (long-chain n-alkanes) reflect both meteoric water ?D values and additional D-enrichment caused by evapotranspiration. The enrichment factor between water ?D and n-alkane ?D can therefore be used as a proxy for relative humidity (RH). In this study, ?18O of surface water is estimated using the ?18O of Coryphodon tooth enamel. We use these ?18O values to estimate surface water ?D values using the Global Meteoric Water Line (?D = 8?18O + 10). We then calculate relative humidity from n-alkane ?D 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 relative humidity during the first half of the PETM followed by a decline during the second half of the event. The rise is punctuated by at least one small drop in relative humidity. Other proxies for available soil moisture (soil weathering indices) and mean annual precipitation (leaf physiognomy) suggest an initial drying at the onset of the PETM followed by subsequent periods of wetter and dryer conditions in the southeastern Bighorn Basin. In contrast, the isotope results presented here suggest that the onset of the PETM was marked by an increase in relative humidity. This discrepancy might indicate increased seasonality during the PETM. Leaf wax hydrogen isotope values are likely biased to record primarily the growing season, which may have become more humid, while soil and plant proxies could reflect an overall decrease in available moisture as a result of increased seasonality of precipitation.

McInerney, F. A.; Bloch, J. I.; Secord, R.; Wing, S. L.; Kraus, M. J.; Boyer, D. M.

2009-12-01

267

The Absolute Isotopic Composition of Zn in Terrestrial Materials Determined Using Double Spike Thermal Ionization Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Although long suspected to be widespread in nature, until recently, little was known about the extent of the variation of the isotopic composition, or isotopic fractionation, of Zn in natural materials. During the last decade an increasing number of high precision Zn isotopic fractionation data have been reported using MC- ICP-MS (MARECHAL et al., 1999; PETIT et al., 2008; PICHAT et al., 2003), but none have been reported on an absolute scale which is essential for interlaboratory comparison of results. In this work we report sub- permil Zn fractionation in a range of natural materials relative to the internationally proposed absolute Zn isotopic reference material (? zero) (PONZEVERA et al., 2006)using the Thermal Ionization Mass Spectrometry double spike technique. Repeated double spike analysis of the laboratory standard relative to itself demonstrated a long term reproducibility of +0.006 0.039 permil amu-1. The measured isotopic composition of Zn in minerals and igneous rocks SRMs was found to be the same as the proposed absolute (? zero) which makes it possible to consider the proposed absolute Zn isotopic standard as being representative of "bulk earth" Zn. A significant and consistent fractionation of ~+0.3 permil amu-1 was found in 5 sediments from a range of localities. The results obtained for metamorphic SRMs indicate that the fractionation of Zn in these rocks is the same as found in igneous rocks but are different from the Zn found in sedimentary rocks. A clay SRM sample TILL-3 appears to exhibit a consistently Zn fractionation of +0.12 0.10 permil amu-1. The isotopic composition of Zn was also measured in two plant SRMs and one animal SRM sample. The fractionation of (-0.088 0.070 permil amu-1) of Zn in the Rice (a C3 type plant material) sample suggested that Zn may be used to study Zn systematics in plants. The result obtained for MURST-ISS-A2 (Antarctic Krill) was +0.21 0.11 permil amu-1 relative to the laboratory standard which is similar to the average Zn fractionation results of +0.281 0.083 permil amu-1 obtained for marine sediments. The fractionation of Zn in seven ultra pure Zn standard materials was also measured relative to the laboratory standard and found to range from -5.11 0.36 permil amu-1 for AE 10760 to +0.12 0.16 permil amu-1 for Zn IRMM 10440 confirming that that significant care must be exercised in the selection of Zn isotope laboratory standards (TANIMIZU et al., 2002). A pilot study to determine the concentration and the isotopic composition of Zn in river and tap water, and a number of processed materials was also performed. The implications and applications of these results, such as on the atomic weight of Zn will be presented.

Ghidan, O. Y.; Loss, R. D.

2008-12-01

268

Quantification of viral proteins of the avian H7 subtype of influenza virus: an isotope dilution mass spectrometry method applicable for producing more rapid vaccines in the case of an influenza pandemic.  

PubMed

Vaccination is the most effective means to prevent influenza and its serious complications. Influenza viral strains undergo rapid mutations of the surface proteins hemagglutinin (HA) and neuraminidase (NA) requiring vaccines to be frequently updated to include current circulating strains. It is nearly impossible to predict which strains will be circulating in the next influenza season. It is, therefore, imperative that the process of producing a vaccine be streamlined and as swift as possible. We have developed an isotope dilution mass spectrometry (IDMS) method to quantify HA and NA in H7N7, H7N2, and H7N9 influenza. The IDMS method involves enzymatic digestion of viral proteins and the specific detection of evolutionarily conserved target peptides. The four target peptides that were initially chosen for analysis of the HA protein of H7N2 and H7N7 subtypes were conserved and available for analysis of the H7N9 subtype that circulated in China in the spring of 2013. Thus, rapid response to the potential pandemic was realized. Quantification of a protein is performed by employing multiple peptides to ensure that the enzymatic digestion of the protein is efficient in the region of the target peptides, verify the accuracy of the measurement, and provide flexibility in the case of amino acid changes among newly emerging strains. The IDMS method is an accurate, sensitive, and selective method to quantify the amount of HA and NA antigens in primary liquid standards, crude allantoic fluid, purified virus samples, and final vaccine presentations. PMID:24689548

Santana, Wanda I; Williams, Tracie L; Winne, Emily K; Pirkle, James L; Barr, John R

2014-05-01

269

Development, validation and application of a stable isotope dilution liquid chromatography electrospray ionization/selected reaction monitoring/mass spectrometry (SID-LC/ESI/SRM/MS) method for quantification of keto-androgens in human serum?, ??  

PubMed Central

Prostate cancer is the most frequently diagnosed form of cancer in males in the United States. The disease is androgen driven and the use of orchiectomy or chemical castration, known as androgen deprivation therapy (ADT) has been employed for the treatment of advanced prostate cancer for over 70 years. Agents such as GnRH agonists and non-steroidal androgen receptor antagonists are routinely used in the clinic, but eventually relapse occurs due to the emergence of castration-resistant prostate cancer. With the appreciation that androgen signaling still persists in these patients and the development of new therapies such as abiraterone and enzalutamide that further suppresses androgen synthesis or signaling, there is a renewed need for sensitive and specific methods to quantify androgen precursor and metabolite levels to assess drug efficacy. We describe the development, validation and application of a stable isotope dilution liquid chromatography electrospray ionization selected reaction monitoring mass spectrometry (SID-LC/ESI/SRM/MS) method for quantification of serum keto-androgens and their sulfate and glucuronide conjugates using Girard-T oxime derivatives. The method is robust down to 0.24 pg on column, depending on the androgen metabolite quantified, and can also quantify dehydroepiandrosterone sulfate (DHEA-S) in only 1 ?L of serum. The clinical utility of this method was demonstrated by analyzing serum androgens from patients enrolled in a clinical trial assessing combinations of pharmacological agents to maximally suppress gonadal and adrenal androgens (Targeted Androgen Pathway Suppression, TAPS clinical trial). The method was validated by correlating the results obtained with a hydroxylamine derivatization procedure coupled with tandem mass spectrometry using selected reaction monitoring that was conducted in an independent laboratory. PMID:23851165

Tamae, Daniel; Byrns, Michael; Marck, Brett; Mostaghel, Elahe A.; Nelson, Peter S.; Lange, Paul; Lin, Daniel; Taplin, Mary-Ellen; Balk, Steven; Ellis, William; True, Larry; Vessella, Robert; Montgomery, Bruce; Blair, Ian A.; Penning, Trevor M.

2013-01-01

270

Development, validation and application of a stable isotope dilution liquid chromatography electrospray ionization/selected reaction monitoring/mass spectrometry (SID-LC/ESI/SRM/MS) method for quantification of keto-androgens in human serum.  

PubMed

Prostate cancer is the most frequently diagnosed form of cancer in males in the United States. The disease is androgen driven and the use of orchiectomy or chemical castration, known as androgen deprivation therapy (ADT) has been employed for the treatment of advanced prostate cancer for over 70 years. Agents such as GnRH agonists and non-steroidal androgen receptor antagonists are routinely used in the clinic, but eventually relapse occurs due to the emergence of castration-resistant prostate cancer. With the appreciation that androgen signaling still persists in these patients and the development of new therapies such as abiraterone and enzalutamide that further suppresses androgen synthesis or signaling, there is a renewed need for sensitive and specific methods to quantify androgen precursor and metabolite levels to assess drug efficacy. We describe the development, validation and application of a stable isotope dilution liquid chromatography electrospray ionization selected reaction monitoring mass spectrometry (SID-LC/ESI/SRM/MS) method for quantification of serum keto-androgens and their sulfate and glucuronide conjugates using Girard-T oxime derivatives. The method is robust down to 0.2-4pg on column, depending on the androgen metabolite quantified, and can also quantify dehydroepiandrosterone sulfate (DHEA-S) in only 1?L of serum. The clinical utility of this method was demonstrated by analyzing serum androgens from patients enrolled in a clinical trial assessing combinations of pharmacological agents to maximally suppress gonadal and adrenal androgens (Targeted Androgen Pathway Suppression, TAPS clinical trial). The method was validated by correlating the results obtained with a hydroxylamine derivatization procedure coupled with tandem mass spectrometry using selected reaction monitoring that was conducted in an independent laboratory. PMID:23851165

Tamae, Daniel; Byrns, Michael; Marck, Brett; Mostaghel, Elahe A; Nelson, Peter S; Lange, Paul; Lin, Daniel; Taplin, Mary-Ellen; Balk, Steven; Ellis, William; True, Larry; Vessella, Robert; Montgomery, Bruce; Blair, Ian A; Penning, Trevor M

2013-11-01

271

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

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 ?-ray irradiation. The material was re-mixed and packaged into 250 glass bottles (15g each) and these were stored in a freezer at ?30C. Certification was performed by use of three different types of species-specific isotope-dilution mass spectrometry (SSIDMS)SSIDGCICPMS, SSIDGCMS, and SSIDLCICPMS, 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 443?g kg?1 as Sn, DBT 51 2?g kg?1 as Sn, MBT 67 3?g kg?1 as Sn, TPhT 6.9 1.2?g kg?1 as Sn, and DPhT 3.4 1.2?g kg?1 as Sn. These levels are lower than in other sediment CRMs currently available for analysis of organotin compounds. PMID:16874473

Takatsu, Akiko; Watanabe, Takuro; Aoyagi, Yoshie; Yarita, Takashi; Okamoto, Kensaku; Chiba, Koichi

2006-01-01

272

Thermal evolution of Cretaceous Tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels  

Microsoft Academic Search

The evolution of subtropical (3035N) upper ocean temperatures through the Cretaceous is inferred from the oxygen isotope compositions of 64 fish teeth (enamel) coming from the western Tethyan platform. Mean ?18O values of 22 at the Berriasian-Valanginian boundary decrease, with oscillations to 18.5 around the Cenomanian-Turonian boundary, and progressively increase to 21.5 by the end of the Cretaceous. The similarity

Emmanuelle Pucat; Christophe Lcuyer; Simon M. F. Sheppard; Gilles Dromart; Stphane Reboulet; Patricia Grandjean

2003-01-01

273

Unusually large secondary deuterium isotope effect. Thermal trans-cis isomerization of trans-1-phenylcyclohexene  

SciTech Connect

The magnitudes of secondary deuterium isotope effects (SDIE) are generally in the range of 0.9 < kH/kD < 1.25, and are often satisfactorily rationalized by the zero-point energy (ZPE) change on going from reactant to transition state due to C-H rehybridization. We now report a far larger SDIE for the title reaction. Its rationalization on the basis of transition-state theory suggests that it more closely resembles a primary isotope effect. Laser flash photolysis of cis-1-phenylcyclohexene (direct, 266 nm, or sensitized by thioxanthone, 355 nm) affords its trans isomer which in heptane exclusively reverts to 1, k = 2.1 x 10/sup 5/ s at 300 K. Isotopically substituted 2-2-d1 or 2-2,6-6-d3 (generated similarly from the corresponding cis isomers5) both have rates of reversion longer than 2 itself by a factor of 2.0 at room temperature. No previously reported SDIE approaches this magnitude.

Caldwell, R.A.; Misawa, H.; Healy, E.F.; Dewar, M.J.

1987-01-01

274

Fission yields in the symmetric region: Yields of the stable isotopes of tin and cadmium in the thermal neutron fission of ²³⁵U and ²³⁹Pu  

Microsoft Academic Search

The relative isotopic abundances of five isotopes of cadmium (111, 112, 113, 114, and 116) and eight isotopes of tin (117, 118, 119, 120, 121, 122, 124, and 126) have been measured in the thermal neutron fission of ²³⁵U and ²³⁹Pu. Samples of ²³⁵U and ²³⁹Pu were irradiated in a reactor; the elements were chemically separated and the isotopic abundances

1977-01-01

275

Isotope ratio analysis of actinides, fission products, and geolocators by high-efficiency multi-collector thermal ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

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.

Brger, S.; Riciputi, L. R.; Bostick, D. A.; Turgeon, S.; McBay, E. H.; Lavelle, M.

2009-09-01

276

Thermal desorption studies of isotopically-labeled oxygen-induced superconductivity in La2CuO(4+delta)  

NASA Astrophysics Data System (ADS)

Isotopically-labeled oxygen enrichment and thermal desorption mass spectroscopy (TDMS) have been combined to study interstitial oxygen desorption from superconducting La2CuO(4+delta) (delta less than or equal to 0.032). Single crystal samples of magnetic insulating La2CuO(4.00) were annealed at 860 K under 1-3 kbar oxygen pressure for 12-100 hours to yield hole-doped, superconducting La2CuO(4+delta) samples with Tc between 35 and 40 K. Whereas no TDMS signals were observed for the insulator, rapid bursts (full width at half maximum less than 0.5 sec) of molecular oxygen were observed above 350 K while heating the superconductor at less than 1 K per sec in high vacuum. A kinetic model is proposed in which the interstitial oxygen diffuses to internal grain boundaries and defects during heating, thereby inducing stress in the lattice as it attempts to revert to the LaCuO(4.00) crystal structure. This stress is relieved by lattice fracture at grain boundaries during the TDMS experiment, releasing the trapped oxygen from the sample as micro-cracks are formed. In addition, the facile oxygen exchange between interstitial and lattice oxygen sites has been discovered by TDMS and weight gain measurements from isotopically-enriched crystals, supporting the structural model of Chaillout, et al. in which the interstitial oxygen atom dimerizes with a lattice oxygen ion.

Shinn, N. D.; Bartram, M. E.; Schirber, J. E.; Overmyer, D. L.; Rogers, J. W., Jr.; Fisk, Z.; Cheong, S. W.

277

Helium isotope systematics of volcanic gases and thermal waters of Guadeloupe Island, Lesser Antilles  

NASA Astrophysics Data System (ADS)

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 Soufrire 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 Soufrire 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 Soufrire fumaroles and the Bouillante geothermal system are the two end-members of a spatial trend of decreasing 3He/4He ratio with distance from La Soufrire summit dome, implying an increasing addition of radiogenic 4He from the host rocks away from the present-day active volcanic edifice.

Jean-Baptiste, P.; Allard, P.; Fourr, E.; Parello, F.; Aiuppa, A.

2014-08-01

278

?D and ?13C analyses of atmospheric volatile organic compounds by thermal desorption gas chromatography isotope ratio mass spectrometry.  

PubMed

This paper describes the establishment of a robust method to determine compound specific ?D and ?(13)C values of volatile organic compounds (VOCs) in a standard mixture ranging between C(6) and C(10) and was applied to various complex emission samples, e.g. from biomass combustion and car exhaust. A thermal desorption (TD) unit was linked to a gas chromatography isotope ratio mass spectrometer (GC-irMS) to enable compound specific isotope analysis (CSIA) of gaseous samples. TenaxTA was used as an adsorbent material in stainless steel TD tubes. We determined instrument settings to achieve a minimal water background level for reliable ?D analysis and investigated the impact of storage time on ?D and ?(13)C values of collected VOCs (176 days and 40 days of storage, respectively). Most of the standard compounds investigated showed standard deviations (SD)<6 (?D) when stored for 148 days at 4 C. However, benzene revealed occasionally D depleted values (21 SD) for unknown reasons. ?(13)C analysis demonstrated that storage of 40 days had no effect on VOCs investigated. We also showed that breakthrough (benzene and toluene, 37% and 7%, respectively) had only a negligible effect (0.7 and 0.4, respectively) on ?(13)C values of VOCs on the sample tube. We established that the sample portion collected at the split flow effluent of the TD unit can be used as a replicate sample for isotope analysis saving valuable sampling time and resources. We also applied TD-GC-irMS to different emission samples (biomass combustion, petrol and diesel car engines exhaust) and for the first time ?D values of atmospheric VOCs in the above range are reported. Significant differences in ?D of up to 130 were observed between VOCs in emissions from petrol car engine exhaust and biomass combustion (Karri tree). However, diesel car emissions showed a high content of highly complex unresolved mixtures thus a baseline separation of VOCs was not achieved for stable hydrogen isotope analysis. The ability to analyse ?D by TD-GC-irMS complements the characterisation of atmospheric VOCs and is maybe used for establishing further source(s). PMID:21807368

von Eckstaedt, Christiane Vitzthum; Grice, Kliti; Ioppolo-Armanios, Marisa; Chidlow, Geoff; Jones, Mark

2011-09-16

279

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)

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 clumped isotope compositions either (1) reordered extensively, but not completely, during heating or (2) equilibrated with ambient burial temperature during heating and now reflect ';closure temperatures' achieved during cooling. Our data also suggest that different carbonate components that experience the same T-t history can yield different clumped isotope temperatures.

Shenton, B.; Grossman, E. L.; Passey, B. H.; Henkes, G. A.; Becker, S. P.; Pottorf, R. J.

2013-12-01

280

Development and evaluation of a reference measurement procedure for the determination of total 3,3',5-triiodothyronine in human serum using isotope-dilution liquid chromatography-tandem mass spectrometry.  

PubMed

3,3',5-Triiodothyronine (T3) is an important diagnostic marker for thyroid function. A reference measurement procedure (RMP) for total T3 in serum involving isotope dilution coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been developed and critically evaluated. The method uses solid-phase extraction with mixed-mode retention mechanisms of reversed phase and ion exchange prior to reversed-phase LC/MS/MS. In addition to a labeled T3 internal standard (T3-13C9), labeled thyroxine (T4-d5) is also added to serum samples in order to monitor the degradation of T4 to T3. The accuracy of the measurement was evaluated by a recovery study for added T3 and was supported by a comparison study with the other RMP. The recovery of the added T3 ranged from 98.9% to 99.4%. The results of this method and the other RMP agreed to within 1%. Samples of frozen serum pools were prepared and measured in three separate sets. Excellent reproducibility was obtained with within-set coefficients of variation (CVs) ranging from 0.8% to 1.6% and between-set CVs ranging from 1.9% to 2.6%. Excellent linearity was also obtained with correlation coefficients of all linear regression lines (measured intensity ratios vs mass ratios) ranging from 0.9995 to 0.9996. The detection limit at a signal-to-noise ratio of approximately 3 was 1 pg of T3. The T4 degradation during sample preparation was minimized to a small percentage (no more than 3% of the T3 values) by use of antioxidants (ascorbic acid, dithiothreitol, citric acid) and can be accounted for in the T3 measurement process. This well-characterized LC/MS/MS method for total serum T3, which demonstrates good accuracy and precision, low susceptibility to interferences, accountability of the conversion of T4 to T3, and comparability with the other RMP, qualifies as a reference measurement procedure and can be used to provide an accuracy base to which routine methods for T3 can be compared. PMID:15373447

Tai, Susan S-C; Bunk, David M; White, Edward; Welch, Michael J

2004-09-01

281

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

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)-HETEA showed much less. It should be noted that since the interstrand cross-linked adduct is believed to stall DNA replication and finally induce a double-strand break, the higher abundance of Bis-G is a great indication of a more serious DNA lesion by SM alkylation. PMID:24467472

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

282

The mathematics of dilution.  

PubMed

The major objection to homeopathic medicine is that the doses of medicine prescribed in some cases are too dilute for any active ingredient to be present. The medicines would hence be rendered inactive, necessitating novel explanations for the action. A further examination of dilution in the light of the Langmuir equation shows that homeopathic medicines may not be as dilute as a simplistic application of Avogadro's Principle suggests, due to surface effects. PMID:24685420

Chatterjee, Barun Kumar

2014-04-01

283

A robust methodology for high precision isotopic analysis of boron by thermal ionization mass spectrometry using Na2BO2+ ion  

NASA Astrophysics Data System (ADS)

A detailed study to develop a robust methodology for determining 11B/10B isotope ratio using sodium metaborate (Na2BO2+) in positive thermal ionisation mass spectrometry (P-TIMS) was performed. Different parameters of sample preparation and sample loading procedure, using single tantalum filament assembly, were optimized and their effects on ion intensity and precision in isotope ratio were evaluated. A comparative evaluation of precision achievable using Na2CO3 and NaCl to adjust the B/Na mole ratio in the sample was also carried out. This was done to confirm the robustness of the approach for analysing different kinds of sample matrices e.g., solids and solutions which require chemical purification and pre-concentration prior to TIMS analysis. NIST isotopic reference material SRM-951 with 11B/10B isotope ratio of 4.044 +/- 0.003 was used for various experiments. Loading of boron in the form of boromannitol complex along with sodium carbonate (for solid samples) and with NaCl (for solutions) on the graphite coated single tantalum filament assembly was found to give high precision (better than 1[per mille sign]) in the isotope ratios using 500 ng to 1 [mu]g of boron. The results were not influenced by variations in the B/Na mole ratio, which is an important aspect of using this methodology for analyzing unknown samples. Robustness of the developed methodology is demonstrated by analyzing solid samples as well as solutions for boron isotopic composition.

Rao, Radhika M.; Parab, Ankush R.; Sasibhushan, K.; Aggarwal, Suresh K.

2009-08-01

284

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)

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.

Nakamura, N.; Nyquist, L. E.; Reese, Y.; Shih, C.-Y.; Fujitani, T.; Okano, O.

2011-01-01

285

Ammonium in thermal waters of Yellowstone National Park: Processes affecting speciation and isotope fractionation  

Microsoft Academic Search

Dissolved inorganic nitrogen, largely in reduced form (NH(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

Joann M. Holloway; D. Kirk Nordstrom; J. K. Bhlke; R. Blaine McCleskey; James W. Ball

2011-01-01

286

Ammonium in thermal waters of Yellowstone National Park: Processes affecting speciation and isotope fractionation  

Microsoft Academic Search

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

JoAnn M. Holloway; D. Kirk Nordstrom; J. K. Bhlke; R. Blaine McCleskey; James W. Ball

2011-01-01

287

Determination of ultratrace boron concentrations in uranium oxide by isotope dilution-thermal ionization mass spectrometry using a simplified separation procedure  

Microsoft Academic Search

Boron was determined at sub-ppm levels in uranium oxide by ID-TIMS. Following nitric acid dissolution, a solvent extraction\\u000a method was adapted for extraction of boron by 5% 2-ethylhexane-1,3-diol in chloroform followed by evaporation of the extractant\\u000a in presence of sodium carbonate and mannitol. This procedure allowed TIMS analysis of boron by monitoring the Na2BO2+ ions formed from the sodium borate

Radhika M. Rao; Ankush R. Parab; K. Sasi Bhushan; Suresh K. Aggarwal

2010-01-01

288

Magnitude and profile of organic carbon isotope records from the Paleocene-Eocene Thermal Maximum: Evidence from northern Spain  

NASA Astrophysics Data System (ADS)

The Paleocene-Eocene Thermal Maximum (PETM), a hyperthermal event that occurred ca. 56 Ma, has been attributed to the release of substantial amounts of carbon, affecting the atmosphere, biosphere and the oceans. Current issues with respect to our understanding of the PETM include the amount of carbon released, the duration of carbon release, and the mechanism(s) of release, all of which are related to the magnitude and profile of the associated Carbon Isotope Excursion (CIE). High-resolution organic carbon profiles (?13C) of six PETM sections in northern Spain are presented that span a transect from continental to marine environments. These data represent the highest-resolution isotope records for these sections and allow a comparison of the magnitude of the excursion, the shape of the vertical ?13C profile during the PETM episode, and the relative timing of the onset of the excursion across a linked sediment routing system. Previous studies using carbonate ?13C data have suggested that the continental Claret Conglomerate, found in this region, formed synchronously with a marine clay-rich siliciclastic unit, with these key lithological changes interpreted to be driven by increased seasonal rainfall-runoff in the warmer PETM climate. Our data suggest that deposition of these units did not immediately follow the CIE onset, indicating that there may be a temporal lag between the onset of the PETM warming and the response of the depositional systems in northern Spain. No systematic variation in the magnitude of the CIE between different depositional environments was found; the marine CIE magnitudes are at the higher end of those previously described (3.71.4), and the continental ranges are lower (3.11.3).

Manners, Hayley R.; Grimes, Stephen T.; Sutton, Paul A.; Domingo, Laura; Leng, Melanie J.; Twitchett, Richard J.; Hart, Malcolm B.; Dunkley Jones, Tom; Pancost, Richard D.; Duller, Robert; Lopez-Martinez, Nieves

2013-08-01

289

MECHANICAL ALLOYING AND THERMAL TREATMENT FOR PRODUCTION OF ZIRCONIUM IRON HYDROGEN ISOTOPE GETTERS  

SciTech Connect

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.

Fox, K.

2008-02-20

290

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  

Microsoft Academic Search

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

C. L. Schofield; D. Josephson; C. Keleher; S. P. Gloss

1993-01-01

291

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

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.

Schofield, C.L.; Josephson, D.; Keleher, C.; Gloss, S.P.

1993-04-01

292

Thorium and uranium isotopes in a manganese nodule from the Peru basin determined by alpha spectrometry and thermal ionization mass spectrometry (TIMS): Are manganese supply and growth related to climate?  

Microsoft Academic Search

Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4mm to gain a high-resolution 230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We got

A. Bollhfer; A. Eisenhauer; N. Frank; D. Pech; A. Mangini

1996-01-01

293

Thorium and uranium isotopes in a manganese nodule from the Peru basin determined by alpha spectrometry and thermal ionization mass spectrometry (TIMS): Are manganese supply and growth related to climate?  

Microsoft Academic Search

Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal\\u000a ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain\\u000a a high-resolution230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We\\u000a got

A. Bollhfer; A. Eisenhauer; N. Frank; D. Pech; A. Mangini

1996-01-01

294

Rhenium-osmium isotope systematics of ordinary chondrites and iron meteorites  

NASA Technical Reports Server (NTRS)

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.

Walker, R. J.; Morgan, J. W.; Horan, M. F.; Grossman, J. N.

1993-01-01

295

Thermal decomposition of barium sulfate-vanadium pentaoxide-silica glass mixtures for preparation of sulfur dioxide in sulfur isotope ratio measurements  

Microsoft Academic Search

A previously reported procedure for the thermal decomposition of BaSO-VO-SiO for the preparation of SO in sulfur isotope ratio measurements has been studied in detail, certain portions of the procedure have been modified, and certain aspects of the reaction mechanism have been defined. It was determined that the ¹⁸O\\/¹⁶O ratio of SO must be kept constant in order to apply

F. Yanaglsawa; Hitoshi. Sakai

1983-01-01

296

Geochemical monitoring of the 20022003 eruption at Stromboli volcano (Italy): precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters  

Microsoft Academic Search

Significant changes in the helium and carbon isotopic composition of shallow thermal waters vs. gas and a crater fumarolic gas have been recorded at Stromboli prior and during the 20022003 eruption. The3He\\/4He ratios corrected for air contamination (Rc\\/Ra), and ?13C of fumarolic gases gradually increased from May to November 2002 before the eruption onset. These variations imply early degassing of

G. Capasso; M. L. Carapezza; C. Federico; S. Inguaggiato; A. Rizzo

2005-01-01

297

Soret and Dilution Effects on Premixed Flames  

Microsoft Academic Search

The structure of a wrinkled premixed flame is analysed theoretically. By assuming the reactive mixture diluted in an inert gas and a weak cross-diffusion coupling between the heat and mass fluxes, the effect of the change by the reaction of the physical gas properties (thermal conductivity, specific heat, number of molecules) and Soret and Dufour diffusions have been investigated in

PEDRO GARCA-YBARRA; COLETTE NICOLI; PAUL CLAVIN

1984-01-01

298

Certification of a 15N-enriched nitrate species-specific spike isotopic reference material IRMM-627  

NASA Astrophysics Data System (ADS)

A new 15N-enriched nitrate species-specific spike isotopic reference material IRMM-627 has been prepared in the form of KNO3 in NaOH solution (pH = 10). It is a 64.6% enriched 15N-nitrate material, certified for its nitrogen isotope ratio (in nitrate species) n(14NO3-)/n(15NO3-) = 0.548 0.012 and its nitrate concentration c(NO3-)/mmol kg-1 = 3.124 0.080 (expanded uncertainty, coverage factor k = 2). The isotopic composition was determined using negative thermal ionisation mass spectrometry and the concentration via reverse isotope dilution mass spectrometry (IDMS). The mass fractionation of the mass spectrometric procedure was determined using synthetic isotope mixtures. Isotopic homogeneity, stability and impurity content of IRMM-627 were investigated. Orthodox uncertainty evaluation was done by examining the different uncertainty contributions. The species specific spike isotopic reference material can be used to perform isotope dilution analysis of nitrate with c(NO3-)/mmol kg-1 > 0.016. It is available in quartz ampoules containing approximately 4.5 g of solution.

Wolff, J.-C.; Dyckmans, B.; Taylor, P. D. P.; de Bivre, P.

1996-11-01

299

Coupled variations in helium isotopes and fluid chemistry: Shoshone Geyser Basin, Yellowstone National Park  

USGS Publications Warehouse

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.

Hearn, E.H.; Kennedy, B.M.; Truesdell, A.H.

1990-01-01

300

Combustion selective temperature dilution  

SciTech Connect

In a gas turbine engine having a hot gas flowing in an annular path partially defined by inner and outer liners of a combustor and inner and outer vane shrouds, the combustor including at its upstream end injectors for admitting an original mixture of air and fuel to the upstream end of the combustor for burning of the mixture in the combustor, the improvement is described comprising: circumferentially spaced-apart stationary turbine vanes disposed in the hot gas flow path downstream of the combustor; circumferentially spaced-apart dilution apertures disposed in the combustor downstream of the injectors, upstream of the turbine vanes and in axial alignment with leading edges of the turbine vanes, for admitting dilution air into the combustor for mixing with the original mixture to promote partial mixing thereof; and circumferentially spaced dilution apertures for admitting dilution air into the combustor to promote partial mixing with the original mixture. The first and second apertures are axially located in a secondary combustion zone of the combustor and upstream of the turbine vanes to induce partial mixing of the dilution air with the hot gases for generating a preselected circumferential temperature gradient in the hot gas for providing a flow of hot gas at a relatively higher temperature through the gaps and a flow of hot gas at relatively lower temperature upon the turbine vanes.

Vdoviak, J.W.; Weinstein, B.

1988-03-29

301

Microfluidic Serial Dilution Circuit  

PubMed Central

In vitro evolution of RNA molecules requires a method for executing many consecutive serial dilutions. To solve this problem, a microfluidic circuit has been fabricated in a three-layer glass-PDMS-glass device. The 400-nL serial dilution circuit contains five integrated membrane valves: three two-way valves arranged in a loop to drive cyclic mixing of the diluent and carryover, and two bus valves to control fluidic access to the circuit through input and output channels. By varying the valve placement in the circuit, carryover fractions from 0.04 to 0.2 were obtained. Each dilution process, which is comprised of a diluent flush cycle followed by a mixing cycle, is carried out with no pipeting, and a sample volume of 400 nL is sufficient for conducting an arbitrary number of serial dilutions. Mixing is precisely controlled by changing the cyclic pumping rate, with a minimum mixing time of 22 s. This microfluidic circuit is generally applicable for integrating automated serial dilution and sample preparation in almost any microfluidic architecture. PMID:17073422

Paegel, Brian M.; Grover, William H.; Skelley, Alison M.; Mathies, Richard A.; Joyce, Gerald F.

2008-01-01

302

Helium dilution refrigeration system  

DOEpatents

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.

Roach, P.R.; Gray, K.E.

1988-09-13

303

Helium dilution refrigeration system  

DOEpatents

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.

Roach, Patrick R. (Darien, IL); Gray, Kenneth E. (Naperville, IL)

1988-01-01

304

The abundance and isotopic composition of Cd in iron meteorites  

NASA Astrophysics Data System (ADS)

Cadmium is a highly volatile element and its abundance in meteorites may help better understand volatility-controlled processes in the solar nebula and on meteorite parent bodies. The large thermal neutron capture cross section of 113Cd suggests that Cd isotopes might be well suited to quantify neutron fluences in extraterrestrial materials. The aims of this study were (1) to evaluate the range and magnitude of Cd concentrations in magmatic iron meteorites, and (2) to assess the potential of Cd isotopes as a neutron dosimeter for iron meteorites. Our new Cd concentration data determined by isotope dilution demonstrate that Cd concentrations in iron meteorites are significantly lower than in some previous studies. In contrast to large systematic variations in the concentration of moderately volatile elements like Ga and Ge, there is neither systematic variation in Cd concentration amongst troilites, nor amongst metal phases of different iron meteorite groups. Instead, Cd is strongly depleted in all iron meteorite groups, implying that the parent bodies accreted well above the condensation temperature of Cd (i.e., ?650 K) and thus incorporated only minimal amounts of highly volatile elements. No Cd isotope anomalies were found, whereas Pt and W isotope anomalies for the same iron meteorite samples indicate a significant fluence of epithermal and higher energetic neutrons. This observation demonstrates that owing to the high Fe concentrations in iron meteorites, neutron capture mainly occurs at epithermal and higher energies. The combined Cd-Pt-W isotope results from this study thus demonstrate that the relative magnitude of neutron capture-induced isotope anomalies is strongly affected by the chemical composition of the irradiated material. The resulting low fluence of thermal neutrons in iron meteorites and their very low Cd concentrations make Cd isotopes unsuitable as a neutron dosimeter for iron meteorites.

Kruijer, Thomas S.; Sprung, Peter; Kleine, Thorsten; Leya, Ingo; Wieler, Rainer

2013-12-01

305

The effect of steam-heating processes on the chemical and isotopic composition of the shallow thermal aquifer in Vulcano Island (Aeolian Arc, Sicily).  

NASA Astrophysics Data System (ADS)

We report on a comprehensive study of major-ion chemistry, dissolved gases, and stable isotopes measured in water wells at Vulcano Island since 1988. Particularly, we focus on chemical and hydrological modifications of groundwaters observed in the last two decades, interpreted according to a quantitative model describing steam condensation and boiling phenomena in shallow water bodies (Federico et al., 2010). According to this model, we infer that (i) strong isotope enrichment observed in some shallow thermal waters can result from an increasing mass rate of condensing deep vapor, even in water being meteoric in origin; (ii) the high pCO2 measured in the coldest and peripheral waters are explained by the progressive CO2 enrichment in the vapor phase during multistep boiling; and (iii) the high Cl- and SO4-- contents in the hottest waters can be attributed to the direct condensation (single-step) of volcanic vapor. The model also takes into account both the mass fluxes and the compositions of the involved endmembers (steam and shallow groundwater), which provides important inferences on the modifications observed during the periods of increasing mass and heat input from depth occurred at Vulcano Island. The volcanic crisis that occurred in 1988-1993 profoundly affected the composition of some thermal wells that were more-directly affected by ascending vapour. In particular, higher Cl-, SO4--, and HCO3- contents, temperature, and pCO2 values were measured. These variations are all explained by a different composition of the vapor entering the aquifer paralleled by a higher mass rate relative to the shallow meteoric endmember. Minor effects on the shallow thermal aquifer are observed during the following periods of increasing heat and mass flux from depth, mostly recorded in the crater area. This implies that the shallow thermal aquifer is affected by magmatic fluids ascending along central conduits only when there is a significant increase in the heat and mass fluxes from depth, which are able to vaporize the deep hydrothermal aquifer and modify the chemical and isotopic compositions of a larger portion of the volcanic edifice. Otherwise, the shallow thermal aquifer is chiefly affected by the vapor separating from the 400C- hydrothermal system and, therefore, by its P-T conditions. On these grounds, once apportioned the effect of rainwater, we tentatively evaluate the effect of variations of physico-chemical conditions of the hydrothermal aquifer on both the water level and the composition of sampled thermal waters.

Capasso, G.; Federico, C.; Madonia, P.; Paonita, A.

2012-04-01

306

Evaluation of the n(235U)/n(238U) isotope ratio measurements in a set of uranium samples by thermal ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

The measurement of n(235U)/n(238U) isotope amount ratio in a set of representative uranium samples with enrichment levels ranging from 0.5 to 20.0 wt.% of 235U was carried out by thermal ionization mass spectrometry using the traditional and the total evaporation methods. The uncertainties of the measurement results were evaluated according to the recommendations of the ISO guide to the expression of uncertainty in measurement. They were then compared to the requirements of the IAEA international target values for measurement uncertainties in safeguarding nuclear materials.

de Oliveira, O. Pereira; Bolle, W. De; Richter, S.; Alonso, A.; Khn, H.; Sarkis, J. E. S.; Wellum, R.

2005-11-01

307

The influence of optimum power level change on boration and dilution operations  

Microsoft Academic Search

Xenon and samarium concentrations changes occur in a nuclear reactor as a consequence of power level variations. To compensate for the reactivity introduced by these isotopes, the boron concentration in the reactor coolant also needs to be changed. Boron concentration changes result from boration or dilution operations. Both boration and dilution operations have economic effects due to the cost of

A. S. Martinez; E. de Andrade Oliveira

1993-01-01

308

Isotopically controlled semiconductors  

SciTech Connect

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.

Haller, Eugene E.

2001-12-21

309

A novel isotope analysis of oxygen in uranium oxides: comparison of secondary ion mass spectrometry, glow discharge mass spectrometry and thermal ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

The natural variation of the oxygen isotopic composition is used among geologists to determine paleotemperatures and the origin of minerals. In recent studies, oxygen isotopic composition has been recognized as a possible tool for identification of the origin of seized uranium oxides in nuclear forensic science. In the last 10 years, great effort has been made to develop new direct and accurate n( 18O)/ n( 16O) measurements methods. Traditionally, n( 18O)/ n( 16O) analyses are performed by gas mass spectrometry. In this work, a novel oxygen isotope analysis by thermal ionization mass spectrometry (TIMS), using metal oxide ion species (UO +), is compared to the direct methods: glow discharge mass spectrometry (GDMS) and secondary ion mass spectrometry (SIMS). Because of the possible application of the n( 18O)/ n( 16O) ratio in nuclear forensics science, the samples were solid, pure UO 2 or U 3O 8 particles. The precision achieved using TIMS analysis was 0.04%, which is similar or even better than the one obtained using the SIMS technique (0.05%), and clearly better if compared to that of GDMS (0.5%). The samples used by TIMS are micrograms in size. The suitability of TIMS as a n( 18O)/ n( 16O) measurement method is verified by SIMS measurements. In addition, TIMS results have been confirmed by characterizing the n( 18O)/ n( 16O) ratio of UO 2 sample also by the traditional method of static vacuum mass spectrometry at the University of Chicago.

Pajo, L.; Tamborini, G.; Rasmussen, G.; Mayer, K.; Koch, L.

2001-05-01

310

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)

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 (?13C) of TC. The stable carbon isotopic composition of TC (?13CTC) 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 ?13CTC 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.

Jung, J.; Kawamura, K.

2011-11-01

311

Diluted magnetic oxides  

NASA Astrophysics Data System (ADS)

In this review, we review the progress of research on ZnO- and In2O3-based diluted magnetic oxides (DMOs). Firstly, we present the preparation and characterization of DMOs. The former includes the preparation methods and conditions, and the latter includes the characterization techniques for measuring microstructures. Secondly, we introduce the magnetic and transport properties of DMOs, as well as the relationship between them. Thirdly, the origin and mechanism of the ferromagnetism are discussed. Fourthly, we introduce other related work, including computational work and pertinent heterogeneous structures, such as multilayers and magnetic tunnel junctions. Finally, we provide an overview and outlook for DMOs.

Li, XiaoLi; Qi, ShiFei; Jiang, FengXian; Quan, ZhiYong; Xu, XiaoHong

2013-01-01

312

Diluted magnetic semiconductors  

Microsoft Academic Search

Diluted magnetic semiconductors (DMSs), i.e. semiconducting crystals whose lattice is made up in part of substitutional magnetic ions (e.g. Cd1-xMnxTe, Hg1-xFex Se, Zn1-xCoxS), are reviewed. The focus is on materials of the type A1-xII MnxB VI, which are the most thoroughly understood. However, the similarities and differences between these materials and the A1-x IIFexBVI and A1-IICoxBVI systems are discussed wherever

Nitin Samarth; J. K. Furdyna

1990-01-01

313

He dilution refrigerator  

NASA Astrophysics Data System (ADS)

We describe the preparation of ultracold atomic clouds in a dilution refrigerator. The closed-cycle 3He/4He cryostat was custom made to provide optical access for laser cooling, optical manipulation and detection of atoms. We show that the cryostat meets the requirements for cold atom experiments, specifically in terms of operating a magneto-optical trap, magnetic traps and magnetic transport under ultrahigh vacuum conditions. The presented system is a step toward the creation of a quantum hybrid system combining ultracold atoms and solid-state quantum devices.

Jessen, F.; Knufinke, M.; Bell, S. C.; Vergien, P.; Hattermann, H.; Weiss, P.; Rudolph, M.; Reinschmidt, M.; Meyer, K.; Gaber, T.; Cano, D.; Gnther, A.; Bernon, S.; Koelle, D.; Kleiner, R.; Fortgh, J.

2014-09-01

314

Evaluation of two gas-dilution methods for instrument calibration  

NASA Technical Reports Server (NTRS)

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.

Evans, A., Jr.

1977-01-01

315

Geothermal reservoir temperatures estimated from the oxygen isotope compositions of dissolved sulfate and water from hot springs and shallow drillholes  

USGS Publications Warehouse

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.

McKenzie, W. F.; Truesdell, A. H.

1977-01-01

316

Structure of the carbon isotope excursion in a high-resolution lacustrine Paleocene-Eocene Thermal Maximum record from central China  

NASA Astrophysics Data System (ADS)

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 ?13CTOC and ?13CBC values is possibly attributable to increased humidity and elevated pCO2 concentration. The ? - 4 CIE recorded in the ?13Ccalcite, 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 ?13C 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 ?13C 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 ?13C 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.

Chen, Zuoling; Wang, Xu; Hu, Jianfang; Yang, Shiling; Zhu, Min; Dong, Xinxin; Tang, Zihua; Peng, Ping'an; Ding, Zhongli

2014-12-01

317

Dilution jet mixing program  

NASA Technical Reports Server (NTRS)

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.

Srinivasan, R.; Coleman, E.; Johnson, K.

1984-01-01

318

Cool bottom processes on the thermally-pulsing AGB and the isotopic composition of circumstellar dust grains  

E-print Network

(Abridged) We examine the effects of cool bottom processing (CBP) on several isotopic ratios in the convective envelope during the TP-AGB phase of evolution in a 1.5 M_sun initial-mass star of solar initial composition. We use a parametric model which treats extra mixing by introducing mass flow between the convective envelope and the underlying radiative zone. The parameters of this model are the mass circulation rate (Mdot) and the maximum temperature (T_P) experienced by the circulating material. The effects of nuclear reactions in the flowing matter were calculated using a set of structures of the radiative zone selected from a complete stellar evolution calculation. The compositions of the flowing material were obtained and the resulting changes in the envelope determined. Abundant ^26Al was produced by CBP for log T_P > 7.65. While ^26Al/^27Al depends on T_P, the isotopic ratios in CNO elements depend dominantly on the circulation rate. The correspondence is shown between models of CBP as parameterized by a diffusion formalism within the stellar evolution model and those using the mass-flow formalism employed here. The isotopic ratios are compared with the data on circumstellar dust grains. It is found that the ratios ^{18}O/^{16}O, ^{17}O/^{16}O, and ^26Al/^27Al observed for oxide grains formed at C/O 1) require many stellar sources with ^14N/^15N at least a factor of 4 below solar. The rare grains with ^12C/^13C < 10 cannot be produced by any red-giant or AGB source.

Kenneth M. Nollett; M. Busso; G. J. Wasserburg

2002-11-13

319

Uranium-lead Isotope Evidence in the Shelyabinsk LL5 Chondrite Meteorite for Ancient and Recent Thermal Events  

NASA Technical Reports Server (NTRS)

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].

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

320

Springtime carbon episodes at Gosan background site revealed by total carbon, stable carbon isotopic composition, and thermal characteristics of carbonaceous particles  

NASA Astrophysics Data System (ADS)

In order to investigate the carbon episodes at Gosan background super-site (33.17 N, 126.10 E) in East Asia during spring of 2007 and 2008, total suspended particles (TSP) were collected and analyzed for particulate organic carbon, elemental carbon, total carbon (TC), total nitrogen (TN), and stable carbon isotopic composition (?13C) of TC. The carbon episodes at the Gosan site were categorized as long-range transported anthropogenic pollutant (LTP) from Asian continent, Asian dust (AD) accompanying with LTP, and local pollen episodes. The stable carbon isotopic composition of TC (?13CTC) was found to be lowest during the pollen episodes (range: -26.2 to -23.5 , avg.: -25.2 0.9 ), followed by the LTP episodes (range: -23.5 to -23.0 , avg.: -23.3 0.3 ) and the AD episodes (range: -23.3 to -20.4 %, avg.: -21.8 2.0 ). The ?13CTC of the airborne pollens (-28.0 ) collected at the Gosan site showed value similar to that of tangerine fruit (-28.1 ) produced from Jeju Island. Based on the carbon isotope mass balance equation and the TN and TC regression approach, we found that ∼40-45 % of TC in the TSP samples during the pollen episodes was attributed to airborne pollens from Japanese cedar trees planted around tangerine farms in Jeju Island. The ?13C of citric acid in the airborne pollens (-26.3 ) collected at the Gosan site was similar to that in tangerine fruit (-27.4 ). The negative correlation between the citric acid-carbon/TC ratios and ?13CTC were obtained during the pollen episodes. These results suggest that citric acid emitted from tangerine fruit may be adsorbed on the airborne pollens and then transported to the Gosan site. Based on the thermal evolution pattern of organic aerosols during the carbon episodes, we found that organic aerosols originated from East China are more volatile on heating and are more likely to form pyrolized organic carbon than the pollen-enriched organic aerosols and organic aerosols originated from Northeast China. 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 during the long-range atmospheric transport and the source regions of organics.

Jung, J.; Kawamura, K.

2011-05-01

321

Transient phenomena initiating phase transition in dilution refrigerator  

NASA Astrophysics Data System (ADS)

We have analysed the transient processes in a Dilution Refrigerator (DR) leading to phase separation of 3He-4He mixture into concentrated and dilute solutions using an extended SIDFO (Simulation of Integrated Dilution refrigerator For Optimisation) Pradhan et al. (2013) analysis tool. The evolution of the phase separation interface along the concentrated channel and its arrival in the mixing chamber for a given physical situation has been thoroughly examined. The significance of the 3He/4He composition in the mixer, the flow rate and the still power on the phase separation is presented here. The consequences of several relevant thermodynamic parameters and the composition of isotopic mixture for successful function of the DR is also discussed in this paper.

Pradhan, Jedidiah; Das, Nisith K.; Chakrabarti, Alok

2014-09-01

322

Hydrogen isotope inventory in the graphite divertor tiles of ASDEX Upgrade as measured by thermal desorption spectroscopy  

Microsoft Academic Search

The hydrogen and deuterium inventories of the ASDEX Upgrade divertor tiles were measured after the experimental period from December 1994 to July 1995 by thermal desorption spectroscopy (TDS) of samples cut out of the divertor tiles. The samples were heated by electron bombardment up to 2100 K; the released gases were measured by means of a calibrated quadrupole mass spectrometer.

P. Franzen; R. Behrisch; C. Garcia-Rosales; D. Schleussner; D. Rosler; J. Becker; W. Knapp; C. Edelmann

1997-01-01

323

Stress in dilute suspensions  

NASA Technical Reports Server (NTRS)

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.

Passman, Stephen L.

1989-01-01

324

THE ANISOTROPIC TRANSPORT EFFECTS ON DILUTE PLASMAS  

SciTech Connect

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.

Devlen, Ebru, E-mail: ebru.devlen@ege.edu.tr [Department of Astronomy and Space Sciences, Faculty of Science, University of Ege, Bornova 35100, Izmir (Turkey)

2011-04-20

325

Extinction of diffusion flames burning diluted methane and diluted propane in diluted air  

Microsoft Academic Search

A theoretical and experimental investigation of the extinction limits of counterflow diffusion flames burning methane and propane is outlined. A diffusion flame is stabilized between counterflowing streams of a fuel diluted with nitrogen and air diluted with nitrogen. Extinction limits for such flames were measured over a wide parametric range. Results for methane and propane were found to be in

I.K. Puri; K. Seshadri

1986-01-01

326

Dilution refrigeration for space applications  

NASA Technical Reports Server (NTRS)

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.

Israelsson, U. E.; Petrac, D.

1990-01-01

327

Origins of large-volume, compositionally zoned volcanic eruptions: New constraints from U-series isotopes and numerical thermal modeling for the 1912 Katmai-Novarupta eruption  

USGS Publications Warehouse

We present the results of a combined U-series isotope and numerical modeling study of the 1912 Katmai-Novarupta eruption in Alaska. A stratigraphically constrained set of samples have compositions that range from basalt through basaltic andesite, andesite, dacite, and rhyolite. The major and trace element range can be modeled by 8090% closed-system crystal fractionation over a temperature interval from 1279C to 719C at 100 MPa, with an implied volume of parental basalt of ?65 km3. Numerical models suggest, for wall rock temperatures appropriate to this depth, that 90% of this volume of magma would cool and crystallize over this temperature interval within a few tens of kiloyears. However, the range in 87Sr/86Sr, (230Th/238U), and (226Ra/230Th) requires open-system processes. Assimilation of the host sediments can replicate the range of Sr isotopes. The variation of (226Ra/230Th) ratios in the basalt to andesite compositional range requires that these were generated less than several thousand years before eruption. Residence times for dacites are close to 8000 years, whereas the rhyolites appear to be 50200 kyr old. Thus, the magmas that erupted within only 60 h had a wide range of crustal residence times. Nevertheless, they were emplaced in the same thermal regime and evolved along similar liquid lines of descent from parental magmas with similar compositions. The system was built progressively with multiple inputs providing both mass and heat, some of which led to thawing of older silicic material that provided much of the rhyolite.

Turner, Simon; Sandiford, Mike; Reagan, Mark; Hawkesworth, Chris; Hildreth, Wes

2010-01-01

328

Geochemical monitoring of the 2002 2003 eruption at Stromboli volcano (Italy): precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters  

NASA Astrophysics Data System (ADS)

Significant changes in the helium and carbon isotopic composition of shallow thermal waters vs. gas and a crater fumarolic gas have been recorded at Stromboli prior and during the 2002 2003 eruption. The3He/4He ratios corrected for air contamination (Rc/Ra), and ?13C of fumarolic gases gradually increased from May to November 2002 before the eruption onset. These variations imply early degassing of a gas-rich magma at depth that likely fed both the intense Strombolian activity and small lava overflows recorded during that period. The lava effusion of late December 2002 was shortly preceded by a marked Rc/Ra decrease both in water and fumarolic gases. Comparison of He/CO2 and CH4/CO2 ratios in dissolved gas and with{? }^{13} C_{CO_2 } values rules out the Rc/Ra decrease due to an increasing input of radiogenic4He. The Rc/Ra decrease is attributed to the He isotope fractionation during rapid magma ascent and degassing. A new uprising of 3He-rich magma probably occurred in January to February 2003, when Rc/Ra ratios displayed the highest values in dissolved gases ever measured before (4.56 Rc/Ra). The increase in He/CO2 and CH4/CO2 ratios and decrease in ?13C of dissolved CO2 was recorded after the 5 April 2003 explosive paroxysm, likely caused by enhanced gas-water interaction inducing CO2 dissolution. No anomalous Rc/Ra values were recorded in the same period, when usual Strombolian activity gradually resumed.

Capasso, G.; Carapezza, M. L.; Federico, C.; Inguaggiato, S.; Rizzo, A.

2005-12-01

329

DAVINCI: Dilute Aperture VIsible Nulling Coronagraphic Imager  

NASA Technical Reports Server (NTRS)

This slide presentation gives an overview of DAVINCI (Dilute Aperture VIsible Nulling Coronagraphic Imager). The presentation also includes information about dilute aperture coronagraph, and lyot efficiency.

Shao, Michael; Levine, B. M.; Vasisht, G.; Lane, B. F.; Woodruff, R.; Vasudevan, G.; Samuele, R.; Lloyd, C. A.; Clampin, M.; Lyon, R.; Guyon, O.

2008-01-01

330

Physics with isotopically controlled semiconductors  

NASA Astrophysics Data System (ADS)

Control of the isotopic composition of semiconductors offers a wide range of new scientific opportunities. In this paper a number of recent results obtained with isotopically pure as well as deliberately mixed diamond and Ge bulk single crystals and Ge isotope superlattices will be reviewed. Isotopic composition affects several properties such as phonon energies, bandstructure and lattice constant in subtle but theoretically well understood ways. Large effects are observed for thermal conductivity, local vibrational modes of impurities and after neutron transmutation doping (NTD). Several experiments which could profit greatly from isotope control are proposed.

Haller, E. E.

1994-08-01

331

Potential energy surface for the CH3+HBr-->CH4+Br hydrogen abstraction reaction: Thermal and state-selected rate constants, and kinetic isotope effects  

NASA Astrophysics Data System (ADS)

The gas-phase hydrogen abstraction title reaction was carefully investigated. First, ab initio molecular orbital theory was used to study the stationary points along the reaction path: reactants, hydrogen-bonded complex, saddle point, and products. Optimized geometries and harmonic vibrational frequencies were calculated at the second-order Mller-Plesset perturbation theory level, and then single-point calculations were performed at a higher level of calculation: coupled-cluster with triple-zeta basis set. The effects of the level of calculation, zero-point energy (ZPE), thermal corrections [TC (298.15 K)], spin-orbit coupling, and basis set superposition error (BSSE) on the energy changes were analyzed. It was concluded that at room temperature (i.e., with ZPE and TC), when the BSSE was included, the complex disappears and the activation enthalpy is +0.39 kcal mol-1 above the reactants. Second, an analytical potential energy surface was constructed with suitable functional forms to represent vibrational modes, and was calibrated by using experimental and theoretical stationary point properties and the tendency of the kinetic isotope effects. On this surface, the forward and reverse thermal rate constants were calculated using variational transition state theory with semiclassical transmission coefficients over a wide temperature range. In both cases, we found a direct dependence on temperature and, therefore, positive activation energies. The influence of the tunneling factor was very small due to the flattening of the surface in the entrance valley. This surface was also used to analyze dynamical features, such as reaction-path curvature, the coupling between the reaction coordinate and vibrational modes, and the effect of vibrational excitation on the rate constants. It was found that excitation of the BrH stretching mode enhances the forward reaction, whereas the excitation of the CH3 umbrella mode has the opposite effect.

Espinosa-Garca, J.

2002-08-01

332

Cadmium measurements in coral skeleton using isotope dilutioninductively coupled plasmamass spectrometry  

E-print Network

Cadmium measurements in coral skeleton using isotope dilution­inductively coupled plasma for the precise analysis of Cd/Ca in coral skeleton using inductively coupled plasma­ mass spectrometry (ICP. McDonough, and A. G. Grottoli (2006), Cadmium measurements in coral skeleton using isotope dilution

Mcdonough, William F.

333

The chemical composition of red giants. III. Further CNO isotopic and s-process abundances in thermally pulsing asymptotic giant branch stars  

SciTech Connect

Near-IR and IR spectra are analyzed to obtain elemental and isotopic C, N, and O abundance, iron peak abundances, and heavy element s-process abundances for a sample of M, MS, and S giants. The compositions of the M giants are similar to those of G and K giants and consistent with predictions for giants that have deep convective envelopes and so have experienced the first dredge-up. The MS and S giants have compositions that show the signatures of the third dredge-up that occurs in thermally pulsing AGB stars. The sample shows that C-12, a principal product of the He-burning shell, has been added to the envelopes of MS and S stars. The C-12 enrichment is correlated with a more marked enrichment of the s-process elements that are predicted to be synthesized when a neutron source is ignited in the He-burning shell. The MS and S giants show a higher N abundance than the M giants, attributed to the expected deep mixing that occurs with the onset of the episodic third dredge-up. 122 refs.

Smith, V.V.; Lambert, D.L. (Texas Univ., Austin (USA) McDonald Observatory, Austin, TX (USA))

1990-02-01

334

Evidence of magnetic isotope effects during thermochemical sulfate reduction  

E-print Network

Thermochemical sulfate reduction experiments with simple amino acid and dilute concentrations of sulfate reveal significant degrees of mass-independent sulfur isotope fractionation. Enrichments of up to 13 for [superscript ...

Oduro, Harry D.

335

Bicosomes: bicelles in dilute systems.  

PubMed

Bicelles are discoidal phospholipid nanostructures at high lipid concentrations. Under dilute conditions, bicelles become larger and adopt a variety of morphologies. This work proposes a strategy to preserve the discoidal morphology of bicelles in environments with high water content. Bicelles were formed in concentrated conditions and subsequently encapsulated in liposomes. Later dilution of these new structures, called bicosomes, demonstrated that lipid vesicles were able to isolate and protect bicelles entrapped inside them from the medium. Characterization of systems before and after dilution by dynamic light-scattering spectroscopy and cryo-transmission electron microscopy showed that free bicelles changed in size and morphology, whereas encapsulated bicelles remained unaltered by the effect of dilution. Free and entrapped bicelles (containing the paramagnetic contrast agent gadodiamide) were injected into rat brain lateral ventricles. Coronal and sagittal visualization was performed by magnetic resonance imaging. Whereas rats injected with free bicelles did not survive the surgery, those injected with bicosomes did, and a hyperintensity effect due to gadodiamide was observed in the cerebrospinal fluid. These results indicate that bicosomes are a good means of preserving the morphology of bicelles under dilution conditions. PMID:20643066

Rodrguez, Gelen; Soria, Guadalupe; Coll, Elisenda; Rubio, Laia; Barbosa-Barros, Lucyanna; Lpez-Iglesias, Carmen; Planas, Anna M; Estelrich, Joan; de la Maza, Alfons; Lpez, Olga

2010-07-21

336

Quasiclassical molecular dynamics for the dilute Fermi gas at unitarity  

NASA Astrophysics Data System (ADS)

We study the dilute Fermi gas at unitarity using molecular dynamics with an effective quantum potential constructed to reproduce the quantum two-body density matrix at unitarity. Results for the equation of state, the pair-correlation function, and the shear viscosity are presented. These quantities are well understood in the dilute, high-temperature limit. Using molecular dynamics we determine higher-order corrections in the diluteness parameter n?3, where n is the density and ? is the thermal de Broglie wavelength. In the case of the contact density, which parameterizes the short distance behavior of the correlation function, we find that the results of molecular dynamics interpolate between the truncated second- and third-order virial expansion and are in excellent agreement with existing T-matrix calculations. For the shear viscosity we reproduce the expected scaling behavior at high temperature, ?1/?3, and we determine the leading density-dependent correction to this result.

Dusling, K.; Schfer, T.

2012-12-01

337

DETERMINATION OF SMALL AMOUNTS OF THALLIUM BY ISOTOPE DILUTION METHOD  

Microsoft Academic Search

A method of extracting Tl, labeled with Tl²°⁴ of a known activity, ; was developed. It consists of extraction by chloroform solution of dithizone ; from solutions containing sodium hydroxide, sodium potassium tartrate, and ; potassium cyanide. Thallium is stripped from the chloroform solution of ; dithizonates with triple distilled water. From the aqueous solution Tl is ; repeatedly extracted

J. Minczewski; C. Rozychi

1963-01-01

338

Chromatographic hydrogen isotope separation  

DOEpatents

Intermetallic compounds with the CaCu.sub.5 type of crystal structure, particularly LaNiCo.sub.4 and CaNi.sub.5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors.

Aldridge, Frederick T. (Livermore, CA)

1981-01-01

339

EAS 6216 Environmental Isotope Geochemistry Fall 2010 TuTh 3:05-4:25, 1229 ES&T  

E-print Network

, Jochen. 2004. Stable isotope geochemistry. Springer-Verlag. Criss, Robert. 1999. Principles of Stable/30 Analytical methods: isotope dilution and ICPMS 10/5 Data analysis for geochemists (Take-home MIDTERM) PART 2: STABLE ISOTOPES 10/7 Physical fundamentals 10/12 Stable isotope mass spectrometry 10/14 Raleigh

Black, Robert X.

340

Dilution and the elusive baseline.  

PubMed

Knowledge of baseline conditions is critical for evaluating quantitatively the effect of human activities on environmental conditions, such as the impact of acid deposition. Efforts to restore ecosystems to prior, "pristine" condition require restoration targets, often based on some presumed or unknown baseline condition. Here, we show that rapid and relentless dilution of surface water chemistry is occurring in the White Mountains of New Hampshire, following decades of acid deposition. Extrapolating measured linear trends using a unique data set of up to 47 years, suggest that both precipitation and streamwater chemistry (r(2) >0.84 since 1985) in the Hubbard Brook Experimental Forest (HBEF) will approximate demineralized water within one to three decades. Because such dilute chemistry is unrealistic for surface waters, theoretical baseline compositions have been calculated for precipitation and streamwater: electrical conductivity of 3 and 5 ?S/cm, base cation concentrations of 7 and 39 ?eq/liter, acid-neutralizing capacity values of <1 and 14 ?eq/liter, respectively; and pH 5.5 for both. Significantly large and rapid dilution of surface waters to values even more dilute than proposed for Pre-Industrial Revolution (PIR) conditions has important ecological, biogeochemical and water resource management implications, such as for the success of early reproductive stages of aquatic organisms. PMID:22455659

Likens, Gene E; Buso, Donald C

2012-04-17

341

Primary system boron dilution analysis  

Microsoft Academic Search

The results are presented for an analysis conducted to determine the potential paths through which nonborated water or water with insufficient boron concentration might enter the LOFT primary coolant piping system or reactor vessel to cause dilution of the borated primary coolant water. No attempt was made in the course of this analysis to identify possible design modifications nor to

R. J. Crump; C. J. Naretto; R. A. Borgen; H. C. Rockhold

1978-01-01

342

Resource Dilution or Resource Augmentation?  

E-print Network

Resource Dilution or Resource Augmentation? Number of Siblings, Birth Order, Sex of the Child Augmentation? Number of Siblings, Birth Order, Sex of the Child and Frequency of Mother's Activities" This project extends research on the genesis and effects of individual heterogeneity to cover psychological

Moeller, Ralf

343

40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.  

Code of Federal Regulations, 2010 CFR

...air and diluted exhaust flow meters. 1065.240...AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurement Instruments Flow-Related Measurements 1065.240 Dilution air and diluted exhaust...

2010-07-01

344

40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.  

Code of Federal Regulations, 2013 CFR

...air and diluted exhaust flow meters. 1065.240...AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurement Instruments Flow-Related Measurements 1065.240 Dilution air and diluted exhaust...

2013-07-01

345

40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.  

Code of Federal Regulations, 2011 CFR

...air and diluted exhaust flow meters. 1065.240...AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurement Instruments Flow-Related Measurements 1065.240 Dilution air and diluted exhaust...

2011-07-01

346

40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.  

Code of Federal Regulations, 2012 CFR

...air and diluted exhaust flow meters. 1065.240...AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurement Instruments Flow-Related Measurements 1065.240 Dilution air and diluted exhaust...

2012-07-01

347

Isotopically controlled semiconductors  

SciTech Connect

A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

Haller, E.E.

2004-11-15

348

Analysis of boron dilution in a four-loop PWR  

SciTech Connect

Thermal mixing and boron dilution in a pressurized water reactor were analyzed with COMMIX codes. The reactor system was the four-loop Zion reactor. Two boron dilution scenarios were analyzed. In the first scenario, the plant is in cold shutdown and the reactor coolant system has just been filled after maintenance on the steam generators. To flush the air out of the steam generator tubes, a reactor coolant pump (RCP) is started, with the water in the pump suction line devoid of boron and at the same temperature as the coolant in the system. In the second scenario, the plant is at hot standby and the reactor coolant system has been heated to operating temperature after a long outage. It is assumed that an RCP is started, with the pump suction line filled with cold unborated water, forcing a slug of diluted coolant down the downcomer and subsequently through the reactor core. The subsequent transient thermal mixing and boron dilution that would occur in the reactor system is simulated for these two scenarios. The reactivity insertion rate and the total reactivity are evaluated and a sensitivity study is performed to assess the accuracy of the numerical modeling of the geometry of the reactor coolant system.

Sun, J.G.; Sha, W.T. [Argonne National Lab., IL (United States)

1995-03-01

349

Analysis of boron dilution in a four-loop PWR  

SciTech Connect

Thermal mixing and boron dilution in a pressurized water reactor were analyzed with COMMIX codes. The reactor system was the four loop Zion reactor. Two boron dilution scenarios were analyzed. In the first scenario, the plant is in cold shutdown and the reactor coolant system has just been filled after maintenance on the steam generators. To flush the air out of the steam generator tubes, a reactor coolant pump (RCP) is started, with the water in the pump suction line devoid of boron and at the same temperature as the coolant in the system. In the second scenario, the plant is at hot standby and the reactor coolant system has been heated up to operating temperature after a long outage. It is assumed that an RCP is started, with the pump suction line filled with cold unborated water, forcing a slug of diluted coolant down the downcomer and subsequently through the reactor core. The subsequent transient thermal mixing and boron dilution that would occur in the reactor system is simulated for these two scenarios. The reactivity insertion rate and the total reactivity are evaluated.

Sun, J.G.; Sha, W.T.

1995-12-31

350

Chemical, isotopic, and dissolved gas compositions of the hot springs of the Owyhee Uplands, Malheur County, Oregon  

USGS Publications Warehouse

Hot springs along the Owyhee River in southeastern Oregon between Three Forks and Lake Owyhee could be part of a north flowing regional system or a series of small separate geothermal systems Heat for the waters could be from a very young (Holocene) volcanic activity (basalt flows) of the Owyhee Uplands or the regional heat flow. The springs discharge warm to hot, dilute, slightly alkaline, sodium bicarbonate water. Chemically they are similar to the dilute thermal water at Bruneau Grand View and Twin Falls, Idaho. Maximum aquifer temperatures in the Owyhee Uplands, estimated from chemical geothermometry, are about 100C. Dissolved helium concentrations, carbon 14 activity, and chemical and isotope data are examined fro systematic trends which would indicate a geothermal system of regional extent.

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

1994-01-01

351

Donor impurity band exchange in dilute ferromagnetic oxides  

Microsoft Academic Search

Dilute ferromagnetic oxides having Curie temperatures far in excess of 300 K and exceptionally large ordered moments per transition-metal cation challenge our understanding of magnetism in solids. These materials are high-k dielectrics with degenerate or thermally activated n-type semiconductivity. Conventional super-exchange or double-exchange interactions cannot produce long-range magnetic order at concentrations of magnetic cations of a few percent. We propose

M. Venkatesan; C. B. Fitzgerald; J. M. D. Coey

2005-01-01

352

Isotopically controlled semiconductors  

SciTech Connect

The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecturer for his 'pioneering achievements and leadership in establishing the field of isotopically engineered semiconductors; for outstanding contributions to materials growth, doping and diffusion; and for excellence in lecturing, writing, and fostering international collaborations'. The scientific interest, increased availability, and technological promise of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This article reviews results obtained with isotopically controlled semiconductor bulk and thin-film heterostructures. Isotopic composition affects several properties such as phonon energies, band structure, and lattice constant in subtle, but, for their physical understanding, significant ways. Large isotope-related effects are observed for thermal conductivity in local vibrational modes of impurities and after neutron transmutation doping. Spectacularly sharp photoluminescence lines have been observed in ultrapure, isotopically enriched silicon crystals. Isotope multilayer structures are especially well suited for simultaneous self- and dopant-diffusion studies. The absence of any chemical, mechanical, or electrical driving forces makes possible the study of an ideal random-walk problem. Isotopically controlled semiconductors may find applications in quantum computing, nanoscience, and spintronics.

Haller, Eugene E.

2006-06-19

353

Chemical, multi-isotopic (Li-B-Sr-U-H-O) and thermal characterization of Triassic formation waters from the Paris Basin  

E-print Network

from the Paris Basin R. Millot1* , C. Guerrot1 , C. Innocent1 , Ph. Négrel1 and B. Sanjuan2 (1) BRGM Basin in France. Four samples were collected in the central part of the Basin (saline waters) and three were collected at the edge of the Basin near the recharge zone (dilute waters). The saline waters

Boyer, Edmond

354

Dispersion of Sound in Dilute Suspensions with Nonlinear Particle Relaxation  

NASA Technical Reports Server (NTRS)

The theory accounting for nonlinear particle relaxation (viscous and thermal) has been applied to the prediction of dispersion of sound in dilute suspensions. The results suggest that significant deviations exist for sound dispersion between the linear and nonlinear theories at large values of Omega(Tau)(sub d), where Omega is the circular frequency, and Tau(sub d) is the Stokesian particle relaxation time. It is revealed that the nonlinear effect on the dispersion coefficient due to viscous contribution is larger relative to that of thermal conduction

Kandula, Max

2010-01-01

355

1. Isotope Definitions and terms a) Isotopes and isotope ratios.  

E-print Network

3/24/2011 1 Outline 1. Isotope Definitions and terms a) Isotopes and isotope ratios. Isotopes fractionation c) Simple illustration with the water cycle 2. CO2 isotopes in photosynthesis a) Photosynthetic discrimination in C3 plants b) C3 vs C4 photosynthesis and the distinction in isotopes c) Measuring isotopic

Saleska, Scott

356

Serial Dilution & Parts Per Million  

NSDL National Science Digital Library

This activity provides a real world application of the ATEEC Recommended Core Curriculum. This curriculum was identified by ATEEC Fellows as necessary preparation for environmental technology occupation. In this activity, students will experiment with serial dilution and parts per million. At the end of the activity, students will understand how to perform lab procedures, translate real world problems into math relationship, apply ratios and proportions to solve problems, manipulate and substitute variables to solve formulas, and demonstrate safe practices. The activity is appropriate for a high school biology or chemistry class.

2013-11-04

357

[Blood volume measurement of newborn using stable isotope 50Cr].  

PubMed

A technique for the blood volume measurement of newborns was established in which nonradioactive 50Cr was used in patients for whom radioactive labels were not advisable. The red blood cells (RBC) in the newborn's blood withdrawn from umbilical cord after birth were tagged with enriched stable isotope 50Cr (96%, normal abundance 4.3%) and reinjected into the newborn. Blood samples (0.5 ml) were withdrawn at 30 min and thereafter at 6, 12, 24, 48, 72 and 120 hours old. Samples were centrifugalized and portion of RBC was then freeze-dried, weighed and sealed into polyethylene sheet bag together with 50Cr standard. Neutron irradiation was performed in the reactors of the JAERI with thermal neutron flux 5 X 10(13), 2 X 10(13), 8 X 10(13) cm-2s-1 at JRR-2, -3 and -4 respectively for 20 min and samples were left for about two weeks after irradiation. Induced radioactivity (51Cr, 59Fe) of the sample was measured with a Ge(Li) gamma-ray detector system and 4096 channels pulse height analyzer. Analysis of activity data was carried out by BOB-76 code. The RBC and total blood volume of the newborn was calculated using an isotopic dilution technique. We have investigated on tagging efficiency of 50Cr to RBC, washing effect and dilution rate by 50Cr content or 51Cr/59Fe ratio. Significant difference was observed in the total blood volume of newborns depending on the delivery style and in addition, it changed dynamically along the time elapsed after birth. PMID:4011960

Yamabayashi, H; Izumo, M; Motoki, R; Yamamoto, T; Nishida, H; Shin, S; Sato, K; Suzuki, Y

1985-03-01

358

Carbonaceous substances associated with the Paleoproterozoic natural nuclear fission reactors of Oklo, Gabon: paragenesis, thermal maturation and carbon isotopic and trace element compositions  

Microsoft Academic Search

Field relationships, textural and reflectance characteristics and carbon isotopic compositions indicate that at least eight different categories of carbonaceous substances (CS) occur in the black shales, uranium ores and fossil nuclear fission reactors of Oklo. The categories include kerogens of the Mikouloungou coal in the FA Formation, the C1 pelites of the FA Formation, the black shale of the FB

David J. Mossman; Franois Gauthier-Lafaye; Simon E. Jackson

2001-01-01

359

Dilution in single pass arc welds  

SciTech Connect

A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to develop an expression for dilution as a function of welding variables and thermophysical properties of the filler metal and substrate. Comparison of calculated and experimentally determined dilution values shows the approach provides reasonable predictions of dilution when the melting efficiency can be accurately predicted. The conditions under which such accuracy is obtained are discussed. A diagram is developed from the dilution equation which readily reveals the effect of processing parameters on dilution to aid in parameter optimization.

DuPont, J.N.; Marder, A.R. [Lehigh Univ., Bethlehem, PA (United States). Dept. of Materials Science and Engineering

1996-06-01

360

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Imbibition in an originally oil-wet 2D capillary is the fastest in the case of Alf-38 and slowest in the case of DTAB (among the surfactants studied). Force of adhesion studies and contact angle measurements show that greater wettability alteration is possible with these anionic surfactants than the cationic surfactant studied. The water imbibition rate does not increase monotonically with an increase in the surfactant concentration. A numerical model has been developed that fits the rate of imbibition. Plans for the next quarter include conducting simulation and imbibition studies.

Kishore K. Mohanty

2005-01-01

361

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior and wettability studies. Addition of Na{sub 2}CO{sub 3} decreases IFT with a minimum at about 0.2 M. Addition of surfactant decreases IFT further. In the absence of surfactant the minerals are oil wet after aging with crude oil. Addition of surfactant solution decreases the contact angle to intermediate wettability. Addition of Na{sub 2}CO{sub 3} decreases anionic surfactant adsorption on calcite surface. Plans for the next quarter include conducting adsorption, phase behavior and wettability studies.

Kishore K. Mohanty

2003-07-01

362

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior, interfacial tension (IFT) and wettability studies. Addition of Na{sub 2}CO{sub 3} decreases IFT with a minimum at about 0.2 M. Addition of surfactant decreases IFT further. In the absence of surfactant the minerals are oil-wet after aging with crude oil. Addition of surfactant solution decreases the contact angle to intermediate-wet for many surfactants and water-wet for one surfactant. Addition of Na{sub 2}CO{sub 3} decreases anionic surfactant adsorption on calcite surface. Plans for the next quarter include conducting core adsorption, phase behavior, wettability and mobilization studies.

Kishore K. Mohanty

2003-07-01

363

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Laboratory imbibition tests show about 61% oil recovery in the case of Alf-38 and 37% in the case of DTAB. A numerical model has been developed that fits the rate of imbibition of the laboratory experiment. Field-scale fracture block simulation shows that as the fracture spacing increases, so does the time of recovery. Plans for the next quarter include simulation studies.

Kishore K. Mohanty

2005-04-01

364

A compact rotating dilution refrigerator.  

PubMed

We describe the design and performance of a new rotating dilution refrigerator that will primarily be used for investigating the dynamics of quantized vortices in superfluid (4)He. All equipment required to operate the refrigerator and perform experimental measurements is mounted on two synchronously driven, but mechanically decoupled, rotating carousels. The design allows for relative simplicity of operation and maintenance and occupies a minimal amount of space in the laboratory. Only two connections between the laboratory and rotating frames are required for the transmission of electrical power and helium gas recovery. Measurements on the stability of rotation show that rotation is smooth to around 10(-3) rad s(-1) up to angular velocities in excess of 2.5 rad s(-1). The behavior of a high-Q mechanical resonator during rapid changes in rotation has also been investigated. PMID:24182127

Fear, M J; Walmsley, P M; Chorlton, D A; Zmeev, D E; Gillott, S J; Sellers, M C; Richardson, P P; Agrawal, H; Batey, G; Golov, A I

2013-10-01

365

A compact rotating dilution refrigerator  

NASA Astrophysics Data System (ADS)

We describe the design and performance of a new rotating dilution refrigerator that will primarily be used for investigating the dynamics of quantized vortices in superfluid 4He. All equipment required to operate the refrigerator and perform experimental measurements is mounted on two synchronously driven, but mechanically decoupled, rotating carousels. The design allows for relative simplicity of operation and maintenance and occupies a minimal amount of space in the laboratory. Only two connections between the laboratory and rotating frames are required for the transmission of electrical power and helium gas recovery. Measurements on the stability of rotation show that rotation is smooth to around 10-3 rad s-1 up to angular velocities in excess of 2.5 rad s-1. The behavior of a high-Q mechanical resonator during rapid changes in rotation has also been investigated.

Fear, M. J.; Walmsley, P. M.; Chorlton, D. A.; Zmeev, D. E.; Gillott, S. J.; Sellers, M. C.; Richardson, P. P.; Agrawal, H.; Batey, G.; Golov, A. I.

2013-10-01

366

RADIATIVE AND DYNAMIC STABILITY OF A DILUTE PLASMA  

SciTech Connect

We analyze the linear stability of a dilute, hot plasma, taking into account the effects of stratification and anisotropic thermal conduction. The work is motivated by attempts to understand the dynamics of the intracluster medium in galaxy clusters. We show that magnetic field configurations that nominally stabilize either the heat-flux driven buoyancy instability (associated with a positive thermal gradient) or the magnetothermal instability (negative thermal gradient) can lead to previously unrecognized g-mode overstabilities. The driving source of the overstability is either radiative cooling (positive temperature gradient) or the heat flux itself (negative temperature gradient). While the implications of these overstabilities have yet to be explored, we speculate that the cold fronts observed in many relaxed galaxy clusters may be related to their nonlinear evolution.

Balbus, Steven A. [Laboratoire de Radioastronomie, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris Cedex 05 (France); Reynolds, Christopher S., E-mail: steven.balbus@lra.ens.f [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

2010-09-01

367

Evidence of magnetic isotope effects during thermochemical sulfate reduction.  

PubMed

Thermochemical sulfate reduction experiments with simple amino acid and dilute concentrations of sulfate reveal significant degrees of mass-independent sulfur isotope fractionation. Enrichments of up to 13 for (33)S are attributed to a magnetic isotope effect (MIE) associated with the formation of thiol-disulfide, ion-radical pairs. Observed (36)S depletions in products are explained here by classical (mass-dependent) isotope effects and mixing processes. The experimental data contrasts strongly with multiple sulfur isotope trends in Archean samples, which exhibit significant (36)S anomalies. These results support an origin other than thermochemical sulfate reduction for the mass-independent signals observed for early Earth samples. PMID:21997216

Oduro, Harry; Harms, Brian; Sintim, Herman O; Kaufman, Alan J; Cody, George; Farquhar, James

2011-10-25

368

EPS dilution after SEOs and earnings management  

Microsoft Academic Search

Purpose Firms are concerned about earnings per share (EPS) dilution after equity issues. The purpose of this paper is to investigate whether firms manage upward their discretionary accruals around seasoned equity offerings (SEOs) to mitigate the impact of dilution on reported earnings. Design\\/methodology\\/approach The authors employ adjusted discretionary accruals from cash flow statements, normalized by the average common

Hui Di; Dalia Marciukaityte; Eugenie A. Goodwin

2012-01-01

369

The influence of optimum power level change on boration and dilution operations  

SciTech Connect

Xenon and samarium concentrations changes occur in a nuclear reactor as a consequence of power level variations. To compensate for the reactivity introduced by these isotopes, the boron concentration in the reactor coolant also needs to be changed. Boron concentration changes result from boration or dilution operations. Both boration and dilution operations have economic effects due to the cost of boric acid and the treatment of the effluent. A method is presented that finds the nuclear power level change that leads to an optimization of the boration and dilution operations. The use of the method for practical applications is demonstrated by comparing the absolute reactivity change for the optimum power ramp and a ramp of [plus minus]3%/h. The numerical calculations are very fast. Thus, the method may be implemented in the process computer of any nuclear power plant.

Martinez, A.S.; Andrade Oliveira, E. de (COPPE/UFRJ, Rio de Janeiro (Brazil). Programa de Engenharia Nuclear.)

1993-08-01

370

Development and Comparison of Two Types of Cryogen-Free Dilution Refrigerator  

NASA Astrophysics Data System (ADS)

Dilution refrigerators are an important tool used in solid state and quantum fluid physics for cooling to temperatures below 0.3 K. Conventional dilution refrigerators consume a lot of liquid helium, which has to be recharged in a helium bath every few days. Cryogen-free dilution refrigerators, however, do not use liquid helium and then automatic operation by electricity can be possible from room temperature to the mK region. In near future, therefore, most conventional dilution refrigerators will be replaced by cryogen-free refrigerators because they are easy to operate, do not require maintenance and do not consume helium. We have developed two types of cryogen-free dilution refrigerator. One is directly cooled by a pulse tube refrigerator in the same cryostat using copper thin wires as a thermal link, and the other is cooled by a separate Gifford McMahon refrigerator using circulating helium gas through a flexible syphon tube. The latter has been developed as a vibration-free cryogen-free dilution refrigerator. These two types of cryogen-free dilution refrigerator are compared considering several key points: base temperature, precooling time, minimum temperature and vibration amplitude.

Hata, T.; Matsumoto, T.; Obara, K.; Yano, H.; Ishikawa, O.; Handa, A.; Togitani, S.; Nishitani, T.

2014-04-01

371

Construction of a dilution refrigerator cooled scanning force microscope  

NASA Astrophysics Data System (ADS)

We present a scanning force microscope that operates in a dilution refrigerator at temperatures of about 100 mK. We use tuning fork sensors for scanning gate experiments on mesoscopic semiconductor nanostructures. Slip-stick motors allow sample coarse-positioning at base temperature. The construction, thermal anchoring, and a procedure to optimize the settings of the phase-locked loop that we use for sensor control are discussed in detail. We present low-temperature topographic and scanning gate images as examples of successful operation.

Gildemeister, A. E.; Ihn, T.; Barengo, C.; Studerus, P.; Ensslin, K.

2007-01-01

372

Construction of a dilution refrigerator cooled scanning force microscope.  

PubMed

We present a scanning force microscope that operates in a dilution refrigerator at temperatures of about 100 mK. We use tuning fork sensors for scanning gate experiments on mesoscopic semiconductor nanostructures. Slip-stick motors allow sample coarse-positioning at base temperature. The construction, thermal anchoring, and a procedure to optimize the settings of the phase-locked loop that we use for sensor control are discussed in detail. We present low-temperature topographic and scanning gate images as examples of successful operation. PMID:17503925

Gildemeister, A E; Ihn, T; Barengo, C; Studerus, P; Ensslin, K

2007-01-01

373

Isotope pattern deconvolution as rising tool for isotope tracer studies in environmental research  

NASA Astrophysics Data System (ADS)

During the last decade stable isotope tracers have emerged as versatile tool in ecological research. Besides 'intrinsic' isotope tracers caused by the natural variation of isotopes, the intentional introduction of 'extrinsic' enriched stable isotope tracers into biological systems has gained significant interest. Hereby the induced change in the natural isotopic composition of an element allows amongst others for studying the fate and fluxes of metals, trace elements and species in organisms or provides an intrinsic marker or tag of particular biological samples. Due to the shoreless potential of this methodology, the number of publications dealing with applications of isotope (double) spikes as tracers to address research questions in 'real world systems' is constantly increasing. However, some isotope systems like the natural Sr isotopic system, although potentially very powerful for this type of application, are still rarely used, mainly because their adequate measurement/determination poses major analytical challenges; as e.g. Sr is available in significant amounts in natural samples. In addition, biological systems underlie complex processes such as metabolism, adsorption/desorption or oxidation/reduction. As a consequence, classic evaluation approaches such as the isotope dilution mass spectrometry equation are often not applicable because of the unknown amount of tracer finally present in the sample. Isotope pattern deconvolution (IPD), based on multiple linear regression, serves as simplified alternative data processing strategy to double spike isotope dilution calculations. The outstanding advantage of this mathematical tool lies in the possibility of deconvolving the isotope pattern in a spiked sample without knowing the quantities of enriched isotope tracer being incorporated into the natural sample matrix as well as the degree of impurities and species-interconversion (e.g. from sample preparation). Here, the potential of IPD for environmental tracer studies is critically discussed, where special emphasis is set on evaluating different data processing strategies on the example of enriched stable Sr isotopes.1 The analytical key parameters such as blank (Kr, Sr and Rb), variation of the natural Sr isotopic composition in the sample, mass bias, interferences (Rb) and total combined uncertainty are considered. A full metrological protocol for data processing using IPD is presented based on data gained during two transgenerational marking studies of fish, where the transfer of a Sr isotope double spike (84Sr and 86Sr) from female spawners of common carp (Cyprinus carpio L.) and brown trout (Salmo trutta f.f.)2 to the centre of the otoliths of their offspring was studied by (LA)-MC-ICP-MS. 1J. Irrgeher, A. Zitek, M. Cervicek and T. Prohaska, J. Anal. At. Spectrom., 2014, 29, 193-200. 2A. Zitek, J. Irrgeher, M. Kletzl, T. Weismann and T. Prohaska, Fish. Manage. Ecol., 2013, 20, 654-361.

Irrgeher, Johanna; Zitek, Andreas; Prohaska, Thomas

2014-05-01

374

Chemical characteristics of the major thermal springs of Montana  

USGS Publications Warehouse

Twenty-one thermal springs in western Montana were sampled for chemical, isotope, and gas compositions. Most of the springs issue dilute to slightly saline sodium-bicarbonate waters of neutral to slightly alkaline pH. A few of the springs issue sodium-mixed anion waters of near neutral pH. Fluoride concentrations are high in most of the thermal waters, up to 18 milligramsper litre, while F/Cl ratios range from 3/1 in the dilute waters to 1/10 in the slightly saline waters. Most of the springs are theoretically in thermodynamic equilibrium with respect to calcite and fluorite. Nitrogen is the major gas escaping from most of the hot springs; however, Hunters Hot Springs issue principally methane. The deuterium content of the hot spring waters is typical of meteoric water in western Montana. Geothermal calculations based on silica concentrations and Na-K-Ca ratios indicate that most of the springs are associated with low temperature aquifers (less than 100?C). Chalcedony may be controlling the silica concentrations in these low temperature aquifers even in 'granitic' terranes.

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

1976-01-01

375

Isotope spectroscopy  

NASA Astrophysics Data System (ADS)

The measurement of isotopic ratios provides a privileged insight both into nucleosynthesis and into the mechanisms operating in stellar envelopes, such as gravitational settling. In this article, we give a few examples of how isotopic ratios can be determined from high-resolution, high-quality stellar spectra. We consider examples of the lightest elements, H and He, for which the isotopic shifts are very large and easily measurable, and examples of heavier elements for which the determination of isotopic ratios is more difficult. The presence of 6Li in the stellar atmospheres causes a subtle extra depression in the red wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the highest quality. But even with the best spectra, the derived 6Li abundance can only be as good as the synthetic spectra used for their interpretation. It is now known that 3D non-LTE modelling of the lithium spectral line profiles is necessary to account properly for the intrinsic line asymmetry, which is produced by convective flows in the atmospheres of cool stars, and can mimic the presence of 6Li. We also discuss briefly the case of the carbon isotopic ratio in metal-poor stars, and provide a new determination of the nickel isotopic ratios in the solar atmosphere.

Caffau, E.; Steffen, M.; Bonifacio, P.; Ludwig, H.-G.; Monaco, L.; Lo Curto, G.; Kamp, I.

2014-01-01

376

21 CFR 864.5240 - Automated blood cell diluting apparatus.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

2010-04-01

377

21 CFR 864.5240 - Automated blood cell diluting apparatus.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

2013-04-01

378

40 CFR 1065.667 - Dilution air background emission correction.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Dilution air background emission correction...AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...1065.667 Dilution air background emission correction...first determine the total flow of dilution air, n...

2011-07-01

379

40 CFR 1065.667 - Dilution air background emission correction.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Dilution air background emission correction...AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...1065.667 Dilution air background emission correction...first determine the total flow of dilution air, n...

2010-07-01

380

40 CFR 1065.667 - Dilution air background emission correction.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Dilution air background emission correction...AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...1065.667 Dilution air background emission correction...first determine the total flow of dilution air, n...

2012-07-01

381

40 CFR 1065.667 - Dilution air background emission correction.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Dilution air background emission correction...AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...1065.667 Dilution air background emission correction...first determine the total flow of dilution air, n...

2013-07-01

382

21 CFR 864.5240 - Automated blood cell diluting apparatus.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

2011-04-01

383

Dilution and resonance-enhanced repulsion in nonequilibrium fluctuation forces  

NASA Astrophysics Data System (ADS)

In equilibrium, forces induced by fluctuations of the electromagnetic field between electrically polarizable objects (microscopic or macroscopic) in vacuum are generically attractive. The force may, however, become repulsive for microscopic particles coupled to thermal baths with different temperatures. We demonstrate that this nonequilibrium repulsion can be realized also between macroscopic objects, as planar slabs, if they are kept at different temperatures. It is shown that repulsion can be enhanced by (i) tuning of material resonances in the thermal region and by (ii) reducing the dielectric contrast due to dilution. This can lead to stable equilibrium positions. We discuss the realization of these effects for aerogels, yielding repulsion down to submicron distances at realistic porosities.

Bimonte, Giuseppe; Emig, Thorsten; Krger, Matthias; Kardar, Mehran

2011-10-01

384

Differential isospin-fractionation in dilute asymmetric nuclear matter  

NASA Astrophysics Data System (ADS)

The differential isospin-fractionation (IsoF) during the liquid-gas phase transition in dilute asymmetric nuclear matter is studied as a function of nucleon momentum. Within a self-consistent thermal model it is shown that the neutron/proton ratio of the gas phase becomes smaller than that of the liquid phase for energetic nucleons, although the gas phase is overall more neutron-rich. Clear indications of the differential IsoF consistent with the thermal model predictions are demonstrated within a transport model for heavy-ion reactions. Future comparisons with experimental data will allow us to extract critical information about the momentum dependence of the isovector strong interaction.

Li, Bao-An; Chen, Lie-Wen; Ma, Hong-Ru; Xu, Jun; Yong, Gao-Chan

2007-11-01

385

Stability of a Planar Interface During Solidification of a Dilute Binary Alloy  

Microsoft Academic Search

The stability of the shape of a moving planar liquid-solid interface during the unidirectional freezing of a dilute binary alloy is theoretically investigated by calculating the time dependence of the amplitude of a sinusoidal perturbation of infinitesimal amplitude introduced into the planar shape. The calculation is accomplished by using gradients of the steady-state thermal and diffusion fields satisfying the perturbed

W. W. Mullins; R. F. Sekerka

1964-01-01

386

Dynamics of Homogeneous Charge Compression Ignition (HCCI) Engines with High Dilution  

E-print Network

, which we refer to as the rebreathing lift (RBL), as shown in the valve profiles in Fig. 1. Using highDynamics of Homogeneous Charge Compression Ignition (HCCI) Engines with High Dilution C. J. Chiang (HCCI) engines in light of the cycle-to-cycle thermal feedback due to the high percentage of exhaust

Stefanopoulou, Anna

387

Helium Dilution Cryocooler for Space Applications  

NASA Technical Reports Server (NTRS)

NASA's New Millenium Program Space Technology presents the Helium Dilution Cryocooler for Space Applications. The topics include: 1) Capability; 2) Applications; and 3) Advantages. This paper is in viewgraph form.

Roach, Pat; Hogan, Robert (Technical Monitor)

2001-01-01

388

Isotopic Analysis of OS and RE with Negative Thermal Ion Mass Spectrometry and Application to the Age and Evolution of Iron Meteorites  

NASA Astrophysics Data System (ADS)

The ^187Re-^187Os isotope system has long been recognized as a method by which the age of iron meteorites can be directly determined (Herr et al., 1961). Pioneering work by Luck and Allegre (1983) established a whole-rock isochron for iron meteorites and the results, were used to determine indirectly the half-life of ^187Re. We have developed: a) high ionization efficiency mass spectrometry techniques for platinum group elements, including both Re and Os separated from iron meteorites (Creaser et al., 1991, 1992); b) low filament loading blanks for both Re and Os (<0.1 picogram, each); c) high yield and low blanks for the chemical separation techniques (yields 70-80%; blanks 1 pg for Os, <10 pg for Re). We have developed a new method for the rapid, clean and efficient separation of Os and Re from 10^-2 g samples of iron meteorites. This will permit taking advantage of variations of Re/Os on a small scale. The chemical separation scheme involves acid dissolution, preconcentration of Os and Re from Fe-Ni, oxidative solvent extraction of Os and ion exchange chromatography to recover Re. We have established that Os and Re thus chemically separated from iron meteorites show the same ionization efficiency as Os and Re from standard solutions, namely ~20% for each element. Of primary importance is the degree of isotope exchange and equilibration between sample and spike for Os. By analyzing the isotopic composition of Os at different stages of the chemical separation we are able to demonstrate that isotopic equilibration can be achieved to the level of +-1o/oo. However, this is not yet a routinely resolved issue. We believe, based on experience during the development of this technique, that isotope equilibration for Os prior to chemical separation is a critical issue that needs further attention. The results we have obtained so far from iron meteorites are given in Table 1. We have started analyses of the large magmatic group of IIA irons, which are little shocked and little metamorphosed, in order to attempt to establish a high precision isochron for these objects. For two samples, where we have high precision data for both Os and Re, the slope indicated is 0.077, which yields an age of 4530 Ma using the best estimate of the ^187Re half-life by direct measurement (Lindner et al., 1989). These results are in close agreement with the revised data of Horan et al. (1992) but markedly different from published iron meteorite data using the lower precision techniques where slopes of 0.070-0.074 indicate apparent ages of 4150-4350 Ma. We believe that previously reported data, including the data on the half-life of ^187Re, require confirmation using the current high-precision and high- sensitivity techniques, before the reliability and utility of the Re-Os technique can be ascertained. Acknowledgement. This work was supported by NASA, Grant NAG 943. Contribution No. 779. References Creaser, R. A., Papanastassiou, D. A., and Wasserburg, G. J. (1991a) Geochim. Cosmochim. Acta 55, 397-401. Creaser, R. A., Papanastassiou, D. A., and Wasserburg, G. J. (1992) Lunar Planet. Sci. XXIII (abstract), 255-256. Herr, W., Hoffmeister, W., Hirt, B., Geiss, J., and Houtermans, F. G. (1961) Z. Naturforsch. 16a, 1053-1058. Horan, M. F., Morgan, J. W., Walker, R. J., and Grossman, J. N. (1992) Science 255, 1118-1121. Lindner, M., Leich, D. A., Russ, G. P., Bazan, J. M., and Borg, R. J. (1989) Geochim. Cosmochim. Acta 53, 1597-1606. Luck, J. M. and Allegre, C. J. (1983) Nature 302, 130-132. Table 1. Re-Os isotopic data from iron meteorites. Os ppm Re ppb 187Os/188Os 187Re/188Os Bennett County IIA 59.6+-0.1 0.12503+-5 Coahuila IIA 9.87+-0.02 0.14158+-7 Tocopilla IIA 1.062+-0.002 207.9 0.16913+-15 0.9451 Negrillos IIA 69.4+-0.1 5022.7 0.12315+-2 0.3497 Cape York IIIA 0.13374+-9 Canyon Diablo IA 0.13464+-11 Tlacotepc IVB 0.12068+-8 Osmium standard (NHr)2OsCl6 0.14911+-3

Creaser, R. A.; Papanastassiou, D. A.; Wasserburg, G. J.

1992-07-01

389

Biodilution of heavy metals in a stream macroinvertebrate food web: Evidence from stable isotope analysis  

Microsoft Academic Search

Analysis of carbon (?13C) and nitrogen (?15N) stable isotopes provides an increasingly important means of understanding the complex trophic structure of macroinvertebrate communities in streams. We coupled a stable isotope approach with a contaminant analysis of six metals (Pb, Ag, Zn, Hg, Cu, As) to trace the accumulation and dilution of metals from an abandoned mine across trophic levels of

Kozo Watanabe; Michael T. Monaghan; Yasuhiro Takemon; Tatsuo Omura

2008-01-01

390

Calorimetric Study of Diluted Spin Ice Materials  

NASA Astrophysics Data System (ADS)

Spin ice materials Dy2Ti2O7 and Ho2Ti2O7 have been the subject of ongoing interest for over ten years. The cooperative magnetic ground state can be mapped onto the proton disordered ground state in water ice, and its residual entropy follows the same Pauling's estimate. Interestingly it was found in a previous study that, upon dilution of the magnetic rare earth ions Dy^3+ and Ho^3+ by non-magnetic substitutes Y^3+, the residual entropy depends non-monotonically on the dilution level. In this work we investigate through Monte Carlo simulations microscopic models to account quantitatively for the calorimetric experimental measurements, and thus also the residual entropies as a function of dilution. Features of the dilution physics in the specific heat are captured quantitatively by the microscopic models and the interplay between dilution and frustration is understood on the basis of a Bethe lattice calculation. The effect of the dipolar interactions between magnetic spins are exposed numerically for various dilution concentrations. Our work explains the previous discrepancy of the residual entropy between different species of rare earth ions and the generalized Pauling's estimate.

Lin, Taoran; Ke, Xianglin; Thesberg, Mischa; Schiffer, Peter; Melko, Roger; Gingras, Michel

2012-02-01

391

Dilute Oxygen Combustion Phase 2 Final Report  

SciTech Connect

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NOx emissions below 5-10-3 g/MJ (10 ppm-air equivalent at 3% O2 dry) were obtained for furnace temperatures below 1533 K (2300?F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in-furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, wit6h increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of lower utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, required additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

Ryan, H.M.; Riley, M.F.; Kobayashi, H.

2005-09-30

392

Dilute Oxygen Combustion Phase I Final Report  

SciTech Connect

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NOx emissions below 5-10-3 g/MJ (10 ppm-air equivalent at 3% O2 dry) were obtained for furnace temperatures below 1533 K (2300°F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in-furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, wit6h increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of lower utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, required additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

Ryan, H.M.; Riley, M.F.; Kobayashi, H.

1997-10-31

393

Dilute oxygen combustion. Phase I report  

SciTech Connect

A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NO{sub x}) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NO{sub x} through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NO{sub x} production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature ({approximately}1366 K) oxidant (7-27% O{sub 2} vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d{sup +} scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d{sup +} scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW ({approximately}0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NO{sub x} emissions increased with increasing furnace nitrogen content and furnace temperature, but remained relatively insensitive to variations in fuel injection velocity and firing rate. NO{sub x} emissions below 5{times}10{sup -3} g/MJ (10 ppm-air equivalent at 3% O{sub 2} dry) were obtained for furnace temperatures below 1533 K (2300{degree}F) and furnace nitrogen levels between 1 and 40%. CO emissions were typically low (<35 ppm). Detailed in- furnace species measurements revealed the importance of the interior furnace circulation patterns, as influenced by fuel and oxidant injection schemes, on pollutant emissions. The combustion stability traits of several DOC burner arrangements were ascertained through furnace pressure measurements, with increased stability occurring as furnace temperature increased and as the separation distance between fuel and oxidant inputs decreased. Based on current market conditions, oxy-fuel conversion of batch steel reheat furnaces with a DOC burner is justified on the basis of utility costs alone. However, conversion of continuous steel reheat furnaces, which are responsible for most steel production, requires additional economic incentives, such as further fuel savings, increased furnace productivity, or emission credits.

NONE

1997-10-01

394

Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi Shibuta  

E-print Network

Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi that the inclusion of only 1 % of 13 C natural isotope dramatically reduces the thermal conductivity of diamond. However,