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1

Determination of uranium and thorium concentrations in soils: Comparison of isotope dilution-secondary ion mass spectrometry and isotope dilution-thermal ionization mass spectrometry  

SciTech Connect

The purpose of the present study existed in making a comparison between isotope dilution-thermal ionization mass spectrometry (ID-TIMS) and isotope dilution-secondary ion mass spectrometry (ID-SIMS) on the basis of their precision and accuracy. Three different sets of soils were therefore analyzed to determine their uranium and thorium contents. An analysis of variance (ANOVA) demonstrated that the precision of TIMS was about 6 times better than that of SIMS. It was clear in the case of TIMS that the overall precision can almost completely be explained by the variation in composition between samples, while for the SIMS analyses, the instrumental error plays an important role in determining the precision. The overall SIMS/TIMS ratio for all data and for both elements equals 0.994 with a standard error of 0.004. As a result of this, it is statistically not fully proven that there is a systematic difference in accuracy between the two techniques. For the chemical separation of the analytes, a new element-specific resin was used and evaluated. The newer resin was able to remove metals such as iron, lead, and bismuth better than that traditional strong anion resin, but the uranium fraction obtained using the newer resin contained a larger amount of thorium. 14 refs., 7 figs., 4 tabs.

Adriaens, A.G.; Adams, F.C. (Univ. of Antwerp, Wilrijk (Belgium)); Fassett, J.D.; Kelly, W.R.; Simons, D.S. (National Inst. of Standards and Technology, Gaithersburg, MD (United States))

1992-12-01

2

The application of isotope dilution thermal ionization mass spectrometry to traceability of chemical measurement and interlaboratory comparisons  

Microsoft Academic Search

In this work, the method of isotope dilution thermal ionization mass spectrometry able to trace to SI was developed to accurately\\u000a measure trace amount of Cd, Pb, Zn and Cu in sediment, rice, wine, and human serum samples for interlaboratory comparisons.\\u000a The research focuses on how to apply the primary method correctly, uncertainty evaluation of measurement results, and how\\u000a to

Jun Wang; Motain Zhao; Na Guan; Hai Lu

2006-01-01

3

Determination of Cd and Zn by isotope dilution–thermal ionisation mass spectrometry using a sequential analysis procedure  

Microsoft Academic Search

Isotope dilution–thermal ionisation mass spectrometry (ID-TIMS) was used to examine the certified Cd and Zn content of 4 Certified Reference Materials (CRMs); 2 soils: GBW07401 and GBW07405, 1 plant CRM060 and an animal tissue SRM1566a. The CRMs were chosen to be of contrasting origin and Cd:Zn content. Three digestion procedures were compared: (i) an open tube aqua regia procedure (ii)

Ahmed S Ayoub; Brian A McGaw; Andrew J Midwood

2002-01-01

4

Liquid Volumes Measurements by Isotopic Dilution.  

National Technical Information Service (NTIS)

By the nuclear technique of isotopic dilution, industrial liquid volumes may be measured in large size reservoirs of irregular shapes using radiotracers. In the present work laboratory and pilot test are made with 2 radiotracers for optimizing the techniq...

J. M. Herrera M

1981-01-01

5

Stable Isotope Dilution for Hazardous Waste Incineration.  

National Technical Information Service (NTIS)

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

P. W. Ryan

1984-01-01

6

Numerical calibration of the Devonian-Carboniferous boundary: Two new U-Pb isotope dilution thermal ionization mass spectrometry single-zircon ages from Hasselbachtal (Sauerland, Germany)  

NASA Astrophysics Data System (ADS)

The Hasselbachtal section (Sauerland, Germany) is an auxiliary global stratotype of the Devonian-Carboniferous boundary and one of the most important reference sections for the evolution of the latest Famennian to earliest Tournaisian pelagic fauna. Biostratigraphically well controlled altered volcanic ash layers (metabentonites) intercalated in the section afford a perfect opportunity for a numerical fixing of this important Paleozoic period boundary. We have performed U-Pb isotope dilution thermal ionization mass spectrometry (ID-TIMS) analyses on (sub)microgram-sized single zircons and zircon fragments extracted from two metabentonites (beds 79 and 70) in the lowermost Tournaisian part of the section. Bed 79 metabentonite is positioned directly above the Devonian-Carboniferous boundary within the Siphonodella sulcata conodont zone. Five concordant analyses form a cluster with a 206Pb/238U concordia age of 360.5 ± 0.8 Ma. Zircons of the next younger metabentonite (bed 70), in the lower Siphonodella duplicata conodont zone, yielded a tightly grouped cluster of 10 concordant analyses with a 206Pb/238U concordia age of 360.2 ± 0.7 Ma. On the basis of these two new single-zircon ages and previously published late Famennian U-Pb ID-TIMS ages, the Devonian-Carboniferous boundary is reinterpolated herein to 360.7 ± 0.7 Ma.

Trapp, Endres; Kaufmann, Bernd; Mezger, Klaus; Korn, Dieter; Weyer, Dieter

2004-10-01

7

Stable isotope dilution assays in mycotoxin analysis.  

PubMed

The principle and applications of stable isotope dilution assays (SIDAs) in mycotoxin analysis are critically reviewed. The general section includes historical aspects of SIDAs, the prerequisites and limitations of the use of stable isotopically labelled internal standards, and possible calibration procedures. In the application section actual SIDAs for the analysis of trichothecenes, zearalenone, fumonisins, patulin, and ochratoxin A are presented. The syntheses and availability of labelled mycotoxins for use as internal standards is reviewed and specific advances in food analysis and toxicology are demonstrated. The review indicates that LC-MS applications, in particular, require the use of stable isotopically labelled standards to compensate for losses during clean-up and for discrimination due to ion suppression. As the commercial availability of these compounds continues to increase, SIDAs can be expected to find expanding use in mycotoxin analysis. PMID:18060393

Rychlik, Michael; Asam, Stefan

2007-12-01

8

Measurement of isotope abundance variations in nature by gravimetric spiking isotope dilution analysis (GS-IDA).  

PubMed

Subtle variations in the isotopic composition of elements carry unique information about physical and chemical processes in nature and are now exploited widely in diverse areas of research. Reliable measurement of natural isotope abundance variations is among the biggest challenges in inorganic mass spectrometry as they are highly sensitive to methodological bias. For decades, double spiking of the sample with a mix of two stable isotopes has been considered the reference technique for measuring such variations both by multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS) and multicollector-thermal ionization mass spectrometry (MC-TIMS). However, this technique can only be applied to elements having at least four stable isotopes. Here we present a novel approach that requires measurement of three isotope signals only and which is more robust than the conventional double spiking technique. This became possible by gravimetric mixing of the sample with an isotopic spike in different proportions and by applying principles of isotope dilution for data analysis (GS-IDA). The potential and principle use of the technique is demonstrated for Mg in human urine using MC-TIMS for isotopic analysis. Mg is an element inaccessible to double spiking methods as it consists of three stable isotopes only and shows great potential for metabolically induced isotope effects waiting to be explored. PMID:23419016

Chew, Gina; Walczyk, Thomas

2013-03-19

9

Further development of IDGS: Isotope dilution gamma-ray spectrometry  

SciTech Connect

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% for {sup 239}Pu and {sup 240}Pu isotopic analyses and {approximately}1% for the plutonium concentration analysis. 5 refs., 2 figs., 7 tabs.

Li, T.K.; Parker, J.L. (Los Alamos National Lab., NM (United States)); Kuno, Y.; Sato, S.; Kamata, M.; Akiyama, T. (Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan))

1991-01-01

10

FUNCTIONAL ERRORS IN THE METHOD OF DETERMINATION BY ISOTOPIC DILUTION  

Microsoft Academic Search

BS>The statistical nature of the emission of radioelements limits the ; precision of determinations by isotopic dilution. Theoretical considerations ; supported by an experimental model were used to study the optimum conditions for ; radiochemical work on a given problem in which the technique of counting at ; predetermined times is used. (tr-auth);

Lebreton

1960-01-01

11

THE DETERMINATION OF NITROGEN IN METALS BY ISOTOPE DILUTION  

Microsoft Academic Search

A wet chemical procedure for determining the amount of nitrogen in a ; metal or alloy has been developed which utilizes the isotope dilution technique. ; Ammonium sulfate, either enriched or depleted in N¹⁵, is added to the metal ; sample during solution procedures. Ammonium ions resulting from the hydrolysis ; of bound nitrogen in the metals mix with that

H Gene Staley; H. J. Svec

1959-01-01

12

Application of isotope dilution technique in vitamin A nutrition.  

PubMed

The isotope dilution technique involving deuterated retinol has been developed to quantitatively estimate total body reserves of vitamin A in humans. The technique provided good estimates in comparison to hepatic vitamin A concentrations in Bangladeshi surgical patients. Kinetic studies in the United States, Bangladesh, and Guatemala indicated the mean equilibration time of 17 to 20 days irrespective of the size of hepatic reserves. Due to the controversy surrounding the efficacy of a carotene-rich diet on improvement of vitamin A status, the isotope dilution technique was proposed to pursue this research question further (IAEA's coordinated research program). In the Philippines, schoolchildren with low serum retinol concentrations showed significant improvement in total body vitamin A stores following intake of carotene-rich foods (orange fruits and vegetables), using a three-day deuterated-retinol-dilution procedure. When Chinese kindergarten children were fed green and yellow vegetables during the winter, their total body vitamin A stores were sustained as compared to a steady decline of vitamin A stores in the control children. Likewise, daily consumption of purified beta-carotene or diet rich in provitamin A carotenoids were shown to prevent a loss in total body vitamin A stores among Thai lactating women during the rice-planting season. These studies demonstrate potentials of the isotope dilution technique to evaluate the impact of provitamin A carotenoid intervention programs. PMID:12362775

Wasantwisut, Emorn

2002-09-01

13

Development of resin-bead isotope-dilution mass spectrometric techniques for Tc99 analysis  

Microsoft Academic Search

An isotope dilution mass spectrometric method was developed for the analysis of Tc-99 after isolating it onto anion exchange resin beads. A single resin bead containing Tc-99 and Tc-97 spike is loaded onto a rhenium V-shaped filament for thermal emission mass spectrometry. The application of this technique requires the use of a mass spectrometer of high abundance sensitivity and pulse

1979-01-01

14

Iodine determination in milk by isotope dilution analysis  

Microsoft Academic Search

Iodine is an essential trace element in the human diet. It is utilized in the synthesis of L-monoiodothyrosine, which is a\\u000a precursor of the thyroid hormones, thyroxin and triiodothyronin. In this study, a method that can determine iodine concentrations\\u000a in milk has been developed. The method is based on substoichiometric isotope dilution analysis (IDA). Iodine concentrations\\u000a were measured in milk,

P. Ünak; F. Yurt Lambrecht; F. Z. Biber; S. Teksoz; P. Eri?kin; N. Kansu

2004-01-01

15

Tungsten isotope ratio determinations by negative thermal ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

A precise determination of the isotopic abundances of tungsten with natural isotopic composition is presented. WO-3 ions are generated by negative thermal ionization (NTI) in a double-filament ion source. La2O3 is used as a chemical substance to reduce the electron work function of the rhenium filament material. An ionization efficiency of 1% is obtained for sample loadings of 100 ng. The isotopic abundances are measured with relative standard deviations of 0.2% for the least abundant 180W isotope and 0.02-0.004% for the other tungsten isotopes. These improved isotopic data are used to recalculate the atomic weight of tungsten as 183.8417 ± 0.0001. The new NTI technique is an ideal tool for the application of isotope dilution mass spectrometry to analyse tungsten traces and for the measurement of isotopic shifts of this element in meteorites produced by the decay of 182Hf.

Völkening, Joachim; Köppe, Manfred; Heumann, Klaus G.

1991-07-01

16

Trace determination of zinc by substoichiometric isotope dilution analysis  

SciTech Connect

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

Sandhya, D.; Priya, S.; Subramanian, M.O.S. [Indian Institute of Technology, Madras (India)

1996-09-01

17

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

18

Thermal diffusion in dilute nanofluids investigated by photothermal interferometry  

NASA Astrophysics Data System (ADS)

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

Philip, J.; Nisha, M. R.

2010-03-01

19

Accurate determination of 87Rb\\/ 86Sr and 147Sm\\/ 144Nd ratios by inductively-coupled-plasma mass spectrometry in isotope geoscience: an alternative to isotope dilution analysis  

Microsoft Academic Search

The precise determination of 87Rb\\/86Sr and 147Sm\\/144Nd ratios in rocks and minerals is essential for isotope geology and geochronology. These determinations usually involve isotope dilution analysis, which requires the use of expensive isotopic spikes, consumes a significant fraction of precious thermal ionization mass spectrometer working time and, due to the repeated measurement of Rb isotopes, causes the performance of the

Pilar Montero; Fernando Bea

1998-01-01

20

The optimal amount of isotopic spike solution for ultratrace analysis by isotope dilution mass spectrometry  

Microsoft Academic Search

Inductively coupled plasma mass spectrometry (ICP-MS) and high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS)\\u000a are powerful methods of determining metallic impurities in the low- and sub-ppt level in process media such as ultra-pure\\u000a water used in semiconductor and wafer manufacturing. By using mass spectrometers for analysis, an isotope dilution analysis\\u000a (IDMS) is possible. The reproducibility of an IDMS is

R. Hoelzl; Christian Hoelzl; Ludwig Kotz; Lazlo Fabry

1998-01-01

21

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.

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

2012-04-01

22

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.

Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

2012-01-01

23

Quantitative determination of oxidative base damage in DNA by stable isotope-dilution mass spectrometry.  

PubMed

For understanding of the role of oxidative DNA damage in biological processes such as mutagenesis and carcinogenesis, it is essential to identify and quantify this type of DNA damage in cells. This can be achieved by gas chromatography/mass spectrometry. The present study describes the quantification of modified bases in DNA by isotope-dilution mass spectrometry with the use of stable isotope-labeled analogues as internal standards. A number of isotopically labeled DNA bases were synthesized. The mass spectra of their trimethylsilyl derivatives were recorded. Calibration plots were obtained for known quantities of modified bases and their isotope-labeled analogues. Quantification of various modified DNA bases by isotope-dilution mass spectrometry was demonstrated in isolated chromatin exposed to ionizing radiation. The results indicate that gas chromatography/stable isotope-dilution mass spectrometry is an ideally suited technique for selective and sensitive quantification of modified bases in DNA. PMID:8416801

Dizdaroglu, M

1993-01-01

24

Determination of dissolved selenium species in environmental water samples using isotope dilution mass spectrometry.  

PubMed

In order to clarify the species composition of selenium in environmental water samples, analytical methods have been developed for the selective determination of different chemical forms of this element (selenite, selenate, and organic species including trimethylselenonium) using isotope dilution mass spectrometry (IDMS). The species analysis was made possible by means of chromatographic separation procedures and an 82Se-enriched selenate, selenite, and trimethylselenonium spike for the isotope dilution process. The total selenium concentration was determined after decomposition of organic compounds with a HNO3/HCIO4 mixture. Selenium was measured in the mass spectrometer by producing negative Se- thermal ions for detection. Precise determination at the parts-per-trillion level was achieved. This new methodology was applied to different types of natural water samples (groundwater, pond water, river water, moorland lake water) with total selenium concentrations in the range of 200 pg/g to 15 ng/g. Selenite and selenate have been the only detected species in most of the investigated samples, with selenate dominating all except one. In samples with high contents of dissolved organic carbon, however, different organoselenium compounds including trimethylselenonium ions were additionally quantified in the range of 10-95 pg/g. In these cases, the sum of all selenium species agreed well with the independently determined total element concentration. PMID:1750700

Tanzer, D; Heumann, K G

1991-09-15

25

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

26

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

27

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; Kühn, H; Hedberg, M; Aregbe, Y

2012-08-23

28

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 (0.2315±0.0008) and IAEA-443 (0.2325±0.0008) are in good agreement with the IAEA information value (0.229±0.006), 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

2012-02-24

29

Determination of Cyanide in Blood by Isotope Dilution Gas Chromatography-Mass Spectrometry  

Microsoft Academic Search

Background: Cyanide (CN) is a lethal toxin. Quantifi- cation in blood is necessary to indicate exposure from many sources, including food, combustion byproducts, and terrorist activity. We describe an automated proce- dure based on isotope-dilution gas chromatography- mass spectrometry (ID GC\\/MS) for the accurate and rapid determination of CN in whole blood. Methods: A known amount of isotopically labeled po-

Karen E. Murphy; Michele M. Schantz; Therese A. Butler; Bruce A. Benner; Laura J. Wood; Gregory C. Turk

30

Entropy production and thermal conductivity of a dilute gas  

NASA Astrophysics Data System (ADS)

It is known that the thermal conductivity of a dilute gas can be derived by using kinetic theory. We present here a new derivation by starting with two known entropy production principles: the steepest entropy ascent (SEA) principle and the maximum entropy production (MEP) principle. A remarkable feature of the new derivation is that it does not require the specification of the existence of the temperature gradient. The known result is reproduced in a similar form.

Zhang, Yong-Jun

2011-05-01

31

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

32

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

SciTech Connect

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

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

2001-04-01

33

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, Zoltán

2008-11-28

34

Abut sound science, stable isotope dilution, blasphemy and heresy.  

PubMed

The molar ratio between an analyte and its equal labeled with stable isotope(s), used as a bioanalytical IS, is here suggested as an essential (and currently not commonly applied) validation parameter. This parameter, when calculated and measured, gives the possibility for the bioanalyst to compare calibration graphs and QC samples over time independently of added amount of IS. Additionally, when QC samples and calibration samples do not agree it is obvious to identify where the discrepancies are. Whether calibration samples are needed when this parameter is extensively and carefully validated and understood, is also discussed. PMID:23937136

Svensson, Leif D

2013-08-01

35

Mercury speciation analysis in seafood by species-specific isotope dilution: method validation and occurrence data  

Microsoft Academic Search

Methylmercury (MeHg) and total mercury (THg) in seafood were determined using species-specific isotope dilution analysis and\\u000a gas chromatography combined with inductively coupled plasma mass spectrometry. Sample preparation methods (extraction and\\u000a derivation step) were evaluated on certified reference materials using isotopically enriched Hg species. Solid–liquid extraction,\\u000a derivation by propylation and automated agitation gave excellent accuracy and precision results. Satisfactory figures of

Stéphanie Clémens; Mathilde Monperrus; Olivier F. X. Donard; David Amouroux; Thierry Guérin

36

INVESTIGATIONS OF THE POTASSIUM-ARGON METHOD OF AGE DETERMINATION USING SOLID ISOTOPIC DILUTION AND GAS REMOVAL BY CRUSHING  

Microsoft Academic Search

Preliminary work on a new technique of isotopic dilution analysis useful ; in the measurement of radiogenic Ar content of rocks or mineral samples in age ; determination is reported. Argon-38 is added to the sampies as the diluting ; isotope dissolved in a solid glassy silicate which approximates the pertinent ; properties of the sample. Crushing as well as

Naughton

1961-01-01

37

Putting a spin on LA-ICP-MS analysis combined to isotope dilution.  

PubMed

The determination of Zn, Sr, Ba, and Pb in solid samples has been achieved by laser ablation inductively coupled plasma isotope dilution mass spectrometry using a spinning platform. The fast rotation of a sample and an isotopically enriched spike placed close together on a sample holder allowed performing the isotope dilution directly inside the ablation cell. The proportion of spike versus sample of the aerosol mixture obtained has been determined online by isotope dilution in order to correct for differences in ablation rate although both materials were placed on the axis of rotation of the motor. Homogeneous, time-stable, and reusable samples were prepared by lithium borate fusion. A unique isotopically enriched spike glass was used to analyze four Standard Reference Materials of different matrix (after a simple polishing): two sediments Standard Reference Material (SRM) 1944 and SRM 2702 and two soils SRM 2586 and SRM 2711a. The proposed method yielded mass fractions with a deviation from the certified value usually lower than 12% and a precision of less than 9% RSD (except for Zn in SRM 2586 and 2711a). Although direct spiking of the solid before fusion could presumably provide better isotopic mixing, the presented methodology allows the reuse of the spike glass (thus, decreasing drastically the cost of the analysis) and is relatively faster because the spike does not need to be weighted, added, and evaporated each time. These results demonstrate the potential of this newly developed method for fast analysis of solid samples using isotope dilution at a low cost. PMID:23307123

Claverie, Fanny; Malherbe, Julien; Bier, Naomi; Molloy, John L; Long, Stephen E

2013-01-11

38

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

ERIC Educational Resources Information Center

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

Williams, Kathryn R.; Lipford, Levin C.

1985-01-01

39

Isotope Dilution and Sampling Factors of the Quality Assurance and TQM of Environmental Analysis  

Microsoft Academic Search

Sampling and preparatory treatment of environmental objects is discussed from the view of their information content, functional speciation of the pollutant, statistical distribution treatment and uncertainty assessment. During homogenization of large samples, a substantial information may be lost and validity of environmental information becomes vague. Isotope dilution analysis (IDA) is discussed as the most valuable tool for both validity of

M. Macášek

2000-01-01

40

Substoichiometric determination of heavy rare earths by isotopic dilution analysis.  

PubMed

A substoichiometric method for the determination of heavy rare earths (holmium, thulium) has been developed. After the addition of a substoichiometric amount of EDTA to the test sample of rare earth labelled with its radioactive isotopes, the negatively charged complex formed was separated by passage through a column of Dowex 50 x 8. Interfering metals can be removed by preliminary cupferron and diethylammonium diethyldithiocarbamate extraction. Concentrations of rare earth down to 4 x 10(-7)g 5 ml have been determined. PMID:18960041

Prásilová, J

1966-11-01

41

Development of isotope dilution gamma-ray spectrometry for plutonium analysis  

SciTech Connect

We are studying the feasibility of determining the plutonium concentration and isotopic distribution of highly radioactive, spent-fuel dissolver solutions by employing high-resolution gamma-ray spectrometry. The study involves gamma-ray plutonium isotopic analysis for both dissolver and spiked dissolver solution samples, after plutonium is eluted through an ion-exchange column and absorbed in a small resin bead bag. The spike is well characterized, dry plutonium containing {approximately}98% of {sup 239}Pu. By using measured isotopic information, the concentration of elemental plutonium in the dissolver solution can be determined. Both the plutonium concentration and the isotopic composition of the dissolver solution obtained from this study agree well with values obtained by traditional isotope dilution mass spectrometry (IDMS). Because it is rapid, easy to operate and maintain, and costs less, this new technique could be an alternative method to IDMS for input accountability and verification measurements in reprocessing plants. 7 refs., 4 figs., 4 tabs.

Li, T.K.; Parker, J.L. (Los Alamos National Lab., NM (United States)); Kuno, Y.; Sato, S.; Kurosawa, A.; Akiyama, T. (Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan))

1991-01-01

42

Application of isotopically labeled methylmercury for isotope dilution analysis of biological samples using gas chromatography/ICPMS.  

PubMed

An isotope dilution (ID) procedure for the determination of methylmercury (MMHg) in biological samples using an inductively coupled plasma mass spectrometer as detector after the capillary gas chromatographic separation (CGC/ICPMS) has been developed. For the first time, open-focused-microwave pretreatment has been used in conjunction with ID. Optimum conditions for the measurement of isotope ratios on the fast transient chromatographic peaks have been established. Mass bias was found to be about 1.5%/mass unit and was corrected by using the simultaneously measured thallium signals at 203Tl and 205Tl. After mass-bias correction, deviation of the theoretical mercury ratio values was found to be as low as 0.2%. Isotope ratio precisions based on the peak areas measurements were 0.3% RSD for 20 pg injected (as Hg absolute). The absolute detection limits were in the range of 20-30 fg for 202Hg and 201Hg. Methylmercury enriched in 201Hg has been synthesized by direct reaction with methylcobalamine. The concentration of the MMHg spike has been measured by reverse isotope dilution with a natural MMHg standard. The capabilities of CGC/ICPMS to measure isotope ratios were used to optimize sample derivatization by aqueous ethylation with NaBEt4 with respect to MMHg degradation pathways and quantitative recovery. The accuracy of the method developed has been validated with biological certified reference materials (CRM-463, DORM-1). PMID:12069230

Rodriguez Martín-Doimeadios, R C; Krupp, E; Amouroux, D; Donard, O F X

2002-06-01

43

Thermal conductivity of liquid-neon isotopes  

Microsoft Academic Search

The thermal conductivity of liquefied20Ne and22Ne isotopes was determined on the boiling line between 25 and 29 K using the plate method. A linear dependence on temperature could be observed. In a diagram of the reduced thermal conductivity ?* as function of the reduced temperatureT* the values are compared with those of the heavier rare gases, and in the case

L. Bewilogua; T. Yoshimura

1972-01-01

44

Thermal conductivity of isotopically modified graphene.  

PubMed

In addition to its exotic electronic properties graphene exhibits unusually high intrinsic thermal conductivity. The physics of phonons--the main heat carriers in graphene--has been shown to be substantially different in two-dimensional (2D) crystals, such as graphene, from in three-dimensional (3D) graphite. Here, we report our experimental study of the isotope effects on the thermal properties of graphene. Isotopically modified graphene containing various percentages of 13C were synthesized by chemical vapour deposition (CVD). The regions of different isotopic compositions were parts of the same graphene sheet to ensure uniformity in material parameters. The thermal conductivity, K, of isotopically pure 12C (0.01% 13C) graphene determined by the optothermal Raman technique, was higher than 4,000?W?mK(-1) at the measured temperature T(m)~320?K, and more than a factor of two higher than the value of K in graphene sheets composed of a 50:50 mixture of 12C and 13C. The experimental data agree well with our molecular dynamics (MD) simulations, corrected for the long-wavelength phonon contributions by means of the Klemens model. The experimental results are expected to stimulate further studies aimed at a better understanding of thermal phenomena in 2D crystals. PMID:22231598

Chen, Shanshan; Wu, Qingzhi; Mishra, Columbia; Kang, Junyong; Zhang, Hengji; Cho, Kyeongjae; Cai, Weiwei; Balandin, Alexander A; Ruoff, Rodney S

2012-01-10

45

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

PubMed

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

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

2013-06-04

46

Isotope dilution GC\\/MS determination of anandamide and other fatty acylethanolamides in rat blood plasma  

Microsoft Academic Search

Anandamide and allied fatty acylethanolamides (AEs) may act as signalling molecules in brain and peripheral tissues. In the present study, we describe an electron-impact gas chromatography\\/mass spectrometry (GC\\/MS) method based on isotope dilution, which may be used for the identification and quantification of anandamide and other AEs in biological matrices. The calibration curves for standard AEs were linear over the

Andrea Giuffrida; Daniele Piomelli

1998-01-01

47

Coprecipitation as a means of separation in substoichiometric isotope dilution analysis  

Microsoft Academic Search

Coprecipitation is proposed as a means of obtaining the necessary separation in substoichiometric isotope dilution analysis.\\u000a It is shown with examples that by applying coprecipitation for separation and by using complexometric and oxidimetric or reductometric\\u000a reactions as the substoichiometric reaction, a wide field of complexometric determinations of metal ions (e.g., with EDTA)\\u000a and many types of redox determinations open up

H. L. Polak

1971-01-01

48

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. Çoker

1999-01-01

49

Determination of iodide in common salts consumed in Turkey by isotope dilution analysis  

Microsoft Academic Search

Iodide traces in common salts consumed in Turkey have been determined by isotope dilution analysis. Iodide was precipitated\\u000a by stoichiometric amount of AgNO3. Iodide-131 was used as tracer. Electrophoresis was performed to separate Ag131I from excess131I?. Zone of Ag131I was cut off electrophoresis paper and counted with a NaI(Tl) scintillation counter. Count rates were plotted versus added\\u000a KI concentrations. Unknown

Z. Biber; H. Özakay; P. Ünak; F. Yurt

1999-01-01

50

Iodine measurements by isotope dilution analysis in drinking water in Western Turkey  

Microsoft Academic Search

This study was designed to evaluate iodine concentrations in drinking water samples using isotope dilution analysis (IDA)\\u000a in the Aegean region of Turkey A total of 76 drinking water samples from rural and urban areas in regional cities were analyzed.\\u000a The mean iodine concentration was 78±27 ?g\\/l and iodine concentration ranges were within 69±26 ?g\\/l and 103±6 ?g\\/l.

P. Ünak; F. Yurt Lambrecht; F. Z. Biber; S. Darcan

2007-01-01

51

Determination of butyltin compounds in environmental samples by isotope-dilution GC-ICP-MS.  

PubMed

Isotope-dilution analysis in combination with GC-ICP-MS detection has been applied to the determination of butyltin species in environmental samples. Different spikes containing the isotopically labeled butyltin species have been synthesized in the laboratory after optimization of the reaction conditions. The isotopic compositions of the tin species in the different spike solutions were determined by GC-ICP-MS after derivatization by aqueous ethylation with sodium tetraethylborate. Reverse isotope-dilution analysis was used for quantitation of the spike solutions by means of natural MBT, DBT, and TBT standards. The mixed spikes were used for simultaneous analysis of MBT, DBT and TBT in the certified reference materials, PACS-2, CRM 462, and CRM 646, with satisfactory results. The excellent agreement of the different speciation results obtained by use of the different spikes is a good indicator of the precision, accuracy, and reliability which can be achieved by using isotope-dilution analysis for trace metal speciation. Application of a double spike containing (119)Sn-enriched MBT (79.7 At%), (118)Sn-enriched DBT (86.7 At%), and (119)Sn-enriched TBT (83.1 At%) also enabled evaluation of the conditions resulting in quantitative extraction of the species from the solid matrix, in combination with possible alterations depending on the different extraction procedures used (mechanical shaking, ultrasounds, and microwaves). Mathematical equations used for this purpose computed the correct species concentrations directly and, additionally, the decomposition factors (from TBT to DBT and from DBT to MBT) after precise measurement of the (119)Sn/(120)Sn and (118)Sn/(120)Sn ratios for all butyltin species by GC-ICP-MS. PMID:12172678

Alonso, J Ignacio García; Encinar, Jorge Ruiz; González, Pablo Rodríguez; Sanz-Medel, Alfredo

2002-04-27

52

New method of determining very slight traces of nitrogen peroxide (NOâ) in polluted atmospheres, by isotope dilution and mass spectrometry  

Microsoft Academic Search

The authors propose a new method of determining nitrogen peroxide ; (NOâ) in the atmosphere or the stratosphere at very low concentrations, of ; the order of pp10⁹ by volume or even less. This method employs isotopic ; dilution with ¹⁵NOâ followed by conversion into Nâ and isotopic ; analysis by mass spectrometry. It consists of mixing homogeneously a known

C. M. Stevens; F. Barat; H. Nguyen-Nghi

1975-01-01

53

Plutonium and americium determination in mosses by laser ablation ICP-MS combined with isotope dilution technique  

Microsoft Academic Search

Environmental contamination by artificial radionuclides and the evaluation of their sources requires precise isotopic analysis and accurate determination of transuranium elements, above all plutonium and americium. This can be achieved by alpha spectrometry or by inductively coupled plasma mass spectrometry (ICP-MS) after chemical separation of actinides. In the present work, laser ablation (LA) ICP-MS was combined with isotope dilution for

Sergei F. Boulyga; Donatella Desideri; Maria Assunta Meli; Corrado Testa; J. Sabine Becker

2003-01-01

54

Isotope dilution SPME GC/MS for the determination of methylmercury in tuna fish samples.  

PubMed

The development of a rapid, precise and accurate analytical method for the determination of methylmercury in tuna fish samples is described. The method is based on the use of isotope dilution GC/MS with electron impact ionization, a widespread technique in routine testing laboratories. A certified spike containing (202)Hg-enriched methylmercury was used for the isotope dilution of the samples. After extraction of the methylmercury from the sample, methylmercury was propylated using sodium tetrapropyl borate in SPME vials and the analytes were sampled from the headspace for 15 min. For isotope measurements, the molecular ion (MePrHg(+)) was used in the SIM mode. Five molecular ions were monitored, corresponding to the (198)Hg, (199)Hg, (200)Hg, (201)Hg and (202)Hg isotopes. The detection at masses corresponding to (198)Hg was used to correct for m + 1 contributions of (13)C from the organic groups attached to the mercury atom on the (199)Hg, (200)Hg, (201)Hg and (202)Hg masses with simple mathematical equations, and the concentration of methylmercury was calculated on the basis of the corrected (200)Hg/(202)Hg isotope ratio. The (202)Hg-enriched methylmercury spike was applied, with satisfactory results, to the determination of methylmercury in the certified reference material BCR 464. The method was successfully applied to the determination of methylmercury in tuna fish samples, and the obtained results were included in the CCQM-P39 interlaboratory exercise, organized by the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) with excellent agreement between our results and the average obtained by the other participants. PMID:16287033

Centineo, Giuseppe; Blanco González, Elisa; García Alonso, J Ignacio; Sanz-Medel, Alfredo

2006-01-01

55

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

56

Candidate reference method: Determination of valproic acid in serum by isotope-dilution mass spectrometry  

Microsoft Academic Search

Summary  A method has been developed for the determination of valproic acid, without derivatization, in human serum by isotope-dilution\\u000a mass spectrometry using labelled 2-propyl[3,3,3-d3] valeric[5,5,5-d3] acid as internal standard for accurate quantification of the concentration of valproic acid in the sample. After acidification,\\u000a the analyte and internal standard are extracted withn-hexane. The amounts of valproic acid in the serum are calculated

F. Susanto; H. Reinauer

1995-01-01

57

Candidate reference method: Determination of valproic acid in serum by isotope-dilution mass spectrometry  

Microsoft Academic Search

Summary  A method has been developed for the determination of valproic acid, without derivatization, in human serum by isotope-dilution\\u000a mass spectrometry using labelled 2-propyl[3,3,3-d3]valeric[5,5,5-d3] acid as internal standard for accurate quantification of the concentration of valproic acid in the sample. After acidification,\\u000a the analyte and internal standard are extracted withn-hexane. The amounts of valproic acid in the serum are calculated from

F. Susanto; H. Reinauer

1995-01-01

58

Reference Soret coefficients of natural isotopes and diluted alloys of tin  

NASA Astrophysics Data System (ADS)

Measurements of Soret coefficients of tin alloys have been performed in the MFA-067 experiment of the automatic retrievable satellite EURECA. They complete the set of measurements performed in tin dilute alloys in microgravity manned laboratories. They allow also for an accurate determination of the isotopic thermomigration and for a better evaluation of the accuracy of microgravity measurements of the thermodiffusion factors. These data are compared to nonequilibrium condensed matter theories. A reasonable agreement has been obtained with the revised Enskog theory, and no electronic contribution could be identified.

van Vaerenbergh, S.; Garandet, J. P.; Praizey, J. P.; Legros, J. C.

1998-08-01

59

Measurement equations for the determination of the Si molar mass by isotope dilution mass spectrometry  

NASA Astrophysics Data System (ADS)

A new method applying isotope dilution mass spectrometry to determine the molar mass of a silicon sample, highly enriched with respect to 28Si, has been proposed recently. This paper describes a different way of calculating the molar mass by solving an equation linking the measurement results to the ratio between the amount-of-substance fractions of 28Si and 30Si in the sample. The mathematical model and the final measurement equation are much more straightforward than those previously reported, though fully equivalent.

Mana, G.; Rienitz, O.; Pramann, A.

2010-08-01

60

An isotope dilution model for partitioning leucine uptake by the liver of the lactating dairy cow.  

PubMed

An isotope dilution model for partitioning leucine uptake by the liver of the lactating dairy cow is constructed and solved in the steady state. If assumptions ae made, model solution permits calculation of the rate of leucine uptake from portal and hepatic arterial blood supply, leucine export into the hepatic vein, leucine oxidation and transamination, and synthesis and degradation of hepatic constitutive and export proteins. The model requires the measurement of plasma flow rate through the liver in combination with leucine concentrations and plateau isotopic enrichments in arterial, portal and hepatic plasma during a constant infusion of [1-13C]leucine tracer. The model can be applied to other amino acids with similar metabolic fates and will provide a means for assessing the impact of hepatic metabolism on amino acid availability to peripheral tissues. This is of particular importance when considering the dairy cow and the requirements of the mammary gland for milk protein synthesis. PMID:10329119

France, J; Hanigan, M D; Reynolds, C K; Dijkstra, J; Crompton, L A; Maas, J A; Bequette, B J; Metcalf, J A; Lobley, G E; MacRae, J C; Beever, D E

1999-05-01

61

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

62

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, 25–38 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.

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

2013-01-01

63

Discovery and validation of colonic tumor-associated proteins via metabolic labeling and stable isotopic dilution  

PubMed Central

The unique biology of a neoplasm is reflected by its distinct molecular profile compared with normal tissue. To understand tumor development better, we have undertaken a quantitative proteomic search for abnormally expressed proteins in colonic tumors from ApcMin/+ (Min) mice. By raising pairs of Min and wild-type mice on diets derived from natural-abundance or 15N-labeled algae, we used metabolic labeling to compare protein levels in colonic tumor versus normal tissue. Because metabolic labeling allows internal control throughout sample preparation and analysis, technical error is minimized as compared with in vitro labeling. Several proteins displayed altered expression, and a subset was validated via stable isotopic dilution using synthetic peptide standards. We also compared gene and protein expression among tumor and nontumor tissue, revealing limited correlation. This divergence was especially pronounced for species showing biological change, highlighting the complementary perspectives provided by transcriptomics and proteomics. Our work demonstrates the power of metabolic labeling combined with stable isotopic dilution as an integrated strategy for the identification and validation of differentially expressed proteins using rodent models of human disease.

Huttlin, Edward L.; Chen, Xiaodi; Barrett-Wilt, Gregory A.; Hegeman, Adrian D.; Halberg, Richard B.; Harms, Amy C.; Newton, Michael A.; Dove, William F.; Sussman, Michael R.

2009-01-01

64

Thermal properties of dilute (La, Ce)Al 2 alloys  

Microsoft Academic Search

We report on measurements of the specific heat and transport properties (resistivity, heat conductivity and thermopower) of dilute (La1-xCex)Al2 alloys withx?0.04 between 0.3 and 10 K. The specific heat experiments were extended to a magnetic field of 47 kØe; the transport measurements were performed on single crystals. For Ce concentrations less than 0.5 a\\/o Kondo type single impurity behavior was

Frank Steglich

1976-01-01

65

Simultaneous determination of mono-, di-, and tributyltin in sediments by isotope dilution analysis using gas chromatography--ICPMS.  

PubMed

A mixed spike containing 119Sn-enriched monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) was prepared by direct butylation of 119Sn-enriched tin metal using a 1:3 molar excess of butyl chloride with iodide and triethylamine as catalysts. The isotopic composition of the different tin species in the spike solution was determined by gas chromatography- ICPMS after aqueous ethylation using sodium tetraethylborate. Reverse isotope dilution analysis was used for the characterization of the spike by means of natural MBT, DBT, and TBT standards. No species transformation was evident during derivatization from the reverse isotope dilution experiments based on the measured isotope ratios both before and after spiking. The mixed spike was applied to the simultaneous analysis of MBT, DBT, and TBT in certified reference materials, PACS-2 and CRM 646, with satisfactory results. PMID:11467570

Encinar, J R; Villar, M I; Santamaría, V G; Alonso, J I; Sanz-Medel, A

2001-07-01

66

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

Microsoft Academic Search

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

Sergei F. Boulyga; Klaus G. Heumann

2005-01-01

67

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

Microsoft Academic Search

Laser ablation inductively coupled plasma isotope dilution mass spectrometry (LA-ICP-IDMS) with a special laser ablation system for bulk analyses (LINA-Spark™-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

Sergei F. Boulyga; Klaus G. Heumann

2005-01-01

68

Application of stable isotopes in environmental tracer studies – Measurement of monomethylmercury (CH3Hg+) by isotope dilution ICP-MS and detection of species transformation  

Microsoft Academic Search

The monovalent cation monomethylmercury (CH3Hg+) was determined in certified reference materials by isotope dilution GC\\/ICP-MS and good agreement between measured and certified\\u000a values has been found. The use of enriched stable isotopes with subsequent detection by ICP-MS is a powerful tracer technique\\u000a to study dynamic environmental processes. For the first time, it was possible to monitor opposite processes like Hg2+

H. Hintelmann; R. D. Evans

1997-01-01

69

Assay of tyrosol and hydroxytyrosol in olive oil by tandem mass spectrometry and isotope dilution method.  

PubMed

Hydroxytyrosol and tyrosol, the strong antioxidant present in large amount in virgin olive oil have been assayed by LC-MS/MS under MRM condition and isotope dilution method, using d(2)-labelled internal standards obtained by simple synthetic procedures. The assay has been performed under MRM condition monitoring two transitions for each analyte to improve the specificity. This paper deals with a modern approach for assaying the content of this polyphenols in virgin olive oil down to a limit of a few hundreds of parts per billion. Tyrosol and hydroxytyrosol ranged from 10 to 47ppm and from 5 to 25ppm in commercial olive oil, respectively. The accuracy (98-107%) and analytical parameters values confirm the reliability of the proposed approach. The method can be extended to any natural matrices, including mill wastes, after a simple step of sample preparation. PMID:22953817

Mazzotti, Fabio; Benabdelkamel, Hicham; Di Donna, Leonardo; Maiuolo, Loredana; Napoli, Anna; Sindona, Giovanni

2012-05-31

70

Three-dimensional infrared spectroscopy of isotope-diluted ice Ih  

NASA Astrophysics Data System (ADS)

Using three-dimensional infrared (3D-IR) spectroscopy, we investigate the vibrational dynamics of isotope-diluted ice Ih. By probing the OD stretch mode of HOD in H2O, we observe an extremely rapid decay (~200 fs) of the population from the second vibrational excited state. Quantum simulations based on a two-dimensional Lippincott-Schroeder potential agree nearly quantitatively with the experimental 3D-IR lineshapes and dynamics. The model suggests that energy dissipation is enhanced due to nonadiabatic effects between vibrational states, which arise from strong mode-mixing between the OD stretch mode with lattice degrees of freedom. Furthermore, we compare the simulation results to ab initio based potentials, in which the hydrogen bond anharmonicity is too small to reproduce the experimental 3D-IR spectra. We thus conclude that the Lippincott-Schroeder potential effectively coalesces many degrees of freedom of the crystal into one intermolecular coordinate.

Perakis, Fivos; Borek, Joanna A.; Hamm, Peter

2013-07-01

71

Three-dimensional infrared spectroscopy of isotope-diluted ice Ih.  

PubMed

Using three-dimensional infrared (3D-IR) spectroscopy, we investigate the vibrational dynamics of isotope-diluted ice Ih. By probing the OD stretch mode of HOD in H2O, we observe an extremely rapid decay (?200 fs) of the population from the second vibrational excited state. Quantum simulations based on a two-dimensional Lippincott-Schroeder potential agree nearly quantitatively with the experimental 3D-IR lineshapes and dynamics. The model suggests that energy dissipation is enhanced due to nonadiabatic effects between vibrational states, which arise from strong mode-mixing between the OD stretch mode with lattice degrees of freedom. Furthermore, we compare the simulation results to ab initio based potentials, in which the hydrogen bond anharmonicity is too small to reproduce the experimental 3D-IR spectra. We thus conclude that the Lippincott-Schroeder potential effectively coalesces many degrees of freedom of the crystal into one intermolecular coordinate. PMID:23822308

Perakis, Fivos; Borek, Joanna A; Hamm, Peter

2013-07-01

72

Quantification of the mycotoxin patulin by a stable isotope dilution assay.  

PubMed

Two stable isotope dilution assays for the quantification of patulin [4-hydroxy-4H-furo[3,2-c]pyran-2(6H)-one] in foods were developed using (13)C-labeled patulin as the internal standard. One method was performed by means of LC/MS in negative electrospray ionization mode without derivatization; the other used HRGC/HRMS after trimethylsilylation of the patulin isotopomers. In comparison with previously reported methods based on high-performance liquid chromatography with UV detection, HRGC/HRMS of the derivatized samples showed better repeatability, higher recovery rates (96% at a spike level of 200 ng/L), and a 100 times lower detection limit (12 ng/L). In contrast, LC/MS showed a much lower performance as compared to HPLC/UV or HRGC/HRMS. Using HRGC/HRMS, the mycotoxin was quantified in many different fruit products and in molded wheat bread. PMID:10552717

Rychlik, M; Schieberle, P

1999-09-01

73

Comparison of two isotope dilution/mass spectrometric methods for determination of total serum cholesterol  

SciTech Connect

Isotope dilution/mass spectrometric methods for total serum cholesterol, developed separately at the Karolinska Institutet (KI) and the National Bureau of Standards (NBS), were compared by applying them to a common set of serum pools. A search for the cause of a systematic difference of a few percent in results from the two methods revealed that the KI cholesterol standard contained lathosterol, which interfered with the calibration of the method. With NBS Standard Reference Material cholesterol used for new analyses at the KI, the average difference in mean values dropped to 0.2%. The NBS results are more precise. This is attributed to the protocols NBS used for sample preparation and mass spectrometry. However, these protocols make the NBS method more complex and time-consuming. A recent critical article on the use of this technique for total cholesterol is also examined.

Schaffer, R.; Sniegoski, L.T.; Welch, M.J.; White, V.E.; Cohen, A.; Hertz, H.S.; Mandel, J.; Paule, R.C.; Svensson, L.; Bjoerkhem, I.; Blomstrand, R.

1982-01-01

74

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

SciTech Connect

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

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

1981-04-24

75

Determination of tenuazonic acid in human urine by means of a stable isotope dilution assay.  

PubMed

The content of tenuazonic acid in human urine was determined by a stable isotope dilution assay (SIDA) that was recently developed for the analysis of food commodities and extensively re-validated for urine matrix in this study. Linearity of the response curve was proven between molar ratios n(labeled standard)/n(analyte) of 0.02-100. The limits of detection and determination were 0.2 and 0.6 ?g/L, respectively. The mean recovery of the stable isotope dilution assay was 102 ± 3 % in the range between 1.0 and 100 ?g/L. Interassay precision was 6.7 % (relative standard deviation of three triplicate analyses of a human urine sample during 3 weeks). The method was applied to two studies dealing with urinary excretion of tenuazonic acid: In the first study, tenuazonic acid was quantified in the 24-h urine of six volunteers from Germany (three female, three male) in a concentration range of 1.3-17.3 ?g/L or 2.3-10.3 ng/mg(-1) creatinine, respectively. In the second study, two volunteers (one female, one male) ingested 30 ?g tenuazonic acid by consumption of naturally contaminated whole meal sorghum infant cereals and tomato juice, respectively. The urinary excretion of the ingested tenuazonic acid was 54-81 % after 6 h, depending on matrix and volunteer. After 24 h, 87-93 % of the ingested amount of tenuazonic acid was excreted, but the fate of the remaining about 10 % is open. Thus, it is not possible to exclude potential health hazards for the consumer, completely. PMID:23397093

Asam, Stefan; Habler, Katharina; Rychlik, Michael

2013-02-09

76

Determination of technetium-99 in aqueous samples by isotope dilution inductively coupled plasma-mass spectrometry  

SciTech Connect

An isotope dilution/inductively coupled plasma mass spectrometric method (ID/ICP-MS) for measuring the concentration of technetium-99 in aqueous samples was developed at the Savannah River Technology Center (SRTC). The procedure is faster than radiometric techniques, is also less subject to interferences, and has equal or better detection limits. It is currently being used to measure the concentration of {sup 99}Tc in samples of Savannah River water collected in the vicinity of the Savannah River Site. In this method, one liter samples of water are spiked with {sup 97}Tc. After equilibration, the technetium is extracted from the sample with a chromatographic resin. Interfering elements, molybdenum and ruthenium, are either not retained by the resin or are washed off with dilute nitric acid. The technetium is then eluted with more concentrated nitric acid, and the {sup 99}Tc/{sup 97}Tc ratio in the eluant is measured with an ICP-MS. The {sup 99}Tc concentration in the original sample is calculated from the {sup 99}Tc/{sup 97}Tc ratio. The chemical recovery of the extraction procedure is greater than 90%. The detection limit of the instrument, taken as three times the background counts at m/z = 99, is 0.6 part per trillion (ppt). The detection limit of the procedure, taken as three times the standard deviation of several reagent blank analyses, is 0.33 pCi/L.

Beals, D.M.

1992-09-01

77

Determination of technetium-99 in aqueous samples by isotope dilution inductively coupled plasma-mass spectrometry  

SciTech Connect

An isotope dilution/inductively coupled plasma mass spectrometric method (ID/ICP-MS) for measuring the concentration of technetium-99 in aqueous samples was developed at the Savannah River Technology Center (SRTC). The procedure is faster than radiometric techniques, is also less subject to interferences, and has equal or better detection limits. It is currently being used to measure the concentration of {sup 99}Tc in samples of Savannah River water collected in the vicinity of the Savannah River Site. In this method, one liter samples of water are spiked with {sup 97}Tc. After equilibration, the technetium is extracted from the sample with a chromatographic resin. Interfering elements, molybdenum and ruthenium, are either not retained by the resin or are washed off with dilute nitric acid. The technetium is then eluted with more concentrated nitric acid, and the {sup 99}Tc/{sup 97}Tc ratio in the eluant is measured with an ICP-MS. The {sup 99}Tc concentration in the original sample is calculated from the {sup 99}Tc/{sup 97}Tc ratio. The chemical recovery of the extraction procedure is greater than 90%. The detection limit of the instrument, taken as three times the background counts at m/z = 99, is 0.6 part per trillion (ppt). The detection limit of the procedure, taken as three times the standard deviation of several reagent blank analyses, is 0.33 pCi/L.

Beals, D.M.

1992-01-01

78

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

Microsoft Academic Search

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

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

1991-01-01

79

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...

80

The determination of dissolved zirconium and hafnium from seawater using isotope dilution inductively coupled plasma mass spectrometry  

Microsoft Academic Search

This paper describes the development of an analytical technique utilizing isotope dilution and inductively coupled plasma mass spectrometry (ICP\\/MS) to determine the picomolar and femtomolar concentrations of dissolved Zr and Hf found in seawater. Data acquired using this technique are presented to verify the method; in the subarctic North Pacific Zr ranges from 25 to 366 pmol\\/kg and Hf from

Brad A McKelvey; Kristin J Orians

1998-01-01

81

Method 1613: Tetra-Through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS.  

National Technical Information Service (NTIS)

Method 1613 was developed for isomer-specific determination of the 2,3,7,8-substituted, tetra- through octa-chlorinated, dibenzo-p-dioxin and dibenzofurans in aqueous, solid and tissue matrices by isotope dilution, high resolution capillary column gas chr...

1994-01-01

82

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

PubMed

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

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

2011-01-20

83

Lattice position and thermal stability of diluted As in Ge  

NASA Astrophysics Data System (ADS)

We present a lattice location study of the n-type dopant arsenic after ion implantation into germanium. By means of electron emission channeling experiments, we have observed that the implanted As atoms substitute the Ge host atoms and that, in contrast to several implanted metal impurities in Ge, no significant fraction of As is found on interstitial sites. The substitutional As impurities are found to be thermally stable up to 600 °C. After 700 °C annealing a strong reduction of emission channeling effects was observed, in full accordance with the expected diffusion-induced broadening of the As profile.

Decoster, S.; Wahl, U.; Cottenier, S.; Correia, J. G.; Mendonça, T.; Amorim, L. M.; Pereira, L. M. C.; Vantomme, A.

2012-03-01

84

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

PubMed

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

Fang, Mingchih; Cadwallader, Keith R

2013-04-09

85

Determination of hafnium in zirconium metal and zircaloy 4 metal Standard Reference Materials by isotope dilution spark source mass spectrometry  

SciTech Connect

A procedure has been developed for the determination of microgram per gram concentrations of hafnium in zirconium metal and zircaloy 4 metal Standard Reference Materials (SRM's) by stable isotope dilution spark source mass spectrometry. The concentration of hafnium in these SRM's ranges from 200 ..mu..g/g in SRM 1236 to 32 ..mu..g/g in SRM 1237. One-half-gram samples were spiked with /sup 179/Hf and dissolved in a mixture of hydrofluoric and sulfuric acids and the isotopically altered Hf was separated from Zr by cation exchange chromatography using 0.32 M sulfuric acid as an eluant. The isotopically altered, purified hafnium was evaporated onto 200 mesh gold powder which was subsequently homogenized and pressed into electrodes. The altered isotopic ratios were determined by spark source mass spectrometry using electrical detection. 8 references, 4 tables.

Powell, L.J.; Paulsen, P.J.

1984-03-01

86

Improved folate extraction and tracing deconjugation efficiency by dual label isotope dilution assays in foods.  

PubMed

A dual label stable isotope dilution assay was developed to trace the deconjugation efficiency of polyglutamic folate vitamers converted to their monoglutamic analogues. For this purpose, [(13)C(5)]-pteroylheptaglutamate was synthesized and added during extraction of foods as a tracer isotopologue along with [(2)H(4)]-5-methyltetrahydrofolate, [(2)H(4)]-5-formyltetrahydrofolate, [(2)H(4)]-tetrahydrofolate, [(2)H(4)]-10-formylfolate, and [(2)H(4)]-folic acid. The [(2)H(4)]-labeled folates were used as internal standards for the monoglutamates. Deconjugation converted the addition tracer [(13)C(5)]-pteroylheptaglutamate to the detection tracer [(13)C(5)]-folic acid, which was quantified along with unlabeled folic acid using [(2)H(4)]-folic acid as the internal standard. LC-MS/MS enabled the unequivocal differentiation of the three isotopologues. This tracing was used to optimize deconjugation efficiency, which was achieved by using 4-morpholineethanesulfonic acid buffer for extraction at pH 5.0 . The optimized assay revealed limits of detection for the folate vitamers ranging between 2.0 and 5.6 pmol per assay (equivalent to 2.2-6.6 ?g/100 g dry mass), recoveries ranging between 98 and 105% and relative standard deviations in inter-assay precision ranging between 2 and 6%. The assay was applied to quantitate folates in spinach, beans, cheeses, bread, wheat germs, and yeast . PMID:22235748

Mönch, Sabine; Rychlik, Michael

2012-02-07

87

Cadmium measurements in coral skeleton using isotope dilution-inductively coupled plasma-mass spectrometry  

NASA Astrophysics Data System (ADS)

Here a method for the precise analysis of Cd/Ca in coral skeleton using inductively coupled plasma-mass spectrometry (ICP-MS) is presented. Isotope dilution and gravimetric standards with internal standardization were used for Cd and Ca determination, respectively. Separation of alkaline earth metals from Cd using ion chromatography reduced the high total dissolved solids while maintaining a strong Cd signal. Repeated Cd/Ca measurements of a coral standard yielded a precision of ±2.2% (one standard deviation as a fraction of signal). Analyses of reference materials (BCR-1, BHVO-1, W-2, GSR-3, GSR-6, CACB-1, JCp-1, and JCt-1) fell within established ranges, with a precision comparable to other ICP-MS measurements. Advantages of this approach over existing methods for corals are as follows: (1) reduced introduction of high-concentration elements into the mass spectrometer, (2) sample requirements as low as 15 mg (i.e., ?1 pmol Cd/sample), and (3) determination of multiple element ratios on the same sample aliquot with a precision of ±7% or better.

Matthews, Kathryn A.; McDonough, William F.; Grottoli, AndréA. G.

2006-11-01

88

Measurement of 2-Carboxyarabinitol 1-Phosphate in Plant Leaves by Isotope Dilution 1  

PubMed Central

The level of 2-carboxyarabinitol 1-phosphate (CA1P) in leaves of 12 species was determined by an isotope dilution assay. 14C-labeled standard was synthesized from [2-14C]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 CO2 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, Brandon d.; Kobza, John; Seemann, Jeffrey R.

1991-01-01

89

[Determination of indicator toxaphene in soil by isotope dilution-gas chromatography-tandem mass spectrometry].  

PubMed

Although toxaphene is now banned in use, the analysis of toxaphene has attracted increasing interest due to its persistence and widespread atmospheric transport in the environment. A new method based on isotope dilution-gas chromatography-tandem mass spectrometry (ID-GC-MS/MS) has been developed for the determination of three toxaphene specific congeners comprised of Parlar No. 26 (P26), Parlar No. 50 (P50) and Parlar No. 62 (P62) in soil. (13)C10-labeled indicator toxaphene solution was added to the sample prior to pretreatment. Then the sample was extracted using pressurized liquid extraction (PLE) followed by purification on multilayer acidic silica column and neutral silica column. The eluent was concentrated under gentle nitrogen gas flow and spiked with the injection of internal standard of (13)C10-chlordane. Identification and quantification of the analytes were carried out in the multiple reaction monitoring (MRM) mode after the GC separation. The linear range was 20-800 microg/L for three congeners, limits of detection (LOD) ranged from 3.0 to 6.0 pg. The five point calibration curves showed a good linearity for all the congeners (R2 > 0.99). The relative standard deviations (RSDs) were below 11% for and the spiked recoveries were in the range of 55%-110%. The developed analytical method is suitable for the determination of toxaphene specific congeners in soil. PMID:20812620

Zhang, Bing; Wu, Jiajia; Liu, Guorui; Gao, Lirong; Zheng, Minghui

2010-05-01

90

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

PubMed

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

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

2010-05-01

91

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

92

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

93

Initial results from isotope dilution for Cl and 36Cl measurements at the PSI/ETH Zurich AMS facility  

NASA Astrophysics Data System (ADS)

The first results of our use of isotope dilution for determining total Cl and 36Cl in the same rock sample material are presented here. Tests with a dilution series of hypothetical rock Cl concentrations between 5 and 200 ppm verified that our accelerator set-up is appropriate for the low-energy side 37Cl/35Cl measurements. Results from limestone and dolomite samples from the Flims rockslide (Switzerland) indicate the extraction methods described here yield highly reproducible total Cl and 36Cl concentrations with excellent precision to very low values. Replicate measurements suggest that the rocks we are analyzing from the Flims rockslide are closed to uptake or loss of the isotopes of Cl. Present address: Geological Sciences, University of Michigan, Ann Arbor MI 48109, USA.

Ivy-Ochs, Susan; Synal, Hans-Arno; Roth, Christine; Schaller, Mirjam

2004-08-01

94

Thermal Neutron Capture Cross Sections of The Palladium Isotopes.  

National Technical Information Service (NTIS)

We have measured precise thermal neutron capture (gamma)-ray cross sections (sigma)(sub (gamma)) for all stable Palladium isotopes with the guided thermal neutron beam from the Budapest Reactor. The data were compared with other data from the literature a...

R. B. Firestone M. Krticka D. P. McNabb B. Sleaford U. Agvaanluvsan T. Belgya Z. Revay

2005-01-01

95

Simultaneous analysis of folic acid and pantothenic acid in foods enriched with vitamins by stable isotope dilution assays  

Microsoft Academic Search

Folic and pantothenic acid were quantified in multivitamin products by stable isotope dilution assays using [2H4]folic acid and [13C3,15N]pantothenic acid as the internal standards. Detection was achieved by liquid chromatography\\/mass spectrometry which enabled unequivocal determination of the vitamins. Due to the very simple extraction procedure, analysis of the vitamins was completed within 2h. When analyzing multivitamin sweets, the intra-assay and

Michael Rychlik

2003-01-01

96

Field application of the 15 N isotope dilution technique for the reliable quantification of plant-associated biological nitrogen fixation  

Microsoft Academic Search

To apply the isotope dilution (ID) technique, it is necessary to grow the “N2-fixing” crop in a soil where the mineral N is labelled with15N. Normally the “N2-fixing” crop and a suitable non-N2-fixing control crop are grown in the same labelled soil and the15N enrichment of the control crop is assumed to be equal to the15N enrichment of the nitrogen

Robert M. Boddey; Octávio C. Oliveira; Bruno J. R. Alves; Segundo Urquiaga

1995-01-01

97

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

98

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

Microsoft Academic Search

Isotope dilution liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS\\/MS) was applied to the quantification of acrylamide in chocolate matrixes (dark chocolate, milk chocolate, chocolate with nuts, chocolate with almonds, and chocolate with wheat best element). The method included defatting with petroleum ether, extracting with aqueous solution of 2?mol?l sodium chloride and clean-up by solid-phase (SPE) with OASIS

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

2006-01-01

99

Quantitative determination of formaldehyde in cosmetics using a combined solid-phase microextraction–isotope dilution mass spectrometry method  

Microsoft Academic Search

Solid-phase microextraction (SPME) in conjunction with isotope dilution mass spectrometry (ID-MS) was employed for the analysis of formaldehyde in cosmetic products. The formaldehyde is derivatized in situ with pentafluorophenyl hydrazine. The formed hydrazone is adsorbed over a poly(dimethylsiloxane)–divinylbenzene-coated fiber and analyzed using gas chromatography–mass spectrometry. The adsorption–time profiles and salting effect were studied. The quantitation was performed by using a

René Thomas Rivero; Vinod Topiwala

2004-01-01

100

Use of N?amino acid isotope dilution techniques to determine endogenous amino acids in ileal digesta in growing pigs  

Microsoft Academic Search

An experiment was carried out to determine the contribution of endogenous amino acids (AA) to total AA, using the N?AA and N?leucine isotope dilution techniques, in ileal digesta from growing pigs. Four barrows, initial body weight (BW) 33.8 ± 1.0 kg, were fitted with a simple T?cannula at the distal ileum and one catheter in each of the external jugular

Vince M. Gabert; Nuria Canibe; Henry Jørgensen; Bjørn O. Eggum; Willem C. Sauer

1997-01-01

101

Isotopic dilution analysis of zinc in some tissue samples of urogenital systems of rats using 65 Zn  

Microsoft Academic Search

Zinc plays an important role in prostate functions. For this reason, in this study some rats have been nourished with foods\\u000a containing different zinc levels and some tissue samples removed at different intervals of time from their prostate, testis,\\u000a and seminal vesicle. The zinc contents of these samples have been determined using the isotopic dilution analysis technique\\u000a applied with 65Zn.

T. Ünak; Ç. Çal; Y. Yildirim; U. Avc?ba??; G. Ünak

2009-01-01

102

Thermal conductivity of isotopically modified single crystal diamond  

NASA Astrophysics Data System (ADS)

We present new experimental results on the thermal conductivity of isotopically enriched 12C diamond crystals at low temperatures. To our knowledge, the measured value for a 99.9% 12C crystal at 104 K, 410 W/cm K, is the highest measured thermal conducitivity for a solid above liquid nitrogen temperature. Our measured temperature dependent conductivities for the isotopically enriched diamond and natural abundance diamond specimens are well described by Callaway's theoretical model. We predict that the thermal conductivity of a 99.999% 12C diamond crystal should exceed 2000 W/cm K at ~80 K.

Wei, Lanhua; Kuo, P. K.; Thomas, R. L.; Anthony, T. R.; Banholzer, W. F.

1993-06-01

103

Low uncertainty reverse isotope dilution ICP-MS applied to certifying an isotopically enriched Cd candidate reference material: A case study  

Microsoft Academic Search

An analytical method is presented based on reverse isotope dilution single detector inductively coupled plasma magnetic sector\\u000a mass spectrometry (ID-ICP-SMS) and applied to the specific case of the certification of a 111Cd enriched candidate Cd spike calibration material (nominal mass fraction 10 mg kg?1 in 5% HNO3 solution). Uncertainty propagation was used as a tool for both determining the analytical

Ivan Trešl; Christophe R. Quétel

2005-01-01

104

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

SciTech Connect

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

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

1982-02-01

105

Transient thermal performance of axially and radially diluted nuclear fuel cells  

SciTech Connect

A numerical investigation is presented of steady and unsteady heat transfer in axially and readily diluted nuclear fuel rods. The transient performance is assumed to follow a sudden and complete loss of coolant starting from steady state operation. Steady state conditions are obtained from solving numerically a conjugate conduction problem in the fuel rod and a turbulent forced convection problem in the coolant section. To model turbulence, the mixing length model is used. Dilution is accomplished by adding high thermal property materials, either axially or radially, to the original fuel rods with the intention of increasing the time delay before melting of the reactor in case of loss of coolant. The effects of the amount, distribution, and material of added diluent on steady and unsteady heat transfer are studied. Results indicate that axial dilution has negligible influence on the thermal performance of the reactor. Radial dilution, however, holds great promise and shows a reduction in the maximum wall and fuel temperature sunder steady operation and substantial increase in the time delay before melting under transient conditions. The value of this time delay increases as the amount of added diluent is increased. Moreover, the distribution of the added diluent is shown to have small effects on the steady and unsteady performance of the reactor, while the type of diluent material is found to affect the transient performance only.

Moukalled, F.; Nuwayhid, R.; Lakkis, I. [American Univ. of Beirut (Lebanon). Mechanical Engineering Dept.

1995-08-01

106

Cellular lipid extraction for targeted stable isotope dilution liquid chromatography-mass spectrometry analysis.  

PubMed

The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including numerous stereoisomers(1,2). These metabolites can be formed from free or esterified fatty acids. Many of these oxidized metabolites have biological activity and have been implicated in various diseases including cardiovascular and neurodegenerative diseases, asthma, and cancer(3-7). Oxidized bioactive lipids can be formed enzymatically or by reactive oxygen species (ROS). Enzymes that metabolize fatty acids include cyclooxygenase (COX), lipoxygenase (LO), and cytochromes P450 (CYPs)(1,8). Enzymatic metabolism results in enantioselective formation whereas ROS oxidation results in the racemic formation of products. While this protocol focuses primarily on the analysis of AA- and some LA-derived bioactive metabolites; it could be easily applied to metabolites of other fatty acids. Bioactive lipids are extracted from cell lysate or media using liquid-liquid (l-l) extraction. At the beginning of the l-l extraction process, stable isotope internal standards are added to account for errors during sample preparation. Stable isotope dilution (SID) also accounts for any differences, such as ion suppression, that metabolites may experience during the mass spectrometry (MS) analysis(9). After the extraction, derivatization with an electron capture (EC) reagent, pentafluorylbenzyl bromide (PFB) is employed to increase detection sensitivity(10,11). Multiple reaction monitoring (MRM) is used to increase the selectivity of the MS analysis. Before MS analysis, lipids are separated using chiral normal phase high performance liquid chromatography (HPLC). The HPLC conditions are optimized to separate the enantiomers and various stereoisomers of the monitored lipids(12). This specific LC-MS method monitors prostaglandins (PGs), isoprostanes (isoPs), hydroxyeicosatetraenoic acids (HETEs), hydroxyoctadecadienoic acids (HODEs), oxoeicosatetraenoic acids (oxoETEs) and oxooctadecadienoic acids (oxoODEs); however, the HPLC and MS parameters can be optimized to include any fatty acid metabolites(13). Most of the currently available bioanalytical methods do not take into account the separate quantification of enantiomers. This is extremely important when trying to deduce whether or not the metabolites were formed enzymatically or by ROS. Additionally, the ratios of the enantiomers may provide evidence for a specific enzymatic pathway of formation. The use of SID allows for accurate quantification of metabolites and accounts for any sample loss during preparation as well as the differences experienced during ionization. Using the PFB electron capture reagent increases the sensitivity of detection by two orders of magnitude over conventional APCI methods. Overall, this method, SID-LC-EC-atmospheric pressure chemical ionization APCI-MRM/MS, is one of the most sensitive, selective, and accurate methods of quantification for bioactive lipids. PMID:22127066

Gelhaus, Stacy L; Mesaros, A Clementina; Blair, Ian A

2011-11-17

107

Measurement of extravascular lung water by thermal-dye dilution technique: Mechanisms of cardiac output dependence  

Microsoft Academic Search

The extent to which extravascular lung water (EVLW) is dependent on cardiac output was analysed in anaesthetized and mechanically ventilated pigs. EVLW was measured by thermal-dye dilution technique, by a fibreoptic thermistor catheter system (system 1), and by a thermistor catheter-external optical cuvette system (system 2). During baseline conditions, at which cardiac output was 3.65 l\\/min, EVLW was 11.7 and

C.-J. Wickerts; J. Jakobsson; C. Frostell; G. Hedenstierna

1990-01-01

108

Thermoionic Emission Characteristics of Uranium with Application to Its Determination by MSID (Mass Spectrometric Isotope Dilution) Technique Using (233)U Tracer.  

National Technical Information Service (NTIS)

Experimental details of the uranium determination in geological samples (50-1500 ppm range) by mass spectrometric isotope dilution technique (MSID) employing (233)U tracer are presented. For this purpose the thermoionic emission characteristics of uranium...

H. M. Shihomatsu S. S. Iyer

1988-01-01

109

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; Künnemeyer, Jens; Nowak, Sascha; Sperling, Michael; Karst, Uwe

2012-10-26

110

Determination of chromium species in dietary supplements using speciated isotope dilution mass spectrometry with mass balance.  

PubMed

In order to determine the health impact of chromium in dietary supplements, the Cr(III) and Cr(VI) must be independently measured and verified with mass balance (sum of both species equaling independent measurements of total chromium), as both may be present in finished products. Because Cr(III) is stable in acidic conditions and Cr(VI) in alkaline conditions, interconversions between species may occur in complex matrices and during analytical extraction, increasing the difficulty of quantification. A study was conducted to determine Cr(VI) and Cr(III) in dietary supplements. EPA Method 3060A extraction protocol was performed to extract Cr(VI), and EPA Method 3052 was performed on the extracted residue to digest the remaining Cr(III). Speciated isotope dilution mass spectrometry (SIDMS), as described in the EPA Method 6800 (update V), was implemented with ion-exchange chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS). Method 6800 uniquely enables tracking and correcting for the bidirectional chromium interspecies conversions that occur during extraction and sample handling prior to instrumental analysis. Mass balance results indicated that the off-the-shelf dietary supplements analyzed during this study contained hexavalent chromium ranging from

Martone, Naudia; Rahman, G M Mizanur; Pamuku, Matt; Kingston, H M Skip

2013-10-07

111

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

PubMed

Cadmium was quantified at 80.15±0.86ng/g (mean±95% 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 11.1±0.9mg/kg and 70.7±4.5mg/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

2013-05-09

112

A crowding factor model for the thermal conductivity of particulate composites at non-dilute limit  

NASA Astrophysics Data System (ADS)

The effective thermal conductivity models for particulate composites are usually restricted to the dilute limit, with volumetric concentrations of particles typically less than 15%. By considering the particle interactions through a crowding factor, in this work, a new formula is developed to describe the thermal conductivity of composites with a dielectric matrix, for volume fractions of particles up to their maximum packing fraction. The crowding factor model is then applied to analyze two particulate composites with dielectric or metallic particles, where the effects of both interfacial thermal resistance and the electron-phonon coupling are taken into account. It is shown that the predictions of the proposed crowding factor model are larger than the ones predicted by the dilute-limit models, for composites with high volume fractions of particles, due to the particle interactions. The proposed crowding factor model extends the applicability of various thermal conductivity models for composites reported in the literature and its predictions are in good agreement with published experimental data.

Ordonez-Miranda, J.; Yang, Ronggui; Alvarado-Gil, J. J.

2013-08-01

113

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

SciTech Connect

DOE has initiated numerous activities to focus on identifying material management strategies to disposition various excess fissile materials. In particular the INEEL has stored 1,700 Kg of offspec HEU at INTEC in CPP-651 vault facility. Currently, the proposed strategies for dispositioning are (a) aqueous dissolution and down blending to LEU via facilities at SRS followed by shipment of the liquid LEU to NFS for fabrication into LWR fuel for the TVA reactors and (b) dilution of the HEU to 0.9% for discard as a waste stream that would no longer have a criticality or proliferation risk without being processed through some type of enrichment system. Dispositioning this inventory as a waste stream via aqueous processing at SRS has been determined to be too costly. Thus, dry blending is the only proposed disposal process for the uranium oxide materials in the CPP-651 vault. Isotopic dilution of HEU to typically less than 20% by dry blending is the key to solving the dispositioning issue (i.e., proliferation) posed by HEU stored at INEEL. RM-2 mill is a technology developed and successfully tested for producing ultra-fine particles by dry grinding. Grinding action in RM-2 mill produces a two million-fold increase in the number of particles being blended in a centrifugal field. In a previous study, the concept of achieving complete and adequate blending and mixing (i.e., no methods were identified to easily separate and concentrate one titanium compound from the other) in remarkably short processing times was successfully tested with surrogate materials (titanium dioxide and titanium mono-oxide) with different particle sizes, hardness and densities. In the current project, the RM-2 milling technology was thoroughly tested with mixtures of natural uranium oxide (NU) and depleted uranium oxide (DU) stock to prove its performance. The effects of mill operating and design variables on the blending of NU/DU oxides were evaluated. First, NU and DU both made of the same oxide, UO{sub 3}, was used in the testing. Next, NU made up of UO{sub 3} and DU made up of UO{sub 2} was used in the test work. In every test, the blend achieved was characterized by spatial sampling of the ground product and analyzing for {sup 235}U concentration. The test work proved that these uranium oxide materials can be blended successfully. The spatial concentration was found to be uniform. Next, sintered thorium oxide pellets were used as surrogate for light water breeder reactor pellets (LWBR). To simulate LWBR pellet dispositioning, the thorium oxide pellets were first ground to a powder form and then the powder was blended with NU. In these tests also the concentration of {sup 235}U and {sup 232}Th in blended products fell within established limits proving the success of RM-2 milling technology. RM-2 milling technology is applicable to any dry radioactive waste, especially brittle solids that can be ground up and mixed with the non-radioactive stock.

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

2003-08-01

114

Application of isotope dilution gas chromatography-mass spectrometry in analysis of organochlorine pesticide residues in ginseng root.  

PubMed

A highly accurate and precise method based on isotope dilution gas chromatography-mass spectrometry was developed for the determination of five matrix-bound organochlorine pesticides, namely, hexachlorobenzene and hexachlorocyclohexanes (alpha-, beta-, delta-, and gamma- isomers), in a reference sample of Panax gingseng. Identification of the analytes was confirmed under selective ion monitoring mode by the presence of two dominant ion fragments within the specific time windows (+/-1% of the relative retention time with respect to the calibration standards) and matching of relative ion intensities of the concerned ions in samples and calibration standards (within +/-5%). Quantification was based on the measurement of concentration ratios of the natural and isotopic analogues in the sample and calibration blends. To circumvent the tedious iterative process of exact isotope matching that is often used in isotope dilution mass spectrometry analysis, a single-point calibration procedure was adopted with the isotopic amount ratios in the sample and calibration blends close to unity (0.9-1.1). Under the described approach, intraday and interday repeatability of replicate analyses of organochlorine pesticides in the ginseng root sample were below 1.4%. The expanded relative uncertainty ranging from 4.0 to 6.5% at a coverage factor of 2 was significantly lower than those of conventional gas chromatographic methods using other calibration techniques (internal or external standards). A deviation of less than 2.0% from the certified values was achieved when applying the developed method to determine hexachlorobenzene, alpha-, and beta-hexachlorocyclohexane in a certified reference material (CRM), BCR-CRM 115. Because of the unavailability of relevant CRMs of herbal origins, the concerned ginseng root sample, after verification of the "true values" of the concerned organochlorine pesticides by the valid primary method, is suitable for serving as an in-house reference material for quality assurance and method validation purposes. PMID:17407316

Chan, Serena; Kong, Mei-Fong; Wong, Yiu-Chung; Wong, Siu-Kay; Sin, Della W M

2007-04-04

115

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

PubMed

Stable isotope dilution assays (SIDAs) for the determination of the most important mycotoxins of the black mold Alternaria, namely, alternariol and alternariol monomethyl ether, have been developed. For this purpose, deuterated alternariol and alternariol methyl ether were synthesized by palladium catalyzed protium-deuterium exchange from the unlabeled toxins. Reaction conditions were chosen in such a manner that the formation of the [(2)H(4)]-isotopologues was favored. The synthesized products were characterized by LC-MS, NMR, and UV-spectroscopy. On the basis of the use of [(2)H(4)]-alternariol and [(2)H(4)]-alternariol methyl ether as internal standards, SIDAs were developed and applied to the determination of alternariol and alternariol methyl ether in beverages using LC-MS/MS. Method validation revealed a high sensitivity, i.e., low limits of detection (alternariol, 0.03 microg/kg; alternariol methyl ether, 0.01 microg/kg) and limits of quantitation (alternariol, 0.09 microg/kg; alternariol methyl ether, 0.03 microg/kg), respectively. Recovery from spiked apple juice was 100.5 +/- 3.4% for alternariol (range 0.1-1 microg/kg) and 107.3 +/- 1.6% for alternariol methyl ether (range 0.05-0.5 microg/kg). Interassay precision (expressed as coefficient of variation, CEV) for alternariol was 4.0% (7.82 +/- 0.31 microg/kg; vegetable juice, naturally contaminated) and 4.6% (1.04 +/- 0.05 microg/kg; grape juice, naturally contaminated). For alternariol methyl ether, a CEV of 2.3% (0.79 +/- 0.02 microg/kg; vegetable juice, naturally contaminated) was obtained. Analysis of fruit juices showed low contamination with alternariol and alternariol methyl ether in general, but higher values of both toxins were found in wine and vegetable juices. The values for alternariol were higher than those for alternariol methyl ether in nearly any case. However, the developed SIDA has proven to be optimally suited for further studies on alternariol and alternariol methyl ether content in food samples to obtain further insight into possible health hazards for the consumer. PMID:19530709

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

2009-06-24

116

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

NASA Astrophysics Data System (ADS)

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 used to separate the earth alkaline metals (Ca, Sr, Ba) from Cd to reduce the high total dissolved solids (TDS) while maintaining a strong Cd signal. Each sample is then processed as a pair, once for Ca (and Sr and Ba, if desired) and once for Cd. Although not yet explored, other possible elements that could be run in the Cd set include vanadium, zinc and manganese. Reproducibility with this method is comparable to other ICP-MS methods, yielding 1sd precision of ~2% and repeated analyses of reference materials (BCR-1, BHVO-1, W-2, GSR-6, JCp-1) fall within established ranges. The removal of TDS has a distinct advantage over other ICP-MS methods that use more concentrated coral solutions; reducing the introduction of high-concentration elements, such as Ca, Mg and Sr, to the mass spectrometer is necessary in a multi-use laboratory that requires low background at those masses. Currently sample size is <30mg (allows for duplicate measurements), which is similar to that used for coral Cd analysis via GFAAS, but with ICP-MS multiple elements can be measured simultaneously. Preliminary results from coral samples ( Pavona gigantea) in the seasonally-upwelling Gulf of Panama (Pacific) indicate that, while average Cd concentrations are higher during upwelling than nonupwelling, the range due to natural variability among the P. gigantea individuals renders this difference statistically insignificant. These results suggest that for P. gigantea, much of the variability observed in single-core coral records of Cd/Ca may not be caused by upwelling. Additional results from different depths and species will also be presented to further address the impact of the natural variability of coral Cd/Ca and the implications for paleoclimate reconstruction using this proxy.

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

2005-12-01

117

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

118

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

119

The longevity of the South Pacific isotopic and thermal anomaly  

USGS Publications Warehouse

The South Pacific is anomalous in terms of the Sr, Nd, and Pb isotope ratios of its hot spot basalts, a thermally enhanced lithosphere, and possibly a hotter mantle. We have studied the Sr, Nd, and Pb isotope characteristics of 12 Cretaceous seamounts in the Magellans, Marshall and Wake seamount groups (western Pacific Ocean) that originated in this South Pacific Isotopic and Thermal Anomaly (SOPITA). The range and values of isotope ratios of the Cretaceous seamount data are similar to those of the island chains of Samoa, Tahiti, Marquesas and Cook/Austral in the SOPITA. These define two major mantle components suggesting that isotopically extreme lavas have been produced at SOPITA for at least 120 Ma. Shallow bathymetry, and weakened lithosphere beneath some of the seamounts studied suggests that at least some of the thermal effects prevailed during the Cretaceous as well. These data, in the context of published data, suggest: 1. (1)|SOPITA is a long-lived feature, and enhanced heat transfer into the lithosphere and isotopically anomalous mantle appear to be an intrinsic characteristic of the anomaly. 2. (2)|The less pronounced depth anomaly during northwesterly plate motion suggests that some of the expressions of SOPITA may be controlled by the direction of plate motion. Motion parallel to the alignment of SOPITA hot spots focusses the heat (and chemical input into the lithosphere) on a smaller cross section than oblique motion. 3. (3)|The lithosphere in the eastern and central SOPITA appears to have lost its original depleted mantle characteristics, probably due to enhanced plume/lithosphere interaction, and it is dominated by isotopic compositions derived from plume materials. 4. (4)|We speculate (following D.L. Anderson) that the origin of the SOPITA, and possibly the DUPAL anomaly is largely due to focussed subduction through long periods of the geological history of the earth, creating a heterogeneous distribution of recycled components in the lower mantle. ?? 1991.

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

1991-01-01

120

Thermal Neutron Capture onto the Stable Tungsten Isotopes  

NASA Astrophysics Data System (ADS)

Thermal neutron-capture measurements of the stable tungsten isotopes have been carried out using the guided thermal-neutron beam at the Budapest Reactor. Prompt singles spectra were collected and analyzed using the HYPERMET ?-ray analysis software package for the compound tungsten systems 183W, 184W, and 187W, prepared from isotopically-enriched samples of 182W, 183W, and 186W, respectively. These new data provide both confirmation and new insights into the decay schemes and structure of the tungsten isotopes reported in the Evaluated Gamma-ray Activation File based upon previous elemental analysis. The experimental data have also been compared to Monte Carlo simulations of ?-ray emission following the thermal neutron-capture process using the statistical-decay code DICEBOX. Together, the experimental cross sections and modeledfeeding contribution from the quasi continuum, have been used to determine the total radiative thermal neutron-capture cross sections for the tungsten isotopes and provide improved decay-scheme information for the structural- and neutron-data libraries.

Hurst, A. M.; Firestone, R. B.; Sleaford, B. W.; Summers, N. C.; Revay, Zs.; Szentmiklósi, L.; Belgya, T.; Basunia, M. S.; Capote, R.; Choi, H.; Dashdorj, D.; Escher, J.; Krticka, M.; Nichols, A.

2012-02-01

121

Quantitative determination of formaldehyde in cosmetics using a combined solid-phase microextraction-isotope dilution mass spectrometry method.  

PubMed

Solid-phase microextraction (SPME) in conjunction with isotope dilution mass spectrometry (ID-MS) was employed for the analysis of formaldehyde in cosmetic products. The formaldehyde is derivatized in situ with pentafluorophenyl hydrazine. The formed hydrazone is adsorbed over a poly(dimethylsiloxane)-divinylbenzene-coated fiber and analyzed using gas chromatography-mass spectrometry. The adsorption-time profiles and salting effect were studied. The quantitation was performed by using a stable isotope labeled analogue as an internal standard. The precision, recovery and detection limits were determined with spiked samples. The relative standard deviations from different spiked cosmetic samples were all less than 10% and the recoveries were between 89.00 and 101.23%. The limit of detection was of 0.39 microg/l. Compared with other techniques, the study shown here provides a simple, fast and reliable method for the analysis of formaldehyde in cosmetic products. PMID:15032367

Rivero, René Thomas; Topiwala, Vinod

2004-03-12

122

Thermal diffusion of dilute polymer solutions: The role of solvent viscosity  

NASA Astrophysics Data System (ADS)

We have performed measurements of the thermal diffusion coefficient DT in the dilute limit on polystyrene in cyclo-octane, cyclohexane, benzene, toluene, tetrahydrofuran, ethyl acetate, and methyl ethyl ketone and of poly(dimethyl-siloxane) in toluene. These data have been combined with literature data to test various theoretical predictions. The viscosity is identified as the dominating and only relevant solvent parameter. On the polymer side, the size or mass of an effective correlated segment determines the strength of the Soret effect. Large and heavy effective segments, as found in stiffer chains, lead to higher DT.

Hartung, M.; Rauch, J.; Köhler, W.

2006-12-01

123

Species-specific isotope dilution with permeation tubes for determination of gaseous mercury species.  

PubMed

Instrumentation and methodology for determination of the gaseous mercury species Hg0, (CH3)2Hg, and CH3Hg+ has been developed. The method is based on continuous addition of gaseous isotopically enriched Hg species (tracers) at the point of sample acquisition, in combination with reduced pressure sampling on Carbotrap adsorbent tubes. Permeation tubes are used for generation of the tracers. Collected species are thermally desorbed and purged through an aqueous sodium tetraethylborate solution for derivatization of CH3Hg+. The purged gas is dried with a Nafion membrane, and the Hg species are subsequently collected on a smaller Tenax TA adsorbent tube. Species are then thermally desorbed from the Tenax TA and introduced into a gas chromatograph connected to an inductively coupled plasma mass spectrometer for separation and detection. To be able to add tracers during field sampling, we developed a portable device, supplying the permeation tubes with a thermostated and mass flow-controlled air stream of 5.0 +/- 0.1 degrees C and 50.0 mL min(-1), respectively. Typical permeation rates obtained during a period of more than 6 weeks were 12.93 +/- 0.56, 0.42 +/- 0.01, and 0.49 +/- 0.03 (mean +/- standard deviation) pg of Hg min(-1) for a set of 199Hg0, (CH3)2 198Hg, and CH3 200Hg+ tubes, respectively. Methodological detection limits (3sigma) were determined to 700 pg of Hg m(-3) for Hg0 and 50 pg of Hg m(-3) for (CH3)2Hg and CH3Hg+. The collection efficiencies for sampled volumes of 400 L of synthetic air on the Carbotrap tubes used in this study were 13 +/- 2, 102 +/- 2, and 99 +/- 4% for Hg0, (CH3)2Hg, and CH3Hg+, respectively. Desorption efficiencies for the above species and tubes were 98 +/- 2, 98 +/- 1, and 90 +/- 4%, respectively. Fractions (20-40%) of the added (CH3)2 198Hg and CH3 200Hg+ tracers were found to be transformed during the analytical processing of collected air samples. Determined concentrations in the research laboratory air, corrected for species transformations, were 3-53, 8-11, and 1-2 ng of Hg m(-3) for Hg0, (CH3)2Hg, and CH3Hg+, respectively. Concentrations in the ambient air were determined to be 2.1-2.6 ng m(-3) for Hg0 and below the detection limit for (CH3)2Hg and CH3Hg+. PMID:14710842

Larsson, T; Frech, W

2003-10-15

124

Separation of Hydrogen Isotopes by Thermal Diffusion  

SciTech Connect

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

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

1985-09-01

125

Quantification of VX vapor in ambient air by liquid chromatography isotope dilution tandem mass spectrometric analysis of glass bead filled sampling tubes.  

PubMed

An analysis method has been developed for determining low parts-per-quadrillion by volume (ppqv) concentrations of nerve agent VX vapor actively sampled from ambient air. The method utilizes glass bead filled depot area air monitoring system (DAAMS) sampling tubes with isopropyl alcohol extraction and isotope dilution using liquid chromatography coupled with a triple-quadrupole mass spectrometer (LC/MS/MS) with positive ion electrospray ionization for quantitation. The dynamic range was from one-tenth of the worker population limit (WPL) to the short-term exposure limit (STEL) for a 24 L air sample taken over a 1 h period. The precision and accuracy of the method were evaluated using liquid-spiked tubes, and the collection characteristics of the DAAMS tubes were assessed by collecting trace level vapor generated in a 1000 L continuous flow chamber. The method described here has significant improvements over currently employed thermal desorption techniques that utilize a silver fluoride pad during sampling to convert VX to a higher volatility G-analogue for gas chromatographic analysis. The benefits of this method are the ability to directly analyze VX with improved selectivity and sensitivity, the injection of a fraction of the extract, quantitation using an isotopically labeled internal standard, and a short instrument cycle time. PMID:21235231

Evans, Ronald A; Smith, Wendy L; Nguyen, Nam-Phuong; Crouse, Kathy L; Crouse, Charles L; Norman, Steven D; Jakubowski, E Michael

2011-01-14

126

Fourier transforms method for measuring thermal lens induced in diluted liquid samples  

NASA Astrophysics Data System (ADS)

Drawing on interferometry and Fourier analysis, this paper describes the use of a two-beam thermal lens technique for measuring thermo-optical properties in optical materials. The procedure consists of yield interference patterns deformed by a localized photothermal effect. The photothermal phase shift is locally induced by the pump beam focused on a tested sample located on an on-axis probe beam, which is the first arm of a Mach Zehnder interferometer. The plane where the effect is localized is imaged onto a CCD camera. Then two interferograms are recorded: one without effect and the other one with the induced photothermal phase. Fourier analysis performed on these interferograms allow us to plot the thermal lens map and, therefore, to estimate thermo-optic constant of Malachite Green in water solution. The method is applied to measure low linear absorptions of a diluted sample of Rhodamine B in water solution at 633 nm, showing that the proposed technique allows to measure photothermal phase shift as low as 3.1 mrad at 8 mW of input power in diluted materials.

Rodriguez, L.; Escalona, R.

2007-09-01

127

Precise Re isotope ratio measurements by negative thermal ionization mass spectrometry (NTI-MS) using total evaporation technique  

NASA Astrophysics Data System (ADS)

High precision rhenium isotope ratios, 187Re/185Re, have been determined by negative thermal ionization mass spectrometry (NTI-MS) using a total evaporation technique. The salient features of this method are evaporation of the entire sample and simultaneous integration of the signal from each isotope, which effectively eliminates isotope fractionation effects during the evaporation process. The 187Re/185Re ratio is obtained with a high reproducibility (1.6755+/-0.0014 (2[sigma]), R.S.D.=0.083%, n=28) for 50 pg-1 ng of a Re natural standard using the total evaporation with NTI-MS. This value is within analytical uncertainty of the previously reported accurate 187Re/185Re ratio (1.6740+/-0.0011) adopted by IUPAC as the Re isotopic composition, and is significantly more precise than the ratio obtained from conventional NTI-MS isotopic measurements in our laboratory (1.6772+/-0.0037 (2[sigma]), R.S.D.=0.22%, n=34). Based on these results, the total evaporation technique allows us to precisely determine Re isotope ratios, even for small sample amounts. In addition, this method is effective for highly precise Re abundance determinations using isotope dilution.

Suzuki, Katsuhiko; Miyata, Yoshiki; Kanazawa, Nobuyuki

2004-06-01

128

Peptide Production and Decay Rates Affect the Quantitative Accuracy of Protein Cleavage Isotope Dilution Mass Spectrometry (PC-IDMS)*  

PubMed Central

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.

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

2012-01-01

129

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

ERIC Educational Resources Information Center

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

Moehs, Peter J.; Levine, Samuel

1982-01-01

130

Thermal conductivity of germanium crystals with different isotopic compositions  

NASA Astrophysics Data System (ADS)

We have measured the thermal conductivity of seven germanium crystals with different isotopic compositions in the temperature range between 2 K and 300 K. These samples, including one made of highly enriched 70Ge(99.99%), show intrinsic behavior at room temperature with the exception of a p-type sample with \\|Nd-Na\\|?2×1016 cm-3. The ``undoped'' samples exhibit a T3 dependence at low temperatures, basically determined by boundary scattering. The maximum value of ? (which falls in the range between 13 K and 23 K) is found to be a monotonically decreasing function of the isotopic mass variance parameter g. The maximum ?m measured for the most highly enriched 70Ge(99.99%) sample is 10.5 kW/mK, one order of magnitude higher than for natural germanium. The experimental data have been fitted with the full Callaway theory, modified by treating transverse and longitudinal modes separately, using three free adjustable parameters for each set of modes to represent anharmonic effects plus the calculated contributions from isotopic and boundary scattering. For the isotopically purest 70Ge(99.99%) sample, dislocation scattering, or a similar mechanism, must be added in order to fit the data. We have also checked the effect of various surface treatments on the thermal conductivity in the low temperature region. The highest values of ? are found after polish etching with a SYTON suspension.

Asen-Palmer, M.; Bartkowski, K.; Gmelin, E.; Cardona, M.; Zhernov, A. P.; Inyushkin, A. V.; Taldenkov, A.; Ozhogin, V. I.; Itoh, K. M.; Haller, E. E.

1997-10-01

131

Liquid chromatography, chemical oxidation, and online carbon isotope dilution mass spectrometry as a universal quantification system for nonvolatile organic compounds.  

PubMed

A procedure for the universal detection and quantification of polar organic compounds separated by liquid chromatography (LC) based on postcolumn carbon isotope dilution mass spectrometry (IDMS) was developed. The eluent from the LC column is mixed online with a continuous flow of (13)C-enriched sodium bicarbonate, and the sodium persulfate oxidation reaction in acidic media is employed to achieve isotope equilibration. All carbon-containing compounds eluting from the column are oxidized to (12)CO(2) and (13)CO(2), respectively, and the carbon dioxide is separated from the aqueous phase using a gas-permeable membrane. The gaseous carbon dioxide is then carried to the mass spectrometer for isotope ratio measurements. Different water-soluble organic compounds were evaluated using a flow injection configuration to assess the efficiency of the oxidation process. Most water-soluble organic compounds tested showed quantitative oxidation. However, chemical structures involving conjugated C?N double bounds and guanidinium-like structures were found to be resistant to the oxidation and were further studied. For this purpose, (13)C(1)-labeled creatine (with the isotopic label in the guanidinium group) was employed as model compound. Specific conditions for the quantitative oxidation of these compounds required lower flow rates and the addition of metallic catalysts. This novel approach was tested as a universal detection and quantification system for LC. A simple standard mixture of four amino acids was separated under 100% aqueous conditions and quantified without the need for specific standards with good accuracy and precision using potassium hydrogen phthalate as internal standard. The main field of application of the developed method is for the purity assessment of organic standards with direct traceability to the International System of Units (SI). PMID:23252800

Díaz, Sergio Cueto; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo; Alonso, J Ignacio García

2013-01-07

132

Europium-labeled activity-based probe through click chemistry: absolute serine protease quantification using (153)Eu isotope dilution ICP/MS.  

PubMed

Click and analyze: the titled probe was synthesized by conjugating a sulfonyl fluoride and azido unit using click chemistry to give SF-Eu, which can react specifically with serine (Ser) in the active site of serine protease (SP). Combination of the method with (153)Eu-isotope dilution ICP/MS enables absolute protein quantification of active SPs in biological samples using only one (153)Eu(NO(3))(3) isotopic standard. PMID:22344943

Yan, Xiaowen; Luo, Yacui; Zhang, Zhubao; Li, Zhaoxin; Luo, Qiang; Yang, Limin; Zhang, Bo; Chen, Haifeng; Bai, Peiming; Wang, Qiuquan

2012-02-17

133

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

Microsoft Academic Search

One of the main advantages of garnet geochronology is a possibility of establishing a direct link between isotopic ages and PT conditions. However, both Lu-Hf and Sm-Nd garnet dating can strongly be affected by submicroscopic inclusions capable of dominating the Sm-Nd and Lu-Hf budget. We investigated possible effects of various inclusions on Sm-Nd and Lu-Hf systems by combined isotope dilution

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

2003-01-01

134

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

Microsoft Academic Search

A method has been developed for the analysis of phytoestrogens and their conjugates in human urine using liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS\\/MS). Stable isotopically labeled [13C3]daidzein and [13C3]genistein were synthesized and used as internal standards for isotope dilution mass spectrometry. Free aglycons and intact glucuronide, sulfate, diglucuronide, disulfate, and mixed sulfoglucuronide conjugates of isoflavones and lignans were

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

2002-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

136

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

137

Studies on accuracy of trichothecene multitoxin analysis using stable isotope dilution assays.  

PubMed

Critical parameters in mycotoxin analysis were examined by using stable isotope-labelled tricho-thecenes. Sample weight was downsized to 1 g without loosing precision when sufficiently homogenized samples were taken for analysis. Complete extraction of trichothecenes could be achieved with a solvent mixture of acetonitrile+water (84+16; v+v) even without the use of stable isotope labelled standards. However, in particular for the analysis of deoxynivalenol the absolute amount of water in the solvent volume used for extraction appeared critical. Depending on the matrix a low water amount resulted in too low quantitative values when no stable isotope-labelled standards are applied to correct for incomplete extraction. In this case the used extraction volume had to be at least 10 ml for 1 g sample when acetonitrile + water (84+16; v+v) was used as extraction solvent.Losses during sample preparation using two different clean-up columns were not observed. On the contrary, matrix suppression in the ESI-interface of the LC-MS equipment was found to be a serious problem. Depending on the matrix, the latter effect resulted in considerably lower values for trichothecenes when no stable isotope-labelled standards were used to counterbalance this suppression. PMID:23606024

Asam, S; Rychlik, M

2007-12-01

138

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

SciTech Connect

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

Huang, L.Q.

1989-03-01

139

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

140

Determination of hafnium in zirconium and its alloys by stable isotope dilution-neutron activation analysis. [Neutron reactions  

SciTech Connect

A new method, an isotope dilution method combined with neutron activation analysis, has been applied to the determination of traces of hafnium in zirconium and Zircaloys. A known amount of /sup 174/Hf-enriched hafnium solution was added to the sample as a spike. The mixture was dissolved and then irradiated in a reactor, together with natural and spike hafnium solutions. After cooling, the spiked hafnium was separated and the ..gamma..-ray spectra were measured, together with the natural and spike hafniums. The content of hafnium in the sample was calculated from the measured /sup 175/Hf//sup 181/Hf count rate ratio. A few parts-per-million of hafnium was determined with a relative standard deviation of 0.93%. The method was used to determine the value of hafnium in zirconium and Zircaloy reference materials, prepared by the National Bureau of Standards (NBS) and the Japan Atomic Energy Research Institute (JAERI). 3 figures, 4 tables.

Yonezawa, C.; Komori, T.

1983-11-01

141

The assay of pterostilbene in spiked matrices by liquid chromatography tandem mass spectrometry and isotope dilution method.  

PubMed

Pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene) is an active component found in several plant species, exhibiting important pharmacological properties. A new and reliable method of assaying this phyto compound in various matrices is presented; the assay is based on (1) the selectivity of liquid chromatography (LC) hyphenated with electrospray ionisation (ESI), (2) the specificity of a two-step mass spectrometric analysis (MS/MS) and (3) the accuracy of the isotope dilution method. The labelled analogue may be conveniently synthesised in a few steps. The sensitivity of the method is confirmed by the very low limit of detection (LOD) and limit of quantitation (LOQ) values achieved in the assay of pterostilbene in two distinct fortified matrices, and is further supported by the observed accuracy values. PMID:20198601

Mazzotti, Fabio; Di Donna, Leonardo; Benabdelkamel, Hicham; Gabriele, Bartolo; Napoli, Anna; Sindona, Giovanni

2010-04-01

142

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.

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

1991-01-01

143

Thermal neutron capture cross sections of the palladium isotopes  

NASA Astrophysics Data System (ADS)

Precise thermal neutron capture ?-ray cross sections ?? were measured for all elements with Z=1-83,90, and 92, except for He and Pm, at the Budapest Reactor. These data were evaluated with additional information from the literature to generate the Evaluated Gamma-ray Activation File (EGAF). Isotopic radiative neutron cross sections can be deduced from the total transition cross section feeding the ground state, ?0=???(GS) if the decay scheme is complete. The EGAF file contains partial ?-ray cross sections for all stable palladium isotopes. None of these decay schemes are complete, although in each case transitions de-exciting low-lying levels are known. We have performed Monte Carlo simulations of the palladium thermal neutron capture decay schemes using the computer code DICEBOX. The simulated populations of low low-lying levels are normalized to the measured ?? values from EGAF and the total radiative neutron cross section ?0 is obtained. The ?0 values derived for the palladium isotopes agree well with previous measurements and were in several cases more precise. Complementary use of ?-ray cross-section data and Monte Carlo calculations has proven effective in determining both the palladium total radiative cross sections and new nuclear structure information.

Krti?ka, M.; Firestone, R. B.; McNabb, D. P.; Sleaford, B.; Agvaanluvsan, U.; Belgya, T.; Revay, Z. S.

2008-05-01

144

Thermal neutron capture cross sections of the palladium isotopes  

SciTech Connect

Precise thermal neutron capture {gamma}-ray cross sections {sigma}{sub {gamma}} were measured for all elements with Z=1-83,90, and 92, for He and Pm, at the Budapest Reactor. These data were evaluated with additional information from the literature to generate the Evaluated Gamma-ray Activation File (EGAF). Isotopic radiative neutron cross sections can be deduced from the total transition cross section feeding the ground state, {sigma}{sub 0}={sigma}{sigma}{sub {gamma}}(GS) if the decay scheme is complete. The EGAF file contains partial {gamma}-ray cross sections for all stable palladium isotopes. None of these decay schemes are complete, although in each case transitions de-exciting low-lying levels are known. We have performed Monte Carlo simulations of the palladium thermal neutron capture decay schemes using the computer code DICEBOX. The simulated populations of low low-lying levels are normalized to the measured {sigma}{sub {gamma}} values from EGAF and the total radiative neutron cross section {sigma}{sub 0} is obtained. The {sigma}{sub 0} values derived for the palladium isotopes agree well with previous measurements and were in several cases more precise. Complementary use of {gamma}-ray cross-section data and Monte Carlo calculations has proven effective in determining both the palladium total radiative cross sections and new nuclear structure information.

Krticka, M. [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-180 00 Prague 8 (Czech Republic); North Carolina State University, Raleigh, NC 27695 (United States); Firestone, R. B. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); McNabb, D. P.; Sleaford, B.; Agvaanluvsan, U. [Lawrence Livermore National Laboratory, L-414, 7000 East Avenue, Livermore, CA 94551 (United States); Belgya, T.; Revay, Z. S. [Institute of Isotope and Surface Chemistry, H-1525, Budapest (Hungary)

2008-05-15

145

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

146

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

Microsoft Academic Search

Boron isotopic fractionation factor (S) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17MPa at 25°C, using 0.1mM boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same

Masaaki Musashi; Takao Oi; Motoyuki Matsuo; Masao Nomura

2008-01-01

147

Method for measurement of glucose enrichment in serum using isotope dilution mass spectrometry and its application for measurement of glucose kinetics  

SciTech Connect

An isotope dilution mass spectrometric method has been developed for kinetic studies of D-glucose in humans, using 6,6-dideuteroglucose as the internal standard. Glucose in plasma samples was purified by anion and cation exchange column chromatography after deproteinization and derivatized to ..cap alpha..-D-glucofuranose cyclic 1,2:3,5-bis (butylboronate)-6-acetate.

Dan, P.; Clemons, P.M.; Sperling, M.I.; Gelfand, M.J.; Chen, I.W.; Sperling, M.A.; Norman, E.J.

1983-01-01

148

Use of 15 N isotope dilution for quantification of N 2 fixation associated with roots of kallar grass ( Leptochloa fusca (L.))  

Microsoft Academic Search

Leptochloa fusca (L.) Kunth (kallar grass) has previously been found to exhibit high rates of nitrogen fixation. A series of experiments to determine the level of biological nitrogen fixation using 15N isotopic dilution were carried out in nutrient solution and saline soil. In the nutrient solution, E. coli inoculated plants were taken as non-nitrogen-fixing control. It was observed that nearly

K. A. Malik; Y. Zafar; R. Bilal; E. Azam

1987-01-01

149

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

SciTech Connect

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

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

1985-12-01

150

[Accurate determination of chloramphenicol in pork by isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry].  

PubMed

An accurate method was described for the determination of chloramphenicol (CAP) in pork. The analyte was quantified by isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) operating in negative ion multiple reaction monitoring (MRM) mode. The sample was treated by liquid-liquid extraction with ethyl acetate followed by a clean-up step on an HLB solid-phase extraction cartridge. Chloramphenicol-D5 (CAP-D5) was added as an isotope internal standard. Under the optimized conditions, the calibration curve showed a good linearity in ranging from 0.01 to 0.5 ng/g CAP. The correlation coefficient r2 was 0.9998. The limit of detection and the limit of quantification were 0.004 and 0.02 ng/g, respectively. The average recoveries of CAP at 0.02 ng/g and 1.0 ng/g spiked levels ranged from 95.2%-109.1%, 99.7%-102.5%, respectively. The relative standard deviations (RSDs) of intra-day and inter-day were less than 2%. Meanwhile, matrix effect factors k of CAP and CAP-D5 were determined under different mobile phases and the sample solvent composition, the k was in the range of 0.950-1.015. The method can be used as a confirmed method for the determination of CAP in pork. PMID:22233085

Yang, Zong; Li, Xiuqin; Wang, Juan; Zhang, Qinghe

2011-09-01

151

Shallow thermal donors in silicon doped with isotopic oxygen  

NASA Astrophysics Data System (ADS)

The shallow thermal donors (STDs) in silicon doped with isotopic oxygen 16O and 18O have been investigated. The sample annealed at 1275°C for 4h in a nitrogen ambient was measured by a Fourier transform infrared (FTIR) spectrometer at 10K. In comparison, a nitrogen doped Czochralski (NCZ) silicon sample in which nitrogen-oxygen complexes existed was also checked by the FTIR spectrometer. It was found that STDs were formed in the oxygen isotope doped silicon during annealing at high temperature. It is considered that nitrogen could be involved in the generation of STDs. The line positions of the STDs were almost the same as that of the N-O complexes in NCZ silicon. The small shift of some absorption lines of STDs was also observed. In addition, a new unidentified shallow center was found and discussed.

Yang, D.; Klevermann, M.; Murin, L. I.

2001-01-01

152

Determination of selenium in sediment by isotope-dilution inductively coupled plasma mass spectrometry with an octapole reaction cell.  

PubMed

A method is described for determination of selenium in sediment by isotope-dilution inductively coupled plasma mass spectrometry with an octapole reaction cell (ID-ICP-ORCMS). Sediment samples were digested with HNO3, HClO4, and HF, and the digestion included an elaborate evaporation process to remove bromine from the digested solution. Simple strong cation-exchange disk filtration was used to remove rare earth elements (REE) from the digested solution, because REE2+ seriously interfere with Se isotopes (i.e. 156Gd2+ with 78Se+, 160Gd2+ with 80Se+). Addition of acetic acid to the filtrate was examined to improve the sensitivity of ICP-ORCMS measurement of Se+ by means of a carbon-enhancement effect. The interfering Ar2+ for selenium isotopes were almost eliminated by use of H2 as reaction gas. Interference from BrH+ formed in the reaction cell was negligible because the Br was removed in the evaporation process. Approximately 99.5% of REE were removed by cation-exchange disk filtration yet more than 99% of Se remained in the filtrate solution. The intensity for Se+ was enhanced approximately fourfold by addition of 5% (v/v) of acetic acid whereas that for Ar2+ was barely enhanced. Measured 80Se/78Se ratios in unspiked digested solutions of the sample were in good agreement with that for an Se standard solution. The analytical results for Se in the certified reference materials MESS-3 and PACS-1 were in good agreement with their certified values, with small uncertainties. PMID:16557408

Inagaki, Kazumi; Takatsu, Akiko; Nakama, Atsuko; Eyama, Sakae; Yarita, Takashi; Okamoto, Kensaku; Chiba, Koichi

2006-03-24

153

Low blank rhenium isotope ratio determinations by V2O5 coated nickel filaments using negative thermal ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

Thenium isotope ratio determinations are, in principle, possible by negative thermal ionization mass spectrometry (NTI-MS). Relatively high rhenium blanks from the commonly-used filament materials prevent accurate isotope ratio determinations, especially for small rhenium sample amounts which are of importance, for example, in geochronology in connection with the Re/Os dating method. Platinum and nickel filaments were tested by different preparation techniques to reduce the rhenium blank contribution from the filament material. The lowest rhenium blank of less than 1 pg was achieved by coating nickel filaments with V2O5 prior to degassing under high vacuum conditions at 850°C. Obviously, the vanadium--nickel oxide layer formed on the surface of the filament during this process prevents further emission of rhenium ions from the filament material. Using Ba(OH)2 for the enhancement of negative thermal ions, 1 ng of rhenium resulted in ion currents at the detector side of about 10-11 A with an ionization efficiency of up to 20%. The 185Re/187Re isotope ratio of a sample of natural isotopic composition could be determined to be 0.59818 ± 0.00026 with a relative precision of 0.04%. The isotope ratio determination for an 187Re spike was comparable in precision but the relative standard deviation of an 185Re spike was significantly higher, which could be explained by mass fractionations of oxygen in the measured ReO-4 ion. The ReO-4 ion is about 200 to 2500 times more abundant than the only other detectable rhenium ion in NTI-MSReO-3. The ReO-4/ReO-4 ratio decreases with increasing temperature. By the low blank NTI-MS technique described in this work, more precise and accurate determinations of the rhenium isotope ratio and the rhenium concentration by isotope dilution analysis from nanogramme samples are possible.

Walczyk, Thomas; Hebeda, Erhard H.; Heumann, Klaus G.

1994-02-01

154

Stable Isotope Dilution Multidimensional Liquid Chromatography-Tandem Mass Spectrometry for Pancreatic Cancer Serum Biomarker Discovery  

PubMed Central

A novel approach to pancreatic cancer biomarker discovery has been developed, which employs a stable isotope labeled proteome (SILAP) standard coupled with extensive multidimensional separation coupled with tandem mass spectrometry (MS/MS). Secreted proteins from CAPAN-2 human pancreatic cancer derived cells were collected after conducting stable isotope labeling by amino acids in cell culture (SILAC). The resulting SILAP standard contained <0.5% of individual unlabeled proteins. Pooled sera from patients with early stage pancreatic cancer or controls were prepared, and an equal amount of the SILAP standard was added to each sample. Proteins were separated by isoelectric focusing (IEF) prior to two-dimensional liquid chromatography (2D-LC)–MS/MS analysis. A total of 1065 proteins were identified of which 121 proteins were present at 1.5-fold or greater concentrations in the sera of patients with pancreatic cancer. ELISA validation of these findings was successfully performed for two proteins, ICAM-1 and BCAM. Results of these studies have provided proof of principle that a SILAP standard derived from the CAPAN-2 secreted proteome can be used in combination with extensive multidimensional LC-MS/MS for the identification and relative quantitation of potential biomarkers of pancreatic cancer. This technique allows for the detection of low-abundance proteins, and focuses only on biologically relevant proteins derived from pancreatic cancer cells.

2009-01-01

155

Isotope dilution models and the mystery of the vanishing /sup 15/N  

SciTech Connect

An examination of recently published /sup 15/NH/sub 4//sup +/ uptake data shows that the amount of /sup 15/N which disappeared from the NH/sub 4//sup +/ phase was consistently greater than that which appeared in the particulate phase. The discrepancy, which ranged from 1.5 to 5.6 times at nine stations, did not seem to be caused by analytical errors in NH/sub 4//sup +/ or isotope ratio measurements. A new method for calculating the average atom % excess of the NH/sub 4//sup +/ improves estimates of NH/sub 4//sup +/ assimilation in cases where experimental data indicate that uptake and regeneration are not in balance. Correction of a mathematical misconception regarding the Blackburr-Caperon model allows more accurate estimates of NH/sub 4//sup +/ uptake and regeneration rates.

Laws, E.

1984-03-01

156

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

NASA Astrophysics Data System (ADS)

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 mass spectrometry (TIMS, ThermoElectron Triton), which draws on the pioneering work of Rosman et al. (1980). We observe pronounced anomalous odd-even isotope mass bias during TIMS measurement of Cd with silica gel activator, and avoid such effects by utilizing even isotopes of Cd only. The double spike and its composition were carefully optimized (cf. Galer, 1999), and the "natural" Cd isotope fractionation is expressed as the relative deviations in ^{112}Cd/^{110}Cd (in parts per 104) from our JMC Cd shelf standard. The external reproducibility for 100 ng loads of double-spiked JMC Cd shelf is ± 0.14 ?^{112/110}Cd (2SD, N=57) -- i.e. ±7 ppm/amu -- which is a factor of 4 to 10 times better than that reported in published studies using MC-ICP-MS techniques (e.g. Wombacher et al., 2003; Cloquet et al., 2005). The DS-TIMS method offers further benefits in terms of superior sensitivity, while Cd abundances are obtained as a biproduct by isotope dilution. We have analyzed ?^{112/110}Cd in over sixty samples from different terrestrial reservoirs and environments in order to delimit the extent of natural isotope fractionation of Cd. Most samples were duplicated or triplicated. To facilitate inter-lab comparison, our measured ?^{112/110}Cd for the standards "Münster Cd" and BAM-1012 averaged +21.46 and -7.42, respectively. On the whole, our study confirms the conclusions of Wombacher et al. (2003) that Cd isotope variations in terrestrial materials are limited -- nearly all samples fall within the range -1.0 to +1.0 in ?^{112/110}Cd. Nevertheless, we are able for the first time to resolve clearly differences far outside of analytical error. Analyses of 31 hydrogenous Fe-Mn deposits (and phosphorites) worldwide range from -0.6 to +2.0; those from the Indian and Circum- Antarctic Oceans lie at ~0, whíle Pacific and Atlantic samples generally having positive values. We suggest these differences reflect different rates of vertical inorganic scavenging and remineralization. Oceanic basalts (MORB, Hawaii) and continental loess samples generally have negative ?^{112/110}Cd (-1.2 to -0.5) which may imply that the bulk silicate Earth has a mildly negative value relative to our Cd standard. Major sphalerite deposits worldwide are clustered between -1.0 and 0 suggesting that the mechanisms of ore deposit formation do not result in large isotopic fractionations of Cd. Ocean floor hydrothermal sulphide and Fe-Mn deposits mostly cluster around -0.5, but a few of the sulphides exhibit large variations -- as fractionated as -3.0 to +1.0. Overall, natural variations in ?^{112/110}Cd appear to be quite limited -- and are now resolvable -- but are dwarfed by the extreme Cd isotope fractionations found in meteorites (Rosman et al., 1980; Wombacher et al., 2003) and anthropogenic Cd (Cloquet et al., 2005). References: Cloquet C. et al. (2005), Geostand. Geoanal. Res. 1, 95-106; Galer S.J.G. (1999), Chem. Geol. 157, 255-274; Rosman K.J.R. et al. (1980), Geochem. J. 14, 269-277; Wombacher F. et al. (2003), Geochim. Cosmochim. Acta 67, 4639-4654.

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

2006-12-01

157

Thermal Neutron Capture Cross Sections Of The Palladium Isotopes  

NASA Astrophysics Data System (ADS)

We have measured precise thermal neutron capture ?-ray cross sections cry for all stable Palladium isotopes with the guided thermal neutron beam from the Budapest Reactor. The data were compared with other data from the literature and have been evaluated into the Evaluated Gamma-ray Activation File (EGAF). Total radiative neutron capture cross-sections ?? can be deduced from the sum of transition cross sections feeding the ground state of each isotope if the decay scheme is complete. The Palladium isotope decay schemes are incomplete, although transitions deexciting low-lying levels are known for each isotope. We have performed Monte Carlo simulations of the Palladium thermal neutron capture deexcitation schemes using the computer code DICEBOX. This program generates level schemes where levels below a critical energy Ecrit are taken from experiment, and those above Ecrit are calculated by a random discretization of an a priori known level density formula ?(E,J?). Level de-excitation branching intensities are taken from experiment for levels below Ecrit the capture state, or calculated for levels above Ecrit assuming an a priori photon strength function and applying allowed selection rules and a Porter-Thomas distribution of widths. The advantage of this method is that calculational uncertainties can be investigated systematically. Calculated feeding to levels below Ecrit can be normalized to the measured cross section deexciting those levels to determine the total radiative neutron cross-section ??. In this paper we report the cross section measurements ??[102Pd(n,?)]=0.9+/-0.3 b, ??[104Pd(n,?)=0.61+/-0.11 b, ??[105Pd(n,?)]=2.1.1+/-1.5 b, ??[106Pd(n,?)]=0.36+/-0.05 b, ??[108Pd(n,?)(0)]=7.6+/-0.6 b, ??[108Pd(n,?)(189)]=0.185+/-0.011 b, and ??[110Pd(n,?)]=0.10+/-0.03 b. We have also determined from our statistical calculations that the neutron capture states in 107Pd are best described as 2+[59(4)%]+3+[41(4)%]. Agreement with literature values was excellent in most cases. We found significant discrepancies between our results for 102Pd and 110Pd and earlier values that could be resolved by re-evaluation of the earlier results.

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

2006-03-01

158

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

Microsoft Academic Search

We have used the isotope dilution technique to study changes in the body composition of a migratory shorebird species (Red Knot, Calidris canutus) through an assessment of the amount of body water in it. Birds were quantitatively injected with a dose of water with elevated concentrations of H, O, and O. Thereafter, blood samples were taken and distilled. The resulting

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

2006-01-01

159

Solvent extraction\\/anion exchange separation and determination of PGEs (Os, Ir, Pt, Pd, Ru) and Re–Os isotopes in geological samples by isotope dilution ICP-MS  

Microsoft Academic Search

A method is described that allows the separation of Re, Os, Pt, Pd, Ir and Ru for determination by isotope dilution via inductively coupled mass spectrometry (ICP-MS) at pg levels, from the same sample aliquot. Samples are digested in Carius tubes, enabling effective attack of PGEs in a wide range of geological materials, including pure chromite separates. Os is isolated

D. G Pearson; S. J Woodland

2000-01-01

160

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

Microsoft Academic Search

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

Matthew S. Fantle; Thomas D. Bullen

2009-01-01

161

Zinc isotope fractionation analyses by thermal ionization mass spectrometry and a double spiking technique  

Microsoft Academic Search

The aim of this work was to develop thermal ionization mass spectrometry (TIMS) isotopic procedures to measure Zn isotope fractionation (?Zn) in natural materials. This work represents the most recent development of Zn isotope measurements and the first ?Zn identification in terrestrial materials using TIMS and a double spike technique. The developed procedures evaluate and solve several critical analytical issues

Osama Y. Ghidan; Robert D. Loss

162

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

PubMed Central

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

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

2011-01-01

163

Measurement of testosterone and its 5-alfa-reduced metabolites in human prostatic tissue using isotope dilution mass spectrometry.  

PubMed

5 alpha-Dihydrotestosterone (DHT) has been widely measured in human prostatic tissue using RIA since it is found to be involved in pathogenesis of human prostatic hyperplasia (BHP) and to be the best index for the follow-up of patients affected by prostatic cancer under endocrine treatment. A GC/MS method for the simultaneous determination of testosterone (T), dihydrotestosterone (DHT), 5 alpha-androstan-3 alpha,17 beta-diol (3 alpha-diol) and 5 alpha-androstan-3 beta-17 beta-diol (3 beta-diol) in prostatic tissue was developed based on the isotopic dilution technique. Trideuterated internal standards of each compound were previously synthesized in our laboratory. After previous extraction and purification on Sep-Pak C-18 cartridges and Lipidex DEAP columns, T and its metabolites were measured as heptafluorobutyric esters (HFB). Quantitative analysis was performed on a VG 7070 EQ mass spectrometer equipped with a fused silica capillary column using the Selected Ion Monitoring technique. Steroid values (means +/- SD; ng/g tissue) found in 9 human hypertrophic prostates were: T, 0.71 +/- 0.43; DHT, 4.46 +/- 1.41; 3 alpha-diol, 0.34 +/- 0.23; 3 beta-diol, 0.14 +/- 0.32. PMID:3807362

Moneti, G; Costantini, A; Guarna, A; Salerno, R; Pazzagli, M; Natali, A; Goti, A; Serio, M

1986-11-01

164

A stable isotope dilution assay for the quantification of the Pseudomonas quinolone signal in Pseudomonas aeruginosa cultures.  

PubMed

A stable isotope dilution method was developed to analyse 2-heptyl-3,4-dihydroxyquinoline, also called the Pseudomonas quinolone signal (PQS), directly in Pseudomonas aeruginosa cultures by liquid chromatography coupled to mass spectrometry (LC/MS). PQS, along with the isobaric 2-heptyl-4-hydroxyquinoline N-oxide (HQNO), were quantified in various Pseudomonas liquid cultures using a deuterated PQS analog as internal standard. The kinetic of production of these quinolines in a growing culture of P. aeruginosa PA14 showed that their production starts at the end of the logarithmic growth phase and is maximal at the onset of the stationary growth phase. The concentration of PQS reached a maximum at 13 mg/l and then decreased, while the HQNO concentration reached 18 mg/l and then remained stable. Culture supernatants of P. aeruginosa strains PAO1 and PA14 produced similar concentrations of PQS whereas no PQS or HQNO could be detected in culture supernatants of the P. aeruginosa strain PAK or in the other Pseudomonas species tested, including phytopathogenic pseudomonads. PMID:12829259

Lépine, F; Déziel, E; Milot, S; Rahme, L G

2003-06-20

165

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

PubMed Central

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

2009-01-01

166

Quality evaluation of olive oil by statistical analysis of multicomponent stable isotope dilution assay data of aroma active compounds.  

PubMed

An instrumental method for the evaluation of olive oil quality was developed. Twenty-one relevant aroma active compounds were quantified in 95 olive oil samples of different quality by headspace solid phase microextraction (HS-SPME) and dynamic headspace coupled to GC-MS. On the basis of these stable isotope dilution assay results, statistical evaluation by partial least-squares discriminant analysis (PLS-DA) was performed. Important variables were the odor activity values of ethyl isobutanoate, ethyl 2-methylbutanoate, 3-methylbutanol, butyric acid, E,E-2,4-decadienal, hexanoic acid, guaiacol, 2-phenylethanol, and the sum of the odor activity values of Z-3-hexenal, E-2-hexenal, Z-3-hexenyl acetate, and Z-3-hexenol. Classification performed with these variables predicted 88% of the olive oils' quality correctly. Additionally, the aroma compounds, which are characteristic for some off-flavors, were dissolved in refined plant oil. Sensory evaluation of these models demonstrated that the off-flavors rancid, fusty, and vinegary could be successfully simulated by a limited number of odorants. PMID:22117816

Dierkes, Georg; Bongartz, Annette; Guth, Helmut; Hayen, Heiko

2011-12-12

167

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

168

Isotopic test of a thermally driven intraplate orogenic model, Australia  

NASA Astrophysics Data System (ADS)

A recently proposed model for intraplate orogenesis couples long-term self-heating of basement rocks by radioactive decay with thermal blanketing by overlying sedimentary deposits. This model has been tested in one of the type areas in central Australia, the Proterozoic Musgrave Complex, which was reworked in an Early Cambrian orogeny. We have determined the source of the pre orogenic and postorogenic sediments in the Amadeus basin immediately to the north of the reworked basement, including the fan deposits associated with uplift, comprising Uluru (Ayers Rock) and Kata Tjuta (Olgas). Detrital-zircon age populations indicate that all basin sediments were derived from the Musgrave Complex, which was therefore emergent rather than covered by sediments as required by the model. In the basement, the preservation of Mesoproterozoic mica ages during transpressive burial to depths of ˜40 km ca. 550 Ma indicates that the associated thermal pulse was short-lived, not long-lived as envisaged in the model. We conclude therefore that the thermal-blanketing model is inconsistent with the isotopic data and that the localization of deformation in intracratonic settings is associated with regions of contrasting strengths; in central Australia, these are along the margins of the Amadeus basin with the Musgrave Complex and Arunta inlier.

Camacho, A.; Hensen, B. J.; Armstrong, R.

2002-10-01

169

Nitrification and Denitrification Estimates in a Louisiana Swamp Forest Soil as Assessed by 15 N Isotope Dilution and Direct Gaseous Measurements  

Microsoft Academic Search

The transformations of applied (100 kg N ha-1)15 N labelled NO3 and NH4 in Mississippi River deltaic plain swamp forest soil which receives agriculture run-off from adjacent sugarcane fields were determined. Using an isotopic dilution technique, the rates of NO3 production (nitrification) and reduction in the 15NO3 treated soil-water-columns were approximately 240 and 2,320 g N ha-1 d-1, whereas NH4

R. D. Delaune; C. W. Lindau; A. Jugsujinda

1998-01-01

170

Isotope Dilution Gas Chromatographic-Mass Spectrometric Method for the Determination of Unconjugated Lignans and Isoflavonoids in Human Feces, with Preliminary Results in Omnivorous and Vegetarian Women  

Microsoft Academic Search

We describe an isotope dilution gas chromatographic-mass spectrometric (GC\\/MS) method for the identification and quantitative determination of the lignans enterolactone, enterodiol, and matairesinol and the isoflavonoids daidzein, equol, O-desmethylangolensin, and genistein in feces. Following the addition of deuterated internal standards for all compounds, the feces samples are extracted and purified in several ion exchange chromatographic steps. Following formation of trimethylsilyl

H. Adlercreutz; T. Fotsis; M. S. Kurzer; K. Wahala; T. Makela; T. Hase

1995-01-01

171

Determination of iron in seawater by high-resolution isotope dilution inductively coupled plasma mass spectrometry after Mg(OH) 2 coprecipitation  

Microsoft Academic Search

A simple, accurate and highly sensitive method has been developed for determining the concentration of Fe in seawater. The technique applies the low-blank Mg(OH)2 coprecipitation method of Wu and Boyle [Anal. Chem. 69 (1997) 2464–2470] to preconcentrate Fe from seawater, and uses isotope dilution high-resolution ICPMS detection to ensure accuracy and enable high sensitivity. This method has been used to

Jingfeng Wu; Edward A Boyle

1998-01-01

172

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

Microsoft Academic Search

This improved isotope-dilution gas chromatographic\\/mass spectrometric (GC\\/MS) method, in which (¹³C)glucose is the internal standard, meets the requirements of a Definitive Method. In a first study with five reconstituted lyophilized sera, a nested analysis of variance of GC\\/MS values indicated considerable among-vial variation. The CV for 32 measurements per serum ranged from 0.5 to 0.9%. However, concentration and uncertainty values

O. Pelletier; C. Arratoon

1987-01-01

173

Rb isotope dilution analyses by MC-ICPMS using Zr to correct for mass fractionation: towards improved Rb–Sr geochronology?  

Microsoft Academic Search

A new technique is presented where mass fractionation during Rb isotope dilution analyses by multi-collector inductively coupled plasma mass spectrometry is corrected for by measuring the amount of fractionation on admixed Zr. Replicate analyses of natural Rb interspersed with analyses of 87Rb tracer enriched samples yield a mean 87Rb\\/85Rb=0.38540±19 (0.05%, 2 s.d.), assuming a natural 90Zr\\/91Zr of 4.588. Each Rb

Tod Waight; Joel Baker; Bart Willigers

2002-01-01

174

Determination of Folate Vitamers in Human Serum by Stable-Isotope-Dilution Tandem Mass Spectrometry and Comparison with Radioassay and Microbiologic Assay  

Microsoft Academic Search

Background: Current clinical methods for folate give different results and cannot measure the various forms of folate. We developed an isotope-dilution tandem mass spectrometric method coupled to liquid chroma- tography (LC\\/MS\\/MS) as a candidate reference method for 5-methyltetrahydrofolic acid (5MeTHF), 5-formyltet- rahydrofolic acid (5FoTHF), and folic acid (FA) in hu- man serum. Methods: We quantitatively isolated folates from 275 L

Christine M. Pfeiffer; Zia Fazili; Ming Zhang; Elaine W. Gunter

175

Simultaneous determination of amphetamine and methamphetamine enantiomers in urine by simultaneous liquid–liquid extraction and diastereomeric derivatization followed by gas chromatographic–isotope dilution mass spectrometry  

Microsoft Academic Search

A simple, rapid, reliable, and economic analytical scheme starting with in situ liquid–liquid extraction and asymmetric (or diastereomeric) chemical derivatization (ChD) followed by gas chromatography (GC)-isotope dilution mass spectrometry (MS) is described for the simultaneous determination of d- and l-amphetamine (AP) and methamphetamine (MA) in urine which could have resulted from the administration of various forms of questioned amphetamines or

Sheng-Meng Wang; Ting-Cheng Wang; Yun-Seng Giang

2005-01-01

176

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

2013-05-27

177

Quantitative precursor studies on di- and trihydroxybenzene formation during coffee roasting using "in bean" model experiments and stable isotope dilution analysis.  

PubMed

The objective of this study was to investigate the potential of various raw bean components as precursors of pyrogallol (1), hydroxyhydroquinone (2), catechol (3), 4-ethylcatechol (4), 4-methylcatechol (5), and 3-methylcatechol (6) under quasi "natural" roasting conditions by using the recently developed "in bean" model roast experiments. Freeze-dried, fully extracted bean shells were loaded with aqueous solutions of either single coffee compounds or fractions isolated from the raw bean solubles. After freeze-drying, these reconstituted beans were roasted, aqueous coffee brews were prepared, and the target phenols were quantified by means of a stable isotope dilution assay with LC-MS/MS detection. On the basis of the quantitative data, it can be concluded that upon coffee bean roasting, catechol (3) is primarily formed by degradation of caffeoylquinic acids from both the caffeic acid and the quinic acid moiety of the molecule, as well as from Maillard-type reactions from carbohydrates and amino acids. In contrast, pyrogallol (1) and hydroxyhydroquinone (2) are efficiently generated from carbohydrates and amino acids and, in addition, from free or chlorogenic acid bound quinic acid moieties. 4-Ethylcatechol (4) is exclusively generated upon thermal breakdown of caffeic acid moieties. 3-Methylcatechol (6) is formed primarily from the Maillard reactions and, to a minor extent, also from various phenolic precursors, whereas 4-methylcatechol (5) is produced in trace amounts only from all of the different precursors investigated. On the basis of this precursor study, reaction routes explaining the formation of the target phenols are proposed. PMID:17177545

Müller, Christoph; Lang, Roman; Hofmann, Thomas

2006-12-27

178

Muon transfer from thermalized muonic hydrogen isotopes to argon  

NASA Astrophysics Data System (ADS)

Recent experimental results on the muon exchange from muonic hydrogen to argon show that the reaction rate is energy dependent near 0.1 eV. A muonic hydrogen atom, formed by muon capture in H2 gas at 15 bars, is thermalized in a few hundreds of nanoseconds. If the muon transfer reaction occurs before that time, the rate is shown to be slightly lower compared to thermalized muonic atoms [?pAr=(1.63+/-0.09)×1011fs-1]. As an indirect consequence, the muon transfer rate from ?p to helium, determined by our group [R. Jacot-Guillarmod and co-workers, Phys. Rev. A 38, 6151 (1988)] is lowered by about 40%. The present value ?pHe=(0.51+/-0.19)×108fs-1 is in good agreement with other experiments. The transfer rate from muonic deuterium to argon shows also an energy dependence. The muon transfer rate to argon from the deuteron is ?dAr=(0.86+/-0.04)×1011fs-1 at room temperature. The intensity patterns of the muonic Lyman series of argon obtained by muon transfer from both hydrogen isotopes are determined and compared with theoretical predictions.

Jacot-Guillarmod, R.; Mulhauser, F.; Piller, C.; Schaller, L. A.; Schellenberg, L.; Schneuwly, H.; Thalmann, Y.-A.; Tresch, S.; Werthmüautller, A.; Adamczak, A.

1997-05-01

179

Muon transfer from thermalized muonic hydrogen isotopes to argon  

SciTech Connect

Recent experimental results on the muon exchange from muonic hydrogen to argon show that the reaction rate is energy dependent near 0.1 eV. A muonic hydrogen atom, formed by muon capture in H{sub 2} gas at 15 bars, is thermalized in a few hundreds of nanoseconds. If the muon transfer reaction occurs before that time, the rate is shown to be slightly lower compared to thermalized muonic atoms [{lambda}{sub pAr}=(1.63{plus_minus}0.09){times}10{sup 11} s{sup {minus}1}]. As an indirect consequence, the muon transfer rate from {mu}p to helium, determined by our group [R. Jacot-Guillarmod and co-workers, Phys. Rev. A {bold 38}, 6151 (1988)] is lowered by about 40{percent}. The present value {lambda}{sub pHe}=(0.51{plus_minus}0.19){times}10{sup 8} s{sup {minus}1} is in good agreement with other experiments. The transfer rate from muonic deuterium to argon shows also an energy dependence. The muon transfer rate to argon from the deuteron is {lambda}{sub dAr}=(0.86{plus_minus}0.04){times}10{sup 11} s{sup {minus}1} at room temperature. The intensity patterns of the muonic Lyman series of argon obtained by muon transfer from both hydrogen isotopes are determined and compared with theoretical predictions. {copyright} {ital 1997} {ital The American Physical Society}

Jacot-Guillarmod, R.; Mulhauser, F.; Piller, C.; Schaller, L.A.; Schellenberg, L.; Schneuwly, H.; Thalmann, Y.; Tresch, S.; Werthmueller, A. [Institut de Physique, Universite de Fribourg, CH-1700 Fribourg (Switzerland); Adamczak, A. [Institute of Nuclear Physics, 31-342 Krakow (Poland)

1997-05-01

180

Improved Isotopic Measurement of Plutonium by Thermal Ionization Mass Spectrometry  

SciTech Connect

Thermal ionization mass spectrometry (TIMS) is accepted widely as the benchmark method for precise and accurate isotopic determination of plutonium. TIMS is one of the few analytical methods capable of determining Pu in bioassay samples at the level required for detecting a 50 yr committed dose of 100 mRem resulting from an inhalation exposure to highly insoluble forms of Pu. Typically, Pu is measured in bioassay samples by radiochemical separation, electrodeposition onto a planchet, and radiometric determination by alpha spectrometry. If, based on the alpha spectrometry results, a sample is deemed to need a more sensitive analysis (i.e. suspected uptake, borderline alpha spectrometry positive for Pu uptake, etc.), then the sample is prepared for analysis by TIMS. Part of the development process for establishing a program to determine Pu in bioassay samples by TIMS at the Savannah River Site involved a careful evaluation of the Pu blank value in the reagents used for sample preparation and in urine blanks. This exercise allowed for the evaluation of the newly developed radiochemical separation procedure, the resin bead loading procedure, and the detection limits of the thermal ionization mass spectrometer.

Shick, C. Jr.

2002-02-07

181

Development of a stable isotope dilution analysis for the quantification of the Bacillus cereus toxin cereulide in foods.  

PubMed

An increasing number of severe food borne intoxications are caused by a highly stable depsipeptide, named cereulide, which is produced by emetic Bacillus cereus strains. As cereulide poses a health risk to humans, the development of an appropriate method for the analysis of this toxin is mandatory. Therefore, the reference material of cereulide as well as its (13)C(6)-isotopologue was prepared by means of a biosynthetic approach using a B. cereus culture, followed by a rapid but efficient downstream purification. After structure confirmation by means of liquid chromatography (LC)-time-of-flight mass spectrometry, LC-tandem mass spectrometry, and one-/two-dimensional NMR spectroscopy, a stable isotope dilution analysis (SIDA) was developed for the quantification of cereulide in foods using the (13)C(6)-cereulide as the internal standard. Validation experiments were performed, and the data were compared to the quantitative analysis using the structurally related valinomycin instead of the (13)C(6)-cereulide as an internal standard. Trueness, repeatability, and reproducibility expressed as relative standard deviation showed values <10 or <8% for valinomycin or <8% for (13)C(6)-cereulide, respectively. Furthermore, the MS response of the valinomycin was found to be significantly influenced by the food matrix, thus leading to rather low recovery rates of 91% from boiled rice and 80% from boiled rice supplemented with 10% sunflower oil. In comparison, the use of (13)C(6)-cereulide as an internal standard gave good recovery rates of 104 and 111% from both matrices, thus demonstrating the robustness and accuracy of the developed SIDA. PMID:19994891

Bauer, Tobias; Stark, Timo; Hofmann, Thomas; Ehling-Schulz, Monika

2010-02-10

182

Nitrogen Transformations in Wetland Soil Cores Measured by (sup15)N Isotope Pairing and Dilution at Four Infiltration Rates  

PubMed Central

The effect of water infiltration rate (IR) on nitrogen cycling in a saturated wetland soil was investigated by applying a (sup15)N isotope dilution and pairing method. Water containing [(sup15)N]nitrate was infiltrated through 10-cm-long cores of sieved and homogenized soil at rates of 72, 168, 267, and 638 mm day(sup-1). Then the frequencies of (sup30)N(inf2), (sup29)N(inf2), (sup15)NO(inf3)(sup-), and (sup15)NH(inf4)(sup+) in the outflow water were measured. This method allowed simultaneous determination of nitrification, coupled and uncoupled denitrification, and nitrate assimilation rates. From 3% (at the highest IR) to 95% (at the lowest IR) of nitrate was removed from the water, mainly by denitrification. The nitrate removal was compensated for by the net release of ammonium and dissolved organic nitrogen. Lower oxygen concentrations in the soil at lower IRs led to a sharper decrease in the nitrification rate than in the ammonification rate, and, consequently, more ammonium leaked from the soil. The decreasing organic-carbon-to-nitrogen ratio (from 12.8 to 5.1) and the increasing light A(inf250)/A(inf365) ratio (from 4.5 to 5.2) indicated an increasing bioavailability of the outflowing dissolved organic matter with increasing IR. The efflux of nitrous oxide was also very sensitive to IR and increased severalfold when a zone of low oxygen concentration was close to the outlet of the soil cores. N(inf2)O then constituted 8% of the total gaseous N lost from the soil.

Stepanauskas, R.; Davidsson, E. T.; Leonardson, L.

1996-01-01

183

Detection of DNA adducts originating from 1-methoxy-3-indolylmethyl glucosinolate using isotope-dilution UPLC-ESI-MS/MS.  

PubMed

1-Methoxy-3-indolylmethyl (1-MIM) glucosinolate, present at substantial levels in several food crops (e.g., broccoli and cabbage), forms DNA adducts in vitro and is mutagenic to bacterial and mammalian cells after activation by the plant enzyme myrosinase. Moreover, a breakdown product, 1-MIM alcohol, is metabolized to a secondary reactive intermediate by some mammalian sulfotransferases (SULTs). First, we incubated herring-sperm DNA with 1-MIM glucosinolate in the presence of myrosinase. We identified and synthesized the predominant adducts, N(2)-(1-MIM)-dG and N(6)-(1-MIM)-dA, and developed an UPLC-ESI-MS/MS method for their specific detection using isotopic dilution. Second, we demonstrated both DNA adducts in target cells (Salmonella typhimurium TA100 and Chinese hamster V79) of standard mutagenicity tests treated with 1-MIM glucosinolate/myrosinase as well as in 1-MIM alcohol-treated Salmonella and V79 cells engineered for expression of human SULT1A1. Similar excesses of N(2)-(1-MIM)-dG over N(6)-(1-MIM)-dA adducts were found in all cellular models independent of the test compound (1-MIM glucosinolate or alcohol), whereas dA adducts predominated in the cell-free system. Finally, we detected both DNA adducts in colon tissue of a mouse orally treated with 1-MIM glucosinolate. We are going to use this specific and sensitive method for investigating genotoxic risks of food-borne exposure to 1-MIM glucosinolate in animal and human studies. PMID:22816785

Schumacher, Fabian; Engst, Wolfram; Monien, Bernhard H; Florian, Simone; Schnapper, Anke; Steinhauser, Lisa; Albert, Klaus; Frank, Heinz; Seidel, Albrecht; Glatt, Hansruedi

2012-07-03

184

Application of the isotope dilution technique for 93Zr determination in an irradiated cladding material by multiple collector-inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

The determination of 93Zr concentration, a long-lived radionuclide present in spent nuclear fuel and in the structural components of nuclear reactors, is a major issue for nuclear waste disposal purpose and to validate neutronic calculation codes. To measure 93Zr concentration in irradiated cladding material with a high precision, an analytical method based on the use of multiple collector-inductively coupled plasma mass spectrometer (MC-ICPMS) combined to isotope dilution technique was developed. First a radiochemical separation of zirconium from a zircaloy sample (a zirconium alloy used as a cladding material for nuclear fuel elements), has allowed to obtain a very pure zirconium fraction with no potential isobaric interferences for mass spectrometric measurements. Then as the determination of all zirconium isotope ratios in the sample is necessary for the isotope dilution method, a MC-ICPMS procedure was developed to perform these precise measurements. Finally, the determination of 93Zr concentration in the same sample was performed, after preparation and calibration of a 96Zr spike solution. The uncertainties obtained on isotope ratios of zirconium by MC-ICPMS were in the order of 0.1%. The final uncertainty obtained on the 93Zr concentration in the nuclear material used and after chemical purification was lower than 0.6%.

Chartier, F.; Isnard, H.; Degros, J. P.; Faure, A. L.; Fréchou, C.

2008-03-01

185

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

PubMed

This work demonstrates, for the first time, the applicability of multiple spiking isotope dilution analysis to molecular mass spectrometry exemplified by the speciation analysis of mercury using GC(EI)MS instrumentation. A double spike isotope dilution approach using isotopically enriched mercury isotopes has been applied for the determination of inorganic mercury Hg(II) and methylmercury (MeHg) in fish reference materials. The method is based on the application of isotope pattern deconvolution for the simultaneous determination of degradation-corrected concentrations of methylmercury and inorganic mercury. Mass isotopomer distributions are employed instead of isotope ratios to calculate the corrected concentrations of the Hg species as well as the extent of species degradation reactions. The isotope pattern deconvolution equations developed here allow the calculation of the different molar fractions directly from the GC(EI)MS mass isotopomer distribution pattern and take into account possible impurities present in the spike solutions employed. The procedure has been successfully validated with the analysis of two different certified reference materials (BCR-464 and DOLT-4) and with the comparison of the results obtained by GC(ICP)MS. For the tuna fish matrix (BCR-464), no interconversion reactions were observed at the optimized conditions of open focused microwave extraction at 70 degrees C during 8 min. However, significant demethylation was found under the same conditions in the case of the certified dogfish liver DOLT-4. Methylation and demethylation factors were confirmed by GC(ICP)MS. Transformation reactions have been found to depend on the sample matrix and on the derivatization reagent employed. Thus, it is not possible to recommend optimum extraction conditions suitable for all types of matrices demonstrating the need to apply multiple spiking methodologies for the determination of MeHg and Hg(II) in biological samples. Double spike isotope dilution analysis methodologies using widespread GC(EI)MS instrumentation are proposed here for the routine analysis of inorganic mercury and methylmercury in fish samples. The estimated method detection limits were below 10 ng g(-1) for both mercury species. Precision was evaluated for the concentrations present in the certified reference materials (CRMs) which vary from 0.1 to 5 microg g(-1), achieving values of coefficients of variation ranging from 7% to 2%. The concentrations obtained in both CRMs analyzed were in excellent agreement with the certified values, demonstrating the accuracy of the method at these concentration levels. PMID:20192179

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

2010-04-01

186

Determination of Hg Content in a Shallow Firn Core From Summit, Greenland Using Isotope Dilution Cold Vapor Inductively Coupled Plasma - Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Considerable attention has recently been focused on mercury (Hg) owing to its ability to bioaccumulate as highly toxic species in the biosphere. Hg in the environment is derived from both natural and anthropogenic sources and present day emissions for both are thought to be of similar magnitude. Once introduced into the atmosphere, Hgo can be transported long distances and as a result is considered to have global environmental influence. High levels of Hg have been found in Arctic food supplies and elevated levels have been observed in the native people of the circumpolar countries including Greenland. Mercury content was determined in surface snow and a 7 m shallow snow/firn core, recovered in May 2001 from Summit, Greenland (72.58oN, 38.53oW; elevation 3238 m), using a new method employing isotope dilution cold vapor inductively coupled plasma - mass spectrometry (ID-CV-ICPMS). The method, recently developed at the National Institute of Standards and Technology, uses a 201Hg spike that is equilibrated with the sample. Hg is measured by chemical reduction with tin (II) chloride and generation of a "cold vapor" (elemental Hg vapor) whereby the Hg vapor is separated from the matrix using a gas-liquid separator and is collected on gold guaze. Hg is then released by thermal desorption and the Hg isotope ratio (201Hg/202Hg) measured by quadrapole ICP-MS. There are considerable advantages to this new method in the analysis of very low concentration snow/firn/ice samples which include: 1) very high sensitivity (detection limit < 1 pg/mL, 3 sigma); 2) accuracy and precision of the order of one percent or better; and 3) complete freedom from spectral and matrix interferences. The concentrations determined ranged from 0.1 to 1.1 pg/g, which fall within the range of those previously determined by Boutron et al. (1998). Hg contributed from core processing, storage in LDPE bottles, and the analytical procedure yielded a blank value of 0.10 pg Hg/g equivalent. This was used to correct the measured Hg values. The uncertainty in the reported Hg concentrations was 0.1 to 0.2 pg Hg/g for a 10 mL aliquot. This new method may allow the examination of the high-resolution (sub-seasonal) snow/firn/ice record for better understanding of the short-term variability in Hg concentrations and their relationship to atmospheric mercury depletion events.

Mann, J. L.; Long, S. E.; Shuman, C. A.

2002-05-01

187

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

NASA Astrophysics Data System (ADS)

Geochemical investigations were carried out to define the origin of the low- to moderate-temperature thermal waters feeding the Monfalcone springs in northern Italy. Chemical data indicate that waters approach the composition of seawater. Mixing processes with cold low-salinity waters are highlighted. The ?18O and ?D values are in the range -5.0 to -6.4 ‰, and -33 to -40 ‰, respectively, suggesting the dilution of the saline reservoir by karst-type freshwaters. A surplus of Ca2+ and Sr2+ ions with respect to a conservative mixing is ascribed to diagenetic reactions of the thermal waters with Cretaceous carbonates at depth. The measured Sr isotopic composition (87Sr/86Sr ratio) ranges between 0.70803 and 0.70814; after correction for the surplus Sr, a 87Sr/86Sr ratio indicating Miocene paleo-seawater is obtained. The dissolved gases indicate long-lasting gas-water interactions with a deep-originated gas phase of crustal origin, dominated by CO2 and marked by a water TDIC isotopic composition in the range -5.9 to-8.8 and helium signature with 0.08 < R/Ra < 0.27, which is a typical range for the crust. A possible scenario for the Monfalcone thermal reservoir consists of Miocene marine paleowaters which infiltrated through the karstic voids formed within the prevalently Cretaceous carbonates during the upper Eocene emersion of the platform, and which were entrapped by the progressive burial by terrigenous sediments.

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

2013-09-01

188

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

189

Evaluation of the Mass Spectrometric Isotope Dilution Technique with the Addition of Two Tracers ((233)U and (235)U) in the Determination of the Concentration and Distribution of Uranium in Minerals.  

National Technical Information Service (NTIS)

Mass spectrometric isotope dilution technique employing two tracers (/sup 233/U and /sup 235/U), where two independant values of uranium are obtained in single dilution, is developed for the determination of the uranium in mineral samples with a range of ...

H. M. Shihomatsu S. S. Iyer

1988-01-01

190

The Magmatic Structure of Mt. Vesuvius: Isotopic and Thermal Constraints  

NASA Astrophysics Data System (ADS)

Mt. Vesuvius is an active volcano famous for the AD 79 eruption that destroyed Pompeii, Herculaneum and Stabiae. Because of the intense urbanization around and on the volcano, the risk today is very high. Therefore, the knowledge of the structure and behavior of the magmatic system is fundamental both for the interpretation of any change in the dynamics of the volcano and for prediction of eruptions. A review of available and new isotopic data on rocks from Mt. Vesuvius, together with mineralogical and geochemical data and recent geophysical results, allow us to constrain a thermal modeling that describes history and present state of Mt. Vesuvius magmatic system. This system is formed by a "deep", complex magmatic reservoir where mantle-derived magmas arrive, stagnate and differentiate. The reservoir extends discontinuously between 10 and 20 km of depth, is hosted in densely fractured crustal rocks, where magmas and crust can interact, and has been fed more than once since 400 ka. The hypothesis of crustal contamination is favored by the high temperatures reached by crustal rocks as a consequence of repetitive intrusions of magma. From the "deep" reservoir magmas of K-basaltic to K-tephritic to K-phonotephritic composition rise to shallow depths where they stagnate at 3-5 km of depth before plinian eruptions, and through crystallization and mixing processes with the residual portion of the feeding systems, generate isotopically and geochemically layered reservoirs. Alternatively, during "open conduit" conditions deep, volatile-rich magma batches rise from the "deep" reservoir to less than 1 km of depth and mix with the crystal-rich, volatile-poor resident magma, triggering eruptions.

Civetta, L.; D'Antonio, M.; de Lorenzo, S.; Gasparini, P.

2002-12-01

191

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

National Technical Information Service (NTIS)

Mass flow and compositional gradient (elemental and isotope separation) occurs when flu-id(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been theoretically ...

H. Bao P. Niles R. Socki T. Sun Y. Liu

2013-01-01

192

Body composition in mink (Mustela vison) kits during 21-42 days postpartum using estimates of hydrogen isotope dilution and direct carcass analysis.  

PubMed

We compared carcass analysis and hydrogen isotope dilution methods to measure total body water (TBW) and body composition in a small altricial carnivore, the mink. Dilution space (D) of mink at 21-42 days of age (n=20), was determined after subcutaneous administration of tritiated water. The same animals were then used to determine TBW and body composition by carcass analysis and to derive predictive empirical relationships between TBW and total body fat, protein and energy. A separate validation set of 27 kits was used to test the accuracy of predicting body composition from TBW. D overestimated TBW by a consistent and predictable 4.1% (R(2)=0.999, P<0.001). Our estimates of fat, protein and energy content, using equations derived from TBW, were not significantly different than those obtained from direct carcass analysis (P>0.980) in either the initial or validation set of mink. TBW was shown to decrease from 81 to 76% and total body protein to increase from 14 to 19% of LBM of the kits from 21 to 42 days of age. Although a rapidly changing hydration state was apparent in neonates, we conclude that when this is taken into account, accurate estimates of body composition can be obtained from hydrogen isotope dilution. PMID:10936769

Layton, H N; Rouvinen-Watt, K I; Iverson, S J

2000-06-01

193

GC-EI-TOF-MS analysis of in vivo carbon-partitioning into soluble metabolite pools of higher plants by monitoring isotope dilution after 13CO2 labelling.  

PubMed

The established GC-EI-TOF-MS method for the profiling of soluble polar metabolites from plant tissue was employed for the kinetic metabolic phenotyping of higher plants. Approximately 100 typical GC-EI-MS mass fragments of trimethylsilylated and methoxyaminated metabolite derivatives were structurally interpreted for mass isotopomer analysis, thus enabling the kinetic study of identified metabolites as well as the so-called functional group monitoring of yet non-identified metabolites. The monitoring of isotope dilution after (13)CO(2) labelling was optimized using Arabidopsis thaliana Col-0 or Oryza sativa IR57111 plants, which were maximally labelled with (13)C. Carbon isotope dilution was evaluated for short (2h) and long-term (3 days) kinetic measurements of metabolite pools in root and shoots. Both approaches were shown to enable the characterization of metabolite specific partitioning processes and kinetics. Simplifying data reduction schemes comprising calculation of (13)C-enrichment from mass isotopomer distributions and of initial (13)C-dilution rates were employed. Metabolites exhibited a highly diverse range of metabolite and organ specific half-life of (13)C-label in their respective pools ((13)C-half-life). This observation implied the setting of metabolite specific periods for optimal kinetic monitoring. A current experimental design for the kinetic metabolic phenotyping of higher plants is proposed. PMID:17475294

Huege, Jan; Sulpice, Ronan; Gibon, Yves; Lisec, Jan; Koehl, Karin; Kopka, Joachim

2007-05-01

194

Transient Thermal Performance of Axially and Radially Diluted Nuclear Fuel Cells  

Microsoft Academic Search

A numerical investigation is presented of steady and unsteady heat transfer in axially and radially diluted nuclear fuel rods. The transient performance is assumed to follow a sudden and complete loss of coolant starting from steady state operation. Steady state conditions are obtained from solving numerically a conjugate conduction problem in the fuel rod and a turbulent forced convection problem

F. Moukalled; R. Nuwayhid; I. Lakkis

1995-01-01

195

The effect of thermal treatment on the metallographic structure of beryllium and dilute beryllium alloys  

Microsoft Academic Search

Electron microscopy and electron-probe microanalysis techniques were ; used to study the microstructure of beryllium and some dilute beryllium alloys. ; The effect of tuermal treatment on the dissemination of impurities and alloying ; elements was investigated with particular reference to the mechanical properties ; of the metal at 600 deg C. In beryllium-iron alloys annealed to improve high-; temperature

G. V. T. Ranzetta; V. D. Scott

1963-01-01

196

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

197

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 obtained in the prior art.

Rutherford, W.M.

1985-12-04

198

Osmium isotope ratio measurements by negative thermal ionization mass spectrometry (NTI-MS)  

Microsoft Academic Search

A negative thermal ionization technique using a Faraday cup as detector is presented, which allows precise isotope ratio measurements of osmium. For the major isotopes the relative standard deviation is in the range of 0.004% to 0.07%. Sample amounts down to 1 ng were loaded as hexachloroosmic acid. From the results it is concluded that also sample amounts in the

Thomas Walczyk; Erhard H. Hebeda; Klaus G. Heumann

1991-01-01

199

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

Microsoft Academic Search

The thermal springs of Oregon range in composition from dilute NaHCOâ waters to moderately saline COâ-charged NaCl-NaHCOâ 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

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

1981-01-01

200

Transient thermal performance of a radially diluted and centrally cooled nuclear fuel cell  

SciTech Connect

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 lost. Results show a great reduction in the maximum wall temperature under steady operation and a substantial increase in the time delay under transient conditions, with its value increasing with increasing the amount of added diluent. Moreover, results indicate the presence of an optimum value of the ratio of inner to outer channel flow rates for which the maximum inner and outer wall temperatures are minimum. Finally, the distribution of the added diluent is shown to mildly affect the steady and unsteady performance of the reactor.

Moukalled, F.; Nuwayhid, R.; Lakkis, I. [American Univ. of Beirut (Lebanon). Mechanical Engineering Dept.

1995-12-01

201

Thermal and percolative properties of a diluted Ising metamagnet in a field  

NASA Astrophysics Data System (ADS)

We calculated thermodynamic quantities such as the staggered and direct susceptibilities, internal energy and specific heat of a diluted Ising layered metamagnet in an external field, by the use of an effective field theory (EFT) with correlations, developed for this model in our previous paper. We also extensively investigated how an inter- and intra-layer exchange interaction ratio can influence critical, tricritical and percolative properties of the system.

Žukovi?, M.; Bobák, A.; Idogaki, T.

1998-09-01

202

Simultaneous multi-species determination of trimethyllead, monomethylmercury and three butyltin compounds by species-specific isotope dilution GC–ICP–MS in biological samples  

Microsoft Academic Search

An accurate and sensitive multi-species species-specific isotope dilution GC–ICP–MS method was developed for the simultaneous\\u000a determination of trimethyllead (Me3Pb+), monomethylmercury (MeHg+) and the three butyltin species Bu3Sn+, Bu2Sn2+, and BuSn3+ in biological samples. The method was validated by three biological reference materials (CRM 477, mussel tissue certified\\u000a for butyltins; CRM 463, tuna fish certified for MeHg+; DORM 2, dogfish muscle

Nataliya Poperechna; Klaus G. Heumann

2005-01-01

203

Simultaneous determination of androstenediol 3-sulfate and dehydroepiandrosterone sulfate in human serum using isotope diluted liquid chromatography–electrospray ionization-mass spectrometry  

Microsoft Academic Search

A simple method for simultaneous determination of androstenediol 3-sulfate (Adiol-3S) and dehydroepiandrosterone sulfate (DHEA-S) in human serum using isotope diluted liquid chromatography–electrospray ionization-ion trap-mass spectrometry (LC–ESI-ion trap-MS) was developed. After addition of deuterated internal standards ([2H5]Adiol-3S and [2H4]DHEA-S), human serum (100?l) was deproteinized with acetonitrile and then applied to a solid-phase extraction cartridge, Oasis HLB. The obtained steroid sulfates fraction

Kuniko Mitamura; Yoko Nagaoka; Kazutake Shimada; Seijiro Honma; Mikio Namiki; Eitetsu Koh; Atsushi Mizokami

2003-01-01

204

Quantitation of metabolites of the nerve agents sarin, soman, cyclohexylsarin, VX, and Russian VX in human urine using isotope-dilution gas chromatography-tandem mass spectrometry.  

PubMed

Organophosphorus nerve agents are among the most toxic organic compounds known and continue to be a threat for both military and terrorist use. We have developed an isotope-dilution gas chromatography-tandem mass spectrometric (GC-MS-MS) method for quantitating the urinary metabolites of the organophosphorus nerve agents sarin (GB), soman (GD), VX, Russian VX (RVX), and cyclohexylsarin (GF). Urine samples were acidified, extracted into ether-acetonitrile, derivatized by methylation with diazomethane, and analyzed by GC-MS-MS. The limits of detection were less than 1 micro g/L for all analytes. PMID:15239858

Barr, John R; Driskell, W J; Aston, Linda S; Martinez, Rodolfo A

205

Enhanced cardiac thermal dilution analysis for cardiac output, volumes, stroke volumes, and regurgitation rates--sensitivity analysis using digital simulation.  

PubMed

Cardiac output is measured by placing a double lumen catheter with a thermistor on the tip through the right ventricle into the pulmonary artery, injecting cold saline into the right atrium, and integrating the resulting pulmonary artery temperature profile. If a similar procedure is performed with thermistors located in the right atrium, right ventricle, and pulmonary artery, the resulting temperature curves are determined by the known or easily measured quantities: injectate temperature, injectate volume, heart rate, systolic time interval, body temperature, and time in the cardiac cycle at which injection begins and the unknown quantities: right atrial, right ventricular, pulmonary artery mean and stroke volumes, inflow and outflow valve regurgitation rates, and cardiac output. A digital computer program using a lumped parameter model has been developed to use these quantities to produce thermal dilution curves and optimize the fit of the model curves to the temperature curves from the thermal dilution measurement to determine the unknown quantities. The program is used to investigate the effects of measuring system time constant, heat transfer, and noise on the accuracy of these measurements. The results indicate that the method is practical. PMID:10999367

Donovan, F M; Taylor, B C

2000-01-01

206

Groundwater dilution and residence times, and constraints on chloride source, in the Mokai geothermal system, New Zealand, from chemical, stable isotope, tritium, and sup 36 Cl data  

Microsoft Academic Search

The maximum measured temperature of the production wells is near 323C at 2500 m depth, whereas temperatures in two wells on the northern margin of the upflow are <200C, with thermal inversions at 350 and 1,000 m indicating lateral flow. These two marginal wells have about 50% of the chloride of the deep fluid, indicating dilution by cold groundwater. Chloride-bearing

Jeffrey W. Hedenquist; Fraser Goff; Fred M. Phillips; David Elmore; Michael K. Stewart

1990-01-01

207

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

NASA Astrophysics Data System (ADS)

Water plays a fundamental role in affecting geochemical transport and physical properties of magmas. Here we show the previously undocumented behavior of water within partially molten silicate resting in a temperature gradient, producing O, Li and H isotope redistribution by thermal diffusion leading to enrichment of light isotopes at the hot end of the gradient. After weeks to months, fully molten as well as mostly crystalline portions of water-bearing experiments develop remarkably large isotope and chemical redistributions: up to 28‰ for ?18O, 144‰ for ?D, and 18‰ for ?7Li. In contrast, long-term dry experiments develop smaller (˜5‰ ?18O) isotopic fractionations only in the hotter end where it is molten or partially molten. Isotope fractionation of oxygen is linearly related to temperature, and the magnitude of isotopic separation per °C is ˜2× larger for wet experiments than dry ones. We explain this by water de-polymerizing the silicate structure leading to a smaller size of diffusing SiOx fragments. The magnitude of isotope separation between the hot and cold ends for Li, Mg, Fe, O, and H isotopes increases linearly with ?Mheavy-light/Mlight. These relationships provide predictive tests for natural rocks and highlight the role of water in isotope and compositional redistribution during temperature gradient mediated processes. We discuss the implications to natural environments in which the lightest stable isotopes (H, Li, O) with the greatest ?Mheavy-light/Mlight and fastest diffusion coefficients are capable of achieving mass-dependent redistribution in a transient temperature gradient. These experiments underscore the importance of solution-reprecipitation in wet subsolidus systems and demonstrate that isotopic redistribution can be established ˜6 orders of magnitude quicker than by diffusion through a traditional silicate melt at higher temperature. This has important implications for timescales of natural isotope and chemical redistribution by thermal diffusion.

Bindeman, I. N.; Lundstrom, C. C.; Bopp, C.; Huang, F.

2013-03-01

208

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

SciTech Connect

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

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

1980-05-01

209

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

PubMed

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

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

2013-06-20

210

Development of isotope dilution-liquid chromatography tandem mass spectrometry for the accurate determination of fluoroquinolones in animal meat products: optimization of chromatographic separation for eliminating matrix effects on isotope ratio measurements.  

PubMed

Isotope dilution-liquid chromatography/tandem mass spectrometry (ID-LC-MS/MS) has been established as a candidate reference method for the accurate determination of three representative fluoroquinolone antibiotics (enrofloxacin, ciprofloxacin, and norfloxacin) in meat products. Enrofloxacin-d?, ciprofloxacin-¹³C?¹?N, and norfloxacin-d? were used as internal standards. After extraction and SPE clean-up, samples were analyzed by using LC-MS/MS in positive ion mode. We observed that the deuterium-labeled internal standards have slightly different LC retention time from their native analogues, which reduces the benefits of using isotope dilution techniques as ion suppression/enhancement effects caused by co-eluting matrix interferences are not completely compensated. In this study, LC conditions were optimized to minimize matrix effects causing different ionization efficiency between the target analytes and their isotope analogues by separating them from significant matrix interferences. The analytical method was validated by measuring samples (chicken breast, bovine muscle, and porcine muscle) gravimetrically fortified in various levels with the target analytes. The method provided accurate analytical results of the target analytes in the range of 5-50 ?g/kg with the relative expanded uncertainty of 1-5%. PMID:23332302

Lee, Suyoung; Kim, Byungjoo; Kim, Jeongkwon

2012-12-29

211

A novel sample decomposition technique at atmospheric pressure for the determination of Os abundances in iron meteorites using isotope dilution inductively coupled plasma-mass spectrometry.  

PubMed

A safe and reliable analytical technique for the determination of Os abundances in ten iron meteorites of various chemical groups was developed using isotope dilution inductively coupled plasma-mass spectrometry coupled with a sample decomposition technique. A major advantage of the sample decomposition technique developed here is that the pressure inside the reaction flask is not increased through the decomposition reaction because the flask is a fully opened system, obviating the risk of explosion of the glass apparatus. Another advantage is that there is no restriction in the sample size being decomposed. In this study, about 2 g of metallic sample were decomposed safely, and this sample size, > 10 times larger than that typically used for the Carius tube technique, allows one to obtain more reliable Os data for heterogeneous samples. The metallic samples were decomposed in a glass flask purged with Ar. Since the O2 was purged from the reaction flask, Os was not oxidised to volatile OsO4, thereby preventing significant evaporation loss of Os. The typical recovery of Os throughout the sample decomposition and separation processes was > 80%, and the total Os blank through the decomposition of a 1 g amount of sample was less than 20 pg. Os abundances were determined by means of stable isotope dilution mass spectrometry using a 190Os-enriched isotopic tracer. Except for Sikhote-Alin, the measured Os abundances in almost all the iron meteorites exhibited a good agreement with the previously published Os abundance data, within the analytical uncertainty achieved in this study (2-5%). For the Sikhote-Alin meteorite, on the basis of a better correlation between Os and Ir abundances, we believe that our Os abundance data should be more reliable. The Os abundance data obtained in this work clearly demonstrated the suitability of the newly developed sample decomposition procedure for low level Os determinations. PMID:11445949

Hattori, M; Hirata, T

2001-06-01

212

A method for determining isotopic composition of elements by thermal ionization source mass spectrometry  

Microsoft Academic Search

It is shown that in thermal ionization source mass spectrometry, if isotope fractionation of the element in the sample follows a linear law, straight-line distributions in xm versus xm\\/ym diagrams are observed, where xm and ym are two measured isotope ratios. The slopes and y-intercepts of these linear distributions are functions of the ‘true’ (starting) values xt and yt of

Giancarlo Cavazzini

2005-01-01

213

Iron isotope signatures within chondrules from Allende and Chainpur as indicators of thermal history  

Microsoft Academic Search

Introduction: We have studied the petrography and Fe-isotope composition of seven chondrules, four from Allende (CV3) and three from Chainpur (LL3.4). A range of textural-chemical chondrule types are represented, allowing us to examine the Fe-isotope signature in material with different thermal histories, with a view to constraing the chondrule forming process and elucidating the nature of chondrule precursor material. Analytical

E. Mullane; S. S. Russell; M. Gounelle; T. F. D. Mason

2003-01-01

214

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

PubMed

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

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

2006-03-01

215

Fourier transforms method for measuring thermal lens induced in diluted liquid samples  

Microsoft Academic Search

Drawing on interferometry and Fourier analysis, this paper describes the use of a two-beam thermal lens technique for measuring thermo-optical properties in optical materials. The procedure consists of yield interference patterns deformed by a localized photothermal effect. The photothermal phase shift is locally induced by the pump beam focused on a tested sample located on an on-axis probe beam, which

L. Rodriguez; R. Escalona

2007-01-01

216

Isotope dilution determination of polycyclic aromatic hydrocarbons in olive pomace oil by gas chromatography–mass spectrometry  

Microsoft Academic Search

A gas chromatographic (GC) method with mass spectrometry detection (MS) for the determination of eight polycyclic aromatic hydrocarbons (PAHs) in olive pomace oil has been developed. The oil was diluted with n-pentane and extracted by liquid–liquid partition with dimethyl sulphoxide (DMSO). After water addition and back-extraction with cyclohexane, a thin-layer chromatography on silica gel was performed as a further purification

Gianfranco Diletti; Giampiero Scortichini; Rossana Scarpone; Giuseppe Gatti; Luigi Torreti; Giacomo Migliorati

2005-01-01

217

Thermal conductivity of diamond between 170 and 1200 K and the isotope effect  

NASA Astrophysics Data System (ADS)

Measurements on the thermal conductivity of natural and synthetic single-crystal diamond are presented over a wide temperature range. The large isotope effect reported previously has been confirmed. The data have been analyzed using both the Debye model of thermal conductivity, which ignores the N processes, and the Callaway model in the limit that the N processes dominate the phonon scattering. It is found that the observed isotope effect can be accounted for by including the N processes alone, without having to postulate the existence of additional defects.

Olson, J. R.; Pohl, R. O.; Vandersande, J. W.; Zoltan, A.; Anthony, T. R.; Banholzer, W. F.

1993-06-01

218

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 70W of applied radiofrequency power, 250Pa of pressure, 2ms of pulse width and 4ms 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 81-5770mg/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

2013-06-22

219

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  

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 chromatography–mass spectrometry (GC–MS) 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

220

Revisiting type-A uncertainties relating to the measurement of mass fraction of lead using isotope-dilution inductively coupled plasma mass spectrometry: a way of improving measurement precision and expanded uncertainty  

Microsoft Academic Search

A quadrupole inductively coupled plasma mass spectrometer (Q-ICP-MS) has been used for determination of lead in plant materials\\u000a using isotope-dilution inductively coupled plasma mass spectrometry. The accuracy of the method was demonstrated by analysis\\u000a of a matrix certified reference material, NIST SRM 1547 Peach Leaves. Specific instrumental parameters of Q-ICP-MS, including\\u000a isotope analysis mode, integration time per point, number of

James Chung Wah Lam; Yiu Chung Yip; Wai Fong Tong

2008-01-01

221

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 Björn

2004-01-01

222

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

Microsoft Academic Search

A gas chromatograph\\/mass spectrometer is described for determining atmospheric sulfur dioxide, carbon disulfide, dimethyl sulfide, and carbonyl sulfide from aircraft and ship platforms. Isotopically labelled variants of each analyte were used as internal standards to achieve high precision. The lower limit of detection for each species for an integration time of 3 min was 1 pptv for sulfur dioxide and

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

1993-01-01

223

Evaluation of extraction techniques for the determination of butyltin compounds in sediments using isotope dilution-GC/ICPMS with 118Sn and 119Sn-enriched species.  

PubMed

Different liquid-solid extraction techniques, including room-temperature leaching with mechanical shaking, ultrasonic, and microwave-assisted extractions, have been evaluated for the quantitative speciation of tin for mono-, di-, and tributyltin (MBT, DBT, and TBT, respectively) in PACS-2 and BCR-646 certified reference materials. A methanol-acetic acid mixture was used as the extractant reagent in all cases. For this purpose, a mixed spike containing 119Sn-enriched MBT (79.7 At%), 118Sn-enriched DBT (86.7 At%), and 119Sn-enriched TBT (83.1 At%), was synthesized, characterized, and used for isotope dilution analysis. The isotopic composition of the mixed spike was determined by gas chromatography/ICPMS after aqueous ethylation using sodium tetraethylborate, and the determination of the concentration of the different species in the spike was performed by means of reverse isotope-dilution analysis using natural MBT, DBT, and TBT standards. In the analysis of the certified sediments, the sample was spiked with the mixed spike, extracted under different conditions, derivatized with sodium tetraethylborate, and extracted into hexane, and the isotope ratios 120/118 and 120/119 were measured as peak area ratios for all butyltin species after GC/ICPMS. Mass bias was corrected using a derivatized natural standard every three sample injections. Sequential degradation reactions during extraction (from TBT to DBT, from DBT to MBT, and from MBT to inorganic tin) were assumed, and mathematical equations were developed that allowed the determination of the correct species concentration and the decomposition factor for each of the transformation reactions. For ultrasonic extraction and mechanical shaking, negligible degradation reactions were observed. However, for microwave assisted extractions, degradation factors up to 7% (TBT to DBT) and 16% (DBT to MBT) were obtained for both reference materials when high-MW energy was applied in the extraction step. For the three extraction techniques tested, the DBT and TBT concentration values obtained for PACS-2 closely matched the certified values. However, for MBT the concentrations found by microwave and ultrasonic extraction were much higher than the certified value. This was not the case for mechanical shaking. The results obtained for BCR-646 using microwave assisted extraction were in good agreement with the certified values for all tin species. PMID:11797650

Ruiz Encinar, Jorge; Rodriguez Gonzalez, Pablo; García Alonso, J Ignacio; Sanz-Medel, Alfredo

2002-01-01

224

Shear viscosity and thermal conductivity in liquid helium-4 and dilute mixtures of helium-3 in helium-4  

SciTech Connect

An oscillating disk viscometer, with a frequency of 273 s/sup -1/, was used to measure the viscosity of liquid /sup 4/He and four /sup 3/He-/sup 4/He mixtures between 1.4K and 4.2 K. The mixtures had /sup 3/He molar concentrations chi = 0.0127, 0.0491, 0.0893, and 0.0916. Simultaneously, the thermal conductivity of the samples was measured with a parallel-plate cell, in order independently to determine the temperature of the lambda transition. Values of the product of normal fluid density and viscosity are presented, as well as absolute values of the conductivity. It was found that the superfluid transition in the mixtures sensed by the viscometer did not coincide with that indicated by the thermal conductivity; rather, it always occurred at a temperature higher than the transition in the conductivity. Within the scatter of the data, the difference in the transition temperatures, ..delta..T/sub lambda/, was a linearly increasing function of concentration, with ..delta..T/sub lambda//chi = 0.16 K. Apparently, this represents the first observation of a surface effect peculiar to the dilute mixtures in which, over a distance of approximately one viscous penetration depth (5 ..mu..m in the present situation), the /sup 3/He concentration is depleted near the walls of the viscometer.

Shaumeyer, J.N.

1984-01-01

225

Shear Viscosity and Thermal Conductivity in Liquid HELIUM-4 and Dilute Mixtures of HELIUM-3 in HELIUM-4.  

NASA Astrophysics Data System (ADS)

An oscillating disk viscometer, with a frequency of 273 s('-1), has been used to measure the viscosity of liquid ('4)He and four ('3)He-('4)He mixtures between 1.4 K and 4.2 K. The mixtures had ('3)He molar concentrations (chi) = 0.0127, 0.0491, 0.0893, and 0.0916. Simultaneously, the thermal conductivity of the samples was measured with a parallel-plate cell, in order independently to determine the temperature of the (lamda) transition. Values of the product of normal fluid density and viscosity are presented, as well as absolute values of the conductivity. It was found that the superfluid transition in the mixtures sensed by the viscometer did not coincide with that indicated by the thermal conductivity; rather, it always occurred at a temperature higher than the transition in the conductivity. Within the scatter of the data, the difference in the transition temperatures, (DELTA)T(,(lamda)), was a linearly increasing function of concentration, with (DELTA)T(,(lamda))/(chi) = 0.16 K. Apparently, this represents the first observation of a surface effect peculiar to the dilute mixtures in which, over a distance of approximately one viscous penetration depth (5 (mu)m in the present situation), the ('3)He concentration is depleted near the walls of the viscometer.

Shaumeyer, Jeffrey Neal

226

Characterization of Sources of Lead Pollution by Isotope Ratio Measurement and Determination of Lead and Thallium in Coals by the Isotope Dilution Method.  

National Technical Information Service (NTIS)

The dissertation presents basic data on the concentrations of the toxic metals lead and thallium in fossil fuels. Apart from the metals concentrations, also isotope ratios of Pb were measured in order to establish criteria on the origins of Pb pollution i...

J. D. Schladot

1982-01-01

227

Determination of ultratrace neodymium in high-purity lanthanum compounds by high-accuracy isotope dilution inductively coupled plasma mass spectrometric analysis with chemical preconcentration  

SciTech Connect

Direct, accurate quantitation of ultratrace Nd in La compounds was not possible by ICPMS. The La/Nd ratio of > 10[sup 6] required chemical separations to provide a suitable sample solution for instrumental analysis. Separation of Nd from the La matrix is problematic since the two elements are close in mass and similar in chemical behavior. The ICPMS in a semiquantitative survey mode proved to be a valuable tool in developing the required separations. Nd was quantified using isotope dilution which requires neither 100% recovery nor absolute isolation of the Nd, resulting in considerable flexibility in the design of preconcentration procedures. Nanogram per gram quantities of Nd in high-purity La compounds were determined using this procedure. 18 refs., 8 figs., 3 tabs.

Beary, E.S.; Paulsen, P.J. (National Inst. of Standards and Technology, Gaithersburg, MD (United States))

1994-02-15

228

Sectional power-law correction for the accurate determination of lutetium by isotope dilution multiple collector-inductively coupled plasma-mass spectrometry  

NASA Astrophysics Data System (ADS)

In this study, we employ a sectional power-law (SPL) correction that provides accurate and precise measurements of 176Lu/ 175Lu ratios in geological samples using multiple collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS). Three independent power laws were adopted based on the 176Lu/ 176Yb ratios of samples measured after chemical chromatography. Using isotope dilution (ID) techniques and the SPL correction method, the measured lutetium contents of United States Geological Survey rock standards (BHVO-1, BHVO-2, BCR-2, AGV-1, and G-2) agree well with the recommended values. Results obtained by conventional ICP-MS and INAA are generally higher than those obtained by ID-TIMS and ID-MC-ICP-MS; this discrepancy probably reflects oxide interference and inaccurate corrections.

Yuan, Hong-Lin; Gao, Shan; Zong, Chun-Lei; Dai, Meng-Ning

2009-11-01

229

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

PubMed

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

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

2006-03-23

230

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

2006-07-26

231

A rapid, sensitive method for the quantitation of specific metabolites of sulfur mustard in human urine using isotope-dilution gas chromatography-tandem mass spectrometry.  

PubMed

Sulfur mustard agent (HD) (2,2'-dichloroethyl sulfide), a Schedule I compound on the Chemical Weapons Convention Schedule of Chemicals, remains a public health concern because it is simple to synthesize and it is in the chemical weapon stockpiles of several countries. A sensitive, rapid, accurate, and precise method was developed to quantitate trace levels of 1,1'-sulfonylbis [2-(methylthio) ethane] (SBMTE) in human urine as a means of assessing exposure to HD. The method used immobilized liquid-liquid extraction with diatomaceous earth, followed by the analysis of the urine extract using isotope-dilution gas chromatography-tandem mass spectrometry. Relative standard deviations were less than 8.6% at 1 ng/mL and 3.6% at 20 ng/mL. The limit of detection for SBMTE was 0.038 ng/mL in 0.5 mL of urine. PMID:15239853

Young, Carrie L; Ash, Doris; Driskell, W J; Boyer, Anne E; Martinez, Rodolfo A; Silks, L A; Barr, John R

232

Ultrasonication extraction and gel permeation chromatography clean-up for the determination of polycyclic aromatic hydrocarbons in edible oil by an isotope dilution gas chromatography–mass spectrometry.  

PubMed

An analytical method for the determination of US EPA priority pollutant 16 polycyclic aromatic hydrocarbons (PAHs) in edible oil was developed by an isotope dilution gas chromatography-mass spectrometry (GC-MS). Extraction was performed with ultrasonication mode using acetonitrile as solvent, and subsequent clean-up was applied using narrow gel permeation chromatographic column. Three deuterated PAHs surrogate standards were used as internal standards for quantification and analytical quality control. The limits of quantification (LOQs) were globally below 0.5 ng/g, the recoveries were in the range of 81-96%, and the relative standard deviations (RSDs) were lower than 20%. Further trueness assessment of the method was also verified through participation in international cocoa butter proficiency test (T0638) organised by the FAPAS with excellent results in 2008. The results obtained with the described method were satisfying (z ? 2). The method has been applied to determine PAH in real edible oil samples. PMID:20627308

Wang, Jian-Hua; Guo, Cui

2010-07-01

233

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

2012-07-26

234

Proposal of a FT-IR methodology to monitor oxidation level in used engine oils: effects of thermal degradation and fuel dilution  

Microsoft Academic Search

This paper describes a particular procedure, based on ASTM D7214 and ASTM E 2412, which has been defined to improve oil oxidation quantification in used engine oils. Taking into account typical problems that can be found in this type of samples, thermal oxidation and fuel dilution, response on FT-IR spectra has been analyzed considering also the effect of oil formulation.

V. Macián; B. Tormos; Y. A. Gómez; J. M. Salavert

2012-01-01

235

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

236

The thermal transport properties of dilute sup 3 He- sup 4 He mixtures near the superfluid transition temperatures  

SciTech Connect

Measurements of the average thermal conductivity, {kappa}{sub exp} = hQ/{Delta}T, were made for dilute mixtures of {sup 3}He in {sup 4}He around their superfluid transitions. The temperature difference was measured with germanium resistors across a layer of fluid mixture. Here c and X are mass and molar concentration respectively. The ratio is k{sub T}* in superfluid phase and k{sub T} in normal fluid phase. The measurements covered the reduced temperature range of 10{sup {minus}6} {le} {vert bar}{var epsilon} = (T - T{sub {lambda}})/T{sub {lambda}}{vert bar} < 0.3, and the heat current range up to 46{mu}W/cm{sup 2}. The anomalous Kapitza boundary resistance for {sup 4}He was observed. The result was consistent with those by Duncan and Ahlers. The {kappa}{sub eff} data were consistent with those by Dingus et al, which deviate from the theoretical prediction of {kappa}{sub eff} {approximately} X{sup {minus}1}. The deviation was less than that by Dingus et al.. The finite heat effect of {kappa}{sub exp} was observed, and it was internally consistent with the deviation as predicted by Behringer. The dilute mixtures offer an ideal test for Khalatnikov's theory of two fluid model. The disagreement for {kappa}{sub eff} and k{sub T}* with the theory indicates that further improvement is needed in the two fluid model especially for very small X. The size and geometry of the sample may have to be considered in order to compare experimental results with the theory.

Zhong, Fang.

1989-01-01

237

Inoculation of Bacillus sphaericus UPMB-10 to young oil palm and measurement of its uptake of fixed nitrogen using the ¹?N isotope dilution technique.  

PubMed

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 N? fixation by the diazotroph Bacillus sphaericus strain UPMB-10, using the ¹?N isotope dilution method. Eight months after ¹?N application, young immature oil palms that received 67% of standard N fertilizer application together with B. sphaericus inoculation had significantly lower ¹?N enrichment than uninoculated palms that received similar N fertilizers. The dilution of labeled N served as a marker for the occurrence of biological N? 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; Abdul Rahim, Khairuddin; Zawawi Zakaria, Zin; Abdul Rahim, Anuar

2012-03-23

238

Experimental Study of Isotope Scaling of Radial Ion Thermal Transport in Axisymmetric Magnetic Field  

SciTech Connect

A series of basic transport physics experiments are performed in Columbia Linear Machine, which generates a steady-state collisionless cylindrical plasma column in uniform axial magnetic field. The focus is on the isotopic scaling of ion thermal conductivity due to ion temperature gradient-driven modes. The experiments are performed using two different gases: Hydrogen and Deuterium. The results indicate reduction of thermal transport with increasing isotopic mass leading to a scaling K{sub perpindicular{approx}} A{sub i}{sup -0.5}, where A{sub i} is the mass number of the isotope of hydrogen. This inverse gyro-Bohm scaling is similar to the tokamak results, but is in stark contradiction to most present theoretical models predicting Bohm (A{sub i}{sup 0}) or gyro-Bohm (A{sub i}{sup 0.5}) scaling. A series of experiments to explore the physics basis of this scaling has been also performed.

Sokolov, V.G.; Sen, A.K. [Plasma Research Laboratory, Columbia University (United States)

2005-01-15

239

Comparison of different extraction methods for simultaneous determination of B complex vitamins in nutritional yeast using LC/MS-TOF and stable isotope dilution assay.  

PubMed

The application of LC/MS-TOF method combined with stable isotope dilution assay was studied for determination of thiamine, riboflavin, nicotinamide, nicotinic acid, pantothenic acid, pyridoxal, and pyridoxine in food. Nutritional yeast powder was used as a model food matrix. Acid extraction was compared with various enzymatic treatments in ammonium formate buffer to find a suitable method for the conversion of more complex vitamers into the same forms as the used isotope-labeled internal standards. The enzyme preparations ?-amylase, takadiastase, ?-glucosidase, and acid phosphatase were all able to liberate thiamine and riboflavin. The diastatic enzyme preparations ?-amylase and takadiastase also expressed proteolytic side activities resulting in the formation of small peptides which interfered with the mass spectra of thiamine and riboflavin. Liberation of nicotinamide and pantothenic acid from NAD(+) and CoA, respectively, could not be achieved with any of the studied enzyme preparations. Hydrochloric acid extraction at 121 °C for 30 min was found to be destructive to pantothenic acid, but increased the liberation of pyridoxal. PMID:23150051

Hälvin, Kristel; Paalme, Toomas; Nisamedtinov, Ildar

2012-11-13

240

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

241

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

2012-04-30

242

Capture of the volatile carbonyl metabolite of flecainide on 2,4-dinitrophenylhydrazine cartridge for quantitation by stable-isotope dilution mass spectrometry coupled with chromatography  

PubMed Central

Carbonyl compounds are common byproducts of many metabolic processes. These volatile chemical entities are usually derivatized before mass spectrometric analysis to enhance the sensitivity of their detections. The classically used reagent for this purpose is 2,4-dinitrophenylhydrazine (DNPH) that forms the corresponding hydrazones. When DNPH is immobilized on specific cartridges it permits solvent-free collection and simultaneous derivatization of aldehydes and ketones from gaseous samples. The utility of this approach was tested by assembling a simple apparatus for the in vitro generation of trifluoroacetaldehyde (TFAA) and its subsequent capture on the attached DNPH cartridge. TFAA was generated via cytochrome P450-catalyzed dealkylation of flecainide, an antiarrhythmic agent, in pooled human liver microsomes. Stable-isotope dilution mass spectrometry coupled with GC and LC using negative chemical ionization (NCI) and electrospray ionization (ESI) was evaluated for quantitative analyses. To eliminate isotope effects observed with the use of deuterium-labeled DNPH, we selected its 15N4-labeled analog to synthesize the appropriate TFAA adduct, as internal standard. Quantitation by GC–NCI-MS using selected-ion monitoring outperformed LC–ESI-MS methods considering limits of detection and linearity of the assays. The microsomal metabolism of 1.5 ?mol of flecainide for 1.5 h resulted in 2.6 ± 0.5 ?g TFAA-DNPH, corresponding to 9.3 ± 1.7 nmol TFAA, captured by the cartridge.

Prokai, Laszlo; Szarka, Szabolcs; Wang, Xiaoli; Prokai-Tatrai, Katalin

2012-01-01

243

A Thermal Conductivity Method for the Determination of Isotopic Exchanges in the Simpler Gaseous Molecules  

Microsoft Academic Search

A simple high pressure thermal conductivity gauge of good mechanical stability, freedom from poisoning effects and high accuracy has been described in detail. Its physical characteristics have been studied and optimum conditions for operation indicated. Its applicability to a wide variety of analyses is discussed and specific data quoted for those of the isotopic isomers of the lower aliphatic hydrocarbons

Nelson R. Trenner

1937-01-01

244

Thermal neutron cross sections for the 1991 table of the isotopes  

SciTech Connect

It has been a decade since the last publication of the Barn Book,'' BNL-325. In preparing a revision to the Table of the Isotopes, a re-evaluation of all of the thermal neutron cross sections has been performed, utilizing the previous data base of the Barn Book'' and all of the more recently published experiments. 5 refs.

Holden, N.E.

1991-05-01

245

Iron isotope ratio measurements by negative thermal ionisation mass spectrometry using FeF 4 ? molecular ions  

Microsoft Academic Search

Based on the formation of molecular FeF4? ions under thermal ion source conditions, a negative thermal ionisation technique for iron was developed. Compared with the widely used iron isotopic analysis by positive thermal ionisation mass spectrometry, a better control of mass-dependent isotopic fractionation is possible by generating molecular FeF4? ions instead of an atomic Fe+ ion beam at comparable ionisation

Thomas Walczyk

1997-01-01

246

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

SciTech Connect

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

Bandy, A.R.; Thornton, D.C.; Driedger, A.R. III [Drexel Univ., Philadelphia, PA (United States)

1993-12-01

247

Thermal-hydraulic analysis of the HFIR (High Flux Isotope Reactor)  

SciTech Connect

The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) is a high performance research reactor used to produce transuranium isotopes and perform material irradiation studies. HFIR was operated for about 20 years prior to its shutdown in November 1986 and has remained shutdown while the results of safety studies are completed and reviewed. This paper highlights results from ongoing studies which have revisited system thermal-hydraulic safety limits with present day analytical tools and experimental investigations. Long term decay heat removal requirements have been examined as well as the response of the system to small break loss of coolant accidents (SBLOCA). 10 refs., 1 fig.

Morris, D.G.; Ruggles, A.E. (Oak Ridge National Lab., TN (USA)); Wendel, M.W. (Oak Ridge Gaseous Diffusion Plant, TN (USA))

1990-01-01

248

Quantification of Activated NF-?B/RelA Complexes Using ssDNA Aptamer Affinity - Stable Isotope Dilution--Selected Reaction Monitoring--Mass Spectrometry*  

PubMed Central

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

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

2011-01-01

249

Muon transfer from thermalized muonic hydrogen isotopes to argon  

Microsoft Academic Search

Recent experimental results on the muon exchange from muonic hydrogen to argon show that the reaction rate is energy dependent near 0.1 eV. A muonic hydrogen atom, formed by muon capture in H2 gas at 15 bars, is thermalized in a few hundreds of nanoseconds. If the muon transfer reaction occurs before that time, the rate is shown to be

R. Jacot-Guillarmod; F. Mulhauser; C. Piller; L. A. Schaller; L. Schellenberg; H. Schneuwly; Y.-A. Thalmann; S. Tresch; A. Werthmüautller; A. Adamczak

1997-01-01

250

Determination of 5-methyltetrahydrofolic acid and folic acid in citrus juices using stable isotope dilution-mass spectrometry.  

PubMed

A stable isotope liquid chromatography-mass spectrometry (LC-MS) method was developed for the quantitative determination of 5-methyltetrahydrofolic acid (5-MTHFA) and folic acid in a variety of commercial citrus juices. Folates were extracted from juices, and the polyglutamyl side chain of 5-MTHFA was cleaved to the monoglutamate form using rat plasma conjugase. The folates were purified on a Bond-Elut column and analyzed by LC-MS with electrospray ionization. The analytes were quantified using the (13)C(5) analogues of 5-MTHFA and folic acid as internal standards. The relative standard error of the method was 3.35% based on replicate analyses (n = 4). This method was then applied to the determination of 5-MTHFA and folic acid in a variety of citrus juices obtained from local supermarkets. It was observed that although both "store" brands and "national" brands of fresh (nonfrozen) juices contained similar concentrations of 5-MTHFA, the "store" brands of fresh juices had on average >5-fold the amount of folic acid compared to the "national" brands. In addition, the "total" folate concentrations were generally below values listed on the food label. PMID:12590471

Thomas, Paul M; Flanagan, Vincent P; Pawlosky, Robert J

2003-02-26

251

Precise Re isotope ratio measurements by negative thermal ionization mass spectrometry (NTI-MS) using total evaporation technique  

Microsoft Academic Search

High precision rhenium isotope ratios, 187Re\\/185Re, have been determined by negative thermal ionization mass spectrometry (NTI-MS) using a total evaporation technique. The salient features of this method are evaporation of the entire sample and simultaneous integration of the signal from each isotope, which effectively eliminates isotope fractionation effects during the evaporation process. The 187Re\\/185Re ratio is obtained with a high

Katsuhiko Suzuki; Yoshiki Miyata; Nobuyuki Kanazawa

2004-01-01

252

Negative thermal ionization mass spectrometry of selenium part 3.* Selenium trace determination in food samples  

Microsoft Academic Search

Summary Selenium traces are analysed in different animal tissue samples with isotope dilution mass spectrometry using the formation of negative Se- thermal ions (NTI-IDMS) for isotope ratio measurements. An enriched82Se spike is applied for the isotope dilution technique. After decomposition of the food samples with a HNO3\\/HCIO4 mixture selenium is separated by the formation of SeH2 using a hydride generation

Klaus G. Heumann; Norbert Rädlein

1989-01-01

253

Determination of mercury in SRM crude oils and refined products by isotope dilution cold vapor ICP-MS using closed-system combustion.  

PubMed

Mercury was determined by isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS) in four different liquid petroleum SRMs. Samples of approximately 0.3 g were spiked with stable (201)Hg and wet ashed in a closed system (Carius tube) using 6 g of high-purity nitric acid. Three different types of commercial oils were measured: two Texas crude oils, SRM 2721 (41.7+/-5.7 pg g(-1)) and SRM 2722 (129+/-13 pg g(-1)), a low-sulfur diesel fuel, SRM 2724b (34+/-26 pg g(-1)), and a low-sulfur residual fuel oil, SRM 1619b (3.5+/-0.74 ng g(-1)) (mean value and 95% CI). The Hg values for the crude oils and the diesel fuel are the lowest values ever reported for these matrices. The method detection limit, which is ultimately limited by method blank uncertainty, is approximately 10 pg g(-1) for a 0.3 g sample. Accurate Hg measurements in petroleum products are needed to assess the contribution to the global Hg cycle and may be needed in the near future to comply with reporting regulations for toxic elements. PMID:12802572

Kelly, W Robert; Long, Stephen E; Mann, Jacqueline L

2003-06-11

254

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

255

Precise determination of the Alternaria mycotoxins alternariol and alternariol monomethyl ether in cereal, fruit and vegetable products using stable isotope dilution assays.  

PubMed

Cereal, fruit and vegetable products were analyzed for contamination with the Alternaria mycotoxins alternariol (AOH) and alternariol monomethyl ether (AME) using stable isotope dilution assays (SIDAs). Both toxins were practically not detected in cereals and cereal products: AOH-one out of 13 samples at a content of 4.1 ?g/kg; AME-two out of 13 samples at contents ranging between 0.2 and 0.6 ?g/kg. However, if cereals for animal nutrition were analyzed, much higher values were found: AOH-five out of six samples (13-250 ?g/kg); AME-six out of six samples (3-100 ?g/kg). This finding may pose a potential problem concerning animal health. AOH and AME were frequently detected in vegetable products: AOH-5 out of 10 samples (2.6-25 ?g/kg); AME-6 out of 10 samples (0.1-5 ?g/kg). Tomato products were affected, especially. The highest content of AOH (25 ?g/kg) and AME (5 ?g/kg) were found in triple concentrated tomato paste. Special wines like "Trockenbeerenauslese" or "Spätlese" (affected by noble rot in the vineyard) contained AOH (4/6 samples; 1.2-4.9 ?g/kg) and AME (4/6 samples; 0.1-0.3 ?g/kg), but the values did not exceed the values of both toxins that were found generally in wines. PMID:23605619

Asam, Stefan; Konitzer, Katharina; Rychlik, Michael

2010-11-11

256

Quantitative investigation of trigonelline, nicotinic acid, and nicotinamide in foods, urine, and plasma by means of LC-MS/MS and stable isotope dilution analysis.  

PubMed

A straightforward stable isotope dilution analysis (SIDA) for the quantitative determination of trigonelline, nicotinic acid, and nicotinamide in foods such as coffee, as well as in biological samples by means of LC-MS/MS (MRM) has been developed. The coefficients of variation for their quantitative analysis in a coffee sample were 2.1% for trigonelline, 1.1% for nicotinic acid, and 3.1% for nicotinamide, and recovery experiments showed good results between 98.5 and 104.5%. Application of this SIDA for the quantification of trigonelline, nicotinic acid, and nicotinamide in coffee samples of different roasting degrees revealed a drastic degradation of trigonelline as well as the generation of nicotinic acid accounting for 4-6% of the initial trigonelline content, whereas nicotinamide remained rather constant at a low level. Besides the analysis of coffee samples, the feasibility of the developed SIDA was verified by analysis of other foods including breakfast cereals, rice, liver, and herring, as well as human urine and plasma samples. PMID:19007232

Lang, Roman; Yagar, Erkan Firat; Eggers, Rudolf; Hofmann, Thomas

2008-12-10

257

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

PubMed

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

Lindenmeier, Michael; Schieberle, Peter; Rychlik, Michael

2011-02-12

258

Trimester-specific reference intervals for thyroxine and triiodothyronine in pregnancy in iodine-sufficient women using isotope dilution tandem mass spectrometry and immunoassays  

PubMed Central

Background Accurate assessment of the pregnant woman’s thyroid status is critical, for both the initiation of thyroid hormone therapy and for the adjustment of thyroid hormone dose in those already receiving thyroid hormone. Trimester-specific intervals are especially important during pregnancy when thyroid insufficiency may be associated with adverse obstetric outcome and fetal neurodevelopmental deficits. We defined pregnancy-specific reference intervals for thyroxine (T4) and 3,5,3?-triiodothyronine (T3). We used a novel isotope dilution tandem mass spectrometry (LC/MS/MS) method, and compare these to reference intervals obtained by immunoassays (IAs) performed on the same samples. Methods Concentrations of circulating T4 and T3 were measured simultaneously during first, second and third trimesters and postpartum in iodine-sufficient, healthy, singleton pregnancies using API-3000 LC/MS/MS with deuterium-labeled internal standard (l-thyroxine-d2). Immunoassays were conducted on the same samples (T4 Dade Behring RxL, T3 DPC-Immunolite). Results Linear regression is reported for method comparisons; for T4, the slope decreased from r=0.900 in nonpregnant women to 0.802–0.820 during pregnancy. For T3, correlations between LC/MS/MS and immunoassays were weaker in all cases (r=0.407–0.574). Conclusion In this longitudinal study, we established trimester-specific reference intervals for T4 and T3 by LC/MS/MS and compare these to intervals obtained by immunoassays.

Soldin, O.P.; Hilakivi-Clarke, L.; Weiderpass, E.; Soldin, S.J.

2013-01-01

259

An optimised method for the accurate determination of zeranol and diethylstilbestrol in animal tissues using isotope dilution-liquid chromatography/mass spectrometry.  

PubMed

Isotope dilution-liquid chromatography/mass spectrometry (ID-LC/MS) has been established as a candidate reference method for the accurate determination of growth promoters (zeranol, taleranol, and diethylstilbesterol) in raw meat samples. Sample preparation processes including an enzymatic hydrolysis, extraction, and SPE clean-up were optimised. The sensitivity difference of trans- and cis-diethylstilbestrol (isomerizing in sample preparation processes) by the LC/MS was measured by running a trans/cis mixture (ratio measured by a quantitative NMR) with and without sample matrices, and applied for the determination of total diethylstilbestrol. Validity, repeatability, and reproducibility of the analytical method were tested by measuring gravimetrically fortified samples (chicken breast, bovine muscles, and porcine muscle) in a number of different time periods. Measurement results agreed with the fortified values within their uncertainties. The method provided accurate results of the target analytes in the range of 0.05-15 ?g/kg with the relative expanded uncertainty of 2-15%. PMID:23578613

Han, Hyesun; Kim, Byungjoo; Lee, Sueg Geun; Kim, Jeongkwon

2013-02-27

260

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

PubMed Central

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

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

2009-01-01

261

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

PubMed

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

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

2009-04-01

262

Medium-chain acyl-CoA dehydrogenase deficiency. Diagnosis by stable-isotope dilution measurement of urinary n-hexanoylglycine and 3-phenylpropionylglycine  

SciTech Connect

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, one of the most common inherited metabolic disorders, is often mistaken for the sudden infant death syndrome or Reye's syndrome. Diagnosing it has been difficult because of a lack of fast and reliable diagnostic methods. We developed a stable-isotope dilution method to measure urinary n-hexanoylglycine, 3-phenylpropionylglycine, and suberylglycine, and we retrospectively tested its accuracy in diagnosing MCAD deficiency. We measured the concentrations of these three acylglycines in 54 urine samples from 21 patients with confirmed MCAD deficiency during the acute and asymptomatic phases of the illness and compared the results with the concentrations in 98 samples from healthy controls and patient controls with various diseases. The levels of urinary hexanoylglycine and phenylpropionylglycine were significantly increased in all samples from the patients with MCAD deficiency, clearly distinguishing them from both groups of controls. Although urinary suberylglycine was increased in the patients, the range of values in the normal controls who were receiving formula containing medium-chain triglycerides was very wide, overlapping somewhat with the values in the patients with asymptomatic MCAD deficiency. These results indicate that the measurement of urinary hexanoylglycine and phenylpropionylglycine by our method is highly specific for the diagnosis of MCAD deficiency. The method is fast and can be applied to random urine specimens, without any pretreatment of patients.

Rinaldo, P.; O'Shea, J.J.; Coates, P.M.; Hale, D.E.; Stanley, C.A.; Tanaka, K.

1988-11-17

263

Mass spectrometric profiling of Bacillus cereus strains and quantitation of the emetic toxin cereulide by means of stable isotope dilution analysis and HEp-2 bioassay.  

PubMed

A fast and robust high-throughput ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC-TOF MS) profiling method was developed and successfully applied to discriminate a total of 78 Bacillus cereus strains into no/low, medium and high producers of the emetic toxin cereulide. The data obtained by UPLC-TOF MS profiling were confirmed by absolute quantitation of cereulide in selected samples by means of high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) and stable isotope dilution assay (SIDA). Interestingly, the B. cereus strains isolated from four vomit samples and five faeces samples from patients showing symptoms of intoxication were among the group of medium or high producers. Comparison of HEp-2 bioassay data with those determined by means of mass spectrometry showed differences, most likely because the HEp-2 bioassay is based on the toxic action of cereulide towards mitochondria of eukaryotic cells rather than on a direct measurement of the toxin. In conclusion, the UPLC-electrospray ionization (ESI)-TOF MS and the HPLC-ESI-MS/MS-SIDA analyses seem to be promising tools for the robust high-throughput analysis of cereulide in B. cereus cultures, foods and other biological samples. PMID:23079954

Stark, Timo; Marxen, Sandra; Rütschle, Andrea; Lücking, Genia; Scherer, Siegfried; Ehling-Schulz, Monika; Hofmann, Thomas

2012-10-19

264

Double Spike Isotope Dilution GC-ICP-MS for Evaluation of Mercury Species Transformation in Real Fish Samples Using Ultrasound-Assisted Extraction.  

PubMed

Sample preparation continues being a key factor to obtain fast and reliable quantification of Hg species. Assisted procedures enhance the efficiency and reduce the extraction time; however, collateral species transformations have been observed. Moreover, differential interconversions have been observed even between similar matrixes, which introduce an important uncertainty for real sample analysis. Trying to minimize Hg species transformations, we have tested a soft ultrasound-assisted extraction procedure. Species quantification and transformations have been evaluated using double spike isotope dilution analysis (IDA) together with gas chromatography inductively coupled plasma mass spectrometry (GC-ICP-MS) for a CRM material (Tort-2) and shark and swordfish muscle samples. Optimum extraction solution and sonication time led to quantitative extraction and accurate determination of MeHg and IHg in a short time, although different behaviors regarding species preservation were observed depending on the sample. Negligible species transformations were observed in the analysis of the CRM, while a small but significant demethylation factor was observed in the case of real samples. In comparison with other extraction procedures, species transformations became smaller, and fewer differences between fish species were found. Similar results were obtained for fresh and lyophilized samples of both fish samples, which permit one to analyze the fresh sample directly and save time in the sample preparation step. The high grade of species preservation and the affordability of the extraction procedure allow one to obtain accurate determinations even for routine laboratories using quantification techniques, which do not estimate species transformations. PMID:22827829

Esteban-Fernández, Diego; Mirat, Manuela; de la Hinojosa, M Ignacia Martín; Alonso, J Ignacio García

2012-08-16

265

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

PubMed

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

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

2006-09-07

266

Bentonites from ishirini (libya) as natural analogues of long term thermal and chemical effects: isotopic and fluid inclusion evidence  

Microsoft Academic Search

Smectites from the Ishirini bentonite deposit (Libya) were analyzed for their oxygen and hydrogen isotopic ratios. Based on published isotopic fractionation data the results argue for a main meteoric water origin of the fluids responsible for the transformation of pyroclastic rocks to bentonite at temperature range from 30° to 90 °C.The thermal effect of later volcanic intrusions was further evaluated

Irena Kola?íková; Radek Hanus

2004-01-01

267

The separation study of hydrogen isotopes with Cryogenic-Wall thermal diffusion column  

SciTech Connect

The thermal diffusion is one of the useful methods of the hydrogen isotope separation. This paper reports on the experiments using Cryogenic-Wall thermal diffusion column cooled by liquid nitrogen which have been performed in the total reflux and the withdraw modes. As using the same inner diameter column, Cryogenic-Wall thermal diffusion column has the higher separation factor, but the lower optimum pressure than Ordinary-Wall thermal diffusion column cooled by water. It is obtained that Cryogenic-Wall column with a smaller inner diameter has the remarkable high separation factor and the higher optimum pressure. In the withdraw mode, the characteristics of the separation factor as a function of the feed rates is obtained about the several inner diameter columns.

Okada, Y.; Sakai, F.; Mitsui, J. (Sumitomo Heavy Industries Ltd., Hiratsuka (Japan))

1992-03-01

268

Strontium isotopes as an indicator of water-rock reaction for the Coupled Thermal-Hydrological-Mechanical-Chemical-Biological (THMCB) Experimental Facility at DUSEL  

NASA Astrophysics Data System (ADS)

The Thermal-Hydrological-Mechanical-Chemical-Biological (THMCB) Experimental Facility is a proposed facility at the DUSEL-Homestake that will be used to investigate reactive transport, heat transfer and the resulting biological responses within a natural fractured rock. As part of THMCB facility design we are characterizing the current geochemical conditions and developing geochemical and isotopic indicators for fluid flow paths and reaction rates. The proposed experimental site is located at a depth of 4850 feet, primarily in the Homestake and Poorman Formations. At the experimental site, these formations are a quartz-chlorite-siderite iron formation and alumina-poor metapelite, respectively. Water samples from fractures and boreholes indicate that the pore fluid is a dilute Na-HCO3 water. The strontium isotope 87Sr/86Sr composition of surface waters is approximately 0.7106 based on stream water collected near the DUSEL site. The 87Sr/86Sr of subsurface waters sampled from fractures and boreholes throughout the mine varies from 0.7144 to 0.8145. 87Sr/86Sr and strontium concentrations suggest that calcite precipitation removes strontium and calcium from solution at shallow depths in the mine (< 3000 ft), consistent with pervasive calcite accumulation observed in the tunnels at these levels. 87Sr/86Sr values generally increase with depth and are highest in slow flowing fractures where they approach the isotopic value of the Poorman Formation (ca. 0.83±0.06). Collectively the data suggest that the Sr isotopic composition of the mine water is controlled by the flow rate of water and the extent of exchange with the surrounding rock matrix. Additionally, 87Sr/86Sr and temperature are positively correlated in the Poorman and Homestake Formations suggesting that temperature may be an additional tracer for fluid flow. Other isotopic tracers including 234U/238U, ?18O, ?D, ?13C and ?30Si are also being evaluated for use in the THMCB experimental facility.

Maher, K.; Olsen, N. J.; Harris, C.; Jones, T. L.; Conrad, M. E.; Sonnenthal, E. L.; Elsworth, D.; Uzunlar, N.; Mailloux, B. J.; Lowell, R. P.

2010-12-01

269

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

270

Folate content in sea buckthorn berries and related products ( Hippophaë 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 chromatography–tandem 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 (Hippophaë rhamnoides).

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

2008-01-01

271

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

SciTech Connect

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

Rinaldo, P.; O'Shea, J.J.; Welch, R.D.; Tanaka, K. (Yale Univ. School of Medicine, New Haven, CT (USA))

1990-01-01

272

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

SciTech Connect

Based on the mineralogy and petrography, coarse-grained, igneous, anorthite-rich (Type C) calcium-aluminum-rich inclusions (CAIs) in the CV3 carbonaceous chondrite Allende have been recently divided into three groups: (i) CAIs with melilite and Al,Ti-diopside of massive and lacy textures (coarse grains with numerous rounded inclusions of anorthite) in a fine-grained anorthite groundmass (6-1-72, 100, 160), (ii) CAI CG5 with massive melilite, Al,Ti-diopside and anorthite, and (iii) CAIs associated with chondrule material: either containing chondrule fragments in their peripheries (ABC, TS26) or surrounded by chondrule-like, igneous rims (93) (Krot et al., 2007a,b). Here, we report in situ oxygen isotopic measurements of primary (melilite, spinel, Al,Ti-diopside, anorthite) and secondary (grossular, monticellite, forsterite) minerals in these CAIs. Spinel ({Delta}{sup 17}O = -25{per_thousand} to -20{per_thousand}), massive and lacy Al,Ti-diopside ({Delta}{sup 17}O = -20{per_thousand} to -5{per_thousand}) and fine-grained anorthite ({Delta}{sup 17}O = -15{per_thousand} to -2{per_thousand}) in 100, 160 and 6-1-72 are {sup 16}O-enriched relative spinel and coarse-grained Al,Ti-diopside and anorthite in ABC, 93 and TS26 ({Delta}{sup 17}O ranges from -20{per_thousand} to -15{per_thousand}, from -15{per_thousand} to -5{per_thousand}, and from -5{per_thousand} to 0{per_thousand}, respectively). In 6-1-72, massive and lacy Al,Ti-diopside grains are {sup 16}O-depleted ({Delta}{sup 17}O {approx} -13{per_thousand}) relative to spinel ({Delta}{sup 17}O = -23{per_thousand}). Melilite is the most {sup 16}O-depleted mineral in all Allende Type C CAIs. In CAI 100, melilite and secondary grossular, monticellite and forsterite (minerals replacing melilite) are similarly {sup 16}O-depleted, whereas grossular in CAI 160 is {sup 16}O-enriched ({Delta}{sup 17}O = -10{per_thousand} to -6{per_thousand}) relative to melilite ({Delta}{sup 17}O = -5{per_thousand} to -3{per_thousand}). We infer that CAIs 100, 160 and CG5 experienced melting in an {sup 16}O-rich ({Delta}{sup 17}O < -20{per_thousand}) nebular gas in the CAI-forming region. The Type C and Type-B-like portions of CAI 6-1-72 experienced melting in an {sup 16}O-depleted ({Delta}{sup 17}O {ge} -13{per_thousand}) nebular gas. CAIs ABC, TS26 and 93 experienced isotopic exchange during re-melting in the presence of an {sup 16}O-poor ({Delta}{sup 17}O {ge} -10{per_thousand}) nebular gas in the chondrule-forming region(s). Subsequently, Allende Type C CAIs experienced post-crystallization isotopic exchange with an {sup 16}O-poor reservoir that affected largely melilite and anorthite. Because pseudomorphic replacement of lacy melilite by grossular, monticellite and forsterite occurred during thermal metamorphism, some oxygen isotopic exchange of melilite and anorthite must have continued after formation of these secondary minerals. We suggest that some or all oxygen isotopic exchange in melilite and anorthite occurred during fluid-assisted thermal metamorphism on the CV parent asteroid. Similar processes may have also affected melilite and anorthite of CAIs in metamorphosed CO chondrites.

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

2008-02-21

273

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

PubMed

A stable isotope dilution assay and liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of 12 mycotoxins, aflatoxins B1, B2, G1, G2, and M1, deoxynivalenol, fumonisins B1, B2, and B3, ochratoxin A, T-2 toxin, and zearalenone, in milk-based infant formula and foods. Samples were fortified with 12 (13)C uniformly labeled mycotoxins ([(13)C]-mycotoxins) that correspond to the 12 target mycotoxins and prepared by dilution and filtration, followed by LC-MS/MS analysis. Quantitation was achieved using the relative response factors of [(13)C]-mycotoxins and target mycotoxins. The average recoveries in fortified milk, milk-based infant formula, milk powder, and baby yogurt of aflatoxins B1, B2, G1, and G2 (2, 10, and 50 ?g/kg), aflatoxin M1 (0.5, 2.5, and 12.5 ?g/kg), deoxynivalenol, fumonisins B1, B2, and B3 (40, 200, and 1000 ?g/kg), ochratoxin A, T-2 toxin, and zearalenone (20, 100, and 500 ?g/kg), range from 89 to 126% with RSDs of <20%. The individual recoveries in the four fortified matrices range from 72% (fumonisin B3, 20 ?g/kg, milk-based infant formula) to 136% (T-2 toxin, 20 ?g/kg, milk powder), with RSDs ranging from 2 to 25%. The limits of quantitation (LOQs) were from 0.01 ?g/kg (aflatoxin M1) to 2 (fumonisin B1) ?g/kg. Aflatoxin M1 was detected in two European Reference materials at 0.127 ± 0.013 ?g/kg (certified value = 0.111 ± 0.018 ?g/kg) and 0.46 ± 0.04 ?g/kg (certified value = 0.44 ± 0.06 ?g/kg), respectively. In 60 local market samples, aflatoxins B1 (1.14 ± 0.10 ?g/kg) and B2 (0.20 ± 0.03 ?g/kg) were detected in one milk powder sample. Aflatoxin M1 was detected in three imported samples (condensed milk, milk-based infant formula, and table cream), ranging from 0.10 to 0.40 ?g/kg. The validated method provides sufficient selectivity, sensitivity, accuracy, and reproducibility to screen for aflatoxin M1 at nanograms per kilogram concentrations and other mycotoxins, without using standard addition or matrix-matched calibration to compensate for matrix effects. PMID:23746324

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

2013-06-24

274

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

275

Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology  

SciTech Connect

Shock and thermal metamorphism of meteorites from differentiated bodies such as the Moon and Mars have the potential to disturb chronometric information contained in these meteorites. In order to understand the impact-related mechanisms and extent of disturbance to isochrons, we undertook experiments to shock and heat samples of 10017, a 3.6 billion year old lunar basalt. One sub-sample was shocked to 55 GPa, a second subsample was heated to 1000 C for one week, and a third sub-sample was maintained as a control sample. Of the isotope systems analyzed, the Sm-Nd system was the least disturbed by shock or heat, followed by the Rb-Sr system. Ages represented by the {sup 238}U-{sup 206}Pb isotope system were degraded by shock and destroyed with heating. In no case did either shock or heating alone result in rotated or reset isochrons that represent a spurious age. In some cases the true crystallization age of the sample was preserved, and in other cases age information was degraded or destroyed. Although our results show that neither shock nor thermal metamorphism alone can account for the discordant ages represented by different isotope systems in martian meteorites, we postulate that shock metamorphism may render a meteorite more susceptible than unshocked material to subsequent disturbance during impact-related heating or aqueous alteration on Mars or Earth. The combination of these processes may result in the disparate chronometric information preserved in some meteorites.

Gaffney, A M; Borg, L E; Asmerom, Y

2008-12-10

276

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

277

Absence of 2'-deoxyguanosine-carbon 8-bound ochratoxin A adduct in rat kidney DNA monitored by isotope dilution LC-MS/MS.  

PubMed

The contribution of DNA adduct formation in the carcinogenic action of the mycotoxin ochratoxin A (OTA) has been subject to much debate. Recently, a carbon-bonded ochratoxin A-2'-deoxyguanosine adduct (dGuoOTA) formed by photochemical reaction in vitro has been shown by 32P-postlabeling/TLC to comigrate with a spot detected in DNA isolated from rat and pig kidney following exposure to OTA. Considering the large body of evidence arguing against covalent DNA binding of OTA and the poor resolution and specificity of postlabeling analysis, we developed a stable isotope dilution LC-MS/MS method to analyze dGuoOTA in kidney DNA isolated from rats treated with OTA. dGuoOTA and nitrogen-15-labeled dGuoOTA (15N(5)-dGuoOTA) were prepared by photoirradiation of OTA in the presence of dGuo or nitrogen-15-labeled dGuo. Conditions for DNA hydrolysis were optimized using a synthetic oligonucleotide containing dGuoOTA to ensure complete release of dGuoOTA. The LOD of the method (S/N > 3) was 10 fmol dGuoOTA on-column. However, dGuoOTA was not detected in DNA samples isolated from male F344 rats treated with OTA for up to 90 days at doses known to cause renal tumor formation. Detection limits, calculated for each individual sample based on the absolute LOD and the amount of DNA injected, were as low as 3.5 dGuoOTA/10(9) nucleotides. These data are consistent with previous results showing lack of DNA adduct formation by OTA and demonstrate that dGuoOTA is not formed in biologically relevant amounts under physiological conditions in vivo. PMID:18381679

Delatour, Thierry; Mally, Angela; Richoz, Janique; Ozden, Sibel; Dekant, Wolfgang; Ihmels, Heiko; Otto, Daniela; Gasparutto, Didier; Marin-Kuan, Maricel; Schilter, Benoît; Cavin, Christophe

2008-04-01

278

Simultaneous determination of amphetamine and methamphetamine enantiomers in urine by simultaneous liquid-liquid extraction and diastereomeric derivatization followed by gas chromatographic-isotope dilution mass spectrometry.  

PubMed

A simple, rapid, reliable, and economic analytical scheme starting with in situ liquid-liquid extraction and asymmetric (or diastereomeric) chemical derivatization (ChD) followed by gas chromatography (GC)-isotope dilution mass spectrometry (MS) is described for the simultaneous determination of D- and L-amphetamine (AP) and methamphetamine (MA) in urine which could have resulted from the administration of various forms of questioned amphetamines or amphetamines-generating drugs. By using L-N-trifluoroacetyl-1-prolyl chloride (L-TPC) as chiral derivatizing agent, resolutions of 2.2 and 2.0 were achieved for the separation of AP and MA enantiomeric pairs, respectively, on an ordinary HP-5MS capillary column. The GC-MS quantitation was carried out in the selected ion monitoring (SIM) mode using m/z 237 and 251 as the quantifier ions for the respective diastereomeric pairs of AP-L-TPC and MA-L-TPC. The calibration curves plotted for the two pairs of analytes stretch with good linearity down to 45 ng/mL, and the limits of detection and quantitation determined were as low as 40 and 45 ng/mL, respectively. Also, a comparative study using 10 real-case urine specimens previously screened as positive for MA administration showed mostly tolerable biases between the two sums (of concentration) of D- and L-MA obtained via an asymmetric L-TPC-ChD approach and via an ordinary pentafluoropropionylation (PFPA-ChD) approach, respectively, as well as between the two sums of D- and L-AP obtained thereupon, thus validating the proposed analytical scheme as a promising forensic protocol for the detailed analysis of enantiomeric amphetamines in urine. PMID:15664343

Wang, Sheng-Meng; Wang, Ting-Cheng; Giang, Yun-Seng

2005-02-25

279

Quantification of N-acetyl-seryl-aspartyl-lysyl-proline in hemodialysis patients administered angiotensin-converting enzyme inhibitors by stable isotope dilution liquid chromatography-tandem mass spectrometry.  

PubMed

We developed a sensitive, selective and accurate method based on liquid chromatography with tandem mass spectrometry (LC-MS/MS) to determine N-terminal thymosin-? peptides of Ac-SDKP and Ac-ADKP in human plasma samples. Quantification of Ac-SDKP and Ac-ADKP was performed using solid phase extraction (SPE) based on C(18), reversed phase LC separation, and stable isotope dilution electrospray ionization-MS/MS in multiple reaction-monitoring (MRM) mode. The Ac-SDKP-(13)C(6), (15)N(2) and Ac-ADKP-d(7) were synthesized for the internal standards. These MRM monitoring ions were m/z 488?129 (quantitative ion)/226 for Ac-SDKP, m/z 496?137 for Ac-SDKP-(13)C(6), (15)N(2), m/z 472?129 (quantitative ion)/226 for Ac-ADKP, and m/z 479?129 for Ac-ADKP-d(7), respectively. Lower limit of quantitation (LLOQ) of Ac-SDKP and Ac-ADKP was 0.1ng/mL in human plasma. Recovery values were ranged from 94.7% to 106.3% for inter- (RSD: 0.6-3.5%) and intra- (RSD: 0.4-4.9%) day assays. Plasma Ac-SDKP levels were significantly higher in hemodialyzed subjects treated with angiotensin-converting enzyme inhibitors of enalapril (27.3±24.6ng/mL, n=10) and trandolapril (12.3±16.9ng/mL, n=18) than healthy (0.4±0.2ng/mL, n=7) and hemodialyzed subjects (0.6±0.2ng/mL, n=34). This analytical method would be useful to measure N-terminal thymosin-? peptides in human plasma for the clinical study. PMID:21074346

Inoue, Koichi; Ikemura, Ayaka; Tsuruta, Yoshinari; Watanabe, Kazuki; Tsutsumiuchi, Kaname; Hino, Tomoaki; Oka, Hisao

2010-10-21

280

Release behavior of hydrogen isotopes thermally sorbed in Li2TiO3 single crystal  

NASA Astrophysics Data System (ADS)

Understanding of fundamental processes governing tritium release in tritium breeder materials is important for blanket design in fusion reactors. In this paper, the release behavior of hydrogen isotopes in Li2TiO3 single crystal samples with different sizes was studied by thermal desorption spectroscopy (TDS). It was indicated that with the size of single crystal samples decreasing to several ?m, the rate-controlling step in the release of hydrogen isotopes moves from bulk diffusion to surface processes. Regarding the amount of hydroxyl groups, the surface hydroxyl groups became predominant for the grains smaller than several tens of ?ms. The amount of surface hydroxyl groups was influenced by the specific surface area and surface conditions.

Zhu, Deqiong; Oda, Takuji; Shono, Yohei; Tanaka, Satoru

2013-11-01

281

Global warming leads the carbon isotope excursion at the Paleocene-Eocene thermal maximum  

NASA Astrophysics Data System (ADS)

The prominent negative carbon isotope excursion (CIE) at the Paleocene-Eocene thermal maximum (55.5 Ma) is generally accepted to reflect a transient, massive input of isotopically light carbon into the ocean- atmosphere system. Many authors have assumed that this carbon led to pronounced global greenhouse warming. Here we show, from an expanded record in New Jersey, that both the onset of the global abundance of the subtropical dinoflagellate Apectodinium and surface-ocean warming as recorded by TEX86 preceded the CIE by several thousands of years. The offset between Apectodinium and the CIE was confirmed in other sites from New Jersey, the North Sea and New Zealand. The approximately 3 kyrs time lag between the onset of warming and the CIE is consistent with the expected lag between bottom water warming and submarine methane hydrate dissociation, suggesting that the latter mechanism indeed caused the CIE.

Sluijs, A.; Brinkhuis, H.; Schouten, S.; Zachos, J. C.; Bohaty, S.; John, C.; Deltrap, R.; Reichart, G.; Sinninghe Damsté, J.; Crouch, E.

2006-12-01

282

Multiple Export Production and Sulfur Isotope Records over the Paleocene Eocene Thermal Maximum  

NASA Astrophysics Data System (ADS)

The Paleocene Eocene Thermal Maximum (PETM) was a global climatic event that occurred 55 million years ago. ?18O values from benthic foraminifera indicate that temperatures rose 4-5°C coeval with a precipitous drop in ?13C values that indicate a new source of carbon rapidly entered the global carbon cycle. Marine barite (BaSO4) was used to evaluate the 1) barite accumulation rate that serves a proxy for export production and 2) the sulfur isotopic composition of seawater that reflects the mass balance of oceanic sulfate (SO42-). Increased barite accumulation rates at the PETM suggest that increased export production and CO2 sequestration was in direct response to the carbon isotope excursion, although not all of the increases are accounted for. High resolution ?34S values are lower but within reasonable range of previously observed values and indicate a decrease in sulfate removal by pyrite deposition.

Gray, E.; Paytan, A.

2007-12-01

283

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

284

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

NASA Astrophysics Data System (ADS)

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 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, Joann M.; Nordstrom, D. Kirk; Böhlke, J. K.; McCleskey, R. Blaine; Ball, James W.

2011-08-01

285

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.; Bohlke, J. K.; McCleskey, R. B.; Ball, J. W.

2011-01-01

286

METHOD OF AND APPARATUS FOR WITHDRAWING LIGHT ISOTOPIC PRODUCT FROM A LIQUID THERMAL DIFFUSION PLANT  

DOEpatents

An improved process and apparatus are described for removing enriched product from the columns of a thermal diffusion plant for separation of isotopes. In the removal cycle, light product at the top cf the diffusion columns is circulated through the column tops and a shipping cylinder connected thereto unttl the concertation of enriched product in the cylinder reaches the desired point. During the removal, circulation through the bottoms is blocked bv freezing. in the diffusion cycle, the bottom portion is unfrozen, fresh feed is distributed to the bottoms of the columns, ard heavy product is withdrawn from the bottoms, while the tops of the columns are blocked by freezing.

Dole, M.

1959-09-22

287

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

288

Thermal conductivity of Si nanostructures containing defects: Methodology, isotope effects, and phonon trapping  

NASA Astrophysics Data System (ADS)

A first-principles method to calculate the thermal conductivity in nanostructures that may contain defects or impurities is described in detail. The method mimics the so-called “laser-flash” technique to measure thermal conductivities. It starts with first-principles density-functional theory and involves the preparation of various regions of a supercell at slightly different temperatures. The temperature fluctuations are minimized without using a thermostat and, after averaging over random initial conditions, temperature changes as small as 5 K can be monitored (from 120 to 125 K). The changes to the phonon density of states and the specific heat induced by several atomic percent of impurities are discussed. The thermal conductivity of Si supercells is calculated as a function of the temperature and of the impurity content. For most impurities, the drop in thermal conductivity is unremarkable. However, there exist narrow ranges of impurity parameters (mass, bond strength, etc.) for which substantial drops in the thermal conductivity are predicted. These drops are isotope dependent and appear to be related to the vibrational lifetime of specific impurity-related modes.

Gibbons, T. M.; Kang, By.; Estreicher, S. K.; Carbogno, C.

2011-07-01

289

Estimation of the isotope effect on the lattice thermal conductivity of group IV and group III-V semiconductors  

NASA Astrophysics Data System (ADS)

The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and transverse phonon Grüneisen constants and the effective sample diameter. The model can quantitatively account for the observed isotope effect in diamond and germanium but not in silicon. The magnitude of the isotope effect is predicted for silicon carbide, boron nitride, and gallium nitride. In the case of boron nitride the predicted increase in the room-temperature thermal conductivity with isotopic enrichment is in excess of 100%. Finally, a more general method of estimating normal phonon-scattering rate coefficients for other types of solids is presented.

Morelli, D. T.; Heremans, J. P.; Slack, G. A.

2002-11-01

290

Determination of the four natural Ra isotopes in thermal waters by gamma-ray spectrometry.  

PubMed

Our method for the simultaneous determination of the four natural Ra isotopes ((226)Ra, (228)Ra, (224)Ra and (223)Ra) in thermal waters involves a separation of Ra on a selective filter (3M EMPORE Radium Rad disk), and a single counting using a broad-energy HPGe detector (BE Ge manufactured by CANBERRA). The calculation of (223)Ra and (228)Ra activities requires interference and cascade summing corrections. The (226)Ra activities in CO(2)-rich thermal waters of the Lodève Basin (South of France) range from 530 to 2240mBq/l. The low ((228)Ra/(226)Ra) activity ratios (0.19-0.29) suggest that Ra is mostly derived from the aquifer carbonates. The short-lived (224)Ra and (223)Ra are probably added to the water through recoil or desorption processes from Th-enriched coatings on the fracture walls. PMID:19954987

Condomines, M; Rihs, S; Lloret, E; Seidel, J L

2009-11-10

291

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

292

On a thermal analysis of a second stripper for rare isotope accelerator.  

SciTech Connect

This memo summarizes simple calculations and results of the thermal analysis on the second stripper to be used in the driver linac of Rare Isotope Accelerator (RIA). Both liquid (Sodium) and solid (Titanium and Vanadium) stripper concepts were considered. These calculations were intended to provide basic information to evaluate the feasibility of liquid (thick film) and solid (rotating wheel) second strippers. Nuclear physics calculations to estimate the volumetric heat generation in the stripper material were performed by 'LISE for Excel'. In the thermal calculations, the strippers were modeled as a thin 2D plate with uniform heat generation within the beam spot. Then, temperature distributions were computed by assuming that the heat spreads conductively in the plate in radial direction without radiative heat losses to surroundings.

Momozaki, Y.; Nolen, J.; Nuclear Engineering Division

2008-08-04

293

Effect of carbon dilution on the low temperature thermal and magnetic properties of f.c.c. nickel base alloys  

Microsoft Academic Search

The low temperature specific heat of ternary dilute alloys of carbon with f.c.c. binary nickel-cobalt and nickel-iron matrices have been measured between 1.2 and 8K. The results have been compared with former experiments on the parent alloys without carbon. The electronic specific heat coefficient is in the case of nickel increased by 35 mJK-2 mol-1 unit atomic carbon concentration. When

R. Caudron; J. J. Meunier; P. Costa

1974-01-01

294

Examining possible effects of seawater pH decline on foraminiferal stable isotopes during the Paleocene-Eocene Thermal Maximum  

Microsoft Academic Search

A large body of paleoceanographic data for the Paleocene-Eocene Thermal Maximum (PETM) is based on foraminiferal stable carbon and oxygen isotope composition (?13C and ?18O). However, the proxy records could be biased due to a “pH effect” on stable isotopes during times when the ocean became more acidic, as has been demonstrated for modern planktonic foraminifera. In this paper, we

Joji Uchikawa; Richard E. Zeebe

2010-01-01

295

Quantitation of Benzo[a]pyrene Metabolic Profiles in Human Bronchoalveolar H358) Cells by Stable Isotope Dilution Liquid Chromatography-Atmospheric Chemical Ionization Mass Spectrometry  

PubMed Central

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants and are carcinogenic in multiple organs and species. Benzo[a]pyrene (B[a]P) is a representative PAH and has been studied extensively for its carcinogenicity and toxicity. B[a]P itself is chemically inert and requires metabolic activation to exhibit its toxicity and carcinogenicity. Three major metabolic pathways have been well documented. The signature metabolites generated from the radical cation (peroxidase or monooxygenase mediated) pathway are B[a]P-1,6-dione and B[a]P-3,6-dione, the signature metabolite generated from the diol-epoxide (P450 mediated) pathway is B[a]P-r-7,t-8,t-9,c-10-tetrahydrotetrol (B[a]P-tetrol-1) and the signature metabolite generated from the o-quinone (aldo-keto reductase mediated) pathway is B[a]P-7,8-dione. The contributions of these different metabolic pathways to cancer initiation and the exploitation of this information for cancer prevention are still under debate. With the availability of a library of [13C4]-labeled B[a]P metabolite internal standards, we developed a sensitive stable isotope dilution atmospheric pressure chemical ionization tandem mass spectrometry method to address this issue by quantitating B[a]P metabolites from each metabolic pathway in human lung cells. This analytical method represents a 500 fold increased sensitivity compared with a method using HPLC-radiometric detection. The limit of quantitation (LOQ) was determined to be 6 fmol on column for 3-hydroxybenzo[a]pyrene (3-OH-B[a]P), the generally accepted biomarker for B[a]P exposure. This high level of sensitivity and robustness of the method was demonstrated in a study of B[a]P metabolic profiles in human bronchoalveolar H358 cells induced or uninduced with the AhR ligand, 2,3,7,8-tetrachlorodibenzodioxin (TCDD). All the signature metabolites were detected and successfully quantitated. Our results suggest that all three metabolic pathways contribute equally in the overall metabolism of B[a]P in H358 cells with or without TCDD induction. The sensitivity of the method should permit the identification of cell-type differences in B[a]P activation and detoxication and could also be used for biomonitoring human exposure to PAH.

Lu, Ding; Harvey, Ronald G.; Blair, Ian A.; Penning, Trevor M.

2013-01-01

296

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

2013-09-18

297

Enhanced cardiac thermal dilution measurement of cardiac output, volumes, regurgitation, valve effective diameters, ventricular power and efficiency -- Feasibility analysis using digital simulation.  

PubMed

Cardiac output is measured by the thermal dilution method which uses a quadruple lumen catheter, with a thermistor on the tip, through the right atrium, right ventricle and into the pulmonary artery. Cold saline is injected into the right atrium and the resulting pulmonary artery temperature profile is integrated. The same procedure performed with three thermistors and three pressure sensors located on the catheter to measure temperature and pressure in the atrium, ventricle and artery respectively will produce a set of temperature and pressure curves with shapes determined by injectate temperature, injectate volume, heart rate, systolic time interval, body temperature, cardiac output, volumes, flow rates and valve openings. A digital computer program has been developed to optimize the fit of a lumped parameter model to the thermodilution curves in order to determine heart rate, systolic time as a fraction of cardiac cycle, right atrial systolic and diastolic volumes, ventricular systolic and diastolic volumes, cardiac output, inflow valve forward and reverse flow rates and effective diameters, outflow valve forward and reverse flow rates and effective diameters, ventricular power and efficiency. The program has been tested over a range of operating conditions including noise in the temperature and pressure signals, randomly varying heart rate and cardiac cycle. All of the data for the tests were produced by a digital computer simulation of a pulsatile artificial heart. The results of these tests indicate that the enhanced thermal dilution analysis method is feasible. PMID:11673669

Donovan, F M; Taylor, B C

2001-01-01

298

METHOD FOR REMOVAL OF LIGHT ISOTOPE PRODUCT FROM LIQUID THERMAL DIFFUSION UNITS  

DOEpatents

A method and apparatus are described for removing the lighter isotope of a gaseous-liquid product from a number of diffusion columns of a liquid thermal diffusion system in two stages by the use of freeze valves. The subject liquid flows from the diffusion columns into a heated sloping capsule where the liquid is vaporized by the action of steam in a heated jacket surrounding the capsule. When the capsule is filled the gas flows into a collector. Flow between the various stages is controlled by freeze valves which are opened and closed by the passage of gas and cool water respectively through coils surrounding portions of the pipes through which the process liquid is passed. The use of the dual stage remover-collector and the freeze valves is an improvement on the thermal diffusion separation process whereby the fraction containing the lighter isotope many be removed from the tops of the diffusion columns without intercolumn flow, or prior stage flow while the contents of the capsule is removed to the final receiver.

Hoffman, J.D.; Ballou, J.K.

1957-11-19

299

Stable carbon isotope compositions during the thermal alteration of organic matter  

SciTech Connect

The use of the amount and carbon isotopic composition of methane as a maturation index was tested by pyrolysis of sedimentary organic carbon (kerogen) at 600 C. The parameters used to describe the maturity are CMR (CH{sub 4}-C/kerogen carbon) and the {Delta}{sup 13}C ({delta}{sup 13}C{sub CH4-} {delta}{sup 13}C{sub OC}). With increasing maturities, smaller amounts of methane are generated and there is a decrease in the fraction between methane and the parent carbon. The pyrolysis of Bakken shale samples, with varying maturities, show high correlation coefficients between the CMR and {Delta}{sup 13}C vs. the atomic H/C ratios (r = +0.91 and {minus}0.89 respectively) which indicates that each of these parameters, independently, can be used as a maturity index. The Bakken shale pyrolysis experiments also show that methane generated from the most thermally altered samples is up to 2% heavier than the parent carbon. In addition, methane-CO{sub 2} exchange experiments, at 600 C, show a shift toward heavier methane values after heating of CH{sub 4} and CO{sub 2} for 504 hrs. The isotopic composition of methane formed under high temperature regimes may be determined by exchange reactions if any CO{sub 2} is present. For these reasons, it becomes difficult to use carbon isotope compositions of methane to distinguish between thermogenic and mantle methane without any other supporting evidence. The effect of metagenesis on the isotopic composition of organic carbon was determined for a suite kerogen samples from the Cape Verde Rise, DSDP Leg 41, Site 386. With increasing maturities, the {delta}{sup 13}C-OC values are heavier due to a loss of lighter carbon in the form of methane. This is shown by a decrease in the carbon mole ratio, with increasing maturities.

Conkright, M.E.

1989-01-01

300

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

301

Application of isotope dilution method for mass- and alpha-spectrometric determination of burn-up and uranium, plutonium and transplutonium element content in VVER-440 spent fuel  

Microsoft Academic Search

In this report the procedures and the methodology of our versions of alpha- and mass-spectrometric techniques for destructive\\u000a analysis of VVER spent fuel are discussed. These techniques allow the determination of the content of americium and curium\\u000a isotopes with relative error 3–5%, that of plutonium isotopes with error ?1% and of uranium isotopes ?0.3–0.4%. They allow\\u000a one to determine the

T. P. Makarova; L. D. Preobrazhenskaya; A. V. Lovtsyus; A. M. Fridkin; A. V. Stepanov; A. A. Lipovskii; B. N. Belyaev

1983-01-01

302

Isotope Geochemistry of Calcite Coatings and the Thermal History of the Unsaturated Zone at Yucca Mountain, Nevada  

SciTech Connect

Calcite and opal coatings found on fracture footwalls and lithophysal cavity bottoms in the volcanic section at Yucca Mountain (exposed in a tunnel) contain a record of gradual chemical and isotopic changes that have occurred in the unsaturated zone. The thin (less than 6 cm) coatings are composed primarily of calcite, opal, chalcedony, and quartz. Fluid inclusions in calcite that homogenize at greater than ambient temperatures provide impetus for geochronologic studies in order to determine the thermal history. In the welded Topopah Spring Tuff (12.7 Ma), U-Pb ages of opal and chalcedony layers provide evidence of a long history of deposition throughout the past 10 m.y. However, these ages can constrain the ages of associated calcite layers only in samples with an easily interpretable microstratigraphy. Strontium isotope ratios in calcite increase with microstratigraphic position from the base up to the outermost surface of the coatings. The strontium incorporated in these coatings records the systematic change in pore-water isotopic composition due to water-rock interaction primarily in the overlying nonwelded tuffs. A one-dimensional advection-reaction model simulates strontium isotope ratios measured in pore water extracted from core in three vertical boreholes adjacent to the tunnel. By calculating the strontium isotope compositions of the rocks at various past times, the model predicts a history of the strontium isotope ratios in the water that matches the record in the calcite and therefore provides approximate ages. Oxygen isotope ratios measured in calcite gradually increase with decreasing model strontium age. Assuming that the oxygen isotope ratio of the percolating water was relatively constant, this trend indicates a gradual cooling of the rocks over millions of years, in agreement with thermal modeling of magma beneath the 12-Ma Timber Mountain caldera just north of Yucca Mountain. This model predicts that temperatures significantly exceeding current geotherm values occurred prior to 6 Ma. We find no evidence for Quaternary or recent thermal perturbations to the cooling rocks.

B.D. Marshall; J.F. Whelan

2000-07-27

303

Stable-isotope dilution gas chromatography–mass spectrometric measurement of 3-hydroxyglutaric acid, glutaric acid and related metabolites in body fluids of patients with glutaric aciduria type 1 found in newborn screening  

Microsoft Academic Search

We developed a simple and sensitive stable-isotope dilution method for the quantification of 3-hydroxyglutaric acid (3HGA) and glutaric acid (GA) in body fluids. In our method, tert-butyldimethylsilyl (tBDMS) derivatives of 3HGA and GA were measured with a conventional electron-impact ionization (EI) mode in gas chromatography–mass spectrometry (GC–MS). The control values for 3HGA in nmol\\/ml were 0.15±0.08 (serum; n=10) and 0.07±0.03

Yosuke Shigematsu; Ikue Hata; Yukie Tanaka; Go Tajima; Nobuo Sakura; Etsuo Naito; Toru Yorifuji

2005-01-01

304

Development of an accurate, sensitive, and robust isotope dilution laser ablation ICP-MS method for simultaneous multi-element analysis (chlorine, sulfur, and heavy metals) in coal samples  

Microsoft Academic Search

A method for the direct multi-element determination of Cl, S, Hg, Pb, Cd, U, Br, Cr, Cu, Fe, and Zn in powdered coal samples\\u000a has been developed by applying inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with laser-assisted\\u000a introduction into the plasma. A sector-field ICP-MS with a mass resolution of 4,000 and a high-ablation rate laser ablation\\u000a system provided

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

2007-01-01

305

The HFSE budget of arc magmas: new models from Hf isotopes and isotope dilution measurements of Nb/Ta, Zr/Hf and Lu/Hf in Kamchatka arc rocks  

NASA Astrophysics Data System (ADS)

There is still no consensus as to whether the HFSE depletion in subduction rocks is caused by the immobile behaviour of these elements during slab dehydration or by the presence of residual accessory phases in the magma sources. To assess this problem, we analysed Nb/Ta, Zr/Hf and Lu/Hf by isotope dilution, together with Hf isotopes, in arc rocks from Kamchatka. Using a mixed 180Ta-94Zr-180Hf-176Lu tracer and the MC-ICPMS in Münster, we are able to achieve external precisions and accuracies of +/-0.5 to +/-1% for Lu/Hf and Zr/Hf and of +/-5% for Nb/Ta (2? uncertainties). In contrast to older techniques (e.g. quadropole ICPMS), this analytical protocol results in a nearly 10-fold improvement in analytical resolution. The investigated suite of Kamchatka arc rocks comprises a cross-arc transect at 56° (element budget largely controlled by variable fluid flux into the subarc mantle, Dohrendorf et al. 2000) and a suite from volcanoes in the Northern Central Kamchatka depression (NCKD, largely controlled by slab melts, Yogodzinski et al. 2001). Coupled Hf-Nd isotope variations (? Hf = 12-18, ? Nd = 6-10) in all samples from the central Kamchatka depression (CKD) and from the back-arc suggest mixing between an OIB source and a MORB source in the wedge. However, samples from the arc front are slightly displaced from the Hf-Nd array towards less radiogenic Nd, indicating selective addition of minor sediment derived Nd to the mantle wedge by fluids high in Nd/Hf. The Zr/Hf (30-42) in all arc rocks are anti-correlated with Lu/Hf (176Lu/177Hf= 0.01-0.03), suggesting that the budget of Zr and Hf is controlled by the degree of mantle depletion rather than by the slab component. NCKD samples are slightly offset from the southern array towards lower Lu/Hf-Zr/Hf, suggesting that Zr-Hf is controlled by slab melts. The back-arc samples show superchondritic Zr/Hf (>35), consistent with the presence of an OIB source component (typical Zr/Hf>35) in their source. Nb/Ta in the Kamchatka rocks range from 11-18 and are decoupled from Zr/Hf and Lu/Hf. The samples from the arc front show an increase in Nb/Ta with Sr/Nd and Ba/Th, indicating that the Nb-Ta budget in these samples is controlled by fluids derived from the subducted slab. Samples from the NCKD (slab melt controlled) overlap in their Nb/Ta and Zr/Hf with samples from the CKD further south (fluid controlled). Such overlapping HFSE patterns, similar in range to MORB, suggest that accessory phases in the slab, if present, can only cause minor Zr/Hf and Nb/Ta fractionation in the subarc fluids or melts. References Dorendorf, F., Wiechert, U. and Worner, G. (2000): Earth and Planetary Science Letters 175: 69-86. Yogodzinski, G.M., Lees, J.M., Churikova, T., Dorenforf, F., Worner, G., and Volynets, O.N., (2000): Nature 409, 500-504.

Münker, C.; Wörner, G.; Churikova, T.; Mezger, K.

2001-12-01

306

Mineralogical and isotopic constraints on chondrule formation from shock wave thermal histories  

NASA Astrophysics Data System (ADS)

When a shock wave passes through a nebular gas, increasing water enrichment leads to higher temperatures and post-shock P, but lower cooling rates. A kinetic evaporation model is developed for tracking the chemical and isotopic changes that would occur in a clump of chondrule precursor dust surrounded by nebular gas in a closed system traversed by a nebular shock wave, taking into account effects of non-equilibrium melting and fractional crystallization on the liquid composition and the temperature difference between the gas and the droplet. A range of shock wave temperature-pressure histories computed for systems enriched relative to solar composition by factors of 550 in water, to achieve the redox state of chondrules, and 600 in dust, to retard evaporation, are employed, and redox changes are assumed to occur on the time-scale of heating and cooling in each. Two different system compositions are assumed, with the mean Fe/Si ratios of Types I and II chondrules. Two different textural outcomes are modeled, PO, in which nuclei are preserved and olivine crystallization begins immediately upon reaching saturation, and BO, in which no nuclei are preserved and olivine crystallization begins only after 300-400 K of supersaturation. In all cases, all iron evaporates, regardless of its oxidation state, as well as alkalis and smaller fractions of Mg and Si. In most cases, recondensation occurs on the time-scale of cooling, resulting in droplets whose bulk compositions have small isotopic anomalies in Mg, Si and Fe, comparable to those seen in bulk chondrules. Because fractional crystallization of olivine occurs before recondensation is complete, however, large isotopic variations, especially for iron, would have been recorded both within olivine crystals and between olivine and glass within these objects. Even after diffusive relaxation during crystal growth and cooling, variations in ?25Mg of several tenths of a ‰ to several ‰, in ?29Si of 0.1‰ to several ‰ and in ?56Fe of several ‰ would be measurable within large grains that grew throughout the olivine crystallization interval in many cases, and olivine-glass differences of ?several tenths of a ‰ in ?29Si, and of several ‰ in ?56Fe would be preserved. Such internal isotopic heterogeneities have not yet been observed in chondrules, suggesting that the latter did not form in these shock wave thermal histories. Suppression of production of internal isotopic variations requires heating times that are shorter by a factor of 100, combined with dust enrichments ? 6 × 104 and/or P?10-2 bar. Together with relatively high f, these constraints suggest that chondrules formed in clouds of liquid and vapor generated by impact on ice-rich planetesimals.

Fedkin, Alexei V.; Grossman, Lawrence; Ciesla, Fred J.; Simon, Steven B.

2012-06-01

307

A case for a comet impact trigger for the Paleocene\\/Eocene thermal maximum and carbon isotope excursion  

Microsoft Academic Search

We hypothesize that the rapid onset of the carbon isotope excursion (CIE) at the Paleocene\\/Eocene boundary (?55 Ma) may have resulted from the accretion of a significant amount of 12C-enriched carbon from the impact of a ?10 km comet, an event that would also trigger greenhouse warming leading to the Paleocene\\/Eocene thermal maximum and, possibly, thermal dissociation of seafloor methane

D. V. Kent; B. S. Cramer; L. Lanci; D. Wang; J. D. Wright; R. van der Voo

2003-01-01

308

Iridium isotope ratio measurements by negative thermal ionization mass spectrometry and atomic weight of iridium  

NASA Astrophysics Data System (ADS)

A technique of negative thermal ionization mass spectrometry (NTI-MS) for the precise iridium isotope ratio determination is presented. IrO-2 and IrO-3 ions are formed in a double-filament (Pt) ion source using (NH4)2IrCl6 as a sample compound. The IrO-2 ion current always exceeds the IrO-3 current by a factor of about 50-300 depending on the filament temperature and the oxygen gas introduced into the ion source. IrO-3 ion currents of more than 10-11 A can be obtained at the detector side from 100 ng iridium samples. The relative standard deviation of the 191Ir/193 ratio determination is 0.06%, which is much better than the data quoted in past literature. From such data the atomic weight of iridium could be calculated to be 192.21661 ± 0.00029. This value is a great improvement when compared with the iridium atomic weight of 192.22 ± 0.03 recommended by IUPAC. Additionally, an NTI-MS technique has been developed which allows the simultaneous measurement of iridium and osmium isotope ratio from osmiridium samples without any chemical separation. The iridium isotope ratios of three osmiridium samples agree well with the ratios determined from the hexachloroiridate compound. The direct 187Os/186OS determination from osmiridium samples opens the possibility of studying the evolution of osmium in the Earth's mantle due to the radioactive decay of 187Re into 187Os.

Walczyk, Thomas; Heumann, Klaus G.

1993-02-01

309

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

310

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

311

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; Jain, Prashant K [ORNL; Freels, James D [ORNL

2012-01-01

312

Evidence of an Impact Trigger for the Paleocene/Eocene Thermal Maximum and Carbon Isotope Excursion  

NASA Astrophysics Data System (ADS)

The Paleocene/Eocene (P/E) boundary is known to be associated with an extraordinarily rapid (probably less than 1 k.y.) and large (about -2.5 per mil) carbon isotope excursion (CIE) recorded in marine and terrestrial systems that coincided with a dramatic and equally rapid oxygen isotopic excursion interpreted as the Paleocene/Eocene (formerly latest Paleocene) Thermal Maximum (PETM). A widely accepted explanation for the rapid onset and magnitude of the CIE is the sudden dissociation of large amounts of 12C-enriched marine gas hydrates on a global scale. Such a large dissociation event could not have occurred spontaneously and requires either a thermal or mechanical trigger whose origin and efficacy remain uncertain. We postulate that the globally rapid simultaneous onsets of the CIE and PETM at about 55 Ma were induced by the impact of a large carbonaceous bolide (asteroid, or more likely, a comet). New evidence that an impact was involved is the discovery at three drill sites on the Atlantic Coastal Plain (Ancora, Bass River and Clayton in NJ) of abundant magnetic nanoparticles (MNP) in deposits that exactly coincide with the onset and nadir of the CIE as recorded in kaolinite-rich clays. The high concentration of MNP material is interpreted as derived from an impact plume condensate. The kaolinitic clay deposits are thus thought to represent the rapidly weathered product of impact ejecta dust. An iridium anomaly reported at the base of the CIE in Zumaya, Spain, and increased concentrations of extraterrestrial osmium and helium isotopes reported at around the P/E boundary level in a poorly dated North Pacific core, are interpreted as encouraging evidence for a P/E impact event. We suggest that the hypothesized bolide was of sufficient mass to deliver enough 12C-enriched carbon (-20 per mil and less) to initiate the CIE and the greenhouse warming at the PETM that coincide with a massive marine benthic extinction event and terrestrial mammalian turnover. If we are correct, then the P/E impact would be one of the few cases of a bolide encounter with a demonstrated biotic effect.

Kent, D. V.; Kent, D. V.; Cramer, B. S.; Lanci, L.

2001-12-01

313

Low-temperature thermal expansion of single-Q chromium and of dilute antiferromagnetic CrV alloys  

Microsoft Academic Search

Measurements of the uniaxial thermal expansion of a Cr single crystal having a single spin-density-wave vector Q show that the large negative term linear in temperature in the expansivity at low temperatures has an anisotropy of about 50%. This linear term is found to increase in magnitude in multidomain antiferromagnetic CrV alloys as the impurity concentration increases, although the Néel

A. B. Kaiser; G. K. White; E. Fawcett

1985-01-01

314

Shear Viscosity and Thermal Conductivity in Liquid HELIUM4 and Dilute Mixtures of HELIUM3 in HELIUM4  

Microsoft Academic Search

An oscillating disk viscometer, with a frequency of 273 s('-1), has been used to measure the viscosity of liquid ('4)He and four ('3)He-('4)He mixtures between 1.4 K and 4.2 K. The mixtures had ('3)He molar concentrations (chi) = 0.0127, 0.0491, 0.0893, and 0.0916. Simultaneously, the thermal conductivity of the samples was measured with a parallel-plate cell, in order independently to

Jeffrey Neal Shaumeyer

1984-01-01

315

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans from catalytic and thermal oxidizers burning dilute chlorinated vapors.  

PubMed

Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (dioxins) have been found from 57 field tests on the oxidation of low (a few to a few hundred) parts per million levels of chlorinated and non-chlorinated volatile organic compounds (VOCs). The oxidation occurs in catalytic oxidizers with platinum, platinum/palladium or chromium(IV) oxide combustion catalysts, or in thermal oxidizers (without a catalyst). The catalyst inlet temperatures ranged from 293 to 573 degrees C. The thermal oxidizer operating temperatures (post-flame) were from 773 to 927 degrees C. Data of the toxic dioxin and furan isomers are reported and also weighted and expressed as international toxic equivalents (TEQ) of 2,3,7,8-tetrachlorodibenzo-p-dioxin. The maximum stack emissions, 1.07 ng/m3 TEQ, occurred at 293 degrees C. Salient results of this field study are: (1) TEQ levels in the stack exponentially increase with a decrease in operating temperature, an empirical equation is TEQ (ng/dscm)=8.4 exp(-0.0084T degrees C); (2) dioxin/furan production occurs at the combustion catalyst; (3) small variations in temperature cause large changes in the congener distribution of the dioxin and furan isomers; (4) molar TEQ yields from the parent compounds fed to the oxidizers are very small (10(-9)-10(-13)); (5) catalytic and thermal oxidizers may destroy dioxins fed from the ambient air; and (6) the oxidation of chlorinated VOCs with non-chlorinated VOCs reduces emissions of dioxins, likely due to the consumption of Cl in producing HCl. Laboratory investigations are needed to understand how dioxins are formed (and emitted) under conditions of this study. PMID:14659956

Hart, John R

2004-03-01

316

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…

Fishel, Laurence A.

2010-01-01

317

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

318

Thermal transport properties in helium near the superfluid transition. III. Dilute /sup 3/He-/sup 4/He mixtures in the normal phase  

SciTech Connect

An experimental study is presented for the thermal conductivity kappa and the thermal relaxation for dilute mixtures of /sup 3/He in /sup 4/He with concentration 9 x 10/sup -4/ less than or equal to X(/sup 3/He) less than or equal to 5 x 10/sup -2/ at saturated vapor pressure and in the normal phase near the superfluid transition. The conductivity results for kappa are compared with predictions by Dohm and Folk from field-theoretic renormalization group (RG) theory. The conductivity kappa/sub s/ = (kappa/sup -1/ (t) - kappa/sup -1/ (T/sub lambda/))/sup -1/, is compared with Ahlers' phenomenological arguments, and also with predictions by Dohm and Folk and by Onuki. The temperature difference transient ..delta..T(t) across the fluid, measured as a function of time t after switching on and off the heat current is analyzed. The thermal diffusion ratio k/sub T/ and the mass diffusion coefficient D are obtained by fitting the calculated transient to the experimental one. The results are compared with the predictions that follow from the RG approach by Dohm and Folk. Very good agreement is obtained for k/sub T/. The transient is not very sensitive to D, and hence the determination is not accurate. Yet within the uncertainty, the deduced D also agrees with predictions. Appendices give (1) the corrections to kappa from finite heat effects, (2) the calculation of the concentration susceptibility (deltaX/delta..delta..)/sub T,P/, and (3) the calculation procedure for kappa, k/sub T/, and D using the RG approach of Dohm and Folk.

Zhong, F.; Gestrich, D.; Dingus, M.; Meyer, H.

1987-07-01

319

Beams of isotopes produced at LISOL by laser ionization after thermalization of energetic ions in a gas cell  

NASA Astrophysics Data System (ADS)

The laser ion source (LIS) at the Leuven isotope separator on-line facility has been used to produce beams of exotic nuclei obtained in different types of nuclear reactions. The application of a gas cell filled by noble gas for thermalizing, storing and transporting trace radioactive ions and atoms, has been studied in off- and on-line conditions. Two-step laser resonance ionization has been used to produce ions of stable and radioactive isotopes inside the cell of the LIS. Results from proton-induced fission on 238U and light-/heavy-ion-induced fusion reactions are presented. The interactions of ions with impurity molecules, with noble gas atoms, with electrons and with electrical fields have been investigated in order to specify the requirements for the gas cell as a source of radioactive rare isotopes for the next generation radioactive ion beam facilities.

Kudryavtsev, Yu.; Facina, M.; Huyse, M.; Gentens, J.; van den Bergh, P.; van Duppen, P.

2003-05-01

320

Simultaneous determination of mercury and butyltin species using a multiple species-specific isotope dilution methodology on the European, Anguilla anguilla glass eel and yellow eel  

Microsoft Academic Search

A methodology to simultaneously determine mercury (MeHg, IHg) and butyltin (TBT, DBT, MBT) compounds in eel samples was assessed and validated using multiple isotopically enriched species. The developed methodology was able to analyse simultaneously the organometal species accurately and precisely and to correct for the potential transformations\\/degradations of the different species during the various steps of the analytical procedure. Low

Patricia Navarro; Stéphanie Clémens; Vincent Perrot; Valérie Bolliet; Hélène Tabouret; Thierry Guérin; Mathilde Monperrus; David Amouroux

2012-01-01

321

Independent Yields of Krypton and Xenon Isotopes in Thermal-Neutron Fission of 235U. Observation of an Odd-Even Effect in the Element Yield Distribution  

Microsoft Academic Search

The fractional and independent fission yields of krypton isotopes (masses 87 to 94) and xenon isotopes (masses 137-143) produced in thermal-neutron fission of 235U were measured using a mass separator operating in an on-line mode with a fission source exposed to time-controlled neutron fluxes. The noble-gas isotopes were collected simultaneously at given times and each mass was measured separately. The

B. Ehrenberg; S. Amiel

1972-01-01

322

Internal Strain and Thermal History of Carbonado Inferred From Photoluminescence Spectroscopy: Relationship to Carbon Isotopic Compositions  

NASA Astrophysics Data System (ADS)

Carbonado exhibits intense photoluminescence (PL) due to the radiation-induced damage and it is possible to estimate the thermal history from PL because radiation damages change its structure at high temperature. Carbonado samples from Central African Republic can be classified into two groups (Group A: low temperature group and Group B: high temperature group) in terms of PL. Correlation between carbon isotopic composition and the PL-based grouping on a suite of carbonado samples from the Central African Republic was reported (Kagi and Akagi, 1996). In this study, we investigated the width of 575 nm band on PL spectra of carbonado at 120K statistically. It is known that the width of 575 nm band can be a sensitive indicator for the internal strain of sintered diamonds (e.g., Collins and Robertson, 1985). All our PL observations were carried out on non-polished crushed samples because we experienced a transition of PL spectra induced by significant heating due to the polishing even if coolant liquid was carefully introduced. Group A carbonado samples gave an average band width of 3.80 nm with a standard deviation of 0.54 nm, Group B carbonado gave an average band width of 2.80 nm with a standard deviation of 0.38 nm. These widths correspond to a residual stress of the order of 1 GPa. It is noteworthy that Group B carbonado exhibited less internal broadening, which means that the internal stress was less than Group A carbonado. These results reconfirm that Group B carbonado has thermally annealed at higher temperature compared to Group A carbonado. In addition, cathodoluminescence images of polished samples revealed the presence of circular luminescence with a diameter of approximately 20 micrometers. This luminescence is assumed to be a trace of the radiation-damage track which was induced by high energy particles from radioactive nuclides at the center of luminescence circle.

Kagi, H.; Sato, S.; Kanda, H.; Akagi, T.

2002-05-01

323

Fission-product formation in the thermal-neutron-induced fission of odd Cm isotopes  

SciTech Connect

Thermal-neutron-induced fission of {sup 243}Cm was studied at the Lohengrin mass separator. The light-mass peak of the fission-yield curve was investigated, and yields of masses from A=72 to A=120 were obtained. Independent-product yields were determined for nuclear charges Z=28-37. The yield of masses in the superasymmetric region was found to be identical to other fission reactions studied at Lohengrin. The multimodal approach to fission and the macroscopic-microscopic method for the calculation of charge-distribution parameters in isobaric chains were used to analyze experimental results from the fission of {sup 243}Cm and {sup 245}Cm. A systematics on fission modes was derived from the analysis and extended to the {sup 247}Cm case. The weight of the {sup 132}Sn mode was found to decrease in {sup 243}Cm, relative to the {sup 245}Cm nucleus. A prediction of the {sup 78}Ni yield in the fission of Cm isotopes was made. The feasibility of the study of {sup 78}Ni at Lohengrin has been demonstrated.

Tsekhanovich, I.; Varapai, N.; Rubchenya, V.; Rochman, D.; Simpson, G.S.; Sokolov, V.; Fioni, G.; Al Mahamid, Ilham [Institut Laue-Langevin, 38042 Grenoble (France); Petersburg Nuclear Physics Institute, 188350 Gatchina (Russian Federation); Commissariat a l'Energie Atomique, Siege, 75752 Paris Cedex 15 (France); Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2004-10-01

324

Chemical and Isotopic Composition of Waters and Dissolved Gases in Some Thermal Springs of Sicily and Adjacent Volcanic Islands, Italy  

Microsoft Academic Search

Hydrochemical (major and some minor constituents), stable isotope ( and , ?13CTDIC total dissolved inorganic carbon) and dissolved gas composition have been determined on 33 thermal discharges located throughout\\u000a Sicily (Italy) and its adjacent islands. On the basis of major ion contents, four main water types have been distinguished:\\u000a (1) a Na-Cl type; (2) a Ca-Mg > Na-SO4-Cl type; (3)

Fausto Grassa; Giorgio Capasso; Rocco Favara; Salvatore Inguaggiato

2006-01-01

325

Sonochemistry of alcohol-water mixtures: Spin-trapping evidence for thermal decomposition and isotope-exchange reactions  

Microsoft Academic Search

The sonochemistry of argon-saturated water-alcohol mixtures has been studied by ESR and spin trapping with 3,5-dibromo-4-nitrosobenzenesulfonate. Free-radical intermediates induced by 50-kHz ultrasound in aqueous solutions of ethanol, 1-propanol, 2-propanol, and 2-methyl-2-propanol were identified. Spin adducts typical of thermal decomposition of the alcohols and of H- and OH-induced abstraction reactions were observed. In the sonolysis of mixed-isotope systems of the type

C. Murali Krishna; Takashi Kondo; Peter Riesz

1989-01-01

326

Carbon and hydrogen isotopic compositions and their evolutions of gases generated by herbaceous swamp peat at different thermal maturity stages  

Microsoft Academic Search

Coalbed methane (CBM) accumulation models include continuous gas accumulation and staged gas accumulation. However, studied\\u000a on the geochemical characteristics and indices to evaluate staged accumulation CBM are lacking. This study for the first time\\u000a obtained the carbon and hydrogen isotopic compositions of methane and ethane generated at different evolution stages using\\u000a thermal simulation of samples prepared by treating an herbaceous

Yi Duan; XiaoLi Zhang; Tao Sun; BaoXiang Wu; JinXian He; Li Xu

2011-01-01

327

Preliminary Results on Fractionation of H, C, S and Cl Isotopes by Thermal Diffusion in Silicate Melts  

Microsoft Academic Search

Molten silicates containing dissolved volatiles (H2O, CO2, SO2 or Cl) were placed in a thermal gradient and the resulting 'hot-to-cold' fractionation of H, C, S and Cl isotopes was characterized in the quenched samples by ion microprobe. The specific melt compositions were tailored to the volatile species of interest: natural obsidian for H-D, Fe-free haplobasalt for C, natural MORB basalt

E. B. Watson; N. Shimizu; R. L. Hervig

2008-01-01

328

Evidence for rapid climate change in North America during the latest Paleocene thermal maximum: oxygen isotope compositions of biogenic phosphate from the Bighorn Basin (Wyoming)  

Microsoft Academic Search

Oxygen isotope records of Cenozoic sea water temperatures indicate that a rapid warming event known as the Latest Paleocene Thermal Maximum (LPTM) occurred during the otherwise gradual increase in world temperatures during the Late Paleocene and Early Eocene. Oxygen isotope analysis of the carbonate and phosphate components of hydroxyapatite found in mammalian tooth enamel and body scales of river-dwelling fish

Henry C. Fricke; William C. Clyde; James R. O'Neil; Philip D. Gingerich

1998-01-01

329

Beta-decay half-lives of neutron rich Cu and Ni isotopes produced by thermal fission of (sup 235)U and (sup 239)Pu.  

National Technical Information Service (NTIS)

The half-lives of very neutron rich isotopes of Ni and Cu have been measured. The isotopes are produced in very asymmetric thermal fission of (sup 235)U and (sup 239)Pu at the I.L.L. high flux reactor. They are separated by means of the Lohengrin spectrom...

M. Bernas J. L. Sida J. P. Bocquet H. Faust R. Brissot

1989-01-01

330

A method for determining isotopic composition of elements by thermal ionization source mass spectrometry: Application to strontium  

NASA Astrophysics Data System (ADS)

It is shown that in thermal ionization source mass spectrometry, if isotope fractionation of the element in the sample follows a linear law, straight-line distributions in xm versus xm/ym diagrams are observed, where xm and ym are two measured isotope ratios. The slopes and y-intercepts of these linear distributions are functions of the [`]true' (starting) values xt and yt of the element in the sample and of the masses of the isotopes involved in ratios x and y. Since the masses of the nuclides are known, true ratios xt and yt can be calculated. This theoretical result is used to determine the non-radiogenic part of the isotopic composition of strontium in NBS SRM 987, one 84Sr-enriched isotopic tracer prepared at the Oak Ridge National Laboratory, and two natural samples (rocks from the metamorphic basement of the Italian Eastern Alps) without any assumption about the isotopic composition itself. Strontium was loaded as nitrate on single tungsten filaments, and 88Sr/86Sr and 84Sr/86Sr ratios were measured up to a fractionation of ~1% u-1 in a single-collector VG 54E mass spectrometer. For each run, 86Sr/88Sr, 84Sr/86Sr and 84Sr/88Sr ratios were calculated for all useful xm versus xm/ym distributions. The respective weighted average values are considered the true values of the isotope ratios in the sample. Four runs of isotopic standard NBS SRM 987 and one run of the isotopic tracer gave accurate and reproducible results which are identical, within error limits, to the respective certified values. The four determinations of NBS 987 resulted in the following weighted average values: 86Sr/88Sr = 0.11942 +/- 0.00018; 84Sr/86Sr = 0.056485 +/- 0.000075; 84Sr/88Sr = 0.006746 +/- 0.000017 (error at 2[sigma] level). The values of the natural 86Sr/88Sr ratio (two rocks: 0.11956 +/- 0.00017 and 0.11957 +/- 0.00008; NBS 987: 0.11942 +/- 0.00018) are identical within error limits, and identical or very close to the recommended value of 0.1194, the worldwide assumed [`]true' 86Sr/88Sr value in the commonly used procedure of determining 87Sr/86Sr ratio by normalization. However, due to the accuracy of the above determinations, it is suggested that, in nature, significant differences exist in the non-radiogenic part of the isotopic composition of strontium.

Cavazzini, Giancarlo

2005-01-01

331

Absolute thermal fission yields for ²³⁵U  

Microsoft Academic Search

Absolute ²³⁵U thermal fission yields are given for the stable and long-lived isotopes of krypton, rubidium, strontium, zirconium, molybdenum, ruthenium, xenon, cesium, barium, lanthanum, cerium, neodymium, and samarium. The principal measurement technique for the fission product isotopes was isotope-dilution mass spectrometry. The number of fissions was established by summing the number of fission product atoms in the heavy mass peak.

W. J. Maeck; W. A. Emel; F. A. Duce; R. L. Tromp; J. W. Meteer

1978-01-01

332

Thermal Property Characterization of Single Crystal Diamond with Varying Isotopic Composition  

Microsoft Academic Search

The mirage-effect\\/thermal wave technique as a modern technique for thermal property characterization is described. In this technique, the thermal diffusivity of a material is determined by measuring the time and space varying temperature distribution (thermal wave) in the material generated by a intensity modulated heating laser beam. These thermal waves, whose propagating features are directly related to the thermal properties

Lanhua Wei

1993-01-01

333

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

2006-07-14

334

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; Sánchez-Brunete, Consuelo; Miguel, Esther; Pérez, Rosa A; Tadeo, José L

2013-02-08

335

Stable carbon isotope patterns of marine biomarker lipids in the Arctic Ocean during Eocene Thermal Maximum 2  

NASA Astrophysics Data System (ADS)

The middle Paleocene through early Eocene long-term gradual warming was superimposed by several transient warming events, such as the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM2). Both events show evidence for extreme global warming associated with a major injection of carbon into the ocean-atmosphere system, but the mechanisms of carbon injection and many aspects of the environmental response are still poorly understood. In this study, we analyzed the concentration and stable carbon isotopic (?13C) composition of several sulfur-bound biomarkers derived from marine photoautotrophs, deposited in the Arctic Ocean at ˜85°N, during ETM2. The presence of sulfur-bound biomarkers across this event points toward high primary productivity and anoxic bottom water conditions. The previously reported presence of isorenieratene derivatives indicates euxinic conditions in the photic zone, likely caused by a combination of enhanced primary productivity and salinity stratification. The negative carbon isotope excursion measured at the onset of ETM2 for several biomarkers, ranges between 3‰ and 4.5‰, much larger than the ˜1.4‰ recorded in marine carbonates elsewhere, suggesting substantial enhanced isotopic fractionation by the primary producers likely due to a significant rise in pCO2. In the absence of biogenic carbonates in the ETM2 section of our core we use coeval planktonic ?13C from elsewhere to estimate surface water ?13C in the Arctic Ocean and then apply the relation between isotopic fractionation and pCO2, originally calibrated for haptophyte alkenones, to three selected organic biomarkers (i.e., S-bound phytane, C35 hopane, and a C25 highly branched isoprenoid). This yields pCO2 values potentially in the range of four times preindustrial levels. However, these estimates are uncertain because of a lack of knowledge on the importance of pCO2 on photosynthetic isotopic fractionation.

Schoon, Petra L.; Sluijs, Appy; Sinninghe Damsté, Jaap S.; Schouten, Stefan

2011-09-01

336

Changes in Nutrient Burial, Export Production, and the Sulfur Isotopic Composition of Seawater During the Paleocene Eocene Thermal Maximum  

NASA Astrophysics Data System (ADS)

We are comparing nutrient burial, using phosphorus (P, micromol P cm-2 kyr-1) mass accumulation rates (MARs), to export productivity, using barite (BaSO4, micromol BaSO4 cm-2 kyr-1) MARs, across the Paleocene Eocene Thermal Maximum (PETM) in sediments from the eastern equatorial Pacific (ODP Leg 199 Sites 1221 and 1215), the western equatorial Pacific (ODP Leg 198, Site 1210), and the western equatorial Atlantic (ODP Leg 171B, Site 1051). Reactive phosphorus (the sum of oxide associated, authigenic, and organic P; sequentially extracted from bulk sediment) is used to distinguish the signal of bio-reactive P from detrital P. Barite, correlated with export productivity in the modern ocean, is separated from bulk sediment. The ratio of nutrient burial (phosphorus) to export productivity (barite) may provide an indication of relative organic C burial. Organic C must be efficiently sequestered in the sediments for the proposed PETM global warmth termination by productivity feedback to be effective. We are comparing relative organic C burial rates for sites in both the equatorial Pacific and the equatorial Atlantic. Initial results from ODP Site 1221 in the Pacific indicate that the nutrient burial to export productivity ratio is high before and immediately after the PETM, possibly indicating enhanced relative organic C burial. To better understand the possible relationship of the seawater sulfur isotopic minimum at the time of the PETM to productivity changes, we are measuring S isotopes in marine barite at high resolution. Seawater S isotopic values in marine barite from the PETM section for ODP Leg 199 Site 1221 yield values of ~17 per mil, reflecting the global marine sulfur isotopic value. These preliminary values indicate that minimum sulfur isotopic values occurred before the C isotopic excursion associated with the PETM, and are probably unrelated to short-term productivity and/or relative organic C burial changes occurring during the PETM.

Faul, K.; Sayo, J.; Paytan, A.; Gray, E.

2005-12-01

337

U-Pb dating of Plinian-eruption ashfalls by the isotope dilution method: A reliable and precise tool for time-scale calibration and biostratigraphic correlation  

SciTech Connect

Through a combination of low analytical blanks, clean Pb-205 enriched tracer-solution, and refined procedures of sample preparation, it is possible to isolate and measure minute quantities of radiogenic Pb in concordant zircon, thereby permitting accurate isotopic age determinations of small multigrain samples of Paleozoic zircon with 7--20 ppm radiogenic Pb. Refinement of these procedures, including reduction of laboratory blank, allows for analysis of single grains of Paleozoic zircon with greater than 25 ppm radiogenic Pb with an age precision of better than 1%. Mass spectrometric measurement of all Pb and U isotopes allows for the calculation of three isotopic ages from a single sample. Concordant multigrain and single-grain U-Pb zircon analyses from 13 biostratigraphically dated K-bentonites in Europe and North America define an internally consistent, absolute chronostratigraphy of Middle ordovician to Upper silurian stratotypes. As a test of trans-Atlantic stratigraphic correlation, a volcanic ash from Middle Ordovician (Rocklandian) strata of North America was found to be in excellent age agreement with Caradocian K-bentonites in Britain and Sweden, demonstrating age equivalence of sedimentary sequences lacking directly comparable fauna. In other case, precise dating of single zircons from three Caradocian K-bentonite in Sweden and Virginia was performed to test a hypothesis that a single ultraplinian volcanic eruption deposited airborne debris on both Larentia and Baltica. The ages of these presumed correlative ashes will be shown to provide quantitative information about the depositional rates of their enclosing strata, as well as tectonic events affecting the margins of Iapetus in Ordovician time.

Tucker, R.D. (Washington Univ., St. Louis, MO (United States). Dept. of Earth and Planetary Sciences)

1992-01-01

338

Simultaneous determination of monomethylmercury, monobutyltin, dibutyltin and tributyltin in environmental samples by multi-elemental-species-specific isotope dilution analysis using electron ionisation GC-MS.  

PubMed

In this work, the simultaneous determination of four organometallic species (monomethylmercury, monobutyltin, dibutyltin and tributyltin) in environmental samples by using a GC-MS system with electron ionisation has been established. The measurement of isotope ratios in each species was accomplished by selecting the most adequate molecular cluster, and simple mathematical equations were applied to correct the contributions of 13C from the organic groups attached to the tin and mercury atoms. The influence of different parameters such as dwell time on the precision and accuracy of the measured isotope ratios in each target species has also been studied. The determination and the sample preparation procedures presented in this work were first individually validated by analysing several certified reference materials for butyltin compounds (mussel tissue CRM-477 and marine sediment SOPH-1) and for monomethylmercury (tuna fish CRM-464) using an innovative focused microwave technology for the extraction of the species from the solid samples. Additionally, the simultaneous determination of the four species was successfully validated by obtaining quantitative recoveries in spiked natural waters and by analysing the certified reference material BCR-710 (certified in tributyltin and monomethylmercury). The values obtained in such certified tissue were fully in agreement not only with the certified mass fractions but also with the proposed indicative values for mono- and dibutyltin. PMID:17103388

Moreno, Maria Jimenez; Pacheco-Arjona, Jaime; Rodríguez-González, Pablo; Preud'Homme, Hugues; Amouroux, David; Donard, Olivier F X

2006-11-01

339

Biochemical fractionation and stable isotope dilution liquid chromatography-mass spectrometry for targeted and microdomain-specific protein quantification in human postmortem brain tissue.  

PubMed

Synaptic architecture and its adaptive changes require numerous molecular events that are both highly ordered and complex. A majority of neuropsychiatric illnesses are complex trait disorders, in which multiple etiologic factors converge at the synapse via many signaling pathways. Investigating the protein composition of synaptic microdomains from human patient brain tissues will yield valuable insights into the interactions of risk genes in many disorders. These types of studies in postmortem tissues have been limited by the lack of proper study paradigms. Thus, it is necessary not only to develop strategies to quantify protein and post-translational modifications at the synapse, but also to rigorously validate them for use in postmortem human brain tissues. In this study we describe the development of a liquid chromatography-selected reaction monitoring method, using a stable isotope-labeled neuronal proteome standard prepared from the brain tissue of a stable isotope-labeled mouse, for the multiplexed quantification of target synaptic proteins in mammalian samples. Additionally, we report the use of this method to validate a biochemical approach for the preparation of synaptic microdomain enrichments from human postmortem prefrontal cortex. Our data demonstrate that a targeted mass spectrometry approach with a true neuronal proteome standard facilitates accurate and precise quantification of over 100 synaptic proteins in mammalian samples, with the potential to quantify over 1000 proteins. Using this method, we found that protein enrichments in subcellular fractions prepared from human postmortem brain tissue were strikingly similar to those prepared from fresh mouse brain tissue. These findings demonstrate that biochemical fractionation methods paired with targeted proteomic strategies can be used in human brain tissues, with important implications for the study of neuropsychiatric disease. PMID:22942359

MacDonald, Matthew L; Ciccimaro, Eugene; Prakash, Amol; Banerjee, Anamika; Seeholzer, Steven H; Blair, Ian A; Hahn, Chang-Gyu

2012-08-31

340

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

341

Measurement of urinary desmosine by isotope dilution and high performance liquid chromatography. Correlation between elastase-induced air-space enlargement in the hamster and elevation of urinary desmosine  

SciTech Connect

The accuracy of methods employed to measure the elastin-specific crosslinks, desmosine (DES) and isodesmosine (IDES), has been called into question because contaminants in the urine may cause elevated values. In the present study urine samples were spiked with a known amount of (14C)DES and refluxed in 6 N HCl. Sephadex G-15 chromatography of the hydrolyzed urine employed to remove contaminants. DES and IDES were quantified by high performance liquid chromatography (HPLC) as well as by amino acid analysis. The amount of isotope recovered was used to determine losses during the overall procedure and the isotope dilution to calculate the amounts of endogenous DES and IDES originally present in the urine. Because similar values were obtained by both methods, the more rapid HPLC method was used for all succeeding analyses. In one experiment, the DES amounts in urine collected from hamsters for 3 days after intratracheal treatment with human neutrophil elastase (300 micrograms) or porcine pancreatic elastase (300 micrograms) were 0.212 {plus minus} 0.012 (mean {plus minus} SEM, two measurements on a single pool) and 0.816 {plus minus} 0.005 (two measurements) microgram per hamster per day, respectively. Urine from control hamsters had a mean value of 0.074 {plus minus} 0.008 (eight measurements) microgram per hamster per day. The HNE- and PPE-treated hamsters had mean linear intercept values of 119 and 159% of control values, respectively, giving a positive correlation between increase in airspace size and elevation of urinary DES.

Stone, P.J.; Bryan-Rhadfi, J.; Lucey, E.C.; Ciccolella, D.E.; Crombie, G.; Faris, B.; Snider, G.L.; Franzblau, C. (Department of Biochemistry, Boston University School of Medicine, MA (USA))

1991-08-01

342

Determination of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in a urine-based standard reference material by isotope-dilution liquid chromatography-mass spectrometry with electrospray ionization.  

PubMed

A new method is presented for the determination of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THC-9-COOH) in urine-based standard reference materials (SRMs) for marijuana metabolite. This method is based on isotope-dilution liquid chromatography-mass spectrometry (LC-MS) using electrospray for ionization (ESI). An isotopically labeled compound, 5',11-nor-delta9-THC-9-carboxylic acid-d3, was used as an internal standard. Solid-phase extraction (SPE) was used to prepare samples for LC-MS analyses. LC was performed on a C18 column with an isocratic mobile phase consisting of 0.05 M of ammonium acetate in methanol/water (75:25). Electrospray ionization in the negative ion mode was used to monitor the [M-H]- ions at m/z 343 and 346 for THC-9-COOH and its labeled internal standard, respectively. Samples of SRM 1507b (THC-9-COOH in freeze-dried urine) were prepared and measured on three separate sets. The within-set coefficients of variation ranged from 0.32% to 2.77%. The correlation coefficients of the regression lines were 0.999 to 1.000. The detection limit for THC-9-COOH with this method is estimated to be 5 pg/mL. This method compared well with the gas chromatography-mass spectrometry method used for certification, and results were within the certified values of THC-9-COOH for SRM 1507b. PMID:10999343

Tai, S S; Welch, M J

2000-09-01

343

Quantitation of fluoride ion released sarin in red blood cell samples by gas chromatography-chemical ionization mass spectrometry using isotope dilution and large-volume injection.  

PubMed

A new method for measuring fluoride ion released isopropyl methylphosphonofluoridate (sarin, GB) in the red blood cell fraction was developed that utilizes an autoinjector, a large-volume injector port (LVI), positive ion ammonia chemical ionization detection in the SIM mode, and a deuterated stable isotope internal standard. This method was applied to red blood cell (RBC) and plasma ethyl acetate extracts from spiked human and animal whole blood samples and from whole blood of minipigs, guinea pigs, and rats exposed by whole-body sarin inhalation. Evidence of nerve agent exposure was detected in plasma and red blood cells at low levels of exposure. The linear method range of quantitation was 10-1000 pg on-column with a detection limit of approximately 2-pg on-column. In the course of method development, several conditions were optimized for the LVI, including type of injector insert, injection volume, initial temperature, pressure, and flow rate. RBC fractions had advantages over the plasma with respect to assessing nerve agent exposure using the fluoride ion method especially in samples with low serum butyrylcholinesterase activity. PMID:15239856

Jakubowski, E M; McGuire, J M; Evans, R A; Edwards, J L; Hulet, S W; Benton, B J; Forster, J S; Burnett, D C; Muse, W T; Matson, K; Crouse, C L; Mioduszewski, R J; Thomson, S A

344

Modified method for determination of sulfur metabolites in plant tissues by stable isotope dilution-based liquid chromatography-electrospray ionization-tandem mass spectrometry.  

PubMed

A wide variety of sulfur metabolites play important roles in plant functions. We have developed a precise and sensitive method for the simultaneous measurement of several sulfur metabolites based on liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and (34)S metabolic labeling of sulfur-containing metabolites in Arabidopsis thaliana seedlings. However, some sulfur metabolites were unstable during the extraction procedure. Our proposed method does not allow for the detection of the important sulfur metabolite homocysteine because of its instability during sample extraction. Stable isotope-labeled sulfur metabolites of A. thaliana shoot were extracted and utilized as internal standards for quantification of sulfur metabolites with LC-MS/MS using S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), methionine (Met), glutathione (GSH), and glutathione disulfide (GSSG) as example metabolites. These metabolites were detected using electrospray ionization in positive mode. Standard curves were linear (r(2)>0.99) over a range of concentrations (SAM 0.01-2.0?M, SAH 0.002-0.10?M, Met 0.05-4.0?M, GSH 0.17-20.0?M, GSSG 0.07-20.0?M), with limits of detection for SAM, SAH, Met, GSH, and GSSG of 0.83, 0.67, 10, 0.56, and 1.1nM, respectively; and the within-run and between-run coefficients of variation based on quality control samples were less than 8%. PMID:23911527

Chang, Ya-Lan; Hsieh, Chin-Lin; Huang, Yao-Moan; Chiou, Wen-Liang; Kuo, Yueh-Hsiung; Tseng, Mei-Hwei

2013-07-31

345

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, René J J; Irth, Hubertus; Floris, Virgilio; Hoogveld, Hans; Pel, Roel

2007-09-11

346

The hydrogen-bonding transition and isotope-dependent negative thermal expansion in H3Co(CN)6  

NASA Astrophysics Data System (ADS)

We investigate the structures of H3Co(CN)6 and D3Co(CN)6 and their temperature dependence using a combination of advanced neutron and x-ray diffraction techniques. Lattice parameter refinements show marked temperature- and isotope-dependent effects in the thermal expansion behaviour. Reverse Monte Carlo modelling of neutron total scattering data characterizes the distribution of D atom positions in the deuterated compound; analysis of these distributions reveals that the two N-H/D bonds become increasingly different with increasing temperature, suggesting a mechanism for the observed thermal expansion anomalies. We discuss these results in the context of the previous crystallographic, spectroscopic and theoretical results for H3Co(CN)6 and 'super-short' {N}{\\cdots } {H}{\\cdots } {N} systems in general.

Keen, David A.; Dove, Martin T.; Evans, John S. O.; Goodwin, Andrew L.; Peters, Lars; Tucker, Matthew G.

2010-10-01

347

Supported liquid extraction in the quantitation of plasma enterolignans using isotope dilution GC/MS with application to flaxseed consumption in healthy adults.  

PubMed

Dietary interventions involving foods that are enriched in lignans, such as flaxseed, are drawing attention due to their beneficial protective effects in various diseases and human conditions. Accurate quantitation of key lignan metabolites such as enterodiol (END) and enterolactone (ENL) is necessary in order to identify factors that may influence overall bioavailability. Here we describe the validation of a novel supported liquid extraction (SLE) method for isolation of plasma enterolignans, END and ENL, using (2)H(6)-labeled isotopes with gas chromatography-mass spectrometry in micro selected ion storage (GC/MS-?SIS) mode. Following enzymatic hydrolysis and SLE extraction with 70:30 diethyl ether:ethyl acetate, enterolignans were rapidly separated within 8min. SLE in combination with GC/MS-?SIS gave high recoveries of 96.4% and 96.0% for END and ENL. Intra-assay precision ranged from 2.5 to 5.9% for both compounds whereas the inter-assay precision was 2.6-6.9%. SLE was also directly compared to liquid liquid extraction (LLE). Both techniques offered high precision and accuracy, however, SLE consistently enabled successful analyte extractions and derivatizations, unlike LLE, which had an ?4% failure rate. SLE was also tested in a study where dietary milled flaxseed supplementation (30g/day for 1month) and enterolignan bioavailability was examined in a healthy, human population (n=10). Plasma total enterolignan levels significantly increased (P=0.002) at 4weeks relative to baseline. Average concentrations for END and ENL were 209nM and 304nM, respectively. PMID:23290922

Edel, Andrea L; Aliani, Michel; Pierce, Grant N

2012-11-01

348

Preparation, certification and validation of a stable solid spike of uranium and plutonium coated with a cellulose derivative for the measurement of uranium and plutonium content in dissolved nuclear fuel by isotope dilution mass spectrometry.  

PubMed

A stable solid spike for the measurement of uranium and plutonium content in nitric acid solutions of spent nuclear fuel by isotope dilution mass spectrometry has been prepared at the European Commission Institute for Reference Materials and Measurements in Belgium. The spike contains about 50 mg of uranium with a 19.838% (235)U enrichment and 2 mg of plutonium with a 97.766% (239)Pu abundance in each individual ampoule. The dried materials were covered with a thin film of cellulose acetate butyrate as a protective organic stabilizer to resist shocks encountered during transportation and to eliminate flaking-off during long-term storage. It was found that the cellulose acetate butyrate has good characteristics, maintaining a thin film for a long time, but readily dissolving on heating with nitric acid solution. The solid spike containing cellulose acetate butyrate was certified as a reference material with certified quantities: (235)U and (239)Pu amounts and uranium and plutonium amount ratios, and was validated by analyzing spent fuel dissolver solutions of the Tokai reprocessing plant in Japan. This paper describes the preparation, certification and validation of the solid spike coated with a cellulose derivative. PMID:18270417

Surugaya, Naoki; Hiyama, Toshiaki; Verbruggen, André; Wellum, Roger

2008-02-01

349

Can Edman degradation be used for quantification? Isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry and the long-term stability of 20 phenylthiohydantoin-amino acids.  

PubMed

Edman degradation is a well-known method for obtaining amino acid (AA) sequences from a peptide by means of sequential reactions that release the N-terminal AAs from the peptide as a phenylthiohydantoin (PTH) derivative. Because of unexpected loss during the reaction and handling, there are few reports of use of this reaction for quantification. This manuscript describes the development of isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry for 20 PTH-AA derivatives, and long-term stability testing of PTH-AAs to ensure quantitative quality in the reaction. The 20 corresponding [(13)C6]-PTH-AAs were prepared by use of a one-pot reaction involving a mixture of [(13)C6]-Edman reagent and 20 AAs. Good linearity was observed for standard curves for the PTH-AAs, using the corresponding [(13)C6]-PTH-AAs as internal standards (1-100 pmol per injection, r (2)?=?0.989-1.000). Serum albumin (human), pepsin (porcine stomach mucosa), ?-casein (bovine milk), ribonuclease A (bovine), lysozyme (chicken egg white), and insulin (bovine) subjected to Edman degradation were examined as model proteins and peptides for N-terminal AA analysis. The results of the impurity test were satisfactory. Yield from the entire reaction with human serum albumin was estimated to be at least 75 %, indicating great potential for absolute quantification of proteins without protein standards. PMID:23545858

Satoh, Ryo; Goto, Takaaki; Lee, Seon Hwa; Oe, Tomoyuki

2013-04-02

350

Synthesis of trans-4,5-epoxy-(E)-2-decenal and its deuterated analog used for the development of a sensitive and selective quantification method based on isotope dilution assay with negative chemical ionization.  

PubMed

The volatile compound trans-4,5-epoxy-(E)-2-decenal (1) was synthesized in two steps with good overall yields. The newly developed method is based on trans-epoxidation of (E)-2-octenal with alkaline hydrogen peroxide followed by a Wittig-type chain elongation with the ylide formylmethylene triphenylphosphorane. For the synthesis of [4,5-2H2]-trans-4,5-epoxy-(E)-2-decenal (d-1), [2,3-2H2]-(E)-2-octenal was prepared by reduction of 2-octyn-1-ol with lithium aluminum deuteride and subsequent oxidation of [2,3-2H2]-(E)-2-octen-1-ol with manganese oxide. Compound d1 was used as internal standard for the quantification of 1 by isotope dilution assay. Among various mass spectrometry (MS) ionization techniques tested, negative chemical ionization with ammonia as reagent gas gave best results with respect to both sensitivity and selectivity. The detection limit was found to be at about 1 pg of the analyte introduced into the gas chromatography-MS system. PMID:10580339

Lin, J; Fay, L B; Welti, D H; Blank, I

1999-10-01

351

Development of a stable isotope dilution assay for an accurate quantification of protein-bound N(epsilon)-(1-deoxy-D-fructos-1-yl)-L-lysine using a (13)C-labeled internal standard.  

PubMed

Syntheses of the labeled Amadori compound [(13)C(6)]-N(epsilon)-(1-deoxy-D-fructos-1-yl)-L-lysine ([(13)C(6)]-DFLys) and the labeled glycated tetrapeptide Ala-[(13)C(6)]-DFLys-Leu-Gly are presented. The compounds were used in the development of stable isotope dilution assays for the quantification of the degree of glycosylation of bovine serum albumin treated for 20 min at 95 degrees C in the presence of glucose. The experiments revealed that the use of the labeled standards in combination with LC/MS allowed the exact quantification of protein-bound DFLys with the high recovery rate of 95% (at a spike level of 150 nmol/mg of protein) and a low detection limit of 5 nmol/mg of protein. The data revealed, however, that DFLys is significantly degraded during the enzymic hydrolysis of the protein backbone generally needed in the quantification procedure and, furthermore, incomplete digestion of the protein was observed. Both sources of errors were clearly overcome by using in particular the labeled peptide as the internal standard. PMID:10606577

Vinale, F; Fogliano, V; Schieberle, P; Hofmann, T

1999-12-01

352

Development and application of a stable isotope dilution analysis for the quantitation of advanced glycation end products of creatinine in biofluids of type 2 diabetic patients and healthy volunteers.  

PubMed

N-(1-Methyl-4-oxoimidazolidin-2-ylidene) ?-amino acids were recently identified in roasted meat as so far unknown advanced glycation end products (AGEs) of creatinine. For the first time, this paper reports on the preparation of (13)C-labeled twin molecules of six N-(1-methyl-4-oxoimidazolidin-2-ylidene) ?-amino acids and the development of a stable isotope dilution analysis (SIDA) for their simultaneous quantitation in meat, plasma, and urine samples by means of HPLC-MS/MS. Method validation demonstrated good precision (<14% RSD) and accuracy (97-118%) for all analytes and a lower limit of quantitation of 1 pg injected onto the column. The SIDA was applied to monitor plasma appearance and urinary excretion of these AGEs in type 2 diabetes mellitus patients (DM, n = 7) and healthy controls (n = 10) prior to and after ingestion of a bolus of processed beef meat. Interestingly, the basal concentration of N-(1-methyl-4-oxoimidazolidin-2-ylidene) aminopropionic acid was elevated in plasma and urine of DM patients compared to healthy individuals. Further, ingestion of processed meat led to a significantly higher concentration of this AGE in biofluids from DM patients when compared to healthy controls. These findings suggest a favored in vivo formation, as demonstrated by physiological model incubations of creatinine and carbohydrates (37 °C, pH 7.4), or a more efficient dietary up-take of N-(1-methyl-4-oxoimidazolidin-2-ylidene) ?-amino acids in hyperglycemic diabetes patients. PMID:23379726

Kunert, Christof; Skurk, Thomas; Frank, Oliver; Lang, Roman; Hauner, Hans; Hofmann, Thomas

2013-02-19

353

Analysis of Heat Exchangers for Dilution Refrigerators.  

National Technical Information Service (NTIS)

Numerical calculations of the behavior of dilution refrigerator heat exchangers are discussed and some results for both discrete and continuous exchangers are presented. It is shown that thermal conductance along the stream is negligible for a typical con...

J. D. Siegwarth R. Radebaugh

1971-01-01

354

Induced fission and signature studies of actinide isotopes using ANL/IPNS thermal neutrons and an array of detectors  

SciTech Connect

Since the mid-1980s when multidetector arrays of high-purity germanium (HPGe) detectors became available, several studies of the prompt fragments from spontaneous fission of {sup 252}Cf, {sup 242}Pu, and {sup 235}U have been undertaken. The data from these measurements have formed the basis of new insights into the fission process. The current series of experiments is aimed at collecting information on the prompt fission fragments arising from thermal neutron-induced fission. The first experiment uses an array of compton-suppressed HPGe detectors and fast liquid scintillation detectors to observe the radiation emitted from the induced fission of {sup 235}U with a beam of thermal neutrons. The experiment was performed at the Argonne National Laboratory Intense Pulsed Neutron Source. A target of {approximately}2 g of uranium was used for this measurement. The array gathers multiple types of time-correlated radiation data. These fission studies and their new results are the basis of an NDA system under development to measure fissile mass, fissile isotopic ratios, radiation source term, and specific fission product isotopes. This system will have applications for the National and Idaho National Environmental and Engineering Laboratory (INEEL) SNF Programs, the Advanced Mixed Waste Focus Area, the Transuranic Waste Program, the safeguards and Security Office, and the Nonproliferation and National Security Office.

Cole, J.D.; Drigert, M.W.; Aryaeinejad, R. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States)] [and others

1999-09-01

355

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

356

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

357

Use of K-Ar Dating and Oxygen Isotopes for Determining the Thermal History of Shales.  

National Technical Information Service (NTIS)

A review of the literature suggests that the isotopes of potassium and oxygen can be used to determine the paleotemperatures of shales and other rocks containing clay minerals. During diagenesis K-bearing smectites and illites lose Ar and gain K over a te...

C. A. Weaver

1980-01-01

358

Limited Value of the Thermal Inactivation Point, Longevity in vitro and Dilution Endpoint as Criteria for the Characterization, Identification and Classification of Plant Viruses  

Microsoft Academic Search

Summary Published data on the thermostability, longevity in vitro, and tolerance to dilution of viruses in sap from infected plants have been analyzed. It appears that none of these properties is a reliable criterion for virus classification or identification.Copyright © 1980 S. Karger AG, Basel

Richard I. B. Francki

1980-01-01

359

Radioisotope Dilution Assay for Vitamin B12 Experiences.  

National Technical Information Service (NTIS)

Serum with a high unsaturated Transcobalamine I: Transcobalamine II ratio from patients with chronic myelocytic leukemia was used as the binder for a radioactive isotope dilution assay of serum vitamin B12 by the method of Rothenberg. This method distingu...

G. M. Dudley C. A. Coltman

1968-01-01

360

Isotope and thermal effects in chemiosmotic coupling to the flagellar motor of Streptococcus  

SciTech Connect

The torque generated by the flagellar motor of Streptococcus strain V4051 has been determined from rates of rotation of cells tethered by a single flagellum in media of different isotopic composition and temperature. Starved cells were energized artificially with either a potassium diffusion potential or a pH gradient. The torque increased linearly with protonmotive force. Identical results were obtained in media made with D2O or H2O; there was no solvent isotope effect. At a fixed protonmotive force, the torque was approximately constant over a temperature range of 4 degrees -38 degrees C. In cells chemotactically inert to changes in cytoplasmic pH, the motor turned counterclockwise when protons moved inward and clockwise when they moved outward. We conclude that the motor is a reversible engine driven by simple acid-base dissociation. A detailed model is discussed.

Khan, S.; Berg, H.C.

1983-03-01

361

Universal isotope effect in thermal diffusion of mixtures containing cyclohexane and cyclohexane-d12  

NASA Astrophysics Data System (ADS)

The Soret coefficients ST of the liquids acetone, benzene, benzene-d1, 1,3,5-benzene-d3, benzene-d5, benzene-13C6, benzene-d6, n-hexane, toluene, 1,2,3,4-tetrahydronaphthalene, isobutylbenzene, and 1,6-dibromohexane have been measured in protonated and perdeuterated cyclohexane by a transient holographic grating technique. It has been found that ST can be either positive or negative and even change its sign as a function of concentration. The isotope effect ?ST=-0.99×10-3 K-1, which is the change of ST after isotopic substitution of cyclohexane, neither depends on concentration nor on the nature of the mixing partner. Only in the case of the polar acetone is ?ST approximately 30% larger but still concentration independent. Based on the experimental findings, some general conclusions about the dependence of the Soret coefficient on molecular properties are drawn.

Wittko, G.; Köhler, W.

2005-07-01

362

The thermal desorption of CO2 from amine carbamate solutions for the 13C isotope enrichment  

NASA Astrophysics Data System (ADS)

The CO2 desorption from amine carbamate in non-aqueous solvents is of major importance for isotopic enrichment of 13C. A series of experiments were carried out in order to set up the conditions for the CO2 desorption. For this purpose, a laboratory- scale plant for 13C isotope separation by chemical exchange between CO2 and amine carbamate was designed and used. The decomposition of the carbamate solution was mostly produced in the desorber and completed in the boiler. Two different-length desorbers were used, at different temperatures and liquid flow rates of the amine-non-aqueous solvent solutions. The residual CO2 was determined by using volumetric and gaschromatographic methods. These results can be used for enrichment of 13C by chemical exchange between CO2 and amine carbamate in nonaqueous solvents.

Dronca, S.; Varodi, C.; Gligan, M.; Stoia, V.; Baldea, A.; Hodor, I.

2012-02-01

363

Y(BD4)3, an efficient store of deuterium, and impact of isotope effects on its thermal decomposition  

NASA Astrophysics Data System (ADS)

Y(BD4)3, which stores as much as 16.6 wt.% and 252 kg/m3 D, has been synthesized via high-energy disk milling. The thermal decomposition of Y(BD4)3 has been investigated using thermogravimetric and calorimetric analyses combined with the spectroscopic evolved gas analysis. Two major endothermic events corresponding to thermal decomposition could be distinguished in the DSC profile up to 400 °C at ca. 231 and 285 °C, preceded by a phase transition (at ca. 198 °C) from the low-temperature Pa-3 form to a high-temperature polymorph of Y(BD4)3 (F-43c). The high-temperature phase forming at the onset of thermal decomposition may be prepared quantitatively by heating of the low-temperature phase to ca. 216 °C followed by rapid quenching.Effects of isotope H?D substitution on various properties of yttrium borohydride have been analyzed. Y(BD4)3 constitutes a very efficient low-temperature source of deuterium gas on the laboratory scale.

Jaro?, Tomasz; Grochala, Wojciech

2012-01-01

364

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

Microsoft Academic Search

The evolution of subtropical (30–35°N) 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 Pucéat; Christophe Lécuyer; Simon M. F. Sheppard; Gilles Dromart; Stéphane Reboulet; Patricia Grandjean

2003-01-01

365

Use of KAr dating and oxygen isotopes for determining the thermal history of shales  

Microsoft Academic Search

A review of the literature suggests that the isotopes of potassium and oxygen can be used to determine the paleotemperatures of shales and other rocks containing clay minerals. During diagenesis K-bearing smectites and illites lose Ar and gain K over a temperature range of 40° to 400°C. This causes a decrease in the apparent K-Ar age. The release of ⁴°Ar\\/³⁹Ar

1980-01-01

366

Reactivity, Isotopic, and Thermal Steady-State Analysis of Homogeneous Thoria-Urania Fuel  

Microsoft Academic Search

Recent investigations into the performance and economics of mixed thoria-urania fuel cycles demonstrate potential advantages at high burnup. Initial neutronic and fuel behavior calculations for several ThOâ-UOâ mixtures being considered for use in commercial nuclear power plants are described.The Monte Carlo N-Particle -Origen2 Coupled Utility Program (MOCUP) was used to analyze the reactivity characteristics and isotopic concentrations of unit fuel

Eric P. Loewen; Kevan D. Weaver; Judith K. Hohorst

2002-01-01

367

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

368

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 (15 g each) and these were stored in a freezer at ?30 °C. Certification was performed by use of three different types of species-specific isotope-dilution mass spectrometry (SSID–MS)—SSID–GC–ICP–MS, SSID–GC–MS, and SSID–LC–ICP–MS, with 118Sn-enriched organotin compounds synthesized from 118Sn-enriched metal used as a spike. The 118Sn-enriched mono-butyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) were synthesized as a mixture whereas the 118Sn-enriched di-phenyltin (DPhT) and triphenyltin (TPhT) were synthesized individually. Four different extraction methods, mechanical shaking, ultrasonic, microwave-assisted, and pressurized liquid extraction, were adopted to avoid possible analytical bias caused by non-quantitative extraction and degradation or inter-conversion of analytes in sample preparations. Tropolone was used as chelating agent in all the extraction methods. Certified values are given for TBT 44±3 ?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.

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

2006-01-01

369

Fluid mixing and thermal regimes beneath the PACMANUS hydrothermal field, Papua New Guinea: Helium and oxygen isotope data  

NASA Astrophysics Data System (ADS)

Fluid mixing processes and thermal regimes within the Snowcap and Roman Ruins vent sites of the PACMANUS hydrothermal system, Papua New Guinea, were investigated using 3He/ 4He ratios from fluid inclusions within pyrite and anhydrite and the ?18O signature of anhydrite. Depressed 3He/ 4He ratios of 0.2-6.91R A appear to be caused by significant atmospheric diffusive exchange, whilst He-Ne diffusive fractionation precludes correction using 20Ne. 40Ar/ 36Ar ratios of 295-310 are elevated above seawater, indicating the majority of argon is seawater derived but with a magmatic component. ?18O anhydrite ratios are 6.5‰ to 11‰ for Snowcap and 6.4‰ to 11.9‰ for Roman Ruins. Using oxygen isotope fractionation factors for the anhydrite-water system, the temperatures calculated assuming isotopic equilibrium at depth are up to 100 °C cooler than fluid inclusion trapping temperatures. It is likely that anhydrite is precipitated rapidly, preventing ?18O equilibration. By comparing new ?18O values for anhydrite with corresponding published 87Sr/ 86Sr ratios, seawater is inferred to penetrate deep into the Snowcap system with little conductive heating. A simple fluid mixing model has been constructed whereby the differing venting styles can be explained by a plumbing system at depth which favors delivery of end-member hydrothermal fluid to the high temperature sites.

Webber, A. P.; Roberts, S.; Burgess, R.; Boyce, A. J.

2011-04-01

370

Effect of carbon and hydrogen isotopic substitutions on the thermal diffusion of benzene  

SciTech Connect

Measurements of the thermal diffusion factor of the benzene/carbon 13 substituted benzene pair and of the benzene/deuterated benzene pair are reported. The results show some interesting effects of mass distribution. (AIP)

Rutherford, W.M.

1989-01-01

371

Isotope Analysis of Seawater by Mass Spectrometry.  

National Technical Information Service (NTIS)

The review includes a discussion of a suitable mass spectrometer, the isotope dilution technique and the scope of its applicability, a description of analytic procedure, and a case history involving the determination of lead isotopes in sea water.

T. J. Chow

1967-01-01

372

Dilutions Made Easy.  

ERIC Educational Resources Information Center

Presents problems appropriate for high school and college students that highlight dilution methods. Promotes an understanding of dilution methods in order to prevent the unnecessary waste of chemicals and glassware in biology laboratories. (JRH)

Kamin, Lawrence

1996-01-01

373

Evidence for rapid climate change in North America during the latest Paleocene thermal maximum: oxygen isotope compositions of biogenic phosphate from the Bighorn Basin (Wyoming)  

NASA Astrophysics Data System (ADS)

Oxygen isotope records of Cenozoic sea water temperatures indicate that a rapid warming event known as the Latest Paleocene Thermal Maximum (LPTM) occurred during the otherwise gradual increase in world temperatures during the Late Paleocene and Early Eocene. Oxygen isotope analysis of the carbonate and phosphate components of hydroxyapatite found in mammalian tooth enamel and body scales of river-dwelling fish from the Bighorn Basin in Wyoming were made to investigate corresponding changes in the terrestrial climate. A comparison of carbonate and phosphate isotope data from modern and fossil material indicates that some diagenetic alteration of the fossil material has occurred, although systematically larger intra-tooth ranges in the oxygen isotope composition of carbonate indicate that it is more likely to have been affected than phosphate. Carbonate and phosphate from the ecologically diverse mammals and fishes both record a shift to higher oxygen isotope ratios at the same time and of the same duration as the LPTM. These shifts reflect a change in the isotopic composition of regional precipitation, which in turn provides the first evidence for continental climate change during the LPTM. Assuming the present-day relation between the oxygen isotope composition of precipitation and temperature applies to conditions in the past, and that animal physiology and behavior is relatively invariant over time, the isotopic shift is equivalent to an increase of surface temperature in western North America of several degrees. This result is consistent with the magnitude of high-latitude ocean warming, and provides a basis for relating marine and terrestrial oxygen isotope records to records of terrestrial biotic change.

Fricke, Henry C.; Clyde, William C.; O'Neil, James R.; Gingerich, Philip D.

1998-07-01

374

Serial Dilution Simulation Lab  

ERIC Educational Resources Information Center

|Serial dilution is often a difficult concept for students to understand. In this short dry lab exercise, students perform serial dilutions using seed beads. This exercise helps students gain skill at performing dilutions without using reagents, bacterial cultures, or viral cultures, while being able to visualize the process.|

Keler, Cynthia; Balutis, Tabitha; Bergen, Kim; Laudenslager, Bryanna; Rubino, Deanna

2010-01-01

375

A case for a comet impact trigger for the Paleocene/Eocene thermal maximum and carbon isotope excursion  

NASA Astrophysics Data System (ADS)

We hypothesize that the rapid onset of the carbon isotope excursion (CIE) at the Paleocene/Eocene boundary (~55 Ma) may have resulted from the accretion of a significant amount of 12C-enriched carbon from the impact of a ~10 km comet, an event that would also trigger greenhouse warming leading to the Paleocene/Eocene thermal maximum and, possibly, thermal dissociation of seafloor methane hydrate. Indirect evidence of an impact is the unusual abundance of magnetic nanoparticles in kaolinite-rich shelf sediments that closely coincide with the onset and nadir of the CIE at three drill sites on the Atlantic Coastal Plain. After considering various alternative mechanisms that could have produced the magnetic nanoparticle assemblage and by analogy with the reported detection of iron-rich nanophase material at the Cretaceous/Tertiary boundary, we suggest that the CIE occurrence was derived from an impact plume condensate. The sudden increase in kaolinite is thus thought to represent the redeposition on the marine shelf of a rapidly weathered impact ejecta dust blanket. Published reports of a small but significant iridium anomaly at or close to the Paleocene/Eocene boundary provide supportive evidence for an impact.

Kent, D. V.; Cramer, B. S.; Lanci, L.; Wang, D.; Wright, J. D.; van der Voo, R.

2003-06-01

376

A molybdenum isotope record of Eocene Thermal Maximum 2: Implications for global ocean redox during the early Eocene  

NASA Astrophysics Data System (ADS)

During the early Eocene, a series of short-term global warming events ("hyperthermals") occurred in response to the rapid release of carbon into the oceans and atmosphere. In order to investigate the response of ocean redox to global warming, we have determined the molybdenum isotope compositions (?98/95Mo) of samples spanning one such hyperthermal (Eocene Thermal Maximum 2 (ETM-2, 54.1 Ma)), from Integrated Ocean Drilling Program Expedition 302 Site M0004A in the Arctic Ocean. The highest?98/95Mo in our sample set (2.00 ± 0.11‰) corresponds to the development of local euxinia at Site M0004A during the peak of ETM-2, which we interpret as recording the global seawater?98/95Mo at that time. The ETM-2 seawater?98/95Mo is indistinguishable from a recent estimate of seawater ?98/95Mo from an earlier hyperthermal (Paleocene Eocene Thermal Maximum (PETM, 55.9 Ma), ?98/95Mo = 2.08 ± 0.11‰). We argue that the similarity in seawater ?98/95Mo during ETM-2 and the PETM was caused by the development of transient euxinia in the Arctic Ocean during each hyperthermal that allowed sediments accumulating in this basin to capture the long-term?98/95Mo of early Eocene seawater. Our new data therefore place a minimum constraint on the magnitude of transient global seafloor deoxygenation during early Eocene hyperthermals.

Dickson, Alexander J.; Cohen, Anthony S.

2012-09-01

377

Development of AN Analytical Method Based on Isotope Dilution Gas Chromatography - Mass Spectrometry for the Determination of Trace Quantities of Aqueous Dimethyl Sulfide and Dimethyl Sulfoxide: Application to Rain and Sea Water.  

NASA Astrophysics Data System (ADS)

This dissertation reports the development of a method for determining trace quantities of aqueous dimethyl sulfide (DMS) and dimethyl sulfoxide (DMSO) by isotope dilution gas chromatography - mass spectrometry (GC/MS). Dimethyl sulfide was determined directly, while DMSO was determined indirectly by first reducing DMSO to DMS in situ with sodium borohydride, and subsequently determining the DMS yield. A Purge and trap method was used to strip DMS from solution and cryogenically preconcentrate DMS in unpacked teflon traps. Samples were collected at remote locations and cryogenically preserved in liquid nitrogen for transport to and analysis in the GC/MS laboratory at Drexel University. Perdeuterated DMS (d_6-DMS) and DMSO (d _6-DMSO) were used as internal standards for the determination of DMS and DMSO, respectively. The standards were prepared as ethylene glycol solutions. The precision of this method for determining both DMS and DMSO was +/-2-3%. The relationship between DMS and DMSO isotopomer aqueous concentration ratios and DMS isotopomer MS signal ratios was determined by calibrating the signal ratios as a function of concentration ratios for samples collected from test solutions prepared by adding known quantities of each isotopomer to solution. The ability of this method for determining true solution phase DMS concentrations was demonstrated by plotting the DMS signal ratio as a function of the volume of purge gas passing through solution. Extrapolation of this curve to zero purge gas yielded an intercept ratio that was statistically equivalent to the signal obtained after only a small volume (10 1) of purge gas passed through solution. The detection limit of the DMSO determination was 15 pM. The detection limit of the DMS determination was <10 pM. These methods were applied to the determination of DMS and DMSO in sea water and the determination of DMSO in rain. Dimethyl sulfide determinations made during two research cruises are reported. In addition, sampling procedures such as sample storage and sample filtration were investigated. The DMSO concentration found in rain was ca. 2-4 nM for samples collected at inland locations (Phila. PA) and 8-10 nM for samples collected at coastal locations (Lewes DE).

Ridgeway, Robert Gordon

1991-02-01

378

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 (3.7±1.4‰), and the continental ranges are lower (3.1±1.3‰).

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

379

Analytical Laboratories Method No. 6005 - the Determination of the Uranium Isotopes (Wt %) by Thermal Ionization Mass Spectrometry (TMS).  

National Technical Information Service (NTIS)

Uranium isotopic analyses at all levels of isotopic concentrations can be performed on microgram quantities of uranium using this solid sample mass spectrometric technique. The uranium, extracted from the matrix material, must be purified prior to perform...

1987-01-01

380

Isotopic yield measurement in the heavy mass region for 239Pu thermal neutron induced fission  

NASA Astrophysics Data System (ADS)

Despite the huge number of fission yield data available in the different evaluated nuclear data libraries, such as JEFF-3.1.1, ENDF/B-VII.0, and JENDL-4.0, more accurate data are still needed both for nuclear energy applications and for our understanding of the fission process itself. It is within the framework of this that measurements on the recoil mass spectrometer Lohengrin (at the Institut Laue-Langevin, Grenoble, France) was undertaken, to determine isotopic yields for the heavy fission products from the 239Pu(nth,f) reaction. In order to do this, a new experimental method based on ?-ray spectrometry was developed and validated by comparing our results with those performed in the light mass region with completely different setups. Hence, about 65 fission product yields were measured with an uncertainty that has been reduced on average by a factor of 2 compared to that previously available in the nuclear data libraries. In addition, for some fission products, a strongly deformed ionic charge distribution compared to a normal Gaussian shape was found, which was interpreted as being caused by the presence of a nanosecond isomeric state. Finally, a nuclear charge polarization has been observed in agreement, with the one described on other close fissioning systems.

Bail, A.; Serot, O.; Mathieu, L.; Litaize, O.; Materna, T.; Köster, U.; Faust, H.; Letourneau, A.; Panebianco, S.

2011-09-01

381

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

Microsoft Academic Search

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

O. Y. Ghidan; R. D. Loss

2008-01-01

382

Intercomparison experiment on isotope dilution thermal ionisation mass spectrometry using plutonium-239 spike for the determination of plutonium concentration in dissolver solution of irradiated fuel.  

National Technical Information Service (NTIS)

Determination of plutonium concentration in the dissolver solution of irradiated fuel is one of the key measurements in the nuclear fuel cycle. This report presents the results of an intercomparison experiment performed between Fuel Chemistry Division (FC...

S. K. Aggarwal P. M. Shah M. K. Saxena H. C. Jain P. B. Gurba

1996-01-01

383

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

1996-01-01

384

Determination of the hydrogen isotopic compositions of organic materials and hydrous minerals using thermal combustion laser spectroscopy.  

PubMed

Hydrogen isotopic compositions of hydrous minerals and organic materials were measured by combustion to water, followed by optical isotopic analysis of the water vapor by off-axis integrated cavity output spectroscopy. Hydrogen and oxygen isotopic compositions were calculated by numerical integration of the individual isotopologue concentrations measured by the optical spectrometer. Rapid oxygen isotope exchange occurs within the combustion reactor between water vapor and molecular oxygen so that only hydrogen isotope compositions may be determined. Over a wide range in sample sizes, precisions were ±3-4 per mil. This is comparable but worse than continuous flow-isotope ratio mass spectroscopy (CF-IRMS) methods owing to memory effects inherent in water vapor transfer. Nevertheless, the simplicity and reduced cost of this analysis compared to classical IRMS or CF-IRMS methods make this an attractive option to determine the hydrogen isotopic composition of organic materials where the utmost precision or small sample sizes are not needed. PMID:22432837

Koehler, Geoff; Wassenaar, Leonard I

2012-04-04

385

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

SciTech Connect

A ThermoFisher 'Triton' multi-collector thermal ionization mass spectrometer (MC-TIMS) was evaluated for trace and ultra-trace level isotoperatioanalysis 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 (10{sup 4} atoms to 10{sup 5} atoms) for {sup 239-242+244}Pu, {sup 233+236}U, {sup 241-243}Am, {sup 89,90}Sr, and {sup 134,135,137}Cs, and {le} 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 x 10{sup 6} or better using a SEM are reported here. Precisions of RSD {approx} 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.

Bürger, Stefan [New Brunswick Laboratory, Argonne, IL; Riciputi, Lee R [Los Alamos National Laboratory (LANL); Bostick, Debra A [ORNL; Turgeon, Steven [University of Alberta, Edmondton, Canada; McBay, Eddie H [ORNL; Lavelle, Mark [ORNL

2009-01-01

386

Determination of thermal and cementation histories from [sup 40]Ar/[sup 39]Ar and ion microprobe stable isotope analyses: A San Joaquin Basin example  

SciTech Connect

Knowledge of the temperature and cementation histories of sedimentary basins is key to appraisal of their liquid hydrocarbon potential. Understanding the thermal history permits assessment of whether source rocks have experienced conditions appropriate for petroleum formation. The mobility of hydrocarbons and their storage capacity in sandstone reservoirs are directly related to porosity changes during diagenesis. Recent advances in [sup 40]Ar/[sup 39]Ar dating (stripping of Cl-correlated Ar[sub xs] Multi-Diffusion Domain model) and development of ion micro-probe techniques for precise ([+-]0.6[per thousand]) [mu]m-scale oxygen isotopic analysis provide a basis to quantitatively determine thermal and cementation histories. Arkosic sandstones of the Stevens turbidities, San Joaquin basin, are cemented by carbonates with minor amounts of clay and quartz. Detrital K-spars from depths of 4.12 (A4) and 6.61 km (Al) in the Stevens zone at Elk Hills yield thermal histories via the MDD model. These results indicate a broadly linear temperature rise of 9[+-]3[degrees]C/Ma over the past 10 Ma and predict current peak temperatures that are within error ([+-]25[degrees]C) of the measured values of 200[degrees] (Al) and 150[degrees]C (A4). Previous bulk isotopic analyses of cements from Stevens sands at North Coles Levee indicate that diagenetic pore fluids were modified by the introduction of hydrocarbons and CO[sub 2] from maturing source horizons. In situ O isotopic analyses of 10 [mu]m spots in these cements confirms this heterogeneity. A model cementation history can then be calculated by linking the oxygen isotopic composition of the cements (and temperature-dependent fractionation factor) with the thermal history independently established from thermochronometry.

Mahon, K.I.; Harrison, T.M.; Grove, M.; Lovera, O.M. (UCLA, Los Angeles, CA (United States))

1996-01-01

387

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 BaSOâ-VâOâ-SiOâ for the preparation of SOâ 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 SOâ must be kept constant in order to apply

F. Yanaglsawa; Hitoshi. Sakai

1983-01-01

388

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  

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 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

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

2005-01-01

389

Species-specific isotope dilution analysis of mono-, di, and tri-butyltin compounds in sediment using gas chromatography-inductively coupled plasma mass spectrometry with synthesized 118Sn-enriched butyltins.  

PubMed

A species-specific isotope dilution (ID) method is described for the determination of mono-, di, and tri-butyltin compounds in sediment by gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP-MS), where the mixture of 118Sn-enriched butyltin compounds synthesized in our laboratory was used as a spike. A correction method for the mass bias, a quantitative extraction of the butyltins from sediment, and an assay for the concentration of the standard solution for the reverse ID procedure were investigated to achieve a reliable ID analysis. The spike solution was added with tri-propyltin (TPrT), and the butyltins were extracted by mechanical shaking into acetic acid-tropolone-toluene. The extracted butyltins were ethylated with sodium tetraethylborate and measured by GC-ICP-MS. The mass bias correction factor for the butyltins was calculated with the measured area ratio of 120Sn/118Sn of TPrT in each chromatographic run, and the correction was carried out. The mass bias was well corrected with this in-run correction (the standard uncertainties of the corrected 120Sn/118Sn for the butyltins were in the range 0.03-0.45%, typically 0.25%, with triplicate measurement corresponding to 0.02-0.37% mass bias). The extraction efficiency of mono-butyltin (MBT) from sediment was improved by using tropolone-toluene as the solvent. Well-defined standard solutions for the reverse-ID procedure could be obtained by an assay for the purities of the natural abundance butyltin chloride reagents used for preparing the standard solutions. Overall uncertainties associated with the present method were estimated, where the sediment certified reference materials, PACS-2 and BCR 646, were analyzed. The uncertainty arising from the extraction was the main contributor to the overall uncertainties for MBT and di-butyltin (DBT) determinations, while with the case of tri-butyltin (TBT) determination the uncertainties arising from the purity of TBT chloride reagent used for preparing the standard solution was a large contributor to the overall uncertainties although the uncertainty arising from the extraction was also a main contributor. The analytical results of MBT, DBT, and TBT in both reference materials, except for MBT results in PACS-2, were in good agreement with the certified values in each. The result of MBT in PACS-2 (0.677 +/- 0.049 microg g(-1) as tin, mean +/- expanded uncertainty) was significantly higher than the certified value (0.45 +/- 0.05 microg g(-1)), but closely matched with the lately reported values (Rajendran, Tao, Nakazato and Miyazaki, Analyst, 2000, 125, 1757: 0.62 +/- 0.02 microg g(-1); Chiron, Roy, Cottier and Jeannot, J. Chromatogr. A, 2000, 879, 137: 0.634 +/- 0.082 microg g(-1); Alonso, Encinar, Gonzalez and Sanz-Medal, Anal. Bioanal. Chem., 2002, 373, 432: 0.64 +/- 0.04 microg g(-1). The present method is concluded to be reliable for the determination of MBT, DBT, and TBT in sediment. PMID:12705386

Inagaki, Kazumi; Takatsu, Akiko; Watanabe, Takuro; Aoyagi, Yoshie; Okamoto, Kensaku

2003-03-01

390

Dilution of cosmological densities by saxino decay  

SciTech Connect

Saxino decay can generate significant cosmological entropy, and hence dilute theoretical estimates of the present mass density of a given particle species. The dilution factor depends on the saxino and axion masses, and is constrained by the requirement that saxino decay should not affect nucleosynthesis, as well as by the usual requirement that the axion density be less than the critical density. The latter constraint is evaluated carefully, under both the Harari-Sikivie and Davis proposals about the emission spectrum from axionic strings. Uncertainties are carefully evaluated, points of principle are addressed, and with an eye to future numerical simulation the spacing and typical oscillation wavelength of the strings are represented by parameters varying in the range 1 to 3. Within the constraints, the entropy dilution varies from 1 to 10[sup [minus]4]. Only saxinos originating from thermal equilibrium are considered, so that more dilution might arise from nonthermal saxinos.

Lyth, D.H. (School of Physics and Materials, Lancaster University, Lancaster LA1 4YB (United Kingdom))

1993-11-15

391

Dilution of cosmological densities by saxino decay  

NASA Astrophysics Data System (ADS)

Saxino decay can generate significant cosmological entropy, and hence dilute theoretical estimates of the present mass density of a given particle species. The dilution factor depends on the saxino and axion masses, and is constrained by the requirement that saxino decay should not affect nucleosynthesis, as well as by the usual requirement that the axion density be less than the critical density. The latter constraint is evaluated carefully, under both the Harari-Sikivie and Davis proposals about the emission spectrum from axionic strings. Uncertainties are carefully evaluated, points of principle are addressed, and with an eye to future numerical simulation the spacing and typical oscillation wavelength of the strings are represented by parameters varying in the range 1 to 3. Within the constraints, the entropy dilution varies from 1 to 10-4. Only saxinos originating from thermal equilibrium are considered, so that more dilution might arise from nonthermal saxinos.

Lyth, David H.

1993-11-01

392

Beyond the dilute Bose gas  

NASA Astrophysics Data System (ADS)

We discuss problems of three dimensional Bose gases in interaction but non-dilute. We then use the theory of a “weakly interacting” Bose gas recently analyzed as an attempt to obtain further insights into non-dilute systems. In particular, we develop the theory with additional remarks, discussions and a slight modification. The article concludes with a much more detailed analysis of the Bose condensate depletion, as well as a study of the two-fluid model of Tisza and Landau: the coexistence of normal and superfluid liquids at sufficiently low temperatures. In fact, even if it is based on one debatable hypothesis, this non-dilute gas qualitatively leads, up to Landau's “T law”, to a rigorous derivation of most of the previous theoretical studies on liquid helium. It also provides new observations, such as, for example, the coexistence of four subsystems of linked pair of particles: a thermal quasi-particle gas, a frozen jelly, a mixture between the previous ones, and a non-conventional Bose condensation of “Cooper-type pairs”. Moreover, the entropic gas is shown to be different from Landau's form associated with the normal liquid.

Bru, Jean-Bernard

2006-01-01

393

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 Bièvre, P.

1996-11-01

394

Extraction chromatographic methods in the sample preparation sequence for thermal ionization mass spectrometric analysis of plutonium isotopes.  

PubMed

A sample preparation sequence for actinide isotopic analysis by thermal ionization mass spectrometry (TIMS) is described that includes column-based extraction chromatography as the first separation step, followed by anion-exchange column separations. The sequence is designed to include a wet ashing step after the extraction chromatography to prevent any leached extractant or oxalic acid eluent reagents from interfering with subsequent separations, source preparation, or TIMS ionization. TEVA resin and DGA resin materials, containing extractants that consist only of C, N, O, and H atoms, were investigated for isolation of plutonium. Radiotracer level studies confirmed expected high yields from column-based separation procedures. Femtogram-level studies were carried out with TIMS detection, using multiple monoisotopic spikes applied sequentially throughout the separation sequence. Pu recoveries were 87% and 86% for TEVA and DGA resin separations, respectively. The Pu recoveries from 400 ?L anion-exchange column separation sequences were 89% and 93% for trial sequences incorporating TEVA and DGA resin. Thus, a prior extraction chromatography step in the sequence did not interfere with the subsequent anion-exchange separation when a simple wet ash step was carried out in between these column separations. The average measurement efficiency for Pu, encompassing the chemical separation recoveries and the TIMS ionization efficiency, was 2.73% ± 0.77% (2?) for the DGA resin trials and 2.67% ± 0.54% for the TEVA resin trials, compared to 3.41% and 2.37% (average 2.89%) for two control trials. These compare with an average measurement efficiency of 2.78% ± 1.70%, n = 33 from process benchmark analyses using Pu spikes processed through a sequence of oxalate precipitation, wet ash, iron hydroxide precipitation, and anion-exchange column separations. We conclude that extraction chromatography can be a viable separation procedure as part of a multistep sequence for TIMS sample preparation. PMID:22004461

Grate, Jay W; O'Hara, Matthew J; Farawila, Anne F; Douglas, Matthew; Haney, Morgan M; Petersen, Steven L; Maiti, Tapas C; Aardahl, Christopher L

2011-11-01

395

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

SciTech Connect

Early studies of {sup 3}He/{sup 4}He variations in geothermal systems have generally attributed these fluctuations to either differences in the source of the magmatic {sup 3}He-rich helium or to local differences in the deep flux of magmatic {sup 3}He-rich helium. Kennedy et al, however, show that near-surface processes such as boiling and dilution may also drastically affect {sup 3}He/{sup 4}He ratios of geothermal vapors. Helium isotope ratios were determined for several hot springs at Shoshone Geyser Basin of Yellowstone National Park for this study, along with other noble gas data. Stable isotope data and water and gas chemistry data for each spring were also compiled. The water chemistry indicates that there is one deep, hot thermal water in the area which is mixing with dilute meteoric water that has entered the system at depth. Spring HCO{sub 3}{sup {minus}} concentrations correlate with {sup 3}He/{sup 4}He values, as in nearby Lower Geyser Basin. This correlation is attributed to variable amounts of deep dilution of thermal waters with a relatively cool water that inhibits boiling at depth, thus preventing the loss of CO{sub 2} and magmatic He in the most diluted samples. Oxygen and hydrogen isotope data also support a boiling and dilution model, but to produce the observed fractionations, the boiling event would have to be extensive, with steam loss at the surface, whereas the boiling that affected the helium isotope ratios was probably a small scale event with steam loss at depth. It is possible that deep boiling occurred in the basin and that small amounts of steam escaped along fractures at about 500 m below the surface while all subsequently produced steam was lost near or at the surface.

Hearn, E.H.; Kennedy, B.M. (Univ. of California, Berkeley (USA)); Truesdell, A.H. (Geological Survey, Menlo Park, CA (USA))

1990-11-01

396

Improvement in Thermal-Ionization Mass Spectrometry (TIMS) using Total Flash Evaporation (TFE) method for lanthanides isotope ratio measurements in transmutation targets  

SciTech Connect

The experiments involved in the PHENIX french nuclear reactor to obtain precise and accurate data on the total capture cross sections of the heavy isotopes and fission products require isotopic ratios measurements with uncertainty of a few per mil. These accurate isotopic ratio measurements are performed with mass spectrometer equipped with multi-collector system. The major difficulty for the analyses of these actinides and fission products is the low quantity of the initial powder enclosed in steel container (3 to 5 mg) and the very low quantities of products formed (several {mu}g) after irradiation. Specific analytical developments are performed by Thermal Ionization Mass Spectrometry (TIMS) to be able to analyse several nanograms of elements with this technique. A specific method of acquisition named Total Flash Evaporation was adapted in this study in the case of lanthanide measurements for quantity deposited on the filament in the order of 2 ng and applied on irradiated fuel. To validate the analytical approach and discuss about the accuracy of the data, the isotopic ratios obtained by TIMS are compared with other mass spectrometric techniques such as Multiple-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). (authors)

Mialle, S.; Gourgiotis, A.; Aubert, M.; Stadelmann, G.; Gautier, C.; Isnard, H. [Commissariat a l'Energie Atomique, CEA Saclay, DEN/DPC/SECR/LANIE, 91191 Gif sur Yvette (France); Chartier, F. [Commissariat a l'Energie Atomique, CEA Saclay, DEN/DPC, 91191 Gif sur Yvette (France)

2011-07-01

397

Determination of Oxygen Self-Diffusion in Akermanite, Anorthite, Diopside, and Spinel: Implications for Oxygen Isotopic Anomalies and the Thermal Histories of Ca-Al-rich Inclusions  

NASA Astrophysics Data System (ADS)

Oxygen self-diffusion coefficients have been measured for three natural clinopyroxenes (diopside end member), a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic akermanite over oxygen fugacities ranging from the NNO to IW buffers. The experiments employed a gas-solid isotopic exchange technique utilizing 99% ^18O-enriched COCO2 gas mixtures to control both the oxygen fugacity and the isotopic composition of the exchange reservoir. Diffusion profiles of the ^18O tracer were obtained by in-depth analysis with an ion microprobe. The experimental results yield Arrhenius relations that appear here in the hard copy. At a given temperature, oxygen diffuses about 100 times more slowly in diopside than indicated by previous bulk-exchange experiments [1]. Our data for anorthite, spinel, and akermanite agree well with prior results obtained by gas-solid isotopic exchange and depth profiling methods [2-4]. Since these other experiments were conducted at different oxygen fugacities, this agreement indicates that diffusion of oxygen in these nominally iron-free minerals is not greatly affected by fO2 in the range between pure oxygen and the iron-wustite buffer. The oxygen diffusion data are used to evaluate the effects of three different types of therrnal histories upon the oxygen isotopic compositions of minerals found in Type B calciumaluminum-rich inclusions (CAIBs): (1) gas-solid exchange during isothermal heating, (2) gassolid exchange due to instantaneous heating followed by cooling at different rates, and (3) isotopic exchange with a gaseous reservoir during partial melting and recrystallization. With the assumptions that the mineral compositions within a CAIB were uniformly enriched in ^16O prior to any thermal processing, that effective diffusion dimensions may be estimated from observed grain sizes, and that diffusion in diopside is similar to that in fassaite, all the above scenarios fail to reproduce either the relative oxygen isotopic anomalies observed in CAIBs and/or yield improbably long or unrealistically intense thermal histories relative to both current theoretical models of nebular evolution and inferences from other isotopic systems. The failure of these simple models, coupled with recent observations of "disturbed" Mg isotopic abundances and petrographic features in anorthite and melilite indicative of alteration and recrystallization [5,6], suggests that the oxygen isotopic compositions of these phases may have also been modified by alteration and recrystallization during multiple melting events. Because the modal abundance of spinel remains relatively constant for plausible melting scenarios and its relatively sluggish diffusion kinetics prevent substantial equilibration, Mg-Al spinel is a reliable indicator of the oxygen isotopic composition of precursor material that formed CAIBs. References: [1] Connolly C. and Muehlenbachs K. (1988) GCA, 52, 1585-1592. [2] Elphick S. C. et al. (1988) Contrib. Mineral. Petrol., 100, 490-495. [3] Reddy K. P. and Cooper A. R. (1981) J. Am. Ceram. Soc., 64, 368-371. [4] Yunmoto H. et al. (1989) GCA, 53, 2387-2394. [5] Podosek F. A. et al. (1991) GCA, 55, 1083-1110. [6] MacPherson G. J. and Davis A. M. (1993) GCA, 57, 231-243.

Ryerson, F. J.; McKeegan, K. D.

1993-07-01

398

The Environmental Impact of the Paleocene-Eocene Thermal Maximum on the Coastal Ocean, New Jersey: Inferences from Stable Isotope, Trace Metal, and Organic/Inorganic Carbon Records  

NASA Astrophysics Data System (ADS)

Approximately 55 million years ago, the Earth experienced an abrupt transient global warming, the Paleocene-Eocene Thermal Maximum (PETM). Two shallow marine sections across the PETM were cored near Clayton, New Jersey. Nannofossil biostratigraphy along with carbon isotope stratigraphy were used to identify the boundary and to constrain the thickness of the PETM. The excursion layer appears to be expanded (~15 m), though the early Eocene is truncated by erosion. The Wilson Lake and Clayton cores, along with data from other northeastern U.S. localities within the same embayment, reveal significant biologic and mineralogical anomalies across the CIE. For example, the Wilson Lake core contains a pronounced increase in relative abundance of dinoflagellate cysts (dinocysts) assigned to the genus Apectodinium around the event, increasing from <1% below the CIE transition to 52% within, as well as a pronounced spike in kaolinite content. A suite of geochemical analyses including stable isotopes was generated for the Wilson Lake core at high resolution to constrain temperature/salinity, organic/inorganic C fluxes and redox conditions. The isotope records show dramatic negative excursions in ? 13C and ? 18O, with a 6‰ negative carbon shift in bulk sediments. Carbonate content decreases to <1% at the ? 13C bulk minimum and then increases to a maximum of 15% 3 m above. The benthic and planktonic foraminifer isotope records show excursions but of much smaller magnitudes than recorded in bulk carbonate implying a meteoric diagenetic overprint on the bulk isotope signal. Uranium, manganese, and barium data indicate minor shifts in the redox conditions of bottom waters during the excursion. Substantial manganese enrichment over much of the interval suggests that oxidative conditions dominate during the event consistent with the low organic carbon content (<1%). At the top of the section, a spike in uranium indicates a shift to suboxia in the late stages of system recovery. The lack of barium enrichment during the event suggests that there was little change in local paleoproductivity.

Quattlebaum, T. G.; Bohaty, S.; Zachos, J. C.; Delaney, M.; Anderson, L.; Bybell, L.

2003-12-01

399

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 400°C- 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

400

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

401

High precision Hf isotope measurements of MORB and OIB by thermal ionisation mass spectrometry: insights into the depleted mantle  

Microsoft Academic Search

The existing Hf isotope database for mid-ocean ridge basalts (MORB) is limited in both quantity and precision. Nevertheless, in Hf–Nd isotope space, MORBs show a wide variation in 176Hf\\/177Hf over a relatively restricted range in 143Nd\\/144Nd. The highest 176Hf\\/177Hf ratios (?0.283355) within the MORB range are restricted to just four samples (<6.5% of total). Of these high 176Hf\\/177Hf MORBs, three

G. M. Nowell; P. D. Kempton; S. R. Noble; J. G. Fitton; A. D. Saunders; J. J. Mahoney; R. N. Taylor

1998-01-01

402

Determination of oxygen self-diffusion in åkermanite, anorthite, diopside, and spinel: Implications for oxygen isotopic anomalies and the thermal histories of Ca-Al-rich inclusions  

NASA Astrophysics Data System (ADS)

Oxygen self-diffusion coefficients have been measured for three natural diopsidic clinopyroxenes, a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic åkermanite for oxygen fugacities ranging from the NNO to IW buffers. The experiments employed a gas-solid isotopic exchange technique utilizing 99% 18O-enriched CO-CO2 gas mixtures to control both the oxygen fugacity and the isotopic composition of the exchange reservoir. Diffusion profiles of the 18O tracer were obtained by in-depth analysis with an ion microprobe. The experimental results, fit to the Arrhenius relation D = D0e(-QRT), yield the following: Do (m2 s-1)Q (kJ mol-1)diopside4.3- 3.8+32.6× 10 - 4457 ± 26åkermanite4.7- 4.4+83.5× 10 - 7457 ± 26278 ± 33spinel2.2- 1.8+8.7× 10 - 7404 ± 21anorthite8.4- 8.0+174× 10 - 13162 ± 36At a given temperature, oxygen diffuses about 100 times more slowly in diopside than indicated by previous bulk-exchange experiments (CONNOLLY and MUEHLENBACHS, 1988). Our data for anorthite, spinel, and åkermanite agree well with prior results obtained by gas-solid exchange and depth profiling methods (ELPHICK et al., 1988; REDDY and COOPER, 1981; YURIMOTO et al., 1989, respectively). Since these other experiments were conducted at different oxygen fugacities, this agreement indicates that diffusion of oxygen in these nominally Fe-free minerals is not greatly affected by fO2 in the range between pure oxygen and the iron-wüstite buffer. However, our diffusion coefficients for anorthite, melilite, and spinel are also uniformly lower than those obtained by bulk analysis of crushed powders at similar temperatures (MUEHLENBACHS and KUSHIRO, 1974; HAYASHI and MUEHLENBACHS, 1986; ANDO and OISHI, 1974).The oxygen diffusion data are used to evaluate the effects of three different types of thermal histories upon the oxygen isotopic compositions of minerals found in Type B Ca-Al-rich inclusions (CAIBs) in carbonaceous chondrites: (1) gas-solid exchange during isothermal heating,(2) gas-solid exchange as a function of cooling rate subsequent to instantaneous heating, and(3) isotopic exchange with a gaseous reservoir during partial melting and recrystallization. With the assumptions that the mineral compositions within a CAIB were uniformly enriched in 16O prior to any thermal processing, that effective diffusion dimensions may be estimated from observed grain sizes, and that diffusion in diopside is similar to that in fassaitic clinopyroxene, none of the above scenarios can reproduce the relative oxygen isotopic anomalies observed in CAIBs without improbably long or unrealistically intense thermal histories relative to current theoretical models of nebular evolution. The failure of these simple models, coupled with recent observations of “disturbed” magnesium isotopic abundances and correlated petrographic features in anorthite and melilite indicative of alteration and recrystallization, suggests that the oxygen isotopic compositions of these phases may have also been modified by alteration and recrystallization possibly interspersed with multiple melting events. Because the modal abundance of spinel remains relatively constant for plausible melting scenarios, and its relatively sluggish diffusion kinetics prevent substantial equilibration, Mg-Al spinel is the most reliable indicator of the oxygen isotopic composition of precursor material which formed Type B CAIs.

Ryerson, F. J.; McKeegan, Kevin D.

1994-09-01

403

Effective elimination of organic matter interference in boron isotopic analysis by thermal ionization mass spectrometry of coral/foraminifera: micro-sublimation technology combined with ion exchange.  

PubMed

In order to better estimate the effectiveness of micro-sublimation technology on the elimination of organic matter interference during boron isotopic analysis, a series of improved experiments was carried out using simple apparatus. Recovery rates after micro-sublimation were measured for boric acid solutions with different B contents or different B/organic matter ratios. The improved micro-sublimation procedure combined with ion-exchange technology was then used to test natural samples (coral and foraminifera) for the separation of boron. Our results show that the time taken for 100% recovery of different amounts of B differed and that the proportions of B/organic matter within the natural organic matter have little effect on the relationship between the recovery rates of B and the micro-sublimation times. The experiments further confirm that the organic matter does indeed have an effect on boron isotope analyses by positive thermal ionization mass spectrometry and that the use of micro-sublimation can effectively remove interferences from the organic matter during boron isotopic analysis. PMID:21337635

He, Maoyong; Xiao, Yingkai; Ma, Yunqi; Jin, Zhangdong; Xiao, Jun

2011-03-30

404

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

405

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

SciTech Connect

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 appropriate agreement with previous measurements. The experimental results are interpreted by use of activation energy asymptotic theories developed previously. The gas-phase chemical reaction is approximated as a one step, irreversible process with a large value for the ratio of the activation energy characterizing the chemical reaction to the thermal energy in the flame. Equilibrium dissociation of products is neglected. The theoretical predictions are compared with experimental results, and the overall chemical kinetic rate parameters characterizing the gas-phase oxidation of methane and propane in a diffusion flame are deduced. The overall chemical kinetic rate parameters deduced by use of this procedure are valid only at flame temperatures where equilibrium dissociation is negligible. The scalar dissipation rate at extinction is predicted over a wide range.

Puri, I.K.; Seshadri, K.

1986-08-01