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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

Evaluation of Duluth Complex anorthositic series (AS3) zircon as a UPb geochronological standard: new high-precision isotope dilution thermal ionization mass spectrometry results  

Microsoft Academic Search

U-Pb zircon geochronology is increasingly called upon to achieve the resolution of absolute time at the 0.1% to 1% level for rocks of Phanerozoic to Hadean age. Doing so requires accurate calibration of the several methods (conventional isotope dilution thermal ionization mass spectrometry [ID-TIMS], Pb evaporation, high-resolution ion microprobe [e.g. SHRIMP], and laser ablation inductively coupled plasma mass spectrometry [LA-ICPMS])

Mark D Schmitz; Samuel A Bowring; Trevor R Ireland

2003-01-01

3

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

E-print Network

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

McLean, Noah Morgan

4

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

PubMed

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

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

2003-03-01

5

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

2013-04-01

6

Simultaneous determination of 143Nd/144Nd and 147Sm/144Nd ratios and Sm-Nd contents from the same filament loaded with purified Sm-Nd aliquot from geological samples by isotope dilution thermal ionization mass spectrometry.  

PubMed

Isotope dilution thermal ionization mass spectrometry (ID-TIMS) is the standard technique used to achieve precise (143)Nd/(144)Nd and (147)Sm/(144)Nd isotope ratios and accurate elemental concentrations of Sm-Nd. However, in previous studies, purified Sm and Nd fractions must be individually loaded onto different filaments for their accurate determination using TIMS because of severe isobaric interferences. Thus, the classical ID-TIMS technique is time consuming and laborious. In this study, a new method is proposed, which is able to acquire both ratios of (143)Nd/(144)Nd and (147)Sm/(144)Nd and concentrations of Sm-Nd simultaneously on the same filament arrangement. The measurement time and filament consumption are reduced by 50% with the current method, and therefore, the operation cost of TIMS is significantly reduced. A mixed (152)Sm-(148)Nd spike was employed to achieve accurate results after spike subtraction and isobaric interference corrections. Results obtained from a series of standard rock samples are in good agreement with recommended values, within ±0.003% for the (143)Nd/(144)Nd ratio and ±1% for the (147)Sm/(144)Nd ratio. PMID:22746207

Li, Chao-Feng; Li, Xian-Hua; Li, Qiu-Li; Guo, Jing-Hui; Li, Xiang-Hui; Feng, Lian-Jun; Chu, Zhu-Yin

2012-07-17

7

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

SciTech Connect

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

Miller, P.

1998-01-05

8

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

USGS Publications Warehouse

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

Matsumoto, A.; Hinkley, T.K.

1997-01-01

9

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

10

Mechanism of Thermal Transport in Dilute Nanocolloids  

NASA Astrophysics Data System (ADS)

Thermal conduction modes in a nanocolloid (nanofluid) are quantitatively assessed by combining linear response theory with molecular dynamics simulations. The microscopic heat flux is decomposed into three additive fluctuation modes, namely, kinetic, potential, and collision. For low volume fractions (<1%) of nanosized platinum clusters which interact strongly with xenon host liquid, a significant thermal conductivity enhancement results from the self correlation in the potential flux. Our findings reveal a molecular-level mechanism for enhanced thermal conductivity in nanocolloids with short-ranged attraction and offer predictions that can be experimentally tested.

Eapen, Jacob; Li, Ju; Yip, Sidney

2007-01-01

11

Geochronology of the Jack Hills detrital zircons by precise U–Pb isotope dilution analysis of crystal fragments  

Microsoft Academic Search

U–Pb ages were determined for 12 whole grains and 45 fragments from further 14 grains of detrital zircon from the Jack Hills metaconglomerate, Western Australia, using isotope dilution thermal ionization mass-spectrometry in combination with air abrasion and HF leaching. These data indicate the presence of two groups of detrital zircons with ages of 3.31–3.52 Ga (`young group') and 3.82–4.11 Ga

Yuri V Amelin

1998-01-01

12

Quantitation of DNA adducts by stable isotope dilution mass spectrometry  

PubMed Central

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

Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

2012-01-01

13

Thermal Conductivity and Sound Attenuation in Dilute Atomic Fermi Gases  

E-print Network

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_c, the quasi-particles are fermions, whereas below T_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 ~ T^{3/2}. In the superfluid phase we find \\kappa ~ T^{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_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.

Matt Braby; Jingyi Chao; Thomas Schaefer

2010-10-15

14

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

15

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

2012-10-20

16

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

SciTech Connect

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

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

1997-07-01

17

Dilute and concentrated phases of vesicles at thermal equilibrium  

NASA Astrophysics Data System (ADS)

A quaternary system made of an ionic surfactant (SDS), octanol, water and sodium chloride has been investigated. We present experimental results that demonstrate the existence of a phase of vesicles at thermal equilibrium. We show that vesicles can be prepared both in a dilute regime leading to an isotropic liquid phase of low viscosity and in a concentrated regime leading to a phase of close packed vesicles (probably multilayered) exhibiting high viscosity and viscoelasticity.

Hervé, P.; Roux, D.; Bellocq, A.-M.; Nallet, F.; Gulik-Krzywicki, T.

1993-08-01

18

Entropy Production and Thermal Conductivity of A Dilute Gas  

E-print Network

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.

Yong-Jun Zhang

2011-02-16

19

Determination of Key Intermediates in Cholesterol and Bile Acid Biosynthesis by Stable Isotope Dilution Mass Spectrometry  

PubMed Central

For more than a decade, we have developed stable isotope dilution mass spectrometry methods to quantify key intermediates in cholesterol and bile acid biosynthesis, mevalonate and oxysterols, respectively. The methods are more sensitive and reproducible than conventional radioisotope (RI), gas-chromatography (GC) or high-performance liquid chromatography (HPLC) methods, so that they are applicable not only to samples from experimental animals but also to small amounts of human specimens. In this paper, we review the development of stable isotope dilution mass spectrometry for quantifying mevalonate and oxysterols in biological materials, and demonstrate the usefulness of this technique. PMID:19609389

Yoshida, Tadashi; Honda, Akira; Miyazaki, Hiroshi; Matsuzaki, Yasushi

2008-01-01

20

Thermal conductivity of isotopically enriched Si  

SciTech Connect

We have used an optical pump-and-probe technique to measure the temperature dependence of the thermal conductivity, {kappa}(T), of isotopically pure Si. The sample was made from 99.7{percent} {sup 28}Si by liquid phase epitaxy. Measurements were performed over the temperature range of 100{endash}375 K. We found an increase in the thermal conductivity of isotopically pure Si, as compared to Si of natural isotopic abundance, throughout the entire temperature range. The results were theoretically reproduced by appropriately scaling the parameters used recently to fit the thermal conductivity of Ge samples with different isotopic compositions. A maximum in {kappa}(T) of {approximately}4{times}10{sup 4}thinspWthinspm{sup {minus}1}thinspK{sup {minus}1} is predicted for {sup 28}Si at T{approx_equal}33thinspK. {copyright} {ital 1997 American Institute of Physics.}

Capinski, W.S.; Maris, H.J. [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States); Bauser, E.; Silier, I.; Asen-Palmer, M.; Ruf, T.; Cardona, M.; Gmelin, E. [Max-Planck-Institut fuer Festkoerperforschung, D-70569 Stuttgart (Germany)] [Max-Planck-Institut fuer Festkoerperforschung, D-70569 Stuttgart (Germany)

1997-10-01

21

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

PubMed

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

Ren, Yao; Walczyk, Thomas

2014-09-01

22

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

PubMed

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

Meitinger, Michael; Hartmann, Sandra; Schieberle, Peter

2014-06-01

23

Molecular-weight dependent thermal diusion in dilute polymer solutions Alois Wrger  

E-print Network

Molecular-weight dependent thermal di¤usion in dilute polymer solutions Alois Würger Centre de-, 82.70.-y, 82.20.-w Introduction. Di¤usion in dilute polymer solutions de- pends strongly Talence, France Thermal di¤usion of high polymers in a continous medium is independent of the molecular

Boyer, Edmond

24

Determination of aflatoxins in animal feeds by liquid chromatography/tandem mass spectrometry with isotope dilution.  

PubMed

The objective of the present study is to develop a simple, fast method for detection of aflatoxins in animal feeds. Simultaneous quantitation of four aflatoxins (AFB(1), AFB(2), AFG(1) and AFG(2)) in animal feeds was achieved in a single liquid chromatography/tandem mass spectrometry (LC/MS/MS) run. The solid-phase extraction cleanup step is eliminated with the stable isotope dilution method. Matrix effects were observed and overcome by isotope dilution. The method was tested in a variety of animal feed matrices and proved to be accurate and reliable. Method ruggedness tests resulted in recoveries of 78% to 122% with an intra-day assay precision of 2% to 15% and an inter-day assay precision of 3% to 17%. These results indicate that this method is suitable for quantitation of aflatoxins in animal feeds. PMID:21491528

Li, Wei; Herrman, Timothy J; Dai, Susie Y

2011-05-15

25

Standard test method for uranium and plutonium concentrations and isotopic abundances by thermal ionization mass spectrometry  

E-print Network

1.1 This test method covers the determination of the concentration and isotopic composition of uranium and plutonium in solutions. The purified uranium or plutonium from samples ranging from nuclear materials to environmental or bioassay matrices is loaded onto a mass spectrometric filament. The isotopic ratio is determined by thermal ionization mass spectrometry, the concentration is determined by isotope dilution. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish safety and health practices and determine the applicability of regulatory limitations prior to use.

American Society for Testing and Materials. Philadelphia

2005-01-01

26

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

PubMed

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

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

2015-05-01

27

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

PubMed

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

Kawaguchi, Migaku; Eyama, Sakae; Takatsu, Akiko

2014-08-01

28

Stable isotope dilution—mass spectrometry for determining total selenium levels in plants, soils and sewage sludges  

Microsoft Academic Search

Quantitation of selenium in plants, soils and sludges was achieved by isotope dilution-mass spectrometry using a benchtop instrument. Samples for analysis were spiked with 76Se isotope solution. Plant material was digested on a heating block at 150 °C using a mixture of nitric acid and hydrogen peroxide. Selenium in soils and sludges was released by treatment with nitric acid followed

F. MacLeod; B. A. McGaw; C. A. Shand

1996-01-01

29

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

30

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

Microsoft Academic Search

The United States Department of Energy (DOE) is evaluating options for rendering its surplus inventories of highly enriched uranium (HEU) incapable of being used to produce nuclear weapons. Weapons-capable HEU was earlier produced by enriching uranium in the fissile ²³⁵U isotope from its natural occurring 0.71 percent isotopic concentration to at least 20 percent isotopic concentration. Now, by diluting its

Snider

1996-01-01

31

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

PubMed

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

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

2014-07-15

32

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

NASA Astrophysics Data System (ADS)

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

Horj, Elena; Iordache, Andreea; Culea, Monica

2011-10-01

33

Stable-isotope dilution LC–MS for quantitative biomarker analysis  

PubMed Central

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

Ciccimaro, Eugene; Blair, Ian A

2010-01-01

34

Ultralow Thermal Conductivity of Isotope-Doped Silicon Nanowires  

E-print Network

Ultralow Thermal Conductivity of Isotope-Doped Silicon Nanowires Nuo Yang, Gang Zhang,*, and Baowen that the thermal conductivity of SiNWs can be reduced exponentially by isotopic defects at room temperature. The thermal conductivity reaches the minimum, which is about 27% of that of pure 28Si NW, when doped with 50

Li, Baowen

35

A human in vivo model for the determination of lead bioavailability using stable isotope dilution.  

PubMed Central

Beverages stored in lead-crystal glass accumulate extraordinary concentrations of lead. We obtained a lead-crystal decanter manufactured with lead from Australia, where the ratio of 206Pb/207Pb is distinctly different from that in the United States. We sought to determine the bioavailability of crystal-derived lead, using the technique of stable isotope dilution in blood. We conducted a single-dose, nonrandomized cross-over study in which participants were admitted to the Clinical Research Center twice, 1 week apart. During the first admission, subjects ingested sherry obtained from the original bottle. During the second admission, they ingested sherry that had been stored in the crystal decanter and that had achieved a lead concentration of 14.2 mu mol/l. After ingesting decanter-stored sherry, mean blood lead rose significantly (p = 0.0003) from 0.10 to 0.18 mu mol/l, while mean 206Pb/207Pb fell from 1.202 to 1.137 (p = 0.0001). On average, 70% of the ingested dose of lead was absorbed. We conclude that lead derived from crystal glass is highly bioavailable; repeated ingestions could cause elevated blood lead concentration. The technique of stable isotope dilution lends itself to the study of the bioavailability of lead in other matrices, including soil. Images Figure 1. A Figure 1. B Figure 1. C Figure 2. PMID:8820585

Graziano, J H; Blum, C B; Lolacono, N J; Slavkovich, V; Manton, W I; Pond, S; Moore, M R

1996-01-01

36

Accurate determination and certification of bromine in plastic by isotope dilution inductively coupled plasma mass spectrometry.  

PubMed

The accurate analytical method of bromine (Br) in plastic was developed by an isotope dilution inductively coupled plasma mass spectrometry (ID-ICPMS). The figures of merit of microwave acid digestion procedures using polytetrafluoroethylene (PTFE) or quartz vessels were studied and the latter one was suitable for Br analysis since its material was free from Br contamination. The sample dilution procedures using Milli-Q water or ammonium (NH3) solution were also studied to remove memory effect for ICPMS measurement. Although severe memory effect was observed on Milli-Q water dilution, NH3 solution could remove it successfully. The accuracy of the ID-ICPMS was validated by a certified reference material (CRM) as well as the comparison with the analytical result obtained by an instrumental neutron activation analysis (INAA) as different analytical method. From these results, the ID-ICPMS developed in the present study could be evaluated as accurate analytical method of Br in plastic materials and it could apply to certification of Br in candidate plastic CRM with respect to such regulations related to RoHS (restriction of the use of hazardous substances in electrical and electronics equipment) directive. PMID:25000854

Ohata, Masaki; Miura, Tsutomu

2014-07-21

37

Alternative approach to post column online isotope dilution ICP-MS.  

PubMed

An alternative post column online double isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) method was developed. The resulting equation allows a straightforward calculation of the mass concentration of the analyte in the sample from the measured isotope ratio chromatogram. The use of a balance to determine and monitor the mass flow of the spike and a solution of the species under investigation as the reference are the two core components of this new method. Changes in the viscosity of the system eluent-analyte-spike will not affect the results due to the direct determination of the mass flow rate. The use of the species under investigation as the reference makes the method independent of the injected volume. To simplify matters, the integration of the isotope ratio chromatogram was done with Excel using Simpson's rule instead of sophisticated programs for transformation and integration. The advantages of the new approach were demonstrated with the help of the determination of selenomethionine in the selenized yeast reference material SELM-1 with liquid chromatography coupled to ICP-MS (HPLC ID-ICP-MS) applying the new online double IDMS method. PMID:21238750

Swart, Claudia; Rienitz, Olaf; Schiel, Detlef

2011-02-15

38

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

PubMed

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

Perkola, Noora; Sainio, Pirjo

2014-01-01

39

Determination of dithiocarbamate fungicide residues by liquid chromatography/mass spectrometry and stable isotope dilution assay.  

PubMed

A rapid and very sensitive high-performance liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) method for the simultaneous determination of dithiocarbamate (DTC) fungicide residues in fruits and vegetables was developed. The surface extraction of samples used an alkaline buffer consisting of sodium hydrogen carbonate and DL-penicillamine. The three DTC subclasses, i.e. dimethyldithiocarbamates (DMDs), ethylenebis(dithiocarbamates) (EBDs), and propylenebis(dithiocarbamates) (PBDs), were separated on a Sequant ZIC-pHILIC column using an acetonitrile/10 mM ammonia gradient. Because of the instability of DTC residues extracted from plant samples, a stable isotope dilution assay was applied. For each DTC subclass, the limits of detection and quantification were approximately 0.03 mg kg(-1) and 0.05 mg kg(-1), respectively. Recoveries from grapes, cucumbers, tomatoes, and rucola, spiked in the range of 0.01-0.9 mg kg(-1), averaged between 90 and 100%. PMID:18000839

Crnogorac, Goranka; Schwack, Wolfgang

2007-01-01

40

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

41

Low-level mercury speciation in freshwaters by isotope dilution GC-ICP-MS.  

PubMed

Atmospheric deposition of anthropogenic Hg has led to increased Hg concentrations in many ecosystems. Modeling is an effective method for predicting the complex dynamics of Hg transport in watersheds. Such models require accurate concentrations of water column methylmercury, CH3Hg+, for input parameters, yet these concentrations are very difficult to measure precisely because they are so low. We developed a method for aqueous CH3Hg+ quantification in Lake Champlain, VT, where ambient CH3Hg+ concentrations are < 0.04 ng L(-1). The analysis utilized species-specific isotope dilution, purge and trap gas chromatography inductively coupled plasma mass spectrometry and provided instrument detection limits of about 0.3 fM (0.06 pg L(-1)) and method detection limits of 15 fM (0.003 ng L(-1)) for CH3Hg+, which are among the lowest reported. Artifactual methylation of inorganic Hg(2+) was shown to be minor, and the precision of the isotope dilution method was generally <5% relative standard deviation, which is much lower than would have been the case for an external calibration approach. The method is accurate even at low concentrations of 0.025 ng L(-1). This combination of precision, accuracy, and low detection allows for quantification of significant differences in CH3Hg+ concentration between bays and over time within bays of Lake Champlain, where mean CH3Hg+ concentrations differ by only 0.006 ng L(-1) at concentrations as low as 0.014 ng L(-1). PMID:19452902

Jackson, Brian; Taylor, Vivien; Baker, R Arthur; Miller, Eric

2009-04-01

42

Low level mercury speciation in freshwaters by isotope dilution GC-ICP-MS  

PubMed Central

Atmospheric deposition of anthropogenic Hg has led to increased Hg concentrations in many ecosystems. Modeling is an effective method for predicting the complex dynamics of Hg fate and transport in watersheds; such models require accurate concentrations for water column methylmercury, CH3Hg+, as input parameters, yet these concentrations are very difficult to measure precisely as they are so low. We developed a method for aqueous CH3Hg+ quantification in Lake Champlain VT, where ambient CH3Hg+ concentrations are < 0.04 ng l-1. The analysis utilized species specific isotope dilution, purge and trap, gas chromatography ICP-MS and provided instrument detection limits of ca 0.2 fM (0.04 pg l-1) and method detection limits of 15 fM (0.003 ng l-1) for CH3Hg+ which are amongst the lowest reported. Artifactual methylation of inorganic Hg2+ was shown to be minor and the precision of the isotope dilution method was generally < 5% relative standard deviation; much lower than would have been the case for an external calibration approach. The method is accurate even at low concentrations of ca. 0.025 ng l-1. This combination of precision, accuracy and low detection allow for quantification of significant differences in CH3Hg+ concentration between bays and over time within bays of Lake Champlain where mean CH3Hg+ concentrations differ by only 0.006 ng l-1 at concentrations as low as 0.014 ng l-1. PMID:19452902

Jackson, Brian; Taylor, Vivien; Baker, R. Arthur; Miller, Eric

2009-01-01

43

Determination of acrylamide in roasted chestnuts and chestnut-based foods by isotope dilution HPLC-MS\\/MS  

Microsoft Academic Search

A collaboratively trial tested isotope dilution liquid chromatographic method with positive electrospray ionisation tandem mass spectrometry for the analysis of acrylamide in bakery ware and potato products has been extended to the determination of acrylamide in roasted chestnuts and chestnut-based foods. As chestnuts have a similar composition to potatoes, considerable amounts of acrylamide can be expected, especially in roasted chestnut

Lubomir Karasek; Thomas Wenzl; Elke Anklam

2009-01-01

44

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...

45

0M Bioavailability of Soilborne Lead in Adults, by Stable Isotope Dilution  

E-print Network

Using stable isotope dilution, we determined the bioavailability of soilborne lead (Pb) in human adult volunteers. Soil from a residential yard at a mining-impacted federal Superfund site that had negligible amounts of other priority pollutants was dried and screened through a 25- pm mesh sieve. The 1.190 were admitted to the clinical research center and fasted overnight prior to dosing with 250 pg Pb/70 kg bw (i.e., 85.5 mg soilf70 kg) in a gelatin capsule. Blood for Pb and 206Pb/207Pb ratios was obtained at 14 time Results of the isotopic analyses from these subjects indicate that on points through 30 hr. average 26.2 % ±8.1 of the administered dose was absorbed. Six additional subjects were subsequently studied but ingested soil immediately after a standardized breakfast. Bioavailability in this group was only 2.52 % ± 1.7. Collectively, this study provides the first experimental estimates of soil Pb absorption in humans, and should allow for more precise estimates of health risks due to Pb-contaminated soil. Environ Health Perspect 106(Suppl 6):1589-1594 (1998).

Mark Maddaloni; L Nancy Lolacono; L William Manton; Conrad Bium; John Drexler; Joseph Grazianol

46

Evaluation of online carbon isotope dilution mass spectrometry for the purity assessment of synthetic peptide standards.  

PubMed

We present a novel method for the purity assessment of peptide standards which is applicable to any water soluble peptide. The method is based on the online (13)C isotope dilution approach in which the peptide is separated from its related impurities by liquid chromatography (LC) and the eluent is mixed post-column with a continuous flow of (13)C-enriched sodium bicarbonate. An online oxidation step using sodium persulfate in acidic media at 99°C provides quantitative oxidation to (12)CO2 and (13)CO2 respectively which is extracted to a gaseous phase with the help of a gas permeable membrane. The measurement of the isotope ratio 44/45 in the mass spectrometer allows the construction of the mass flow chromatogram. As the only species that is finally measured in the mass spectrometer is CO2, the peptide content in the standard can be quantified, on the base of its carbon content, using a generic primary standard such as potassium hydrogen phthalate. The approach was validated by the analysis of a reference material (NIST 8327), and applied to the quantification of two commercial synthetic peptide standards. In that case, the results obtained were compared with those obtained using alternative methods, such as amino acid analysis and ICP-MS. The results obtained proved the value of the method for the fast, accurate and precise mass purity assignment of synthetic peptide standards. PMID:25172815

Cueto Díaz, Sergio; Ruiz Encinar, Jorge; García Alonso, J Ignacio

2014-09-24

47

Quantification of growth hormone in serum by isotope dilution mass spectrometry.  

PubMed

Interassay variation of antibody-based routine tests hampers comparability of measurement results for growth hormone (GH) between different laboratories and decision making in clinical practice. Here it is demonstrated that quantification of GH by isotope dilution mass spectrometry (IDMS) constitutes a way to obtain precise and reliable results that can be referred to in evaluation of performance of commercial test kits. With the IDMS method developed, tryptic cleavage products YSFLQNPQTSLCFSESIPTPSNR (T6) and LEDGSPR (T12) of GH are quantified by liquid chromatography tandem mass spectrometry (LC-MS/MS) using isotopically labeled forms of the peptides as internal standards. The GH cleavage fragments are obtained by whole serum tryptic proteolysis and then extracted from the resulting mixture by semipreparative reversed-phase LC followed by strong cation exchange chromatography. Analysis of blank serum spiked with recombinant 22-kDa GH at different concentration levels would result in a mean recovery of 101.6%, a standard deviation (SD) of 2.5%, a combined uncertainty (u(c)) of 3.0%, and a limit of quantification (LOQ) of 1.7 microg/L when quantifying T6 as a GH-derived fragment, whereas recovery=100.7%, SD=2.4%, u(c)=2.5%, and LOQ=2.7 microg/L were found with T12. The potential to acquisition of reference values is exemplified by application to serum materials used in a recent quality assessment exercise for routine laboratories. PMID:20226156

Arsene, Cristian G; Henrion, André; Diekmann, Nina; Manolopoulou, Jenny; Bidlingmaier, Martin

2010-06-15

48

[Determination of endogenous agmatine in rat plasma by isotope dilution-gas chromatography-mass spectrometry].  

PubMed

A method for the determination of endogenous agmatine in rat plasma was developed by isotope dilution-gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The plasma samples were analyzed after protein precipitation, evaporation, derivatization by hexafluoroacetone (HFAA), and clean-up on a Florisil SPE column. The GC-MS analysis utilized stable isotope d8-agmatine as internal standard. The samples after treatme were tested by negative chemical ionization with selected ion monitoring (SIM) which was set at m/z 492 (molecular ion of agmatine) and m/z 500 (molecular ion of internal standard). The limit of detection (LOD) of agmatine standard solution was 0.005 7 ng/mL. The calibration curve of the agmatine spiked in rat plasma showed a good linear relationship at the range of 1.14-57.0 ng/mL (r = 0.997). The recoveries of agmatine spiked in rat plasma ranged from 92.3% to 109.8%. Inter-day and intra-day precisions were less than 15%. The average concentration level of agmatine in rat plasma was (22 +/- 9) ng/mL, and there was no significant difference between male and female SD rats (p > 0.05). The method is high sensitive and specific, and can be used for the determination of endogenous agmatine in plasma. It provides a strong support for the subsequent research of agmatine. PMID:25255573

Qiu, Zhongli; Lin, Ying; Xiong, Zhili; Xie, Jianwei

2014-07-01

49

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

50

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

51

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

PubMed

Cyanamide is a multifunctional agrochemical used, for example, as a pesticide, herbicide, and fertilizer. Recent research has revealed that cyanamide is a natural product biosynthesized in a leguminous plant, hairy vetch (Vicia villosa). In the present study, gas chromatography-mass spectrometry (GC-MS) equipped with a capillary column for amines was used for direct quantitative determination of cyanamide. Quantitative signals for ((14)N(2))cyanamide, ((15)N(2))cyanamide (internal standard for stable isotope dilution method), and m-(trifluoromethyl)benzonitrile (internal standard for correcting errors in GC-MS analysis) were recorded as peak areas on mass chromatograms at m/z 42 (A(42)), 44 (A(44)), and 171 (A(IS)), respectively. Total cyanamide content, ((14)N(2))cyanamide plus ((15)N(2))cyanamide, was determined as a function of (A(42)+A(44))/A(IS). Contents of ((14)N(2))cyanamide and ((15)N(2))cyanamide were then calculated by multiplying the total cyanamide content by A(42)/(A(42)+A(44)) and A(44)/(A(42)+A(44)), respectively. The limit of detection for the total cyanamide content by the GC-MS analysis was around 1ng. The molar ratio of ((14)N(2))cyanamide to ((15)N(2))cyanamide in the injected sample was equal to the observed A(42)/A(44) value in the range from 0.1 to 5. It was, therefore, possible to use the stable isotope dilution method to quantify the natural cyanamide content in samples; i.e., the natural cyanamide content was derived by subtracting the A(42)/A(44) ratio of the internal standard from the A(42)/A(44) ratio of sample spiked with internal standard, and then multiplying the resulting difference by the amount of added ((15)N(2))cyanamide (SID-GC-MS method). This method successfully gave a reasonable value for the natural cyanamide content in hairy vetch, concurring with the value obtained by a conventional method in which cyanamide was derivatized to a photometrically active compound 4-cyanimido-1,2-naphthoquinone and analyzed with reversed-phase HPLC (CNQ-HPLC method). The determination range of cyanamide in the SID-GC-MS method was almost the same as that in the CNQ-HPLC method; however, the SID-GC-MS method was much simpler than the CNQ-HPLC method. PMID:16314170

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

2005-12-01

52

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

53

User's manual for the ARMLID (Argonne metallic lithium/isotopic dilution) tritium assay system  

SciTech Connect

The Argonne Metallic Lithium - Isotopic Dilution (ARMLID) system described in this report, originally developed at ANL for other purposes, was recently redeployed to measure the tritium production rate (TPR) in a series of US/Japanese collaborative fusion blanket integral experiments, involving large assemblies of fusion breeder blanket materials that were irradiated with a fusion neutron source at FNS/JAERI, Japan. Whereas previous uses of the ARMUD scheme involved just a few samples, its application infusion blanket TPR mapping called for large sample numbers per experiment, implying a commensurate scale of sample fabrication and encapsulation, on one hand, and tritium extraction and counting on the other hand. To shorten the time required for these various tasks, yet still yield reliable and accurate results, both the sample fabrication - encapsulation facility and the tritium extraction system had to be extensively revised from original versions that were designed for accuracy, but not necessarily for speed. The present report describes overall revisions in sufficient detail to serve as a User's Manual for this facility, and/or suggest how a new system might be put together. Either possibility may develop in the near future, in support of ITER design studies. Preliminary and partial descriptions of various aspects and features of the system were presented orally, in the course of annual ANL/JAERI/UCLA workshops'', over the last 34 years, as well as elsewhere.

Porges, K.G.; Bretscher, M.M.; Bennett, E.F.; DiIorio, G.; Mattas, R.F.; Lewandowski, E.F.

1992-08-01

54

User`s manual for the ARMLID (Argonne metallic lithium/isotopic dilution) tritium assay system  

SciTech Connect

The Argonne Metallic Lithium - Isotopic Dilution (ARMLID) system described in this report, originally developed at ANL for other purposes, was recently redeployed to measure the tritium production rate (TPR) in a series of US/Japanese collaborative fusion blanket integral experiments, involving large assemblies of fusion breeder blanket materials that were irradiated with a fusion neutron source at FNS/JAERI, Japan. Whereas previous uses of the ARMUD scheme involved just a few samples, its application infusion blanket TPR mapping called for large sample numbers per experiment, implying a commensurate scale of sample fabrication and encapsulation, on one hand, and tritium extraction and counting on the other hand. To shorten the time required for these various tasks, yet still yield reliable and accurate results, both the sample fabrication - encapsulation facility and the tritium extraction system had to be extensively revised from original versions that were designed for accuracy, but not necessarily for speed. The present report describes overall revisions in sufficient detail to serve as a User`s Manual for this facility, and/or suggest how a new system might be put together. Either possibility may develop in the near future, in support of ITER design studies. Preliminary and partial descriptions of various aspects and features of the system were presented orally, in the course of annual ANL/JAERI/UCLA ``workshops``, over the last 34 years, as well as elsewhere.

Porges, K.G.; Bretscher, M.M.; Bennett, E.F.; DiIorio, G.; Mattas, R.F.; Lewandowski, E.F.

1992-08-01

55

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

56

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

PubMed

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

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

2013-12-15

57

Microwave-assisted deuterium exchange: the convenient preparation of isotopically labelled analogues for stable isotope dilution analysis of volatile wine phenols.  

PubMed

This study reports the convenient, low cost, one-step synthesis of labelled analogues of six volatile phenols, guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol and vanillin, using microwave-assisted deuterium exchange, for use as internal standards for stable isotope dilution analysis. The current method improves on previous strategies in that it enables incorporation of deuterium atoms on the aromatic ring, thereby ensuring retention of the isotope label during mass spectrometry fragmentation. When used as standards for SIDA, these labelled volatile phenols will improve the accuracy and reproducibility of quantitative food and beverage analysis. PMID:24874385

Crump, Anna M; Sefton, Mark A; Wilkinson, Kerry L

2014-11-01

58

Quantifying gross fluxes of nitrous oxide and dinitrogen gas using a novel isotope pool dilution technique  

NASA Astrophysics Data System (ADS)

One of the existing challenges in trace gas biogeochemistry lies in understanding the environmental controls on the net and gross fluxes of soil-derived compounds. This is because gross production and consumption fluxes of these gases often occur simultaneously or in close spatial proximity, making it difficult to make inferences about the effects of environmental variables (e.g. temperature, soil water content, porosity, redox, etc.) on gross fluxes based on bulk concentration measurements alone. One novel approach for quantifying gross fluxes of N2O and N2 is 'stable isotope pool dilution;' a technique that has been successfully applied to study bidirectional fluxes of other biogenic compounds, such as CH4 and halocarbons. To evaluate the efficacy of this method for quantifying gross N2O and N2 fluxes, we conducted a combined field and laboratory test of the pool dilution technique along side conventional measures of nitrification and denitrification. Experiments were conducted in a N-rich managed peatland pasture in the Sacramento-San Joaquin Delta, California, USA. Field and laboratory measurements were performed in a broad range of microforms and microtopes spanning a range of hydrologic and environmental conditions. Field experiments focussed on gross fluxes of N2O and N2 in upper soil horizons; the soil layers that exchange most rapidly with the atmosphere. Laboratory experiments indicated that 15N pool dilution compares favourably with more conventional measures of N2O and N2 flux, such as acetylene inhibition or the 15NO3- pulse-trace approach. Gross N2O fluxes greatly exceeded N2 fluxes by as much as an order of magnitude or more, and averaged 6.1 ± 2.2 mg N m-2 d-1, with a range from 0.06 to 63.13 mg N m-2 d-1. N2O:N2 emissions ratios generally exceeded 1 except along slopes, with an overall range of 0.2 to 30.9. NH4+ concentrations and denitrifying enzyme activity were the best predictors of gross N2O fluxes in the field (r2 = 0.65). Net N2O production rates explained 53 percent of the variability in gross N2 fluxes, whereas N2O:N2 ratios were best predicted by the combination of water-filled pore space and mineral N concentration (r2 = 0.44). This research highlights the potential of the pool dilution approach for quantifying gross fluxes of N2O and N2 from surface soils under both field and laboratory conditions. Future experiments will couple these measures of soil surface fluxes with push-pull methods for determining gross N2O and N2 fluxes at depth, and natural abundance isotopomer measurements to determine sources of N2O.

Arn Teh, Yit; Yang, Wendy; Silver, Whendee L.

2010-05-01

59

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

USGS Publications Warehouse

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

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

1982-01-01

60

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

61

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

PubMed

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

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

2013-07-21

62

Isotopic effects on the thermal conductivity of graphene nanoribbons: Localization mechanism  

E-print Network

Isotopic effects on the thermal conductivity of graphene nanoribbons: Localization mechanism Jin; accepted 30 January 2010; published online 8 March 2010 Thermal conductivity of graphene nanoribbons GNR correction. Two interesting phenomena are found, 1 isotopic doping reduces thermal conductivity effectively

Li, Baowen

63

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

64

Stable isotope dilution analysis of wine fermentation products by HS-SPME-GC-MS.  

PubMed

The aim of this study was to quantify, in a single analysis, 31 volatile fermentation-derived products that contribute to the aroma of red and white wine. We developed a multi-component method based on headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS). The 31 volatile compounds analysed include ethyl esters, acetates, acids and alcohols. Although these compounds have a range of functional groups, chemical properties, volatilities, affinities for the SPME fibre, and are found in wine at various concentrations, the accuracy of the analysis was achieved with the use of polydeuterated internal standards for stable isotope dilution analyses (SIDA). Nine of the labelled standards were commercially available, while 22 were synthesised. The method was validated by a series of duplicate spiked standard additions to model, white and red wine matrices over the concentration range relevant for each compound in wine. This demonstrated that the appropriate use of SIDA helped to account for matrix effects, for instance potential sources of variation such as the relative response to the MS detector, ionic strength, ethanol content and pH of different wine matrices. The resultant calibration functions had correlation coefficients (R(2)) ranging from 0.995 to 1.000. Each compound could be quantified at levels below its aroma threshold in wine. Relative standard deviations were all <5%. The method was optimised for the best compromise (over the 31 compounds) of wine dilution factor, level of sodium chloride addition, SPME fibre, SPME temperature, SPME time, GC column and MS conditions. Confirmation of identity was achieved by retention time and peak shape, and measurement of at least three ions for each analyte and internal standard with the MS operating in selected ion monitoring mode to facilitate more precise quantitation with a high sampling rate. The method is a valuable research tool with many relevant applications. A novel method for the combined chiral separation and SIDA quantification of 2- and 3-methylbutanoic acid is also demonstrated. PMID:15660221

Siebert, Tracey E; Smyth, Heather E; Capone, Dimitra L; Neuwöhner, Corinna; Pardon, Kevin H; Skouroumounis, George K; Herderich, Markus J; Sefton, Mark A; Pollnitz, Alan P

2005-02-01

65

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

PubMed

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

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

2014-07-01

66

Thermal conductivity of dilute 3He4He mixtures near the superfluid transition  

Microsoft Academic Search

Thermal conductivity measurements of 4He and very dilute mixtures of 3He in 4He (7 × 10-4 < X3 < 1 × 10-2) at saturated vapor pressures near the superfluid transition Tlambda(X) are reported. The results for the mixtures in the normal phase are compared with recent predictions by Dohm, Folk and Bhattacharjee, and Onuki. In the superfluid phase the data

D. Gestrich; M. Dingus; H. Meyer

1983-01-01

67

Thermal conductivity of dilute 3He? 4He mixtures near the superfluid transition  

NASA Astrophysics Data System (ADS)

Thermal conductivity measurements of 4He and very dilute mixtures of 3He in 4He (7 × 10 -4 < X3 < 1 × 10 -2) at saturated vapor pressures near the superfluid transition T?( X) are reported. The results for the mixtures in the normal phase are compared with recent predictions by Dohm, Folk and Bhattacharjee, and Onuki. In the superfluid phase the data extrapolated to T?( X) are compared with previous experiments and with predictions.

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

1983-12-01

68

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

Microsoft Academic Search

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

Heather N. Layton; Kirsti I. Rouvinen-Watt; Sara J. Iverson

2000-01-01

69

Hydrogen bonding at the water surface revealed by isotopic dilution spectroscopy  

NASA Astrophysics Data System (ADS)

The air-water interface is perhaps the most common liquid interface. It covers more than 70 per cent of the Earth's surface and strongly affects atmospheric, aerosol and environmental chemistry. The air-water interface has also attracted much interest as a model system that allows rigorous tests of theory, with one fundamental question being just how thin it is. Theoretical studies have suggested a surprisingly short `healing length' of about 3ångströms (1Å = 0.1nm), with the bulk-phase properties of water recovered within the top few monolayers. However, direct experimental evidence has been elusive owing to the difficulty of depth-profiling the liquid surface on the ångström scale. Most physical, chemical and biological properties of water, such as viscosity, solvation, wetting and the hydrophobic effect, are determined by its hydrogen-bond network. This can be probed by observing the lineshape of the OH-stretch mode, the frequency shift of which is related to the hydrogen-bond strength. Here we report a combined experimental and theoretical study of the air-water interface using surface-selective heterodyne-detected vibrational sum frequency spectroscopy to focus on the `free OD' transition found only in the topmost water layer. By using deuterated water and isotopic dilution to reveal the vibrational coupling mechanism, we find that the free OD stretch is affected only by intramolecular coupling to the stretching of the other OD group on the same molecule. The other OD stretch frequency indicates the strength of one of the first hydrogen bonds encountered at the surface; this is the donor hydrogen bond of the water molecule straddling the interface, which we find to be only slightly weaker than bulk-phase water hydrogen bonds. We infer from this observation a remarkably fast onset of bulk-phase behaviour on crossing from the air into the water phase.

Stiopkin, Igor V.; Weeraman, Champika; Pieniazek, Piotr A.; Shalhout, Fadel Y.; Skinner, James L.; Benderskii, Alexander V.

2011-06-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

71

Stable deuterium internal standard for the isotope-dilution LC-MS/MS analysis of elastin degradation.  

PubMed

Chemical synthesis of the deuterium isotope desmosine-d4 has been achieved. This isotopic compound possesses all four deuterium atoms at the alkanyl carbons of the alkyl amino acid substitution in the desmosine molecule and is stable toward acid hydrolysis; this is required in the measurement of two crosslinking molecules, desmosine and isodesmosine, as biomarkers of elastic tissue degradation. The degradation of elastin occurs in several widely prevalent diseases. The synthesized desmosine-d? is used as the internal standard to develop an accurate and sensitive isotope-dilution liquid chromatography-tandem mass spectrometry analysis, which can serve as a generalized method for an accurate analysis of desmosine and isodesmosine as biomarkers in many types of biological tissues involving elastin degradation. PMID:23727558

Ma, Shuren; Turino, Gerard M; Hayashi, Takahiro; Yanuma, Hiroto; Usuki, Toyonobu; Lin, Yong Y

2013-09-15

72

Volatile organic compounds in whole blood - determination by heated dynamic headspace purge and trap isotope-dilution GC/MS. Special report, November 1984-August 1987  

SciTech Connect

The method described was developed for the determination of a selected list of 30 organic compounds in whole human blood. The method is a heated dynamic head-space purge and trap gas chromatographic method using mass spectrometry in the limited mass-scan mode. A whole blood sample is diluted with organic free water and the mixture fortified with isotopically labeled compounds. The mixture is subsequently heated to 50/sup 0/C while stirred, and the volatile components are purged from the mixture and collected on an adsorbent trap. The volatile compounds are thermally desorbed from the trap onto a wide-bore fused-silica capillary column. Detection of the compounds is accomplished using mass spectrometry in the limited mass-scan mode where only selected ions are scanned. Quantitation of the analytes is accomplished by using the specific ion responses from standards of the analytes and their corresponding labeled analogs or internal standards.

Cramer, P.H.; Boggess, K.E.; Hosenfeld, J.M.

1987-07-01

73

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

PubMed

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

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

2011-12-15

74

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

75

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

76

Detection of Human Urinary 5-Hydroxymethylcytosine by Stable Isotope Dilution HPLC-MS/MS Analysis.  

PubMed

The sixth DNA base 5-hydroxymethylcytosine (5hmC) is the major oxidation product of the epigenetic modification 5-methylcytosine (5mC), mediating DNA demethylation in mammals. Reduced 5hmC levels are found to be linked with various tumors and neurological diseases; therefore, 5hmC is an emerging biomarker for disease diagnosis, treatment, and prognosis. Due to its advantages of being sterile, easily accessible in large volumes, and noninvasive to patients, urine is a favored diagnostic biofluid for 5hmC analysis. Here we developed an accurate, sensitive, and specific assay for quantification of 5mC, 5hmC, and other DNA demethylation intermediates in human urine. The urinary samples were desalted and enriched using off-line solid-phase extraction, followed by stable isotope dilution HPLC-MS/MS analysis for 5hmC and 5mC. By the use of ammonium bicarbonate (NH4HCO3) as an additive to the mobile phase, we improved the online-coupled MS/MS detection of 5mC, 5hmC, and 5-formylcytosine (5fC) by 1.8-14.3 times. The recovery of the method is approximately 100% for 5hmC, and 70-90% for 5mC. The relative standard deviation (RSD) of the interday precision is about 2.9-10.6%, and that of the intraday precision is about 1.4-7.7%. By the analysis of 13 volunteers using the developed method, we for the first time demonstrate the presence of 5hmC in human urine. Unexpectedly, we observed that the level of 5hmC (22.6 ± 13.7 nmol/L) is comparable to that of its precursor 5mC (52.4 ± 50.2 nmol/L) in human urine. Since the abundance of 5hmC (as a rare DNA base) is 1 or 2 orders of magnitude lower than 5mC in genomic DNA, our finding probably implicates a much higher turnover of 5hmC than 5mC in mammalian genomic DNA and underscores the importance of DNA demethylation in daily life. PMID:25551771

Yin, Ruichuan; Mo, Jiezhen; Lu, Meiling; Wang, Hailin

2015-02-01

77

Biosynthesis of 15N3-labeled enniatins and beauvericin and their application to stable isotope dilution assays.  

PubMed

The first stable isotope dilution assay for the determination of enniatins A, A1, B, and B1 and beauvericin was developed. The (15)N(3)-labeled enniatins and beauvericin were biosynthesized by feeding two Fusarium strains Na(15)NO(3) and subsequently isolated from the fungal culture. The chemical structures of the biosynthesized products were characterized by LC-MS/MS and (1)H NMR. Standard solutions of (15)N(3)-labeled beauvericin, enniatin A, and enniatin A1 were accurately quantitated by quantitative NMR. On the basis of the use of the labeled products as internal standards, stable isotope dilution assays were developed and applied to various food samples using LC-MS/MS. The sample extracts were directly injected without any tedious cleanup procedures. The limits of detection were 3.9, 2.6, 3.7, 1.9, and 4.4 ?g/kg for enniatins A, A1, B, and B1 and beauvericin, respectively. Limits of quantitation were 11.5 (enniatin A), 7.6 (enniatin A1), 10.9 (enniatin B), 5.8 (enniatin B1), and 13.1 ?g/kg (beauvericin). Recoveries were within the range between 90 and 120%, and good intraday and interday precisions with coefficients of variation between 1.35 and 8.61% were obtained. Thus, the stable isotope dilution assay presented here is similarly sensitive and precise but more accurate than assays reported before. Analyses of cereals and cereal products revealed frequent contaminations of barley, wheat, rye, and oats with enniatins B and B1, whereas beauvericin was not quantifiable. PMID:22734473

Hu, Ling; Rychlik, Michael

2012-07-25

78

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

USGS Publications Warehouse

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

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

1973-01-01

79

Quantitative determination of 4-ethylphenol and 4-ethyl-2-methoxyphenol in wines by a stable isotope dilution assay  

Microsoft Academic Search

The deuterium-labelled standards 4-ethylphenol-d3 and 4-ethyl-2-methoxyphenol-d3 were synthesized and utilized in a rapid, sensitive, and accurate stable isotope dilution assay for 4-ethylphenol and 4-ethyl-2-methoxyphenol in wine. For a 5-mL sample of a Merlot wine, quantitation was reliable down to 500ng\\/L for 4-ethylphenol and 100ng\\/L for 4-ethyl-2-methoxyphenol at estimated signal-to-noise ratio of 3:1, respectively. The concentrations of 4-ethylphenol and 4-ethyl-2-methoxyphenol were

Sierra Rayne; Nigel J. Eggers

2007-01-01

80

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

E-print Network

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

Bindeman, Ilya N.

81

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

82

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

SciTech Connect

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

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

1990-03-22

83

Thermal conductivity for a bidimensional dilute gas within the Chapman-Enskog approximation  

E-print Network

In this work we explicitly calculate the thermal conductivity for a bidimensional dilute gas of neutral molecules by solving Boltzmann's equation. Chapman-Enskog's method is used in order to analytically obtain the transport coefficient to first approximation. The result is expressed in terms of a collision integral for a unspecified molecular interaction model. The particular case of a hard disks model is addressed yielding a T 1/2 dependence with the temperature which is consistent with the one obtained by J. V. Sengers [1] and widely used in the literature as the low density limit in the Enskog expansion. The corresponding value for bidimensional Maxwellian molecules is also obtained.

Mendez, A R; Escobar, Eric

2015-01-01

84

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

85

Analysis of methoxypyrazines in wine using headspace solid phase microextraction with isotope dilution and comprehensive two-dimensional gas chromatography.  

PubMed

This study reports an optimized headspace-solid phase microextraction (HS-SPME) method for the determination of methoxypyrazines in wine. Analysis was performed by using comprehensive two-dimensional gas chromatography with novel detection capabilities, including nitrogen phosphorus detection (GC x GC-NPD) and time-of-flight mass spectrometry (GC x GC-TOFMS). In the latter, stable isotope dilution was performed for the quantitation of 2-methoxy-3-(2-methylpropyl) pyrazine (IBMP), using labelled 2-(2H3)methoxy-3-(2-methylpropyl)pyrazine (d3-IBMP) as the internal standard, and resolution of the two analogues was facilitated using the deconvolution capabilities of the TOFMS. This research represents the first report of HS-SPME with isotope dilution and GC x GC-TOFMS (GC x GC-IDTOFMS). Analysis by GC x GC-NPD enabled detection limits of 0.5 ng/L for the quantitation of IBMP, which was superior to that obtained using GC x GC-IDTOFMS (1.95 ng/L). Nevertheless, both methods were adequately sensitive for real wine analysis, yielding highly comparable IBMP concentrations of 26.1 and 27.8 ng/L, respectively, from a Sauvignon blanc wine. The complexity of the real wine headspace was simplified as a result of selective detection using GC x GC-NPD and, in the case of GC x GC-IDTOFMS, the use of extracted ion chromatograms (EICs). PMID:16013834

Ryan, Danielle; Watkins, Peter; Smith, Jason; Allen, Malcolm; Marriott, Philip

2005-06-01

86

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

PubMed

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

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

2012-03-16

87

Quantitation of odor-active compounds in rye flour and rye sourdough using stable isotope dilution assays.  

PubMed

Application of the aroma extract dilution analysis on a flavor distillate prepared from freshly ground rye flour (type 1150) revealed 1-octen-3-one (mushroom-like), methional (cooked potato), and (E)-2-nonenal (fatty, green) with the highest flavor dilution (FD) factors among the 26 odor-active volatiles identified. Quantitative measurements performed by stable isotope dilution assays and a comparison to the odor thresholds of selected odorants in starch suggested methional, (E)-2-nonenal, and hexanal as contributors to the flour aroma, because their concentrations exceeded their odor thresholds by factors >100. Application of the same approach on a rye sourdough prepared from the same batch of flour revealed 3-methylbutanal, vanillin, 3-methylbutanoic acid, methional, (E,E)-2,4-decadienal, 2,3-butanedione, and acetic acid as important odorants; their concentrations exceeded their odor thresholds in water and starch by factors >100. A comparison of the concentrations of 20 odorants in rye flour and the sourdough made therefrom indicated that flour, besides the fermentation process, is an important source of aroma compounds in dough. However, 3-methylbutanol, acetic acid, and 2,3-butanedione were much increased during fermentation, whereas (E,E)-2,4-decadienal and 2-methylbutanal were decreased. Similar results were obtained for five different flours and sourdoughs, respectively, although the amounts of some odorants in the flour and the sourdough differed significantly within batches. PMID:12207478

Kirchhoff, Eva; Schieberle, Peter

2002-09-11

88

Isotope fractionation by thermal diffusion in silicate melts.  

PubMed

Isotopes fractionate in thermal gradients, but there is little quantitative understanding of this effect in complex fluids. Here we present results of experiments and molecular dynamics simulations on silicate melts. We show that isotope fractionation arises from classical mechanical effects, and that a scaling relation based on Chapman-Enskog theory predicts the behavior seen in complex fluids without arbitrary fitting parameters. The scaling analysis reveals that network forming elements (Si and O) fractionate significantly less than network modifiers (e.g., Mg, Ca, Fe, Sr, Hf, and U). PMID:22401089

Lacks, Daniel J; Goel, Gaurav; Bopp, Charles J; Van Orman, James A; Lesher, Charles E; Lundstrom, Craig C

2012-02-10

89

Simultaneous isotopic analysis of uranium and plutonium by thermal ionisation mass spectrometry coupled to a variable multicollection detection system  

NASA Astrophysics Data System (ADS)

Simultaneous isotopic analysis of uranium and plutonium employing a thermal ionisation mass spectrometer coupled to a variable multicollection Faraday cup detector system is reported. Factors such as the U/Pu ratio in the sample, filament currents during sample de-gassing and data acquisition have been investigated to arrive at optimum conditions for analysis. A simple correction to the observed 235/238 peak ratio is necessary to account for the 238Pu isotope's contribution to 238U. The precision and accuracy achievable in the measurement of isotopic ratios is better than 0.2%. An attempt was also made to show that uranium and plutonium vaporise predominantly through their oxides and not through direct metal evaporation when the samples are loaded from dilute nitric acid medium. This might explain the earlier appearance of U+ ions in preference to Pu+ ions in the mass spectra of all the U/Pu mixtures investigated.

Ramakumar, K. L.; Rao, R. M.; Gnanayyan, L.; Jain, H. C.

1994-06-01

90

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

PubMed

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

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

2012-09-01

91

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

PubMed

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

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

2012-01-01

92

Mass Independent Fractionation of Cadmium Isotopes During Thermal Ionization  

NASA Astrophysics Data System (ADS)

We have previously reported that Cd isotopes exhibit anomalous, non-mass dependent fractionation of odd versus even isotopes when measured by TIMS using silica gel-phosphoric acid activator. The deviation from mass dependent fractionation (MDF) on the odd masses 111 and 113 varies by fractions of a per-cent between runs. The effects cannot be explained by isobaric interferences, but seem, instead, to reflect mass independent fractionation (MIF) of Cd isotopes, much like that recently documented for Hg isotopes in natural systems (Bergquist and Blum, 2007). The absence of comparable Cd isotope anomalies in the ICP torch, and during extreme in-vacuo volatilization of Cd metal (Wombacher et al., 2004) conclusively implicates the silica gel activator in the process. So far, MIF has been documented for Cd, Zn and Pb isotopes when measured using the silica gel technique (Thirlwall, 2000; Schmitt et al., 2006; Manhes and Göpel, 2007). These MIF effects on Cd isotopes might perhaps be related to the non-mass dependence of nuclear volume with mass number, as described by Bigeleisen (1996) - also known as the "nuclear field shift". The MIF caused by the nuclear field shift results is a departure from MDF broadly characterized by a odd-even staggering with mass number. These effects have been quantified by Schauble (2007) who showed that the magnitude of the non-mass dependence for Hg and Tl isotopes lies in the ppm range for some simple reactions. Such MIF effects would appear, overall, far too small to account for our data, which require MIF offsets on the odd masses 111 and 113 approaching a per-cent. Moreover, an in-depth examination along the lines of Fujii et al. (2006) predicts tell-tale offsets for the even-even isotope pairs 114Cd/112Cd and 116Cd/112Cd as well, based upon the theory and the respective nuclear radii, but such accompanying offsets are unequivocally absent in our data. The odd-even isotope effects seen in our runs using silica gel activator are better explained by appealing to the nuclear spin (and magnetic moment) of odd nuclei alone. The "magnetic isotope effect" is a consequence of hyperfine coupling, in which an electron interacts with a nucleus of non-zero magnetic moment - i.e. one that has an odd number of nucleons (Turro, 1983; Buchachenko, 1995, 2001). This is purely a kinetic phenomenon in which the life-time, and thus the outcome, of reaction transition states is altered by the hyperfine splitting present in atoms with odd nuclei. The mechanism by which silica gel activator enhances the thermal ionization of elements such as Cd, Pb and Zn has been outlined by Kessinger and Delmore (2002). The first step involves the in-situ reduction of Cd2+ ions to Cd metal in the molten silica gel-phosphoric acid glass. It is most likely in this step - whereby two electrons are added - that a suitably long-lived transition state exists, during which the magnetic isotope effect enhances (or inhibits) reduction of masses 111 and 113 to metal species compared to those of even isotopes of Cd. The resulting "odd" and "even" populations of Cd-metal in the molten silica gel then cannot be related simply in terms of MDF. Overall, the magnetic isotope effect provides the best explanation of the MIF effects observed for Pb, Cd and Zn during thermal ionization with silica gel activator, and, probably, why the measured fractionation is always biased towards light isotopes.

Abouchami, W.; Galer, S. J.; Feldmann, H.; Schmitt, A. D.

2008-12-01

93

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

94

Characterization of neutron transmuted zinc traces in pure copper materials by isotope dilution mass spectrometry  

Microsoft Academic Search

The neutron transmutation doping (NTD) of highly pure copper with zinc was investigated as a promising means of achieving\\u000a controlled gradation of the zinc content in the range 1–20 ?g g–1. The doping process leads to the enrichment of two stable isotopes 64Zn and 66Zn in a ratio which differs from that of natural isotopic distribution. Mass spectrometric investigations by

G. Wermann; D. Alber; W. Pritzkow; G. Riebe; W. Görner

2001-01-01

95

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

PubMed

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

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

2001-08-01

96

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

NASA Astrophysics Data System (ADS)

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

Dwyer, G. S.; Vengosh, A.

2008-12-01

97

Systematic studies on the determination of Hg-labelled proteins using laser ablation-ICPMS and isotope dilution analysis.  

PubMed

A method was developed for the precise and accurate determination of ovalbumin labelled with p-hydroxy-mercuribenzoic acid (pHMB) using polyacrylamide gel electrophoresis with ns-laser ablation-inductively coupled plasma mass spectrometry. Following systematic optimisation of the ablation process in terms of detection sensitivity, two different quantification strategies were applied: external calibration using standards of the derivatized protein after (13)C(+) normalization and, as a proof of concept, label-specific isotope dilution analysis (IDA) using pHMB enriched in the isotope (199)Hg. Due to the inhomogeneous distribution of the protein within the gel bands, it could be demonstrated that the IDA approach was superior in terms of precision and accuracy. Furthermore, it permits a reliable quantification, if more complex separation protocols are applied, as typically occurring analyte loss and degradation can be compensated for as soon as complete mixture of spike and sample is achieved. The estimated limit of detection was 160 fmol in the case of ovalbumin. In contrast to earlier studies using metals naturally present in proteins, no loss of mercury was observed during separation under denaturing conditions and other sample preparation steps. Using label-specific IDA, the measured isotope ratios in the gel corresponded to recoveries between 95% and 103%. PMID:21773737

Kutscher, Daniel J; Fricker, Mattias B; Hattendorf, Bodo; Bettmer, Jörg; Günther, Detlef

2011-11-01

98

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

99

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

2013-02-01

100

Measurement of Pyrethroid, Organophosphorus, and Carbamate Insecticides in Human Plasma using Isotope Dilution Gas Chromatography-High Resolution Mass Spectrometry  

PubMed Central

We have developed a gas chromatography-high resolution mass spectrometry method for measuring pyrethroid, organophosphorus, carbamate and fipronil pesticides and the synergist piperonyl butoxide in human plasma. Plasma samples were extracted using solid phase extraction and were then concentrated for injection and analysis using isotope dilution gas chromatography-high resolution mass spectrometry. The limits of detection ranged from 10 to 158 pg/mL with relative recoveries at concentrations near the LODs (e.g., 25 or 250 pg/mL) ranging from 87% to 156% (9 of the 16 compounds were withing ± 15% of 100%). The extraction recoveries ranged from 20% to 98% and the overall method relative standard deviations were typically less than 20% with some exceptions. Analytical characteristics were determined at 25, 250, and 1000 pg/mL. PMID:20434413

Pérez, José J.; Williams, Megan K.; Weerasekera, Gayanga; Smith, Kimberly; Whyatt, Robin M.; Needham, Larry L.; Barr, Dana Boyd

2010-01-01

101

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

102

Determination of Mercury in Coal by Isotope Dilution Cold-Vapor Generation Inductively  

E-print Network

the endocrine system.1 Although mercury enters the aquatic environment from a number of domestic sources- system digestion process employing a Carius tube is used to completely oxidize the coal matrix(II) chloride. Measurements of 201Hg/202Hg isotope ratios are made using a quadru- pole ICPMS system in time

103

COMPARISON OF ISOTOPE DILUTION WITH BIOIMPEDNACE SPECTROSCOPY AND ANTHROPOMETRY FOR ASSESSMENT OF BODY COMPOSITION IN ASYMPTOMAIC HIV-UNINFECTED BREASTFEEDING MOTHERS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The effect of breastfeeding on the nutrition of HIV-infected (HIV+) mothers is unknown. Simple, valid methods are needed for body composition assessment of HIV+ women. We compared the ability of bioimpedance spectroscopy (BIS) and anthropometry with that of isotope dilution (2H20) to measure fat-...

104

Thermal conductivity reduction in Si-isotope-multilayers  

NASA Astrophysics Data System (ADS)

We employ the atomistic Green?s function (AGF) formalism to investigate phonon transport in silicon isotope multilayers. Since we use the AGF method, we can distinguish between coherent scattering at isotope multilayers and incoherent phonon–phonon scattering. Our investigations show that there are two different regimes for coherent scattering at isotope multilayers: the periodic regime, with periodically arranged layers, and a random regime, with layers of different thicknesses. The phonon scattering is stronger in the random regime, whereas in the periodic regime the phonon scattering rapidly saturates with the number of layers. Even though the phonon scattering in the random regime is stronger than in the periodic regime, the resulting thermal resistance in both regimes is much lower than the one obtained by combining the interfaces of the multilayer incoherently. We also found that the periodic regime is sensitive to small deviations. A small deviation from the perfect periodic arrangement leads to the behavior of the random regime. These deviations are so small that it is extremely difficult to actually grow perfect periodic isotope multilayers and observe the periodic regime experimentally.

Bachmann, M.; Czerner, M.; Heiliger, C.

2014-12-01

105

An isotope dilution model for partitioning phenylalanine and tyrosine uptake by the mammary gland of lactating dairy cows.  

PubMed

An isotope dilution model for partitioning phenylalanine and tyrosine uptake by the mammary gland of the lactating dairy cow is constructed and solved in the steady state. The model contains four intracellular and four extracellular pools and conservation of mass principles are applied to generate the fundamental equations describing the behaviour of the system. The experimental measurements required for model solution are milk secretion and plasma flow rate across the gland in combination with phenylalanine and tyrosine concentrations and plateau isotopic enrichments in arterial and venous plasma and free and protein bound milk during a constant infusion of [1-(13)C]phenylalanine and [2,3,5,6-(2)H]tyrosine tracer. If assumptions are made, model solution enables determination of steady state flows for phenylalanine and tyrosine inflow to the gland, outflow from it and bypass, and flows representing the synthesis and degradation of constitutive protein and phenylalanine hydroxylation. The model is effective in providing information about the fates of phenylalanine and tyrosine in the mammary gland and could be used as part of a more complex system describing amino acid metabolism in the whole ruminant. PMID:24846729

Crompton, L A; France, J; Reynolds, C K; Mills, J A N; Hanigan, M D; Ellis, J L; Bannink, A; Bequette, B J; Dijkstra, J

2014-10-21

106

Analysis of N-nitrosamines in water by isotope dilution gas chromatography-electron ionisation tandem mass spectrometry.  

PubMed

A method has been developed for the determination of eight N-nitrosamines in drinking water and treated municipal effluent. The method uses solid phase extraction (SPE), gas chromatography (GC) and analysis by tandem mass spectrometry (MS-MS) with electron ionization (EI). The target compounds are N-nitrosodimethylamine (NDMA), N-nitrosomethyethylamine (NMEA), N-nitrosodiethylamine NDEA), N-nitrosodipropylamine (NDPA), N-nitrosodi-n-butylamine (NDBuA), N-nitrosodiphenylamine (NDPhA), N-nitrosopyrrolidine (NPyr), N-nitrosopiperidine (NPip), N-nitrosomorpholine (NMorph). The use of direct isotope analogues for isotope dilution analysis of all analytes ensures accurate quantification, accounting for analytical variabilities that may occur during sample processing, extraction and instrumental analysis. Method detection levels (MDLs) were determined to describe analyte concentrations sufficient to provide a signal with 99% certainty of detection. The established MDLs for all analytes were 0.4-4 ng L(-1) in a variety of aqueous matrices. Sample matrices were observed to have only a minor impact on MDLs and the method validation confirmed satisfactory method stability over intra-day and inter-day analyses of tap water and tertiary treated effluent samples. PMID:22967534

McDonald, James A; Harden, Nick B; Nghiem, Long D; Khan, Stuart J

2012-09-15

107

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

108

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

PubMed

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

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

2014-01-01

109

Stable isotope dilution multidimensional liquid chromatography-tandem mass spectrometry for pancreatic cancer serum biomarker discovery.  

PubMed

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. PMID:19199705

Yu, Kenneth H; Barry, Colin G; Austin, David; Busch, Christine M; Sangar, Vineet; Rustgi, Anil K; Blair, Ian A

2009-03-01

110

Bioavailability of organic phosphorus to Pseudokirchneriella subcapitata as affected by phosphorus starvation: an isotope dilution study.  

PubMed

Phosphorus (P) starved algae have a capacity to rapidly take up P when resupplied to P. This study was set-up to measure to what extent P starvation enhances the potential of algae to utilize organic P forms. The initial (<0.5 h) PO4 uptake rates of cells of Pseudokirchneriella subcapitata increased up to 18-fold with increasing starvation. Algae from different levels of P starvation were subsequently exposed to different model organic P forms and carrier-free (33)PO4. Uptake (1h) of P from organic P-increased up to 5-fold with increasing P starvation. The bioavailability of organic P, relative to PO4, was calculated from uptake of (31)P and (33)P isotopes assuming no isotopic exchange with organic P-forms. This relative bioavailability ranged from 0 to 57% and remained generally unaffected by the extent of P-starvation. This result was found for cells that were either or not treated by a wash method to remove extracellular phosphatases. Short-term P uptake rate sharply increases with decreasing internal P content of the algal cells but the bioavailability of organic P, relative to PO4, is not enhanced. Such finding suggests that P-starvation enhances PO4 uptake capacity and organic P hydrolysis capacity to about the same extent. PMID:23561496

Van Moorleghem, Christoff; De Schutter, Nynke; Smolders, Erik; Merckx, Roel

2013-06-01

111

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

112

Thermal transport properties in dilute sup 3 He- sup 4 He mixtures near the superfluid transition  

SciTech Connect

The author describes measurements of various transport properties of dilute liquid {sup 3}He-{sup 4}He mixtures in two different sample cells. One cell was designed to measure the temperature drop {Delta}T across a fluid layer due to an applied heat flux Q, and the other allowed measurement of both {Delta}T and {Delta}X, the molar concentration drop. He studied the anomalous boundary resistance, {Delta}R{sub b}, in superfluid {sup 4}He near T{sub {lambda}} for Q between 4 and 100{mu}W/cm{sup 2}. He presents results for both the weakly divergent and the heat dependent, more strongly divergent contributions. He compares his data with those of Duncan and Ahlers and with theoretical predictions by Frank and Dohm. He also presents similar R{sub b} data for a mixture with X = 2.5 {times} 10{sup {minus}6}. He determined the relaxation time {tau} for transients observed during thermal conductivity {kappa}{sub eff} and thermal diffusion k{sub T}{asterisk} measurements in superfluid mixtures between 1.7K and T{sub {lambda}} with X ranging from 10{sup {minus}6} to 5 {times} 10{sup {minus}2}. He compares these results, taken with a fluid layer thickness h = 1.81 mm, with theoretical predictions and with earlier data for h = 1.47 mm. He shows the mass diffusion coefficient D computed both from {tau} and from {kappa}{sub eff} data for 0.001 < X < 0.01 between 1.7 K and T{sub {lambda}}, and he compares the results of these two different determinations. In addition, he presents the {sup 3}He-roton scattering cross section calculated using D results. In the normal phase he measured the thermal diffusion ratio k{sub T} and the thermal conductivity {kappa} for 0.009 {le} X {le} 0.05 near T{sub {lambda}}, and he compares these results with predictions by Dohm and Folk.

Tuttle, J.G.

1991-01-01

113

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

E-print Network

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

Paris-Sud XI, Université de

114

Isotopic fractionation of the major elements of molten basalt by chemical and thermal diffusion  

E-print Network

by chemical diffusion between a natural basalt and rhyolite. The thermal isotopic fractionations for isotopes of the same element. The iron isotopic mea- surements of the basalt­rhyolite diffusion couple by chemical diffusion between molten basalt and rhyolite (Richter et al., 2003) and large fractionations

Watkins, Jim

115

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

Microsoft Academic Search

The negative thermal ionization mass spectrometry technique has become the major tool for investigating boron isotopes in the environment. The high sensitivity of BO2- ionization enables measurements of ng levels of boron. However, B isotope measurement by this technique suffers from two fundamental problems (1) fractionation induced by selective ionization of B isotopes in the mass spectrometer; and (2) CNO-

G. S. Dwyer; A. Vengosh

2008-01-01

116

Quantification of saxitoxin and neosaxitoxin in human urine utilizing isotope dilution tandem mass spectrometry.  

PubMed

Saxitoxin and neosaxitoxin are potent neurotoxins that can cause paralytic shellfish poisoning when consumed. A new assay is presented here to quantify saxitoxin (STX) and neosaxitoxin (NEO) in human urine samples. Sample preparation of 500-microL samples included the use of weak-cation-exchange solid-phase extraction in a multiplexed 96-well format. Extracts were preconcentrated and analyzed via 10-min hydrophilic interaction liquid chromatography followed by electrospray ionization. Protonated molecular ions were quantified via multiple reaction monitoring mode in a Qtrap mass spectrometer. The method uses novel 15N7-isotopically enriched STX and NEO internal standards. Method validation included the characterization of two enriched urine pools. The lowest reportable limits for STX and NEO were 4.80 and 10.1 ng/mL, respectively, using both quantification and confirmation ions. These two toxins were not detected in a reference range of humans who consumed seafood in the preceding 72 h, suggesting that few false positives would occur when trying to identify people exposed to STX or NEO. PMID:19161664

Johnson, Rudolph C; Zhou, Yingtao; Statler, Kristen; Thomas, Jerry; Cox, Frederick; Hall, Sherwood; Barr, John R

2009-01-01

117

The Thermal Transport Properties of Dilute Helium -3 - HELIUM-4 Mixtures Near the Superfluid Transition Temperatures  

NASA Astrophysics Data System (ADS)

Measurements of the average thermal conductivity, kappa_{rm exp} = hQ/Delta T, were made for dilute mixtures of ^3He in ^4 He around their superfluid transitions. The temperature difference was measured with germanium resistors across a layer of fluid mixture. A capacitor inside a newly designed isothermal chamber above the fluid layer enable us to measure the average ratio of concentration gradient over temperature gradient, Tnabla c/nabla T, from X = 2 times 10^{-5} to X = 5.11 times 10^{ -2}. Here c and X are mass and molar concentration respectively. The ratio is k_sp{T}{*} in superfluid phase and k_{T } in normal fluid phase. The measurements covered the reduced temperature range of 10^ {-6} <=q|varepsilon = (T - T_lambda)/T_lambda| < 0.3, and the heat current range up to 46 muW/cm^2. The anomalous Kapitza boundary resistance for ^4He was observed. The result was consistent with those by Duncan and Ahlers (1988). R _{K} rises weakly for varepsilon_{c} <=q| varepsilon| < 3 times 10^{ -3} but sharply for |varepsilon | < varepsilon_{c}. varepsilon_{c} was found to be approximately proportional to Q^ {a} with alpha ~ 0.95. The kappa_{rm eff} data were consistent with those by Dingus et al. (1986), which deviate from the theoretical prediction of kappa_{rm eff} ~ X^{-1}. The deviation was less than that by Dingus et al.. The finite heat effect of kappa_{rm exp} was observed, and it was internally consistent with the deviation as predicted by Behringer (1986). The kappa_{rm exp}(Q) data had less quantitative agreement with the calculation of Behringer's theory than those of Dingus et al. The k_sp{T}{*} data shows an unexpected uprising from Khalatnikov's prediction of k_sp{T}{*} = 0.57 as X --> 0 and T ~ T_{lambda }, which is qualitatively consistent with the measurement of kappa_{rm exp}(Q). The k_sp{T} {*} data is lower than the theoretical value for 3.10 times 10^{-2} <=q X <=q 5.11 times 10^{ -2}. The dilute mixtures offer an ideal test for Khalatnikov's theory of two fluid model. The disagreement for kappa_{rm eff} and k_sp{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

1989-03-01

118

Thermal Conductivity of Nanotubes Revisited: Effects of Chirality, Isotope Impurity, Tube Length, and Temperature  

E-print Network

We study the dependence of thermal conductivity of single walled nanotubes (SWNT) on chirality, isotope impurity, tube length and temperature by nonequilibrium molecular dynamics method with accurate potentials. It is found that, contrary to electronic conductivity, the thermal conductivity is insensitive to the chirality. The isotope impurity, however, can reduce the thermal conductivity up to 60% and change the temperature dependence behavior. We also found that the tube length dependence of thermal conductivity is different for nanotubes of different radius at different temperatures.

Gang Zhang; Baowen Li

2005-11-02

119

Assay of blood and tissue oxaloacetate and alpha-ketoglutarate by isotope dilution gas chromatography-mass spectrometry.  

PubMed

The assay of oxaloacetate and alpha-ketoglutarate in biological samples is complicated by their chemical instability and low concentrations. We present a quantitative assay for physiological concentrations of these metabolites by isotope dilution gas chromatography-mass spectrometry. Samples are spiked with the corresponding internal standards of [U-13C4]oxaloacetate and [U-13C5] alpha-ketoglutarate prior to their treatment with hydroxylamine. After ethyl acetate extraction and evaporation of the organic phases, the oximes are converted to t-butyldimethylsilyl ethers and analyzed by selected ion monitoring gas chromatography-mass spectrometry of the [M-57]+ ion in electron impact. Although the internal standards of [U-13C4]oxaloacetate and [U-13C5] alpha-ketoglutarate are not commercially available, they can easily be synthesized in 30 min by reacting [1,2,3,6-13C4]citrate with citrate lyase, and L-[U-13C5]glutamate with pyruvate and glutamate-pyruvate transaminase, respectively. Because of their chemical instability, the internal standards are prepared on the day of the analysis. A stock solution of [1,2,3,6-13C4]citrate is prepared from L-[U-13C4]aspartate using citrate synthase and glutamate-oxaloacetate transaminase and then purified and kept frozen until required. The detection limit of the method is 0.05 nmol in a given sample. The method was applied to measurements of oxaloacetate and alpha-ketoglutarate in human blood and rat liver. PMID:7733461

Laplante, A; Comte, B; Des Rosiers, C

1995-01-20

120

Degradation of polyethoxylated nonylphenols in a sewage treatment plant. Quantitative analysis by isotopic dilution-HRGC/MS.  

PubMed

Polyethoxylated alkylphenols (APnEO, where n is the number of ethylene oxide molecules), are non-ionic surfactants widely used for domestic and industrial purposes. Most of APnEO are polyethoxylated nonylphenols (NPnEO). NPnEO are widespread environmental pollutants with relatively low toxicity for mammals and higher toxicity for aquatic organisms. In addition, they have been described as endocrine disrupters in recent publications. One of the main problems related to these surfactants is their uncomplete degradation, even in the most effective sewage treatment plants. Usually, the final products, more toxic and resistant to biological degradation than NPnEO, are nonylphenol (NP), monoethoxylated nonylphenol (NP1EO), diethoxylated nonylphenol (NP2EO), nonylphenoxy acetic acid (NP1EC), and nonylphenoxyethoxy acetic acid (NP2EC). In this paper, the degradation of NPnEO was studied in the different processes of a sewage treatment plant. For this purpose, NP, NP1EO and NP2EO were analysed in composite samples collected at different points along the plant (influent, pre-treatment effluent, primary effluent, plant effluent). Analyses were carried out by isotopic dilution-HRGC/MS, using available labelled nonylphenols (13C6-NP, 13C6-NP1EO, 13C6-NP2EO) as internal standards. Extraction of NPnEO from aqueous samples, previous to analysis, was performed by the Likens-Nickerson method (simultaneous steam distillation/solvent extraction, SDE). PMID:11848370

Planas, C; Guadayol, J M; Droguet, M; Escalas, A; Rivera, J; Caixach, J

2002-02-01

121

An isotope dilution headspace method with gas chromatography-mass spectrometry for determination of propylene oxide in food.  

PubMed

A method based on isotope dilution headspace and gas chromatography-mass spectrometry was developed for the determination of propylene oxide in foods. Optimum method sensitivity was achieved by the addition of NaCl in water at saturation and with the sample solution incubated at 90 degrees C. The method had good repeatability with relative standard deviations of 6.0, 7.6 and 2.2% at 5, 20 and 40 microg l(-1), respectively. The method was used to determine propylene oxide in 36 selected food composite samples from the 2007 Canadian total diet study. Propylene oxide was not detected in any samples analyzed with an average method detection limit of 0.5 ng g(-1). Hydrolysis of propylene oxide in water was observed as a first-order reaction with a half-life of 15 h at room temperature and less than 10 min at 90 degrees C. This confirms that it is very unlikely to find propylene oxide in foods as consumed due to its volatility and reaction with water. PMID:19680922

Cao, Xu-Liang; Corriveau, Jeannette

2009-04-01

122

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. PMID:19716838

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

2009-01-01

123

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

PubMed

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

Fernández-Fernández, Mario; González-Antuña, Ana; Rodríguez-González, Pablo; Añón Álvarez, M Elena; Álvarez, Francisco V; García Alonso, J Ignacio

2014-04-20

124

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

PubMed

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

Liu, Yang; Rychlik, Michael

2013-03-27

125

Quantification of recombinant human erythropoietin by amino acid analysis using isotope dilution liquid chromatography-tandem mass spectrometry.  

PubMed

Herein, we describe an accurate method for protein quantification based on conventional acid hydrolysis and an isotope dilution-ultra performance liquid chromatography-tandem mass spectrometry method. The analyte protein, recombinant human erythropoietin (rhEPO), was effectively hydrolyzed by incubation with 8 mol/L hydrochloric acid at 130 °C for 48 h, in which at least 1 ?mol/kg of rhEPO was treated to avoid possible degradation of released amino acids during hydrolysis. Prior to hydrolysis, sample solution was subjected to ultrafiltration to eliminate potential interfering substances. In a reversed-phase column, the analytes (phenylalanine, proline, and valine) were separated within 3 min using gradient elution comprising 20 % (v/v) acetonitrile and 10 mmol/L ammonium acetate, both containing 0.3 % (v/v) trifluoroacetic acid. The optimized hydrolysis and analytical conditions in our study were strictly validated in terms of accuracy and precision, and were suitable for the accurate quantification of rhEPO. Certified rhEPO was analyzed using a conventional biochemical assay kit as an additional working calibrant for the quantification of EPO and improved the accuracy. The optimized protocol is suitable for the accurate quantification of rhEPO and satisfactorily serves as a reference analytical procedure for the certification of rhEPO and similar proteins. PMID:24842400

Yim, Jung-Hyuk; Yoon, Ina; Yang, Hyo-Jin; Kim, Sook-Kyung; Park, Sang-Ryoul; Lee, Yong-Moon; Jeong, Ji-Seon

2014-07-01

126

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

SciTech Connect

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

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

2009-10-15

127

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

PubMed

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

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

2005-03-01

128

Development of an SI-Traceable HPLC-Isotope Dilution Mass Spectrometry Method To Quantify ?-Lactoglobulin in Milk Powders.  

PubMed

?-Lactoglobulin (?-LG) is one of the major allergenic proteins in milk. There is an urgent demand for an accurate and traceable method to develop ?-LG certified reference material (CRM). In this work, ?-LG was enzymatically digested and a specific peptide was chosen for quantitation by isotope-dilution mass spectrometry (IDMS). With amino acid CRMs as standards, the results could be traced to SI unit. By the proposed method, the recovery ranged from 86.0% to 118.3% with CVs <9.0%. The LOD and LOQ were 4.8 × 10(-5) g/g and 1.6 × 10(-4) g/g of ?-LG in milk powder, respectively. Ten samples from domestic market were analyzed with CVs <5.6%, and the relative expanded uncertainties ranged from 4.2% to 5.9% (k = 2). With the CRMs, it is expected that the comparability of ?-LG quantitation results will be improved among different laboratories. PMID:24628306

Yang, Wang; Liqing, Wu; Fei, Duan; Bin, Yang; Yi, Yang; Jing, Wang

2014-03-31

129

Isotope Effect on the Thermal Conductivity of Boron Nitride Nanotubes C. W. Chang,1,5  

E-print Network

Isotope Effect on the Thermal Conductivity of Boron Nitride Nanotubes C. W. Chang,1,5 A. M-dependent thermal conductivity T of individual multiwall boron nitride nanotubes using a microfabricated test. T is exceptionally sensitive to isotopic substitution, with a 50% enhancement in T resulting for boron nitride

Zettl, Alex

130

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

Microsoft Academic Search

Polycyclic aromatic hydrocarbons (PAHs) are pollutants found in living and working environments. The aim of this study was\\u000a to develop a solid-phase microextraction (SPME) gas chromatography (GC)–isotope dilution mass spectrometry method for the\\u000a quantification of 10 four- to six-ring PAHs in urine samples. Seven of the selected PAHs have been classified as carcinogenic.\\u000a Under the final conditions, analytes were sampled

Laura Campo; Silvia Fustinoni; PierAlberto Bertazzi

131

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

Microsoft Academic Search

A method was developed for isolating neptunium from Pu, U or mixed oxide (MOX) samples and its determination by isotope dilution -spectrometry (IDGS) using239Np (243Am) as a spike. Extraction chromatography with trilaurylamine fixed on a SGX-C18 support was used for the isolation of Np. The decontamination factors for U, Pu, Am and Pa vary between 1000–2000 and 100, respectively. The

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

1996-01-01

132

Non-Mass Dependent Isotope Fractionations of Rarefied Gases (O2, SF6) Under a Thermal Gradient  

NASA Astrophysics Data System (ADS)

Thermal diffusion induced isotope fractionation has long been intensely studied both experimentally and theoretically. It was usually used for small scale isotope separations in nuclear industry, both in gas and liquid phase. Previous research focus has mainly been on convective, high pressure and binary mixture systems, serving the purpose of efficient isotope separations. However, multiple-isotope behavior of rarefied gases under a thermal gradient has not been carefully examined, especially for a non-convective system. In addition to the limited practical applications of such a system, the lack of interest is largely due to the fact that thermal diffusion has never been considered outside the classical thermodynamic and kinetic realm and that the associated multiple isotope fractionation has to be mass dependent. When an otherwise homogeneous gas is superimposed by a thermal gradient, the coupled thermal and chemical diffusions occur. The multiple isotope (16O, 17O, 18O, or 32S, 33S, 34S, and 36S) fractionations associated with the dynamic process are indeed predicted to be entirely mass dependent as we calculate from Jones and Furry (1946) and Huang et al (2010). However, our thermal-gradient experiments on O2 and SF6 have proven otherwise. We found that a simple superimposed external thermal gradient on low pressure O2 or SF6 gas in a closed (but not isolated) system can produce measurable non-mass-dependent 17O or 33S anomalies. A series tests were conducted using two sets of apparatus to constrain the controlling factors. We obtained up to -0.51 or +0.82‰ (s. d., 1? = 0.03) for the ?17O and -0.111‰ (1? = 0.018) for the ?33S from different ends of our thermal gradients. We found that the magnitude of the 17O or 33S anomaly is a function of the initial gas pressure, temperature gradient, experimental duration, average temperature of the whole apparatus, and the geometry of the apparatus. The ? value (ln?17/ln?18 or ln?33/ln?34) ranges from ~ -0.3 to ~ +0.3 for ?’17O-?’18O and is at ~1.4 for ?’33S-?’34S in our apparatus. We propose that the observed non-mass-dependent fractionation is probably the result of nuclear spin effect amplified by a sharp thermal gradient. We predict that thermal-gradient effect exists in many other molecules, especially at dilute states. The discovery of thermal-gradient induced non-mass-dependent isotope fractionation helps to explain some of the puzzling non-mass-dependent fractionation reported in recent literature, and provokes us to consider alternative interpretations of the triple oxygen or quadruple sulfur isotope heterogeneity in the Solar system.

Sun, T.; Bao, H.; Oxy-Anion Stable Isotope Consortium

2010-12-01

133

Thermal Conductivity of Dilute HELIUM-3 - Helium -4 Mixtures Near the Lambda Line.  

NASA Astrophysics Data System (ADS)

Measurements of the thermal conductivity of dilute mixtures of ('3)He in ('4)He are presented. The conductivity was obtained at the saturated vapor pressure in the temperature region near the superfluid transition. The temperature was controlled over a T-T(,(lamda)) range of 2(mu)K to 0.2K around the transition, to obtain the critical and background behaviors of the conductivity, for both the superfluid and normal fluid. The ('3)He molar concentration was varied from X = 0 to 0.05, with X usually less than 0.01. The value of the conductivity at the transition was obtained as a function of concentration. By-products of the experiment were the evaluation of the transition temperature's dependence upon the concentration and the value for dX/dT(,(lamda)) in the region of X less than 0.01. An additional result was the temperature gradient's characteristic relaxation time (tau)((')VT), whose temperature and concentration dependence could be studied. The basic cell design is described, and measurements concerning the empty cell are used to describe the conductivity of the stainless steel spacer. The data taking procedure is outlined, as is the data analysis technique. Comparisons of the data to both theoretical models and previous experimental results are made. Other measurements of the conductivity for pure ('4)He are readily available, while those for mixtures are sparse. Experimentally determined dX/dT(,(lamda)) values exist for X > 0.01, but are lacking in the region of interest. The expectations of Behringer and Meyer provide a guide for the dependencies of (tau)((')VT) on X and T. Theoretically, the conductivity has been recently receiving a great deal of attention for both the pure fluid and the mixtures. The results of the nonlinear renormalization -group calculations are reviewed. Our results for pure ('4)He are compared with those of Ahlers and theoretically described by the model F calculations. The mixture results are well explained in both their concentration and temperature dependence by the works of Onuki, and Dohm and Folk. Analysis of the relaxation times leads to an explanation of when the coupling of the thermal modes to the concentration modes becomes important, and how the uncoupled behavior resembles that of pure ('4)He.

Gestrich, David Allen

134

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

USGS Publications Warehouse

The U.S. Geological Survey method (0-2141-09) presented is approved for the determination of glyphosate, its degradation product aminomethylphosphonic acid (AMPA), and glufosinate in water. It was was validated to demonstrate the method detection levels (MDL), compare isotope dilution to standard addition, and evaluate method and compound stability. The original method USGS analytical method 0-2136-01 was developed using liquid chromatography/mass spectrometry and quantitation by standard addition. Lower method detection levels and increased specificity were achieved in the modified method, 0-2141-09, by using liquid chromatography/tandem mass spectrometry (LC/MS/MS). The use of isotope dilution for glyphosate and AMPA and pseudo isotope dilution of glufosinate in place of standard addition was evaluated. Stable-isotope labeled AMPA and glyphosate were used as the isotope dilution standards. In addition, the stability of glyphosate and AMPA was studied in raw filtered and derivatized water samples. The stable-isotope labeled glyphosate and AMPA standards were added to each water sample and the samples then derivatized with 9-fluorenylmethylchloroformate. After derivatization, samples were concentrated using automated online solid-phase extraction (SPE) followed by elution in-line with the LC mobile phase; the compounds separated and then were analyzed by LC/MS/MS using electrospray ionization in negative-ion mode with multiple-reaction monitoring. The deprotonated derivatized parent molecule and two daughter-ion transition pairs were identified and optimized for glyphosate, AMPA, glufosinate, and the glyphosate and AMPA stable-isotope labeled internal standards. Quantitative comparison between standard addition and isotope dilution was conducted using 473 samples analyzed between April 2004 and June 2006. The mean percent difference and relative standard deviation between the two quantitation methods was 7.6 plus or minus 6.30 (n = 179), AMPA 9.6 plus or minus 8.35 (n = 206), and glufosinate 9.3 plus or minus 9.16 (n = 16). The analytical variation of the method, comparison of quantitation by isotope dilution and multipoint linear regressed standard curves, and method detection levels were evaluated by analyzing six sets of distilled-water, groundwater, and surface-water samples spiked in duplicate at 0.0, 0.05, 0.10 and 0.50 microgram per liter and analyzed on 6 different days during 1 month. The grand means of the normalized concentration percentage recovery for glyphosate, AMPA, and glufosinate among all three matrices and spiked concentrations ranged from 99 to 114 plus or minus 2 to 7 percent of the expected spiked concentration. The grand mean of the percentage difference between concentrations calculated by standard addition and linear regressed multipoint standard curves ranged from 8 to 15 plus or minus 2 to 9 percent for the three compounds. The method reporting levels calculated from all the 0.05- microgram per liter spiked samples were 0.02 microgram per liter for all three compounds. Compound stability experiments were conducted on 10 samples derivatized four times for periods between 136 to 269 days. The glyphosate and AMPA concentrations remained relatively constant in samples held up to 136 days before derivatization. The half life of glyphosate varied from 169 to 223 days in the underivatized samples. Derivatized samples were analyzed the day after derivitization, and again 54 and 64 days after derivatization. The derivatized samples analyzed at days 52 and 64 were within 20 percent of the concentrations of the derivatized samples analyzed the day after derivatization.

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

2009-01-01

135

Analysis of aflatoxin B1-lysine adduct in serum using isotope-dilution liquid chromatography/tandem mass spectrometry.  

PubMed

A method for quantitative analysis of aflatoxin B1-lysine adduct (B1-Lys) in serum by liquid chromatography using tandem mass spectrometry (LC/MS/MS) is presented. The protein in a 250-microL sample was digested in the presence of a stable-isotope internal standard during a 4-h incubation at 37 degrees C with Pronasetrade mark. B1-Lys and the internal standard were extracted using mixed-mode solid-phase extraction cartridges and eluted with 2% formic acid in methanol. Following evaporation and reconstitution, extracts were injected onto a Luna C-18(2) column and eluted with a step gradient of acetonitrile and 0.06% formic acid. The B1-Lys and the internal standard were detected in a positive ionization selective reaction monitoring mode with a ThermoFinnigan TSQ Quantum triple quadrupole mass spectrometer. Calibration curves were linear for concentrations from 0.05-8.0 ng/mL. The method was validated with aflatoxin B1 dosed rat serum diluted to anticipated high and low concentrations. Total imprecision determined from 30 measurements over 15 days was 5.6% and 9.1%, respectively. Recoveries of 78.8 +/- 6.4% for B1-Lys and 85.4 +/- 12.4% for the internal standard were based on the full extraction and reconstitution processes. The method can be used to quantitate B1-Lys at the 0.5 pg/mg albumin level and is suitable for routine analysis. PMID:16015671

McCoy, Leslie F; Scholl, Peter F; Schleicher, Rosemary L; Groopman, John D; Powers, Carissa D; Pfeiffer, Christine M

2005-01-01

136

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

137

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

PubMed

Different sources of folate may have different bioavailability and hence may impact the standard definition of folate equivalents. In order to examine this, a short term human study was undertaken to evaluate the relative native folate bioavailabilities from spinach, Camembert cheese and wheat germs compared to pteroylmonoglutamic acid as the reference dose. The study had a single-centre, randomised, four-treatment, four-period, four-sequence, cross-over design, i.e. the four (food) items to be tested (referred to as treatments) were administered in sequences according to the Latin square, so that each experimental treatment occurred only once within each sequence and once within each study period. Each of the 24 subjects received the four experimental items separated by a 14-day equilibrium phase and received a pteroylmonoglutamic acid supplement for 14 days before the first testing and between the testings for saturation of body pools. Folates in test foods, plasma and urine samples were determined by stable isotope dilution assays, and in urine and plasma, the concentrations of 5-methyltetrahydrofolate were evaluated. Standard non-compartmental methods were applied to determine the biokinetic parameters Cmax, tmax and AUC from baseline corrected 5-methyltetrahydrofolate concentrations within the interval from 0 to 12 hours. The variability of AUC and Cmax was moderate for spinach and oral solution of pteroylmonoglutamic acid but high for Camembert cheese and very high for wheat germs. The median tmax was lowest for spinach, though tmax showed a high variability among all treatments. When comparing the ratio estimates of AUC and Cmax for the different test foods, highest bioavailability was found for spinach followed by that for wheat germs and Camembert cheese. The results underline the dependence of folate bioavailability on the type of food ingested. Therefore, the general assumption of 50% bioavailability as the rationale behind the definition of folate equivalents has to be questioned and requires further investigation. PMID:25407846

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

2015-01-24

138

Microhomogeneity assessments using ultrasonic slurry sampling coupled with electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

Ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) is a very powerful technique for the direct analysis of solid materials prepared as slurries. The use of isotope dilution USS-ETV-ICP-MS (USS-ETV-ID-ICP-MS) for micro-homogeneity characterization studies of powdered reference materials based on elemental analyses, was investigated. Slurry analysis conditions were optimized taking into consideration density, particle size, analyte extraction, slurry mixing, analyte transport and sampling depth. Slurries were prepared using 1-20 mg of material and adding 1.0 ml of 5% nitric acid diluent containing 0.005% Triton X-100®. Three reference materials were analyzed (RM 8431a Mixed Diet, SRM 1548a Typical Diet and SRM 2709 San Joaquin Soil). Cu and Ni were determined in each material and Fe was also determined in RM 8431a Mixed Diet. ETV conditions were optimized and the benefit of using Pd as a carrier to enhance transport, combined with oxygen ashing was demonstrated. The accuracy of the method was verified by comparing analytical results with certified values. The precision of the method was demonstrated by comparing R.S.D.'s for slurry samples and aqueous standards and elemental 'homogeneity' was quantified based on the slurry sampling variability. The representative sample mass analyzed was calculated taking into consideration extraction of analyte into the liquid phase of the slurry. Representative sample masses of approximately 4 mg of RM 8431a provided slurry sampling variabilities of 10% or less for Cu, Fe and Ni. Representative sample masses of approximately 10 mg of SRM 1548a provided slurry sampling variabilities of approximately 10% for Cu and Ni. Representative sample masses of approximately 0.3 mg of SRM 2709 resulted in total analytical variabilities of less than 7%, highlighting the fact that the San Joaquin Soil is clearly the most homogeneous of the materials characterized.

Miller-Ihli, Nancy J.; Baker, Scott A.

2001-09-01

139

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

PubMed

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

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

2014-02-01

140

Certification of methylmercury in cod fish tissue certified reference material by species-specific isotope dilution mass spectrometric analysis.  

PubMed

A new cod fish tissue certified reference material, NMIJ CRM 7402-a, for methylmercury analysis was certified by the National Metrological Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Cod fish was collected from the sea close to Japan. The cod muscle was powdered by freeze-pulverization and was placed into 600 glass bottles (10 g each), which were sterilized with gamma-ray irradiation. The certification was carried out using species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID-GC-ICPMS), where (202)Hg-enriched methylmercury (MeHg) was used as the spike compound. In order to avoid any possible analytical biases caused by nonquantitative extraction, degradation and/or formation of MeHg in sample preparations, two different extraction methods (KOH/methanol and HCl/methanol extractions) were performed, and one of these extraction methods utilized two different derivatization methods (ethylation and phenylation). A double ID method was adopted to minimize the uncertainty arising from the analyses. In order to ensure not only the reliability of the analytical results but also traceability to SI units, the standard solution of MeHg used for the reverse-ID was prepared from high-purity MeHg chloride and was carefully assayed as follows: the total mercury was determined by ID-ICPMS following aqua regia digestion, and the ratio of Hg as MeHg to the total Hg content was estimated by GC-ICPMS. The certified value given for MeHg is 0.58 +/- 0.02 mg kg(-1) as Hg. PMID:18335211

Inagaki, Kazumi; Kuroiwa, Takayoshi; Narukawa, Tomohiro; Yarita, Takashi; Takatsu, Akiko; Okamoto, Kensaku; Chiba, Koichi

2008-07-01

141

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

142

Isotope and strain effects on thermal conductivity of silicon thin film  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

143

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

144

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

145

Experimental design for TBT quantification by isotope dilution SPE-GC-ICP-MS under the European water framework directive.  

PubMed

In Europe the maximum allowable concentration for tributyltin (TBT) compounds in surface water has been regulated by the water framework directive (WFD) and daughter directive that impose a limit of 0.2ngL(-1) in whole water (as tributyltin cation). Despite the large number of different methodologies for the quantification of organotin species developed in the last two decades, standardised analytical methods at required concentration level do not exist. TBT quantification at picogram level requires efficient and accurate sample preparation and preconcentration, and maximum care to avoid blank contamination. To meet the WFD requirement, a method for the quantification of TBT in mineral water at environmental quality standard (EQS) level, based on solid phase extraction (SPE), was developed and optimised. The quantification was done using species-specific isotope dilution (SSID) followed by gas chromatography (GC) coupled to inductively coupled plasma mass spectrometry (ICP-MS). The analytical process was optimised using a design of experiment (DOE) based on a factorial fractionary plan. The DOE allowed to evaluate 3 qualitative factors (type of stationary phase and eluent, phase mass and eluent volume, pH and analyte ethylation procedure) for a total of 13 levels studied, and a sample volume in the range of 250-1000mL. Four different models fitting the results were defined and evaluated with statistic tools: one of them was selected and optimised to find the best procedural conditions. C18 phase was found to be the best stationary phase for SPE experiments. The 4 solvents tested with C18, the pH and ethylation conditions, the mass of the phases, the volume of the eluents and the sample volume can all be optimal, but depending on their respective combination. For that reason, the equation of the model conceived in this work is a useful decisional tool for the planning of experiments, because it can be applied to predict the TBT mass fraction recovery when the experimental conditions are drawn. This work shows that SPE is a convenient technique for TBT pre-concentration at pico-trace levels and a robust approach: in fact (i) number of different experimental conditions led to satisfactory results and (ii) the participation of two institutes to the experimental work did not impact the developed model. PMID:25618710

Alasonati, Enrica; Fabbri, Barbara; Fettig, Ina; Yardin, Catherine; Del Castillo Busto, Maria Estela; Richter, Janine; Philipp, Rosemarie; Fisicaro, Paola

2015-03-01

146

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

147

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

148

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

PubMed

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

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

2013-09-01

149

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

NASA Astrophysics Data System (ADS)

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

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

2006-02-01

150

Analysis of alkyl and 2-6-ringed polycyclic aromatic hydrocarbons by isotope dilution gas chromatography/mass spectrometry. Quality assurance and determination in Spanish river sediments.  

PubMed

An accurate, precise and sensitive method is described for the analysis of 29 polycyclic aromatic hydrocarbons (PAHs), including 19 2-6-ringed PAHs and 10 alkyl-PAHs. The method is based on an isotope dilution technique using gas chromatography/mass spectrometry (GC/MS) and available labeled PAHs as internal standards. Quality parameters were calculated with satisfactory results and 36 Spanish river sediments were analysed. Results were evaluated regarding to the sediment quality guidelines (SQGs) based on the effects range-low (ERL) and the effects range-median (ERM) values. Most analysed sediments showed a good quality, since only 7 of them exceeded ERL values, including one sample surpassing ERM values. PAH profiles were studied in order to identify PAH sources as mainly petrogenic or pyrogenic. Most samples showed petrogenic-type fingerprints, although 6 of the 11 sediments with the highest PAH concentrations (> 1000 ng/g) were classified as pyrogenic, including 4 of the 7 samples exceeding ERL values. Quality assurance was carried out by the triplicate analysis of one preanalysed river sediment without PAHs subsequently spiked at a medium (500 ng/g) and a low concentration level (10 ng/g) of each analyte. Main quality requirements for methods based on isotope dilution were accomplished. Method accuracy was 80-120% for most PAHs, method precision was <15% for all the analysed compounds and method detection limits (MDLs) were 1-3 ng/g. PMID:16513126

Planas, Carles; Puig, Alejandra; Rivera, Josep; Caixach, Josep

2006-04-28

151

Determination of key aroma compounds in the crumb of a three-stage sourdough rye bread by stable isotope dilution assays and sensory studies.  

PubMed

An investigation of the volatile fraction of a freshly prepared sourdough rye bread crumb by means of the aroma extract dilution analysis (AEDA), followed by identification experiments, revealed 22 flavor compounds in the flavor dilution (FD) factor range of 128 to 2048. Quantitations performed by stable isotope dilution assays (SIDA) and a calculation of odor activity values (OAV; ratio of concentration to odor threshold) revealed the following as contributors to the overall crumb flavor: 3-methylbutanal (malty), (E)-2-nonenal (green, fatty), (E,E)-2,4-decadienal (fatty, waxy), hexanal (green), acetic acid (sour, pungent), phenylacetaldehyde (honey-like), methional (boiled potato-like), vanillin (vanilla-like), 2,3-butandione (buttery), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (spicy), and 2- and 3-methylbutanoic acid (sweaty). Using either citrate buffer, starch, or deodorized crumb as model matrixes, the typical malty and sour rye bread crumb flavor was reproduced by adding a mixture of 20 reference odorants in the "natural" concentrations as quantitatively determined in the fresh crumb. PMID:11559129

Kirchhoff, E; Schieberle, P

2001-09-01

152

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

153

Thermal diffusive conductivity of dilute superfluid (He-3)-(He-4) mixtures  

NASA Technical Reports Server (NTRS)

A new technique is described for measuring the effective thermal conductivity of superfluid (He-3)-(He-4) mixtures. The results confirm the large departures from hydrodynamic theory reported previously. The analysis suggests that the measured conductivity is the finite thermal diffusive conductivity of superfluid helium in the absence of counterflow. This conductivity need not diverge in the limit of small He-3 concentration.

Chui, T. C. P.; Lipa, J. A.

1987-01-01

154

The 2H thermal diffusion isotope effect in benzene and methanol  

NASA Astrophysics Data System (ADS)

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

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

1983-06-01

155

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

156

Zn isotope compositions of the thermal spring waters of La Soufrière volcano, Guadeloupe Island  

NASA Astrophysics Data System (ADS)

To trace the sources and pathways of Zn in hydrothermal systems, the Zn isotope compositions of seventeen water samples from eight thermal springs and six gas samples from two fumaroles from La Soufrière, an active volcano on Guadeloupe Island (French West Indies, FWI), were analyzed using a method adapted for purifying Zn from Fe- and SO4-enriched thermal solutions. The fumaroles are enriched in Zn 100 to 8000 times compared to the local bedrock and have isotopic compositions (?66Zn values from +0.21‰ to +0.35‰) similar to or slightly higher than fresh andesite (+0.21‰). The enrichment of Zn in the thermal springs compared with the surface waters shows that Zn behaves as a soluble element during hydrothermal alteration but is significantly less mobile than Na. The ?66Zn values of most of the spring waters are relatively constant (approximately 0.70‰), indicating that the thermal springs from La Soufrière are enriched in heavy isotopes (i.e., 66Zn) compared to the host rocks (from -0.14‰ to +0.42‰). Only three thermal springs have lower ?66Zn values (as low as -0.43%). While the Zn in the fumaroles is essentially derived from magma degassing, which is consistent with a previous study on Merapi volcano (Toutain et al., 2008), we show that the Zn in the thermal springs is mainly derived from water-rock interactions. The 66Zn-enriched isotopic signature in most of the spring waters can be explained qualitatively by the precipitation at depth of sulfide minerals that preferentially incorporate the light isotopes. This agrees with the isotopic fractionation that was recently calculated for aqueous complexes of Zn. The few thermal springs with lower ?66Zn values also have low Zn concentrations, indicating the preferential scavenging of heavy Zn isotopes in the hydrothermal conduits. This study shows that unlike chemical weathering under surface conditions, hydrothermal alteration at high temperatures significantly fractionates Zn isotopes and enriches thermal waters in heavy Zn isotopes (e.g., 66Zn). Continental hydrothermal systems therefore constitute a source of heavy Zn isotopes to the oceans; this should be taken into account in the global oceanic budget of Zn.

Chen, Jiu-Bin; Gaillardet, Jérôme; Dessert, Céline; Villemant, Benoit; Louvat, Pascale; Crispi, Olivier; Birck, Jean-Louis; Wang, Yi-Na

2014-02-01

157

Laser-induced migration and isotope separation of epi-thermal monomers and dimers in supercooled free jets  

NASA Astrophysics Data System (ADS)

Explicit relations are developed to estimate the outflux of migrating isotopomers iQF6 to the outskirts of a supersonic supercooled free jet whose core is irradiated by a co-axial laser beam and intercepted by a skimmer that separates core gas from peripheral gases. The QF6 target gas is diluted in carrier gas G (G = He, N2, Ar, Xe, SF6, etc.) which determines the jet's supersonic characteristics and forms QF6:G dimers at low temperatures. Under isotope-selective laser excitation, excited iQF6* convert their vibrational energy V into kinetic energy T after forming transient iQF6*:G dimers that dissociate in sub-microseconds. Three migrating groups with different transport parameters are created in the jet: thermal monomers, faster-moving epithermal monomers, and slower-moving dimers. Jet-core-fleeing QF6 is enriched in iQF6 due to enhanced outwards migration of iQF6! epithermals and reduced escape of jQF6:G dimers in the jet. Isotope enrichments in the rim gases are highest for heavier carrier gases such as G = Xe or G = SF6.

Eerkens, Jeff W.

2005-04-01

158

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

Microsoft Academic Search

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

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

2009-01-01

159

Thermal transport properties in helium near the superfluid transition. III. Dilute3He-4He mixtures in the normal phase  

NASA Astrophysics Data System (ADS)

An experimental study is presented for the thermal conductivity ? and the thermal relaxation for dilute mixtures of3He in4He with concentration 9×10-4?X(3He)?5×10-2 at saturated vapor pressure and in the normal phase near the superfluid transition. The conductivity results for ? are compared with predictions by Dohm and Folk from field-theoretic renormalization group (RG ) theory. The conductivity ? s =[?-1( T)-?-1(T?)]-1, is compared with Ahlers' phenomenological arguments, and also with predictions by Dohm and Folk and by Onuki. The temperature difference transient ? 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 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 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 ? from finite heat effects, (2) the calculation of the concentration susceptibility (? X/??) T,P , and (3) the calculation procedure for ?, k T, and D using the RG approach of Dohm and Folk.

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

1987-07-01

160

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

SciTech Connect

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

Arndt Schimmelmann; Maria Mastalerz

2010-03-30

161

Lithium isotope analysis by thermal ionization mass spectrometry of lithium tetraborate  

SciTech Connect

A mass spectrometric method based on the thermal ionization of lithium tetraborate has been developed for the isotopic analysis of lithium. The measurement of Li/sub 2/BO/sub 2//sup +/ reduces isotopic fractionation during analysis compared to the normal use of Li/sup +/ ions. The technique is capable of achieving a relative precision of 1.3 per thousand (1sigma) in the determination of lithium isotopic ratios. A chemical procedure for quantitative and clean extraction of lithium from natural waters is described. This method has been applied to sea water with reproductivity within the analytical uncertainty. Preliminary study indicates this technique is also applicable to silicate rocks.

Chan, L.H.

1987-11-15

162

Validation of an isotope dilution, ICP-MS method based on internal mass bias correction for the determination of trace concentrations of Hg in sediment cores.  

PubMed

The development and validation of a method for the determination of mercury in sediments using a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS) for detection is described. The utilization of isotope dilution (ID) calibration is shown to solve analytical problems related to matrix composition. Mass bias is corrected using an internal mass bias correction technique, validated against the traditional standard bracketing method. The overall analytical protocol is validated against NRCC PACS-2 marine sediment CRM. The estimated limit of detection is 12ng/g. The proposed procedure was applied to the analysis of a real sediment core sampled to a depth of 160m in Lake Como, where Hg concentrations ranged from 66 to 750ng/g. PMID:18371687

Ciceri, E; Recchia, S; Dossi, C; Yang, L; Sturgeon, R E

2008-01-15

163

Development and validation of a high-throughput analysis of glutathione in grapes, musts and wines by Stable Isotope Dilution Assay and LC-MS/MS.  

PubMed

For the first time, we proposed a high-throughput method to quantify glutathione in grapes, musts and wines for all grape varieties using Stable Isotope Dilution Assay (SIDA). Indeed, the use of SIDA as a quantification method is essential to overcome the chemical instability of glutathione. In practice, glutathione was derivatized in-situ with N-ethylmaleimide to block the cysteine residue and to enhance its lipophilic properties. After quenching with acetic acid, samples were directly analyzed by LC-MS/MS (run of 13min) in Multiple Reaction Monitoring mode using labeled glutathione as internal standard. The validation according to the International Organization of Vine and Wine recommendations demonstrated the high sensitivity (LOD=45?gL(-1)), accuracy (recovery=112%) and intermediate reproducibility (RSD=12%) of the method. This high-throughput method that requires only 1mL of matrix, allowed us to analyze 70 samples per day for a moderate cost. PMID:25660871

Roland, Aurélie; Schneider, Rémi

2015-06-15

164

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

165

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

PubMed

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

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

2012-12-15

166

Suitability and use of 15N-isotope dilution method to estimate nitrogen fixation by actinorhizal shrubs. Forest Ecology and Management 136  

E-print Network

Nitrogen ®xation rates were estimated by the 15 N-isotope dilution method for Ceanothus velutinus and Purshia tridentata in the understory of central Oregon ponderosa pine forests. Field rates were measured in small pole-, large pole-, and sawtimbersized pine stands using two shrubs (Arctostaphylos patula, Ribes cereum) and one graminoid (Carex rossii) as non-®xing reference species. Shrub cover ranged from 23 to 59 % for Ceanothus and from 9 to 15 % for Purshia. Foliage samples were collected monthly following two applications of 15 N ammonium sulfate (5 kg N ha ?1 at 10 atom % 15 N) to compare N uptake patterns and determine the fraction of N derived from ®xation (Ndff). Several violations of the underlying assumption of the isotope dilution method that N ®xing and reference plants have access to similar pools of soil 15 N were identi®ed. These included non-uniform distribution of 15 N in the soil pro®le and dissimilarities in rooting volumes, N uptake patterns, and plant ages between the reference and N ®xing plants. Despite these compromises, there were only minor differences in percentage of Ndff when calculated independently using each reference species. Low 15 N uptake by Ceanothus and Purshia evidently negated the requirement that N ®xing and reference plants have comparable spatial and temporal access to soil 15 N. Both Ceanothus and Purshia were highly effective, obtaining more than 80 % of their N from ®xation regardless of pine stand, shrub cover, or shrub age. Annual N ®xation by Ceanothus ranged from 4 to 15 kg ha ?1 year ?1. This rate is lower than previously reported for Ceanothus in other ecosystems in the western United States, yet is suf®cient to replace N losses from disturbances such as prescribed ®re. Purshia ®xed considerably less N, ca. 1 kg ha ?1 year ?1, roughly equivalent to the rate of atmospheric

Matt D. Busse

167

Determination of low methylmercury concentrations in peat soil samples by isotope dilution GC-ICP-MS using distillation and solvent extraction methods.  

PubMed

Most often, only total mercury concentrations in soil samples are determined in environmental studies. However, the determination of extremely toxic methylmercury (MeHg) in addition to the total mercury is critical to understand the biogeochemistry of mercury in the environment. In this study, N2-assisted distillation and acidic KBr/CuSO4 solvent extraction methods were applied to isolate MeHg from wet peat soil samples collected from boreal forest catchments. Determination of MeHg was performed using a purge and trap GC-ICP-MS technique with a species-specific isotope dilution quantification. Distillation is known to be more prone to artificial MeHg formation compared to solvent extraction which may result in the erroneous MeHg results, especially with samples containing high amounts of inorganic mercury. However, methylation of inorganic mercury during the distillation step had no effect on the reliability of the final MeHg results when natural peat soil samples were distilled. MeHg concentrations determined in peat soil samples after distillation were compared to those determined after the solvent extraction method. MeHg concentrations in peat soil samples varied from 0.8 to 18?gkg(-1) (dry weight) and the results obtained with the two different methods did not differ significantly (p=0.05). The distillation method with an isotope dilution GC-ICP-MS was shown to be a reliable method for the determination of low MeHg concentrations in unpolluted soil samples. Furthermore, the distillation method is solvent-free and less time-consuming and labor-intensive when compared to the solvent extraction method. PMID:25434268

Pietilä, Heidi; Perämäki, Paavo; Piispanen, Juha; Starr, Mike; Nieminen, Tiina; Kantola, Marjatta; Ukonmaanaho, Liisa

2015-04-01

168

Development of a multiresidue method for analysis of pesticides in sediments based on isotope dilution and liquid chromatography-electrospray-tandem mass spectrometry.  

PubMed

Because of the complexity of the sediment matrix, selective methods are necessary to identify and quantify different kinds of pesticides at a time. In this context, a multiresidue method based on isotope dilution and final analysis by liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS) was developed for the determination of 26 pesticides and transformation products in sediment. The method developed comprises pressurized liquid extraction (PLE) and further purification of the extract by solid phase extraction (SPE) prior to analysis. In the process of method optimization various SPE cartridges as well as PLE and SPE elution solvents were evaluated. Due to the relatively high volatility of some compounds (e.g., propanil), special attention was paid to the evaporation step. Experiments comparing different pressures and times during solvent evaporation were performed with the aim to improve the recovery of these compounds. Matrix effects were also studied even though they were corrected through the use of 23 deuterated compounds as surrogate standards for quantification. The analytical method developed showed good validation parameters in terms of linearity, sensitivity (limits of detection in the pgg(-1) or low ngg(-1) range and limits of determination below 80ngg(-1)), accuracy (relative recoveries between 92 and 118%, except for malaoxon (66.5%)), and repeatability (relative standard deviations between 1.5 and 17%, for all compounds except the acidic herbicides). Its main advantage is the simultaneous analysis of pesticides with a large variety of physical-chemical properties, as well as its improved accuracy due to the use of the isotope dilution method. Application of the method to the analysis of 5 real samples from 4 different Spanish rivers revealed the presence of 5 of the 26 target compounds, being chlorpyrifos, diuron and diazinon the most ubiquitous, as expected, due to their high bioaccumulation and low mobility features. PMID:23890546

Köck-Schulmeyer, Marianne; Olmos, Mar; López de Alda, Miren; Barceló, Damià

2013-08-30

169

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

PubMed

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

Campo, Laura; Fustinoni, Silvia; Bertazzi, Pieralberto

2011-08-01

170

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

171

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

PubMed Central

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

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

2012-01-01

172

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

2012-01-01

173

Thermal property characterization of single crystal diamond with varying isotopic composition  

SciTech Connect

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

Wei, L.

1993-01-01

174

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

SciTech Connect

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

Mariner, R.H. [Geological Survey, Menlo Park, CA (United States); Young, H.W. [Geological Survey, Boise, ID (United States)

1995-12-31

175

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

176

Development of a quantitative method for the analysis of tobacco-specific nitrosamines in mainstream cigarette smoke using isotope dilution liquid chromatography/electrospray ionization tandem mass spectrometry.  

PubMed

An improved method has been developed for the determination of the four major tobacco-specific nitrosamines (TSNA) in mainstream cigarette smoke. The new method offers decreased sample preparation and analysis time as compared to traditional methodologies. This method uses isotope dilution liquid chromatography coupled to a tandem mass spectrometer with electrospray ionization and is significantly more sensitive than traditional methods. It also shows no evidence of artifactual formation of TSNA. Sample concentrations were determined for four TSNA in mainstream smoke using two isotopically labeled TSNA analogues as internal standards. Mainstream smoke was collected on an industry standard 44-mm Cambridge filter pad, extracted with an aqueous buffer solution, and analyzed without further sample cleanup. This method has been validated through intra- and interlaboratory studies and has shown excellent recoveries, sensitivity, and repeatability. The limits of detection of each TSNA varied from 0.01 to 0.1 ng/mL, and the linear calibration range of the instrument in sample matrix spanned 0.5-200 ng/ mL, which allowed for the determination of the TSNA levels in cigarettes with a wide range of deliveries. Data are also reported from two commercially available industry reference cigarettes and show excellent agreement and reproducibility over a six-month time period (n > 50). PMID:15858978

Wagner, Karl A; Finkel, Nancy H; Fossett, J Eric; Gillman, I Gene

2005-02-15

177

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

PubMed

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

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

2013-09-15

178

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

PubMed Central

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

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

2013-01-01

179

Temperature-dependent ordinary and thermal diffusion of hydrogen isotopes through thermonuclear reactor components  

Microsoft Academic Search

To permit more accurate calculations of tritium permeation for design purposes, theoretical expressions for quasiunidirectional ordinary diffusion of hydrogen isotopes through nonisothermal plane, cylindrical shell, and spherical shell barriers are presented. Arrhenium-type dependence of mass diffusivity on temperature and steady-state constant-thermal-conductivity temperature gradients through the barriers are considered. Analyses that consider thermal diffusion with both constant and temperature-dependent heat of

Pendergrass

1976-01-01

180

A study of thermal diffusion in dilute solutions of polystyrene in toluene  

E-print Network

, ~as not been 1'ully testeR. In an attempt to nrov1Re s mn-rt!ne Ra!. a for th!s theory anR to answer other q?est!o~s concernin~ thermal Riftus!on, an exper!mental study &as !ust &een c~~nlete! !n t&is laboratory by &&! tmore in (1) w&! c~ eq ~!31&r...Ion, we have lf now a?nIf~r~ temperature sradlent is used such that anrI ) equatIon (&) bec~~es gc g'c Jc ? = D ? -D o g a 7 &y al) owinp the &iffusion process to take place for a short tIrre only, such t'hat the end effects oi' the cell may be neg...

Herren, Cecil LeRoy

1961-01-01

181

Helium-carbon isotopic composition of thermal waters from Tunisia  

NASA Astrophysics Data System (ADS)

Tunisia has numerous thermo-mineral springs. Previous studies have shown that their chemical composition and occurrence are strongly influenced by the regional geology, however little work has been conducted to date to investigate the isotopic composition of volatiles associated with these geothermal manifestations. Here, we report the results of an extensive survey of both natural hot springs and production wells across Tunisia aimed at investigating the spatial distribution of the 3He/4He ratio and associated carbon isotopic compositions. With respect to helium isotopes, not unexpectedly, the lowest 3He/4He values (0.01-0.02 Ra) are associated with the old groundwaters of the “Continental Intercalaire” aquifer of the stable Saharan Platform. The 3He/4He values are equal to the crustal production ratio, with no detectable amount of mantle-derived 3He, in agreement with previous studies of helium isotopes in sedimentary basin, which conclude that tectonically-stable regions are essentially impermeable to mantle volatiles. The low 3He/4He domain extends to the entire Atlasic domain of central Tunisia. This Atlasic domain also displays the highest helium concentrations : along the Gafsa Fault, helium concentrations of 1777 and 4723 x 10-8 cm3STP/g (the highest value of our data set) are observed in the production wells of Sidi Ahmed Zarrouk. This emphasizes the role of deep tectonic features in channelling and transporting deep crustal volatiles to shallow levels. The eastern margin of Tunisia displays higher 3He/4He values indicative of a substantial mantle volatile input. The highest value is recorded in the carbo-gaseous mineral water of Ain Garci (2.4 Ra). This northeastern part of the African plate commonly referred to as the Pelagian block extends from Tunisia to Sicily and is characterized by strong extensional tectonics (Pantelleria rift zone) and present-day magmatic activity. This lithospheric stretching and decompressional mantle melts production in the central portion of the Pelagian Block may facilitate the transport of mantle helium through the thinned crust away from the rift zone across the existing network of fractures and deep faults. Samples were also collected for water chemistry, ?D, ?18O, and carbon isotopic composition. ?13C(TDC) data are highly heterogeneous (ranging from -11.2 to +2.9 ‰ vs. V-PDB), in particular, revealing a complex origin for total dissolved carbon (TDC) in groundwaters. We interpret these variable isotopic compositions as reflecting mixture of biogenically derived carbon with abiogenic (mantle-derived or metamorphic) CO2. A detailed discussion of the whole chemistry and isotopic data set will be presented and the results will be examined in relation to the geological and structural framework of Tunisia.

Fourré, E.; Aiuppa, A.; di Napoli, R.; Parello, F.; Gaubi, E.; Jean-Baptiste, P.; Allard, P.; Calabrese, S.; Ben Mammou, A.

2010-12-01

182

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

PubMed

The cadmium content in surface water is regulated by the last European Water Framework Directive to a maximum between 0.08 and 0.25 ?g L(-1) depending on the water type and hardness. Direct measurement of cadmium at this low level is not straightforward in real samples, and we hereby propose a validated method capable of addressing cadmium content below ?g L(-1) level in natural water. It is based on solid-phase extraction using TiO(2) nanoparticles as solid sorbent (0.05 g packed in mini-columns) to allow the separation and preconcentration of cadmium from the sample, combined to direct isotope dilution and detection by inductively coupled plasma mass spectrometry (ID-ICP-MS). The extraction setup is miniaturised and semi-automated to reduce risks of sample contamination and improve reproducibility. Procedural blanks for the whole measurement process were 5.3 ± 2.8 ng kg(-1) (1 s) for 50 g of ultrapure water preconcentrated ten times. Experimental conditions influencing the separation (including loading pH, sample flow rates, and acid concentration in the eluent) were evaluated. With isotope dilution the Cd recovery rate does not have to be evaluated carefully. Moreover, the mathematical model associated to IDMS is known, and provides transparency for the uncertainty propagation. Our validation protocol was in agreement with guidelines of the ISO/IEC 17025 standard (chapter 5.4.5). Firstly, we assessed the experimental factors influencing the final result. Secondly, we compared the isotope ratios measured after our separation procedure to the reference values obtained with a different protocol for the digested test material IMEP-111 (mineral feed). Thirdly, we analysed the certified reference material BCR-609 (groundwater). Finally, combined uncertainties associated to our results were estimated according to ISO-GUM guidelines (typically, 3-4% k = 2 for a cadmium content of around 100 ng kg(-1)). We applied the developed method to the groundwater and wastewater samples ERM-CA615 and BCR-713, respectively, and results agreed with certificate values within uncertainty statements. PMID:21858497

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

2011-11-01

183

Thermal equilibration times in very dilute superfluid mixtures of {sup 3}He in {sup 4}He  

SciTech Connect

The authors analyze the time dependence of the observed temperature difference {Delta}T(t) between the warmer and the colder parallel plates bounding a fluid layer (height h) after switching on and off the heat current through this layer. From the measurements of {Delta}T(t) in the steady state, the thermal conductivity {Kappa}{sub eff} is obtained after correction for the boundary resistance. Measurements include those for cell spacings 0.5

Murphy, D.; Meyer, H.

1993-04-01

184

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

185

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. PMID:21502374

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

2011-01-01

186

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

NASA Technical Reports Server (NTRS)

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

1993-01-01

187

Substoichiometric isotope dilution mass spectrometry of boron by the ion-pair extraction with halogenated salicyl alcohol derivatives and a quaternary ammonium salt.  

PubMed

Novel salicyl alcohol derivatives (H(2)X(n)sal), 5-bromo-, 3,5-dibromo-, and 3,5-diiodosalicyl alcohol which were abbreviated to H(2)Brsal, H(2)Br(2)sal, and H(2)I(2)sal, respectively, were synthesized and used for the selective extraction of boric acid. Boric acid was extracted with each H(2)X(n)sal into chlorobenzene containing trioctylmethylammonium chloride (TOMACl) as an ion-pair complex, TOMA·B(X(n)sal)(2), at a different pH range. The extraction constant (K(ex)) of boric acid was determined by the equilibrium analyses including the formation of hydrogen-bonded complex of each H(2)X(n)sal with TOMACl in the organic phase. The K(ex) values obtained by salicyl alcohol (H(2)sal) and its derivatives were decreased in the order of H(2)I(2)sal ? H(2)Br(2)sal > H(2)Brsal > H(2)sal. The most powerful extractant, H(2)I(2)sal, was employed for the substoichiometric extraction of boric acid, which was extracted at pH 5 - 9 with a substoichiometric amount of TOMACl in the presence of an excess of H(2)I(2)sal. The present substoichiometric separation method combined with the stable isotope dilution analysis using inductively coupled plasma mass spectrometry (ICP-MS) could be successfully applied to the determination of boron in a reference material of high-analysis compound fertilizer (FAMIC-A-08) without any correction as to the isotopic abundance. PMID:22451364

Morita, Keisuke; Imura, Hisanori

2012-01-01

188

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

USGS Publications Warehouse

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

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

1991-01-01

189

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

2013-09-01

190

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

PubMed

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

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

2001-03-01

191

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

PubMed

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

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

2015-01-01

192

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

SciTech Connect

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

Jaruga, Pawel [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States) [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Department of Clinical Biochemistry, Collegium Medicum, Nicolaus Copernicus University, Bydgoszcz (Poland); Xiao, Yan; Nelson, Bryant C. [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)] [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Dizdaroglu, Miral, E-mail: miral@nist.gov [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)] [Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)

2009-09-04

193

Synthesis and stable isotope dilution assay of ethanethiol and diethyl disulfide in wine using solid phase microextraction. Effect of aging on their levels in wine.  

PubMed

Ethanethiol and diethyl disulfide (DEDS) most often occurred at levels above their olfactive threshold in wines with nauseous sulfur-linked smells. As ethanethiol is very oxidizable and chemically reactive, a stable isotopic dilution analysis of both ethanethiol and its disulfide in wines using solid phase microextraction and GC-MS was developed. The latter involved the determination of the proportion of DEDS formed by oxidation of the thiol during the analysis conditions, which was obtained by the use of two differently labeled disulfide standards. An original synthesis of labeled ethanethiol standards in conditions minimizing oxidation was developed, and the corresponding labeled diethyl disulfides were obtained from these thiols. This analytical method was used to follow the levels of these sulfur compounds during aging in a young red wine spiked with ethanethiol and added with enological tannins, with or without oxygen addition. The total levels of these two sulfur compounds were shown to decrease steadily after 60 days of aging, up to 83%. The effect of oxygen sped this decrease, but the effect of enological tannins was very slight. Residual ethanethiol was detected in its disulfide form from approximately 36% in the nonoxygenated wines to 69% in the oxygenated samples. PMID:12405756

Belancic Majcenovic, Andrea; Schneider, Rémi; Lepoutre, Jean-Paul; Lempereur, Valérie; Baumes, Raymond

2002-11-01

194

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

PubMed

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

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

2014-08-01

195

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

PubMed Central

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

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

2014-01-01

196

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

PubMed

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

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

2004-08-25

197

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

PubMed

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

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

2014-03-01

198

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. PMID:18714297

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

2009-01-01

199

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

PubMed

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

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

2014-12-01

200

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

Microsoft Academic Search

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

Heather M. Stoll

2005-01-01

201

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

202

Isotope dilution sector-field inductively coupled plasma mass spectrometry combined with extraction chromatography for rapid determination of 241 Am in marine sediment samples: A case study in Sagami Bay, Japan  

Microsoft Academic Search

241Am is a useful tracer for understanding biogeochemical processes in the marine environment. 241Am also poses a potential radiation threat to human health due to the continuous increase of its concentration in the global\\u000a environment. We report a rapid analytical method for determining 241Am in marine sediments using isotope dilution sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) combined\\u000a with a

Jian Zheng; Masatoshi Yamada

2008-01-01

203

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

204

Thermal transport in very dilute /sup 3/He-/sup 4/He mixtures near the superfluid transition  

SciTech Connect

Measurements of the average thermal conductivity K/sub exp/ = hQ/..delta..T were made in the superfluid phase for dilute mixtures of /sup 3/He in /sup 4/He. Here h is the cell height, Q is the heat flux, and ..delta..T is the temperature difference across the fluid layer. The measurements were made over the impurity range 2 x 10/sup -9/ < X < 3 x 10/sup -2/, where X is the /sup 3/He molar concentration, and with heat fluxes 0.3 < Q < 160 ..mu..W/cm/sup 2/. K/sub exp/ was calculated assuming that the boundary resistance R/sub b/, measured for X < 10/sup -5/, to be independent of X for all X values investigated. For Q smaller than a well defined critical heat flux Q/sub c/(X), K/sub exp/ was found to be independent of Q and could be independent of the reduced temperature epsilon = (T - T/sub lambda/)T/sub lambda/ for absolute value of epsilon < T/sub lambda/. The value of K/sub eff/ extrapolated to T/sub lambda/ was found to depart from the prediction K/sub lambda/ varies as X/sup -1/ for X < 10/sup -3/, tending instead to a weaker divergence K/sub lambda/ approx.X/sup -a/ with a approx. =0.08. For Q > Q/sub c/, a nonlinear regime is entered. For X approximately less than or equal to 10/sup -6/, the measurements with the available temperature resolution are limited to the nonlinear regime, but can be extrapolated is not the linear regime for X > 2 x 10/sup -7/. A finite conductivity as X ..-->.. 0 is not excluded by the data. The results fr K/sub exp/(Q), Q/sub c/(X), and K/sub eff/(X) are found to be internally consistent. The data obtained in the nonlinear regime are presented, and unexplained phenomena observed in this regime are discussed.

Dingus, M.L.

1986-01-01

205

Targeted stable-isotope dilution GC-MS/MS analysis of the endocannabinoid anandamide and other fatty acid ethanol amides in human plasma.  

PubMed

Anandamide (arachidonoyl ethanol amide, AEA) is an endocannabinoid, acting on CB1 and CB2 receptors. Elevated plasma AEA concentrations in humans have been associated amongst others with obesity, psychological disorders and miscarriage. The occurrence in human plasma of ethanol amides of other unsaturated and saturated fatty acids, including oleic acid and palmitic acid, has also been reported. Most data available on anandamide and other fatty acid ethanol amides (FAEA) until now have been generated by using the LC-MS/MS methodology. Here, we describe a stable-isotope dilution GC-MS/MS method for the quantitative determination of AEA, oleic acid ethanol amide (OEA) and palmitic acid ethanol amide (PEA) in human plasma using their stable-isotope labeled analogs as internal standards. Other FAEA were found in plasma and their concentration was estimated. The present method involves a single solvent extraction of FAEA and their internal standards from plasma (50-1000 microl) with toluene, derivatization to the pentafluorobenzamide pentafluoropropionyl derivatives (FAEA-PFBz-PFP), and simultaneous quantification by selected reaction monitoring of the carboxylate anions produced by collision-induced dissociation of the parent ions [M-PFBz](-). The present method was fully validated for anandamide. Thus, accuracy and imprecision of the method were within the range of 100+/-20% and less than 20%, respectively, in the range investigated (0-4 nM). Mean overall recovery was 90+/-3%. The LOQ and LOD values of the method were determined to be 0.25 nM of added AEA in plasma samples and 400 amol of injected AEA-PFBz-PFP derivative, respectively. In plasma of 16 healthy individuals AEA concentration was measured to be 1.35+/-0.32 nM. This finding is concordant to literature AEA plasma concentrations as measured by LC-MS/MS. The plasma concentrations of OEA, PEA and other FAEA are higher than that of AEA. This GC-MS/MS method is straightforward, accurate, precise, highly specific for FAEA and useful in basic and clinical research. PMID:19414283

Zoerner, Alexander A; Gutzki, Frank M; Suchy, Maria T; Beckmann, Bibiana; Engeli, Stefan; Jordan, Jens; Tsikas, Dimitrios

2009-09-15

206

Application of isotope dilution analysis for the evaluation of extraction conditions in the determination of total selenium and selenomethionine in yeast-based nutritional supplements.  

PubMed

Isotope dilution analysis (IDA) has been used to quantify total selenium, total solubilized selenium, and the selenomethionine (SeMet) amount in yeast and yeast-based nutritional supplements after acid microwave digestion and different enzymatic extraction procedures. For this purpose, both a (77)Se-enriched SeMet spike, previously synthesized and characterized in our laboratory, and a (77)Se(VI) spike were used. In the analysis of the nutritional supplements, the SeMet spike was added to the sample and extracted under different conditions, and the (78)Se/(77)Se and (80)Se/(77)Se isotope ratios were measured as peak area ratios after high-performance liquid chromatography (HPLC) separation and inductively coupled plasma mass spectrometry (ICP-MS) detection. The formation of SeH(+) and mass discrimination were corrected using a natural SeMet standard injected every three samples. Similarly, total solubilized selenium was measured in the extracts after enzymatic hydrolysis using the (77)Se-enriched SeMet as a spike by direct nebulization without a chromatographic separation. To establish a mass balance, total selenium was also determined by IDA-ICP-MS on the yeast tablets after microwave digestion using (77)Se(VI) as a spike. Results showed that all enzymatic procedures tested were able to solubilize total selenium quantitatively from the solid. However, the recovery for the species SeMet, the major selenium compound detected, was seriously affected by the enzymatic procedure employed and also by the matrix composition of the supplement evaluated. For the yeast sample, SeMet recovery increased from 68 to 76% by the combined use of driselase and protease. For the nutritional supplements, the two most effective procedures appeared to be protease and driselase/protease, with a SeMet recovery ranging from 49 to 63%, depending upon the supplement evaluated. In the case of in vitro gastrointestinal enzymolysis, the results obtained showed 26-37% SeMet recovery, while the rest of selenium was solubilized as other unknown compounds (probably Se-containing peptides). PMID:16506800

Hinojosa Reyes, L; Marchante-Gayón, J M; García Alonso, J I; Sanz-Medel, A

2006-03-01

207

An update on the Thermal Gradient Induced Non -Mass-Dependent Isotope Fractionation  

NASA Astrophysics Data System (ADS)

Mass flow and compositional gradient (elemental and isotope separation) occur when fluid(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been experimentally and theoretically investigated for more than a century, although there has not been a satisfactory theory to date. Nevertheless, theories predict that when dealing with a multi-isotope system, such as O16-O17-O18, S32-S33-S34-S36, or Ne20-Ne21-Ne22, the mass difference is the only term in the thermal diffusion separation factors that distinguish one isotope pair from another. Thus a mass dependent relationship is expected. For O-bearing molecules the ?17O/ ? 18O is expected to be at 0.5 to 0.515, and for S-bearing molecules the ?33S/ ? 34S at 0.5 to 0.508, where ? is isotope fractionation factor between cold and warm reservoirs. We recently reported that thermal diffusion generates non-mass dependent (NMD) isotope fractionation for low-pressure O2 and SF6 gases. The observed NMD phenomenon in the simple thermal-diffusion experiments demands quantitative validation and theoretical explanation. It was suggested that additional (not mass related) terms need to be theoretically considered in the order to account for the observations. In addition to the pressure and temperature dependency illustrated in our earlier report, the role of turbulence, batch gas effects, and whether it is only a transient, non-equilibrium effect have been examined in this study. We report here new results on low-pressure O2 gas thermal diffusion. (1) In a purely diffusive vertical two-bulb setting with colder reservoir at lower position, time course experiments showed that the NMD effect persists after the system reaches isotopic steady state between warmer and colder compartments, suggesting that the effect is not a transient one. (2) When the average temperature approaching condensation point for O2, the 17O switches to migrating preferentially towards the warmer reservoir instead of the colder one. (3) The NMD effects are observed within a range of turbulence in a light-bulb-type system with a hot center (~700C) and a cold wall (-20C).(4) When batch gases, e.g. N2, He, are added, the NMD effect for O2 does not vanish but its temperature and pressure dependencies are affected. Our new data further indicate that the NMD effect is largely controlled by the nature of molecular collisions during thermal diffusion and the effect may be considerable in natural environments, e.g. planetary atmosphere and interstellar nebulae.

Sun, T.; Niles, P. B.; Bao, H.; Socki, R. A.

2012-12-01

208

Simple and rapid analytical method for detection of amino acids in blood using blood spot on filter paper, fast-GC/MS and isotope dilution technique.  

PubMed

A simple and rapid method for quantitative analysis of amino acids, including valine (Val), leucine (Leu), isoleucine (Ile), methionine (Met) and phenylalanine (Phe), in whole blood has been developed using GC/MS. In this method, whole blood was collected using a filter paper technique, and a 1/8 in. blood spot punch was used for sample preparation. Amino acids were extracted from the sample, and the extracts were purified using cation-exchange resins. The isotope dilution method using ²H?-Val, ²H?-Leu, ²H?-Met and ²H?-Phe as internal standards was applied. Following propyl chloroformate derivatization, the derivatives were analyzed using fast-GC/MS. The extraction recoveries using these techniques ranged from 69.8% to 87.9%, and analysis time for each sample was approximately 26 min. Calibration curves at concentrations from 0.0 to 1666.7 ?mol/l for Val, Leu, Ile and Phe and from 0.0 to 333.3 ?mol/l for Met showed good linearity with regression coefficients=1. The method detection limits for Val, Leu, Ile, Met and Phe were 24.2, 16.7, 8.7, 1.5 and 12.9 ?mol/l, respectively. This method was applied to blood spot samples obtained from patients with phenylketonuria (PKU), maple syrup urine disease (MSUD), hypermethionine and neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD), and the analysis results showed that the concentrations of amino acids that characterize these diseases were increased. These results indicate that this method provides a simple and rapid procedure for precise determination of amino acids in whole blood. PMID:20971689

Kawana, Shuichi; Nakagawa, Katsuhiro; Hasegawa, Yuki; Yamaguchi, Seiji

2010-11-15

209

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

PubMed

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

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

2014-10-21

210

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

211

[Determination of 18 pesticide residues in red wine by ultra high performance liquid chromatography-high resolution mass spectrometry with isotope dilution technique].  

PubMed

A method for the simultaneous determination of 18 pesticide residues in red wine was developed using ultra high performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) with isotope dilution technique. The red wine samples were extracted with acetonitrile, and the extracts were cleaned up with dispersive solid phase extraction (dSPE) using the mixture of N-propyl ethylene diamine (PSA) and C18 powder as sorbent. The extracted components were separated on a BEH C18 column by gradient elution. The qualitative and quantitative analyses were operated under full scan/data dependent MS/MS (ddms2) and targeted selective ion monitoring (tSIM) by high resolution mass spectrometry, respectively. Carbendazim-D4, chlorpyrifos-D10, imidacloprid-D4, methoxyfenozide-D9, pyrimethanil-D5 and tebuconazole-D6 were used as the internal standards to reduce the matrix effects. The response of each pesticide showed a good linearity in the range of 0.5-50 microg/kg with the correlation coefficient more than 0.999. The limits of detection and quantification for the 18 pesticides in the spiked blank red wine were 0.5 microg/kg and 1.0 microg/kg, respectively. The recovery results with spiked blank red wine samples at the levels of 1 to 40 microg/kg were satisfactory with average recoveries of 85.4% - 117.9% and the RSDs of 0.5%-6.1%. The method was applied for the determination of the red wine real samples from the market. Carbendazim, imidacloprid, pyrimethanil, tebuconazole and triadimenol were detected in the samples. The results show that the method is suitable for the rapid screening and quantitative analysis of pesticide residues in red wine. PMID:25185308

Chen, Dawei; Lü, Bing; Ding, Hao; Zou, Jianhong; Yang, Xin; Zhao, Yunfeng; Miao, Hong

2014-05-01

212

Determination of the cardiac glycosides digoxin and digitoxin by liquid chromatography combined with isotope-dilution mass spectrometry (LC-IDMS)--a candidate reference measurement procedure.  

PubMed

This article describes a method of high analytical sensitivity, reproducibility and trueness for the determination of digoxin and digitoxin in serum or plasma at therapeutic levels using a combination of high-pressure liquid chromatography (HPLC), isotope-dilution mass spectrometry (IDMS) and caesium-adduct formation. A method for threefold deuterium substitution in the glycosides was developed, which could be performed within 24 hours without distillation giving yields > 98% of the theoretical value. Extraction from a serum or plasma matrix was performed using a liquid-phase extraction with ammonium acetate buffer/tertiary butylmethyl ether/ethyl acetate at pH 9.5. The HPLC-separation used a 10 x 2 mm LiChrospher RP-18 5 microm guard column in combination with a 125 x 2 mm main column of the same material and a gradient containing methanol, caesium ions and formic acid. Quantification of digoxin and digitoxin was made with IDMS using deuterated internal standards and the system run in single ion monitoring (SIM) mode. The methods had a lower limit of determination of 0.25 microg/l for digoxin and digitoxin, a trueness between 97.5 and 104% for digoxin and between 98 and 101% for digitoxin, respectively and had a coefficient of variation of less than 3% in the therapeutic range for both glycosides. Maximally 1 ml serum or plasma was needed for the procedure. The method is used to set target values for materials used in external quality assessment surveys (EQAS) run by INSTAND as part of a national EQAS-programme.) PMID:12908733

Kaiser, Patricia; Kramer, Udo; Meissner, Dieane; Kress, Michael; Wood, William Graham; Reinauer, Hans

2003-01-01

213

Effects of dispersion, correction term, and isotopes on the thermal conductivity of LiF crystal  

NASA Astrophysics Data System (ADS)

We have adapted the Callaway-Holland model so that the dispersive effect and correction term ?c can be included in the theoretical analysis of the lattice thermal conductivity of LiF over the temperature range 1 300 K, for varying concentration of the isotopic content 7Li. Some different empirical expressions for different three-phonon relaxation rates ?-13ph for the entire temperature range have been proposed. Anisotropic and dispersive point defect scattering relaxation rate for LiF is also introduced. Our main findings are as follows: ?c even for moderate isotopic concentration of 7Li in LiF gives sizable contribution at temperatures where ?-13ph umklapp U processes dominate, which was considered to be negligible by earlier workers; contribution of longitudinal phonons is substantial beyond the conductivity maximum; theoretical value of the isotope scattering parameter A1 has to be increased only by 1.8 1.9 times in going from 50.8% to 97.2% of 7Li content as against 5 times increase taken by Callaway and Baeyer; and in conformity with Callaway’s findings the presence of small chemical impurities has to be assumed to explain the phonon-conductivity data of the isotopically pure sample (7Li 99.99%) of LiF. Theoretically justified parameters are used to obtain excellent agreement with the results reported by Thacher as well as by Berman and Brock.

Singh, B. K.; Roy, M. K.; Menon, V. J.; Sood, K. C.

2003-01-01

214

Deuterium isotopic exchangeability of resin and amber at low thermal stress under hydrous conditions  

NASA Astrophysics Data System (ADS)

Hydrous deuterium-exchange experiments have shown that a significant fraction of the original D/H composition of bulk kerogens, bitumens and expelled oils may participate in isotopic exchange reactions during burial diagenesis. However, it is unknown to what extent plant-derived secondary metabolites, namely resins and their fossil counterpart amber, exchange hydrogen isotopes following their biosynthesis. This situation hinders the application of resin D/H measurements in paleoenvironmental reconstruction. Here, we assess explicitly hydrogen exchange in resins and ambers using a series of immersion experiments in deuterated (D-enriched) waters over a period of several months at several temperatures. We are especially interested in assessing whether significant H-isotopic exchange occurs between resins and meteoric waters during early thermal maturation and polymerization. At 90°C, equivalent to ~3km of burial in most diagenetic regimes, modern conifer and angiosperm resins have an average post-metabolic H exchange of 4.6%, compared to only 1.1% for mature, polymerized ambers. At 55°C the degree of exchange is considerably lower: 1.9% for resins and 0.6% for ambers. These results indicate that most D/H isotopic exchange occurs prior to polymerization reactions, thereby confirming that D/H measurements from amber constitute a potentially sensitive proxy for environmental change.

Gonzalez, G.; Tappert, R.; Wolfe, A. P.; Muehlenbachs, K.

2012-04-01

215

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

216

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

SciTech Connect

The property of selective temperature dependence of adsorption and desorption of hydrogen isotopes by palladium is used for isotope separation. A proposal to use natural circulation of nitrogen to alternately heat and cool a packed bed of palladium coated beads is under active investigation, and a device consisting of two interlocking natural convection loops is being designed. A transient numerical model of the device has been developed to aid the design process. It is a one-dimensional finite-difference model, using the Boussinesq approximation. The thermal inertia of the pipe walls and other heat structures as well as the heater control logic is included in the model. Two system configurations were modeled and results are compared.

SHADDAY, MARTIN

2005-07-12

217

ISOTOPES  

E-print Network

over ammonia-hydrogen exchange include higher separationAmmonia-hydrogen Exchange This reaction has both a larger separationammonia) fraction with which it is in isotopic equilibrium, necessitating the separation

Lederer, C. Michael

2013-01-01

218

Gas and isotope chemistry of thermal features in Yellowstone National Park, Wyoming  

USGS Publications Warehouse

This report presents 130 gas analyses and 31 related water analyses on samples collected from thermal features at Yellowstone between 2003 and 2009. An overview of previous studies of gas emissions at Yellowstone is also given. The analytical results from the present study include bulk chemistry of gases and waters and isotope values for water and steam (delta18O, dealtaD), carbon dioxide (delta13C only), methane (delta13C only), helium, neon, and argon. We include appendixes containing photos of sample sites, geographic information system (GIS) files including shape and kml formats, and analytical results in spreadsheets. In addition, we provide a lengthy discussion of previous work on gas chemistry at Yellowstone and a general discussion of the implications of our results. We demonstrate that gases collected from different thermal areas often have distinct chemical signatures, and that differences across the thermal areas are not a simple function of surface temperatures or the type of feature. Instead, gas chemistry and isotopic composition are linked to subsurface lithologies and varying contributions from magmatic, crustal, and meteoric sources.

Bergfeld, Deborah; Lowenstern, Jacob B.; Hunt, Andrew G.; Shanks, W.C. Pat, III; Evans, William

2011-01-01

219

RELAP5 model of the high flux isotope reactor with low enriched fuel thermal flux profiles  

SciTech Connect

The High Flux Isotope Reactor (HFIR) currently uses highly enriched uranium (HEU) fabricated into involute-shaped fuel plates. It is desired that HFIR be able to use low enriched uranium (LEU) fuel while preserving the current performance capability for its diverse missions in material irradiation studies, isotope production, and the use of neutron beam lines for basic research. Preliminary neutronics and depletion simulations of HFIR with LEU fuel have arrived to feasible fuel loadings that maintain the neutronics performance of the reactor. This article illustrates preliminary models developed for the analysis of the thermal-hydraulic characteristics of the LEU core to ensure safe operation of the reactor. The beginning of life (BOL) LEU thermal flux profile has been modeled in RELAP5 to facilitate steady state simulation of the core cooling, and of anticipated and unanticipated transients. Steady state results are presented to validate the new thermal power profile inputs. A power ramp, slow depressurization at the outlet, and flow coast down transients are also evaluated. (authors)

Banfield, J.; Mervin, B.; Hart, S.; Ritchie, J.; Walker, S.; Ruggles, A.; Maldonado, G. I. [Dept. of Nuclear Engineering, Univ. of Tennessee Knoxville, Knoxville, TN 37996-2300 (United States)

2012-07-01

220

An osmium isotope excursion associated with the Late Paleocene thermal maximum: Evidence of intensified chemical weathering  

NASA Astrophysics Data System (ADS)

In the latest Paleocene an abrupt shift to more negative ?13C values has been documented at numerous marine and terrestrial sites [Bralower et al., 1997; Cramer et al., 1999; Kaiho et al., 1996; Kennett and Stott, 1991; Koch et al., 1992; Stott et al., 1996; Thomas and Shackleton, 1996; Zachos et al., 1993]. This carbon isotope event (CIE) is coincident with oxygen isotope data that indicate warming of surface waters at high latitudes of nearly 4°-6°C [Kennett and Stott, 1991] and more moderate warming in the subtropics [Thomas et al., 1999]. Here we report 187Os/188Os isotope records from the North Atlantic and Indian Oceans which demonstrate a >10% increase in the 187Os/188Os ratio of seawater coincident with the late Paleocene CIE. This excursion to higher 187Os/188Os ratios is consistent with a global increase in weathering rates. The inference of increased chemical weathering during this interval of unusual warmth is significant because it provides empirical evidence supporting the operation of a feedback between chemical weathering rates and warm global climate, which acts to stabilize Earth's climate [Walker et al., 1981]. Estimates of the duration of late Paleocene CIE [Bains et al., 1999; Bralower et al., 1997; Norris and Röhl, 1999; Röhl et al., 2000] in conjunction with the Os isotope data imply that intensified chemical weathering in response to warm, humid climates can occur on timescales of 104-105 years. This interpretation requires that the late Paleocene thermal maximum Os isotope excursion be produced mainly by increased Os flux to the ocean rather than a transient excursion to higher 187Os/188Os ratios in river runoff. Although we argue that the former is more likely than the latter, we cannot rule out significant changes in the 187Os/188Os ratio of rivers.

Ravizza, G.; Norris, R. N.; Blusztajn, J.; Aubry, M.-P.

2001-04-01

221

Light-stable-isotope studies of spring and thermal waters from the Roosevelt Hot Springs and Cove Fort/Sulphurdale Thermal areas and of clay minerals from the Roosevelt Hot Springs thermal area  

SciTech Connect

The isotopic compositions of hydrogen and oxygen have been determined for spring waters and thermal fluids from the Roosevelt Hot Springs and Cove Fort-Sulphurdale thermal areas, for clay mineral separates from shallow alteration of the acid-sulfate type in the Roosevelt Hot Springs area, and for spring and well waters from the Goshen Valley area of central Utah. The water analyses in the Roosevelt Hot Springs thermal area confirm the origin of the thermal fluids from meteoric water in the Mineral Range. The water analyses in the Cove Fort-Sulphurdale thermal area restrict recharge areas for this system to the upper elevations of the Pavant and/or Tushar Ranges. The low /sup 18/O shift observed in these thermal fluids (+0.7 permil) implies either high water/rock ratios or incomplete isotope exchange or both, and further suggests minimal interaction between the thermal fluid and marble country rock in the system. Hydrogen and oxygen-isotope data for clay mineral separates from shallow alteration zones in the Roosevelt Hot Springs thermal system suggest that the fluids responsible for the shallow acid-sulfate alteration were in part derived from condensed steam produced by boiling of the deep reservoir fluid. The isotope evidence supports the chemical model proposed by Parry et al. (1980) for origin of the acid-sulfate alteration at Roosevelt Hot Springs. The isotope analyses of spring and well waters from the Goshen Valley area indicate only a general correlation of isotope composition, salinity and chemical temperatures.

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

1981-10-01

222

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

2011-01-01

223

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

224

Analysis of pesticides and metabolites in Spanish surface waters by isotope dilution gas chromatography/mass spectrometry with previous automated solid-phase extraction Estimation of the uncertainty of the analytical results.  

PubMed

A method based on isotope dilution gas chromatography/mass spectrometry (GC/MS) with automated solid-phase extraction (SPE) is described for the analysis of 32 pesticides and metabolites in surface waters. This approach consist in the use of nine isotopically labelled representative pesticides as internal standards, which allows high accuracy (trueness and precision) and sensitivity for most analysed compounds, as it is required for isotope dilution-based methods. Uncertainties associated with pesticide determination in real samples were estimated using quality assurance/quality control (QA/QC) data. For most pesticides expanded uncertainty was below 40%, according to the commonly established requirements for analytical results. Ninety three Spanish surface waters collected in June-July and September-November 2004 were analysed. Concentration and occurrence of pesticides were evaluated. These parameters were higher in the summer than in the autumn period. In summer four pesticides were found in more than 50% of the analysed samples and four compounds were detected above the concentration level of 1 microg/l (atrazine, terbutylazine, 3,4-dichloroaniline and fenitrothion), while in autumn percentage of detection was below 50% for all pesticides and only one compound (terbutylazine) exceeded 1 microg/l. PMID:16962600

Planas, Carles; Puig, Alejandra; Rivera, Josep; Caixach, Josep

2006-10-27

225

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

226

Quantification of o,o'-dityrosine, o-nitrotyrosine, and o-tyrosine in cat urine samples by LC/ electrospray ionization-MS/MS using isotope dilution.  

PubMed

Quantification of o-tyrosine, o-nitrotyrosine, and o,o'dityrosine from cat urine samples was achieved by LC/ electrospray ionization-MS/MS (LC/ESI-MS/MS) using an isotope dilution technique in multiple reaction monitoring mode before butylation of o,o'-dityrosine and after butylation of o-tyrosine and o-nitrotyrosine. This novel approach of amino acids butylation enhanced the MS response by a factor of 7-fold for o-tyrosine and 6-fold for o-nitrotyrosine and decreased the overall chemical background noise. Butylation of o,o'-dityrosine resulted in a lower MS response as a result of the formation of both mono- and doubly butylated species. The mean recovery for the oxidized amino acids was estimated at 73 +/- 2%. The limits of quantitation of NO2-Tyr butyl ester, o-Tyr butyl ester, and di-Tyr in cat urine samples were calculated at 14.5, 28.2 and 140.9 nM, respectively. The oxidized amino acids levels in cat urine extracts ranged from 157 to 250 ng/day for o-Tyr and from 3,289 to 11,803 ng/day for di-Tyr. NO2-Tyr was found in only two urine extracts at levels below 58 ng/day. A certain trend of correlation was observed between o,o'-dityrosine and o-tyrosine when comparing these values against their respective creatinine amounts. A comparison of the data gathered from the ThermoFinnigan TSQ 7000 and Micromass Q-TOF instruments revealed several advantages of using the Q-TOF regarding the exact mass measurement, a lower ion suppression effect and the possibility to perform analyses in full scan product ion mode. These results demonstrate that a Q-TOF instrument can be a good alternative to classical triple quadrupole for quantitative purposes on a relatively small linear dynamic range (4 orders of magnitude for the Q-TOF, as compared to 6 for the triple quadrupole). PMID:12553760

Marvin, Laure Féline; Delatour, Thierry; Tavazzi, Isabelle; Fay, Laurent Bernard; Cupp, Carolyn; Guy, Philippe Alexandre

2003-01-15

227

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. PMID:21962213

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

2013-01-01

228

Thermal conductivity of silicon bulk and nanowires: Effects of isotopic composition, phonon confinement, and surface roughness  

NASA Astrophysics Data System (ADS)

We present a rigorous analysis of the thermal conductivity of bulk silicon (Si) and Si nanowires (Si NWs) which takes into account the exact physical nature of the various acoustic and optical phonon mechanisms. Following the Callaway solution for the Boltzmann equation, where resistive and nonresistive phonon mechanisms are discriminated, we derived formalism for the lattice thermal conductivity that takes into account the phonon incidence angles. The phonon scattering processes are represented by frequency-dependent relaxation time. In addition to the commonly considered acoustic three-phonon processes, a detailed analysis of the role of the optical phonon decay into acoustic phonons is performed. This optical phonon decay mechanism is considered to act as acoustic phonon generation rate partially counteracting the acoustic phonon scattering rates. We have derived the analytical expression describing this physical mechanism which should be included in the general formalism as a correction to the resistive phonon-point-defects and phonon-boundary scattering expressions. The phonon-boundary scattering mechanism is taken as a function of the phonon frequency, incidence angles, and surface roughness. The importance of all the mechanisms we have involved in the model is demonstrated clearly with reference to reported data regarding the isotopic composition effect in bulk Si and Si NW samples. Namely, our model accounts for previously unexplained experimental results regarding (i) the isotope composition effect on the thermal conductivity of bulk silicon reported by Ruf et al. [Solid State Commun. 115, 243 (2000)], (ii) the size effect on ?(T ) of individual Si NWs reported by Li et al. [Appl. Phys. Lett. 83, 2934 (2003)], and (iii) the dramatic decrease in the thermal conductivity for rough Si NWs reported by Hochbaum et al. [Nature (London) 451, 163 (2008)].

Kazan, M.; Guisbiers, G.; Pereira, S.; Correia, M. R.; Masri, P.; Bruyant, A.; Volz, S.; Royer, P.

2010-04-01

229

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

230

Noble gas isotopic signatures in thermal waters of the Dead Sea Transform  

NASA Astrophysics Data System (ADS)

Noble gas isotope composition in thermal groundwater provides information about crust-mantle interactions, in form of geotectonic activity, volcanism and advective heat transfer. The knowledge of the geothermal state of the crust is useful for the indication of thermal energy resources, which are of significant environmental and economic importance. In this study, groundwater samples were collected in Israel and Jordan in 2012, along the east and west sides of the central Dead Sea Transform. The helium isotope ratio, 3He/4He, is a well-established marker to discriminate three different geochemical reservoirs: Atmosphere, crust and mantle. The distinct isotope ratios in each reservoir make it possible to separate the total helium concentration in groundwater into mantle, crustal (radiogenic) and atmospheric components. The 3He/4He ratios of all sampled waters exceed the typical crustal ratio, indicating contributions of mantle-derived helium to the total helium concentration. Most of the samples contain less than 3% atmospheric helium, whereas the mantle-derived helium component ranges from 1% to 61%. In Israel, a clear trend is observed. Samples from the northern parts of the sampling area show higher 3He/4He ratios than samples from southern parts. These findings confirm Torfstein et al. [1], who analyzed thermal groundwaters from Israel. In our data from Jordan, however, no north-south trend is seen, but a local anomaly is observed in the area between the Dead Sea and the Sea of Galilee, with a 3He/4He ratio that is 5 times higher than the atmospheric 3He/4He ratio. Moreover, some samples from North Jordan exhibit only minor mantle contributions, compared to the samples from the north of Israel. Our results emphasize the importance of local faulting patterns, which enable a better transfer of mantle derived helium into the shallow crust. In addition to helium, the origin of CO2 in the water was examined. Measurements of ?13C suggest that CO2 originates from metamorphic processes rather than from the mantle. Furthermore, ?18O and ?2H data indicate a water reservoir temperature above 100°C only at one location. References: [1] Torfstein, A. et al. 2013: Helium isotopes in Dead Sea Transform waters. Chemical Geology, 352, 188-201

Tsur, Neta; Kaudse, Tillmann; Aeschbach-Hertig, Werner

2014-05-01

231

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

232

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

SciTech Connect

The United States Department of Energy has initiated numerous activities to identify strategies to disposition various excess fissile materials. Two such materials are the off-specification highly enriched uranium-235 oxide powder and the uranium-233 contained in unirradiated nuclear fuel both currently stored at the Idaho National Engineering and Environmental Laboratory. This report describes the development of a technology that could dilute these materials to levels categorized as low-enriched uranium, or further dilute the materials to a level categorized as waste. This dilution technology opens additional pathways for the disposition of these excess fissile materials as existing processing infrastructure continues to be retired.

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

2004-02-01

233

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

NASA Astrophysics Data System (ADS)

Radium isotope activities ( 226Ra, 228Ra, and 224Ra), chemical compositions, and sulfur isotope ratios in sulfate were determined for water samples from thermal areas in Yellowstone National Park, Wyoming. Activities of 226Ra in these waters range from <0.2 to 37.9 dpm/kg. Activity ratios of 228Ra /226Ra range from 0.26 to 14.2, and those of 224Ra /228Ra range from 0.73 to 3.1. Radium concentrations are inversely correlated with aquifer equilibration temperatures (estimated from dissolved silica concentrations), while[ Ra/Ba] aq and 228Ra /226Ra activity ratios depend upon U/Ba and Th/U ratios in aquifer rocks. Major controls on Ra concentration in Yellowstone thermal waters are inferred to be (1) barite saturation (at Morris Geyser Basin, Mammoth Hot Springs, and other northern areas) and (2) zeolitewater ion exchange (at Upper Geyser Basin). The data are consistent with a model in which (1) radium and barium are supplied to water by bulk dissolution of aquifer rock, and (2) chemical equilibration of water with rock is rapid relative to the 1602 year half-life of 226Ra. The 228Ra /226Ra activity ratios of the waters may in some cases reflect surface enrichments of 232Th and/or may indicate that ?-recoil input of 228Ra is rapid relative to water-rock chemical equilibration. Activity ratios of 224Ra /228Ra indicate a nearly ubiquitous 224Ra excess that generally increases with decreasing pH. Near-surface (?100 m) thermal water flow velocities at Mammoth Hot Springs are estimated from 224Ra /228Ra variation to be ? 1 m h -1.

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

1993-03-01

234

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

235

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

236

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

USGS Publications Warehouse

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

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

1977-01-01

237

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

238

A structural evaluation of the tungsten isotopes via thermal neutron capture  

E-print Network

Total radiative thermal neutron-capture $\\gamma$-ray cross sections for the $^{182,183,184,186}$W isotopes were measured using guided neutron beams from the Budapest Research Reactor to induce prompt and delayed $\\gamma$ rays from elemental and isotopically-enriched tungsten targets. These cross sections were determined from the sum of measured $\\gamma$-ray cross sections feeding the ground state from low-lying levels below a cutoff energy, E$_{\\rm crit}$, where the level scheme is completely known, and continuum $\\gamma$ rays from levels above E$_{\\rm crit}$, calculated using the Monte Carlo statistical-decay code DICEBOX. The new cross sections determined in this work for the tungsten nuclides are: $\\sigma_{0}(^{182}{\\rm W}) = 20.5(14)$ b and $\\sigma_{11/2^{+}}(^{183}{\\rm W}^{m}, 5.2 {\\rm s}) = 0.177(18)$ b; $\\sigma_{0}(^{183}{\\rm W}) = 9.37(38)$ b and $\\sigma_{5^{-}}(^{184}{\\rm W}^{m}, 8.33 \\mu{\\rm s}) = 0.0247(55)$ b; $\\sigma_{0}(^{184}{\\rm W}) = 1.43(10)$ b and $\\sigma_{11/2^{+}}(^{185}{\\rm W}^{m}, 1.67 ...

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

2014-01-01

239

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

SciTech Connect

Simulation models for steady state thermal hydraulics analyses of Oak Ridge National Laboratory s High Flux Isotope Reactor (HFIR) have been developed using the COMSOL Multiphysics simulation software. A single fuel plate and coolant channel of each type of HFIR fuel element was modeled in three dimensions; coupling to adjacent plates and channels was accounted for by using periodic boundary conditions. The standard k- turbulence model was used in simulating turbulent flow with conjugate heat transfer. The COMSOL models were developed to be fully parameterized to allow assessing impacts of fuel fabrication tolerances and uncertainties related to low enriched uranium (LEU) fuel design and reactor operating parameters. Heat source input for the simulations was obtained from separate Monte Carlo N Particle calculations for the axially non-contoured LEU fuel designs at the beginning of the reactor cycle. Mesh refinement studies have been performed to calibrate the models against the pressure drop measured across the HFIR core.

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

2012-01-01

240

Neodymium and strontium isotopic study of Australasian tektites - New constraints on the provenance and age of target materials  

Microsoft Academic Search

The Nd and Sr isotopic compositions of Australasian tectites (including two flanged Australian tectites, two low-SiO2 Muong Nong-type tectites, and three high-SiO2 Muong Nong-type tectites) and the Nd, Sm, Sr, and Rb concentrations were investigated by isotope-dilution thermal ionization mass spectrometry, and the Sm-Nd and Rb-Sr isotope systematics were used to study the characteristics of the parental material. It is

Joel D. Blum; D. A. Papanastassiou; G. J. Wasserburg; C. Koeberl

1992-01-01

241

On the Optical, Thermal, and Vibrational Properties of Nano-ZnO:Mn, A Diluted Magnetic Semiconductor  

Microsoft Academic Search

Nano-zinc oxide and Mn-doped zinc oxide were synthesized by a chemical process, and the average size of the particles observed\\u000a was 35 nm for nano-ZnO. Optical and thermal characterizations were carried out by means of photoluminescence and photoacoustic\\u000a spectroscopy. It was found that nano-ZnO has a thermal diffusivity one order of magnitude larger than bulk ZnO. Similarly,\\u000a a less explored localized

P. Vinotha Boorana Lakshmi; K. Ramachandran

2007-01-01

242

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

243

Polarized Raman spectra for the full range of isotopic dilution for ice I/sub c/ and amorphous ice: Mixtures of intact H/sub 2/O and D/sub 2/O  

SciTech Connect

The 90 K polarized Raman scattering of thin films of ice I/sub c/ and ice I/sub a/ containing mixtures of intact H/sub 2/O and D/sub 2/O have been measured using the interference-enhanced internal-reflection technique. The effects of isotopic dilution reported for samples with a D/sub 2/O content ranging from 0% to 100% are consistent with the commonly held view that intermolecular coupling produces collective vibrational modes that determine the appearance of the Raman spectra in the stretching mode region of crystalline and amorphous ice. The convergence of bands produced by the collective modes on the isotopically decoupled mode frequencies of both ..nu../sub 1/ and ..nu../sub 3/ is displayed in this study. Bands at 3323 and 3209 cm/sup -1/ in the anisotropic scattering of protiated ice I/sub c/ are shown to converge on the decoupled antisymmetric stretch frequency of 3370 cm/sup -1/. The gradual shift of the dominant isotropic scattering at 3085 cm/sup -1/ towards the frequency of the decoupled ..nu../sub 1/ mode is also revealed, with bands for the first stage in the evolution of the in-phase ..nu../sub 1/ collective mode, i.e., the neighbor coupled mode, observed at 3180 (H/sub 2/O) and 2340 cm/sup -1/ (D/sub 2/O). The data also suggest that the shift of the in-phase coupled ..nu../sub 1/ band begins with the first traces of added diluent, a behavior that indicates a macroscopic extension of the resonant coupling for both crystalline and amorphous ice. By contrast, the insensitivity of isotropic scattering near 3420 cm/sup -1/ to isotopic dilution suggests that the overtone of the bending mode is the likely source.

Devlin, J.P.

1989-02-01

244

Dilution Confusion: Conventions for Defining a Dilution  

ERIC Educational Resources Information Center

Two conventions for preparing dilutions are used in clinical laboratories. The first convention defines an "a:b" dilution as "a" volumes of solution A plus "b" volumes of solution B. The second convention defines an "a:b" dilution as "a" volumes of solution A diluted into a final volume of "b". Use of the incorrect dilution convention could affect…

Fishel, Laurence A.

2010-01-01

245

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

E-print Network

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

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

2006-06-07

246

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

NASA Technical Reports Server (NTRS)

Physical processes that unmix elements/isotopes of gas molecules involve phase changes, diffusion (chemical or thermal), effusion and gravitational settling. Some of those play significant roles for the evolution of chemical and isotopic compositions of gases in planetary bodies which lead to better understanding of surface paleoclimatic conditions, e.g. gas bubbles in Antarctic ice, and planetary evolution, e.g. the solar-wind erosion induced gas escaping from exosphere on terrestrial planets.. A mass dependent relationship is always expected for the kinetic isotope fractionations during these simple physical processes, according to the kinetic theory of gases by Chapman, Enskog and others [3-5]. For O-bearing (O16, -O17, -O18) molecules the alpha O-17/ alpha O-18 is expected at 0.5 to 0.515, and for S-bearing (S32,-S33. -S34, -S36) molecules, the alpha S-33/ alpha S-34 is expected at 0.5 to 0.508, where alpha is the isotope fractionation factor associated with unmixing processes. Thus, one isotope pair is generally proxied to yield all the information for the physical history of the gases. However, we recently] reported the violation of mass law for isotope fractionation among isotope pairs of multiple isotope system during gas diffusion or convection under thermal gradient (Thermal Gradient Induced Non-Mass Dependent effect, TGI-NMD). The mechanism(s) that is responsible to such striking observation remains unanswered. In our past studies, we investigated polyatomic molecules, O2 and SF6, and we suggested that nuclear spin effect could be responsible to the observed NMD effect in a way of changing diffusion coefficients of certain molecules, owing to the fact of negligible delta S-36 anomaly for SF6.. On the other hand, our results also showed that for both diffusion and convection under thermal gradient, this NMD effect is increased by lower gas pressure, bigger temperature gradient and lower average temperature, which indicate that the nuclear spin effect may not be the significant contributor as the energies involved in the hyperfine effect are much smaller than those with molecular collisions, especially under convective conditions.

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

2014-01-01

247

Optical absorption of isotopically enriched Li 2B 4O 7 single crystals irradiated by thermal neutrons  

Microsoft Academic Search

Induced absorption spectra in the range 200–900nm at 77 and 290K for Li2B4O7 single crystals, isotopically Li and B enriched are presented after irradiation of these crystals by thermal neutrons with fluence 1.8×1016cm?2. The dependence of induced absorption spectra on the isotope composition was revealed: for 6Li210B4O7 and 7Li210B4O7 crystals intensive band in the region of 280–294nm was observed. Under

Ya. V. Burak; V. T. Adamiv; I. M. Teslyuk; V. M. Shevel

2004-01-01

248

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

249

Isotope and chemical compositions of meteoric and thermal waters and snow from the greater Yellowstone National Park region  

USGS Publications Warehouse

An intensive hydrogeologic investigation, mandated by U.S. Congress and centered on the Norris-Mammoth corridor was conducted by USGS and other scientists during 1988-90 to determine the effects of using thermal water from a private well located in the Corwin Springs Known Geothermal Resources Area, Montana, on the thermal springs of Yellowstone National Park (YNP), especially Mammoth Hot Springs. As part of this investigation, we carried out a detailed study of the isotopic and chemical compositions of meteoric water from cold springs and wells, of thermal water, especially from the Norris-Mammoth corridor and of snow. Additional sampling of meteoric and thermal waters from YNP and surrounding region in northwest Wyoming, southwest Montana and southeast Idaho was carried out in 1991-92 to characterize the distribution of water isotopes in this mountainous region and to determine the origin and possible recharge locations of thermal waters in and adjacent to the Park. The D and 18O values for 40 snow samples range from ?88 to ?178? and ?12.5 to ?23.9?, respectively, and define a well constrained line given by D = 8.2 18O + 14.7 (r2 = 0.99) that is nearly identical to the Global Meteoric Water Line. The D and 18O values of 173 cold water samples range from ?115 to ?153? and ?15.2 to ?20.2?, respectively, and exhibit a similar relationship although with more scatter and with some shift to heavier isotopes, most likely due to evaporation effects. The spatial distribution of cold-water isotopes shows a roughly circular pattern with isotopically lightest waters centered on the mountains and high plateau in the northwest corner of Yellowstone National Park and becoming heavier in all directions. The temperature effect due to altitude is the dominant control on stable water isotopes throughout the region; however, this effect is obscured in narrow 'canyons' and areas of high topographic relief. The effects due to distance (i.e. 'continental') and latitude on water isotopes probably are relatively minor and difficult to resolve from the major controls. The data indicate that the groundwater are derived predominantly from cold, isotopically light winter precipitation, and that the isotope values of groundwater from elevations above about 2.5-3.0 km in the Gallatin and northern Absaroka Ranges are light enough (The D ?149?) to be the presumed recharge water for the hydrothermal system in the Park. However, estimation of the present-day volume of this recharged, isotopically light water indicates that it is not adequate to supply the high (3-4 m3/s) thermal water discharges from YNP, and cooler temperatures at the time of recharge would be required. The volume of meteoric water with D values lighter than ?145? may be adequate for recharging the hydrothermal system, and this may be a more plausible value than the ?149? originally calculated from data that are subject to moderate uncertainties.

Kharaka, Yousif K.; Thordsen, James J.; White, Lloyd D.

2002-01-01

250

Thermal transport in very dilute mixtures of /sup 3/He in /sup 4/He near the superfluid transition  

SciTech Connect

We report measurements of the temperature difference across layers of liquid /sup 3/He-/sup 4/He mixtures in the superfluid phase as produced by a heat current at temperatures very close to T/sub lambda/(X). Here X is the /sup 3/He molar concentration that covers the range 2 x 10/sup -9/thermal relaxation times are consistent with this observation. An alternative analysis invoking an anomalous boundary resistance is presented.

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

1985-05-27

251

Analysis of nitrosamines in water by automated SPE and isotope dilution GC/HRMS Occurrence in the different steps of a drinking water treatment plant, and in chlorinated samples from a reservoir and a sewage treatment plant effluent.  

PubMed

A method based on automated solid-phase extraction (SPE) and isotope dilution gas chromatography/high resolution mass spectrometry (GC/HRMS) has been developed for the analysis of nine nitrosamines in water samples. The combination of automated SPE and GC/HRMS for the analysis of nitrosamines has not been reported previously. The method shows as advantages the selectivity and sensitivity of GC/HRMS analysis and the high efficiency of automated SPE with coconut charcoal EPA 521 cartridges. Low method detection limits (MDLs) were achieved, along with a greater facility of the procedure and less dependence on the operator with regard to the methods based on manual SPE. Quality requirements for isotope dilution-based methods were accomplished for most analysed nitrosamines, regarding to trueness (80-120%), method precision (<15%) and MDLs (0.08-1.7 ng/L). Nineteen water samples (16 samples from a drinking water treatment plant {DWTP}, 2 chlorinated samples from a sewage treatment plant {STP} effluent, and 1 chlorinated sample from a reservoir) were analysed. Concentrations of nitrosamines in the STP effluent were 309.4 and 730.2 ng/L, being higher when higher doses of chlorine were applied. N-Nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) were the main compounds identified in the STP effluent, and NDEA was detected above 200 ng/L, regulatory level for NDMA in effluents stated in Ontario (Canada). Lower concentrations of nitrosamines were found in the reservoir (20.3 ng/L) and in the DWTP samples (n.d. -28.6 ng/L). NDMA and NDEA were respectively found in the reservoir and in treated and highly chlorinated DWTP samples at concentrations above 10 ng/L (guide value established in different countries). The highest concentrations of nitrosamines were found after chlorination and ozonation processes (ozonated, treated and highly chlorinated water) in DWTP samples. PMID:18656677

Planas, Carles; Palacios, Oscar; Ventura, Francesc; Rivera, Josep; Caixach, Josep

2008-08-15

252

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

253

Compound-specific stable isotope analysis of soil mesofauna using thermally assisted hydrolysis and methylation for ecological investigations.  

PubMed

Stable isotope mass spectrometric approaches are proving to be valuable tools in unravelling biotic interactions in complex ecosystems, yielding information on trophic preferences and functional roles of individual species. Gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) provides considerable opportunities to assist in studies concerned with ecosystem processes mediated by soil invertebrates and microorganisms by determination of delta(13)C values of individual compounds, for example, lipids, amino acids etc. However, techniques conventionally adopted for "wet" chemical extractions and derivatizations necessary for compound-specific stable isotope determinations restrict the size of soil organism that can be studied and can limit investigations of individuals or even parts of individuals. We demonstrate here that individual soil mesofauna can be probed directly for their fatty acid stable isotope signatures by pyrolysis-GC/C/IRMS. A thermally assisted hydrolysis and methylation (THM) reaction is described for the determination of delta(13)C fatty acid values using trimethylsulfonium hydroxide (TMSH). Authentic fatty acids, acyl lipids, and individual Collembola (Folsomia candida) raised on C(3) and C(4) isotopically labeled yeast were analyzed initially by py-GC/MS with TMSH and then by py-GC/C/IRMS. A kinetic isotope effect (KIE) observed with the THM reaction prevents direct calculation of the fatty acid delta(13)C values by simple mass balance equations. However, the KIE is shown to be both reproducible and robust and can therefore be accounted for by the use of correction factors. The fatty acid methyl ester compositions of individual F. candida and their respective delta(13)C values were determined and shown to agree with those obtained by conventional "wet" chemical procedures applied to much larger numbers of Collembola, thus enhancing the scope to which stable isotopes can be applied to the study of invertebrates in complex food webs in any environment. PMID:14615981

Evans, Claire J; Evershed, Richard P; Black, Helaina I J; Ineson, Philip

2003-11-15

254

Measurement of the stable carbon isotope ratio of atmospheric volatile organic compounds using chromatography, combustion, and isotope ratio mass spectrometry coupled with thermal desorption  

NASA Astrophysics Data System (ADS)

The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular of their stable carbon isotope ratio (?13C), could potentially be used as an effective tool for identifying the sources of VOCs. However, to date, there have been very few such analyses. In this work, we analyze the ?13C values of VOCs using thermal desorption coupled with chromatography, combustion, and isotope ratio mass spectrometry (TD-GC/C/IRMS). The measured peak shapes were of high quality and 36 compounds in a standard gas containing 58 VOCs (C5-C11) were detected. The measured ?13C varied widely, from -49.7‰ to -22.9‰, while the standard deviation of the ?13C values varied from 0.07‰ to 0.85‰ (n = 5). We then measured samples from two passenger cars in hot and cold modes, three gas stations, roadside air, and ambient air. In comparison with existing studies, the analytical precision for the 36 compounds in this study was reasonable. By comparing the ?13C values obtained from the cars and gas stations, we could identify some degree of the sources of VOCs in the roadside and ambient air samples.

Kawashima, Hiroto; Murakami, Mai

2014-06-01

255

Influence of longitudinal isotope substitution on the thermal conductivity of carbon nanotubes: Results of nonequilibrium molecular dynamics and local density functional calculations  

SciTech Connect

We report reverse nonequilibrium molecular dynamics calculations of the thermal conductivity of isotope substituted (10,10) carbon nanotubes (CNTs) at 300 K. {sup 12}C and {sup 14}C isotopes both at 50% content were arranged either randomly, in bands running parallel to the main axis of the CNTs or in bands perpendicular to this axis. It is found that the systems with randomly distributed isotopes yield significantly reduced thermal conductivity. In contrast, the systems where the isotopes are organized in patterns parallel to the CNTs axis feature no reduction in thermal conductivity when compared with the pure {sup 14}C system. Moreover, a reduction of approximately 30% is observed in the system with the bands of isotopes running perpendicular to the CNT axis. The computation of phonon dispersion curves in the local density approximation and classical densities of vibrational states reveal that the phonon structure of carbon nanotubes is conserved in the isotope substituted systems with the ordered patterns, yielding high thermal conductivities in spite of the mass heterogeneity. In order to complement our conclusions on the {sup 12}C-{sup 14}C mixtures, we computed the thermal conductivity of systems where the {sup 14}C isotope was turned into pseudo-atoms of 20 and 40 atomic mass units.

Leroy, Frédéric, E-mail: f.leroy@theo.chemie.tu-darmstadt.de; Böhm, Michael C., E-mail: boehm@theo.chemie.tu-darmstadt.de [Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, D-64287 Darmstadt (Germany); Schulte, Joachim [Bruker Biospin GmbH, Silberstreifen, D-76287 Rheinstetten (Germany)] [Bruker Biospin GmbH, Silberstreifen, D-76287 Rheinstetten (Germany); Balasubramanian, Ganesh [Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)] [Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)

2014-04-14

256

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

NASA Technical Reports Server (NTRS)

Superplumes offer a new approach for understanding global C cycles. Isotopes help to discern the impacts of geological, environmental and biological processes ujpun the evolution of these cycles. For example, C-13/C-12 values of coeval sedimentary organics and carbonates give global estimates of the fraction of C buried as organics (Forg), which today lies near 0.2. Before Oxygenic photosynthesis arose, our biosphere obtained reducing power for biosynthesis solely from thermal volatiles and rock alteration. Thus Forg was dominated by the mantle redox state, which has remained remarkably constant for greater than Gy. Recent data confirm that the long-term change in Forg had been small, indicating that the mantle redox buffer remains important even today. Oxygenic photosynthesis enabled life to obtain additional reducing power by splitting the water molecule. Accordingly, biological organic production rose above the level constrained by the mantle-derived flux of reduced species. For example, today, chemoautotrophs harvesting energy from hydrothermal emanations can synthesize at most between 0.2 x 10(exp 12) and 2x 10(exp 12) mol C yr-1 of organic C globally. In contrast, global photosynthetic productivity is estimated at 9000 x 10(exp 12) mol C yr-1. Occasionally photosynthetic productivity did contribute to dramatically -elevated Forg values (to 0.4 or more) as evidenced by very high carbonate C-13/C-12. The interplay between biological, tectonic and other environmental factors is illustrated by the mid-Archean to mid-Proterozoic isotopic record. The relatively constant C-13/C-12 values of Archean carbonates support the view that photosynthetically-driven Forg increases were not yet possible. In contrast, major excursions in C-13/C-12, and thus also in Forg, during the early Proterozoic confirmed the global importance of oxygenic photosynthesis by that time. Remarkably, the superplume event at 1.9 Ga did not trigger another major Forg increase, despite the favorable conditions for organic burial that were evidenced by elevated sea levels and higher black shale abundances. Perhaps those superplume-rated processes that favored enhanced organic burial were offset by the ability of mantle-derived redox buffering, which was enhanced during the superplume event, to limit excursions in Forg.

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

2000-01-01

257

The isotopic composition of waters from the El Tatio geothermal field, Northern Chile  

Microsoft Academic Search

On the basis of isotopic and chemical analyses of 45 spring, well and meteoric water samples from the El Tatio geothermal field in Northern Chile, four main processes giving rise to the formation of a wide range of thermal discharges can be distinguished. (1) Deep dilution of a predominant, primary high chloride (5500 mg\\/l, 260°) supply water derived from precipitation

Werner F. Giggenbach

1978-01-01

258

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

259

Thermal transport properties of the helium near the superfluids transition II. Dilute /sup 3/He-He mixtures in the superfluid phase  

SciTech Connect

Measurements of the average thermal conductivity k/sub exp/ is identical to hQ/BETAT and of the thermal relaxation time GAMMA to reach steady-state equilibrium conditions are reported in the superfluid phase for dilute mixtures of /sup 3/He in /sup 4/He. Here h is the cell height, Q is the heat flux, and BETAT is the temperature difference across the fluid layer. The measurements were made over the impurity range 2 x 10/sup -9/ < x (/sup 3/He) < 3 x 10/sup -2/ and with heat fluxes 0.3 < q < 160 ..mu.. w/cm/sup 2/. Assuming the boundary resistance R /sub b/, measured for x < 10/sup -5/, to be independent of x over the whole range of x, a calculation is given for k/sub exp/. for Q smaller than a well-defined critical heat flux Q /sub c/ (X) proportional to X/sup 0.9/, k/sub exp/. for Q of Q and can be identified with the local conductivity K/sub eff/, which is found to be independent of the reduced temperature epsilon = (T - T/sub lambda/)/ T/sub lambda/ for -epsilon less than or equal to 10/sup -2/ from the prediction extrapolated value at T/sub lambda/ is found to depart for X less than or equal to 10/sup -3/ from the prediction k/sub lambda/ proportional to X/sup -1/, tending instead to a weaker divergence k/sub lambda/ proportional to X/sup -a/ with aapprox. = 0.8. A finite conductivity as X tends to zero is not excluded by the data, however. For Q > Q/sub c/ (X) a nonlinear regime is entered. for X less than or equal to 10/sup -6/, the measurements with the availavle temperature resolution are limited to the nonlinear conditions, but can be extrapolated into the linear regime for X greater than or equal to 2 x 10/sup -7/. the results for K /sub exp/ (Q), Q/sub c/ (X), and k /sub eff/ (XX) are found to be internally consistent, as shown by comparison with a theory by Behringer based on Khalatnikov's transport equations.

Dingus, M.; Meyer, H.; Tuttle, J.; Zhong, F.

1986-11-01

260

Chitin: 'Forgotten' Source of Nitrogen: From Modern Chitin to Thermally Mature Kerogen: Lessons from Nitrogen Isotope Ratios  

USGS Publications Warehouse

Chitinous biomass represents a major pool of organic nitrogen in living biota and is likely to have contributed some of the fossil organic nitrogen in kerogen. We review the nitrogen isotope biogeochemistry of chitin and present preliminary results suggesting interaction between kerogen and ammonium during thermal maturation. Modern arthropod chitin may shift its nitrogen isotope ratio by a few per mil depending on the chemical method of chitin preparation, mostly because N-containing non-amino-sugar components in chemically complex chitin cannot be removed quantitatively. Acid hydrolysis of chemically complex chitin and subsequent ion-chromatographic purification of the "deacetylated chitin-monomer" D-glucosamine (in hydrochloride form) provides a chemically well-defined, pure amino-sugar substrate for reproducible, high-precision determination of ??15N values in chitin. ??15N values of chitin exhibited a variability of about one per mil within an individual's exoskeleton. The nitrogen isotope ratio differed between old and new exoskeletons by up to 4 per mil. A strong dietary influence on the ??15N value of chitin is indicated by the observation of increasing ??15N values of chitin from marine crustaceans with increasing trophic level. Partial biodegradation of exoskeletons does not significantly influence ??15N values of remaining, chemically preserved amino sugar in chitin. Diagenesis and increasing thermal maturity of sedimentary organic matter, including chitin-derived nitrogen-rich moieties, result in humic compounds much different from chitin and may significantly change bulk ??15N values. Hydrous pyrolysis of immature source rocks at 330??C in contact with 15N-enriched NH4Cl, under conditions of artificial oil generation, demonstrates the abiogenic incorporation of inorganic nitrogen into carbon-bound nitrogen in kerogen. Not all organic nitrogen in natural, thermally mature kerogen is therefore necessarily derived from original organic matter, but may partly result from reaction with ammonium-containing pore waters.

Schimmelmann, A.; Wintsch, R.P.; Lewan, M.D.; DeNiro, M.J.

1998-01-01

261

Simultaneous determination of asymmetric and symmetric dimethylarginine, L-monomethylarginine, L-arginine, and L-homoarginine in biological samples using stable isotope dilution liquid chromatography tandem mass spectrometry.  

PubMed

Production of the endogenous vasodilator nitric oxide (NO) from L-arginine by NO synthase is modulated by L-homoarginine, l-monomethylargine (MMA), asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). Here we report on a stable isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of these metabolites in plasma, cells and tissues. After addition of the internal standards (D(7)-ADMA, D(4)-L-homoarginine and (13)C(6)-L-arginine), analytes were extracted from the samples using Waters Oasis MCX solid phase extraction cartridges. Butylated analytes were separated isocratically on a Waters XTerra MS C18 column (3.5 ?m, 3.9 mm × 100 mm) using 600 mg/L ammonium formate in water - acetonitrile (95.5:4.5, v/v) containing 0.1 vol% formic acid, and subsequently measured on an AB Sciex API 3000 triple quadrupole mass spectrometer. Multiple reaction monitoring in positive mode was used for analyte quantification. Validation was performed in plasma. Calibration lines were linear (r(2)?0.9979) and lower limits of quantification in plasma were 0.4 nM for ADMA and SDMA and 0.8 nM for the other analytes. Accuracy (% bias) was <3% except for MMA (<7%), intra-assay precision (expressed as CV) was <3.5%, inter-assay precision <9.6%, and recovery 92.9-103.2% for all analytes. The method showed good correlation (r(2)?0.9125) with our previously validated HPLC-fluorescence method for measurement in plasma, and was implemented with good performance for measurement of tissue samples. Application of the method revealed the remarkably fast (i.e. within 60 min) appearance in plasma of stable isotope-labeled ADMA, SDMA, and MMA during infusion of D(3)-methyl-1-(13)C-methionine in healthy volunteers. PMID:22682940

Davids, Mariska; Swieringa, Eliane; Palm, Fredrik; Smith, Desirée E C; Smulders, Yvo M; Scheffer, Peter G; Blom, Henk J; Teerlink, Tom

2012-07-01

262

Optimisation of sample preparation protocols for measurement of PGE and Re-Os in organic-rich shales by isotope dilution ICP-MS  

NASA Astrophysics Data System (ADS)

Platinum-group elements (PGE) and Re-Os isotopes, which are variably redox-sensitive and fluid-soluble, have potential as proxies for the oxygenation of the atmosphere and oceans (e.g. [1]). However, analysis of these elements in organic rich shales (ORS) is challenging due to abundances of <1 ng/g and the presence of interfering isotopes or molecules of matrix elements. Furthermore, PGE-ReOs systematics in detrital and hydrogenous components may vary, and the choice of digestion parameters (reagents, temperature and pressure) during decomposition of rock powder affects the ratio of digested components [2,3]. Additional treatment to remove the matrix and pre-concentrate PGE-Re by column chromatography is necessary to minimise the effects of interfering elements, but presents its own challenges. We are in the process of conducting variations of acid digestion and column chromatographic protocols on reference sample SDO-1 (Devonian Ohio Shale, USGS). We aim to identify the optimum protocol to investigate PGE-Re-Os systematics of ORS that were sampled as part of the Barberton Drilling Project BARB5 drill core, in order to constrain the changes in detrital and hydrogenous contributions to the sediment with time, to assess the extent of euxinity in the sedimentary basin and to look for evidence of transient "whiffs of oxygen" [1]. The following digestion methods were tested: (1) 4h acid digestion in High Pressure Asher (HPA) apparatus with reverse aqua regia at 300°C and 130 bar (only this digestion allows extraction of volatilised Os in CHCl3 followed by HBr); (2) 3h reverse aqua regia digestion in centrifuge vials on hotplate at 80°C; (3) 48h reverse aqua regia digestion in closed Teflon beakers on hotplate at 140°C followed by a HF/HNO3 digestion step; (4) 48h HF/HNO3 digestion of ashed sample powder in closed Teflon beaker at 140°C on hotplate followed by an aqua regia digestion step. Column chromatographic approaches to decrease the concentrations of interfering elements (Y, Zr, Mo, Cd, Hf, Hg) include the use of cation- and anion resins, and variations of the molarity and composition of the eluent. Preliminary results show that digestion method (1) leaves behind small amounts of presumably PGE-free silica gel; (2) yields consistently higher Re concentrations with an expectedly large amount of solid residue; (3) produces an insoluble sludge; (4) allows complete digestion, but precludes the collection of Os. Column calibrations show the best recovery of PGE-Re in cation resin using 0.2 mol/l HCl as eluent, but intolerably high ratios of interfering over elements of interest, whereas the best matrix separation is achieved using 0.05 mol/l HCl as eluent, but is accompanied by low PGE-Re yields presumably due to the instability of Cl complexes in this medium. They also show that U elutes separately from PGE-Re in 6 mol/l HCl and could be collected with a view to analysing U isotopes as an additional redox proxy. Further tests will be carried out using alternative high-pressure digestion systems. [1] Anbar, et al. (2007) Science 317:1903-1906; [2] Meisel et al. (2003) JAAS 18:720-726; [3] Xu et al. (2012) CG 324:132-147

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

2013-04-01

263

Measuring environmental phenols and chlorinated organic chemicals in breast milk using automated on-line column-switching-high performance liquid chromatography-isotope dilution tandem mass spectrometry.  

PubMed

Breast milk is one possible route of exposure to environmental chemicals, including phenols and chlorinated organic chemicals for breast-fed infants. We developed a highly sensitive method of analyzing breast milk for triclocarban (3,4,4'-trichlorocarbanilide) and eight phenolic compounds: bisphenol A (BPA), 4-tert-octylphenol (4-tOP), ortho-phenylphenol (OPP), 2,4-dichlorophenol, 2,5-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, and 2-hydroxy-4-metoxybenzophenone (BP-3). The method includes adding a solution containing a stable isotope of each chemical, enzymatic hydrolysis of the conjugated chemicals in the milk, and on-line solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry. It can also be used to measure the free (unconjugated) species by omitting the enzymatic deconjugation step. The method, validated using pooled breast milk samples, has inter-day coefficient of variations ranging from 4.8 to 18.9% for most analytes, and spiked recoveries generally about 100%. Detection limits for most analytes are below 1 ng/mL in 100 microL of breast milk. We tested the usefulness of the method by measuring concentrations of these nine compounds in 20 breast milk samples. BPA, OPP, and BP-3 were detected in more than 60% of the samples tested. The free species of these compounds appear to be most prevalent in milk. PMID:16377264

Ye, Xiaoyun; Kuklenyik, Zsuzsanna; Needham, Larry L; Calafat, Antonia M

2006-02-01

264

Quantitative method for the analysis of tobacco-specific nitrosamines in cigarette tobacco and mainstream cigarette smoke by use of isotope dilution liquid chromatography tandem mass spectrometry.  

PubMed

An improved liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed for the determination of tobacco specific nitrosamines (TSNA). It utilizes four stable isotope-labeled internal standards instead of two as reported by others. A separate internal standard for each analyte is required to minimize sample matrix effects on each analyte, which can lead to poor analyte recoveries and decreases in method accuracy and precision if only one or two of the internal standards are used, especially for complex sample matrixes and when no sample cleanup steps are performed as in this study. In addition, two ion-transition pairs (instead of one) are used for each analyte for the confirmation and quantification, further enhancing the method's accuracy and robustness. These improvements have led to a new LC-MS/MS method that is faster, more sensitive, and selective than the traditional methods and more accurate and robust than the published LC-MS/MS methods. The linear range of the method was from 0.2 to 250 ng/mL with a limit of detection of each TSNA varied from 0.027 to 0.049 ng/mL. Good correlations between the results obtained by the new method and the traditional method were observed for the samples studied. PMID:18189372

Wu, Jingcun; Joza, Peter; Sharifi, Mehran; Rickert, William S; Lauterbach, John H

2008-02-15

265

Simultaneous determination of five tobacco-specific nitrosamines in mainstream cigarette smoke by isotope dilution liquid chromatography/electrospray ionization tandem mass spectrometry.  

PubMed

Tobacco-specific nitrosamines (TSNAs) have been previously implicated as a source of carcinogenicity in tobacco and cigarette smoke. Accurate quantification of these chemicals is needed to help assess public health risk. We have developed and validated a specific and sensitive method to simultaneously measure five TSNAs in the particulate phase of mainstream tobacco smoke. Cigarette smoke particulate, produced using standardized machine smoking protocols, was collected on a Cambridge filter pad. The particulate matter was extracted using methylene chloride, back extracted into aqueous solution, further purified by solid-phase extraction, and analyzed by liquid chromatography/electrospray ionization tandem mass spectrometry using isotopically labeled analogues as internal standards. Limits of detection for this method ranged from 0.05 to 1.23 ng/mL using an injection volume of 20 microL. A linear calibration range spanning 2.5-2500 ng/mL was adequate to measure TSNA levels in cigarette smoke. The method achieved excellent reproducibility and accuracy. The identity of each TSNA was established by chromatographic retention time, analyte-specific fragmentation patterns, and relative peak area ratios of two product/precursor ion pairs. This new method provides higher sensitivity, specificity, and throughput than earlier methods for TSNA determination. PMID:14674460

Wu, Weijia; Ashley, David L; Watson, Clifford H

2003-09-15

266

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

267

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

268

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

2013-10-01

269

Use of recombinantly produced 15N3-labelled nicotianamine for fast and sensitive stable isotope dilution ultra-performance liquid chromatography/electrospray ionization time-of-flight mass spectrometry.  

PubMed

Nicotianamine (NA) is an important metal chelator, implicated in the intra- and intercellular trafficking of several transition metal ions in plants. To decipher its roles in physiological processes such as micronutrient acquisition, distribution or storage, fast and sensitive analytical techniques for quantification of this non-proteinogenic amino acid will be required. The use of a recombinant Schizosaccharomyces pombe strain expressing a nicotianamine synthase (NAS) gene allowed for the production of [(15)N(3)]-NA, which was enriched from cell extracts through cation exchange and used for stable isotope dilution analysis of NA. Such an approach should be widely applicable to important bioanalytes that are difficult to synthesize. The analytical procedure comprises mild aqueous extraction and rapid Fmoc derivatization, followed by fast separation using ultra-performance liquid chromatography (UPLC) and sensitive detection by positive ion electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) with a chromatographic cycle time of only 8 min. Derivatization was optimized with respect to incubation time and species suitable for quantification. The limit of detection was 0.14 to 0.23 pmol in biological matrices with the response being linear up to 42 pmol. Recovery rates were between 83% and 104% in various biological matrices including fission yeast cells, fungal mycelium, plant leaves and roots. PMID:21110009

Schmidt, Holger; Böttcher, Christoph; Trampczynska, Aleksandra; Clemens, Stephan

2011-01-01

270

Determination of the antihypertensive drug 1-[2-ethoxy-2-(3'-pyridyl)ethyl]-4-(2'-methoxyphenyl) piperazine (IP/66) in rat and human plasma by high-performance liquid chromatography and isotope dilution mass spectrometry.  

PubMed

In connection with pharmacokinetic studies on the antihypertensive drug 1-[2-ethoxy-2-(3'-pyridyl)ethyl]-4-(2'-methoxyphenyl)piperazine (IP/66) (I), appropriate high-performance liquid chromatographic (HPLC) and gas chromatographic-mass spectrometric isotope dilution (GC-MS-ID) methods for its determination in rat and human plasma, respectively, were developed. In both techniques, deproteinized and basified plasma samples were extracted and purified by adsorption on an Extrelut-1 column, then the drug was eluted with dichloromethane. Quantitative HPLC analysis was performed on a C8 reversed-phase column. The mobile phase was phosphate buffer (0.02 M, pH 2.8)-acetonitrile (65:35), with UV detection at 208 nm. The internal standard was 1-[2-butoxy-2-(3'-pyridyl)ethyl]-4-(2'-methoxyphenyl)piperazine, a homologue of I. The inter-assay coefficient of variation (C.V.) was 9.9% for a drug level of 2 micrograms/ml. Quantitative GC-MS-ID analysis was performed with a DB-17 fused-silica capillary column using the selected-ion monitoring technique. The deuterated form of I, 1-[2-ethoxy-2-(3'-pyridyl)ethyl]-4-2'-trideuteromethoxyphenyl)pipe razine, utilized as internal standard, was synthesized. The inter-assay C.V. was 7.36% for a drug level of 1 ng/ml. PMID:2723000

Agostini, O; Moneti, G; Bonacchi, G; Fedi, M; Manzini, S

1989-02-24

271

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

PubMed

We investigate the structures of H(3)Co(CN)(6) and D(3)Co(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 H(3)Co(CN)(6) and 'super-short' N···H···N systems in general. PMID:21386563

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

2010-10-13

272

A Case for the Rapid Release of Carbon during the Paleocene-Eocene Thermal Maximum Carbon Isotope Excursion  

NASA Astrophysics Data System (ADS)

The Paleocene/Eocene Thermal Maximum (PETM) and associated Carbon Isotope Excursion (CIE) are often touted as the best geologic analog for the current anthropogenic rise in pCO2. However, a causal mechanism for the PETM CIE remains unidentified because of large uncertainties in the duration of the CIE's onset. Here, we report on a sequence of rhythmic sedimentary couplets comprising the Paleocene/Eocene Marlboro Clay (Salisbury Embayment). These couplets have corresponding ?18O cycles that imply a climatic cause. We have counted over 650 couplets at two different sites precluding orbital- and millennial-scale forcing for their origin. %CaCO3 decreases from ~6 to <1% across one couplet. High-resolution stable isotope records show 3.5‰ ?13C decrease over 13 couplets defining the CIE onset, which requires a large, instantaneous release of 13C-depleted carbon. Seasonal forcing of the sedimentary couplets best explains: 1) ?18O cycles and amplitudes; 2) the difference in response times between surface water carbonate chemistry (instantaneous) and carbon isotopic exchange (decadal); and 3) total layer counts. We conclude that the 'Marlboro Clay' sediments and its ?13C excursion record the initial release of carbon into the atmosphere, invasion into the surface waters, and only the initial mixing into the deep ocean. Therefore, the recovery observed in the Marlboro Clay is not equivalent to the 'recovery' observed in the open ocean records in either its timing or root cause.

Wright, J. D.; Schaller, M. F.

2013-12-01

273

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

USGS Publications Warehouse

Thermal ionization mass spectrometry (TI-MS) has long been the method of choice for Pb-isotope determinations. More recently, however, inductively coupled plasma mass spectrometry (ICP-MS) has been used to determine Pb-isotope ratios for mineral exploration. The ICP-MS technique, although not as precise as TI-MS, may promote a wider application of Ph-isotope ratio methods because it allows individual isotopes to be determined more rapidly, generally without need for chemical separation (e.g., Smith et al., 1984; Hinners et al., 1987). To demonstrate the utility of the ICP-MS method, we have conducted a series of Pb-isotope measurements on several suites of samples using both TI-MS and ICP-MS. ?? 1989.

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

1989-01-01

274

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

PubMed

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

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

2014-11-01

275

Alternative Methodology for Boron Isotopic Analysis of CaCO3 by Negative Thermal Ionization Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Negative thermal ionization mass spectrometry (NTIMS) has been a common tool for investigating boron isotopes in CaCO3 and other environmental samples, the high sensitivity of BO2- ionization enabling measurements of ng levels of boron. However, B isotope measurement by this technique suffers from a number of problems, including: (1) fractionation induced by selective ionization of B isotopes in the mass spectrometer; (2) CNO- interference on mass 42 ([10BO2]-) that may be present in some filament load solutions (such as B-free seawater processed through ion-exchange resin), and (3) potential matrix effects due to widely differing chemistry of samples and standards. Here we examine a potentially improved NTIMS methodology that incudes removal of sample-related calcium (and other cations) by ion exchange and uses an alternative filament loading solution prepared from high-purity single-element solutions of Ca, Mg, Na, and K. Initial results suggest that this new method may offer significant improvement over the more traditional NTIMS approach in which digested CaCO3 samples are directly loaded onto filaments in B-free seawater. Replicate analyses of standards and samples yield a typical standard deviation of approximately 0.3‰ ?11B and boron isotopic compositions comparable to reported or consensus values. Fractionation during analysis has thus far typically been less than 0.5‰ ?11B. The method delivers boron ionization efficiency similar to directly-loaded seawater, and negligible signal at mass 26 (CN-), a proxy for the possible interfering molecular CNO- ion. Standards and samples behave similarly and predictably during filament heating and analysis, thus allowing for fully automated data acquisition, which in turn may increase sample throughput and reduce potential analytical inconsistencies associated with operator-controlled heating and analysis.

Dwyer, G. S.; Vengosh, A.

2012-12-01

276

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

SciTech Connect

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

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

1987-10-28

277

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

278

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

279

Rapid determination of furan in heated foodstuffs by isotope dilution solid phase micro-extraction-gas chromatography--mass spectrometry (SPME-GC-MS).  

PubMed

An analytical method is reported to determine trace amounts of furan in several different commercial foodstuffs that are subjected to thermal treatment. The SPME-GC-MS method is rapid and robust, and entails the following steps: addition of deuterated furan to the sample, sodium chloride-assisted extraction into the headspace, cryofocussing, and finally fibre desorption and GC-MS analysis. Furan is quantified by the use of an external calibration curve, achieving a decision limit (CC alpha) and detection capability (CC beta) of 17 pg and 43 pg, respectively, as absolute furan concentration in a 10 ml headspace vial. The method is applicable to a wide variety of foods, including fruits juices, baby foods in jars, canned foods, pet food, coffee and coffee substitutes. Typical amounts of furan found in selected foodstuffs range from about 1 microg kg(-1) (fruit juice) to 110 microg kg(-1) (baby food containing cooked vegetables). In-house validation data show good precision and accuracy of the method, with a typical repeatability of between 5 and 16% in different food matrices, and trueness determined in orange juice and coffee as 87 and 93%, respectively. Moreover, the measurement uncertainty has been evaluated for two matrices (fruit juice and coffee). Studies on short-term stability of furan in certain foods are also presented, and show that the furan content decreases in food while heating for preparation or reconstitution. PMID:15912236

Goldmann, Till; Périsset, Adrienne; Scanlan, Francis; Stadler, Richard H

2005-06-01

280

Comprehensive two-dimensional gas chromatography with isotope dilution time-of-flight mass spectrometry for the measurement of dioxins and polychlorinated biphenyls in foodstuffs. Comparison with other methods.  

PubMed

A comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC x GC-TOF-MS) experimental setup was tested for the measurement of seven 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs), ten 2,3,7,8-substituted polychlorinated dibenzofurans (PCDFs), four non-ortho-polychlorinated biphenyls (PCBs), eight mono-ortho-PCBs, and six indicator PCBs (Aroclor 1260) in foodstuff samples. A 40m RTX-500 (0.18mm I.D., 0.10 microm df) was used as the first dimension (1D) and a 1.5 m BPX-50 (0.10mm I.D., 0.10 microm df) as the second dimension (2D). The GC x GC chromatographic separation was completed in 45 min. Quantification was performed using 13C-label isotope dilution (ID). Isotope ratios of the selected quantification ions were checked against theoretical values prior to peak assignment and quantification. The dynamic working range spanned three orders of magnitude. The lowest detectable amount of 2,3,7,8-TCDD was 0.2 pg. Fish, pork, and milk samples were considered. On a congener basis, the GC x GC-ID-TOF-MS method was compared to the reference GC-ID high resolution mass spectrometry (HRMS) method and to the alternative GC-ID tandem-in-time quadrupole ion storage mass spectrometry (QIST-MS/MS). PCB levels ranged from low picogram (pg) to low nanogram (ng) per gram of sample and data compared very well between the different methods. For all matrices, PCDD/Fs were at a low pg level (0.05-3 pg) on a fresh weight basis. Although congener profiles were accurately described, RSDs of GC x GC-ID-TOF-MS and GC-QIST-MS/MS were much higher than for GC-ID-HRMS, especially for low level pork and milk. On a toxic equivalent (TEQ) basis, all methods, including the dioxin-responsive chemically activated luciferase gene expression (DR-CALUX) assay, produced similar responses. A cost comparison is also presented. PMID:16130655

Focant, Jean-François; Eppe, Gauthier; Scippo, Marie-Louise; Massart, Anne-Cécile; Pirard, Catherine; Maghuin-Rogister, Guy; De Pauw, Edwin

2005-09-01

281

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

282

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

283

Combining the quick, easy, cheap, effective, rugged and safe approach and clean-up by immunoaffinity column for the analysis of 15 mycotoxins by isotope dilution liquid chromatography tandem mass spectrometry.  

PubMed

Optimization and validation of a multi-mycotoxin method by LC-MS/MS is presented. The method covers the EU-regulated mycotoxins (aflatoxins, fumonisins, ochratoxin A, deoxynivalenol, zearalenone, T-2 and HT-2), as well as nivalenol and 3- and 15-acetyldeoxynivalenol for analysis of cereals, cocoa, oil, spices, infant formula, coffee and nuts. The proposed procedure combines two clean-up strategies: First, a generic preparation suitable for all mycotoxins based on the QuEChERS (for quick, easy, cheap, effective, rugged and safe) protocol. Second, a specific clean-up devoted to aflatoxins and ochratoxin A using immunoaffinity column (IAC) clean-up. Positive identification of mycotoxins in matrix was conducted according to the confirmation criteria defined in EU Commission Decision 2002/657/EC while quantification was performed by isotopic dilution using (13)C-labeled mycotoxins as internal standards. Limits of quantification were at or below the maximum levels set in the EC/1886/2006 document for all mycotoxin/matrix combinations under regulation. In particular, the inclusion of an IAC step allowed achieving LOQs as low as 0.05 and 0.25?g/kg in cereals for aflatoxins and ochratoxin A, respectively. Other performance parameters like linearity [(r)(2)>0.99], recovery [71-118%], precision [(RSDr and RSDiR)<33%], and trueness [78-117%] were all compliant with the analytical requirements stipulated in the CEN/TR/16059 document. Method ruggedness was proved by a verification process conducted by another laboratory. PMID:24636559

Desmarchelier, Aurélien; Tessiot, Sabine; Bessaire, Thomas; Racault, Lucie; Fiorese, Elisa; Urbani, Alessandro; Chan, Wai-Chinn; Cheng, Pearly; Mottier, Pascal

2014-04-11

284

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

285

Coherent pattern and timing of the carbon isotope excursion and warming during Eocene Thermal Maximum 2 as recorded in planktic and benthic foraminifera  

Microsoft Academic Search

Eocene Thermal Maximum 2 (ETM2; ?53.7 Ma) occurred approximately 2 Myr after the Paleocene-Eocene Thermal Maximum (?55.5 Ma) and was characterized by a deep-sea warming of >3°C, associated with massive release of carbon into the ocean-atmosphere system. We performed single-specimen stable isotope analyses of the planktic foraminiferal genera Acarinina (surface dweller) and Subbotina (thermocline dweller) from Ocean Drilling Program Sites

Lucy Stap; Lucas Lourens; Arnold van Dijk; Stefan Schouten; Ellen Thomas

2010-01-01

286

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

NASA Astrophysics Data System (ADS)

A ThermoFisher "Triton" multi-collector thermal ionization mass spectrometer (MC-TIMS) was evaluated for trace and ultra-trace level isotope ratio analysis of actinides (uranium, plutonium, and americium), fission products and geolocators (strontium, cesium, and neodymium). Total efficiencies (atoms loaded to ions detected) of up to 0.5-2% for U, Pu, and Am, and 1-30% for Sr, Cs, and Nd can be reported employing resin bead load techniques onto flat ribbon Re filaments or resin beads loaded into a millimeter-sized cavity drilled into a Re rod. This results in detection limits of <0.1 fg (104 atoms to 105 atoms) for 239-242+244Pu, 233+236U, 241-243Am, 89,90Sr, and 134,135,137Cs, and <=1 pg for natural Nd isotopes (limited by the chemical processing blank) using a secondary electron multiplier (SEM) or multiple-ion counters (MICs). Relative standard deviations (RSD) as small as 0.1% and abundance sensitivities of 1 × 106 or better using a SEM are reported here. Precisions of RSD [approximate]0.01-0.001% using a multi-collector Faraday cup array can be achieved at sub-nanogram concentrations for strontium and neodymium and are suitable to gain crucial geolocation information. The analytical protocols reported herein are of particular value for nuclear forensic and nuclear safeguard applications.

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

2009-09-01

287

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  

Microsoft Academic Search

Oxygen self-diffusion coefficients have been measured for three natural diopsidic clinopyroxenes, a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic akermanite for oxygen fugacities ranging from the NNO to IW buffers. The oxygen diffusion data are used to evaluate the effects of three different types of thermal histories upon the oxygen isotopic compositions of minerals found in Type

F. J. Ryerson; K. D. McKeegan

1994-01-01

288

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

289

Stable Chlorine Isotopes and Elemental Chlorine by Thermal Ionization Mass Spectrometry and Ion Chromatography; Martian Meteorites, Carbonaceous Chondrites and Standard Rocks  

NASA Technical Reports Server (NTRS)

Recently significantly large mass fractionation of stable chlorine isotopes has been reported for terrestrial and lunar samples [1,2]. In addition, in view of possible early solar system processes [3] and also potential perchlorate-related fluid/microbial activities on the Martian surface [4,5], a large chlorine isotopic fractionation might be expected for some types of planetary materials. Due to analytical difficulties of isotopic and elemental analyses, however, current chlorine analyses for planetary materials are controversial among different laboratories, particularly between IRMS (gas source mass spectrometry) and TIMS (Thermal Ionization Mass Spectrometry) groups [i.e. 1,6,7] for isotopic analyses, as well as between those doing pyrohydrolysis and other groups [i.e. 6,8]. Additional careful investigations of Cl isotope and elemental abundances are required to confirm real chlorine isotope and elemental variations for planetary materials. We have developed a TIMS technique combined with HF-leaching/ion chromatography at NASA JSC that is applicable to analysis of small amounts of meteoritic and planetary materials. We present here results for several standard rocks and meteorites, including Martian meteorites.

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

2011-01-01

290

Diffusion artifacts in dating by stepwise thermal release of rare gases. [Ar isotope lunar chronology  

NASA Technical Reports Server (NTRS)

It is demonstrated that the age of an isochron of apparent age plateau can be easily altered during a thermal release experiment, and that constant rare gas compositions can be observed which are artifacts of the experimental technique and are not chronologically meaningful. Examples are selected from 40Ar-39Ar dating of lunar samples in which anomalous variations in apparent ages can be ascribed to such experimental artifacts.

Huneke, J. C.

1976-01-01

291

Constraining Groundwater Discharge in a Large Watershed: Integrated Isotopic, Hydraulic and Thermal Data from the Canadian Shield  

NASA Astrophysics Data System (ADS)

Understanding the rate and pattern of groundwater discharge to lakes and rivers is critical for watershed budgets and for protecting the ecological integrity of lake and river ecosystems. A 900 km2 study watershed contains a river and over 3000 lakes and wetlands, mostly underlain by exposed crystalline bedrock or a thin veneer of coarse-grained sediments. The objective of this study is to constrain the rate and pattern of groundwater discharge at the watershed-scale. Groundwater discharge points were identified by conducting detailed transects of the river and lakes using temperature, conductivity and radon-222 tracers. Surface water samples from representative lakes were analyzed for ä2H, ä18O, radon-222 and chloride during three consecutive summers. Radon and chloride concentrations are used in a new steady-state advective model to determine groundwater fluxes to the representative lakes. The detailed transects identified minor and highly localized groundwater discharge locations which did not coincide with mapped geological structures or exposed bedrock fractures. Stable isotope, temperature and conductivity data identified only one subsidiary stream with significant groundwater discharge. The steady-state model indicates that the groundwater flux to lakes is generally less than 0.1 percent of the total input. This integrated thermal, chemical, isotopic and hydraulic dataset indicates that the rate of groundwater discharge to lakes in this crystalline bedrock watershed is not significant and that discharge is localized but not focused at exposed geological structures or bedrock fractures. This conclusion implies that in the watershed groundwater and surface water is largely decoupled, which has significant ecological and water management implications.

Gleeson, T.; Novakowski, K.; Cook, P. G.; Kyser, K.

2009-05-01

292

Effect of pH decline on foraminiferal stable isotopes during the Paleocene-Eocene Thermal Maximum?  

NASA Astrophysics Data System (ADS)

Pioneering culture experiments by Spero et al. (1997) demonstrated that seawater pH (or carbonate chemistry) has a marked effect on planktonic foraminiferal stable oxygen and carbon isotopes (?18O and ?13C). Both ?18O and ?13C become isotopically heavier as seawater pH decreases (the “pH effect”). Several studies now argue that ?18O and ?13C of benthic foraminifera are similarly influenced by the pH effect. As a result, paleooceanographic information based on foraminiferal ?18O and ?13C can be significantly biased for the time-window during which seawater pH was notably different from the modern condition or varied rapidly. A prime example of such is the Paleocene-Eocene Thermal Maximum (PETM). Widespread dissolution of sedimentary CaCO3 in the PETM strata (e.g., Zachos et al., 2005) suggests significant ocean acidification during this time interval. In this study, we examine the magnitude of the pH effect on foraminiferal ?18O and ?13C during the PETM. First we will estimate the relative pH decline from the pre-PETM steady state in the surface and deep ocean reservoirs in response to 2,000 ~ 5,000 Pg of carbon input using a carbon cycle model (Zeebe et al., 2009). We will then apply the empirical relationships obtained from the culture experiments by Spero et al. (1997) to calculate the ranges of errors in the foraminiferal ?18O and ?13C that could arise due to the pH effect during the PETM. {REFERENCES} Spero et al. (1997) Nature, v390, p497-500: Zachos et al. (2005) Science, v308, p1611-1615: Zeebe et al. (2009) Nature Geoscience, v2, p576-580.

Uchikawa, J.; Zeebe, R. E.

2009-12-01

293

The W isotope composition of eucrite metals: constraints on the timing and cause of the thermal metamorphism of basaltic eucrites  

NASA Astrophysics Data System (ADS)

Basaltic eucrites formed as lava flows at or near the surface of asteroid Vesta. After crystallization, most eucrites were affected by thermal metamorphism, the timing and cause of which are enigmatic. We present Hf-W data for magnetic (largely metal) and non-magnetic fractions (mostly silicates and oxides) from six basaltic eucrites that allow the first direct dating of this thermal metamorphism. All metals have high W contents and show excesses in the abundance of 182W (between 2 and 16 ?W) relative to the initial ?W of the whole-rock isochron ( ?W˜-0.5), indicating a late re-mobilization of radiogenic W from silicates into metal. The Hf-W ages of metal formation/re-equilibration in five out of six eucrites agree and give a weighted average of 16±2 Myr after mantle-crust differentiation in Vesta, corresponding to an 'absolute' age of 4547±2 Myr when using the H chondrite Ste. Marguerite as an absolute time marker. Hf-W isotopic closure in metal from Stannern occurred 0.5-3.6 Myr after mantle-crust differentiation, which is significantly earlier than in the other eucrites. The different whole-rock and non-magnetic fractions from Bouvante, Ibitira and Juvinas plot along the eucrite whole-rock isochron but are not collinear with their respective metal fractions. Thus, metal and silicates in eucrites have not been in complete W isotopic equilibrium, indicating that the Hf-W metal ages correspond to a short re-heating rather than a magmatic event. Based primarily on age comparison, the temperature required for W diffusion from silicates into metal is estimated to be at least ˜600 °C, similar to the peak metamorphic temperatures deduced from diffusion profiles in eucritic pyroxenes. The Hf-W ages of metal formation/re-equilibration, therefore, provide the first direct age constraints on the thermal metamorphism that affected almost all eucrites. The ˜16 Myr time gap between mantle-crust differentiation and metal formation/re-equilibration indicates that the thermal metamorphism cannot be related to differentiation of a magma ocean into layers or rapid burial of early crust. Impacts instead must have provided the energy for re-heating of early-erupted basalts. Given that five out of six eucrites studied here exhibit identical Hf-W ages, the thermal metamorphism may have been caused by a large impact on Vesta. The Hf-W systematics in Stannern were not affected by this event, indicating that Stannern is derived from a different part of Vesta's crust than the other examined eucrites. Ar-Ar ages for unbrecciated and brecciated eucrites [Bogard and Garrison, Meteorit. Planet. Sci. 38 (2003) 669-710] are ˜50 Myr and more than ˜450 Myr younger than the Hf-W metal ages, reflecting later impact-induced heating events that caused resetting of Ar-Ar ages but did not affect the Hf-W systematics.

Kleine, T.; Mezger, K.; Palme, H.; Scherer, E.; Münker, C.

2005-02-01

294

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

SciTech Connect

The objective of this task was to demonstrate that metal hydrides could be produced by mechanical alloying in the quantities needed to support production-scale hydrogen isotope separations. Three starting compositions (ratios of elemental Zr and Fe powders) were selected and attritor milled under argon for times of 8 to 60 hours. In general, milling times of at least 24 hours were required to form the desired Zr{sub 2}Fe and Zr{sub 3}Fe phases, although a considerable amount of unalloyed Zr and Fe remained. Milling in liquid nitrogen does not appear to provide any advantages over milling in hexane, particularly due to the formation of ZrN after longer milling times. Carbides of Zr formed during some of the milling experiments in hexane. Elemental Zr was present in the as-milled material but not detected after annealing for milling times of 48 and 60 hours. It may be that after intimate mixing of the powders in the attritor mill the annealing temperature was sufficient to allow for the formation of a Zr-Fe alloy. Further investigation of this conversion is necessary, and could provide an opportunity for reducing the amount of unreacted metal powder after milling.

Fox, K.

2008-02-20

295

Intracrystalline fractionation of oxygen isotopes between hydroxyl and non-hydroxyl sites in kaolinite measured by thermal dehydroxylation and partial fluorination  

NASA Astrophysics Data System (ADS)

Thermal dehydroxylation and partial fluorination techniques were used to measure intracrystalline fractionation of oxygen isotopes between hydroxyl and non-hydroxyl sites in kaolinite. Several aliquots of a well characterized, fine-grained (<1 ?m) kaolinite from Macon, GA, were dehydroxylated in vacuo using a variety of heating procedures, heating rates, and target temperatures. Measured ?18O values of both the liberated water and the dehydroxylated residue are consistent over a wide range of temperatures (550-850°C) when dehydroxylation is performed in a single-step fashion at a rapid heating rate (>50°C/min.). Similar dehydroxylation experiments indicate that brucite dehydroxylation occurs without any significant isotopic fractionation of the oxygen isotopes. By extrapolation we postulate that no significant fractionation occurs during single-step thermal dehydroxylation of fine-grained kaolinite, provided that dehydroxylation is performed under well controlled conditions. In contrast, gibbsite dehydroxylation is accompanied by substantial isotopic fractionation. This is probably the result of the complex, multi-pathway dehydroxylation reaction of this mineral. Similarly, thermal dehydroxylation of coarsegrained (>1 ?m) kaolinites and dickites of weathering and hydrothermal origin yield results that are dependent on the temperature of dehydroxylation. We suggest that this effect may be caused by isotopic exchange during diffusion of water molecules through coarse particles. Partial fluorination of fine-grained kaolinite in the presence of excess F2 at low temperatures (<185°C) yields unreproducible ?18O values. When performed at high temperatures (220-240°C) in the presence of insufficient F2, ?18O values are systematically lower than the bulk ?18O value and increase linearly with the percent stoichiometric yield. They are consistent with a greater rate of reaction of hydroxyl oxygen than of non-hydroxyl oxygen, but examination of the isotopic data as well as XRD and IR analyses of the residues after partial fluorination indicates that the separation between the two types of oxygen is not complete. The results, therefore, do not yield a reliable ?18O value of the hydroxyl oxygen. The results of this study suggest that the thermal dehydroxylation technique may be appropriate for analysis of OH groups in fine-grained kaolinite. The partial fluorination approach appears less suitable. Intracrystalline fractionation of oxygen isotopes between hydroxyl and non-hydroxyl sites in kaolinite may be larger than previously reported in experimental studies. Based on the results obtained for the finer-than 1 ?m Macon kaolinite a value of 1.0272 is proposed for the intracrystalline fractionation factor, ?non-OH/OH, of kaolinite at 20 ± 10°C.

Girard, Jean-Pierre; Savin, Samuel M.

1996-02-01

296

Intracrystalline fractionation of oxygen isotopes between hydroxyl and non-hydroxyl sites in kaolinite measured by thermal dehydroxylation and partial fluorination  

NASA Astrophysics Data System (ADS)

Thermal dehydroxylation and partial fluorination techniques were used to measure intracrystalline fractionation of oxygen isotopes between hydroxyl and non-hydroxyl sites in kaolinite. Several aliquots of a well characterized, fine-grained (<1 ?m) kaolinite from Macon, GA, were dehydroxylated in vacuo using a variety of heating procedures, heating rates, and target temperatures. Measured ?18O values of both the liberated water and the dehydroxylated residue are consistent over a wide range of temperatures (550 850°C) when dehydroxylation is performed in a single-step fashion at a rapid heating rate (>50°C/min.). Similar dehydroxylation experiments indicate that brucite dehydroxylation occurs without any significant isotopic fractionation of the oxygen isotopes. By extrapolation we postulate that no significant fractionation occurs during single-step thermal dehydroxylation of fine-grained kaolinite, provided that dehydroxylation is performed under well controlled conditions. In contrast, gibbsite dehydroxylation is accompanied by substantial isotopic fractionation. This is probably the result of the complex, multi-pathway dehydroxylation reaction of this mineral. Similarly, thermal dehydroxylation of coarsegrained (>1 ?m) kaolinites and dickites of weathering and hydrothermal origin yield results that are dependent on the temperature of dehydroxylation. We suggest that this effect may be caused by isotopic exchange during diffusion of water molecules through coarse particles. Partial fluorination of fine-grained kaolinite in the presence of excess F2 at low temperatures (<185°C) yields unreproducible ?18O values. When performed at high temperatures (220 240°C) in the presence of insufficient F2, ?18O values are systematically lower than the bulk ?18O value and increase linearly with the percent stoichiometric yield. They are consistent with a greater rate of reaction of hydroxyl oxygen than of non-hydroxyl oxygen, but examination of the isotopic data as well as XRD and IR analyses of the residues after partial fluorination indicates that the separation between the two types of oxygen is not complete. The results, therefore, do not yield a reliable ?18O value of the hydroxyl oxygen. The results of this study suggest that the thermal dehydroxylation technique may be appropriate for analysis of OH groups in fine-grained kaolinite. The partial fluorination approach appears less suitable. Intracrystalline fractionation of oxygen isotopes between hydroxyl and non-hydroxyl sites in kaolinite may be larger than previously reported in experimental studies. Based on the results obtained for the finer-than 1 ?m Macon kaolinite a value of 1.0272 is proposed for the intracrystalline fractionation factor, ?non-OH/OH, of kaolinite at 20 ± 10°C.

Girard, Jean-Pierre; Savin, Samuel M.

1996-02-01

297

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

298

Thermal desorption measurements of hydrogen--isotope retention in the Alcator-A tokamak  

SciTech Connect

Results are presented for deuterium retention measurements in type 304 stainless steel exposed in the edge plasma of the Alcator-A tokamak. Stainless steel samples, at 300 K, with surface conditions characterized by Auger electron spectroscopy, were introduced into the limiter shadow region for exposure to deuterium plasmas, and then withdrawn into an appended UHV chamber for thermal desorption measurements. For unoxidized samples exposed at the vacuum vessel wall radius, 1 x 10/sup 15/ D cm/sup -2/ was retained after exposure to high density (n-bar/sub e/=3 x 10/sup 14/ cm/sup -3/) discharges. Exposure to consecutive series of N discharges produced retention proportional to N/sup 1/2/.

Razdow, A.M.; Marmar, E.S.; Cohen, S.A.; Dylla, H.F.

1980-01-01

299

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

300

Determination of Pu and U isotopes in safeguard swipe sample with extraction chromatographic techniques.  

PubMed

A simple and reliable separation method of plutonium and uranium was developed using extraction chromatographic techniques. Using the separation method of plutonium and uranium developed in this study, recoveries of plutonium and uranium were compared with those by commercial separation methods of Pu and U. The redox reactions of hydrogen peroxide with plutonium in a nitric acid medium were investigated by UV-vis-NIR absorption spectroscopic techniques. The separation method of Pu and U isotopes with the UTEVA resin updated in this study could be effective to measure quantitatively nano- and picogram amounts of uranium and plutonium in swipe samples using isotope dilution thermal ionization mass spectrometry (ID-TIMS). PMID:22063516

Lee, M H; Park, J H; Oh, S Y; Ahn, H J; Lee, C H; Song, K; Lee, M S

2011-10-30

301

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

2011-12-01

302

Constraining groundwater discharge in a large watershed: Integrated isotopic, hydraulic, and thermal data from the Canadian shield  

NASA Astrophysics Data System (ADS)

The objective of this study is to evaluate the pattern and rate of groundwater discharge in a large, regulated fractured rock watershed using novel and standard methods that are independent of base flow recession. Understanding the rate and pattern of groundwater discharge to surface water bodies is critical for watershed budgets, as a proxy for recharge rates, and for protecting the ecological integrity of lake and river ecosystems. The Tay River is a low-gradient, warm-water river that flows over exposed and fractured bedrock or a thin veneer of coarse-grained sediments. Natural conservative (?2H, ?18O, Cl, and specific conductance), radioactive (222Rn), and thermal tracers are integrated with streamflow measurements and a steady state advective model to delimit the discharge locations and quantify the discharge fluxes to lakes, wetlands, creeks, and the Tay River. The groundwater discharge rates to most surface water body types are low, indicating that the groundwater and surface water system may be largely decoupled in this watershed compared to watersheds underlain by porous media. Groundwater discharge is distributed across the watershed rather than localized around lineaments or high-density zones of exposed brittle fractures. The results improve our understanding of the rate, localization, and conceptualization of discharge in a large, fractured rock watershed. Applying hydraulic, isotopic, or chemical hydrograph separation techniques would be difficult because the groundwater discharge "signal" is small compared to the "background" surface water inflows or volumes of the surface water bodies. Although this study focuses on a large watershed underlain by fractured bedrock, the methodology developed is transferable to any large regulated or unregulated watershed. The low groundwater discharge rates have significant implications for the ecology, sustainability, and management of large, crystalline watersheds.

Gleeson, Tom; Novakowski, Kent; Cook, Peter G.; Kyser, T. Kurt

2009-08-01

303

Standard test method for determination of uranium or plutonium isotopic composition or concentration by the total evaporation method using a thermal ionization mass spectrometer  

E-print Network

1.1 This method describes the determination of the isotopic composition and/or the concentration of uranium and plutonium as nitrate solutions by the thermal ionization mass spectrometric (TIMS) total evaporation method. Purified uranium or plutonium nitrate solutions are loaded onto a degassed metal filament and placed in the mass spectrometer. Under computer control, ion currents are generated by heating of the filament(s). The ion beams are continually measured until the sample is exhausted. The measured ion currents are integrated over the course of the run, and normalized to a reference isotope ion current to yield isotopic ratios. 1.2 In principle, the total evaporation method should yield isotopic ratios that do not require mass bias correction. In practice, some samples may require this bias correction. When compared to the conventional TIMS method, the total evaporation method is approximately two times faster, improves precision from two to four fold, and utilizes smaller sample sizes. 1.3 The tot...

American Society for Testing and Materials. Philadelphia

2007-01-01

304

Characterization of Volatile Nylon 6.6 Thermal-Oxidative Degradation Products by Selective Isotopic Labeling and Cryo-GC/MS  

NASA Astrophysics Data System (ADS)

Aged materials, such as polymers, can exhibit modifications to their chemical structure and physical properties, which may render the material ineffective for its intended purpose. Isotopic labeling was used to characterize low-molecular weight volatile thermal-oxidative degradation products of nylon 6.6 in an effort to better understand and predict changes in the aged polymer. Headspace gas from aged (up to 243 d at 138 °C) nylon 6.6 monomers (adipic acid and 1,6-hexanediamine) and polymer were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). Observations regarding the relative concentrations observed in each chromatographic peak with respect to aging time were used in conjunction with mass spectra for samples aged under ambient air to determine the presence and identity of 18 degradation products. A comparison of the National Institute of Standards and Technology (NIST) library, unlabeled, and isotopically labeled mass spectra (C-13 or N-15) and expected fragmentation pathways of each degradation product were used to identify the location of isotopically labeled atoms within the product's chemical structure, which can later be used to determine the exact origin of the species. In addition, observations for unlabeled nylon 6.6 aged in an O-18 enriched atmosphere were used to determine if the source of oxygen in the applicable degradation products was from the gaseous environment or the polymer. Approximations for relative isotopic ratios of unlabeled to labeled products are reported, where appropriate.

Smith, Jonell N.; V. White, Gregory; White, Michael I.; Bernstein, Robert; Hochrein, James M.

2012-09-01

305

Characterization of volatile nylon 6.6 thermal-oxidative degradation products by selective isotopic labeling and cryo-GC/MS.  

PubMed

Aged materials, such as polymers, can exhibit modifications to their chemical structure and physical properties, which may render the material ineffective for its intended purpose. Isotopic labeling was used to characterize low-molecular weight volatile thermal-oxidative degradation products of nylon 6.6 in an effort to better understand and predict changes in the aged polymer. Headspace gas from aged (up to 243 d at 138 °C) nylon 6.6 monomers (adipic acid and 1,6-hexanediamine) and polymer were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). Observations regarding the relative concentrations observed in each chromatographic peak with respect to aging time were used in conjunction with mass spectra for samples aged under ambient air to determine the presence and identity of 18 degradation products. A comparison of the National Institute of Standards and Technology (NIST) library, unlabeled, and isotopically labeled mass spectra (C-13 or N-15) and expected fragmentation pathways of each degradation product were used to identify the location of isotopically labeled atoms within the product's chemical structure, which can later be used to determine the exact origin of the species. In addition, observations for unlabeled nylon 6.6 aged in an O-18 enriched atmosphere were used to determine if the source of oxygen in the applicable degradation products was from the gaseous environment or the polymer. Approximations for relative isotopic ratios of unlabeled to labeled products are reported, where appropriate. PMID:22711515

Smith, Jonell N; White, Gregory V; White, Michael I; Bernstein, Robert; Hochrein, James M

2012-09-01

306

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

307

The abundance and isotopic composition of Cd in iron meteorites  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

308

Direct isotope ratio analysis of individual uranium-plutonium mixed particles with various U/Pu ratios by thermal ionization mass spectrometry.  

PubMed

Uranium and plutonium isotope ratios in individual uranium-plutonium (U-Pu) mixed particles with various U/Pu atomic ratios were analyzed without prior chemical separation by thermal ionization mass spectrometry (TIMS). Prior to measurement, micron-sized particles with U/Pu ratios of 1, 5, 10, 18, and 70 were produced from uranium and plutonium certified reference materials. In the TIMS analysis, the peaks of americium, plutonium, and uranium ion signals were successfully separated by continuously increasing the evaporation filament current. Consequently, the uranium and plutonium isotope ratios, except the (238)Pu/(239)Pu ratio, were successfully determined for the particles at all U/Pu ratios. This indicates that TIMS direct analysis allows for the measurement of individual U-Pu mixed particles without prior chemical separation. PMID:25479434

Suzuki, Daisuke; Esaka, Fumitaka; Miyamoto, Yutaka; Magara, Masaaki

2015-02-01

309

Thermal ionization cavity source for mass spectrometry  

SciTech Connect

Thermal ionization mass spectrometry (TIMS) is widely used for isotopic determination, and elemental concentration measurements by isotope dilution. TIMS is applicable to over 70 elements in the periodic table, often, with very high sensitivity, low detection limits, high precision, and high accuracy. Probably due to its success and simplicity, the traditional resistively heated filament type ion source, used in TIMS, has remained relatively unchanged in the past 50 years. Only minor changes in the number of filaments used for vaporization and ionization, and the shape of the filament have been employed. Much of the science of thermal ionization has focused on sample preparation, and chemical ionization enhancers. Beyer et al., in the USSR, and Johnson et al., later in the US, introduced a new high temperature cavity-type thermal ionization source for isotope separation on-line (ISOL) projects. Delmore et al. introduced a similar cavity-type source for the study of thermal emission of primary ions for secondary ionization mass spectrometry (SIMS). A new thermal ionization cavity-type source for mass spectrometry has been developed in this laboratory.

Olivares, J.A.; Chamberlin, E.P.; Duan, Yixiang [Los Alamos National Lab., NM (United States)

1995-12-31

310

Helium dilution refrigeration system  

DOEpatents

A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains .sup.3 He and .sup.4 He liquids which are precooled by a coupled container containing .sup.3 He liquid, enabling the phase separation of a .sup.3 He rich liquid phase from a dilute .sup.3 He-.sup.4 He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the .sup.3 He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute .sup.3 He-.sup.4 He liquid phase.

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

1988-01-01

311

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

312

Mass-dependent and Mass-independent Sulphur Isotope Fractionation Accompanying Thermal- and Photo-chemical Decomposition of Sulphur Bearing Organic Compounds  

NASA Astrophysics Data System (ADS)

The bimodal S-isotope record, specifically the transition from mass independent (MIF) to mass dependent fractionation (MDF), is perhaps the most widely cited line of evidence for an irreversible rise in atmospheric oxygen at ca. 2.4Ga. The production and preservation of S-MIF, manifested in both ?33S and ?36S, within the geological record are linked to atmospheric O2 via a number of arguments. However, to date, the only mechanism capable of generating S-MIF consistent with the Archaean sedimentary records involves gas-phase ultraviolet irradiation of SO21 photolysis. More recently, ?33S S-MIF trends have been reported from en vitro thermochemical sulphate reduction (TSR) experiments, prompting authors to question the importance of S-MIF as a proxy for Earth oxidation2. Importantly, whilst emerging TSR experiments3,4 affirm the reported ?33S trends2, these experiments fail to identify correlated S-MIF between ?33S and ?36S values3,4. Realization that S-MIF is confined to ?33S during TSR, precludes TSR as a mechanism responsible for the origin of the Archaean S-MIF record but strongly suggests the effect originating from a magnetic isotope effect (MIE) associated with 33S nucleus3,4. Clearly, photochemical and thermochemical processes impart different ?36S/?33S trends with significant variation in ?34S; however, a complete experimental elucidation of mechanisms responsible for the S-MIF and S-MIE signatures is lacking. Interestingly, a complete understanding of the S-isotope chemistry during thermal- and photo-chemical decomposition may reveal wavelength and thermal dependence archived in the sedimentary record. Here we extend the experimental database to explore the magnitude and sign of ?36S/?33S and ?34S produced during both photo- and thermochemical processes. Here the organic sulphur compounds (OSC) utilized in these experiments carries diagnostic ?36S/?33S patterns that differ from those reported from photolysis experiment SO2 and from the Archaean sedimentary record. Further thermal decomposition of several sulphur containing compounds with; 1) an aliphatic-S (e.g., diphenyl disulphide), 2) tri-substituted aromatic-S (trithiane), and S-amino acids (e.g., cysteine, methionine, taurine, and glutathionine) were tested for four S-isotope fractionation under vacuum. Among these, aromatic trithiane produced anomalous 33S up to 1.3‰, indicating thermal decomposition through radical chemistry, producing S-MIE. While taurine with sulphonic acid (R-SO2OH) functional groups yielded S-MDF up to 15‰ (between the AVS and the residual OSC), which is consistent with estimated zero-point energy shifts for thiol (R-SH), and thiyl (R-S-CH3) groups of cysteine and methionine, respectively. These results suggest that OSC might undergo either thermal or photochemical decomposition and the S-MIF, S-MDF, and S-MIE signatures may be archived in the geologic record. The emerging mechanisms responsible for these isotope signals and their implications will be discussed in more detail. Ultimately this work offers a framework where these signals can be used as a diagnostic marker to distinguish between thermo- and photochemical processes. References: 1. Farquhar et al., Science 2000 2. Watanabe et al., Science 2010; 3. Oduro et al., PNAS 2011; 4. Kopf and Ono, GCA 2012.

Oduro, Harry; Izon, Gareth; Ono, Shuhei

2014-05-01

313

Sequential separation of light rare-earth elements, thorium and uranium by miniaturized extraction chromatography: Application to isotopic analyses of silicate rocks  

Microsoft Academic Search

A new method for the concomitant separation of the light rare-earth elements (LREEs), thorium and uranium is described, and applied to the determination of 143Nd144Nd ratios, and concentrations of Sm, Nd, Th and U in silicate rocks, using isotope dilution and thermal ionization mass spectrometry. The proposed scheme is based on two recently introduced extraction chromatographic materials, referred to as

Christian Pin; JoséFrancisco Santos Zalduegui

1997-01-01

314

A new series of uranium isotope reference materials for investigating the linearity of secondary electron multipliers in isotope mass spectrometry  

NASA Astrophysics Data System (ADS)

A new series of gravimetrically prepared uranium isotope reference materials, the so-called IRMM-074 series, with the n(235U)/n(238U) isotope ratio held constant at unity and the n(233U)/n(238U) isotope ratios varying from 1.0 to 10-6 has been prepared and certified. This series is suited for calibration of secondary electron multipliers used widely in isotope mass spectrometry, in particular for techniques such as thermal ionization mass spectrometry (TIMS), inductively coupled plasma mass spectrometry (ICPMS), accelerator mass spectrometry (AMS) and resonance ionization mass spectrometry (RIMS). The new IRMM-074 was prepared as a replacement for the already exhausted IRMM-072 predecessor series. Uranium materials with high isotopic enrichments of 233U, 235U and 238U were purified using identical methods involving separation on anion and cation column followed by a precipitation as peroxide. The oxides were calcined to convert them to U3O8 simultaneously, in an oven installed in a glove-box that provided a controlled low-humidity environment. The oxides of 235U and 238U were weighed and mixed with a mole ratio n(235U)/n(238U) = 1.0 and then dissolved. The 233U oxide was dissolved to form a separate solution with the same concentration and 6rom this primary solution three dilutions were made by weighing. A weighed amount of the n(235U)/n(238U) solution and weighed amounts of the 233U solutions were mixed in various proportions in order to achieve n(233U)/n(238U) isotope ratios varying from 1.0 to 10-6. The methods for the preparation, the mixing and the mixing calculations are described. The expanded uncertainties (coverage factor k = 2) of the certified isotope ratios for the IRMM-074 series are 0.015% for the n(235U)/n(238U) ratio and 0.025% for the n(233U)/n(238U) ratios, which constitutes an improvement compared to those of the predecessor IRMM-072 series. In addition, recent observations regarding the linearity response of secondary electron multipliers (SEMs) and suitable reference materials for investigating detector linearity are reviewed. Two measurement procedures for applying the IRMM-072 and IRMM-073 (diluted from the remaining fraction of IRMM-072) series as well as the new IRMM-074 series for assessing SEM linearity are suggested. The procedures are tailor-made for the specific instrumental characteristics of thermal ionization mass spectrometers (TIMS) and multiple-collector inductively coupled plasma mass spectrometers (MC-ICPMS) but can be adapted also for further types of isotope ratio mass spectrometers.

Richter, S.; Alonso, A.; Aregbe, Y.; Eykens, R.; Kehoe, F.; Kühn, He; Kivel, N.; Verbruggen, A.; Wellum, R.; Taylor, P. D. P.

2009-04-01

315

A Novel Approach to Investigate Soil Organic Matter Development Using Isotopes and Thermal Analysis: C Sourcing from Various Plant Materials and Mineral Influence on Stability  

NASA Astrophysics Data System (ADS)

Biomolecular input quality and mineral constituents are important factors that regulate turnover and stabilization of natural organic matter. The complexity and variability of natural soil systems might shadow basic mechanisms occurring between organic and mineral components. Utilizing an in vitro model decomposition system allows for control over inputs and turnover time. We created a model soil system with composted plant litter that was enriched with 13-C in order to investigate C use during the formation of stabilized SOM. The litter was subjected to microbially-mediated, aerobic decomposition before pure clays were added and allowed to incubate further. Isotopically labeled organic inputs allowed us to focus on C derived from known plant sources as a qualitative assessment of SOM formation. Thermogravimetry-Differential Scanning Calorimetry (TG-DSC) has been used successfully to quantify thermochemical properties of SOM reactivity/stability in three regions of exothermic activity corresponding generally to carbohydrates and lipids (Exo 1; 150-350 C), aromatic and condensed polymers (Exo 2; 400-460 C) and refractory/mineral associated C (Exo 3; 500-550 C). Thermal separation of the organics allows for in-line evolved gas analysis via Isotope Ratio Mass Spectrometry (IRMS) to measure 13-C isotopic values of those thermally separated organic compound classes. This coupled analysis is ideal in that it is fast, reproducible, and requires no sample pretreatment other than drying/grinding and it provides stability, mass loss, and isotopic data from a single sample. DSC results show the development of a higher temperature, energetically recalcitrant C pool over the course of decomposition in mineral-free litters and its absence in clay-litter mixtures, implicating the influence of mineral surfaces on soil organic matter energetic stability. Preliminary IRMS results indicate that mineral presence influences C sourcing from particular plant materials in some SOM compound classes. For example, in mineral-free treatments containing 13-C enriched woody material, gas evolution from Exo 3 that was enriched in 13-C and was therefore derived from the woody material. However, the presence of montmorillonite clay minerals resulted in gas evolution that was depleted in 13-C and was therefore derived from the non-woody plant inputs present (grass and leaves). This shows a change in mechanism: either the microbial sourcing of C from woody material to produce Exo 3 compounds changed in the presence of the mineral or mineral interaction with the organics altered the thermal reactivity of those wood-derived compounds, causing them to thermally separate differently. We are also exploring the effect of bridging metal interaction with minerals and plant litter as SOM develops. We are able to show that this analytical method is useful for probing mineral influence on SOM stability and differentiation in litter C utilization during decomposition in a single sample. TG-DSC-IRMS analysis can be used for any soil-organic matter investigation, with isotopically enriched or natural abundance materials: applications range from measuring terrestrial C sequestration efforts and organic waste management efficacy to sustainable agricultural practices.

Bower, J.; Horwath, W. R.

2012-12-01

316

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

USGS Publications Warehouse

The oxygen isotope compositions of dissolved sulfate and water from hot springs and shallow drillholes have been tested as a geothermometer in three areas of the western United States. Limited analyses of spring and borehole fluids and existing experimental rate studies suggest that dissolved sulfate and water are probably in isotopic equilibrium in all reservoirs of significant size with temperatures above ca. 140??C and that little re-equilibration occurs during ascent to the surface. The geothermometer is, however, affected by changes in ??18O of water due to subsurface boiling and dilution and by addition of sulfate of nearsurface origin. Methods are described to calculate the effects of boiling and dilution. The geothermometer, is applied to thermal systems of Yellowstone Park, Wyoming, Long Valley, California, and Raft River, Idaho to estimate deep reservoir temperatures of 360, 240, and 142??C, respectively. ?? 1976.

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

1977-01-01

317

Considerations in the Application of Multiple Ion Counting for the Trace Analysis of Plutonium and Uranium Isotope Ratios Using Thermal Ionization and Inductively-Coupled Plasma Mass Spectrometry  

NASA Astrophysics Data System (ADS)

The use of simultaneous multiple-ion counting for the analysis of small samples of plutonium and uranium has been investigated using three different instruments, the ThermoElectron Neptune inductively-coupled plasma mass spectrometer, the ThermoElectron Triton thermal ionization mass spectrometer, and the Isotopex Iso-T thermal ionization mass spectrometer. The Neptune and Triton instruments utilize identical multiple ion counter arrays, with ions impinging directly on the channeltron surface. The Isotopex instruments utilize a different style of channeltron detector. The most significant difference in the Isotopex detectors is the presence of a conversion dynode at the entrance to the channeltron. Results suggest that the performance of the ThermoElectron MIC system varies between the Neptune and Triton instruments, which probably reflects both differences in the inherent characteristics of plasma and thermal sources and the performance of the MICS themselves. Differences in performance and stability between the '"naked"' and conversion dynode equipped channeltrons on the two thermal ionization instruments support these observations. These differences suggest that different analytical approaches to calibration of the multiple-ion counters may be required. Differences in potential analytical strategies employing multiple ion counters on the different instruments, including calibration schemes, precision and accuracy limits, and analytical strategies that can be employed, will be discussed. Results from both thermal ionization and inductively-coupled plasma sources suggest that the dominant source of uncertainty in isotope ratio measurement using multiple ion counting shifts from counting limitations for very small signals to uncertainties in gain calibration and detector drift among the ion counters at higher count rates. These characteristics place limits on the applicability of multiple ion counters; results from mixed Faraday/multiple ion counting analysis will illustrate the potential to overcome some of these limitations.

Riciputi, L. R.

2008-12-01

318

Thermal history and origin of the Tanzanian Craton from Pb isotope thermochronology of feldspars from lower crustal xenoliths  

NASA Astrophysics Data System (ADS)

Common and radiogenic Pb isotopic compositions of plagioclase and anti-perthitic feldspars from granulite-facies lower crustal xenoliths from the Labait Volcano on the eastern margin of the Tanzanian Craton have been measured via laser ablation MC-ICP-MS. Common Pb in plagioclase and a single stage Pb evolution model indicate that the lower crust of the Tanzanian Craton was extracted from mantle having a 238U/ 204Pb of 8.1 ± 0.3 and a 232Th/ 238U of 4.3 ± 0.1 at 2.71 ± 0.09 Ga (all uncertainties are 2?). Since 2.4 Ga, some orthoclase domains within anti-perthites have evolved with a maximum 238U/ 204Pb of 6 and 232Th/ 238U of 4.3. The spread in Pb isotopic composition in the anti-perthitic feldspars yields single crystal Pb-Pb isochrons of ˜ 2.4 Ga, within uncertainty of U-Pb zircon ages from the same sample suite. The Pb isotopic heterogeneities imply that these granulites resided at temperatures < 600 °C in the lower crust of the Tanzanian Craton from ca. 2.4 Ga to the present. In concert with the chemistry of surface samples, mantle xenoliths, and lower crustal xenoliths, our data imply that the cratonic lithosphere in Tanzania formed ca. ˜ 2.7 Ga, in a convergent margin setting, and has remained undisturbed since 2.7 Ga.

Bellucci, Jeremy J.; McDonough, William F.; Rudnick, Roberta L.

2011-01-01

319

Evaluation of two gas-dilution methods for instrument calibration  

NASA Technical Reports Server (NTRS)

Two gas dilution methods were evaluated for use in the calibration of analytical instruments used in air pollution studies. A dual isotope fluorescence carbon monoxide analyzer was used as the transfer standard. The methods are not new but some modifications are described. The rotary injection gas dilution method was found to be more accurate than the closed loop method. Results by the two methods differed by 5 percent. This could not be accounted for by the random errors in the measurements. The methods avoid the problems associated with pressurized cylinders. Both methods have merit and have found a place in instrument calibration work.

Evans, A., Jr.

1977-01-01

320

Diluted magnetic semiconductors  

Microsoft Academic Search

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

Nitin Samarth; J. K. Furdyna

1990-01-01

321

Dispersion serial dilution methods using the gradient diluter device.  

PubMed

A solute aspirated into a prefilled tube of diluent undergoes a dilution effect known as dispersion. Traditionally the effects of dispersion have been considered a negative consequence of using liquid-filled fixed-tip liquid handlers. We present a novel device and technique that utilizes the effects of dispersion to the benefit of making dilutions. The device known as the Gradient Diluter extends the dilution range of practical serial dilutions to six orders of magnitude in final volumes as low as 10??L. Presented are the device, dispersion methods, and validation tests using fluorescence detection of sulforhodamine and the high-performance liquid chromatography/ultraviolet detection of furosemide. In addition, a T-cell inhibition assay of a relevant downstream protein is used to demonstrate IC(50) curves made with the Gradient Diluter compare favorably with those generated by hand. PMID:22364546

Walling, Leslie; Schulz, Craig; Johnson, Michael

2012-12-01

322

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

NASA Technical Reports Server (NTRS)

The impact histories on chondrite parent bodies can be deduced from thermochronologic analyses of materials and isotope systems with distinct apparent closure temperatures. It is especially critical to better understand the geological histories and physical properties of potenally hazardous near-Earth asteroids. Chelyabinsk is an LL5 chondrite meteorite that was dispersed over a wide area tens of kilometers south of the town of Chelyabinsk, Russia by an explosion at an altitude of 27 km at 3:22 UT on 15 Feb 2013 [1,2]. The explosion resulted in significant damage to surrounding areas and over 1500 injuries along with meteorite fragments being spread over a wide area [1].

Lapen, T. J.; Kring, D. A.; Zolensky, M. E.; Andreasen, R.; Righter, M.; Swindle, T. D.; Beard, S. P.; Swindle, T. D.

2014-01-01

323

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

NASA Astrophysics Data System (ADS)

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

Jung, J.; Kawamura, K.

2011-05-01

324

Sensitive determination of RDX, nitroso-RDX metabolites, and other munitions in ground water by solid-phase extraction and isotope dilution liquid chromatography–atmospheric pressure chemical ionization mass spectrometry  

Microsoft Academic Search

Recent improvements in the LC–MS interface have increased the sensitivity and selectivity of this instrument in the analysis of polar and thermally-labile aqueous constituents. Determination of RDX, nitroso-RDX metabolites, and other munitions was enhanced using LC–MS with solid-phase extraction, 15N3-RDX internal standard, and electrospray ionization (ESI) in negative ion mode. ESI produced a five-fold increase in detector response over atmospheric

D. A. Cassada; S. J. Monson; D. D. Snow; R. F. Spalding

1999-01-01

325

Quantification of Thiazolidine-4-carboxylic Acid in Toxicant-Exposed Cells by Isotope-Dilution Liquid Chromatography-Mass Spectrometry Reveals an Intrinsic Antagonistic Response to Oxidative Stress-Induced Toxicity.  

PubMed

Carcinogenic formaldehyde is produced by endogenous protein oxidation and various exogenous sources. With formaldehyde being both ubiquitous in the ambient environment and one of the most common reactive carbonyls produced from endogenous metabolism, quantifying formaldehyde exposure is an essential step in risk assessments. We present in this study an approach to assess the risk of exposure to oxidative stress by quantifying thiazolidine-4-carboxylic acid (TA), a cysteine-conjugated metabolite of formaldehyde in toxicant-exposed Escherichia coli. The method entails TA derivatization with ethyl chloroformate, addition of isotope-labeled TA derivatives as internal standards, solid-phase extraction of the derivatives, and quantification by liquid chromatography-mass spectrometry (LC-MS). After validating for accuracy and precision, the developed method was used to detect TA in oxidizing agent-exposed E. coli samples. Dose-dependent TA formation was observed in E. coli exposed to hydroxyl radical mediators Fe(2+)-EDTA, H2O2, and NaOCl, indicating the potential use of TA as a biomarker of exposure to oxidative stress and disease risk. PMID:25325739

Liu, Jingjing; Chan, Wan

2014-10-30

326

Simultaneous determination of testosterone, cortisol, and dehydroepiandrosterone in saliva by stable isotope dilution on-line in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry.  

PubMed

We have developed a simple and sensitive method for the simultaneous determination of testosterone (TES), cortisol (CRT), and dehydroepiandrosterone (DHEA) in saliva by automated online in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a Discovery HS F5 column. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 ?L of sample at a flow rate of 200 ?L/min using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. The in-tube SPME LC-MS/MS method showed good linearity with correlation coefficients r ? 0.9998 for TES, CRT, and DHEA using their respective stable isotope-labeled internal standards. The intra-day and inter-day precisions (relative standard deviations) were below 4.9 and 8.5 % (n = 5), respectively. This method was successfully utilized to analyze TES, CRT, and DHEA in saliva samples without any other pretreatment or interference peaks, and the quantification limits (S/N = 10) of TES, CRT and DHEA were about 0.01, 0.03 and 0.29 ng/mL saliva, respectively. The recoveries of these compounds spiked into saliva samples were each above 94%. This method was applied to analyze changes in salivary TES, CRT, and DHEA levels resulting from stress and fatigue load. PMID:23064711

Kataoka, Hiroyuki; Ehara, Kentaro; Yasuhara, Rie; Saito, Keita

2013-01-01

327

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

Microsoft Academic Search

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

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

1997-01-01

328

Dilution jet mixing program  

NASA Technical Reports Server (NTRS)

Parametric tests were conducted to quantify the mixing of opposed rows of jets (two-sided injection) in a confined cross flow. Results show that jet penetrations for two sided injections are less than that for single-sided injections, but the jet spreading rates are faster for a given momentum ratio and orifice plate. Flow area convergence generally enhances mixing. Mixing characteristics with asymmetric and symmetric convergence are similar. For constant momentum ratio, the optimum S/H(0) with in-line injections is one half the optimum value for single sided injections. For staggered injections, the optimum S/H(0) is twice the optimum value for single-sided injection. The correlations developed predicted the temperature distributions within first order accuracy and provide a useful tool for predicting jet trajectory and temperature profiles in the dilution zone with two-sided injections.

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

1984-01-01

329

Extraction Chromatographic Methods in the Sample Preparation Sequence for Thermal Ionization Mass Spectrometric Analysis of Plutonium Isotopes  

SciTech Connect

A sample preparation sequence for actinide isotopic analysis by 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 isotopic spikes through the separation sequence. Pu recoveries were 87% and 86% for TEVA- and DGA-resins separations respectively. The Pu recoveries from 400 {mu}L anion-exchange column separations 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-sigma) 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 spikes in the experimental set. 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.

Grate, Jay W.; O'Hara, Matthew J.; Farawila, Anne F.; Douglas, Matthew; Haney, Morgan M.; Peterson, Steve L.; Maiti, Tapas C.; Aardahl, Christopher L.

2011-10-17

330

Standard dilution analysis.  

PubMed

Standard dilution analysis (SDA) is a novel calibration method that may be applied to most instrumental techniques that will accept liquid samples and are capable of monitoring two wavelengths simultaneously. It combines the traditional methods of standard additions and internal standards. Therefore, it simultaneously corrects for matrix effects and for fluctuations due to changes in sample size, orientation, or instrumental parameters. SDA requires only 200 s per sample with inductively coupled plasma optical emission spectrometry (ICP OES). Neither the preparation of a series of standard solutions nor the construction of a universal calibration graph is required. The analysis is performed by combining two solutions in a single container: the first containing 50% sample and 50% standard mixture; the second containing 50% sample and 50% solvent. Data are collected in real time as the first solution is diluted by the second one. The results are used to prepare a plot of the analyte-to-internal standard signal ratio on the y-axis versus the inverse of the internal standard concentration on the x-axis. The analyte concentration in the sample is determined from the ratio of the slope and intercept of that plot. The method has been applied to the determination of FD&C dye Blue No. 1 in mouthwash by molecular absorption spectrometry and to the determination of eight metals in mouthwash, wine, cola, nitric acid, and water by ICP OES. Both the accuracy and precision for SDA are better than those observed for the external calibration, standard additions, and internal standard methods using ICP OES. PMID:25599250

Jones, Willis B; Donati, George L; Calloway, Clifton P; Jones, Bradley T

2015-02-17

331

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

USGS Publications Warehouse

We present the results of a combined U-series isotope and numerical modeling study of the 1912 Katmai-Novarupta eruption in Alaska. A stratigraphically constrained set of samples have compositions that range from basalt through basaltic andesite, andesite, dacite, and rhyolite. The major and trace element range can be modeled by 80–90% closed-system crystal fractionation over a temperature interval from 1279°C to 719°C at 100 MPa, with an implied volume of parental basalt of ?65 km3. Numerical models suggest, for wall rock temperatures appropriate to this depth, that 90% of this volume of magma would cool and crystallize over this temperature interval within a few tens of kiloyears. However, the range in 87Sr/86Sr, (230Th/238U), and (226Ra/230Th) requires open-system processes. Assimilation of the host sediments can replicate the range of Sr isotopes. The variation of (226Ra/230Th) ratios in the basalt to andesite compositional range requires that these were generated less than several thousand years before eruption. Residence times for dacites are close to 8000 years, whereas the rhyolites appear to be 50–200 kyr old. Thus, the magmas that erupted within only 60 h had a wide range of crustal residence times. Nevertheless, they were emplaced in the same thermal regime and evolved along similar liquid lines of descent from parental magmas with similar compositions. The system was built progressively with multiple inputs providing both mass and heat, some of which led to thawing of older silicic material that provided much of the rhyolite.

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

2010-01-01

332

The Anisotropic Transport Effects on Dilute Plasmas  

NASA Astrophysics Data System (ADS)

We examine the linear stability analysis of a hot, dilute, and differentially rotating plasma by considering anisotropic transport effects. In dilute plasmas, the ion Larmor radius is small compared with its collisional mean free path. In this case, the transport of heat and momentum along the magnetic field lines becomes important. This paper presents a novel linear instability that may be more powerful and greater than ideal magnetothermal instability and ideal magnetorotational instability in the dilute astrophysical plasmas. This type of plasma is believed to be found in the intracluster medium (ICM) of galaxy clusters and radiatively ineffective accretion flows around black holes. We derive the dispersion relation of this instability and obtain the instability condition. There is at least one unstable mode that is independent of the temperature gradient direction for a helical magnetic field geometry. This novel instability is driven by the gyroviscosity coupled with differential rotation. Therefore, we call it gyroviscous-modified magnetorotational instability (GvMRI). We examine how the instability depends on signs of the temperature gradient and the gyroviscosity and also on the magnitude of the thermal frequency and on the values of the pitch angle. We provide a detailed physical interpretation of the obtained results. The GvMRI is applicable not only to the accretion flows and ICM but also to the transition region between cool dense gas and the hot low-density plasma in stellar coronae, accretion disks, and the multiphase interstellar medium because it is independent of the temperature gradient direction.

Devlen, Ebru

2011-04-01

333

Cadmium measurements in coral skeleton using isotope dilutioninductively coupled plasmamass spectrometry  

E-print Network

Cadmium measurements in coral skeleton using isotope dilution­inductively coupled plasma. Components: 4699 words, 2 figures, 4 tables. Keywords: Cd/Ca; upwelling; cadmium; ID-ICP-MS; coral. Index. McDonough, and A. G. Grottoli (2006), Cadmium measurements in coral skeleton using isotope dilution

Mcdonough, William F.

334

Stress in dilute suspensions  

NASA Technical Reports Server (NTRS)

Generally, two types of theory are used to describe the field equations for suspensions. The so-called postulated equations are based on the kinetic theory of mixtures, which logically should give reasonable equations for solutions. The basis for the use of such theory for suspensions is tenuous, though it at least gives a logical path for mathematical arguments. It has the disadvantage that it leads to a system of equations which is underdetermined, in a sense that can be made precise. On the other hand, the so-called averaging theory starts with a determined system, but the very process of averaging renders the resulting system underdetermined. A third type of theory is proposed in which the kinetic theory of gases is used to motivate continuum equations for the suspended particles. This entails an interpretation of the stress in the particles that is different from the usual one. Classical theory is used to describe the motion of the suspending medium. The result is a determined system for a dilute suspension. Extension of the theory to more concentrated systems is discussed.

Passman, Stephen L.

1989-01-01

335

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

... 2014-07-01 false Dilution air and diluted exhaust flow meters...ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES...Measurements § 1065.240 Dilution air and diluted exhaust flow...

2014-07-01

336

Effects of self-heating and phase change on the thermal profile of hydrogen isotopes in confined geometries  

SciTech Connect

Growth of high-quality single-crystal hydrogen in confined geometries relies on the in situ formation of seed crystals. Generation of deuterium-tritium seed crystals in a confined geometry is governed by three effects: self-heating due to tritium decay, external thermal environment, and latent heat of phase change at the boundary between hydrogen liquid and vapor. A detailed computation of the temperature profile for liquid hydrogen inside a hollow shell, as is found in inertial confinement fusion research, shows that seeds are likely to form at the equatorial plane of the shell. Radioactive decay of tritium to helium slowly alters the composition of the hydrogen vapor, resulting in a modified temperature profile that encourages seed formation at the top of the shell. We show that the computed temperature profile is consistent with a variety of experimental observations.

Baxamusa, S., E-mail: baxamusa1@llnl.gov; Field, J.; Dylla-Spears, R.; Kozioziemski, B.; Suratwala, T.; Sater, J. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)

2014-03-28

337

Sea Urchin Embryology: Sperm Dilution  

NSDL National Science Digital Library

Lab directions for up to two 50 min periods and the last of the dilution labs. Includes set up information, materials, procedure, experimental design, things to observe, math possibilities, thought-provoking questions and an assessment.

PhD David Epel (Stanford U. Hopkins Marine Station)

2007-04-20

338

Sea Urchin Embryology: Simple Dilutions  

NSDL National Science Digital Library

Starting from a known concentration students learn to use dilutions to determine the concentration of an unknown. The following skills are used in this lesson: 1. making dilutions 2. reading the meter on a simple homemade spectrophotometer 3. keeping careful laboratory records 4. graphing on linear graph paper 5. determining an unknown concentration from known 6. using a colored filter to enhance contrast and sensitivity

PhD David Epel (Stanford U. Hopkins Marine Station)

2006-12-20

339

Chromatographic hydrogen isotope separation  

DOEpatents

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

Aldridge, Frederick T. (Livermore, CA)

1981-01-01

340

Calcite Fluid Inclusion, Paragenetic, and Oxygen Isotopic Records of Thermal Event(s) at Yucca Mountain, Nevada  

SciTech Connect

Yucca Mountain, Nevada, is under consideration as a potential high-level radioactive waste repository situated above the water table in 12.7 Ma tuffs. A wealth of textural and geochemical evidence from low-temperature deposits of calcite and silica, indicates that their genesis is related to unsaturated zone (UZ) percolation and that the level of the potential repository has never been saturated. Nonetheless, some scientists contend that thermal waters have periodically risen to the surface depositing calcite and opal in the tuffs and at the surface. This hypothesis received some support in 1996 when two-phase fluid inclusions (FIs) with homogenization temperatures (Th) between 35 and 75 C were reported from UZ calcite. Calcite deposition likely followed closely on the cooling of the tuffs and continues into the present. The paragenetic sequence of calcite and silica in the UZ is early stage calcite followed by chalcedony and quartz, then calcite with local opal during middle and late stages. Four types of FIs are found in calcite assemblages: (1) all-liquid (L); (2) all-vapor (V); (3) 2-phase with large and variable V:L ratios; and (4) a few 2-phase with small and consistent V:L ratios. Late calcite contains no FI assemblages indicating elevated depositional temperatures. In early calcite, the Th of type 4 FIs ranges from {approx} 40 to {approx} 85 C. Such temperatures (sub-boiling) and the assemblage of FIs are consistent with deposition in the UZ. Some delta 18O values < 10 permil in early calcite support such temperatures. Type 4 FIs, however, seem to be restricted to the early calcite stage, during which either cooling of the tuffs or regional volcanism were possible heat sources. Nonetheless, at present there is no compelling evidence of upwelling water as a source for the calcite/opal deposits.

B. Peterman; R. Moscati

2000-08-10

341

Strontium isotope composition of Rotorua geothermal waters  

SciTech Connect

This paper reports that strontium isotope compositions of Rotorua geothermal waters, taken in conjunction with chemical and stable isotope data, are broadly consistent with existing hydrogeologic models, and provide new insights into complex water-rock interactions and fluid-fluid mixing processes. Primary alkali chloride water upwelling in the eastern part of the field have {sup 87}Sr/{sup 86}Sr ratios higher than their presumed aquifer wall rocks, implying a component of more radiogenic strontium from metasedimentary basement. Secondary waters, in contrast, have relatively low {sup 87}Sr/{sup 86}Sr ratios consistent with interaction of primary fluids (variably diluted by deep groundwaters) with rhyolite country rock, followed by shallow dilution by young groundwater. Although complicated by the non-conservative behavior of strontium, the strontium isotope data require significant water-rock interaction in the central and western parts of the Rotorua geothermal field, a feature not made obvious by other chemical or isotope studies.

Graham, I.J. (DSIR Physical Sciences, Nuclear Sciences Group, P.O. Box 31-312, Lower Hutt (NZ))

1992-04-01

342

Isotopically controlled semiconductors  

SciTech Connect

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

Haller, E.E.

2004-11-15

343

Measuring oxygen yields of a thermal conversion/elemental analyzer-isotope ratio mass spectrometer for organic and inorganic materials through injection of CO.  

PubMed

The thermal conversion/elemental analyzer-isotope ratio mass spectrometer (TC/EA-IRMS) is widely used to measure the ?(18) O value of various substances. A premise for accurate ?(18) O measurement is that the oxygen in the sample can be converted into carbon monoxide (CO) quantitatively or at least proportionally. Therefore, a precise method to determine the oxygen yield of TC/EA-IRMS measurements is needed. Most studies have used the CO peak area obtained from a known amount of a solid reference material (for example, benzoic acid) to calibrate the oxygen yield of the sample. Although it was assumed that the oxygen yield of the solid reference material is 100%, no direct evidence has been provided. As CO is the analyte gas for ?(18) O measurement by IRMS, in this study, we use a six-port valve to inject CO gas into the TC/EA. The CO is carried to the IRMS by the He carrier gas and the CO peak area is measured by the IRMS. The CO peak area thus obtained from a known amount of the injected CO is used to calibrate the oxygen yield of the sample. The oxygen yields of commonly used organic and inorganic reference materials such as benzoic acid (C6 H5 COOH), silver phosphate (Ag3 PO4 ), calcium carbonate (CaCO3 ) and silicon dioxide (SiO2 ) are investigated at different reactor temperatures and sample sizes. We obtained excellent linear correlation between the peak area for the injected CO and its oxygen atom amount. C6 H5 COOH has the highest oxygen yield, followed by Ag3 PO4 , CaCO3 and SiO2 . The oxygen yields of TC/EA-IRMS are less than 100% for both organic and inorganic substances, but the yields are relatively stable at the specified reactor temperature and for a given quantity of sample. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25476948

Yin, Xijie; Chen, Zhigang

2014-12-01

344

Isotopic dilution and solvent effect studies using raman difference spectroscopy  

E-print Network

and pyridine-dS, and pyridine-d and benzene-d . An attempt was made to interpret the results in terms of Schweizer and Chandler's theory for the effects of repulsive and spatially slowly varying attractive forces on the vibrational frequency of polyatomic... for this the presence of energy trans- fer processes between excited vibrational states of these molecules is shown. ACKNOWLEDGEMENTS I would like to express my appreciation to the following: To Dr. Jaan Laane for his assistance and support during my stay at Texas...

Johnson, Andrew Norman

2012-06-07

345

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

USGS Publications Warehouse

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

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

1994-01-01

346

Biomathematical modeling for diluted drugs.  

PubMed

Several workers have proven that succussed ultra high dilution of a drug molecule in water or alcoholic medium, even exceeding Avogadro number, can bring forth noticeable physiological changes of an organism. Homeopathic drugs are prepared by dissolving such drug ingredients in distilled water and then the solution is centesimally diluted serially by ethanol. A mathematical model has been proposed by the present worker, which explains why the drug does not become non-molecular even in ultra-high dilution. This is due to loss of homogeneity in the solution, caused by increase of dielectric constant of the medium during the process of potentization. Facilitated binding of the drug molecules with minute physiologically important protein factors may be the cause of visible physiological alterations. PMID:12781641

Chattopadhyay, S

2003-07-01

347

Isotopically controlled semiconductors  

SciTech Connect

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

Haller, Eugene E.

2006-06-19

348

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

E-print Network

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

Saleska, Scott

349

Study of high gain spherical shell ICF targets containing uniform layers of liquid deuterium tritium fuel. A numericial model for analyzing thermal layering of liquid mixtures of hydrogen isotopes inside a spherical inertial confinement fusion target: Final report  

SciTech Connect

A numerical model has been developed to describe the thermally induced behavior of a liquid layer of hydrogen isotopes inside a spherical Inertial Confinement Fusion (ICF) target and to calculate the far-field temperature gradient which will sustain a uniform liquid layer. This method is much faster than the trial-and-error method previously employed. The governing equations are the equations of continuity, momentum, energy, mass diffusion-convection, and conservation of the individual isotopic species. Ordinary and thermal diffusion equations for the diffusion of fluxes of the species are included. These coupled equations are solved by a finite-difference method using upwind schemes, variable mesh, and rigorous boundary conditions. The solution methodology unique to the present problem is discussed in detail. in particular, the significance of the surface tension gradient driven flows (also called Marangoni flows) in forming uniform liquid layers inside ICF targets is demonstrated. Using the theoretical model, the values of the externally applied thermal gradients that give rise to uniform liquid layers of hydrogen inside a cryogenic spherical-shell ICF target are calculated, and the results compared with the existing experimental data.

Simpson, E.M.; Kim, Kyekyoon [Lawrence Livermore National Lab., CA (United States)

1994-05-01

350

Resource Dilution or Resource Augmentation?  

E-print Network

Resource Dilution or Resource Augmentation? Number of Siblings, Birth Order, Sex of the Child Augmentation? Number of Siblings, Birth Order, Sex of the Child and Frequency of Mother's Activities, the labor market, equality, migration, health, or gender. One goal of the SFB is to integrate these fields

Moeller, Ralf

351

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  

Microsoft Academic Search

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% 18 O-enriched CO-CO 2 gas mixtures to control both the oxygen fugacity and the isotopic composition of

F. J. Ryerson; D. Kevin McKeegan

1994-01-01

352

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  

Microsoft Academic Search

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

F. J. Ryerson; K. D. McKeegan

1993-01-01

353

Plume-ridge interaction in the Easter-Salas y Gomez seamount chain-Easter Microplate system: Pb isotope evidence  

NASA Astrophysics Data System (ADS)

Lead isotope ratios are reported on fresh basalt glasses from 28 seamounts located along the western end of the Easter-Salas y Gomez seamount chain (ESC), southeast Pacific for the purpose of testing the mantle plume source-migrating ridge sink (MPS-MRS) model for the origin of this extensive intraplate neovolcanic seamount chain. Most of these basalts west of 103°W are less than 1.5 m.y. old. Results reveal a 1100-km-long westward gradient decreasing in radiogenic Pb from Salas y Gomez to the Easter microplate (EMP). The results confirm the previously established four-point average trend based on data from Salas y Gomez, Easter Island, the east rift, and the west rift of the Easter microplate [Hanan and Schilling, 1989]. Tight linear arrays in Pb isotope space of the combined EMP and ESC data sets indicate binary mixing between the radiogenic isotope-rich Salas y Gomez plume and the depleted asthenosphere source is the dominant factor in controlling Pb isotopic variation in the region. Mapping of the plume component mass fraction reveals not only a westward dilution of the plume component from Salas y Gomez to the EMP but also dilution with depleted material across the ESC on both flanks. The mapping is consistent with the MPS-MRS model which calls for a subhorizontal, sublithospheric plume channel connecting the mantle plume conduit near Salas y Gomez with the East Pacific Rise, where plume flow is confined along a thermal groove. Mixing by entrainment of surrounding depleted material takes place progressively downstream. A numerical thermal lithosphere cooling model reveals a rheological boundary layer (i.e., the base of the lithosphere) shoaling by 1.3° to 3.5° from Salas y Gomez to about 100 km east of the EMP. The slope magnitude is consistent with those suggested by laboratory and numerical fluid dynamic models for hot buoyant plume-ridge channeled flow to develop and be maintained.

Kingsley, Richard H.; Schilling, Jean-Guy

1998-10-01

354

Sea Urchin Embryology: Simple Dilutions 2  

NSDL National Science Digital Library

SUMMARY: Building on what was learned in SIMPLE DILUTION, students will determine the best dilution strategy to solve a dilution problem. 1. Students are given an unknown dye solution and asked to determine its concentration by comparing it with standards they create. 2. Repeated "serial" dilutions will be necessary to determine accurate concentration readings. 3. Varying the color of the filters and the path length will aid in seeing lower concentrations.

PhD David Epel (Stanford U. Hopkins Marine Station)

2006-12-20

355

Science Notes: Dilution of a Weak Acid  

ERIC Educational Resources Information Center

This "Science note" arose out of practical work involving the dilution of ethanoic acid, the measurement of the pH of the diluted solutions and calculation of the acid dissociation constant, K[subscript a], for each diluted solution. The students expected the calculated values of K[subscript a] to be constant but they found that the…

Talbot, Christopher; Wai, Chooi Khee

2014-01-01

356

Rapid accurate isotopic measurements on boron in boric acid and boron carbide.  

PubMed

A procedure is described whereby rapid and accurate isotopic measurements can be performed on boron in boric acid and boron carbide after fusion of these compounds with calcium carbonate. It allows the determination of the isotopic composition of boron in boric acid and boron carbide and the direct assay of boron or the (10)B isotope in boron carbide by isotope-dilution mass spectrometry. PMID:18964086

Duchateau, N L; Verbruggen, A; Hendrickx, F; De Bièvre, P

1986-04-01

357

Heat Transfer Characteristics of Sulfur and Sulfur Diluted with Hydrogen Sulfide Flowing Through Circular Tubes  

E-print Network

diluted with H2S, added as persulfide. Viscosity of sulfur diluted with H2S, added as liquid. . . 50 51 Viscosity of liquid sulfur 52 Characteristics of sulfur-density and thermal conductivity. . . . 53 Heat capacity of sulfur 54 Characteristics... from a reactor. It has a high heat capacity and excellent heat transfer characteris- tics, and does not require special corrosion-resistant system components. Its nuclear properties are also favorable. It is not subject to destructive or hazardous...

Stone, Porter Walwyn

2012-06-07

358

Foraminifera isotopic records... with special attention to high northern latitudes and the impact of sea-ice distillation  

E-print Network

oxygen isotopes in seawater and the ice/ocean volume, thus some linkage with salinity, sea level, etc the isotopic properties of the fresh water end-member that dilutes the ocean, rates of sea-ice formation. Thus, the oxygen 18-salinity relationship carries a specific isotopic signature for any given water

Long, Bernard

359

A Microgravity Helium Dilution Cooler  

NASA Technical Reports Server (NTRS)

We are developing a He-3-He-4 dilution cooler to operate in microgravity. It uses charcoal adsorption pumps and heaters for its operation; it has no moving parts. It currently operates cyclically to well below 0.1 K and we have designed a version to operate continuously. We expect that the continuous version will be able to provide the long-duration cooling that many experiments need at temperatures down to 0.040 K. More importantly, such a dilution cooler could provide the precooling that enables the use of adiabatic demagnetization techniques that can reach temperatures below 0.001 K. At temperatures below 0.002 K many fascinating microgravity experiments on superfluid He-3 become possible. Among the possibilities are: research into a superfluid He-3 gyroscope, study of the nucleation of the B-phase of superfluid He-3 when the sample is floating out of contact with walls, study of the anisotropy of the surface tension of the B-phase, and NMR experiments on tiny free-floating clusters of superfluid He-3 atoms that should model the shell structure of nuclei.

Roach, Pat R.; Sperans, Joel (Technical Monitor)

1994-01-01

360

Dilute Acid and Autohydrolysis Pretreatment  

NASA Astrophysics Data System (ADS)

Exposure of cellulosic biomass to temperatures of about 120-210°C can remove most of the hemicellulose and produce cellulose-rich solids from which high glucose yields are possible with cellulase enzymes. Furthermore, the use of dilute sulfuric acid in this pretreatment operation can increase recovery of hemicellulose sugars substantially to about 85-95% of the maximum possible versus only about 65% if no acid is employed. The use of small-diameter tubes makes it possible to employ high solids concentrations similar to those preferred for commercial operations, with rapid heat-up, good temperature control, and accurate closure of material balances. Mixed reactors can be employed to pretreat larger amounts of biomass than possible in such small-diameter tubes, but solids concentrations are limited to about 15% or less to provide uniform temperatures. Pretreatment of large amounts of biomass at high solids concentrations is best carried out using direct steam injection and rapid pressure release, but closure of material balances in such “steam gun” devices is more difficult. Although flow of water alone or containing dilute acid is not practical commercially, such flow-through configurations provide valuable insight into biomass deconstruction kinetics not possible in the batch tubes, mixed reactors, or steam gun systems.

Yang, Bin; Wyman, Charles E.

361

Rb-Sr Isotope Dating of Neoproterozoic (Malani Group) Magmatism from Southwest Rajasthan, India: Evidence of Younger Pan-African Thermal Event by 40Ar 39Ar Studies  

Microsoft Academic Search

This paper reports Rb-Sr isotope ages of the Neoproterozoic volcanics, and associated granitoids of the trans-Aravalli belt of northwestern India. All these rocks along with the earlier reported 779±10 Ma old felsic volcanics from Diri, and Gurapratap Singh of Pali district, Rajasthan, constitute the Malani Group. The study indicates that different rock suites belonging to the Malani Group represent a

S. S. Rathore; T. R. Venkatesan; R. K. Srivastava

1999-01-01

362

Potassium isotopic composition of Australasian tektites  

Microsoft Academic Search

We have analyzed the potassium isotopic composition of four tektites from the Australasian strewn field, spanning a wide diversity of thermal histories, inferred from textures and volatile element contents. Our results indicate no isotopic differences between tektites and terrestrial crustal rocks, placing stringent limits of £2% loss of potassium during the brief duration of high temperature heating experienced by these

Munir Humayun; Christian Koeberl

2004-01-01

363

Dilution in single pass arc welds  

SciTech Connect

A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to develop an expression for dilution as a function of welding variables and thermophysical properties of the filler metal and substrate. Comparison of calculated and experimentally determined dilution values shows the approach provides reasonable predictions of dilution when the melting efficiency can be accurately predicted. The conditions under which such accuracy is obtained are discussed. A diagram is developed from the dilution equation which readily reveals the effect of processing parameters on dilution to aid in parameter optimization.

DuPont, J.N.; Marder, A.R. [Lehigh Univ., Bethlehem, PA (United States). Dept. of Materials Science and Engineering

1996-06-01

364

Neodymium and strontium isotopic study of Australasian tektites - New constraints on the provenance and age of target materials  

NASA Technical Reports Server (NTRS)

The Nd and Sr isotopic compositions of Australasian tectites (including two flanged Australian tectites, two low-SiO2 Muong Nong-type tectites, and three high-SiO2 Muong Nong-type tectites) and the Nd, Sm, Sr, and Rb concentrations were investigated by isotope-dilution thermal ionization mass spectrometry, and the Sm-Nd and Rb-Sr isotope systematics were used to study the characteristics of the parental material. It is shown that the Nd and Sr isotopic data provide evidence that all Australasian tektites were derived from a single sedimentary formation with a narrow range of stratigraphic ages close to 170 Ma. It is suggested that all of the Australasian tektites were derived from a single impact event and that the australites represent the upper part of a melt sheet ejected at high velocity, whereas the indochinites represent melts formed at a lower level in the target material distributed closer to the area of the impact.

Blum, Joel D.; Papanastassiou, D. A.; Wasserburg, G. J.; Koeberl, C.

1992-01-01

365

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Imbibition in an originally oil-wet 2D capillary is the fastest in the case of Alf-38 and slowest in the case of DTAB (among the surfactants studied). Force of adhesion studies and contact angle measurements show that greater wettability alteration is possible with these anionic surfactants than the cationic surfactant studied. The water imbibition rate does not increase monotonically with an increase in the surfactant concentration. A numerical model has been developed that fits the rate of imbibition. Plans for the next quarter include conducting simulation and imbibition studies.

Kishore K. Mohanty

2005-01-01

366

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Laboratory imbibition tests show about 61% oil recovery in the case of Alf-38 and 37% in the case of DTAB. A numerical model has been developed that fits the rate of imbibition of the laboratory experiment. Field-scale fracture block simulation shows that as the fracture spacing increases, so does the time of recovery. Plans for the next quarter include simulation studies.

Kishore K. Mohanty

2005-04-01

367

Dilute Surfactant Methods for Carbonate Formations  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Anionic surfactants (Alfoterra 35, 38) recover more than 40% of the oil in about 50 days by imbibition driven by wettability alteration in the core-scale. Anionic surfactant, Alfoterra-68, recovers about 28% of the oil by lower tension aided gravity-driven imbibition in the core-scale. Residual oil saturation showed little capillary number dependence between 10{sup -5} and 10{sup -2}. Wettability alteration increases as the number of ethoxy groups increases in ethoxy sulfate surfactants. Plans for the next quarter include conducting mobilization, and imbibition studies.

Kishore K. Mohanty

2004-03-31

368

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior, interfacial tension (IFT) and wettability studies. Alfoterra-38 (0.05 wt%), Alfoterra-35 (0.05 wt%), SS-6656 (0.05 wt%), and DTAB (1 wt%) altered the wettability of the initially oil-wet calcite plate to an intermediate/water-wet state. Low IFT ({approx}10{sup -3} dynes/cm) is obtained with surfactants 5-166, Alfoterra-33 and Alfoterra-38. Plans for the next quarter include conducting wettability and mobilization studies.

Kishore K. Mohanty

2003-10-01

369

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Anionic surfactants (SS-6656, Alfoterra 35, 38, 63,65,68) have been identified which can change the wettability of the calcite surface to intermediate/water-wet condition as well or better than the cationic surfactant DTAB with a West Texas crude oil in the presence of Na{sub 2}CO{sub 3}. All the carbonate surfaces (Lithographic Limestone, Marble, Dolomite and Calcite) show similar behavior with respect to wettability alteration with surfactant 4-22. Anionic surfactants (5-166, Alfoterra-33 and Alfoterra-38 and Alfoterra-68), which lower the interfacial tension with a West Texas crude oil to very low values (<10{sup -2} nM/m), have also been identified. Plans for the next quarter include conducting wettability, mobilization, and imbibition studies.

Kishore K. Mohanty

2004-01-01

370

DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS  

SciTech Connect

There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Simulation studies indicate that both wettability alteration and gravity-driven flow play significant role in oil recovery from fractured carbonates. Anionic surfactants (Alfoterra 35, 38) recover about 55% of the oil in about 150 days by imbibition driven by wettability alteration and low tension in the core-scale. Anionic surfactant, Alfoterra-68, recovers about 40% of the oil by lower tension aided gravity-driven imbibition in the core-scale. Cationic surfactant, DTAB recovers about 35% of the oil. Plans for the next quarter include conducting simulation and imbibition studies.

Kishore K. Mohanty

2004-10-01

371

Theoretical study of the hyperfine field at Cu impurities diluted in an iron host  

E-print Network

Magnetic hyperfine field at Cu isotopes as impurities in Fe were recently measured at low temperature. A model to explain these experimental results is proposed. The diluted Cu impurities in the ferromagnetic Fe host are described by an extension of the Daniel-Friedel model, including the next neighbor perturbation. In order to account for the available experimental data in Cu isotopes with atomic masses $A$ = 59, 67, 69 and 71 as impurity, we needed to incorporate the Cu anomaly volume in the effective charge to be screened and in the self-consistent procedures.

A. L. de Oliveira; C. M. Chaves; N. A. de Oliveira; A. Troper

2012-07-13

372

An evaluation of a single-step extraction chromatography separation method for Sm-Nd isotope analysis of micro-samples of silicate rocks by high-sensitivity thermal ionization mass spectrometry.  

PubMed

A single-step separation scheme is presented for Sm-Nd radiogenic isotope system on very small samples (1-3 mg) of silicate rock. This method is based on Eichrom(®) LN Spec chromatographic material and affords a straightforward separation of Sm-Nd from complex matrix with good purity and satisfactory blank levels, suitable for thermal ionization mass spectrometry (TIMS). This technique, characterized by high efficiency (single-step Sm-Nd separation) and high sensitivity (TIMS on NdO(+) ion beam), is able to process rapidly (3-4 h), with low procedure blanks (<10 pg) and very small sample (1-3 mg). Replicate measurements by TIMS on (143)Nd/(144)Nd ratios and Sm-Nd concentrations are presented for eleven international silicate rock reference materials, spanning a wide range of Sm-Nd contents and bulk compositions. The analytical results show a good agreement with recommended values within ±0.004% for the (143)Nd/(144)Nd isotopic ratio and ±2% for Sm-Nd quantification at the 95% confidence level. It is noted that the uncertainty of this method is about 3 times larger than typical precision achievable with two-stage full separation followed by state-of-the-art conventional TIMS using Nd(+) ion beams which require much larger amounts of Nd. Hence, our single-step separation followed by NdO(+) ion beam technique is preferred to the analysis for microsamples. PMID:22023865

Li, Chao-Feng; Li, Xian-Hua; Li, Qiu-Li; Guo, Jing-Hui; Li, Xiang-Hui; Liu, Tao

2011-11-14

373

Turbulence in Dilute Polymer Solutions  

NASA Astrophysics Data System (ADS)

We report measurements of particle trajectories in bulk turbulence of Re < 3200 for a dilute polymer solution of polyethylene oxide or polyacrylamide in water. Dissipation range Lagrangian statistics such as the rms acceleration of fluid particles and the acceleration autocorrelation are extracted from the trajectories. We compare these statistics with those for pure water. At high enough Re we find the rms acceleration for the polymer solution to be significantly less than that of water. The acceleration autocorrelation function decays more slowly for the polymer solution which indicates a change in the small scales of turbulence. More information is available at http:// milou.msc.cornell.edu/turbulence.html. This work is supported by the NSF under grant PHY9988755.

Mordant, Nicholas; Crawford, Alice; Laporta, Arthur; Bodenschatz, Eberhard

2002-03-01

374

Band anticrossing in dilute nitrides  

SciTech Connect

Alloying III-V compounds with small amounts of nitrogen leads to dramatic reduction of the fundamental band-gap energy in the resulting dilute nitride alloys. The effect originates from an anti-crossing interaction between the extended conduction-band states and localized N states. The interaction splits the conduction band into two nonparabolic subbands. The downward shift of the lower conduction subband edge is responsible for the N-induced reduction of the fundamental band-gap energy. The changes in the conduction band structure result in significant increase in electron effective mass and decrease in the electron mobility, and lead to a large enhance of the maximum doping level in GaInNAs doped with group VI donors. In addition, a striking asymmetry in the electrical activation of group IV and group VI donors can be attributed to mutual passivation process through formation of the nearest neighbor group-IV donor nitrogen pairs.

Shan, W.; Yu, K.M.; Walukiewicz, W.; Wu, J.; Ager III, J.W.; Haller, E.E.

2003-12-23

375

Physics with isotopically controlled semiconductors  

SciTech Connect

This paper is based on a tutorial presentation at the International Conference on Defects in Semiconductors (ICDS-25) held in Saint Petersburg, Russia in July 2009. The tutorial focused on a review of recent research involving isotopically controlled semiconductors. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, is the most prominent effect for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples.

Haller, E. E., E-mail: eehaller@lbl.gov [University of California at Berkeley, Department of Materials Science and Engineering (United States)

2010-07-15

376

Chemical characteristics of the major thermal springs of Montana  

USGS Publications Warehouse

Twenty-one thermal springs in western Montana were sampled for chemical, isotope, and gas compositions. Most of the springs issue dilute to slightly saline sodium-bicarbonate waters of neutral to slightly alkaline pH. A few of the springs issue sodium-mixed anion waters of near neutral pH. Fluoride concentrations are high in most of the thermal waters, up to 18 milligramsper litre, while F/Cl ratios range from 3/1 in the dilute waters to 1/10 in the slightly saline waters. Most of the springs are theoretically in thermodynamic equilibrium with respect to calcite and fluorite. Nitrogen is the major gas escaping from most of the hot springs; however, Hunters Hot Springs issue principally methane. The deuterium content of the hot spring waters is typical of meteoric water in western Montana. Geothermal calculations based on silica concentrations and Na-K-Ca ratios indicate that most of the springs are associated with low temperature aquifers (less than 100?C). Chalcedony may be controlling the silica concentrations in these low temperature aquifers even in 'granitic' terranes.

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

1976-01-01

377

Molecular dynamics of a dilute solution of hydrogen in palladium  

SciTech Connect

Molecular-dynamics results on a dilute solution of H in Pd are presentedand compared with available incoherent inelastic neutron-scattering results.The embedded-atom model adopted here does a good job of describing the H-Pdatomic forces probed by incoherent inelastic neutron scattering. The timecorrelation functions associated with the computed spectra are strongly dampedand indicative of the anharmonicity that has been suggested as the principalcontribution to the anomalous isotope dependence of the superconductingtransition temperature in PdH. These results highlight the fact that the H-atomvibrations in Pd-H solutions are low-frequency, large-amplitude vibrationsrelative to vibrations of H atoms in usual covalent interactions. The rmsdisplacement of the H atom from its mean position in the center of the Pdoctahedron compares favorably with the available neutron-diffraction results.

Pratt, L. R.; Eckert, J.

1989-06-15

378

Boiling and dilution in the shallow portion of the Waiotapu geothermal system, New Zealand  

NASA Astrophysics Data System (ADS)

The Waiotapu geothermal system is the largest in terms of surface extent and heat flow (17 km 2 and 600 MW, respectively) of the 20 major geothermal systems in the Taupo Volcanic Zone, New Zealand. Two extinct dacite cones and a rhyolite dome rise about 500 m above the Waiotapu valley. The majority of thermal features occurs in the valley over a relief of only 100 m and lies within coincident apparent resistivity and 30 m depth thermal anomalies. Thermal features comprise near-neutral pH chloride springs (often boiling), acid sulfate springs and mud pools, and mixed waters, the latter including both bicarbonate-chloride and acid sulfate-chloride springs. The majority of the sulfate discharges to the surface in the northern, higher altitude area, while most chloride that reaches the surface does so in the southern portion of the system. Comparison of measured and calculated surface chloride flux (the latter from measured heat flow and reservoir chloride concentrations) indicates that at least half of the deep chloride does not discharge at the surface, but flows laterally to the south at shallow depths, mixing with groundwater. The composition of well discharges indicates a shallow (400 m) reservoir of chloride fluid (about 1350 mg Cl/kg at 230°C) is diluted by a CO 2-rich steam-heated water (nil chloride at about 160°C), the latter located on the margins of the system. This same dilution trend is apparent from the compositional variation and K-Na and K-Mg geothermometry of hot spring waters. However, there is chemical and stable isotope evidence from hot springs that cold groundwater also acts as a diluent at shallow levels, and very near the surface steam-heated acid sulfate waters mix with the upflow. Boiling of the deep chloride fluids prior to dilution results in the stabilization of K-feldspar. In contrast, dilution at shallower depths by the steam-heated waters (both CO 2-rich and acid sulfate) leads to the water compositions initially shifting to K-mica (and interstratified clay) stability, and to kaolinite stability with further dilution and temperature decrease. The composition and distribution of these fluids are consistent with alteration mineralogy and zonation observed in drill core. Although boiling occurs at deeper levels and up to the surface in the upflow zone at Waiotapu, mixing is also common and is the dominant process on the margin and in the near-surface portion of the system. Boiling of deep chloride fluid is very common in the upper 1-2 km of the upflow zone of most geothermal systems, though it may be quenched by mixing with marginal waters, either cold groundwater in high relief terrane, or steam-heated waters in areas of lower relief. CO 2-rich steam-heated waters are common on the margins of systems and will generally underlie the near-surface, acid sulfate steam-heated waters. Interaction with CO 2-rich waters will form K-mica and interstratified clays, while acid sulfate waters cause kaolinite and even alunite to form. The former assemblage is commonly associated with typical low sulfidation epithermal gold mineralization as wallrock alteration, where gold-bearing veins comprise adularia and illite. In contrast, kaolinite is rare, and alunite absent, from a direct spatial and genetic association with gold mineralization in this environment. This implies that mixing of the deep, neutral pH chloride fluid with surficial acid sulfate waters does not commonly lead to ore-grade gold deposition. Mixing with (and cooling by) CO 2-rich, steam-heated waters leads to clay stability, accounting for the large halos of clay alteration and low-grade metal anomalies which often surround veins of high gold grade. In contrast, mixing with surficial acid sulfate waters is unlikely to cause precious metal mineralization because the chloride fluids have already lost the majority of their gold through deeper boiling and dilution.

Hedenquist, Jeffrey W.

1991-10-01

379

Effective Thermal Conductivity of Composites with Interfacial Thermal Barrier Resistance  

Microsoft Academic Search

A modification of the original theories of Rayleigh and Maxwell permitted the deriva tion of expressions for the effective thermal conductivity of composites consisting of a continuous matrix phase with dilute concentrations of dispersions with spherical, cylin drical and flat plate geometry with a thermal barrier resistance at the interface between the components.

D. P. H. Hasselman; Lloyd F. Johnson

1987-01-01

380

Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi Shibuta  

E-print Network

Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi that the inclusion of only 1 % of 13 C natural isotope dramatically reduces the thermal conductivity of diamond. However, isotope effects on heat conduction of SWNTs have not been elucidated. We estimated isotope

Maruyama, Shigeo

381

Turbulence of Dilute Polymer Solution  

E-print Network

In fully developed three dimensional fluid turbulence the fluctuating energy is supplied at large scales, cascades through intermediate scales, and dissipates at small scales. It is the hallmark of turbulence that for intermediate scales, in the so called inertial range, the average energy flux is constant and independent of viscosity [1-3]. One very important question is how this range is altered, when an additional agent that can also transport energy is added to the fluid. Long-chain polymers dissolved at very small concentrations in the fluid are such an agent [4,5]. Based on prior work by de Gennes and Tabor [6,7] we introduce a theory that balances the energy flux through the turbulent cascade with that of the energy flux into the elastic degrees of freedom of the dilute long-chain polymer solution. We propose a refined elastic length scale, $r_\\varepsilon$, which describes the effect of polymer elasticity on the turbulence energy cascade. Our experimental results agree excellently with this new energy ...

Xi, Heng-Dong; Xu, Haitao

2013-01-01

382

Isotopically pure magnesium isotope-24 is prepared from magnesium-24 oxide  

NASA Technical Reports Server (NTRS)

Apparatus is used to prepare isotopically pure magnesium isotope-24, suitable for use in neutron scattering and polarization experiments. The apparatus permits thermal reduction of magnesium-24 oxide with aluminum and calcium oxide, and subsequent vaporization of the product metal in vacuum. It uses a resistance-heated furnace tube and cap assembly.

Chellew, N. R.; Schilb, J. D.; Steunenberg, R. K.

1968-01-01

383

Isotope Science and Production  

E-print Network

Isotope Science and Production 35 years of experience in isotope production, processing. Contact: Kevin John LANL Isotope Program Manager kjohn@lanl.gov 505-667-3602 Sponsored by the Department of Energy National Isotope Program http://www.nuclear.energy.gov/isotopes/nelsotopes2a.html Isotopes

384

Simultaneous in situ determination of U-Pb and Sm-Nd isotopes in monazite by laser ablation ICP-MS  

NASA Astrophysics Data System (ADS)

are presented for in situ simultaneous determination of U-Pb and Sm-Nd isotopes in monazite using the Laser Ablation Split-Stream (LASS) method. This method uses a laser ablation system coupled to a magnetic-sector inductively coupled plasma mass spectrometer (HR) (ICP-MS) for measuring U-Pb isotopes and a multicollector (MC) ICP-MS for measuring Sm-Nd isotopes. Ablated material is split using a Y-connector and transported simultaneously to both mass spectrometers. In addition to Sm and Nd isotopes, the MC-ICP-MS is configured to also acquire Ce, Nd, Sm, Eu, and Gd elemental abundances. This approach provides age, tracer isotope, and trace element data in the same ablation volume, reducing sampling problems associated with fine-scale zoning in accessory minerals and minimizing the material needed for ablation. Precision and accuracy of the U-Pb method (and the precision of the Sm-Nd method) is demonstrated with results from well-characterized monazite reference materials. The LASS results agree within uncertainty with the isotope dilution thermal ionization mass spectrometry (ID-TIMS) U-Pb dates. The accuracy of the Sm-Nd method is assessed by comparing the LA-MC-ICP-MS results with ID-TIMS determinations on a well-characterized, in-house monazite reference material. The LASS method is then applied to monazite from the Birch Creek Pluton in the White Mountains of California as a case study to illustrate the utility of this method for solving geologic problems. The U-Pb ages and Sm-Nd isotopic data from the LASS method support the conclusions drawn from previous results that monazite can record timing and information about the source region(s) of hydrothermal fluids.

Goudie, Dylan J.; Fisher, Christopher M.; Hanchar, John M.; Crowley, James L.; Ayers, John C.

2014-06-01

385

Ionic liquids behave as dilute electrolyte solutions  

PubMed Central

We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force–distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin–Landau–Verwey–Overbeek theory with an additive repulsive steric (entropic) ion–surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high–free-ion density ionic liquids and ionic liquid blends. PMID:23716690

Gebbie, Matthew A.; Valtiner, Markus; Banquy, Xavier; Fox, Eric T.; Henderson, Wesley A.; Israelachvili, Jacob N.

2013-01-01

386

21 CFR 864.5240 - Automated blood cell diluting apparatus.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

2010-04-01

387

21 CFR 864.5240 - Automated blood cell diluting apparatus.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell diluting apparatus is a fully...

2011-04-01

388

21 CFR 864.5240 - Automated blood cell diluting apparatus.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Automated blood cell diluting apparatus. 864.5240 Section...Devices § 864.