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Sample records for isotopic mass chain

  1. Chiral two- and three-nucleon forces along medium-mass isotope chains

    NASA Astrophysics Data System (ADS)

    Somà, V.; Cipollone, A.; Barbieri, C.; Navrátil, P.; Duguet, T.

    2014-06-01

    Ab initio calculations have shown that chiral two- and three-nucleon interactions correctly reproduce binding energy systematics and neutron drip lines of oxygen and nearby isotopes. Exploiting the novel Gorkov-Green's function approach applicable to genuinely open-shell nuclei, we present the first ab initio investigation of Ar, K, Ca, Sc, and Ti isotopic chains. In doing so, stringent tests of internucleon interaction models are provided in the medium-mass region of the nuclear chart. Leading chiral three-nucleon interactions are shown to be mandatory to reproduce the trend of binding energies throughout these chains and to obtain a good description of two-neutron separation energies. At the same time, nuclei in this mass region are systematically overbound by about 40 MeV. While the fundamental N =20 and 28 magic numbers do emerge from basic internucleon interactions, the former is shown to be significantly overestimated, which points to deficiencies of state-of-the-art chiral potentials. The present results demonstrate that ab initio many-body calculations can now access entire medium-mass isotopic chains including degenerate open-shell nuclei and provide a critical testing ground for modern theories of nuclear interactions.

  2. Mass-independent isotope effects.

    PubMed

    Buchachenko, Anatoly L

    2013-02-28

    Three fundamental properties of atomic nuclei-mass, spin (and related magnetic moment), and volume-are the source of isotope effects. The mostly deserved and popular, with almost hundred-year history, is the mass-dependent isotope effect. The first mass-independent isotope effect which chemically discriminates isotopes by their nuclear spins and nuclear magnetic moments rather than by their masses was detected in 1976. It was named as the magnetic isotope effect because it is controlled by magnetic interaction, i.e., electron-nuclear hyperfine coupling in the paramagnetic species, the reaction intermediates. The effect follows from the universal physical property of chemical reactions to conserve angular momentum (spin) of electrons and nuclei. It is now detected for oxygen, silicon, sulfur, germanium, tin, mercury, magnesium, calcium, zinc, and uranium in a great variety of chemical and biochemical reactions including those of medical and ecological importance. Another mass-independent isotope effect was detected in 1983 as a deviation of isotopic distribution in reaction products from that which would be expected from the mass-dependent isotope effect. On the physical basis, it is in fact a mass-dependent effect, but it surprisingly results in isotope fractionation which is incompatible with that predicted by traditional mass-dependent effects. It is supposed to be a function of dynamic parameters of reaction and energy relaxation in excited states of products. The third, nuclear volume mass-independent isotope effect is detected in the high-resolution atomic and molecular spectra and in the extraction processes, but there are no unambiguous indications of its importance as an isotope fractionation factor in chemical reactions.

  3. Advanced Mass Spectrometers for Hydrogen Isotope Analyses

    SciTech Connect

    Chastagner, P.

    2001-08-01

    This report is a summary of the results of a joint Savannah River Laboratory (SRL) - Savannah River Plant (SRP) ''Hydrogen Isotope Mass Spectrometer Evaluation Program''. The program was undertaken to evaluate two prototype hydrogen isotope mass spectrometers and obtain sufficient data to permit SRP personnel to specify the mass spectrometers to replace obsolete instruments.

  4. Evaluation of on-line pyrolysis coupled to isotope ratio mass spectrometry for the determination of position-specific (13)C isotope composition of short chain n-alkanes (C6-C12).

    PubMed

    Gilbert, Alexis; Yamada, Keita; Yoshida, Naohiro

    2016-06-01

    We measured (13)C intramolecular isotopic composition of commercially available short-chain hydrocarbons (n-C6-n-C12) using (13)C-NMR. Results show that the main variation is between the terminal and the sub-terminal C-atom positions. Site-preference (difference in δ(13)C values between terminal and sub-terminal C-atom positions) among all the samples varies between -12.2‰ and +8.4‰. Comparison of these results with those obtained using on-line pyrolysis coupled with GC-C-IRMS show that the thermal cracking of hydrocarbons occurs with a good isotopic fidelity between terminal and sub-terminal C-atom positions of the starting material and the related pyrolysis products (methane and ethylene). On-line pyrolysis coupled with GC-C-IRMS can thus be used for tracing hydrocarbons biogeochemical processes.

  5. Calcium isotope analysis by mass spectrometry.

    PubMed

    Boulyga, Sergei F

    2010-01-01

    The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abundances in natural samples has challenged the analysts for more than three decades. Practically all Ca isotopes suffer from significant isobaric interferences, whereas low-abundant isotopes can be particularly affected by neighboring major isotopes. The extent of natural variations of stable isotopes appears to be relatively limited, and highly precise techniques are required to resolve isotopic effects. Isotope fractionation during sample preparation and measurements and instrumental mass bias can significantly exceed small isotope abundance variations in samples, which have to be investigated. Not surprisingly, a TIMS procedure developed by Russell et al. (Russell et al., 1978. Geochim Cosmochim Acta 42: 1075-1090) for Ca isotope measurements was considered as revolutionary for isotopic measurements in general, and that approach is used nowadays (with small modifications) for practically all isotopic systems and with different mass spectrometric techniques. Nevertheless, despite several decades of calcium research and corresponding development of mass spectrometers, the available precision and accuracy is still not always sufficient to achieve the challenging goals. The present article discusses figures of merits of presently used analytical methods and instrumentation, and attempts to critically assess their limitations. In Sections 2 and 3, mass spectrometric methods applied to precise stable isotope analysis and to the determination of (41)Ca are described. Section 4 contains a short summary of selected applications, and includes tracer experiments and the potential use

  6. High-precision lead isotopes and stripy plumes: Revisiting the Society chain in French Polynesia

    NASA Astrophysics Data System (ADS)

    Cordier, Carole; Chauvel, Catherine; Hémond, Christophe

    2016-09-01

    An increasing number of geochemical studies looked for spatial organization of the isotopic variations along Pacific volcanic island chains (e.g., Hawaii, Marquesas, Samoa and Society Islands) in order to discuss the possible zoning of the plume conduits. Here, we reexamine the occurrence of isotopic stripes in the Society archipelago in French Polynesia, using new Sr-Nd-Hf-Pb isotope ratios of sixty-six lavas from six islands (Mehetia, Moorea, Maupiti, Huahine, Raiatea, Bora-Bora). We demonstrate that the Pb isotope variability observed using literature data is an analytical artifact related to the poor control of mass fractionation during Pb measurements by conventional TIMS technique. New MC-ICP-MS Pb data demonstrate that the isotopic stripes as previously defined disappear. They rather show that individual islands cover a significant part of the entire isotopic range of the chain. We suggest, therefore, that the dominant characteristic of the Society plume is small-scale heterogeneities, evenly distributed within the plume conduit. At a global scale, we show that some ocean island chains with similar geochemical and isotopic characteristics, such as Samoa and Society Islands, define different arrays when variations of Nd with high-precision Pb isotopes are considered. We proposed that this puzzling observation might record differences in recycling age of the basalt + sediment mixture subducted into the mantle and sampled by mantle plume.

  7. Mass Fractionation Laws, Mass-Independent Effects, and Isotopic Anomalies

    NASA Astrophysics Data System (ADS)

    Dauphas, Nicolas; Schauble, Edwin A.

    2016-06-01

    Isotopic variations usually follow mass-dependent fractionation, meaning that the relative variations in isotopic ratios scale with the difference in mass of the isotopes involved (e.g., δ17O ≈ 0.5×δ18O). In detail, however, the mass dependence of isotopic variations is not always the same, and different natural processes can define distinct slopes in three-isotope diagrams. These variations are subtle, but improvements in analytical capabilities now allow precise measurement of these effects and make it possible to draw inferences about the natural processes that caused them (e.g., reaction kinetics versus equilibrium isotope exchange). Some elements, in some sample types, do not conform to the regularities of mass-dependent fractionation. Oxygen and sulfur display a rich phenomenology of mass-independent fractionation, documented in the laboratory, in the rock record, and in the modern atmosphere. Oxygen in meteorites shows isotopic variations that follow a slope-one line (δ17O ≈ δ18O) whose origin may be associated with CO photodissociation. Sulfur mass-independent fractionation in ancient sediments provides the tightest constraint on the oxygen partial pressure in the Archean and the timing of Earth's surface oxygenation. Heavier elements also show departures from mass fractionation that can be ascribed to exotic effects associated with chemical reactions such as magnetic effects (e.g., Hg) or the nuclear field shift effect (e.g., U or Tl). Some isotopic variations in meteorites and their constituents cannot be related to the terrestrial composition by any known process, including radiogenic, nucleogenic, and cosmogenic effects. Those variations have a nucleosynthetic origin, reflecting the fact that the products of stellar nucleosynthesis were not fully homogenized when the Solar System formed. Those anomalies are found at all scales, from nanometer-sized presolar grains to bulk terrestrial planets. They can be used to learn about stellar

  8. Iron, copper and zinc isotopic fractionation up mammal trophic chains

    NASA Astrophysics Data System (ADS)

    Jaouen, Klervia; Pons, Marie-Laure; Balter, Vincent

    2013-07-01

    There is a growing body of evidence that some non-traditional elements exhibit stable isotope compositions that are distinct in botanical and animal products, providing potential new tracers for diet reconstructions. Here, we present data for iron (Fe), copper (Cu) and zinc (Zn) stable isotope compositions in plants and bones of herbivores and carnivores. The samples come from trophic chains located in the Western Cape area and in the Kruger National Park in South Africa. The Fe, Cu and Zn isotope systematics are similar in both parks. However, local Cu, and possibly Zn, isotopic values of soils influence that of plants and of higher trophic levels. Between plants and bones of herbivores, the Zn isotope compositions are 66Zn-enriched by about 0.8‰ whereas no significant trophic enrichment is observed for Fe and Cu. Between bones of herbivores and bones of carnivores, the Fe isotope compositions are 56Fe-depleted by about 0.6‰, the Cu isotope compositions are 65Cu-enriched by about 1.0‰, and the Zn isotope compositions are slightly 66Zn-depleted by about 0.2‰. The isotopic distributions of the metals in the body partly explain the observed trophic isotopic systematics. However, it is also necessary to invoke differential intestinal metal absorption between herbivores and carnivores to account for the observed results. Further studies are necessary to fully understand how the Fe, Cu and Zn isotope values are regulated within the ecosystem's trophic levels, but the data already suggests significant potential as new paleodietary and paleoecological proxies.

  9. Penning trap mass measurements on nobelium isotopes

    SciTech Connect

    Dworschak, M.; Block, M.; Ackermann, D.; Herfurth, F.; Hessberger, F. P.; Hofmann, S.; Vorobyev, G. K.; Audi, G.; Blaum, K.; Droese, C.; Marx, G.; Schweikhard, L.; Eliseev, S.; Ketter, J.; Fleckenstein, T.; Haettner, E.; Plass, W. R.; Scheidenberger, C.; Ketelaer, J.; Kluge, H.-J.

    2010-06-15

    The Penning trap mass spectrometer SHIPTRAP at GSI Darmstadt allows accurate mass measurements of radionuclides, produced in fusion-evaporation reactions and separated by the velocity filter SHIP from the primary beam. Recently, the masses of the three nobelium isotopes {sup 252-254}No were determined. These are the first direct mass measurements of transuranium elements, which provide new anchor points in this region. The heavy nuclides were produced in cold-fusion reactions by irradiating a PbS target with a {sup 48}Ca beam, resulting in production rates of the nuclei of interest of about one atom per second. In combination with data from decay spectroscopy our results are used to perform a new atomic-mass evaluation in this region.

  10. Compact hydrogen/helium isotope mass spectrometer

    DOEpatents

    Funsten, Herbert O.; McComas, David J.; Scime, Earl E.

    1996-01-01

    The compact hydrogen and helium isotope mass spectrometer of the present invention combines low mass-resolution ion mass spectrometry and beam-foil interaction technology to unambiguously detect and quantify deuterium (D), tritium (T), hydrogen molecule (H.sub.2, HD, D.sub.2, HT, DT, and T.sub.2), .sup.3 He, and .sup.4 He concentrations and concentration variations. The spectrometer provides real-time, high sensitivity, and high accuracy measurements. Currently, no fieldable D or molecular speciation detectors exist. Furthermore, the present spectrometer has a significant advantage over traditional T detectors: no confusion of the measurements by other beta-emitters, and complete separation of atomic and molecular species of equivalent atomic mass (e.g., HD and .sup.3 He).

  11. Isotopic trace analysis by atomic mass spectrometry

    SciTech Connect

    Stoffels, J.J.

    1993-12-01

    All the production facilities at Hanford are now shut down. However, the legacy from half a century of plutonium production includes 177 underground storage tanks of up to one million gallons each containing the largest accumulation of high-level radioactive waste in what used to be called ``the free world.`` Hanford`s new mission, in addition to a spectrum of ongoing research and development, is radioactive waste management and environmental restoration. Isotope-ratio mass spectrometry will continue to be an essential tool in monitoring the progress of that mission.

  12. Mass Distributions of Linear Chain Polymers

    PubMed Central

    Hubler, Shane L.; Craciun, Gheorghe

    2012-01-01

    Biochemistry has many examples of linear chain polymers, i.e., molecules formed from a sequence of units from a finite set of possibilities; examples include proteins, RNA, single-stranded DNA, and paired DNA. In the field of mass spectrometry, it is useful to consider the idea of weighted alphabets, with a word inheriting weight from its letters. We describe the distribution of the mass of these words in terms of a simple recurrence relation, the general solution to that relation, and a canonical form that explicitly describes both the exponential form of this distribution and its periodic features, thus explaining a wave pattern that has been observed in protein mass databases. Further, we show that a pure exponential term dominates the distribution and that there is exactly one such purely exponential term. Finally, we illustrate the use of this theorem by describing a formula for the integer mass distribution of peptides and we compare our theoretical results with mass distributions of human and yeast peptides. PMID:23024448

  13. Comparison of aquatic food chains using nitrogen isotopes.

    PubMed Central

    Cabana, G; Rasmussen, J B

    1996-01-01

    Recent studies have shown the utility of delta(15)N to model trophic structure and contaminant bioaccumulation in aquatic food webs. However, cross-system comparisons in delta(15)N can be complicated by differences in delta(15)N at the base of the food chain. Such baseline variation in delta(15)N is difficult to resolve using plankton because of the large temporal variability in the delta(15)N of small organisms that have fast nitrogen turnover. Comparisons using large primary consumers, which have stable tissue isotopic signatures because of their slower nitrogen turnover, show that delta(15)N increases markedly with the human population density in the lake watershed. This shift in delta(15)N likely reflects the high delta(15)N of human sewage. Correcting for this baseline variation in delta(15)N, we report that, contrary to expectations based on previous food-web analysis, the food chains leading up to fish varied by about only one trophic level among the 40 lakes studied. Our results also suggest that the delta(15)N signatures of nitrogen at the base of the food chain will provide a useful tool in the assessment of anthropogenic nutrient inputs. Images Fig. 4 PMID:8855268

  14. The Mass-Dependence of Cadmium Isotope Fractionation During Evaporation

    NASA Astrophysics Data System (ADS)

    Rehkamper, M.; Wombacher, F.; Mezger, K.; Wiechert, U.

    2002-12-01

    Isotope fractionation laws relate the isotope fractionation factor αA of one isotope ratio to the fractionation factor αB of a second isotope ratio of the same element with a fractionation exponent β, such that αA = αBβ. In a recent paper, Young et al. (GCA 66, 1095-1104 (2002)) inferred that kinetic and equilibrium isotope fractionations are characterized by different mass functions, such that βkin is not equal to βeq. As a consequence, kinetic isotope fractionation is expected to produce fractionation lines in three isotope space that are different from those generated by equilibrium fractionation processes. Young et al. furthermore stated that the variability in mass-dependent fractionation laws may be sufficient to account for the negative Δ17O of tropospheric O2 and the Δ17O anomalies of minerals in SNC meteorites. Such variations have otherwise been interpreted as evidence of non-mass dependant isotope fractionations (Luz et al., Nature 400, 547-550 (1999); Farquhar et al., Science 280, 1589-1582 (1998)). In the present study, we investigated the mass-dependence of isotope fractionation by evaluating the results of evaporation experiments that produced very large differences in Cd isotope compositions (up to about 100‰ ). In these experiments, liquid Cd was evaporated into a vacuum at a temperature of about 200°C. The metal residues remaining after evaporation were analyzed for their Cd isotope composition by multiple-collector inductively coupled plasma-mass spectrometry (MC-ICPMS) relative to the unfractionated starting material. The precision of the measurements is sufficient to clearly distinguish between different fractionation mechanisms. In linearized three-isotope space, the residual Cd metals plot on fractionation lines (e.g., with a slope β = 2.049 +/- 2 for 106}Cd/{114Cd vs. 110}Cd/{114Cd) that are intermediate between the kinetic (β = 2.036) and the equilibrium (β = 2.075) fractionation lines. This can be explained by an

  15. A carbon isotope mass balance for an anoxic marine sediment: Isotopic signatures of diagenesis

    NASA Technical Reports Server (NTRS)

    Boehme, Susan E.

    1993-01-01

    A carbon isotope mass balance was determined for the sediments of Cape Lookout Bight, NC to constrain the carbon budgets published previously. The diffusive, ebullitive and burial fluxes of sigma CO2 and CH4, as well as the carbon isotope signatures of these fluxes, were measured. The flux-weighted isotopic signature of the remineralized carbon (-18.9 plus or minus 2.7 per mil) agreed with the isotopic composition of the remineralized organic carbon determined from the particulate organic carbon (POC) delta(C-13) profiles (-19.2 plus or minus 0.2), verifying the flux and isotopic signature estimates. The measured delta(C-13) values of the sigma CO2 and CH4 diffusive fluxes were significantly different from those calculated from porewater gradients. The differences appear to be influenced by methane oxidation at the sediment-water interface, although other potential processes cannot be excluded. The isotope mass balance provides important information concerning the locations of potential diagenetic isotope effects. Specifically, the absence of downcore change in the delta(C-13) value of the POC fraction and the identical isotopic composition of the POC and the products of remineralization indicate that no isotopic fractionation is expressed during the initial breakdown of the POC, despite its isotopically heterogeneous composition.

  16. SIPT--An Ultrasensitive Mass Spectrometer for Rare Isotopes

    NASA Astrophysics Data System (ADS)

    Ringle, Ryan

    2014-09-01

    Over the last few decades, advances in radioactive beam facilities like the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) have made short-lived, rare-isotope beams available for study in various science areas, and new facilities, like the Facility for Rare Isotope Beams (FRIB) under construction at MSU, will provide even more exotic rare isotopes. The determination of the masses of these rare isotopes is of utmost importance since it provides a direct measurement of the binding energy of the nucleons in the atomic nucleus. For this purpose we are currently developing a dedicated Single-Ion Penning Trap (SIPT) mass spectrometer at NSCL to handle the specific challenges posed by rare isotopes. These challenges, which include short half-lives and extremely low production rates, are dealt with by employing the narrowband FT-ICR detection method under cryogenic conditions. Used in concert with the 9.4-T time-of-flight mass spectrometer, the 7-T SIPT system will ensure that the LEBIT mass measurement program at MSU will make optimal use of the wide range of rare isotope beams provided by the future FRIB facility, addressing such topics as nuclear structure, nuclear astrophysics, and fundamental interactions. Over the last few decades, advances in radioactive beam facilities like the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) have made short-lived, rare-isotope beams available for study in various science areas, and new facilities, like the Facility for Rare Isotope Beams (FRIB) under construction at MSU, will provide even more exotic rare isotopes. The determination of the masses of these rare isotopes is of utmost importance since it provides a direct measurement of the binding energy of the nucleons in the atomic nucleus. For this purpose we are currently developing a dedicated Single-Ion Penning Trap (SIPT) mass

  17. Isotopic mass-dependence of noble gas diffusion coefficients inwater

    SciTech Connect

    Bourg, I.C.; Sposito, G.

    2007-06-25

    Noble gas isotopes are used extensively as tracers inhydrologic and paleoclimatic studies. These applications requireknowledge of the isotopic mass (m) dependence of noble gas diffusioncoefficients in water (D), which has not been measured but is estimatedusing experimental D-values for the major isotopes along with an untestedrelationship from kinetic theory, D prop m-0.5. We applied moleculardynamics methods to determine the mass dependence of D for four noblegases at 298 K, finding that D prop m-beta with beta<0.2, whichrefutes the kinetic theory model underlying all currentapplications.

  18. High Resolution Double-Focusing Isotope Ratio Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Radke, J.; Deerberg, M.; Hilkert, A.; Schlüter, H.-J.; Schwieters, J.

    2012-04-01

    In recent years isotope ratio mass spectrometry has extended to the capability of quantifying very small isotope signatures related with low abundances and simultaneously detecting molecular masses such as isotopomers and isotopologues containing clumped isotopes. Some of those applications are limited by molecular interferences like different gas molecules with the same nominal mass, e.g. Ar/O2, adducts of the same molecule or of different molecules, and very small isotope abundances. The Thermo Scientific MAT 253 ULTRA is the next generation of high precision gas isotope ratio mass spectrometry, which combines a 10 KV gas ionization source (Thermo Scientific MAT 253) with a double focusing multi-collector mass analyzer (Thermo Scientific Neptune) and reduces those limitations by measuring isotope ratios on a larger dynamic range with high precision. Small ion beam requirements and high sensitivity are achieved by signal-to-noise improvements through enhanced ion beam amplification in faraday cups and ion counters. Interfering backgrounds, e.g. interfering isotopologues or isobaric ions of contaminants, are dramatically decreased by a dynamic range increase combined with high evacuation leading to undisturbed ion transmission through the double-focusing analyser. Furthermore, automated gain calibration for mathematical baseline corrections, switchable detector arrays, ion source control, analyser focusing and full data export is controlled under Isodat data control. New reference/sample strategies are under investigation besides incorporation of the continuous-flow technique and its versatile inlet devices. We are presenting first results and applications of the MAT 253 Ultra.

  19. Mass-dependent fractionation of nickel isotopes in meteoritic metal

    NASA Astrophysics Data System (ADS)

    Cook, David L.; Wadhwa, Meenakshi; Clayton, Robert N.; Dauphas, Nicolas; Janney, Philip E.; Davis, Andrew M.

    We measured nickel isotopes via multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) in the bulk metal from 36 meteorites, including chondrites, pallasites, and irons (magmatic and non-magmatic). The Ni isotopes in these meteorites are mass fractionated; the fractionation spans an overall range of ≈0.4‰ amu-1. The ranges of Ni isotopic compositions (relative to the SRM 986 Ni isotopic standard) in metal from iron meteorites (≈0.0 to ≈0.3‰ amu-1) and chondrites (≈0.0 to ≈0.2‰ amu-1) are similar, whereas the range in pallasite metal (≈-0.1 to 0.0‰ amu-1) appears distinct. The fractionation of Ni isotopes within a suite of fourteen IIIAB irons (≈0.0 to ≈0.3‰ amu-1) spans the entire range measured in all magmatic irons. However, the degree of Ni isotopic fractionation in these samples does not correlate with their Ni content, suggesting that core crystallization did not fractionate Ni isotopes in a systematic way. We also measured the Ni and Fe isotopes in adjacent kamacite and taenite from the Toluca IAB iron meteorite. Nickel isotopes show clearly resolvable fractionation between these two phases; kamacite is heavier relative to taenite by ≈0.4‰ amu-1. In contrast, the Fe isotopes do not show a resolvable fractionation between kamacite and taenite. The observed isotopic compositions of kamacite and taenite can be understood in terms of kinetic fractionation due to diffusion of Ni during cooling of the Fe-Ni alloy and the development of the Widmanstätten pattern.

  20. An isotopic mass effect on the intermolecular potential

    SciTech Connect

    Herman, Michael F.; Currier, Robert Patrick; Clegg, Samuel M.

    2015-09-28

    The impact of isotopic variation on the electronic energy and intermolecular potentials is often suppressed when calculating isotopologue thermodynamics. Intramolecular potential energy surfaces for distinct isotopologues are in fact equivalent under the Born–Oppenheimer approximation, which is sometimes used to imply that the intermolecular interactions are independent of isotopic mass. In this paper, the intermolecular dipole–dipole interaction between hetero-nuclear diatomic molecules is considered. It is shown that the intermolecular potential contains mass-dependent terms even though each nucleus moves on a Born–Oppenheimer surface. Finally, the analysis suggests that mass dependent variations in intermolecular potentials should be included in comprehensive descriptions of isotopologue thermodynamics.

  1. Mono-isotope Prediction for Mass Spectra Using Bayes Network

    PubMed Central

    Li, Hui; Rwebangira, Mugizi Robert; Burge, Legand

    2015-01-01

    Mass spectrometry is one of the widely utilized important methods to study protein functions and components. The challenge of mono-isotope pattern recognition from large scale protein mass spectral data needs computational algorithms and tools to speed up the analysis and improve the analytic results. We utilized naïve Bayes network as the classifier with the assumption that the selected features are independent to predict mono-isotope pattern from mass spectrometry. Mono-isotopes detected from validated theoretical spectra were used as prior information in the Bayes method. Three main features extracted from the dataset were employed as independent variables in our model. The application of the proposed algorithm to publicMo dataset demonstrates that our naïve Bayes classifier is advantageous over existing methods in both accuracy and sensitivity. PMID:25620856

  2. Solvent extraction, ion chromatography, and mass spectrometry of molybdenum isotopes.

    PubMed

    Dauphas, N; Reisberg, L; Marty, B

    2001-06-01

    A procedure was developed that allows precise determination of molybdenum isotope abundances in natural samples. Purification of molybdenum was first achieved by solvent extraction using di(2-ethylhexyl) phosphate. Further separation of molybdenum from isobar nuclides was obtained by ion chromatography using AG1-X8 strongly basic anion exchanger. Finally, molybdenum isotopic composition was measured using a multiple collector inductively coupled plasma hexapole mass spectrometer. The abundances of molybdenum isotopes 92, 94, 95, 96, 97, 98, and 100 are 14.8428(510), 9.2498(157), 15.9303(133), 16.6787(37), 9.5534(83), 24.1346(394), and 9.6104(312) respectively, resulting in an atomic mass of 95.9304(45). After internal normalization for mass fractionation, no variation of the molybdenum isotopic composition is observed among terrestrial samples within a relative precision on the order of 0.00001-0.0001. This demonstrates the reliability of the method, which can be applied to searching for possible isotopic anomalies and mass fractionation.

  3. Isotope Ratio Monitoring Gas Chromatography Mass Spectrometry (IRM-GCMS)

    NASA Technical Reports Server (NTRS)

    Freeman, K. H.; Ricci, S. A.; Studley, A.; Hayes, J. M.

    1989-01-01

    On Earth, the C-13 content of organic compounds is depleted by roughly 13 to 23 permil from atmospheric carbon dioxide. This difference is largely due to isotope effects associated with the fixation of inorganic carbon by photosynthetic organisms. If life once existed on Mars, then it is reasonable to expect to observe a similar fractionation. Although the strongly oxidizing conditions on the surface of Mars make preservation of ancient organic material unlikely, carbon-isotope evidence for the existence of life on Mars may still be preserved. Carbon depleted in C-13 could be preserved either in organic compounds within buried sediments, or in carbonate minerals produced by the oxidation of organic material. A technique is introduced for rapid and precise measurement of the C-13 contents of individual organic compounds. A gas chromatograph is coupled to an isotope-ratio mass spectrometer through a combustion interface, enabling on-line isotopic analysis of isolated compounds. The isotope ratios are determined by integration of ion currents over the course of each chromatographic peak. Software incorporates automatic peak determination, corrections for background, and deconvolution of overlapped peaks. Overall performance of the instrument was evaluated by the analysis of a mixture of high purity n-alkanes of know isotopic composition. Isotopic values measured via IRM-GCMS averaged withing 0.55 permil of their conventionally measured values.

  4. Masses of exotic calcium isotopes pin down nuclear forces.

    PubMed

    Wienholtz, F; Beck, D; Blaum, K; Borgmann, Ch; Breitenfeldt, M; Cakirli, R B; George, S; Herfurth, F; Holt, J D; Kowalska, M; Kreim, S; Lunney, D; Manea, V; Menéndez, J; Neidherr, D; Rosenbusch, M; Schweikhard, L; Schwenk, A; Simonis, J; Stanja, J; Wolf, R N; Zuber, K

    2013-06-20

    The properties of exotic nuclei on the verge of existence play a fundamental part in our understanding of nuclear interactions. Exceedingly neutron-rich nuclei become sensitive to new aspects of nuclear forces. Calcium, with its doubly magic isotopes (40)Ca and (48)Ca, is an ideal test for nuclear shell evolution, from the valley of stability to the limits of existence. With a closed proton shell, the calcium isotopes mark the frontier for calculations with three-nucleon forces from chiral effective field theory. Whereas predictions for the masses of (51)Ca and (52)Ca have been validated by direct measurements, it is an open question as to how nuclear masses evolve for heavier calcium isotopes. Here we report the mass determination of the exotic calcium isotopes (53)Ca and (54)Ca, using the multi-reflection time-of-flight mass spectrometer of ISOLTRAP at CERN. The measured masses unambiguously establish a prominent shell closure at neutron number N = 32, in excellent agreement with our theoretical calculations. These results increase our understanding of neutron-rich matter and pin down the subtle components of nuclear forces that are at the forefront of theoretical developments constrained by quantum chromodynamics.

  5. Water balance along a chain of tundra lakes: A 20-year isotopic perspective

    NASA Astrophysics Data System (ADS)

    Gibson, J. J.; Reid, R.

    2014-11-01

    Stable isotope measurements and isotope mass balance (IMB) calculations are presented in support of an unprecedented 20-year water balance assessment for a tailings pond and a chain of downstream lakes at the Salmita-Tundra mine site, situated near Courageous Lake, Northwest Territories, Canada (65°03‧N; 111°11‧W). The method is shown to provide a comprehensive annual and interannual perspective of water balance fluxes along a chain of lakes during the period 1991-2010, without the need for continuous streamflow gauging, and reveals important lake-order-dependent patterns of land-surface runoff, discharge accumulation, and several key diagnostic ratios, i.e., evaporation/inflow, evaporation/evapotranspiration, land-surface-runoff/precipitation and discharge/ precipitation. Lake evaporation is found to be a significant component of the water balance, accounting for between 26% and 32% of inflow to natural lakes and between 72% and 100% of inflow to mine-tailings ponds. Evaporation/evapotranspiration averages between 7% and 22% and is found to be higher in low-precipitation years, and in watersheds with a higher proportion of lakes. Runoff ratios for land-surface drainages and runoff ratios for watersheds (including lakes) ranged between 14-47% and 20-47%, respectively, and were higher in low precipitation years, in watersheds with a higher proportion of lakes, and in watersheds less affected by mining development. We propose that in general these two runoff ratios will likely converge as lake order increases and as land cover conditions become regionally representative. Notably, the study demonstrates application of IMB, validated with streamflow measurements, to constrain local water balance in a remote low-arctic region. For IMB chain-of-lakes applications, it underlines the importance of accounting for evaporatively-enriched upstream sources to avoid overestimation of evaporation losses.

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

    SciTech Connect

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

    1990-01-01

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

  7. Ion Mobility Mass Spectrometry Direct Isotope Abundance Analysis

    SciTech Connect

    Manuel J. Manard, Stephan Weeks, Kevin Kyle

    2010-05-27

    The nuclear forensics community is currently engaged in the analysis of illicit nuclear or radioactive material for the purposes of non-proliferations and attribution. One technique commonly employed for gathering nuclear forensics information is isotope analysis. At present, the state-of-the-art methodology for obtaining isotopic distributions is thermal ionization mass spectrometry (TIMS). Although TIMS is highly accurate at determining isotope distributions, the technique requires an elementally pure sample to perform the measurement. The required radiochemical separations give rise to sample preparation times that can be in excess of one to two weeks. Clearly, the nuclear forensics community is in need of instrumentation and methods that can expedite their decision making process in the event of a radiological release or nuclear detonation. Accordingly, we are developing instrumentation that couples a high resolution IM drift cell to the front end of a MS. The IM cell provides a means of separating ions based upon their collision cross-section and mass-to-charge ratio (m/z). Two analytes with the same m/z, but with different collision cross-sections (shapes) would exit the cell at different times, essentially enabling the cell to function in a similar manner to a gas chromatography (GC) column. Thus, molecular and atomic isobaric interferences can be effectively removed from the ion beam. The mobility selected chemical species could then be introduced to a MS for high-resolution mass analysis to generate isotopic distributions of the target analytes. The outcome would be an IM/MS system capable of accurately measuring isotopic distributions while concurrently eliminating isobaric interferences and laboratory radiochemical sample preparation. The overall objective of this project is developing instrumentation and methods to produce near real-time isotope distributions with a modular mass spectrometric system that performs the required gas-phase chemistry and

  8. Fe and Cu isotope mass balances in the human body

    NASA Astrophysics Data System (ADS)

    Balter, V.; Albarede, F.; Jaouen, K.

    2011-12-01

    The ranges of the Fe and Cu isotope compositions in the human body are large, i.e. ~3% and ~2%, respectively. Both isotopic fractionations appear to be mainly controlled by redox conditions. The Fe and Cu isotope compositions of the tissues analyzed so far plot on a mixing hyperbolae between a reduced and an oxidized metals pools. The reduced metals pool is composed by erythrocytes, where Fe is bounded to hemoglobin as Fe(II) and Cu to superoxide-dismutase as Cu(I). The oxidized metals pool is composed by hepatocytes, where Fe and Cu are stored as Fe(III) ferritin and as Cu(II) ceruloplasmine, respectively. The position of each biological component in the δ56Fe-δ65Cu diagram therefore reflects the oxidation state of Fe and Cu of the predominant metal carrier protein and allows to quantify Fe and Cu fluxes between organs using mass balance calculations. For instance, serum and clot Fe and Cu isotope compositions show that current biological models of erythropoiesis violates mass conservation requirements, and suggest hidden Fe and Cu pathways during red blood cells synthesis. The results also show that a coupled Fe-Cu strong gender isotopic effect is observed in various organs. The isotopic difference between men and women is unlikely to be due to differential dietary uptake or endometrium loss, but rather reflects the effect of menstrual losses and a correlative solicitation of hepatic stores. We speculate that thorough studies of the metabolism of stable isotopes in normal conditions is a prerequisite for the understanding of the pathological dysregulations.

  9. Quantitative imaging of subcellular metabolism with stable isotopes and multi-isotope imaging mass spectrometry.

    PubMed

    Steinhauser, Matthew L; Lechene, Claude P

    2013-01-01

    Multi-isotope imaging mass spectrometry (MIMS) is the quantitative imaging of stable isotope labels in cells with a new type of secondary ion mass spectrometer (NanoSIMS). The power of the methodology is attributable to (i) the immense advantage of using non-toxic stable isotope labels, (ii) high resolution imaging that approaches the resolution of usual transmission electron microscopy and (iii) the precise quantification of label down to 1 part-per-million and spanning several orders of magnitude. Here we review the basic elements of MIMS and describe new applications of MIMS to the quantitative study of metabolic processes including protein and nucleic acid synthesis in model organisms ranging from microbes to humans.

  10. Mass Spectrometric Measurement of Martian Krypton and Xenon Isotopic Abundance

    NASA Technical Reports Server (NTRS)

    Mahaffy, P.; Mauersberger, K.

    1993-01-01

    The Viking gas chromatograph mass spectrometer experiment provided significant data on the atmospheric composition at the surface of Mars, including measurements of several isotope ratios. However, the limited dynamic range of this mass spectrometer resulted in marginal measurements for the important Kr and Xe isotopic abundance. The Xe-129 to Xe-132 ratio was measured with an uncertainty of 70%, but none of the other isotope ratios for these species were obtained. Accurate measurement of the Xe and Kr isotopic abundance in this atmosphere provides an important data point in testing theories of planetary formation and atmospheric evolution. The measurement is also essential for a stringent test for the Martian origin of the SNC meteorites, since the Kr and Xe fractionation pattern seen in gas trapped in glassy nodules of an SNC (EETA 79001) is unlike any other known solar system resevoir. Current flight mass spectrometer designs combined with the new technology of a high-performance vacuum pumping system show promise for a substantial increase in gas throughput and the dynamic range required to accurately measure these trace species. Various aspects of this new technology are discussed.

  11. Changes in nuclear structure along the Mn isotopic chain studied via charge radii

    NASA Astrophysics Data System (ADS)

    Heylen, H.; Babcock, C.; Beerwerth, R.; Billowes, J.; Bissell, M. L.; Blaum, K.; Bonnard, J.; Campbell, P.; Cheal, B.; Day Goodacre, T.; Fedorov, D.; Fritzsche, S.; Garcia Ruiz, R. F.; Geithner, W.; Geppert, Ch.; Gins, W.; Grob, L. K.; Kowalska, M.; Kreim, K.; Lenzi, S. M.; Moore, I. D.; Maass, B.; Malbrunot-Ettenauer, S.; Marsh, B.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Otsuka, T.; Papuga, J.; Rossel, R.; Rothe, S.; Sánchez, R.; Tsunoda, Y.; Wraith, C.; Xie, L.; Yang, X. F.; Yordanov, D. T.

    2016-11-01

    The hyperfine spectra of 51,53 -64Mn were measured in two experimental runs using collinear laser spectroscopy at ISOLDE, CERN. Laser spectroscopy was performed on the atomic 3 d54 s25/2 6S →3 d54 s 4 p 3/2 6P and ionic 3 d54 s 5S2→3 d54 p 5P3 transitions, yielding two sets of isotope shifts. The mass and field shift factors for both transitions have been calculated in the multiconfiguration Dirac-Fock framework and were combined with a King plot analysis in order to obtain a consistent set of mean-square charge radii which, together with earlier work on neutron-deficient Mn, allow the study of nuclear structure changes from N =25 across N =28 up to N =39 . A clear development of deformation is observed towards N =40 , confirming the conclusions of the nuclear moments studies. From a Monte Carlo shell-model study of the shape in the Mn isotopic chain, it is suggested that the observed development of deformation is not only due to an increase in static prolate deformation but also due to shape fluctuations and triaxiality. The changes in mean-square charge radii are well reproduced using the Duflo-Zuker formula except in the case of large deformation.

  12. An isotopic mass effect on the intermolecular potential

    DOE PAGES

    Herman, Michael F.; Currier, Robert Patrick; Clegg, Samuel M.

    2015-09-28

    The impact of isotopic variation on the electronic energy and intermolecular potentials is often suppressed when calculating isotopologue thermodynamics. Intramolecular potential energy surfaces for distinct isotopologues are in fact equivalent under the Born–Oppenheimer approximation, which is sometimes used to imply that the intermolecular interactions are independent of isotopic mass. In this paper, the intermolecular dipole–dipole interaction between hetero-nuclear diatomic molecules is considered. It is shown that the intermolecular potential contains mass-dependent terms even though each nucleus moves on a Born–Oppenheimer surface. Finally, the analysis suggests that mass dependent variations in intermolecular potentials should be included in comprehensive descriptions of isotopologuemore » thermodynamics.« less

  13. Exploring Mass Perception with Markov Chain Monte Carlo

    ERIC Educational Resources Information Center

    Cohen, Andrew L.; Ross, Michael G.

    2009-01-01

    Several previous studies have examined the ability to judge the relative mass of objects in idealized collisions. With a newly developed technique of psychological Markov chain Monte Carlo sampling (A. N. Sanborn & T. L. Griffiths, 2008), this work explores participants; perceptions of different collision mass ratios. The results reveal…

  14. Reporting and measurement of mass-dependent and mass-independent fractionation of mercury isotopes

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Blum, J. D.

    2007-12-01

    Hg isotope analysis by MC-ICP-MS is an important new approach for fingerprinting Hg sources and monitoring Hg redox reactions and bioaccumulation, especially with the recent discovery of mass independent Hg isotope fractionation. Unfortunately research groups have adopted different standards, definitions of delta values, and methods of isotopic measurement. We suggest that a single standard, NIST SRM 3133, be adopted for reporting the isotopic variability of Hg isotopes. Isotope ratios should be determined by sample-standard bracketing (SSB) during analysis and reported as permil (‰) deviation from SRM 3133. For the highest precision and accuracy, a Tl internal standard along with SSB should be used to correct instrumental mass bias. Measurement routines should also include on-peak zero corrections and matching of concentration and matrix between the samples and bracketing standard. For samples that display mass-dependent fractionation (MDF), only one delta value needs to be reported (δ202/198Hg). Mass-independent fractionation (MIF) (Jackson et al., 2006; Bergquist et al., 2006; Bergquist and Blum, submitted) requires additional nomenclature, and we suggest reporting MIF as the deviation in isotope ratios from the theoretical mass dependent kinetic isotope fractionation (Δxxx/198Hg)¬. External reproducibility should be monitored by analysis of secondary standards. For studies of MDF, we use an in-house secondary standard solution made from metallic Hg mined from Almaden Spain and obtain a δ202Hg of -0.55 ±0.06‰ (2SD). For studies of MIF, we use NRCC CRM DORM-2 (dogfish muscle) and obtain a mean value of δ202Hg of +0.19 ±0.13‰ (2SD), Δ201Hg of +0.89 ±0.07‰ (2SD) , and Δ199Hg of +1.07 ±0.08‰ (2SD).

  15. Multi-collector Isotope Ratio Mass Spectrometer -- Operational Performance Report

    SciTech Connect

    Appelhans, Anthony D; Olson, John E; Watrous, Matthew G; Ward, Michael B.; Dahl, David A.

    2010-12-01

    This report describes the operational testing of a new magnetic sector mass spectrometer that utilizes seven full-sized discrete dynode electron multipliers operating simultaneously. The instrument includes a newly developed ion dispersion lens that enables the mass dispersed individual isotope beams to be separated sufficiently to allow a full-sized discrete dynode pulse counting multiplier to be used to measure each isotope beam. The performance of the instrument was measured using SRM 996 (244Pu spike) at loadings of 2.4 and 12 fg on resin beads and with SRM 4350B Columbia River Sediment samples. The measured limit of detection (3s) for 240Pu was 3.4 attograms for SRM 996. The limit of quantitation (LOQ), defined as 10 s, was 11.2 attograms. The measured concentration of 239Pu in the CRS standard was 152 ± 6 fg/g.

  16. Searching critical-point nuclei in Te- and Xe-isotopic chains using sextic oscillator potential

    SciTech Connect

    Kharb, S.; Chand, F.

    2012-02-15

    We have identified the nuclei in the Te- and Xe-isotopic chains lying close to the critical point, through which the shape phase transition occurs, by using the sextic oscillator potential formalism. It has been found that {sup 110}Te, {sup 124}Te, and {sup 124}Xe isotopes are the most promising candidates for the critical-point nuclei slightly above the Z = 50 proton shell closure.

  17. Stable isotope, site-specific mass tagging for protein identification

    DOEpatents

    Chen, Xian

    2006-10-24

    Proteolytic peptide mass mapping as measured by mass spectrometry provides an important method for the identification of proteins, which are usually identified by matching the measured and calculated m/z values of the proteolytic peptides. A unique identification is, however, heavily dependent upon the mass accuracy and sequence coverage of the fragment ions generated by peptide ionization. The present invention describes a method for increasing the specificity, accuracy and efficiency of the assignments of particular proteolytic peptides and consequent protein identification, by the incorporation of selected amino acid residue(s) enriched with stable isotope(s) into the protein sequence without the need for ultrahigh instrumental accuracy. Selected amino acid(s) are labeled with .sup.13C/.sup.15N/.sup.2H and incorporated into proteins in a sequence-specific manner during cell culturing. Each of these labeled amino acids carries a defined mass change encoded in its monoisotopic distribution pattern. Through their characteristic patterns, the peptides with mass tag(s) can then be readily distinguished from other peptides in mass spectra. The present method of identifying unique proteins can also be extended to protein complexes and will significantly increase data search specificity, efficiency and accuracy for protein identifications.

  18. Calcium isotope constraints on the end-Permian mass extinction

    PubMed Central

    Payne, Jonathan L.; Turchyn, Alexandra V.; Paytan, Adina; DePaolo, Donald J.; Lehrmann, Daniel J.; Yu, Meiyi; Wei, Jiayong

    2010-01-01

    The end-Permian mass extinction horizon is marked by an abrupt shift in style of carbonate sedimentation and a negative excursion in the carbon isotope (δ13C) composition of carbonate minerals. Several extinction scenarios consistent with these observations have been put forward. Secular variation in the calcium isotope (δ44/40Ca) composition of marine sediments provides a tool for distinguishing among these possibilities and thereby constraining the causes of mass extinction. Here we report δ44/40Ca across the Permian-Triassic boundary from marine limestone in south China. The δ44/40Ca exhibits a transient negative excursion of ∼0.3‰ over a few hundred thousand years or less, which we interpret to reflect a change in the global δ44/40Ca composition of seawater. CO2-driven ocean acidification best explains the coincidence of the δ44/40Ca excursion with negative excursions in the δ13C of carbonates and organic matter and the preferential extinction of heavily calcified marine animals. Calcium isotope constraints on carbon cycle calculations suggest that the average δ13C of CO2 released was heavier than -28‰ and more likely near -15‰; these values indicate a source containing substantial amounts of mantle- or carbonate-derived carbon. Collectively, the results point toward Siberian Trap volcanism as the trigger of mass extinction. PMID:20421502

  19. Resonance ionization mass spectrometry for isotopic abundance measurements

    NASA Technical Reports Server (NTRS)

    Miller, C. M.

    1986-01-01

    Resonance ionization mass spectrometry (RIMS) is a relatively new laser-based technique for the determination of isotopic abundances. The resonance ionization process depends upon the stepwise absorption of photons from the laser, promoting atoms of the element of interest through progressively higher electronic states until an ion is formed. Sensitivity arises from the efficiency of the resonant absorption process when coupled with the power available from commercial laser sources. Selectivity derives naturally from the distinct electronic structure of different elements. This isobaric discrimination has provided the major impetus for development of the technique. Resonance ionization mass spectrometry was used for analysis of the isotopic abundances of the rare earth lutetium. Isobaric interferences from ytterbium severely effect the ability to measure small amounts of the neutron-deficient Lu isotopes by conventional mass spectrometric techniques. Resonance ionization for lutetium is performed using a continuous-wave laser operating at 452 nm, through a sequential two-photon process, with one photon exciting the intermediate resonance and the second photon causing ionization. Ion yields for microgram-sized quantities of lutetium lie between 10(6) and 10(7) ions per second, at overall ionization efficiencies approaching 10(-4). Discrimination factors against ytterbium greater than 10(6) have been measured. Resonance ionization for technetium is also being explored, again in response to an isobaric interference, molybdenum. Because of the relatively high ionization potential for Tc, three-photon, two-color RIMS processes are being developed.

  20. Calcium isotope constraints on the end-Permian mass extinction.

    PubMed

    Payne, Jonathan L; Turchyn, Alexandra V; Paytan, Adina; Depaolo, Donald J; Lehrmann, Daniel J; Yu, Meiyi; Wei, Jiayong

    2010-05-11

    The end-Permian mass extinction horizon is marked by an abrupt shift in style of carbonate sedimentation and a negative excursion in the carbon isotope (delta(13)C) composition of carbonate minerals. Several extinction scenarios consistent with these observations have been put forward. Secular variation in the calcium isotope (delta(44/40)Ca) composition of marine sediments provides a tool for distinguishing among these possibilities and thereby constraining the causes of mass extinction. Here we report delta(44/40)Ca across the Permian-Triassic boundary from marine limestone in south China. The delta(44/40)Ca exhibits a transient negative excursion of approximately 0.3 per thousand over a few hundred thousand years or less, which we interpret to reflect a change in the global delta(44/40)Ca composition of seawater. CO(2)-driven ocean acidification best explains the coincidence of the delta(44/40)Ca excursion with negative excursions in the delta(13)C of carbonates and organic matter and the preferential extinction of heavily calcified marine animals. Calcium isotope constraints on carbon cycle calculations suggest that the average delta(13)C of CO(2) released was heavier than -28 per thousand and more likely near -15 per thousand; these values indicate a source containing substantial amounts of mantle- or carbonate-derived carbon. Collectively, the results point toward Siberian Trap volcanism as the trigger of mass extinction.

  1. Raman spectroscopic and mass spectrometric investigations of the hydrogen isotopes and isotopically labelled methane

    SciTech Connect

    Jewett, J.R., Fluor Daniel Hanford

    1997-02-24

    Suitable analytical methods must be tested and developed for monitoring the individual process steps within the fuel cycle of a fusion reactor and for tritium accountability. The utility of laser-Raman spectroscopy accompanied by mass spectrometry with an Omegatron was investigated using the analysis of all hydrogen isotopes and isotopically labeled methanes as an example. The Omegatron is useful for analyzing all hydrogen isotopes mixed with the stable helium isotopes. The application of this mass spectrometer were demonstrated by analyzing mixtures of deuterated methanes. In addition, it was employed to study the radiochemical Witzbach exchange reaction between tritium and methanes. A laser-Raman spectrometer was designed for analysis of tritium-containing gases and was built from individual components. A tritium-compatible, metal-sealed Raman cuvette having windows with good optical properties and additional means for measuring the stray light was first used successfully in this work. The Raman spectra of the hydrogen isotopes were acquired in the pure rotation mode and in the rotation-vibration mode and were used for on. The deuterated methanes were measured by Raman spectroscopy, the wavenumbers determined were assigned to the corresponding vibrations, and the wavenumbers for the rotational fine-structure were summarized in tables. The fundamental Vibrations of the deuterated methanes produced Witzbach reactions were detected and assigned. The fundamental vibrations of the molecules were obtained with Raman spectroscopy for the first time in this work. The @-Raman spectrometer assembled is well suited for the analysis of tritium- containing gases and is practical in combination with mass spectrometry using an Omegatron, for studying gases used in fusion.

  2. Chemical and Isotopic Thresholds in Charring: Implications for the Interpretation of Charcoal Mass and Isotopic Data.

    PubMed

    Pyle, Lacey A; Hockaday, William C; Boutton, Thomas; Zygourakis, Kyriacos; Kinney, Timothy J; Masiello, Caroline A

    2015-12-15

    Charcoal plays a significant role in the long-term carbon cycle, and its use as a soil amendment is promoted as a C sequestration strategy (biochar). One challenge in this research area is understanding the heterogeneity of charcoal properties. Although the maximum reaction temperature is often used as a gauge of pyrolysis conditions, pyrolysis duration also changes charcoal physicochemical qualities. Here, we introduce a formal definition of charring intensity (CI) to more accurately characterize pyrolysis, and we document variation in charcoal chemical properties with variation in CI. We find two types of responses to CI: either linear or threshold relationships. Mass yield decreases linearly with CI, while a threshold exists across which % C, % N, and δ(15)N exhibit large changes. This CI threshold co-occurs with an increase in charcoal aromaticity. C isotopes do not change from original biomass values, supporting the use of charcoal δ(13)C signatures to infer paleoecological conditions. Fractionation of N isotopes indicates that fire may be enriching soils in (15)N through pyrolytic N isotope fractionation. This influx of "black N" could have a significant impact on soil N isotopes, which we show theoretically using a simple mass-balance model.

  3. Issues and opportunities in accelerator mass spectrometry for stable isotopes.

    PubMed

    Matteson, Sam

    2008-01-01

    Accelerator mass spectrometry (AMS) has developed in the last 30 years many notable applications to the spectrometry of radioisotopes, particularly in radiocarbon dating. The instrumentation science of trace element AMS (TEAMS) that analyzes stable isotopes, also called Accelerator SIMS or MegaSIMS, while unique in many features, has also shared in many of these significant advances and has pushed TEAMS sensitivity to concentration levels surpassing many competing mass spectroscopic technologies. This review examines recent instrumentation developments, the capabilities of the new instrumentation and discernable trends for future development.

  4. Traveling waves for the mass in mass model of granular chains

    SciTech Connect

    Kevrekidis, Panayotis G.; Stefanov, Atanas G.; Xu, Haitao

    2016-06-03

    In this work, we consider the mass in mass (or mass with mass) system of granular chains, namely, a granular chain involving additionally an internal (or, respectively, external) resonator. For these chains, we rigorously establish that under suitable “anti-resonance” conditions connecting the mass of the resonator and the speed of the wave, bell-shaped traveling-wave solutions continue to exist in the system, in a way reminiscent of the results proven for the standard granular chain of elastic Hertzian contacts. Finally, we also numerically touch upon settings, where the conditions do not hold, illustrating, in line also with recent experimental work, that non-monotonic waves bearing non-vanishing tails may exist in the latter case.

  5. Traveling waves for the mass in mass model of granular chains

    DOE PAGES

    Kevrekidis, Panayotis G.; Stefanov, Atanas G.; Xu, Haitao

    2016-06-03

    In this work, we consider the mass in mass (or mass with mass) system of granular chains, namely, a granular chain involving additionally an internal (or, respectively, external) resonator. For these chains, we rigorously establish that under suitable “anti-resonance” conditions connecting the mass of the resonator and the speed of the wave, bell-shaped traveling-wave solutions continue to exist in the system, in a way reminiscent of the results proven for the standard granular chain of elastic Hertzian contacts. Finally, we also numerically touch upon settings, where the conditions do not hold, illustrating, in line also with recent experimental work, thatmore » non-monotonic waves bearing non-vanishing tails may exist in the latter case.« less

  6. Rotation and instabilities for isotope and mass separation

    NASA Astrophysics Data System (ADS)

    Rax, J.-M.; Gueroult, R.

    2016-10-01

    Rotating plasmas have the potential to offer unique capabilities for isotope and mass separation. Among the various electric and magnetic field configurations offering mass separation capabilities, rotating plasmas produced through static or oscillating fields are shown to be a leading candidate for tackling the unsolved problem of large-scale plasma separation. The successful development and deployment of industrial-scale plasma separation technologies could, among many other applications, provide an innovative path towards advanced sustainable nuclear energy. In this context, the potential and versatility of plasma rotation induced by rotating magnetic fields is uncovered and analysed. Analytical stability diagrams are derived from rotating ion orbits as a function of ion mass. Based on these findings, the basic principles of a rotating field plasma separator are then introduced. In light of these results, challenges associated with this original separation process are underlined, and the main directions for a future research program aimed at this important unsolved problem of applied plasma physics are identified.

  7. Oxygen isotopic ratios in intermediate-mass red giants

    NASA Astrophysics Data System (ADS)

    Lebzelter, T.; Straniero, O.; Hinkle, K. H.; Nowotny, W.; Aringer, B.

    2015-06-01

    Context. The abundances of the three main isotopes of oxygen are altered in the course of the CNO-cycle. When the first dredge-up mixes the burning products to the surface, the nucleosynthesis processes can be probed by measuring oxygen isotopic ratios. Aims: By measuring 16O/17O and 16O/18O in red giants of known mass we compare the isotope ratios with predictions from stellar and galactic evolution modelling. Methods: Oxygen isotopic ratios were derived from the K-band spectra of six red giants. The sample red giants are open cluster members with known masses of between 1.8 and 4.5 M⊙. The abundance determination employs synthetic spectra calculated with the COMARCS code. The effect of uncertainties in the nuclear reaction rates, the mixing length, and of a change in the initial abundance of the oxygen isotopes was determined by a set of nucleosynthesis and mixing models using the FUNS code. Results: The observed 16O/17O ratios are in good agreement with the model results, even if the measured values do not present clear evidence of a variation with the stellar mass. The observed 16O/18O ratios are clearly lower than the predictions from our reference model. Variations in nuclear reaction rates and mixing length parameter both have only a very weak effect on the predicted values. The 12C/13C ratios of the K giants studied implies the absence of extra-mixing in these objects. Conclusions: A comparison with galactic chemical evolution models indicates that the 16O/18O abundance ratio underwent a faster decrease than predicted. To explain the observed ratios, the most likely scenario is a higher initial 18O abundance combined with a lower initial 16O abundance. Comparing the measured 18O/17O ratio with the corresponding value for the interstellar medium points towards an initial enhancement of 17O as well. Limitations imposed by the observations prevent this from being a conclusive result.

  8. Mass spectrometric measurements of the isotopic anatomies of molecules (Invited)

    NASA Astrophysics Data System (ADS)

    Eiler, J. M.; Krumwiede, D.; Schlueter, H.

    2013-12-01

    Site-specific and multiple isotopic substitutions in molecular structures potentially provide an extraordinarily rich set of constraints on their sources, conditions of formation, reaction and transport histories, and perhaps other issues. Examples include carbonate ';clumped isotope' thermometry, clumped isotope measurements of CO2, O2, and, recently, methane, ethane and N2O; site-specific 15N measurements in N2O and 13C and D analyses of fatty acids, sugars, cellulose, food products, and, recently, n-alkanes. Extension of the principles behind these tools to the very large number of isotopologues of complex molecules could potentially lead to new uses of isotope chemistry, similar to proteomics, metabolomics and genomics in their complexity and depth of detail (';isotomics'?). Several technologies are potentially useful for this field, including ';SNIF-NMR', gas source mass spectrometry and IR absorption spectroscopy. However, all well established methods have restrictive limits in the sizes of samples, types of analyzes, and the sorts of isotopologues that can be measured with useful precision. We will present an overview of several emerging instruments and techniques of high-resolution gas source mass spectrometry that may enable study of a large proportion of the isotopologues of a wide range of volatile and semi-volatile compounds, including many organics, with precisions and sample sizes suitable for a range of applications. A variety of isotopologues can be measured by combining information from the Thermo 253 Ultra (a new high resolution, multi-collector gas source mass spectrometer) and the Thermo DFS (a very high resolution single collector, but used here on a novel mode to achieve ~per mil precision ratio measurements), sometimes supplemented by conventional bulk isotopic measurements. It is possible to design methods in which no one of these sources of data meaningfully constrain abundances of specific isotopologues, but their combination fully and

  9. Flame ionization mass spectrometry--Isotope ratio determinations for potassium

    USGS Publications Warehouse

    Taylor, Howard E.; Garbarino, John R.; Koirtyohann, S.R.

    1991-01-01

    The air/acetylene flame provides a convenient ion source for the determination of potassium isotopic ratios by mass spectrometry. Unlike the argon inductively coupled plasma (ICP), the flame provides low background in the mass region of interest. Ion production is quite satisfactory for isotope ratio measurements at the micrograms per milliliter (μg/mL) level and slightly below, with 1 μg/mL potassium giving about 105counts/second at a nominal mass-to-charge ratio of 39. The detection limit for potassium was 2-3 nanograms per milliliter (ng/mL). The ratio of 41K/39K was measured with 0.5-1% relative standard deviation, and a 41K spike representing 0.2% of the total potassium was readily detected. Both signal levels and signal stability were improved by adding a second easily ionized element such as cesium to samples and standards. Alternatively, a cesium solution could be aspirated for about 1 minute between sample measurements to ensure signal stability.

  10. Isotope ratio measurements by secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS)

    NASA Astrophysics Data System (ADS)

    Betti, Maria

    2005-04-01

    The basic principles of secondary ion mass spectrometry and glow discharge mass spectrometry have been shortly revisited. The applications of both techniques as exploited for the isotope ratio measurements in several matrices have been reviewed. Emphasis has been given to research fields in expansions such as solar system studies, medicine, biology, environment and nuclear forensic. The characteristics of the two techniques are discussed in terms of sensitivity and methodology of quantification. Considerations on the different detection possibilities in SIMS are also presented.

  11. Mass-independent sulfur isotopic compositions in stratospheric volcanic eruptions.

    PubMed

    Baroni, Mélanie; Thiemens, Mark H; Delmas, Robert J; Savarino, Joël

    2007-01-05

    The observed mass-independent sulfur isotopic composition (Delta33S) of volcanic sulfate from the Agung (March 1963) and Pinatubo (June 1991) eruptions recorded in the Antarctic snow provides a mechanism for documenting stratospheric events. The sign of Delta33S changes over time from an initial positive component to a negative value. Delta33S is created during photochemical oxidation of sulfur dioxide to sulfuric acid on a monthly time scale, which indicates a fast process. The reproducibility of the results reveals that Delta33S is a reliable tracer to chemically identify atmospheric processes involved during stratospheric volcanism.

  12. Exploring mass perception with Markov chain Monte Carlo.

    PubMed

    Cohen, Andrew L; Ross, Michael G

    2009-12-01

    Several previous studies have examined the ability to judge the relative mass of objects in idealized collisions. With a newly developed technique of psychological Markov chain Monte Carlo sampling (A. N. Sanborn & T. L. Griffiths, 2008), this work explores participants' perceptions of different collision mass ratios. The results reveal interparticipant differences and a qualitative distinction between the perception of 1:1 and 1:2 ratios. The results strongly suggest that participants' perceptions of 1:1 collisions are described by simple heuristics. The evidence for 1:2 collisions favors heuristic perception models that are sensitive to the sign but not the magnitude of perceived mass differences.

  13. Mechanisms of Mass-independent Fractionation of Sulfur Isotopes

    NASA Astrophysics Data System (ADS)

    Lyons, J. R.

    2006-05-01

    Sulfur mass-independent fractionation (MIF) is believed to arise from gas-phase atmospheric reactions involving SO2 and H2S [1]. However, a quantitative understanding of the mechanisms remains elusive. Here I will discuss two MIF mechanisms for sulfur isotopes, and use existing laboratory data to place constraints on these mechanisms. The relevant laboratory data includes the following: 1) Photolysis of H2S [2]; 2) spark discharge of SO2 [3]; 3) SO2 photolysis from 190-210 nm [3]; 4) SO2 photolysis at wavelengths > 220 nm [4]. Experiments 1 and 2 yielded elemental sulfur (Sel) that exhibited primarily mass-dependent fractionation, while experiment 3 produced Sel with a large MIF signature, and experiment 4 yielded sulfate with a smaller MIF signature. One likely MIF mechanism is intramolecular disequilibrium (or non-RRKM) effects, as proposed for O + O2 -- > O3 [5]. The isoelectronic sulfur reaction, S + S2 --> S3, may also exhibit non-RRKM effects, but for several reasons that I will discuss such effects may either be reduced in magnitude or of negligible importance. A second possible source of MIF is isotope-selective photodissociation during predissociation. This process is likely in SO and SH, may occur in SO2, and unlikely in H2S, but in all cases depends on wavelength. SO2 dissociation is also likely to depend on the oxygen isotopes present, because an O isotope substitution will change SO2 symmetry. Although this may produce a MIF signature in oxygen isotopes, it's not clear that this would be accompanied by a MIF effect in S. I will present kinetics simulations of the above H2S and SO2 photolysis experiments, and show how it is possible to use the results of these experiments to constrain the mechanism of MIF for atmospheric sulfur species. For example, simulations of Sel formation by H2S photolysis predict little MIF in experiments, but possible MIF in the atmosphere. [1] J. Farquhar et al. (2000) Science 289 756-758. [2] J. Farquhar et al. (2000) Nature

  14. Large deviations in the alternating mass harmonic chain

    NASA Astrophysics Data System (ADS)

    Fogedby, Hans C.

    2014-08-01

    We extend the work of Kannan et al and derive the cumulant generating function (CGF) for the alternating mass harmonic chain consisting of N particles and driven by heat reservoirs. The main result is a closed expression for the (CGF) in the thermodynamic large N limit. This expression is independent of N, but depends on whether the chain consists of an even or odd number of particles, in accordance with the results obtained by Kannan et al for the heat current. This result is in accordance with the absence of local thermodynamic equilibrium in a linear system.

  15. Isotope ratio monitoring gas chromatography/Mass spectrometry of D/H by high temperature conversion isotope ratio mass spectrometry.

    PubMed

    Hilkert; Douthitt; Schlüter; Brand

    1999-07-01

    Of all the elements, hydrogen has the largest naturally occurring variations in the ratio of its stable isotopes (D/H). It is for this reason that there has been a strong desire to add hydrogen to the list of elements amenable to isotope ratio monitoring gas chromatography/mass spectrometry (irm-GC/MS). In irm-GC/MS the sample is entrained in helium as the carrier gas, which is also ionized and separated in the isotope ratio mass spectrometer (IRMS). Because of the low abundance of deuterium in nature, precise and accurate on-line monitoring of D/H ratios with an IRMS requires that low energy helium ions be kept out of the m/z 3 collector, which requires the use of an energy filter. A clean mass 3 (HD(+.)) signal which is independent of a large helium load in the electron impact ion source is essential in order to reach the sensitivity required for D/H analysis of capillary GC peaks. A new IRMS system, the DELTA(plus)XL(trade mark), has been designed for high precision, high accuracy measurements of transient signals of hydrogen gas. It incorporates a retardation lens integrated into the m/z 3 Faraday cup collector. Following GC separation, the hydrogen bound in organic compounds must be quantitatively converted into H(2) gas prior to analysis in the IRMS. Quantitative conversion is achieved by high temperature conversion (TC) at temperatures >1400 degrees C. Measurements of D/H ratios of individual organic compounds in complicated natural mixtures can now be made to a precision of 2 per thousand (delta notation) or, better, with typical sample amounts of approximately 200 ng per compound. Initial applications have focused on compounds of interest to petroleum research (biomarkers and natural gas components), food and flavor control (vanillin and ethanol), and metabolic studies (fatty acids and steroids). Copyright 1999 John Wiley & Sons, Ltd.

  16. Seven Channel Multi-collector Isotope Ratio Mass Spectrometer

    SciTech Connect

    Anthony D. Appelhans

    2008-07-01

    A new magnetic sector mass spectrometer that utilizes seven full-sized discrete dynode electron multipliers operating simultaneously has been designed, constructed and is in preliminary testing. The instrument utilizes a newly developed ion dispersion lens that enables the mass dispersed individual isotope beams to be separated sufficiently (35 mm) to allow a full-sized discrete dynode pulse counting multiplier to be used for each beam. The ion dispersion lens is a two element electrostatic 90 degree sector device that causes the beam-to-beam dispersion to increase faster than the intra-beam dispersion. Each multiplier is contained in an isolated case with a deflector/condenser lens at the entrance. A 9-sample filament cartridge is mounted on a micro-manipulator two-axis stage that enables adjustment of the filament position with 10 micron resolution within the ion lens. Results of initial testing with actinides will be presented.

  17. Mass Independent Fractionation of Hg Isotopes Preserved in the Precambrian

    NASA Astrophysics Data System (ADS)

    Thibodeau, A. M.; Bergquist, B. A.; Kah, L. C.; Ono, S.; Ghosh, S.; Hazen, R. M.

    2013-12-01

    Mercury (Hg) is a photochemically active, redox-sensitive, chalcophilic metal with complex biogeochemistry that displays a wide range of mass-dependent (MDF) and mass-independent (MIF) stable isotopic fractionation. In the past decade, Hg isotopes have emerged as important tracers of both the sources and cycling of Hg in the modern environment. However, their utility as environmental proxies in ancient rocks remains largely unexplored. The potential of Hg isotopes to inform Precambrian environments derives from the observation that Hg isotopes with odd atomic mass numbers (199Hg and 201Hg) undergo large MIF by the magnetic isotope effect (MIE) and smaller MIF through the nuclear volume effect (NVE). Small MIF produced via NVE has been observed for numerous transformations and is characterized by MIF ratios (Δ199Hg/Δ201Hg) of about 1.6. Large Hg-MIF driven by MIE has been observed during photochemical transformations and is characterized by Δ199Hg/Δ201Hg ratios between 1 and 1.3. This MIF signal is sensitive to a range of environmental conditions, including the amount and type of solar radiation, the presence and type of complexing organic ligands, and the Hg/dissolved organic carbon (DOC) ratio. Thus, it is hoped that Hg-MIF signals may indirectly record changes in atmospheric composition or seawater chemistry if preserved in marine sedimentary records. Previous work has clearly demonstrated that Hg-MIF signals are preserved in Archean and Paleoproterozoic marine shales and massive sulfide deposits. Here, we present evidence that such signals are also preserved in marine shales of mid-Proterozoic age, including the ~1.3 Ga Sulky formation (Dismal Lakes Group, NW Arctic), the ~1.45 Ga Greyson Shale (Belt Basin, Montana), and the ~1.5 Ga Katalsy formation (Kypry Group, Eastern European Platform). We observe that the Greyson shale and shales within the Sulky formation yield negative Hg-MIF with Δ199Hg/Δ201Hg ratios close to 1 and that Kaltasy group sediments

  18. Theory analysis of mass spectra of long-chain isocyanates.

    PubMed

    Liu, Dongliang; Hao, Ce; Zhang, Hua; Qiao, Weihong; Li, Zongshi; Yu, Guanghui; Yan, Kelu; Guo, Yuliang; Cheng, Lvbo

    2008-07-01

    Electron impact mass spectra of four long-chain isocyanates, lauryl isocyanate, tetradecyl isocyanate, hexadecyl isocyanate and octadecyl isocyanate, were obtained with a GCT high-resolution time-of-flight mass spectrometer. The four isocyanates studied gave a common base peak of m/z 99, which suggested the formation of a stable six-membered ring structure to decentralize the positive charge. Quantum-mechanical energy calculation justified that the six-membered ring base peak had the lowest energy. The positive charge assigned during the fragmentation of the radical cation, and the relative intensity of the fragment ion peaks, were explained by quantum-mechanical calculations as well.

  19. Nitrogen isotopic analyses by isotope-ratio-monitoring gas chromatography/mass spectrometry

    NASA Technical Reports Server (NTRS)

    Merritt, D. A.; Hayes, J. M.

    1994-01-01

    Amino acids containing natural-abundance levels of 15N were derivatized and analyzed isotopically using a technique in which individual compounds are separated by gas chromatography, combusted on-line, and the product stream sent directly to an isotope-ratio mass spectrometer. For samples of N2 gas, standard deviations of ratio measurement were better than 0.1% (Units for delta are parts per thousand or per million (%).) for samples larger than 400 pmol and better than 0.5% for samples larger than 25 pmol (0.1% 15N is equivalent to 0.00004 atom % 15N). Results duplicated those of conventional, batchwise analyses to within 0.05%. For combustion of organic compounds yielding CO2/N2 ratios between 14 and 28, in particular for N-acetyl n-propyl derivatives of amino acids, delta values were within 0.25% of results obtained using conventional techniques and standard deviations were better than 0.35%. Pooled data for measurements of all amino acids produced an accuracy and precision of 0.04 and 0.23%, respectively, when 2 nmol of each amino acid was injected on column and 20% of the stream of combustion products was delivered to the mass spectrometer.

  20. First observation of a mass independent isotopic fractionation in a condensation reaction

    NASA Technical Reports Server (NTRS)

    Thiemens, M. H.; Nelson, R.; Dong, Q. W.; Nuth, Joseph A., III

    1994-01-01

    Thiemens and Heidenreich (1983) first demonstrated that a chemically produced mass independent isotopic fractionation process could produce an isotopic composition which is identical to that observed in Allende inclusions. This raised the possibility that the meteoritic components could be produced by chemical, rather than nuclear processes. In order to develop a mechanistic model of the early solar system, it is important that relevant reactions be studied, particularly, those which may occur in the earliest condensation reactions. The isotopic results for isotopic fractionations associated with condensation processes are reported. A large mass independent isotopic fractionation is observed in one of the experiments.

  1. Microbial mass-dependent fractionation of chromium isotopes

    USGS Publications Warehouse

    Sikora, E.R.; Johnson, T.M.; Bullen, T.D.

    2008-01-01

    Mass-dependent fractionation of Cr isotopes occurs during dissimilatory Cr(VI) reduction by Shewanella oneidensis strain MR-1. Cells suspended in a simple buffer solution, with various concentrations of lactate or formate added as electron donor, reduced 5 or 10 ??M Cr(VI) to Cr(III) over days to weeks. In all nine batch experiments, 53Cr/52Cr ratios of the unreacted Cr(VI) increased as reduction proceeded. In eight experiments covering a range of added donor concentrations up to 100 ??M, isotopic fractionation factors were nearly invariant, ranging from 1.0040 to 1.0045, with a mean value somewhat larger than that previously reported for abiotic Cr(VI) reduction (1.0034). One experiment containing much greater donor concentration (10 mM lactate) reduced Cr(VI) much faster and exhibited a lesser fractionation factor (1.0018). These results indicate that 53Cr/52Cr measurements should be effective as indicators of Cr(VI) reduction, either bacterial or abiotic. However, variability in the fractionation factor is poorly constrained and should be studied for a variety of microbial and abiotic reduction pathways. ?? 2008 Elsevier Ltd.

  2. Microbial mass-dependent fractionation of chromium isotopes

    NASA Astrophysics Data System (ADS)

    Sikora, Eric R.; Johnson, Thomas M.; Bullen, Thomas D.

    2008-08-01

    Mass-dependent fractionation of Cr isotopes occurs during dissimilatory Cr(VI) reduction by Shewanella oneidensis strain MR-1. Cells suspended in a simple buffer solution, with various concentrations of lactate or formate added as electron donor, reduced 5 or 10 μM Cr(VI) to Cr(III) over days to weeks. In all nine batch experiments, 53Cr/ 52Cr ratios of the unreacted Cr(VI) increased as reduction proceeded. In eight experiments covering a range of added donor concentrations up to 100 μM, isotopic fractionation factors were nearly invariant, ranging from 1.0040 to 1.0045, with a mean value somewhat larger than that previously reported for abiotic Cr(VI) reduction (1.0034). One experiment containing much greater donor concentration (10 mM lactate) reduced Cr(VI) much faster and exhibited a lesser fractionation factor (1.0018). These results indicate that 53Cr/ 52Cr measurements should be effective as indicators of Cr(VI) reduction, either bacterial or abiotic. However, variability in the fractionation factor is poorly constrained and should be studied for a variety of microbial and abiotic reduction pathways.

  3. Invited review article: Recent developments in isotope-ratio mass spectrometry for geochemistry and cosmochemistry.

    PubMed

    Ireland, Trevor R

    2013-01-01

    Mass spectrometry is fundamental to measurements of isotope ratios for applications in isotope geochemistry, geochronology, and cosmochemistry. Magnetic-sector mass spectrometers are most common because these provide the best precision in isotope ratio measurements. Where the highest precision is desired, chemical separation followed by mass spectrometric analysis is carried out with gas (noble gas and stable isotope mass spectrometry), liquid (inductively coupled plasma mass spectrometry), or solid (thermal ionization mass spectrometry) samples. Developments in in situ analysis, including ion microprobes and laser ablation inductively coupled plasma mass spectrometry, have opened up issues concerning homogeneity according to domain size, and allow ever smaller amounts of material to be analyzed. While mass spectrometry is built solidly on developments in the 20th century, there are new technologies that will push the limits in terms of precision, accuracy, and sample efficiency. Developments of new instruments based on time-of-flight mass spectrometers could open up the ultimate levels of sensitivity per sample atom.

  4. Introduction to Chemistry and Applications in Nature of Mass Independent Isotope Effects Special Feature

    PubMed Central

    Thiemens, Mark H.

    2013-01-01

    Stable isotope ratio variations are regulated by physical and chemical laws. These rules depend on a relation with mass differences between isotopes. New classes of isotope variation effects that deviate from mass dependent laws, termed mass independent isotope effects, were discovered in 1983 and have a wide range of applications in basic chemistry and nature. In this special edition, new applications of these effects to physical chemistry, solar system origin models, terrestrial atmospheric and biogenic evolution, polar paleo climatology, snowball earth geology, and present day atmospheric sciences are presented. PMID:24167299

  5. Introduction to chemistry and applications in nature of mass independent isotope effects special feature.

    PubMed

    Thiemens, Mark H

    2013-10-29

    Stable isotope ratio variations are regulated by physical and chemical laws. These rules depend on a relation with mass differences between isotopes. New classes of isotope variation effects that deviate from mass dependent laws, termed mass independent isotope effects, were discovered in 1983 and have a wide range of applications in basic chemistry and nature. In this special edition, new applications of these effects to physical chemistry, solar system origin models, terrestrial atmospheric and biogenic evolution, polar paleo climatology, snowball earth geology, and present day atmospheric sciences are presented.

  6. Asteroid mass estimation using Markov-Chain Monte Carlo techniques

    NASA Astrophysics Data System (ADS)

    Siltala, Lauri; Granvik, Mikael

    2016-10-01

    Estimates for asteroid masses are based on their gravitational perturbations on the orbits of other objects such as Mars, spacecraft, or other asteroids and/or their satellites. In the case of asteroid-asteroid perturbations, this leads to a 13-dimensional inverse problem where the aim is to derive the mass of the perturbing asteroid and six orbital elements for both the perturbing asteroid and the test asteroid using astrometric observations. We have developed and implemented three different mass estimation algorithms utilizing asteroid-asteroid perturbations into the OpenOrb asteroid-orbit-computation software: the very rough 'marching' approximation, in which the asteroid orbits are fixed at a given epoch, reducing the problem to a one-dimensional estimation of the mass, an implementation of the Nelder-Mead simplex method, and most significantly, a Markov-Chain Monte Carlo (MCMC) approach. We will introduce each of these algorithms with particular focus on the MCMC algorithm, and present example results for both synthetic and real data. Our results agree with the published mass estimates, but suggest that the published uncertainties may be misleading as a consequence of using linearized mass-estimation methods. Finally, we discuss remaining challenges with the algorithms as well as future plans, particularly in connection with ESA's Gaia mission.

  7. Carbon isotopic analysis of atmospheric methane by isotope-ratio-monitoring gas chromatography-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Merritt, Dawn A.; Hayes, J. M.; Marais, David J. Des

    1995-01-01

    Less than 15 min are required for the determination of δ13CPDB with a precision of 0.2‰ (1σ, single measurement) in 5-mL samples of air containing CH4 at natural levels (1.7 ppm). An analytical system including a sample-introduction unit incorporating a preparative gas chromatograph (GC) column for separation of CH4 from N2, O2, and Ar is described. The 15-min procedure includes time for operation of that system, high-resolution chromatographic separation of the CH4, on-line combustion and purification of the products, and isotopic calibration. Analyses of standards demonstrate that systematic errors are absent and that there is no dependence of observed values of δ on sample size. For samples containing 100 ppm or more CH4, preconcentration is not required and the analysis time is less than 5 min. The system utilizes a commercially available, high-sensitivity isotope-ratio mass spectrometer. For optimal conditions of sample handling and combustion, performance of the system is within a factor of 2 of the shot-noise limit. The potential exists therefore for analysis of samples as small as 15 pmol CH4 with a standard deviation of <1‰.

  8. Carbon isotopic analysis of atmospheric methane by isotope-ratio-monitoring gas chromatography-mass spectrometry

    NASA Technical Reports Server (NTRS)

    Merritt, Dawn A.; Hayes, J. M.; Des Marais, David J.

    1995-01-01

    Less than 15 min are required for the determination of delta C(sub PDB)-13 with a precision of 0.2 ppt(1 sigma, single measurement) in 5-mL samples of air containing CH4 at natural levels (1.7 ppm). An analytical system including a sample-introduction unit incorporating a preparative gas chromatograph (GC) column for separation of CH4 from N2, O2, and Ar is described. The 15-min procedure includes time for operation of that system, high-resolution chromatographic separation of the CH4, on-line combustion and purification of the products, and isotopic calibration. Analyses of standards demonstrate that systematic errors are absent and that there is no dependence of observed values of delta on sample size. For samples containing 100 ppm or more CH4, preconcentration is not required and the analysis time is less than 5 min. The system utilizes a commercially available, high-sensitivity isotope-ratio mass spectrometer. For optimal conditions of smaple handling and combustion, performance of the system is within a factor of 2 of the shot-noise limit. The potential exists therefore for analysis of samples as small as 15 pmol CH4 with a standard deviation of less than 1 ppt.

  9. Optical spectroscopy using mass-separated beams: Nuclear properties of unstable indium and tin isotopes

    NASA Astrophysics Data System (ADS)

    Kuehl, T.; Kirchner, R.; Klepper, O.; Marx, D.; Dinger, U.; Eberz, J.; Huber, G.; Lochmann, H.; Menges, R.; Ulm, G.

    1987-05-01

    Collinear fast-beam laser-spectroscopy has been used to measure the hyperfine structure and isotope shift of several indium and tin isotopes. The related experimental techniques are described, including the preparation of mass-separated beams of neutron-deficient indium and tin isotopes at the GSI on-line mass separator following fusion-evaporation reactions. The deviation of the observed dependence of the charge radii upon the neutron number from the expected behaviour is briefly discussed.

  10. Using Punnett Squares to Facilitate Students' Understanding of Isotopic Distributions in Mass Spectrometry

    ERIC Educational Resources Information Center

    Sein, Lawrence T., Jr.

    2006-01-01

    The isotopic distribution in mass spectroscopy is described for identifying pure compounds, being able to distinguish molecular fragments by masses. Punnett squares are familiar, easy to compute, and often graphical which makes helpful to students and the relative distribution of isotopic combination is easily generated for even isotopic…

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

    PubMed Central

    Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

    2012-01-01

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

  12. Non-mass-dependent oxygen isotope effect observed in water vapor from Alert, Canada

    NASA Astrophysics Data System (ADS)

    Lin, Ying

    Twenty-seven precipitation samples from Chicago, IL and northwest part of Indiana were collected from 2003 to 2005. Twenty-five water vapor samples were collected at Alert, Canada (82° 30'N, 62° 19'W) from 2002 to 2005 by Lin Huang and her co-workers. Seven ice core samples from Dasuopu glacier, Chinese Himalayas (28° 23' N, 85° 43'W) were drilled by Lonnie G. Thompson and prepared by Mary E. Davis. Sample of Standard Light Antarctic Precipitation (SLAP) is available in the laboratory. Water samples were reacted with bromine pentafluoride to produce oxygen, which were then purified through molecular sieve and measured by Delta E gas source mass spectrometer. A lambda(MDF) = 0.529 +/- 0.003 (2sigma) for water is determined from measurement of local precipitation samples. No significant oxygen isotopic anomaly is found in SLAP and in ice core samples from Dasuopu glacier, Chinese Himalayas. Delta17O(CLP), oxygen isotopic anomaly relative to Chicago local precipitation, of -0.009‰ to 0.167‰ with a mean of 0.076‰ and a 2sigma standard error of 0.016‰ is observed in water vapor from Alert, Canada. About half of these Delta17O(CLP) data exhibit statistically significant excesses. Stacked seasonal trend of Delta17O(CLP) observed at Alert, Canada points to a maximum in late spring when the intrusion of stratospheric air is at its maximum and the height of Arctic tropopause is the lowest. However, no significant oxygen isotopic anomalies are found in ice core samples from Dasuopu and in SLAP. The positive excesses in Delta17O(CLP) seen in tropospheric water vapor at Alert, Canada could be explained by the transfer of positive oxygen isotopic anomalies through O3 → NOx → HOx → H2O chain in the stratosphere, and the subsequent mixing of this anomalous stratospheric water with tropospheric water vapor at Alert, Canada where the tropopause is low and where downward mixing of stratospheric air with tropospheric air takes place. The positive oxygen isotopic

  13. Phenotyping polyclonal kappa and lambda light chain molecular mass distributions in patient serum using mass spectrometry.

    PubMed

    Barnidge, David R; Dasari, Surendra; Ramirez-Alvarado, Marina; Fontan, Adrian; Willrich, Maria A V; Tschumper, Renee C; Jelinek, Diane F; Snyder, Melissa R; Dispenzieri, Angela; Katzmann, Jerry A; Murray, David L

    2014-11-07

    We previously described a microLC-ESI-Q-TOF MS method for identifying monoclonal immunoglobulins in serum and then tracking them over time using their accurate molecular mass. Here we demonstrate how the same methodology can be used to identify and characterize polyclonal immunoglobulins in serum. We establish that two molecular mass distributions observed by microLC-ESI-Q-TOF MS are from polyclonal kappa and lambda light chains using a combination of theoretical molecular masses from gene sequence data and the analysis of commercially available purified polyclonal IgG kappa and IgG lambda from normal human serum. A linear regression comparison of kappa/lambda ratios for 74 serum samples (25 hypergammaglobulinemia, 24 hypogammaglobulinemia, 25 normal) determined by microflowLC-ESI-Q-TOF MS and immunonephelometry had a slope of 1.37 and a correlation coefficient of 0.639. In addition to providing kappa/lambda ratios, the same microLC-ESI-Q-TOF MS analysis can determine the molecular mass for oligoclonal light chains observed above the polyclonal background in patient samples. In 2 patients with immune disorders and hypergammaglobulinemia, we observed a skewed polyclonal molecular mass distribution which translated into biased kappa/lambda ratios. Mass spectrometry provides a rapid and simple way to combine the polyclonal kappa/lambda light chain abundance ratios with the identification of dominant monoclonal as well as oligoclonal light chain immunoglobulins. We anticipate that this approach to evaluating immunoglobulin light chains will lead to improved understanding of immune deficiencies, autoimmune diseases, and antibody responses.

  14. Multi-isotopic signatures of organic and conventional Italian pasta along the production chain.

    PubMed

    Bontempo, L; Camin, F; Paolini, M; Micheloni, C; Laursen, K H

    2016-09-01

    The variability of stable isotope ratios (δ(2) H, δ(13) C, δ(15) N, δ(18) O and δ(34) S) along the production chain of pasta (durum wheat, flour and pasta) produced by using both conventional and organic farming systems in four Italian regions in 2 years was investigated. The aim was to evaluate if and how the farming system and geographical origin affect stable isotope ratios determined along the production chain. Irrespective of the processing technology, 65% of the samples were correctly classified according to the farming system and 98% were correctly classified regarding the geographical region. When considering both farming system and geographical region simultaneously, 80% of the samples were correctly classified. The measured isotope parameters were thus primarily affected by the geographical origin. In conclusion, it is expected that the use of these parameters will allow the development of analytical control procedures that can be used to check the geographical origin of Italian organic and conventional pasta and its raw materials. Copyright © 2016 John Wiley & Sons, Ltd.

  15. Mass-independent isotope fractionation of Mo, Ru, Cd, and Te

    NASA Astrophysics Data System (ADS)

    Fujii, T.; Moynier, F.; Albarède, F.

    2006-12-01

    The variation of the mean charge distribution in the nucleus with the neutron number of different isotopes induces a tenuous shift of the nuclear field. The mass fractionation induced during phase changes is irregular, notably with 'staggering' between odd and even masses, and becomes increasingly non-linear for neutron-rich isotopes. A strong correlation is observed between the deviation of the isotopic effects from the linear dependence with mass and the corresponding nuclear charge radii. We first demonstrated on a number of elements the existence of such mass-independent isotope fractionation in laboratory experiments of solvent extraction with a macrocyclic compound. The isotope ratios were analyzed by multiple-collector inductively coupled plasma mass spectrometry with a typical precision of <100 ppm. The isotopes of odd and even atomic masses are enriched in the solvent to an extent that closely follows the variation of their nuclear charge radii. The present results fit Bigeleisen's (1996) model, which is the standard mass-dependent theory modified to include a correction term named the nuclear field shift effect. For heavy elements like uranium, the mass-independent effect is important enough to dominate the mass-dependent effect. We subsequently set out to compare the predictions of Bigeleisen's theory with the isotopic anomalies found in meteorites. Some of these anomalies are clearly inconsistent with nucleosynthetic effects (either s- or r-processes). Isotopic variations of Mo and Ru in meteorites, especially in Allende (CV3), show a clear indication of nucleosynthetic components. However, the mass-independent anomaly of Ru observed in Murchison (CM2) is a remarkable exception which cannot be explained by the nucleosynthetic model, but fits the nuclear field shift theory extremely well. The abundances of the even atomic mass Te isotopes in the leachates of carbonaceous chondrites, Allende, Murchison, and Orgueil, fit a mass-dependent law well, but the

  16. Mass-dependent and -independent fractionation of isotopes in Ni and Pb chelate complex formation reactions

    NASA Astrophysics Data System (ADS)

    Nomura, Masao; Kudo, Takashi; Adachi, Atsuhiko; Aida, Masao; Fujii, Yasuhiko

    2013-11-01

    Mass independent fractionation (MIF) has been a very interesting topic in the field of inorganic isotope chemistry, in particular, geo- and cosmo- chemistry. In the present work, we studied the isotope fractionation of Ni(II) and Pb(II) ions in complex formation with chelating reagent EDTA. To obtain clear results on the mass dependence of the isotope fractionation, we have conducted long-distance ion exchange chromatography of Ni(II) and Pb(II), using chelate complex reagent EDTA. The results apparently show that the isotope fractionation in Ni complex formation system is governed by the mass dependent rule. On the other hand the isotope fractionation in the Pb complex system is governed by the mass independent rule or the nuclear volume effect.

  17. Mass-dependent and -independent fractionation of isotopes in Ni and Pb chelate complex formation reactions

    SciTech Connect

    Nomura, Masao; Kudo, Takashi; Adachi, Atsuhiko; Aida, Masao; Fujii, Yasuhiko

    2013-11-13

    Mass independent fractionation (MIF) has been a very interesting topic in the field of inorganic isotope chemistry, in particular, geo- and cosmo- chemistry. In the present work, we studied the isotope fractionation of Ni(II) and Pb(II) ions in complex formation with chelating reagent EDTA. To obtain clear results on the mass dependence of the isotope fractionation, we have conducted long-distance ion exchange chromatography of Ni(II) and Pb(II), using chelate complex reagent EDTA. The results apparently show that the isotope fractionation in Ni complex formation system is governed by the mass dependent rule. On the other hand the isotope fractionation in the Pb complex system is governed by the mass independent rule or the nuclear volume effect.

  18. Chemical and Isotopic Thresholds in Charring: Implications for the Interpretation of Charcoal Mass and Isotopic Data

    NASA Astrophysics Data System (ADS)

    Pyle, L.; Hockaday, W. C.; Boutton, T. W.; Zygourakis, K.; Kinney, T.; Masiello, C. A.

    2014-12-01

    Charcoal plays a significant role in the long-term carbon cycle and its use as a soil amendment is becoming a viable carbon sequestration strategy (biochar). One challenge in this research area has been comparing results between studies in part due to the diversity of lab and field production conditions. Although the highest treatment temperature (HTT) is often used to describe pyrolysis conditions, several studies have shown that length of time at the highest temperature can also cause changes to the physicochemical qualities of charcoal and ignoring this effect may introduce inter-comparison problems. Addressing this issue becomes especially important in the discussion of optimizing biochar for soil remediation and carbon sequestration, and in discussions of charcoal use in reconstructing past fire regimes, as increasing time at temperature may cause changes in charcoal properties similar to the changes caused by increasing HTT. Here we introduce a formal definition of charring intensity (CI) to more accurately characterize pyrolysis, and we document variation in this property with pyrolysis temperature and reaction duration. We found two types of responses to CI: either a linear or a threshold relationship. We show that a threshold exists where %C, %N and δ15N begin exhibiting large changes, and this CI threshold co-occurred with an increase in charcoal aromaticity. Mass yield decreased linearly with charring intensity and carbon isotopes did not change from original biomass values in our controlled laboratory experiments. Analysis of these data shows that pyrolysis parameters should be defined in the literature as a combination of temperature and duration conditions, and that biomass that has undergone pyrolysis may be influencing soil organic nitrogen. Additionally, the lack of alteration in carbon isotopes across our matrix supports the efficacy of using pyrolyzed material for archaeological reconstructions.

  19. Stable nitrogen isotope ratios and accumulation of various HOCs in northern Baltic aquatic food chains

    SciTech Connect

    Broman, D.; Axelman, J.; Bergqvist, P.A.; Naef, C.; Rolff, C.; Zebuehr, Y.

    1995-12-31

    Ratios of naturally occurring stable isotopes of nitrogen ({delta}{sup 15}N) can be used to numerically classify trophic levels of organisms in food chains. By combining analyses results of various HOCs (e.g. PCDD/Fs, PCBs, DDTs, HCHs and some other pesticides) the biomagnification of these substances can be quantitatively estimated. In this paper different pelagic and benthic northern Baltic food chains were studied. The {delta}{sup 15}N-data gave food chain descriptions qualitatively consistent with previous conceptions of trophic arrangements in the food chains. The different HOCs concentrations were plotted versus the {delta}{sup 15}N-values for the different trophic levels and an exponential model of the form e{sup (A+B*{delta}N)} was fitted to the data. The estimates of the constant B in the model allows for an estimation of a biomagnification power (B) of different singular, or groups of, contaminants. A B-value around zero indicates that a substance is flowing through the food chain without being magnified, whereas a value > 0 indicates that a substance is biomagnified. Negative B-values indicate that a substance is not taken up or is metabolized. The A-term of the expression is only a scaling factor depending on the background level of the contaminant.

  20. Forensic applications of isotope ratio mass spectrometry--a review.

    PubMed

    Benson, Sarah; Lennard, Chris; Maynard, Philip; Roux, Claude

    2006-02-10

    The key role of a forensic scientist is to assist in determining whether a crime has been committed, and if so, assist in the identification of the offender. Many people hold the belief that a particular item can be conclusively linked to a specific person, place or object. Unfortunately, this is often not achievable in forensic science. In performing their role, scientists develop and test hypotheses. The significance of those hypotheses that cannot be rejected upon completion of all available examinations/analyses is then evaluated. Although one can generally identify the substances present using available techniques, it is generally not possible to distinguish one source of the same substance from another. In such circumstances, although a particular hypothesis cannot be rejected, it cannot be conclusively proven, i.e. the samples could still have originated from different sources. This limitation of not being able to distinguish between sources currently extends to the analysis of other forensic samples including, but not limited to, ignitable liquids, paints, adhesives, textile fibres, plastics, and illicit drugs. Stable isotope ratio mass spectrometry (IRMS) is an additional technique that can be utilised to test a given hypothesis. This technique shows the potential to be able to individualise a range of materials of forensic interest. This paper provides a brief description of the technique, followed by a review of the various applications of IRMS in different scientific fields. The focus of this summary is on forensic applications of IRMS, in particular the analysis of explosives, ignitable liquids and illicit drugs.

  1. Lightning and Mass Independent Oxygen Isotopic Fractionation in Nebular Silicates

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A.

    2009-01-01

    Lightning has long been postulated as the agent of Chondru|e formation in the solar nebula, but it may have an additional role to play as well. Lightning bolts of almost any scale will both vaporize dust and liberate oxygen atoms that will then interact with both nebular gases as well as the refractory silicate vapor as it re-condenses. Such processes should result in the addition of the heavy oxygen isotopes to the growing silicate grains while the light oxygen-16 becomes part of the gas phase water. This process will proceed to some extent throughout the history of any turbulent nebula and will result in the gradual increase of O-16 in the gas phase and in a much larger relative increase in the O-17 and O-18 content of the nebular dust. Laboratory experiments have demonstrated the production of such "heavy oxygen enriched", non-mass-dependently-fractionated dust grains in a high voltage discharge in a hydrogen rich gas containing small quantities of silane, pentacarbonyl iron and oxygen.

  2. Nagel scaling, relaxation, and universality in the kinetic ising model on an alternating isotopic chain

    PubMed

    Goncalves; Lopez De Haro M; Taguena-Martinez; Stinchcombe

    2000-02-14

    The dynamic critical exponent and the frequency and wave-vector dependent susceptibility of the kinetic Ising model on an alternating isotopic chain with Glauber dynamics are examined. The analysis provides a connection between a microscopic model and the Nagel scaling curve originally proposed to describe dielectric susceptibility measurements of several glass-forming liquids. While support is given to the hypothesis relating the Nagel scaling to multiple relaxation processes, it is also found that the scaling function may exhibit plateau regions and does not hold for all temperatures.

  3. Methods and limitations of 'clumped' CO2 isotope (Delta47) analysis by gas-source isotope ratio mass spectrometry.

    PubMed

    Huntington, K W; Eiler, J M; Affek, H P; Guo, W; Bonifacie, M; Yeung, L Y; Thiagarajan, N; Passey, B; Tripati, A; Daëron, M; Came, R

    2009-09-01

    The geochemistry of multiply substituted isotopologues ('clumped-isotope' geochemistry) examines the abundances in natural materials of molecules, formula units or moieties that contain more than one rare isotope (e.g. (13)C(18)O(16)O, (18)O(18)O, (15)N(2), (13)C(18)O(16)O(2) (2-)). Such species form the basis of carbonate clumped-isotope thermometry and undergo distinctive fractionations during a variety of natural processes, but initial reports have provided few details of their analysis. In this study, we present detailed data and arguments regarding the theoretical and practical limits of precision, methods of standardization, instrument linearity and related issues for clumped-isotope analysis by dual-inlet gas-source isotope ratio mass spectrometry (IRMS). We demonstrate long-term stability and subtenth per mil precision in 47/44 ratios for counting systems consisting of a Faraday cup registered through a 10(12) ohm resistor on three Thermo-Finnigan 253 IRMS systems. Based on the analyses of heated CO(2) gases, which have a stochastic distribution of isotopes among possible isotopologues, we document and correct for (1) isotopic exchange among analyte CO(2) molecules and (2) subtle nonlinearity in the relationship between actual and measured 47/44 ratios. External precisions of approximately 0.01 per thousand are routinely achieved for measurements of the mass-47 anomaly (a measure mostly of the abundance anomaly of (13)C-(18)O bonds) and follow counting statistics. The present technical limit to precision intrinsic to our methods and instrumentation is approximately 5 parts per million (ppm), whereas precisions of measurements of heterogeneous natural materials are more typically approximately 10 ppm (both 1 s.e.). These correspond to errors in carbonate clumped-isotope thermometry of +/-1.2 degrees C and +/-2.4 degrees C, respectively.

  4. Attogram measurement of rare isotopes by CW resonance ionization mass spectrometry

    SciTech Connect

    Bushaw, B.A.

    1992-05-01

    Three-color double-resonance ionization mass spectrometry, using two single-frequency cw dye lasers and a cw carbon dioxide laser, has been applied to the detection of attogram quantities of rare radionuclides. {sup 210}Pb has been measured in human hair and brain tissue samples to assess indoor radon exposure. Measurements on {sup 90}Sr have shown overall isotopic selectivity of greater than 10{sup 9} despite unfavorable isotope shifts relative to the major stable isotope, {sup 88}Sr.

  5. Analysis of the site-specific carbon isotope composition of propane by gas source isotope ratio mass spectrometer

    NASA Astrophysics Data System (ADS)

    Piasecki, Alison; Sessions, Alex; Lawson, Michael; Ferreira, A. A.; Neto, E. V. Santos; Eiler, John M.

    2016-09-01

    Site-specific isotope ratio measurements potentially provide valuable information about the formation and degradation of complex molecules-information that is lost in conventional bulk isotopic measurements. Here we discuss the background and possible applications of such measurements, and present a technique for studying the site-specific carbon isotope composition of propane at natural abundance based on mass spectrometric analysis of the intact propane molecule and its fragment ions. We demonstrate the feasibility of this approach through measurements of mixtures of natural propane and propane synthesized with site-specific 13C enrichment, and we document the limits of precision of our technique. We show that mass balance calculations of the bulk δ13C of propane based on our site-specific measurements is generally consistent with independent constraints on bulk δ13C. We further demonstrate the accuracy of the technique, and illustrate one of its simpler applications by documenting the site-specific carbon isotope signature associated with gas phase diffusion of propane, confirming that our measurements conform to the predictions of the kinetic theory of gases. This method can be applied to propane samples of moderate size (tens of micromoles) isolated from natural gases. Thus, it provides a means of studying the site-specific stable isotope systematics of propane at natural isotope abundances on sample sizes that are readily recovered from many natural environments. This method may also serve as a model for future techniques that apply high-resolution mass spectrometry to study the site-specific isotopic distributions of larger organic molecules, with potential applications to biosynthesis, forensics and other geochemical subjects.

  6. Stable isotope markers differentiate between mass-reared and wild Lepidoptera in sterile insect technique programs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this comprehensive study a number of Sterile Insect Technique (SIT) target moth species were identified and the feasibility was assessed of using isotope signatures to distinguish mass reared from wild moth species as a marking tool. Large natural differences in the isotopic signatures of commer...

  7. Preparation of the anapole moment measurement in a chain of isotopes

    NASA Astrophysics Data System (ADS)

    Sheng, Dong; Hood, Jonathan; Orozco, Luis

    2010-02-01

    We present the current status of the experimental effort towards the measurement of the anapole moment in different isotopes of francium. The anapole is a parity violating, time reversal conserving nuclear moment that arises from the weak interaction among nucleons, and should be sensitive to the changes in the nuclear structure configuration among the isotopes. The anapole is a unique probe of the weak interaction in the presence of the strong interaction. The system is currently being tested with rubidium and we have analyzed the sensitivity to measurements with a chain of Rb isotopes. Our experimental scheme involves a collection of cold atoms in a blue-detuned dipole trap located at the anti-node of a microwave cavity. The standing wave would drive a parity forbidden E1 transition between hyperfine ground states, interfering with an allowed transition. The rate of transitions depends on the positive or negative handedness of the apparatus and the measurement of their difference is proportional to the anapole moment. The experiment will use of the ISAC radioactive beam facility at TRIUMF. )

  8. Discrete breathers in a mass-in-mass chain with Hertzian local resonators

    NASA Astrophysics Data System (ADS)

    Wallen, S. P.; Lee, J.; Mei, D.; Chong, C.; Kevrekidis, P. G.; Boechler, N.

    2017-02-01

    We report on the existence of discrete breathers in a one-dimensional, mass-in-mass chain with linear intersite coupling and nonlinear, precompressed Hertzian local resonators, which is motivated by recent studies of the dynamics of microspheres adhered to elastic substrates. After predicting theoretically the existence of discrete breathers in the continuum and anticontinuum limits of intersite coupling, we use numerical continuation to compute a family of breathers interpolating between the two regimes in a finite chain, where the displacement profiles of the breathers are localized around one lattice site. We then analyze the frequency-amplitude dependence of the breathers by performing numerical continuation on a linear eigenmode (vanishing amplitude) solution of the system near the upper band gap edge. Finally, we use direct numerical integration of the equations of motion to demonstrate the formation and evolution of the identified localized modes in energy-conserving and dissipative scenarios, including within settings that may be relevant to future experimental studies.

  9. Discrete breathers in a mass-in-mass chain with Hertzian local resonators.

    PubMed

    Wallen, S P; Lee, J; Mei, D; Chong, C; Kevrekidis, P G; Boechler, N

    2017-02-01

    We report on the existence of discrete breathers in a one-dimensional, mass-in-mass chain with linear intersite coupling and nonlinear, precompressed Hertzian local resonators, which is motivated by recent studies of the dynamics of microspheres adhered to elastic substrates. After predicting theoretically the existence of discrete breathers in the continuum and anticontinuum limits of intersite coupling, we use numerical continuation to compute a family of breathers interpolating between the two regimes in a finite chain, where the displacement profiles of the breathers are localized around one lattice site. We then analyze the frequency-amplitude dependence of the breathers by performing numerical continuation on a linear eigenmode (vanishing amplitude) solution of the system near the upper band gap edge. Finally, we use direct numerical integration of the equations of motion to demonstrate the formation and evolution of the identified localized modes in energy-conserving and dissipative scenarios, including within settings that may be relevant to future experimental studies.

  10. Molecular Isotopic Distribution Analysis (MIDAs) with Adjustable Mass Accuracy

    NASA Astrophysics Data System (ADS)

    Alves, Gelio; Ogurtsov, Aleksey Y.; Yu, Yi-Kuo

    2014-01-01

    In this paper, we present Molecular Isotopic Distribution Analysis (MIDAs), a new software tool designed to compute molecular isotopic distributions with adjustable accuracies. MIDAs offers two algorithms, one polynomial-based and one Fourier-transform-based, both of which compute molecular isotopic distributions accurately and efficiently. The polynomial-based algorithm contains few novel aspects, whereas the Fourier-transform-based algorithm consists mainly of improvements to other existing Fourier-transform-based algorithms. We have benchmarked the performance of the two algorithms implemented in MIDAs with that of eight software packages (BRAIN, Emass, Mercury, Mercury5, NeutronCluster, Qmass, JFC, IC) using a consensus set of benchmark molecules. Under the proposed evaluation criteria, MIDAs's algorithms, JFC, and Emass compute with comparable accuracy the coarse-grained (low-resolution) isotopic distributions and are more accurate than the other software packages. For fine-grained isotopic distributions, we compared IC, MIDAs's polynomial algorithm, and MIDAs's Fourier transform algorithm. Among the three, IC and MIDAs's polynomial algorithm compute isotopic distributions that better resemble their corresponding exact fine-grained (high-resolution) isotopic distributions. MIDAs can be accessed freely through a user-friendly web-interface at http://www.ncbi.nlm.nih.gov/CBBresearch/Yu/midas/index.html.

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

    ERIC Educational Resources Information Center

    Hill, Devon W.; And Others

    1988-01-01

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

  12. Mass transfer and carbon isotope evolution in natural water systems

    USGS Publications Warehouse

    Wigley, T.M.L.; Plummer, L.N.; Pearson, F.J.

    1978-01-01

    This paper presents a theoretical treatment of the evolution of the carbon isotopes C13 and C14 in natural waters and in precipitates which derive from such waters. The effects of an arbitrary number of sources (such as dissolution of carbonate minerals and oxidation of organic material) and sinks (such as mineral precipitation, CO2 degassing and production of methane), and of equilibrium fractionation between solid, gas and aqueous phases are considered. The results are expressed as equations relating changes in isotopic composition to changes in conventional carbonate chemistry. One implication of the equations is that the isotopic composition of an aqueous phase may approach a limiting value whenever there are simultaneous inputs and outputs of carbonate. In order to unambiguously interpret isotopic data from carbonate precipitates and identify reactants and products in reacting natural waters, it is essential that isotopic changes are determined chiefly by reactant and product stoichiometry, independent of reaction path. We demonstrate that this is so by means of quantitative examples. The evolution equations are applied to: 1. (1) carbon-14 dating of groundwaters; 2. (2) interpretation of the isotopic composition of carbonate precipitates, carbonate cements and diagenetically altered carbonates; and 3. (3) the identification of chemical reaction stoichiometry. These applications are illustrated by examples which show the variation of ??C13 in solutions and in precipitates formed under a variety of conditions involving incongruent dissolution, CO2 degassing, methane production and mineral precipitation. ?? 1978.

  13. Mass-dependent and -independent signature of Fe isotopes in magnetotactic bacteria

    NASA Astrophysics Data System (ADS)

    Amor, Matthieu; Busigny, Vincent; Louvat, Pascale; Gélabert, Alexandre; Cartigny, Pierre; Durand-Dubief, Mickaël; Ona-Nguema, Georges; Alphandéry, Edouard; Chebbi, Imène; Guyot, François

    2016-05-01

    Magnetotactic bacteria perform biomineralization of intracellular magnetite (Fe3O4) nanoparticles. Although they may be among the earliest microorganisms capable of biomineralization on Earth, identifying their activity in ancient sedimentary rocks remains challenging because of the lack of a reliable biosignature. We determined Fe isotope fractionations by the magnetotactic bacterium Magnetospirillum magneticum AMB-1. The AMB-1 strain produced magnetite strongly depleted in heavy Fe isotopes, by 1.5 to 2.5 per mil relative to the initial growth medium. Moreover, we observed mass-independent isotope fractionations in 57Fe during magnetite biomineralization but not in even Fe isotopes (54Fe, 56Fe, and 58Fe), highlighting a magnetic isotope effect. This Fe isotope anomaly provides a potential biosignature for the identification of magnetite produced by magnetotactic bacteria in the geological record.

  14. Mass-dependent and -independent signature of Fe isotopes in magnetotactic bacteria.

    PubMed

    Amor, Matthieu; Busigny, Vincent; Louvat, Pascale; Gélabert, Alexandre; Cartigny, Pierre; Durand-Dubief, Mickaël; Ona-Nguema, Georges; Alphandéry, Edouard; Chebbi, Imène; Guyot, François

    2016-05-06

    Magnetotactic bacteria perform biomineralization of intracellular magnetite (Fe3O4) nanoparticles. Although they may be among the earliest microorganisms capable of biomineralization on Earth, identifying their activity in ancient sedimentary rocks remains challenging because of the lack of a reliable biosignature. We determined Fe isotope fractionations by the magnetotactic bacterium Magnetospirillum magneticum AMB-1. The AMB-1 strain produced magnetite strongly depleted in heavy Fe isotopes, by 1.5 to 2.5 per mil relative to the initial growth medium. Moreover, we observed mass-independent isotope fractionations in (57)Fe during magnetite biomineralization but not in even Fe isotopes ((54)Fe, (56)Fe, and (58)Fe), highlighting a magnetic isotope effect. This Fe isotope anomaly provides a potential biosignature for the identification of magnetite produced by magnetotactic bacteria in the geological record.

  15. Mass-dependent and non-mass-dependent isotope effects in ozone photolysis: Resolving theory and experiments

    SciTech Connect

    Cole, Amanda S.; Boering, Kristie A.

    2006-11-14

    In addition to the anomalous {sup 17}O and {sup 18}O isotope effects in the three-body ozone formation reaction O+O{sub 2}+M, isotope effects in the destruction of ozone by photolysis may also play a role in determining the isotopic composition of ozone and other trace gases in the atmosphere. While previous experiments on ozone photolysis at 254 nm were interpreted as evidence for preferential loss of light ozone that is anomalous (or 'non-mass-dependent'), recent semiempirical theoretical calculations predicted a preferential loss of heavy ozone at that wavelength that is mass dependent. Through photochemical modeling results presented here, we resolve this apparent contradiction between experiment and theory. Specifically, we show that the formation of ozone during the UV photolysis experiments is not negligible, as had been assumed, and that the well-known non-mass-dependent isotope effects in ozone formation can account for the non-mass-dependent enrichment of the heavy isotopologs of ozone observed in the experiment. Thus, no unusual non-mass-dependent fractionation in ozone photolysis must be invoked to explain the experimental results. Furthermore, we show that theoretical predictions of a mass-dependent preferential loss of the heavy isotopologs of ozone during UV photolysis are not inconsistent with the experimental data, particularly if mass-dependent isotope effects in the chemical loss reactions of ozone during the photolysis experiments or experimental artifacts enrich the remaining ozone in {sup 17}O and {sup 18}O. Before the calculated fractionation factors can be quantitatively evaluated, however, further investigation of possible mass-dependent isotope effects in the reactions of ozone with O({sup 1}D), O({sup 3}P), O{sub 2}({sup 1}{delta}), and O{sub 2}({sup 1}{sigma}) is needed through experiments we suggest here.

  16. Competition between pairing correlations and deformation from the odd-even mass staggering of francium and radium isotopes

    NASA Astrophysics Data System (ADS)

    Kreim, S.; Beck, D.; Blaum, K.; Borgmann, Ch.; Breitenfeldt, M.; Cocolios, T. E.; Gottberg, A.; Herfurth, F.; Kowalska, M.; Litvinov, Yu. A.; Lunney, D.; Manea, V.; Mendonca, T. M.; Naimi, S.; Neidherr, D.; Rosenbusch, M.; Schweikhard, L.; Stora, Th.; Wienholtz, F.; Wolf, R. N.; Zuber, K.

    2014-08-01

    The masses of Fr222,224,226-233 and Ra233,234 have been determined with the Penning-trap mass spectrometer ISOLTRAP at the ISOLDE facility at CERN, including the previously unknown mass and half-life of Fr233. We study the evolution of the odd-even staggering of binding energies along the francium and radium isotopic chains and of its lowest-order estimator, Δ3(N). An enhancement of the staggering of Δ3(N) is observed towards neutron number N =146, which points to contributions beyond pairing correlations. These contributions are investigated in the Hartree-Fock and Hartree-Fock-Bogoliubov approaches, emphasizing the connections to the single-particle level density and nuclear deformation.

  17. Multi-isotope SPECT imaging of the 225Ac decay chain: feasibility studies.

    PubMed

    Robertson, Andrew K H; Ramogida, Caterina; Rodriguez-Rodriguez, Cristina; Blinder, Stephan; Kunz, Peter; Sossi, Vesna; Schaffer, Paul

    2017-03-31

    Purpose: Effective use of the 225Ac decay chain in targeted internal radioimmunotherapy requires the retention of both 225Ac and progeny isotopes at the target site. Imaging-based pharmacokinetic tests of these pharmaceuticals must therefore separately yet simultaneously image multiple isotopes that may not be colocalized despite being part of the same decay chain. This work presents feasibility studies demonstrating the ability of a microSPECT/CT scanner equipped with a high energy collimator to simultaneously image two components of the 225Ac decay chain: 221Fr (218 keV) and 213Bi (440 keV). Methods: Image quality phantoms were used to assess the performance of two collimators for simultaneous 221Fr and 213Bi imaging in terms of contrast and noise. A hotrod resolution phantom containing clusters of thin rods with diameters ranging between 0.85 and 1.70 mm was used to assess resolution. To demonstrate ability to image dynamic 221Fr and 213Bi activity distributions, a phantom containing a 213Bi generator from 225Ac was imaged. These tests were performed with two collimators, a high-energy ultra-high resolution (HEUHR) collimator and an ultra-high sensitivity (UHS) collimator. Results: Values consistent with activity concentrations determined independently via gamma spectroscopy observed in high activity regions of the images. In hotrod phantom images, the HEUHR collimator resolved all rods for both 221Fr and 213Bi images. With the UHS collimator, no rods were resolvable in 213Bi images and only rods ≥1.3 mm were resolved in 221Fr images. After eluting the 213Bi generator, images accurately visualized the reestablishment of transient equilibrium of the 225Ac decay chain. Conclusion: A novel imaging method with potential to evaluate the pharmacokinetics of the 225

  18. Determination of carbon isotopic measurement conditions for ceramide in skin using gas chromatography-combustion-isotope ratio mass spectrometry.

    PubMed

    Haraguchi, Hiroyuki; Yamada, Keita; Miyashita, Rumiko; Aida, Kazuhiko; Ohnishi, Masao; Gilbert, Alexis; Yoshida, Naohiro

    2014-01-01

    The ceramide (Cer) content of skin and glucosylceramide (GlcCer) intake affect skin moisture conditions, but their mutual relation in skin remains unclear. For clarification of that mutual relation, carbon stable isotopes ((12)C and (13)C) are useful as a tracer. However, carbon isotopic measurement has not been applied to the study of clarifying their skin moisturizing effects. Therefore, we used gas chromatography / combustion / isotope ratio mass spectrometry (GC-C-IRMS) to ascertain the appropriate conditions for carbon isotopic measurements using synthesized Cer (SCer) in substitution for very low concentrations of Cer in skin. SCer was derivatized to trimethylsilylated SCer (TMS-SCer) quantitatively using N-trimethylsilylimidazole (TMSI) depending on the amount of SCer. The derivatization rates were 75-85%. Excess TMSI was removed using three cycles of hexane-water distribution. Under these conditions, carbon isotopic measurements of TMS-SCer conducted using GC-C-IRMS showed high repeatability and good inter-day variation (S.D. < 0.3‰). The carbon stable isotope ratio value (δ(13)C) of SCer calculated using a mass balance equation was compared with δ(13)C of underivatized SCer, which was regarded as the actual δ(13)C of SCer obtained using sealed tube combustion method. The difference between the calculated δ(13)C of SCer and δ(13)C of the underivatized SCer depended on the TMSI reagent supplier and on the number of hydroxyl groups to be derivatized in SCer. For accurate δ(13)C of Cer in skin using GC-C-IRMS, the measured δ(13)C of a target TMS-Cer must be calculated using a correction factor representing the difference in δ(13)C of underivatized standard SCer from that of TMS-standard SCer having a structure resembling that of the target Cer in skin. In addition, we show that the same lot of TMSI reagent from a specific supplier must be used throughout the experiments.

  19. A specialized isotope mass spectrometer for noninvasive diagnostics of Helicobacter pylori infection in human beings

    NASA Astrophysics Data System (ADS)

    Blashenkov, N. M.; Sheshenya, E. S.; Solov'ev, S. M.; Sachenko, V. D.; Gall, L. N.; Zarutskii, I. V.; Gall, N. R.

    2013-05-01

    A specialized isotope mass spectrometer for noninvasive diagnostics of Helicobacter pylori infection in human beings based on the carbon-13 isotope breath test has been designed and constructed. Important stages of the work included (i) calculating a low-aberration mass analyzer, (ii) manufacturing and testing special gas inlet system, and (iii) creating a small-size collector of ions. The proposed instrument ensures 13C/12C isotopic ratio measurement to within 1.7‰ (pro mille) accuracy, which corresponds to requirements for a diagnostic tool. Preliminary medical testing showed that the mass spectrometer is applicable to practical diagnostics. The instrument is also capable of measuring isotopic ratios of other light elements, including N, O, B (for BF2+ ions), Ar, Cl, and S.

  20. Molybdenum isotopes and mass balance during early stages of pedogenesis

    NASA Astrophysics Data System (ADS)

    King, E. K.; Thompson, A.; Chadwick, O.; Pett-Ridge, J. C.

    2015-12-01

    Molybdenum (Mo) is an essential micronutrient and redox sensitive trace metal that has the potential to be a tracer of pedogenic processes. Globally, riverine δ98Mo values are elevated relative to bedrock, suggesting weathering processes preferentially retain light Mo isotopes, however, the mechanisms governing this process in soils are poorly understood. To elucidate these mechanisms, we studied seven soil profiles developed on a 10ka lava flow in Hawaii receiving 600 to 2000 mm mean annual precipitation. We assessed Mo abundance and isotopic composition as a function of soil organic matter (OM) content, iron (Fe) and manganese (Mn) (oxyhydr)oxide abundance, and Mo loss/gain. We found net accumulation of Mo across all sites (+48% to +289%) that was positively correlated with increasing precipitation, OM content, and Fe and Mn (oxyhydr)oxide content and inversely correlated with soil depth. Thus, the highest Mo gains are in the wettest surface soil horizons, which also have high OM content. Selective extractions of surface soils indicate that 13% to 40% of mobile Mo is predominately associated with OM; whereas Mo associated with Fe and Mn (oxyhydr)oxides is an order of magnitude lower (0.6% to 6%). The isotopic composition of soil Mo deviated from parent material values (δ98Mo ~-0.15‰). Mo isotopic values were lightest at the dry sites (δ98Mo values of -0.29‰ to -0.63‰) and become heavy with increasing precipitation (δ98Mo -0.2‰ to +0.3‰). At all sites, the surface horizons were isotopically heavy relative to the subsurface horizons, and samples with the heaviest δ98Mo values corresponded with horizons that have gained Mo and have higher OM content. Subsurface Mo isotopic values are lighter than bedrock isotopic composition and may reflect associations with Fe and Mn (oxyhydr)oxides. In order further to constrain Mo fluxes into and out of the soil system, we measured Mo isotopes in local rainwater, groundwater, and vegetation. Based on this data, we

  1. Coupled sulfur isotopic and chemical mass transfer modeling: Approach and application to dynamic hydrothermal processes

    SciTech Connect

    Janecky, D.R.

    1988-09-21

    A computational modeling code (EQPSreverse arrowS) has been developed to examine sulfur isotopic distribution pathways coupled with calculations of chemical mass transfer pathways. A post processor approach to EQ6 calculations was chosen so that a variety of isotopic pathways could be examined for each reaction pathway. Two types of major bounding conditions were implemented: (1) equilibrium isotopic exchange between sulfate and sulfide species or exchange only accompanying chemical reduction and oxidation events, and (2) existence or lack of isotopic exchange between solution species and precipitated minerals, parallel to the open and closed chemical system formulations of chemical mass transfer modeling codes. All of the chemical data necessary to explicitly calculate isotopic distribution pathways is generated by most mass transfer modeling codes and can be input to the EQPS code. Routines are built in to directly handle EQ6 tabular files. Chemical reaction models of seafloor hydrothermal vent processes and accompanying sulfur isotopic distribution pathways illustrate the capabilities of coupling EQPSreverse arrowS with EQ6 calculations, including the extent of differences that can exist due to the isotopic bounding condition assumptions described above. 11 refs., 2 figs.

  2. Leaf waxes in riparian trees: hydrogen isotopes, concentrations, and chain-length patterns

    NASA Astrophysics Data System (ADS)

    Tipple, B. J.; Ehleringer, J.; Doman, C.; Khachaturyan, S.

    2011-12-01

    The stable hydrogen isotope ratios of epicuticular leaf wax n-alkanes record aspects of a plant's ecophysiological conditions. However, it remains unclear as to whether n-alkane hydrogen isotope values (δ2H) directly reflect environmental water (source water or tissue water) or environmental water in combination with a biochemical fractionation. Furthermore, it is uncertain if leaf n-alkane δ2H values reflect a single time interval during leaf expansion or if n-alkane δ2H values record the combination of inputs throughout the entire lifespan of a leaf. These different possibilities will influence how leaf wax biomarkers are interpreted in both ecological and environmental reconstruction contexts. To address these issues, we sampled leaves/buds, stems, and water sources of five common western U.S. riparian species under natural field conditions throughout the growing season. Riparian species were selected because the input water source is most likely to be nearly constant through the growing season. We found that species in this study demonstrated marked and systematic variations in n-alkane concentration, average chain length, and δ2H values. Intraspecific patterns were consistent: average chain lengths and δ2H values increased from bud opening through full leaf expansion with little variation during the remainder of the sampling interval, while leaf-wax concentration as a fraction of total biomass increased throughout the growing season. These data imply that leaf-wax δ2H values reflect multiple periods of wax growth and that the leaf wax is continually produced throughout a leaf's lifespan.

  3. Stable strontium mass dependent isotopic fractionation in authigenic continental barite

    NASA Astrophysics Data System (ADS)

    Griffith, E. M.; Widanagamage, I. H.; Scher, H. D.; Senko, J.

    2013-12-01

    The use of stable Sr-isotopic measurements (δ88Sr) of barite precipitates from terrestrial environments will be evaluated as a new geochemical proxy to identify mode of barite mineralization for use in earth science applications including understanding similar ancient barite deposits. Stable Sr-isotope measurements of barite and waters from three warm artesian springs in the continental United States where barite precipitates under a variety of conditions (e.g., temperatures, saturation states, microbial communities) will be presented. Initial results show a large range of fractionation factors during barite precipitation from aqueous solution between and within some of the field sites of >0.6 permil. The waters range from δ88Sr = -0.04 to +0.50 permil. The solid barite precipitates that have been separated from the bulk sediment using a modified sequential leaching procedure range from δ88Sr = -0.43 to +0.16 permil. Average 2σ for the isotopic analyses is 0.05 permil, similar to previously published estimates for error on this measurement by MC-ICPMS. Barite is a highly stable and widely-distributed mineral found in magmatic, metamorphic, and sedimentary rocks (of all ages), as well as in soils, aerosol dust, and extraterrestrial material. Establishing the controlling parameters of stable Sr-isotopic fractionation in barite is important as barite may be an ideal vehicle to address critical questions in the earth sciences, including early earth biogeochemistry.

  4. Verification of Nd Isotopes as a Water Mass Tracer Based on Isotopic Evaluation of Cretaceous Detrital Residues from Demerara Rise

    NASA Astrophysics Data System (ADS)

    Pugh, E.; Martin, E. E.; MacLeod, K. G.

    2011-12-01

    The Late Cretaceous was one of the most recent major greenhouse intervals. Numerous studies focus on temperature trends and CO2 concentrations during this event, but little is known about ocean circulation and structure at that time. Recently published Nd isotopes of fossil fish teeth/debris recovered from Ocean Drilling Program (ODP) sites on Demerara Rise off Suriname, South America highlight the presence of unusual, nonradiogenic background ɛNd values (-14 to -17) that span much of the record from the Cenomanian through Santonian and continue in the Campanian and Maastrichtian following an ~10 my hiatus. This value is less radiogenic than any major water mass documented in the Cretaceous or today and is interrupted by a dramatic positive excursion of 8 ɛNd units during Ocean Anoxic Event 2 (OAE2, ~94 my). The nonradiogenic ɛNd signal has been interpreted to represent local formation of a warm, saline bottom water mass [Demerara Bottom Water (DBW)] on the proximal Guyana Shield, while the positive ɛNd excursion has been attributed to a temporary shutdown of DBW production or enhanced input of a North Atlantic/Tethyan water mass associated with peak greenhouse conditions (MacLeod et al., 2008, Geology; Jiménez Berrocoso et al., 2010, Geology). The goal of this study was to evaluate Nd and Pb isotopic compositions of detrital silicates from ODP sites 1260 and 1261 on Demerara Rise to verify that Nd isotopes preserved in fish debris record a water mass signal rather than sediment-seawater interactions, such as boundary exchange or sediment diagenesis. Results demonstrate no correlation between seawater and residue Nd isotopes for the Cenomanian to Maastrichtian. Over this interval the offset between seawater and residue ɛNd values is highly variable (0.2 to 6 ɛNd units), but there is no relationship between the long term patterns of seawater and residue variations. In particular, residue ɛNd values record no change during the dramatic increase in seawater

  5. Iron and nickel isotopic mass fractionation in deep-sea spherules

    NASA Technical Reports Server (NTRS)

    Davis, Andrew M.; Brownlee, Donald E.

    1993-01-01

    Magnetite-wuestite spherules collected from deep-sea sediments are thought to have originally been Fe-Ni metal particles at the top of the atmosphere that were oxidized and melted during entry into the earth's atmosphere. Some likely sources for the metal particles are Fe-Ni interplanetary dust particles (IDP's) and metal or sulfide from stony IDP's that separated after melting. Davis et al. reported that four of these spherules are enriched in the heavy isotopes of iron, with enrichments of 8-23%/amu. We have developed a technique for analysis of both iron and nickel isotopes on the same ion microprobe spot and have applied this technique to a number of deep-sea spherules in order to better understand the processes leading to isotopic mass fractionation. Eight spherules show iron and nickel isotopic mass fractionation, with iron and nickel enriched in the heavy isotopes by 10-19%/amu and 4-32%/amu, respectively. If the mass fractionations are due to Rayleigh fractionation during evaporation, these spherules lost 76-94% of their original mass. We have analyzed the four magnetite-wuestite spherules for which iron isotopic data were reported by Davis et al. as well as four new spherules.

  6. On the Fine Isotopic Distribution and Limits to Resolution in Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Dittwald, Piotr; Valkenborg, Dirk; Claesen, Jürgen; Rockwood, Alan L.; Gambin, Anna

    2015-08-01

    Mass spectrometry enables the study of increasingly larger biomolecules with increasingly higher resolution, which is able to distinguish between fine isotopic variants having the same additional nucleon count, but slightly different masses. Therefore, the analysis of the fine isotopic distribution becomes an interesting research topic with important practical applications. In this paper, we propose the comprehensive methodology for studying the basic characteristics of the fine isotopic distribution. Our approach uses a broad spectrum of methods ranging from generating functions—that allow us to estimate the variance and the information theory entropy of the distribution—to the theory of thermal energy fluctuations. Having characterized the variance, spread, shape, and size of the fine isotopic distribution, we are able to indicate limitations to high resolution mass spectrometry. Moreover, the analysis of "thermorelativistic" effects (i.e., mass uncertainty attributable to relativistic effects coupled with the statistical mechanical uncertainty of the energy of an isolated ion), in turn, gives us an estimate of impassable limits of isotopic resolution (understood as the ability to distinguish fine structure peaks), which can be moved further only by cooling the ions. The presented approach highlights the potential of theoretical analysis of the fine isotopic distribution, which allows modeling the data more accurately, aiming to support the successful experimental measurements.

  7. Differences in the Elemental Isotope Definition May Lead to Errors in Modern Mass-Spectrometry-Based Proteomics.

    PubMed

    Claesen, Jürgen; Lermyte, Frederik; Sobott, Frank; Burzykowski, Tomasz; Valkenborg, Dirk

    2015-11-03

    The elemental isotope definition used to calculate the theoretical masses and isotope distribution of (bio)molecules is considered to be a fixed, universal standard in mass-spectrometry-based proteomics. However, this is an incorrect assumption. In view of the ongoing advances in mass spectrometry technology, and in particular the ever-increasing mass precision, the elemental isotope definition and its variations should be taken into account. We illustrate the effect of the elemental isotope uncertainty on the theoretical and experimental masses with theoretical calculations and examples.

  8. In Vivo Mass-independent Fractionation of Mercury Isotopes in Fish

    NASA Astrophysics Data System (ADS)

    Das, R.; Odom, L. A.

    2008-12-01

    Recent experimental work and analyses of natural samples have revealed both mass-dependent and mass- independent isotope fractionation effects in mercury. These findings portend new avenues toward understanding the global mercury cycle. It has been shown experimentally that photo reduction of Hg+2 and methylmercury in water with concomitant release of the reduced, gaseous species Hg° results in the residual methylmercury possessing a mass-independent isotope effect. This effect is a relative enrichment of isotopes 199Hg and 201Hg over the even mass number isotopes when compared to the mercury standard NIST SRM3133. Large mass independent fractionation (MIF) effects (Δ199Hg values of a few ‰) have been found in mercury in fish and interpreted as isotope effects inherited from the water. To evaluate the possibility that MIF might be produced within the fish, we have analyzed 38 samples that include zooplankton and twelve different species of fish from a single lake collected over a 2-month time period for mercury isotopic compositions. Trophic levels of the same fish specimens had previously been determined from stomach contents and nitrogen isotopes. Zooplankton in the lake contain mercury with Δ199Hg and Δ201Hg values of +0.43 (±0.07) and +0.44 (±0.07) respectively. Among the fish species there is a striking correspondence between trophic level and Δ199Hg and Δ201Hg values for primary, secondary, and tertiary consumers. The Δ199Hg values ranges over ~1‰ from ~+0.4 in zooplankton, juvenile bluegill and several other small fishes to Δ199Hg = + 1.36 for the Florida gar that is the top predator fish in the lake. These observations indicate that the MIF effect, rather than being an artifact of the water column is produced in vivo. Partial separation of 199Hg and 201Hg from isotopes of even neutron number can be achieved by the magnetic isotope effect in reactions involving sufficiently long-lived intermediate free radicals, where nuclear - electron

  9. Prediction, Detection, and Validation of Isotope Clusters in Mass Spectrometry Data

    PubMed Central

    Treutler, Hendrik; Neumann, Steffen

    2016-01-01

    Mass spectrometry is a key analytical platform for metabolomics. The precise quantification and identification of small molecules is a prerequisite for elucidating the metabolism and the detection, validation, and evaluation of isotope clusters in LC-MS data is important for this task. Here, we present an approach for the improved detection of isotope clusters using chemical prior knowledge and the validation of detected isotope clusters depending on the substance mass using database statistics. We find remarkable improvements regarding the number of detected isotope clusters and are able to predict the correct molecular formula in the top three ranks in 92% of the cases. We make our methodology freely available as part of the Bioconductor packages xcms version 1.50.0 and CAMERA version 1.30.0. PMID:27775610

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  11. Three-stage mass spectrometer for isotopic analysis of radionuclides in environmental samples

    SciTech Connect

    Halverson, J.E.

    1981-09-01

    A three-stage mass spectrometer was constructed for isotopic analysis of several radioactive as well as stable elements at environmental levels. The spectrometer is interfaced to a digital computer, which controls the operation of the spectrometer, accumulates data, reduces data, and prints a final result. The spectrometer has demonstrated the capability of measuring the isotopic composition of plutonium samples as small as 0.005 picogram and has an abundance sensitivity greater than 10/sup 8/.

  12. Mass spectrometric study of the mercury isotopes in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Nier, A. O.; Schlutter, D. J.

    1986-01-01

    Isotopic abundance ratios for mercury were determined by mass spectrometry in six samples of bulk material and in one sample of chondrules from the Allende meteorite. A primary purpose of the work was to attempt to verify the anomalous ratios reported for Hg-196/Hg-202 by neutron activation. Measurements were made on the mercury released at temperatures of 250, 450, 600 C, and in some cases, higher temperatures. The precision of the measurements was such that if an anomaly of the magnitude reported exists, it should have been seen. The isotopic abundance ratios for the other mercury isotopes were also measured. Within the errors of measurement these agreed with normal terrestrial values.

  13. Mass-independent fractionation of mercury isotopes in compact fluorescent light bulbs

    NASA Astrophysics Data System (ADS)

    Mead, C.; Anbar, A. D.; Lyons, J. R.; Johnson, T. M.

    2010-12-01

    Compact fluorescent lightbulbs (CFLs) are a growing source of Hg pollution. The high-energy environment of the CFLs combined with the known partitioning of Hg into the bulb walls could provide an environment for unusual isotope fractionation that could be used to trace pollution from improper bulb disposal. To investigate this possibility, we analyzed the isotope composition of Hg in CFL glass, phosphor powder, and whole bulbs from CFLs of known ages. We observed large, mass-independent fractionation of Hg isotopes between Hg embedded in the bulb wall and Hg in the liquid and vapor phases, which are the initial reservoir of Hg in the bulb. This fractionation results in the bulb wall showing enrichment of 198Hg, 199Hg, 200Hg, 201Hg, and 204Hg relative to 202Hg, the most abundant isotope. Both the amount of Hg embedded in the glass and the magnitude of the isotope enrichment were found to increase with the number of hours of light bulb use. For a CFL used for 3600 hours (with a rated lifetime of 10,000 hours), the isotopic composition of the Hg in the glass was enriched by 34.5‰, 4.1‰, 6.3‰, 21.1‰, and 12.1‰ for 198Hg/202Hg, 199Hg/202Hg, 200Hg/202Hg, 201Hg/202Hg, and 204Hg/202Hg, respectively, compared to NIST SRM-3133. This pattern of isotope enrichments is not correlated with mass differences for any of the isotope ratios. In contrast, the other mass-independent effects that have recently been observed in Hg isotopes (i.e., the nuclear volume and magnetic isotope effects) resemble mass-dependent fractionation for the even mass isotopes and are anomalous only for the odd mass isotopes, 199Hg and 201Hg. First order theoretical calculations using Hg absorption and emission data for each of the hyperfine components of the 253.7 nm line have shown that similar fractionation can be produced through an optical self-shielding effect. This effect occurs because each Hg isotope has a different degree of optical saturation at their respective absorption wavelength

  14. Caution on the use of liquid nitrogen traps in stable hydrogen isotope-ratio mass spectrometry

    USGS Publications Warehouse

    Coplen, T.B.; Qi, H.

    2010-01-01

    An anomalous stable hydrogen isotopic fractionation of 4 ??? in gaseous hydrogen has been correlated with the process of adding liquid nitrogen (LN2) to top off the dewar of a stainless-steel water trap on a gaseous hydrogen-water platinum equilibration system. Although the cause of this isotopic fractionation is unknown, its effect can be mitigated by (1) increasing the capacity of any dewars so that they do not need to be filled during a daily analytic run, (2) interspersing isotopic reference waters among unknowns, and (3) applying a linear drift correction and linear normalization to isotopic results with a program such as Laboratory Information Management System (LIMS) for Light Stable Isotopes. With adoption of the above guidelines, measurement uncertainty can be substantially improved. For example, the long-term (months to years) ??2H reproducibility (1?? standard deviation) of nine local isotopic reference waters analyzed daily improved substantially from about 1 ??? to 0.58 ???. This isotopically fractionating mechanism might affect other isotope-ratio mass spectrometers in which LN2 is used as a moisture trap for gaseous hydrogen. ?? This article not subject to U.S. Copyright. Published 2010 by the American Chemical Society.

  15. Caution on the use of liquid nitrogen traps in stable hydrogen isotope-ratio mass spectrometry

    USGS Publications Warehouse

    Coplen, Tyler B.; Qi, Haiping

    2010-01-01

    An anomalous stable hydrogen isotopic fractionation of 4 ‰ in gaseous hydrogen has been correlated with the process of adding liquid nitrogen (LN2) to top off the dewar of a stainless-steel water trap on a gaseous hydrogen-water platinum equilibration system. Although the cause of this isotopic fractionation is unknown, its effect can be mitigated by (1) increasing the capacity of any dewars so that they do not need to be filled during a daily analytic run, (2) interspersing isotopic reference waters among unknowns, and (3) applying a linear drift correction and linear normalization to isotopic results with a program such as Laboratory Information Management System (LIMS) for Light Stable Isotopes. With adoption of the above guidelines, measurement uncertainty can be substantially improved. For example, the long-term (months to years) δ2H reproducibility (1& sigma; standard deviation) of nine local isotopic reference waters analyzed daily improved substantially from about 1‰ to 0.58 ‰. This isotopically fractionating mechanism might affect other isotope-ratio mass spectrometers in which LN2 is used as a moisture trap for gaseous hydrogen

  16. Fractionated Mercury Isotopes in Fish: The Effects of Nuclear Mass, Spin, and Volume

    NASA Astrophysics Data System (ADS)

    Das, R.; Odom, A. L.

    2007-12-01

    Mercury is long known as a common environmental contaminant. In methylated form it is even more toxic and the methylation process is facilitated by microbial activities. Methyl mercury easily crosses cell membrane and accumulates in soft tissues of fishes and finally biomagnifies with increasing trophic levels. Natural variations in the isotopic composition of mercury have been reported and such variations have emphasized mass dependent fractionations, while theory and laboratory experiments indicate that mass-independent isotopic fractionation (MIF) effects are likely to be found as well. This study focuses on the MIF of mercury isotopes in the soft tissues of fishes. Samples include both fresh water and marine fish, from different continents and oceans. Approximately 1 gm of fish soft tissue was dissolved in 5 ml of conc. aqua regia for 24 hrs and filtered through a ¬¬¬100 μm filter paper and diluted with DI water. Hg is measured as a gaseous phase generated by reduction of the sample with SnCl2 in a continuous- flow cold-vapor generator connected to a Thermo-Finnigan Neptune MC-ICPMS. To minimize instrumental fractionation isotope ratios were measured by sample standard bracketing and reported as δ‰ relative to NIST SRM 3133 Hg standard where δAHg = [(A Hg/202Hg)sample/(A Hg/202Hg)NIST313] -1 ×1000‰. In this study we have measured the isotope ratios 198Hg/202Hg, 199Hg/202Hg, 200Hg/202Hg, 201Hg/202Hg and 204Hg/202Hg. In all the fish samples δ198Hg, δ200Hg, δ202Hg, δ204Hg define a mass- dependent fractionation sequence, where as the δ199Hg and δ201Hg depart from the mass- dependent fractionation line and indicate an excess of the odd-N isotopes. The magnitude of the deviation (ΔAHg where A=199 or 201) as obtained by difference between the measured δ199Hg and δ201Hg of the samples and the value obtained by linear scaling defined by the even-N isotopes ranges from approximately 0.2 ‰ to 3‰. The ratios of Δ199Hg /Δ201Hg range from 0.8 to 1

  17. Stable isotope ratio mass spectrometry of nanogram quantities of boron and sulfur

    NASA Astrophysics Data System (ADS)

    Wieser, Michael Eugene

    1998-09-01

    Instrumentation and analytical techniques were developed to measure isotope abundances from nanograms of sulfur and boron. Sulfur isotope compositions were determined employing continuous flow isotope ratio mass spectroscopy (CF-IRMS) procedures and AsS+ thermal ionization mass spectrometry techniques (AsS+-TIMS). Boron isotope abundances were determined by BO2/sp--TIMS. CF-IRMS measurements realized δ34S values from 10 μg sulfur with precisions of ±0.3/perthous. To extend sulfur isotope measurements to much smaller samples, a TIMS procedure was developed to measure 75As32S+ and 75As34S+ at masses 108 and 109 from 200 ng S on a Finnigan MAT 262 with an ion counter. This is possibly the smallest amount of sulfur which has been successfully analyzed isotopically. The internal precision of 32S/34S ratios measured by AsS+-TIMS was better than ±0.15 percent. δ34S-values calculated relative to the measured 32S/34S value of an IAEA AG2S standard (S-1) agreed with those determined by CF-IRMS to within ±3/perthous. The increasing sensitivity of S-isotope analyses permits hiterto impossible investigations e.g. sulfur in tree rings and ice cores. Boron isotope abundances were measured as BO2/sp- from 50 ng B using an older thermal ionization mass spectrometer which had been extensively upgraded including the addition of computer control electronics, sensitive ion current amplification and fiber optic data bus. The internal precisions of the measured 11B/10B ratios were ±0.15 percent and the precisions of δ11B values calculated relative to the accepted international standard (SRM-951) were ±3/perthous. Two applications of boron isotope abundance variations were initiated (1) ground waters of Northern Alberta and (2) coffee beans in different regions of the world. In the first it was demonstrated that boron isotopes could be used to trace boron released during steam injection of oil sands into the surrounding environment. Data from the second study suggest that boron

  18. High sensitivity measurement of amino acid isotope enrichment using liquid chromatography-mass spectrometry.

    PubMed

    van Eijk, Hans M H; Wijnands, Karolina A P; Bessems, Babs A F M; Olde Damink, Steven W; Dejong, Cornelis H C; Poeze, Martijn

    2012-09-15

    Measurement of the incorporation or conversion of infused stable isotope enriched metabolites in vivo such as amino acids plays a key role in metabolic research. Specific routes are frequently probed in knockout mouse models limiting the available amount of sample. Although less precise as compared to combustion-isotope ratio mass spectrometry (C-IRMS), gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS) techniques are therefore often the method of choice to measure isotopic enrichment of target metabolites. However, under conditions of metabolic depletion, the precision of these systems becomes limiting. In this paper, studies were performed to enhance the sensitivity and precision of isotope enrichment measurements using LC-MS. Ion-statistics and resolution were identified as critical factors for this application when using a linear trap mass spectrometer. The combination with an automated pre-column derivatization and a carefully selected solvent mix allowed us to measure isotopic enrichments down to 0.005% at plasma concentrations as low as 5 μmol/l, an improvement by a factor of 100 compared to alternative methods. The resulting method now allowed measurement of the in vivo conversion of the amino acid arginine into citrulline as a marker for the production of nitric oxide in an in vivo murine endotoxemia model with depleted plasma levels of arginine and citrulline.

  19. Investigation of mass dependence effects for the accurate determination of molybdenum isotope amount ratios by MC-ICP-MS using synthetic isotope mixtures.

    PubMed

    Malinovsky, Dmitry; Dunn, Philip J H; Petrov, Panayot; Goenaga-Infante, Heidi

    2015-01-01

    Methodology for absolute Mo isotope amount ratio measurements by multicollector inductively coupled plasma-mass spectrometry (MC-ICP-MS) using calibration with synthetic isotope mixtures (SIMs) is presented. For the first time, synthetic isotope mixtures prepared from seven commercially available isotopically enriched molybdenum metal powders ((92)Mo, (94)Mo, (95)Mo, (96)Mo, (97)Mo, (98)Mo, and (100)Mo) are used to investigate whether instrumental mass discrimination of Mo isotopes in MC-ICP-MS is consistent with mass-dependent isotope distribution. The parent materials were dissolved and mixed as solutions to obtain mixtures with accurately known isotope amount ratios. The level of elemental impurities in the isotopically enriched molybdenum metal powders was quantified by ICP-MS by using both high-resolution and reaction cell instruments to completely resolve spectral interferences. The Mo isotope amount ratio values with expanded uncertainty (k = 2), determined by MC-ICP-MS for a high-purity Mo rod from Johnson Matthey, were as follows: (92)Mo/(95)Mo = 0.9235(9), (94)Mo/(95)Mo = 0.5785(8), (96)Mo/(95)Mo = 1.0503(9), (97)Mo/(95)Mo = 0.6033(6), (98)Mo/(95)Mo = 1.5291(20), and (100)Mo/(95)Mo = 0.6130(7). A full uncertainty budget for the measurements is presented which shows that the largest contribution to the uncertainty budget comes from correction for elemental impurities (∼51%), followed by the contribution from weighing operations (∼26 %). The atomic weight of molybdenum was calculated to be 95.947(2); the uncertainty in parentheses is expanded uncertainty with the coverage factor of 2. A particular advantage of the developed method is that calibration factors for all six Mo isotope amount ratios, involving the (95)Mo isotope, were experimentally determined. This allows avoiding any assumption on mass-dependent isotope fractions in MC-ICP-MS, inherent to the method of double spike previously used for Mo isotope amount ratio

  20. Reduction of chemical formulas from the isotopic peak distributions of high-resolution mass spectra.

    PubMed

    Roussis, Stilianos G; Proulx, Richard

    2003-03-15

    A method has been developed for the reduction of the chemical formulas of compounds in complex mixtures from the isotopic peak distributions of high-resolution mass spectra. The method is based on the principle that the observed isotopic peak distribution of a mixture of compounds is a linear combination of the isotopic peak distributions of the individual compounds in the mixture. All possible chemical formulas that meet specific criteria (e.g., type and number of atoms in structure, limits of unsaturation, etc.) are enumerated, and theoretical isotopic peak distributions are generated for each formula. The relative amount of each formula is obtained from the accurately measured isotopic peak distribution and the calculated isotopic peak distributions of all candidate formulas. The formulas of compounds in simple spectra, where peak components are fully resolved, are rapidly determined by direct comparison of the calculated and experimental isotopic peak distributions. The singular value decomposition linear algebra method is used to determine the contributions of compounds in complex spectra containing unresolved peak components. The principles of the approach and typical application examples are presented. The method is most useful for the characterization of complex spectra containing partially resolved peaks and structures with multiisotopic elements.

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

    PubMed Central

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

    2015-01-01

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

  2. High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry.

    PubMed

    Paul, Maxence; Bridgestock, Luke; Rehkämper, Mark; van DeFlierdt, Tina; Weiss, Dominik

    2015-03-10

    A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a (207)Pb-(204)Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28±21 pg (1sd) and typical Pb recoveries of 40-60%. The Pb concentrations are determined by isotope dilution (ID) on 50 mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50 pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12±4 pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700-1500 ppm and 1000-2000 ppm were achieved for (207)Pb/(206)Pb, (208)Pb/(206)Pb and (206)Pb/(204)Pb, (207)Pb/(204)Pb, (208)Pb/(204)Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor (204)Pb isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the (206)Pb/(204)Pb ratios are well correlated

  3. The study of trace metal absoption using stable isotopes and mass spectrometry

    NASA Astrophysics Data System (ADS)

    Fennessey, P. V.; Lloyd-Kindstrand, L.; Hambidge, K. M.

    1991-12-01

    The absorption and excretion of zinc stable isotopes have been followed in more than 120 human subjects. The isotope enrichment determinations were made using a standard VG 7070E HF mass spectrometer. A fast atom gun (FAB) was used to form the ions from a dry residue on a pure silver probe tip. Isotope ratio measurements were found to have a precision of better than 2% (relative standard deviation) and required a sample size of 1-5 [mu]g. The average true absorption of zinc was found to be 73 ± 12% (2[sigma]) when the metal was taken in a fasting state. This absorption figure was corrected for tracer that had been absorbed and secreted into the gastrointestinal (GI) tract over the time course of the study. The average time for a majority of the stable isotope tracer to pass through the GI tract was 4.7 ± 1.9 (2[sigma]) days.

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

    USGS Publications Warehouse

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

    2009-01-01

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

  5. A mass-independent sulfur isotope effect in the nonthermal formation

    NASA Technical Reports Server (NTRS)

    Bains-Sahota, Swroop K.; Thiemens, Mark H.

    1989-01-01

    A nonmass-dependent sulfur isotope effect is present in the rotationally symmetric S2F10 molecule, produced in an electrical discharge through sulfur tetrafluoride. A similar isotopic fractionation was observed in the product S2F10 from the electrodissociation of SF5Cl and in the reaction between fluorine atoms produced by F2 photolysis and SF2, collectively ruling out the SF5 formation process as the source of the mass-independent fractionation. The secondary dissociation of S2F10 as a source of the mass-independent fractionation is ruled out by control S2F10 dissociation experiments which are shown to produce small mass-dependent fractionations. Mass-dependent effects such as sulfur isotopic exchange and secondary dissociation reactions are significant processes for the system under study, and have been quantitatively accounted for. The role of symmetry in nonmass-dependent isotope effects is strengthened by the present experiments, and the search and characterization of mass-independent effects is extended to sulfur-containing molecules.

  6. New Short-Lived Isotope 221U and the Mass Surface Near N =126

    NASA Astrophysics Data System (ADS)

    Khuyagbaatar, J.; Yakushev, A.; Düllmann, Ch. E.; Ackermann, D.; Andersson, L.-L.; Block, M.; Brand, H.; Cox, D. M.; Even, J.; Forsberg, U.; Golubev, P.; Hartmann, W.; Herzberg, R.-D.; Heßberger, F. P.; Hoffmann, J.; Hübner, A.; Jäger, E.; Jeppsson, J.; Kindler, B.; Kratz, J. V.; Krier, J.; Kurz, N.; Lommel, B.; Maiti, M.; Minami, S.; Mistry, A. K.; Mrosek, Ch. M.; Pysmenetska, I.; Rudolph, D.; Sarmiento, L. G.; Schaffner, H.; Schädel, M.; Schausten, B.; Steiner, J.; De Heidenreich, T. Torres; Uusitalo, J.; Wegrzecki, M.; Wiehl, N.; Yakusheva, V.

    2015-12-01

    Two short-lived isotopes 221U and 222U were produced as evaporation residues in the fusion reaction 50Ti + 176Yb at the gas-filled recoil separator TASCA. An α decay with an energy of Eα=9.31 (5 ) MeV and half-life T1 /2=4.7 (7 ) μ s was attributed to 222U. The new isotope 221U was identified in α -decay chains starting with Eα=9.71 (5 ) MeV and T1 /2=0.66 (14 ) μ s leading to known daughters. Synthesis and detection of these unstable heavy nuclei and their descendants were achieved thanks to a fast data readout system. The evolution of the N =126 shell closure and its influence on the stability of uranium isotopes are discussed within the framework of α -decay reduced width.

  7. Improved Polymerase Chain Reaction-restriction Fragment Length Polymorphism Genotyping of Toxic Pufferfish by Liquid Chromatography/Mass Spectrometry

    PubMed Central

    Miyaguchi, Hajime

    2016-01-01

    An improved version of a polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method for genotyping toxic pufferfish species by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) is described. DNA extraction is carried out using a silica membrane-based DNA extraction kit. After the PCR amplification using a detergent-free PCR buffer, restriction enzymes are added to the solution without purifying the reaction solution. A reverse-phase silica monolith column and a Fourier transform high resolution mass spectrometer having a modified Kingdon trap analyzer are employed for separation and detection, respectively. The mobile phase, consisting of 400 mM 1,1,1,3,3,3-hexafluoro-2-propanol, 15 mM triethylamine (pH 7.9) and methanol, is delivered at a flow rate of 0.4 ml/min. The cycle time for LC/ESI-MS analysis is 8 min including equilibration of the column. Deconvolution software having an isotope distribution model of the oligonucleotide is used to calculate the corresponding monoisotopic mass from the mass spectrum. For analysis of oligonucleotides (range 26-79 nucleotides), mass accuracy was 0.62 ± 0.74 ppm (n = 280) and excellent accuracy and precision were sustained for 180 hr without use of a lock mass standard. PMID:27684516

  8. Further study of α-decay in heavy isotopic chains considering the isospin effect

    NASA Astrophysics Data System (ADS)

    Qian, Yibin; Ren, Zhongzhou

    2016-06-01

    We have enhanced the deformed density-dependent cluster model to improve the quantitative description of α-decay in heavy even-even nuclei with 84≤slant Z≤slant 92. To preliminarily introduce the isospin effect into α-decay, the neutron excess term is added in the establishment of the crucial α-core potential. The proton and neutron density distributions are respectively considered in different parameterized formulas by combining them with available experimental data of both the charge radius and the neutron skin thickness. The calculated α-decay half-lives are found to be in somewhat better agreement with the experimental data as compared with our previous results. Strikingly, it is noted that the relatively large deviation between theory and experiment, along the tail of the isotopic chain, is obviously reduced and smoother. This may indicate the necessity of considering the isospin effect in α-decay, especially for extremely neutron-rich nuclei, which appears to be essential for the extended study of heaviest nuclei as well.

  9. Isotopic and trace element sensors for fluid flow, heat- and mass transport in fractured rocks

    NASA Astrophysics Data System (ADS)

    DePaolo, D. J.

    2012-12-01

    The flow of fluids through fractured rocks is critically important in hydrothermal systems associated with geothermal energy production, base metal ore deposits, and global geochemical cycles through the enormous volumes of fluids in mid-ocean ridge systems. The nature of heat and mass transport in hydrothermal systems is determined by the spacing and volume of fractures, the nature of chemical transport in matrix blocks between fractures, the dissolution and precipitation rates of minerals in the matrix blocks, and the rates of fluid flow. Directly measuring these properties in active systems is extremely difficult, but the chemical and isotopic composition of fluids, where they can be adequately sampled, provides this information in coded form. Deciphering the signals requires appropriate models for the mineral-fluid chemical reactions and transport in the inter-fracture rock matrix. Ultimately, numerical reactive transport models are required to properly account for coupling between mineral reaction kinetics and fluid phase transport, but it is surprisingly difficult to adequately represent isotopic exchange in these models. The difficulty comes partly from the additional bookkeeping that is necessary, but more fundamentally from limitations in the detailed molecular dynamics of the mineral-fluid interfaces and how they control isotopic exchange and partitioning. Nevertheless, relatively simple analytical models illustrate how the isotopic and trace element composition of fluids relates to fracture aperture and spacing, mineral dissolution kinetics, competition between diffusive and advective transport, and competition between chemical exchange and heat exchange. The large number of geochemical parameters that can be measured potentially allows for detailed characterization of the effective mass transport and system characteristics like average fracture spacing and mineral dissolution rates. Examples of useful analytical models and applications to available data

  10. Pyrolysis-gas chromatography-isotope ratio mass spectrometry of polyethylene.

    PubMed

    González-Pérez, J A; Jiménez-Morillo, N T; de la Rosa, J M; Almendros, G; González-Vila, F J

    2015-04-03

    Polyethylene is probably the most used plastic material in daily life and its accurate analysis is of importance. In this communication the chemical structure of polyethylenes is studied in detail using conventional analytical pyrolysis (Py-GC/MS), bulk stable isotopic analysis (IRMS) and pyrolysis compound specific stable isotopic analysis (Py-CSIA) to measure stable isotope proportions (δ(13)C, δ(15)N and δD) of polyethylene pyrolysis compounds. Polyethylene pyrolysis yields triplet peaks of n-alkanes, α-alkenes and α,ω-alkanedienes. No differences were found for bulk δ(13)C among different polyethylene types. However, conspicuous differences in δD were evident. It was possible to assign structure δ(13)C and δD values to specific polyethylene pyrolysis products in the range 12-18 carbon chain length. Conspicuous differences were found for the pyrolysis products with unsaturated moieties showing significant higher δD values than saturated chains (alkanes) that were deuterium depleted. In addition, a full isotopic fingerprinting (δ(13)C, δ(15)N and δD) for a dye (o-chloroaniline) contained in a polyethylene is reported. To the best of our knowledge this is the first application Py-CSIA to the study of a synthetic polymer. This hyphenated analytical technique is a promising tool to study synthetic materials, providing not only a fingerprinting, but also allowing the traceability of the polymerization process and the origin of the materials.

  11. Mercury (Hg) in meteorites: Variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M. M.; Cloquet, Christophe; Marty, Bernard

    2016-06-01

    We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ppb to 14,000 ppb), with the highest concentration orders of magnitude above the expected bulk solar system silicates value. From the presence of several different Hg carrier phases in thermal release profiles (150-650 °C), we argue that these variations are unlikely to be mainly due to terrestrial contamination. The Hg abundance of meteorites shows no correlation with petrographic type, or mass-dependent fractionation of Hg isotopes. Most carbonaceous chondrites show mass-independent enrichments in the odd-numbered isotopes 199Hg and 201Hg. We show that the enrichments are not nucleosynthetic, as we do not find corresponding nucleosynthetic deficits of 196Hg. Instead, they can partially be explained by Hg evaporation and redeposition during heating of asteroids from primordial radionuclides and late-stage impact heating. Non-carbonaceous chondrites, most achondrites and the Earth do not show these enrichments in vapor-phase Hg. All meteorites studied here have however isotopically light Hg (δ202Hg = ∼-7 to -1) relative to the Earth's average crustal values, which could suggest that the Earth has lost a significant fraction of its primordial Hg. However, the late accretion of carbonaceous chondritic material on the order of ∼2%, which has been suggested to account for the water, carbon, nitrogen and noble gas inventories of the Earth, can also contribute most or all of the Earth's current Hg budget. In this case, the isotopically heavy Hg of the Earth's crust would have to be the result of isotopic fractionation between surface and deep-Earth reservoirs.

  12. Isotope ratio mass spectrometry as a tool for source inference in forensic science: A critical review.

    PubMed

    Gentile, Natacha; Siegwolf, Rolf T W; Esseiva, Pierre; Doyle, Sean; Zollinger, Kurt; Delémont, Olivier

    2015-06-01

    Isotope ratio mass spectrometry (IRMS) has been used in numerous fields of forensic science in a source inference perspective. This review compiles the studies published on the application of isotope ratio mass spectrometry (IRMS) to the traditional fields of forensic science so far. It completes the review of Benson et al. [1] and synthesises the extent of knowledge already gathered in the following fields: illicit drugs, flammable liquids, human provenancing, microtraces, explosives and other specific materials (packaging tapes, safety matches, plastics, etc.). For each field, a discussion assesses the state of science and highlights the relevance of the information in a forensic context. Through the different discussions which mark out the review, the potential and limitations of IRMS, as well as the needs and challenges of future studies are emphasized. The paper elicits the various dimensions of the source which can be obtained from the isotope information and demonstrates the transversal nature of IRMS as a tool for source inference.

  13. Long chain n-alkanes and their carbon isotopes in lichen species from western Hubei Province: implication for geological records

    NASA Astrophysics Data System (ADS)

    Huang, Xianyu; Xue, Jiantao; Guo, Shouyu

    2012-03-01

    Five coticolous lichen samples were collected from western Hubei Province of China to analyze the long chain n-alkanes and their carbon isotope compositions. The n-alkanes range in carbon number from C17 to C33 with strong odd-over-even predominance between C21 and C33. Lichens are dominated by n-C29 in the samples of Dajiuhu, Shennongjia Mountain, but by both n-C23 and n-C29 at Qizimei Mountain. This difference may result from the different environmental conditions in these two sites. The δ 13C values of long chain n-alkanes in lichen samples show the signature of C3 plants. Based on compoundspecific carbon isotopic values and previous results, we state that alkane homologs >C23 mainly originate from the symbiotic fungi, while symbiotic algae only contribute trace amount of long chain alkanes. Of great interesting is the occurrence of long chain 3-methylalkanes in the Qizimei samples. These anteiso compounds range from C24 to C32, displaying obvious even-over-odd predominance. This study reveals that the association of long chain 3-methylalkanes with n-C23 alkane might be used as proxies to reconstruct the paleoecological implications of lichens in Earth history.

  14. High Spatial Resolution Isotopic Abundance Measurements by Secondary Ion Mass Spectrometry: Status and Prospects

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.

    2007-12-01

    Secondary Ion Mass Spectrometry, SIMS or ion microprobe analysis, has become an important tool for geochemistry because of its ability study the distributions of elemental and isotopic abundances in situ on polished samples with high (typically a few microns to sub-micron) spatial resolution. In addition, SIMS exhibits high sensitivity for a wide range of elements (H to Pu) so that isotope analyses can sometimes be performed for elements that comprise only trace quantities of some mineral phase (e.g., Pb in zircon) or on major and/or minor elements in very small samples (e.g., presolar dust grains). Offsetting these positive attributes are analytical difficulties due to the complexity of the sputtering source of analyte ions: (1) relatively efficient production of molecular ion species (especially from a complex matrix such as most natural minerals) that cause interferences at the same nominal mass as atomic ions of interest, and (2) quantitation problems caused by variations in the ionization efficiencies of different elements and/or isotopes depending upon the chemical state of the sample surface during sputtering--the so-called "matrix effects". Despite the availability of high mass resolution instruments (e.g., SHRIMP II/RG, CAMECA 1270/1280/NanoSIMS), the molecular ion interferences effectively limit the region of the mass table that can be investigated in most samples to isotope systems at Ni or lighter or at Os or heavier. The matrix effects and the sensitivity of instrumental mass discrimination to the physical state of the sample surface can hamper reproducibility and have contributed to a view that SIMS analyses, especially for so- called stable isotopes, are most appropriate for extraterrestrial samples which are often small, rare, and can exhibit large magnitude isotopic effects. Recent improvements in instrumentation and technique have extended the scope of SIMS isotopic analyses and applications now range from geochronology to paleoclimatology to

  15. Using Theoretical Protein Isotopic Distributions to Parse Small-Mass-Difference Post-Translational Modifications via Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Rhoads, Timothy W.; Williams, Jared R.; Lopez, Nathan I.; Morré, Jeffrey T.; Bradford, C. Samuel; Beckman, Joseph S.

    2013-01-01

    Small-mass-difference modifications to proteins are obscured in mass spectrometry by the natural abundance of stable isotopes such as 13C that broaden the isotopic distribution of an intact protein. Using a ZipTip (Millipore, Billerica, MA, USA) to remove salt from proteins in preparation for high-resolution mass spectrometry, the theoretical isotopic distribution intensities calculated from the protein's empirical formula could be fit to experimentally acquired data and used to differentiate between multiple low-mass modifications to proteins. We could readily distinguish copper from zinc bound to a single-metal superoxide dismutase (SOD1) species; copper and zinc only differ by an average mass of 1.8 Da and have overlapping stable isotope patterns. In addition, proteins could be directly modified while bound to the ZipTip. For example, washing 11 mM S-methyl methanethiosulfonate over the ZipTip allowed the number of free cysteines on proteins to be detected as S-methyl adducts. Alternatively, washing with the sulfhydryl oxidant diamide could quickly reestablish disulfide bridges. Using these methods, we could resolve the relative contributions of copper and zinc binding, as well as disulfide reduction to intact SOD1 protein present from <100 μg of the lumbar spinal cord of a transgenic, SOD1 overexpressing mouse. Although techniques like ICP-MS can measure total metal in solution, this is the first method able to assess the metal-binding and sulfhydryl reduction of SOD1 at the individual subunit level and is applicable to many other proteins.

  16. Quadrupole mass spectrometer for a mobile laboratory to measure isotope ratios

    SciTech Connect

    Walton, J.R.; Smith, D.H.; McKown, H.S.; Carter, J.A.

    1981-01-01

    A mobile laboratory has been assembled for on-site inspection of plant operations handlng special nuclear materials. The isotopic composition of U, Pu, and other elements can be analyzed using a quadrupole mass spectrometer. Some results of analysis of uranium and boron standards are given. (DLC)

  17. Falling Chains as Variable-Mass Systems: Theoretical Model and Experimental Analysis

    ERIC Educational Resources Information Center

    de Sousa, Celia A.; Gordo, Paulo M.; Costa, Pedro

    2012-01-01

    In this paper, we revisit, theoretically and experimentally, the fall of a folded U-chain and of a pile-chain. The model calculation implies the division of the whole system into two subsystems of variable mass, allowing us to explore the role of tensional contact forces at the boundary of the subsystems. This justifies, for instance, that the…

  18. High-resolution quantitative imaging of mammalian and bacterial cells using stable isotope mass spectrometry

    PubMed Central

    Lechene, Claude; Hillion, Francois; McMahon, Greg; Benson, Douglas; Kleinfeld, Alan M; Kampf, J Patrick; Distel, Daniel; Luyten, Yvette; Bonventre, Joseph; Hentschel, Dirk; Park, Kwon Moo; Ito, Susumu; Schwartz, Martin; Benichou, Gilles; Slodzian, Georges

    2006-01-01

    Background Secondary-ion mass spectrometry (SIMS) is an important tool for investigating isotopic composition in the chemical and materials sciences, but its use in biology has been limited by technical considerations. Multi-isotope imaging mass spectrometry (MIMS), which combines a new generation of SIMS instrument with sophisticated ion optics, labeling with stable isotopes, and quantitative image-analysis software, was developed to study biological materials. Results The new instrument allows the production of mass images of high lateral resolution (down to 33 nm), as well as the counting or imaging of several isotopes simultaneously. As MIMS can distinguish between ions of very similar mass, such as 12C15N- and 13C14N-, it enables the precise and reproducible measurement of isotope ratios, and thus of the levels of enrichment in specific isotopic labels, within volumes of less than a cubic micrometer. The sensitivity of MIMS is at least 1,000 times that of 14C autoradiography. The depth resolution can be smaller than 1 nm because only a few atomic layers are needed to create an atomic mass image. We illustrate the use of MIMS to image unlabeled mammalian cultured cells and tissue sections; to analyze fatty-acid transport in adipocyte lipid droplets using 13C-oleic acid; to examine nitrogen fixation in bacteria using 15N gaseous nitrogen; to measure levels of protein renewal in the cochlea and in post-ischemic kidney cells using 15N-leucine; to study DNA and RNA co-distribution and uridine incorporation in the nucleolus using 15N-uridine and 81Br of bromodeoxyuridine or 14C-thymidine; to reveal domains in cultured endothelial cells using the native isotopes 12C, 16O, 14N and 31P; and to track a few 15N-labeled donor spleen cells in the lymph nodes of the host mouse. Conclusion MIMS makes it possible for the first time to both image and quantify molecules labeled with stable or radioactive isotopes within subcellular compartments. PMID:17010211

  19. Performance and limits of liquid chromatography isotope ratio mass spectrometry system for halogenated compounds

    NASA Astrophysics Data System (ADS)

    Gilevska, Tetyana; Gehre, Matthias; Richnow, Hans

    2014-05-01

    Compound Specific Isotope Analysis (CSIA) has been an important step for the assessment of the origin and fate of compounds in environmental science.[1] Biologically or pharmaceutically important compounds often are not amenable for gas chromatographic separation because of high polarity and lacking volatility, thermostability. In 2004 liquid chromatography isotope ratio mass spectrometry (LC-IRMS) became commercially available. LC-IRMS system intent a quantitative conversion of analytes separation into CO2 via wet oxidation with sodium persulfate in the presence of phosphoric acid while analytes are still dissolved in the aqueous liquid phase.[2] The aim of this study is to analyze the oxidation capacity of the interface of the LC-IRMS system and determine which parameters could improve oxidation of compounds which are resistant to persulfate oxidation. Oxidation capacity of the liquid chromatography isotope ratio mass spectrometry system was tested with halogenated acetic acid and a set of aromatic compounds with different substitutes. Acetic acid (AA) was taken as a model compound for complete oxidation and compared to the oxidation of other analytes on a molar basis. Correct values were obtained for di- and mono chlorinated and fluorinated and also for tribrominated acetic acid and for all studied aromatic compounds. Incomplete oxidation for trichloroacetic (TCAA) and trifluoroacetic (TFAA) acid was revealed with lower recovery compared to acetic acid and isotope fractionation leading to depleted carbon isotope composition compared to values obtained with an elementary analyzer connected to an isotope mass spectrometer Several optimization steps were tried in order to improve the oxidation of TCAA and TFAA: (i) increasing the concentration of the oxidizing agent, (ii) variation of flow rate of the oxidizing and acid solution, (iii) variation of flow rate of liquid chromatography pump (iv) addition of a catalyzer. These modifications lead to longer reaction time

  20. Isotope ratio analysis of individual sub-micrometer plutonium particles with inductively coupled plasma mass spectrometry.

    PubMed

    Esaka, Fumitaka; Magara, Masaaki; Suzuki, Daisuke; Miyamoto, Yutaka; Lee, Chi-Gyu; Kimura, Takaumi

    2010-12-15

    Information on plutonium isotope ratios in individual particles is of great importance for nuclear safeguards, nuclear forensics and so on. Although secondary ion mass spectrometry (SIMS) is successfully utilized for the analysis of individual uranium particles, the isobaric interference of americium-241 to plutonium-241 makes difficult to obtain accurate isotope ratios in individual plutonium particles. In the present work, an analytical technique by a combination of chemical separation and inductively coupled plasma mass spectrometry (ICP-MS) is developed and applied to isotope ratio analysis of individual sub-micrometer plutonium particles. The ICP-MS results for individual plutonium particles prepared from a standard reference material (NBL SRM-947) indicate that the use of a desolvation system for sample introduction improves the precision of isotope ratios. In addition, the accuracy of the (241)Pu/(239)Pu isotope ratio is much improved, owing to the chemical separation of plutonium and americium. In conclusion, the performance of the proposed ICP-MS technique is sufficient for the analysis of individual plutonium particles.

  1. Coupled effects of temperature and mass transport on the isotope fractionation of zinc during electroplating

    NASA Astrophysics Data System (ADS)

    Black, Jay R.; John, Seth G.; Kavner, Abby

    2014-01-01

    The isotopic composition of zinc metal electrodeposited on a rotating disc electrode from a Zn-citrate aqueous solution was investigated as a function of overpotential (electrochemical driving force), temperature, and rotation rate. Zn metal was measured to be isotopically light with respect to Zn+2 in solution, with observed fractionations varying from Δ66/64Znmetal-aqueous = -1.0‰ to -3.9‰. Fractionation varies continuously as a function of a dimensionless parameter described by the ratio of observed deposition rate to calculated mass-transport limiting rate, where larger fractionations are observed at lower deposition rates, lower temperature, and at faster electrode rotation rates. Thus, the large fractionation and its rate dependence is interpreted as a competition between the two kinetic processes with different effective activation energies: mass-transport-limited (diffusion limited) kinetics with a large activation energy, which creates small fractionations close to the predicted diffusive fractionation; and electrochemical deposition kinetics, with a smaller effective activation energy, which creates large fractionations at low deposition rates and high hydrodynamic fluxes of solute to the electrode. The results provide a framework for predicting isotope fractionation in processes controlled by two competing reactions with different kinetic isotope effects. Light isotopes are electroplated. In all cases light stable isotopes of the metals are preferentially electroplated, with mass-dependent behavior evident where three or more isotopes are measured. Fractionation is time-independent, meaning that the fractionation factor does not vary with the extent of reaction. In most of our experiments, we have controlled the extent of reaction such that only a small amount of metal is deposited from the stock solution, thus avoiding significant evolution of the reservoir composition. In such experiments, the observed isotope fractionation is constant as a

  2. Temperature dependence of the symmetry energy and neutron skins in Ni, Sn, and Pb isotopic chains

    NASA Astrophysics Data System (ADS)

    Antonov, A. N.; Kadrev, D. N.; Gaidarov, M. K.; Sarriguren, P.; de Guerra, E. Moya

    2017-02-01

    The temperature dependence of the symmetry energy for isotopic chains of even-even Ni, Sn, and Pb nuclei is investigated in the framework of the local density approximation (LDA). The Skyrme energy density functional with two Skyrme-class effective interactions, SkM* and SLy4, is used in the calculations. The temperature-dependent proton and neutron densities are calculated through the hfbtho code that solves the nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical transformed deformed harmonic-oscillator basis. In addition, two other density distributions of 208Pb, namely the Fermi-type density determined within the extended Thomas-Fermi (TF) method and symmetrized-Fermi local density obtained within the rigorous density functional approach, are used. The kinetic energy densities are calculated either by the hfbtho code or, for a comparison, by the extended TF method up to second order in temperature (with T2 term). Alternative ways to calculate the symmetry energy coefficient within the LDA are proposed. The results for the thermal evolution of the symmetry energy coefficient in the interval T =0 -4 MeV show that its values decrease with temperature. The temperature dependence of the neutron and proton root-mean-square radii and corresponding neutron skin thickness is also investigated, showing that the effect of temperature leads mainly to a substantial increase of the neutron radii and skins, especially in the more neutron-rich nuclei, a feature that may have consequences on astrophysical processes and neutron stars.

  3. A Mass Spectrometry Study of Isotope Separation in the Laser Plume

    NASA Astrophysics Data System (ADS)

    Suen, Timothy Wu

    Accurate quantification of isotope ratios is critical for both preventing the development of illicit weapons programs in nuclear safeguards and identifying the source of smuggled material in nuclear forensics. While isotope analysis has traditionally been performed by mass spectrometry, the need for in situ measurements has prompted the development of optical techniques, such as laser-induced breakdown spectroscopy (LIBS) and laser ablation molecular isotopic spectrometry (LAMIS). These optical measurements rely on laser ablation for direct solid sampling, but several past studies have suggested that the distribution of isotopes in the ablation plume is not uniform. This study seeks to characterize isotope separation in the laser plume through the use of orthogonal-acceleration time-of-flight mass spectrometry. A silver foil was ablated with a Nd:YAG at 355 nm at an energy of 50 muJ with a spot size of 71 mum, for a fluence of 1.3 J/cm2 and an irradiance of 250 MW/cm2. Flat-plate repellers were used to sample the plume, and a temporal profile of the ions was obtained by varying the time delay on the high-voltage pulse. A spatial profile along the axis of the plume was generated by changing the position of the sample, which yielded snapshots of the isotopic composition with time. In addition, the reflectron time-of-flight system was used as an energy filter in conjunction with the repellers to sample slices of the laser plasma orthogonal to the plume axis. Mass spectrometry of the plume revealed a fast ion distribution and a slow ion distribution. Measurements taken across the entire plume showed the fast 109Ag ions slightly ahead in both space and time, causing the 107Ag fraction to drop to 0.34 at 3 mus, 4 mm from the sample surface. Although measurements centered on the near side of the plume did not show isotope separation, the slow ions on the far side of the plume included much more 109Ag than 107Ag. In addition to examining the isotope content of the ablation

  4. Mass-dependent and mass-independent fractionation of mercury isotopes in precipitation from Guiyang, SW China

    NASA Astrophysics Data System (ADS)

    Wang, Zhuhong; Chen, Jiubin; Feng, Xinbin; Hintelmann, Holger; Yuan, Shengliu; Cai, Hongming; Huang, Qiang; Wang, Shuxiao; Wang, Fengyang

    2015-11-01

    The isotopic composition of mercury (Hg) is increasingly used to constrain the sources and pathways of this metal in the atmosphere. Though China has the highest Hg production, consumption and emission in the world, Hg isotope ratios are rarely reported for Chinese wet deposition. In this study, we examined, for the first time outside North America, both mass-dependent fractionation (MDF, expressed as δ202Hg) and mass-independent fractionation of odd (odd-MIF, Δ199Hg) and even (even-MIF, Δ200Hg) Hg isotopes in 15 precipitation samples collected from September 2012 to August 2013 in Guiyang (SW China). All samples displayed significant negative δ202Hg (-0.44 ∼ -4.27‰), positive Δ199Hg (+0.19 to +1.16‰) and slightly positive Δ200Hg (-0.01‰ to +0.20‰). Potential sources of Hg in precipitation were identified by coupling both MDF and MIF of Hg isotopes with a back-trajectory model. The results showed that local emission from coal-fired power plants and cement plants and western long-range transportation are two main contributing sources, while the contribution of Hg from south wind events would be very limited on an annual basis. The relatively lower Δ200Hg values in Guiyang precipitation may indicate a dilution effect by local sources and/or insignificant even-MIF in the tropopause contribution of this subtropical region. Our study demonstrates the usefulness of isotope fractionation, especially MIF for tracing sources and pathways of Hg in the atmosphere.

  5. Isotope-ratio-monitoring gas chromatography-mass spectrometry: methods for isotopic calibration

    NASA Technical Reports Server (NTRS)

    Merritt, D. A.; Brand, W. A.; Hayes, J. M.

    1994-01-01

    In trial analyses of a series of n-alkanes, precise determinations of 13C contents were based on isotopic standards introduced by five different techniques and results were compared. Specifically, organic-compound standards were coinjected with the analytes and carried through chromatography and combustion with them; or CO2 was supplied from a conventional inlet and mixed with the analyte in the ion source, or CO2 was supplied from an auxiliary mixing volume and transmitted to the source without interruption of the analyte stream. Additionally, two techniques were investigated in which the analyte stream was diverted and CO2 standards were placed on a near-zero background. All methods provided accurate results. Where applicable, methods not involving interruption of the analyte stream provided the highest performance (sigma = 0.00006 at.% 13C or 0.06% for 250 pmol C as CO2 reaching the ion source), but great care was required. Techniques involving diversion of the analyte stream were immune to interference from coeluting sample components and still provided high precision (0.0001 < or = sigma < or = 0.0002 at.% or 0.1 < or = sigma < or = 0.2%).

  6. Energy and mass dependence of isotopic enrichment in sputtering

    SciTech Connect

    Shutthanandan, V.; Zhang, J.; Ray, Pradosh

    2003-05-01

    When a solid surface containing more than one component is bombarded by energetic particles, the sputtered flux is found to deviated from the stoichiometric composition of the target. This is known as preferential sputtering. Usually the sputtered flux is enriched with the lighter-mass particles, particularly at small emission angles. As the bombardment of the target is continued, the target surface becomes depleted in the particles that are preferentially emitted and a steady state is eventually established, where the ratio of the sputtered particles becomes equal to the natural abundance ratio of the particles in the target.

  7. Amino and Acetamide Functional Group Effects on the Ionization and Fragmentation of Sugar Chains in Positive-Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Yamagaki, Tohru; Sugahara, Kohtaro; Watanabe, Takehiro

    2014-01-01

    To elucidate the influence of amino (-NH2) and acetamide (-NHCOCH3, -NAc) groups in sugar chains on their ionization and fragmentation, cycloamyloses (cyclodextrins, CyDs) and lacto-oligosaccharide are analyzed by MALDI TOF/TOF and ESI Q-TOF mass spectrometry. CyD derivatives substituted by amino or acetamide groups are ideal analytes to extract the function group effects, which are amino-CyD with one hexosamine (HexNH2) and acetamide-CyD with one N-acetyl hexosamine (HexNAc). Interestingly, the relative ion intensities and isotope-like patterns in their product ion spectra depend on the functional groups and ion forms of sugar chains. Consequently, the results indicate that a proton (H+) localizes on the amino group of the amino sugar, and that the proton (H+) induces their fragmentation. Sodium cation (Na+) attachment is independent from amino group and exerts no influence on their fragmentation patterns in amino group except for mono- and disaccharide fragment ions because there is the possibility of the reducing end effect. In contrast, a sodium cation localizes much more frequently on the acetamide group in acetamide-CyDs because the chemical species with HexNAc are stable. Thus, their ions with HexNAc are abundant. These results are consistent with the fragmentation of lacto-neo- N-tetraose and maltotetraose, suggesting that a sodium cation generally localizes much more frequently on the acetamide group in sugar chains.

  8. Stable isotope composition of waters in the Great Basin, United States 1. Air-mass trajectories

    USGS Publications Warehouse

    Friedman, I.; Harris, J.M.; Smith, G.I.; Johnson, C.A.

    2002-01-01

    Isentropic trajectories, calculated using the NOAA/Climate Monitoring and Diagnostics Laboratory's isentropic transport model, were used to determine air-parcel origins and the influence of air mass trajectories on the isotopic composition of precipitation events that occurred between October 1991 and September 1993 at Cedar City, Utah, and Winnemucca, Nevada. Examination of trajectories that trace the position of air parcels backward in time for 10 days indicated five distinct regions of water vapor origin: (1) Gulf of Alaska and North Pacific, (2) central Pacific, (3) tropical Pacific, (4) Gulf of Mexico, and (5) continental land mass. Deuterium (??D) and oxygen-18 (??18O) analyses were made of precipitation representing 99% of all Cedar City events. Similar analyses were made on precipitation representing 66% of the precipitation falling at Winnemucca during the same period. The average isotopic composition of precipitation derived from each water vapor source was determined. More than half of the precipitation that fell at both sites during the study period originated in the tropical Pacific and traveled northeast to the Great Basin; only a small proportion traversed the Sierra Nevada. The isotopic composition of precipitation is determined by air-mass origin and its track to the collection station, mechanism of droplet formation, reequilibration within clouds, and evaporation during its passage from cloud to ground. The Rayleigh distillation model can explain the changes in isotopic composition of precipitation as an air mass is cooled pseudo-adiabatically during uplift. However, the complicated processes that take place in the rapidly convecting environment of cumulonimbus and other clouds that are common in the Great Basin, especially in summer, require modification of this model because raindrops that form in the lower portion of those clouds undergo isotopic change as they are elevated to upper levels of the clouds from where they eventually drop to the

  9. Probing the homogeneity of the isotopic composition and molar mass of the ‘Avogadro’-crystal

    NASA Astrophysics Data System (ADS)

    Pramann, Axel; Lee, Kyoung-Seok; Noordmann, Janine; Rienitz, Olaf

    2015-12-01

    Improved measurements on silicon crystal samples highly enriched in the 28Si isotope (known as ‘Si28’ or AVO28 crystal material) have been carried out at PTB to investigate local isotopic variations in the original crystal. This material was used for the determination of the Avogadro constant NA and therefore plays an important role in the upcoming redefinition of the SI units kilogram and mole, using fundamental constants. Subsamples of the original crystal have been extensively studied over the past few years at the National Research Council (NRC, Canada), the National Metrology Institute of Japan (NMIJ, Japan), the National Institute of Standards and Technology (NIST, USA), the National Institute of Metrology (NIM, People’s Republic of China), and multiple times at PTB. In this study, four to five discrete, but adjacent samples were taken from three distinct axial positions of the crystal to obtain a more systematic and comprehensive understanding of the distribution of the isotopic composition and molar mass throughout the crystal. Moreover, improved state-of-the-art techniques in the experimental measurements as well as the evaluation approach and the determination of the calibration factors were utilized. The average molar mass of the measured samples is M  =  27.976 970 12(12) g mol-1 with a relative combined uncertainty uc,rel(M)  =  4.4 ×10-9. This value is in astounding agreement with the values of single samples measured and published by NIST, NMIJ, and PTB. With respect to the associated uncertainties, no significant variations in the molar mass and the isotopic composition as a function of the sample position in the boule were observed and thus could not be traced back to an inherent property of the crystal. This means that the crystal is not only ‘homogeneous’ with respect to molar mass but also has predominantly homogeneous distribution of the three stable Si isotopes.

  10. Recombination reactions as a possible mechanism of mass-independent fractionation of sulfur isotopes in the Archean atmosphere of Earth.

    PubMed

    Babikov, Dmitri

    2017-03-21

    A hierarchy of isotopically substituted recombination reactions is formulated for production of sulfur allotropes in the anoxic atmosphere of Archean Earth. The corresponding system of kinetics equations is solved analytically to obtain concise expressions for isotopic enrichments, with focus on mass-independent isotope effects due to symmetry, ignoring smaller mass-dependent effects. Proper inclusion of atom-exchange processes is shown to be important. This model predicts significant and equal depletions driven by reaction stoichiometry for all rare isotopes: (33)S, (34)S, and (36)S. Interestingly, the ratio of capital [Formula: see text] values obtained within this model for (33)S and (36)S is -1.16, very close to the mass-independent fractionation line of the Archean rock record. This model may finally offer a mechanistic explanation for the striking mass-independent fractionation of sulfur isotopes that took place in the Archean atmosphere of Earth.

  11. Absolute isotopic composition and atomic weight of neodymium using thermal ionization mass spectrometry.

    PubMed

    Zhao, Motian; Zhou, Tao; Wang, Jun; Lu, Hai; Fang, Xiang; Guo, Chunhua; Li, Qiuli; Li, Chaofeng

    2005-01-01

    Synthetic mixtures prepared gravimetrically from highly enriched isotopes of neodymium in the form of oxides of well-defined purity were used to calibrate a thermal ionization mass spectrometer. A new error analysis was applied to calculate the final uncertainty of the atomic weight value. Measurements on natural neodymium samples yielded an absolute isotopic composition of 27.153(19) atomic percent (at.%) 142Nd, 12.173(18) at.% 143Nd, 23.798(12) at.% 144Nd, 8.293(7) at.% 145Nd, 17.189(17) at.% 146Nd, 5.756(8) at.% 148Nd, and 5.638(9) at.% 150Nd, and the atomic weight of neodymium as 144.2415(13), with uncertainties given on the basis of 95% confidence limits. No isotopic fractionation was found in terrestrial neodymium materials.

  12. Detection of plutonium isotopes at lowest quantities using in-source resonance ionization mass spectrometry.

    PubMed

    Raeder, S; Hakimi, A; Stöbener, N; Trautmann, N; Wendt, K

    2012-11-01

    The in-source resonance ionization mass spectrometry technique was applied for quantification of ultratrace amounts of plutonium isotopes as a proof of principle study. In addition to an overall detection limit of 10(4) to 10(5) atoms, this method enables the unambiguous identification and individual quantification of the plutonium isotopes (238)Pu and (241)Pu which are of relevance for dating of radiogenic samples. Due to the element-selective ionization process, these isotopes can be measured even under a high surplus of isobaric contaminations from (238)U or (241)Am, which considerably simplifies chemical preparation. The technique was developed, tested, and characterized on a variety of synthetic and calibration samples and is presently applied to analyze environmental samples.

  13. [Determination of nicotinamide in formula milk powder using liquid chromatography-isotope dilution mass spectrometry].

    PubMed

    Huang, Ting; Zhang, Wei; Liu, Yang; Liu, Jun

    2007-11-01

    It is important to determine trace compounds in complex matrices. Internal standards are often introduced to circumvent loss of analytes during the preparation to achieve accurate measurement. Isotope internal standards are better than other types of internal standards, due to its high similarity to analyte in chemical properties. By introducing isotope-labeled nicotinamide, as an internal standard, a method for determining nicotinamide in formula milk powder by liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) was developed with a relative standard deviation of 0.94%. The results suggested that the developed LC-IDMS method has high accuracy, high specificity, high repeatability, and is suitable for the determination of vitamins in complex matrices. This method was used to perform international comparison for CCQM-P78, and the result was consistent with that of international laboratories.

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

    USGS Publications Warehouse

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

    1987-01-01

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

  15. Oxygen isotope analysis of fossil organic matter by secondary ion mass spectrometry

    NASA Astrophysics Data System (ADS)

    Tartèse, Romain; Chaussidon, Marc; Gurenko, Andrey; Delarue, Frédéric; Robert, François

    2016-06-01

    We have developed an analytical procedure for the measurement of oxygen isotope composition of fossil organic matter by secondary ion mass spectrometry (SIMS) at the sub-per mill level, with a spatial resolution of 20-30 μm. The oxygen isotope composition of coal and kerogen samples determined by SIMS are on average consistent with the bulk oxygen isotope compositions determined by temperature conversion elemental analysis - isotope ratio mass spectrometry (TC/EA-IRMS), but display large spreads of δ18O of ∼5-10‰, attributed to mixing of remnants of organic compounds with distinct δ18O signatures. Most of the δ18O values obtained on two kerogen residues extracted from the Eocene Clarno and Early Devonian Rhynie continental chert samples and on two immature coal samples range between ∼10‰ and ∼25‰. Based on the average δ18O values of these samples, and on the O isotope composition of water processed by plants that now constitute the Eocene Clarno kerogen, we estimated δ18Owater values ranging between around -11‰ and -1‰, which overall correspond well within the range of O isotope compositions for present-day continental waters. SIMS analyses of cyanobacteria-derived organic matter from the Silurian Zdanow chert sample yielded δ18O values in the range 12-20‰. Based on the O isotope composition measured on recent cyanobacteria from the hypersaline Lake Natron (Tanzania), and on the O isotope composition of the lake waters in which they lived, we propose that δ18O values of cyanobacteria remnants are enriched by about ∼18 ± 2‰ to 22 ± 2‰ relative to coeval waters. This relationship suggests that deep ocean waters in which the Zdanow cyanobacteria lived during Early Silurian times were characterised by δ18O values of around -5 ± 4‰. This study, establishing the feasibility of micro-analysis of Phanerozoic fossil organic matter samples by SIMS, opens the way for future investigations of kerogens preserved in Archean cherts and of the

  16. Quantitative Gingival Crevicular Fluid Proteome in Health and Periodontal Disease Using Stable-Isotope Chemistries and Mass Spectrometry

    PubMed Central

    Carneiro, Leandro G.; Nouh, Hesham; Salih, Erdjan

    2014-01-01

    Aim Application of quantitative stable-isotope-labeling chemistries and mass spectrometry (MS) to determine alterations in gingival crevicular fluid (GCF) proteome in periodontal disease. Materials and Methods Quantitative proteome of GCF from 40 healthy individuals versus 40 patients with periodontal disease was established using 320 GCF samples and stable-isotope-labeling reagents, ICAT and mTRAQ, with MS technology and validated by enzyme-linked immunosorbent methods. Results We have identified 238 distinct proteins of which 180 were quantified in GCF of both healthy and periodontal patients with additional 26 and 32 distinct proteins that were found only in GCF of healthy or periodontal patients. In addition, 42 pathogenic bacterial proteins and 11 yeast proteins were quantified. The data highlighted a series of proteins not quantified previously by large-scale MS approaches in GCF with relevance to periodontal disease, such as host derived Ig alpha-2 chain C, Kallikrein-4, S100-A9, transmembrane proteinase 13, peptidase S1 domain, several collagen types and pathogenic bacterial proteins e.g., formamidase, leucine amidopeptidase and virulence factor OMP85. Conclusions The innovative analytical approaches provided detailed novel changes in both host and microbial derived GCF proteomes of periodontal patients. The study defined 50 host and 16 pathogenic bacterial proteins significantly elevated in periodontal disease most of which were novel with significant potential for application in the clinical arena of periodontal disease. PMID:24738839

  17. Flow injection analysis-isotope ratio mass spectrometry for bulk carbon stable isotope analysis of alcoholic beverages.

    PubMed

    Jochmann, Maik A; Steinmann, Dirk; Stephan, Manuel; Schmidt, Torsten C

    2009-11-25

    A new method for bulk carbon isotope ratio determination of water-soluble samples is presented that is based on flow injection analysis-isotope ratio mass spectrometry (FIA-IRMS) using an LC IsoLink interface. Advantages of the method are that (i) only very small amounts of sample are required (2-5 microL of the sample for up to 200 possible injections), (ii) it avoids complex sample preparation procedures such as needed for EA-IRMS analysis (only sample dilution and injection,) and (iii) high throughput due to short analysis times is possible (approximately 15 min for five replicates). The method was first tested and evaluated as a fast screening method with industrially produced ethanol samples, and additionally the applicability was tested by the measurement of 81 alcoholic beverages, for example, whiskey, brandy, vodka, tequila, and others. The minimal sample concentration required for precise and reproducible measurements was around 50 microL L(-1) ethanol/water (1.71 mM carbon). The limit of repeatability was determined to be r=0.49%. FIA-IRMS represents a fast screening method for beverage authenticity control. Due to this, samples can be prescreened as a decisive criterion for more detailed investigations by HPLC-IRMS or multielement GC-IRMS measurements for a verification of adulteration.

  18. On-line determination of oxygen isotope ratios of water or ice by mass spectrometry.

    PubMed

    Leuenberger, M; Huber, C

    2002-09-15

    Oxygen isotope ratio determination on any of the water phases (water vapor, water, ice) is of great relevance in different research fields such as climate and paleoclimate studies, geological surveys, and hydrological studies. The conventional technique for oxygen isotope measurement involves equilibration with carbon dioxide gas for a given time with a subsequent isotope determination. The equilibration technique is available in different layouts, but all of them are rather time-consuming. Here we report a new on-line technique that processes water samples as well as ice samples. The same principal, CO2 hydration, is used but speeded up by (i) a direct injection and full dissolution of CO2 in the water, (ii) an increased isotope exchange temperature at 50 degrees C, and (iii) a rapid gas extraction by means of an air-permeable membrane into a continuous helium flux supplying the isotope ratio mass spectrometer with the sample gas. The precision is better than 0.1/1000 which is only slightly larger than with the conventional equilibration technique. This on-line technique allows analysis of 1 m of ice with a resolution of 1-3 cm, depending on the meltwater flux, within 1 h. Similarly, continuous and fast analysis can be performed for aqueous samples for hydrological, geological, and perhaps medical applications.

  19. Pathways for Neoarchean pyrite formation constrained by mass-independent sulfur isotopes.

    PubMed

    Farquhar, James; Cliff, John; Zerkle, Aubrey L; Kamyshny, Alexey; Poulton, Simon W; Claire, Mark; Adams, David; Harms, Brian

    2013-10-29

    It is generally thought that the sulfate reduction metabolism is ancient and would have been established well before the Neoarchean. It is puzzling, therefore, that the sulfur isotope record of the Neoarchean is characterized by a signal of atmospheric mass-independent chemistry rather than a strong overprint by sulfate reducers. Here, we present a study of the four sulfur isotopes obtained using secondary ion MS that seeks to reconcile a number of features seen in the Neoarchean sulfur isotope record. We suggest that Neoarchean ocean basins had two coexisting, significantly sized sulfur pools and that the pathways forming pyrite precursors played an important role in establishing how the isotopic characteristics of each of these pools was transferred to the sedimentary rock record. One of these pools is suggested to be a soluble (sulfate) pool, and the other pool (atmospherically derived elemental sulfur) is suggested to be largely insoluble and unreactive until it reacts with hydrogen sulfide. We suggest that the relative contributions of these pools to the formation of pyrite depend on both the accumulation of the insoluble pool and the rate of sulfide production in the pyrite-forming environments. We also suggest that the existence of a significant nonsulfate pool of reactive sulfur has masked isotopic evidence for the widespread activity of sulfate reducers in the rock record.

  20. Pathways for Neoarchean pyrite formation constrained by mass-independent sulfur isotopes

    PubMed Central

    Farquhar, James; Cliff, John; Zerkle, Aubrey L.; Kamyshny, Alexey; Poulton, Simon W.; Claire, Mark; Adams, David; Harms, Brian

    2013-01-01

    It is generally thought that the sulfate reduction metabolism is ancient and would have been established well before the Neoarchean. It is puzzling, therefore, that the sulfur isotope record of the Neoarchean is characterized by a signal of atmospheric mass-independent chemistry rather than a strong overprint by sulfate reducers. Here, we present a study of the four sulfur isotopes obtained using secondary ion MS that seeks to reconcile a number of features seen in the Neoarchean sulfur isotope record. We suggest that Neoarchean ocean basins had two coexisting, significantly sized sulfur pools and that the pathways forming pyrite precursors played an important role in establishing how the isotopic characteristics of each of these pools was transferred to the sedimentary rock record. One of these pools is suggested to be a soluble (sulfate) pool, and the other pool (atmospherically derived elemental sulfur) is suggested to be largely insoluble and unreactive until it reacts with hydrogen sulfide. We suggest that the relative contributions of these pools to the formation of pyrite depend on both the accumulation of the insoluble pool and the rate of sulfide production in the pyrite-forming environments. We also suggest that the existence of a significant nonsulfate pool of reactive sulfur has masked isotopic evidence for the widespread activity of sulfate reducers in the rock record. PMID:23407162

  1. New developments in high-resolution gas source isotope ratio mass spectrometers

    NASA Astrophysics Data System (ADS)

    Clog, M. D.; Ellam, R. M.; Hilkert, A.; Schwieters, J. B.; Hamilton, D.

    2015-12-01

    Gas source isotope ratio mass spectrometry (IRMS) is one of the main tools for the study of the isotopic compositions of light elements, extended in the last 10 years to the measurements of molecules bearing several rare isotopes (e.g., clumped isotopes of CO2) as well as position-specific isotopic substitutions in a few choice analytes (e.g., in N2O). Measuring those low-abundance species creates several technical challenges, with the main one being the presence of numerous isobaric interferences. Those can come either from contaminants (background gases present in the source of the instrument or impurities introduced with the analyte), or unwanted beams created by the analyte itself during the ionization process (for example adducts and fragments). In order to avoid those isobaric species, new high-resolution, double-focusing IRMS have been developed. We present here the capabilities of the production series version of the ThermoFisher Scientific 253 Ultra, which was installed at SUERC in July 2015. The instrument is capable of reaching high mass resolving power (above 40,000) and is similar in design to the Caltech 253 Ultra prototype. The collector array has 9 detector positions, 8 of which are movable. Faraday cups at each detector can be linked to amplifiers with gains ranging from 3.108 to 1012 Ohm (and 1013 Ohm amplifiers being currently developped). There are also 4 ion counters, one of which located behind a retardation lens (RPQ) to limit background noise and improve abundance sensitivity. Additionally, one of the Faraday cup in the new instrument has a very narrow entrance slit, allowing high mass resolving power and high resolution, with a complete separation of the ion beams instead of complex peak shapes corresponding to overlapping ion beams. This will potentially remove the need for adduct lines or peak stripping schemes for analytes like CH4.

  2. Accuracy of delta 18O isotope ratio measurements on the same sample by continuous-flow isotope-ratio mass spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The doubly labeled water method is considered the reference method to measure energy expenditure. Conventional mass spectrometry requires a separate aliquot of the same sample to be prepared and analyzed separately. With continuous-flow isotope-ratio mass spectrometry, the same sample could be analy...

  3. Separation Of Uranium And Plutonium Isotopes For Measurement By Multi Collector Inductively Coupled Plasma Mass Spectroscopy

    SciTech Connect

    Martinelli, R E; Hamilton, T F; Williams, R W; Kehl, S R

    2009-03-29

    Uranium (U) and plutonium (Pu) isotopes in coral soils, contaminated by nuclear weapons testing in the northern Marshall Islands, were isolated by ion-exchange chromatography and analyzed by mass spectrometry. The soil samples were spiked with {sup 233}U and {sup 242}Pu tracers, dissolved in minerals acids, and U and Pu isotopes isolated and purified on commercially available ion-exchange columns. The ion-exchange technique employed a TEVA{reg_sign} column coupled to a UTEVA{reg_sign} column. U and Pu isotope fractions were then further isolated using separate elution schemes, and the purified fractions containing U and Pu isotopes analyzed sequentially using multi-collector inductively coupled plasma mass spectrometer (MCICP-MS). High precision measurements of {sup 234}U/{sup 235}U, {sup 238}U/{sup 235}U, {sup 236}U/{sup 235}U, and {sup 240}Pu/{sup 239}Pu in soil samples were attained using the described methodology and instrumentation, and provide a basis for conducting more detailed assessments of the behavior and transfer of uranium and plutonium in the environment.

  4. High-precision isotopic analysis of palmitoylcarnitine by liquid chromatography/electrospray ionization ion-trap tandem mass spectrometry.

    PubMed

    Guo, ZengKui; Yarasheski, Kevin; Jensen, Michael D

    2006-01-01

    Single quadrupole gas chromatography/mass spectrometry (GC/MS) has been widely used for isotopic analysis in metabolic investigations using stable isotopes as tracers. However, its inherent shortcomings prohibit it from broader use, including low isotopic precision and the need for chemical derivatization of the analyte. In order to improve isotopic detection power, liquid chromatography/electrospray ionization ion-trap tandem mass spectrometry (LC/ESI-itMS2) has been evaluated for its isotopic precision and chemical sensitivity for the analysis of [13C]palmitoylcarnitine. Over the enrichment range of 0.4-10 MPE (molar % excess), the isotopic response of LC/ESI-itMS2 to [13C]palmitoylcarnitine was linear (r = 1.00) and the average isotopic precision (standard deviation, SD) was 0.11 MPE with an average coefficient of variation (CV) of 5.6%. At the lower end of isotopic enrichments (0.4-0.9 MPE), the isotopic precision was 0.05 MPE (CV = 8%). Routine analysis of rat skeletal muscle [13C4]palmitoylcarnitine demonstrated an isotopic precision of 0.03 MPE for gastrocnemius (n = 16) and of 0.02 MPE for tibialis anterior (n = 16). The high precision enabled the detection of a small (0.08 MPE) but significant (P = 0.01) difference in [13C4]palmitoylcarnitine enrichments between the two muscles, 0.51 MPE (CV = 5.8%) and 0.43 MPE (CV = 4.6%), respectively. Therefore, the system demonstrated an isotopic lower detection limit (LDL) of < or =0.1 MPE (2 x SD) that has been impossible previously with other organic mass spectrometry instruments. LC/ESI-itMS2 systems have the potential to advance metabolic investigations using stable isotopes to a new level by significantly increasing the isotopic solving power.

  5. Natural variation of magnesium isotopes in mammal bones and teeth from two South African trophic chains

    NASA Astrophysics Data System (ADS)

    Martin, Jeremy E.; Vance, Derek; Balter, Vincent

    2014-04-01

    Isotopic fractionations accompanying element transfer through terrestrial ecosystems have the potential to shed light on ecological interactions between primary producers and consumers, but with the exception of carbon and nitrogen this potential has barely been exploited. Here, the magnesium stable isotope composition of bones and teeth of extant mammals from Kruger National Park (KNP) and Western Cape (WC), South Africa was measured for the first time. The nature of the geological substrate proves to be a major determinant of the ecosystem isotope baseline, as indicated by the lighter magnesium isotope ratios measured in WC mammals (ranging from -1.58‰ to -0.79‰) compared to those from KNP mammals (ranging from -1.01‰ to -0.04‰). Therefore, comparisons between the isotope signatures of taxa must be restricted to a pre-defined geographic area with a homogeneous substrate. In both parks, Mg shows slight enrichment in heavier isotopes from herbivores to carnivores. Plant remains trapped in the dentition of herbivores provide direct evidence of dietary source and, when available, were measured. In KNP only, δ26Mg of plant remains is systematically lighter than the values for herbivore teeth. These results invite further exploration of the variability of Mg isotopes in vertebrate ecosystems in order to test whether magnesium, a bio-essential element present in relatively large proportions in bone and teeth apatite, may serve as an additional trophic tracer to nitrogen, which is a constituent of collagen that rapidly degrades after burial.

  6. Development of a dedicated isotope mass spectrometer for the noninvasive diagnostics of humans infected with Helicobacter Pylori

    NASA Astrophysics Data System (ADS)

    Blashenkov, N. M.; Sheshenya, E. S.; Solov'ev, S. M.; Gall', L. N.; Sachenko, V. M.; Zarutskii, I. V.; Gall', N. R.

    2013-06-01

    A dedicated isotope mass spectrometer for the noninvasive diagnostics of humans infected with Helicobacter Pylori using the isotope respiratory test is developed. A low-aberration mass analyzer is calculated, an input system that makes it possible to eliminate the memory effects is developed, and a small-size ion detector is constructed. The mass spectrometer is created, and the tests are performed. The measurement accuracy of the 13C/12C and 16O/18O isotope ratios are 1.7 and 2.2‰, respectively. Preliminary medical tests show that the spectrometer can be employed for the desired diagnostics.

  7. Explaining the structure of the Archean mass-independent sulfur isotope record.

    PubMed

    Halevy, Itay; Johnston, David T; Schrag, Daniel P

    2010-07-09

    Sulfur isotopes in ancient sediments provide a record of past environmental conditions. The long-time-scale variability and apparent asymmetry in the magnitude of minor sulfur isotope fractionation in Archean sediments remain unexplained. Using an integrated biogeochemical model of the Archean sulfur cycle, we find that the preservation of mass-independent sulfur is influenced by a variety of extra-atmospheric mechanisms, including biological activity and continental crust formation. Preservation of atmospherically produced mass-independent sulfur implies limited metabolic sulfur cycling before approximately 2500 million years ago; the asymmetry in the record indicates that bacterial sulfate reduction was geochemically unimportant at this time. Our results suggest that the large-scale structure of the record reflects variability in the oxidation state of volcanic sulfur volatiles.

  8. Mass-independent isotopic compositions in terrestrial and extraterrestrial solids and their applications.

    PubMed

    Thiemens, M H; Savarino, J; Farquhar, J; Bao, H

    2001-08-01

    In 1983, Thiemens and Heidenreich reported the first chemically produced mass-independent isotope effect. This work has been shown to have a wide range of applications, including atmospheric chemistry, solar system evolution, and chemical physics. This work has recently been reviewed (Weston, R. E. Chem. Rev. 1999, 99, 2115-2136; Thiemens, M. H. Science 1999, 283, 341-345). In this Account, observations of mass-independent isotopic compositions in terrestrial and Martian solids are reviewed. A wide range of applications, including formation and transport of aerosols in the present atmosphere, chemistry of ancient atmospheres and oceans, history and coupling of the atmosphere-surface in the Antarctic dry valleys, origin and evolution of oxygen in the Earth's earliest environment, and the chemistry of the atmosphere and surface of Mars, are discussed.

  9. High precision Penning trap mass spectrometry of rare isotopes produced by projectile fragmentation

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, A. A.; Barquest, B. R.; Block, M.; Bollen, G.; Campbell, C. M.; Ferrer, R.; Lincoln, D. L.; Morrissey, D. J.; Pang, G. K.; Redshaw, M.; Ringle, R.; Schwarz, S.; Savory, J.

    2011-09-01

    The Low Energy Beam and Ion Trap (LEBIT) is the only present facility to combine high precision Penning trap mass spectrometry with fast beam projectile fragmentation. Located at the National Superconducting Cyclotron Laboratory (NSCL), LEBIT is able to measure radionuclides produced in a chemically independent process with minimal decay losses. Recent exotic mass measurements include 66As, 63-66Fe, and 32Si. 66As is a new candidate to test the Conserved Vector Current (CVC) hypothesis. The masses of the neutron-rich iron isotopes provide additional information about the mass surface and the subshell closure at N = 40. 32Si is a member of the A = 32, T = 2 quintet; its measurement permits the most stringent test of the validity of the isobaric multiplet mass equation (IMME). An overview of some recent measurements will be presented as well as advanced techniques for ion manipulation.

  10. Experimental study of the variation of alpha elastic scattering cross sections along isotopic and isotonic chains at low energies

    SciTech Connect

    Kiss, G. G.; Gyuerky, Gy.; Elekes, Z.; Fueloep, Zs.; Somorjai, E.; Galaviz, D.; Sonnabend, K.; Zilges, A.; Mohr, P.; Goerres, J.; Wiescher, M.; Oezkan, N.; Gueray, T.; Yalcin, C.; Avrigeanu, M.

    2008-05-21

    To improve the reliability of statistical model calculations in the region of heavy proton rich isotopes alpha elastic scattering experiments have been performed at ATOMKI, Debrecen, Hungary. The experiments were carried out at several energies above and below the Coulomb barrier with high precision. The measured angular distributions can be used for testing the predictions of the global and regional optical potential parameter sets. Moreover, we derived the variation of the elastic alpha scattering cross section along the Z = 50 ({sup 112}Sn-{sup 124}Sn) isotopic and N = 50 ({sup 89}Y-{sup 92}Mo) isotonic chains. In this paper we summarize the efforts to provide high precision experimental angular distributions for several A{approx_equal}100 nuclei to test the global optical potential parameterizations applied to p-process network calculations.

  11. 2H/(1)H and (13)C/(12)C isotope ratios of trans-anethole using gas chromatography-isotope ratio mass spectrometry.

    PubMed

    Bilke, Steffi; Mosandl, Armin

    2002-07-03

    Authenticity assessment of trans-anethole is deduced from (2)H/(1)H and (13)C/(12)C isotope ratios, determined by gas chromatography-isotope ratio mass spectrometry (GC-IRMS). For that purpose, self-prepared anise and fennel oils, and synthetic and "natural" samples of trans-anethole, as well as commercially available anise and fennel oils have been investigated. Authenticity ranges of (2)H/(1)H and (13)C/(12)C isotope ratios of trans-anethole were defined. Scope and limitations of the applied online GC-IRMS techniques are discussed.

  12. Liquid and gas chromatography coupled to isotope ratio mass spectrometry for the determination of 13C-valine isotopic ratios in complex biological samples.

    PubMed

    Godin, Jean-Philippe; Breuillé, Denis; Obled, Christiane; Papet, Isabelle; Schierbeek, Henk; Hopfgartner, Gérard; Fay, Laurent-Bernard

    2008-10-01

    On-line gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) is commonly used to measure isotopic ratios at natural abundance as well as for tracer studies in nutritional and medical research. However, high-precision (13)C isotopic enrichment can also be measured by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). Indeed, LC-IRMS can be used, as shown by the new method reported here, to obtain a baseline separation and to measure (13)C isotopic enrichment of underivatised amino acids (Asp, Thr-Ser, Glu, Pro, Gly, Ala, Cys and Val). In case of Val, at natural abundance, the SD(delta(13)C) reported with this method was found to be below 1 per thousand . Another key feature of the new LC-IRMS method reported in this paper is the comparison of the LC-IRMS approach with the conventional GC-C-IRMS determination. To perform this comparative study, isotopic enrichments were measured from underivatised Val and its N(O, S)-ethoxycarbonyl ethyl ester derivative. Between 0.0 and 1.0 molar percent excess (MPE) (delta(13)C= -12.3 to 150.8 per thousand), the calculated root-mean-square (rms) of SD was 0.38 and 0.46 per thousand and the calculated rms of accuracy was 0.023 and 0.005 MPE, respectively, for GC-C-IRMS and LC-IRMS. Both systems measured accurately low isotopic enrichments (0.002 atom percent excess (APE)) with an SD (APE) of 0.0004. To correlate the relative (delta(13)C) and absolute (atom%, APE and MPE) isotopic enrichment of Val measured by the GC-C-IRMS and LC-IRMS devices, mathematical equations showing the slope and intercept of the curves were established and validated with experimental data between 0.0 to 2.3 MPE. Finally, both GC-C-IRMS and LC-IRMS instruments were also used to assess isotopic enrichment of protein-bound (13)C-Val in tibial epiphysis in a tracer study performed in rats. Isotopic enrichments measured by LC-IRMS and GC-C-IRMS were not statistically different (p>0.05). The results of this work indicate that

  13. Inductively coupled plasma mass spectrometry for stable isotope metabolic tracer studies of living systems

    SciTech Connect

    Luong, Elise

    1999-05-10

    This dissertation focuses on the development of methods for stable isotope metabolic tracer studies in living systems using inductively coupled plasma single and dual quadrupole mass spectrometers. Sub-nanogram per gram levels of molybdenum (Mo) from human blood plasma are isolated by the use of anion exchange alumina microcolumns. Million-fold more concentrated spectral and matrix interferences such as sodium, chloride, sulfate, phosphate, etc. in the blood constituents are removed from the analyte. The recovery of Mo from the alumina column is 82 ± 5% (n = 5). Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) is utilized for the quantitative ultra-trace concentration determination of Mo in bovine and human blood samples. The average Mo concentration in reference bovine serum determined by this method is 10.2 ± 0.4 ng/g, while the certified value is 11.5 ± 1.1 ng/g (95% confidence interval). The Mo concentration of one pool of human blood plasma from two healthy male donors is 0.5 ± 0.1 ng/g. The inductively coupled plasma twin quadrupole mass spectrometer (ICP-TQMS) is used to measure the carbon isotope ratio from non-volatile organic compounds and bio-organic molecules to assess the ability as an alternative analytical method to gas chromatography combustion isotope ratio mass spectrometry (GC-combustion-IRMS). Trytophan, myoglobin, and β-cyclodextrin are chosen for the study, initial observation of spectral interference of 13C+ with 12C 1H+ comes from the incomplete dissociation of myoglobin and/or β-cyclodextrin.

  14. Theoretical study of band structure of odd-mass 115,117I isotopes

    NASA Astrophysics Data System (ADS)

    Singh, Dhanvir; Kumar, Amit; Sharma, Chetan; Singh, Suram; Bharti, Arun

    2016-05-01

    By using the microscopic approach of Projected Shell Model (PSM), negative-parity band structures of odd mass neutron-rich 115,117I nuclei have been studied with the deformed single-particle states generated by the standard Nilsson potential. For these isotopes, the band structures have been analyzed in terms of quasi-particles configurations. The phenomenon of back bending in moment of inertia is also studied in the present work.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  16. Accounting for isotopic clustering in Fourier transform mass spectrometry data analysis for clinical diagnostic studies.

    PubMed

    Kakourou, Alexia; Vach, Werner; Nicolardi, Simone; van der Burgt, Yuri; Mertens, Bart

    2016-10-01

    Mass spectrometry based clinical proteomics has emerged as a powerful tool for high-throughput protein profiling and biomarker discovery. Recent improvements in mass spectrometry technology have boosted the potential of proteomic studies in biomedical research. However, the complexity of the proteomic expression introduces new statistical challenges in summarizing and analyzing the acquired data. Statistical methods for optimally processing proteomic data are currently a growing field of research. In this paper we present simple, yet appropriate methods to preprocess, summarize and analyze high-throughput MALDI-FTICR mass spectrometry data, collected in a case-control fashion, while dealing with the statistical challenges that accompany such data. The known statistical properties of the isotopic distribution of the peptide molecules are used to preprocess the spectra and translate the proteomic expression into a condensed data set. Information on either the intensity level or the shape of the identified isotopic clusters is used to derive summary measures on which diagnostic rules for disease status allocation will be based. Results indicate that both the shape of the identified isotopic clusters and the overall intensity level carry information on the class outcome and can be used to predict the presence or absence of the disease.

  17. Hydroponic isotope labeling of entire plants and high-performance mass spectrometry for quantitative plant proteomics.

    PubMed

    Bindschedler, Laurence V; Mills, Davinia J S; Cramer, Rainer

    2012-01-01

    Hydroponic isotope labeling of entire plants (HILEP) combines hydroponic plant cultivation and metabolic labeling with stable isotopes using (15)N-containing inorganic salts to label whole and mature plants. Employing (15)N salts as the sole nitrogen source for HILEP leads to the production of healthy-looking plants which contain (15)N proteins labeled to nearly 100%. Therefore, HILEP is suitable for quantitative plant proteomic analysis, where plants are grown in either (14)N- or (15)N-hydroponic media and pooled when the biological samples are collected for relative proteome quantitation. The pooled (14)N-/(15)N-protein extracts can be fractionated in any suitable way and digested with a protease for shotgun proteomics, using typically reverse phase liquid chromatography nanoelectrospray ionization tandem mass spectrometry (RPLC-nESI-MS/MS). Best results were obtained with a hybrid ion trap/FT-MS mass spectrometer, combining high mass accuracy and sensitivity for the MS data acquisition with speed and high-throughput MS/MS data acquisition, increasing the number of proteins identified and quantified and improving protein quantitation. Peak processing and picking from raw MS data files, protein identification, and quantitation were performed in a highly automated way using integrated MS data analysis software with minimum manual intervention, thus easing the analytical workflow. In this methodology paper, we describe how to grow Arabidopsis plants hydroponically for isotope labeling using (15)N salts and how to quantitate the resulting proteomes using a convenient workflow that does not require extensive bioinformatics skills.

  18. INTERLABORATORY COMPARISON OF MASS SPECTROMETRIC METHODS FOR LEAD ISOTOPES AND TRACE ELEMENTS IN NIST SRM 1400 BONE ASH

    EPA Science Inventory

    The results of an interlaboratory comparison are reported for he lead isotope composition and for trace element concentrations in NIST SRM 1400 Bone Ash obtained using quadrupole and magnetic-sector inductively coupled plasma mass spectrometry (ICP-MS) and (for the Pb isotopes on...

  19. Re-Os isotope and platinum group elements of a FOcal ZOne mantle source, Louisville Seamounts Chain, Pacific ocean

    NASA Astrophysics Data System (ADS)

    Tejada, Maria Luisa G.; Hanyu, Takeshi; Ishikawa, Akira; Senda, Ryoko; Suzuki, Katsuhiko; Fitton, Godfrey; Williams, Rebecca

    2015-02-01

    The Louisville Seamount Chain (LSC) is, besides the Hawaiian-Emperor Chain, one of the longest-lived hotspot traces. We report here the first Re-Os isotope and platinum group element (PGE) data for Canopus, Rigil, and Burton Guyots along the chain, which were drilled during IODP Expedition 330. The LSC basalts possess (187Os/188Os)i = 0.1245-0.1314 that are remarkably homogeneous and do not vary with age. A Re-Os isochron age of 64.9 ± 3.2 Ma was obtained for Burton seamount (the youngest of the three seamounts drilled), consistent with 40Ar-39Ar data. Isochron-derived initial 187Os/188Os ratio of 0.1272 ± 0.0008, together with data for olivines (0.1271-0.1275), are within the estimated primitive mantle values. This (187Os/188Os)i range is similar to those of Rarotonga (0.124-0.139) and Samoan shield (0.1276-0.1313) basalts and lower than those of Cook-Austral (0.136-0.155) and Hawaiian shield (0.1283-0.1578) basalts, suggesting little or no recycled component in the LSC mantle source. The PGE data of LSC basalts are distinct from those of oceanic lower crust. Variation in PGE patterns can be largely explained by different low degrees of melting under sulfide-saturated conditions of the same relatively fertile mantle source, consistent with their primitive mantle-like Os and primordial Ne isotope signatures. The PGE patterns and the low 187Os/188Os composition of LSC basalts contrast with those of Ontong Java Plateau (OJP) tholeiites. We conclude that the Re-Os isotope and PGE composition of LSC basalts reflect a relatively pure deep-sourced common mantle sampled by some ocean island basalts but is not discernible in the composition of OJP tholeiites.

  20. Constraints on continental crustal mass loss via chemical weathering using lithium and its isotopes

    NASA Astrophysics Data System (ADS)

    Rudnick, R. L.; Liu, X. M.

    2012-04-01

    The continental crust has an "intermediate" bulk composition that is distinct from primary melts of peridotitic mantle (basalt or picrite). This mismatch between the "building blocks" and the "edifice" that is the continental crust points to the operation of processes that preferentially remove mafic to ultramafic material from the continents. Such processes include lower crustal recycling (via density foundering or lower crustal subduction - e.g., relamination, Hacker et al., 2011, EPSL), generation of evolved melts via slab melting, and/or chemical weathering. Stable isotope systems point to the influence of chemical weathering on the bulk crust composition: the oxygen isotope composition of the bulk crust is distinctly heavier than that of primary, mantle-derived melts (Simon and Lecuyer, 2005, G-cubed) and the Li isotopic composition of the bulk crust is distinctly lighter than that of mantle-derive melts (Teng et al., 2004, GCA; 2008, Chem. Geol.). Both signatures mark the imprint of chemical weathering on the bulk crust composition. Here, we use a simple mass balance model for lithium inputs and outputs from the continental crust to quantify the mass lost due to chemical weathering. We find that a minimum of 15%, a maximum of 60%, and a best estimate of ~40% of the original juvenile rock mass may have been lost via chemical weathering. The accumulated percentage of mass loss due to chemical weathering leads to an average global chemical weathering rate (CWR) of ~ 1×10^10 to 2×10^10 t/yr since 3.5 Ga, which is about an order of magnitude higher than the minimum estimates based on modern rivers (Gaillardet et al., 1999, Chem. Geol.). While we cannot constrain the exact portion of crustal mass loss via chemical weathering, given the uncertainties of the calculation, we can demonstrate that the weathering flux is non-zero. Therefore, chemical weathering must play a role in the evolution of the composition and mass of the continental crust.

  1. Confirmation of mass-independent Ni isotopic variability in iron meteorites

    NASA Astrophysics Data System (ADS)

    Steele, Robert C. J.; Elliott, Tim; Coath, Christopher D.; Regelous, Marcel

    2011-12-01

    We report high-precision analyses of internally-normalised Ni isotope ratios in 12 bulk iron meteorites. Our measurements of 60Ni/ 61Ni, 62Ni/ 61Ni and 64Ni/ 61Ni normalised to 58Ni/ 61Ni and expressed in parts per ten thousand (‱) relative to NIST SRM 986 as ɛ60Ni,ɛ62Ni and ɛ64Ni, vary by 0.146, 0.228 and 0.687, respectively. The precision on a typical analysis is 0.03‱, 0.05‱ and 0.08‱ for ɛ60Ni, ɛ62Ni and ɛ64Ni, respectively, which is comparable to our sample reproducibility. We show that this 'mass-independent' Ni isotope variability cannot be ascribed to interferences, inaccurate correction of instrumental or natural mass-dependent fractionation, fractionation controlled by nuclear field shift effects, nor the influence of cosmic ray spallation. These results thus document the presence of mass-independent Ni isotopic heterogeneity in bulk meteoritic samples, as previously proposed by Regelous et al. (2008) (EPSL 272, 330-338), but our new analyses are more precise and include determination of 64Ni. Intriguingly, we find that terrestrial materials do not yield homogenous internally-normalised Ni isotope compositions, which, as pointed out by Young et al. (2002) (GCA 66, 1095-1104), may be the expected result of using the exponential (kinetic) law and atomic masses to normalise all fractionation processes. The certified Ni isotope reference material NIST SRM 986 defines zero in this study, while appropriate ratios for the bulk silicate Earth are given by the peridotites JP-1 and DTS-2 and, relative to NIST SRM 986, yield deviations in ɛ60Ni, ɛ62Ni and ɛ64Ni of -0.006‱, 0.036‱ and 0.119‱, respectively. There is a strong positive correlation between ɛ64Ni and ɛ62Ni in iron meteorites analyses, with a slope of 3.03 ± 0.71. The variations of Ni isotope anomalies in iron meteorites are consistent with heterogeneous distribution of a nucleosynthetic component from a type Ia supernova into the proto-solar nebula.

  2. Applications of Structural Mass Spectrometry to Metabolomics: Clarifying Bond Specific Spectral Signatures with Isotope Edited Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gorlova, Olga; Wolke, Conrad T.; Fournier, Joseph; Colvin, Sean; Johnson, Mark; Miller, Scott

    2015-06-01

    Comprehensive FTIR, MS/MS and NMR of pharmaceuticals are generally readily available but characterization of their metabolites has been an obstacle. Atorvastatin is a statin drug responsible for the maintenance of cholesterol in the body. Diovan is an angiostensin receptor antagonist used to treat high blood pressure and congestive heart failure. The field of metabolomics, however, is struggling to obtain the identity of their structures. We implement mass spectrometry with cryogenic ion spectroscopy to study gaseous ions of the desired metabolites which, in combination, not only identify the mass of the metabolite but also elucidate their structures through isotope-specific infrared spectroscopy.

  3. Application of nitrogen and carbon stable isotopes (δ(15)N and δ(13)C) to quantify food chain length and trophic structure.

    PubMed

    Perkins, Matthew J; McDonald, Robbie A; van Veen, F J Frank; Kelly, Simon D; Rees, Gareth; Bearhop, Stuart

    2014-01-01

    Increasingly, stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ(15)N, and carbon range (CR) using δ(13)C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ(15)N or δ(13)C from source to consumer) between trophic levels and among food chains. δ(15)N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ(13)C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ(13)C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of

  4. Isotopic mass-dependence of metal cation diffusion coefficients in liquid water

    SciTech Connect

    Bourg, I.C.; Richter, F.M.; Christensen, J.N.; Sposito, G.

    2009-01-11

    Isotope distributions in natural systems can be highly sensitive to the mass (m) dependence of solute diffusion coefficients (D) in liquid water. Isotope geochemistry studies routinely have assumed that this mass dependence either is negligible (as predicted by hydrodynamic theories) or follows a kinetic-theory-like inverse square root relationship (D {proportional_to} m{sup -0.5}). However, our recent experimental results and molecular dynamics (MD) simulations showed that the mass dependence of D is intermediate between hydrodynamic and kinetic theory predictions (D {proportional_to} m{sup -{beta}} with 0 {<=} {beta} < 0.2 for Li{sup +}, Cl{sup -}, Mg{sup 2+}, and the noble gases). In this paper, we present new MD simulations and experimental results for Na{sup +}, K{sup +}, Cs{sup +}, and Ca{sup 2+} that confirm the generality of the inverse power-law relation D {proportional_to} m{sup -{beta}}. Our new findings allow us to develop a general description of the influence of solute valence and radius on the mass dependence of D for monatomic solutes in liquid water. This mass dependence decreases with solute radius and with the magnitude of solute valence. Molecular-scale analysis of our MD simulation results reveals that these trends derive from the exponent {beta} being smallest for those solutes whose motions are most strongly coupled to solvent hydrodynamic modes.

  5. Variations of the glacio-marine air mass front in West Greenland through water vapor isotopes

    NASA Astrophysics Data System (ADS)

    Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

    2012-12-01

    While the isotopic distribution of precipitation has been widely used for research in hydrology, paleoclimatology, and ecology for decades, intensive isotopic studies of atmospheric water vapor has only recently been made possible by spectral-based technology. New instrumentation based on this technology opens up many opportunities to investigate short-term atmospheric dynamics involving the water cycle and moisture transport. We deployed a Los Gatos Water Vapor Isotope Analyzer (WVIA) at Kangerlussuaq, Greenland from July 21 to August 15, and measured the water vapor concentration and its isotopic ratios continuously at 10s intervals. A Danish Meteorological Institute site is located about 1 km from the site of the deployment, and meteorological data is collected at 30 min intervals. During the observation period, the vapor concentration of the ambient air ranges from 5608.4 to 11189.4 ppm; dD and d18O range from -254.5 to -177.7 ‰ and -34.2 to -23.2 ‰, respectively. The vapor content (dew point) and the isotopic ratios are both strongly controlled by the wind direction. The easterly winds are associated with dry, isotopically depleted air masses formed over the glacier, while westerly winds are associated with moist and isotopically enriched air masses from the marine/fjord surface. This region typically experiences katabatic winds off of the ice sheet to the east. However, during some afternoons, the wind shifts 180 degrees, blowing off the fjord to the west. This wind switch marks the onset of a sea breeze, and significant isotopic enrichment results. Enrichment in deuterium is up to 60 ‰ with a mean of 15‰, and oxygen-18 is enriched by 3‰ on average and up to 8 ‰. Other afternoons have no change in wind, and only small changes in humidity and vapor isotopic ratios. The humidity and isotopic variations suggest the local atmosphere circulation is dominated by relatively high-pressure systems above the cold glaciers and cool sea surface, and diurnal

  6. MAST - A mass spectrometer telescope for studies of the isotopic composition of solar, anomalous, and galactic cosmic ray nuclei

    NASA Technical Reports Server (NTRS)

    Cook, Walter R.; Cummings, Alan C.; Cummings, Jay R.; Garrard, Thomas L.; Kecman, Branislav; Mewaldt, Richard A.; Selesnick, Richard S.; Stone, Edward C.; Von Rosenvinge, T. T.

    1993-01-01

    The Mass Spectrometer Telescope (MAST) on SAMPEX is designed to provide high resolution measurements of the isotopic composition of energetic nuclei from He to Ni (Z = 2 to 28) over the energy range from about 10 to several hundred MeV/nuc. During large solar flares MAST will measure the isotopic abundances of solar energetic particles to determine directly the composition of the solar corona, while during solar quiet times MAST will study the isotopic composition of galactic cosmic rays. In addition, MAST will measure the isotopic composition of both interplanetary and trapped fluxes of anomalous cosmic rays, believed to be a sample of the nearby interstellar medium.

  7. Performance and optimization of a combustion interface for isotope ratio monitoring gas chromatography/mass spectrometry.

    PubMed

    Merritt, D A; Freeman, K H; Ricci, M P; Studley, S A; Hayes, J M

    1995-07-15

    Conditions and systems for on-line combustion of effluents from capillary gas chromatographic columns and for removal of water vapor from product streams were tested. Organic carbon in gas chromatographic peaks 15 s wide and containing up to 30 nanomoles of carbon was quantitatively converted to CO2 by tubular combustion reactors, 200 x 0.5 mm, packed with CuO or NiO. No auxiliary source of O2 was required because oxygen was supplied by metal oxides. Spontaneous degradation of CuO limited the life of CuO reactors at T > 850 degrees C. Since NiO does not spontaneously degrade, its use might be favored, but Ni-bound carbon phases form and lead to inaccurate isotopic results at T < 1050 degrees C if gas-phase O2 is not added. For all compounds tested except CH4, equivalent isotopic results are provided by CuO at 850 degrees C, NiO + O2 (gas-phase mole fraction, 10(-3)) at 1050 degrees C and NiO at 1150 degrees C. The combustion interface did not contribute additional analytical uncertainty, thus observed standard deviations of 13C/12C ratios were within a factor of 2 of shot-noise limits. For combustion and isotopic analyses of CH4, in which quantitative combustion required T approximately 950 degrees C, NiO-based systems are preferred, and precision is approximately 2 times lower than that observed for other analytes. Water must be removed from the gas stream transmitted to the mass spectrometer or else protonation of CO2 will lead to inaccuracy in isotopic analyses. Although thresholds for this effect vary between mass spectrometers, differential permeation of H2O through Nafion tubing was effective in both cases tested, but the required length of the Nafion membrane was 4 times greater for the more sensitive mass spectrometer.

  8. Performance and optimization of a combustion interface for isotope ratio monitoring gas chromatography/mass spectrometry

    NASA Technical Reports Server (NTRS)

    Merritt, D. A.; Freeman, K. H.; Ricci, M. P.; Studley, S. A.; Hayes, J. M.

    1995-01-01

    Conditions and systems for on-line combustion of effluents from capillary gas chromatographic columns and for removal of water vapor from product streams were tested. Organic carbon in gas chromatographic peaks 15 s wide and containing up to 30 nanomoles of carbon was quantitatively converted to CO2 by tubular combustion reactors, 200 x 0.5 mm, packed with CuO or NiO. No auxiliary source of O2 was required because oxygen was supplied by metal oxides. Spontaneous degradation of CuO limited the life of CuO reactors at T > 850 degrees C. Since NiO does not spontaneously degrade, its use might be favored, but Ni-bound carbon phases form and lead to inaccurate isotopic results at T < 1050 degrees C if gas-phase O2 is not added. For all compounds tested except CH4, equivalent isotopic results are provided by CuO at 850 degrees C, NiO + O2 (gas-phase mole fraction, 10(-3)) at 1050 degrees C and NiO at 1150 degrees C. The combustion interface did not contribute additional analytical uncertainty, thus observed standard deviations of 13C/12C ratios were within a factor of 2 of shot-noise limits. For combustion and isotopic analyses of CH4, in which quantitative combustion required T approximately 950 degrees C, NiO-based systems are preferred, and precision is approximately 2 times lower than that observed for other analytes. Water must be removed from the gas stream transmitted to the mass spectrometer or else protonation of CO2 will lead to inaccuracy in isotopic analyses. Although thresholds for this effect vary between mass spectrometers, differential permeation of H2O through Nafion tubing was effective in both cases tested, but the required length of the Nafion membrane was 4 times greater for the more sensitive mass spectrometer.

  9. Development and Deployment of Retrofit PolarisQ Ion Trap Mass Spectrometer for Isotope Ratio Measurements

    SciTech Connect

    Thompson, Cyril V.; Whitten, William B.

    2015-11-01

    This report describes Oak Ridge National Laboratory’s (ORNL) FY15 progress in support of National Nuclear Security Administration’s (NNSA) Portable Mass Spectrometer project. A retrofit PolarisQ ion trap mass spectrometer (RPMS) has been assembled from components of two PolarisQ ion trap mass spectrometers used in previous isotope ratio programs. The retrofit mass spectrometer includes a custom Hastelloy vacuum chamber which is about ¼ the size of the standard aluminum vacuum chamber and reduces the instrument weight from the original by nine pounds. In addition, the new vacuum chamber can be independently heated to reduce impurities such as water, which reacts with UF6 to produce HF in the vacuum chamber. The analyzer and all components requiring service are mounted on the chamber lid, facilitating quick and easy replacement of consumable components such as the filament and electron multiplier.

  10. Measuring technique for thermal ionisation mass spectrometry of human tracer kinetic study with stable cerium isotopes.

    PubMed

    Keiser, Teresa; Höllriegl, Vera; Giussani, Augusto; Oeh, Uwe

    2011-06-01

    Thermal ionisation mass spectrometry (TIMS) method has been developed for the simultaneous detection of different cerium isotopes in biological samples (i.e., blood and urine) at very low concentrations. The work has been done in the frame of a biokinetic study, where different stable cerium isotopes have been administered orally and intravenously as tracers to the human body. In order to develop an appropriate detection method for the tracers in the biological samples, an optimum sample preparation technique has been set and adapted to the specific requirements of the analysis technique used, i.e., TIMS. For sample evaporation and ionisation, the double tantalum filament technique showed the best results. The ions produced were simultaneously collected on a secondary electron multiplier so that the isotopic ratios of the cerium isotopes in the biological samples could be measured. The technique has been optimised for the determination of cerium down to 1 ng loaded on the evaporation filament corresponding to cerium concentrations of down to 1 ng ml(-1) in the blood or urine samples. It has been shown that the technique is reliable in application and enables studies on cerium metabolism and biokinetics in humans without employing radioactive tracers.

  11. Advancement and application of gas chromatography isotope ratio mass spectrometry techniques for atmospheric trace gas analysis

    NASA Astrophysics Data System (ADS)

    Giebel, Brian M.

    2011-12-01

    The use of gas chromatography isotope ratio mass spectrometry (GC-IRMS) for compound specific stable isotope analysis is an underutilized technique because of the complexity of the instrumentation and high analytical costs. However stable isotopic data, when coupled with concentration measurements, can provide additional information on a compounds production, transformation, loss, and cycling within the biosphere and atmosphere. A GC-IRMS system was developed to accurately and precisely measure delta13C values for numerous oxygenated volatile organic compounds having natural and anthropogenic sources. The OVOCs include methanol, ethanol, acetone, methyl ethyl ketone, 2-pentanone, and 3-pentanone. Guided by the requirements for analysis of trace components in air, the GC-IRMS system was developed with the goals of increasing sensitivity, reducing dead-volume and peak band broadening, optimizing combustion and water removal, and decreasing the split ratio to the IRMS. The technique relied on a two-stage preconcentration system, a low-volume capillary reactor and water trap, and a balanced reference gas delivery system. Measurements were performed on samples collected from two distinct sources (i.e. biogenic and vehicle emissions) and ambient air collected from downtown Miami and Everglades National Park. However, the instrumentation and the method have the capability to analyze a variety of source and ambient samples. The measured isotopic signatures that were obtained from source and ambient samples provide a new isotopic constraint for atmospheric chemists and can serve as a new way to evaluate their models and budgets for many OVOCs. In almost all cases, OVOCs emitted from fuel combustion were enriched in 13C when compared to the natural emissions of plants. This was particularly true for ethanol gas emitted in vehicle exhaust, which was observed to have a uniquely enriched isotopic signature that was attributed to ethanol's corn origin and use as an alternative

  12. Assessment of Non-traditional Isotopic Ratios by Mass Spectrometry for Analysis of Nuclear Activities. Annual Report 2011

    SciTech Connect

    Biegalski, Steven R.; Buchholz, Bruce A.

    2011-08-24

    The objective of this work is to identify isotopic ratios suitable for analysis via mass spectrometry that distinguish between commercial nuclear reactor fuel cycles, fuel cycles for weapons grade plutonium, and products from nuclear weapons explosions. Methods will also be determined to distinguish the above from medical and industrial radionuclide sources. Mass spectrometry systems will be identified that are suitable for field measurement of such isotopes in an expedient manner.

  13. Isolation and derivatization of plasma taurine for stable isotope analysis by gas chromatography-mass spectrometry

    SciTech Connect

    Irving, C.S.; Klein, P.D.

    1980-09-01

    A method for the isolation and derivatization of plasma taurine is described that allows stable isotope determinations of taurine to be made by gas chromatography-mass spectrometry. The isolation procedure can be applied to 0.1 ml of plasma; the recovery of plasma taurine was 70 to 80%. For gc separation, taurine was converted to its dimethylaminomethylene methyl ester derivative which could not be detected by hydrogen flame ionization, but could be monitored readily by NH/sub 3/ chemical ionization mass spectrometry. The derivatization reaction occurred partially on-column and required optimization of injection conditions. Using stable isotope ratiometry multiple ion detection, (M + 2 + H)/sup +//(M + H)/sup +/ ion ratio of natural abundance taurine was determined with a standard deviation of less than +-0.07% of the ratio. The (1,2-/sup 13/C)taurine/taurine mole ratios of standard mixtures could be accurately determined to 0.001. This stable isotope gc-ms method is suitable for studying the plasma kinetics of (1,2-/sup 13/C)taurine in infants who are at risk with respect to taurine depletion.

  14. Stable nitrogen isotope ratios and accumulation of PCDD/F and PCB in Baltic aquatic food chains

    SciTech Connect

    Broman, D.; Naef, C.; Rolff, C.; Zebuehr, Y.

    1994-12-31

    Ratios of naturally occurring stable isotopes of nitrogen ({delta}{sup 15}N) can be used to numerically classify trophic levels of organisms in food chains. By combining analyses results of PCDD/Fs and non-ortho PCBs the biomagnification of these substances can be quantitatively estimated. The two Baltic food chains studied were one pelagic (phytoplankton -- settling particulate matter (SPM) -- zooplankton -- mysids -- herring -- cod) and one littoral (phytoplankton -- SPM -- blue mussel -- eider duck). The {delta}{sup 15}N-data gave food chain descriptions qualitatively consistent with previous conceptions of trophic arrangements in the food chains. Phytoplankton showed the lowest average {delta}{sup 15}N-value and the juvenile eider duck and the cod showed the highest average {delta}{sup 15}N-values for the littoral and pelagic food chains, respectively. The PCDD/Fs and PCBs concentrations were plotted versus the {delta}{sup 15}N-values for the different trophic levels and an exponential model of the form e{sup (A + B*{delta}N)} was fitted to the data. The estimates of the constant B in the model allows for an estimation of a biomagnification power (B) of different singular, or groups of, contaminants. A B-value around zero indicates that a substance is flowing through the food chain without being magnified, whereas a value > 0 indicates that a substance is biomagnified. Negative B-values indicate that a substance is not taken up or is metabolized. The A-term of the expression is only a scaling factor depending on the background level of the contaminant.

  15. Water masses along the OVIDE 2010 section as identified by oxygen and hydrogen stable isotope values

    NASA Astrophysics Data System (ADS)

    Voelker, Antje; Salgueiro, Emilia; Thierry, Virginie

    2016-04-01

    The OVIDE transect between the western Iberian Peninsula and the southern tip of Greenland is one of the hydrographic sections in the North Atlantic that is measured regularly to identify changes in water mass formation and transport and thus to evaluate the state of the Atlantic Meridional Overturning Circulation (Mercier et al., 2015; García-Ibáñez et al., 2015; both in Progr. in Oceanography). During the OVIDE 2010 campaign seawater samples covering the complete water column were collected on the section between Portugal and the Reykjanes ridge for stable isotope analyses. Oxygen (δ18O) and hydrogen (δD) stable isotope values were measured simultaneously by cavity ring-down laser spectroscopy using a L1102-i Picarro water isotope analyser at the Godwin Laboratory for Paleoclimate Research (Univ. Cambridge, UK). Within the upper water column the stable isotope values clearly mark the positions of the Portugal Current (40.3°N 11°W), the North Atlantic Drift (46.2°N 19.4°W) and of the subarctic front (51°N 23.5°W). Up to Station 36 (47.7°N 20.6°W) an upper (around 600 m) and lower (around 1000 m) branch of the Mediterranean Outflow water (MOW) can clearly be distinguished by high oxygen (0.5-0.7‰) and hydrogen (3-5‰) values. At Station 28 (42.3°N 15.1°W) strong MOW influence is also indicated between 1400 and 1600 m. In the west European Basin, lower oxygen isotope values reveal the presence of Labrador Sea Water (LSW) below the MOW (down to 2200 m). Close to and west of the subarctic front this water mass shallows and occupies the complete interval between 1000 and 2000 m water depth. In the Iceland basin, two additional levels with lower oxygen isotope values are observed. The deeper level (2200-3500 m) marks Iceland Scotland Overflow Water (ISOW) that based on its distinct isotopic signature (δ18O ≤ 0.25‰) can be traced as far east as 18.5°W (down to at least 3500 m). Close to the Reykjanes ridge both, the ISOW and LSW, are also

  16. Simultaneous measurement of denitrification and nitrogen fixation using isotope pairing with membrane inlet mass spectrometry analysis.

    PubMed

    An, S; Gardner, W S; Kana, T

    2001-03-01

    A method for estimating denitrification and nitrogen fixation simultaneously in coastal sediments was developed. An isotope-pairing technique was applied to dissolved gas measurements with a membrane inlet mass spectrometer (MIMS). The relative fluxes of three N(2) gas species ((28)N(2), (29)N(2), and (30)N(2)) were monitored during incubation experiments after the addition of (15)NO(3)(-). Formulas were developed to estimate the production (denitrification) and consumption (N(2) fixation) of N(2) gas from the fluxes of the different isotopic forms of N(2). Proportions of the three isotopic forms produced from (15)NO(3)(-) and (14)NO(3)(-) agreed with expectations in a sediment slurry incubation experiment designed to optimize conditions for denitrification. Nitrogen fixation rates from an algal mat measured with intact sediment cores ranged from 32 to 390 microg-atoms of N m(-2) h(-1). They were enhanced by light and organic matter enrichment. In this environment of high nitrogen fixation, low N(2) production rates due to denitrification could be separated from high N(2) consumption rates due to nitrogen fixation. Denitrification and nitrogen fixation rates were estimated in April 2000 on sediments from a Texas sea grass bed (Laguna Madre). Denitrification rates (average, 20 microg-atoms of N m(-2) h(-1)) were lower than nitrogen fixation rates (average, 60 microg-atoms of N m(-2) h(-1)). The developed method benefits from simple and accurate dissolved-gas measurement by the MIMS system. By adding the N(2) isotope capability, it was possible to do isotope-pairing experiments with the MIMS system.

  17. Light Isotopes and Trace Organics Analysis of Mars Samples with Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Mahaffy, P.; Niemann, Hasso (Technical Monitor)

    2001-01-01

    Precision measurement of light isotopes in Mars surface minerals and comparison of this isotopic composition with atmospheric gas and other, well-mixed reservoirs such as surface dust are necessary to understand the history of atmospheric evolution from a possibly warmer and wetter Martian surface to the present state. Atmospheric sources and sinks that set these ratios are volcanism, solar wind sputtering, photochemical processes, and weathering. Measurement of a range of trace organic species with a particular focus on species such as amino acids that are the building blocks of terrestrial life are likewise important to address the questions of prebiotic and present or past biological activity on Mars. The workshop topics "isotopic mineralogy" and "biology and pre-biotic chemistry" will be addressed from the point of view of the capabilities and limitations of insitu mass spectrometry (MS) techniques such as thermally evolved gas analysis (TEGA) and gas chromatography (GC) surface experiments using MS, in both cases, as a final chemical and isotopic composition detector. Insitu experiments using straightforward adaptations of existing space proven hardware can provide a substantial improvement in the precision and accuracy of our present knowledge of isotopic composition both in molecular and atomic species in the atmosphere and those chemically bound in rocks and soils. Likewise, detection of trace organic species with greatly improved sensitivity from the Viking GCMS experiment is possible using gas enrichment techniques. The limits to precision and accuracy of presently feasible insitu techniques compared to laboratory analysis of returned samples will be explored. The insitu techniques are sufficiently powerful that they can provide a high fidelity method of screening samples obtained from a diverse set of surface locations such as the subsurface or the interior of rocks for selection of those that are the most interesting for return to Earth.

  18. Photon Scattering from the Stable Even-Mass Mo Isotopes Below the Neutron-Separation Energy

    NASA Astrophysics Data System (ADS)

    Rusev, G.; Hutcheson, A.; Kwan, E.; Tonchev, A. P.; Tornow, W.; Angell, C.; Hammond, S.; Karwowski, H. J.; Kelley, J. H.; Schwengner, R.; Dönau, F.; Wagner, A.

    2008-10-01

    We present results from photon-scattering experiments on the stable even-mass molybdenum isotopes below the neutron-separation energy carried out with bremsstrahlung at the superconducting electron accelerator ELBE at the Research Center Dresden-Rossendorf in Germany, and with monoenergetic photon beams at the HIγS facility at TUNL. We applied statistical methods in order to correct for the branching and cascade transitions and to determine the photoabsorption cross section. The obtained results allowed us to extend the tail of the Giant Dipole Resonance below the (,) threshold down to 4 MeV. The photoabsorption cross sections deduced from the present experiments show that the dipole strength increases with the neutron number of the Mo isotopes. The experimental results are discussed in the frame of Quasiparticle-Random-Phase-Approximation in a deformed basis which describe the increasing strength as a result of the deformation.

  19. Multiple S-isotopic evidence for episodic shoaling of anoxic water during Late Permian mass extinction.

    PubMed

    Shen, Yanan; Farquhar, James; Zhang, Hua; Masterson, Andrew; Zhang, Tonggang; Wing, Boswell A

    2011-02-22

    Global fossil data show that profound biodiversity loss preceded the final catastrophe that killed nearly 90% marine species on a global scale at the end of the Permian. Many hypotheses have been proposed to explain this extinction and yet still remain greatly debated. Here, we report analyses of all four sulphur isotopes ((32)S, (33)S, (34)S and (36)S) for pyrites in sedimentary rocks from the Meishan section in South China. We observe a sulphur isotope signal (negative δ(34)S with negative Δ(33)S) that may have resulted from limitation of sulphate supply, which may be linked to a near shutdown of bioturbation during shoaling of anoxic water. These results indicate that episodic shoaling of anoxic water may have contributed to the profound biodiversity crisis before the final catastrophe. Our data suggest a prolonged deterioration of oceanic environments during the Late Permian mass extinction.

  20. Multiple S-isotopic evidence for episodic shoaling of anoxic water during Late Permian mass extinction

    PubMed Central

    Shen, Yanan; Farquhar, James; Zhang, Hua; Masterson, Andrew; Zhang, Tonggang; Wing, Boswell A.

    2011-01-01

    Global fossil data show that profound biodiversity loss preceded the final catastrophe that killed nearly 90% marine species on a global scale at the end of the Permian. Many hypotheses have been proposed to explain this extinction and yet still remain greatly debated. Here, we report analyses of all four sulphur isotopes (32S, 33S, 34S and 36S) for pyrites in sedimentary rocks from the Meishan section in South China. We observe a sulphur isotope signal (negative δ34S with negative Δ33S) that may have resulted from limitation of sulphate supply, which may be linked to a near shutdown of bioturbation during shoaling of anoxic water. These results indicate that episodic shoaling of anoxic water may have contributed to the profound biodiversity crisis before the final catastrophe. Our data suggest a prolonged deterioration of oceanic environments during the Late Permian mass extinction. PMID:21343928

  1. Laser ablation inductively coupled plasma mass spectrometry measurement of isotope ratios in depleted uranium contaminated soils.

    PubMed

    Seltzer, Michael D

    2003-09-01

    Laser ablation of pressed soil pellets was examined as a means of direct sample introduction to enable inductively coupled plasma mass spectrometry (ICP-MS) screening of soils for residual depleted uranium (DU) contamination. Differentiation between depleted uranium, an anthropogenic contaminant, and naturally occurring uranium was accomplished on the basis of measured 235U/238U isotope ratios. The amount of sample preparation required for laser ablation is considerably less than that typically required for aqueous sample introduction. The amount of hazardous laboratory waste generated is diminished accordingly. During the present investigation, 235U/238U isotope ratios measured for field samples were in good agreement with those derived from gamma spectrometry measurements. However, substantial compensation was required to mitigate the effects of impaired pulse counting attributed to sample inhomogeneity and sporadic introduction of uranium analyte into the plasma.

  2. Changes in Holocene to LGM water mass stratification near Southern Africa inferred from Nd isotopes

    NASA Astrophysics Data System (ADS)

    Jones, K. M.; Goldstein, S. L.; Hemming, S. R.; Hall, I. R.; Zahn, R.

    2009-12-01

    Global thermohaline circulation (THC) is an important component of the climate system that initiates or amplifies abrupt climate change. A major driver of THC is the formation of North Atlantic Deep Water (NADW), which is sandwiched by northward flowing Southern Ocean water masses as it is advected southward. An important exit route of NADW out of the South Atlantic is through flow around the southern tip of Africa, which makes the South African Margin an excellent location to investigate changes in THC and water mass stratification through time. We measured the Nd isotopes of modern seawater from three depth profiles collected along the South African Margin, which were collected on RSS Charles Darwin Cruise 154. All seawater profiles show a similar pattern with higher ɛNd values at intermediate depths (ɛNd ~ -9.5 at 600-1200m), lower values for the core of NADW (ɛNd ~ -11.5 at 2000-3500m), and higher values in the deepest waters sampled (ɛNd -9.8 at 4150m). This pattern is consistent with conservative mixing of major North Atlantic and Southern Ocean end-member water masses and is not consistent with inputs from, or exchange with margin sediments, for most depths. We also measured the Nd isotopes of multiple sedimentary archives in proximal Holocene coretop sediments collected from depths spanning intermediate to deep/bottom waters. The Nd isotopes of a fish tooth, several foram coating leachates, and multiple bulk sediment Fe-Mn leachates display the same pattern as the local seawater. We had no seawater for comparison with our deepest core (VM19-224; depth ~ 4600m), but the eNd value from it (ɛNd = -8.4) is consistent with Antarctic Bottom Water (ɛNd ~ -8.5). These results suggest: (1) that Nd isotopes of seawater in the region behave conservatively; (2) that the local margin sediments faithfully record the Nd isotope composition of the waters they are bathed in and (3) this “ground-truthing” implies that it is valid to use Nd isotopes as a circulation

  3. Evaluation of meteoric calcite cements as a proxy material for mass-47 clumped isotope thermometry

    NASA Astrophysics Data System (ADS)

    Defliese, William F.; Lohmann, Kyger C.

    2016-01-01

    Meteoric diagenetic cements are ubiquitous throughout geologic history, affecting most carbonate exposures worldwide. They can often be difficult to interpret, as it is usually difficult to separate the influences of water δ18O and temperature on isotopic signals contained within the carbonate rock body. Despite this difficulty in interpretation, meteoric phreatic cements can potentially be a useful proxy material, as they form slowly in equilibrium at mean annual temperature and are not affected by any biogenic effects that can bias other proxy materials. We applied the mass-47 clumped isotope paleothermometer to Pleistocene and Holocene carbonates from Bermuda and Barbados in order to investigate the effects of meteoric diagenesis on Δ47 signals, and to determine their suitability as a paleotemperature proxy. Phreatic calcite cements are found to record the same temperatures as unaltered carbonate sediments, while any sample exhibiting vadose characteristics is biased towards unreasonably hot apparent formation temperatures. Burial heating and re-equilibration are not geologically viable explanations for the anomalously hot temperatures recorded in vadose cements, as neither Bermuda or Barbados has any burial history. Instead, it is likely that precipitation in the vadose zone occurs on timescales quicker than isotopic equilibrium can be achieved, driven by a combination of CO2 degassing and evaporation, which have been previously shown to cause problems in speleothems and pedogenic carbonates. We conclude by suggesting that meteoric phreatic calcites may be an ideal phase for paleotemperature reconstruction, as they accurately record mean annual temperatures and form under equilibrium conditions, while also being resistant to further mineral driven diagenesis. Vadose cements, and any sample likely affected by processes similar to vadose diagenesis, should be avoided for climate reconstructions using the mass-47 clumped isotope thermometer.

  4. Use of stable carbon and nitrogen isotopes to trace the larval striped bass food chain in the Sacramento-San Joaquin Estuary, California, April to September 1985

    USGS Publications Warehouse

    Rast, Walter; Sutton, J.E.

    1989-01-01

    To assess one potential cause for the decline of the striped bass fishery in the Sacramento-San Joaquin Estuary, stable carbon and nitrogen isotope ratios were used to examine the trophic structures of the larval striped bass food chain, and to trace the flux of these elements through the food chain components. Study results generally confirm a food chain consisting of the elements, phytoplankton/detritus-->zooplankton/Neomysis shrimp-->larval striped bass. The stable isotope ratios generally become more positive as one progresses from the lower to the higher trophic level food chain components, and no unusual trophic structure was found in the food chain. However, the data indicate an unidentified consumer organism occupying an intermediate position between the lower and higher trophic levels of the larval striped bass food chain. Based on expected trophic interactions, this unidentified consumer would have a stable carbon isotope ratio of about 28/mil and a stable nitrogen isotope ratio of about 8/mi. Three possible feeding stages for larval striped bass also were identified, based on their lengths. The smallest length fish seem to subsist on their yolk sac remnants, and the largest length fish subsist on Neomysis shrimp and zooplankton. The intermediate-length fish represent a transition stage between primary food sources and/or use of a mixture of food sources. (USGS)

  5. Integration of Stable Isotope and other Mass Spectral Data for Microbial Forensics

    NASA Astrophysics Data System (ADS)

    Kreuzer-Martin, H. W.; Jarman, K. H.

    2008-12-01

    The nascent field of microbial forensics requires the development of diverse signatures as indicators of various aspects of the production environment of microorganisms. We have characterized isotopic relationships between Bacillus subtilis ATCC 6051 spores and their growth environment, using as a database the carbon, nitrogen, oxygen and hydrogen stable isotope ratios of a total of 247 separate cultures of spores produced on a total of 32 different culture media. We have analyzed variation within individual samples, between cultures produced in tandem, and between cultures produced in the same medium but at different times in the context of using stable isotope ratios as a signature for sample matching. We have correlated the stable isotope ratios of carbon, nitrogen, oxygen, and hydrogen of growth medium nutrients or water and spores and show examples of how these relationships can be used to exclude nutrient or water samples as possible growth substrates for specific cultures. The power of stable isotope ratio data can be greatly enhanced by combining it with orthogonal datasets that speak to different aspects of an organism's production environment. We developed a Bayesian network that follows the causal relationship from culture medium recipe to spore elemental content as measured by secondary ion mass spectrometry (SIMS), carbon and nitrogen stable isotope ratios, and to the presence of residual agar by electrospray ionization MS (ESI-MS). The network was developed and tested on data from three replicate cultures of B. subtilis ATCC 49760 in broth and agar-containing versions of four different nutrient media. To test the network, data from SIMS analyses of B. subtilis 49760 produced in a different medium, from approximately 200 ESI MS analyses of B. thuringensis ATCC 58890 and B. anthracis Sterne grown in five additional media, and the stable isotope data from the 247 cultures of B. subtilis 6051 spores were used. This network was able to characterize

  6. A novel approach for the chromatographic purification and peptide mass fingerprinting of urinary free light chains.

    PubMed

    Mali, Bhupesh C; Badgujar, Shamkant B; Shukla, Kunal K; Bhanushali, Paresh B

    2017-02-01

    We describe a chromatographic approach for the purification of urinary free light chains (FLCs) viz., lambda free light chains (λ-FLCs) and kappa free light chains (κ-FLCs). Isolated urinary FLCs were analyzed by SDS-PAGE, immunoblotting and mass spectrometry (MS). The relative molecular masses of λ-FLC and κ-FLC are 22,933.397 and 23,544.336Da respectively. Moreover, dimer forms of each FLC were also detected in mass spectrum which corresponds to 45,737.747 and 47,348.028Da respectively for λ-FLCs and κ-FLCs. Peptide mass fingerprint analysis of the purified λ-FLCs and κ-FLCs has yielded peptides that partially match with known light chain sequences viz., gi|218783338 and gi|48475432 respectively. The tryptic digestion profile of isolated FLCs infers the exclusive nature of them and they may be additive molecules in the dictionary of urinary proteins. This is the first report of characterization and validation of FLCs from large volume samples by peptide sequencing. This simple and cost-effective approach to purification of FLCs, together with the easy availability of urine samples make the large-scale production of FLCs possible, allowing exploration of various bioclinical as well as biodiagnostic applications.

  7. Detection and analysis of polymerase chain reaction products by mass spectrometry

    SciTech Connect

    Hurst, G.B., Doktycz, M.J., Britt, P.F., Vass, A.A., Buchanan, M.V.

    1997-02-01

    This paper describes recent and ongoing efforts to overcome some of the obstacles to more routine and robust application of MALDI-TOF to analysis of polymerase chain reaction products and other information- bearing nucleic acid molecules. Methods for purifying nucleic acid samples are described, as is the application of delayed extraction TOF mass spectrometry to analysis of short oligonucleotides.

  8. Positive parity low spin states of odd-mass tellurium isotopes

    NASA Astrophysics Data System (ADS)

    Yazar, Harun Reşit

    2006-11-01

    In this work, we analyse the positive parity of states of odd-mass nucleus within the framework of interacting boson fermion model. The result of an IBFM-1 multilevel calculation with the lg 9/2, 2d 5/2, 2d 3/2, 3s 1/2 and one level, 1h 11/2 with negative parity, single particle orbits is reported for the positive parity states of the odd mass nucleus 123-125Te. Also, an IBM-1 calculation is presented for the low-lying states in the even-even 124-126Te core nucleus. The energy levels and B (E2) transition probabilities were calculated and compared with the experimental data. It was found that the calculated positive parity low spin state energy spectra of the odd-mass 123-125Te isotopes agree quite well with the experimental data.

  9. Determination of short chain carboxylic acids in vegetable oils and fats using ion exclusion chromatography electrospray ionization mass spectrometry.

    PubMed

    Viidanoja, Jyrki

    2015-02-27

    A new method for quantification of short chain C1-C6 carboxylic acids in vegetable oils and fats by employing Liquid Chromatography Mass Spectrometry (LC-MS) has been developed. The method requires minor sample preparation and applies non-conventional Electrospray Ionization (ESI) liquid phase chemistry. Samples are first dissolved in chloroform and then extracted using water that has been spiked with stable isotope labeled internal standards that are used for signal normalization and absolute quantification of selected acids. The analytes are separated using Ion Exclusion Chromatography (IEC) and detected with Electrospray Ionization Mass Spectrometry (ESI-MS) as deprotonated molecules. Prior to ionization the eluent that contains hydrochloric acid is modified post-column to ensure good ionization efficiency of the analytes. The averaged within run precision and between run precision were generally lower than 8%. The accuracy was between 85 and 115% for most of the analytes. The Lower Limit of Quantification (LLOQ) ranged from 0.006 to 7mg/kg. It is shown that this method offers good selectivity in cases where UV detection fails to produce reliable results.

  10. Analytical Validation of Accelerator Mass Spectrometry for Pharmaceutical Development: the Measurement of Carbon-14 Isotope Ratio.

    SciTech Connect

    Keck, B D; Ognibene, T; Vogel, J S

    2010-02-05

    Accelerator mass spectrometry (AMS) is an isotope based measurement technology that utilizes carbon-14 labeled compounds in the pharmaceutical development process to measure compounds at very low concentrations, empowers microdosing as an investigational tool, and extends the utility of {sup 14}C labeled compounds to dramatically lower levels. It is a form of isotope ratio mass spectrometry that can provide either measurements of total compound equivalents or, when coupled to separation technology such as chromatography, quantitation of specific compounds. The properties of AMS as a measurement technique are investigated here, and the parameters of method validation are shown. AMS, independent of any separation technique to which it may be coupled, is shown to be accurate, linear, precise, and robust. As the sensitivity and universality of AMS is constantly being explored and expanded, this work underpins many areas of pharmaceutical development including drug metabolism as well as absorption, distribution and excretion of pharmaceutical compounds as a fundamental step in drug development. The validation parameters for pharmaceutical analyses were examined for the accelerator mass spectrometry measurement of {sup 14}C/C ratio, independent of chemical separation procedures. The isotope ratio measurement was specific (owing to the {sup 14}C label), stable across samples storage conditions for at least one year, linear over 4 orders of magnitude with an analytical range from one tenth Modern to at least 2000 Modern (instrument specific). Further, accuracy was excellent between 1 and 3 percent while precision expressed as coefficient of variation is between 1 and 6% determined primarily by radiocarbon content and the time spent analyzing a sample. Sensitivity, expressed as LOD and LLOQ was 1 and 10 attomoles of carbon-14 (which can be expressed as compound equivalents) and for a typical small molecule labeled at 10% incorporated with {sup 14}C corresponds to 30 fg

  11. Radium isotopes to investigate the water mass pathways on the Kerguelen plateau (KEOPS project)

    NASA Astrophysics Data System (ADS)

    Bourquin, M.; van Beek, P.; Reyss, J.; Souhaut, M.; Charette, M.; Jeandel, C.

    2006-12-01

    High biological productivity takes place on the Kerguelen Plateau in the Indian sector of the Southern Ocean known to be a HNLC region. Natural iron fertilization is suspected in that area. One goal of the KEOPS project is to understand the mechanisms controlling iron fertilization. We measured radium isotopes (228Ra, T1/2=5.75 y; 226Ra, T1/2=1602 y) in seawater in order to provide information on the water mass pathways on the Kerguelen plateau. Ra isotopes are produced in the sediment and diffuse in the water column. Ra isotopes may thus be a good analogue for tracing the input of sedimentary iron and its fate on the Kerguelen Plateau. The large volumes of seawater needed for Ra analysis were collected using either the ship-intake, Niskin bottles or in-situ pumping. MnO2 fibers were then used to separate Ra from seawater. 228Ra activities are extremely low in the plateau area, being in most cases <0.1 dpm/100 kg (ca. 1 ag/kg). Station A3 (520 m depth), located on the plateau in the middle of the bloom zone, also displays such low values with, however, higher 228Ra activities in the upper 50-150 m. Such a pattern suggests the presence of a water mass that has been advected on the Kerguelen Plateau. This water mass could have been enriched in 228Ra in contact with the sediment of Heard Island, south of the Kerguelen Plateau. The Ra data agree with the REE results of Zhang et al.

  12. Stable isotope mass balances versus concentration differences of dissolved inorganic carbon - implications for tracing carbon turnover in reservoirs.

    PubMed

    Barth, Johannes A C; Mader, Michael; Nenning, Franziska; van Geldern, Robert; Friese, Kurt

    2017-02-13

    The aim of this study was to identify sources of carbon turnover using stable isotope mass balances. For this purpose, two pre-reservoirs in the Harz Mountains (Germany) were investigated for their dissolved and particulate carbon contents (dissolved inorganic carbon (DIC), dissolved organic carbon, particulate organic carbon) together with their stable carbon isotope ratios. DIC concentration depth profiles from March 2012 had an average of 0.33 mmol L(-1). Increases in DIC concentrations later on in the year often corresponded with decreases in its carbon isotope composition (δ(13)CDIC) with the most negative value of -18.4 ‰ in September. This led to a carbon isotope mass balance with carbon isotope inputs of -28.5 ‰ from DOC and -23.4, -31.8 and -30.7 ‰ from algae, terrestrial and sedimentary matter, respectively. Best matches between calculated and measured DIC gains were achieved when using the isotope composition of algae. This shows that this type of organic material is most likely responsible for carbon additions to the DIC pool when its concentrations and δ(13)CDIC values correlate negatively. The presented isotope mass balance is transferable to other surface water and groundwater systems for quantification of organic matter turnover.

  13. Determination of tin isotope ratios in cassiterite by femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Schulze, Marie; Ziegerick, Marco; Horn, Ingo; Weyer, Stefan; Vogt, Carla

    2017-04-01

    In comparison to isotope analysis of dissolved samples femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry (fs-LA-MC-ICP-MS) enables precise isotope ratio analyses consuming much less sample material and with a minimum effort in sample preparation. This is especially important for the investigation of valuable historical objects for which visual traces of sampling are unwanted. The present study provides a basis for tin isotope ratio measurements using LA-MC-ICP-MS technique. For this, in house isotope standards had to be defined. Investigations on interferences and matrix effects illustrate that beside Sb only high Te contents (with values above those to be expected in cassiterite) result in a significant shift of the measured tin isotope ratios. This effect can partly be corrected for using natural isotope abundances. However, a natural isotope fractionation of Te cannot be excluded. Tin beads reduced from cassiterite were analysed by laser ablation and after dissolution. It was shown that tin isotope ratios can be determined accurately by using fs-LA-MC-ICP-MS. Furthermore the homogeneity of tin isotope ratios in cassiterite was proven.

  14. New FORTRAN computer programs to acquire and process isotopic mass spectrometric data: Operator`s manual

    SciTech Connect

    Smith, D.H.; McKown, H.S.

    1993-09-01

    This TM is one of a pair that describes ORNL-developed software for acquisition and processing of isotope ratio mass spectral data. This TM is directed at the laboratory analyst. No technical knowledge of the programs and programming is required. It describes how to create and edit files, how to acquire and process data, and how to set up files to obtain the desired results. The aim of this TM is to serve as a utilitarian instruction manual, a {open_quotes}how to{close_quotes} approach rather than a {open_quotes}why?{close_quotes}

  15. Stable isotope labeling of entire Bacillus atrophaeus spores and vegetative cells using bioaerosol mass spectrometry.

    PubMed

    Czerwieniec, Gregg A; Russell, Scott C; Tobias, Herbert J; Pitesky, Maurice E; Fergenson, David P; Steele, Paul; Srivastava, Abneesh; Horn, Joanne M; Frank, Matthias; Gard, Eric E; Lebrilla, Carlito B

    2005-02-15

    Single vegetative cells and spores of Bacillus atrophaeus, formerly Bacillus subtilis var. niger, were analyzed using bioaerosol mass spectrometry. Key biomarkers were identified from organisms grown in 13C and 15N isotopically enriched media. Spore spectra contain peaks from dicipolinate and amino acids. The results indicate that compounds observed in the spectra correspond to material from the spore's core and not the exosporium. Standard compounds and mixtures were analyzed for comparison. The biomarkers for vegetative cells were clearly different from those of the spores, consisting mainly of phosphate clusters and amino acid fragments.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Mass flow and compositional gradient (elemental and isotope separation) occur when fluid(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been experimentally and theoretically investigated for more than a century, although there has not been a satisfactory theory to date. Nevertheless, theories predict that when dealing with a multi-isotope system, such as O16-O17-O18, S32-S33-S34-S36, or Ne20-Ne21-Ne22, the mass difference is the only term in the thermal diffusion separation factors that distinguish one isotope pair from another. Thus a mass dependent relationship is expected. For O-bearing molecules the α17O/ α 18O is expected to be at 0.5 to 0.515, and for S-bearing molecules the α33S/ α 34S at 0.5 to 0.508, where α is isotope fractionation factor between cold and warm reservoirs. We recently reported that thermal diffusion generates non-mass dependent (NMD) isotope fractionation for low-pressure O2 and SF6 gases. The observed NMD phenomenon in the simple thermal-diffusion experiments demands quantitative validation and theoretical explanation. It was suggested that additional (not mass related) terms need to be theoretically considered in the order to account for the observations. In addition to the pressure and temperature dependency illustrated in our earlier report, the role of turbulence, batch gas effects, and whether it is only a transient, non-equilibrium effect have been examined in this study. We report here new results on low-pressure O2 gas thermal diffusion. (1) In a purely diffusive vertical two-bulb setting with colder reservoir at lower position, time course experiments showed that the NMD effect persists after the system reaches isotopic steady state between warmer and colder compartments, suggesting that the effect is not a transient one. (2) When the average temperature approaching condensation point for O2, the 17O switches to migrating

  17. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification

    PubMed Central

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-01-01

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents. PMID:27713563

  18. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification.

    PubMed

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-10-07

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents.

  19. Tailoring Thermal Conductivity of Single-stranded Carbon-chain Polymers through Atomic Mass Modification

    NASA Astrophysics Data System (ADS)

    Liao, Quanwen; Zeng, Lingping; Liu, Zhichun; Liu, Wei

    2016-10-01

    Tailoring the thermal conductivity of polymers is central to enlarge their applications in the thermal management of flexible integrated circuits. Progress has been made over the past decade by fabricating materials with various nanostructures, but a clear relationship between various functional groups and thermal properties of polymers remains to be established. Here, we numerically study the thermal conductivity of single-stranded carbon-chain polymers with multiple substituents of hydrogen atoms through atomic mass modification. We find that their thermal conductivity can be tuned by atomic mass modifications as revealed through molecular dynamics simulations. The simulation results suggest that heavy homogeneous substituents do not assist heat transport and trace amounts of heavy substituents can in fact hinder heat transport substantially. Our analysis indicates that carbon chain has the biggest contribution (over 80%) to the thermal conduction in single-stranded carbon-chain polymers. We further demonstrate that atomic mass modifications influence the phonon bands of bonding carbon atoms, and the discrepancies of phonon bands between carbon atoms are responsible for the remarkable drops in thermal conductivity and large thermal resistances in carbon chains. Our study provides fundamental insight into how to tailor the thermal conductivity of polymers through variable substituents.

  20. The mid-cretaceous water bearer: Isotope mass balance quantification of the Albian hydrologic cycle

    USGS Publications Warehouse

    Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.

    2002-01-01

    A latitudinal gradient in meteoric ??18O compositions compiled from paleosol sphaerosiderites throughout the Cretaceous Western Interior Basin (KWIB) (34-75??N paleolatitude) exhibits a steeper, more depleted trend than modern (predicted) values (3.0??? [34??N latitude] to 9.7??? [75??N] lighter). Furthermore, the sphaerosiderite meteoric ??18O latitudinal gradient is significantly steeper and more depleted (5.8??? [34??N] to 13.8??? [75??N] lighter) than a predicted gradient for the warm mid-Cretaceous using modern empirical temperature-??18O precipitation relationships. We have suggested that the steeper and more depleted (relative to the modern theoretical gradient) meteoric sphaerosiderite ??18O latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the KWIB during the mid-Cretaceous. The sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable 'greenhouse' Albian Stage in the KWIB. The mass balance model tracks the evolving isotopic composition of an air mass and its precipitation, and is driven by latitudinal temperature gradients. Our simulations indicate that significant increases in Albian precipitation (34-52%) and evaporation fluxes (76-96%) are required to reproduce the difference between modern and Albian meteoric siderite ??18O latitudinal gradients. Calculations of precipitation rates from model outputs suggest mid-high latitude precipitation rates greatly exceeded modern rates (156-220% greater in mid latitudes [2600-3300 mm/yr], 99% greater at high latitudes [550 mm/yr]). The calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models (GCMs) for the warm Cretaceous, particularly in the mid to high latitudes. Our mass balance model by no means replaces GCMs. However, it is a simple and effective means of obtaining

  1. Stable Isotope Labeling for Improved Comparative Analysis of RNA Digests by Mass Spectrometry.

    PubMed

    Paulines, Mellie June; Limbach, Patrick A

    2017-03-01

    Even with the advent of high throughput methods to detect modified ribonucleic acids (RNAs), mass spectrometry remains a reliable method to detect, characterize, and place post-transcriptional modifications within an RNA sequence. Here we have developed a stable isotope labeling comparative analysis of RNA digests (SIL-CARD) approach, which improves upon the original (18)O/(16)O labeling CARD method. Like the original, SIL-CARD allows sequence or modification information from a previously uncharacterized in vivo RNA sample to be obtained by direct comparison with a reference RNA, the sequence of which is known. This reference is in vitro transcribed using a (13)C/(15)N isotopically enriched nucleoside triphosphate (NTP). The two RNAs are digested with an endonuclease, the specificity of which matches the labeled NTP used for transcription. As proof of concept, several transfer RNAs (tRNAs) were characterized by SIL-CARD, where labeled guanosine triphosphate was used for the reference in vitro transcription. RNase T1 digestion products from the in vitro transcript will be 15 Da higher in mass than the same digestion products from the in vivo tRNA that are unmodified, leading to a doublet in the mass spectrum. Singlets, rather than doublets, arise if a sequence variation or a post-transcriptional modification is present that results in a relative mass shift different from 15 Da. Moreover, the use of the in vitro synthesized tRNA transcript allows for quantitative measurement of RNA abundance. Overall, SIL-CARD simplifies data analysis and enhances quantitative RNA modification mapping by mass spectrometry. Graphical Abstract ᅟ.

  2. Stable Isotope Labeling for Improved Comparative Analysis of RNA Digests by Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Paulines, Mellie June; Limbach, Patrick A.

    2017-03-01

    Even with the advent of high throughput methods to detect modified ribonucleic acids (RNAs), mass spectrometry remains a reliable method to detect, characterize, and place post-transcriptional modifications within an RNA sequence. Here we have developed a stable isotope labeling comparative analysis of RNA digests (SIL-CARD) approach, which improves upon the original 18O/16O labeling CARD method. Like the original, SIL-CARD allows sequence or modification information from a previously uncharacterized in vivo RNA sample to be obtained by direct comparison with a reference RNA, the sequence of which is known. This reference is in vitro transcribed using a 13C/15N isotopically enriched nucleoside triphosphate (NTP). The two RNAs are digested with an endonuclease, the specificity of which matches the labeled NTP used for transcription. As proof of concept, several transfer RNAs (tRNAs) were characterized by SIL-CARD, where labeled guanosine triphosphate was used for the reference in vitro transcription. RNase T1 digestion products from the in vitro transcript will be 15 Da higher in mass than the same digestion products from the in vivo tRNA that are unmodified, leading to a doublet in the mass spectrum. Singlets, rather than doublets, arise if a sequence variation or a post-transcriptional modification is present that results in a relative mass shift different from 15 Da. Moreover, the use of the in vitro synthesized tRNA transcript allows for quantitative measurement of RNA abundance. Overall, SIL-CARD simplifies data analysis and enhances quantitative RNA modification mapping by mass spectrometry.

  3. Stable Isotope Labeling for Improved Comparative Analysis of RNA Digests by Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Paulines, Mellie June; Limbach, Patrick A.

    2017-01-01

    Even with the advent of high throughput methods to detect modified ribonucleic acids (RNAs), mass spectrometry remains a reliable method to detect, characterize, and place post-transcriptional modifications within an RNA sequence. Here we have developed a stable isotope labeling comparative analysis of RNA digests (SIL-CARD) approach, which improves upon the original 18O/16O labeling CARD method. Like the original, SIL-CARD allows sequence or modification information from a previously uncharacterized in vivo RNA sample to be obtained by direct comparison with a reference RNA, the sequence of which is known. This reference is in vitro transcribed using a 13C/15N isotopically enriched nucleoside triphosphate (NTP). The two RNAs are digested with an endonuclease, the specificity of which matches the labeled NTP used for transcription. As proof of concept, several transfer RNAs (tRNAs) were characterized by SIL-CARD, where labeled guanosine triphosphate was used for the reference in vitro transcription. RNase T1 digestion products from the in vitro transcript will be 15 Da higher in mass than the same digestion products from the in vivo tRNA that are unmodified, leading to a doublet in the mass spectrum. Singlets, rather than doublets, arise if a sequence variation or a post-transcriptional modification is present that results in a relative mass shift different from 15 Da. Moreover, the use of the in vitro synthesized tRNA transcript allows for quantitative measurement of RNA abundance. Overall, SIL-CARD simplifies data analysis and enhances quantitative RNA modification mapping by mass spectrometry.

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

    NASA Astrophysics Data System (ADS)

    Brandon, A.

    2006-12-01

    The technique for measuring Os isotopes to high precision (e.g. +/-30-50 ppm on the 186/188 ratio, 2 sigma) via negative thermal ionization mass spectrometry (NTIMS) was established a decade ago at the University of Maryland. Recent technical advances have resulted in the production of a new generation of TIMS that allows isotopic measurements with substantial improvement in accuracy and precision. Because of the improved capability, the new generation TIMS holds great potential to examine a variety of problems in geochemistry and cosmochemistry. Over the past 5 years, I have refined the technique for higher precision measurements of Os isotopes using the Triton TIMS from Thermo Electron. The measurements are made in static mode using 7 Faraday collectors. 70 or more nanograms of Os is loaded onto a Pt filament with barium hydroxide, the latter is an electron emitter that promotes efficient production of Os trioxide. Oxygen is bled into the source at constant pressures. Signal intensities of 120-180 mV 186Os trioxide are generated and measured as negative ions. Oxygen corrections to the raw data are made using the oxygen isotopic composition obtained for 2 ng loads of Re tetroxide measured on the Faraday cups. Multiple runs over the course of 3 years for the same lecture bottle used to bleed in oxygen to the source showed no change in the oxygen isotopic composition. Oxygen corrections are followed by instrumental mass fractionation corrections using 189/188, 192/189, or 192/188 using the exponential law. Both the internal and external precision for standard and unknown data are best when using 192/188, by a factor of 1.4 over 189/188, and 1.8 over 192/189. Replicate runs on 100 ng standard loads of a single filament shows no change in corrected values within external precision for all Os isotopic ratios over a wide range of fractionation, confirming adherence to the exponential law during emission. 39 runs for a standard solution gave +/-14 ppm (2 sigma) on the

  5. Observations of Carbon Chain Chemistry in the Envelopes of Low-Mass Protostars

    NASA Technical Reports Server (NTRS)

    Cordiner, M.; Charnley, S.; Buckle, J. V.; Walsh, C.; Millar, T. J.

    2012-01-01

    Observational results are reported from our surveys in the Northern Hemisphere (using the Onsala 20 m telescope) and the Southern Hemisphere (using the Mopra 22 m telescope) to search for 3 mm emission lines from carbon-chain-bearing species and other complex molecules in the envelopes of low-mass protostars. Based on a sample of approximately 60 sources, we find that carbon-chain-bearing species including HC3N (and C4H) are highly abundant in the vicinity of more than half of the observed protostars. The origin and evolution of these species, including their likely incorporation into ices in protoplanetary disks will be discussed

  6. Removing costs from the health care supply chain: lessons from mass retail.

    PubMed

    Agwunobi, John; London, Paul A

    2009-01-01

    Improved supply-chain management and high-volume purchasing have benefited other industries. This same approach could also reduce health care costs. Streamlining layers in the supply chain and using purchasing volume to reduce prices can save money and may improve care. Providing access to in-store health clinics and low-cost generic drugs are examples of how this approach is being tested by mass retailers. We examine lessons learned from these and similar initiatives and identify opportunities to cut the costs of generic and name-brand drugs, medical supplies, over-the-counter remedies, and vision care.

  7. Isotope mass balances in deep formations: How to consider the influence of pressure, temperature and salinity

    NASA Astrophysics Data System (ADS)

    Becker, Veith; Myrttinen, Anssi; Barth, Johannes A. C.

    2010-05-01

    Stable carbon isotopes are a sensitive tool to trace migration and to quantify mixing of CO2 from different sources. This technique is well described for application at the surface and under close-to-surface conditions. However, in order to use isotope mass balances when monitoring the fate of CO2 at carbon storage sites, some distinctive characteristics of deep formations have to be considered. High pressures (from 30 to 200 bar), temperatures (up to over 120 ° C) and salinities (approx. 100 to 400 g/L) influence the carbonate equilibrium as activities, fugacities and the stoichiometric equilibrium constants (fCO2, Kcalcite*, K1*, K2*) change with these parameters. Furthermore, isotopic fractionation is also affected by these parameters. Various relations are published, describing these dependencies with approaches of different complexity and exactness. In this field of application, available sampling data is usually limited, so that averaging and interpolation of input data may lead to noticeable error ranges. Under these conditions, the most elaborated algorithms do not necessarily perform better than more simple ones with respect to the overall error of the calculations. This work therefore compares the available approaches to describe temperature, pressure and salinity dependence in carbonate equilibrium calculations, as well as carbon isotope fractionation in this process with respect to the best ratio of accuracy in carbon storage site monitoring applications. It stands out that the fugacity and the stoichiometric constants involved in DIC-speciation are heavily influenced by pressure, temperature and salinity in general, whereas the individual composition of the solution may be simplified, at least for NaCl-type brines. With respect to fractionation, temperature plays a key role; pressure and salinity variations contribute to the species distribution only to a small amount. This study was conducted as a part of the R&D programme CLEAN, which is funded by

  8. Mass independently fractionated sulfur isotopes reveal recycling of Archean lithosphere in modern oceanic hotspot lavas

    NASA Astrophysics Data System (ADS)

    Jackson, Matthew; Cabral, Rita; Rose-Koga, Estelle; Koga, Ken; Whitehouse, Martin; Antonelli, Michael; Farquhar, James; Day, James; Hauri, Erik

    2013-04-01

    Oceanic crust and sediments are introduced to the mantle at subduction zones, but the fate of this subducted material within the mantle, as well as the antiquity of this process, is unknown. The mantle is compositionally and isotopically heterogeneous, and it is thought that much of this heterogeneity derives from incorporation of diverse subducted components—both crustal and oceanic lithosphere—over geologic time. Basaltic lavas erupted at some oceanic hotspot volcanoes have long been considered to be melts of ancient subducted lithosphere. However, compelling evidence for the return of subducted materials in mantle plumes is lacking. We report mass independently fractionated (MIF) S-isotope signatures in olivine-hosted sulfides from 20-million-year-old ocean island basalts (OIBs) from Mangaia, Cook Islands (Polynesia). Terrestrial MIF S-isotope signatures were generated exclusively through atmospheric photochemical reactions until ~2.45 billion years ago. Therefore, the discovery of MIF-S in young OIBs indicates that sulfur—likely derived from hydrothermally-altered oceanic crust—was subducted into the mantle before 2.45 Ga and recycled into the mantle source of Mangaia lavas. These new data provide evidence for ancient materials, with MIF 33S depletions, in the mantle source for Mangaia lavas. An Archean age for recycled oceanic crust provides key constraints on the length of time that subducted crustal material can survive in the mantle and on the timescales of mantle convection from subduction to melting and eruption at plume-fed hotspots. The new S-isotope measurements confirm inferences about the cycling of sulfur between the major reservoirs from the Archean to the Phanerozoic, extending from the atmosphere and oceans to the crust and mantle, and ultimately through a return cycle to the surface that, here, is completed in Mangaia lavas. It remains to be seen whether hotspots lavas sampling different compositional mantle endmembers (e.g., EM1, EM2

  9. The direct determination of the masses of unstable atoms with the chalk river on-line isotope separator

    NASA Astrophysics Data System (ADS)

    Sharma, K. S.; Schmeing, H.; Evans, H. C.; Hagberg, E.; Hardy, J. C.; Koslowsky, V. T.

    1989-02-01

    A new technique has been developed to measure the spacing of atomic mass doublets of radioactive isotopes directly with an on-line isotope separator. It relies not on ion detection but on observation of the specific radioactive signature of the isotopes under study. Consequently, line shapes and centroids can be determined, free of interference and with great accuracy, even if the corresponding beams strongly overlap or if they are contaminated by unwanted isobars or isomers. In particular, it is of no consequence if one or both members of the doublet are masked by stable background peaks. Doublets are peak matched as in a conventional mass spectrometer. The technique has been evaluated with beams of radioactive nuclides whose masses are known independently. Based on careful calibrations, two new mass values have been obtained: 72Br, 71 936 340 ± 430 μu and 63Ga, 62 939 570 ± 150 μu.

  10. Evaluation of the 34S/32S ratio of Soufre de Lacq elemental sulfur isotopic reference material by continuous flow isotope-ratio mass spectrometry

    USGS Publications Warehouse

    Qi, H.P.; Coplen, T.B.

    2003-01-01

    Soufre de Lacq elemental sulfur reference material (IAEA-S-4) isotopically is homogeneous in amounts as small as 41 ??g as determined by continuous flow isotope-ratio mass spectrometry. The ??34S value for this reference material is +16.90 ?? 0.12??? (1??) on a scale (Vienna Can??on Diablo troilite, VCDT) where IAEA-S-1 Ag2S is -0.3??? and IAEA-S-2 Ag2S is +22.67???. Published by Elsevier Science B.V.

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

    SciTech Connect

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

    1985-11-15

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

  12. Factors controlling precision and accuracy in isotope-ratio-monitoring mass spectrometry

    NASA Technical Reports Server (NTRS)

    Merritt, D. A.; Hayes, J. M.

    1994-01-01

    The performance of systems in which picomole quantities of sample are mixed with a carrier gas and passed through an isotope-ratio mass spectrometer system was examined experimentally and theoretically. Two different mass spectrometers were used, both having electron-impact ion sources and Faraday cup collector systems. One had an accelerating potential of 10kV and accepted 0.2 mL of He/min, producing, under those conditions, a maximum efficiency of 1 CO2 molecular ion collected per 700 molecules introduced. Comparable figures for the second instrument were 3 kV, 0.5 mL of He/min, and 14000 molecules/ion. Signal pathways were adjusted so that response times were <200 ms. Sample-related ion currents appeared as peaks with widths of 3-30 s. Isotope ratios were determined by comparison to signals produced by standard gases. In spite of rapid variations in signals, observed levels of performance were within a factor of 2 of shot-noise limits. For the 10-kV instrument, sample requirements for standard deviations of 0.1 and 0.5% were 45 and 1.7 pmol, respectively. Comparable requirements for the 3-kV instrument were 900 and 36 pmol. Drifts in instrumental characteristics were adequately neutralized when standards were observed at 20-min intervals. For the 10-kV instrument, computed isotopic compositions were independent of sample size and signal strength over the ranges examined. Nonlinearities of <0.04%/V were observed for the 3-kV system. Procedures for observation and subtraction of background ion currents were examined experimentally and theoretically. For sample/ background ratios varying from >10 to 0.3, precision is expected and observed to decrease approximately 2-fold and to depend only weakly on the precision with which background ion currents have been measured.

  13. The Bremen mass spectrometric facility for the measurement of helium isotopes, neon, and tritium in water.

    PubMed

    Sültenfuss, Jürgen; Roether, Wolfgang; Rhein, Monika

    2009-06-01

    We describe the mass spectrometric facility for measuring helium isotopes, neon, and tritium that has been operative at this institute since 1989, and also the sampling and sample preparation steps that precede the mass spectrometric analysis. For water samples in a near-equilibrium with atmospheric air, the facility achieves precision for (3)He/(4)He ratios of+/-0.4% or better, and+/-0.8 % or better for helium and neon concentrations. Tritium precision is typically+/-3 % and the detection limit 10 mTU ( approximately 1.2.10(-3) Bq/kg of pure water). Sample throughputs can reach some thousands per year. These achievements are enabled, among other features, by automation of the measurement procedure and by elaborate calibration, assisted by continual development in detail. To date, we have measured more than 15,000 samples for tritium and 23,000 for helium isotopes and neon, mostly in the context of oceanographic and hydrologic work. Some results of such work are outlined. Even when atmospheric tritium concentrations have become rather uniform, tritium provides water ages if (3)He data are taken concurrently. The technique can resolve tritium concentrations in waters of the pre-nuclear era.

  14. Predicting molecular formulas of fragment ions with isotope patterns in tandem mass spectra.

    PubMed

    Zhang, Jingfen; Gao, Wen; Cai, Jinjin; He, Simin; Zeng, Rong; Chen, Runsheng

    2005-01-01

    A number of different approaches have been proposed to predict elemental component formulas (or molecular formulas) of molecular ions in low and medium resolution mass spectra. Most of them rely on isotope patterns, enumerate all possible formulas for an ion, and exclude certain formulas violating chemical constraints. However, these methods cannot be well generalized to the component prediction of fragment ions in tandem mass spectra. In this paper, a new method, FFP (Fragment ion Formula Prediction), is presented to predict elemental component formulas of fragment ions. In the FFP method, the prediction of the best formulas is converted into the minimization of the distance between theoretical and observed isotope patterns. And, then, a novel local search model is proposed to generate a set of candidate formulas efficiently. After the search, FFP applies a new multiconstraint filtering to exclude as many invalid and improbable formulas as possible. FFP is experimentally compared with the previous enumeration methods, and shown to outperform them significantly. The results of this paper can help to improve the reliability of de novo in the identification of peptide sequences.

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

    PubMed Central

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

    2013-01-01

    Objective To establish normal, trimester-specific reference intervals for serum 17β-estradiol, progesterone (P), 17α-hydroxyprogesterone, cortisol, 11-deoxycortisol, androstenedione, DHEA, and DHEAS, measured simultaneously using isotope dilution tandem mass spectrometry. Design Sequential cohort study. Patient(s) Healthy women undergoing a normal pregnancy (age, 25–38 years; mean, 30 years) attending a prenatal well clinic at gestation weeks 12, 22, and 32 and approximately 1 year postpartum. Main Outcome Measure(s) Trimester-specific reference intervals of endogenous steroid hormones analyzed using an isotope dilution tandem mass spectrometer equipped with an atmospheric pressure photoionization source with deuterium-labeled internal standards. Result(s) Serum estradiol, P, 17α-hydroxyprogesterone, and 11-deoxycortisol increased throughout pregnancy; cortisol increased up to the second trimester and then remained steady, while androstenedione increased by 80 percent by gestation week 12, then remained constant. Serum DHEA-S decreased by 50% by the third trimester. Conclusion(s) Trimester-specific reference intervals are reported for eight serum steroids. The ratios of individual serum hormone concentrations during pregnancy relative to their 1-year postpartum concentrations illustrate the expected normal trends of changes in hormone concentrations during pregnancy. PMID:16169406

  16. Accurate and Efficient Resolution of Overlapping Isotopic Envelopes in Protein Tandem Mass Spectra

    PubMed Central

    Xiao, Kaijie; Yu, Fan; Fang, Houqin; Xue, Bingbing; Liu, Yan; Tian, Zhixin

    2015-01-01

    It has long been an analytical challenge to accurately and efficiently resolve extremely dense overlapping isotopic envelopes (OIEs) in protein tandem mass spectra to confidently identify proteins. Here, we report a computationally efficient method, called OIE_CARE, to resolve OIEs by calculating the relative deviation between the ideal and observed experimental abundance. In the OIE_CARE method, the ideal experimental abundance of a particular overlapping isotopic peak (OIP) is first calculated for all the OIEs sharing this OIP. The relative deviation (RD) of the overall observed experimental abundance of this OIP relative to the summed ideal value is then calculated. The final individual abundance of the OIP for each OIE is the individual ideal experimental abundance multiplied by 1 + RD. Initial studies were performed using higher-energy collisional dissociation tandem mass spectra on myoglobin (with direct infusion) and the intact E. coli proteome (with liquid chromatographic separation). Comprehensive data at the protein and proteome levels, high confidence and good reproducibility were achieved. The resolving method reported here can, in principle, be extended to resolve any envelope-type overlapping data for which the corresponding theoretical reference values are available. PMID:26439836

  17. Stable Isotope Labeling Strategy for Curcumin Metabolite Study in Human Liver Microsomes by Liquid Chromatography-Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Gao, Dan; Chen, Xiaowu; Yang, Xiaomei; Wu, Qin; Jin, Feng; Wen, Hongliang; Jiang, Yuyang; Liu, Hongxia

    2015-04-01

    The identification of drug metabolites is very important in drug development. Nowadays, the most widely used methods are isotopes and mass spectrometry. However, the commercial isotopic labeled reagents are usually very expensive, and the rapid and convenient identification of metabolites is still difficult. In this paper, an 18O isotope labeling strategy was developed and the isotopes were used as a tool to identify drug metabolites using mass spectrometry. Curcumin was selected as a model drug to evaluate the established method, and the 18O labeled curcumin was successfully synthesized. The non-labeled and 18O labeled curcumin were simultaneously metabolized in human liver microsomes (HLMs) and analyzed by liquid chromatography/mass spectrometry (LC-MS). The two groups of chromatograms obtained from metabolic reaction mixture with and without cofactors were compared and analyzed using Metabolynx software (Waters Corp., Milford, MA, USA). The mass spectra of the newly appearing chromatographic peaks in the experimental sample were further analyzed to find the metabolite candidates. Their chemical structures were confirmed by tandem mass spectrometry. Three metabolites, including two reduction products and a glucuronide conjugate, were successfully detected under their specific HLMs metabolic conditions, which were in accordance with the literature reported results. The results demonstrated that the developed isotope labeling method, together with post-acquisition data processing using Metabolynx software, could be used for fast identification of new drug metabolites.

  18. Stable isotope labeling strategy for curcumin metabolite study in human liver microsomes by liquid chromatography-tandem mass spectrometry.

    PubMed

    Gao, Dan; Chen, Xiaowu; Yang, Xiaomei; Wu, Qin; Jin, Feng; Wen, Hongliang; Jiang, Yuyang; Liu, Hongxia

    2015-04-01

    The identification of drug metabolites is very important in drug development. Nowadays, the most widely used methods are isotopes and mass spectrometry. However, the commercial isotopic labeled reagents are usually very expensive, and the rapid and convenient identification of metabolites is still difficult. In this paper, an (18)O isotope labeling strategy was developed and the isotopes were used as a tool to identify drug metabolites using mass spectrometry. Curcumin was selected as a model drug to evaluate the established method, and the (18)O labeled curcumin was successfully synthesized. The non-labeled and (18)O labeled curcumin were simultaneously metabolized in human liver microsomes (HLMs) and analyzed by liquid chromatography/mass spectrometry (LC-MS). The two groups of chromatograms obtained from metabolic reaction mixture with and without cofactors were compared and analyzed using Metabolynx software (Waters Corp., Milford, MA, USA). The mass spectra of the newly appearing chromatographic peaks in the experimental sample were further analyzed to find the metabolite candidates. Their chemical structures were confirmed by tandem mass spectrometry. Three metabolites, including two reduction products and a glucuronide conjugate, were successfully detected under their specific HLMs metabolic conditions, which were in accordance with the literature reported results. The results demonstrated that the developed isotope labeling method, together with post-acquisition data processing using Metabolynx software, could be used for fast identification of new drug metabolites.

  19. Tracing subarctic Pacific water masses with benthic foraminiferal stable isotopes during the LGM and late Pleistocene

    NASA Astrophysics Data System (ADS)

    Cook, Mea S.; Ravelo, A. Christina; Mix, Alan; Nesbitt, Ian M.; Miller, Nari V.

    2016-03-01

    As the largest ocean basin, the Pacific helps to set the global climate state, since its circulation affects mean ocean properties, air-sea partitioning of carbon dioxide, and the distribution of global oceanic poleward heat transport. There is evidence that during the Last Glacial Maximum (LGM) the subarctic Pacific contained a better-ventilated, relatively fresh intermediate water mass above ~2000 m that may have formed locally. The source and spatial extent of this water mass is not known, nor do we know how formation of this water mass varied during Pleistocene glaciations with different orbital and ice sheet boundary conditions. Here we present a 0.5 My multi-species benthic stable isotope record from Site U1345 (1008 m) on the northern Bering slope and a 1.0 My record from U1339 (1868 m) from the Umnak Plateau in the southeastern basin. We find that the relatively well-ventilated low-δ18O intermediate water reaches 1000 m in the Bering Sea during MIS2, but that the hydrographic divide between this water mass and poorly-ventilated deep water was shallower than 1000 m for earlier glaciations. We also compare Bering Sea piston core and IODP Expedition 323 Uvigerina data from the Holocene and LGM with the modern hydrography, and to previously published profiles from the Okhotsk Sea and Emperor Seamounts. We find that the carbon and oxygen stable isotope signatures of well-ventilated water in the Bering and Okhotsk Seas are distinct, suggesting that there may have been intermediate water formation in both basins during the LGM.

  20. Improved isotope ratio measurement performance in liquid chromatography/isotope ratio mass spectrometry by removing excess oxygen.

    PubMed

    Hettmann, Elena; Brand, Willi A; Gleixner, Gerd

    2007-01-01

    A low dead volume oxygen scrubbing system was introduced in a commercially available liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) interface to enhance the analytical capability of the system. In the LC/IRMS interface carbon from organic samples is converted into CO(2) inside the mobile phase by wet chemical oxidation using peroxodisulfate (Na(2)S(2)O(8)). After passing the hot reaction zone, surplus oxygen (O(2)) remains dissolved in the liquid phase. Both CO(2) and O(2) diffuse through a transfer membrane into the helium carrier and are transferred to the mass spectrometer. The presence of O(2) in the ion source may have detrimental effects on measurement accuracy and precision as well as on filament lifetime. As a remedy, a new on-line O(2)-removing device has been incorporated into the system. The new O(2) scrubber consists of two parallel hot copper reduction reactors (0.8 mm i.d., active length 120 mm) and a switch-over valve between them. One reactor is regenerated using He/H(2) while the other is actively scavenging O(2) from the gas stream. The capacity of each reduction reactor, expressed as usage time, is between 40 and 50 min. This is sufficient for a single LC run for sugars and organic acids. A further increase of the reduction capacity is accompanied by a peak broadening of about 100%. After switching to a freshly reduced reactor the oxygen background and the delta(13)C values of the reference gas need up to 500 s to stabilize. For repeated injections the delta(13)C values of sucrose remain constant (+/-0.1 per thousand) for about 3000 s. The long-term stability for measurements of sucrose was 0.11 per thousand without the reduction oven and improved slightly to 0.08 per thousand with the reduction oven. The filament lifetime improved by more than 600%, thereby improving the long-term system stability and analytical efficiency. In addition the costs per analysis were reduced considerably.

  1. Stellar (n ,γ ) cross sections of neutron-rich nuclei: Completing the isotope chains of Yb, Os, Pt, and Hg

    NASA Astrophysics Data System (ADS)

    Marganiec, J.; Dillmann, I.; Domingo-Pardo, C.; Käppeler, F.

    2014-12-01

    The (n ,γ ) cross sections of the most neutron-rich stable isotopes of Yb, Os, Pt, and Hg have been determined in a series of activation measurements at the Karlsruhe 3.7 MV Van de Graaff accelerator, using the quasistellar neutron spectrum for k T =25 keV that can be produced with the 7Li(p ,n ) 7Be reaction. In this way, Maxwellian averaged cross sections could be directly obtained with only minor corrections. After irradiation the induced activities were counted with a HPGe detector via the strongest γ -ray lines. The stellar neutron capture cross sections of Yb,176174, Os,192190, Pt,198196, and Hg,204202, extrapolated to k T =30 keV, were found to be 157 ±6 mb, 114 ±8 mb, 278 ±11 mb, 160 ±7 mb, 171 ±19 mb, 94 ±4 mb, 62 ±2 mb, and 32 ±15 mb, respectively. In the case of 196Pt the partial cross section to the isomeric state at 399.5 keV could be determined as well. With these results the cross section data for long isotopic chains could be completed for a discussion of the predictive power of statistical model calculations towards the neutron-rich and proton-rich sides of the stability valley.

  2. Olive oil or lard?: distinguishing plant oils from animal fats in the archeological record of the eastern Mediterranean using gas chromatography/combustion/isotope ratio mass spectrometry.

    PubMed

    Steele, Valerie J; Stern, Ben; Stott, Andy W

    2010-12-15

    Distinguishing animal fats from plant oils in archaeological residues is not straightforward. Characteristic plant sterols, such as β-sitosterol, are often missing in archaeological samples and specific biomarkers do not exist for most plant fats. Identification is usually based on a range of characteristics such as fatty acid ratios, all of which indicate that a plant oil may be present, none of which uniquely distinguish plant oils from other fats. Degradation and dissolution during burial alter fatty acid ratios and remove short-chain fatty acids, resulting in degraded plant oils with similar fatty acid profiles to other degraded fats. Compound-specific stable isotope analysis of δ(13)C(18:0) and δ(13)C(16:0), carried out by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), has provided a means of distinguishing fish oils, dairy fats, ruminant and non-ruminant adipose fats, but plant oils are rarely included in these analyses. For modern plant oils where C(18:1) is abundant, δ(13)C(18:1) and δ(13)C(16:0) are usually measured. These results cannot be compared with archaeological data or data from other modern reference fats where δ(13)C(18:0) and δ(13)C(16:0) are measured, as C(18:0) and C(18:1) are formed by different processes resulting in different isotopic values. Eight samples of six modern plant oils were saponified, releasing sufficient C(18:0) to measure the isotopic values, which were plotted against δ(13)C(16:0). The isotopic values for these oils, with one exception, formed a tight cluster between ruminant and non-ruminant animal fats. This result complicates the interpretation of mixed fatty residues in geographical areas where both animal fats and plant oils were in use.

  3. Preparing the measurement of anapole moment in a chain of francium isotopes

    NASA Astrophysics Data System (ADS)

    Sheng, Dong

    This thesis presents the current status of the experimental efforts towards the measurement of the anapole moment in francium. The anapole moment is a parity violating, time-reversal conserving nuclear moment that arises from the weak interaction among nucleons. It is nuclear spin dependent and sensitive to the configuration of nuclear structure. Our experimental scheme is to perform a direct measurement of the anapole moment, by driving a parity forbidden E1 transition between ground hyperfine states in a series of francium isotopes inside a blue detuned dipole trap at the electric anti-node of a microwave cavity. We explore the tests using rubidium isotopes. The francium experiment will be moved to the ISAC radioactive beam facility of TRIUMF, Canada. During the preparation of the apparatus, we test the coherent control of the ground states via microwave and Raman beams, characterize the performance of a blue detuned dipole trap and study the atomic dynamics inside it using both classical and quantum methods. We also measure the lifetime of excited 5d states in Rb, with less than 1% uncertainty, to test and help to improve the current atomic structure theories.

  4. High-temperature pyrolysis/gas chromatography/isotope ratio mass spectrometry: simultaneous measurement of the stable isotopes of oxygen and carbon in cellulose.

    PubMed

    Woodley, Ewan J; Loader, Neil J; McCarroll, Danny; Young, Giles H F; Robertson, Iain; Heaton, Timothy H E; Gagen, Mary H; Warham, Joseph O

    2012-01-30

    Stable isotope analysis of cellulose is an increasingly important aspect of ecological and palaeoenvironmental research. Since these techniques are very costly, any methodological development which can provide simultaneous measurement of stable carbon and oxygen isotope ratios in cellulose deserves further exploration. A large number (3074) of tree-ring α-cellulose samples are used to compare the stable carbon isotope ratios (δ(13)C) produced by high-temperature (1400°C) pyrolysis/gas chromatography (GC)/isotope ratio mass spectrometry (IRMS) with those produced by combustion GC/IRMS. Although the two data sets are very strongly correlated, the pyrolysis results display reduced variance and are strongly biased towards the mean. The low carbon isotope ratios of tree-ring cellulose during the last century, reflecting anthropogenic disturbance of atmospheric carbon dioxide, are thus overestimated. The likely explanation is that a proportion of the oxygen atoms are bonding with residual carbon in the reaction chamber to form carbon monoxide. The 'pyrolysis adjustment', proposed here, is based on combusting a stratified sub-sample of the pyrolysis results, across the full range of carbon isotope ratios, and using the paired results to define a regression equation that can be used to adjust all the pyrolysis measurements. In this study, subsamples of 30 combustion measurements produced adjusted chronologies statistically indistinguishable from those produced by combusting every sample. This methodology allows simultaneous measurement of the stable isotopes of carbon and oxygen using high-temperature pyrolysis, reducing the amount of sample required and the analytical costs of measuring them separately.

  5. Determination of the sulfur isotope ratio in carbonyl sulfide using gas chromatography/isotope ratio mass spectrometry on fragment ions 32S+, 33S+, and 34S+.

    PubMed

    Hattori, Shohei; Toyoda, Akari; Toyoda, Sakae; Ishino, Sakiko; Ueno, Yuichiro; Yoshida, Naohiro

    2015-01-06

    Little is known about the sulfur isotopic composition of carbonyl sulfide (OCS), the most abundant atmospheric sulfur species. We present a promising new analytical method for measuring the stable sulfur isotopic compositions (δ(33)S, δ(34)S, and Δ(33)S) of OCS using nanomole level samples. The direct isotopic analytical technique consists of two parts: a concentration line and online gas chromatography-isotope ratio mass spectrometry (GC-IRMS) using fragmentation ions (32)S(+), (33)S(+), and (34)S(+). The current levels of measurement precision for OCS samples greater than 8 nmol are 0.42‰, 0.62‰, and 0.23‰ for δ(33)S, δ(34)S, and Δ(33)S, respectively. These δ and Δ values show a slight dependence on the amount of injected OCS for volumes smaller than 8 nmol. The isotope values obtained from the GC-IRMS method were calibrated against those measured by a conventional SF6 method. We report the first measurement of the sulfur isotopic composition of OCS in air collected at Kawasaki, Kanagawa, Japan. The δ(34)S value obtained for OCS (4.9 ± 0.3‰) was lower than the previous estimate of 11‰. When the δ(34)S value for OCS from the atmospheric sample is postulated as the global signal, this finding, coupled with isotopic fractionation for OCS sink reactions in the stratosphere, explains the reported δ(34)S for background stratospheric sulfate. This suggests that OCS is a potentially important source for background (nonepisodic or nonvolcanic) stratospheric sulfate aerosols.

  6. In vivo investigation of homocysteine metabolism to polyamines by high-resolution accurate mass spectrometry and stable isotope labeling.

    PubMed

    Ruseva, Silviya; Lozanov, Valentin; Markova, Petia; Girchev, Radoslav; Mitev, Vanio

    2014-07-15

    Polyamines are essential polycations, playing important roles in mammalian physiology. Theoretically, the involvement of homocysteine in polyamine synthesis via S-adenosylmethionine is possible; however, to our knowledge, it has not been established experimentally. Here, we propose an original approach for investigation of homocysteine metabolites in an animal model. The method is based on the combination of isotope-labeled homocysteine supplementation and high-resolution accurate mass spectrometry analysis. Structural identity of the isotope-labeled metabolites was confirmed by accurate mass measurements of molecular and fragment ions and comparison of the retention times and tandem mass spectrometry fragmentation patterns. Isotope-labeled methionine, spermidine, and spermine were detected in all investigated plasma and tissue samples. The induction of moderate hyperhomocysteinemia leads to an alteration in polyamine levels in a different manner. The involvement of homocysteine in polyamine synthesis and modulation of polyamine levels could contribute to a better understanding of the mechanisms connected with homocysteine toxicity.

  7. Applications and Advantages of Stable Isotope Phosphate Labeling of RNA in Mass Spectrometry.

    PubMed

    Borland, Kayla; Limbach, Patrick A

    2017-04-01

    Mass spectrometry (MS) has become an enabling technology for the characterization of post-transcriptionally modified nucleosides within ribonucleic acids (RNAs). These modified RNAs tend to be more challenging to completely characterize using conventional genomic-based sequencing technologies. As with many biological molecules, information relating to the presence or absence of a particular compound (i.e., qualitative measurement) is only one step in sample characterization. Additional useful information is found by performing quantitative measurements on the levels of the compound of interest in the sample. Phosphate labeling of modified RNAs has been developed by our laboratory to enhance conventional mass spectrometry techniques. By taking advantage of the mechanism of action of many ribonucleases (RNases), digesting RNA samples in the presence of (18)O-labeled water generates an (18)O-labeled 3'-phosphate in each digestion product. We describe the historical development of this approach, contrast this stable isotope labeling strategy with others used in RNA mass spectrometry, and provide examples of new analytical mass spectrometry methods that are enabled by phosphate labeling in this fashion.

  8. Quantifying in situ transformation rates of chlorinated ethenes by combining compound-specific stable isotope analysis, groundwater dating, and carbon isotope mass balances.

    PubMed

    Aeppli, Christoph; Hofstetter, Thomas B; Amaral, Helena I F; Kipfer, Rolf; Schwarzenbach, René P; Berg, Michael

    2010-05-15

    We determined in situ reductive transformation rates of tetrachloroethene (PCE) in a contaminated aquifer by combining compound-specific carbon stable isotope analysis (CSIA) of the contaminants with tracer-based ((3)H-(3)He) groundwater dating. With increasing distance from the source, PCE was gradually transformed to trichloroethene (TCE), cis-dichloroethene (cDCE), and vinyl chloride (VC). Using the in situ determined carbon isotopic enrichment factor of -3.3 +/- 1.2 per thousand allowed for quantification of the PCE-to-TCE transformation based on isotopic (delta(13)C) shifts. By combining these estimates of the extent of PCE transformation with measured groundwater residence times (between 16 and 36 years) we calculated half-lives of 2.8 +/- 0.8 years (k = 0.27 +/- 0.09 yr(-1)) for the PCE-to-TCE transformation. Carbon isotope mass balances including the chloroethenes PCE, TCE, cDCE, and VC (delta(13)C(Sigma(CEs))) enabled an assessment of complete PCE dechlorination to nonchlorinated products. Shifts of delta(13)C(Sigma(CEs)) at the fringe of the plume of more than 25 per thousand pointed to dechlorination beyond VC of up to 55 +/- 17% of the chloroethene mass. Calculated rates for this multistep dechlorination were highly variable throughout the aquifer (k = 0.4 +/- 0.4 yr(-1)), suggesting that PCE reduction to nonchlorinated products occurred only in locally restricted zones of the investigated site.

  9. Stable isotope probing and Raman spectroscopy for monitoring carbon flow in a food chain and revealing metabolic pathway.

    PubMed

    Li, Mengqiu; Huang, Wei E; Gibson, Christopher M; Fowler, Patrick W; Jousset, Alexandre

    2013-02-05

    Accurately measuring carbon flows is a challenge for understanding processes such as diverse intracellular metabolic pathways and predator-prey interactions. Combined with stable isotope probing (SIP), single-cell Raman spectroscopy was demonstrated for the first time to link the food chain from carbon substrate to bacterial prey up to predators at the single-cell level in a quantitative and nondestructive manner. Escherichia coli OP50 with different (13)C content, which were grown in a mixture of (12)C- and fully carbon-labeled (13)C-glucose (99%) as a sole carbon source, were fed to the nematode. The (13)C signal in Caenorhabditis elegans was proportional to the (13)C content in E. coli. Two Raman spectral biomarkers (Raman bands for phenylalanine at 1001 cm(-1) and thymine at 747 cm(-1) Raman bands), were used to quantify the (13)C content in E. coli and C. elegans over a range of 1.1-99%. The phenylalanine Raman band was a suitable biomarker for prokaryotic cells and thymine Raman band for eukaryotic cells. A biochemical mechanism accounting for the Raman red shifts of phenylalanine and thymine in response to (13)C-labeling is proposed in this study and is supported by quantum chemical calculation. This study offers new insights of carbon flow via the food chain and provides a research tool for microbial ecology and investigation of biochemical pathways.

  10. Assessment of Non-traditional Isotopic Ratios by Mass Spectrometry for Analysis of Nuclear Activities: Annual Report Year 2

    SciTech Connect

    Biegalski, S; Buchholz, B

    2009-08-26

    The objective of this work is to identify isotopic ratios suitable for analysis via mass spectrometry that distinguish between commercial nuclear reactor fuel cycles, fuel cycles for weapons grade plutonium, and products from nuclear weapons explosions. Methods will also be determined to distinguish the above from medical and industrial radionuclide sources. Mass spectrometry systems will be identified that are suitable for field measurement of such isotopes in an expedient manner. Significant progress has been made with this project within the past year: (1) Isotope production from commercial nuclear fuel cycles and nuclear weapons fuel cycles have been modeled with the ORIGEN and MCNPX codes. (2) MCNPX has been utilized to calculate isotopic inventories produced in a short burst fast bare sphere reactor (to approximate the signature of a nuclear weapon). (3) Isotopic ratios have been identified that are good for distinguishing between commercial and military fuel cycles as well as between nuclear weapons and commercial nuclear fuel cycles. (4) Mass spectrometry systems have been assessed for analysis of the fission products of interest. (5) A short-list of forensic ratios have been identified that are well suited for use in portable mass spectrometry systems.

  11. First direct mass measurements of stored neutron-rich 129,130,131Cd isotopes with FRS-ESR

    NASA Astrophysics Data System (ADS)

    Knöbel, R.; Diwisch, M.; Bosch, F.; Boutin, D.; Chen, L.; Dimopoulou, C.; Dolinskii, A.; Franczak, B.; Franzke, B.; Geissel, H.; Hausmann, M.; Kozhuharov, C.; Kurcewicz, J.; Litvinov, S. A.; Martinez-Pinedo, G.; Matoš, M.; Mazzocco, M.; Münzenberg, G.; Nakajima, S.; Nociforo, C.; Nolden, F.; Ohtsubo, T.; Ozawa, A.; Patyk, Z.; Plaß, W. R.; Scheidenberger, C.; Stadlmann, J.; Steck, M.; Sun, B.; Suzuki, T.; Walker, P. M.; Weick, H.; Wu, M.-R.; Winkler, M.; Yamaguchi, T.

    2016-03-01

    A 410 MeV/u 238U projectile beam was used to create cadmium isotopes via abrasion-fission in a beryllium target placed at the entrance of the in-flight separator FRS at GSI. The fission fragments were separated by the FRS and injected into the isochronous storage ring ESR for mass measurements. Isochronous Mass Spectrometry (IMS) was performed under two different experimental conditions, with and without Bρ-tagging at the high-resolution central focal plane of the FRS. In the experiment with Bρ-tagging the magnetic rigidity of the injected fragments was determined with an accuracy of 2 ṡ10-4. A new method of data analysis, which uses a correlation matrix for the combined data set from both experiments, has provided experimental mass values of 25 rare isotopes for the first time. The high sensitivity and selectivity of the method have given access to nuclides detected with a rate of a few atoms per week. In this letter we present for the 129,130,131Cd isotopes mass values directly measured for the first time. The experimental mass values of cadmium as well as for tellurium and tin isotopes show a pronounced shell effect towards and at N = 82. Shell quenching cannot be deduced from a single new mass value, nor by a better agreement with a theoretical model which explicitly takes into account a quenching feature. This is in agreement with the conclusion from γ-ray spectroscopy and confirms modern shell-model calculations.

  12. Time-of-flight mass measurements of neutron-rich chromium isotopes up to N = 40 and implications for the accreted neutron star crust

    DOE PAGES

    Meisel, Z.; George, S.; Ahn, S.; ...

    2016-03-22

    Here, we present the mass excesses of 59-64Cr, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of 64Cr is determined for the first time, with an atomic mass excess of -33.48(44) MeV. We find a significantly different two-neutron separation energy S2n trend for neutron-rich isotopes of chromium, removing the previously observed enhancement in binding at N = 38. Additionally, we extend the S2n trend for chromium to N = 40, revealing behavior consistent with the previously identified island of inversion in this region. We compare our results to state-of-the-artmore » shell-model calculations performed with a modified Lenzi-Nowacki-Poves-Sieja interaction in the fp shell, including the g9/2 and d5/2 orbits for the neutron valence space. We employ our result for the mass of 64Cr in accreted neutron star crust network calculations and find a reduction in the strength and depth of electron-capture heating from the A = 64 isobaric chain, resulting in a cooler than expected accreted neutron star crust. This reduced heating is found to be due to the >1-MeV reduction in binding for 64Cr with respect to values from commonly used global mass models.« less

  13. Mass-independent fractionation of mercury isotopes during photochemical reduction in freshwater systems

    NASA Astrophysics Data System (ADS)

    Rose, C. H.; Bergquist, B. A.; Blum, J. D.

    2009-12-01

    Mercury is a globally distributed environmental toxin. Both inorganic and methylated species have severe detrimental effects on humans and animals, but it is methyl mercury (MeHg) that bioaccumulates in food webs and results in significant human exposure via fish consumption. Photochemical reduction of aqueous Hg species to dissolved gaseous Hg(0) can result in a net transfer of Hg from aquatic systems to the atmosphere, making it unavailable for methylation. In addition, photo-reduction of MeHg is an alternative fate to bioaccumulation for this powerful neurotoxin. Both mass-dependent isotope fractionation (MDF) and mass-independent fractionation (MIF) are observed in natural samples. MIF is the deviation in isotope ratios from those predicted by MDF based on 202Hg/198Hg. Bergquist and Blum 2007 showed that aqueous photo-reduction of Hg2+ and MeHg in the presence of dissolved natural organic matter results not only in Rayleigh-type MDF but also significant MIF, with the odd isotopes 199Hg and 201Hg being preferentially retained in the reactant (soluble) phase. Berquist and Blum 2007 also observed that the ratio of the MIF for the odd isotopes was different for each of the photo-reduction pathways (MeHg versus Hg2+) and suggested this ratio could be unique to certain pathways, which might allow identification of photo-reduction among other pathways in natural samples. They also suggested that the magnitude of MIF might relate quantitatively to the amount of photo-reduction Hg undergoes in aqueous systems. To better understand the causes of MIF and its capacity along with MDF as a tool for tracing photo-reduction of Hg, further experiments mimicking the freshwater photo-reduction of Hg2+ and MeHg were carried out. Each species was photo-reduced in the presence of Suwannee River Fulvic Acid with different portions of the electromagnetic spectrum blocked by filters. Bergquist and Blum 2007 suggested the magnetic isotope effect (MIE) as the cause of the MIF they

  14. Sulfur Isotope Variation in Melt Inclusions From Arc Basalts Revealed By Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Mandeville, C. W.; Shimizu, N.; Kelley, K. A.

    2009-12-01

    Subduction zones are sites where elements once at the Earth’s surface are recycled back to the mantle. Arc volcanoes return volatiles and hydrous melts to the surface. Understanding of sulfur recycling in magmatic arcs is hampered by insufficient data on net sulfur isotopic composition of slab inputs, that range from δ34S of seawater (21‰) to negative δ34S of -70‰ for secondary sulfides, to values of 0 ± 3‰ in relict magmatic sulfides. We lack sufficient knowledge of the sulfur concentration and isotopic composition of the mantle wedge. Degassing and assimilation of crustal sulfur may produce changes to initial sulfur isotope ratios of magmas. To preclude degassing effects, we measured S isotope ratios in mafic melt inclusions by secondary ionization mass spectrometry (SIMS) from three arc volcanoes, Galunggung, and Krakatau in Indonesia, and Augustine, in Alaska. These data provide a view of the variability of initial sulfur isotope ratios of mafic arc magmas and are being evaluated for correlations with sulfur and iron oxidation state, dissolved volatiles, trace elements, and degassing effects in order to determine the origin(s) of dissolved S. Olivine-hosted melt inclusions from a basaltic bomb from the 1982-1983 Galunggung eruption represent the relatively dry adiabatic decompression melting end member of primary arc magma genesis (Sisson and Bronto,1998). New SIMS δ34S measurements of Galunggung melt inclusions yield ratios from -3.0‰ to +5.0‰ with S concentrations of 1950 ppm - 990 ppm. A few Galunggung inclusions have δ34S between 0.5‰ and 1.4‰ with S conc.'s of 1690 - 1760 ppm, that are within the mantle range, and have low water contents of 0.25 to 0.30 wt.% (Kelley et al. 2005). A subgroup of inclusions yield δ34S of 2.8‰ to 5.0‰ and 990 - 1920 ppm S. Pre-1883 basaltic scoria from Krakatau volcano contain olivine-hosted melt inclusions with water and CO2 concentrations from 1.8 - 4.1 wt.% and 79 - 1017 ppm, respectively

  15. ISOTOPIC MASS FRACTIONATION OF SOLAR WIND: EVIDENCE FROM FAST AND SLOW SOLAR WIND COLLECTED BY THE GENESIS MISSION

    SciTech Connect

    Heber, Veronika S.; Baur, Heinrich; Wieler, Rainer; Bochsler, Peter; McKeegan, Kevin D.; Neugebauer, Marcia; Reisenfeld, Daniel B.; Wiens, Roger C.

    2012-11-10

    NASA's Genesis space mission returned samples of solar wind collected over {approx}2.3 years. We present elemental and isotopic compositions of He, Ne, and Ar analyzed in diamond-like carbon targets from the slow and fast solar wind collectors to investigate isotopic fractionation processes during solar wind formation. The solar wind provides information on the isotopic composition for most volatile elements for the solar atmosphere, the bulk Sun and hence, on the solar nebula from which it formed 4.6 Ga ago. Our data reveal a heavy isotope depletion in the slow solar wind compared to the fast wind composition by 63.1 {+-} 2.1 per mille for He, 4.2 {+-} 0.5 per mille amu{sup -1} for Ne and 2.6 {+-} 0.5 per mille amu{sup -1} for Ar. The three Ne isotopes suggest that isotopic fractionation processes between fast and slow solar wind are mass dependent. The He/H ratios of the collected slow and fast solar wind samples are 0.0344 and 0.0406, respectively. The inefficient Coulomb drag model reproduces the measured isotopic fractionation between fast and slow wind. Therefore, we apply this model to infer the photospheric isotopic composition of He, Ne, and Ar from our solar wind data. We also compare the isotopic composition of oxygen and nitrogen measured in the solar wind with values of early solar system condensates, probably representing solar nebula composition. We interpret the differences between these samples as being due to isotopic fractionation during solar wind formation. For both elements, the magnitude and sign of the observed differences are in good agreement with the values predicted by the inefficient Coulomb drag model.

  16. Can Lightning Produce Significant Levels of Mass-Independent Oxygen Isotopic Fractionation in Nebular Dust?

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A.; Paquette, John A.; Farquhar, Adam

    2012-01-01

    Based on recent evidence that oxide grains condensed from a plasma will contain oxygen that is mass independently fractionated compared to the initial composition of the vapor, we present a first attempt to evaluate the potential magnitude of this effect on dust in the primitive solar nebula. This assessment relies on previous studies of nebular lightning to provide reasonable ranges of physical parameters to form a very simple model to evaluate the plausibility that lightning could affect a significant fraction of nebular dust and that such effects could cause a significant change in the oxygen isotopic composition of solids in the solar nebula over time. If only a small fraction of the accretion energy is dissipated as lightning over the volume of the inner solar nebula, then a large fraction of nebular dust will be exposed to lightning. If the temperature of such bolts is a few percent of the temperatures measured in terrestrial discharges, then dust will vaporize and recondense in an ionized environment. Finally, if only a small average decrease is assumed in the O-16 content of freshly condensed dust, then over the last 5 million years of nebular accretion the average delta O-17 of the dust could increase by more than 30 per mil. We conclude that it is possible that the measured " slope 1" oxygen isotope line measured in meteorites and their components represents a time-evolution sequence of nebular dust over the last several million years of nebular evolution O-16-rich materials formed first, then escaped further processing as the average isotopic composition of the dust graduaUy became increasingly depleted in O-16 .

  17. Oxygen Isotope Mass-Balance Constraints on Pliocene Sea Level and East Antarctic Ice Sheet Stability

    NASA Astrophysics Data System (ADS)

    Winnick, M. J.; Caves, J. K.

    2015-12-01

    The mid-Pliocene Warm Period (MPWP, 3.3-2.9 Ma), with reconstructed atmospheric pCO2 of 350-450 ppm, represents a potential analogue for climate change in the near future. Current highly cited estimates place MPWP maximum global mean sea level (GMSL) at 21 ± 10 m above modern, requiring total loss of the Greenland (GIS) and marine West Antarctic Ice Sheets (WAIS) and a substantial loss of the East Antarctic Ice Sheet (EAIS), with only a concurrent 2-3 ºC rise in global temperature. Many estimates of Pliocene GMSL are based on the partitioning of oxygen isotope records from benthic foraminifera (δ18Ob) into changes in deep-sea temperatures and terrestrial ice sheets. These isotopic budgets are underpinned by the assumption that the δ18O of Antarctic ice (δ18Oi) was the same in the Pliocene as it is today, and while the sensitivity of δ18Ob to changing meltwater δ18O has been previously considered, these analyses neglect conservation of 18O/16O in the ocean-ice system. Using well-calibrated δ18O-temperature relationships for Antarctic precipitation along with estimates of Pliocene Antarctic surface temperatures, we argue that the δ18Oi of the Pliocene Antarctic ice sheet was at minimum 1‰-4‰ higher than present. Assuming conservation of 18O/16O in the ocean-ice system, this requires lower Pliocene seawater δ18O (δ18Osw) without a corresponding change in ice sheet mass. This effect alone accounts for 5%-20% of the δ18Ob difference between the MPWP interglacials and the modern. With this amended isotope budget, we suggest that Pliocene GMSL was likely 9-13.5 m and very likely 5-17 m above modern, which suggests the EAIS is less sensitive to radiative forcing than previously inferred from the geologic record.

  18. Authenticity of carbon dioxide bubbles in French ciders through multiflow-isotope ratio mass spectrometry measurements.

    PubMed

    Gaillard, Laetitia; Guyon, Francois; Salagoïty, Marie-Hélène; Médina, Bernard

    2013-12-01

    A procedure to detect whether carbon dioxide was added to French ciders has been developed. For this purpose, an optimised and simplified method is proposed to determine (13)C/(12)C isotope ratio of carbon dioxide (δ(13)C) in ciders. Three critical steps were checked: (1) influence of atmospheric CO2 remaining in the loaded vial, (2) impact of helium flush, (3) sampling speed. This study showed that atmospheric CO2 does not impact the measurement, that helium flush can lead to isotopic fractionation and finally, that a fractionation occurs only 5h after bottle opening. The method, without any other preparation, consists in sampling 0.2 mL of cold (4 °C) cider in a vial that is passed in an ultrasonic bath for 10 min at room temperature to enhance cider de-carbonation. The headspace CO2 is then analysed using the link Multiflow®-isotope ratio mass spectrometer. Each year, a data bank is developed by fermenting authentic apples juices in order to control cider authenticity. Over a four year span (2008-2011), the CO2 produced during the fermentation step was studied. This set of 61 authentic ciders, from various French production areas, was used to determine a δ(13)C value range of -22.59±0.92‰ for authentic ciders CO2 bubbles. 75 commercial ciders were analysed with this method. Most of the samples analysed present a gas δ(13)C value in the expected range. Nevertheless, some ciders have δ(13)C values outside the 3σ limit, revealing carbonation by technical CO2. This practice is not allowed for organic, "Controlled Appellation of Origin" ciders and ciders specifying natural carbonation on the label.

  19. Detecting animal by-product intake using stable isotope ratio mass spectrometry (IRMS).

    PubMed

    da Silva, D A F; Biscola, N P; Dos Santos, L D; Sartori, M M P; Denadai, J C; da Silva, E T; Ducatti, C; Bicudo, S D; Barraviera, B; Ferreira, R S

    2016-11-01

    Sheep are used in many countries as food and for manufacturing bioproducts. However, when these animals consume animal by-products (ABP), which is widely prohibited, there is a risk of transmitting scrapie - a fatal prion disease in human beings. Therefore, it is essential to develop sensitive methods to detect previous ABP intake to select safe animals for producing biopharmaceuticals. We used stable isotope ratio mass spectrometry (IRMS) for (13)C and (15)N to trace animal proteins in the serum of three groups of sheep: 1 - received only vegetable protein (VP) for 89 days; 2 - received animal and vegetable protein (AVP); and 3 - received animal and vegetable protein with animal protein subsequently removed (AVPR). Groups 2 and 3 received diets with 30% bovine meat and bone meal (MBM) added to a vegetable diet (from days 16-89 in the AVP group and until day 49 in the AVPR group, when MBM was removed). The AVPR group showed (15)N equilibrium 5 days after MBM removal (54th day). Conversely, (15)N equilibrium in the AVP group occurred 22 days later (76th day). The half-life differed between these groups by 3.55 days. In the AVPR group, (15)N elimination required 53 days, which was similar to this isotope's incorporation time. Turnover was determined based on natural (15)N signatures. IRMS followed by turnover calculations was used to evaluate the time period for the incorporation and elimination of animal protein in sheep serum. The δ(13)C and δ(15)N values were used to track animal protein in the diet. This method is biologically and economically relevant for the veterinary field because it can track protein over time or make a point assessment of animal feed with high sensitivity and resolution, providing a low-cost analysis coupled with fast detection. Isotopic profiles could be measured throughout the experimental period, demonstrating the potential to use the method for traceability and certification assessments.

  20. Dissolved inorganic carbon isotopic composition of the Gulf of Mexico deep-water masses.

    NASA Astrophysics Data System (ADS)

    Quintanilla-Terminel, J. G.; Herguera, J. C.; Ferreira-Bartrina, V.; Hernández-Ayón, J. M.; Camacho-Ibar, V.

    2014-12-01

    This study provides new data for the establishment of a carbon biogeochemical dynamics baseline in the deep Gulf of Mexico (GM) based on carbon isotopes in dissolved inorganic carbon. Water samples from 40 deep-water stations south of 25˚N were collected during XIXIMI-2 cruise, July 2011, aboard BO/Justo Sierra. Vertical profiles of temperature, salinity and dissolved oxygen (DO) were further measured in each station. In the Stable Isotopes Laboratory at CICESE we determined the carbon isotopic composition of the dissolved inorganic carbon (DIC) (δ13CDIC). Remarkably, density, DO and δ13CCID profiles showed a clear difference between the Loop current and the deep-waters of the GM south of 25˚N. We found the following average δ13CCID values in the Loop current and in the deep-waters of the Gulf: subtropical underwater (SUW): 0.73±0.06‰ and 0.86±0.04‰; 18 degree water (18W): 0.76 ± 0.08‰ and 0.58± 0.06‰; North Atlantic central water (NACW): 0.77 ± 0.05‰ and 0.71 ± 0.09‰; South Atlantic central water (SACW): 0.80 ± 0.08‰ and 0.77 ± 0.07‰; Antartic intermediate water (AAIW): 1.00 ± 0.06‰ and 0.90 ± 0.08‰; North Atlantic deep water (NADW): 1.03 ± 0.06‰ and 1.01 ± 0.10‰. We will discuss how the biological component, δ13CCID-BIO, of subsurface water masses match very closely the apparent oxygen utilization relation described by Kroopnick, 1985, with the exception of SUW, and as a consequence the 18W is probably the water mass most affected by organic carbon remineralization processes in the GM south of 25˚N. We further show how these waters seem to store a larger proportion of anthropogenic carbon than the deeper water masses.

  1. SO2 photolysis as a source for sulfur mass-independent isotope signatures in stratospehric aerosols

    NASA Astrophysics Data System (ADS)

    Whitehill, A. R.; Jiang, B.; Guo, H.; Ono, S.

    2015-02-01

    Signatures of sulfur isotope mass-independent fractionation (S-MIF) have been observed in stratospheric sulfate aerosols deposited in polar ice. The S-MIF signatures are thought to be associated with stratospheric photochemistry following stratospheric volcanic eruptions, but the exact mechanism responsible for the production and preservation of these signatures is debated. In order to identify the origin and the mechanism of preservation for these signatures, a series of laboratory photochemical experiments were carried out to investigate the effect of temperature and added O2 on the S-MIF produced by two absorption band systems of SO2: photolysis in the 190 to 220 nm region and photoexcitation in the 250 to 350 nm region. The SO2 photolysis (SO2 + hν → SO + O) experiments showed S-MIF signals with large 34S/34S fractionations, which increases with decreasing temperature. The overall S-MIF pattern observed for photolysis experiments, including high 34S/34S fractionations, positive mass-independent anomalies in 33S, and negative anomalies in 36S, is consistent with a major contribution from optical isotopologue screening effects and data for stratospheric sulfate aerosols. In contrast, SO2 photoexcitation produced products with positive S-MIF anomalies in both 33S and 36S, which is different from stratospheric sulfate aerosols. SO2 photolysis in the presence of O2 produced SO3 with S-MIF signals, suggesting the transfer of the S-MIF anomalies from SO to SO3 by the SO + O2 + M → SO3 + M reaction. This is supported with energy calculations of stationary points on the SO3 potential energy surfaces, which indicate that this reaction occurs slowly on a single adiabatic surface, but that it can occur more rapidly through intersystem crossing. Based on our experimental results, we estimate a termolecular rate constant on the order of 10-37 cm6 molecule-2 s-1. This rate can explain the preservation of mass independent isotope signatures in stratospheric sulfate

  2. Estimating ground-water inflow to lakes in central Florida using the isotope mass-balance approach

    USGS Publications Warehouse

    Sacks, Laura A.

    2002-01-01

    The isotope mass-balance approach was used to estimate ground-water inflow to 81 lakes in the central highlands and coastal lowlands of central Florida. The study area is characterized by a subtropical climate and numerous lakes in a mantled karst terrain. Ground-water inflow was computed using both steady-state and transient formulations of the isotope mass-balance equation. More detailed data were collected from two study lakes, including climatic, hydrologic, and isotopic (hydrogen and oxygen isotope ratio) data. For one of these lakes (Lake Starr), ground-water inflow was independently computed from a water-budget study. Climatic and isotopic data collected from the two lakes were similar even though they were in different physiographic settings about 60 miles apart. Isotopic data from all of the study lakes plotted on an evaporation trend line, which had a very similar slope to the theoretical slope computed for Lake Starr. These similarities suggest that data collected from the detailed study lakes can be extrapolated to the rest of the study area. Ground-water inflow computed using the isotope mass-balance approach ranged from 0 to more than 260 inches per year (or 0 to more than 80 percent of total inflows). Steady-state and transient estimates of ground-water inflow were very similar. Computed ground-water inflow was most sensitive to uncertainty in variables used to calculate the isotopic composition of lake evaporate (isotopic compositions of lake water and atmospheric moisture and climatic variables). Transient results were particularly sensitive to changes in the isotopic composition of lake water. Uncertainty in ground-water inflow results is considerably less for lakes with higher ground-water inflow than for lakes with lower ground-water inflow. Because of these uncertainties, the isotope mass-balance approach is better used to distinguish whether ground-water inflow quantities fall within certain ranges of values, rather than for precise

  3. Carbon Isotope Measurements of Experimentally-Derived Hydrothermal Mineral-Catalyzed Organic Products by Pyrolysis-Isotope Ratio Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Socki, Richard A.; Fu, Qi; Niles, Paul B.

    2011-01-01

    We report results of experiments to measure the C isotope composition of mineral catalyzed organic compounds derived from high temperature and high pressure synthesis. These experiments make use of an innovative pyrolysis technique designed to extract and measure C isotopes. To date, our experiments have focused on the pyrolysis and C isotope ratio measurements of low-molecular weight intermediary hydrocarbons (organic acids and alcohols) and serve as a proof of concept for making C and H isotope measurements on more complicated mixtures of solid-phase hydrocarbons and intermediary products produced during high temperature and high pressure synthesis on mineral-catalyzed surfaces. The impetus for this work stems from recently reported observations of methane detected within the Martian atmosphere [1-4], coupled with evidence showing extensive water-rock interaction during Martian history [5-7]. Methane production on Mars could be the result of synthesis by mineral surface-catalyzed reduction of CO2 and/or CO by Fischer-Tropsch Type (FTT) reactions during serpentization reactions [8,9]. Others have conducted experimental studies to show that FTT reactions are plausible mechanisms for low-molecular weight hydrocarbon formation in hydrothermal systems at mid-ocean ridges [10-12]. Further, recent experiments by Fu et al. [13] focus on examining detailed C isotope measurements of hydrocarbons produced by surface-catalyzed mineral reactions. Work described in this paper details the experimental techniques used to measure intermediary organic reaction products (alcohols and organic acids).

  4. An interlaboratory study to test instrument performance of hydrogen dual-inlet isotope-ratio mass spectrometers

    USGS Publications Warehouse

    Brand, Willi A.; Coplen, T.B.

    2001-01-01

    An interlaboratory comparison of forty isotope-ratio mass spectrometers of different ages from several vendors has been performed to test 2H/1H performance with hydrogen gases of three different isotopic compositions. The isotope-ratio results (unsufficiently corrected for H3+ contribution to the m/z = 3 collector, uncorrected for valve leakage in the change-over valves, etc.) expressed relative to one of these three gases covered a wide range of values: -630??? to -790??? for the second gas and -368??? to -462??? for the third gas. After normalizing the isotopic abundances of these test gases (linearly adjusting the ?? values so that the gases with the lowest and highest 2H content were identical for all laboratories), the standard deviation of the 40 measurements of the intermediate gas was a remarkably low 0.85???. It is concluded that the use of scaling factors is mandatory for providing accurate internationally comparable isotope-abundance values. Linear scaling for the isotope-ratio scales of gaseous hydrogen mass spectrometers is completely adequate. ?? Springer-Verlag 2001.

  5. Isotope dilution gas chromatography/mass spectrometry method for determination of pyrethroids in apple juice.

    PubMed

    Wong, Siu-kay; Yu, Kwok-chiu; Lam, Chi-ho

    2010-03-01

    This paper presents the development of a highly precise and accurate analytical method for the determination of three matrix-bound pyrethroids, namely, cypermethrin, permethrin, and bifenthrin, using an isotope dilution gas chromatography/mass spectrometry technique. Identification of the analytes was confirmed under selective ion monitoring mode by the presence of two dominant ion fragments within specific time windows and matching of relative ion intensities of the ions concerned in samples and calibration standards. Quantitation was based on the measurement of concentration ratios of the natural and isotope analogues in the sample and calibration blends. Intraday and interday repeatabilities of replicate analyses of the pyethroids in an apple juice sample were below 0.5%. The expanded relative uncertainty ranged from 3 to 6%, which was significantly lower than the range obtained using internal or external calibration methods. As a labeled analogue is not available for bifenthrin, bifenthrin was determined using labeled cis-permethrin as the internal standard. The results were counterchecked by a gas chromatography-electron capture detection technique using PCB 209 as the internal standard. The method developed was applied to a recent pilot study organized by CCQM and the results were consistent with those of other participants.

  6. Comparison of femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry for uranium isotopic measurements

    SciTech Connect

    Havrilla, George Joseph; McIntosh, Kathryn Gallagher; Judge, Elizabeth; Dirmyer, Matthew R.; Campbell, Keri; Gonzalez, Jhanis J.

    2016-10-20

    Feasibility tests were conducted using femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry for rapid uranium isotopic measurements. The samples used in this study consisted of a range of pg quantities of known 235/238 U solutions as dried spot residues of 300 pL drops on silicon substrates. The samples spanned the following enrichments of 235U: 0.5, 1.5, 2, 3, and 15.1%. In this direct comparison using these particular samples both pulse durations demonstrated near equivalent data can be produced on either system with respect to accuracy and precision. There is no question that either LA-ICP-MS method offers the potential for rapid, accurate and precise isotopic measurements of U10Mo materials whether DU, LEU or HEU. The LA-ICP-MS equipment used for this work is commercially available. The program is in the process of validating this work for large samples using center samples strips from Y-12 MP-1 LEU-Mo Casting #1.

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

    DOE PAGES

    Horkley, J. J.; Carney, K. P.; Gantz, E. M.; ...

    2015-03-17

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

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

    SciTech Connect

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

    2015-03-01

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

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

    SciTech Connect

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

    2015-03-17

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

  10. Using Lanthanide Nanoparticles as Isotopic Tags for Biomarker Detection by Mass Cytometry

    NASA Astrophysics Data System (ADS)

    Cao, Pengpeng

    The development of robust, versatile, and high-throughput biosensing techniques has widespread implications for early disease detection and accurate diagnosis. An innovative technology, mass cytometry, has been developed to use isotopically-labelled antibodies to simultaneously study multiple parameters of single cells. The current detection sensitivity of mass cytometry is limited by the number of copies of a given isotope that can be attached to a given antibody. This thesis describes research on the synthesis, characterization, and bioconjugation of a new class of nanoparticle-based labelling agents to be employed for the detection of low-abundance biomarkers by mass cytometry. Hydrophobic lanthanide nanoparticles (Ln NPs) have been prepared by the Winnik group. To render the NPs water-soluble for biological applications, we coated the NP surface with a first generation of multidentate poly(ethylene glycol) (PEG)-based ligands via ligand exchange. We measured the size, morphology, and polydispersity of these hydrophilic NPs by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The colloidal stability of the NPs was determined at various pH and in phosphate buffered saline (PBS) solutions. Tetradentate-PEG-coated NPs (Tetra-NPs) exhibited the best stability at pH 3 to 9, and in PBS. However, when cells were treated with Tetra-NPs in preliminary in vitro studies, significant undesirable non-specific binding (NSB) was observed. In order to tackle the NSB issue presented in the Tetra-NPs, we prepared a second generation of polymer-based ligands using ring-opening metathesis polymerization (ROMP). A small library of ROMP polymers was synthesized, characterized, and used to stabilize NPs in aqueous solutions. The ROMP-NPs were found to have significantly reduced NSB to cells by inductively coupled plasma-mass spectrometry (ICP-MS). To further modify the NPs, amine groups were introduced as functional handles to both the tetradentate-PEG and

  11. Small Scale Heterogeneity in the Mantle Beneath the Southern Cascades: Isotope and Trace-Element Geochemistry of Primitive Basalts in the Poison Lake Chain

    NASA Astrophysics Data System (ADS)

    Wenner, J. M.; Teasdale, R.

    2009-12-01

    We present new trace-element and isotope data for four of nine stratigraphically and petrographically defined groups of primitive basalts in the Poison Lake chain, east of Lassen Volcanic National Park in northern California. The Poison Lake chain is located near the Basin and Range, which provides conduits for magma to reach the surface efficiently with little contamination. Its limited area (5 km east-west and 20 km north-south) and proximity to the Basin and Range make the Poison Lake chain an ideal location to study the mantle beneath the southern Cascades. The volcanic field encompasses 43 vents that comprise nine groups of chemically distinct primitive calc-alkaline basalts. The four groups analyzed for this study, are the basalts of Robbers Spring (~202 ka), Pittville Road (~117 ka), old railroad grade (~102 ka) and Bogard Buttes (~100 ka), which were chosen based on their spatial distribution and age relationships. Our new trace-element and isotope data confirm distinct geochemical groups that were previously recognized with major-element data. Lead isotopes suggest derivation from a mantle source modified by subducted sediment; however, primitive and mantle-like Sr-isotope ratios (0.7037-0.7042) preclude significant crustal contamination as these basalts ascended through the crust. Isotopic and trace-element compositions are distinct among groups despite their proximity to one another, essentially ruling out direct genetic relationships or a common source for these basalts. Instead, slight major- and trace-element variations suggest that within-group compositional diversity may be produced by one of the following processes: variable degrees of partial melting, minimal fractional crystallization, or mixing with mafic magmas of similar composition. Well-defined groups of primitive basalts erupted in the Poison Lake chain are interpreted to represent small, independent batches of mantle melt that rapidly traversed the crust. The small volume erupted, distinct

  12. Inductively Coupled Plasma/Mass Spectrometric Isotopic Determination of Nuclear Wastes Sources Associated with Hanford Tank Leaks

    SciTech Connect

    Evans, John C.; Dresel, P. Evan; Farmer, Orville T.

    2007-11-01

    The subsurface distribution of a nuclear waste tank leak on the U.S. Department of Energy’s Hanford Site was sampled by slant drilling techniques in order to characterize the chemical and radiological characteristics of the leaked material and assess geochemical transport properties of hazardous constituents. Sediment core samples recovered from the borehole were subjected to distilled water and acid leaching procedures with the resulting leachates analyzed for isotopic and chemical signatures. High-sensitivity inductively coupled plasma/mass spectrometry (ICP/MS) techniques were used for determination of isotopic ratios for Cs, I, Mo. Analysis of the isotopic patterns of I and Mo combined with associated chemical data showed evidence for at least two separate intrusions of nuclear waste into the subsurface. Isotopic data for Cs was inconclusive with respect to a source attribution signature.

  13. Highly accurate isotope composition measurements by a miniature laser ablation mass spectrometer designed for in situ investigations on planetary surfaces

    NASA Astrophysics Data System (ADS)

    Riedo, A.; Meyer, S.; Heredia, B.; Neuland, M. B.; Bieler, A.; Tulej, M.; Leya, I.; Iakovleva, M.; Mezger, K.; Wurz, P.

    2013-10-01

    An experimental procedure for precise and accurate measurements of isotope abundances by a miniature laser ablation mass spectrometer for space research is described. The measurements were conducted on different untreated NIST standards and galena samples by applying pulsed UV laser radiation (266 nm, 3 ns and 20 Hz) for ablation, atomisation, and ionisation of the sample material. Mass spectra of released ions are measured by a reflectron-type time-of-flight mass analyser. A computer controlled performance optimiser was used to operate the system at maximum ion transmission and mass resolution. At optimal experimental conditions, the best relative accuracy and precision achieved for Pb isotope compositions are at the per mill level and were obtained in a range of applied laser irradiances and a defined number of accumulated spectra. A similar relative accuracy and precision was achieved in the study of Pb isotope compositions in terrestrial galena samples. The results for the galena samples are similar to those obtained with a thermal ionisation mass spectrometer (TIMS). The studies of the isotope composition of other elements yielded relative accuracy and precision at the per mill level too, with characteristic instrument parameters for each element. The relative accuracy and precision of the measurements is degrading with lower element/isotope concentration in a sample. For the elements with abundances below 100 ppm these values drop to the percent level. Depending on the isotopic abundances of Pb in minerals, 207Pb/206Pb ages with accuracy in the range of tens of millions of years can be achieved.

  14. A chain kinematic model to assess the movement of lower-limb including wobbling masses.

    PubMed

    Thouzé, A; Monnet, T; Bélaise, C; Lacouture, P; Begon, M

    2016-01-01

    Computer simulation models have shown that wobbling mass on the lower limb affects the joint kinetics. Our objective was to propose a non-invasive method to estimate bones and wobbling mass kinematics in the lower limb during hopping. The chain kinematic model has set degrees of freedom at the joints and free wobbling bodies. By comparison to a model without wobbling bodies, the marker residual was reduced by 20% but the joint kinematics remains unchanged. Wobbling bodies' displacements reached 6.9 ± 3.5° and 6.9 ± 2.4 mm relative to the modelled bones. This original method is a first step to assess wobbling mass effect on joint kinetics.

  15. Screening of dimethoate in food by isotope dilution and electrospray ionization tandem mass spectrometry.

    PubMed

    Mazzotti, Fabio; Di Donna, Leonardo; Macchione, Barbara; Maiuolo, Loredana; Perri, Enzo; Sindona, Giovanni

    2009-05-01

    Crop control is an important issue in both developed and developing countries. An environmentally friendly approach is represented by the so-called Integrated Pest Management (IPM), whereby synthetic pesticides are only applied as a last resort, under the strict control of suitable experts. European and US regulatory authorities, such as the US EPA, are constantly assessing the risks of exposure to the organophosphate (OP) class of pesticides and, among these, specifically dimethoate. The use of dimethoate is still allowed in many crops, including olives, which once was based in the Mediterranean area but now is expanding rapidly throughout the world. An important aspect of IPM protocols is represented by the availability of reliable and sensitive methods to detect pesticides residues. This paper describes an isotope dilution dimethoate assay based on the application of electrospray ionization tandem mass spectrometry (ESI-MS/MS) by means of a deuterium-labeled internal standard.

  16. Alpha heating and isotopic mass effects in JET plasmas with sawteeth

    SciTech Connect

    Budny, R. V.; Team, JET

    2016-02-09

    The alpha heating experiment in the Joint European Torus (JET) 1997 DTE1 campaign is re-examined. Several effects correlated with tritium content and thermal hydrogenic isotopic mass < A> weaken the conclusion that alpha heating was clearly observed. These effects delayed the occurrence of significant sawtooth crashes allowing the electron and ion temperatures T e and T i to achieve higher values. Under otherwise equal circumstances T e and T i were typically higher for discharges with higher < A >, and significant scaling of T i, T e, and total stored energy with < A > were observed. The higher T i led to increased ion–electron heating rates with magnitudes comparable to those computed for alpha electron heating. Rates of other heating/loss processes also had comparable magnitudes. Simulations of T e assuming the observed scaling of T i are qualitatively consistent with the measured profiles, without invoking alpha heating

  17. Volcanism, mass extinction, and carbon isotope fluctuations in the Middle Permian of China.

    PubMed

    Wignall, Paul B; Sun, Yadong; Bond, David P G; Izon, Gareth; Newton, Robert J; Védrine, Stéphanie; Widdowson, Mike; Ali, Jason R; Lai, Xulong; Jiang, Haishui; Cope, Helen; Bottrell, Simon H

    2009-05-29

    The 260-million-year-old Emeishan volcanic province of southwest China overlies and is interbedded with Middle Permian carbonates that contain a record of the Guadalupian mass extinction. Sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations. These show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae. The temporal coincidence of these two phenomena supports the idea of a cause-and-effect relationship. The crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean-atmosphere carbon cycle.

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

    PubMed

    Perkola, Noora; Sainio, Pirjo

    2014-01-01

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

  19. Ion exchange separation of chromium from natural water matrix for stable isotope mass spectrometric analysis

    USGS Publications Warehouse

    Ball, J.W.; Bassett, R.L.

    2000-01-01

    A method has been developed for separating the Cr dissolved in natural water from matrix elements and determination of its stable isotope ratios using solid-source thermal-ionization mass spectrometry (TIMS). The separation method takes advantage of the existence of the oxidized form of Cr as an oxyanion to separate it from interfering cations using anion-exchange chromatography, and of the reduced form of Cr as a positively charged ion to separate it from interfering anions such as sulfate. Subsequent processing of the separated sample eliminates residual organic material for application to a solid source filament. Ratios for 53Cr/52Cr for National Institute of Standards and Technology Standard Reference Material 979 can be measured using the silica gel-boric acid technique with a filament-to-filament standard deviation in the mean 53Cr/52Cr ratio for 50 replicates of 0.00005 or less. (C) 2000 Elsevier Science B.V. All rights reserved.

  20. Application of Screening Experimental Designs to Assess Chromatographic Isotope Effect upon Isotope-Coded Derivatization for Quantitative Liquid Chromatography–Mass Spectrometry

    PubMed Central

    2015-01-01

    Isotope effect may cause partial chromatographic separation of labeled (heavy) and unlabeled (light) isotopologue pairs. Together with a simultaneous matrix effect, this could lead to unacceptable accuracy in quantitative liquid chromatography–mass spectrometry assays, especially when electrospray ionization is used. Four biologically relevant reactive aldehydes (acrolein, malondialdehyde, 4-hydroxy-2-nonenal, and 4-oxo-2-nonenal) were derivatized with light or heavy (d3-, 13C6-, 15N2-, or 15N4-labeled) 2,4-dinitrophenylhydrazine and used as model compounds to evaluate chromatographic isotope effects. For comprehensive assessment of retention time differences between light/heavy pairs under various gradient reversed-phase liquid chromatography conditions, major chromatographic parameters (stationary phase, mobile phase pH, temperature, organic solvent, and gradient slope) and different isotope labelings were addressed by multiple-factor screening using experimental designs that included both asymmetrical (Addelman) and Plackett–Burman schemes followed by statistical evaluations. Results confirmed that the most effective approach to avoid chromatographic isotope effect is the use of 15N or 13C labeling instead of deuterium labeling, while chromatographic parameters had no general influence. Comparison of the alternate isotope-coded derivatization assay (AIDA) using deuterium versus 15N labeling gave unacceptable differences (>15%) upon quantifying some of the model aldehydes from biological matrixes. On the basis of our results, we recommend the modification of the AIDA protocol by replacing d3-2,4-dinitrophenylhydrazine with 15N- or 13C-labeled derivatizing reagent to avoid possible unfavorable consequences of chromatographic isotope effects. PMID:24922593

  1. Ion-optical studies for improved ion transmission in multistage isotope-ratio mass spectrometers

    SciTech Connect

    Stoffels, J.J. ); Laue, H.J. )

    1991-10-01

    Theoretical and experimental ion-optical studies of multistage isotope-ratio mass spectrometers were conducted to determine what improvement in ion transmission efficiency might be attainable through design changes. The computer program GIOS (General Ion Optical Systems) was used to perform theoretical calculations of focusing properties and ion transmission efficiency. Actual transmission through multiple-sector instruments was determined from measurements of the ion beam vertical profile at the focus of each stage. For existing mass spectrometers with tandem magnets of normal geometry, our studies determined a feasible design change that significantly increases ion transmission through the analyzer. The use of a cylindrical einzel lens or an electrostatic quadrupole lens near the focal point between the magnets provides vertical focusing of the ion beam to achieve the improved transmission. We also established a new mass spectrometer design that give 100% transmission through tandem magnetic analyzers and through a third-stage electrostatic analyzer without the use of an intermediate focusing lens. Non-normal magnetic field boundaries provide ion beam focusing in the vertical plant to achieve this complete transmission. 19 refs., 27 figs., 3 tabs.

  2. Refinement and evaluation of an automated mass spectrometer for nitrogen isotope analysis by the Rittenberg technique

    PubMed Central

    Mulvaney, R. L.; Liu, Y. P.

    1991-01-01

    An apparatus designed to automatically perform hypobromite oxidations of ammonium salt samples for nitrogen isotope analyses with a mass spectrometer was modified to improve performance and reduce analysis time. As modified, reference N2 is admitted to the mass spectrometer between samples from a dedicated inlet manifold, for calibration at the same pressure as that of the preceding sample. Analyses can be performed on samples containing 10 μg to 1 mg of N (or more), at a rate of up to 350 samples/day. When operated with a double-collector mass spectrometer, the standard deviation at the natural abundance level (10 analyses, 50-150 μg N) was <0.0001 atom % 15N. Very little memory was observed when natural abundance samples (0.366 atom % 15N) were analysed. following samples containing 40 atom % 15N. Analyses in the range, 0.2 to 1 atom % 15N (50-150 μg N), were in good agreement with manual Rittenberg analyses (1 mg N) using a dual-inlet system, and precision was comparable. For enrichments of 2 to 20 atom % 15N, automated analyses were slightly lower than manual analyses, which was attributed to outgassing of N2 from the plastic microplate used to contain samples. PMID:18924914

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

    PubMed

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

    2014-02-21

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

  4. Compound-specific carbon isotopes from Earth's largest flood basalt eruptions directly linked to the end-Triassic mass extinction.

    PubMed

    Whiteside, Jessica H; Olsen, Paul E; Eglinton, Timothy; Brookfield, Michael E; Sambrotto, Raymond N

    2010-04-13

    A leading hypothesis explaining Phanerozoic mass extinctions and associated carbon isotopic anomalies is the emission of greenhouse, other gases, and aerosols caused by eruptions of continental flood basalt provinces. However, the necessary serial relationship between these eruptions, isotopic excursions, and extinctions has never been tested in geological sections preserving all three records. The end-Triassic extinction (ETE) at 201.4 Ma is among the largest of these extinctions and is tied to a large negative carbon isotope excursion, reflecting perturbations of the carbon cycle including a transient increase in CO(2). The cause of the ETE has been inferred to be the eruption of the giant Central Atlantic magmatic province (CAMP). Here, we show that carbon isotopes of leaf wax derived lipids (n-alkanes), wood, and total organic carbon from two orbitally paced lacustrine sections interbedded with the CAMP in eastern North America show similar excursions to those seen in the mostly marine St. Audrie's Bay section in England. Based on these results, the ETE began synchronously in marine and terrestrial environments slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco, a CO(2) super greenhouse, and marine biocalcification crisis. Because the temporal relationship between CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same place, this is the strongest case for a volcanic cause of a mass extinction to date.

  5. Evaluation Of Sensitivity Of Mass-independent Oxygen Isotopes In Aerosol Nitrate To Environmental Factors Using A Photochemical Box Model

    NASA Astrophysics Data System (ADS)

    Dominguez, G.; Wilkins, G.; Jackson, T.; Brothers, L.; McCabe, J.; Thiemens, M. H.

    2007-12-01

    An existing photochemical box model for use in polluted marine boundary layers was modified to allow for the explicit tracking of the mass-independent isotopic composition of oxygen in aerosol nitrate as well as other atmospheric species such as OH and H2O2. This modified model was then used to study the sensitivity of the mass-independent isotopic composition of atmospheric nitrate(HNO3) to variables such as relative humidity, temperature ozone and NOx concentrations. Here we present the results of these studies and compare model predictions of the mass-independent oxygen isotopic composition of aerosol nitrate to measurements taken in fine (<1micron) and coarse (>1 micron) aerosol samples taken in a variety of locations, from coastal urban environments, the tropics (Ecuador), inland California (Riverside), and Antarctica. Regarding Antarctica, we comment on the isotopic composition of OH there and the ramifications of these findings for the isotopic composition of other oxygen bearing compounds in the Antarctic atmosphere.

  6. (238)U/(235)U isotope ratios of crustal material, rivers and products of hydrothermal alteration: new insights on the oceanic U isotope mass balance.

    PubMed

    Noordmann, Janine; Weyer, Stefan; Georg, R Bastian; Jöns, Svenja; Sharma, Mukul

    2016-01-01

    significantly lower δ(238)U (-0.55 and -0.59 ‰) than seawater (-0.38 ‰). These findings, together with the heavier U isotope composition observed for some altered basalts and carbonate veins support a model, in which redox processes mostly drive U isotope fractionation. This may result in a slightly heavier U isotope composition of U that is removed from seawater during hydrothermal seafloor alteration compared to that of seawater. Using the estimated isotope compositions of rivers and all U sinks from the ocean (of this study and the literature) for modelling of the isotopic U mass balance, this gives reasonable results for recent estimates of the oceanic U budget. It furthermore provides additional constraints on the relative size of the diverse U sinks and respective net isotope fractionation during U removal.

  7. Video analysis of sliding chains: A dynamic model based on variable-mass systems

    NASA Astrophysics Data System (ADS)

    Moreno, R.; Page, A.; Riera, J.; Hueso, J. L.

    2015-06-01

    This paper presents an experimental study of the dynamics of a chain sliding off of a table, using video analysis to test a theoretical model. The model consists of two variable-mass subsystems, with friction between the chain and the table and assumes that all links move at the same speed. In order to check the model, the chain position x(t) is obtained using video analysis. The smoothed function x(t) and its derivatives v(t) and a(t) are numerically computed using a local regression algorithm. In this way, the differential equation governing the motion can be directly tested, instead of comparing the position with the solution of the differential equation. Our procedure is very sensitive to deviations between the model and reality, so we can detect the point at which the chain ceases to be in tension and the model is no longer valid. This experiment shows students the limitations of simplified models and offers an opportunity to assess a model's range of validity.

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

    PubMed

    Ren, Yao; Walczyk, Thomas

    2014-09-01

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

  9. Biomedical applications of accelerator mass spectrometry-isotope measurements at the level of the atom.

    PubMed

    Barker, J; Garner, R C

    1999-01-01

    Accelerator mass spectrometry (AMS) is a nuclear physics technique developed about twenty years ago, that uses the high energy (several MeV) of a tandem Van de Graaff accelerator to measure very small quantities of rare and long-lived isotopes. Elements that are of interest in biomedicine and environmental sciences can be measured, often to parts per quadrillion sensitivity, i.e. zeptomole to attomole levels (10(-21)-10(-18) mole) from milligram samples. This is several orders of magnitude lower than that achievable by conventional decay counting techniques, such as liquid scintillation counting (LSC). AMS was first applied to geochemical, climatological and archaeological areas, such as for radiocarbon dating (Shroud of Turin), but more recently this technology has been used for bioanalytical applications. In this sphere, most work has been conducted using aluminium, calcium and carbon isotopes. The latter is of special interest in drug metabolism studies, where a Phase 1 adsorption, distribution, metabolism and excretion (ADME) study can be conducted using only 10 nanoCurie (37 Bq or ca. 0.9 microSv) amounts or less of 14C-labelled drugs. In the UK, these amounts of radioactivity are below those necessary to request specific regulatory approval from the Department of Health's Administration of Radioactive Substances Advisory Committee (ARSAC), thus saving on valuable development time and resources. In addition, the disposal of these amounts is much less an environmental issue than that associated with microCurie quantities, which are currently used. Also, AMS should bring an opportunity to conduct "first into man" studies without the need for widespread use of animals. Centre for Biomedical Accelerator Mass Spectrometry (CBAMS) Ltd. is the first fully commercial company in the world to offer analytical services using AMS. With its high throughput and relatively low costs per sample analysis, AMS should be of great benefit to the pharmaceutical and biotechnology

  10. Determination of mass-dependent isotopic fractionation of cerium and neodymium in geochemical samples by MC-ICPMS.

    PubMed

    Ohno, Takeshi; Hirata, Takafumi

    2013-01-01

    We have developed a new analytical method to determine the mass-dependent isotopic fractionations on Ce and Nd in geochemical samples. Mass discrimination effects on Ce and Nd were externally corrected by normalizing (149)Sm/(147)Sm and (153)Eu/(151)Eu, being 0.92124 and 1.0916, respectively based on an exponential law. The reproducibility of the isotopic ratio measurements on (142)Ce/(140)Ce, (146)Nd/(144)Nd and (148)Nd/(144)Nd were 0.08‰ (2SD, n = 25), 0.06‰ (2SD, n = 39) and 0.12‰ (2SD, n = 39), respectively. The present technique was applied to determine the variations of the Ce and Nd isotopic ratios for five geochemical reference materials (igneous rocks, JB-1a and JA-2; sedimentary rocks, JMn-1, JCh-1 and JDo-1). The resulting ratios for two igneous rocks (JB-1a and JA-2) and two sedimentary rocks (JMn-1 and JCh-1) did not vary significantly among the samples, whereas the Ce and Nd isotope ratios for the carbonate samples (JDo-1) were significantly higher than those for igneous and sedimentary rock samples. The 1:1 simple correlation between δ(142)Ce and δ(146)Nd indicates that there were no significant difference in the degree of isotopic fractionation between the Ce and Nd. This suggests that the isotopic fractionation for Ce found in the JDo-1 could be induced by geochemical or physicochemical processes without changing the oxidation status of Ce, since the redox-reaction can produce larger isotopic fractionation than the reactions without changing the oxidation state. The variations in the Ce and Nd isotope ratios for geochemical samples could provide new information concerning the physico-chemical processes of the sample formation.

  11. Gas-phase Mechanisms of Sulfur Isotope Mass-independent Fractionation

    NASA Astrophysics Data System (ADS)

    Lyons, J. R.

    2006-12-01

    Mass-independent fractionation (MIF) in sulfur isotopes in ancient sulfur-bearing rocks (Farquhar et al. 2000a) is interpreted as evidence for gas-phase MIF processes in the early Earth atmosphere. This interpretation is made by analogy with oxygen isotope MIF in the modern atmosphere (produced during ozone formation), and by laboratory photolysis experiments on SO2 (Farquhar et al. 2001; Wing et al. 2004) that yield both elemental sulfur and sulfate with S MIF signatures at wavelengths above and below the SO2 dissociation limit. What is lacking is a quantitative understanding of the mechanisms of gas-phase S MIF. Quantification is essential in order to extract the full implications of sulfur MIF throughout Earth history, including for bacterial sulfate reduction processes which largely conserve D33S and D36S. Several sulfur MIF mechanisms are possible. The most obvious is the gas-phase thiozone reaction, which is isovalent to the ozone formation reaction. Ozone formation produces a well-known MIF signature in oxygen isotopes (Thiemens and Heidenreich 1983), and a symmetry-dependent non-RRKM mechanism has been proposed as the origin of O MIF (Gao and Marcus 2001). It is possible and perhaps likely that S3 formation also proceeds by a non-RRKM process. Data are lacking on isotopic (an even non-isotopic) rates of S3 formation, so it is not possible to make definitive statements about MIF in S3 at this time. However modeling results suggest that the vapor pressure of S2 is too low for gas-phase S3 formation to be significant. Two additional species that may exhibit a non-RRKM MIF signature are S2O2 and S4. Again, there is a lack of isotopomer-specific kinetic data for these reactions, and gas-phase formation of S4 is likely inconsequential. Perhaps the most obvious mechanism is simply the primary act of SO2 photolysis. The SO2 absorption spectrum is highly structured, with strong vibronic bands above and below the dissociation limit. In contrast H2S, with its mostly

  12. Precision mass measurements of some isotopes of tungsten and mercury for an adjustment to the mass table in the region A = 184 to A = 204

    NASA Astrophysics Data System (ADS)

    Barillari, Domenico K.

    This thesis concerns the precise re-measurement of mass values in the region of the mercury isotopes, such that important discrepancies in the high-mass end of the mass table could be resolved. Scope and contents. Four mass spectroscopic doublets involving a comparison between 201Hg, 199Hg and 183W (and using a chlorocarbon reference) are reported from measurements made with the upgraded Manitoba 11 deflection instrument. The measurements address the problem of a mass table mis-adjustment in the region of the valley of β-stability between the tungsten group and the noble metals. The results, forming a well-closed loop of mass differences, support the earlier results of Kozier [Ko(1977)] regarding the (stable) mercury isotope masses and confirm an approximate 20 μu discrepancy in the mass adjustment of Audi et al [Au(1993)]. A local least- square re-adjustment conducted using these and existing mass table data suggests that the error originates with mass differences pertaining to one or more other nuclide pairs, perhaps 193Ir-192Ir. The work on upgrading the precision voltage supply and potentiometry system of the Manitoba II instrument is also reported, as is a new assessment on the data processing method. (Abstract shortened by UMI.)

  13. Simultaneous hydrogen and heavier element isotopic ratio images with a scanning submicron ion probe and mass resolved polyatomic ions.

    PubMed

    Slodzian, Georges; Wu, Ting-Di; Bardin, Noémie; Duprat, Jean; Engrand, Cécile; Guerquin-Kern, Jean-Luc

    2014-04-01

    In situ microanalysis of solid samples is often performed using secondary ion mass spectrometry (SIMS) with a submicron ion probe. The destructive nature of the method makes it mandatory to prevent information loss by using instruments combining efficient collection of secondary ions and a mass spectrometer with parallel detection capabilities. The NanoSIMS meets those requirements with a magnetic spectrometer but its mass selectivity has to be improved for accessing opportunities expected from polyatomic secondary ions. We show here that it is possible to perform D/H ratio measurement images using 12CD-/12CH-, 16OD-/16OH-, or 12C2D-/12C2H- ratios. These polyatomic species allow simultaneous recording of D/H ratios and isotopic compositions of heavier elements like 15N/14N (via 12C15N-/12C14N-) and they provide a powerful tool to select the phase of interest (e.g., mineral versus organics). We present high mass resolution spectra and an example of isotopic imaging where D/H ratios were obtained via the 12C2D-/12C2H- ratio with 12C2D- free from neighboring mass interferences. Using an advanced mass resolution protocol, a "conventional" mass resolving power of 25,000 can be achieved. Those results open many perspectives for isotopic imaging at a fine scale in biology, material science, geochemistry, and cosmochemistry.

  14. Stable carbon isotope analyses of nanogram quantities of particulate organic carbon (pollen) with laser ablation nano combustion gas chromatography/isotope ratio mass spectrometry

    PubMed Central

    Sluijs, Appy; Laks, Jelmer J.; Reichart, Gert‐Jan

    2016-01-01

    Rationale Analyses of stable carbon isotope ratios (δ 13C values) of organic and inorganic matter remains have been instrumental for much of our understanding of present and past environmental and biological processes. Until recently, the analytical window of such analyses has been limited to samples containing at least several μg of carbon. Methods Here we present a setup combining laser ablation, nano combustion gas chromatography and isotope ratio mass spectrometry (LA/nC/GC/IRMS). A deep UV (193 nm) laser is used for optimal fragmentation of organic matter with minimum fractionation effects and an exceptionally small ablation chamber and combustion oven are used to reduce the minimum sample mass requirement compared with previous studies. Results Analyses of the international IAEA CH‐7 polyethylene standard show optimal accuracy, and precision better than 0.5‰, when measuring at least 42 ng C. Application to untreated modern Eucalyptus globulus (C3 plant) and Zea mays (C4 plant) pollen grains shows a ~ 16‰ offset between these species. Within each single Z. mays pollen grain, replicate analyses show almost identical δ 13C values. Conclusions Isotopic offsets between individual pollen grains exceed analytical uncertainties, therefore probably reflecting interspecimen variability of ~0.5–0.9‰. These promising results set the stage for investigating both δ 13C values and natural carbon isotopic variability between single specimens of a single population of all kinds of organic particles yielding tens of nanograms of carbon. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd. PMID:27766694

  15. High-precision, automated stable isotope analysis of atmospheric methane and carbon dioxide using continuous-flow isotope-ratio mass spectrometry.

    PubMed

    Fisher, Rebecca; Lowry, David; Wilkin, Owen; Sriskantharajah, Srimathy; Nisbet, Euan G

    2006-01-01

    Small-scale developments have been made to an off-the-shelf continuous-flow gas chromatography/isotope-ratio mass spectrometry (CF-GC/IRMS) system to allow high-precision isotopic analysis of methane (CH(4)) and carbon dioxide (CO(2)) at ambient concentrations. The repeatability (1sigma) obtainable with this system is 0.05 per thousand for delta(13)C of CH(4), 0.03 per thousand for delta(13)C of CO(2), and 0.05 per thousand for delta(18)O of CO(2) for ten consecutive analyses of a standard tank. An automated inlet system, which allows diurnal studies of CO(2) and CH(4) isotopes, is also described. The improved precision for CH(4) analysis was achieved with the use of a palladium powder on quartz wool catalyst in the combustion furnace, which increased the efficiency of oxidation of CH(4) to CO(2). The automated inlet further improved the precision for both CH(4) and CO(2) analysis by keeping the routine constant. The method described provides a fast turn-around in samples, with accurate, reproducible results, and would allow a long-term continuous record of CH(4) or CO(2) isotopes at a site to be made, providing information about changing sources of the gases both seasonally and interannually.

  16. Longitudinal profiling of urinary steroids by gas chromatography/combustion/isotope ratio mass spectrometry: diet change may result in carbon isotopic variations.

    PubMed

    Saudan, Christophe; Kamber, Matthias; Barbati, Giulia; Robinson, Neil; Desmarchelier, Aurélien; Mangin, Patrice; Saugy, Martial

    2006-02-02

    Longitudinal profiling of urinary steroids was investigated by using a gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) method. The carbon isotope ratio of three urinary testosterone (T) metabolites: androsterone, etiocholanolone, 5beta-androstane-3alpha,17beta-diol (5beta-androstanediol) together with 16(5alpha)-androsten-3alpha-ol (androstenol) and 5beta-pregnane-3alpha,20alpha-diol (5beta-pregnanediol) were measured in urine samples collected from three top-level athletes over 2 years. Throughout the study, the subjects were living in Switzerland and were residing every year for a month or two in an African country. (13)C-enrichment larger than 2.5 per thousand was observed for one subject after a 2-month stay in Africa. Our findings reveal that (13)C-enrichment caused by a diet change might be reduced if the stay in Africa was shorter or if the urine sample was not collected within the days after return to Switzerland. The steroids of interest in each sample did not show significant isotopic fractionation that could lead to false positive results in anti-doping testing. In contrast to the results obtained with the carbon isotopic ratio, profiling of urinary testosterone/epitestosterone (T/E) ratios was found to be unaffected by a diet change.

  17. Application of isotopic labeling, and gas chromatography mass spectrometry, to understanding degradation products and pathways in the thermal-oxidative aging of Nylon 6.6

    SciTech Connect

    White, Gregory Von; Clough, Roger L.; Hochrein, James M.; Bernstein, Robert

    2013-12-01

    Nylon 6.6 containing 13C isotopic labels at specific positions along the macromolecular backbone has been subjected to extensive thermal-oxidative aging at 138 °C for time periods up to 243 days. In complementary experiments, unlabeled Nylon 6.6 was subjected to the same aging conditions under an atmosphere of 18O2. Volatile organic degradation products were analyzed by cryofocusing gas chromatography mass spectrometry (cryo-GC/MS) to identify the isotopic labeling. The labeling results, combined with basic considerations of free radical reaction chemistry, provided insights to the origin of degradation species, with respect to the macromolecular structure. A number of inferences on chemical mechanisms were drawn, based on 1) the presence (or absence) of the isotopic labels in the various products, 2) the location of the isotope within the product molecule, and 3) the relative abundance of products as indicated by large differences in peak intensities in the gas chromatogram. The overall degradation results can be understood in terms of free radical pathways originating from initial attacks on three different positions along the nylon chain which include hydrogen abstraction from: the (CH2) group adjacent to the nitrogen atom, at the (CH2) adjacent the carbonyl group, and direct radical attack on the carbonyl. Understanding the pathways which lead to Nylon 6.6 degradation ultimately provides new insight into changes that can be leveraged to detect and reduce early aging and minimize problems associated with material degradation.

  18. The confines of triple oxygen isotope exponents in elemental and complex mass-dependent processes

    NASA Astrophysics Data System (ADS)

    Bao, Huiming; Cao, Xiaobin; Hayles, Justin A.

    2015-12-01

    Small differences in triple isotope relationships, or Δ17O in the case of oxygen, have been increasingly used to study a range of problems including hydrological cycles, stratosphere-troposphere exchange, biogeochemical pathways and fluxes, and the Moon's origin in the geochemical and cosmochemical communities. A Δ17O value depends on the triple isotope exponent θ of involved reaction steps. However, the probabilistic distribution of the intrinsic and apparent θ values has not been examined for elemental processes and for processes that are out of equilibrium or bearing reservoir-transport complexities. A lack of knowledge on the confines of θ may hamper our understanding of the subtle differences among mass-dependent processes and may result in mischaracterization of a set of mass-dependent processes as being in violation of mass-dependent rules. Here we advocate a reductionist approach and explore θ confines starting from kinetic isotope effects (KIEs) within the framework of transition state theory (TST). The advantage of our KIE approach is that any elemental or composite, equilibrium or non-equilibrium process can be reduced to a set of KIEs with corresponding θKIE. We establish that the KIE between a reactant and a transition state (TS) is intrinsic. Given a range of KIEs known for Earth processes involving oxygen, we use a Monte Carlo calculation method and a range of oxygen-bonded molecular masses to obtain a distribution of θKIE values and subsequently that of θeq. Next, complexities are examined by looking into expected effects due to reaction progress, unbalanced fluxes, and reference frame. Finally, compounded reservoir-transport effects are examined using two simple processes - Rayleigh Distillation (RD) and Fractional Distillation (FD). Our results show that the apparent θ values between two species or two states of the same evolving species have much broader confines than the commonly used "canonical" confines of 0.51-0.53, particularly

  19. Nucleosynthetic and Mass-Dependent Titanium Isotope Variations in Individual Chondrules of Ordinary Chondrites

    NASA Astrophysics Data System (ADS)

    Schönbächler, M.; Bauer, K. K.; Fehr, M. A.; Chaumard, N.; Zanda, B.

    2017-02-01

    We present evidence for nucleosynthetic Ti isotope heterogeneity between individual chondrules of ordinary chondrites difficult to reconcile with chondrule formation from molten planetesimals. Metamorphism resulted in stable Ti isotope fractionation.

  20. The Determination of the Natural Abundance of the Isotopes of Chlorine: An Introductory Experiment in Mass Spectrometry.

    ERIC Educational Resources Information Center

    O'Malley, Rebecca M.

    1982-01-01

    Describes a laboratory experiment which introduces basic principles and experimental techniques of mass spectrometry for fourth year undergraduate (B.Sc.) students. Laboratory procedures, background information, and discussion of results are provided for the experiment in which the natural isotopic abundance of chlorine is determined. (Author/JN)

  1. Spatially tracking 13C labeled substrate (bicarbonate) accumulation in microbial communities using laser ablation isotope ratio mass spectrometry

    SciTech Connect

    Moran, James J.; Doll, Charles G.; Bernstein, Hans C.; Renslow, Ryan S.; Cory, Alexandra B.; Hutchison, Janine R.; Lindemann, Stephen R.; Fredrickson, Jim K.

    2014-08-25

    This is a manuscript we would like to submit for publication in Environmental Microbiology Reports. This manuscript contains a description of a laser ablation isotope ratio mass spectrometry methodology developed at PNNL and applied to a microbial system at a PNNL project location – Hot Lake, Washington. I will submit a word document containing the entire manuscript with this Erica input request form.

  2. Determination of Peptide and Protein Ion Charge States by Fourier Transformation of Isotope-Resolved Mass Spectra

    SciTech Connect

    Tabb, Dave L; Shah, Manesh B; Strader, Michael B; Connelly, Heather M; Hettich, Robert {Bob} L; Hurst, Gregory {Greg} B

    2006-01-01

    We report an automated method for determining charge states from high-resolution mass spectra. Fourier transforms of isotope packets from high-resolution mass spectra are compared to Fourier transforms of modeled isotopic peak packets for a range of charge states. The charge state for the experimental ion packet is determined by the model isotope packet that yields the best match in the comparison of the Fourier transforms. This strategy is demonstrated for determining peptide ion charge states from 'zoom scan' data from a linear quadrupole ion trap mass spectrometer, enabling the subsequent automated identification of singly-through quadruply-charged peptide ions, while reducing the numbers of conflicting identifications from ambiguous charge state assignments. We also apply this technique to determine the charges of intact protein ions from LC-FTICR data, demonstrating that it is more sensitive under these experimental conditions than two existing algorithms. The strategy outlined in this paper should be generally applicable to mass spectra obtained from any instrument capable of isotopic resolution.

  3. Silicon isotope ratio measurements by inductively coupled plasma tandem mass spectrometry for alteration studies of nuclear waste glasses.

    PubMed

    Gourgiotis, Alkiviadis; Ducasse, Thomas; Barker, Evelyne; Jollivet, Patrick; Gin, Stéphane; Bassot, Sylvain; Cazala, Charlotte

    2017-02-15

    High-level, long-lived nuclear waste arising from spent fuel reprocessing is vitrified in silicate glasses for final disposal in deep geologic formations. In order to better understand the mechanisms driving glass dissolution, glass alteration studies, based on silicon isotope ratio monitoring of (29)Si-doped aqueous solutions, were carried out in laboratories. This work explores the capabilities of the new type of quadrupole-based ICP-MS, the Agilent 8800 tandem quadrupole ICP-MS/MS, for accurate silicon isotope ratio determination for alteration studies of nuclear waste glasses. In order to avoid silicon polyatomic interferences, a new analytical method was developed using O2 as the reaction gas in the Octopole Reaction System (ORS), and silicon isotopes were measured in mass-shift mode. A careful analysis of the potential polyatomic interferences on SiO(+) and SiO2(+) ion species was performed, and we found that SiO(+) ion species suffer from important polyatomic interferences coming from the matrix of sample and standard solutions (0.5M HNO3). For SiO2(+), no interferences were detected, and thus, these ion species were chosen for silicon isotope ratio determination. A number of key settings for accurate isotope ratio analysis like, detector dead time, integration time, number of sweeps, wait time offset, memory blank and instrumental mass fractionation, were considered and optimized. Particular attention was paid to the optimization of abundance sensitivity of the quadrupole mass filter before the ORS. We showed that poor abundance sensitivity leads to a significant shift of the data away from the Exponential Mass Fractionation Law (EMFL) due to the spectral overlaps of silicon isotopes combined with different oxygen isotopes (i.e. (28)Si(16)O(18)O(+), (30)Si(16)O(16)O(+)). The developed method was validated by measuring a series of reference solutions with different (29)Si enrichment. Isotope ratio trueness, uncertainty and repeatability were found to be <0

  4. Stable Isotope Peptide Mass Spectrometry To Decipher Amino Acid Metabolism in Dehalococcoides Strain CBDB1

    PubMed Central

    Marco-Urrea, Ernest; Seifert, Jana; von Bergen, Martin

    2012-01-01

    Dehalococcoides species are key players in the anaerobic transformation of halogenated solvents at contaminated sites. Here, we analyze isotopologue distributions in amino acid pools from peptides of Dehalococcoides strain CBDB1 after incubation with 13C-labeled acetate or bicarbonate as a carbon source. The resulting data were interpreted with regard to genome annotations to identify amino acid biosynthesis pathways. In addition to using gas chromatography-mass spectrometry (GC-MS) for analyzing derivatized amino acids after protein hydrolysis, we introduce a second, much milder method, in which we directly analyze peptide masses after tryptic digest and peptide fragments by nano-liquid chromatography-electrospray ionization-tandem mass spectrometry (nano-LC-ESI-MS/MS). With this method, we identify isotope incorporation patterns for 17 proteinaceous amino acids, including proline, cysteine, lysine, and arginine, which escaped previous analyses in Dehalococcoides. Our results confirmed lysine biosynthesis via the α-aminoadipate pathway, precluding lysine formation from aspartate. Similarly, the isotopologue pattern obtained for arginine provided biochemical evidence of its synthesis from glutamate. Direct peptide MS/MS analysis of the labeling patterns of glutamine and asparagine, which were converted to glutamate and aspartate during protein hydrolysis, gave biochemical evidence of their precursors and confirmed glutamate biosynthesis via a Re-specific citrate synthase. By addition of unlabeled free amino acids to labeled cells, we show that in strain CBDB1 none of the 17 tested amino acids was incorporated into cell mass, indicating that they are all synthesized de novo. Our approach is widely applicable and provides a means to analyze amino acid metabolism by studying specific proteins even in mixed consortia. PMID:22661690

  5. Mapping peptide thiol accessibility in membranes using a quaternary ammonium isotope-coded mass tag (ICMT)

    PubMed Central

    Su, Chiao-Yung; London, Erwin; Sampson, Nicole S.

    2013-01-01

    The plasma membrane contains a diverse array of proteins, including receptors, channels, and signaling complexes, that serve as decision-making centers. Investigation of membrane protein topology is important for understanding the function of these types of protein. Here, we report a method to determine protein topology in the membrane that utilizes labeling of cysteine with isotope-coded mass tags. The mass tags contain a thiol reactive moiety, linker, and a quaternary ammonium group to aid ionization in the mass spectrometer and were synthesizes as both light and heavy (deuterated) forms. The probes were found to be membrane impermeable when applied to lipid vesicles. To assess the utility of the probes for mapping peptide thiol topology, we employed a two-step labeling procedure. Vesicles containing α-helical transmembrane peptides were labeled with heavy (or light) probe, solubilized by detergent, and then labeled by an excess of the complementary probe. Peptide for which the cysteine was oriented in the center of the lipid bilayer was not labeled until the lipid vesicles were lysed with detergent, consistent with the membrane impermeability of the probes and reduced ionization of the thiol in the hydrophobic membrane. Peptide for which the cysteine was positioned in the head group zone of the lipid bilayer was labeled rapidly. Peptide for which the cysteine was positioned below the head group abutting the hydrocarbon region was labeled at a reduced rate compared to the fully accessible cysteine. Moreover, the effect of lipid bilayer structure on the kinetics of peptide and lipid flipping in the bilayer was readily measured with our two-step labeling method. The small sample size required, the ease and rapidity of sample preparation, and the amenability of MALDI-TOF mass spectral to analysis in the presence of lipids will enable future facile investigation of membrane proteins in a cellular context. PMID:23725486

  6. Isotopic distributions, element ratios, and element mass fractions from enrichment-meter-type gamma-ray measurements of MOX

    SciTech Connect

    Close, D.A.; Parker, J.L.; Haycock, D.L. ); Dragnev, T. )

    1991-01-01

    The gamma-ray spectra from infinitely'' thick mixed oxide samples have been measured. The plutonium isotopics, the U/Pu ratio, the high-Z mass fractions (assuming only plutonium, uranium, and americium), and the low-Z mass fraction (assuming the matrix is only oxygen) can be determined by carefully analyzing the data. The results agree well with the chemical determination of these parameters. 8 refs., 3 figs., 3 tabs.

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

    PubMed

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

    2016-05-01

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

  8. Isotopic mass fractionation laws for magnesium and their effects on 26Al-26Mg systematics in solar system materials

    NASA Astrophysics Data System (ADS)

    Davis, Andrew M.; Richter, Frank M.; Mendybaev, Ruslan A.; Janney, Philip E.; Wadhwa, Meenakshi; McKeegan, Kevin D.

    2015-06-01

    Magnesium isotope ratios are known to vary in solar system objects due to the effects of 26Al decay to 26Mg and mass-dependent fractionation, but anomalies of nucleosynthetic origin must also be considered. In order to infer the amount of enhancement of 26Mg/24Mg due to 26Al decay or to resolve small nucleogenetic anomalies, the exact relationship between 26Mg/24Mg and 25Mg/24Mg ratios due to mass-dependent fractionation, the mass-fractionation "law", must be accurately known so that the 25Mg/24Mg ratio can be used to correct the 26Mg/24Mg ratio for mass fractionation. Mass-dependent fractionation in mass spectrometers is reasonably well characterized, but not necessarily fully understood. It follows a simple power fractionation law, sometimes referred to as the "exponential law". In contrast, mass fractionation in nature, in particular that due to high temperature evaporation that likely caused the relatively large effects observed in calcium-, aluminum-rich inclusions (CAIs), is reasonably well understood, but mass-fractionation laws for magnesium have not been explored in detail. The magnesium isotopic compositions of CAI-like evaporation residues produced in a vacuum furnace indicate that the slope on a log 25Mg/24Mg vs. log 26Mg/24Mg plot is ∼0.5128, and different from those predicted by any of the commonly used mass-fractionation laws. Evaporation experiments on forsterite-rich bulk compositions give exactly the same slope, indicating that the measured mass-fractionation law for evaporation of magnesium is applicable to a wide range of bulk compositions. We discuss mass-fractionation laws and the implications of the measured fractionation behavior of magnesium isotopes for 26Al-26Mg chronology.

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

    SciTech Connect

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

    1988-03-01

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

  10. SO2 photolysis as a source for sulfur mass-independent isotope signatures in stratospheric aerosols

    NASA Astrophysics Data System (ADS)

    Whitehill, A. R.; Jiang, B.; Guo, H.; Ono, S.

    2014-09-01

    Signatures of sulfur isotope mass-independent fractionation (S-MIF) have been observed in stratospheric sulfate aerosols deposited in polar ice. The S-MIF signatures are associated with stratospheric photochemistry following stratospheric volcanic eruptions, but the exact mechanism responsible for the production and preservation of these signatures is debated. In order to identify the origin and the mechanism of preservation for these signatures, a series of laboratory photochemical experiments were carried out to investigate the effect of temperature and added O2 on S-MIF produced by the two absorption band systems of SO2 photolysis in the 190 to 220 nm region and photoexcitation in the 250 to 350 nm region. The SO2 photolysis (SO2 + hν → SO + O) experiments showed S-MIF signals with large 34S / 32S fractionation, which increases with decreasing temperature. The overall S-MIF pattern observed for photolysis experiments, including high 34S / 32S fractionations, positive mass-independent anomalies in 33S, and negative anomalies in 36S, is consistent with a major contribution from optical isotopologue screening effects and measurements for stratospheric sulfate aerosols. SO2 photoexicitation produced products with positive MIF anomalies in both 33S and 36S that is different from stratospheric aerosols. SO2 photolysis in the presence of O2 produced SO3 with S-MIF signals, suggesting the transfer of the MIF signals of SO to SO3 by the SO + O2 + M → SO3 + M reaction. This is supported with energy calculations of stationary points on the SO3 potential energy surfaces, which indicate that this reaction occurs slowly on a single adiabatic surface, but that it can occur more rapidly through intersystem crossing. The results from our experiments constrain the termolecular reaction rate to between 1.0 × 10-37 cm6 molecule-2 s-1 and 1.0 × 10-36 cm6 molecule-2 s-1. This rate can explain the preservation of mass independent isotope signatures in stratospheric sulfate

  11. Modified ion exchange separation for tungsten isotopic measurements from kimberlite samples using multi-collector inductively coupled plasma mass spectrometry.

    PubMed

    Sahoo, Yu Vin; Nakai, Shun'ichi; Ali, Arshad

    2006-03-01

    Tungsten isotope composition of a sample of deep-seated rock can record the influence of core-mantle interaction of the parent magma. Samples of kimberlite, which is known as a carrier of diamond, from the deep mantle might exhibit effects of core-mantle interaction. Although tungsten isotope anomaly was reported for kimberlites from South Africa, a subsequent investigation did not verify the anomaly. The magnesium-rich and calcium-rich chemical composition of kimberlite might engender difficulty during chemical separation of tungsten for isotope analyses. This paper presents a simple, one-step anion exchange technique for precise and accurate determination of tungsten isotopes in kimberlites using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Large quantities of Ca and Mg in kimberlite samples were precipitated and removed with aqueous H(2)SO(4). Highly pure fractions of tungsten for isotopic measurements were obtained following an anion exchange chromatographic procedure involving mixed acids. That procedure enabled efficient removal of high field strength elements (HFSE), such as Hf, Zr and Ti, which are small ions that carry strong charges and develop intense electrostatic fields. The tungsten yields were 85%-95%. Advantages of this system include less time and less use of reagents. Precise and accurate isotopic measurements are possible using fractions of tungsten that are obtained using this method. The accuracy and precision of these measurements were confirmed using various silicate standard rock samples, JB-2, JB-3 and AGV-1.

  12. Quantifying Uranium Isotope Ratios Using Resonance Ionization Mass Spectrometry: The Influence of Laser Parameters on Relative Ionization Probability

    SciTech Connect

    Isselhardt, Brett H.

    2011-09-01

    Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure relative uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process to provide a distinction between uranium atoms and potential isobars without the aid of chemical purification and separation. We explore the laser parameters critical to the ionization process and their effects on the measured isotope ratio. Specifically, the use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of 235U/238U ratios to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser in a 3-color, 3-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from >10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation. A rate equation model for predicting the relative ionization probability has been developed to study the effect of variation in laser parameters on the measured isotope ratio. This work demonstrates that RIMS can be used for the robust measurement of uranium isotope ratios.

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

    SciTech Connect

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

    1990-02-15

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

  14. Isotopic yield measurement in the heavy mass region for {sup 239}Pu thermal neutron induced fission

    SciTech Connect

    Bail, A.; Serot, O.; Mathieu, L.; Litaize, O.; Materna, T.; Koester, U.; Faust, H.; Letourneau, A.; Panebianco, S.

    2011-09-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  16. Quantitative Metabolome Analysis Based on Chromatographic Peak Reconstruction in Chemical Isotope Labeling Liquid Chromatography Mass Spectrometry.

    PubMed

    Huan, Tao; Li, Liang

    2015-07-21

    Generating precise and accurate quantitative information on metabolomic changes in comparative samples is important for metabolomics research where technical variations in the metabolomic data should be minimized in order to reveal biological changes. We report a method and software program, IsoMS-Quant, for extracting quantitative information from a metabolomic data set generated by chemical isotope labeling (CIL) liquid chromatography mass spectrometry (LC-MS). Unlike previous work of relying on mass spectral peak ratio of the highest intensity peak pair to measure relative quantity difference of a differentially labeled metabolite, this new program reconstructs the chromatographic peaks of the light- and heavy-labeled metabolite pair and then calculates the ratio of their peak areas to represent the relative concentration difference in two comparative samples. Using chromatographic peaks to perform relative quantification is shown to be more precise and accurate. IsoMS-Quant is integrated with IsoMS for picking peak pairs and Zero-fill for retrieving missing peak pairs in the initial peak pairs table generated by IsoMS to form a complete tool for processing CIL LC-MS data. This program can be freely downloaded from the www.MyCompoundID.org web site for noncommercial use.

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

    PubMed

    Fassett, J D; Murphy, T J

    1990-02-15

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

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

    SciTech Connect

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

    1991-01-01

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

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

    PubMed

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

    2012-04-01

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

  20. Analyzing Nuclear Fuel Cycles from Isotopic Ratios of Waste Products Applicable to Measurement by Accelerator Mass Spectrometry

    SciTech Connect

    Biegalski, S R; Whitney, S M; Buchholz, B

    2005-08-24

    An extensive study was conducted to determine isotopic ratios of nuclides in spent fuel that may be utilized to reveal historical characteristics of a nuclear reactor cycle. This forensic information is important to determine the origin of unknown nuclear waste. The distribution of isotopes in waste products provides information about a nuclear fuel cycle, even when the isotopes of uranium and plutonium are removed through chemical processing. Several different reactor cycles of the PWR, BWR, CANDU, and LMFBR were simulated for this work with the ORIGEN-ARP and ORIGEN 2.2 codes. The spent fuel nuclide concentrations of these reactors were analyzed to find the most informative isotopic ratios indicative of irradiation cycle length and reactor design. Special focus was given to long-lived and stable fission products that would be present many years after their creation. For such nuclides, mass spectrometry analysis methods often have better detection limits than classic gamma-ray spectroscopy. The isotopic ratios {sup 151}Sm/{sup 146}Sm, {sup 149}Sm/{sup 146}Sm, and {sup 244}Cm/{sup 246}Cm were found to be good indicators of fuel cycle length and are well suited for analysis by accelerator mass spectroscopy.

  1. High-precision measurement of variations in calcium isotope ratios in urine by multiple collector inductively coupled plasma mass spectrometry

    USGS Publications Warehouse

    Morgan, J.L.L.; Gordon, G.W.; Arrua, R.C.; Skulan, J.L.; Anbar, A.D.; Bullen, T.D.

    2011-01-01

    We describe a new chemical separation method to isolate Ca from other matrix elements in biological samples, developed with the long-term goal of making high-precision measurement of natural stable Ca isotope variations a clinically applicable tool to assess bone mineral balance. A new two-column procedure utilizing HBr achieves the purity required to accurately and precisely measure two Ca isotope ratios (44Ca/42Ca and 44Ca/43Ca) on a Neptune multiple collector inductively coupled plasma mass spectrometer (MC-ICPMS) in urine. Purification requirements for Sr, Ti, and K (Ca/Sr > 10000; Ca/Ti > 10000000; and Ca/K > 10) were determined by addition of these elements to Ca standards of known isotopic composition. Accuracy was determined by (1) comparing Ca isotope results for samples and standards to published data obtained using thermal ionization mass spectrometry (TIMS), (2) adding a Ca standard of known isotopic composition to a urine sample purified of Ca, and (3) analyzing mixtures of urine samples and standards in varying proportions. The accuracy and precision of δ44/42Ca measurements of purified samples containing 25 μg of Ca can be determined with typical errors less than ±0.2‰ (2σ).

  2. Discovering Mercury Protein Modifications in Whole Proteomes Using Natural Isotope Distributions Observed in Liquid Chromatography-Tandem Mass Spectrometry

    SciTech Connect

    Polacco, Benjamin J.; Purvine, Samuel O.; Zink, Erika M.; LaVoie, Stephen P.; Lipton, Mary S.; Summers, Anne O.; Miller, Susan M.

    2011-08-01

    The identification of peptides that result from post-translational modifications is critical for understanding normal pathways of cellular regulation as well as identifying damage from, or exposures to xenobiotics, i.e. the exposome. However, because of their low abundance in proteomes, effective detection of modified peptides by mass spectrometry (MS) typically requires enrichment to eliminate false identifications. We present a new method for confidently identifying peptides with mercury (Hg)-containing adducts that is based on the influence of mercury’s seven stable isotopes on peptide isotope distributions detected by high-resolution MS. Using a pure protein and E. coli cultures exposed to phenyl mercuric acetate, we show the pattern of peak heights in isotope distributions from primary MS single scans efficiently identified Hg adducts in data from chromatographic separation coupled with tandem mass spectrometry with sensitivity and specificity greater than 90%. Isotope distributions are independent of peptide identifications based on peptide fragmentation (e.g. by SEQUEST), so both methods can be combined to eliminate false positives. Summing peptide isotope distributions across multiple scans improved specificity to 99.4% and sensitivity above 95%, affording identification of an unexpected Hg modification. We also illustrate the theoretical applicability of the method for detection of several less common elements including the essential element, selenium, as selenocysteine in peptides.

  3. Review: Current applications and challenges for liquid chromatography coupled to isotope ratio mass spectrometry (LC/IRMS).

    PubMed

    Godin, Jean-Philippe; McCullagh, James S O

    2011-10-30

    High-precision isotope analysis is recognized as an essential research tool in many fields of study. Until recently, continuous flow isotope ratio mass spectrometry (CF-IRMS) was available via an elemental analyzer or a gas chromatography inlet system for compound-specific analysis of light stable isotopes. In 2004, however, an interface that coupled liquid chromatography with IRMS (LC/IRMS) became commercially available for the first time. This brought the capability for new areas of application, in particular enabling compound-specific δ(13)C analysis of non-volatile, aqueous soluble, compounds from complex mixtures. The interface design brought with it several analytical constraints, however, in particular a lack of compatibility with certain types of chromatography as well as limited flow rates and mobile phase compositions. Routine LC/IRMS methods have, however, been established for measuring the δ(13)C isotopic ratios of underivatized individual compounds for application in archeology, nutrition and physiology, geochemistry, hydrology, soil science and food authenticity. Seven years after its introduction, we review the technical advances and constraints, methodological developments and new applications of liquid chromatography coupled to isotope ratio mass spectrometry.

  4. Quantitative analysis of aberrant fatty acid composition of zebrafish hepatic lipids induced by organochlorine pesticide using stable isotope-coded transmethylation and gas chromatography-mass spectrometry.

    PubMed

    Zhong, Hongying; Dong, Linjie; Dong, Qingjian; Ke, Changshu; Fu, Jieying; Wang, Xiaoli; Liu, Cong; Dai, Ling

    2012-07-01

    Organochlorine pesticides have been extensively used worldwide for agricultural purposes. Due to their resistance to metabolism, a major public health concern has been raised. Aberrant hepatic lipid composition has been a hallmark of many liver diseases associated with exposure to various toxins and chemicals. And thus lots of efforts have been focused on the development of analytical techniques that can rapidly and quantitatively determine the changes in fatty acid composition of hepatic lipids. In this work, changes in fatty acid composition of hepatic lipids in response to DDT (dichlorodiphenyltrichloroethane) exposure were quantitatively analyzed by a gas chromatography-mass spectrometric approach based on stable isotope-coded transmethylation. It has been quantitatively demonstrated that polyunsaturated fatty acids including C20:3n3, C20:4n6, and C22:6n3 decrease in response to DDT exposure. However, saturated long chain fatty acids including C16:0, C18:0, as well as monounsaturated long chain fatty acid C18:1n9 consistently increase in a DDT-concentration-dependent manner. In particular, much higher changes in the level of hepatic C16:0 and C18:0 for male fish were observed than that for female fish. These experimental results are in accordance with qualitative histopathological analysis that revealed liver morphological alterations. The stable isotope-coded mass spectrometric approach provides a reliable means for investigating hepatotoxicity associated with fatty acid synthesis, desaturation, mitochondrial beta-oxidation, and lipid mobilization. It should be useful in elucidation of hepatotoxic mechanisms and safety assessment of environmental toxins.

  5. Precise Zn isotopic ratio measurements of human red blood cell and hair samples by multiple collector-ICP-mass spectrometry.

    PubMed

    Ohno, Takeshi; Shinohara, Atsuko; Chiba, Momoko; Hirata, Takafumi

    2005-04-01

    Precise 66Zn/64Zn and 68Zn/64Zn isotopic ratios of biochemical samples have been measured using multiple collector-ICP-mass spectrometry (MC-ICPMS). In order to eliminate the mass spectrometric interferences on Zn isotopes (e.g., 64Ni+ and 136Ba2+), we chemically purified the analyte using an ion chromatographic technique. The resulting precisions of the 66Zn/64Zn and 68Zn/64Zn ratio measurements were 0.05/1000 and 0.10/1000 (2SD), respectively, which were enough to detect the isotopic variation of Zn in nature. Red blood cell (RBC) samples were collected from five volunteers (four males and one female), including a series of 12 RBC samples from one person through monthly-based sampling over a year. These were analyzed to test possible seasonal changes and variations in 66Zn/64Zn and 68Zn/64Zn ratios among the individuals. The 66Zn/64Zn and 68Zn/64Zn ratios for a series of 12 RBC samples collected over a year were 0.43/1000 and 0.83/1000 higher than the values of highly purified Zn metal (JMC Zn), and no seasonal change could be found. The 66Zn/64Zn and 68Zn/64Zn ratios for RBC samples collected from five volunteers did not vary significantly. In order to investigate Zn isotopic heterogeneity in a human body, Zn isotopic ratios of a hair sample collected from one of the volunteers was also analyzed. The 66Zn/64Zn and 68Zn/64Zn ratios for the hair sample were 0.59/1000 and 1.14/1000 lower than the mean value of RBC samples. This result demonstrates that detectable isotopic fractionation occurs in the human body. The data obtained here suggest that the isotopic ratios of trace metals could provide new information about transportation of metal elements in vivo.

  6. Isotope Ratio Mass Spectrometry and Shale Gas - What Is Possible with Current Technology?

    NASA Astrophysics Data System (ADS)

    Barrie, C. D.; Kasson, A.

    2014-12-01

    With ever increasing exploration and exploitation of 'unconventional' hydrocarbon resources, the drive to understand the origins, history and importance of these resources and their effects on the surrounding environment (i.e. ground waters) has never been more important. High-throughput, high-precision isotopic measurements are therefore a key tool in this industry to both understand the gas generated and monitor the development and stability of wells through time. With the advent of cavity ringdown spectroscopy (CRDS) instrumentation, there has been a push in some applications - environmental & atmospheric - to gather more and more data directly at the location of collection or at dedicated field stations. Furthermore, CRDS has resulted in users seeking greater autonomy of instrumentation and so-called black box technology. Traditionally IRMS technology has not met any of these demands, requiring very specific and extensive footprint, power and environmental requirements. This has meant that the 'Oil & Gas' sector, which for natural gases measurements requires GC-IRMS technology - not possible via CRDS - loses time, money and manpower as samples get sent to central facility or contract labs with potentially long lee times. However, recent developments in technology mean that IRMS systems exist which are benchtop, have much lower power requirements, standard power connections and as long as housed in a temperature controlled field stations can be deployed anywhere. Furthermore, with advances in electronics and software IRMS systems are approaching the black box level of newer instrumentation while maintaining the flexibility and abilities of isotope ratio mass spectrometry. This presentation will outline changes in IRMS technology applicable to the Oil & Gas industry, discuss the feasibility of true 'field' deployability and present results from a range of Oil & Gas samples.

  7. Use of stable lead isotopes and trace metals to characterize air mass sources into the eastern North Atlantic

    NASA Astrophysics Data System (ADS)

    VéRon, Alain J.; Church, Thomas M.

    1997-12-01

    Stable lead isotopes (204Pb, 206Pb, 207Pb, 208Pb) and trace metals (Mn, Al, Fe, Ni, Cu, Cd, Zn, Pb) have been analyzed in aerosol collected during the Atlantic Stratocumulus Transition Experiment-Marine Aerosol and Gas Exchange (ASTEX-MAGE) cruise that transited between Miami and the Azores from May to July 1992. Our goal was to define the continental signatures of the air masses encountered between the Azores and the subtropical regions. The combination of air mass trajectories, trace metal concentrations and stable lead isotopes allowed us to characterize the anthropogenic character of encountered air masses. The average 206Pb/207Pb ratio was 1.148±0.021 and corresponded to a mixing between well defined European (such as Great Britain with 1.115<206Pb/207Pb<1.125 and France with 206Pb/207Pb=1.141±0.000) and North American sources (with 206Pb/207Pb=1.184±0.000). On the basis of air mass trajectories and trace metal concentrations, the background isotopic signature associated with the trade winds (206Pb/207Pb=1.161±0.004) is consistent with previous reports by Church et al. [1990] such as 206Pb/207Pb=1.154±0.004 in 1988, (Véron et al., 1993), 206Pb/207Pb=1.155±0.004 in 1989, and Hamelin et al. [1996] (206Pb/207Pb=1.158±0.006) in 1991. Short-term variations of continental air mass sources was particularly investigated by considering the anthropogenic character of aerosols collected during two Lagrangian experiments conducted as part of the ASTEX-MAGE cruise. We demonstrated the utility of stable lead isotopes to assign a "continental source signature" (or mixture thereof) to air masses beyond that normally possible by conventional air mass trajectory analysis in remote oceanic regions.

  8. Relativistic mean-field study of the properties of Z=117 nuclei and the decay chains of the {sup 293,294}117 isotopes

    SciTech Connect

    Bhuyan, M.; Patra, S. K.; Gupta, Raj K.

    2011-07-15

    We have calculated the binding energy, root-mean-square radius, and quadrupole deformation parameter for the recently synthesized superheavy element Z=117, using the axially deformed relativistic mean-field (RMF) model. The calculation is extended to various isotopes of the Z=117 element, starting from A=286 till A=310. We predict almost spherical structures in the ground state for almost all the isotopes. A shape transition appears at about A=292 from a prolate to an oblate shape structure of the Z=117 nucleus in our mean-field approach. The most stable isotope (largest binding energy per nucleon) is found to be the {sup 288}117 nucleus. Also, the Q{sub {alpha}} values and the half-life T{sub 1/2}{sup {alpha}} for the {alpha}-decay chains of {sup 293}117 and {sup 294}117 are calculated, supporting the magic numbers at N=172 and/or 184.

  9. Quantifying groundwater dependence of a sub-polar lake cluster in Finland using an isotope mass balance approach

    NASA Astrophysics Data System (ADS)

    Isokangas, E.; Rozanski, K.; Rossi, P. M.; Ronkanen, A.-K.; Kløve, B.

    2015-03-01

    A stable isotope study of 67 kettle lakes and ponds situated on an esker aquifer (90 km2) in northern Finland was carried out to determine the role and extent of groundwater inflow in groundwater-dependent lakes. Distinct seasonal fluctuations in the δ18O and δ2H values of lakes are the result of seasonal ice cover prohibiting evaporation during the winter. An iterative isotope mass balance approach was used to calculate the inflow-to-evaporation ratios (ITOT/E) of all 67 lakes during the summer of 2013 when the isotopic compositions of the lakes were approaching a steady-state. The balance calculations were carried out independently for 2H and 18O data. Since evaporation rates were derived independently of any mass balance considerations, it was possible to determine the total inflow (ITOT) and mean turnover time (MTT) of the lakes. Furthermore, the groundwater seepage rates to all studied lakes were calculated. A quantitative measure was introduced for the dependence of a lake on groundwater (G index) that is defined as the percentage contribution of groundwater inflow to the total inflow of water to the given lake. The G index values of the lakes studied ranged from ca. 39 to 98%, revealing generally large groundwater dependency among the studied lakes. This study shows the effectiveness of applying an isotope mass balance approach to quantify the groundwater reliance of lakes situated in a relatively small area with similar climatic conditions.

  10. Quantification of Short-Chain Chlorinated Paraffins by Deuterodechlorination Combined with Gas Chromatography-Mass Spectrometry.

    PubMed

    Gao, Yuan; Zhang, Haijun; Zou, Lili; Wu, Ping; Yu, Zhengkun; Lu, Xianbo; Chen, Jiping

    2016-04-05

    Analysis of short-chain chlorinated paraffins (SCCPs) is extremely difficult because of their complex compositions with thousands of isomers and homologues. A novel analytical method, deuterodechlorination combined with high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS), was developed. A protocol is applied in the deuterodechlorination of SCCPs with LiAlD4, and the formed deuterated n-alkanes of different alkane chains can be distinguished readily from each other on the basis of their retention time and fragment mass ([M](+)) by HRGC-HRMS. An internal standard quantification of individual SCCP congeners was achieved, in which branched C10-CPs and branched C12-CPs were used as the extraction and reaction internal standards, respectively. A maximum factor of 1.26 of the target SCCP concentrations were determined by this method, and the relative standard deviations for quantification of total SCCPs were within 10%. This method was applied to determine the congener compositions of SCCPs in commercial chlorinated paraffins and environmental and biota samples after method validation. Low-chlorinated SCCP congeners (Cl1-4) were found to account for 32.4%-62.4% of the total SCCPs. The present method provides an attractive perspective for further studies on the toxicological and environmental characteristics of SCCPs.

  11. Structural identification of skin ceramides containing ω-hydroxy acyl chains using mass spectrometry.

    PubMed

    Wu, Zhexue; Shon, Jong Cheol; Kim, Jong Yei; Cho, Yunhi; Liu, Kwang-Hyeon

    2016-10-01

    The stratum corneum (SC) acts as a barrier that protects organisms against the environment and from transepidermal water loss. It consists of corneocytes embedded in a matrix of lipid metabolites (ceramides, cholesterol, and free fatty acids). Of these lipids, ceramides are sphingolipids consisting of sphingoid bases, linked to fatty acyl chains. Typical fatty acid acyl chains are composed of α-hydroxy fatty acids (A), esterified ω-hydroxy fatty acids (EO), non-hydroxy fatty acids (N), and ω-hydroxy fatty acids (O). Of these, O-type ceramides are ester-linked via their ω-hydroxyl group to proteins in the cornified envelope and can be released and extracted following mild alkaline hydrolysis. Tandem mass spectrometry (MS/MS) analysis of O-type ceramides using chip-based direct infusion nanoelectrospray-ion trap mass spectrometry generated the characteristic fragmentation pattern of both acyl and sphingoid units, suggesting that this method could be applied to the structural identification of O-type ceramides. Based on the MS/MS fragmentation patterns of O-type ceramides, comprehensive fragmentation schemes are proposed. In addition, we have also developed a method for identifying and profiling O-type ceramides in the mouse and guinea pig SC. This information may be used to identify O-type ceramides in the SC of animal skin.

  12. IgD heavy-chain deposition disease: detection by laser microdissection and mass spectrometry.

    PubMed

    Royal, Virginie; Quint, Patrick; Leblanc, Martine; LeBlanc, Richard; Duncanson, Garrett F; Perrizo, Robert L; Fervenza, Fernando C; Kurtin, Paul; Sethi, Sanjeev

    2015-04-01

    Monoclonal Ig deposition disease (MIDD) is a rare complication of monoclonal gammopathy characterized by deposition of monoclonal Ig light chains and/or heavy chains along the glomerular and tubular basement membranes. Here, we describe a unique case of IgD deposition disease. IgD deposition is difficult to diagnose, because routine immunofluorescence does not detect IgD. A 77-year-old man presented with proteinuria and renal failure, and kidney biopsy analysis showed a nodular sclerosing GN with extensive focal global glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Immunofluorescence was negative for Ig deposits, although electron microscopy showed deposits in the glomeruli and along tubular basement membranes. Laser microdissection of glomeruli and mass spectrometry of extracted peptides showed a large spectra number for IgD, and immunohistochemistry showed intense glomerular and tubular staining for IgD. Together, these findings are consistent with IgD deposition disease. Bone marrow biopsy analysis showed 5% plasma cells, which stained for IgD. The patient was treated with bortezomib and dexamethasone, which resulted in improvement of hematologic parameters but no improvement of renal function. The diagnosis of IgD deposition disease underscores the value of laser microdissection and mass spectrometry in further evaluating renal biopsies when routine assessment fails to reach an accurate diagnosis.

  13. Progress toward a search for anomalous spin-mass couplings with a dual-isotope rubidium magnetometer

    NASA Astrophysics Data System (ADS)

    Valdez, Julian; Lacey, Ian; Peregrinaramirez, Rodrigo; Delcheva, Delyana; Jacome, L. R.; Kimball, Derek

    2010-10-01

    A coupling between spin and mass can arise from new spin-0 or spin-1 force-mediating particles or in non-standard gravity with scalar or vector components in addition to the usual tensor interaction. We report on progress toward a search for anomalous couplings between the mass of the earth and Rb spins. In the experiment, a natural isotopic mixture of Rb atoms is contained in an antirelaxation-coated cell. The atomic spins are polarized via laser optical pumping and spin precession is measured in both isotopes using optical rotation. The experiment is particularly sensitive to spin-mass interactions of the proton. We discuss the sensitivity of our experimental scheme and strategies for control of several important systematic effects such as differential light shifts, collisional frequency shifts, and frequency shifts due to the rotation of the earth.

  14. Mass dependence of the activation enthalpy and entropy of unentangled linear alkane chains.

    PubMed

    Jeong, Cheol; Douglas, Jack F

    2015-10-14

    The mass scaling of the self-diffusion coefficient D of polymers in the liquid state, D ∼ M(β), is one of the most basic characteristics of these complex fluids. Although traditional theories such as the Rouse and reptation models of unentangled and entangled polymer melts, respectively, predict that β is constant, this exponent for alkanes has been estimated experimentally to vary from -1.8 to -2.7 upon cooling. Significantly, β changes with temperature T under conditions where the chains are not entangled and at temperatures far above the glass transition temperature Tg where dynamic heterogeneity does not complicate the description of the liquid dynamics. Based on atomistic molecular dynamics simulations on unentangled linear alkanes in the melt, we find that the variation of β with T can be directly attributed to the dependence of the enthalpy ΔHa and entropy ΔSa of activation on the number of alkane backbone carbon atoms, n. In addition, we find a sharp change in the melt dynamics near a "critical" chain length, n ≈ 17. A close examination of this phenomenon indicates that a "buckling transition" from rod-like to coiled chain configurations occurs at this characteristic chain length and distinct entropy-enthalpy compensation relations, ΔSa ∝ ΔHa, hold on either side of this polymer conformational transition. We conclude that the activation free energy parameters exert a significant influence on the dynamics of polymer melts that is not anticipated by either the Rouse and reptation models. In addition to changes of ΔHa and ΔSa with M, we expect changes in these free energy parameters to be crucial for understanding the dynamics of polymer blends, nanocomposites, and confined polymers because of changes of the fluid free energy by interfacial interactions and geometrical confinement.

  15. Mass dependence of the activation enthalpy and entropy of unentangled linear alkane chains

    SciTech Connect

    Jeong, Cheol; Douglas, Jack F.

    2015-10-14

    The mass scaling of the self-diffusion coefficient D of polymers in the liquid state, D ∼ M{sup β}, is one of the most basic characteristics of these complex fluids. Although traditional theories such as the Rouse and reptation models of unentangled and entangled polymer melts, respectively, predict that β is constant, this exponent for alkanes has been estimated experimentally to vary from −1.8 to −2.7 upon cooling. Significantly, β changes with temperature T under conditions where the chains are not entangled and at temperatures far above the glass transition temperature T{sub g} where dynamic heterogeneity does not complicate the description of the liquid dynamics. Based on atomistic molecular dynamics simulations on unentangled linear alkanes in the melt, we find that the variation of β with T can be directly attributed to the dependence of the enthalpy ΔH{sub a} and entropy ΔS{sub a} of activation on the number of alkane backbone carbon atoms, n. In addition, we find a sharp change in the melt dynamics near a “critical” chain length, n ≈ 17. A close examination of this phenomenon indicates that a “buckling transition” from rod-like to coiled chain configurations occurs at this characteristic chain length and distinct entropy-enthalpy compensation relations, ΔS{sub a} ∝ ΔH{sub a}, hold on either side of this polymer conformational transition. We conclude that the activation free energy parameters exert a significant influence on the dynamics of polymer melts that is not anticipated by either the Rouse and reptation models. In addition to changes of ΔH{sub a} and ΔS{sub a} with M, we expect changes in these free energy parameters to be crucial for understanding the dynamics of polymer blends, nanocomposites, and confined polymers because of changes of the fluid free energy by interfacial interactions and geometrical confinement.

  16. Protein Stable Isotope Fingerprinting (P-SIF): Multidimensional Protein Chromatography Coupled to Stable Isotope-Ratio Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Pearson, A.; Bovee, R. J.; Mohr, W.; Tang, T.

    2012-12-01

    As metagenomics increases our insight into microbial community diversity and metabolic potential, new approaches are required to determine the biogeochemical expression of this potential within ecosystems. Because stable isotopic analysis of the major bioactive elements (C, N) has been used historically to map flows of substrates and energy among macroscopic food webs, similar principles may apply to microbes. To address this challenge, we have developed a new analytical approach called Protein Stable Isotope Fingerprinting (P-SIF). P-SIF generates natural stable isotopic fingerprints of microbial individual or community proteomes. The main advantage of P-SIF is the potential to bridge the gap between diversity and function, thereby providing a window into the "black box" of environmental microbiology and helping to decipher the roles of uncultivated species. Our method implements a three-way, orthogonal scheme to separate mixtures of whole proteins into subfractions dominated by single or closely-related proteins. Protein extracts first are isoelectrically focused in a gel-free technique that yields 12 fractions separated over a gradient of pH 3-10. Each fraction then is separated by size-exclusion chromatography into 20 pools, ranging from >100kD to ~10kD. Finally, each of these pools is subjected to HPLC and collected in 40 time-slices based on protein hydrophobicity. Theoretical calculation reveals that the true chromatographic resolution of the total scheme is 5000, somewhat less than the 9600 resulting fractions. High-yielding fractions are subjected to δ13C analysis by spooling-wire microcombustion irMS (SWiM-irMS) optimized for samples containing 1-5 nmol carbon. Here we will present the method, results for a variety of pure cultures, and preliminary data for a sample of mixed environmental proteins. The data show the promise of this method for unraveling the metabolic complexity hidden within microbial communities.

  17. Mass independent sulfur isotope signatures in CMs: Implications for sulfur chemistry in the early solar system

    NASA Astrophysics Data System (ADS)

    Labidi, J.; Farquhar, J.; Alexander, C. M. O.'D.; Eldridge, D. L.; Oduro, H.

    2017-01-01

    We have investigated the quadruple sulfur isotopic composition of inorganic sulfur-bearing phases from 13 carbonaceous chondrites of CM type. Our samples include 4 falls and 9 Antarctic finds. We extracted sulfur from sulfides, sulfates, and elemental sulfur (S0) from all samples. On average, we recover a bulk sulfur (S) content of 2.11 ± 0.39 wt.% S (1σ). The recovered sulfate, S0 and sulfide contents represent 25 ± 12%, 10 ± 7% and 65 ± 15% of the bulk S, respectively (all 1σ). There is no evidence for differences in the bulk S content between falls and finds, and there is no correlation between the S speciation and the extent of aqueous alteration. We report ranges of Δ33S and Δ36S values in CMs that are significantly larger than previously observed. The largest variations are exhibited by S0, with Δ33S values ranging between -0.104 ± 0.012‰ and +0.256 ± 0.018‰ (2σ). The Δ36S/33S ratios of S0 are on average -3.1 ± 1.0 (2σ). Two CMs show distinct Δ36S/33S ratios, of +1.3 ± 0.1 and +0.9 ± 0.1. We suggest that these mass independent S isotopic compositions record H2S photodissociation in the nebula. The varying Δ36S/Δ33S ratios are interpreted to reflect photodissociation that occurred at different UV wavelengths. The preservation of these isotopic features requires that the S-bearing phases were heterogeneously accreted to the CM parent body. Non-zero Δ33S values are also preserved in sulfide and sulfate, and are positively correlated with S0 values. This indicates a genetic relationship between the S-bearing phases: We argue that sulfates were produced by the direct oxidation of S0 (not sulfide) in the parent body. We describe two types of models that, although imperfect, can explain the major features of the CM S isotope compositions, and can be tested in future studies. Sulfide and S0 could both be condensates from the nebula, as the residue and product, respectively, of incomplete H2S photodissociation by UV light (wavelength <150 nm

  18. Subset of Kappa and Lambda Germline Sequences Result in Light Chains with a Higher Molecular Mass Phenotype.

    PubMed

    Barnidge, David R; Lundström, Susanna L; Zhang, Bo; Dasari, Surendra; Murray, David L; Zubarev, Roman A

    2015-12-04

    In our previous work, we showed that electrospray ionization of intact polyclonal kappa and lambda light chains isolated from normal serum generates two distinct, Gaussian-shaped, molecular mass distributions representing the light-chain repertoire. During the analysis of a large (>100) patient sample set, we noticed a low-intensity molecular mass distribution with a mean of approximately 24 250 Da, roughly 800 Da higher than the mean of the typical kappa molecular-mass distribution mean of 23 450 Da. We also observed distinct clones in this region that did not appear to contain any typical post-translational modifications that would account for such a large mass shift. To determine the origin of the high molecular mass clones, we performed de novo bottom-up mass spectrometry on a purified IgM monoclonal light chain that had a calculated molecular mass of 24 275.03 Da. The entire sequence of the monoclonal light chain was determined using multienzyme digestion and de novo sequence-alignment software and was found to belong to the germline allele IGKV2-30. The alignment of kappa germline sequences revealed ten IGKV2 and one IGKV4 sequences that contained additional amino acids in their CDR1 region, creating the high-molecular-mass phenotype. We also performed an alignment of lambda germline sequences, which showed additional amino acids in the CDR2 region, and the FR3 region of functional germline sequences that result in a high-molecular-mass phenotype. The work presented here illustrates the ability of mass spectrometry to provide information on the diversity of light-chain molecular mass phenotypes in circulation, which reflects the germline sequences selected by the immunoglobulin-secreting B-cell population.

  19. Evidence from stable isotopes and (10)Be for solar system formation triggered by a low-mass supernova.

    PubMed

    Banerjee, Projjwal; Qian, Yong-Zhong; Heger, Alexander; Haxton, W C

    2016-11-22

    About 4.6 billion years ago, some event disturbed a cloud of gas and dust, triggering the gravitational collapse that led to the formation of the solar system. A core-collapse supernova, whose shock wave is capable of compressing such a cloud, is an obvious candidate for the initiating event. This hypothesis can be tested because supernovae also produce telltale patterns of short-lived radionuclides, which would be preserved today as isotopic anomalies. Previous studies of the forensic evidence have been inconclusive, finding a pattern of isotopes differing from that produced in conventional supernova models. Here we argue that these difficulties either do not arise or are mitigated if the initiating supernova was a special type, low in mass and explosion energy. Key to our conclusion is the demonstration that short-lived (10)Be can be readily synthesized in such supernovae by neutrino interactions, while anomalies in stable isotopes are suppressed.

  20. Evidence from stable isotopes and 10Be for solar system formation triggered by a low-mass supernova

    PubMed Central

    Banerjee, Projjwal; Qian, Yong-Zhong; Heger, Alexander; Haxton, W C

    2016-01-01

    About 4.6 billion years ago, some event disturbed a cloud of gas and dust, triggering the gravitational collapse that led to the formation of the solar system. A core-collapse supernova, whose shock wave is capable of compressing such a cloud, is an obvious candidate for the initiating event. This hypothesis can be tested because supernovae also produce telltale patterns of short-lived radionuclides, which would be preserved today as isotopic anomalies. Previous studies of the forensic evidence have been inconclusive, finding a pattern of isotopes differing from that produced in conventional supernova models. Here we argue that these difficulties either do not arise or are mitigated if the initiating supernova was a special type, low in mass and explosion energy. Key to our conclusion is the demonstration that short-lived 10Be can be readily synthesized in such supernovae by neutrino interactions, while anomalies in stable isotopes are suppressed. PMID:27873999

  1. Evidence from stable isotopes and 10Be for solar system formation triggered by a low-mass supernova

    NASA Astrophysics Data System (ADS)

    Banerjee, Projjwal; Qian, Yong-Zhong; Heger, Alexander; Haxton, W. C.

    2016-11-01

    About 4.6 billion years ago, some event disturbed a cloud of gas and dust, triggering the gravitational collapse that led to the formation of the solar system. A core-collapse supernova, whose shock wave is capable of compressing such a cloud, is an obvious candidate for the initiating event. This hypothesis can be tested because supernovae also produce telltale patterns of short-lived radionuclides, which would be preserved today as isotopic anomalies. Previous studies of the forensic evidence have been inconclusive, finding a pattern of isotopes differing from that produced in conventional supernova models. Here we argue that these difficulties either do not arise or are mitigated if the initiating supernova was a special type, low in mass and explosion energy. Key to our conclusion is the demonstration that short-lived 10Be can be readily synthesized in such supernovae by neutrino interactions, while anomalies in stable isotopes are suppressed.

  2. The non-mass-dependent oxygen isotopic composition of CO2 formed by O+CO: Anomalous isotope effects in the O+CO recombination reaction or transfer from ozone?

    NASA Astrophysics Data System (ADS)

    Estillore, A. D.; Wiegel, A. A.; Boering, K. A.

    2013-12-01

    A number of oxygen-containing atmospheric species are now known to have non-mass-dependent triple oxygen isotope compositions (i.e., non-mass-dependent relationships between 16O, 17O, and 18O), which in turn are now being broadly applied as probes of biogeochemical cycles and chemical reactivity or as climate proxies on a variety of timescales. For many species, their non-mass-dependent oxygen isotope compositions derive from chemical or O(1D)-mediated photochemical transfer from ozone, which is non-mass-dependently enriched in 17O and 18O due to large non-mass-dependent kinetic isotope effects in the ozone recombination reaction, O+O2+M. For other species, however, there may also be additional non-mass-dependent kinetic isotope effects involved beyond ozone formation. The distinction is important both with respect to the biogeochemical and climate applications and to obtaining a deeper fundamental understanding of non-mass-dependent isotope fractionation in general. In work to be presented here, we have used a photochemical kinetics model to understand the isotopic composition of CO2 formed by O+CO+M in a mixture of O2 and CO gases irradiated with UV light at several wavelengths. We compare our model results with experimental results from Bhattacharya and Thiemens [Z. Naturforsch. 44a, 435-444 (1989)] and Pandey and Bhattacharya [J. Chem. Phys. 124, 234301 (2006)] in order to evaluate the extent to which the non-mass-dependent isotopic composition of CO2 derives from photochemical transfer from ozone formed during the experiment versus possible non-mass-dependent isotope effects in the CO2 recombination reaction.

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    Physical processes that unmix elements/isotopes of gas molecules involve phase changes, diffusion (chemical or thermal), effusion and gravitational settling. Some of those play significant roles for the evolution of chemical and isotopic compositions of gases in planetary bodies which lead to better understanding of surface paleoclimatic conditions, e.g. gas bubbles in Antarctic ice, and planetary evolution, e.g. the solar-wind erosion induced gas escaping from exosphere on terrestrial planets.. A mass dependent relationship is always expected for the kinetic isotope fractionations during these simple physical processes, according to the kinetic theory of gases by Chapman, Enskog and others [3-5]. For O-bearing (O16, -O17, -O18) molecules the alpha O-17/ alpha O-18 is expected at 0.5 to 0.515, and for S-bearing (S32,-S33. -S34, -S36) molecules, the alpha S-33/ alpha S-34 is expected at 0.5 to 0.508, where alpha is the isotope fractionation factor associated with unmixing processes. Thus, one isotope pair is generally proxied to yield all the information for the physical history of the gases. However, we recently] reported the violation of mass law for isotope fractionation among isotope pairs of multiple isotope system during gas diffusion or convection under thermal gradient (Thermal Gradient Induced Non-Mass Dependent effect, TGI-NMD). The mechanism(s) that is responsible to such striking observation remains unanswered. In our past studies, we investigated polyatomic molecules, O2 and SF6, and we suggested that nuclear spin effect could be responsible to the observed NMD effect in a way of changing diffusion coefficients of certain molecules, owing to the fact of negligible delta S-36 anomaly for SF6.. On the other hand, our results also showed that for both diffusion and convection under thermal gradient, this NMD effect is increased by lower gas pressure, bigger temperature gradient and lower average temperature, which indicate that the nuclear spin effect may

  4. Carbon isotopic ratio analysis by gas chromatography/combustion/isotope ratio mass spectrometry for the detection of gamma-hydroxybutyric acid (GHB) administration to humans.

    PubMed

    Saudan, Christophe; Augsburger, Marc; Mangin, Patrice; Saugy, Martial

    2007-01-01

    Since GHB (gamma-hydroxybutyric acid) is naturally produced in the human body, clinical and forensic toxicologists must be able to discriminate between endogenous levels and a concentration resulting from exposure. To suggest an alternative to the use of interpretative concentration cut-offs, the detection of exogenous GHB in urine specimens was investigated by means of gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). GHB was isolated from urinary matrix by successive purification on Oasis MCX and Bond Elute SAX solid-phase extraction (SPE) cartridges prior to high-performance liquid chromatography (HPLC) fractioning using an Atlantis dC18 column eluted with a mixture of formic acid and methanol. Subsequent intramolecular esterification of GHB leading to the formation of gamma-butyrolactone (GBL) was carried out to avoid introduction of additional carbon atoms for carbon isotopic ratio analysis. A precision of 0.3 per thousand was determined using this IRMS method for samples at GHB concentrations of 10 mg/L. The (13)C/(12)C ratios of GHB in samples of subjects exposed to the drug ranged from -32.1 to -42.1 per thousand, whereas the results obtained for samples containing GHB of endogenous origin at concentration levels less than 10 mg/L were in the range -23.5 to -27.0 per thousand. Therefore, these preliminary results show that a possible discrimination between endogenous and exogenous GHB can be made using carbon isotopic ratio analyses.

  5. Compound-specific hydrogen isotope analysis of heteroatom-bearing compounds via gas chromatography-chromium-based high-temperature conversion (Cr/HTC)-isotope ratio mass spectrometry.

    PubMed

    Renpenning, Julian; Kümmel, Steffen; Hitzfeld, Kristina L; Schimmelmann, Arndt; Gehre, Matthias

    2015-09-15

    The traditional high-temperature conversion (HTC) approach toward compound-specific stable isotope analysis (CSIA) of hydrogen for heteroatom-bearing (i.e., N, Cl, S) compounds has been afflicted by fractionation bias due to formation of byproducts HCN, HCl, and H2S. This study presents a chromium-based high-temperature conversion (Cr/HTC) approach for organic compounds containing nitrogen, chlorine, and sulfur. Following peak separation along a gas chromatographic (GC) column, the use of thermally stable ceramic Cr/HTC reactors at 1100-1500 °C and chemical sequestration of N, Cl, and S by chromium result in quantitative conversion of compound-specific organic hydrogen to H2 analyte gas. The overall hydrogen isotope analysis via GC-Cr/HTC-isotope ratio mass spectrometry (IRMS) achieved a precision of better than ± 5 mUr along the VSMOW-SLAP scale. The accuracy of GC-Cr/HTC-IRMS was validated with organic reference materials (RM) in comparison with online EA-Cr/HTC-IRMS and offline dual-inlet IRMS. The utility and reliability of the GC-Cr/HTC-IRMS system were documented during the routine measurement of more than 500 heteroatom-bearing organic samples spanning a δ(2)H range of -181 mUr to 629 mUr.

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

    NASA Astrophysics Data System (ADS)

    Kawashima, Hiroto; Murakami, Mai

    2014-06-01

    The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular of their stable carbon isotope ratio (δ13C), could potentially be used as an effective tool for identifying the sources of VOCs. However, to date, there have been very few such analyses. In this work, we analyze the δ13C values of VOCs using thermal desorption coupled with chromatography, combustion, and isotope ratio mass spectrometry (TD-GC/C/IRMS). The measured peak shapes were of high quality and 36 compounds in a standard gas containing 58 VOCs (C5-C11) were detected. The measured δ13C varied widely, from -49.7‰ to -22.9‰, while the standard deviation of the δ13C values varied from 0.07‰ to 0.85‰ (n = 5). We then measured samples from two passenger cars in hot and cold modes, three gas stations, roadside air, and ambient air. In comparison with existing studies, the analytical precision for the 36 compounds in this study was reasonable. By comparing the δ13C values obtained from the cars and gas stations, we could identify some degree of the sources of VOCs in the roadside and ambient air samples.

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

    NASA Astrophysics Data System (ADS)

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

    Following advances with methods for 13C/ 12C isotopic analysis of methane in small (⩽4 L) air samples, new isotope dilution techniques are proposed for measurement of methane emissions at the paddock scale from grazing ruminant animals. These techniques combine measurement of the isotopic δ13CH 4 composition of air samples with a non-intrusive mass balance method applied in the nocturnal boundary layer. Flux estimates from trials using the isotope dilution techniques are compared with estimates based on scaling up individual animal emission measurements using a rumen gas tracer technique. The methane flux assessed by the latter technique ranged from 35 to 70 mg (CH 4) m -2 d -1 with a stocking density between 10 and 20 sheep ha -1. The isotope dilution based nocturnal boundary-layer estimates generally agreed to better than a factor of 2 and usually to within 20% of the average of individual animal emission rate per unit area of paddock. Both static and advecting mass balance methods are developed. In the advecting case, the upwind/downwind contrast in δ13C was typically 0.2-0.5‰. Care was necessary with air sampling to avoid error in this small contrast contributing to error in the flux. Agreement between concentration- and isotope-based nocturnal boundary layer methods and the sheep breath measurements indicated that sample representativeness was generally good. Factors which affect the accuracy of the method are examined and include variability in nocturnal mixing height, the assumed δ13CH 4 composition of the source sheep breath and diurnal patterns in sheep emission. This paper establishes new techniques useful in the paddock to landscape scale although widespread application awaits further development of technology for rapid and repeatable field analysis of δ13CH 4 in small samples.

  8. Pb, Sr, and Nd isotopes in seamount basalts from the Juan de Fuca Ridge and Kodiak-Bowie seamount chain, northeast Pacific

    USGS Publications Warehouse

    Hegner, E.; Tatsumoto, M.

    1989-01-01

    Pb, Sr, and Nd isotopic ratios and their parent/daughter element concentrations for 28 basalts from 10 hotspot and nonhotspot seamounts are reported. Nd and Sr isotopic compositions (143Nd/144Nd = 0.51325-0.51304; 87Sr/86Sr = 0.70237-0.70275) plot in the envelope for Juan de Fuca-Gorda ridge basalts with tholeiitic basalts showing more depleted sources and a better negative correlation than transitional to alkalic basalts. Pb isotopic ratios in tholeiitic and alkalic basalts overlap (206Pb/204Pb = 18.29-19.44) and display a trend toward more radiogenic Pb in alkalic basalts. The isotopic data for hotspot and nonhotspot basalts are indistinguishable and correlate broadly with rock composition, implying that they are controlled by partial melting. The isotopic variation in the seamount basalts is about 60% (Nd-Sr) to 100% (Pb) of that in East Pacific Rise basalts and is interpreted as a lower limit for the magnitude of mantle heterogeneity in the northeast Pacific. The data indicate absence of a chemically distinct plume component in the linear seamount chains and strongly suggest an origin from mid-ocean ridge basalt-like east Pacific mantle. -Authors

  9. A Lie-Theoretic Perspective on O(n) Mass Matrix Inversion for Serial Manipulators and Polypeptide Chains

    PubMed Central

    Lee, Kiju; Wang, Yunfeng; Chirikjian, Gregory S.

    2010-01-01

    Over the past several decades a number of O(n) methods for forward and inverse dynamics computations have been developed in the multi-body dynamics and robotics literature. A method was developed in 1974 by Fixman for O(n) computation of the mass-matrix determinant for a serial polymer chain consisting of point masses. In other recent papers, we extended this method in order to compute the inverse of the mass matrix for serial chains consisting of point masses. In the present paper, we extend these ideas further and address the case of serial chains composed of rigid-bodies. This requires the use of relatively deep mathematics associated with the rotation group, SO(3), and the special Euclidean group, SE(3), and specifically, it requires that one differentiates functions of Lie-group-valued argument. PMID:20165563

  10. A Lie-Theoretic Perspective on O(n) Mass Matrix Inversion for Serial Manipulators and Polypeptide Chains.

    PubMed

    Lee, Kiju; Wang, Yunfeng; Chirikjian, Gregory S

    2007-11-01

    Over the past several decades a number of O(n) methods for forward and inverse dynamics computations have been developed in the multi-body dynamics and robotics literature. A method was developed in 1974 by Fixman for O(n) computation of the mass-matrix determinant for a serial polymer chain consisting of point masses. In other recent papers, we extended this method in order to compute the inverse of the mass matrix for serial chains consisting of point masses. In the present paper, we extend these ideas further and address the case of serial chains composed of rigid-bodies. This requires the use of relatively deep mathematics associated with the rotation group, SO(3), and the special Euclidean group, SE(3), and specifically, it requires that one differentiates functions of Lie-group-valued argument.

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

    PubMed

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

    2006-08-01

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

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

    SciTech Connect

    Beals, D.M.

    1992-09-01

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

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

    SciTech Connect

    Beals, D.M.

    1992-01-01

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

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

    PubMed

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

    2009-01-01

    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.

  15. Microbial Utilization of Estuarine Dissolved Organic Carbon: a Stable Isotope Tracer Approach Tested by Mass Balance

    PubMed Central

    Hullar, M.; Fry, B.; Peterson, B. J.; Wright, R. T.

    1996-01-01

    The natural stable isotope values of different plants have been used to trace the fate of organic carbon that enters estuarine ecosystems. Experiments were designed to determine the magnitude of (delta) (sup13)C changes of dissolved organic carbon (DOC) derived from tidal marsh vegetation that occurred during bacterial decomposition. Bacteria were grown on DOC leached from estuarine Spartina alterniflora and Typhus angustifolia plants. In four experiments, 25 to 80% of the initial carbon (2.6 to 9.1 mM organic C) was converted to bacterial biomass and CO(inf2). Mass balance calculations showed good recovery of total C and (sup13)C at the end of these experiments (100% (plusmn) 14% total C; (plusmn) 1(permil) (delta) (sup13)C). The (delta) (sup13)C values of DOC, bacterial biomass, and respired CO(inf2) changed only slightly in the four experiments by average values of -0.6, +1.4, and +0.5(permil), respectively. These changes are small relative to the range of (delta) (sup13)C values represented by different organic carbon sources to estuaries. Thus, microbial (delta) (sup13)C values determined in the field helped to identify the source of the carbon assimilated by bacteria. PMID:16535358

  16. Measurement of trimethylamine-N-oxide by stable isotope dilution liquid chromatography tandem mass spectrometry

    PubMed Central

    Wang, Zeneng; Levison, Bruce S.; Hazen, Jennie E.; Donahue, Lillian; Li, Xin-Min; Hazen, Stanley L.

    2014-01-01

    Trimethylamine-N-oxide (TMAO) levels in blood predict future risk for major adverse cardiac events including myocardial infarction, stroke and death. Thus, the rapid determination of circulating TMAO concentration is of clinical interest. Here we report a method to measure TMAO in biological matrices by stable isotope dilution liquid chromatography tandem mass spectrometry (LC/MS/MS) with lower and upper limits of quantification of 0.05 and >200 µM, respectively. Spike and recovery studies demonstrate an accuracy at low (0.5 µM), mid (5 µM) and high (100 µM) levels of 98.2%, 97.3% and 101.6%, respectively. Additional assay performance metrics include intra-day and inter-day coefficients of variance of < 6.4% and < 9.9%, respectively, across the range of TMAO levels. Stability studies reveal TMAO in plasma is stable both during storage at −80 °C for 5 years and to multiple freeze thaw cycles. Fasting plasma normal range studies among apparently healthy subjects (n=349) shows a range of 0.73 – 126 µM, median (interquartile range) levels of 3.45 (2.25–5.79) µM, and increasing values with age. The LC/MS/MS based assay reported should be of value for further studies evaluating TMAO as a risk marker and for examining the effect of dietary, pharmacologic and environmental factors on TMAO levels. PMID:24704102

  17. Impact of Isotope Dilution Mass Spectrometry (IDMS) Standardization on Carboplatin Dose and Adverse Events

    PubMed Central

    Lawson, Justin; Switchenko, Jeffrey M.; McKibbin, Trevor; Harvey, R. Donald

    2017-01-01

    BACKGROUND When using area under the concentration-time curve-based strategies for dosing carboplatin, accurate estimation of glomerular filtration rate is required for determining dose. Commonly, the Cockcroft–Gault equation is used, which is dependent on measurement of serum creatinine (SCr). Because analysis of SCr changed to an isotope dilution mass spectrometry (IDMS) standard, we sought to determine the impact of this assay change on carboplatin dosing and related toxicity. METHODS This was a single-center, retrospective chart review of adults treated with carboplatin between April 2008 and April 2010 divided into cohorts that initiated carboplatin before or after IDMS standardization. End points included grade 3 thrombocytopenia, decrease in platelet count, and hospitalization and were evaluated in cohorts based on concomitant chemotherapy. RESULTS The chart review identified 158 patients, with 63 patients in the pre-IDMS group and 95 patients in the post-IDMS group. Average SCr (pre 1.01 mg/dl vs post 0.86 mg/dl, p<0.001) and average carboplatin dose (pre 580 mg vs post 703 mg, p<0.001) were significantly different between the groups. The frequency of grade 3 thrombocytopenia was not statistically significant across three partner chemotherapy cohorts before and after IDMS implementation. CONCLUSION IDMS standardization led to an overall decrease in SCr with subsequent increase in carboplatin doses. However, no increase in recorded adverse events was observed, suggesting that the clinical relevance in toxicity from higher doses was minimal. PMID:27130286

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

    PubMed Central

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

    2011-01-01

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

  19. Stable isotope ratio mass spectrometry and physical comparison for the forensic examination of grip-seal plastic bags.

    PubMed

    Taylor, Erica; Carter, James F; Hill, Jenny C; Morton, Carolyn; Daeid, Niamh Nic; Sleeman, Richard

    2008-05-20

    Plastic bags are frequently used to package drugs, explosives and other contraband. There exists, therefore, a requirement in forensic casework to compare bags found at different locations. This is currently achieved almost exclusively by the use of physical comparisons such as birefringence patterns. This paper discusses some of the advantages and shortcomings of this approach, and presents stable isotope ratio mass spectrometry (IRMS) as a supplementary tool for effecting comparisons of this nature. Carbon and hydrogen isotopic data are presented for sixteen grip-seal plastic bags from a wide range of sources, in order to demonstrate the range of values which is likely to be encountered. Both isotopic and physical comparison (specifically birefringence) techniques are then applied to the analysis of rolls of bags from different manufacturing lots from a leading manufacturer. Both approaches are able to associate bags from a common production batch. IRMS can be applied to small fragments which are not amenable to physical comparisons, and is able to discriminate bags which could be confused using birefringence patterns alone. Similarly, in certain cases birefringence patterns discriminate bags with similar isotopic compositions. The two approaches are therefore complementary. When more than one isotopically distinct region exists within a bag (e.g. the grip-seal is distinct from the body) the ability to discriminate and associate bags is greatly increased.

  20. Application of Inductively Coupled Plasma Mass Spectrometry to the determination of uranium isotope ratios in individual particles for nuclear safeguards

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao Zhi; Esaka, Fumitaka; Esaka, Konomi T.; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu; Watanabe, Kazuo

    2007-10-01

    The capability of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of uranium isotope ratios in individual particles was determined. For this purpose, we developed an experimental procedure including single particle transfer with a manipulator, chemical dissolution and isotope ratio analysis, and applied to the analysis of individual uranium particles in certified reference materials (NBL CRM U050 and U350). As the result, the 235U/ 238U isotope ratio for the particle with the diameter between 0.5 and 3.9 μm was successfully determined with the deviation from the certified ratio within 1.8%. The relative standard deviation (R.S.D.) of the 235U/ 238U isotope ratio was within 4.2%. Although the analysis of 234U/ 238U and 236U/ 238U isotope ratios gave the results with inferior precision, the R.S.D. within 20% was possible for the measurement of the particle with the diameter more than 2.1 μm. The developed procedure was successfully applied to the analysis of a simulated environmental sample prepared from a mixture of indoor dust (NIST SRM 2583) and uranium particles (NBL CRM U050, U350 and U950a). From the results, the proposed procedure was found to be an alternative analytical tool for nuclear safeguards.

  1. Measurement of 13C/12C of chloroacetic acids by gas chromatography/combustion/isotope ratio mass spectrometry.

    PubMed

    Wong, Charles S; Muir, Derek C G; Mabury, Scott A

    2003-02-01

    This paper describes a novel analytical methodology using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) to measure the 13C/12C ratios of chloroacetic acids (CAAs). CAAs are a major class of environmental pollutants that are widely distributed throughout the world, often at relatively high concentrations, and are of concern due to their toxic effects, particularly on plants. The 13C/12C of CAA reagents was measured by IRMS subsequent to offline combustion. Aqueous solutions of these CAAs were derivatized to the corresponding methyl chloroacetates (MCAAs) with acidic methanol with a known isotopic composition, extracted into pentane, and analyzed by GC/C/IRMS. Measured 13C/12C ratios of derivatized MCAAs were in agreement with calculated values within 1 per thousand for monochloroacetic acid and trichloroacetic acid and within 2 per thousand for dichloroacetic acid, suggesting that methylation and other analytical methodology steps do not isotopically fractionate derivatized MCAAs. 13C/12C ratios of reagent CAAs from different sources had varying isotopic signatures suggesting differences in source carbon and/or production methods. Our results underscore the potential of stable isotopes to serve as tracers of environmental sources of CAAs.

  2. Rate equation model of laser induced bias in uranium isotope ratios measured by resonance ionization mass spectrometry

    DOE PAGES

    Isselhardt, B. H.; Prussin, S. G.; Savina, M. R.; ...

    2015-12-07

    Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process between uranium atoms and potential isobars without the aid of chemical purification and separation. The use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of the 235U/238U ratio to decrease laser-induced isotopic fractionation. In application, isotope standards are used to identify and correct bias in measured isotope ratios, but understanding laser-induced bias from first-principles can improve the precision and accuracy of experimental measurements. A rate equationmore » model for predicting the relative ionization probability has been developed to study the effect of variations in laser parameters on the measured isotope ratio. The model uses atomic data and empirical descriptions of laser performance to estimate the laser-induced bias expected in experimental measurements of the 235U/238U ratio. Empirical corrections are also included to account for ionization processes that are difficult to calculate from first principles with the available atomic data. As a result, development of this model has highlighted several important considerations for properly interpreting experimental results.« less

  3. Rate equation model of laser induced bias in uranium isotope ratios measured by resonance ionization mass spectrometry

    SciTech Connect

    Isselhardt, B. H.; Prussin, S. G.; Savina, M. R.; Willingham, D. G.; Knight, K. B.; Hutcheon, I. D.

    2015-12-07

    Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process between uranium atoms and potential isobars without the aid of chemical purification and separation. The use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of the 235U/238U ratio to decrease laser-induced isotopic fractionation. In application, isotope standards are used to identify and correct bias in measured isotope ratios, but understanding laser-induced bias from first-principles can improve the precision and accuracy of experimental measurements. A rate equation model for predicting the relative ionization probability has been developed to study the effect of variations in laser parameters on the measured isotope ratio. The model uses atomic data and empirical descriptions of laser performance to estimate the laser-induced bias expected in experimental measurements of the 235U/238U ratio. Empirical corrections are also included to account for ionization processes that are difficult to calculate from first principles with the available atomic data. As a result, development of this model has highlighted several important considerations for properly interpreting experimental results.

  4. Quantifying groundwater dependence of a sub-polar lake cluster in Finland using an isotope mass balance approach

    NASA Astrophysics Data System (ADS)

    Isokangas, E.; Rozanski, K.; Rossi, P. M.; Ronkanen, A.-K.; Kløve, B.

    2014-08-01

    A stable isotope study of 67 kettle lakes and ponds situated on an esker aquifer (90 km2) in northern Finland was carried out in the summer of 2013 to determine the role of groundwater inflow in groundwater-dependent lakes. Distinct seasonal fluctuations in the δ18O and δ2H values of lakes are the result of seasonal ice cover prohibiting evaporation during the winter. An isotope mass balance approach was used to calculate the inflow-to-evaporation ratios (ITOT/E) of all 67 lakes during the summer of 2013 when the isotopic compositions of the lakes were approaching a steady-state. The normalised relative humidity needed in this approach came from assuming a terminal lake situation for one of the lakes showing the highest isotope enrichment. Since evaporation rates were derived independently of any mass balance considerations, it was possible to determine the total inflow (ITOT) and mean turnover time (MTT) of the lakes. Furthermore, the groundwater seepage rates of those lakes revealing no visible surface inflow were calculated. Here, a quantitative measure was introduced for the dependence of a lake on groundwater (G index) that is defined as the percentage contribution of groundwater inflow to the total inflow of water to the given lake. The G index values of the lakes studied ranged from 27.8-95.0%, revealing large differences in groundwater dependency among the lakes. This study shows the effectiveness of applying an isotope mass balance approach to quantify the groundwater reliance of lakes situated in a relatively small area with similar climatic conditions.

  5. Identification of bacterial plant pathogens using multilocus polymerase chain reaction/electrospray ionization-mass spectrometry.

    PubMed

    Postinikova, E; Baldwin, C; Whitehouse, C A; Sechler, A; Schaad, N W; Sampath, R; Harpin, V; Li, F; Melton, R; Blyn, L; Drader, J; Hofstadler, S; Schneider, W L

    2008-11-01

    Polymerase chain reaction/electrospray ionization-mass spectrometry (PCR/ESI-MS, previously known as "TIGER") utilizes PCR with broad-range primers to amplify products from a wide array of organisms within a taxonomic group, followed by analysis of PCR amplicons using mass spectrometry. Computer analysis of precise masses allows for calculations of base compositions for the broad-range PCR products, which can then be compared to a database for identification. PCR/ESI-MS has the benefits of PCR in sensitivity and high-throughput capacity, but also has the distinct advantage of being able to detect and identify organisms with no prior characterization or sequence data. Existing broad range PCR primers, designed with an emphasis on human pathogens, were tested for their ability to amplify DNA of well characterized phytobacterial strains, as well as to populate the existing PCR/ESI-MS bacterial database with base counts. In a blinded panel study, PCR/ESI-MS successfully identified 93% of unknown bacterial DNAs to the genus level and 73% to the species/subspecies level. Additionally, PCR/ESI-MS was capable of detecting and identifying multiple bacteria within the same sample. The sensitivity of PCR/ESI-MS was consistent with other PCR based assays, and the specificity varied depending on the bacterial species. Preliminary tests with real life samples demonstrate a high potential for using PCR/ESI-MS systems for agricultural diagnostic applications.

  6. General polytropic self-gravitating cylinder free-fall and accreting mass string with a chain of collapsed objects

    NASA Astrophysics Data System (ADS)

    Lou, Yu-Qing; Hu, Xu-Yao

    2016-06-01

    We present a theoretical model framework for general polytropic (GP) hydrodynamic cylinder under self-gravity of infinite length with axial uniformity and axisymmetry. For self-similar dynamic solutions, we derive valuable integrals, analytic asymptotic solutions, sonic critical curves, shock conditions, and global numerical solutions with or without expansion shocks. Among others, we investigate various dynamic solutions featured with central free-fall asymptotic behaviours, corresponding to a collapsed mass string with a sustained dynamic accretion from a surrounding mass reservoir. Depending on the allowed ranges of a scaling index a < -1, such cylindrical dynamic mass accretion rate could be steady, increasing with time and decreasing with time. Physically, such a collapsed mass string or filament would break up into a sequence of sub-clumps and segments as induced by gravitational Jeans instabilities. Depending on the scales involved, such sub-clumps would evolve into collapsed objects or gravitationally bound systems. In diverse astrophysical and cosmological contexts, such a scenario can be adapted on various temporal, spatial and mass scales to form a chain of collapsed clumps and/or compact objects. Examples include the formation of chains of proto-stars, brown dwarfs and gaseous planets along molecular filaments; the formation of luminous massive stars along magnetized spiral arms and circum-nuclear starburst rings in barred spiral galaxies; the formation of chains of compact stellar objects such as white dwarfs, neutron stars, and black holes along a highly condensed mass string. On cosmological scales, one can perceive the formation of chains of galaxies, chains of galaxy clusters or even chains of supermassive and hypermassive black holes in the Universe including the early Universe. All these chains referred to above include possible binaries.

  7. Time-of-flight mass measurements of neutron-rich chromium isotopes up to N = 40 and implications for the accreted neutron star crust

    SciTech Connect

    Meisel, Z.; George, S.; Ahn, S.; Bazin, D.; Brown, B. A.; Browne, J.; Carpino, J. F.; Chung, H.; Cyburt, R. H.; Estrade, A.; Famiano, M.; Gade, A.; Langer, C.; Matos, M.; Mittig, W.; Montes, F.; Morrissey, D. J.; Pereira, J.; Schatz, H.; Schatz, J.; Scott, M.; Shapira, Dan; Sieja, K.; Smith, K.; Stevens, J.; Tan, W.; Tarasov, O.; Towers, S.; Wimmer, K.; Winkelbauer, J. R.; Yurkon, J.; Zegers, R. G. T.

    2016-03-22

    Here, we present the mass excesses of 59-64Cr, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of 64Cr is determined for the first time, with an atomic mass excess of -33.48(44) MeV. We find a significantly different two-neutron separation energy S2n trend for neutron-rich isotopes of chromium, removing the previously observed enhancement in binding at N = 38. Additionally, we extend the S2n trend for chromium to N = 40, revealing behavior consistent with the previously identified island of inversion in this region. We compare our results to state-of-the-art shell-model calculations performed with a modified Lenzi-Nowacki-Poves-Sieja interaction in the fp shell, including the g9/2 and d5/2 orbits for the neutron valence space. We employ our result for the mass of 64Cr in accreted neutron star crust network calculations and find a reduction in the strength and depth of electron-capture heating from the A = 64 isobaric chain, resulting in a cooler than expected accreted neutron star crust. This reduced heating is found to be due to the >1-MeV reduction in binding for 64Cr with respect to values from commonly used global mass models.

  8. A Global Mass Balance of Isotope Ratios in Hydrologic Fluxes Provides Constraints on Terrestrial and Oceanic Water Cycling

    NASA Astrophysics Data System (ADS)

    Good, S. P.; Noone, D. C.; Kurita, N.; Benetti, M.; Bowen, G. J.

    2014-12-01

    The global budget of isotope ratios in the Earth's water cycle is poorly understood because of large uncertainties in the isotopic composition of continental evapotranspiration. Additional uncertainties exist in the global pattern of marine boundary layer vapor D/H isotope ratios and the magnitude of their influence on oceanic evaporation. Here, we use satellite retrievals of marine boundary layer vapor HDO and H2O from the Tropospheric Emissions Spectrometer (TES) corrected to match surface vapor collected during cruises in the Pacific, Atlantic, Indian, and Arctic Oceans to resolve the global D/H isotope ratio budget. After our correction, satellite retrievals are un-biased, and have an average error of 14 permil when compared with 1341 satellite retrievals that were co-located with surface observations. Using TES retrieval spanning the globe, we calculate the global oceanic evaporation flux isotopic composition as approximately -30 permil, and combined with estimates of precipitation isotope ratios, a global mass balance is applied to quantify terrestrial evapotranspiration and runoff composition. The flux-weighted average isotopic composition of precipitation is estimated at approximately -37 permil, with oceanic precipitation having a value of approximately -32 permil and terrestrial precipitation having a value of approximately -52 permil. Based on our mass balance, terrestrial evapotranspiration has a flux-weighted average composition of -69 permil and terrestrial runoff has an average composition of -16 permil, which corresponds to a terrestrial enrichment of 37 permil for runoff relative to terrestrial precipitation. Knowledge of the entire HDO budget provides constraints on terrestrial evaporation/transpiration partitioning as well as tropospheric entrainment of moisture into the boundary layer, both poorly understood components of the global hydrologic cycle. These calculations provide a critical test of an essential global closure theory upon which many

  9. SO2 photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism

    PubMed Central

    Hattori, Shohei; Schmidt, Johan A.; Johnson, Matthew S.; Danielache, Sebastian O.; Yamada, Akinori; Ueno, Yuichiro; Yoshida, Naohiro

    2013-01-01

    Natural climate variation, such as that caused by volcanoes, is the basis for identifying anthropogenic climate change. However, knowledge of the history of volcanic activity is inadequate, particularly concerning the explosivity of specific events. Some material is deposited in ice cores, but the concentration of glacial sulfate does not distinguish between tropospheric and stratospheric eruptions. Stable sulfur isotope abundances contain additional information, and recent studies show a correlation between volcanic plumes that reach the stratosphere and mass-independent anomalies in sulfur isotopes in glacial sulfate. We describe a mechanism, photoexcitation of SO2, that links the two, yielding a useful metric of the explosivity of historic volcanic events. A plume model of S(IV) to S(VI) conversion was constructed including photochemistry, entrainment of background air, and sulfate deposition. Isotopologue-specific photoexcitation rates were calculated based on the UV absorption cross-sections of 32SO2, 33SO2, 34SO2, and 36SO2 from 250 to 320 nm. The model shows that UV photoexcitation is enhanced with altitude, whereas mass-dependent oxidation, such as SO2 + OH, is suppressed by in situ plume chemistry, allowing the production and preservation of a mass-independent sulfur isotope anomaly in the sulfate product. The model accounts for the amplitude, phases, and time development of Δ33S/δ34S and Δ36S/Δ33S found in glacial samples. We are able to identify the process controlling mass-independent sulfur isotope anomalies in the modern atmosphere. This mechanism is the basis of identifying the magnitude of historic volcanic events. PMID:23417298

  10. SO2 photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism.

    PubMed

    Hattori, Shohei; Schmidt, Johan A; Johnson, Matthew S; Danielache, Sebastian O; Yamada, Akinori; Ueno, Yuichiro; Yoshida, Naohiro

    2013-10-29

    Natural climate variation, such as that caused by volcanoes, is the basis for identifying anthropogenic climate change. However, knowledge of the history of volcanic activity is inadequate, particularly concerning the explosivity of specific events. Some material is deposited in ice cores, but the concentration of glacial sulfate does not distinguish between tropospheric and stratospheric eruptions. Stable sulfur isotope abundances contain additional information, and recent studies show a correlation between volcanic plumes that reach the stratosphere and mass-independent anomalies in sulfur isotopes in glacial sulfate. We describe a mechanism, photoexcitation of SO2, that links the two, yielding a useful metric of the explosivity of historic volcanic events. A plume model of S(IV) to S(VI) conversion was constructed including photochemistry, entrainment of background air, and sulfate deposition. Isotopologue-specific photoexcitation rates were calculated based on the UV absorption cross-sections of (32)SO2, (33)SO2, (34)SO2, and (36)SO2 from 250 to 320 nm. The model shows that UV photoexcitation is enhanced with altitude, whereas mass-dependent oxidation, such as SO2 + OH, is suppressed by in situ plume chemistry, allowing the production and preservation of a mass-independent sulfur isotope anomaly in the sulfate product. The model accounts for the amplitude, phases, and time development of Δ(33)S/δ(34)S and Δ(36)S/Δ(33)S found in glacial samples. We are able to identify the process controlling mass-independent sulfur isotope anomalies in the modern atmosphere. This mechanism is the basis of identifying the magnitude of historic volcanic events.

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

    PubMed

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

    2013-10-15

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

  12. Energy dependence of mass, charge, isotopic, and energy distributions in neutron-induced fission of 235U and 239Pu

    NASA Astrophysics Data System (ADS)

    Pasca, H.; Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.; Kim, Y.

    2016-05-01

    The mass, charge, isotopic, and kinetic-energy distributions of fission fragments are studied within an improved scission-point statistical model in the reactions 235U+n and 239Pu+n at different energies of the incident neutron. The charge and mass distributions of the electromagnetic- and neutron-induced fission of 214,218Ra, 230,232,238U are also shown. The available experimental data are well reproduced and the energy-dependencies of the observable characteristics of fission are predicted for future experiments.

  13. Ion microscopy with resonant ionization mass spectrometry : time-of-flight depth profiling with improved isotopic precision.

    SciTech Connect

    Pellin, M. J.; Veryovkin, I. V.; Levine, J.; Zinovev, A.; Davis, A. M.; Stephan, T.; Tripa, C. E.; King, B. V.; Savina, M. R.

    2010-01-01

    There are four generally mutually exclusive requirements that plague many mass spectrometric measurements of trace constituents: (1) the small size (limited by the depth probed) of many interesting materials requires high useful yields to simply detect some trace elements, (2) the low concentrations of interesting elements require efficient discrimination from isobaric interferences, (3) it is often necessary to measure the depth distribution of elements with high surface and low bulk contributions, and (4) many applications require precise isotopic analysis. Resonant ionization mass spectrometry has made dramatic progress in addressing these difficulties over the past five years.

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

    USGS Publications Warehouse

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

    1973-01-01

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

  15. Nuclear Data Evaluation for Mass Chain A=217:Odd-Proton Nuclei.

    PubMed

    Nafee, Sherif S; Shaheen, Salem A; Al-Ramady, Amir M

    2016-01-01

    Thallium (81(217)Tl, Bismuth (83(217)Bi), Astatine (85(217)At), Francium (87(217)Fr), Actinium (89(217)Ac) and Protactinium (91(217)Pa) are of odd-proton numbers among the mass chain A = 217. In the present work, the half-lives and gamma transitions for the six nuclei have been studied and adopted based on the recently published interactions or unevaluated nuclear data sets XUNDL. The Q (α) has been updated based on the recent published work of the Atomic Mass Evaluation AME2012 as well. Moreover, the total conversion electrons as well as the K-Shell to L-Shell, L-Shell to M-Shell and L-Shell to N-Shell Conversion Electron Ratios have been calculated using BrIcc code v2.3. An updated skeleton decay scheme for each of the above nuclei has been presented here. The decay hindrance factors (HF) calculated using the ALPHAD program, which is available from Brookhaven National Laboratory's website, have been calculated for the α- decay data sets for (221)Fr-, (221)Ac- and (221)Pa-α-decays.

  16. Nuclear Data Evaluation for Mass Chain A=217:Odd-Proton Nuclei

    PubMed Central

    Nafee, Sherif S.; Shaheen, Salem A.; Al-Ramady, Amir M.

    2016-01-01

    Thallium (Tl81217), Bismuth (Bi83217), Astatine (At85217), Francium (Fr87217), Actinium (Ac89217) and Protactinium (Pa91217) are of odd-proton numbers among the mass chain A = 217. In the present work, the half-lives and gamma transitions for the six nuclei have been studied and adopted based on the recently published interactions or unevaluated nuclear data sets XUNDL. The Q (α) has been updated based on the recent published work of the Atomic Mass Evaluation AME2012 as well. Moreover, the total conversion electrons as well as the K-Shell to L-Shell, L-Shell to M-Shell and L-Shell to N-Shell Conversion Electron Ratios have been calculated using BrIcc code v2.3. An updated skeleton decay scheme for each of the above nuclei has been presented here. The decay hindrance factors (HF) calculated using the ALPHAD program, which is available from Brookhaven National Laboratory’s website, have been calculated for the α- decay data sets for 221Fr-, 221Ac- and 221Pa- α-decays. PMID:26761207

  17. Application of Uncertainty in Measurement (GUM) to Isotope Mass Spectrometry: Introduction, Implemention, and Examples

    NASA Astrophysics Data System (ADS)

    Buerger, S.; Essex, R. M.; Mathew, K. J.; Thomas, R. B.

    2008-12-01

    As the measured value and its unit are integral parts of a measurement, so is a statement of the associated measurement uncertainty. The importance of providing an uncertainty that can reasonably be attributed to the measured value is often underrated. An assessment of uncertainty provides confidence in the value of the measurement, judgement on significance of differences between measurement results, information regarding the capability of the measurement procedure, and quality assurance. The limitations of the classical error analysis were seen as a hindrance to communication of scientific and technical measurement results, initiating the development of the Guide to the Expression of Uncertainty in Measurement (GUM) in the late 1970s. Just as the use of the International System of Units brings coherence to measurements, the International Organization for Standardization Guide to the Expression of Uncertainty in Measurement recommends a standardized way of expressing uncertainty in all kinds of measurements. Consequently, GUM has been adopted by most of the national metrology institutes in the world. A short introduction to GUM and the logical steps leading to its development will be presented, as well as a comparison between classical error analysis and GUM. Examples related to mass spectrometry for isotopic and elemental analysis will be discussed. The merits of GUM - transparency of the uncertainty evaluation, the treatment of uncertainties in a consistent logical way, and the presentation of an uncertainty budget resulting in a feedback to the analyst (i.e. identifies the dominant components of uncertainty and allows better understanding and improvement of the measurement process) - will be emphasised.

  18. Carbon isotope ratio mass spectrometry for detection of endogenous steroid use: a testing strategy.

    PubMed

    Ahrens, Brian D; Butch, Anthony W

    2013-07-01

    Isotope ratio mass spectrometry (IRMS) testing is performed to determine if an atypical steroid profile is due to administration of an endogenous steroid. Androsterone (Andro) and etiocholanolone (Etio), and/or the androstanediols (5α- and 5β-androstane-3α,17β-diol) are typically analyzed by IRMS to determine the (13) C/(12) C ratio. The ratios of these target compounds are compared to the (13) C/(12) C ratio of an endogenous reference compound (ERC) such as 5β-pregnane-3α,20α-diol (Pdiol). Concentrations of Andro and Etio are high so (13) C/(12) C ratios can easily be measured in most urine samples. Despite the potentially improved sensitivity of the androstanediols for detecting the use of some testosterone formulations, additional processing steps are often required that increase labour costs and turnaround times. Since this can be problematic when performing large numbers of IRMS measurements, we established thresholds for Andro and Etio that can be used to determine the need for additional androstanediol testing. Using these criteria, 105 out of 2639 urine samples exceeded the Andro and/or Etio thresholds, with 52 of these samples being positive based on Andro and Etio IRMS testing alone. The remaining 53 urine samples had androstanediol IRMS testing performed and 3 samples were positive based on the androstanediol results. A similar strategy was used to establish a threshold for Pdiol to identify athletes with relatively (13) C-depleted values so that an alternative ERC can be used to confirm or establish a true endogenous reference value. Adoption of a similar strategy by other laboratories can significantly reduce IRMS sample processing and analysis times, thereby increasing testing capacity.

  19. Identification of volatile and semivolatile compounds in chemical ionization GC-MS using a mass-to-structure (MTS) Search Engine with integral isotope pattern ranking.

    PubMed

    Liao, Wenta; Draper, William M

    2013-02-21

    The mass-to-structure or MTS Search Engine is an Access 2010 database containing theoretical molecular mass information for 19,438 compounds assembled from common sources such as the Merck Index, pesticide and pharmaceutical compilations, and chemical catalogues. This database, which contains no experimental mass spectral data, was developed as an aid to identification of compounds in atmospheric pressure ionization (API)-LC-MS. This paper describes a powerful upgrade to this database, a fully integrated utility for filtering or ranking candidates based on isotope ratios and patterns. The new MTS Search Engine is applied here to the identification of volatile and semivolatile compounds including pesticides, nitrosoamines and other pollutants. Methane and isobutane chemical ionization (CI) GC-MS spectra were obtained from unit mass resolution mass spectrometers to determine MH(+) masses and isotope ratios. Isotopes were measured accurately with errors of <4% and <6%, respectively, for A + 1 and A + 2 peaks. Deconvolution of interfering isotope clusters (e.g., M(+) and [M - H](+)) was required for accurate determination of the A + 1 isotope in halogenated compounds. Integrating the isotope data greatly improved the speed and accuracy of the database identifications. The database accurately identified unknowns from isobutane CI spectra in 100% of cases where as many as 40 candidates satisfied the mass tolerance. The paper describes the development and basic operation of the new MTS Search Engine and details performance testing with over 50 model compounds.

  20. Development of a combined isotopic and mass-balance approach to determine dissolved organic carbon sources in eutrophic reservoirs.

    PubMed

    Pierson-Wickmann, Anne-Catherine; Gruau, Gérard; Jardé, Emilie; Gaury, Nicolas; Brient, Luc; Lengronne, Marion; Crocq, André; Helle, Daniel; Lambert, Thibault

    2011-04-01

    A combined mass-balance and stable isotope approach was set up to identify and quantify dissolved organic carbon (DOC) sources in a DOC-rich (9mgL(-1)) eutrophic reservoir located in Western France and used for drinking water supply (so-called Rophemel reservoir). The mass-balance approach consisted in measuring the flux of allochthonous DOC on a daily basis, and in comparing it with the effective (measured) DOC concentration of the reservoir. The isotopic approach consisted, for its part, in measuring the carbon isotope ratios (δ(13)C values) of both allochthonous and autochthonous DOC sources, and comparing these values with the δ(13)C values of the reservoir DOC. Results from both approaches were consistent pointing out for a DOC of 100% allochthonous origin. In particular, the δ(13)C values of the DOC recovered in the reservoir (-28.5±0.2‰; n=22) during the algal bloom season (May-September) showed no trace of an autochthonous contribution (δ(13)C in algae=-30.1±0.3‰; n=2) being indistinguishable from the δ(13)C values of allochthonous DOC from inflowing rivers (-28.6±0.1‰; n=8). These results demonstrate that eutrophication is not responsible for the high DOC concentrations observed in the Rophemel reservoir and that limiting eutrophication of this reservoir will not reduce the potential formation of disinfection by-products during water treatment. The methodology developed in this study based on a complementary isotopic and mass-balance approach provides a powerful tool, suitable to identify and quantify DOC sources in eutrophic, DOC-contaminated reservoirs.

  1. Contents of selected B vitamins in NIST SRM 3280 multivitamin/multielement tablets by liquid chromatography isotope dilution mass spectrometry.

    PubMed

    Chen, Pei; Ozcan, Mustafa; Wolf, Wayne R

    2007-09-01

    There is increased interest in accurately assessing the total dietary intake of vitamins from all sources, including foods and dietary supplements. Consequently, a Dietary Supplement Ingredient Database (DSID), based upon analytical values, is being established by USDA with support of the Office of Dietary Supplements (ODS), NIH. The DSID necessitated the development of a new SRM, 3280--Multivitamin/Multimineral Tablets, by the National Institute of Standards and Technology (NIST), with support from the ODS. As a continuation of a long-term project to develop and validate new methods of determining water-soluble B vitamins in foods and dietary supplements, and as part of a collaborative effort with NIST to characterize SRM 3280, values for the vitamin contents of SRM 3280 have been generated by a liquid chromatographic isotope dilution mass spectrometric (LC/IDMS) method. Isotope-labeled ((13)C and/or (2)H) B vitamins (B1-thiamine, B6-pyridoxine, B3-nicotinamide, and B5-pantothenic acid) were obtained from commercial sources, with the support of the ODS/NIH. Our LC/IDMS method uses a C18 reversed phase column, an Agilent 1100 HPLC system, and a Quattro Micro triple-quad mass spectrometer (MS). B vitamin determination was achieved using a gradient LC profile combined with MS/MS detection in multiple reaction monitoring mode. Stock solutions of the isotope-labeled vitamins were calibrated against USP standard solutions. The SRM tablets, with added amounts of the four isotope-labeled B vitamins, were extracted and the vitamins simultaneously determined in a single LC run, in contrast with the single-component determinations performed via IDMS. Unknown vitamin concentrations were calculated by comparing the ratios of the integrated LC peaks at the different masses of the unlabeled and labeled vitamins.

  2. Applications of Inductively Coupled Plasma Mass Spectroscopy to the Isotopically Enriched Tungsten Metal Ring Campaign at DIII-D

    NASA Astrophysics Data System (ADS)

    Donovan, D. C.; Eley, C.; Maan, A.; Duran, J.; Auxier, J., II; Unterberg, E. A.; Rudakov, D. L.; Stangeby, P.; Chrobak, C.; Wampler, W. R.

    2016-10-01

    Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) was used to measure isotopic ratios of deposited W on collector probes inserted during the metal ring campaign. Two toroidal rings of 5 cm wide W-coated TZM inserts were installed in the lower divertor. The inner ring was coated in natural-W and the outer ring was coated with 93% isotopically enriched W-182. A triplet set of replaceable graphite collector probes were mounted at the outboard mid-plane. Over 100 collector probes were exposed. ICP-MS analysis of the collector probes has yielded isotopic ratios of the deposited W, which have been used with the Stable Isotope Mixing Model (SIMM) to estimate the amount of W from each of the divertor rings that contributed to the total W deposition on the probe. Comparisons in strike-point positioning, H-mode/L-mode, and Forward/Reverse Bt are reviewed. Work supported by US DOE under DE-AC05-00OR22725, DE-FG02-07ER54917, DE-FC02-04ER54698, DE-AC04-94AL85000, UT Institute for Nuclear Security.

  3. Performance of the wet oxidation unit of the HPLC isotope ratio mass spectrometry system for halogenated compounds.

    PubMed

    Gilevska, Tetyana; Gehre, Matthias; Richnow, Hans Hermann

    2014-08-05

    The performance of liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) for polar halogenated compounds was evaluated. Oxidation capacity of the system was tested with halogenated acetic acids and halogenated aromatic compounds. Acetic acid (AA) was selected as a reference compound for complete oxidation and compared on the molar basis to the oxidation of other analytes. The isotope values were proofed with calibrated δ(13)C values obtained with an elemental analyzer (EA). Correct isotope values were obtained for mono- and dichlorinated, fluorinated, and tribrominated acetic acids and also for aniline, phenol, benzene, bromobenzene, chlorobenzene, 1,2-dichlorobenzene, 2,4,6-trichlorophenol, pentafluorophenol, and nitrobenzene. Incomplete oxidation of trichloroacetic acid (TCA) and trifluoroacetic acid (TFA) resulted in lower recovery compared to AA (37% and 24%, respectively) and in isotopic shift compared to values obtained with EA (TCA Δδ(13)C(EA/LC-IRMS) = 8.8‰, TFA Δδ(13)C(EA/LC-IRMS) = 6.0‰). Improvement of oxidation by longer reaction time in the reactor and increase in the concentration of sulfate radicals did not lead to complete combustion of TCA and TFA needed for δ(13)C analysis. To the best of our knowledge, this is the first time such highly chlorinated compounds were studied with the LC-IRMS system. This work provides information for method development of LC-IRMS methods for halogenated contaminants that are known as potential threats to public health and the environment.

  4. Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere.

    PubMed

    Pavlov, A A; Kasting, J F

    2002-01-01

    Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (> 2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O2 and high-O2 atmospheres. We show that in atmospheres with O2 concentrations < 10(-5) times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O2 concentrations > or = 10(-5) PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O2 concentration must have been < 10(-5) PAL prior to 2.3 Ga.

  5. The Effect of Isotopic Composition on the Uncertainty of Routine Metal Mass Concentration Measurements in Ambient Air

    PubMed Central

    Brown, Richard J. C.; Goddard, Sharon L.; Brown, Andrew S.; Yardley, Rachel E.

    2008-01-01

    The main sources of uncertainty encountered during the analysis of the mass concentration of metals in ambient air as part of the operation of the UK Heavy Metals Monitoring Network are presented. It is observed that the uncertainty contribution from possible variation in the isotopic composition of the sample depends on the element in question, but can be significant (e.g., for Pb, Cd, and Hg). The working curve method for the ICP-MS analysis of metals in solution, with a low resolution, high throughput instrument measuring at one m/z ratio per element, relies on the relative abundance of the isotopes under consideration being the same in both the sample and the calibration solution. Calculation of the uncertainty in this analysis assumes that the isotopic composition variation within the sample and calibration solution is limited to a defined range. Therefore, in order to confirm the validity of this quantification methodology and its uncertainty budget, the isotopic composition of the calibration standards used for quantification has been determined. The results of this analysis are presented here. PMID:19223968

  6. Discrimination of geographical origin of lentils (Lens culinaris Medik.) using isotope ratio mass spectrometry combined with chemometrics.

    PubMed

    Longobardi, F; Casiello, G; Cortese, M; Perini, M; Camin, F; Catucci, L; Agostiano, A

    2015-12-01

    The aim of this study was to predict the geographic origin of lentils by using isotope ratio mass spectrometry (IRMS) in combination with chemometrics. Lentil samples from two origins, i.e. Italy and Canada, were analysed obtaining the stable isotope ratios of δ(13)C, δ(15)N, δ(2)H, δ(18)O, and δ(34)S. A comparison between median values (U-test) highlighted statistically significant differences (p<0.05) for all isotopic parameters between the lentils produced in these two different geographic areas, except for δ(15)N. Applying principal component analysis, grouping of samples was observed on the basis of origin but with overlapping zones; consequently, two supervised discriminant techniques, i.e. partial least squares discriminant analysis and k-nearest neighbours algorithm were used. Both models showed good performances with external prediction abilities of about 93% demonstrating the suitability of the methods developed. Subsequently, isotopic determinations were also performed on the protein and starch fractions and the relevant results are reported.

  7. The Nd-isotopic fingerprinting of North Atlantic water masses and its influences from local sources such as Iceland

    NASA Astrophysics Data System (ADS)

    Frank, N.; Waldner, A.; Christophe, C.; Montagna, P.; Dubois-Dauphin, Q.; Wu, Q.

    2014-12-01

    The 143Nd/144Nd ratio of seawater has become a valuable tracer of north Atlantic circulation patterns, driven by continental runoff, boundary exchange and water mass advection and mixing. A region of particular interest is the overflow across the Iceland - Scotland Ridge injecting water from the Arctic Ocean into the Iceland basin. However, Iceland itself constitutes a singularity in terms of the release of radiogenic 143Nd/144Nd to seawater, due to leaching of young volcanic basalts, whereas the Atlantic is dominated by less radiogenic Nd inputs from old Canadian crustal rocks and the European continent. Hence, release of volcanic material may affect the Nd-isotopic composition of water masses recirculating throughout the sub-polar gyre. This is of major importance regarding the use of Nd isotopes in sediments and corals to trace changes of recirculation patterns in the past. Here, seawater was analysed on three transects (local to basin scale) to fingerprint advection patterns as well as local radiogenic Nd sources in the sub-polar gyre domain. The first local transect followed open ocean water on to the shelf near the outflow of the Vatnajökull glacier. It demonstrates that freshwater runoff modifies the open ocean Nd signature only very close to the shelf (<40km near the outflow) and thus reflects a very local feature unlikely possible to alter the predominant water mass composition of Northeast Atlantic water or the underlying Iceland-Scotland Overflow Water. The second transect follows the Iceland shelfbreak from north-east towards the Reykjanes ridge and includes seawater samples near the recently formed volcanic island of Surtsey. Again no major modification of the Atlantic water mass compositions is observed, besides samples in direct vicinity of Surtsey island where local release of Nd modifies seawater ɛNd (-14) to values as high as -6. Finally we have monitored the isotopic composition of water masses along a North-South transect from Iceland towards

  8. Trophic transfer of trace elements in an isotopically constructed food chain from a semi-enclosed marine coastal area (Stagnone di Marsala, Sicily, Mediterranean).

    PubMed

    Vizzini, Salvatrice; Costa, Valentina; Tramati, Cecilia; Gianguzza, Paola; Mazzola, Antonio

    2013-11-01

    Trace element accumulation is particularly important in coastal and transitional environments, which act as contaminant buffers between the continental and marine systems. We compared trace element transfer to the biota in two locations with different open-sea exposures in a semi-enclosed marine coastal area (Stagnone di Marsala, Sicily, Italy) using isotopically reconstructed food chains. Samples of sediment, macroalgae, seagrasses, invertebrates, fish, and bird feathers were sampled in July 2006 and analysed for stable carbon and nitrogen isotopes (δ(13)C, δ(15)N) and trace elements (arsenic [As], cadmium [Cd], total mercury [THg], and lead [Pb]). Trophic magnification factors were calculated through the relationships between trace elements and δ(15)N in consumers. As and Pb were greater in organic matter sources (sediments and primary producers), whereas Cd and THg were greater in bird feathers. At the food chain level, an insignificant trophic transfer was found for all elements, suggesting biodilution rather than biomagnification. Sediments were more contaminated in the location with lower open-sea exposure. Macroalgae and seagrasses overall mirrored the spatial pattern highlighted in sediments, whereas differences between the two locations became further decreased moving toward higher trophic levels, indicating that trophic transfer of sediment and macrophyte-bound trace elements to the coastal lagoon food chain may be of relatively minor importance.

  9. A miniaturized laser-ablation mass spectrometer for in-situ measurements of isotope composition on solar body surfaces

    NASA Astrophysics Data System (ADS)

    Riedo, A.; Meyer, S.; Tulej, M.; Neuland, M.; Bieler, A.; Iakovleva, M.; Wurz, P.

    2012-04-01

    The in-situ analysis of extraterrestrial material onboard planetary rovers and landers is of considerable interest for future planetary space missions. Due to the low detection sensitivity of spectroscopic instruments, e.g. α-particle X-ray, γ-ray or neutron spectrometers, it is frequently possible to measure only major/minor elements in extraterrestrial materials. Nevertheless, the knowledge of minor/trace elements is of considerable interest to cosmochemistry. Chemistry puts constraints on the origin of solar system and its evolution enabling also a deeper inside to planetary transformation processes (e.g. volcanic surface alteration, space weathering). The isotopes play special role in analysis of the origin and transformation of planetary matter. They are robust tracers of the early events because their abundances are less disturbed as the elemental once. Nevertheless, if the isotope abundance ratios are fractionated, the underlying chemical and physical processes can be then encoded from the variations of abundance ratios. A detailed analysis of isotopic patterns of radiogenic elements can allow age dating of minerals and temporal evolution of planetary matter. High accuracy and sensitive measurements of isotopic pattern of bio-relevant elements, i.e., sulfur, found on planetary surfaces can be helpful for the identification of possible past and present extraterrestrial life in terms of biomarker identification. Our group has designed a self-optimizing miniaturized laser ablation time-of-flight mass spectrometer (LMS) for in situ planetary measurements (Wurz et al., 2012; Rohner et al., 2003). Initial studies utilizing IR laser radiation for ablation, atomization and ionization of solid materials indicated a high instrumental performance in terms of sensitivity and mass resolution (Tulej et al., 2011). Current studies are conducted with a UV radiation and a high spatial resolution is achieved by focussing the laser beam to 20µm spots onto the sample. The

  10. Compound-Specific Chlorine Isotope Analysis of Tetrachloromethane and Trichloromethane by Gas Chromatography-Isotope Ratio Mass Spectrometry vs Gas Chromatography-Quadrupole Mass Spectrometry: Method Development and Evaluation of Precision and Trueness.

    PubMed

    Heckel, Benjamin; Rodríguez-Fernández, Diana; Torrentó, Clara; Meyer, Armin; Palau, Jordi; Domènech, Cristina; Rosell, Mònica; Soler, Albert; Hunkeler, Daniel; Elsner, Martin

    2017-03-21

    Compound-specific chlorine isotope analysis of tetrachloromethane (CCl4) and trichloromethane (CHCl3) was explored by both, gas chromatography-isotope ratio mass spectrometry (GC-IRMS) and GC-quadrupole MS (GC-qMS), where GC-qMS was validated in an interlaboratory comparison between Munich and Neuchâtel with the same type of commercial GC-qMS instrument. GC-IRMS measurements analyzed CCl isotopologue ions, whereas GC-qMS analyzed the isotopologue ions CCl3, CCl2, CCl (of CCl4) and CHCl3, CHCl2, CHCl (of CHCl3), respectively. Lowest amount dependence (good linearity) was obtained (i) in H-containing fragment ions where interference of (35)Cl- to (37)Cl-containing ions was avoided; (ii) with tuning parameters favoring one predominant rather than multiple fragment ions in the mass spectra. Optimized GC-qMS parameters (dwell time 70 ms, 2 most abundant ions) resulted in standard deviations of 0.2‰ (CHCl3) and 0.4‰ (CCl4), which are only about twice as large as 0.1‰ and 0.2‰ for GC-IRMS. To compare also the trueness of both methods and laboratories, samples from CCl4 and CHCl3 degradation experiments were analyzed and calibrated against isotopically different reference standards for both CCl4 and CHCl3 (two of each). Excellent agreement confirms that true results can be obtained by both methods provided that a consistent set of isotopically characterized reference materials is used.

  11. Asynchronous evolution of the isotopic composition and amount of precipitation in north China during the Holocene revealed by a record of compound-specific carbon and hydrogen isotopes of long-chain n-alkanes from an alpine lake

    NASA Astrophysics Data System (ADS)

    Rao, Zhiguo; Jia, Guodong; Li, Yunxia; Chen, Jianhui; Xu, Qinghai; Chen, Fahu

    2016-07-01

    Both the timing of the maximum East Asian summer monsoon (EASM) intensity in monsoonal China and the environmental significance of the Chinese stalagmite oxygen isotopic record (δ18O) have been debated. Here, we present a ca. 120-year-resolution compound-specific carbon (δ13C) and hydrogen (δD) isotopes of terrestrial long-chain n-alkanes extracted from a well-dated sediment core from an alpine lake in north China. Our δ13C data, together with previously reported pollen data from a parallel core, demonstrate a humid mid-Holocene from ca. 8-5 ka BP. Assuming that the climatic humidity of north China is an indicator of the EASM intensity, then the maximum EASM intensity occurred in the mid-Holocene. Our δD data reveal a similar long-term trend to the δ18O record from nearby Lianhua Cave, indicating that the synchronous δD and δ18O records faithfully record the δD and δ18O of precipitation, respectively. The most negative δD and δ18O values occur in the early-mid Holocene, from ca. 11-5 ka BP. This contrast in the timing of isotopic variations demonstrates a complex relationship between the isotopic composition of precipitation and precipitation amount, or EASM intensity. Further comparisons indicate a possible linkage between the precipitation amount in north China and the west-east thermal gradient in the equatorial Pacific. In addition, the temperature of the moisture source area may play an important role in determining the isotopic composition of precipitation in monsoonal China.

  12. Determination of 237Np and Pu isotopes in large soil samples by inductively coupled plasma mass spectrometry.

    PubMed

    Maxwell, Sherrod L; Culligan, Brian K; Jones, Vernon D; Nichols, Sheldon T; Bernard, Maureen A; Noyes, Gary W

    2010-12-03

    A new method for the determination of (237)Np and Pu isotopes in large soil samples has been developed that provides enhanced uranium removal to facilitate assay by inductively coupled plasma mass spectrometry (ICP-MS). This method allows rapid preconcentration and separation of plutonium and neptunium in large soil samples for the measurement of (237)Np and Pu isotopes by ICP-MS. (238)U can interfere with (239)Pu measurement by ICP-MS as (238)UH(+) mass overlap and (237)Np via (238)U peak tailing. The method provides enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then transferring Pu to DGA resin for additional purification. The decontamination factor for removal of uranium from plutonium for this method is greater than 1×10(6). Alpha spectrometry can also be applied so that the shorter-lived (238)Pu isotope can be measured successfully. (239) Pu, (242)Pu and (237)Np were measured by ICP-MS, while (236)Pu and (238)Pu were measured by alpha spectrometry.

  13. DETERMINATION OF 237NP AND PU ISOTOPES IN LARGE SOIL SAMPLES BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

    SciTech Connect

    Maxwell, S.

    2010-07-26

    A new method for the determination of {sup 237}Np and Pu isotopes in large soil samples has been developed that provides enhanced uranium removal to facilitate assay by inductively coupled plasma mass spectrometry (ICP-MS). This method allows rapid preconcentration and separation of plutonium and neptunium in large soil samples for the measurement of {sup 237}Np and Pu isotopes by ICP-MS. {sup 238}U can interfere with {sup 239}Pu measurement by ICP-MS as {sup 238}UH{sup +} mass overlap and {sup 237}Np via {sup 238}U peak tailing. The method provides enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then transferring Pu to DGA resin for additional purification. The decontamination factor for removal of uranium from plutonium for this method is greater than 1 x 10{sup 6}. Alpha spectrometry can also be applied so that the shorter-lived {sup 238}Pu isotope can be measured successfully. {sup 239}Pu, {sup 242}Pu and {sup 237}Np were measured by ICP-MS, while {sup 236}Pu and {sup 238}Pu were measured by alpha spectrometry.

  14. Fission track-secondary ion mass spectrometry as a tool for detecting the isotopic signature of individual uranium containing particles.

    PubMed

    Esaka, Fumitaka; Lee, Chi-Gyu; Magara, Masaaki; Kimura, Takaumi

    2012-04-06

    A fission track technique was used as a sample preparation method for subsequent isotope abundance ratio analysis of individual uranium containing particles with secondary ion mass spectrometry (SIMS) to measure the particles with higher enriched uranium efficiently. A polycarbonate film containing particles was irradiated with thermal neutrons and etched with 6M NaOH solution. Each uranium containing particle was then identified by observing fission tracks created and a portion of the film having a uranium containing particle was cut out and put onto a glassy carbon planchet. The polycarbonate film, which gave the increases of background signals on the uranium mass region in SIMS analysis, was removed by plasma ashing with 200 W for 20 min. In the analysis of swipe samples having particles containing natural (NBL CRM 950a) or low enriched uranium (NBL CRM U100) with the fission track-SIMS method, uranium isotope abundance ratios were successfully determined. This method was then applied to the analysis of a real inspection swipe sample taken at a nuclear facility. As a consequence, the range of (235)U/(238)U isotope abundance ratio between 0.0276 and 0.0438 was obtained, which was higher than that measured by SIMS without using a fission track technique (0.0225 and 0.0341). This indicates that the fission track-SIMS method is a powerful tool to identify the particle with higher enriched uranium in environmental samples efficiently.

  15. A preliminary report on noble gas isotope analyses using the Helix-MC multi-collector mass spectrometer

    NASA Astrophysics Data System (ADS)

    Honda, M.; Zhang, X.; Phillips, D.; Szczepanski, S.; Deerberg, M.; Hamilton, D.; Krummen, M.; Schwieters, J.

    2013-12-01

    Analyses of noble gas isotopes by multi-collector mass spectrometry substantially improve measurement precision and accuracy, with the potential to revolutionise applications to cosmo-geo-sciences. The Helix-MC noble gas mass spectrometer manufactured by Thermo-Fisher is a 350mm, 120 degree extended geometry, high resolution, multi-collector mass spectrometer for the simultaneous analysis of noble gas isotopes. The detector array includes a fixed axial (Ax) detector, 2 adjustable high mass (H1 and H2) detectors and 2 adjustable low mass (L1 and L2) detectors. Each detector is equipped with a Faraday/ion counting multiplier CFM (Combined Faraday and CDD Multiplier) detector. Mass resolution and mass resolving power on the H2, Ax and L2 detectors of the Helix-MC installed at the Australian National University (ANU) are approximately 1,800 and 8,000, respectively. The noble gas handling system on-line to the Helix-MC consists of: (1) a resistively-heated, double-vacuum, tantalum furnace system, (2) air actuated vacuum crusher, (3) Photon-Machines diode laser heating system, (4) Janis He cryogenic trap assembly, (5) gas purification system and (6) standard gas pipette tanks, which are totally automated and controlled by the Qtegra software platform developed by Thermo-Fisher. Eleven repeat measurements of atmospheric Ar using the H2 Faraday (1E11 ohm resistor) and L2 CDD collectors on the Helix-MC, yield a mean 40Ar/36Ar ratio of 322.09 +- 0.28 (0.089%) with a 4,700 fA 40Ar beam current. This result compares favourably with the precision achieved by the Argus VI at the University of Melbourne (318.12 +- 0.17; 0.052%; n = 10) with a similar beam size of 4,200 fA. The high mass resolution of the L2 collector permits complete separation of the 36Ar and interfering 3 x 12C (required mass resolution (MR) of 1,100) and partial separation of H35Cl (MR = 3,900). This capability enables evaluation of the significance of Ar isotopic interferences related to the correction of

  16. QPNM calculation for the ground state magnetic moments of odd-mass deformed nuclei: 157-167Er isotopes

    NASA Astrophysics Data System (ADS)

    Yakut, H.; Guliyev, E.; Guner, M.; Tabar, E.; Zenginerler, Z.

    2012-08-01

    A new microscopic method has been developed in the framework of the Quasiparticle-Phonon Nuclear Model (QPNM) in order to investigate spin polarization effects on the magnetic properties such as magnetic moment, intrinsic magnetic moment and effective gs factor of the ground state of odd-mass 157-167Er isotopes. The calculations were performed using both Tamm-Dancoff Approximation (TDA) and Quasiparticle Random-Phase Approximation (QRPA). Reasonably good agreement has been obtained between the QRPA results and the relevant experimental data. Furthermore the variation of the intrinsic magnetic moment gK values with the mass number A exhibits similar behavior for both theoretical and experimental results. From the compression of the calculated intrinsic magnetic moment values with the experimental data the spin-spin interaction parameter has been found as χ=(30/A) MeV for odd-mass 157-167Er isotopes. Our results clarify the possibility of using this new method to describe the magnetic properties of odd-mass deformed nuclei.

  17. Abundance Anomaly of the 13C Isotopic Species of c-C3H2 in the Low-mass Star Formation Region L1527

    NASA Astrophysics Data System (ADS)

    Yoshida, Kento; Sakai, Nami; Tokudome, Tomoya; López-Sepulcre, Ana; Watanabe, Yoshimasa; Takano, Shuro; Lefloch, Bertrand; Ceccarelli, Cecilia; Bachiller, Rafael; Caux, Emmanuel; Vastel, Charlotte; Yamamoto, Satoshi

    2015-07-01

    The rotational spectral lines of c-C3H2 and two kinds of the 13C isotopic species, c-{}13{{CCCH}}2 ({C}2v symmetry) and c-{{CC}}13{{CH}}2 (Cs symmetry), have been observed in the 1-3 mm band toward the low-mass star-forming region L1527. We have detected 7, 3, and 6 lines of c-C3H2, c-{}13{{CCCH}}2, and c-{{CC}}13{{CH}}2, respectively, with the Nobeyama 45 m telescope and 34, 6, and 13 lines, respectively, with the IRAM 30 m telescope, where seven, two, and two transitions, respectively, are observed with both telescopes. With these data, we have evaluated the column densities of the normal and 13C isotopic species. The [c-C3H2]/[c-{}13{{CCCH}}2] ratio is determined to be 310 ± 80, while the [c-C3H2]/[c-{{CC}}13{{CH}}2] ratio is determined to be 61 ± 11. The [c-C3H2]/[c-{}13{{CCCH}}2] and [c-C3H2]/[c-{{CC}}13{{CH}}2] ratios expected from the elemental 12C/13C ratio are 60-70 and 30-35, respectively, where the latter takes into account the statistical factor of 2 for the two equivalent carbon atoms in c-C3H2. Hence, this observation further confirms the dilution of the 13C species in carbon-chain molecules and their related molecules, which are thought to originate from the dilution of 13C+ in the gas-phase C+ due to the isotope exchange reaction: {}13{{{C}}}++{CO}\\to {}13{CO}+{{{C}}}+. Moreover, the abundances of the two 13C isotopic species are different from each other. The ratio of c-{}13{{CCCH}}2 species relative to c-{{CC}}13{{CH}}2 is determined to be 0.20 ± 0.05. If 13C were randomly substituted for the three carbon atoms, the [c-{}13{{CCCH}}2]/[c-{{CC}}13{{CH}}2] ratio would be 0.5. Hence, the observed ratio indicates that c-{{CC}}13{{CH}}2 exists more favorably. Possible origins of the different abundances are discussed. Based on observations carried out with the IRAM 30 m Telescope and the NRO 45 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). NRO is a branch of the National Astronomical Observatory of Japan

  18. Isotope-Ratio-Monitoring Liquid Chromatography Mass Spectrometry (IRM-LCMS): First Results from a Moving Wire Interface System.

    PubMed

    Brand, W A; Dobberstein, P

    1996-08-01

    Abstract A Liquid Chromatography-Combustion (LC-C) Interface, based on a moving wire technique, has been built and tested. The LC effluent is deposited onto a transport wire, which carries the sample through solvent evaporation and combustion ovens. CO(2) from the combustion step is analysed in an isotope ratio mass spectrometer. Performance of the interface was tested by loop injections of sucrose and glucose into a liquid flow of methanol/water (80/20). Accuracy and precision of δ(13)C(PDB) < 1‰ was achieved for sample concentrations > 500 ng/ul (5μl loop), sufficient for studies at natural isotope ratios. In case of (13)C tracer applications the detection limit was determined to be about 20 pg carbon tracer (on wire).

  19. High accuracy determination of malachite green and leucomalachite green in salmon tissue by exact matching isotope dilution mass spectrometry.

    PubMed

    Hall, Zoe; Hopley, Chris; O'Connor, Gavin

    2008-10-15

    A high accuracy method for the quantification of malachite green (MG) and leucomalachite green (LMG) in salmon is described. Analytical challenges including the effects of analyte instability and matrix suppression were minimised by the use of exact matching isotope dilution mass spectrometry. The developed method included overnight extraction in acidified acetonitrile/ammonium acetate buffer and analysis by LC-MS/MS utilising isotopic internal standards. This method was used to determine the level of MG and LMG in a sample of salmon used in an international inter-comparison organised by the Comité Consultatif pour la Quantité de Matière (CCQM). The sum of MG and LMG was found to be 9.32+/-0.98ngg(-1) at the 95% confidence interval (relative expanded uncertainty 10.5% (k=2)). This encompassed the mean and median of the CCQM inter-comparison.

  20. Revisiting the metabolism of 19-nortestosterone using isotope ratio and high resolution/high accuracy mass spectrometry.

    PubMed

    Piper, Thomas; Schänzer, Wilhelm; Thevis, Mario

    2016-09-01

    The synthetic anabolic androgenic steroid 19-nortestosterone is prohibited in sports according to the regulations of the World Anti-Doping Agency (WADA) due to its performance-enhancing effects. Today, doping controls focus predominantly on one main urinary metabolite, 19-norandrosterone glucuronide, which offers the required detection windows for an appropriate retrospectivity of sports drug testing programs. As 19-norandrosterone can also be found in urine at low concentrations originating from in situ demethylation of other abundant steroids or from endogenous production, the exogenous source of 19-norandrosterone needs to be verified, which is commonly accomplished by carbon isotope ratio analyses. The aim of this study was to re-investigate the metabolism of 19-nortestosterone in order to probe for additional diagnostic long-term metabolites, which might support the unambiguous attribution of an endo- or exogenous source of detected 19-nortestosterone metabolites. Employing a recently introduced strategy for metabolite identification, threefold deuterated 19-nortestosterone (16,16,17-(2)H3-NT) was administered to one healthy male volunteer and urine samples were collected for 20 days. Samples were prepared with established methods separating unconjugated, glucuronidated and sulfated steroids, and analytes were further purified by means of high-performance liquid chromatography before trimethylsilylation. Deuterated metabolites were identified using gas chromatograph/thermal conversion/isotope ratio mass spectrometer comprising an additional single quadrupole mass spectrometer. Additional structural information was obtained by gas chromatography/time-of-flight mass spectrometry and liquid chromatography/high resolution mass spectrometry. In general, sulfo-conjugated metabolites were excreted for a longer time period than the corresponding glucuronides. Several unexpected losses of the arguably stable isotope labels were observed and characterized, attributed to

  1. High precision nitrogen isotope measurements in oceanic basalts using a static triple collection noble gas mass spectrometer

    NASA Astrophysics Data System (ADS)

    Barry, P. H.; Hilton, D. R.; Halldórsson, S. A.; Hahm, D.; Marti, K.

    2012-01-01

    We describe a new system for the simultaneous static triple-collection of nitrogen isotopes at the <10μcm3 STP [N2] (<1 × 10-5 cm3STP; <0.5 nmol) level using a modified VG-5440 noble gas mass spectrometer. The system consists of an internal N2-STD with aδ15N value of -0.11 ± 0.22 ‰ (1σ) calibrated against an air-standard (Air-STD). The N2-STD was measured repeatedly with an average uncertainty on an individualδ15N measurement being 0.03 ‰ (1σ) versus an average single day reproducibility of 0.38 ‰ (1σ). Additional refinements include (1) monitoring of interfering CO contributions at mass 30, allowing a comprehensive CO correction to be applied to all samples, (2) quantification of procedural N2 blanks (n = 22) in both size (4.2 ± 0.5 μcm3 STP) and isotopic composition (δ15N = 12.64 ± 2.04 ‰), allowing consistent blank corrections to all samples, and (3) independent measurement of N2/Ar ratios using a quadrupole mass spectrometer (QMS). The new system was tested by measuring nitrogen isotopes (δ15N), concentrations and N2/Ar ratios on 11 submarine basalt glasses. Results show that the uncertainty on the δ15N data is improved as a consequence of multiple standards being run per day. Reduced analytical times, afforded by triple collection, also minimize sample depletion and memory effects, thus improving measurement statistics. Additionally, we show that CO corrections can be accomplished using mass 30 to monitor CO interferences, leading to substantial improvements in reproducibility and the overall accuracy of results when the contribution of CO is significant.

  2. Schottky Mass Measurement of the {sup 208}Hg Isotope: Implication for the Proton-Neutron Interaction Strength around Doubly Magic {sup 208}Pb

    SciTech Connect

    Chen, L.; Plass, W. R.; Geissel, H.; Scheidenberger, C.; Litvinov, Yu. A.; Beckert, K.; Beller, P.; Bosch, F.; Caceres, L.; Franzke, B.; Gerl, J.; Gorska, M.; Knoebel, R.; Kozhuharov, C.; Litvinov, S. A.; Mandal, S.; Muenzenberg, G.; Nolden, F.; Saito, N.; Saito, T.

    2009-03-27

    Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the {sup 208}Hg (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in {sup 210}Pb, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.

  3. Light Chain Deposition Disease Diagnosed with Laser Micro-dissection, Liquid Chromatography, and Tandem Mass Spectrometry of Nodular Glomerular Lesions

    PubMed Central

    Kasagi, Tomomichi; Nobata, Hironobu; Suzuki, Keisuke; Miura, Naoto; Banno, Shogo; Takami, Akiyoshi; Yamashita, Taro; Ando, Yukio; Imai, Hirokazu

    2017-01-01

    A 42-year-old man developed nephrotic syndrome and rapidly progressive renal failure. Kidney biopsy demonstrated nodular glomerulosclerosis, negative Congo red staining, and no deposition of light or heavy chains. Laser micro-dissection and liquid chromatography with tandem mass spectrometry of nodular lesions revealed the presence of a kappa chain constant region and kappa III variable region, which signified light chain deposition disease. Dexamethasone and thalidomide were effective in decreasing the serum levels of free kappa light chain from 147.0 to 38.0 mg/L, eliminating proteinuria, and halting the worsening of the kidney dysfunction, with serum creatinine levels stable around 4.0 mg/dL for 3 years. PMID:28050001

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

    PubMed

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

    2013-02-05

    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).

  5. Probing Protein 3D Structures and Conformational Changes Using Electrochemistry-Assisted Isotope Labeling Cross-Linking Mass Spectrometry.

    PubMed

    Zheng, Qiuling; Zhang, Hao; Wu, Shiyong; Chen, Hao

    2016-05-01

    This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca(2+) on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology. Graphical Abstract ᅟ.

  6. Probing Protein 3D Structures and Conformational Changes Using Electrochemistry-Assisted Isotope Labeling Cross-Linking Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zheng, Qiuling; Zhang, Hao; Wu, Shiyong; Chen, Hao

    2016-05-01

    This study presents a new chemical cross-linking mass spectrometry (MS) method in combination with electrochemistry and isotope labeling strategy for probing both protein three-dimensional (3D) structures and conformational changes. For the former purpose, the target protein/protein complex is cross-linked with equal mole of premixed light and heavy isotope labeled cross-linkers carrying electrochemically reducible disulfide bonds (i.e., DSP-d0 and DSP-d8 in this study, DSP = dithiobis[succinimidyl propionate]), digested and then electrochemically reduced followed with online MS analysis. Cross-links can be quickly identified because of their reduced intensities upon electrolysis and the presence of doublet isotopic peak characteristics. In addition, electroreduction converts cross-links into linear peptides, facilitating MS/MS analysis to gain increased information about their sequences and modification sites. For the latter purpose of probing protein conformational changes, an altered procedure is adopted, in which the protein in two different conformations is cross-linked using DSP-d0 and DSP-d8 separately, and then the two protein samples are mixed in 1:1 molar ratio. The merged sample is subjected to digestion and electrochemical mass spectrometric analysis. In such a comparative cross-linking experiment, cross-links could still be rapidly recognized based on their responses to electrolysis. More importantly, the ion intensity ratios of light and heavy isotope labeled cross-links reveal the conformational changes of the protein, as exemplified by examining the effect of Ca2+ on calmodulin conformation alternation. This new cross-linking MS method is fast and would have high value in structural biology.

  7. Higher mass-independent isotope fractionation of methylmercury in the pelagic food web of Lake Baikal (Russia).

    PubMed

    Perrot, Vincent; Pastukhov, Mikhail V; Epov, Vladimir N; Husted, Søren; Donard, Olivier F X; Amouroux, David

    2012-06-05

    Mercury undergoes several transformations that influence its stable isotope composition during a number of environmental and biological processes. Measurements of Hg isotopic mass-dependent (MDF) and mass-independent fractionation (MIF) in food webs may therefore help to identify major sources and processes leading to significant bioaccumulation of methylmercury (MeHg). In this work, δ(13)C, δ(15)N, concentration of Hg species (MeHg, inorganic Hg), and stable isotopic composition of Hg were determined at different trophic levels of the remote and pristine Lake Baikal ecosystem. Muscle of seals and different fish as well as amphipods, zooplankton, and phytoplankton were specifically investigated. MDF during trophic transfer of MeHg leading to enrichment of heavier isotopes in the predators was clearly established by δ(202)Hg measurements in the pelagic prey-predator system (carnivorous sculpins and top-predator seals). Despite the low concentrations of Hg in the ecosystem, the pelagic food web reveals very high MIF Δ(199)Hg (3.15-6.65‰) in comparison to coastal fish (0.26-1.65‰) and most previous studies in aquatic organisms. Trophic transfer does not influence MIF signature since similar Δ(199)Hg was observed in sculpins (4.59 ± 0.55‰) and seal muscles (4.62 ± 0.60‰). The MIF is suggested to be mainly controlled by specific physical and biogeochemical characteristics of the water column. The higher level of MIF in pelagic fish of Lake Baikal is mainly due to the bioaccumulation of residual MeHg that is efficiently turned over and photodemethylated in deep oligotrophic and stationary (i.e., long residence time) freshwater columns.

  8. Correction for the 17O interference in δ(13C) measurements when analyzing CO2 with stable isotope mass spectrometry

    USGS Publications Warehouse

    Coplen, Tyler B.; Brand, Willi A.; Assonov, Sergey S.

    2010-01-01

    Measurements of δ(13C) determined on CO2 with an isotope-ratio mass spectrometer (IRMS) must be corrected for the amount of 17O in the CO2. For data consistency, this must be done using identical methods by different laboratories. This report aims at unifying data treatment for CO2 IRMS by proposing (i) a unified set of numerical values, and (ii) a unified correction algorithm, based on a simple, linear approximation formula. Because the oxygen of natural CO2 is derived mostly from the global water pool, it is recommended that a value of 0.528 be employed for the factor λ, which relates differences in 17O and 18O abundances. With the currently accepted N(13C)/N(12C) of 0.011 180(28) in VPDB (Vienna Peedee belemnite) reevaluation of data yields a value of 0.000 393(1) for the oxygen isotope ratio N(17O)/N(16O) of the evolved CO2. The ratio of these quantities, a ratio of isotope ratios, is essential for the 17O abundance correction: [N(17O)/N(16O)]/[N(13C)/N(12C)] = 0.035 16(8). The equation [δ(13C) ≈ 45δVPDB-CO2 + 2 17R/13R (45δVPDB-CO2 – λ46δVPDB-CO2)] closely approximates δ(13C) values with less than 0.010 ‰ deviation for normal oxygen-bearing materials and no more than 0.026 ‰ in extreme cases. Other materials containing oxygen of non-mass-dependent isotope composition require a more specific data treatment. A similar linear approximation is also suggested for δ(18O). The linear approximations are easy to implement in a data spreadsheet, and also help in generating a simplified uncertainty budget.

  9. High-Precision Tungsten Isotopic Analysis by Multicollection Negative Thermal Ionization Mass Spectrometry Based on Simultaneous Measurement of W and (18)O/(16)O Isotope Ratios for Accurate Fractionation Correction.

    PubMed

    Trinquier, Anne; Touboul, Mathieu; Walker, Richard J

    2016-02-02

    Determination of the (182)W/(184)W ratio to a precision of ± 5 ppm (2σ) is desirable for constraining the timing of core formation and other early planetary differentiation processes. However, WO3(-) analysis by negative thermal ionization mass spectrometry normally results in a residual correlation between the instrumental-mass-fractionation-corrected (182)W/(184)W and (183)W/(184)W ratios that is attributed to mass-dependent variability of O isotopes over the course of an analysis and between different analyses. A second-order correction using the (183)W/(184)W ratio relies on the assumption that this ratio is constant in nature. This may prove invalid, as has already been realized for other isotope systems. The present study utilizes simultaneous monitoring of the (18)O/(16)O and W isotope ratios to correct oxide interferences on a per-integration basis and thus avoid the need for a double normalization of W isotopes. After normalization of W isotope ratios to a pair of W isotopes, following the exponential law, no residual W-O isotope correlation is observed. However, there is a nonideal mass bias residual correlation between (182)W/(i)W and (183)W/(i)W with time. Without double normalization of W isotopes and on the basis of three or four duplicate analyses, the external reproducibility per session of (182)W/(184)W and (183)W/(184)W normalized to (186)W/(183)W is 5-6 ppm (2σ, 1-3 μg loads). The combined uncertainty per session is less than 4 ppm for (183)W/(184)W and less than 6 ppm for (182)W/(184)W (2σm) for loads between 3000 and 50 ng.

  10. Optimized electron-optical system of a static mass-spectrometer for simultaneous isotopic and chemical analysis

    NASA Astrophysics Data System (ADS)

    Gall', L. N.; Masyukevich, S. V.; Sachenko, V. D.; Gall', N. R.

    2016-01-01

    A new approach to control the linear dimensions of analytical electrophysical systems is suggested. This approach uses the lens properties of electron-optical elements with a curvilinear axis. It is shown that such an approach can be effectively applied, in particular, to synthesize ion-optical systems (IOSs) for static magnetic mass spectrometers and can be implemented owing to off-axis fundamental points, the "poles" of an electron-optical system, introduced earlier by one of the authors. The capabilities of the new approach are demonstrated with the synthesis of the IOS of a static mass spectrometer dedicated for isotopic and chemical analysis with an increased resolution. A new IOS not only provides desired high ion-optical parameters at decreased dimensions of the mass spectrometer as a whole but also makes it possible to loosen requirements for the manufacturing accuracy of IOS main elements.

  11. Isotope-Encoded Carboxyl Group Footprinting for Mass Spectrometry-Based Protein Conformational Studies

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Liu, Haijun; Blankenship, Robert E.; Gross, Michael L.

    2016-01-01

    We report an isotope-encoding method coupled with carboxyl-group footprinting to monitor protein conformational changes. The carboxyl groups of aspartic/glutamic acids and of the C-terminus of proteins can serve as reporters for protein conformational changes when labeled with glycine ethyl ester (GEE) mediated by carbodiimide. In the new development, isotope-encoded "heavy" and "light" GEE are used to label separately the two states of the orange carotenoid protein (OCP) from cyanobacteria. Two samples are mixed (1:1 ratio) and analyzed by a single LC-MS/MS experiment. The differences in labeling extent between the two states are represented by the ratio of the "heavy" and "light" peptides, providing information about protein conformational changes. Combining isotope-encoded MS quantitative analysis and carboxyl-group footprinting reduces the time of MS analysis and improves the sensitivity of GEE and other footprinting.

  12. An in-depth evaluation of accuracy and precision in Hg isotopic analysis via pneumatic nebulization and cold vapor generation multi-collector ICP-mass spectrometry.

    PubMed

    Rua-Ibarz, Ana; Bolea-Fernandez, Eduardo; Vanhaecke, Frank

    2016-01-01

    Mercury (Hg) isotopic analysis via multi-collector inductively coupled plasma (ICP)-mass spectrometry (MC-ICP-MS) can provide relevant biogeochemical information by revealing sources, pathways, and sinks of this highly toxic metal. In this work, the capabilities and limitations of two different sample introduction systems, based on pneumatic nebulization (PN) and cold vapor generation (CVG), respectively, were evaluated in the context of Hg isotopic analysis via MC-ICP-MS. The effect of (i) instrument settings and acquisition parameters, (ii) concentration of analyte element (Hg), and internal standard (Tl)-used for mass discrimination correction purposes-and (iii) different mass bias correction approaches on the accuracy and precision of Hg isotope ratio results was evaluated. The extent and stability of mass bias were assessed in a long-term study (18 months, n = 250), demonstrating a precision ≤0.006% relative standard deviation (RSD). CVG-MC-ICP-MS showed an approximately 20-fold enhancement in Hg signal intensity compared with PN-MC-ICP-MS. For CVG-MC-ICP-MS, the mass bias induced by instrumental mass discrimination was accurately corrected for by using either external correction in a sample-standard bracketing approach (SSB) or double correction, consisting of the use of Tl as internal standard in a revised version of the Russell law (Baxter approach), followed by SSB. Concomitant matrix elements did not affect CVG-ICP-MS results. Neither with PN, nor with CVG, any evidence for mass-independent discrimination effects in the instrument was observed within the experimental precision obtained. CVG-MC-ICP-MS was finally used for Hg isotopic analysis of reference materials (RMs) of relevant environmental origin. The isotopic composition of Hg in RMs of marine biological origin testified of mass-independent fractionation that affected the odd-numbered Hg isotopes. While older RMs were used for validation purposes, novel Hg isotopic data are provided for the

  13. Tellurium isotopic composition of the early solar system—A search for effects resulting from stellar nucleosynthesis, 126Sn decay, and mass-independent fractionation

    NASA Astrophysics Data System (ADS)

    Fehr, Manuela A.; Rehkämper, Mark; Halliday, Alex N.; Wiechert, Uwe; Hattendorf, Bodo; Günther, Detlef; Ono, Shuhei; Eigenbrode, Jennifer L.; Rumble, Douglas

    2005-11-01

    New precise Te isotope data acquired by multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS) are presented for selected extraterrestrial and terrestrial materials. Bulk samples of carbonaceous, ordinary and enstatite chondrites as well as the metal and sulfide phases of iron meteorites were analyzed to search for nucleosynthetic isotope anomalies and to find evidence of formerly live 126Sn, which decays to 126Te with a half-life of 234,500 yr. None of the meteorites show evidence of mass dependent Te isotope fractionations larger than 2‰ for δ 126/128Te. Following internal normalization of the data to 125Te/ 128Te, the Te isotope ratios of all analyzed meteorites were found to be identical to a terrestrial standard, within uncertainties. This provides evidence that the regions of the solar disk that were sampled during accretion of the meteorite parent bodies were well mixed and homogeneous on a large scale, with respect to Te isotopes. The data acquired for bulk carbonaceous chondrites indicate that the initial 126Sn/ 118Sn ratio of the solar system was <4 × 10 -5, but this is dependent on the assumption that no redistribution of Sn and Te occurred since the start of the solar system. Five Archean sedimentary sulfides that display both mass dependent and mass-independent isotope effects for S yield internally normalized Te isotope data, which indicate that mass-independent Te isotope effects are absent. The mass dependent fractionations in these samples are constrained to be less than ˜1‰ for δ 126/128Te.

  14. Evaluation of accurate mass and relative isotopic abundance measurements in the LTQ-orbitrap mass spectrometer for further metabolomics database building.

    PubMed

    Xu, Ying; Heilier, Jean-François; Madalinski, Geoffrey; Genin, Eric; Ezan, Eric; Tabet, Jean-Claude; Junot, Christophe

    2010-07-01

    Recently, high-resolution mass spectrometry has been largely employed for compound identification, thanks to accurate mass measurements. As additional information, relative isotope abundance (RIA) is often needed to reduce the number of candidates prior to tandem MS(n). Here, we report on the evaluation of the LTQ-Orbitrap, in terms of accurate mass and RIA measurements for building further metabolomics spectral databases. Accurate mass measurements were achieved in the ppm range, using external calibration within 24 h, and remained at <5 ppm over a one-week period. The experimental relative abundances of (M+1) isotopic ions were evaluated in different data sets. First of all, 137 solutions of commercial compounds were analyzed by flow injection analysis in both the positive and negative ion modes. It was found that the ion abundance was the main factor impacting the accuracy of RIA measurements. It was possible to define some intensity thresholds above which errors were systematically <20% of their theoretical values. The same type of results were obtained with analyses from two biological media. Otherwise, no significant effect of ion transmission between the LTQ ion trap and the Orbitrap analyzer on RIA measurement errors was found, whereas the reliability of RIA measurements was dramatically improved by reducing the mass detection window. It was also observed that the signal integration method had a significant impact on RIA measurement errors, with the most-reliable results being obtained with peak height integrations. Finally, automatic integrations using the data preprocessing software XCMS and MZmine gave results similar to those obtained by manual integration, suggesting that it is relevant to use the RIA information in automatic elemental composition determination software from metabolomic peak tables.

  15. Isotopic Ratio Outlier Analysis of the S. cerevisiae Metabolome Using Accurate Mass Gas Chromatography/Time-of-Flight Mass Spectrometry: A New Method for Discovery.

    PubMed

    Qiu, Yunping; Moir, Robyn; Willis, Ian; Beecher, Chris; Tsai, Yu-Hsuan; Garrett, Timothy J; Yost, Richard A; Kurland, Irwin J

    2016-03-01

    Isotopic ratio outlier analysis (IROA) is a (13)C metabolomics profiling method that eliminates sample to sample variance, discriminates against noise and artifacts, and improves identification of compounds, previously done with accurate mass liquid chromatography/mass spectrometry (LC/MS). This is the first report using IROA technology in combination with accurate mass gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS), here used to examine the S. cerevisiae metabolome. S. cerevisiae was grown in YNB media, containing randomized 95% (13)C, or 5%(13)C glucose as the single carbon source, in order that the isotopomer pattern of all metabolites would mirror the labeled glucose. When these IROA experiments are combined, the abundance of the heavy isotopologues in the 5%(13)C extracts, or light isotopologues in the 95%(13)C extracts, follows the binomial distribution, showing mirrored peak pairs for the molecular ion. The mass difference between the (12)C monoisotopic and the (13)C monoisotopic equals the number of carbons in the molecules. The IROA-GC/MS protocol developed, using both chemical and electron ionization, extends the information acquired from the isotopic peak patterns for formulas generation. The process that can be formulated as an algorithm, in which the number of carbons, as well as the number of methoximations and silylations are used as search constraints. In electron impact (EI/IROA) spectra, the artifactual peaks are identified and easily removed, which has the potential to generate "clean" EI libraries. The combination of chemical ionization (CI) IROA and EI/IROA affords a metabolite identification procedure that enables the identification of coeluting metabolites, and allowed us to characterize 126 metabolites in the current study.

  16. Complementing approaches to demonstrate chlorinated solvent biodegradation in a complex pollution plume: Mass balance, PCR and compound-specific stable isotope analysis

    NASA Astrophysics Data System (ADS)

    Courbet, Christelle; Rivière, Agnès; Jeannottat, Simon; Rinaldi, Sandro; Hunkeler, Daniel; Bendjoudi, Hocine; de Marsily, Ghislain

    2011-11-01

    This work describes the use of different complementing methods (mass balance, polymerase chain reaction assays and compound-specific stable isotope analysis) to demonstrate the existence and effectiveness of biodegradation of chlorinated solvents in an alluvial aquifer. The solvent-contaminated site is an old chemical factory located in an alluvial plain in France. As most of the chlorinated contaminants currently found in the groundwater at this site were produced by local industries at various times in the past, it is not enough to analyze chlorinated solvent concentrations along a flow path to convincingly demonstrate biodegradation. Moreover, only a few data were initially available to characterize the geochemical conditions at this site, which were apparently complex at the source zone due to (i) the presence of a steady oxygen supply to the groundwater by irrigation canal losses and river infiltration and (ii) an alkaline pH higher than 10 due to former underground lime disposal. A demonstration of the existence of biodegradation processes was however required by the regulatory authority within a timeframe that did not allow a full geochemical characterization of such a complex site. Thus a combination of different fast methods was used to obtain a proof of the biodegradation occurrence. First, a mass balance analysis was performed which revealed the existence of a strong natural attenuation process (biodegradation, volatilization or dilution), despite the huge uncertainty on these calculations. Second, a good agreement was found between carbon isotopic measurements and PCR assays (based on 16S RNA gene sequences and functional genes), which clearly indicated reductive dechlorination of different hydrocarbons (Tetrachloroethene—PCE-, Trichloroethene—TCE-, 1,2- cisDichloroethene— cis-1,2-DCE-, 1,2- transDichloroethene— trans-1,2-DCE-, 1,1-Dichloroethene—1,1-DCE-, and Vinyl Chloride—VC) to ethene. According to these carbon isotope measurements

  17. The use of stable isotopes and gas chromatography/mass spectrometry in the identification of steroid metabolites in the equine

    SciTech Connect

    Houghton, E.; Dumasia, M.C.; Teale, P.; Smith, S.J.; Cox, J.; Marshall, D.; Gower, D.B. )

    1990-10-01

    Stable isotope gas chromatography/mass spectrometry has been used successfully in the elucidation of structures of urinary steroid metabolites in the horse and in the identification of metabolites isolated from in vivo perfusion and in vitro incubation studies using equine tissue preparations. Deuterium-labeled steroids, testosterone, dehydroepiandrosterone, and 5-androstene-3 beta,17 beta-diol have been synthesized by base-catalyzed isotope exchange methods and the products characterized by gas chromatography/mass spectrometry. (16,16(-2)H2)Dehydroepiandrosterone (plus radiolabeled dehydroepiandrosterone) was perfused into a testicular artery of a pony stallion and was shown to be metabolized into 2H2-labeled testosterone, 4-androstenedione, isomers of 5-androstene-3,17-diol, 19-hydroxytestosterone, and 19-hydroxy-4-androstenedione. In further studies, equine testicular minces have been incubated with 2H2-labeled and radiolabeled dehydroepiandrosterone and 5-androstene-3 beta, 17 beta-diol. The metabolites, whose identity was confirmed by stable isotope gas chromatography/mass spectrometry, proved the interconversion of the two substrates, as well as formation of testosterone and 4-androstenedione. The aromatization of dehydroepiandrosterone was also confirmed, together with the formation of an isomer of 5(10)-estrene-3,17-diol from both substrates showing 19-demethylation without concomitant aromatization. In studies of the feto-placental unit, the allantochorion was shown to aromatize (2H5)testosterone to (2H4)estradiol, the loss of one 2H from the substrate being consistent with aromatization of the A ring. The formation of 6-hydroxyestradiol was also confirmed in this study. The same technique has been valuable in determining the structure of two metabolites of nandrolone isolated from horse urine.

  18. Analysis of liposoluble carboxylic acids metabolome in human serum by stable isotope labeling coupled with liquid chromatography-mass spectrometry.

    PubMed

    Zhu, Quan-Fei; Zhang, Zheng; Liu, Ping; Zheng, Shu-Jian; Peng, Ke; Deng, Qian-Yun; Zheng, Fang; Yuan, Bi-Feng; Feng, Yu-Qi

    2016-08-19

    Fatty acids (FAs) are groups of liposoluble carboxylic acids (LCAs) and play important roles in various physiological processes. Abnormal contents or changes of FAs are associated with a series of diseases. Here we developed a strategy with stable isotope labeling combined with liquid chromatography-tandem mass spectrometry (IL-LC-MS) analysis for comprehensive profiling and relative quantitation of LCAs in human serum. In this strategy, a pair of isotope labeling reagents (2-dimethylaminoethylamine (DMED)) and d4-2-dimethylaminoethylamine (d4-DMED) were employed to selectively label carboxyl groups of LCAs. The DMED and d4-DMED labeled products can lose four characteristic neutral fragments of 45 and 49Da or 63 and 67Da in collision-induced dissociation. Therefore, quadruple neutral loss scan (QNLS) mode was established and used for non-targeted profiling of LCAs. The peak pairs of DMED and d4-DMED labeling with the same retention time, intensity and characteristic mass differences were extracted from the two NLS spectra respectively, and assigned as potential LCA candidates. Using this strategy, 241 LCA candidates were discovered in the human serum; 156 carboxylic acid compounds could be determined by searching HMDB and METLIN databases (FAs are over 90%) and 21 of these LCAs were successfully identified by standards. Subsequently, a modified pseudo-targeted method with multiple reaction monitoring (MRM) detection mode was developed and used for relative quantification of LCAs in human serum from type 2 diabetes mellitus (T2DM) patients and healthy controls. As a result, 81 LCAs were found to have significant difference between T2DM patients and healthy controls. Taken together, the isotope labeling combined with tandem mass spectrometry analysis demonstrated to be a powerful strategy for identification and quantification of LCA compounds in serum samples.

  19. Accuracy and Reproducibility in Quantification of Plasma Protein Concentrations by Mass Spectrometry without the Use of Isotopic Standards

    PubMed Central

    Kramer, Gertjan; Woolerton, Yvonne; van Straalen, Jan P.; Vissers, Johannes P. C.; Dekker, Nick; Langridge, James I.; Beynon, Robert J.; Speijer, Dave; Sturk, Auguste; Aerts, Johannes M. F. G.

    2015-01-01

    Background Quantitative proteomic analysis with mass spectrometry holds great promise for simultaneously quantifying proteins in various biosamples, such as human plasma. Thus far, studies addressing the reproducible measurement of endogenous protein concentrations in human plasma have focussed on targeted analyses employing isotopically labelled standards. Non-targeted proteomics, on the other hand, has been less employed to this end, even though it has been instrumental in discovery proteomics, generating large datasets in multiple fields of research. Results Using a non-targeted mass spectrometric assay (LCMSE), we quantified abundant plasma proteins (43 mg/mL—40 ug/mL range) in human blood plasma specimens from 30 healthy volunteers and one blood serum sample (ProteomeXchange: PXD000347). Quantitative results were obtained by label-free mass spectrometry using a single internal standard to estimate protein concentrations. This approach resulted in quantitative results for 59 proteins (cut off ≥11 samples quantified) of which 41 proteins were quantified in all 31 samples and 23 of these with an inter-assay variability of ≤ 20%. Results for 7 apolipoproteins were compared with those obtained using isotope-labelled standards, while 12 proteins were compared to routine immunoassays. Comparison of quantitative data obtained by LCMSE and immunoassays showed good to excellent correlations in relative protein abundance (r = 0.72–0.96) and comparable median concentrations for 8 out of 12 proteins tested. Plasma concentrations of 56 proteins determined by LCMSE were of similar accuracy as those reported by targeted studies and 7 apolipoproteins quantified by isotope-labelled standards, when compared to reference concentrations from literature. Conclusions This study shows that LCMSE offers good quantification of relative abundance as well as reasonable estimations of concentrations of abundant plasma proteins. PMID:26474480

  20. Bulk and Compound-Specific Isotope Analysis of Long-Chain, n-alkanes From a 85-kyr Core From Lake Peten Itza, Guatemala

    NASA Astrophysics Data System (ADS)

    Mays, J. L.; Brenner, M.; Bush, M. B.; Correa, A.; Curtis, J. H.; Hodell, D. A.

    2007-12-01

    Drill cores obtained from Lake Petén Itzá, Guatemala, contain a ~85-kyr record of terrestrial climate from lowland Central America. Variations in sediment lithology suggest rapid changes in precipitation during the last glacial and deglacial periods. Previous work in nearby Lake Quexil demonstrated the utility of using the carbon isotopic compositions of leaf wax n-alkanes to infer changes in terrestrial vegetation (Huang et al., 2001). Here we report carbon isotopes of bulk organic and long-chain n-alkanes in 60 samples to reconstruct changes in the relative proportion of C3 and C4 biomass in the watershed under changing climate and atmospheric CO2 conditions during the past 85 kyrs. Compound-specific carbon isotope results are compared directly with pollen analysis from the same samples. Huang, Y., F.A. Street-Perrott, S.E. Metcalfe, M. Brenner, M. Moreland, and K.H. Freeman. 2001. Climate change as the dominant control on glacial-interglacial variations in C3 and C4 plant abundance. Science 293:1647-1651.

  1. On molecular origin of mass-independent fractionation of oxygen isotopes in the ozone forming recombination reaction

    PubMed Central

    Ivanov, Mikhail V.; Babikov, Dmitri

    2013-01-01

    Theoretical treatment of ozone forming reaction is developed within the framework of mixed quantum/classical dynamics. Formation and stabilization steps of the energy transfer mechanism are both studied, which allows simultaneous capture of the delta zero-point energy effect and η-effect and identification of the molecular level origin of mass-independent isotope fractionation. The central role belongs to scattering resonances; dependence of their lifetimes on rotational excitation, asymmetry; and connection of their vibrational wave functions to two different reaction channels. Calculations, performed within the dimensionally reduced model of ozone, are in semiquantitative agreement with experiment. PMID:23431175

  2. Innovations in Mass Spectrometry for Precise and Accurate Isotope Ratio Determination from Very Small Analyte Quantities (Invited)

    NASA Astrophysics Data System (ADS)

    Lloyd, N. S.; Bouman, C.; Horstwood, M. S.; Parrish, R. R.; Schwieters, J. B.

    2010-12-01

    This presentation describes progress in mass spectrometry for analysing very small analyte quantities, illustrated by example applications from nuclear forensics. In this challenging application, precise and accurate (‰) uranium isotope ratios are required from 1 - 2 µm diameter uranium oxide particles, which comprise less than 40 pg of uranium. Traditionally these are analysed using thermal ionisation mass spectrometry (TIMS), and more recently using secondary ionisation mass spectrometry (SIMS). Multicollector inductively-coupled plasma mass spectrometry (MC-ICP-MS) can offer higher productivity compared to these techniques, but is traditionally limited by low efficiency of analyte utilisation (sample through to ion detection). Samples can either be introduced as a solution, or sampled directly from solid using laser ablation. Large multi-isotope ratio datasets can help identify provenance and intended use of anthropogenic uranium and other nuclear materials [1]. The Thermo Scientific NEPTUNE Plus (Bremen, Germany) with ‘Jet Interface’ option offers unparalleled MC-ICP-MS sensitivity. An analyte utilisation of c. 4% has previously been reported for uranium [2]. This high-sensitivity configuration utilises a dry high-capacity (100 m3/h) interface pump, special skimmer and sampler cones and a desolvating nebuliser system. Coupled with new acquisition methodologies, this sensitivity enhancement makes possible the analysis of micro-particles and small sample volumes at higher precision levels than previously achieved. New, high-performance, full-size and compact discrete dynode secondary electron multipliers (SEM) exhibit excellent stability and linearity over a large dynamic range and can be configured to simultaneously measure all of the uranium isotopes. Options for high abundance-sensitivity filters on two ion beams are also available, e.g. for 236U and 234U. Additionally, amplifiers with high ohm (1012 - 1013) feedback resistors have been developed to

  3. Quantitation of organophosphorus nerve agent metabolites in human urine using isotope dilution gas chromatography-tandem mass spectrometry.

    PubMed

    Driskell, W Jack; Shih, Ming; Needham, Larry L; Barr, Dana B

    2002-01-01

    An isotope dilution gas chromatography-tandem mass spectrometric (GC-MS-MS) method was developed for quantitating the urinary metabolites of the organophosphorus nerve agents sarin, soman, tabun (GA), VX, and GF. Urine samples were concentrated by codistillation with acetonitrile, derivatized by methylation with diazomethane, and analyzed by GC-MS-MS. The limits of detection were less than 4 microg/L for all the analytes except for the GA metabolite, which had a limit of detection of less than 20 microg/L.

  4. Urinary 19-norandrosterone purification by immunoaffinity chromatography: application to gas chromatography/combustion/isotope ratio mass spectrometric analysis.

    PubMed

    Desroches, M C; Mathurin, J C; Richard, Y; Delahaut, P; de Ceaurriz, J

    2002-01-01

    The detection of exogenous 19-norandrosterone (19-NA) in urines was investigated by using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). 19-NA is, for the first time to our knowledge, isolated from urinary matrix by specific immunoaffinity chromatography (IAC) before analysis. The sample preparation consisted of a preliminary purification of urine by solid-phase extraction after hydrolysis by beta-glucuronidase. Unconjugated 19-NA was thus isolated by IAC and directly analysed by GC/C/IRMS. Optimisation of IAC purification was achieved and the reliability of the technique for anti-doping control is discussed.

  5. Characterization of Lipid A Variants by Energy-Resolved Mass Spectrometry: Impact of Acyl Chains

    NASA Astrophysics Data System (ADS)

    Crittenden, Christopher M.; Akin, Lucas D.; Morrison, Lindsay J.; Trent, M. Stephen; Brodbelt, Jennifer S.

    2016-12-01

    Lipid A molecules consist of a diglucosamine sugar core with a number of appended acyl chains that vary in their length and connectivity. Because of the challenging nature of characterizing these molecules and differentiating between isomeric species, an energy-resolved MS/MS strategy was undertaken to track the fragmentation trends and map genealogies of product ions originating from consecutive cleavages of acyl chains. Generalizations were developed based on the number and locations of the primary and secondary acyl chains as well as variations in preferential cleavages arising from the location of the phosphate groups. Secondary acyl chain cleavage occurs most readily for lipid A species at the 3' position, followed by primary acyl chain fragmentation at both the 3' and 3 positions. In the instances of bisphosphorylated lipid A variants, phosphate loss occurs readily in conjunction with the most favorable primary and secondary acyl chain cleavages.

  6. Isolation of bicarbonate from equine urine for isotope ratio mass spectrometry.

    PubMed

    Hülsemann, Frank; Flenker, Ulrich; Machnik, Marc; Schänzer, Wilhelm

    2007-12-01

    Sodium bicarbonate administration to horses prior to competition in order to enhance the buffer capacity of the organism is considered as a doping offence. The analysis of the isotopic composition of urinary bicarbonate/CO(2) (TCO(2)) may help to identify an exogenous bicarbonate source, as technical sodium bicarbonate exhibits elevated delta(13)C values compared with urinary total carbon. The isolation of TCO(2) from 60 equine urine samples as BaCO(3) followed by an isotopic analysis shows a significant variability of delta(13)C for TCO(2) of more than 10 per thousand. The delta(13)C of total carbon and TCO(2) seem to reflect different proportions of C3 and C4 plant material in the diet. The isotopic analysis of different mixtures of technical NaHCO(3) and equine urine shows that TCO(2) can be easily isolated without major isotopic fractionation; however, attention has to be paid to the storage time of urine samples, as a shift of delta(13)C of TCO(2) to lower values may occur.

  7. Illustrating the Concepts of Isotopes and Mass Spectrometry in Introductory Courses: A MALDI-TOF Mass Spectrometry Laboratory Experiment

    ERIC Educational Resources Information Center

    Dopke, Nancy Carter; Lovett, Timothy Neal

    2007-01-01

    Mass spectrometry is a widely used and versatile tool for scientists in many different fields. Soft ionization techniques such as matrix-assisted laser desorption/ionization (MALDI) allow for the analysis of biomolecules, polymers, and clusters. This article describes a MALDI mass spectrometry experiment designed for students in introductory…

  8. Mass spectrometric methods for the direct elemental and isotopic analysis of solid material

    NASA Astrophysics Data System (ADS)

    Ganeev, A. A.; Gubal, A. R.; Potapov, S. V.; Agafonova, N. N.; Nemets, V. M.

    2016-04-01

    Methods for the direct analysis of solids have a number of undeniable advantages over the methods that require preliminary dissolution of samples. High sensitivity and selectivity make the direct mass spectrometric techniques the most in-demand. The review concerns spark source mass spectrometry, laser ionization mass spectrometry, laser ablation inductively coupled plasma mass spectrometry, secondary ion mass spectrometry, secondary neutral mass spectrometry and glow discharge mass spectrometry. Basic principles, analytical characteristics and trends in the development of these techniques are discussed. Particular attention is given to applications of the techniques as well as to their competitive advantages and drawbacks. The bibliography includes 123 references.

  9. Determination of the natural abundance δ15N of taurine by gas chromatography-isotope ratio measurement mass spectrometry.

    PubMed

    Tea, Illa; Antheaume, Ingrid; Besnard, Jorick; Robins, Richard J

    2010-12-15

    The measurement of the nitrogen isotope ratio of taurine (2-aminoethanesulphonic acid) in biological samples has a large number of potential applications. Taurine is a small water-soluble molecule which is notoriously difficult to analyze due to its polarity and functionality. A method is described which allows the determination of the natural abundance δ(15)N values of taurine and structural analogues, such as 3-amino-1-propanesulphonic acid (APSA), by isotope ratio mass spectrometry interfaced to gas chromatography (GC-irm-MS). The one-step protocol exploits the simultaneous derivatization of both functionalities of these aminosulphonic acids by reaction with triethylorthoacetate (TEOA). Conditions have been established which ensure quantitative reaction thus avoiding any nitrogen isotope fractionation during derivatization and workup. The differences in the δ(15)N values of derivatized and non-derivatized taurine and APSA all fall within the working range of 0.4‰ (-0.02 to 0.39‰). When applied to four sources of taurine with various δ(15)N values, the method achieved excellent reproducibility and accuracy. The optimized method enables the determination of the natural abundance δ(15)N values of taurine over the concentration range 1.5-7.84 µmol.mL(-1) in samples of biological origin.

  10. Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign

    NASA Astrophysics Data System (ADS)

    Savarino, Joël; Vicars, William C.; Legrand, Michel; Preunkert, Suzanne; Jourdain, Bruno; Frey, Markus M.; Kukui, Alexandre; Caillon, Nicolas; Gil Roca, Jaime

    2016-03-01

    Variations in the stable oxygen isotope composition of atmospheric nitrate act as novel tools for studying oxidative processes taking place in the troposphere. They provide both qualitative and quantitative constraints on the pathways determining the fate of atmospheric nitrogen oxides (NO + NO2 = NOx). The unique and distinctive 17O excess (Δ17O = δ17O - 0.52 × δ18O) of ozone, which is transferred to NOx via oxidation, is a particularly useful isotopic fingerprint in studies of NOx transformations. Constraining the propagation of 17O excess within the NOx cycle is critical in polar areas, where there exists the possibility of extending atmospheric investigations to the glacial-interglacial timescale using deep ice core records of nitrate. Here we present measurements of the comprehensive isotopic composition of atmospheric nitrate collected at Dome C (East Antarctic Plateau) during the austral summer of 2011/2012. Nitrate isotope analysis has been here combined for the first time with key precursors involved in nitrate production (NOx, O3, OH, HO2, RO2, etc.) and direct observations of the transferrable Δ17O of surface ozone, which was measured at Dome C throughout 2012 using our recently developed analytical approach. Assuming that nitrate is mainly produced in Antarctica in summer through the OH + NO2 pathway and using concurrent measurements of OH and NO2, we calculated a Δ17O signature for nitrate on the order of (21-22 ± 3) ‰. These values are lower than the measured values that ranged between 27 and 31 ‰. This discrepancy between expected and observed Δ17O(NO3-) values suggests the existence of an unknown process that contributes significantly to the atmospheric nitrate budget over this East Antarctic region. However, systematic errors or false isotopic balance transfer functions are not totally excluded.

  11. Screening for medium chain acyl-CoA dehydrogenase deficiency using electrospray ionisation tandem mass spectrometry

    PubMed Central

    Clayton, P.; Doig, M.; Ghafari, S.; Meaney, C.; Taylor, C.; Leonard, J.; Morris, M.; Johnson, A.

    1998-01-01

    OBJECTIVE—To establish criteria for the diagnosis of medium chain acyl-CoA dehydrogenase (MCAD) deficiency in the UK population using a method in which carnitine species eluted from blood spots are butylated and analysed by electrospray ionisation tandem mass spectrometry (ESI-MS/MS).
DESIGN—Four groups were studied: (1) 35 children, aged 4 days to 16.2 years, with proven MCAD deficiency (mostly homozygous for the A985G mutation, none receiving carnitine supplements); (2) 2168control children; (3) 482 neonates; and (4) 15 MCAD heterozygotes.
RESULTS—All patients with MCAD deficiency had an octanoylcarnitine concentration ([C8-Cn]) > 0.38 µM and no accumulation of carnitine species > C10 or < C6. Among the patients with MCAD deficiency, the [C8-Cn] was significantly lower in children > 10 weeks old and in children with carnitine depletion (free carnitine < 20 µM). Neonatal blood spots from patients with MCAD deficiency had a [C8-Cn] > 1.5 µM, whereas in heterozygotes and other normal neonates the [C8-Cn] was < 1.0 µM. In contrast, the blood spot [C8-Cn] in eight of 27 patients with MCAD deficiency > 10 weeks old fell within the same range as five of 15 MCAD heterozygotes (0.38-1.0 µM). However, the free carnitine concentrations were reduced (< 20 µM) in the patients with MCAD deficiency but normal in the heterozygotes.
CONCLUSIONS—Criteria for the diagnosis of MCAD deficiency using ESI-MS/MS must take account of age and carnitine depletion. If screening is undertaken at 7-10 days, the number of false positive and negative results should be negligible. Because there have been no instances of death or neurological damage following diagnosis of MCAD deficiency in our patient group, a strong case can be made for neonatal screening for MCAD deficiency in the UK.

 PMID:9797589

  12. Measurement of Uranium Isotopes in Particles of U3O8 by Secondary Ion Mass Spectrometry-Single-Stage Accelerator Mass Spectrometry (SIMS-SSAMS).

    PubMed

    Fahey, Albert J; Groopman, Evan E; Grabowski, Kenneth S; Fazel, Kamron C

    2016-07-19

    A commercial secondary ion mass spectrometer (SIMS) was coupled to a ± 300 kV single-stage accelerator mass spectrometer (SSAMS). Positive secondary ions generated with the SIMS were injected into the SSAMS for analysis. This combined instrument was used to measure the uranium isotopic ratios in particles of three certified reference materials (CRM) of uranium, CRM U030a, CRM U500, and CRM U850. The ability to inject positive ions into the SSAMS is unique for AMS systems and allows for simple analysis of nearly the entire periodic table because most elements will readily produce positive ions. Isotopic ratios were measured on samples of a few picograms to nanograms of total U. Destruction of UH(+) ions in the stripper tube of the SSAMS reduced hydride levels by a factor of ∼3 × 10(4) giving the UH(+)/U(+) ratio at the SSAMS detector of ∼1.4 × 10(-8). These hydride ion levels would allow the measurement of (239)Pu at the 10 ppb level in the presence of U and the equivalent of ∼10(-10 236)U concentration in natural uranium. SIMS-SSAMS analysis of solid nuclear materials, such as these, with signals nearly free of molecular interferences, could have a significant future impact on the way some measurements are made for nuclear nonproliferation.

  13. Limitations in detection of 15N incorporation by mass spectrometry in protein-based stable isotope probing (protein-SIP).

    PubMed

    Taubert, Martin; von Bergen, Martin; Seifert, Jana

    2013-05-01

    The method of protein-based stable isotope probing (protein-SIP) has previously been shown to allow the modeling of carbon fluxes in microbial communities, thus tackling one of the key questions in microbial ecology. The method allows the analysis of stable isotope distribution in peptides, revealing metabolic activities of the species present in an ecosystem. Besides carbon, an application of protein-SIP with nitrogen is of interest for resolving the nitrogen fluxes in microbial communities. Thus, the sensitivity and reliability of a protein-SIP approach employing (15)N was analyzed. For this, cultivations of Pseudomonas fluorescens ATCC 17483 with different ratios of (14)N/(15)N were performed, from 10 % down to 0.1 % (15)N. After incubation leading to complete labeling of biomass, proteins were extracted and separated by one-dimensional gel electrophoresis, followed by tryptic digest and UPLC Orbitrap MS/MS analysis. (15)N relative isotope abundance (RIA) was calculated based on isotopic patterns from identified peptides in mass spectra. Proteomics data have been deposited to ProteomeXchange with identifier PXD000127. The distribution of (15)N RIA values among peptides was analyzed in samples with different (15)N amount, and potential causes for variations within individual samples of either technical or biological origin were investigated. Using a number of 50 peptides, significant differences (p ≤ 0.05) in (15)N incorporation were found between samples of different (15)N RIA down to 0.1 %. The study demonstrates that protein-SIP using (15)N is sufficiently sensitive for quantitative investigation of microbial activity in nitrogen cycling processes.

  14. First online multireflection time-of-flight mass measurements of isobar chains produced by fusion-evaporation reactions: Toward identification of superheavy elements via mass spectroscopy

    NASA Astrophysics Data System (ADS)

    Schury, P.; Wada, M.; Ito, Y.; Kaji, D.; Arai, F.; MacCormick, M.; Murray, I.; Haba, H.; Jeong, S.; Kimura, S.; Koura, H.; Miyatake, H.; Morimoto, K.; Morita, K.; Ozawa, A.; Rosenbusch, M.; Reponen, M.; Söderström, P.-A.; Takamine, A.; Tanaka, T.; Wollnik, H.

    2017-01-01

    Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several α -decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, 204Fr-204Rn-204At-204Po , 205Fr-205Rn-205At-205Po-205Bi , and 206Fr-206Rn-206At , were observed. Precision atomic mass values were determined for Fr-206204, Rn,205204, and At,205204. Identifications of 205Bi, Po,205204, 206Rn, and 206At were made with N ≲10 detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy element ions.

  15. Acetylation and glycation of fibrinogen in vitro occur at specific lysine residues in a concentration dependent manner: A mass spectrometric and isotope labeling study

    SciTech Connect

    Svensson, Jan; Bergman, Ann-Charlotte; Adamson, Ulf; Blombaeck, Margareta; Wallen, Hakan; Joerneskog, Gun

    2012-05-04

    Highlights: Black-Right-Pointing-Pointer Fibrinogen was incubated in vitro with glucose or aspirin. Black-Right-Pointing-Pointer Acetylations and glycations were found at twelve lysine sites by mass spectrometry. Black-Right-Pointing-Pointer The labeling by aspirin and glucose occurred dose-dependently. Black-Right-Pointing-Pointer No competition between glucose and aspirin for binding to fibrinogen was found. -- Abstract: Aspirin may exert part of its antithrombotic effects through platelet-independent mechanisms. Diabetes is a condition in which the beneficial effects of aspirin are less prominent or absent - a phenomenon called 'aspirin resistance'. We investigated whether acetylation and glycation occur at specific sites in fibrinogen and if competition between glucose and aspirin in binding to fibrinogen occurs. Our hypothesis was that such competition might be one explanation to 'aspirin resistance' in diabetes. After incubation of fibrinogen in vitro with aspirin (0.8 mM, 24 h) or glucose (100 mM, 5-10 days), we found 12 modified sites with mass spectrometric techniques. Acetylations in the {alpha}-chain: {alpha}K191, {alpha}K208, {alpha}K224, {alpha}K429, {alpha}K457, {alpha}K539, {alpha}K562, in the {beta}-chain: {beta}K233, and in the {gamma}-chain: {gamma}K170 and {gamma}K273. Glycations were found at {beta}K133 and {gamma}K75, alternatively {gamma}K85. Notably, the lysine 539 is a site involved in FXIII-mediated cross-linking of fibrin. With isotope labeling in vitro, using [{sup 14}C-acetyl]salicylic acid and [{sup 14}C]glucose, a labeling of 0.013-0.084 and 0.12-0.5 mol of acetylated and glycated adduct/mol fibrinogen, respectively, was found for clinically (12.9-100 {mu}M aspirin) and physiologically (2-8 mM glucose) relevant plasma concentrations. No competition between acetylation and glycation could be demonstrated. Thus, fibrinogen is acetylated at several lysine residues, some of which are involved in the cross-linking of fibrinogen. This may

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

    PubMed Central

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

    2010-01-01

    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

  17. Mass balance and isotope effects during nitrogen transport through septic tank systems with packed-bed (sand) filters

    USGS Publications Warehouse

    Hinkle, S.R.; Böhlke, J.K.; Fisher, L.H.

    2008-01-01

    Septic tank systems are an important source of NO3- to many aquifers, yet characterization of N mass balance and isotope systematics following septic tank effluent discharge into unsaturated sediments has received limited attention. In this study, samples of septic tank effluent before and after transport through single-pass packed-bed filters (sand filters) were evaluated to elucidate mass balance and isotope effects associated with septic tank effluent discharge to unsaturated sediments. Chemical and isotopic data from five newly installed pairs and ten established pairs of septic tanks and packed-bed filters serving single homes in Oregon indicate that aqueous solute concentrations are affected by variations in recharge (precipitation, evapotranspiration), NH4+ sorption (primarily in immature systems), nitrification, and gaseous N loss via NH3 volatilization and(or) N2 or N2O release during nitrification/denitrification. Substantial NH4+ sorption capacity was also observed in laboratory columns with synthetic effluent. Septic tank effluent ??15N-NH4+ values were almost constant and averaged + 4.9??? ?? 0.4??? (1 ??). In contrast, ??15N values of NO3- leaving mature packed-bed filters were variable (+ 0.8 to + 14.4???) and averaged + 7.2??? ?? 2.6???. Net N loss in the two networks of packed-bed filters was indicated by average 10-30% decreases in Cl--normalized N concentrations and 2-3??? increases in ??15N, consistent with fractionation accompanying gaseous N losses and corroborating established links between septic tank effluent and NO3- in a local, shallow aquifer. Values of ??18O-NO3- leaving mature packed-bed filters ranged from - 10.2 to - 2.3??? (mean - 6.4??? ?? 1.8???), and were intermediate between a 2/3 H2O-O + 1/3 O2-O conceptualization and a 100% H2O-O conceptualization of ??18O-NO3- generation during nitrification.

  18. Measurement of insulin sensitivity indices using 13C-glucose and gas chromatography/combustion/isotope ratio mass spectrometry.

    PubMed

    Clapperton, Allan T; Coward, W Andrew; Bluck, Leslie J C

    2002-01-01

    Important aspects of glucose metabolism can be quantified by using the minimal model of glucose kinetics to interpret the results of intravenous glucose tolerance tests. The power of this methodology can be greatly increased by the addition of stable isotopically labelled tracer to the glucose bolus dose. This allows the separation of glucose disposal from endogenous glucose production and also increases the precision of the estimates of the physiological parameters measured. Until now the tracer of choice has been deuteriated glucose and the analytical technique has been gas chromatography/mass spectrometry (GC/MS). The consequence of this choice is that nearly 2 g of labelled material are needed and this makes the test expensive. We have investigated the use of (13)C-labelled glucose as the tracer in combination with gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) as the analytical technique. This methodology offers superior analytical precision when compared with the conventional method and so the amount of tracer used, and hence the cost, can be reduced considerably. Healthy non-obese male volunteers were recruited for a standard intravenous glucose tolerance test (IVGTT) protocol but 6,6-(2)H-glucose and 1-(13)C-glucose were administered simultaneously. Tracer/tracee ratios were derived from isotope ratio measurements of plasma glucose using both GC/MS and GC/C/IRMS. The results of these determinations indicated that the two tracers behaved identically under the test protocol. The combination of these results with plasma glucose and insulin concentration data allowed determination of the minimal model parameters S*g and S*i. The parameter relating to insulin-assisted glucose disposal, S*i, was found to be the same in the two techniques, but this was not the case for the non-insulin-dependent parameter S*g.

  19. Production and analysis of mass-deficient neptunium and plutonium isotopes

    NASA Astrophysics Data System (ADS)

    Whittaker, B.

    1984-06-01

    Neptunium-235, 236Pu and 237Pu are produced by cyclotron-irradiation of high-enrichment 238U or 235U targets. Plutonium-236 may be directly assayed and partially analysed by means of alpha-counting and spectrometry techniques, but 235Np and 237Pu are assayed indirectly by their 235U and 237Np ground-state X-ray and gamma emissions, respectively. For 235Np combined alpha, gamma and X-ray analysis is necessary to positively identify and quantify this isotope since 234Np produces an identical X-ray spectrum. The need for new nuclear-data measurements of 237Pu absolute gamma intensities, 235Np alpha branching, and 235Np half-life is stressed. Product isotopic purity is discussed in the context of target material purity and beam energy.

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

    PubMed

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

    2014-06-18

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

  1. Method for ultra-trace cesium isotope ratio measurements from environmental samples using thermal ionization mass spectrometry

    SciTech Connect

    Snow, Mathew S.; Snyder, Darin C.; Mann, Nick R.; White, Byron M.

    2015-05-01

    135Cs/137Cs isotope ratios can provide the age, origin and history of environmental Cs contamination. Relatively high precision 135Cs/137Cs isotope ratio measurements from samples containing femtogram quantities of 137Cs are needed to accurately track contamination resuspension and redistribution following environmental 137Cs releases; however, mass spectrometric analyses of environmental samples are limited by the large quantities of ionization inhibitors and isobaric interferences which are present at relatively high concentrations in the environment. We report a new approach for Cs purification from environmental samples. An initial ammonium molybdophosphate-polyacrylonitrile (AMP-PAN) column provides a robust method for extracting Cs under a wide variety of sample matrices and mass loads. Cation exchange separations using a second AMP-PAN column result in more than two orders of magnitude greater Cs/Rb separation factors than commercially available strong cation exchangers. Coupling an AMP-PAN cation exchanging step to a microcation column (AG50W resin) enables consistent 2-4% (2σ) measurement errors for samples containing 3-6,000 fg 137Cs, representing the highest precision 135Cs/137Cs ratio measurements currently reported for soil samples at the femtogram level.

  2. Determination of dicyandiamide in infant formula by stable isotope dilution hydrophilic interaction liquid chromatography with tandem mass spectrometry.

    PubMed

    Inoue, Koichi; Sakamoto, Tasuku; Min, Jun Zhe; Todoroki, Kenichiro; Toyo'oka, Toshimasa

    2014-08-01

    Dicyandiamide is a compound for reducing the negative effects of greenhouse gas emissions and nitrate leaching into waterways. In this study, the trace contamination of dicyandiamide in infant formula was analysed by stable isotope dilution hydrophilic interaction liquid chromatography with tandem mass spectrometry (HILIC-MS/MS). Dicyandiamide and a stable isotope internal standard were monitored by multiple reaction-monitoring with mass transitions: m/z 85→68/43 and m/z 89→71/45 in the electrospray positive ion mode. For sample preparation of the infant formula, a diluted/filtered procedure was developed for this assay. The calculated LOD and LOQ values were 0.01 or 0.05ng/mL for the standard solution, respectively. The averaged recovery and precision were 110.8% and 7.4%, respectively. This assay was applied to monitor 23 infant formulas, and the dicyandiamide contamination in one sample was detected and quantified at 79.1±1.2ng/g (ppb) powder. We suggest that it is necessary to cautiously monitor the DCD in common products from international countries.

  3. RAPID DETERMINATION OF 237 NP AND PU ISOTOPES IN WATER BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY AND ALPHA SPECTROMETRY

    SciTech Connect

    Maxwell, S.; Jones, V.; Culligan, B.; Nichols, S.; Noyes, G.

    2010-06-23

    A new method that allows rapid preconcentration and separation of plutonium and neptunium in water samples was developed for the measurement of {sup 237}Np and Pu isotopes by inductively-coupled plasma mass spectrometry (ICP-MS) and alpha spectrometry; a hybrid approach. {sup 238}U can interfere with {sup 239}Pu measurement by ICP-MS as {sup 238}UH{sup +} mass overlap and {sup 237}Np via peak tailing. The method provide enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then moving Pu to DGA resin for additional removal of uranium. The decontamination factor for uranium from Pu is almost 100,000 and the decontamination factor for U from Np is greater than 10,000. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration is performed using a streamlined calcium phosphate precipitation method. Purified solutions are split between ICP-MS and alpha spectrometry so that long and short-lived Pu isotopes can be measured successfully. The method allows for simultaneous extraction of 20 samples (including QC samples) in 4 to 6 hours, and can also be used for emergency response. {sup 239}Pu, {sup 242}Pu and {sup 237}Np were measured by ICP-MS, while {sup 236}Pu, {sup 238}Pu, and {sup 239}Pu were measured by alpha spectrometry.

  4. FUN with PANURGE - High mass resolution ion microprobe measurements of Mg in Allende inclusions. [meteoritic composition isotope analysis

    NASA Technical Reports Server (NTRS)

    Huneke, J. C.; Armstrong, J. T.; Wassserburg, G. J.

    1983-01-01

    Isotopic ratios have been determined, at a precision level approaching that of counting statistics using beam switching, by employing PANURGE, a modified CAMECA IMS3F ion microprobe at a mass resolving power of 5000. This technique is used to determine the isotopic composition of Mg and Si and the atomic ratio of Al/Mg in minerals from the Allende inclusion WA and the Allende FUN inclusion C1. Results show enrichment in Mg-26 of up to 260 percent. Results of Mg and Al/Mg measurements on cogenetic spinel inclusion and host plagiclase crystals show Mg-Al isochrons in excellent agreement with precise mineral isochrons determined by thermal emission mass spectrometry. The measurements are found to confirm the presence of substantial excess Mg-26 in WA and its near absence in C1. Data is obtained which indicates a metamorphic reequilibrium of Mg in Allende plagioclase at least 0.6 my after WA formation. Ion probe measurements are obtained which confirm that the Mg composition in Allende C1 is highly fractionated and is uniform among pyroxene, melilite, plagioclase, spinel crystals, and spinel included in melilite and plagioclase crystals.

  5. Discovery of histone modification crosstalk networks by stable isotope labeling of amino acids in cell culture mass spectrometry (SILAC MS).

    PubMed

    Guan, Xiaoyan; Rastogi, Neha; Parthun, Mark R; Freitas, Michael A

    2013-08-01

    In this paper we describe an approach that combines stable isotope labeling of amino acids in cells culture, high mass accuracy liquid chromatography tandem mass spectrometry and a novel data analysis approach to accurately determine relative peptide post-translational modification levels. This paper describes the application of this approach to the discovery of novel histone modification crosstalk networks in Saccharomyces cerevisiae. Yeast histone mutants were generated to mimic the presence/absence of 44 well-known modifications on core histones H2A, H2B, H3, and H4. In each mutant strain the relative change in H3 K79 methylation and H3 K56 acetylation were determined using stable isotope labeling of amino acids in cells culture. This approach showed relative changes in H3 K79 methylation and H3 K56 acetylation that are consistent with known histone crosstalk networks. More importantly, this study revealed additional histone modification sites that affect H3 K79 methylation and H3 K56 acetylation.

  6. A five-collector system for the simultaneous measurement of argon isotope ratios in a static mass spectrometer

    USGS Publications Warehouse

    Stacey, J.S.; Sherrill, N.D.; Dalrymple, G.B.; Lanphere, M.A.; Carpenter, N.V.

    1981-01-01

    A system is described that utilizes five separate Faraday-cup collector assemblies, aligned along the focal plane of a mass spectrometer, to collect simultaneous argon ion beams at masses 36-40. Each collector has its own electrometer amplifier and analog-to-digital measuring channel, the outputs of which are processed by a minicomputer that also controls the mass spectrometer. The mass spectrometer utilizes a 90?? sector magnetic analyzer with a radius of 23 cm, in which some degree of z-direction focussing is provided for all the ion beams by the fringe field of the magnet. Simultaneous measurement of the ion beams helps to eliminate mass-spectrometer memory as a significant source of measurement error during an analysis. Isotope ratios stabilize between 7 and 9 s after sample admission into the spectrometer, and thereafter changes in the measured ratios are linear, typically to within ??0.02%. Thus the multi-collector arrangement permits very short extrapolation times for computation of initial ratios, and also provides the advantages of simultaneous measurement of the ion currents in that errors due to variations in ion beam intensity are minimized. A complete analysis takes less than 10 min, so that sample throughput can be greatly enhanced. In this instrument, the factor limiting analytical precision now lies in short-term apparent variations in the interchannel calibration factors. ?? 1981.

  7. Nicotine, acetanilide and urea multi-level 2H-, 13C- and 15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry.

    PubMed

    Schimmelmann, Arndt; Albertino, Andrea; Sauer, Peter E; Qi, Haiping; Molinie, Roland; Mesnard, François

    2009-11-01

    Accurate determinations of stable isotope ratios require a calibration using at least two reference materials with different isotopic compositions to anchor the isotopic scale and compensate for differences in machine slope. Ideally, the delta values of these reference materials should bracket the isotopic range of samples with unknown delta values. While the practice of analyzing two isotopically distinct reference materials is common for water (VSMOW-SLAP) and carbonates (NBS 19 and L-SVEC), the lack of widely available organic reference materials with distinct isotopic composition has hindered the practice when analyzing organic materials by elemental analysis/isotope ratio mass spectrometry (EA-IRMS). At present only L-glutamic acids USGS40 and USGS41 satisfy these requirements for delta13C and delta15N, with the limitation that L-glutamic acid is not suitable for analysis by gas chromatography (GC). We describe the development and quality testing of (i) four nicotine laboratory reference materials for on-line (i.e. continuous flow) hydrogen reductive gas chromatography-isotope ratio mass-spectrometry (GC-IRMS), (ii) five nicotines for oxidative C, N gas chromatography-combustion-isotope ratio mass-spectrometry (GC-C-IRMS, or GC-IRMS), and (iii) also three acetanilide and three urea reference materials for on-line oxidative EA-IRMS for C and N. Isotopic off-line calibration against international stable isotope measurement standards at Indiana University adhered to the 'principle of identical treatment'. The new reference materials cover the following isotopic ranges: delta2H(nicotine) -162 to -45 per thousand, delta13C(nicotine) -30.05 to +7.72 per thousand, delta15N(nicotine) -6.03 to +33.62 per thousand; delta15N(acetanilide) +1.18 to +40.57 per thousand; delta13C(urea) -34.13 to +11.71 per thousand, delta15N(urea) +0.26 to +40.61 per thousand (recommended delta values refer to calibration with NBS 19, L-SVEC, IAEA-N-1, and IAEA-N-2). Nicotines fill a gap as

  8. Nicotine, acetanilide and urea multi-level2H-,13C- and15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry

    USGS Publications Warehouse

    Schimmelmann, A.; Albertino, A.; Sauer, P.E.; Qi, H.; Molin