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1

Isotope Ratio Mass Spectrometry.  

PubMed

Isotope Ratio Mass Spectrometry (IRMS) is a specialized technique used to provide information about the geographic, chemical, and biological origins of substances. The ability to determine the source of an organic substance stems from the relative isotopic abundances of the elements which comprise the material. Because the isotope ratios of elements such as carbon, hydrogen, oxygen, sulfur, and nitrogen can become locally enriched or depleted through a variety of kinetic and thermodynamic factors, measurement of the isotope ratios can be used to differentiate between samples which otherwise share identical chemical compositions. Several sample introduction methods are now available for commercial isotope ratio mass spectrometers. Combustion is most commonly used for bulk isotopic analysis, whereas gas and liquid chromatography are predominately used for the real-time isotopic analysis of specific compounds within a mixture. Here, highlights of advances in instrumentation and applications within the last three years are provided to illustrate the impact of this rapidly growing area of research. Some prominent new applications include authenticating organic food produce, ascertaining whether or not African elephants are guilty of night-time raids on farmers' crops, and linking forensic drug and soil samples from a crime scene to a suspected point of origin. For the sake of brevity, we focus this Minireview on the isotope ratio measurements of lighter-elements common to organic sources; we do not cover the equally important field of inorganic isotope ratio mass spectrometry. PMID:19173039

Muccio, Zeland; Jackson, Glen P

2009-02-01

2

Isotope dilution mass spectrometry  

NASA Astrophysics Data System (ADS)

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

Heumann, Klaus G.

1992-09-01

3

Accelerator mass spectrometry of plutonium isotopes  

Microsoft Academic Search

The feasibility of measuring plutonium isotope ratios by accelerator mass spectrometry has been demonstrated. Measurements on a test sample of known composition and on a blank showed that isotope ratios could be determined quantitatively, and that the present limit of detection by AMS is ? 106 atoms of plutonium. For 239Pu, this limit is at least two orders of magnitude

L. K. Fifield; R. G. Cresswell; M. L. di Tada; T. R. Ophel; J. P. Day; A. P. Clacher; S. J. King; N. D. Priest

1996-01-01

4

Isotopic trace analysis by atomic mass spectrometry  

SciTech Connect

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.

Stoffels, J.J.

1993-12-01

5

O isotopic composition of CaCO3 measured by continuous ow isotope ratio mass spectrometry  

E-print Network

spectrometry (DI-IRMS). A mass spectrometer is used to determine the ratio (R) of the heavy isotoped13 C and d18 O isotopic composition of CaCO3 measured by continuous ¯ow isotope ratio mass spectrometry: statistical evaluation and veri®cation by application to Devils Hole core DH-11 calcite²³ Kinga M

6

Stable isotope-coded proteomic mass spectrometry  

Microsoft Academic Search

Developing the ability to quantify changes in protein abundance between cells subjected to a variety of physiological and environmental conditions is an extremely active area of proteome research. Although advances in chromatography, mass spectrometry instrumentation, and bioinformatics have contributed to producing a viable method for comparative proteome-wide analyses, the highest precision of quantitation is based, in part, upon improved methods

Michael B. Goshe; Richard D. Smith

2003-01-01

7

Hydrogen isotope analysis by quadrupole mass spectrometry  

Microsoft Academic Search

The analysis of isotopes of hydrogen (H, D, T) and helium (He, He) and selected impurities using a quadrupole mass spectrometer (QMS) has been investigated as a method of measuring the purity of tritium gas for injection into the Tokamak Fusion Test Reactor (TFTR). A QMS was used at low resolution, m\\/..delta..m < 150, for quantifying impurities from m\\/q =

R. E. Ellefson; W. E. Moddeman; H. F. Dylla

1981-01-01

8

Hydrogen isotope analysis by quadrupole mass spectrometry  

Microsoft Academic Search

The analysis of isotopes of hydrogen (H,D,T) and helium (³He,⁴He) and selected impurities using a quadrupole mass spectrometer (QMS) has been investigated as a method of measuring the purity of tritium gas for injection into the Tokamak Fusion Test Reactor (TFTR). A QMS was used at low resolution, m\\/Dm<150, for quantifying impurities from m\\/q = 2 to 44, and at

R. E. Ellefson; W. E. Moddeman; H. F. Dylla

1981-01-01

9

Isotope Peaks of Ionic Fragments in Mass Spectrometry  

NSDL National Science Digital Library

Mass spectrometry: This applet allows you to insert the empirical formula of an ionic fragment and obtain the relative intensities of its isotope peaks. Observe the lines corresponding to this fragment, as they would appeared in a mass spectrum. Theory is provided alongside the applet.

10

Discrepancies between isotope ratio infrared spectroscopy and isotope ratio mass spectrometry for the  

E-print Network

spectroscopy (IRIS) for the stable hydrogen and oxygen isotope analysis of water is increasing. While IRIS hasDiscrepancies between isotope ratio infrared spectroscopy and isotope ratio mass spectrometry for the stable isotope analysis of plant and soil waters Adam G. West1,2*, Gregory R. Goldsmith1 , Paul D. Brooks

West, Adam G.

11

Mass spectrometry and isotopes: a century of research and discussion.  

PubMed

In 1815, the British physician William Prout had advanced the theory that the molecular masses of elements were multiples of the mass of hydrogen. This "whole number rule" (and especially deviations from it) played an important role in the discussion whether elements could be mixtures of isotopes. F. Soddy's discovery (1910) that lead obtained by decay of uranium and of thorium differed in mass was considered a peculiarity of radioactive materials. The question of the existence of isotopes came up when the instruments developed by J.J. Thomson and by W. Wien to study cathode and canal rays by deflection in electric and magnetic fields were steadily improved. In 1913, Thomson mentioned a weak line at mass 22 accompanying the expected one at mass 20 when he analyzed the mass spectrum of neon. Subsequently Aston obtained the mass spectrum of chlorine with masses at 35 and 37. Still in 1921, Thomson objected heavily to the idea of isotopes. The isotope problem was finally settled, but more accurate mass measurements showed that even isotopic weights differed to some extent from the whole numbers. Based on earlier ideas of P. Langevin and J.-L. Costa, F.W. Aston and A.J. Dempster developed the idea of packing fractions and mass defects due to the transformation of a portion of the matter comprising the atomic nucleus into energy. While the determination of the exact isotopic masses had improved over the years, the accurate determination of isotopic abundances remained a problem as long as photographic recording was used. Here especially A.O. Nier pioneered using dual collectors and compensation measurements. This was the prerequisite for the discovery that isotopic ratios varied somewhat in nature. M. Dole discovered the fractionation of oxygen isotopes by photosynthesis and respiration. Today 13C/12C-ratios are employed to detect adulterations of food and in doping analysis, and 14C/13C-ratios obtained by accelerator mass spectrometry are used for dating historical objects, just to give some examples. PMID:16134128

Budzikiewicz, Herbert; Grigsby, Ronald D

2006-01-01

12

Mass spectrometry.  

NASA Technical Reports Server (NTRS)

Review of the current state of mass spectrometry, indicating its unique importance for advanced scientific research. Mass spectrometry applications in computer techniques, gas chromatography, ion cyclotron resonance, molecular fragmentation and ionization, and isotope labeling are covered. Details are given on mass spectrometry applications in bio-organic chemistry and biomedical research. As the subjects of these applications are indicated alkaloids, carbohydrates, lipids, terpenes, quinones, nucleic acid components, peptides, antibiotics, and human and animal metabolisms. Particular attention is given to the mass spectra of organo-inorganic compounds, inorganic mass spectrometry, surface phenomena such as secondary ion and electron emission, and elemental and isotope analysis. Further topics include mass spectrometry in organic geochemistry, applications in geochronology and cosmochemistry, and organic mass spectrometry.

Burlingame, A. L.; Johanson, G. A.

1972-01-01

13

Invited Review Article: Recent developments in isotope-ratio mass spectrometry for geochemistry and cosmochemistry  

NASA Astrophysics Data System (ADS)

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.

Ireland, Trevor R.

2013-01-01

14

Forensic isotope ratio mass spectrometry of packaging tapes.  

PubMed

Pressure sensitive adhesive tape (brown parcel tape) is employed in a great many criminal activities such as the restraint of individuals during robbery and offences against the person, the enclosure of explosive devices and the packaging and concealment of controlled drugs. Packaging materials are ubiquitous in modern society and are produced in such vast quantities that it is increasingly difficult to distinguish between different products or to link materials to a common source. This study demonstrates the potential of stable isotope ratio mass spectrometry to characterise parcel tapes based on a number of properties. The carbon isotopic signature, derived from the substrate polymer, associated additives and adhesive is highly characteristic of a particular tape and allows samples from different sources to be readily distinguished. Further discrimination may be achieved by the incorporation of deuterium and oxygen isotopic data and by analysis of the isolated backing polymer. Recovery of intact tape from simulated forensic samples proved straightforward and the isotopic signature of the tape did not appear to be affected by adverse storage conditions. PMID:15565219

Carter, James F; Grundy, Polly L; Hill, Jenny C; Ronan, Neil C; Titterton, Emma L; Sleeman, Richard

2004-12-01

15

Advances in Isotope Ratio Mass Spectrometry and Required Isotope Reference Materials  

PubMed Central

The article gives a condensed version of the keynote lecture held at the International Mass Spectrometry Conference 2012 in Kyoto. Starting with some examples for isotope research the key requirements for metrologically valid procedures enabling traceable and comparable isotope data are discussed. Of course multi-collector mass spectrometers are required which offer sufficiently high isotope ratio precision for the intended research work. Following this, corrections for mass fractionation/discrimination, validation of the analytical procedure including chemical sample preparation and complete uncertainty budgets are the most important issues for obtaining a metrologically valid procedure for isotope ratio determination. Only the application of such metrologically valid procedures enables the generation of traceable and comparable isotope data. To realize this suitable isotope and/or ?-reference materials are required, which currently are not sufficiently available for most isotope systems. Boron is given as an example, for which the situation regarding isotope and ?-reference materials is excellent. Boron may therefore serve as prototype for other isotope systems. PMID:24349939

Vogl, Jochen

2013-01-01

16

Efficient Analysis of Mass Spectrometry Data Using the Isotope Wavelet  

NASA Astrophysics Data System (ADS)

Mass spectrometry (MS) has become today's de-facto standard for high-throughput analysis in proteomics research. Its applications range from toxicity analysis to MS-based diagnostics. Often, the time spent on the MS experiment itself is significantly less than the time necessary to interpret the measured signals, since the amount of data can easily exceed several gigabytes. In addition, automated analysis is hampered by baseline artifacts, chemical as well as electrical noise, and an irregular spacing of data points. Thus, filtering techniques originating from signal and image analysis are commonly employed to address these problems. Unfortunately, smoothing, base-line reduction, and in particular a resampling of data points can affect important characteristics of the experimental signal. To overcome these problems, we propose a new family of wavelet functions based on the isotope wavelet, which is hand-tailored for the analysis of mass spectrometry data. The resulting technique is theoretically well-founded and compares very well with standard peak picking tools, since it is highly robust against noise spoiling the data, but at the same time sufficiently sensitive to detect even low-abundant peptides.

Hussong, Rene; Tholey, Andreas; Hildebrandt, Andreas

2007-09-01

17

Efficient Analysis of Mass Spectrometry Data Using the Isotope Wavelet  

SciTech Connect

Mass spectrometry (MS) has become today's de-facto standard for high-throughput analysis in proteomics research. Its applications range from toxicity analysis to MS-based diagnostics. Often, the time spent on the MS experiment itself is significantly less than the time necessary to interpret the measured signals, since the amount of data can easily exceed several gigabytes. In addition, automated analysis is hampered by baseline artifacts, chemical as well as electrical noise, and an irregular spacing of data points. Thus, filtering techniques originating from signal and image analysis are commonly employed to address these problems. Unfortunately, smoothing, base-line reduction, and in particular a resampling of data points can affect important characteristics of the experimental signal. To overcome these problems, we propose a new family of wavelet functions based on the isotope wavelet, which is hand-tailored for the analysis of mass spectrometry data. The resulting technique is theoretically well-founded and compares very well with standard peak picking tools, since it is highly robust against noise spoiling the data, but at the same time sufficiently sensitive to detect even low-abundant peptides.

Hussong, Rene; Hildebrandt, Andreas [Center for Bioinformatics, Computer Science Department, Saarland University, 66041 Saarbruecken (Germany); Tholey, Andreas [Center for Bioinformatics, Institute of Biochemical Engineering, Functional Proteomics Group, Saarland University, 66041 Saarbruecken (Germany)

2007-09-18

18

Quantitation of DNA adducts by stable isotope dilution mass spectrometry  

PubMed Central

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

Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

2012-01-01

19

Quantitating isotopic molecular labels with accelerator mass spectrometry.  

PubMed

Accelerator mass spectrometry (AMS) traces isotopically labeled biochemicals and provides significant new directions for understanding molecular kinetics and dynamics in biological systems. AMS traces low-abundance radioisotopes for high specificity but detects them with MS for high sensitivity. AMS reduces radiation exposure doses to levels safe for use in human volunteers of all ages. Total radiation exposures are equivalent to those obtained in very short airplane flights, a commonly accepted radiation risk. Waste products seldom reach the Nuclear Regulatory Commission (NRC) definition of radioactive waste material for (14)C and (3)H. Attomoles of labeled compounds are quantified in milligram-sized samples, such as 20 microl of blood. AMS is available from several facilities that offer services and new spectrometers that are affordable. Detailed examples of designing AMS studies are provided, and the methods of analyzing AMS data are outlined. PMID:16401517

Vogel, John S; Love, Adam H

2005-01-01

20

The Role of Naturally Occurring Stable Isotopes in Mass Spectrometry, Part II: The Instrumentation  

PubMed Central

In the second instalment of this tutorial, the authors explain the instrumentation for measuring naturally occurring stable isotopes, specifically the magnetic sector mass spectrometer. This type of instrument remains unrivalled in its performance for isotope ratio mass spectrometry (IRMS) and the reader is reminded of its operation and its technical advantages for isotope measurements. PMID:23772101

Bluck, Les; Volmer, Dietrich A.

2013-01-01

21

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

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

22

Iron-Isotopic Fractionation Studies Using Multiple Collector Inductively Coupled Plasma Mass Spectrometry  

NASA Technical Reports Server (NTRS)

The importance of Fe biogeochemistry has stimulated interest in Fe isotope fractionation. Recent studies using thermal ionization mass spectrometry (TIMS) and a "double spike" demonstrate the existence of biogenic Fe isotope effects. Here, we assess the utility of multiple-collector inductively-coupled plasma mass spectrometry(MC-ICP-MS) with a desolvating sample introduction system for Fe isotope studies, and present data on Fe biominerals produced by a thermophilic bacterium. Additional information is contained in the original extended abstract.

Anbar, A. D.; Zhang, C.; Barling, J.; Roe, J. E.; Nealson, K. H.

1999-01-01

23

Quantification of stable isotope label in metabolites via mass spectrometry.  

PubMed

Isotope labelling experiments with stable or radioactive isotopes have long been an integral part of biological and medical research. Labelling experiments led to the discovery of new metabolic pathways and made it possible to calculate the fluxes responsible for a metabolic phenotype, i.e., the qualitative and quantitative composition of metabolites in a biological system. Prerequisite for efficient isotope labelling experiments is a reliable and precise method to analyze the redistribution of isotope label in a metabolic network. Here we describe the use of the CORRECTOR program, which utilizes matrix calculations to correct mass spectral data from stable isotope labelling experiments for the distorting effect of naturally occurring stable isotopes (NOIs). CORRECTOR facilitates and speeds up the routine quantification of experimentally introduced isotope label from multiple mass spectral readouts, which are generated by routine metabolite profiling when combined with stable isotope labelling experiments. PMID:24306876

Huege, Jan; Goetze, Jan; Dethloff, Frederik; Junker, Bjoern; Kopka, Joachim

2014-01-01

24

HIGH PRECISION MG ISOTOPE MEASUREMENTS OF METEORITIC SAMPLES BY SECONDARY ION MASS SPECTROMETRY  

E-print Network

1 HIGH PRECISION MG ISOTOPE MEASUREMENTS OF METEORITIC SAMPLES BY SECONDARY ION MASS SPECTROMETRY of isotopic ratios, typically of ± 5 ppm. In this study, we report for the first time a very detailed accuracy and precision of the final isotopic results, factors such as the Faraday cup (FC) background drift

25

Caution on the Use of Liquid Nitrogen Traps in Stable Hydrogen Isotope-Ratio Mass Spectrometry  

E-print Network

Caution on the Use of Liquid Nitrogen Traps in Stable Hydrogen Isotope-Ratio Mass Spectrometry An anomalous stable hydrogen isotopic fractionation of 4 in gaseous hydrogen has been correlated hydrogen-water platinum equilibration system. Al- though the cause of this isotopic fractionation

26

High-fidelity in isotope ratio measurements for resonance ionization mass spectrometry  

SciTech Connect

Calculations are performed to gauge the effect of the convolution of atomic spectral characteristics with laser sources upon isotope ratio measurements by Resonance Ionization Mass Spectrometry (RIMS). Comparison with experimental data is included. 7 refs., 3 figs.

Miller, C.M.; Fearey, B.L.; Palmer, B.A.; Nogar, N.S.

1988-01-01

27

Determination of the H3 Factor in Hydrogen Isotope Ratio Monitoring Mass Spectrometry  

E-print Network

Determination of the H3 Factor in Hydrogen Isotope Ratio Monitoring Mass Spectrometry Alex L-based values led to no systematic errors. Values of K were only weakly dependent on the pressure of He (typically He), a

Sessions, Alex L.

28

Fast atom bombardment mass spectrometry for the determination of zinc stable isotopes in biological samples  

Microsoft Academic Search

Fast atom bombardment mass spectrometry (FAB MS) has been used to measure the relative abundances of zinc stable isotopes in biological samples. Modification of the standard FAB sample target, moderate MS resolution, and ion exchange column chromatography have been used to eliminate interfering ions at the nominal masses of zinc isotopes. Precision of 1.0% coefficient of variation was obtained on

Paula L. Peirce; K. Michael. Hambidge; Christopher H. Goss; Leland V. Miller; Paul V. Fennessey

1987-01-01

29

Precise analysis of copper and zinc isotopic compositions by plasma-source mass spectrometry  

Microsoft Academic Search

The stable isotope geochemistry of Cu and Zn is poorly known because of the lack of a suitable analytical technique. We present a procedure for the analysis of Cu and Zn isotope compositions by plasma-source mass spectrometry (Plasma 54) together with a method to purify Cu and Zn from natural samples of silicates, ores, and biological material. A plasma-source mass

Chlo Nadia Marchal; Philippe Tlouk; Francis Albarde

1999-01-01

30

Optical spectroscopy versus mass spectrometry: The race for fieldable isotopic analysis  

SciTech Connect

Several techniques have been developed to provide on-site isotopic analyses, including decay-counting and mass spectrometry, as well as methods that rely on the accessibility of optical transitions for isotopic selectivity (e.g., laser-induced fluorescence and optogalvanic spectroscopy). The authors have been investigating both mass spectrometry and optogalvanic spectroscopy for several years. Although others have considered these techniques for isotopic analysis, the authors have focussed on the use of a dc glow discharge for atomization and ionization, and a demountable discharge cell for rapid sample exchange. The authors` goal is a fieldable instrument that provides useful uranium isotope ratio information.

Barshick, C.M.; Young, J.P.; Shaw, R.W. [Oak Ridge National Lab., TN (United States)] [and others

1995-12-31

31

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

PubMed

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. PMID:23387630

Ireland, Trevor R

2013-01-01

32

Isotope-ratio-monitoring gas chromatography--mass spectrometry  

Microsoft Academic Search

A 750°C cupric-oxide-packed combustion furnace is inserted between the gas chromatographic column outlet and a GC\\/MS interface attached to a computer-controlled beam-switching isotope ratio mass spectrometer. Monitoring of N and CO ion currents due to the combustion products allows continuous measurement of ¹⁵N\\/¹⁴N or ¹³C\\/¹²C ratios, providing directly comparable isotopic analyses for all eluting compounds regardless of composition and mass

D. E. Matthews; J. M. Hayes

1978-01-01

33

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

34

Application of the total evaporation technique to chromium isotope ratio measurement by thermal ionization mass spectrometry.  

PubMed

The total evaporation technique of thermal ionization mass spectrometry was applied to the isotopic analysis of chromium. High measurement reproducibility of the chromium isotope ratios was verified (2 S.E.<0.05% ((53)Cr/(52)Cr)), while a clear mass fractionation effect was observed by using conventional measurement technique. The chromium isotope ratios analyzed by the total evaporation method were not affected by the sample amount on the rhenium filament (50-500 ng Cr). The isotopic analysis under the coexistence of zinc was also performed, and its effect to the chromium isotope ratios was confirmed. PMID:18970527

Fujii, Toshiyuki; Suzuki, Daisuke; Watanabe, Kazuo; Yamana, Hajimu

2006-03-15

35

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

Microsoft Academic Search

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

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

36

Seized methamphetamine samples with unique profiles of stable nitrogen isotopic composition documented by stable isotope ratio mass spectrometry  

Microsoft Academic Search

We report a case of seized methamphetamine (MA) samples showing unique profiles of stable isotopic compositions. Three packages\\u000a of MA-HCl samples seized simultaneously from one suspect were subjected to gas chromatographic impurity profiling and stable\\u000a isotope ratio mass spectrometry (IRMS). The samples showed similar impurity profiles by gas chromatography, but their stable\\u000a isotopic compositions were complicated. The ?15N values of

Yuko T. Iwata; Kenji Kuwayama; Kenji Tsujikawa; Hajime Miyaguchi; Tatsuyuki Kanamori; Hiroyuki Inoue

2010-01-01

37

Uranium and thorium isotopic and concentration measurements by magnetic sector inductively coupled plasma mass spectrometry  

Microsoft Academic Search

We have developed techniques by sector-field inductively coupled plasma mass spectrometry (ICP-MS) for measuring the isotopic composition and concentration of uranium and thorium, focusing on the rare isotopes, 230Th and 234U. These isotopes have been widely used as tracers in earth sciences, e.g., chronology, paleoclimatology, archeology, hydrology, geochemistry, and oceanography. Measurements made on reference materials demonstrate that the analytical precision

Chuan-Chou Shen; R Lawrence Edwards; Hai Cheng; Jeffrey A Dorale; Rebecca B Thomas; S Bradley Moran; Sarah E Weinstein; Henrietta N Edmonds

2002-01-01

38

Attogram measurement of rare isotopes by CW resonance ionization mass spectrometry  

SciTech Connect

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.

Bushaw, B.A.

1992-05-01

39

Laser ablation isotope ratio mass spectrometry for enhanced sensitivity and spatial resolution in stable isotope analysis.  

PubMed

Stable isotope analysis permits the tracking of physical, chemical, and biological reactions and source materials at a wide variety of spatial scales. We present a laser ablation isotope ratio mass spectrometry (LA-IRMS) method that enables ?(13)C measurement of solid samples at 50?m spatial resolution. The method does not require sample pre-treatment to physically separate spatial zones. We use laser ablation of solid samples followed by quantitative combustion of the ablated particulates to convert sample carbon into CO(2). Cryofocusing of the resulting CO(2) coupled with modulation in the carrier flow rate permits coherent peak introduction into an isotope ratio mass spectrometer, with only 65?ng carbon required per measurement. We conclusively demonstrate that the measured CO(2) is produced by combustion of laser-ablated aerosols from the sample surface. We measured ?(13)C for a series of solid compounds using laser ablation and traditional solid sample analysis techniques. Both techniques produced consistent isotopic results but the laser ablation method required over two orders of magnitude less sample. We demonstrated that LA-IRMS sensitivity coupled with its 50?m spatial resolution could be used to measure ?(13) C values along a length of hair, making multiple sample measurements over distances corresponding to a single day's growth. This method will be highly valuable in cases where the ?(13)C analysis of small samples over prescribed spatial distances is required. Suitable applications include forensic analysis of hair samples, investigations of tightly woven microbial systems, and cases of surface analysis where there is a sharp delineation between different components of a sample. PMID:21488126

Moran, James J; Newburn, Matt K; Alexander, M Lizabeth; Sams, Robert L; Kelly, James F; Kreuzer, Helen W

2011-05-15

40

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

PubMed Central

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

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

2008-01-01

41

A gas chromatography/pyrolysis/isotope ratio mass spectrometry system for high-precision dD measurements  

E-print Network

A gas chromatography/pyrolysis/isotope ratio mass spectrometry system for high-precision d we present a highly automated, high-precision online gas chromatography/pyrolysis/isotope ratio monitoring mass spectrometry (GC/P/irmMS) technique for the analysis of dD(CH4). It includes gas extraction

Fischer, Hubertus

42

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

E-print Network

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

American Society for Testing and Materials. Philadelphia

2005-01-01

43

A gas chromatography/combustion/isotope ratio mass spectrometry system for high-precision  

E-print Network

A gas chromatography/combustion/isotope ratio mass spectrometry system for high-precision d13 C methane cycle in the past. We developed a highly automated (continuous-flow) gas chromatography in the infrared spectrum. Today methane is recognised as an important greenhouse gas that affects the earth

Fischer, Hubertus

44

Protein N- and C-Termini Identification Using Mass Spectrometry and Isotopic Labeling  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new method for protein N- and C-terminal analysis using mass spectrometry is introduced. A novel stable isotopic labeling scheme has been developed to identify terminal peptides generated from an enzyme digestion for the determination of both N- and C-termini of the protein. This method works dire...

45

DETERMINATION OF NIACIN IN FOOD MATERIALS BY ISOTOPE DILUTION MASS SPECTROMETRY  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

46

Isotopic measurement of subnanogram quantities of rhenium and osmium by resonance ionization mass spectrometry  

Microsoft Academic Search

Resonance ionization mass spectrometry has been used to measure the isotopic compositions of microgram and picogram quantities of Re and Os. The high sensitivity required for these measurements was achieved through the optimization of sample atomization and efficient ionization from the resulting gas-phase reservoir. Re and Os are absorbed from chloride solutions onto anion exchange beads as a means of

Richard J. Walker; Jack D. Fassett

1986-01-01

47

Tungsten isotope ratio determinations by negative thermal ionization mass spectrometry  

Microsoft Academic Search

A precise determination of the isotopic abundances of tungsten with natural isotopic composition is presented. WO-3 ions are generated by negative thermal ionization (NTI) in a double-filament ion source. La2O3 is used as a chemical substance to reduce the electron work function of the rhenium filament material. An ionization efficiency of 1% is obtained for sample loadings of 100 ng.

Joachim Vlkening; Manfred Kppe; Klaus G. Heumann

1991-01-01

48

Illustrating the Concepts of Isotopes and Mass Spectrometry in Introductory Courses: A MALDI-TOF Mass Spectrometry Laboratory Experiment  

ERIC Educational Resources Information Center

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

Dopke, Nancy Carter; Lovett, Timothy Neal

2007-01-01

49

Determination of the enrichment of isotopically labelled molecules by mass spectrometry.  

PubMed

A general method for the determination of the enrichment of isotopically labelled molecules by mass spectrometry (MS) is described. In contrast to other published procedures, the method described here takes into account and corrects for measurement errors such as the contribution at M?-?1 due to loss of hydrogen or lack of spectral resolution and provides an uncertainty value for the determined enrichment. The general procedure requires the following steps: (1) evaluation of linearity in the mass spectrometer by injecting the natural abundance compound at different concentration levels, (2) determination of the purity of the mass cluster using the natural abundance analogue, (3) calculation of the theoretical isotope composition of the labelled compound using different tentative isotope enrichments, (4) calculation of 'convoluted' isotope distributions for the labelled compound taking into account the purity of the mass cluster determined with the natural abundance analogue and (5) comparison of the isotope distributions measured for the labelled compound with those calculated for different isotope enrichments using linear regression. The method was applied to a series of commercially available (13)C- and (2)H-labelled compounds and to a suite of singly (13)C-labelled ?2-agonist prepared in-house both by gas chromatography (GC)-MS, GC-tandem MS (MS/MS) and liquid chromatography-MS/MS with satisfactory results. It was observed that the main uncertainty source for the isotope enrichment was the uncertainty in the purity of the measured cluster as determined with the natural abundance compound. PMID:25044895

Gonzlez-Antua, Ana; Rodrguez-Gonzlez, Pablo; Garca Alonso, J Ignacio

2014-08-01

50

A Mass Spectrometry Study of Isotope Separation in the Laser Plume  

NASA Astrophysics Data System (ADS)

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 plume, this study has developed a mass spectrometry characterization technique that may be useful for investigating chemical reactions during laser ablation.

Suen, Timothy Wu

51

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

NASA Astrophysics Data System (ADS)

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 in the coil and increase in the concentration of radical but complete combustion of highly chlorinated or fluorinated compounds was not achieved. Due to these findings the limit for a LC-IRMS system for similar structure compounds can be predicted. 1. Elsner, M., et al., Current challenges in compound-specific stable isotope analysis of environmental organic contaminants. Analytical and Bioanalytical Chemistry, 2012. 403(9): p. 2471-2491. 2. Krummen, M., et al., A new concept for isotope ratio monitoring liquid chromatography/mass spectrometry. Rapid Communications in Mass Spectrometry, 2004. 18(19): p. 2260-2266.

Gilevska, Tetyana; Gehre, Matthias; Richnow, Hans

2014-05-01

52

RAPID DETERMINATION OF 237 NP AND PU ISOTOPES IN WATER BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY AND ALPHA SPECTROMETRY  

SciTech Connect

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.

Maxwell, S.; Jones, V.; Culligan, B.; Nichols, S.; Noyes, G.

2010-06-23

53

Determination of stable isotopes of calcium in biological fluids by fast atom bombardment mass spectrometry  

Microsoft Academic Search

High-resolution fast atom bombardment mass spectrometry was used to measure the isotopic abundances of calcium in plasma and urine. Since the method is very sensitive (>5 x 10¹° ions\\/..mu..g of calcium), only 2 to 5 ..mu..L of sample is required. Repetitive measurements of the ⁴²Ca\\/⁴°Ca ratio in plasma and urine require about 3 min and typically have a relative standard

David L. Smith

1983-01-01

54

Improving precision in resonance ionization mass spectrometry : influence of laser bandwidth in uranium isotope ratio measurements.  

SciTech Connect

The use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of {sup 235}U/{sup 238}U ratios by resonance ionization mass spectrometry (RIMS) to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser in a three-color, three-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.

Isselhardt, B. H.; Savina, M. R.; Knight, K. B.; Pellin, M. J.; Hutcheon, I. D.; Prussin, S. G. (Materials Science Division); (Univ. California at Berkeley); (LLNL)

2011-03-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

56

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

PubMed Central

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

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

2011-01-01

57

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

PubMed

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. PMID:14611049

Seltzer, Michael D

2003-09-01

58

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

PubMed

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 2821pg (1sd) and typical Pb recoveries of 40-60%. The Pb concentrations are determined by isotope dilution (ID) on 50mL 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 50pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (124pg; 1sd). For the Pb isotope analyses, typical reproducibilities (2sd) of 700-1500ppm and 1000-2000ppm 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 with (207)Pb/(206)Pb, underlining the significant improvement achieved in the measurement of the minor (204)Pb isotope. PMID:25732313

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

2015-03-10

59

Elemental and isotopic analysis of inorganic salts by laser desorption ionization mass spectrometry  

SciTech Connect

Laser desorption ionization mass spectrometry is applied for the analysis of elements as well as their isotopic composition in different inorganic salts. At very low laser energies the inorganic ions are desorbed and ionized from the thin layer of the sample surface. The naturally occurring isotopes of alkali and silver ions are resolved using time of flight mass spectrometer. Further increase in laser energy shows the appearance of Al, Cr, and Fe ions in the mass spectra. This indicates the penetration laser beam beyond the sample surface leading to the ablation of sample target at higher energies. The simultaneous appearance of atomic ions from the sample target at relatively higher laser energies hampers the unambiguous identification of amino acid residues from the biomolecular ions in MALDI-MS.

Jayasekharan, T.; Sahoo, N. K. [Applied Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2013-02-05

60

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

PubMed

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. PMID:22865006

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

2012-11-01

61

Penning trap mass spectrometry of neutron-rich Fe and Co isotopes around N=40 with the LEBIT mass spectrometer  

NASA Astrophysics Data System (ADS)

Penning trap mass spectrometry is presented as a complementary tool to nuclear spectroscopy experiments for the study of nuclear structure in the vicinity of N=40, Z=28. High-precision mass measurements of the Fe63-66 and Co64-67 isotopes have been carried out with the Low Energy Beam and Ion Trap (LEBIT) Penning trap mass spectrometer. The newly obtained mass values for Fe66 and Co67 are presented, together with the previously reported LEBIT mass measurements in this region. In the case of Fe65 the existence of a new isomer is reported, and an isomer recently discovered by decay spectroscopy in Co67 is confirmed. Relative mass uncertainties as low as 410-8 are obtained. All mass values are found to be in good agreement with previous experimental results with the exception of Co64, where a 5? deviation is observed. Using these data the two neutron separation energies S2n are calculated. However, the large error bars in the mass values of the neighbor Fe and Co isotopes with N>40 complicate the validation of a weak subshell closure at N=40 for the Co isotopes or the possible reduction in the neutron shell gap in the case of the Fe isotopes, in accordance with the theoretical predictions of an onset of deformation in the region.

Ferrer, R.; Block, M.; Bachelet, C.; Barquest, B. R.; Bollen, G.; Campbell, C. M.; Facina, M.; Folden, C. M., III; Gunaut, C.; Kwiatkowski, A. A.; Lincoln, D. L.; Morrissey, D. J.; Pang, G. K.; Prinke, A. M.; Ringle, R.; Savory, J.; Schury, P.; Schwarz, S.

2010-04-01

62

Application of Inductively Coupled Plasma Mass Spectrometry to the determination of uranium isotope ratios in individual particles for nuclear safeguards  

Microsoft Academic Search

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).

Xiao Zhi Zhang; Fumitaka Esaka; Konomi T. Esaka; Masaaki Magara; Satoshi Sakurai; Shigekazu Usuda; Kazuo Watanabe

2007-01-01

63

Rayleigh's distillation law and linear hypothesis of isotope fractionation in thermal ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

The relationship which exists between Rayleigh's distillation law and linear models of instrumental isotopic fractionation in thermal ionization mass spectrometry is shown. If the process of isotope fractionation in the mass spectrometer source occurs in terms of a Rayleigh's distillation, and, within the range of mass of isotopes of the element, the vapor/residue distribution coefficient is a linear function of mass with a slope which is sufficiently small in absolute value, then the linear hypothesis of isotope fractionation is fulfilled. The model shows that the fractionation factor per amu, defined as the instantaneous difference between the measured and true values of the isotope ratio, per unit of measured/true value and per unit of mass difference between the two isotopes which define the ratio, can be interpreted as a function of two parameters: the residual mass fraction of the sample on the filament, and the rate of change of the distribution coefficient with mass. These two parameters can be calculated and, in particular, the value of the residual mass fraction of the sample when the measured values of the isotopic ratios coincide with the actual values can be calculated as a function of the rate of change with mass of the distribution coefficient. A linear model of instrumental isotopic fractionation can be derived from the exponential hypothesis of fractionation, which can be also interpreted in terms of a Rayleigh's distillation process, but where mass is an exponential function of the distribution coefficient. Experimental results of instrumental isotopic fractionation (up to 1% amu-1) of strontium in NIST standard reference material 987, loaded as a nitrate on a single tungsten filament, can be interpreted in terms of the linear models of isotope fractionation (and therefore of Rayleigh's distillation law) within experimental error. They show: (i) changes in the vapor/residue distribution coefficient with mass in the range -0.006 to -0.004 amu-1; (ii) approximately constant rates of sample consumption in the range of residual mass fraction from ~1 to ~0.3-0.25, which are between 0.05 and 0.13% min-1; (iii) values of the residual mass fraction of the sample, when the measured values of the isotopic ratios coincide with the true ones, between 0.3668 and 0.3671, which correspond to sample consumption of 63.3%. Since the linear hypothesis of fractionation is fulfilled, the values of isotopic ratios of strontium in the standard material can be determined. The global weighted averages of the weighted averages of the results obtained in eleven runs in which 86Sr, 87Sr and 88Sr peaks were sampled are as follows: 86Sr/88Sr = 0.119445 +/- 0.000053, 87Sr/86Sr = 0.71016 +/- 0.00019, and 87Sr/88Sr = 0.084826 +/- 0.000040.

Cavazzini, Giancarlo

2009-12-01

64

MarVis-Filter: Ranking, Filtering, Adduct and Isotope Correction of Mass Spectrometry Data  

PubMed Central

Statistical ranking, filtering, adduct detection, isotope correction, and molecular formula calculation are essential tasks in processing mass spectrometry data in metabolomics studies. In order to obtain high-quality data sets, a framework which incorporates all these methods is required. We present the MarVis-Filter software, which provides well-established and specialized methods for processing mass spectrometry data. For the task of ranking and filtering multivariate intensity profiles, MarVis-Filter provides the ANOVA and Kruskal-Wallis tests with adjustment for multiple hypothesis testing. Adduct and isotope correction are based on a novel algorithm which takes the similarity of intensity profiles into account and allows user-defined ionization rules. The molecular formula calculation utilizes the results of the adduct and isotope correction. For a comprehensive analysis, MarVis-Filter provides an interactive interface to combine data sets deriving from positive and negative ionization mode. The software is exemplarily applied in a metabolic case study, where octadecanoids could be identified as markers for wounding in plants. PMID:22550397

Kaever, Alexander; Landesfeind, Manuel; Possienke, Mareike; Feussner, Kirstin; Feussner, Ivo; Meinicke, Peter

2012-01-01

65

MarVis-Filter: ranking, filtering, adduct and isotope correction of mass spectrometry data.  

PubMed

Statistical ranking, filtering, adduct detection, isotope correction, and molecular formula calculation are essential tasks in processing mass spectrometry data in metabolomics studies. In order to obtain high-quality data sets, a framework which incorporates all these methods is required. We present the MarVis-Filter software, which provides well-established and specialized methods for processing mass spectrometry data. For the task of ranking and filtering multivariate intensity profiles, MarVis-Filter provides the ANOVA and Kruskal-Wallis tests with adjustment for multiple hypothesis testing. Adduct and isotope correction are based on a novel algorithm which takes the similarity of intensity profiles into account and allows user-defined ionization rules. The molecular formula calculation utilizes the results of the adduct and isotope correction. For a comprehensive analysis, MarVis-Filter provides an interactive interface to combine data sets deriving from positive and negative ionization mode. The software is exemplarily applied in a metabolic case study, where octadecanoids could be identified as markers for wounding in plants. PMID:22550397

Kaever, Alexander; Landesfeind, Manuel; Possienke, Mareike; Feussner, Kirstin; Feussner, Ivo; Meinicke, Peter

2012-01-01

66

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

SciTech Connect

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 {beta}-cyclodextrin are chosen for the study, initial observation of spectral interference of {sup 13}C{sup +} with {sup 12}C{sup 1}H{sup +} comes from the incomplete dissociation of myoglobin and/or {beta}-cyclodextrin.

Luong, E.

1999-05-10

67

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

USGS Publications Warehouse

The use of isotopes to understand the behavior of metals in geological, hydrological, and biological systems has rapidly expanded in recent years. One of the mass spectrometric techniques used to analyze metal isotopes is thermal ionization mass spectrometry, or TIMS. While TIMS has been a useful analytical technique for the measurement of isotopic composition for decades and TIMS instruments are widely distributed, there are significant difficulties associated with using TIMS to analyze isotopes of the lighter alkaline earth elements and transition metals. Overcoming these difficulties to produce relatively long-lived and stable ion beams from microgram-sized samples is a non-trivial task. We focus here on TIMS analysis of three geologically and environmentally important elements (Fe, Cr, and Ca) and present an in-depth look at several key aspects that we feel have the greatest potential to trouble new users. Our discussion includes accessible descriptions of different analytical approaches and issues, including filament loading procedures, collector cup configurations, peak shapes and interferences, and the use of isotopic double spikes and related error estimation. Building on previous work, we present quantitative simulations, applied specifically in this study to Fe and Ca, that explore the effects of (1) time-variable evaporation of isotopically homogeneous spots from a filament and (2) interferences on the isotope ratios derived from a double spike subtraction routine. We discuss how and to what extent interferences at spike masses, as well as at other measured masses, affect the double spike-subtracted isotope ratio of interest (44Ca/40Ca in the case presented, though a similar analysis can be used to evaluate 56Fe/54Fe and 53Cr/52Cr). The conclusions of these simulations are neither intuitive nor immediately obvious, making this examination useful for those who are developing new methodologies. While all simulations are carried out in the context of a specific isotope system, it should be noted that the same methods can be used to evaluate any isotope system of interest. ?? 2008 Elsevier B.V.

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

2009-01-01

68

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

SciTech Connect

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 equivalents. AMS provides an sensitive, accurate and precise method of measuring drug compounds in biological matrices.

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

2010-02-05

69

Rapid determination of uranium isotopes in urine by inductively coupled plasma-mass spectrometry.  

PubMed

Following a radiological or nuclear emergency involving uranium exposure, rapid analytical methods are needed to analyze the concentration of uranium isotopes in human urine samples for early dose assessment. The inductively coupled plasma mass spectrometry (ICP-MS) technique, with its high sample throughput and high sensitivity, has advantages over alpha spectrometry for uranium urinalysis after minimum sample preparation. In this work, a rapid sample preparation method using an anion exchange chromatographic column was developed to separate uranium from the urine matrix. A high-resolution sector field ICP-MS instrument, coupled with a high sensitivity desolvation sample introduction inlet, was used to determine uranium isotopes in the samples. The method can analyze up to 24 urine samples in two hours with the limits of detection of 0.0014, 0.10, and 2.0 pg mL(-1) for (234)U, (235)U, and (238)U, respectively, which meet the requirement for isotopic analysis of uranium in a radiation emergency. PMID:21709502

Shi, Y; Dai, X; Collins, R; Kramer-Tremblay, S

2011-08-01

70

Isolation of Pu-isotopes from environmental samples using ion chromatography for accelerator mass spectrometry and alpha spectrometry.  

PubMed

A radiochemical method for the isolation of plutonium-isotopes from environmental samples, based on the use of specific extraction chromatography resins for actinides (TEVA), Eichrom Industries, Inc.), has been set up in our laboratory and optimised for their posterior determination by alpha spectrometry (AS) or accelerator mass spectrometry (AMS). The proposed radiochemical method has replaced in our lab a well-established one based on the use of a relatively un-specific anion-exchange resin (AG) 1X8, Bio-rad Laboratories, Inc.), because it is clearly less time consuming, reduces the amounts and molarities of acid wastes produced, and reproducibly gives high radiochemical yields. In order to check the reliability of the proposed radiochemical method for the determination of plutonium-isotopes in different environmental matrixes, twin aliquots of a set of samples were prepared with TEVA and with AG 1X8 resins and measured by AS. Some samples prepared with TEVA resins were measured as well by AMS. As it is shown in the text, there is a comfortable agreement between AS and AMS, which adequately validates the method. PMID:18082656

Chamizo, E; Jimnez-Ramos, M C; Wacker, L; Vioque, I; Calleja, A; Garca-Len, M; Garca-Tenorio, R

2008-01-14

71

Temperature-programmed high-performance liquid chromatography coupled to isotope ratio mass spectrometry.  

PubMed

The utility of liquid chromatography coupled to the isotope ratio mass spectrometry technique (LC-IRMS) has already been established through a variety of successful applications. However, the analytical constraint related to the use of aqueous mobile phases limits the LC separation mechanism. We report here a new strategy for high-precision (13)C isotopic analyses based on temperature-programmed LC-IRMS using aqueous mobile phases. Under these conditions, the isotopic precision and accuracy were studied. On one hand, experiments were carried out with phenolic acids using isothermal LC conditions at high temperature (170 degrees C); on the other hand, several experiments were performed by ramping the temperature, as conventionally used in a gas chromatography-based method with hydrosoluble fatty acids and pulses of CO 2 reference gas. In isothermal conditions at 170 degrees C, despite the increase of the CO 2 background, p-coumaric acid and its glucuronide conjugate gave reliable isotopic ratios compared to flow injection analysis-isotopic ratio mass spectrometry (FIA-IRMS) analyses (isotopic precision and accuracy are lower than 0.3 per thousand). On the opposite, for its sulfate conjugate, the isotopic accuracy is affected by its coelution with p-coumaric acid. Not surprisingly, this study also demonstrates that at high temperature (170 degrees C), a compound eluting with long residence time (i.e., ferulic acid) is degraded, affecting thus the delta (13)C (drift of 3 per thousand) and the peak area (compared to FIA-IRMS analysis at room temperature). Quantitation is also reported in isothermal conditions for p-coumaric acid in the range of 10-400 ng/mL and with benzoic acid as an internal standard. For temperature gradient LC-IRMS, in the area of the LC gradient (set up at 20 degrees C/min), the drift of the background observed produces a nonlinearity of SD (delta (13)C) approximately 0.01 per thousand/mV. To circumvent this drift, which impacts severely the precision and accuracy, an alternative approach, i.e., eluting the compound on the plateau of temperature studied was reported here. Other experiments with temperature-programmed LC-IRMS experiments are also reported with the presence of methanol in the injected solution to mimic residual solvent originating from the sample preparation or to slightly increase the solubility of the targeted compound for high-precision measurement. PMID:18690698

Godin, Jean-Philippe; Hopfgartner, Grard; Fay, Laurent

2008-09-15

72

Mass spectrometry  

Microsoft Academic Search

A review of mass spectrometry in organic chemistry is given, dealing with advances in instrumentation and computer techniques, selected topics in gas-phase ion chemistry, and applications in such fields as biomedicine, natural-product studies, and environmental pollution analysis. Innovative techniques and instrumentation are discussed, along with chromatographic-mass spectrometric on-line computer techniques, mass spectral interpretation and management techniques, and such topics in

A. L. Burlingame; Cedric H. L. Shackleton; Ian. Howe; O. S. Chizhov

1978-01-01

73

Assessment of carbonate-phosphoric acid analytical technique performed using GasBench II in continuous flow isotope ratio mass spectrometry  

Microsoft Academic Search

The commonly used online automated analytical method (in particular Thermo GasBench II) to determine stable carbon and oxygen isotope ratio composition of calcium carbonate in continuous flow isotope ratio mass spectrometry is evaluated. We have analyzed the isotopic composition of three in-house calcium carbonate standards as unknown samples for assessment of speed, accuracy and precision of isotopic measurements. Isotopic analyses

Debajyoti Paul; Grzegorz Skrzypek

2007-01-01

74

O Isotopic Composition of CaCO3 Measured by Continuous Flow Isotope Ratio Mass Spectrometry: Statistical Evaluation and  

E-print Network

XL continuous flow isotope ratio mass spectrometer. Conditions for which the H3 PO4 CaCO3 reactiond13 C and d18 O Isotopic Composition of CaCO3 Measured by Continuous Flow Isotope Ratio Mass the stable carbon and oxygen isotope ratios of small samples (40020 g) of calcium carbonate. This new

75

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

NASA Astrophysics Data System (ADS)

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 ?g 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.

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

2013-01-01

76

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

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

77

Calibration and data processing in gas chromatography combustion isotope ratio mass spectrometry.  

PubMed

Compound-specific isotope analysis (CSIA) by gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) is a powerful technique for the sourcing of substances, such as determination of the geographic or chemical origin of drugs and food adulteration, and it is especially invaluable as a confirmatory tool for detection of the use of synthetic steroids in competitive sport. We review here principles and practices for data processing and calibration of GCC-IRMS data with consideration to anti-doping analyses, with a focus on carbon isotopic analysis ((13)C/(12)C). After a brief review of peak definition, the isotopologue signal reduction methods of summation, curve-fitting, and linear regression are described and reviewed. Principles for isotopic calibration are considered in the context of the ?(13)C = ?(13)C(M) - ?(13)C(E) difference measurements required for establishing adverse analytical findings for metabolites (M) relative to endogenous (E) reference compounds. Considerations for the anti-doping analyst are reviewed. PMID:22362612

Zhang, Ying; Tobias, Herbert J; Sacks, Gavin L; Brenna, J Thomas

2012-12-01

78

Liquid chromatography coupled to isotope ratio mass spectrometry: a new perspective on honey adulteration detection.  

PubMed

A new procedure to determine individual sugar (sucrose, glucose, and fructose) 13C isotope ratios, using liquid chromatography-isotope ratio mass spectrometry (HPLC-IRMS), has been developed to improve isotopic methods devoted to the study of honey authenticity. For this purpose 79 commercial honey samples from various origins were analyzed. Values of delta13Choney ranged from -14.2 to -27.2", and delta13Cprotein ranged from -23.6 to -26.9". A very strong correlation is observed between the individual sugar 13C ratios, which are altered in the event of sugar addition, even at low levels. The use of Deltadelta13C [fruct-glu], Deltadelta13C [fruct-suc], and Deltadelta13C [gluc-suc] systematic differences as an authenticity criterion permits the sugar addition [C3, beet sugar; or C4, cane sugar, cane syrup, isoglucose syrup, and high-fructose corn syrup (HFCS)] to be reliably detected (DL = 1-10%). The new procedure has advantages over existing methods in terms of analysis time and sensitivity. In addition, it is the first isotopic method developed that allows beet sugar addition detection. PMID:17177492

Cabaero, Ana I; Recio, Jose L; Ruprez, Mercedes

2006-12-27

79

Top-Down MALDI-In-Source Decay-FTICR Mass Spectrometry of Isotopically Resolved Proteins.  

PubMed

An accurate mass measurement of a known protein provides information on potential amino acid deletions and post-translational modifications. Although this field is dominated by strategies based on electrospray ionization, mass spectrometry (MS) methods using matrix-assisted laser desorption/ionization (MALDI) have the advantage of yielding predominantly singly charged precursor ions, thus avoiding peak overlap from different charge states of multiple species. Such MALDI-MS methods require mass measurement at ultrahigh resolution, which is provided by Fourier transform ion cyclotron resonance (FTICR) mass analyzers. Recently, using a MALDI-FTICR-MS platform equipped with a 15 T magnet, we reported on the mass analysis of intact human serum peptides and small proteins with isotopic resolution up to ?15 kDa and identified new proteoforms from an accurate measurement of mass distances. In the current study, we have used this FTICR system after an upgrade with a novel dynamically harmonized ICR cell, i.e., ParaCell, for mapping isotopically resolved intact proteins up to about 17 kDa and performed top-down MALDI in-source decay (ISD) analysis. Standard proteins myoglobin (m/z-value 16?950) and ribonuclease B (m/z-value 14?900) were measured with resolving powers of 62?000 and 61?000, respectively. Furthermore, it will be shown that (singly charged) MALDI-ISD fragment ions can be measured at isotopic resolution up to m/z-value 12?000 (e.g., resolving power 39?000 at m/z-value 12?000) providing more reliable identifications. Moreover, examples are presented of pseudo-MS(3) experiments on ISD fragment ions from RNase B by collisional-induced dissociation (CID). PMID:25719938

Nicolardi, Simone; Switzar, Linda; Deelder, Andr M; Palmblad, Magnus; van der Burgt, Yuri E M

2015-03-17

80

An isotope effect on the comparative quantification of flavonoids by means of methylation-based stable isotope dilution coupled with capillary liquid chromatography/mass spectrometry.  

PubMed

Ionization suppression is a serious problem in liquid chromatography/mass spectrometry-based metabolomics, and stable isotope dilution-based comparative quantification is one of the most important methods of overcoming this problem. Herein, the use of [(13)C]-methylation-based stable isotope dilution for comparative quantification of flavonoids is demonstrated. This is in contrast to the equivalent deuterium labeling methylation method, which has an adverse isotope effect on reverse phase chromatography. PMID:16233758

Fukusaki, Ei'ichiro; Harada, Kazuo; Bamba, Takeshi; Kobayashi, Akio

2005-01-01

81

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

NASA Astrophysics Data System (ADS)

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.

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

2015-04-01

82

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

PubMed

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. PMID:25592681

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

2015-04-01

83

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

84

Analysis of Isotopic Labeling in Peptide Fragments by Tandem Mass Spectrometry  

PubMed Central

Phenotype in multicellular organisms is the consequence of dynamic metabolic events that occur in a spatially dependent fashion. This spatial and temporal complexity presents challenges for investigating metabolism; creating a need for improved methods that effectively probe biochemical events such as amino acid biosynthesis. Isotopic labeling can provide a temporal-spatial recording of metabolic events through, for example, the description of enriched amino acids in the protein pool. Proteins are therefore an important readout of metabolism and can be assessed with modern mass spectrometers. We compared the measurement of isotopic labeling in MS2 spectra obtained from tandem mass spectrometry under either higher energy collision dissociation (HCD) or collision induced dissociation (CID) at varied energy levels. Developing soybean embryos cultured with or without 13C-labeled substrates, and Escherichia coli MG1655 enriched by feeding 7% uniformly labeled glucose served as a source of biological material for protein evaluation. CID with low energies resulted in a disproportionate amount of heavier isotopologues remaining in the precursor isotopic distribution. HCD resulted in fewer quantifiable products; however deviation from predicted distributions were small relative to the CID-based comparisons. Fragment ions have the potential to provide information on the labeling of amino acids in peptides, but our results indicate that without further development the use of this readout in quantitative methods such as metabolic flux analysis is limited. PMID:24626471

Allen, Doug K.; Evans, Bradley S.; Libourel, Igor G. L.

2014-01-01

85

Analysis of isotopic labeling in peptide fragments by tandem mass spectrometry.  

PubMed

Phenotype in multicellular organisms is the consequence of dynamic metabolic events that occur in a spatially dependent fashion. This spatial and temporal complexity presents challenges for investigating metabolism; creating a need for improved methods that effectively probe biochemical events such as amino acid biosynthesis. Isotopic labeling can provide a temporal-spatial recording of metabolic events through, for example, the description of enriched amino acids in the protein pool. Proteins are therefore an important readout of metabolism and can be assessed with modern mass spectrometers. We compared the measurement of isotopic labeling in MS2 spectra obtained from tandem mass spectrometry under either higher energy collision dissociation (HCD) or collision induced dissociation (CID) at varied energy levels. Developing soybean embryos cultured with or without 13C-labeled substrates, and Escherichia coli MG1655 enriched by feeding 7% uniformly labeled glucose served as a source of biological material for protein evaluation. CID with low energies resulted in a disproportionate amount of heavier isotopologues remaining in the precursor isotopic distribution. HCD resulted in fewer quantifiable products; however deviation from predicted distributions were small relative to the CID-based comparisons. Fragment ions have the potential to provide information on the labeling of amino acids in peptides, but our results indicate that without further development the use of this readout in quantitative methods such as metabolic flux analysis is limited. PMID:24626471

Allen, Doug K; Evans, Bradley S; Libourel, Igor G L

2014-01-01

86

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

PubMed

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

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

2013-10-15

87

High-precision determination of osmium and rhenium isotope ratios by in situ oxygen isotope ratio correction using negative thermal ionization mass spectrometry  

Microsoft Academic Search

The Os and Re isotope ratios were determined from the measurements of OsO3 and ReO4? ions by negative thermal ionization mass spectrometry. It was found that the oxygen isotope ratios of OsO3? and ReO4 ions vary to a large extent by the fluctuations in oxygen pressure in the ion source of the mass spectrometer and that the stability of oxygen

Yongzhong Liu; Min Huang; Akimasa Masuda; Masao Inoue

1998-01-01

88

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

89

A Stable-Isotope Mass Spectrometry-Based Metabolic Footprinting Approach to Analyze Exudates from Phytoplankton  

PubMed Central

Phytoplankton exudates play an important role in pelagic ecology and biogeochemical cycles of elements. Exuded compounds fuel the microbial food web and often encompass bioactive secondary metabolites like sex pheromones, allelochemicals, antibiotics, or feeding attractants that mediate biological interactions. Despite this importance, little is known about the bioactive compounds present in phytoplankton exudates. We report a stable-isotope metabolic footprinting method to characterise exudates from aquatic autotrophs. Exudates from 13C-enriched alga were concentrated by solid phase extraction and analysed by high-resolution Fourier transform ion cyclotron resonance mass spectrometry. We used the harmful algal bloom forming dinoflagellate Alexandrium tamarense to prove the method. An algorithm was developed to automatically pinpoint just those metabolites with highly 13C-enriched isotope signatures, allowing us to discover algal exudates from the complex seawater background. The stable-isotope pattern (SIP) of the detected metabolites then allowed for more accurate assignment to an empirical formula, a critical first step in their identification. This automated workflow provides an effective way to explore the chemical nature of the solutes exuded from phytoplankton cells and will facilitate the discovery of novel dissolved bioactive compounds. PMID:24172212

Weber, Ralf J. M.; Selander, Erik; Sommer, Ulf; Viant, Mark R.

2013-01-01

90

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

NASA Astrophysics Data System (ADS)

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 fuel or fuel additive. Results from this effort show that ethanol's unique isotopic signature can be incorporated into air chemistry models for fingerprinting and source apportionment purposes and can be used as a stable isotopic tracer for biofuel inputs to the atmosphere on local to regional scales.

Giebel, Brian M.

2011-12-01

91

Mass Spectrometry for Proteomics  

PubMed Central

Summary Mass spectrometry has been widely used to analyze biological samples and has evolved into an indispensable tool for proteomics research. Our desire to understand the proteome has led to new technologies that push the boundary of mass spectrometry capabilities, which in return has allowed mass spectrometry to address an ever-increasing array of biological questions. The recent development of a novel mass spectrometer (Orbitrap) and new dissociation methods such as electron transfer dissociation have made possible exciting new areas of proteomic application. Although bottom-up proteomics (analysis of proteolytic peptide mixtures) remains the workhorse for proteomic analysis, middle- and top-down strategies (analysis of longer peptides and intact proteins, respectively) should allow more complete characterization of protein isoforms and post-translational modifications. Finally, stable isotope labeling strategies have transformed mass spectrometry from merely descriptive to a tool for measuring dynamic changes in protein expression, interaction and modification. PMID:18718552

Han, Xuemei; Aslanian, Aaron; Yates, John R.

2008-01-01

92

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

ERIC Educational Resources Information Center

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

Sein, Lawrence T., Jr.

2006-01-01

93

Accelerator mass spectrometry measurement of 240Pu\\/ 239Pu isotope ratios in Novaya Zemlya and Kara Sea sediments  

Microsoft Academic Search

Generally low levels of plutonium in environmental samples, often combined with limited sample sizes, necessitate reliable low-level techniques for determination of Pu isotopes. Accelerator mass spectrometry (AMS) has proved to be a powerful method for measuring low-level Pu activity concentrations and Pu isotope ratios. Based on procedural blanks, detection limits for AMS were below 1fg Pu (equivalent to ca. 2?Bq

Deborah H Oughton; Lindis Skipperud; L. Keith Fifield; Richard G Cresswell; Brit Salbu; Philip Day

2004-01-01

94

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

Microsoft Academic Search

Thenium isotope ratio determinations are, in principle, possible by negative thermal ionization mass spectrometry (NTI-MS). Relatively high rhenium blanks from the commonly-used filament materials prevent accurate isotope ratio determinations, especially for small rhenium sample amounts which are of importance, for example, in geochronology in connection with the Re\\/Os dating method. Platinum and nickel filaments were tested by different preparation techniques

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

1994-01-01

95

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

SciTech Connect

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

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

1991-01-01

96

Stable oxygen and hydrogen isotopes of brines - comparing isotope ratio mass spectrometry and isotope ratio infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Today's standard analytical methods for high precision stable isotope analysis of fluids are gas-water equilibration and high temperature pyrolysis coupled to isotope ratio mass spectrometers (IRMS). In recent years, relatively new laser-based analytical instruments entered the market that are said to allow high isotope precision data on nearly every media. This optical technique is referred to as isotope ratio infrared spectroscopy (IRIS). The objective of this study is to evaluate the capability of this new instrument type for highly saline solutions and a comparison of the analytical results with traditional IRMS analysis. It has been shown for the equilibration method that the presence of salts influences the measured isotope values depending on the salt concentration (see Lcuyer et al, 2009; Martineau, 2012). This so-called 'isotope salt effect' depends on the salt type and salt concentration. These factors change the activity in the fluid and therefore shift the isotope ratios measured by the equilibration method. Consequently, correction factors have to be applied to these analytical data. Direct conversion techniques like pyrolysis or the new laser instruments allow the measurement of the water molecule from the sample directly and should therefore not suffer from the salt effect, i.e. no corrections of raw values are necessary. However, due to high salt concentrations this might cause technical problems with the analytical hardware and may require labor-intensive sample preparation (e.g. vacuum distillation). This study evaluates the salt isotope effect for the IRMS equilibration technique (Thermo Gasbench II coupled to Delta Plus XP) and the laser-based IRIS instruments with liquid injection (Picarro L2120-i). Synthetic salt solutions (NaCl, KCl, CaCl2, MgCl2, MgSO4, CaSO4) and natural brines collected from the Stassfurt Salt Anticline (Germany; Stadler et al., 2012) were analysed with both techniques. Salt concentrations ranged from seawater salinity up to full saturation. References Lcuyer, C. et al. (2009). Chem. Geol., 264, 122-126. [doi:10.1016/j.chemgeo.2009.02.017] Martineau, F. et al. (2012). Chem. Geol., 291, 236-240. [doi:10.1016/j.chemgeo.2011.10.017] Stadler, S. et al. (2012). Chem. Geol., 294-295, 226-242. [doi:10.1016/j.chemgeo.2011.12.006

Ahrens, Christian; Koeniger, Paul; van Geldern, Robert; Stadler, Susanne

2013-04-01

97

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

PubMed

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

Perkola, Noora; Sainio, Pirjo

2014-01-01

98

Determination of Cholesterol Oxidation Products in Human Plasma by Isotope Dilution-Mass Spectrometry  

Microsoft Academic Search

A method based on isotope dilution-mass spectrometry was developed for the determination of nine cholesterol oxidation products in human plasma. The cholesterol oxidation products determined were cholest-5-ene-3 ?,7 ?-diol, cholest-5-ene-3 ?,7?-diol (7?- and 7?-hydroxycholesterol, respectively), 3?-hydroxycholest-5-en-7-one (7-oxocholesterol), 5,6?-epoxy-5?-cholestan-3?-ol (cholesterol-5?,6?-epoxide), 5,6?-epoxy- 5?-cholestan-3?-ol (cholesterol-5?,6?-epoxide), cholestane-3?,5?,6?-triol, cholest-5-ene-3?,24-diol (24-hydroxycholesterol), cholest-5-ene-3?,25-diol (25-hydroxycholesterol), and cholest-5-ene-3?,27-diol (27-hydroxycholesterol). A corresponding deuterium-labeled internal standard, containing 3 to 6 deuterium

S. Dzeletovic; O. Breuer; E. Lund; U. Diczfalusy

1995-01-01

99

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

PubMed

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. PMID:19370544

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

2009-05-01

100

Simultaneous quantification of several cholesterol autoxidation and monohydroxylation products by isotope-dilution mass spectrometry  

SciTech Connect

An assay based on isotope-dilution mass spectrometry with deuterium-labeled internal standards was developed for simultaneous quantification of cholest-5-ene-3 beta,7 alpha-diol (7 alpha-hydroxycholesterol), cholest-5 beta,6 beta-epoxy-3 beta-ol (cholesterol-5 beta,6 beta-epoxide), cholest-5 alpha,6 alpha-epoxy-3 beta-ol (cholesterol-5 alpha,6 alpha-epoxide), cholest-5-en-7-one-3 beta-ol (7-oxocholesterol), cholestane-3 beta,5 alpha,6 beta-triol, cholest-5-ene-3 beta,25-diol (25-hydroxycholesterol), and cholest-5-ene-3 beta,26-diol (26-hydroxycholesterol) in one single serum sample. Recovery experiments and replicate analyses showed that the assay was sufficiently sensitive, accurate, and precise. The concentrations of the listed compounds in sera from 19 healthy subjects were determined and are presented.

Breuer, O.; Bjoerkhem, I. (Huddinge Univ. Hospital (Sweden))

1990-04-01

101

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

PubMed

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

Ren, Yao; Walczyk, Thomas

2014-09-01

102

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

ERIC Educational Resources Information Center

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)

O'Malley, Rebecca M.

1982-01-01

103

Facile preparation of deuterium-labeled N-acylhomoserine lactones as internal standards for isotope dilution mass spectrometry.  

PubMed

N-Acylhomoserine lactones (AHLs) are widely conserved signal molecules that mediate quorum sensing in Gram-negative bacteria. In this study, deuterium-labeled AHLs were prepared for use as internal standards for isotope dilution mass spectrometry. Their utility in the sensitive and precise quantification of AHLs in culture supernatants of bacteria by GC/MS was demonstrated. PMID:20471840

Kai, Kenji; Tani, Ayaka; Hayashi, Hideo

2010-06-01

104

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

SciTech Connect

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.

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

105

Isotopically selective, Doppler-free, saturation spectroscopy of lutetium isotopes via resonance ionization mass spectrometry  

SciTech Connect

A new technique utilizing RIMS to obtain very high resolution atomic spectra with isotopic selectivity has been demonstrated. This technique allows the precise determination of HF splitting constants, limited only by the transition's natural linewidth. In addition, it is also feasible with this technique to accurately determine atomic isotope shifts. The exact determination of HF component line positions provides data for isotopically selective ionization which, in turn, will increase RIMS' dynamic range. Future work includes the incorporation of a /open quotes/vibrating/close quotes/ mirror and the study of rarer isotopes, i.e., /sup 174/Lu, /sup 173/Lu, /sup 172/Lu, /sup 171/Lu, and possibly, /sup 170/Lu. 13 refs., 3 figs.

Fearey, B.L.; Parent, D.C.; Keller, R.A.; Miller, C.M.

1988-01-01

106

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

PubMed Central

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 ?-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

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

2012-01-01

107

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

PubMed

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

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

2014-07-01

108

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

PubMed

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

Christopher, Steven J; Thompson, Robert Q

2013-11-15

109

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

PubMed

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

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

2014-02-21

110

Investigation of bn-44 peptide fragments using high resolution mass spectrometry and isotope labeling.  

PubMed

An N-terminal deuterohemin-containing hexapeptide (DhHP-6) was designed as a short peptide cytochrome c (Cyt c) mimetic to study the effect of N-terminal charge on peptide fragmentation pathways. This peptide gave different dissociation patterns than normal tryptic peptides. Upon collision-induced dissociation (CID) with an ion trap mass spectrometer, the singly charged peptide ion containing no added proton generated abundant and characteristic bn-44 ions instead of bn-28 (an) ions. Studies by high resolution mass spectrometry (HRMS) and isotope labeling indicate that elimination of 44 Da fragments from b ions occurs via two different pathways: (1) loss of CH3CHO (44.0262) from a Thr side chain; (2) loss of CO2 (43.9898) from the oxazolone structure in the C-terminus. A series of analogues were designed and analyzed. The experimental results combined with Density Functional Theory (DFT) calculations on the proton affinity of the deuteroporphyrin demonstrate that the production of these novel bn-44 ions is related to the N-terminal charge via a charge-remote rather than radical-directed fragmentation pathway. PMID:25280401

Wang, Bing; Yu, Jiayi; Wang, Huixin; Wei, Zhonglin; Guo, Xinhua; Xiao, Zhaohui; Zeng, Zhoufang; Kong, Wei

2014-12-01

111

Isotopic measurement of subnanogram quantities of rhenium and osmium by resonance ionization mass spectrometry  

SciTech Connect

Resonance ionization mass spectrometry has been used to measure the isotopic compositions of microgram and picogram quantities of Re and Os. The high sensitivity required for these measurements was achieved through the optimization of sample atomization and efficient ionization from the resulting gas-phase reservoir. Re and Os are absorbed from chloride solutions onto anion exchange beads as a means of purifying and concentrating the sample and then loaded onto a miniaturized Ta filament. The molecular species of Re and Os are reduced to metal in the vacuum of the mass spectrometer by gradual heating in the presence of collodion and graphite. Both Re and Os atomize efficiently at 2173-2373 K. Os atomization is optimized further by pulsing the filament temperature to coincide with the pulse rate of the laser system. Pulsed ion signals of >2 ions/s are quantified by signal averaging using a transient digitizer. Ion fluxes <2 ions/s are quantified by ion counting. Measurements of microgram quantities of spike-standard mixtures are reported to precisions and accuracies of about 1%. Measurement precision and accuracy of picogram quantities of Os range from 1 to 5% and are primarily limited by counting statistics.

Walker, R.J.; Fassett, J.D.

1986-12-01

112

Investigation of bn-44 Peptide Fragments Using High Resolution Mass Spectrometry and Isotope Labeling  

NASA Astrophysics Data System (ADS)

An N-terminal deuterohemin-containing hexapeptide (DhHP-6) was designed as a short peptide cytochrome c (Cyt c) mimetic to study the effect of N-terminal charge on peptide fragmentation pathways. This peptide gave different dissociation patterns than normal tryptic peptides. Upon collision-induced dissociation (CID) with an ion trap mass spectrometer, the singly charged peptide ion containing no added proton generated abundant and characteristic bn-44 ions instead of bn-28 (an) ions. Studies by high resolution mass spectrometry (HRMS) and isotope labeling indicate that elimination of 44 Da fragments from b ions occurs via two different pathways: (1) loss of CH3CHO (44.0262) from a Thr side chain; (2) loss of CO2 (43.9898) from the oxazolone structure in the C-terminus. A series of analogues were designed and analyzed. The experimental results combined with Density Functional Theory (DFT) calculations on the proton affinity of the deuteroporphyrin demonstrate that the production of these novel bn-44 ions is related to the N-terminal charge via a charge-remote rather than radical-directed fragmentation pathway.

Wang, Bing; Yu, Jiayi; Wang, Huixin; Wei, Zhonglin; Guo, Xinhua; Xiao, Zhaohui; Zeng, Zhoufang; Kong, Wei

2014-12-01

113

Accelerator mass spectrometry measurement of 240Pu/239Pu isotope ratios in Novaya Zemlya and Kara Sea sediments.  

PubMed

Generally low levels of plutonium in environmental samples, often combined with limited sample sizes, necessitate reliable low-level techniques for determination of Pu isotopes. Accelerator mass spectrometry (AMS) has proved to be a powerful method for measuring low-level Pu activity concentrations and Pu isotope ratios. Based on procedural blanks, detection limits for AMS were below 1 fg Pu (equivalent to ca. 2 microBq 139Pu), which can compete with both TIMS, high sensitivity ICP-MS, and certainly alpha-spectrometry, while showing less interference, memory and matrix effects as compared to routine ICP-MS techniques. In addition to low detection limits, the technique offers the advantage of giving information on Pu isotope ratios. Measurements of sediments collected from dumping sites at Novaya Zemlya showed deviation from global fallout 240Pu/239Pu ratios. PMID:15177353

Oughton, Deborah H; Skipperud, Lindis; Fifield, L Keith; Cresswell, Richard G; Salbu, Brit; Day, Philip

2004-01-01

114

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

NASA Technical Reports Server (NTRS)

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%).

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

1994-01-01

115

An improved measurement of isotopic ratios by high resolution mass spectrometry.  

PubMed

The study of protein kinetics requires an accurate measurement of isotopic ratios of peptides. Although Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometers yield accurate mass measurements of analytes, the isotopologue ratios are consistently lower than predicted. Recently, we demonstrated that the magnitude of the spectral error in the FT-ICR mass spectrometer is proportional to the scan duration of ions. Here, we present a novel isotopic ratio extrapolation (IRE) method for obtaining accurate isotopic ratio measurements. Accuracy is achieved by performing scans with different duration and extrapolation of the data to the initial moment of the ion rotation; IRE minimizes the absolute isotopic ratio error to ?1%. We demonstrate the application of IRE in protein turnover studies using (2)H(2)O-metabolic labeling. Overall, this technique allows accurate measurements of the isotopic ratios of proteolytic peptides, a critical step for enabling routine studies of proteome dynamics. PMID:23283729

Ilchenko, Serguei; Previs, Stephen F; Rachdaoui, Nadia; Willard, Belinda; McCullough, Arthur J; Kasumov, Takhar

2013-02-01

116

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

PubMed Central

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

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

2011-01-01

117

Mass Spectrometry  

NASA Astrophysics Data System (ADS)

For twenty years or so now, mass spectrometry has been used to get exact measurements of the mass of biological molecules such as proteins, nucleic acids,oligosaccharides, and so on. Over the past ten years, this technology has followed the trend toward miniaturisation and the samples required can be much smaller. In particular, the nanoelectrospray source (online or by needle) allow one to work at flow rates of a few tens of nanolitres/min. There are many applications, both in the field of proteomics and in the analysis of protein structure, dynamics, and interactions. Combining this source with nanoHPLC, complex mixtures only available in small quantities can be separated and analysed online. There are also some advantages over conventional HPLC, despite a set of constraints related to the small dimensions and low flow rates. Combining capillary electrophoresis with the electrospray source also gives useful results, with its own set of advantages and constraints. Finally, developments are currently underway to combine this source with chips, providing a means of separation and analysis online.

Pflieger, D.; Forest, E.; Vinh, J.

118

Quantitation of stable isotopic tracers of calcium by fast atom bombardment mass spectrometry  

Microsoft Academic Search

Instrumentation and methodology developed for quantitation of stable isotopic traces in urine are described. Calcium is isolated from urine as the insoluble oxalate salt which is subsequently dissolved in hydrochloric acid. The isotopic content of the acid solution is determined by use of a conventional mass spectrometer equipped with a fast atom bombardment ion source. Calcium ions are desorbed from

Xiangyu. Jiang; David L. Smith

1987-01-01

119

The Role of Naturally Occurring Stable Isotopes in Mass Spectrometry, Part I: The Theory  

PubMed Central

In this tutorial, the authors explain how naturally occurring stable isotopes are contributing to experimentally determined mass spectra and how this information can be exploited in quantitative experiments, structural elucidation studies and tracer methodologies. The first instalment of this two part series focuses on the theoretical aspects of stable isotopes and the calculation of their distribution patterns. PMID:23772100

Bluck, Les; Volmer, Dietrich A.

2013-01-01

120

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

Microsoft Academic Search

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

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

2006-01-01

121

Identification and quantification of N-linked glycoproteins using hydrazide chemistry, stable isotope labeling and mass spectrometry  

Microsoft Academic Search

Quantitative proteome profiling using stable isotope protein tagging and automated tandem mass spectrometry (MS\\/MS) is an emerging technology with great potential for the functional analysis of biological systems and for the detection of clinical diagnostic or prognostic marker proteins. Owing to the enormous complexity of proteomes, their comprehensive analysis is an as-yet-unresolved technical challenge. However, biologically or clinically important information

Hui Zhang; Xiao-jun Li; Daniel B Martin; Ruedi Aebersold

2003-01-01

122

Chemical and isotopic measurements of micrometeoroids by secondary ion mass spectrometry (A0187-2)  

NASA Technical Reports Server (NTRS)

The objective of this experiment is to measure the chemical and isotopic composition of interplanetary dust particles of mass greater than 10 to the minus 10 power G for most of thermator elements expected to be present.

Foote, J. H.; Swan, P. D.; Walker, R. M.; Zinner, E. K.; Bahr, D.; Fechtig, H.; Jessberger, E.; Igenbergs, E.; Kreitmayr, U.; Kuczera, H.

1984-01-01

123

Precise and accurate neodymium isotopic measurements by plasma-source mass spectrometry  

Microsoft Academic Search

The plasma-source mass spectrometer equipped with both a magnetic mass filter and multiple collection (PSMS) of Lyon was tested for high-precision analysis of neodymium isotopic compositions. These can be determined on as little as 70 ng Nd by PSMS with an internal precision of 10 ppm and an external reproducibility of ?30 ppm. A magnetic mass filter, which provides flat

Batrice Luais; Philippe Telouk; Francis Albarde

1997-01-01

124

Discovering Mercury Protein Modifications in Whole Proteomes Using Natural Isotope Distributions Observed in Liquid Chromatography-Tandem Mass Spectrometry*  

PubMed Central

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. PMID:21532010

Polacco, Benjamin J.; Purvine, Samuel O.; Zink, Erika M.; LaVoie, Stephen P.; Lipton, Mary S.; Summers, Anne O.; Miller, Susan M.

2011-01-01

125

Discovering Mercury Protein Modifications in Whole Proteomes Using Natural Isotope Distributions Observed in Liquid Chromatography-Tandem Mass Spectrometry  

SciTech Connect

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 mercurys 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.

Polacco, Benjamin J.; Purvine, Samuel O.; Zink, Erika M.; LaVoie, Stephen P.; Lipton, Mary S.; Summers, Anne O.; Miller, Susan M.

2011-08-01

126

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

127

Mass Spectrometry Mass spectrometry has emerged as  

E-print Network

Mass Spectrometry Mass spectrometry has emerged as the key technology for proteomics experiments 3D protein structures at a proteome scale using mass spectrometry experiments. Data Analysis Data and the development of suitable data analysis routines is a major challenge. Structural Proteomics Proteomics

Heermann, Dieter W.

128

A computational drug metabolite detection using the stable isotopic mass-shift filtering with high resolution mass spectrometry in pioglitazone and flurbiprofen.  

PubMed

The identification of metabolites in drug discovery is important. At present, radioisotopes and mass spectrometry are both widely used. However, rapid and comprehensive identification is still laborious and difficult. In this study, we developed new analytical software and employed a stable isotope as a tool to identify drug metabolites using mass spectrometry. A deuterium-labeled compound and non-labeled compound were both metabolized in human liver microsomes and analyzed by liquid chromatography/time-of-flight mass spectrometry (LC-TOF-MS). We computationally aligned two different MS data sets and filtered ions having a specific mass-shift equal to masses of labeled isotopes between those data using our own software. For pioglitazone and flurbiprofen, eight and four metabolites, respectively, were identified with calculations of mass and formulas and chemical structural fragmentation analysis. With high resolution MS, the approach became more accurate. The approach detected two unexpected metabolites in pioglitazone, i.e., the hydroxypropanamide form and the aldehyde hydrolysis form, which other approaches such as metabolite-biotransformation list matching and mass defect filtering could not detect. We demonstrated that the approach using computational alignment and stable isotopic mass-shift filtering has the ability to identify drug metabolites and is useful in drug discovery. PMID:24084721

Uchida, Masashi; Kanazawa, Mitsuhiro; Ogiwara, Atsushi; Sezaki, Hiroshi; Ando, Akihiro; Miyamoto, Yohei

2013-01-01

129

DETERMINATION OF 237NP AND PU ISOTOPES IN LARGE SOIL SAMPLES BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY  

SciTech Connect

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.

Maxwell, S.

2010-07-26

130

Determination of 237Np and Pu isotopes in large soil samples by inductively coupled plasma mass spectrometry.  

PubMed

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 110(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. PMID:21056724

Maxwell, Sherrod L; Culligan, Brian K; Jones, Vernon D; Nichols, Sheldon T; Bernard, Maureen A; Noyes, Gary W

2010-12-01

131

Determination of sulfur in fossil fuels by isotope dilution thermal ionization mass spectrometry  

SciTech Connect

Total sulfur has been measured in 13 petroleum and 14 coal Standard Reference Materials (SRMs) by isotope dilution thermal ionization mass spectrometry. These materials are suitable as primary and quality control standards for determining the sulfur content of oils and coals by X-ray fluorescence and high-temperature combustion instrumentation. Samples were spiked with enriched stable [sup 34]S and combusted in sealed Carius tubes using nitric and hydrochloric acids. The oxidized sulfur was reduced to H[sub 2]S, precipitated as As[sub 2]S[sub 3], and then dissolved in an ammoniacal solution of As[sub 2]O[sub 3]. A portion of this solution, equivalent to 1.5 [mu]g of sulfur, was added to a single Re filament coated with silica gel. The amount of sulfur in the samples was determined from the [sup 32]S/[sup 34]S ratio by measuring the [sup 75]As[sup 32]S[sup +]/[sup 75]As[sup 34]S[sup +] molecular ions in a Faraday detector. A total of 158 sulfur procedural blanks covering a 10-year period show an approximate log-normal distribution with a grand mean of 0.26 [mu]g of sulfur. This is a negligible correction for most of the data reported here. The total uncertainty (95% confidence interval) for homogeneous materials such as oils is about 0.5%, and for less homogeneous materials such as coals is 1-4%. 30 refs., 4 figs., 4 tabs.

Kelly, W.R.; Paulsen, P.J.; Murphy, K.E.; Vocke, R.D. Jr.; Chen, L.T. (National Inst. of Standards and Technology, Gaithersburg, MD (United States))

1994-08-01

132

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

PubMed

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

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

2011-01-01

133

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

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.

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

2003-01-01

134

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

PubMed

An anomalous stable hydrogen isotopic fractionation of 4 in gaseous hydrogen has been correlated with the process of adding liquid nitrogen (LN(2)) 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) ?(2)H 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 LN(2) is used as a moisture trap for gaseous hydrogen. PMID:20718408

Coplen, Tyler B; Qi, Haiping

2010-09-15

135

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

USGS Publications Warehouse

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.

Coplen, T.B.; Qi, H.

2010-01-01

136

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

USGS Publications Warehouse

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& 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

Coplen, Tyler B.; Qi, Haiping

2010-01-01

137

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

USGS Publications Warehouse

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

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

1973-01-01

138

Ion microscopy with resonant ionization mass spectrometry : time-of-flight depth profiling with improved isotopic precision.  

SciTech Connect

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.

Pellin, M. J.; Veryovkin, I. V.; Levine, J.; Zinovev, A.; Davis, A. M.; Stephan, T.; Tripa, C. E.; King, B. V.; Savina, M. R. (Materials Science Division); (Chicago Center Cosmochemistry); (Univ. of Chicago); (Univ.of Newcastle)

2010-01-01

139

Scientific note A scientific note of an application of isotope ratio mass spectrometry  

E-print Network

) Varroa jacobsoni / feeding / mass spectrometry / 13C labeling / Apis mellifera The parasitic mite, Varroa developed a novel approach, using 13C labeling. A total of 450 A. mellifera honey bee workers were removed workers were kept in each of four small cages without food for a period of 6 h. Female mites removed from

Paris-Sud XI, Universit de

140

Metabolic flux in carbohydrate biosynthesis. New methods using stable isotopes, mass spectrometry, and NMR  

Technology Transfer Automated Retrieval System (TEKTRAN)

Structural analysis of carbohydrates involves three parameters: composition, linkage, and conformation, and tends to rely on the various forms of two techniques; mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. These techniques are enhanced and extended by the use of stable...

141

A new method for determination of plasma homocystine by isotope dilution and electrospray tandem mass spectrometry  

Microsoft Academic Search

A new analytical determination method of homocystine in human plasma has been developed. The method utilises liquid chromatography coupled to ionspray tandem mass spectrometry. Quantitative analysis was achieved using as an internal standard homocystine-d8. Mass spectrometer operated in the multiple reaction mode: homocystine and homocystine-d8 were detected through the transition from the precursor to the product ion (from m\\/z 269.3

Michela Tomaiuolo; Gennaro Vecchione; Elvira Grandone; Nicola Cocomazzi; Bruno Casetta; Giovanni Di Minno; Maurizio Margaglione

2006-01-01

142

The determination of geosmin and 2-methylisoborneol in water using isotope dilution high resolution mass spectrometry  

Microsoft Academic Search

Geosmin and 2-methylisoborneol (2-MIB) are extracted from water onto Ambersorb 572, desorbed into dichloromethane (DCM) and analyzed by gas chromatography-high resolution mass spectrometry (GC-HRMS) at a mass resolution of 7000. The use of the granular adsorbent Ambersorb 572 allows extraction by rolling the sample bottle, isolation of the adsorbent by filtration, desorption of the analytes into DCM in the autosampler

J. P. F. P. Palmentier; Vince Y. Taguchi; Steve W. D. Jenkins; David T. Wang; Kim-Phuong Ngo; Don Robinson

1998-01-01

143

SILEC: a protocol for generating and using isotopically labeled coenzyme A mass spectrometry standards  

PubMed Central

Stable isotope labeling by essential nutrients in cell culture (SILEC) was recently developed to generate isotopically labeled coenzyme A (CoA) and short-chain acyl-CoA thioesters. This was accomplished by modifying the widely used technique of stable isotope labeling by amino acids in cell culture to include [13C315N]-pantothenate (vitamin B5), a CoA precursor, instead of the isotopically labeled amino acids. The lack of a de novo pantothenate synthesis pathway allowed for efficient and near-complete labeling of the measured CoA species. This protocol provides a step-by-step approach for generating stable isotope-labeled short-chain acyl-CoA internal standards in mammalian and insect cells as well as instructions on how to use them in stable isotope dilution mass spectrometric-based analyses. Troubleshooting guidelines, as well as a list of unlabeled and labeled CoA species, are also included. This protocol represents a prototype for generating stable isotope internal standards from labeled essential nutrients such as pantothenate. The generation and use of SILEC standards takes approximately 23 weeks. PMID:22157971

Basu, Sankha S; Blair, Ian A

2013-01-01

144

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

NASA Astrophysics Data System (ADS)

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.

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

1991-12-01

145

Antibody labeling and elemental mass spectrometry (inductively coupled plasma-mass spectrometry) using isotope dilution for highly sensitive ferritin determination and iron-ferritin ratio measurements.  

PubMed

Ferritin, an iron storage protein, is a sensitive clinical biomarker for iron metabolic disorders. It is mainly accumulated in the liver hepatocytes and is present in human plasma at trace levels (picomolar or nanograms per milliliter). Therefore, highly sensitive analytical methods are required to perform ferritin quantification in plasma with high precision and accuracy. For this purpose, we present a mass spectrometry-based analytical strategy (inductively coupled plasma-mass spectrometry, ICP-MS) combined with antibody labeling in a sandwich assay format for ferritin determination. The developed methodology involves two ferritin monoclonal antibodies, one of them biotinylated and the other one labeled with a ruthenium chelate [Ru(bpy)3](2+). The complex formed in solution between ferritin and the two antibodies is then captured using streptavidin-coated magnetic microparticles and directly introduced into ICP-MS for Ru monitoring. Since the Ru complex also allows one to obtain electrogenerated chemiluminescence (ECL), the combination of both sets of data (ICP-MS and ECL) will permit the establishment of the ferritin:Ru stoichiometry. This serves as a basis for further quantification studies using flow injection analysis with isotopically enriched (99)Ru as a carrier with ICP-MS detection. Such strategy permits absolute ferritin determination at a picomolar level with good precision (below 5%) and accuracy (85-109% recovery in the existing ferritin reference material, NIBSC code 94/572). Furthermore, the development of a new strategy to address ferritin:iron-ferritin ratios by ICP-MS opens the door also to address the potential of such ratios as a new clinical biomarker for Fe metabolic disorders. PMID:23889701

Konz, Tobias; An Alvarez, Elena; Montes-Bayon, Maria; Sanz-Medel, A

2013-09-01

146

Quantifying Uranium Isotope Ratios Using Resonance Ionization Mass Spectrometry: The Influence of Laser Parameters on Relative Ionization Probability  

SciTech Connect

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 {sup 235}U/{sup 238}U 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.

Isselhardt, B H

2011-09-06

147

Modified ion exchange separation for tungsten isotopic measurements from kimberlite samples using multi-collector inductively coupled plasma mass spectrometry.  

PubMed

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. PMID:16496054

Sahoo, Yu Vin; Nakai, Shun'ichi; Ali, Arshad

2006-03-01

148

High-precision measurement of variations in calcium isotope ratios in urine by multiple collector inductively coupled plasma mass spectrometry  

USGS Publications Warehouse

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 ?44/42Ca measurements of purified samples containing 25 ?g of Ca can be determined with typical errors less than 0.2 (2?).

Morgan, J.L.L.; Gordon, G.W.; Arrua, R.C.; Skulan, J.L.; Anbar, A.D.; Bullen, T.D.

2011-01-01

149

The Role of Naturally Occurring Stable Isotopes in Mass Spectrometry, Part III: Small Gas Molecule Calculations  

PubMed Central

In the third instalment of this tutorial, the authors explain the determination of the isotopic composition of a sample from a mass spectrometric measurement, and the methods of calculation as well as the units used. This tutorial outlines the practices in common usage, so that researchers new to this field can obtain a good understanding of the fundamentals involved. PMID:23766554

Bluck, Les; Volmer, Dietrich A.

2013-01-01

150

Stable isotope labeling tandem mass spectrometry (SILT): Integration with peptide identification and extension to data-dependent scans  

PubMed Central

Quantitation of relative or absolute amounts of proteins by mass spectrometry can be prone to large errors. The use of MS/MS ion intensities and stable isotope labeling, which we term stable isotope labeling tandem mass spectrometry (SILT), decreases the effects of contamination from unrelated compounds. We present a software package (SILTmass) that automates protein identification and quantification by the SILT method. SILTmass has the ability to analyze the kinetics of protein turnover, in addition to relative and absolute protein quantitation. Instead of extracting chromatograms to find elution peaks, SILTmass uses only scans in which a peptide is identified and that meet an ion intensity threshold. Using only scans with identified peptides, the accuracy and precision of SILT is shown to be superior to precursor ion intensities, particularly at high or low dilutions of the isotope labeled compounds or with low amounts of protein. Using example scans, we demonstrate likely reasons for the improvements in quantitation by SILT. The appropriate use of variable modifications in peptide identification is described for measurement of protein turnover kinetics. The combination of identification with SILT facilitates quantitation without peak detection and helps to ensure the appropriate use of variable modifications for kinetics experiments. PMID:18774841

Elbert, Donald L.; Mawuenyega, Kwasi G.; Scott, Evan A.; Wildsmith, Kristin R.; Bateman, Randall J.

2009-01-01

151

Validation of Sr isotopes in otoliths by laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS): opening avenues in fisheries science applications  

Microsoft Academic Search

Advances in probe-based mass spectrometry allow for high spatial resolution of elemental and isotopic sig- natures in fish otoliths that can be used to address fundamental questions in fisheries ecology. Analyses of Chinook salmon (Oncorhynchus tshawytscha) otoliths from two river populations yield identical 87Sr\\/86Sr ratios using laser abla- tion multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) and thermal ionization mass

Rachel Barnett-Johnson; Frank C. Ramos; Churchill B. Grimes; R. Bruce MacFarlane

2005-01-01

152

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

PubMed

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 (?(33)S, ?(34)S, and ?(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 ?(33)S, ?(34)S, and ?(33)S, respectively. These ? and ? 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 ?(34)S value obtained for OCS (4.9 0.3) was lower than the previous estimate of 11. When the ?(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 ?(34)S for background stratospheric sulfate. This suggests that OCS is a potentially important source for background (nonepisodic or nonvolcanic) stratospheric sulfate aerosols. PMID:25439590

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

2015-01-01

153

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

PubMed

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

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

2006-03-01

154

The use of stable isotopes and gas chromatography/mass spectrometry in the identification of steroid metabolites in the equine  

SciTech Connect

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.

Houghton, E.; Dumasia, M.C.; Teale, P.; Smith, S.J.; Cox, J.; Marshall, D.; Gower, D.B. (Horseracing Forensic Laboratory, Newmarket, Suffolk (England))

1990-10-01

155

mzMatchISO: an R tool for the annotation and relative quantification of isotope-labelled mass spectrometry data  

PubMed Central

Motivation: Stable isotope-labelling experiments have recently gained increasing popularity in metabolomics studies, providing unique insights into the dynamics of metabolic fluxes, beyond the steady-state information gathered by routine mass spectrometry. However, most liquid chromatographymass spectrometry data analysis software lacks features that enable automated annotation and relative quantification of labelled metabolite peaks. Here, we describe mzMatchISO, a new extension to the metabolomics analysis pipeline mzMatch.R. Results: Targeted and untargeted isotope profiling using mzMatchISO provides a convenient visual summary of the quality and quantity of labelling for every metabolite through four types of diagnostic plots that show (i) the chromatograms of the isotope peaks of each compound in each sample group; (ii) the ratio of mono-isotopic and labelled peaks indicating the fraction of labelling; (iii) the average peak area of mono-isotopic and labelled peaks in each sample group; and (iv) the trend in the relative amount of labelling in a predetermined isotopomer. To aid further statistical analyses, the values used for generating these plots are also provided as a tab-delimited file. We demonstrate the power and versatility of mzMatchISO by analysing a 13C-labelled metabolome dataset from trypanosomal parasites. Availability: mzMatch.R and mzMatchISO are available free of charge from http://mzmatch.sourceforge.net and can be used on Linux and Windows platforms running the latest version of R. Contact: rainer.breitling@manchester.ac.uk . Supplementary information: Supplementary data are available at Bioinformatics online PMID:23162054

Chokkathukalam, Achuthanunni; Jankevics, Andris; Creek, Darren J.; Achcar, Fiona; Barrett, Michael P.; Breitling, Rainer

2013-01-01

156

Stable Isotope Analyses of water and Aqueous Solutions by Conventional Dual-inlet Mass Spectrometry  

SciTech Connect

The foundation of various analytical methods for the stable isotope composition of water and other aqueous samples (natural abundance, {sup 1}H : {sup 2}H (D) = 99.985 : 0.015 atom%, and {sup 16}O : {sup 17}O : {sup 18}O = 99.762 : 0.038 : 0.200 atom%) was established during the Manhatten Project in the U.S.A., when large amounts of heavy water were produced for nuclear reactors (see Kirshenbaum, 1951, for a detailed account). From early on, there was great interest in the oxygen and hydrogen isotopic compositions of water, because they are the ideal tracers of water sources and reactions. The increased analytical precisions made possible by the subsequent development of modern gas-source isotope-ratio mass spectrometers with dual-inlets and multi-collectors, have caused the proliferation of new analytical methods and applications for the oxygen and hydrogen isotopic compositions of water. These stable isotopes have found wide applications in basic as well as applied sciences (chemistry, geology, hydrology, biology, medical sciences, and food sciences). This is because water is ubiquitous, is an essential and predominant ingredient of living organisms, and is perhaps the most reactive compound in the Earth.

Horita, Juske [ORNL; Kendall, C. [U.S. Geological Survey, Menlo Park, CA

2004-01-01

157

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

PubMed

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

Fernndez, Beatriz; Rodrguez-Gonzlez, Pablo; Garca Alonso, J Ignacio; Malherbe, Julien; Garca-Fonseca, Sergio; Pereiro, Rosario; Sanz-Medel, Alfredo

2014-12-01

158

Precise ruthenium fission product isotopic analysis using dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS)  

SciTech Connect

99Tc is a subsurface contaminant of interest at numerous federal, industrial, and international facilities. However, as a mono-isotopic fission product, 99Tc lacks the ability to be used as a signature to differentiate between the different waste disposal pathways that could have contributed to subsurface contamination at these facilities. Ruthenium fission-product isotopes are attractive analogues for the characterization of 99Tc sources because of their direct similarity to technetium with regard to subsurface mobility, and their large fission yields and low natural background concentrations. We developed an inductively coupled plasma mass spectrometry (ICP-MS) method capable of measuring ruthenium isotopes in groundwater samples and extracts of vadose zone sediments. Samples were analyzed directly on a Perkin Elmer ELAN DRC II ICP-MS after a single pass through a 1-ml bed volume of Dowex AG 50W-X8 100-200 mesh cation exchange resin. Precise ruthenium isotopic ratio measurements were achieved using a low-flow Meinhard-type nebulizer and long sample acquisition times (150,000 ms). Relative standard deviations of triplicate replicates were maintained at less than 0.5% when the total ruthenium solution concentration was 0.1 ng/ml or higher. Further work was performed to minimize the impact caused by mass interferences using the dynamic reaction cell (DRC) with O2 as the reaction gas. The aqueous concentrations of 96Mo and 96Zr were reduced by more than 99.7% in the reaction cell prior to injection of the sample into the mass analyzer quadrupole. The DRC was used in combination with stable-mass correction to quantitatively analyze samples containing up to 2-orders of magnitude more zirconium and molybdenum than ruthenium. The analytical approach documented herein provides an efficient and cost-effective way to precisely measure ruthenium isotopes and quantitate total ruthenium (natural vs. fission-product) in aqueous matrixes.

Brown, Christopher F.; Dresel, P. Evan; Geiszler, Keith N.; Farmer, Orville T.

2006-05-09

159

Acquisition and processing of data for isotope-ratio-monitoring mass spectrometry  

NASA Technical Reports Server (NTRS)

Methods are described for continuous monitoring of signals required for precise analyses of 13C, 18O, and 15N in gas streams containing varying quantities of CO2 and N2. The quantitative resolution (i.e. maximum performance in the absence of random errors) of these methods is adequate for determination of isotope ratios with an uncertainty of one part in 10(5); the precision actually obtained is often better than one part in 10(4). This report describes data-processing operations including definition of beginning and ending points of chromatographic peaks and quantitation of background levels, allowance for effects of chromatographic separation of isotopically substituted species, integration of signals related to specific masses, correction for effects of mass discrimination, recognition of drifts in mass spectrometer performance, and calculation of isotopic delta values. Characteristics of a system allowing off-line revision of parameters used in data reduction are described and an algorithm for identification of background levels in complex chromatograms is outlined. Effects of imperfect chromatographic resolution are demonstrated and discussed and an approach to deconvolution of signals from coeluting substances described.

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

1994-01-01

160

Water-induced errors in continuous-flow carbon isotope ratio mass spectrometry.  

PubMed

Formation of HCO2+ from CO2 and background H2O in isotope ratio mass spectrometers has been examined in detail. The process is troublesome because its product is not resolved from 13C16O2+. The resulting, artifactual enhancement of the mass 45 ion current (and analogous enhancement of the mass 46 ion current by transfer of hydrogen to mass 45 species) can cause systematic errors in analyses of 13C based on measurement of ion current ratios in the mass spectrum of CO2. Such errors are neutralized when isotopic analyses are based on differential comparisons in which ion currents and background water levels are precisely equal during admission and ionization of both sample and standard gases. In continuous-flow systems, however, that requirement is generally not met. The resulting systematic error is proportional to the 18/44 ion current ratio. When the widely used MAT252 mass spectrometer is tuned to yield maximum sensitivity, the constant of proportionality is 26 +/- 2/1000 (i.e., the error will be 0.26/1000 if the mass 18 ion current is 100 times smaller than that at mass 44). Errors can be reduced 5-fold when the ion-source residence time of CO2+ is decreased by use of stronger ion-extraction potential gradients. Under those same conditions, sensitivity is decreased by 60%. For operation at highest sensitivity, carrier gas dew points on the order of -70 degrees C are required to obtain errors < or = 0.1/1000 for samples yielding mass 44 ion currents of 10 nA. Carrier gas dew points < or = -80 degrees C are conveniently reached by use of a Nafion dryer operated at approximately 0 degree C. PMID:9666739

Leckrone, K J; Hayes, J M

1998-07-01

161

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

Microsoft Academic Search

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

Mark D Schmitz; Samuel A Bowring; Trevor R Ireland

2003-01-01

162

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

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

163

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

PubMed

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

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

2014-06-18

164

Ultrasensitive radioisotope, stable-isotope, and trace-element analysis in the biological sciences using tandem accelerator mass spectrometry.  

PubMed

The new technique of tandem accelerator mass spectrometry (TAMS) has improved the sensitivity for measurement of several long-lived radioisotopes and certain stable isotopes by many orders of magnitude. Nuclear physics tandems and new small dedicated accelerators are now able to measure(14)C,(10)Be,(26)Al,(32)Si,(36)Cl,(41)Ca, and(129)I in natural materials. Sensitivities down to 10(5) atoms per sample can be achieved in favorable cases. By accelerating ions to MeV energies, one can eliminate molecules and uniquely identify the atomic numbers below 20. Although most applications to date have been in the earth sciences, the opportunity now exists for important new applications in biology and toxicology. Trace elements can be measured at the parts per billion (10(9)) level using a secondary ion mass spectrometry (SIMS) ion source. Radioactive tracer measurements can be made for elements, such as aluminum, for which there are no isotopes with suitable half-lives for conventional decay counting methods. For(14)C, counting times become much shorter and dose levels can be reduced. PMID:24254606

Elmore, D

1987-04-01

165

Rapid determination of (237)Np and plutonium isotopes in urine by inductively-coupled plasma mass spectrometry and alpha spectrometry.  

PubMed

A new rapid separation method was developed for the measurement of plutonium and neptunium in urine samples by inductively-coupled plasma mass spectrometry (ICP-MS) and/or alpha spectrometry with enhanced uranium removal. This method allows separation and preconcentration of plutonium and neptunium in urine samples using stacked extraction chromatography cartridges and vacuum box flow rates to facilitate rapid separations. There is an increasing need to develop faster analytical methods for emergency response samples. There is also enormous benefit to having rapid bioassay methods in the event that a nuclear worker has an uptake (puncture wound, etc.) to assess the magnitude of the uptake and guide efforts to mitigate dose (e.g., tissue excision and chelation therapy). This new method focuses only on the rapid separation of plutonium and neptunium with enhanced removal of uranium. For ICP-MS, purified solutions must have low salt content and low concentration of uranium due to spectral interference of (238)U(1)H(+) on m/z 239. Uranium removal using this method is enhanced by loading plutonium and neptunium initially onto TEVA resin, then moving plutonium to DGA resin where additional purification from uranium is performed with a decontamination factor of almost 110(5). If UTEVA resin is added to the separation scheme, a decontamination factor of ~3 10(6) can be achieved. PMID:21709507

Maxwell, Sherrod L; Culligan, Brian K; Jones, Vernon D; Nichols, Sheldon T; Noyes, Gary W; Bernard, Maureen A

2011-08-01

166

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

PubMed

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

Cueto Daz, Sergio; Ruiz Encinar, Jorge; Garca Alonso, J Ignacio

2014-09-24

167

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

USGS Publications Warehouse

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

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

1989-01-01

168

Precise determinations of the isotopic compositions and atomic weights of molybdenum, tellurium, tin and tungsten using ICP magnetic sector multiple collector mass spectrometry  

Microsoft Academic Search

Precise determinations of the isotopic compositions of molybdenum, tellurium, tin and tungsten were obtained utilizing an inductively coupled plasma (ICP) source magnetic sector mass spectrometer equipped with multiple collectors. The results of this study are comparable to those measured by conventional and negative thermal ionization mass spectrometry (TIMS and NTIMS) and the values recommended by the International Union of Pure

Der-Chuen Lee; Alex N. Halliday

1995-01-01

169

Measurement of positional isotope exchange rates in enzyme catalyzed reactions by fast atom bombardment mass spectrometry  

E-print Network

. Instead it offers a direct analysis method based on the 0. 02 ppm upfield shift induced by 18 0 substitution. This method has, however, sufferd. from decreased sensitivity as compared to mass spectrometry. At least 100x more material is required... solution wa, s titrated to pq 7. 6 with KCH. KC10 wa" allowed to precipita+e at 0 0 and then removed by centrifugation. The supernatant wa, s diluted to 100 mL, readjusted to PH 7. 6, and applied to a DEAE-cellulose column (1. 8 x 60 cm). The column...

Hilscher, Larry Wayne

1985-01-01

170

Performance of the wet oxidation unit of the HPLC isotope ratio mass spectrometry system for halogenated compounds.  

PubMed

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 ?(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 ??(13)C(EA/LC-IRMS) = 8.8, TFA ??(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 ?(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. PMID:24975492

Gilevska, Tetyana; Gehre, Matthias; Richnow, Hans Hermann

2014-08-01

171

Measurement of insulin sensitivity indices using 13C-glucose and gas chromatography/combustion/isotope ratio mass spectrometry.  

PubMed

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. PMID:12391573

Clapperton, Allan T; Coward, W Andrew; Bluck, Leslie J C

2002-01-01

172

Simultaneous Determination of Creatinine and Creatine in Human Serum by Double-Spike Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) and Gas Chromatography-Mass Spectrometry (GC-MS).  

PubMed

This work describes the first multiple spiking isotope dilution procedure for organic compounds using (13)C labeling. A double-spiking isotope dilution method capable of correcting and quantifying the creatine-creatinine interconversion occurring during the analytical determination of both compounds in human serum is presented. The determination of serum creatinine may be affected by the interconversion between creatine and creatinine during sample preparation or by inefficient chemical separation of those compounds by solid phase extraction (SPE). The methodology is based on the use differently labeled (13)C analogues ((13)C1-creatinine and (13)C2-creatine), the measurement of the isotopic distribution of creatine and creatinine by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the application of multiple linear regression. Five different lyophilized serum-based controls and two certified human serum reference materials (ERM-DA252a and ERM-DA253a) were analyzed to evaluate the accuracy and precision of the proposed double-spike LC-MS/MS method. The methodology was applied to study the creatine-creatinine interconversion during LC-MS/MS and gas chromatography-mass spectrometry (GC-MS) analyses and the separation efficiency of the SPE step required in the traditional gas chromatography-isotope dilution mass spectrometry (GC-IDMS) reference methods employed for the determination of serum creatinine. The analysis of real serum samples by GC-MS showed that creatine-creatinine separation by SPE can be a nonquantitative step that may induce creatinine overestimations up to 28% in samples containing high amounts of creatine. Also, a detectable conversion of creatine into creatinine was observed during sample preparation for LC-MS/MS. The developed double-spike LC-MS/MS improves the current state of the art for the determination of creatinine in human serum by isotope dilution mass spectrometry (IDMS), because corrections are made for all the possible errors derived from the sample preparation step. PMID:25751287

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

2015-04-01

173

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

174

Use of inductively coupled plasma-mass spectrometry in boron-10 stable isotope experiments with plants, rats, and humans.  

PubMed Central

The commercial availability of inductively coupled plasma-mass spectrometry technology (ICP-MS) has presented the opportunity to measure the boron concentrations and isotope ratios in a large number of samples with minimal sample preparation. A typical analytical sequence for fecal samples consists of 25 acid blanks, 1 digestion blank, 5 calibration solutions, 4 standard reference material solutions, 10 samples, and 4 natural abundance bias standards. Boron detection limits (3 x 1 sigma) for acid blanks are 0.11 ppb for 10B, and 0.40 ppb for 11B. Isotope ratios were measured in fecal samples with 20 to 50 ppb boron with < 2% relative standard deviation. Rapid washout and minimal memory effects were observed for a 50 ppb beryllium internal standard, but a 200 ppb boron biological sample had a 1.0 ppb boron memory after a 6-min washout. Boron isotope ratios in geological materials are highly variable; apparently this variability is reflected in plants of a fixed natural abundance value for boron requires that a natural abundance ratio be determined for each sample or related data set. The natural abundance variability also prevents quantitation and calculation of isotope dilution by instrument-supplied software. To measure boron transport in animal systems, 20 micrograms of 10B were fed to a fasted rat. During the 3 days after a 10B oral dose, 95% of the 10B was recovered from the urine and 4% from the feces. Urinary isotope ratios, 11B/10B, changed from a natural abundance of 4.1140 to an enriched value of 0.95077, a 77% change.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7889873

Vanderpool, R A; Hoff, D; Johnson, P E

1994-01-01

175

Quantitative proteomics using mass spectrometry  

Microsoft Academic Search

The use of stable isotopes as internal standards in mass spectrometry has opened a new era for quantitative proteomics. Depending on the point at which the label is introduced, most procedures can be classified as in vivo labeling, in vitro pre-digestion labeling or in vitro post-digestion labeling. In vivo labeling has been used for cells that can be grown in

Salvatore Sechi; Yoshiya Oda

2003-01-01

176

Advantages of Isotopic Depletion of Proteins for Hydrogen/Deuterium Exchange Experiments Monitored by Mass Spectrometry  

E-print Network

Advantages of Isotopic Depletion of Proteins for Hydrogen/Deuterium Exchange Experiments Monitored, the peaks overlap and the spectra become more and more crowded because of the presence of heavier isotopes.0 667.0 Isotopic depletion (i.e. elimination of heavier isotopes) reduces the complexity of the spectra

177

Quantitative analysis of global phosphorylation changes with high-resolution tandem mass spectrometry and stable isotopic labeling  

PubMed Central

Quantitative measurement of specific protein phosphorylation sites is a primary interest of biologists, as site-specific phosphorylation information provides insights into cell signaling networks and cellular dynamics at a system level. Over the last decade, selective phosphopeptide enrichment methods including IMAC and metal oxides (TiO2 and ZrO2) have been developed and greatly facilitate large scale phosphoproteome analysis of various cells, tissues and living organisms, in combination with modern mass spectrometers featuring high mass accuracy and high mass resolution. Various quantification strategies have been applied to detecting relative changes in expression of proteins, peptides, and specific modifications between samples. The combination of mass spectrometry-based phosphoproteome analysis with quantification strategies provides a straightforward and unbiased method to identify and quantify site-specific phosphorylation. We describe common strategies for mass spectrometric analysis of stable isotope labeled samples, as well as two widely applied phosphopeptide enrichment methods based on IMAC(NTA-Fe3+) and metal oxide (ZrO2). Instrumental configurations for on-line LC-tandem mass spectrometric analysis and parameters of conventional bioinformatic analysis of large data sets are also considered for confident identification, localization, and reliable quantification of site-specific phosphorylation. PMID:23611819

Kweon, Hye Kyong; Andrews, Philip C.

2013-01-01

178

Correction for isotopic interferences between analyte and internal standard in quantitative mass spectrometry by a nonlinear calibration function.  

PubMed

Stable isotope-labeled internal standards are of great utility in providing accurate quantitation in mass spectrometry (MS). An implicit assumption has been that there is no "cross talk" between signals of the internal standard and the target analyte. In some cases, however, naturally occurring isotopes of the analyte do contribute to the signal of the internal standard. This phenomenon becomes more pronounced for isotopically rich compounds, such as those containing sulfur, chlorine, or bromine, higher molecular weight compounds, and those at high analyte/internal standard concentration ratio. This can create nonlinear calibration behavior that may bias quantitative results. Here, we propose the use of a nonlinear but more accurate fitting of data for these situations that incorporates one or two constants determined experimentally for each analyte/internal standard combination and an adjustable calibration parameter. This fitting provides more accurate quantitation in MS-based assays where contributions from analyte to stable labeled internal standard signal exist. It can also correct for the reverse situation where an analyte is present in the internal standard as an impurity. The practical utility of this approach is described, and by using experimental data, the approach is compared to alternative fits. PMID:23480307

Rule, Geoffrey S; Clark, Zlatuse D; Yue, Bingfang; Rockwood, Alan L

2013-04-16

179

Relative Quantification of Serum Proteins from Pancreatic Ductal Adenocarcinoma Patients by Stable Isotope Dilution Liquid Chromatography-Mass Spectrometry  

PubMed Central

We report an innovative multiplexed liquid chromatography-multiple reaction monitoring/mass spectrometry (LC-MRM/MS)-based assay for rapidly measuring a large number of disease specific protein biomarkers in human serum. Furthermore, this approach uses stable isotope dilution methodology to reliably quantify candidate protein biomarkers. Human serum was diluted using a stable isotope labeled proteome (SILAP) standard prepared from the secretome of pancreatic cell lines, subjected to immunoaffinity removal of the most highly abundant proteins, trypsin digested, and analyzed by LC-MRM/MS. The method was found to be precise, linear, and specific for the relative quantification of 72 proteins when analyte response was normalized to the relevant internal standard (IS) from the SILAP. The method made it possible to determine statistically different concentrations for three proteins (cystatin M, IGF binding protein 7, and villin 2) in control and pancreatic cancer patient samples. This method proves the feasibility of using a SILAP standard in combination with stable isotope dilution LC-MRM/MS analysis of tryptic peptides to compare changes in the concentration of candidate protein biomarkers in human serum. PMID:22264027

Wehr, Angela Y.; Hwang, Wei-Ting; Blair, Ian A.; Yu, Kenneth H.

2012-01-01

180

Low blank isotope ratio measurements of rhenium, osmium, and platinum using tantalum filaments with negative thermal ionization mass spectrometry.  

PubMed

Platinum is most commonly used as a filament for Re and Os isotopic measurements, but it contains impurities of Re and Os. Tantalum is low in platinum group elements (PGE) and in Re, but it is not used for negative thermal ionization mass spectrometry because of high electron emission and high reactivity with O(2). High thermal electron emission from Ta distorts the preoptimized ion source optics. In addition, Ta consumes O(2), leaving little for samples, but O(2) is essential for isotopic ratio measurements of PGE and Re as they are measured as negatively charged oxides, such as OsO(3)(-) and PtO(2)(-). These problems are solved by prebaking a filament to remove tantalum oxides before sample loading, keeping relatively high filament temperatures and high O(2) pressures (P(O)((2))) during the sample run, and lowering the potential difference between the filament and the draw-out plate. At P(O)((2)) of ?1 10(-)(5) Torr in the source, strong (>10 V) stable (>6 h) peaks of ReO(4)(-), OsO(3)(-), and PtO(2)(-) are obtained at 750 C for Re, 850 C for Pt, and over 900 C for Os. Accurate isotopic ratio measurements of Re, Os, and Pt at picogram levels are possible using Ta filaments. PMID:21651247

Hattori, K; Menagh, D P; Cole, T J

1998-10-01

181

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

PubMed

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 (?(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 ?(13)C value range of -22.590.92 for authentic ciders CO2 bubbles. 75 commercial ciders were analysed with this method. Most of the samples analysed present a gas ?(13)C value in the expected range. Nevertheless, some ciders have ?(13)C values outside the 3? 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. PMID:23870934

Gaillard, Laetitia; Guyon, Francois; Salagoty, Marie-Hlne; Mdina, Bernard

2013-12-01

182

Rapid simultaneous determination of dexamethasone and betamethasone in milk by liquid chromatography tandem mass spectrometry with isotope dilution.  

PubMed

A simple, sensitive and reliable analytical method for the rapid simultaneous determination of dexamethasone and betamethasone in milk by high performance liquid chromatography-negative electrospray ionization tandem mass spectrometry (HPLC-NESI-MS/MS) with isotope dilution was developed. Samples were directly purified through C(18) cartridge. Then the eluate was dried under nitrogen and residues were dissolved in mobile phase. Samples were analyzed by HPLC-MS/MS on a Hypercarb graphite column with a mixture of acetonitrile-water-formic acid as mobile phase. The samples were quantified using dexamethasone-D(4) as an internal standard. The procedure was validated according to the European Union regulation 2002/657/EC determining specificity, decision limit (CCalpha), detection capability (CCbeta), trueness, precision, linearity and stability. The method is demonstrated to be suitable for the determination of dexamethasone and betamethasone in milk. The total time required for the analysis of one sample was about 35 min. PMID:20015503

Li, Cun; Wu, Yinliang; Yang, Ting; Zhang, Yan

2010-01-15

183

Isotope pattern deconvolution for peptide mass spectrometry by non-negative least squares/least absolute deviation template matching  

PubMed Central

Background The robust identification of isotope patterns originating from peptides being analyzed through mass spectrometry (MS) is often significantly hampered by noise artifacts and the interference of overlapping patterns arising e.g. from post-translational modifications. As the classification of the recorded data points into either noise or signal lies at the very root of essentially every proteomic application, the quality of the automated processing of mass spectra can significantly influence the way the data might be interpreted within a given biological context. Results We propose non-negative least squares/non-negative least absolute deviation regression to fit a raw spectrum by templates imitating isotope patterns. In a carefully designed validation scheme, we show that the method exhibits excellent performance in pattern picking. It is demonstrated that the method is able to disentangle complicated overlaps of patterns. Conclusions We find that regularization is not necessary to prevent overfitting and that thresholding is an effective and user-friendly way to perform feature selection. The proposed method avoids problems inherent in regularization-based approaches, comes with a set of well-interpretable parameters whose default configuration is shown to generalize well without the need for fine-tuning, and is applicable to spectra of different platforms. The R package IPPD implements the method and is available from the Bioconductor platform (http://bioconductor.fhcrc.org/help/bioc-views/devel/bioc/html/IPPD.html). PMID:23137144

2012-01-01

184

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

185

Lead isotope ratios of volcanic glass by laser ablation inductively-coupled plasma mass spectrometry: Application to Miocene tephra beds in Montana, USA and adjacent areas  

Microsoft Academic Search

Recent improvements in spatial resolution and sensitivity of laser ablation inductively-coupled plasma mass spectrometry allow exploration of the tephrochronologic potential of Pb isotope ratios of volcanic glass, in particular, their use in characterization and provenance detection of distal tephra beds. Measurements have good accuracy and precision, as determined by comparison with reference materials. A test suite of samples was taken

J. A. Westgate; N. J. G. Pearce; W. T. Perkins; P. A. Shane; S. J. Preece

186

Potential of ion chromatography coupled to isotope ratio mass spectrometry via a liquid interface for beverages authentication.  

PubMed

New tools for the determination of characteristic parameters for food authentication are requested to prevent food adulteration from which health concerns, unfair competition could follow. A new coupling in the area of compound-specific carbon 13 isotope ratio (?(13)C) analysis was developed to simultaneously quantify ?(13)C values of sugars and organic acids. The coupling of ion chromatography (IC) together with isotope ratio mass spectrometry (IRMS) can be achieved using a liquid interface allowing a chemical oxidation (co) of organic matter. Synthetic solutions containing 1 polyol (glycerol), 3 carbohydrates (sucrose, glucose and fructose) and 12 organic acids (gluconic, lactic, malic, tartaric, oxalic, fumaric, citric and isocitric) were used to optimize chromatographic conditions (concentration gradient and 3 types of column) and the studied isotopic range (-32.28 to -10.65) corresponds to the values found in food products. Optimum chromatographic conditions are found using an IonPac AS15, an elution flow rate of 0.3mLmin(-1) and a linear concentration gradient from 2 to 76mM (rate 21mMmin(-1)). Comparison between ?(13)C value individually obtained for each compound with the coupling IRMS and elemental analyzer, EA-IRMS, and the ones measured on the mixture of compounds by IC-co-IRMS does not reveal any isotope fractionation. Thus, under these experimental conditions, IC-co-IRMS results are accurate and reproducible. This new coupling was tested on two food matrices, an orange juice and a sweet wine. Some optimization is necessary as the concentration range between sugars and organic acids is too large: an increase in the filament intensity of the IRMS is necessary to simultaneously detect the two compound families. These first attempts confirm the good results obtained on synthetic solutions and the strong potential of the coupling IC-co-IRMS in food authentication area. PMID:24267317

Guyon, Francois; Gaillard, Laetitia; Brault, Audrey; Gaultier, Nicolas; Salagoty, Marie-Hlne; Mdina, Bernard

2013-12-27

187

What is Mass Spectrometry?  

NSDL National Science Digital Library

This site from the American Society for Mass Spectrometry includes information about what mass spectometry is and how it is used. It has many useful figures and references to other materials. The material answers questions such as "What is mass spectrometry and what can it do for you?"

Chiu, Chia M.

188

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

PubMed

A sensitive, accurate and simple liquid chromatography coupled with mass spectrometry method for the determination of 10 selected pesticides in soya beans has been developed and validated. The method is intended for use during the characterization of selected pesticides in a reference material. In this process, high accuracy and appropriate uncertainty levels associated to the analytical measurements are of utmost importance. The analytical procedure is based on sample extraction by the use of a modified QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction and subsequent clean-up of the extract with C18, PSA and Florisil. Analytes were separated on a C18 column using gradient elution with water-methanol/2.5mM ammonium acetate mobile phase, and finally identified and quantified by triple quadrupole mass spectrometry in the multiple reaction monitoring mode (MRM). Reliable and accurate quantification of the analytes was achieved by means of stable isotope-labelled analogues employed as internal standards (IS) and calibration with pure substance solutions containing both, the isotopically labelled and native compounds. Exceptions were made for thiodicarb and malaoxon where the isotopically labelled congeners were not commercially available at the time of analysis. For the quantification of those compounds methomyl-(13)C2(15)N and malathion-D10 were used respectively. The method was validated according to the general principles covered by DG SANCO guidelines. However, validation criteria were set more stringently. Mean recoveries were in the range of 86-103% with RSDs lower than 8.1%. Repeatability and intermediate precision were in the range of 3.9-7.6% and 1.9-8.7% respectively. LODs were theoretically estimated and experimentally confirmed to be in the range 0.001-0.005mgkg(-1) in the matrix, while LOQs established as the lowest spiking mass fractionation level were in the range 0.01-0.05mgkg(-1). The method reliably identifies and quantifies the selected pesticides in soya beans at appropriate uncertainty levels, making it suitable for the characterization of candidate reference materials. PMID:25770614

Huertas Prez, J F; Sejere-Olsen, B; Fernndez Alba, A R; Schimmel, H; Dabrio, M

2015-05-01

189

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

PubMed

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

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

2014-01-01

190

Stable isotope tracer and gas-chromatography combustion isotope ratio mass spectrometry to study the in vivo compartmental metabolism of docosahexaenoic acid.  

PubMed

A gas-chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) method using carbon 13 (13C)-stable isotope to trace n-3 polyunsaturated fatty acids (PUFA) turnover in vivo is presented. Natural 13C abundance of commercial n-3 PUFA was measured from 100 to 300 ng of fatty acids and was -27.58, -27.83, and -28.16 for 22:6n-3, 22:5n-3, and 20:5n-3, expressed as delta 13C /1000 versus Pee Dee Belemnite (PDB), respectively. Precision of delta 13C /1000 values was comparable for the three PUFA and gave relative standard deviations of 0.95-0.97%. Isotope enrichment of 0.0010 at.% could be detected. Triglycerides enriched in [13C]22:6n-3 ([13C]22:6-TG) were synthesized by growing a microalgae on [1-13C]glucose. [13C]22:6n-3 represented 36 wt.% of total triglyceride fatty acids and had an isotope enrichment of 2.0420 at.%, which was the double of natural abundance. The isotope enrichment of 22:6n-3 in lipids from rat lipoproteins and red cells could be followed as a function of time after ingestion of 3 mg [13C]22:6-TG and showed specific patterns according to the lipid compartments. The retroconversion of [13C]22:6n-3 was also detected in HDL phosphatidylcholine by the appearance of [13C]22:5n-3 and [13C]20:5n-3. On the other hand, 22:6n-3 natural 13C abundance in human lipid classes of lipoproteins and blood cells has been measured using 10 ml plasma, even for the more limiting lipid compartments in terms of 22:6n-3 dose size.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7978245

Brossard, N; Pachiaudi, C; Croset, M; Normand, S; Lecerf, J; Chirouze, V; Riou, J P; Tayot, J L; Lagarde, M

1994-07-01

191

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

NASA Astrophysics Data System (ADS)

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

Kawashima, Hiroto; Murakami, Mai

2014-06-01

192

Bromine isotopic signature facilitates de novo sequencing of peptides in free-radical-initiated peptide sequencing (FRIPS) mass spectrometry.  

PubMed

We recently showed that free-radical-initiated peptide sequencing mass spectrometry (FRIPS MS) assisted by the remarkable thermochemical stability of (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (TEMPO) is another attractive radical-driven peptide fragmentation MS tool. Facile homolytic cleavage of the bond between the benzylic carbon and the oxygen of the TEMPO moiety in o-TEMPO-Bz-C(O)-peptide and the high reactivity of the benzylic radical species generated in Bz-C(O)-peptide are key elements leading to extensive radical-driven peptide backbone fragmentation. In the present study, we demonstrate that the incorporation of bromine into the benzene ring, i.e. o-TEMPO-Bz(Br)-C(O)-peptide, allows unambiguous distinction of the N-terminal peptide fragments from the C-terminal fragments through the unique bromine doublet isotopic signature. Furthermore, bromine substitution does not alter the overall radical-driven peptide backbone dissociation pathways of o-TEMPO-Bz-C(O)-peptide. From a practical perspective, the presence of the bromine isotopic signature in the N-terminal peptide fragments in TEMPO-assisted FRIPS MS represents a useful and cost-effective opportunity for de novo peptide sequencing. Copyright 2015 John Wiley & Sons, Ltd. PMID:25800020

Nam, Jungjoo; Kwon, Hyuksu; Jang, Inae; Jeon, Aeran; Moon, Jingyu; Lee, Sun Young; Kang, Dukjin; Han, Sang Yun; Moon, Bongjin; Oh, Han Bin

2015-02-01

193

Monitoring protein conformational changes and dynamics using stable-isotope labeling and mass spectrometry (CDSiL-MS)  

PubMed Central

Understanding the mechanism accompanying functional conformational changes associated with protein activation has important implications for drug design. Here, we describe a powerful method, CDSiL-MS (conformational changes and dynamics using stable-isotope labeling and mass-spectrometry), which involves chemical-labeling by isotope-coded forms of N-ethylmaleimide or succinic anhydride to site-specifically label the side-chains of cysteines or lysines, respectively, in native proteins. Subsequent MS-analysis allows the quantitative monitoring of reactivity of residues as a function of time, providing a measurement of the labeling kinetics, thereby enabling elucidation of conformational changes of proteins. We demonstrate the utility of this method using a model G-protein coupled receptor, the ?2-adrenergic receptor including experiments that characterize the functional conformational-changes associated with activation of distinct signaling pathways induced by different ?-adrenoceptor ligands. The procedure requires five days and can easily be adapted to systems where soluble and detergent-solubilized membrane protein targets, which undergo function-dependent conformational-changes, can be interrogated structurally to allow drug screening. PMID:24810039

Kahsai, Alem W.; Rajagopal, Sudarshan; Sun, Jinpeng; Xiao, Kunhong

2015-01-01

194

Geographical origin of cereal grains based on element analyser-stable isotope ratio mass spectrometry (EA-SIRMS).  

PubMed

The stable carbon and nitrogen isotopic compositions (?(13)C and ?(13)N) of different cereal grains from different regions were determined, using element analyser-stable isotope ratio mass spectrometry (EA-SIRMS) as the key method. Systematically, ?(13)C and ?(13)N of 5 kinds of cereal grains of different origins, 30 wheat samples from different cultivation areas and 160 rice samples of different cultivars from Guangdong province of China were examined. The results indicated that the ?(13)C values of rice, soybean, millet, wheat and corn were significantly (P < 0.05) different within different origins (Heilongjiang, Shandong and Jiangsu province of China), respectively, while ?(13)N values were not. Interestingly, there exists discrimination between these 5 kinds of cereals grains, no matter C-3 or C-4 plants. Further study showed that the ?(13)C values of wheat from Australia, the USA, Canada, and Jiangsu and Shandong province of China were also significantly (P < 0.01) different. Furthermore, the P-value test for 160 rice samples of 5 cultivars was not significant (P > 0.05), which indicated that the cultivar of cereal grains was not significant based on ?(13)C value. Thus, the comparison of ?(13)C would be potentially useful for rapid and routine discrimination of geographical origin of cereal grains. PMID:25529718

Wu, Yuluan; Luo, Donghui; Dong, Hao; Wan, Juan; Luo, Haiying; Xian, Yanping; Guo, Xindong; Qin, Fangfang; Han, Wanqing; Wang, Li; Wang, Bin

2015-05-01

195

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

PubMed

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

Rychlik, Michael

2003-07-01

196

Use of isotope ratio mass spectrometry to differentiate between endogenous steroids and synthetic homologues in cattle: a review.  

PubMed

Although substantial technical advances have been achieved during the past decades to extend and facilitate the analysis of growth promoters in cattle, the detection of abuse of synthetic analogs of naturally occurring hormones has remained a challenging issue. When it became clear that the exogenous origin of steroid hormones could be traced based on the (13)C/(12)C isotope ratio of the substances, GC/C/IRMS has been successfully implemented to this aim since the end of the past century. However, due to the costly character of the instrumental setup, the susceptibility of the equipment to errors and the complex and time consuming sample preparation, this method is up until now only applied by a limited number of laboratories. In this review, the general principles as well as the practical application of GC/C/IRMS to differentiate between endogenous steroids and exogenously synthesized homologous compounds in cattle will be discussed in detail, and will be placed next to other existing and to be developed methods based on isotope ratio mass spectrometry. Finally, the link will be made with the field of sports doping, where GC/C/IRMS has been established within the World Anti-Doping Agency (WADA) approved methods as the official technique to differentiate between exogenous and endogenous steroids over the past few years. PMID:23540242

Janssens, Geert; Courtheyn, Dirk; Mangelinckx, Sven; Prvost, Stphanie; Bichon, Emmanuelle; Monteau, Fabrice; De Poorter, Geert; De Kimpe, Norbert; Le Bizec, Bruno

2013-04-15

197

Characterization of exogenous testosterone in livestock by gas chromatography/combustion/isotope ratio mass spectrometry: influence of feeding and age.  

PubMed

The detection of exogenous testosterone in bovine urine was investigated by using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). The carbon isotopic ratio measurement of epitestosterone, etiocholanolone (testosterone metabolite) and DHEA (testosterone precursor) in female bovine urines after testosterone enanthate administration was carried out. An important modification in the 13C/12C ratio of testosterone metabolites was observed, such that significant differences between precursor and metabolites of testosterone occurred until three weeks after intramuscular administration of testosterone enanthate. The factors influencing the 13C/12C of endogenous steroids were studied especially through cattle feeding and age. The DHEA mean delta13C value was found to vary between -25 and -26/1000 when hay and concentrate diet were used for fattening. On the other hand the delta13C value observed when maize silage was used increased to -20/1000. Testosterone metabolites showed the same delta13C increase as their precursor. Moreover, we observed a clear relationship between age and efficiency of misuse determination. Indeed, because of the lower concentration of natural hormones in young animals, the contribution of exogenous molecules increases significantly compared with older subjects. Consequently, demonstration of administration is easier to achieve in calves than in mature animals. PMID:10786902

Ferchaud, V; Le Bizec, B; Monteau, F; Andre, F

2000-01-01

198

Review: mass spectrometry in Russia.  

PubMed

The present review covers the main research in the area of mass spectrometry from the 1990s which was about the same time as the Russian Federation emerged from the collapse of the Soviet Union (USSR). It consists of two main parts-application of mass spectrometry to chemistry and related fields and creation and development of mass spectrometric technique. Both traditional and comparatively new mass spectrometric methods were used to solve various problems in organic chemistry (reactivity of gas-phase ions, structure elucidation and problems of identification, quantitative and trace analysis, differentiation of stereoisomers, derivatization approaches etc.), biochemistry (proteomics and peptidomics, lipidomics), medical chemistry (mainly the search of biomarkers, pharmacology, doping control), environmental, petrochemistry, polymer chemistry, inorganic and physical chemistry, determination of natural isotope ratio etc. Although a lot of talented mass spectrometrists left Russia and moved abroad after the collapse of the Soviet Union, the vitality of the mass spectral community proved to be rather high, which allowed the continuation of new developments in the field of mass spectrometric instrumentation. They are devoted to improvements in traditional magnetic sector mass spectrometers and the development of new ion source types, to analysis and modification of quadrupole, time-of-flight (ToF) and ion cyclotron resonance (ICR) analyzers. The most important achievements are due to the creation of multi-reflecting ToF mass analyzers. Special attention was paid to the construction of compact mass spectrometers, particularly for space exploration, of combined instruments, such as ion mobility spectrometer/mass spectrometer and accelerating mass spectrometers. The comparatively young Russian Mass Spectrometry Society is working hard to consolidate the mass spectrometrists from Russia and foreign countries, to train young professionals on new appliances and regularly holds conferences on mass spectrometry. For ten years, a special journal Mass-spektrometria has published papers on all disciplines of mass spectrometry. PMID:24378462

Zaikin, Vladimir G; Sysoev, Alexander A

2013-01-01

199

The use of ?13C isotope ratio mass spectrometry for methamphetamine profiling: comparison of ephedrine and pseudoephedrine-based samples to P2P-based samples.  

PubMed

Differentiating methamphetamine samples produced from ephedrine and pseudoephedrine from phenyl-2-propanone precursors is critical for assigning synthetic route information for methamphetamine profiling. The use of isotope ratio mass spectrometry data is now a key component for tracking precursor information. Recent carbon (?(13)C) isotope results from the analysis of numerous methamphetamine samples show clear differentiation for ephedrine and pseudoephedrine-produced samples compared to P2P-produced samples. The carbon isotope differences were confirmed from synthetic route precursor studies. PMID:24378294

Toske, Steven G; Morello, David R; Berger, Jennifer M; Vazquez, Etienne R

2014-01-01

200

Differential isotopic enrichment to facilitate characterization of asymmetric multimeric proteins using hydrogen/deuterium exchange mass spectrometry.  

PubMed

Hydrogen/deuterium exchange (HDX) coupled to mass spectrometry has emerged as a powerful tool for analyzing the conformational dynamics of protein-ligand and protein-protein interactions. Recent advances in instrumentation and methodology have expanded the utility of HDX for the analysis of large and complex proteins; however, asymmetric dimers with shared amino acid sequence present a unique challenge for HDX because assignment of peptides with identical sequence to their subunit of origin remains ambiguous. Here we report the use of differential isotopic labeling to facilitate HDX analysis of multimers using HIV-1 reverse transcriptase (RT) as a model. RT is an asymmetric heterodimer of 51 kDa (p51) and 66 kDa (p66) subunits. The first 440 residues of p51 and p66 are identical. In this study differentially labeled RT was reconstituted from isotopically enriched ((15)N-labeled) p51 and unlabeled p66. To enable detection of (15)N-deuterated RT peptides, the software HDX Workbench was modified to follow a 100% (15)N model. Our results demonstrated that (15)N enrichment of p51 did not affect its conformational dynamics compared to unlabeled p51, but (15)N-labeled p51 did show different conformational dynamics than p66 in the RT heterodimer. Differential HDX-MS of isotopically labeled RT in the presence of the non-nucleoside reverse transcriptase inhibitor (NNRTI) efavirenz (EFV) showed subunit-specific perturbation in the rate of HDX consistent with previously published results and the RT-EFV cocrystal structure. PMID:25763479

Goswami, Devrishi; Tuske, Steve; Pascal, Bruce D; Bauman, Joseph D; Patel, Disha; Arnold, Eddy; Griffin, Patrick R

2015-04-01

201

Investigation of the origin of ephedrine and methamphetamine by stable isotope ratio mass spectrometry: a Japanese experience.  

PubMed

Illicit drug abuse is a serious global problem that can only be solved through international cooperation. In Asian countries, the abuse of methamphetamine is one of the most pressing problems. To assist in the control of methamphetamine, the authors investigated in detail the character of ephedrine, which is a key precursor for the illicit manufacture of methamphetamine. Commercial ephedrine is produced by one of three methods: (a) extraction from Ephedra plants, (b) full chemical synthesis or (c) via a semi-synthetic process involving the fermentation of sugar, followed by amination. Although chemically there is no difference between ephedrine samples from different origins (natural, synthetic or semi-synthetic), scientific and analytical tools such as drug-characterization and impurity-profiling programmes may provide valuable information for law enforcement and regulatory activities as part of precursor control strategies. During the research under discussion in the present article, in addition to classical impurity profiling of manufacturing by-products, the use of stable isotope ratio mass spectrometry was investigated for determining the origin of the ephedrine that had been used as a precursor in seized methamphetamine samples. The results of carbon and nitrogen stable isotope ratio (delta13C and delta15N) analysis of samples of crystalline methamphetamine seized in Japan suggested that the drug had been synthesized from either natural or semi-synthetic ephedrine and not from synthetic ephedrine. Stable isotope ratio analysis is expected to be a useful tool for tracing the origins of seized methamphetamine. It has attracted much interest from precursor control authorities in Japan and the East Asian region and may prove useful in the international control of precursors. PMID:21338016

Makino, Y; Urano, Y; Nagano, T

2005-01-01

202

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

203

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

204

Quantifying precision and accuracy of measurements of dissolved inorganic carbon stable isotopic composition using continuous-flow isotope-ratio mass spectrometry  

PubMed Central

RATIONALE We describe an analytical procedure that allows sample collection and measurement of carbon isotopic composition (?13CV-PDB value) and dissolved inorganic carbon concentration, [DIC], in aqueous samples without further manipulation post field collection. By comparing outputs from two different mass spectrometers, we quantify with the statistical rigour uncertainty associated with the estimation of an unknown measurement. This is rarely undertaken, but it is needed to understand the significance of field data and to interpret quality assurance exercises. METHODS Immediate acidification of field samples during collection in evacuated, pre-acidified vials removed the need for toxic chemicals to inhibit continued bacterial activity that might compromise isotopic and concentration measurements. Aqueous standards mimicked the sample matrix and avoided headspace fractionation corrections. Samples were analysed using continuous-flow isotope-ratio mass spectrometry, but for low DIC concentration the mass spectrometer response could be non-linear. This had to be corrected for. RESULTS Mass spectrometer non-linearity exists. Rather than estimating precision as the repeat analysis of an internal standard, we have adopted inverse linear calibrations to quantify the precision and 95% confidence intervals (CI) of the ?13CDIC values. The response for [DIC] estimation was always linear. For 0.050.5 mM DIC internal standards, however, changes in mass spectrometer linearity resulted in estimations of the precision in the ?13CVPDB value of an unknown ranging from 0.44 to 1.33 (mean values) and a mean 95% CI half-width of 1.13.1. CONCLUSIONS Mass spectrometer non-linearity should be considered in estimating uncertainty in measurement. Similarly, statistically robust estimates of precision and accuracy should also be adopted. Such estimations do not inhibit research advances: our consideration of small-scale spatial variability at two points on a small order river system demonstrates field data ranges larger than the precision and uncertainties. However, without such statistical quantification, exercises such as inter-lab calibrations are less meaningful. PMID:24711275

Waldron, Susan; Marian Scott, E; Vihermaa, Leena E; Newton, Jason

2014-01-01

205

Nicotine, acetanilide and urea multi-level 2H-, 13C- and 15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry.  

PubMed

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 the first organic nitrogen stable isotope reference materials for GC-IRMS that are available with different delta15N values. Comparative delta13C and delta15N on-line EA-IRMS data from 14 volunteering laboratories document the usefulness and reliability of acetanilides and ureas as EA-IRMS reference materials. PMID:19844968

Schimmelmann, Arndt; Albertino, Andrea; Sauer, Peter E; Qi, Haiping; Molinie, Roland; Mesnard, Franois

2009-11-01

206

Nicotine, acetanilide and urea multi-level2H-,13C- and15N-abundance reference materials for continuous-flow isotope ratio mass spectrometry  

USGS Publications Warehouse

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 S values of these reference materials should bracket the isotopic range of samples with unknown S 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 ??13C and ??13N, 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: ??2Hnicotine -162 to -45%o, ??13Cnicotine -30.05 to +7.72%, ?? 15Nnicotine -6.03 to +33.62%; ??15N acetanilide +1-18 to +40.57%; ??13Curea -34.13 to +11.71%, ??15Nurea +0.26 to +40.61% (recommended ?? values refer to calibration with NBS 19, L-SVEC, IAEA-N-1, and IAEA-N-2). Nicotines fill a gap as the first organic nitrogen stable isotope reference materials for GC-IRMS that are available with different ??13N values. Comparative ??13C and ??15N on-line EA-IRMS data from 14 volunteering laboratories document the usefulness and reliability of acetanilides and ureas as EA-IRMS reference materials.

Schimmelmann, A.; Albertino, A.; Sauer, P.E.; Qi, H.; Molinie, R.; Mesnard, F.

2009-01-01

207

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

NASA Technical Reports Server (NTRS)

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).

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

2011-01-01

208

Measurements of 13C/12C methane from anaerobic digesters: comparison of optical spectrometry with continuous-flow isotope ratio mass spectrometry.  

PubMed

Methane production by anaerobic digestion of biomass has recently become more attractive because of its potential for renewable energy production. Analytical tools are needed to study and optimize the ongoing processes in biogas reactors. It is considered that optical methods providing continuous measurements at high temporal resolution of carbon isotope ratios of methane (delta(13)C(CH4)) might be of great help for this purpose. In this study we have tested near-infrared laser optical spectrometry and compared it with conventional continuous-flow isotope ratio mass spectrometry (CF-IRMS) using several methane carbon isotope standards and a large number of biogas samples from batch anaerobic reactors. Results from measurements on these samples were used to determine and compare the precision of the two techniques and to quantify for systematic offsets. With pure standards analytical precision of measurements for delta(13)C(CH4) was found to be in the range of 0.33 and 0.48 per thousand, and 0.09 and 0.27 per thousand for the optical method and CF-IRMS, respectively. Biogas samples showed an average mean deviation of delta(13)C(CH4) of 0.38 per thousand and 0.08 per thousand for the optical method and CF-IRMS, respectively. Although the tested laser optical spectrometer showed a dependence of delta(13)C(CH4) on CH(4) mixing ratio in the range of 500 to 8000 ppm this could be easily corrected. After correction, the delta(13)C(CH4) values usually varied within 0.7 per thousand from those measured by conventional CF-IRMS and thus results from both methods agreed within the given analytical uncertainties. Although the precision of the conventional CF-IRMS is higher than the tested optical system, both instruments were well within the acceptable delta(13)C(CH4) precision required for biogas methane measurements. The advantages of the optical system are its simplicity of operation, speed of analysis, good precision, reduced costs in comparison to IRMS, and the potential for field applications. PMID:20540538

Keppler, Frank; Laukenmann, Stephan; Rinne, Jennifer; Heuwinkel, Hauke; Greule, Markus; Whiticar, Michael; Lelieveld, Jos

2010-07-01

209

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

PubMed

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 (?(13)C, ?(15)N and ?D) of polyethylene pyrolysis compounds. Polyethylene pyrolysis yields triplet peaks of n-alkanes, ?-alkenes and ?,?-alkanedienes. No differences were found for bulk ?(13)C among different polyethylene types. However, conspicuous differences in ?D were evident. It was possible to assign structure ?(13)C and ?D 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 ?D values than saturated chains (alkanes) that were deuterium depleted. In addition, a full isotopic fingerprinting (?(13)C, ?(15)N and ?D) 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. PMID:25725959

Gonzlez-Prez, J A; Jimnez-Morillo, N T; de la Rosa, J M; Almendros, G; Gonzlez-Vila, F J

2015-04-01

210

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

PubMed Central

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

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

2012-01-01

211

Measurement of the isotopic composition of uranium micrometer-size particles by femtosecond laser ablation-inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

In this paper, we will describe and indicate the performance of a new method based on the use of femtosecond laser ablation (fs-LA) coupled to a quadrupole-based inductively coupled plasma mass spectrometer (ICP-QMS) for analyzing the isotopic composition of micrometer-size uranium particles. The fs-LA device was equipped with a high frequency source (till 10 kHz). We applied this method to 1-2 ?m diameter-uranium particles of known isotopic composition and we compared this technique with the two techniques currently used for uranium particle analysis: Secondary Ionization Mass Spectrometry (SIMS) and Fission Track Thermal Ionization Mass Spectrometry (FT-TIMS). By optimizing the experimental conditions, we achieved typical accuracy and reproducibility below 4% on 235U/238U for short transient signals of only 15 s related to 10 to 200 pg of uranium. The detection limit (at the 3 sigma level) was ~ 350 ag for the 235U isotope, meaning that 235U/238U isotope ratios in natural uranium particles of ~ 220 nm diameter can be measured. We also showed that the local contamination resulting from the side deposition of ablation debris at ~ 100 ?m from the ablation crater represented only a small percentage of the initial uranium signal of the ablated particle. Despite the use of single collector ICP-MS, we were able to demonstrate that fs-LA-ICP-MS is a promising alternative technique for determining uranium isotopic composition in particle analysis.

Hubert, Amlie; Claverie, Fanny; Pcheyran, Christophe; Pointurier, Fabien

212

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

213

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

PubMed

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

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

2014-12-01

214

A novel methodological approach for ?(18)O analysis of sugars using gas chromatography-pyrolysis-isotope ratio mass spectrometry.  

PubMed

Although the instrumental coupling of gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) for compound-specific ?(18)O analysis has been commercially available for more than a decade, this method has been hardly applied so far. Here we present the first GC-Py-IRMS ?(18)O results for trimethylsilyl-derivatives of plant sap-relevant sugars and a polyalcohol (glucose, fructose, sucrose, raffinose and pinitol). Particularly, we focus on sucrose, which is assimilated in leaves and which is the most important transport sugar in plants and hence of utmost relevance in plant physiology and paleoclimate studies. Replication measurements of sucrose standards and concentration series indicate that the GC-Py-IRMS ?(18)O measurements are not stable over time and that they are amount (area) dependent. We, therefore, suggest running sample batch replication measurements in alternation with standard concentration series of reference material. This allows for carrying out (i) a drift correction, (ii) a calibration against reference material and (iii) an amount (area) correction. Tests with (18)O-enriched water do not provide any evidence for oxygen isotope exchange reactions affecting sucrose and raffinose. We present the first application of GC-Py-IRMS ?(18)O analysis for sucrose from needle extract (soluble carbohydrate) samples. The obtained ?(18)Osucrose/ Vienna Standard Mean Ocean Water (VSMOW) values are more positive and vary in a wider range (32.1-40.1 ) than the ?(18)Obulk/ VSMOW values (24.6-27.2 ). Furthermore, they are shown to depend on the climate parameters maximum day temperature, relative air humidity and cloud cover. These findings suggest that ?(18)Osucrose of the investigated needles very sensitively reflects the climatically controlled evaporative (18)O enrichment of leaf water and thus highlights the great potential of GC-Py-IRMS ?(18)Osucrose analysis for plant physiology and paleoclimate studies. PMID:24313371

Zech, Michael; Saurer, Matthias; Tuthorn, Mario; Rinne, Katja; Werner, Roland A; Siegwolf, Rolf; Glaser, Bruno; Juchelka, Dieter

2013-01-01

215

Discriminating the endogenous and exogenous urinary estrogens in human by isotopic ratio mass spectrometry and its potential clinical value.  

PubMed

Estrogens were prohibited in the food producing animals by European Union (96/22/EC directive) and added to the Report on Carcinogens in United States since 2002. Due to very low concentration in serum or urine (~pg/mL), the method of control its abuse had not been fully developed. The endogenous estrogens were separated from urines of 18 adult men and women. The exogenous estrogens were chemical reference standards and over the counter preparations. Two patients of dysfunctional uterine bleeding (DUB) administered exogenous estradiol and the urines were collected for 72 h. The urinary estrogens were separated by high-performance liquid chromatography (HPLC) and confirmed. The exogenous and exogenous estrogens were analyzed by gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) to determine the (13)C/(12)C ratio (?(13)C). The ?(13)C values of reference standard of E1, E2, and E3 were -29.360.72, -27.980.35, -27.620.51, respectively. The ?(13)C values of the endogenous E1, E2, and E3 were -21.621.07, -22.140.98, and -21.881.16, with P<0.01 (t-test). Two DUB patients' urinary estradiol ?(13)C values was depleted to -28.020.33 after the administration. The progesterone, 17?-hydroxyprogesterone, pregnanediol, as well as desogestrel and ethinylestradiol from contraceptives were also determined. Stable carbon isotope analysis can distinguish the endogenous and exogenous urinary estrogen in human. PMID:23228444

Yang, Sheng; Zhang, Dapeng; Xu, Youxuan; Wang, Xiaobing; Liu, Xin; Wang, Shan; Wang, Jingzhu; Wu, Moutian; He, Zhenwen; Zhao, Jian; Yuan, Hong

2013-02-01

216

Histone H4 acetylation dynamics determined by stable isotope labeling with amino acids in cell culture and mass spectrometry.  

PubMed

This paper describes an integrated approach that couples stable isotope labeling with amino acids in cell culture to acetic acid-urea polyacrylamide gel electrophoresis (AU-PAGE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the quantitation and dynamics of histone H4 acetylation. The 697 acute lymphoblastic cell lines were grown in regular medium and in medium in which lysine was substituted with deuterium-labeled lysine. Histone deacetylase (HDAC) activity was inhibited by addition of the HDAC inhibitor depsipeptide to the culture medium for different exposure times. Histones were extracted from cells pooled from unlabeled, untreated cells and from labeled, treated cells, followed by AU-PAGE separation. Gel bands corresponding to different acetylation states of H4 were excised, in-gel digested with trypsin, and analyzed by MALDI-TOF MS. Detailed information was obtained for both the change of histone H4 acetylation specific to the N terminus and the global transformation of H4 from one acetylation state to another following treatment with the HDAC inhibitor depsipeptide. The kinetics of H4 acetylation was also assessed. This study provides a quantitative basis for developing potential therapies by using epigenetic regulation and the developed methodology can be applied to quantitation of change for other histone modifications induced by external stimuli. PMID:17286952

Su, Xiaodan; Zhang, Liwen; Lucas, David M; Davis, Melanie E; Knapp, Amy R; Green-Church, Kari B; Marcucci, Guido; Parthun, Mark R; Byrd, John C; Freitas, Michael A

2007-04-01

217

Tracing Nitrogenous Disinfection Byproducts after Medium Pressure UV Water Treatment by Stable Isotope Labeling and High Resolution Mass Spectrometry.  

PubMed

Advanced oxidation processes are important barriers for organic micropollutants (e.g., pharmaceuticals, pesticides) in (drinking) water treatment. Studies indicate that medium pressure (MP) UV/H2O2 treatment leads to a positive response in Ames mutagenicity tests, which is then removed after granulated activated carbon (GAC) filtration. The formed potentially mutagenic substances were hitherto not identified and may result from the reaction of photolysis products of nitrate with (photolysis products of) natural organic material (NOM). In this study we present an innovative approach to trace the formation of disinfection byproducts (DBPs) of MP UV water treatment, based on stable isotope labeled nitrate combined with high resolution mass spectrometry. It was shown that after MP UV treatment of artificial water containing NOM and nitrate, multiple nitrogen containing substances were formed. In total 84 N-DBPs were detected at individual concentrations between 1 to 135 ng/L bentazon-d6 equivalents, with a summed concentration of 1.2 ?g/L bentazon-d6 equivalents. The chemical structures of three byproducts were confirmed. Screening for the 84 N-DBPs in water samples from a full-scale drinking water treatment plant based on MP UV/H2O2 treatment showed that 22 of the N-DBPs found in artificial water were also detected in real water samples. PMID:25760315

Kolkman, Annemieke; Martijn, Bram J; Vughs, Dennis; Baken, Kirsten A; van Wezel, Annemarie P

2015-04-01

218

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

PubMed

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

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

2006-03-01

219

Fourier transform mass spectrometry.  

PubMed

This article provides an introduction to Fourier transform-based mass spectrometry. The key performance characteristics of Fourier transform-based mass spectrometry, mass accuracy and resolution, are presented in the view of how they impact the interpretation of measurements in proteomic applications. The theory and principles of operation of two types of mass analyzer, Fourier transform ion cyclotron resonance and Orbitrap, are described. Major benefits as well as limitations of Fourier transform-based mass spectrometry technology are discussed in the context of practical sample analysis, and illustrated with examples included as figures in this text and in the accompanying slide set. Comparisons highlighting the performance differences between the two mass analyzers are made where deemed useful in assisting the user with choosing the most appropriate technology for an application. Recent developments of these high-performing mass spectrometers are mentioned to provide a future outlook. PMID:21742802

Scigelova, Michaela; Hornshaw, Martin; Giannakopulos, Anastassios; Makarov, Alexander

2011-07-01

220

Stable isotope imaging of biological samples with high resolution secondary ion mass spectrometry and complementary techniques  

PubMed Central

Stable isotopes are ideal labels for studying biological processes because they have little or no effect on the biochemical properties of target molecules. The NanoSIMS is a tool that can image the distribution of stable isotope labels with up to 50 nm spatial resolution and with good quantitation. This combination of features has enabled several groups to undertake significant experiments on biological problems in the last decade. Combining the NanoSIMS with other imaging techniques also enables us to obtain not only chemical information but also the structural information needed to understand biological processes. This article describes the methodologies that we have developed to correlate atomic force microscopy and backscattered electron imaging with NanoSIMS experiments to illustrate the imaging of stable isotopes at molecular, cellular, and tissue scales. Our studies make it possible to address 3 biological problems: (1) the interaction of antimicrobial peptides with membranes; (2) glutamine metabolism in cancer cells; and (3) lipoprotein interactions in different tissues. PMID:24556558

Jiang, H.; Favaro, E.; Goulbourne, C. N.; Rakowska, P. D.; Hughes, G. M.; Ryadnov, M. G.; Fong, L.G.; Young, S. G.; Ferguson, D. J. P.; Harris, A. L.; Grovenor, C. R. M.

2014-01-01

221

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

PubMed

A new high-performance thin-layer chromatography/electrospray ionization mass spectrometry (HPTLC/ESI-MS) method for the quantification of caffeine in pharmaceutical and energy drink samples was developed using stable isotope dilution analysis (SIDA). After sample preparation, samples and caffeine standard were applied on silica gel 60 F254 HPTLC plates and over-spotted with caffeine-d3 used for correction of the plunger positioning. After chromatography, densitometric detection was performed by UV absorption at 274 nm. The bands were then eluted by means of a plunger-based extractor into the ESI interface of a single-quadrupole mass spectrometer. For quantification by MS the [M+H]+ ions of caffeine and caffeine-d3 were recorded in the positive ion single ion monitoring (SIM) mode at m/z 195 and 198, respectively. The calibration showed a linear regression with a determination coefficient (R2) of 0.9998. The repeatability (RSD, n=6) in matrix wasmass spectrometry. PMID:17340560

Aranda, Mario; Morlock, Gertrud

2007-01-01

222

Orbitrap mass spectrometry.  

PubMed

Orbitrap is the newest addition to the family of high-resolution mass spectrometry analyzers. With its revolutionarily new, miniature design, Orbitrap combines high speed with excellent quantification properties, ranking favorably in many analytical applications. PMID:23590404

Zubarev, Roman A; Makarov, Alexander

2013-06-01

223

Protein Stable Isotope Fingerprinting (P-SIF): Multidimensional Protein Chromatography Coupled to Stable Isotope-Ratio Mass Spectrometry  

NASA Astrophysics Data System (ADS)

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 ?13C 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.

Pearson, A.; Bovee, R. J.; Mohr, W.; Tang, T.

2012-12-01

224

Fourier Transform Mass Spectrometry.  

ERIC Educational Resources Information Center

Discusses the nature of Fourier transform mass spectrometry and its unique combination of high mass resolution, high upper mass limit, and multichannel advantage. Examines its operation, capabilities and limitations, applications (ion storage, ion manipulation, ion chemistry), and future applications and developments. (JN)

Gross, Michael L.; Rempel, Don L.

1984-01-01

225

Stable isotope gas chromatography-tandem mass spectrometry determination of aminoethylcysteine ketimine decarboxylated dimer in biological samples.  

PubMed

Aminoethylcysteine ketimine decarboxylated dimer (AECK-DD; systematic name: 1,2-3,4-5,6-7,8-octahydro-1,8a-diaza-4,6-dithiafluoren-9(8aH)-one) is a previously described metabolite of cysteamine that has been reported to be present in mammalian brain, urine, plasma, and cells in culture and vegetables and to possess potent antioxidative properties. Here, we describe a stable isotope gas chromatography-tandem mass spectrometry (GC-MS/MS) method for specific and sensitive determination of AECK-DD in biological samples. (13)C(2)-labeled AECK-DD was synthesized and used as the internal standard. Derivatization was carried out by N-pentafluorobenzylation with pentafluorobenzyl bromide in acetonitrile. Quantification was performed by selected reaction monitoring of the mass transitions m/z 328 to 268 for AECK-DD and m/z 330 to 270 for [(13)C(2)]AECK-DD in the electron capture negative ion chemical ionization mode. The procedure was systematically validated for human plasma and urine samples. AECK-DD was not detectable in human plasma above approximately 4nM but was present in urine samples of healthy humans at a maximal concentration of 46nM. AECK-DD was detectable in rat brain at very low levels of approximately 8pmol/g wet weight. Higher levels of AECK-DD were detected in mouse brain (?1nmol/g wet weight). Among nine dietary vegetables evaluated, only shallots were found to contain trace amounts of AECK-DD (?6.8pmol/g fresh tissue). PMID:22858756

Tsikas, Dimitrios; Evans, Christopher E; Denton, Travis T; Mitschke, Anja; Gutzki, Frank-Mathias; Pinto, John T; Khomenko, Tetyana; Szabo, Sandor; Cooper, Arthur J L

2012-11-01

226

Mass fractionation processes of transition metal isotopes  

Microsoft Academic Search

Recent advances in mass spectrometry make it possible to utilise isotope variations of transition metals to address some important issues in solar system and biological sciences. Realisation of the potential offered by these new isotope systems however requires an adequate understanding of the factors controlling their isotope fractionation. Here we show the results of a broadly based study on copper

X. K. Zhu; Y. Guo; R. J. P. Williams; R. K. ONions; A. Matthews; N. S. Belshaw; G. W. Canters; E. C. de Waal; U. Weser; B. K. Burgess; B. Salvato

2002-01-01

227

Comparison of secondary ion mass spectrometry and micromilling/continuous flow isotope ratio mass spectrometry techniques used to acquire intra-otolith delta18O values of wild Atlantic salmon (Salmo salar).  

PubMed

The chemical signals in the sequential layers of fish otoliths have the potential to provide fisheries biologists with temporal and spatial details of migration which are difficult to obtain without expensive tracking methods. Signal resolution depends, however, on the extraction technique used. We compared the use of mechanical micromilling and continuous flow isotope ratio mass spectrometry (CF-IRMS) methods with secondary ion mass spectrometry (SIMS) to obtain delta(18)O profiles from otoliths of wild Atlantic salmon (Salmo salar) and used these to corroborate the time of freshwater emigration of the juvenile with macroscopic patterns within the otolith. Both techniques showed the transition occurring at the same visible feature on the otolith, allowing future analyses to easily identify the juvenile (freshwater) versus adult (marine) life-stages. However, SIMS showed a rapid and abrupt transition whereas micromilling provided a less distinct signal. The number of samples that could be obtained per unit area sampled using SIMS was 2 to 3 times greater than that when using micromilling/CF-IRMS although the delta(18)O values and analytical precisions (approximately 0.2 per thousand) of the two methods were comparable. In addition, SIMS delta(18)O results were used to compare otolith aragonite values with predicted values calculated using various isotope fractionation equations. PMID:20740522

Hanson, N N; Wurster, C M; Todd, C D

2010-09-15

228

Nevan Krogan: Mass Spectrometry  

NSDL National Science Digital Library

This lecture from the iBioSeminars project, presented by Nevan Krogan of the Department of Cellular and Molecular Pharmacology at UC-San Francisco, covers mass spectrometry and its application to molecular biology. Mass spectrometry is a powerful tool for elucidating the elemental composition of a sample or molecule. More recently, it has been used to characterize biological material, in particular proteins and protein complexes, in a variety of organisms. This lecture will review the underlying principles of how a mass spectrometer works, discuss up to date instrumentation that is presently being used in the biological research setting and provide specific examples of how mass spectrometry is being used to reveal functional insight into different biological systems. The video runs 27:36 and can be downloaded in a number of formats: QuickTime, MP4, M4V, and PPT. The video can also be streamed through YouTube or iTunes U.

Krogan, Nevan

229

Mass Spectrometry for the Masses  

ERIC Educational Resources Information Center

A simple, qualitative experiment is developed for implementation, where the gas chromatography-mass spectrometry (GC-MS) plays an important role, into the laboratory curriculum of a chemistry course designed for nonscience majors. This laboratory experiment is well suited for the students as it helps them to determine the validity of their

Persinger, Jared D.; Hoops, Geoffrey, C.; Samide, Michael J.

2004-01-01

230

Mass Spectrometry Primer  

NSDL National Science Digital Library

This website developed by Waters Corporation provides a brief primer on mass spectrometry which includes information on instrumentation, a discussion of mass accuracy, resolution, and LC-MS. As such the site should be a valuable resource for both students and faculty.

231

Comprehensive and highly sensitive urinary steroid hormone profiling method based on stable isotope-labeling liquid chromatography-mass spectrometry.  

PubMed

Steroid hormones are crucial substances that mediate a wide range of vital physiological functions of the body. Determination of the levels of steroid hormones plays an important role in understanding the mechanism of the steroid hormone-related diseases. In this study, we present a novel targeted metabolic profiling method based on the introduction of an easily protonated stable isotope tag to a hydroxyl-containing steroid hormone with a synthesized derivatization reagent, deuterium 4-(dimethylamino)-benzoic acid (d(4)-DMBA), and liquid chromatography-mass spectrometry (LC-MS). Different from other reported derivatization reagents that have been used to enhance the sensitivities for estrogens or androgens, our method is comprehensive with the capability of covering hydroxyl-containing androgens, estrogens, corticoids, and progestogens. Furthermore, the nonderivatized steroid hormones (e.g., 17?-hydroxyprogesterone, progesterone, and androstenedione) were not destroyed during the derivatization process, and their levels could still be obtained in one LC-MS run. We were able to detect 24 steroid hormones at subng/mL levels (the lower limit of detection could reach 5 pg/mL for estrone and 16?-hydroxy estrone, which is equivalent to 0.1 pg on column) with maximum sensitivity enhancement factors of more than 10(3)- to 10(4)-fold after derivatization. The method was successfully applied to the measurement of free (unconjugated) steroid hormones in urine samples of males, females, and pregnant women. Because the significant role the steroid hormone pathway plays in humans, a comprehensive, sensitive, specific, and accurate method for profiling the steroid hormone metabolome shall offer new insights into hormone-related diseases. PMID:23110480

Dai, Weidong; Huang, Qiang; Yin, Peiyuan; Li, Jia; Zhou, Jia; Kong, Hongwei; Zhao, Chunxia; Lu, Xin; Xu, Guowang

2012-12-01

232

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

PubMed

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

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

2013-09-01

233

Resonance ionization mass spectrometry (RIMS) for the measurement of multi-element concentrations and Re-OS isotopes in crustal rocks  

SciTech Connect

Resonance ionization mass spectrometry (RIMS) has been demonstrated to be a viable means of selectively ionizing a variety of elements for isotope ratio measurement with better than 1% precision. With RIMS atomic ions are produced by resonance ionization using a tunable dye laser, from a cloud of neutral atoms formed in a modified conventional thermal ionization filament source. At least 47 elements are amenable to resonance ionization using a simple two-photon process with a Nd:YAG pumped dye laser system. Many of these elements are of geologic interest. The advantages of this system over conventional mass spectrometry include the elimination of isobaric interferences, high sensitivity and the ability to ionize many elements not amenable to thermal ionization. Current research centers on the development of RIMS to precisely measure by isotope dilution a number of elements of interest to geochemists including Hf, Zr, Re, Os, W, Mo and the rare earth elements using minimal chemical separation procedures. Resonance ionization of these elements has been demonstrated. Techniques are being developed to utilize RIMS in the measurement of Os isotope ratios in crustal rocks, requiring picogram sensitivity. Isotope ratio measurement of nanogram quantities of Os have already been achieved.

Walker, R.J.; Moore, L.J.

1985-01-01

234

Accelerator mass spectrometry in pharmaceutical research and development--a new ultrasensitive analytical method for isotope measurement.  

PubMed

Accelerator mass spectrometry (AMS) permits the measurement of elemental isotopes at the individual atom level. The main application of AMS in drug discovery and development will be in the analysis of 14-carbon (14C). The principle behind AMS is the separation of individual positively charged atoms through mass, charge and momentum differences. In order to obtain the high-energy charge state required for separation, negative atoms are accelerated through a high voltage field (up to 10 million volts) generated by a tandem Van de Graaff accelerator. In the middle of the accelerator, the outer valency electrons are stripped from the atom and the resulting charged species are separated and counted. For 14C, AMS counts the number of individual atoms rather than measuring radioactive decays. The result is that AMS is up to one million times more sensitive than decay counting. Radioactivity levels as low 0.0001 dpm can be detected using AMS. The exquisite sensitivity of AMS analysis means that much lower amounts of 14C can be used than for conventional counting methods. This makes it easier to use 14C for in vitro, preclinical and clinical research programmes. As 14C poses both a biological and environmental hazard, AMS permits much lower doses to be used. Human drug mass balance studies have been conducted with doses of 50 nanoCuries and below. Radioactive HPLC metabolite profiles of plasma extracts from subjects given nanoCurie doses of 14C-labelled drug have been obtained by injecting as little as 0.25 dpm onto an HPLC column. In studies of biologics, biosynthetically 14C-labelled recombinant protein has been produced with a specific radioactivity sufficient to conduct human clinical studies with AMS analysis. For one human recombinant protein an increase in sensitivity of 2,000-fold over ELISA was obtained with AMS measurement. AMS is an enabling technology that should prove of value in increasing human and environmental safety as well as allowing new research directions to be followed. PMID:11465084

Garner, R C

2000-09-01

235

High-sensitivity mass spectrometry with a tandem accelerator  

SciTech Connect

The characteristic features of accelerator mass spectrometry are discussed. A short overview is given of the current status of mass spectrometry with high-energy (MeV/nucleon) heavy-ion accelerators. Emphasis is placed on studies with tandem accelerators and on future mass spectrometry of heavier isotopes with the new generation of higher-voltage tandems.

Henning, W.

1983-01-01

236

Understanding Chemistry: Mass Spectrometry  

NSDL National Science Digital Library

This website, which is part of a larger project "ChemGuide" provides a nice introduction to mass spectrometry that is suitable for use by introductory analytical chemistry students. Content includes an introduction to the instrumentation, explanation of fragmentation and how it can be used to identify compound structure, the origin of the M+ and (M+1)+ peaks. Each section is succinct, well written and provides a simple example. As such the site should be useful to faculty introducing mass spectrometry in the analytical classroom and to chemistry students.

Clark, Jim

237

Purification and gas chromatography-combustion-isotope ratio mass spectrometry of aroma compounds from green tea products and comparison to bulk analysis.  

PubMed

A method for carbon isotope ratio (?(13)C) analysis was developed for compound-specific isotope analysis of tea volatiles, and the values were compared with the ?(13)C value from bulk isotope analyses. The ?(13)C value of 2-phenylethanol liberated via enzymatic hydrolysis of the 2-phenylethyl ?-primeveroside standard was examined first. Isotope fractionations for 2-phenylethyl ?-primeveroside from preparative high-performance liquid chromatography (HPLC) were also analyzed. The enzymatic treatment and the preparative HPLC process did not cause carbon isotope fractionations, substantiating the strategies available for ?(13)C analysis of volatile compounds. On the basis of the gas chromatography-combustion-isotope ratio mass spectrometry data from 2-phenylethanol, it was possible to derive the conditions for enzyme treatment and preparative HPLC of the glycoconjugates of 2-phenylethanol, (Z)-3-hexenol, and benzyl alcohol isolated from green tea leaves. Larger variations in ?(13)C were found for individual volatile compounds compared with bulk analytical data from the leaves, indicating the potential to utilize this strategy in assigning the geographical origin of green tea. PMID:24206364

Murata, Ariaki; Engelhardt, Ulrich H; Fleischmann, Peter; Yamada, Keita; Yoshida, Naohiro; Juchelka, Dieter; Hilkert, Andreas; Ohnishi, Toshiyuki; Watanabe, Naoharu; Winterhalter, Peter

2013-11-27

238

Precise determination of 235 U\\/ 238 U isotope ratio in soil samples by using thermal ionisation mass spectrometry  

Microsoft Academic Search

A rapid method based on extraction chromatography was developed for the separation of uranium from soil samples for TIMS. The isotope ratios were measured on three standards using a VG 54-30 thermal ionisation mass spectrometer in static mode with Faraday cup and Daly ion counting system. The use of a WARP (Wide Aperture Retardation Potential) energy filter improves abundance sensitivity

S. K. Sahoo; H. Isobe; T. Sato; K. Fujimoto; Y. Nakamura

2002-01-01

239

Determination of the 87Sr/86Sr isotope ratio in USGS silicate reference materials by multi-collector ICP-mass spectrometry  

NASA Astrophysics Data System (ADS)

Multi-collector ICP-mass spectrometry (MC-ICP-MS) was used for 87Sr/86Sr isotope ratio determination in newly introduced silicate reference materials from the US Geological Survey (USGS): granite G-3, andesite AGV-2, and basalt BCR-2. Next to the SrCO3 isotopic standard NIST SRM 987, also analogous USGS reference materials from the previous generation, and for which reference 87Sr/86Sr data obtained by TIMS are available, were analysed for validation purposes. Sample preparation consisted of acid digestion and subsequent isolation of Sr by means of a dedicated and commercially available crown ether-based resin. The Sr fractions thus obtained were analysed via MC-ICP-MS whereby mass discrimination was corrected for internally, while the isobaric interference at a mass-to-charge ratio of 86 caused by Kr impurities in the Ar gas was mathematically corrected for by using the signal for a Kr isotope free from spectral overlap. Finally, also the effect of the small amount of Rb that may still be present in the Sr fraction was corrected for mathematically on the basis of the signal intensity for 85Rb. The MC-ICP-MS results for G-2, AGV-1 and BCR-1 showed an excellent agreement with the corresponding TIMS values (<0.003% bias in all cases), such that it can be assumed that also the 87Sr/86Sr isotope ratio results obtained for the new reference materials are reliable.

Balcaen, Lieve; Schrijver, Isabel De; Moens, Luc; Vanhaecke, Frank

2005-04-01

240

Determination of cellular redox status by stable isotope dilution liquid chromatography/mass spectrometry analysis of glutathione and glutathione disulfide.  

PubMed

Oxidation of glutathione (GSH) to glutathione disulfide (GSSG) occurs during cellular oxidative stress. The redox potential of the 2GSH/GSSG couple, which is determined by the Nernst equation, provides a means to assess cellular redox status. It is difficult to accurately quantify GSH and GSSG due to the ease with which GSH is oxidized to GSSG during sample preparation. To overcome this problem, a stable isotope dilution liquid chromatography/multiple reaction monitoring mass spectrometry (LC/MRM-MS) method has been developed using 4-fluoro-7-sulfamoylbenzofurazan (ABD-F) derivatization. ABD-F derivatization of the GSH thiol group was rapid, quantitative, and occurred at room temperature. The LC/MRM-MS method, which requires no sample clean-up, was validated within the calibration ranges of 5 to 400 nmol/mL in cell lysates for GSH and 0.5 to 40 nmol/mL in cell lysates for GSSG. Calibration curves prepared by adding known concentrations of GSH and GSSG to cell lysates were parallel to the standard curve prepared in buffers. GSH and GSSG concentrations were determined in two monocyte/macrophage RAW 267.4 cell lines with or without 15-LOX-1 expression (R15LO and RMock cells, respectively) after treatment with the bifunctional electrophile 4-oxo-2(E)-nonenal (ONE). R15LO cells synthesized much higher concentrations of the lipid hydroperoxide, 15(S)-hydroperoxyeicosatetraenoic acid (15-HPETE), which undergoes homolytic decomposition to ONE. GSH was depleted by ONE treatment in both RMock and R15LO cells, leading to significant increases in their redox potentials. However, R15LO cells had higher GSH concentrations (most likely through increased GSH biosynthesis) and had increased resistance to ONE-mediated GSH depletion than RMock cells. Consequently, R15LO cells had lower reduction potentials at all concentrations of ONE. GSSG concentrations were higher in R15LO cells after ONE treatment when compared with the ONE-treated RMock cells. This suggests that increased expression of 15(S)-HPETE modulates the activity of cellular GSH reductases or the transporters involved in removal of GSSG. PMID:18215009

Zhu, Peijuan; Oe, Tomoyuki; Blair, Ian A

2008-01-01

241

VMSL: Virtual Mass Spectrometry Laboratory  

NSDL National Science Digital Library

This site presents a series of case studies that can be explored using modern mass spectrometry methods. The problem-solving nature of the site provides students a virtual laboratory experience that can supplement access to mass spectrometry instrumentation.

2011-07-05

242

Mass Spectrometry and Glycomics  

PubMed Central

Abstract Glycosylation defines the adhesive properties of animal cell surfaces and the surrounding extracellular environments. Because cells respond to stimuli by altering glycan expression, glycan structures vary according to spatial location in tissue and temporal factors. These dynamic structural expression patterns, combined with the essential roles glycans play in physiology, drive the need for analytical methods for glycoconjugates. In addition, recombinant glycoprotein drug products represent a multibillion dollar market. Effective analytical methods are needed to speed the identification of new targets and the development of industrial glycoprotein products, both new and biosimilar. Mass spectrometry is an enabling technology in glycomics. This review summarizes mass spectrometry of glycoconjugate glycans. The intent is to summarize appropriate methods for glycans given their chemical properties as distinct from those of proteins, lipids, and small molecule metabolites. Special attention is given to the uses of mass spectral profiling for glycomics with respect to the N-linked, O-linked, ganglioside, and glycosaminoglycan compound classes. Next, the uses of tandem mass spectrometry of glycans are summarized. The review finishes with an update on mass spectral glycoproteomics. PMID:20443730

2010-01-01

243

New commercial method for the enzymatic determination of creatinine in serum and urine evaluated: Comparison with a kinetic Jaffe method and isotope dilution-mass spectrometry  

SciTech Connect

We evaluated a new, simple, enzymatic kinetic method from Wako Chemicals GmbH in comparison with a kinetic Jaffe method by using isotope dilution-mass spectrometry (ID-MS) as a reference method. An ID-MS-calibrated serum standard was used. Both the enzymatic and the Jaffe method correlated well with ID-MS, except for sera with high concentrations of bilirubin. Ethyl acetoacetate, acetone, and glucose in serum interfered somewhat with the Jaffe method but not with the enzymatic method. We conclude that the present enzymatic method has merit as compared with a Jaffe method for routine work, but is more expensive.

Lindbaeck, B.B.; Bergman, A.

1989-05-01

244

Determination of the exogenous character of testosterone in bovine urine by gas chromatography-combustion-isotope ratio mass spectrometry.  

PubMed

A new approach was developed in order to control testosterone abuse in animal production. A gas chromatographic-combustion-isotope ratio mass spectrometric (GC-C-IRMS) method was used to distinguish the exogenous character from the endogenous character of the main metabolites of testosterone (epitestosterone and etiocholanolone) in cattle urine. This method is based on a comparison between the carbon isotope ratio (13C/12C) of testosterone metabolites and those of testosterone endogenous precursors. After urinary steroid purification, extracts were acetylated with acetic anhydride and injected into the GC-C-IRMS system. In order to validate the method, testosterone enanthate was administered to a 4 year old cow. The 13C/12C isotope ratios of testosterone exogenous metabolites appeared to be significantly different to the 13C/12C precursor ratios and were detected until 3 weeks after the anabolic administration. These preliminary results appear to be promising for the difficult control of natural hormones in livestock. PMID:10435310

Ferchaud, V; Le Bizec, B; Monteau, F; Andr, F

1998-12-01

245

Mass Spectrometry and Protein Analysis  

Microsoft Academic Search

Mass spectrometry is a central analytical technique for protein research and for the study of biomolecules in general. Driven by the need to identify, characterize, and quantify proteins at ever increasing sensitivity and in ever more complex samples, a wide range of new mass spectrometry-based analytical platforms and experimental strategies have emerged. Here we review recent advances in mass spectrometry

Bruno Domon; Ruedi Aebersold

2006-01-01

246

Isotope-ratio measurements of lead in NIST standard reference materials by multiple-collector inductively coupled plasma mass spectrometry.  

PubMed

The capability of a second-generation Nu Instruments multiple collector inductively coupled plasma mass spectrometer (MC-ICP-MS) has been evaluated for precise and accurate isotope-ratio determinations of lead. Essentially the mass spectrometer is a double-focusing instrument of Nier-Johnson analyzer geometry equipped with a newly designed variable-dispersion ion optical device, enabling the measured ion beams to be focused into a fixed array of Faraday collectors and an ion-counting assembly. NIST SRM Pb 981, 982, and 983 isotopic standards were used. Addition of thallium to the lead standards and subsequent simultaneous measurement of the thallium and lead isotopes enabled correction for mass discrimination, by use of the exponential correction law and 205Tl/203Tl = 2.3875. Six measurements of SRM Pb-982 furnished the results 206Pb/204Pb = 36.7326(68), 207Pb/204Pb = 17.1543(30), 208Pb/204Pb = 36.7249(69), 207Pb/206Pb = 0.46700(1), and 208Pb/206Pb = 0.99979(2); the NIST-certified values were 36.738(37), 17.159(25), 36.744(50), 0.46707(20), and 1.00016(36), respectively. Direct isotope lead analysis in silicates can be performed without any chemical separation. NIST SRM 610 glass was dissolved and introduced into the MC-ICP-MS by means of a micro concentric nebulizer. The ratios observed were in excellent agreement with previously reported data obtained by TIMS and laser ablation MC-ICP-MS, despite the high Ca/Pb concentration ratio (200/1) and the presence of many other elements at levels comparable with that of lead. Approximately 0.2 microg lead are sufficient for isotope analysis with ratio uncertainties between 240 and 530 ppm. PMID:11496996

Platzner, I; Ehrlich, S; Halicz, L

2001-07-01

247

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

PubMed

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

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

2015-02-01

248

Standard test method for isotopic analysis of hydrolyzed uranium hexafluoride and uranyl nitrate solutions by thermal ionization mass spectrometry  

E-print Network

1.1 This method applies to the determination of isotopic composition in hydrolyzed nuclear grade uranium hexafluoride. It covers isotopic abundance of 235U between 0.1 and 5.0 % mass fraction, abundance of 234U between 0.0055 and 0.05 % mass fraction, and abundance of 236U between 0.0003 and 0.5 % mass fraction. This test method may be applicable to other isotopic abundance providing that corresponding standards are available. 1.2 This test method can apply to uranyl nitrate solutions. This can be achieved either by transforming the uranyl nitrate solution to a uranyl fluoride solution prior to the deposition on the filaments or directly by depositing the uranyl nitrate solution on the filaments. In the latter case, a calibration with uranyl nitrate standards must be performed. 1.3 This test method can also apply to other nuclear grade matrices (for example, uranium oxides) by providing a chemical transformation to uranyl fluoride or uranyl nitrate solution. 1.4 This standard does not purport to address al...

American Society for Testing and Materials. Philadelphia

2005-01-01

249

Multidimensional enantio gas chromtography/mass spectrometry and gas chromatography-combustion-isotopic ratio mass spectrometry for the authenticity assessment of lime essential oils (C. aurantifolia Swingle and C. latifolia Tanaka).  

PubMed

This article focuses on the genuineness assessment of Lime oils (Citrus aurantifolia Swingle and C. latifolia Tanaka), by Multi Dimensional Gas Chromatography (MDGC) to determine the enantiomeric distribution of ?-thujene, camphene, ?-pinene, sabinene, ?-phellandrene, ?-phellandrene, limonene, linalool, terpinen-4-ol, ?-terpineol and by gas chromatography-combustion isotope ratio mass spectrometry (GC-C-IRMS) to determine the isotopic ratios of ?-pinene, ?-pinene, limonene, ?-terpineol, neral, geranial, ?-caryophyllene, trans-?-bergamotene, germacrene B. To the author's knowledge this is the first attempt to assess the authenticity and differentiate Persian Lime from Key lime oils by GC-C-IRMS. The results of the two analytical approaches were compared. The simultaneous use of the two techniques provides more reliable capability to detect adulteration in Citrus essential oils. In fact, in some circumstance only one of the two techniques allows to discriminate adulterated or contaminated oils. In cases where only small anomalies are detected by the two techniques due to subtle adulterations, their synergic use allows to express judgments. The advantage of both techniques is the low number of components the analyst must evaluate, reducing the complexity of the data necessary to deal with. Moreover, the conventional analytical approach based on the evaluation of the whole volatile fraction can fail to reveal the quality of the oils, if the adulteration is extremely subtle. PMID:22088669

Bonaccorsi, Ivana; Sciarrone, Danilo; Schipilliti, Luisa; Dugo, Paola; Mondello, Luigi; Dugo, Giovanni

2012-02-24

250

Determination of 2H/1H and 13C/12C isotope ratios of (E)-methyl cinnamate from different sources using isotope ratio mass spectrometry.  

PubMed

For the authenticity assessment of (E)-methyl cinnamate from different origins, combustion/pyrolysis-isotope ratio mass spectrometry (C/P-IRMS) was used by an elemental analyzer (EA) and on-line capillary gas chromatography coupling (HRGC-C/P-IRMS). For that reason, (E)-methyl cinnamate self-prepared from synthetic, natural, and semisynthetic educts was analyzed in comparison to the commercial synthetic and natural ester. In addition, (E)-methyl cinnamate from basil extract and a number of commercial natural aromas was investigated. The data of self-synthesized synthetic (E)-methyl cinnamate, i.e., delta(13)C(V)(-)(PDB) = -33.8 per thousand and delta(2)H(V)(-)(SMOW) = +349 per thousand, corresponded with that found for the commercial synthetic samples (-29.5 to -31.4 per thousand and +328 to +360 per thousand for delta(13)C(V)(-)(PDB) and delta(2)H(V)(-)(SMOW), respectively). The ester produced from natural educts by acid as well as Candida antarctica catalysis revealed delta(13)C(V)(-)(PDB) = -25.6 and -30.1 per thousand as well as delta(2)H(V)(-)(SMOW) = -162 and -169 per thousand, respectively. Acid-catalyzed semisynthetic products differed in their delta(13)C(V)(-)(PDB) and delta(2)H(V)(-)(SMOW) values depending on the origin of their educts. For the ester from synthetic methanol and natural cinnamic acid, -27.3 and -126 per thousand were determined for delta(13)C(V)(-)(PDB) and delta(2)H(V)(-)(SMOW), respectively, whereas for the ester produced from natural methanol and synthetic acid delta(13)C(V)(-)(PDB) = -30.6 per thousand and delta(2)H(V)(-)(SMOW) = +287 per thousand were found. Basil extract showed -28.9 and -133 per thousand for delta(13)C(V)(-)(PDB) and delta(2)H(V)(-)(SMOW), respectively. Commercial aromas declared to be natural revealed delta(13)C(V)(-)(PDB) and delta(2)H(V)(-)(SMOW) data ranging from -25.7 to -28.5 per thousand as well as -85 to -191 per thousand, respectively, indicating, in part, incorrect declaration. PMID:15137854

Fink, Kathrin; Richling, Elke; Heckel, Frank; Schreier, Peter

2004-05-19

251

Using Gas Chromatography/Isotope Ratio Mass Spectrometry to Determine the Fractionation Factor for H2 Production by Hydrogenases  

SciTech Connect

Hydrogenases catalyze the reversible formation of H2, and they are key enzymes in the biological cycling of H2. H isotopes should be a very useful tool in quantifying proton trafficking in biological H2 production processes, but there are several obstacles that have thus far limited the use of this tool. In this manuscript, we describe a new method that overcomes some of these barriers and is specifically designed to measure isotopic fractionation during enzyme-catalyzed H2 evolution. A key feature of this technique is that purified hydrogenases are employed, allowing precise control over the reaction conditions and therefore a high level of precision. A custom-designed high-throughput gas chromatography-isotope ratio mass spectrometer is employed to measure the isotope ratio of the H2. Using this method, we determined that the fractionation factor of H2 production by the [NiFe]-hydrogenase from Desulfivibrio fructosovran is 0.27. This result indicates that, as expected, protons are highly favored over deuterons during H2 evolution. Potential applications of this new method are discussed.

Yang, Hui; Ghandi, H.; Shi, Liang; Kreuzer, Helen W.; Ostrom, Nathaniel; Hegg, Eric L.

2012-01-15

252

Neuroscience and Accelerator Mass Spectrometry  

SciTech Connect

Accelerator mass spectrometry (AMS) is a mass spectrometric method for quantifying rare isotopes. It has had great impact in geochronology and archaeology and is now being applied in biomedicine. AMS measures radioisotopes such as {sup 3}H, {sup 14}C, {sup 26}Al, {sup 36}Cl and {sup 41}Ca, with zepto- or attomole sensitivity and high precision and throughput, enabling safe human pharmacokinetic studies involving: microgram doses, agents having low bioavailability, or toxicology studies where administered doses must be kept low (<1 {micro}g/kg). It is used to study long-term pharmacokinetics, to identify biomolecular interactions, to determine chronic and low-dose effects or molecular targets of neurotoxic substances, to quantify transport across the blood-brain barrier and to resolve molecular turnover rates in the human brain on the timescale of decades. We will here review how AMS is applied in neurotoxicology and neuroscience.

Palmblad, M N; Buchholz, B A; Hillegonds, D J; Vogel, J S

2004-08-02

253

Isotope pattern evaluation for the reduction of elemental compositions assigned to high-resolution mass spectral data from electrospray ionization fourier transform ion cyclotron resonance mass spectrometry  

Microsoft Academic Search

The number of possible chemical formulae assigned to an accurate determined mass was significantly reduced by comparing spectral\\u000a and theoretical isotope patterns based on mass measurement obtained with an ultrahigh-resolution electrospray ionization Fourier\\u000a transform ion cyclotron resonance mass spectrometer (ESI-FTICR-MS) at high field intensity (7 T). Reduction is performed by\\u000a rating congruency between experimental and theoretical pattern intensity and mass,

Norbert Stoll; Enrico Schmidt; Kerstin Thurow

2006-01-01

254

Nuclear applications of inorganic mass spectrometry.  

PubMed

There are several basic characteristics of mass spectrometry that are not always fully appreciated by the science community. These characteristics include the distinction between relative and absolute isotope abundances, and the influence of isotope fractionation on the accuracy of isotopic measurements. These characteristics can be illustrated in the field of nuclear physics with reference to the measurement of nuclear parameters, which involve the use of enriched isotopes, and to test models of s-, r-, and p-process nucleosynthesis. The power of isotope-dilution mass spectrometry (IDMS) to measure trace elements in primitive meteorites to produce accurate Solar System abundances has been essential to the development of nuclear astrophysics. The variety of mass spectrometric instrumentation used to measure the isotopic composition of elements has sometimes been accompanied by a lack of implementation of basic mass spectrometric protocols which are applicable to all instruments. These metrological protocols are especially important in atomic weight determinations, but must also be carefully observed in cases where the anomalies might be very small, such as in studies of the daughter products of extinct radionuclides to decipher events in the early history of the Solar System. There are occasions in which misleading conclusions have been drawn from isotopic data derived from mass spectrometers where such protocols have been ignored. It is important to choose the mass spectrometer instrument most appropriate to the proposed experiment. The importance of the integrative nature of mass spectrometric measurements has been demonstrated by experiments in which long, double beta decay and geochronological decay half-lives have been measured as an alternative to costly radioactive-counting experiments. This characteristic is also illustrated in the measurement of spontaneous fission yields, which have accumulated over long periods of time. Mass spectrometry is also a valuable tool in the determination of neutron capture cross-section measurements and the application of such determinations in Planetary Science. PMID:19877268

De Laeter, John

2010-01-01

255

Mass Spectrometry Video  

NSDL National Science Digital Library

This video, distributed on YouTube by the Royal Society of Chemistry is on the basic principles of mass spectrometry, using a magnetic sector instrument to demonstrate how specific m/z ratios can be selected. The theory and operation of MS, including the chemistry of ionization and fragmentation is described at an introductory level. There is also an excellent example of the use of high resolution MS to differentiate between nominal mass and actual mass. The video does a very good job of explaining the concept such that only a little background knowledge is required. The video is short enough (6 mins), that it would be very useful in a class setting or for students outside of class. The ultimate strength of this video is the general nature of the content that makes it appealing to a wide audience. The video may be most appropriate in a lower-level general education science course (i.e forensic science) or as a quick orientation video for instrumental analysis students prior to introducing mathematical or operational concepts. This video would also be helpful for a lay science person who wishes to learn more about mass spectrometry from a general interest perspective.

256

Improved detection of sugar addition to maple syrup using malic acid as internal standard and in 13C isotope ratio mass spectrometry (IRMS).  

PubMed

Stable carbon isotope ratio mass spectrometry (delta13C IRMS) was used to detect maple syrup adulteration by exogenous sugar addition (beet and cane sugar). Malic acid present in maple syrup is proposed as an isotopic internal standard to improve actual adulteration detection levels. A lead precipitation method has been modified to isolate quantitatively malic acid from maple syrup using preparative reversed-phase liquid chromatography. The stable carbon isotopic ratio of malic acid isolated from this procedure shows an excellent accuracy and repeatability of 0.01 and 0.1 per thousand respectively, confirming that the modified lead precipitation method is an isotopic fractionation-free process. A new approach is proposed to detect adulteration based on the correlation existing between the delta13Cmalic acid and the delta13Csugars-delta13Cmalic acid (r = 0.704). This technique has been tested on a set of 56 authentic maple syrup samples. Additionally, authentic samples were spiked with exogeneous sugars. The mean theoretical detection level was statistically lowered using this technique in comparison with the usual two-standard deviation approach, especially when maple syrup is adulterated with beet sugar : 24 +/- 12% of adulteration detection versus 48 +/- 20% (t-test, p = 7.3 x 10-15). The method was also applied to published data for pineapple juices and honey with the same improvement. PMID:17227042

Tremblay, Patrice; Paquin, Ral

2007-01-24

257

Correction for the 17O interference in ?(13C) measurements when analyzing CO2 with stable isotope mass spectrometry  

USGS Publications Warehouse

Measurements of ?(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 ?, 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 [?(13C) ? 45?VPDB-CO2 + 2 17R/13R (45?VPDB-CO2 ?46?VPDB-CO2)] closely approximates ?(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 ?(18O). The linear approximations are easy to implement in a data spreadsheet, and also help in generating a simplified uncertainty budget.

Coplen, Tyler B.; Brand, Willi A.; Assonov, Sergey S.

2010-01-01

258

Study and validity of 13C stable carbon isotopic ratio analysis by mass spectrometry and 2H site-specific natural isotopic fractionation by nuclear magnetic resonance isotopic measurements to characterize and control the authenticity of honey.  

PubMed

Honey samples were analyzed by stable carbon isotopic ratio analysis by mass spectrometry (SCIRA-MS) and site-specific natural isotopic fractionation measured by nuclear magnetic resonance (SNIF-NMR) to first determine their potentials for characterizing the substance and then to combat adulteration. Honey samples from several geographic and botanical origins were analyzed. The delta(13)C parameter was not significant for characterizing an origin, while the (D/H)(I) ratio could be used to differentiate certain single-flower varieties. Application of the official control method of adding a C(4) syrup (AOAC official method 998.12) to our authentic samples revealed anomalies resulting from SCIRA indices that were more negative than -1 per thousand (permil). A filtration step was added to the experimental procedure and provided results that were compliant with the natural origin of our honey samples. In addition, spiking with a C(4) syrup could be detected starting at 9-10%. The use of SNIF-NMR is limited by the detection of a syrup spike starting only at 20%, which is far from satisfying. PMID:17386484

Cotte, J F; Casabianca, H; Lhritier, J; Perrucchietti, C; Sanglar, C; Waton, H; Grenier-Loustalot, M F

2007-01-16

259

Mass Spectrometry and Biotechnology Resource  

NSDL National Science Digital Library

Ionsource is a website that provides access to an index of resources including tutorials, links to downloadable sites, jobs and conference information involving mass spectrometry and biotechnology subjects. Examples of tutorials include lessons on atomic mass and amino acid residue mass. For a review of mass spectrometry or biotechnology or for an introduction, this site provides a well-rounded source of information.

260

Isotopic analysis of Cu in blood serum by multi-collector ICP-mass spectrometry: a new approach for the diagnosis and prognosis of liver cirrhosis?  

PubMed

The isotopic composition of blood serum Cu has been investigated as a potential parameter for the diagnosis and prognosis of liver cirrhosis. Serum samples from supposedly healthy women (reference population) and from a group of female patients suffering from liver cirrhosis of different etiologies were analysed. The procedure for isolation of serum Cu and the measurement protocol for its isotopic analysis by multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) were evaluated. Significant differences in the isotopic composition of Cu were observed between the reference population and the patients. A wide spread in ?(65)Cu was observed within the cirrhosis population and ?(65)Cu seems to be linked to the severity of the disease. Patients with end-stage liver disease showed a significantly lighter serum Cu isotopic composition. Many clinical parameters used for the diagnosis and monitoring of liver diseases, i.e. the levels of aspartate aminotransferase, De Ritis ratio, prothrombin and international normalized ratio, albumin, bilirubin, Na and C-reactive protein, correlate well with the ?(65)Cu values, as did the ceruloplasmin level and the ceruloplasmin/Cu concentration ratio. The isotopic composition of serum Cu appears to reveal the synthetic and hepatocellular function of the liver synergistically with inflammation and fluid retention in the cohort studied. A relevant relationship was also observed between ?(65)Cu and scores of mortality risk, such as the Model for End-stage Liver Disease (MELD) and MELD-Na. Thus, the isotopic composition of serum Cu shows potential as a new approach for the prognosis of liver disease, and although further investigation is required, for evaluation of the mortality risk in end-stage liver disease and prioritization of liver transplants. PMID:25644127

Costas-Rodrguez, Marta; Anoshkina, Yulia; Lauwens, Sara; Van Vlierberghe, Hans; Delanghe, Joris; Vanhaecke, Frank

2015-03-11

261

Amino acid precursors from a simulated lower atmosphere of Titan, Experiments of cosmic ray energy source with 13C- and 18O-stable isotope probing mass spectrometry  

E-print Network

The organic haze of aerosols that shrouds the Saturnian moon Titan has previously been studied by both observations and laboratory simulation experiments. Here we report the abiotic formation of amino acid precursors in complex organic molecules during experimental simulation of the environment near Titan's surface with proton irradiation. Pyrolysis of the organic molecules formed in the simulated Titan atmosphere by proton irradiation at 600 degree-C yielded compounds that contained HCN and NH3. These experimental results are consistent with the molecular information obtained by pyrolysis gas chromatography-mass spectrometry (pyrolysis GC-MS) of samples collected by the Huygens probe to Titan. Scanning electron microscopy (SEM) and three-dimensional atomic force microscopy (AFM) images of the irradiation products reveal nanometer-scale filaments and globules in complex amorphous structures (approximately 1000 Da). Isotope probing experiments by matrix-assisted laser desorption ionization time-of-flight mass ...

Taniuchi, Toshinori; Kobayashi, Kensei

2013-01-01

262

Accelerator mass spectrometry  

SciTech Connect

Accelerator mass spectroscopy (AMS) can be used for efficient detection of long-lived isotopes at part-per-quadrillion sensitivities with good precision. In this article we present an overview of AMS and its recent use in archaeology, geochemistry and biomolecular tracing. All AMS systems use cesium sputter ion sources to produce negative ions from a small button of a solid sample containing the element of interest, such as graphite, metal halide, or metal oxide, often mixed with a metal powder as binder and thermal conductor. Experience shows that both natural and biomedical samples are compatible in a single AMS system, but few other AMS sites make routine {sup 14}C measurements for both dating and tracing. AMS is, in one sense, just `a very sensitive decay counter`, but if AMS sensitivity is creatively coupled to analytical chemistry of certain isotopes, whole new areas of geosciences, archaeology, and life sciences can be explored. 29 refs., 2 figs., 1 tab.

Vogel, J.S.; Turteltaub, K.W.; Finkel, R. [Lawrence Livermore National Lab., CA (United States); Nelson, D.E.

1995-06-01

263

Mass Spectrometry of Glycans  

PubMed Central

Powerful new strategies based on mass spectrometry are revolutionizing the structural analysis and profiling of glycans and glycoconjugates. We survey here the major biosynthetic pathways that underlie the biological diversity in glycobiology, with emphasis on glycoproteins, and the approaches that can be used to address the resulting heterogeneity. Included among these are derivatizations, on- and off-line chromatography, electrospray and matrix-assisted laser desorption/ionization, and a variety of dissociation methods, the recently introduced electron-based techniques being of particular interest. PMID:24010834

Han, Liang; Costello, Catherine E.

2014-01-01

264

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

PubMed

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

Hattori, M; Hirata, T

2001-06-01

265

An inter-laboratory comparative study into sample preparation for both reproducible and repeatable forensic 2H isotope analysis of human hair by continuous flow isotope ratio mass spectrometry.  

PubMed

Stable isotope analysis of organic materials for their hydrogen ((2)H), carbon ((13)C), nitrogen ((15)N) or oxygen ((18)O) isotopic composition using continuous flow isotope ratio mass spectrometry (CF-IRMS) is an increasingly used tool in forensic chemical analysis. (2)H isotopic analysis can present a huge challenge, especially when dealing with exhibits comprising exchangeable hydrogen such as human scalp hair. However, to yield forensic data that are fit for purpose, analysis of the (2)H isotopic composition of the same homogeneous human hair sample by any laboratory worldwide must yield the same isotopic composition within analytical uncertainty. This paper presents longitudinal (2)H isotope data for four human hair samples of different provenance, measured by three different laboratories whose sample preparation was based on a two-stage H exchange equilibration method. Although each laboratory employed varying means to comply with the generic features of the sample preparation protocol such as the (2)H isotopic composition of exchange waters or drying down of samples prior to analysis, within each laboratory the Principle of Identical Treatment (P.I.T.) was applied for each individual experiment. Despite the variation in materials and procedures employed by the three laboratories, repeatable and reproducible 'true' (2)H isotope values (?(2)H(hair,true)) were determined by each laboratory for each of the four stock samples of human scalp hair. The between-laboratory differences for obtained ?(2)H(hair,true) values ranged from 0.1 to 2.5 . With an overall 95% confidence interval of 2.8 , these differences were not significantly different, which suggests that the general method of two-stage exchange equilibration carried out at ambient temperature is suitable for accurately and reproducibly determining 'true' ?(2)H-values for hair and other proteins provided that certain key conditions are met. PMID:22006397

Meier-Augenstein, Wolfram; Chartrand, Michelle M G; Kemp, Helen F; St-Jean, Gilles

2011-11-15

266

Direct determination of Si isotope ratios in natural waters and commercial Si standards by ion exclusion chromatography multicollector inductively coupled plasma mass spectrometry.  

PubMed

Silicon isotope ratios in natural waters and several commercial Si standards were determined by online ion exclusion chromatography (IEC) multicollector inductively couple plasma mass spectrometry (MC-ICPMS). As recent studies have shown that mass-independent fractionation (MIF) also exists in MC-ICPMS, e.g., Nd, Ce, W, Sr, Hf, Ge, Hg, and Pb isotopes, the nature of mass bias for Si isotopes was thus investigated. MIF was observed for Si isotopes on both Neptune and Neptune plus MC-ICPMS instruments in this study. Therefore, a standard-sample bracketing (SSB) mass bias correction model, capable of correcting both mass-dependent and mass-independent bias, was employed to obtain accurate Si isotope ratio results in all samples by using NBS28 Si standard as the bracketing standard. Medium resolution was used for all measurements in order to resolve polyatomic interferences on Si isotopes. NBS28 Si standard solutions prepared in nutrient-free seawater and 0.1% NaOH matrix, respectively, were used for the method validation and subjected to the online IEC MC-ICPMS determination of Si isotope ratios. Values of -0.01 0.06 and 0.00 0.06 (1 SD, n = 10) and -0.01 0.03 and 0.01 0.06 (1 SD, n = 10) for ?(29/28)Si and ?(30/28)Si, respectively, were obtained, confirming accurate results can be obtained using the reported method for natural waters. Significant variations in Si isotope ratios from -0.72 0.09 to -0.24 0.03 (1 SD, n = 10) and -1.36 0.11 to -0.46 0.04 (1 SD, n = 10) for ?(29/28)Si and ?(30/28)Si, respectively, were found among commercial Si standards of NIST SRM3150, SCP Si, and Sigma-Aldrich Si. Values of -0.06 0.07 and -0.20 0.11 (1 SD, n = 10) for ?(29/28)Si and ?(30/28)Si, respectively, were obtained for the MOOS-3 seawater whereas 0.59 0.11 and 1.19 0.15 (1SD, n = 10) for ?(29/28)Si and ?(30/28)Si, respectively, were obtained for the SLRS-5 river water. To the best of our knowledge this is the first report of an application of online IEC MC-ICPMS for the high accuracy and precision determination of Si isotope ratios in natural waters. The reported method provides for a relatively rapid (10 min per run) and simple online technique that requires no sample pretreatment for the Si isotope ratio measurements. PMID:25162683

Yang, Lu; Zhou, Lian; Hu, Zhaochu; Gao, Shan

2014-09-16

267

Single event mass spectrometry  

DOEpatents

A means and method for single event time of flight mass spectrometry for analysis of specimen materials. The method of the invention includes pulsing an ion source imposing at least one pulsed ion onto the specimen to produce a corresponding emission of at least one electrically charged particle. The emitted particle is then dissociated into a charged ion component and an uncharged neutral component. The ion and neutral components are then detected. The time of flight of the components are recorded and can be used to analyze the predecessor of the components, and therefore the specimen material. When more than one ion particle is emitted from the specimen per single ion impact, the single event time of flight mass spectrometer described here furnis This invention was made with Government support under Contract No. W-7405-ENG82 awarded by the Department of Energy. The Government has certain rights in the invention.

Conzemius, Robert J. (Ames, IA)

1990-01-16

268

Molecular formula analysis of fragment ions by isotope-selective collision-induced dissociation tandem mass spectrometry of pharmacologically active compounds.  

PubMed

The purpose of this work is to explore the mass fragment characterization of commonly used drugs through a novel approach, which involves isotope-selective tandem mass spectrometry (MS/MS). Collision-induced dissociation (CID) was performed with a low-resolution linear ion trap mass spectrometer in positive electrospray ionization. Three pharmacologically active ingredients, i.e. omeprazole, meloxicam and brinzolamide, selected as model compounds in their own formulation, were investigated as a sodiated adduct [C17 H19 N3 O3 S?+?Na](+) (omeprazole) and as protonated adducts, [C14 H13 N3 O4 S2 ?+?H](+) and [C12 H21 N3 O5 S3 ?+?H](+) , meloxicam and brinzolamide, respectively. Selecting a narrow window of 0.5 m/z units, precursor ion fragmentation by CID-MS/MS of isotopologues A?+?0, A?+?1 and A?+?2 was found very useful to confirm the chemical formula of product ions, thus aiding the establishment of characteristic fragmentation pathways of all three examined compounds. The correctness of putative molecular formula of product ions was easily demonstrated by exploiting the isotope peak abundance ratios (i.e. IF+0 /IF+1 and IF+0 /IF+2 ) as simple constraints in low-resolution MS instrumentations. PMID:25476951

Bianco, Giuliana; Buchicchio, Alessandro; Lelario, Filomena; Cataldi, Tommaso R I

2014-12-01

269

Investigation of amino acid ? 13C signatures in bone collagen to reconstruct human palaeodiets using liquid chromatography-isotope ratio mass spectrometry  

NASA Astrophysics Data System (ADS)

This research presents the individual amino acid ? 13C values in bone collagen of humans ( n = 9) and animals ( n = 27) from two prehistoric shell midden sites in Korea. We obtained complete baseline separation of 16 of the 18 amino acids found in bone collagen by using liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). The isotopic results reveal that the humans and animals in the two sites had similar patterns in essential amino acids (EAAs) and non-essential amino acids (NEAAs). The EAA and NEAA ? 13C values in humans are intermediate between those in marine and terrestrial animals. However, the threonine ? 13C values in humans and animals measured in this study are more highly enriched than those of other amino acids. At both sites, all amino acids in marine animals are 13C-enriched relative to those of the terrestrial animals. The isotopic evidence suggests that the Tongsamdong human had EAAs and NEAAs from marine food resources, while the Nukdo humans mainly had EAAs from terrestrial food resources but obtained NEAAs from both terrestrial and marine resources. The ? 13C isotopic differences in amino acids between marine and terrestrial animals were the largest for glycine (NEAA) and histidine (EAA) and the smallest for tyrosine (NEAA) and phenylalanine (EAA). In addition, threonine among the EAAs also had a large difference (8) in ? 13C values between marine and terrestrial animals, and has the potential to be used as an isotopic marker in palaeodietary studies. Threonine ? 13C values were used in conjunction with the established ? 13C Glycine-phenylalanine values and produced three distinct dietary groups (terrestrial, omnivorous, and marine). In addition, threonine ? 13C values and ? 13C Serine-phenylalanine values were discovered to separate between two dietary groups (terrestrial vs. marine), and these ? 13C values may provide a potential new indicator for investigating the distinction between marine and terrestrial protein sources in human diets.

Choy, Kyungcheol; Smith, Colin I.; Fuller, Benjamin T.; Richards, Michael P.

2010-11-01

270

Development of new method of ?(13)C measurement for trace hydrocarbons in natural gas using solid phase micro-extraction coupled to gas chromatography isotope ratio mass spectrometry.  

PubMed

Compound specific isotope analysis (CSIA) of normal-level hydrocarbons (C1-C4) in natural gas is often successfully used in natural gas origin identification and classification, but little progress so far has been made for trace level hydrocarbons (C5-C14) in natural gas. In this study, we developed a method for rapid analysis of carbon isotopic ratios for trace hydrocarbons in natural gas samples. This method can be described as a combined approach characterized by solid phase micro-extraction (SPME) technique coupled to gas chromatography isotope ratio mass spectrometry (GC/IRMS). In this study, the CAR-PDMS fiber was chosen as the SPME adsorptive material after comparative experiments with other four fibers, and the parameters, including equilibration time, extraction temperature and desorption time, for efficient extraction of trace hydrocarbons were systematically optimized. The results showed the carbon isotopic fractionation was not observed as a function of equilibration time and extraction temperature. And the ?(13)C signatures determined by SPME-GC/IRMS were in good agreement with the known ?(13)C values of C5-C14 measured by GC-IRMS, and the accuracy is generally within 0.5. Five natural gas samples were analyzed using this method, and the ?(13)C values for C5-C14 components were obtained with satisfied repeatability. The SPME-GC/IRMS approach fitted with CAR-PDMS fiber is well suited for the preconcentration of trace hydrocarbons and provides so far the most reliable carbon isotopic analysis for trace compounds in natural gas. PMID:25465020

Li, Zhongping; Wang, Xibin; Li, Liwu; Zhang, Mingjie; Tao, Mingxin; Xing, Lantian; Cao, Chunhui; Xia, Yanqing

2014-11-01

271

Analysis of triclosan and triclocarban in human nails using isotopic dilution liquid chromatography-tandem mass spectrometry.  

PubMed

In this study, we were able to develop a simple analytical procedure to assay the presence of two antimicrobial agents, triclosan (TCS) and triclocarban (TCC), in human nails. Samples were digested using sodium hydroxide (NaOH), extracted using dichloromethane, and analyzed using ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry operating in the negative ion mode. Mean recoveries were performed at three fortification levels ranging from 98.1% to 106.3% with relative standard deviations between 1.8% and 18.1% (n=6). The limits of quantification (LOQ) for the method were 2.0 and 0.2?g/kg for TCS and TCC, respectively. Both compounds were ubiquitously found in all real samples (n=20) with concentrations ranging from ?g/kg to several mg/kg. PMID:23911541

Shi, Ying; Liu, Xiangjun; Zhang, Jing; Shao, Bing

2013-09-01

272

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

USGS Publications Warehouse

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

Matsumoto, A.; Hinkley, T.K.

1997-01-01

273

Combining Capillary Electrophoresis Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry and Stable Isotopic Labeling Techniques for Comparative Crustacean Peptidomics  

PubMed Central

Herein we describe a sensitive and straightforward off-line capillary electrophoresis (CE) matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) interface in conjunction with stable isotopic labeling (SIL) technique for comparative neuropeptidomic analysis in crustacean model organisms. Two SIL schemes, including a binary H/D formaldehyde labeling technique and novel, laboratory-developed multiplexed dimethylated leucine-based isobaric tagging reagents, have been evaluated in these proof-of-concept experiments. We employ these isotopic labeling techniques in conjunction with CE-MALDI MS for quantitative peptidomic analyses of the pericardial organs isolated from two crustacean species, the European green crab Carcinus maenas and the blue crab Callinectes sapidus. Isotopically labeled peptide pairs are found to co-migrate in CE fractions and quantitative changes in relative abundances of peptide pairs are obtained by comparing peak intensities of respective peptide pairs. Several neuropeptide families exhibit changes in response to salinity stress, suggesting potential physiological functions of these signaling peptides. PMID:20334868

Wang, Junhua; Zhang, Yuzhuo; Xiang, Feng; Zhang, Zichuan; Li, Lingjun

2010-01-01

274

Use of Isotope Ratio Mass Spectrometry (IRMS) Determination ((18)O/(16)O) to Assess the Local Origin of Fish and Asparagus in Western Switzerland.  

PubMed

Here we present the use of isotope ratio mass spectrometry (IRMS) for the detection of mislabelling of food produced in Switzerland. The system is based on the analysis of the oxygen isotope distribution in water (?(18)O). Depending on the location on the earth, lake or groundwater has a specific isotopic distribution, which can serve as a fingerprint in order to verify whether a product has grown by means of the corresponding water. This report presents specifically the IRMS technique and the results obtained in the origin detection of fish grown in selected Swiss lakes as well as asparagus grown in Valais ground. Strengths and limitations of the method are presented for both cited products; on one hand, the technique is relatively universal for any product which contains significant water but on the other hand, it necessitates a rather heavy workload to build up a database of water ?(18)O values of products of different origins. This analytical tool is part of the concept of combating fraud currently in use in Switzerland. PMID:25437160

Rossier, Jol S; Maury, Valrie; de Voogd, Blaise; Pfammatter, Elmar

2014-10-01

275

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

USGS Publications Warehouse

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

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

2009-01-01

276

Deuterium\\/hydrogen ratio analysis of thymol, carvacrol, ?-terpinene and p-cymene in thyme, savory and oregano essential oils by gas chromatographypyrolysisisotope ratio mass spectrometry  

Microsoft Academic Search

Isotope ratio mass spectrometry online coupled with capillary gas chromatography (GCPyIRMS) on column INNOWAX is used in the origin specific analysis and the authenticity control of the phenolic essential oils (EOs). Isotopic data ?2HV-SMOW of thymol and carvacrol in natural essential oils were evidently more depleted than synthetic products (from ?49 to 7 for thymol and ?61 for carvacrol). ?2HV-SMOW

Tran-Thi Nhu-Trang; Herv Casabianca; Marie-Florence Grenier-Loustalot

2006-01-01

277

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

278

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

PubMed

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

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

2011-09-16

279

Analytical approach for the determination of steroid profile of humans by gas chromatography isotope ratio mass spectrometry aimed at distinguishing between endogenous and exogenous steroids.  

PubMed

The contamination of commonly used supplements by unknown steroids as well as their metabolites (parent compounds) become a challenge for the analytical laboratories. Although the determination of steroids profile is not trivial because of the complex matrix and low concentration of single compound, one of the most difficult current problem is to distinguish, during analytical procedure, endogenous androgens such as testosterone, dehydrotestosterone or dehydroepiandrosterone from their synthetic equivalents. The aim of this work was to develop and validate an analytical procedure for determination of the steroid profile in human urine by gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/IRMS) toward distinguishing between endogenous and exogenous steroids. Beside the optimization of the experimental parameters for gas chromatography separation and mass spectrometry, attention was focused on urine sample preparation. Using an optimized sample preparation protocol it was possible to achieve better chromatographic resolutions and better sensitivity enabling the determination of 5 steroids, androsterone, etiocholanolone, testosterone, 5-androstandiol, 11-hydroxyandrdostane, pregnandiol, with the expanded uncertainty (k=2) below 1. This enable to evaluate the significant shift of the ?(13)C/(12)C [] values for each of examined steroids (excluding ERC). The analytical protocol described in this work was successfully used for the confirmation of positive founding urine by evaluation T/E ratio after GC/C/IRMS analysis. PMID:25498150

Bulska, Ewa; Gorczyca, Damian; Zalewska, Izabela; Pokrywka, Andrzej; Kwiatkowska, Dorota

2015-03-15

280

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

PubMed

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

Wang, Jian-Hua; Guo, Cui

2010-07-01

281

Electronic nose and isotope ratio mass spectrometry in combination with chemometrics for the characterization of the geographical origin of Italian sweet cherries.  

PubMed

Sweet cherries from two Italian regions, Apulia and Emilia Romagna, were analysed using electronic nose (EN) and isotope ratio mass spectrometry (IRMS), with the aim of distinguishing them according to their geographic origin. The data were elaborated by statistical techniques, examining the EN and IRMS datasets both separately and in combination. Preliminary exploratory overviews were performed and then linear discriminant analyses (LDA) were used for classification. Regarding EN, different approaches for variable selection were tested, and the most suitable strategies were highlighted. The LDA classification results were expressed in terms of recognition and prediction abilities and it was found that both EN and IRMS performed well, with IRMS showing better cross-validated prediction ability (91.0%); the EN-IRMS combination gave slightly better results (92.3%). In order to validate the final results, the models were tested using an external set of samples with excellent results. PMID:25306321

Longobardi, F; Casiello, G; Ventrella, A; Mazzilli, V; Nardelli, A; Sacco, D; Catucci, L; Agostiano, A

2015-03-01

282

Deciphering the complexity of sainfoin (Onobrychis viciifolia) proanthocyanidins by MALDI-TOF mass spectrometry with a judicious choice of isotope patterns and matrixes.  

PubMed

Use of superdihydroxybenzoic acid as the matrix enabled the analysis of highly complex mixtures of proanthocyanidins from sainfoin (Onobrychis viciifolia) by MALDI-TOF mass spectrometry. Proanthocyanidins contained predominantly B-type homopolymers and heteropolymers up to 12-mers (3400 Da). Use of another matrix, 2,6-dihydroxyacetophenone, revealed the presence of A-type glycosylated dimers. In addition, we report here how a comparison of the isotopic adduct patterns, which resulted from Li and Na salts as MALDI matrix additives, could be used to confirm the presence of A-type linkages in complex proanthocyanidin mixtures. Preliminary evidence suggested the presence of A-type dimers in glycosylated prodelphinidins and in tetrameric procyanidins and prodelphinidins. PMID:21488615

Stringano, Elisabetta; Cramer, Rainer; Hayes, Wayne; Smith, Celia; Gibson, Trevor; Mueller-Harvey, Irene

2011-06-01

283

Measurement of U and Pu isotope ratios in hair and nail samples using extraction chromatography and multi-collector inductively coupled plasma mass spectrometry.  

PubMed

A bioassay capable of monitoring occupational or environmental exposure to special nuclear materials would be a useful tool for nuclear nonproliferation programs. Hair and nail are potential biomonitors of exposure to U and Pu. A method is described to measure isotope ratios of ultra-trace concentrations of U and Pu in hair and nail samples. The method uses multiple extraction chromatography resins to separate U and Pu fractions from the sample matrix. The U recovery was quantitative while the Pu recovery ranged from 81% to 109%, with a U decontamination factor of 510(4). Following the separation (234)U/(238)U, (235)U/(238)U and (240)Pu/(239)Pu were measured in human hair and hair and nail samples using multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The human hair and nail samples had elevated ratios of (234)U/(238)U which could reflect exposure to naturally fractionated U. PMID:25127622

Brown, J N W; Robertson, J D; Brockman, J D

2014-11-01

284

An analytical system for studying the stable isotopes of carbon monoxide using continuous flow-isotope ratio mass spectrometry (CF-IRMS)  

NASA Astrophysics Data System (ADS)

In the atmosphere, carbon monoxide (CO) is the major sink for the hydroxyl radical (OH •), has multiple anthropogenic and natural sources and considerable spatial and seasonal variability. Measurements of CO isotopic composition are useful in constraining the strengths of its individual source and sink processes and thus its global cycle. A fully automated system for ?13C and ?18O analysis has been developed to extract CO from an air sample, convert CO into carbon dioxide (CO2) using the Schtze reagent, and then determine the isotopic composition in an isotope ratio mass spectrometer (IRMS). The entire system is continuously flushed with high-purity helium (He), the carrier gas. The blank signal of the Schtze reagent is only 1-3% of the typical sample size. The repeatability is 0.1 for ?13C and 0.2 for ?18O. The peak area allows simultaneous determination of the mole fraction with an analytical repeatability of ~0.7 nmol mol-1 for 100 mL of typical ambient air (185.4 nmol mol-1 of CO). A single, automated, measurement is performed in 18 min, so multiple measurements can be combined conveniently to improve precision.

Pathirana, S. L.; van der Veen, C.; Popa, M. E.; Rckmann, T.

2015-02-01

285

Glycomics and Mass Spectrometry  

NASA Astrophysics Data System (ADS)

There is an increasing body of evidence indicating that glycans are implicated in numerous biological processes such as cell-cell interactions, intracellular signaling, and immune response. Glycomics emerges from the necessity to understand the mechanisms underlying the interactions responsible for these activities. The term glycomics is used to describe experimental approaches to studying the structure and function of the glycomes of fluids, cells, tissues, organs etc. Glycomics embraces a variety of technologies amongst which mass spectrometry (MS) plays a pivotal role because it is the method of choice for defining the primary structures of glycopolymers. This chapter provides an insight into MS -based structural strategies that are best suited to studying complex glycomes.

Dell, Anne; Jang-Lee, Jihye; Pang, Poh-Choo; Parry, Simon; Sutton-Smith, Mark; Tissot, Berangere; Morris, Howard R.; Panico, Maria; Haslam, Stuart M.

286

Proteome Analysis by Mass Spectrometry  

Microsoft Academic Search

The coupling of high-performance mass spectrometry instrumentation with highly efficient chromatographic and electrophoretic separations has enabled rapid qualitative and quantitative analysis of thousands of proteins from minute samples of biological materials. Here, we review recent progress in the development and application of mass spectrometry-based techniques for the qualitative and quantitative analysis of global proteome samples. Techniques such as multidimensional peptide

Patrick L. Ferguson; Richard D. Smith

2003-01-01

287

Measurement of ?18O, ?17O, and 17O-excess in Water by Off-Axis Integrated Cavity Output Spectroscopy and Isotope Ratio Mass Spectrometry  

PubMed Central

Stable isotopes of water have long been used to improve understanding of the hydrological cycle, catchment hydrology, and polar climate. Recently, there has been increasing interest in measurement and use of the less-abundant 17O isotope in addition to 2H and 18O. Off-axis integrated cavity output spectroscopy (OA-ICOS) is demonstrated for accurate and precise measurements ?18O, ?17O, and 17O-excess in liquid water. OA-ICOS involves no sample conversion and has a small footprint, allowing measurements to be made by researchers collecting the samples. Repeated (514) high-throughput measurements of the international isotopic reference water standard GISP demonstrate the precision and accuracy of OA-ICOS: ?18OVSMOW-SLAP =?24.74 0.07 (1?) and ?17OVSMOW-SLAP = ?13.12 0.05 (1?). For comparison, the IAEA value for ?18OVSMOW-SLAP is ?24.76 0.09 (1?) and an average of previously reported values for ?17OVSMOW-SLAP is ?13.12 0.06 (1?). Multiple (26) high-precision measurements of GISP provide a 17O-excessVSMOW-SLAP of 23 10 per meg (1?); an average of previously reported values for 17O-excessVSMOW-SLAP is 22 11 per meg (1?). For all these OA-ICOS measurements, precision can be further enhanced by additional averaging. OA-ICOS measurements were compared with two independent isotope ratio mass spectrometry (IRMS) laboratories and shown to have comparable accuracy and precision as the current fluorination-IRMS techniques in ?18O, ?17O, and 17O-excess. The ability to measure accurately ?18O, ?17O, and 17O-excess in liquid water inexpensively and without sample conversion is expected to increase vastly the application of ?17O and 17O-excess measurements for scientific understanding of the water cycle, atmospheric convection, and climate modeling among others. PMID:24032448

Berman, Elena S.F.; Levin, Naomi E.; Landais, Amaelle; Li, Shuning; Owano, Thomas

2013-01-01

288

Stable-isotope-labeled histone peptide library for histone post-translational modification and variant quantification by mass spectrometry.  

PubMed

To facilitate accurate histone variant and post-translational modification (PTM) quantification via mass spectrometry, we present a library of 93 synthetic peptides using Protein-Aqua technology. The library contains 55 peptides representing different modified forms from histone H3 peptides, 23 peptides representing H4 peptides, 5 peptides representing canonical H2A peptides, 8 peptides representing H2A.Z peptides, and peptides for both macroH2A and H2A.X. The PTMs on these peptides include lysine mono- (me1), di- (me2), and tri-methylation (me3); lysine acetylation; arginine me1; serine/threonine phosphorylation; and N-terminal acetylation. The library was subjected to chemical derivatization with propionic anhydride, a widely employed protocol for histone peptide quantification. Subsequently, the detection efficiencies were quantified using mass spectrometry extracted ion chromatograms. The library yields a wide spectrum of detection efficiencies, with more than 1700-fold difference between the peptides with the lowest and highest efficiencies. In this paper, we describe the impact of different modifications on peptide detection efficiencies and provide a resource to correct for detection biases among the 93 histone peptides. In brief, there is no correlation between detection efficiency and molecular weight, hydrophobicity, basicity, or modification type. The same types of modifications may have very different effects on detection efficiencies depending on their positions within a peptide. We also observed antagonistic effects between modifications. In a study of mouse trophoblast stem cells, we utilized the detection efficiencies of the peptide library to correct for histone PTM/variant quantification. For most histone peptides examined, the corrected data did not change the biological conclusions but did alter the relative abundance of these peptides. For a low-abundant histone H2A variant, macroH2A, the corrected data led to a different conclusion than the uncorrected data. The peptide library and detection efficiencies presented here may serve as a resource to facilitate studies in the epigenetics and proteomics fields. PMID:25000943

Lin, Shu; Wein, Samuel; Gonzales-Cope, Michelle; Otte, Gabriel L; Yuan, Zuo-Fei; Afjehi-Sadat, Leila; Maile, Tobias; Berger, Shelley L; Rush, John; Lill, Jennie R; Arnott, David; Garcia, Benjamin A

2014-09-01

289

Ultratrace Uranium Fingerprinting with Isotope Selective Laser Ionization Spectrometry  

SciTech Connect

Uranium isotope ratios can provide source information for tracking uranium contamination in a variety of fields, ranging from occupational bioassay to monitoring aftereffects of nuclear accidents. We describe the development of Isotope Selective Laser Ionization Spectrometry (ISLIS) for ultratrace measurement of the minor isotopes 234U, 235U, and 236U with respect to 238U. Optical isotopic selectivity in three-step excitation with single-mode continuous wave lasers is capable of measuring the minor isotopes at relative abundances below 1 ppm, and is not limited by isobaric interferences such as 235UH+ during measurement of 236U. This relative abundance limit approaches the threshold for measurement of uranium minor isotopes with conventional mass spectrometry, typically 10-7, but without mass spectrometric analysis of the laser-created ions. Uranyl nitrate standards from an international blind comparison were used to test analytical performance for different isotopic compositions and with quantities ranging from 11 ng to 10 g total uranium. Isotopic ratio determination was demonstrated over a linear dynamic range of 7 orders of magnitude with a few percent relative precision and detection limits below 500 fg for the minor isotopes.

Ziegler, Summer L.; Bushaw, Bruce A.

2008-08-01

290

High resolution Secondary Ionisation Mass Spectrometry O analyses of Hulu Cave speleothem  

E-print Network

High resolution Secondary Ionisation Mass Spectrometry (SIMS) 18 O analyses of Hulu Cave speleothem The suitability of in situ Secondary Ionisation Mass Spectrometry (SIMS) techniques for measuring O isotopes

291

Quantification of ricin, RCA and comparison of enzymatic activity in 18 Ricinus communis cultivars by isotope dilution mass spectrometry.  

PubMed

The seeds of the Ricinus communis (Castor bean) plant are the source of the economically important commodity castor oil. Castor seeds also contain the proteins ricin and R. communis agglutinin (RCA), two toxic lectins that are hazardous to human health. Radial immunodiffusion (RID) and the enzyme linked immunosorbent assay (ELISA) are two antibody-based methods commonly used to quantify ricin and RCA; however, antibodies currently used in these methods cannot distinguish between ricin and RCA due to the high sequence homology of the respective proteins. In this study, a technique combining antibody-based affinity capture with liquid chromatography and multiple reaction monitoring (MRM) mass spectrometry (MS) was used to quantify the amounts of ricin and RCA independently in extracts prepared from the seeds of eighteen representative cultivars of R.communis which were propagated under identical conditions. Additionally, liquid chromatography and MRM-MS was used to determine rRNA N-glycosidase activity for each cultivar and the overall activity in these cultivars was compared to a purified ricin standard. Of the cultivars studied, the average ricin content was 9.3mg/g seed, the average RCA content was 9.9mg/g seed, and the enzymatic activity agreed with the activity of a purified ricin reference within 35% relative activity. PMID:25576235

Schieltz, David M; McWilliams, Lisa G; Kuklenyik, Zsuzsanna; Prezioso, Samantha M; Carter, Andrew J; Williamson, Yulanda M; McGrath, Sara C; Morse, Stephen A; Barr, John R

2015-03-01

292

Mass Spectrometry in the Postgenomic Era  

E-print Network

Mass Spectrometry in the Postgenomic Era Brian T. Chait Laboratory for Mass Spectrometry spectrometry, lipidomics Abstract Mass spectrometry (MS) is rapidly becoming an essential tool for bi- ologists building blocks after frag- mentation (1). Historically, this simple mass spectrometry (MS) approach proved

Chait, Brian T.

293

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

PubMed Central

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

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

2013-01-01

294

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

PubMed

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

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

2011-08-01

295

Quantitative isomer-specific N-glycan fingerprinting using isotope coded labeling and high performance liquid chromatography-electrospray ionization-mass spectrometry with graphitic carbon stationary phase.  

PubMed

Glycan reductive isotope labeling (GRIL) using (12)C6-/(13)C6-aniline as labeling reagent is reported with the aim of quantitative N-glycan fingerprinting. Porous graphitized carbon (PGC) as stationary phase in capillary scale HPLC coupled to electrospray mass spectrometry with time of flight analyzer was applied for the determination of labeled N-glycans released from glycoproteins. The main benefit of using stable isotope-coding in the context of comparative glycomics lies in the improved accuracy and precision of the quantitative analysis in combined samples and in the potential of correcting for structure-dependent incomplete enzymatic release of oligosaccharides when comparing identical target proteins. The method was validated with respect to mobile phase parameters, reproducibility, accuracy, linearity and limit of detection/quantification (LOD/LOQ) using test glycoproteins. It is shown that the developed method is capable of determining relative amounts of N-glycans (including isomers) comparing two samples in one single HPLC-MS run. The analytical potential and usefulness of GRIL in combination with PGC-ESI-TOF-MS is demonstrated comparing glycosylation in human monoclonal antibodies produced in Chinese hamster ovary cells (CHO) and hybridoma cell lines. PMID:25638265

Michael, Claudia; Rizzi, Andreas M

2015-02-27

296

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

PubMed

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

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

2014-06-01

297

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

PubMed

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

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

2013-07-01

298

Simultaneous analysis of phthalates, adipate and polycyclic aromatic hydrocarbons in edible oils using isotope dilution-gas chromatography-mass spectrometry.  

PubMed

A method for simultaneous determination of 12 priority phthalates, adipate and polycyclic aromatic hydrocarbons (PAHs) in edible oils by isotope dilution-gas chromatography-mass spectrometry (ID-GC-MS) was developed for fast, accurate and trace analysis. The extraction and clean-up procedures were optimised, and using stable isotope-labelled internal standards for each analyte, relative standard deviations (RSDs) of 0.92-10.6% and spiked sample recoveries of 80.6-97.8% were obtained. Limits of detection for PAHs were in the range of 0.15-0.77 g/kg and those for phthalates were in the range of 4.6-10.0 g/kg. The calibration curves exhibited good linearities with regression coefficients of R(2) ? 0.99. Twelve edible oils were examined to evaluate the efficiency of this method. Among the 12 analytes, dibutyl phthalates (DBP), diethylhexyl phthalates (DEHP), diethylhexyl adipate (DEHA), benzo[a]anthracene (B[a]A), chrysene (Chry) and benzo[b]fluoranthene (B[b]F) were detected in the range of 1.17-806 g/kg. PMID:25029399

Oh, Min-Seok; Lee, Seon-Hwa; Moon, Myeong Hee; Lee, Dong Soo; Park, Hyun-Mee

2014-01-01

299

Simultaneous determination of albendazole and its metabolites in fish muscle tissue by stable isotope dilution ultra-performance liquid chromatography tandem mass spectrometry.  

PubMed

A rapid, specific, and sensitive method utilizing ultra-performance liquid chromatography tandem mass spectrometry was developed and validated to determine albendazole, albendazole sulfoxide, albendazole sulfone, and albendazole 2-aminosulfone in fish muscle tissue. The fish samples were extracted with ethyl acetate, then the organic phase was evaporated to dryness, and the residue was reconstituted in methanol-water solution and cleaned up by n-hexane. Reversed-phase separation of target compounds was achieved using a BEH C18 column and a gradient consisting of 0.2% (v/v) formic acid and methanol. Tandem mass spectrometry analyses were performed on a triple-quadrupole tandem mass spectrometer. In the whole procedure, the isotope-labeled internal standards were used to correct the matrix effect and variations associated with the analysis. The method was validated with respect to linearity, specificity, accuracy, and precision. The method exhibited a linear response from 0.1 to 20 ng mL(-1) (r(2)?>?0.9985). The limit of quantitation for albendazole (ABZ), albendazole sulfoxide (ABZSO), albendazole sulfone (ABZSO(2)), and albendazole 2-aminosulfone (ABZ-2-NH(2)SO(2)) was 0.1, 0.1, 0.1, and 0.2 ng g(-1), respectively. The mean recoveries of ABZ, ABZSO, ABZSO(2), and ABZ-2-NH(2)SO(2) spiked at a level of 0.2-5.0 ng g(-1) were 95.3-113.7%, and the relative standard deviations of intra- and inter-day measurements were less than 6.38%. The method was later successfully applied to the determination of albendazole and its three metabolites in 60 fish samples collected from local markets. PMID:21633840

Zhang, Xiaojun; Xu, Hanxiang; Zhang, Hong; Guo, Yuanming; Dai, Zhiyuan; Chen, Xuechang

2011-08-01

300

Mass Spectrometry and Protein Analysis  

NSDL National Science Digital Library

Mass spectrometry is a central analytical technique for protein research and for the study of biomolecules in general. Driven by the need to identify, characterize, and quantify proteins at ever increasing sensitivity and in ever more complex samples, a wide range of new mass spectrometry??based analytical platforms and experimental strategies have emerged. Here we review recent advances in mass spectrometry instrumentation in the context of current and emerging research strategies in protein science.

Bruno Domon (ETH Zurich; Institute of Molecular Systems Biology)

2006-04-14

301

Characterization of TATP gas phase product ion chemistry via isotope labeling experiments using ion mobility spectrometry interfaced with a triple quadrupole mass spectrometer.  

PubMed

Identification of the fragment ion species associated with the ion reaction mechanism of triacetone triperoxide (TATP), a homemade peroxide-based explosive, is presented. Ion mobility spectrometry (IMS) has proven to be a key analytical technique in the detection of trace explosive material. Unfortunately, IMS alone does not provide chemical identification of the ions detected; therefore, it is unknown what ion species are actually formed and separated by the IMS. In IMS, ions are primarily characterized by their drift time, which is dependent on the ion?s mass and molecular cross-section; thus, IMS as a standalone technique does not provide structural signatures, which is in sharp contrast to the chemical and molecular information that is generally obtained from other customary analytical techniques, such as NMR, Raman and IR spectroscopy and mass spectrometry. To help study the ion chemistry that gives rise to the peaks observed in IMS, the hardware of two different commercial IMS instruments has been directly coupled to triple quadrupole (QQQ) mass spectrometers, in order to ascertain each ion?s corresponding mass/charge (m/z) ratios with different dopants at two temperatures. Isotope labeling was then used to help identify and confirm the molecular identity of the explosive fragment and adduct ions of TATP. The m/z values and isotope labeling experiments were used to help propose probable molecular formulas for the ion fragments. In this report, the fragment and adduct ions m/z 58 and 240 of TATP have been confirmed to be [C3H6NHH](+) and [TATPNH4](+), respectively; while the fragment ions m/z 73 and 89 of TATP are identified as having the molecular formulas [C4H9NH2](+) and [C4H9O2](+), respectively. It is anticipated that the work in this area will not only help to facilitate improvements in mobility-based detection (IMS and MS), but also aid in the development and optimization of MS-based detection algorithms for TATP. PMID:24913870

Tomlinson-Phillips, Jill; Wooten, Alfred; Kozole, Joseph; Deline, James; Beresford, Pamela; Stairs, Jason

2014-09-01

302

Mass spectrometry technologies for proteomics.  

PubMed

In the late 1980s, the advent of soft ionization techniques capable of generating stable gas phase ions from thermally unstable biomolecules, namely matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI), laid the way for the development of a set of powerful alternatives to the traditional Edman chemistry for the structural characterization of peptides and proteins. The rapid protein identification capabilities that, coupled with two-dimensional gel electrophoresis, provided insights into all sorts of biological systems since the dawn of proteomics and have been exploited in the last few years for the development of more powerful and automatable gel-free strategies, mainly based on multidimensional chromatographic separations of peptides from proteolytic digests. In parallel to the evolution of ion sources, mass analysers and scan modes, the invention of new elegant biochemical strategies to fractionate or simplify highly complex mixtures, or to introduce isotopic labels in peptides in a variety of ways now makes also possible large-scale, high-coverage quantitative studies in a wide dynamic range. In this review, we provide the fundamental concepts of mass spectrometry (MS) and describe the technological progress of MS-based proteomics since its earliest days. Representative literature examples of their true power, either when employed as exploratory or as targeted techniques, is provided as well. PMID:17202122

Caas, Benito; Lpez-Ferrer, Daniel; Ramos-Fernndez, Antonio; Camafeita, Emilio; Calvo, Enrique

2006-02-01

303

Isotope shifts of C I spectral lines and their application to radioactive dating by laser-assisted mass spectrometry.  

PubMed

We have calculated isotope shifts for several one- and two-photon transitions in neutral carbon. The results provide a unified interpretation of existing experimental data, and they demonstrate the applicability of a new method of ultrasensitive isotope trace analysis to carbon. PMID:19718187

Clark, C W

1983-11-01

304

Compact hydrogen\\/helium isotope mass spectrometer  

Microsoft Academic Search

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,

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

1996-01-01

305

Analysis of LDEF experiment AO187-2: Chemically and isotopic measurements of micrometeoroids by secondary ion mass spectrometry  

NASA Technical Reports Server (NTRS)

Numerous 'extended impacts' found in both leading and trailing edge capture cells have been successfully analyzed for the chemical composition of projectile residues by secondary ion mass spectrometry (SIMS). Most data have been obtained from the trailing edge cells where 45 of 58 impacts have been classified as 'probably natural' and the remainder as 'possibly man-made debris.' This is in striking contrast to leading edge cells where 9 of 11 impacts so far measured are definitely classified as orbital debris. Although all the leading edge cells had lost their plastic entrance foils during flight, the rate of foil failure was similar to that of the trailing edge cells, 10 percent of which were recovered intact. Ultra-violet embrittlement is suspected as the major cause of failure on both leading and trailing edges. The major impediment to the accurate determination of projectile chemistry is the fractionation of volatile and refractory elements in the hypervelocity impact and redeposition processes. This effect had been noticed in simulation experiment but is more pronounced in the Long Duration Exposure Facility (LDEF) capture cells, probably due to the higher average velocities of the space impacts. Surface contamination of the pure Ge surfaces with a substance rich in Si but also containing Mg and Al provides an additional problem for the accurate determination of impactor chemistry. The effect is variable, being much larger on surfaces that were exposed to space than in those cells that remained intact. Future work will concentrate on the analyses of more leading edge impacts and the development of new SIMS techniques for the measurement of elemental abundances in extended impacts.

1992-01-01

306

Validation of a gas chromatography-mass spectrometry isotope dilution method for the determination of 2-butoxyethanol and other common glycol ethers in consumer products.  

PubMed

A gas chromatography-mass spectrometry isotope dilution (GC-MS ID) method was developed and tested for the determination of 14 common glycol ethers in consumer products. Stable isotope labelled standards, 2-methoxyethanol-D(7) and 2-butoxyethanol-(13)C(2) (CDN isotopes) were employed to enhance the accuracy and precision of the glycol ethers determination. A 1000-fold sample dilution with methanol was applied to avoid column overload and contamination. At this dilution matrix effects were in most cases negligible and did not interfere with the analysis. The instrument detection limit (IDL) for analysed compounds varied from 0.01 to 1 ?g/mL; while the estimated limit of quantification (LoQ) varied between different glycol ethers from 0.02 to 3.4 ?g/mL. Calibration was tested in the range of 0.1-200 ?g/mL and showed that the linear fit is upheld from 0.1 to 10 ?g/mL, and extends beyond this range for some of the analytes. Recoveries of glycol ethers from products with different matrices were similar. The recoveries varied from 87% to 116% between the analysed compounds, while measurements precision varied between 2% and 14%. The method is applicable to products with glycol ether concentrations above 0.002-0.2% (w/w). The concentration range can be extended below the specified limits by decreasing the dilution factor; however, with lower dilution the sample matrix effect is expected to be stronger. Products with very high concentrations of glycol ether (>20%) may need to be further diluted prior to injection to avoid column overload. The method can be used for testing liquid and aerosol products designed for household use, such as cleaners, paints, solvents and paint stripers, for compliance and enforcement of regulations which limit glycol ethers content. PMID:20855078

Tokarczyk, Ryszard; Jiang, Ying; Poole, Gary; Turle, Richard

2010-10-29

307

Accelerator mass spectrometry as a bioanalytical tool for nutritional research  

SciTech Connect

Accelerator Mass Spectrometry is a mass spectrometric method of detecting long-lived radioisotopes without regard to their decay products or half-life. The technique is normally applied to geochronology, but recently has been developed for bioanalytical tracing. AMS detects isotope concentrations to parts per quadrillion, quantifying labeled biochemicals to attomole levels in milligram- sized samples. Its advantages over non-isotopeic and stable isotope labeling methods are reviewed and examples of analytical integrity, sensitivity, specificity, and applicability are provided.

Vogel, J.S.; Turteltaub, K.W.

1997-09-01

308

A World without Sample Preparation: Developing Rapid Uranium Isotope Measurement Capabilities by Resonance Ionization Mass Spectrometry (RIMS)  

SciTech Connect

We are developing highly sensitive, highly discriminating laser-based techniques for rapid determination of isotopic compositions. Rapid command of such information is critical to assessment of the origin and history of nuclear materials, particularly in post-detonation scenarios.

Knight, K B; Hutcheon, I D; Isselhardt, B H; Savina, M R; Prussin, S G

2009-06-08

309

High precision Hf isotope measurements of MORB and OIB by thermal ionisation mass spectrometry: insights into the depleted mantle  

Microsoft Academic Search

The existing Hf isotope database for mid-ocean ridge basalts (MORB) is limited in both quantity and precision. Nevertheless, in HfNd isotope space, MORBs show a wide variation in 176Hf\\/177Hf over a relatively restricted range in 143Nd\\/144Nd. The highest 176Hf\\/177Hf ratios (?0.283355) within the MORB range are restricted to just four samples (<6.5% of total). Of these high 176Hf\\/177Hf MORBs, three

G. M. Nowell; P. D. Kempton; S. R. Noble; J. G. Fitton; A. D. Saunders; J. J. Mahoney; R. N. Taylor

1998-01-01

310

External calibration in gas chromatography-combustion-isotope ratio mass spectrometry measurements of endogenous androgenic anabolic steroids in sports doping control.  

PubMed

An alternative calibration procedure for the gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) measurements of the World Antidoping Agency (WADA) Accredited Laboratories is presented. To alleviate the need for externally calibrated CO? gas for GC-C-IRMS analysis of urinary steroid metabolites, calibration using an external standard mixture solution of steroids with certified isotopic composition was investigated. The reference steroids of the calibration mixture and routine samples underwent identical instrumental processes. The calibration standards bracketed the entire range of the relevant ?C values for the endogenous and exogenous steroids as well as their chromatographic retention times. The certified ?C values of the reference calibrators were plotted in relation to measured m/z CO?/CO? (i.e. R(45/44)) mass spectrometric signals of each calibrator. ?C values of the sample steroids were calculated from the least squares fit through the calibration curve. The effect of the external calibration on ?C values, using the same calibration standards and set of urine samples but different brands of GC-C-IRMS instruments, was assessed by an interlaboratory study in the WADA Accredited Laboratories of Sydney, Australia and Athens, Greece. Relative correspondence between the laboratories for determination of androsterone, etiocholanolone, 5?-androstane-3?,17?-diacetate, and pregnanediacetate means were SD(?C)=0.12, 0.58, -0.34, and -0.40, respectively. These data demonstrate that accurate intralaboratory external calibration with certified steroids provided by United States Antidoping Agency (USADA) and without external CO? calibration is feasible and directly applicable to the WADA Accredited Laboratories for the harmonization of the GC-C-IRMS measurements. PMID:21752385

Kioussi, Maroula K; Angelis, Yiannis S; Cawley, Adam T; Koupparis, Michalis; Kazlauskas, Rymantas; Brenna, J Thomas; Georgakopoulos, Costas G

2011-08-19

311

Measurement of progesterone in human serum by isotope dilution liquid chromatography-tandem mass spectrometry and comparison with the commercial chemiluminescence immunoassay.  

PubMed

Progesterone is one of the steroid hormones. The hormone is especially important in preparing the uterus for the implantation of the blastocyst and in maintaining pregnancy. Its concentration in serum is measured to determine ovarian function and to predict early pregnancy. The progesterone concentration is also important for in-vitro fertilization and embryo-transfer outcomes. We have established isotope dilution liquid chromatography-tandem mass spectrometry as a primary method for the measurement of progesterone in human serum. Progesterone and its isotopic analogue, progesterone-(13)C(2), in serum were monitored at mass transitions of m/z 315.2/109.2 and 317.2/111.2 respectively in multiple-reaction monitoring (MRM) mode with electrospray positive ionization. For validation of the method, progesterone in a National Institute of Standards and Technology standard reference material (NIST SRM) was measured, and the measured results were in good agreement with the reference values within the uncertainty. On the basis of the established method, progesterone certified reference material (CRM) was developed in this work. The certified value was (1.41??0.036) ?g kg(-1). The repeatability of 1.1% and reproducibility of 0.14% showed that ID LC-MS-MS is a reliable and reproducible method. The expanded uncertainty for the measurement of progesterone in the CRM was approximately 2.6% within 95% confidence limits. The detection limit of progesterone was approximately 0.6 ?g kg(-1). The progesterone CRMs were distributed to representative clinical laboratories in the Republic of Korea for comparison with the chemiluminescence immunoassay (CLIA), which is the most sensitive immunoassay method. The results from the comparison showed quite a large bias among the participating laboratories. This implies that the CRM is a very important material for establishment of traceability to its practical use. PMID:20107773

Lee, Hwashim; Park, Chang Joon; Lee, Gaeho

2010-03-01

312

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

PubMed

A method is described for quantification of sulfur at low concentrations on the order of mgkg(-1) in biodiesel and diesel fuels using isotope dilution and sector field inductively coupled plasma mass spectrometry (ID-SF-ICP-MS). Closed vessel microwave-assisted digestion was employed using a diluted nitric acid and hydrogen peroxide decomposition medium to reduce sample dilution volumes. Medium resolution mode was employed to eliminate isobaric interferences at (32)S and (34)S related to polyatomic phosphorus and oxygen species, and sulfur hydride species. The method outlined yielded respective limits of detection (LOD) and limits of quantification (LOQ) of 0.7 mg kg(-1) S and 2.5 mg kg(-1) S (in the sample). The LOD was constrained by instrument background counts at (32)S but was sufficient to facilitate value assignment of total S mass fraction in NIST SRM 2723b Sulfur in Diesel Fuel Oil at 9.060.13 mg kg(-1). No statistically significant difference at a 95% confidence level was observed between the measured and certified values for certified reference materials NIST SRM 2773 B100 Biodiesel (Animal-Based), CENAM DRM 272b and NIST SRM 2723a Sulfur in Diesel Fuel Oil, validating method accuracy. PMID:24331043

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

2014-01-01

313

Linear electric field mass spectrometry  

DOEpatents

A mass spectrometer and methods for mass spectrometry are described. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field. 8 figs.

McComas, D.J.; Nordholt, J.E.

1992-12-01

314

Linear electric field mass spectrometry  

DOEpatents

A mass spectrometer and methods for mass spectrometry. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field.

McComas, David J. (Los Alamos, NM); Nordholt, Jane E. (Los Alamos, NM)

1992-01-01

315

Mass Spectrometry & Proteomics Services Unit  

E-print Network

Mass Spectrometry & Proteomics Services Unit Peptide and Protein Submission Form Website: http for analysis is dependent on sample complexity. Normally it takes 1-2 days for mass determination, and 3-5 days for protein identification by in-gel digestion and LC MS/MS analysis. 2. Mass spectrometric analysis Operator

Graham, Nick

316

Stable carbon and hydrogen isotope analysis of methyl tert-butyl ether and tert-amyl methyl ether by purge and trap-gas chromatography-isotope ratio mass spectrometry: method evaluation and application.  

PubMed

In order to monitor the behaviour of contaminants in the aqueous environment effective enrichment techniques often have to be employed due to their low concentrations. In this work a robust and sensitive purge and trap-gas chromatography-isotope ratio mass spectrometry method for carbon and hydrogen isotope analysis of fuel oxygenates in water is presented. The method evaluation included the determination of method detection limits, accuracy and reproducibility of deltaD and delta(13)C values. Lowest concentrations at which reliable delta(13)C values could be determined were 5 microg L(-1) and 28 microg L(-1) for TAME and MTBE, respectively. Stable deltaD values for MTBE and TAME could be achieved for concentrations as low as 25 and 50 microg L(-1). Good long-term reproducibility of delta(13)C and deltaD values was obtained for all target compounds. But deltaD values varying more than 5 per thousand were observed using different thermal conversion tubes. Thus, a correction of deltaD values in the analysis of groundwater samples was necessary to guarantee comparability of the results. The applicability of this method was shown by the analysis of groundwater samples from a gasoline contaminated site. By two dimensional isotope analysis two locations within this site were identified at which anaerobic and aerobic degradation of methyl tert-butyl ether occurred. PMID:20082031

Kujawinski, Dorothea M; Stephan, Manuel; Jochmann, Maik A; Krajenke, Karen; Haas, Joe; Schmidt, Torsten C

2010-01-01

317

Multiplexed analysis of cage and cage free chicken egg fatty acids using stable isotope labeling and mass spectrometry.  

PubMed

Binary stable isotope labeling couple with LC-ESI-MS has been used as a powerful non-targeted approach for the relative quantification of lipids, amino acids, and many other important metabolite classes. A multiplexed approach using three or more isotopic labeling reagents greatly reduces analytical run-time while maintaining excellent sensitivity and reproducibility. Three isotopic cholamine labeling reagents have been developed to take advantage of the pre-ionized character of cholamine, for ESI, and the ease by which stable isotopes can be incorporated into the cholamine structure. These three cholamine labeling reagents have been used to relatively quantify three fatty acid samples simultaneously. The quantification resulted in the observation of 12 fatty acids that had an average absolute error of 0.9% and an average coefficient of variation of 6.1%. Caged versus cage-free isotope labeling experiments showed that cage-free eggs have an increased level of omega-3 fatty acids as compared to caged eggs. This multiplexed fatty acid analysis provides an inexpensive and expedited tool for broad-based lipid profiling that will further aid discoveries in the mechanisms of fatty acid action in cells. PMID:24317525

Torde, Richard G; Therrien, Andrew J; Shortreed, Michael R; Smith, Lloyd M; Lamos, Shane M

2013-01-01

318

JOURNAL OF MASS SPECTROMETRY J. Mass Spectrom. 34, 661669 (1999)  

E-print Network

JOURNAL OF MASS SPECTROMETRY J. Mass Spectrom. 34, 661­669 (1999) Comparative Mass Spectrometric Analyses of Photofrin Oligomers by Fast Atom Bombardment Mass Spectrometry, UV and IR Matrix-assisted Laser Desorption/Ionization Mass Spectrometry, Electrospray Ionization Mass Spectrometry and Laser Desorption

de Vries, Mattanjah S.

319

Quantitative profiling of differentiation-induced microsomal proteins using isotope-coded affinity tags and mass spectrometry  

Microsoft Academic Search

An approach to the systematic identification and quantification of the proteins contained in the microsomal fraction of cells is described. It consists of three steps: (1) preparation of microsomal fractions from cells or tissues representing different states; (2) covalent tagging of the proteins with isotope-coded affinity tag (ICAT) reagents followed by proteolysis of the combined labeled protein samples; and (3)

David K. Han; Jimmy Eng; Huilin Zhou; Ruedi Aebersold

2001-01-01

320

Determination of the 13C/12C ratio of ethanol derived from fruit juices and maple syrup by isotope ratio mass spectrometry: collaborative study.  

PubMed

A collaborative study of the carbon-13 isotope ratio mass spectrometry (13C-IRMS) method based on fermentation ethanol for detecting some sugar additions in fruit juices and maple syrup is reported. This method is complementary to the site-specific natural isotope fractionation by nuclear magnetic resonance (SNIF-NMR) method for detecting added beet sugar in the same products (AOAC Official Methods 995.17 and 2000.19), and uses the same initial steps to recover pure ethanol. The fruit juices or maple syrups are completely fermented with yeast, and the alcohol is distilled with a quantitative yield (>96%). The carbon-13 deviation (delta13C) of ethanol is then determined by IRMS. This parameter becomes less negative when exogenous sugar derived from plants exhibiting a C4 metabolism (e.g., corn or cane) is added to a juice obtained from plants exhibiting a C3 metabolism (most common fruits except pineapple) or to maple syrup. Conversely, the delta13C of ethanol becomes more negative when exogenous sugar derived from C3 plants (e.g., beet, wheat, rice) is added to pineapple products. Twelve laboratories analyzed 2 materials (orange juice and pure cane sugar) in blind duplicate and 4 sugar-adulterated materials (orange juice, maple syrup, pineapple juice, and apple juice) as Youden pairs. The precision of that method for measuring delta13C was similar to that of other methods applied to wine ethanol or extracted sugars in juices. The within-laboratory (Sr) values ranged from 0.06 to 0.16%o (r = 0.17 to 0.46 percent per thousand), and the among-laboratories (SR) values ranged from 0.17 to 0.26 percent per thousand (R = 0.49 to 0.73 percent per thousand). The Study Directors recommend that the method be adopted as First Action by AOAC INTERNATIONAL. PMID:15287660

Jamin, Eric; Martin, Frdrique; Martin, Gilles G

2004-01-01

321

Qualitative Metabolome Analysis of Human Cerebrospinal Fluid by 13C-/12C-Isotope Dansylation Labeling Combined with Liquid Chromatography Fourier Transform Ion Cyclotron Resonance Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Metabolome analysis of human cerebrospinal fluid (CSF) is challenging because of low abundance of metabolites present in a small volume of sample. We describe and apply a sensitive isotope labeling LC-MS technique for qualitative analysis of the CSF metabolome. After a CSF sample is divided into two aliquots, they are labeled by 13C-dansyl and 12C-dansyl chloride, respectively. The differentially labeled aliquots are then mixed and subjected to LC-MS using Fourier-transform ion cyclotron resonance mass spectrometry (FTICR MS). Dansylation offers significant improvement in the performance of chromatography separation and detection sensitivity. Moreover, peaks detected in the mass spectra can be readily analyzed for ion pair recognition and database search based on accurate mass and/or retention time information. It is shown that about 14,000 features can be detected in a 25-min LC-FTICR MS run of a dansyl-labeled CSF sample, from which about 500 metabolites can be profiled. Results from four CSF samples are compared to gauge the detectability of metabolites by this method. About 261 metabolites are commonly detected in replicate runs of four samples. In total, 1132 unique metabolite ion pairs are detected and 347 pairs (31%) matched with at least one metabolite in the Human Metabolome Database. We also report a dansylation library of 220 standard compounds and, using this library, about 85 metabolites can be positively identified. Among them, 21 metabolites have never been reported to be associated with CSF. These results illustrate that the dansylation LC-FTICR MS method can be used to analyze the CSF metabolome in a more comprehensive manner.

Guo, Kevin; Bamforth, Fiona; Li, Liang

2011-02-01

322

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

PubMed

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

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

2009-05-29

323

Quantification of 13 priority polycyclic aromatic hydrocarbons in human urine by headspace solid-phase microextraction gas chromatography-isotope dilution mass spectrometry.  

PubMed

Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants in both living and working environments. The aim of this study was the development of a headspace solid-phase microextraction gas chromatography-isotope dilution mass spectrometry (HS-SPME/GC-IDMS) method for the simultaneous quantification of 13 PAHs in urine samples. Different parameters affecting PAHs extraction by HS-SPME were considered and optimized: type/thickness of fiber coatings, extraction temperature/time, desorption temperature/time, ionic strength and sample agitation. The stability of spiked PAHs solutions and of real urine samples stored up to 90 days in containers of different materials was evaluated. In the optimized method, analytes were absorbed for 60min at 80 degrees C in the sample headspace with a 100mum polydimethylsiloxane fiber. The method is very specific, with linear range from the limit of quantification to 8.67 x 10(3)ngL(-1), a within-run precision of <20% and a between-run precision of <20% for 2-, 3- and 4-ring compounds and of <30% for 5-ring compounds, trueness within 20% of the spiked concentration, and limit of quantification in the 2.28-2.28 x 10(1)ngL(-1) range. An application of the proposed method using 15 urine samples from subjects exposed to PAHs at different environmental levels is shown. PMID:19084626

Campo, Laura; Mercadante, Rosa; Rossella, Federica; Fustinoni, Silvia

2009-01-12

324

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

USGS Publications Warehouse

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

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

2001-01-01

325

Analysis of urinary vitamin D? metabolites by liquid chromatography/tandem mass spectrometry with ESI-enhancing and stable isotope-coded derivatization.  

PubMed

The determination of the urinary vitamin D? metabolites might prove helpful in the assessment of the vitamin D status. We developed a method for the determination of trace vitamin D? metabolites, 25-hydroxyvitamin D? [25(OH)D?] and 24,25-dihydroxyvitamin D? [24,25(OH)?D?], in urine using liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) combined with derivatization using an ESI-enhancing reagent, 4-(4'-dimethylaminophenyl)-1,2,4-triazoline-3,5-dione (DAPTAD), and its isotope-coded analogue, (2)H4-DAPTAD (d-DAPTAD). The urine samples were treated with ?-glucuronidase, purified with an Oasis hydrophilic-lipophilic balanced (HLB) cartridge, and then subjected to the derivatization. The DAPTAD derivatization enabled the highly sensitive detection (detection limit, 0.25 fmol on the column), and the use of d-DAPTAD significantly improved the assay precision [the intra- (n?=?5) and inter-assay (n?=?3) relative standard deviations did not exceed 9.5%]. The method was successfully applied to urine sample analyses and detected the increases of the urinary 25(OH)D? and 24,25(OH)?D? levels due to vitamin D? administration. PMID:25168117

Ogawa, Shoujiro; Ooki, Satoshi; Shinoda, Kenta; Higashi, Tatsuya

2014-10-01

326

A rapid screening assay for measuring urinary androsterone and etiocholanolone delta(13)C ( per thousand) values by gas chromatography/combustion/isotope ratio mass spectrometry.  

PubMed

A gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) method is described and validated for measurement of delta(13)C values of the acetate derivatives of urinary etiocholanolone and androsterone. The analysis was performed with only 2 mL of urine. The sample preparation consisted of deconjugation with beta-glucuronidase, solid phase extraction, and derivatization with acetic anhydride and pyridine. The within-assay precision of two quality control (QC) urine samples ranged from 0.5 to 2.1 CV%. The between-assay precision in the same QC urines ranged from 1.7 to 3.4 CV%. Administration of testosterone enanthate to a subject resulted in a 6 per thousand decrease in delta(13)C values from -25 per thousand (baseline) to -31 per thousand. Two weeks after testosterone administration was discontinued, the delta(13)C values remained abnormally low while the urine testosterone/epitestosterone (T/E) ratio returned to less than 6. This relatively simple method is useful for rapidly screening a large number of urine samples, including those with T/E <6. PMID:11114040

Aguilera, R; Chapman, T E; Catlin, D H

2000-01-01

327

Studies on the analysis of 25-hydroxyvitamin D3 by isotope-dilution liquid chromatographytandem mass spectrometry using enzyme-assisted derivatisation  

PubMed Central

The total serum concentration of 25-hydroxyvitamins D (25-hydroxyvitamin D3 and 25-hydroxyvitamin D2) is currently used as an indicator of vitamins D status. Vitamins D insufficiency is claimed to be associated with multiple diseases, thus accurate and precise reference methods for the quantification of 25-hydroxyvitamins D are needed. Here we present a novel enzyme-assisted derivatisation method for the analysis of vitamins D metabolites in adult serum utilising 25-[26,26,26,27,27,27-2H6]hydroxyvitamin D3 as the internal standard. Extraction of 25-hydroxyvitamins D from serum is performed with acetonitrile, which is shown to be more efficient than ethanol. Cholesterol oxidase is used to oxidize the 3?-hydroxy group in the vitamins D metabolites followed by derivatisation of the newly formed 3-oxo group with Girard P reagent. 17?-Hydroxysteroid dehydrogenase type 10 is shown to oxidize selectively the 3?-hydroxy group in the 3?-hydroxy epimer of 25-hydroxyvitamin D3. Quantification is achieved by isotope-dilution liquid chromatographytandem mass spectrometry. Recovery experiments for 25-hydroxyvitamin D3 performed on adult human serum give recovery of 102106%. Furthermore in addition to 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3 and other uncharacterised dihydroxy metabolites, were detected in adult human serum. PMID:24486315

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

2014-01-01

328

Enantioselective determination of ibuprofen in saliva by liquid chromatography/tandem mass spectrometry with chiral electrospray ionization-enhancing and stable isotope-coded derivatization.  

PubMed

A method was developed and validated for the enantioselective determination of trace ibuprofen (IBU) in saliva using liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) combined with the derivatization using a chiral ESI-enhancing reagent, (S)-1-(4-dimethylaminophenylcarbonyl)-3-aminopyrrolidine (DAPAP), and its isotope-coded analog, (2)H4-DAPAP (d-DAPAP). The DAPAP-derivatization enabled the highly sensitive detection [detection limit, 0.15fmol (equivalent to 30fg of intact IBU) on the column] and complete separation (resolution 3.1) of the IBU enantiomers. The use of d-DAPAP significantly improved the assay precision and accuracy; the intra- (n=5) and inter-assay (n=5) relative standard deviations did not exceed 6.2%, and good accuracy (101.3-106.1%) was obtained. The developed method was successfully applied to the quantitative analysis of IBU in saliva. Using this method, salivary concentration-time profiles of each enantiomer after a single oral administration of the racemic IBU to healthy subjects were obtained. The area under the salivary concentration-time curve of the (S)-enantiomer was ca. twice that of the (R)-enantiomer due to the unidirectional chiral inversion of the (R)- to (S)-enantiomer in vivo. Thus, saliva-based noninvasive pharmacokinetic analyses of IBU enantiomers were achieved by this method. PMID:24999866

Ogawa, Shoujiro; Tadokoro, Hiroaki; Sato, Maho; Higashi, Tatsuya

2014-09-01

329

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

PubMed

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

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

2006-02-01

330

Innovative method for carbon dioxide determination in human postmortem cardiac gas samples using headspace-gas chromatography-mass spectrometry and stable labeled isotope as internal standard.  

PubMed

A novel approach to measure carbon dioxide (CO2) in gaseous samples, based on a precise and accurate quantification by (13)CO2 internal standard generated in situ is presented. The main goal of this study was to provide an innovative headspace-gas chromatography-mass spectrometry (HS-GC-MS) method applicable in the routine determination of CO2. The main drawback of the GC methods discussed in the literature for CO2 measurement is the lack of a specific internal standard necessary to perform quantification. CO2 measurement is still quantified by external calibration without taking into account analytical problems which can often occur considering gaseous samples. To avoid the manipulation of a stable isotope-labeled gas, we have chosen to generate in situ an internal labeled standard gas ((13)CO2) on the basis of the stoichiometric formation of CO2 by the reaction of hydrochloric acid (HCl) with sodium hydrogen carbonate (NaH(13)CO3). This method allows a precise measurement of CO2 concentration and was validated on various human postmortem gas samples in order to study its efficiency. PMID:23746406

Varlet, V; Smith, F; de Froidmont, S; Dominguez, A; Rinaldi, A; Augsburger, M; Mangin, P; Grabherr, S

2013-06-19

331

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

SciTech Connect

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

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

2009-09-04

332

Development of two-dimensional gas chromatography/isotope ratio mass spectrometry for the stable carbon isotopic analysis of C(2)-C(5) non-methane hydrocarbons emitted from biomass burning.  

PubMed

A two-dimensional gas chromatography/combustion/isotope ratio mass spectrometry (2D-GC/C/IRMS) system was developed for stable carbon isotopic measurements of C(2)-C(5) non-methane hydrocarbons (NMHCs) in biomass burning smoke. The 2D-GC/C/IRMS system successfully improved the accuracy and precision for the measurements of C(4) and C(5) saturated compounds in a smoke sample by selective injection of target compounds into a combustion furnace and consequently allowed us to provide complete baseline separation for all individual NMHCs. The analytical precision of the delta(13)C of each compound was better than 0.5 per thousand for more than 500 pmolC injections and 2.1 per thousand for 30 pmolC injections, which was estimated from replicate analysis of standard gases. This system was applied to the analysis of NMHCs in smoke samples collected from laboratory biomass burning experiments. From the combustion of three fuel materials (rice straw, pine wood, and maize), we found that the isotopic fractionation between fuel material and individual NMHCs is almost independent of the fuel material and thus the delta(13)C values of the fuel materials are reflected in delta(13)C values of most of NMHCs. However, only i-butane emitted from maize combustion showed anomalous (13)C-depletion of -11.6 per thousand relative to the delta(13)C value of maize. Such a large (13)C depletion suggests the specific isotopic fractionation process which is attributed to the maize combustion itself or the chemical properties of i-butane during production from a radical recombination reaction. PMID:16345120

Nara, Hideki; Nakagawa, Fumiko; Yoshida, Naohiro

2006-01-01

333

Memory effects in compound-specific D/H analysis by gas chromatography/pyrolysis/isotope-ratio mass spectrometry.  

PubMed

Compound-specific analyses of lipid D/H ratios often encounter ranges of 300 per thousand or more, and experiments using D-enriched water to study fractionations often extend the range up to 1000 per thousand. Here we show that for such large dynamic ranges in D/H ratio, isotopic "memory" between adjacent peaks can be significant. Memory effects have not been previously reported for GC/P/IRMS systems but can have a significant impact on many measurements, even those exploring only natural-abundance variations in D/H. To quantitatively evaluate these effects, we synthesized two series of organic standards with deltaD values varying from -230 to +800 per thousand. We then analyzed chromatograms in which analyte deltaD values, retention times, or relative abundances were independently varied. For two sequential GC peaks, isotopic memory is measured to be typically 2-4% of the difference in deltaD values between the two. Roughly half of this effect can be attributed to unknown processes within the GC itself, and the other half to surface adsorption processes in the pyrolytic conversion of analytes to H2. Isotopic memory increases with decreasing time separation between peaks, with decreasing analyte abundance, and with increasing age of pyrolysis reactors. A simple numerical model that simulates dynamic adsorption of H2 on pyrolytic carbon can reproduce many aspects of the experimental data, suggesting that this is likely to be an important mechanism in isotopic memory. Several steps to mitigate memory effects in routine analyses are suggested. PMID:19551939

Wang, Ying; Sessions, Alex L

2008-12-01

334

Instrumentation for mass spectrometry: 1997  

SciTech Connect

All mass spectrometry experiments involve the manipulation of material, an interface with the mass spectrometer, ionization, ion manipulation/analysis, detection and data collection/reduction. Each of these elements involve instrumentation. The wide range of species now amenable to mass spectrometry and the diverse areas of physical science in which it plays a role have led to a seemingly unlimited array of instrumental combinations. However, only a limited number of mass analyzers, and their combinations, dominate. The dominant analyzers include time-of-flight, Fourier transform ion cyclotron resonance, the Paul trap, the mass filter, and the sector mass spectrometer. Why there are so few (or so many, depending upon one`s point of view) can be understood upon consideration of a set of mass analyzer figures of merit. These include mass resolution, mass accuracy, mass range, dynamic range, abundance sensitivity, precision, efficiency, speed, MS{sup n} capability, compatibility with the ionizer, cost, and size. The most appropriate form of mass spectrometry is determined by the priorities of the particular measurement placed on the various mass analyzer characteristics and the relative strengths of the analyzers in meeting the requirements. Each of the analyzer types has a unique set of figures of merit that makes it optimally suited for particular applications. This paper discusses these figures of merit, provides data illustrating recent developments for each analyzer type, and gives the figures of merit of each type of analyzer as they stand in 1997. 101 refs., 24 figs.

McLuckey, S.A.

1997-08-01

335

A Glossary for Mass Spectrometry  

NSDL National Science Digital Library

This useful article from the journal Mass Spectrometry features a compilation of some of the more widely used terms that non-mass spectrometrists may encounter, and for which a simple definition would be helpful. The link will lead users to a PDF file which may be downloaded or viewed online.

Busch, Kenneth L.

336

Assessment of ultrasound-assisted extraction as sample pre-treatment for the measurement of lead isotope ratios in marine biological tissues by multicollector inductively coupled plasma-mass spectrometry  

Microsoft Academic Search

In this work, ultrasound-assisted extraction (UAE) was evaluated as a sample preparation procedure for lead isotope ratio measurements in marine biological tissues by multicollector inductively coupled plasma-mass spectrometry. 20mg of marine biological tissue and 1mL of acid extractant were sonicated for 3min at 60% ultrasound amplitude. Matrix separation was performed in the supernatant using a chromatographic exchange resin (Sr-Spec). Total

M. Costas-Rodrguez; Isela Lavilla; Carlos Bendicho

2011-01-01

337

Recent advances in biomedical applications of accelerator mass spectrometry  

Microsoft Academic Search

The use of radioisotopes has a long history in biomedical science, and the technique of accelerator mass spectrometry (AMS), an extremely sensitive nuclear physics technique for detection of very low-abundant, stable and long-lived isotopes, has now revolutionized high-sensitivity isotope detection in biomedical research, because it allows the direct determination of the amount of isotope in a sample rather than measuring

Sang Soo Hah

2009-01-01

338

Measurement of ?18O, ?17O, and 17O-excess by Off-Axis Integrated Cavity Output Spectroscopy and Isotope Ratio Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Water stable isotopes have for many years been used to study the hydrological cycle, catchment hydrology, and polar climate. Recently, there has been mounting interest in measurement and use of the less-abundant 17O isotope in addition to 2H and 18O. Off-axis integrated cavity output spectroscopy (OA-ICOS) measures ?18O, ?17O, and 17O-excess in liquid water without sample preparation or highly-trained operators. OA-ICOS allows measurements to be made on a relatively compact and affordable instrument by researchers collecting the samples. Numerous (514) high-throughput measurements of the international water standard GISP are used to demonstrate the precision and accuracy of OA-ICOS: ?18O =-24.74 0.06 (HWHM) and ?17O = -13.12 0.04 (HWHM). For comparison, the IAEA value for ?18O of GISP is 24.76 0.09 (1?) and an average of previously reported values for ?17O of GISP is -13.12 0.06 (1?). Repeated (26) high-precision measurements of GISP provide a 17O-excess of 23 9 per meg (HWHM); an average of previously reported values for 17O-excess is 22 11 per meg (1?). The precision of OA-ICOS measurements of ?18O, ?17O, and 17O-excess can be further enhanced by additional averaging. Comparison with two independent isotope ratio mass spectrometry (IRMS) laboratories shows that OA-ICOS has equivalent accuracy and precision as the current fluorination-IRMS techniques in ?18O, ?17O, and 17O-excess. The capability to accurately measure ?18O, ?17O, and 17O-excess in liquid water inexpensively and without sample preparation is expected to enhance both the number and breadth of applications of ?17O and 17O-excess for understanding of the water cycle, atmospheric convection, and climate modeling among others. 17O-excess measurement accuracy demonstrated by measurements of GISP and four commercially-available USGS standards by OA-ICOS and two independent IRMS labs. Error bars represent one standard error of the mean. The line behind the GISP columns shows the collected average of 3 previously reported IRMS measurements.

Berman, E. S.; Levin, N.; Landais, A.; Li, S.; Owano, T. G.

2013-12-01

339

Counting individual sulfur atoms in a protein by ultrahighresolution Fourier transform ion cyclotron resonance mass spectrometry: Experimental resolution of isotopic fine structure in proteins  

PubMed Central

A typical molecular ion mass spectrum consists of a sum of signals from species of various possible isotopic compositions. Only the monoisotopic peak (e.g., all carbons are 12C; all nitrogens are 14N, etc.) has a unique elemental composition. Every other isotope peak at approximately integer multiples of ?1 Da higher in nominal mass represents a sum of contributions from isotope combinations differing by a few mDa (e.g., two 13C vs. two 15N vs. one 13C and one 15N vs. 34S, vs. 18O, etc., at ?2 Da higher in mass than the monoisotopic mass). At sufficiently high mass resolving power, each of these nominal-mass peaks resolves into its isotopic fine structure. Here, we report resolution of the isotopic fine structure of proteins up to 15.8 kDa (isotopic 13C,15N doubly depleted tumor suppressor protein, p16), made possible by electrospray ionization followed by ultrahigh-resolution Fourier transform ion cyclotron resonance mass analysis at 9.4 tesla. Further, a resolving power of m/?m50% ?8,000,000 has been achieved on bovine ubiquitin (8.6 kDa). These results represent a 10-fold increase in the highest mass at which isotopic fine structure previously had been observed. Finally, because isotopic fine structure reveals elemental composition directly, it can be used to confirm or determine molecular formula. For p16, for example, we were able to determine (5.1 0.3) the correct number (five) of sulfur atoms solely from the abundance ratio of the resolved 34S peak to the monoisotopic peak. PMID:9751700

Shi, Stone D.-H.; Hendrickson, Christopher L.; Marshall, Alan G.

1998-01-01

340

Digital imaging mass spectrometry.  

PubMed

Methods to visualize the two-dimensional (2D) distribution of molecules by mass spectrometric imaging evolve rapidly and yield novel applications in biology, medicine, and material surface sciences. Most mass spectrometric imagers acquire high mass resolution spectra spot-by-spot and thereby scan the object's surface. Thus, imaging is slow and image reconstruction remains cumbersome. Here we describe an imaging mass spectrometer that exploits the true imaging capabilities by ion optical means for the time of flight mass separation. The mass spectrometer is equipped with the ASIC Timepix chip as an array detector to acquire the position, mass, and intensity of ions that are imaged by matrix-assisted laser desorption/ionization (MALDI) directly from the target sample onto the detector. This imaging mass spectrometer has a spatial resolving power at the specimen of (84??35)??m with a mass resolution of 45 and locates atoms or organic compounds on a surface area up to ~2 cm(2). Extended laser spots of ~5 mm(2) on structured specimens allows parallel imaging of selected masses. The digital imaging mass spectrometer proves high hit-multiplicity, straightforward image reconstruction, and potential for high-speed readout at 4 kHz or more. This device demonstrates a simple way of true image acquisition like a digital photographic camera. The technology may enable a fast analysis of biomolecular samples in near future. PMID:21953049

Bamberger, Casimir; Renz, Uwe; Bamberger, Andreas

2011-06-01

341

High resolution Secondary Ionisation Mass Spectrometry O analyses of Hulu Cave speleothem  

E-print Network

High resolution Secondary Ionisation Mass Spectrometry (SIMS) 18 O analyses of Hulu Cave speleothem The suitability of in situ Secondary Ionisation Mass Spectrometry (SIMS) techniques for measuring O isotopes Ionisation Mass Spectrometry (SIMS) 18O analyses of Hulu Cave speleothem at the time of Heinrich Event

342

Colocalization of the Ganglioside GM1 and Cholesterol Detected by Secondary Ion Mass Spectrometry  

E-print Network

Colocalization of the Ganglioside GM1 and Cholesterol Detected by Secondary Ion Mass Spectrometry here the use of secondary ion mass spectrometry (SIMS) to image the cholesterol-dependent cohesive spectrometry, directly measuring the mass of components or isotopically labeled fragments from the co

Boxer, Steven G.

343

On the potential of Raman-spectroscopy-based carbonate mass spectrometry  

E-print Network

On the potential of Raman-spectroscopy-based carbonate mass spectrometry Nicholas P. Mc from standard mass spectrometry methods, confirming that the relative intensities of the n1 symmetric compounds. Copyright © 2012 John Wiley & Sons, Ltd. Keywords: carbonates; isotopes; mass spectrometry

Downs, Robert T.

344

Symposium on accelerator mass spectrometry  

SciTech Connect

The area of accelerator mass spectrometry has expanded considerably over the past few years and established itself as an independent and interdisciplinary research field. Three years have passed since the first meeting was held at Rochester. A Symposium on Accelerator Mass Spectrometry was held at Argonne on May 11-13, 1981. In attendance were 96 scientists of whom 26 were from outside the United States. The present proceedings document the program and excitement of the field. Papers are arranged according to the original program. A few papers not presented at the meeting have been added to complete the information on the status of accelerator mass spectrometry. Individual papers were prepared separately for the data base.

None

1981-01-01

345

Imaging mass spectrometry in microbiology  

PubMed Central

Mass spectrometry tools which allow for the 2-D visualization of the distribution of trace metals, metabolites, surface lipids, peptides and proteins directly from biological samples without the need for chemical tagging or antibodies are becoming increasingly useful for microbiology applications. These tools, comprised of different imaging mass spectrometry techniques, are ushering in an exciting new era of discovery by allowing for the generation of chemical hypotheses based on of the spatial mapping of atoms and molecules that can correlate to or transcend observed phenotypes. In this review, we explore the wide range of imaging mass spectrometry techniques available to microbiologists and describe their unique applications to microbiology with respect to the types of microbiology samples to be investigated. PMID:21822293

Watrous, Jeramie D.; Dorrestein, Pieter C.

2013-01-01

346

[Determination of mono- to tri-chlorinated dibenzo-p-dioxins and dibenzofurans in stack gas using isotope dilution high resolution gas chromatography-high resolution mass spectrometry].  

PubMed

A method for the determination of mono- to tri-chlorinated dibenzo-p-dioxins and dibenzofurans (mono- to tri-CDD/Fs) in stack gas using isotope dilution high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS) was developed. The sam- ples were extracted by Soxhlet extraction, and then the extracts were concentrated and purified using a multilayer silica gel column and a basic alumina column. The analytes were separated by HRGC on a DB-5MS column (30 m x 0.25 mm x 0.25 ?m) and determined by HRMS. The identi- fication of mono- to tri-CDD/Fs was based on the retention times of 13C-labelled standard and the abundance ratios of the two exacted mass-to-charge ratios. The quantitative analysis was performed using the ratios of the integrated areas of the 13C-labelled standards. This method had the recoveries ranging from 66.6% to 112.5% and the relative standard deviations (RSD) ranging from 19.9% to 40.5% (n = 5). The limits of detection (LODs) of this method for the mono- to tri-CDD/Fs were ranging from 0.027 to 0.485 ?g/L. Three stack gas samples from waste incinerators were measured using this method, with the recoveries ranging from 85.7% to 137.0% and the concentrations ranging from 11.4 to 9,183 pg/Nm3. The results indicated that the method can be applied to the precise determination of mono- to tri-CDD/Fs at trace level in stack gas. PMID:25752087

Tang, Chen; Liu, Qipeng; Tian, Zhenyu; Xie, Huiting; Wang, Mengjing; Liu, Wenbin

2014-09-01

347

Simultaneous speciation of selenoproteins and selenometabolites in plasma and serum by dual size exclusion-affinity chromatography with online isotope dilution inductively coupled plasma mass spectrometry.  

PubMed

A method for the simultaneous speciation of selenoproteins and selenometabolites in mouse plasma has been developed based on in series two-dimensional size exclusion and affinity high-performance liquid chromatography (2D/SE-AF-HPLC), using two columns of each type, and hyphenation to inductively coupled plasma-(quadrupole) mass spectrometry (ICP-QMS). The method allows the quantitative determination of selenoprotein P (SeP), extracellular glutathione peroxidase (eGPx), selenoalbumin (SeAlb), and selenometabolites in mouse plasma using species-unspecific isotope dilution (SUID). The 2D chromatographic separation is proposed to remove typical spectral interferences in plasma from chloride and bromide on (77)Se ((40)Ar(37)Cl) and (82)Se ((81)Br(1)H). In addition, the approach increases chromatographic resolution allowing the separation of eGPx from Se metabolites of low molecular mass. The method is robust, reliable, and fast with a typical chromatographic runtime less than 20 min. Precision in terms of relative standard deviation (n?=?5) is in the order of 4 %, and detection limits are in the range of 0.2 to 1.0 ng Se g(-1). Method accuracy for determination of total protein bound to Se was assessed by analyzing human serum reference material (BCR-637) certified for total Se content, and latterly applied to mouse plasma (Mus musculus). In summary, a reliable speciation method for the analysis of eGPx, selenometabolites, SeP, and SeAlb in plasma/serum samples is proposed for the first time and is applicable to the evaluation of Se status in human in clinical studies and other mammals for environmental or toxicological assessment. PMID:24535684

Garca-Sevillano, M A; Garca-Barrera, T; Gmez-Ariza, J L

2014-04-01

348

Selected ion flow tube mass spectrometry analyses of stable isotopes in water: isotopic composition of H3O+ and H3O+ (H2O)3 ions in exchange reactions with water vapor  

PubMed

A new method has been developed for the determination of the isotope abundance ratios of deuterium, D, and oxygen-18, 18O, in water vapor (and water) using selected ion flow tube mass spectrometry (SIFT-MS). H3O+ ions are injected into the helium carrier gas where they associate with the H2O and HDO molecules in a sample of water introduced into the carrier gas. The D and 18O contents of the product cluster ions H8DO4+ and H9(18)OO3+ at m/e = 74 and 75, respectively, are determined by reference to the majority cluster ion H9O4+ at m/e = 73. Allowance is made for the contribution of the H8(17)OO3+ ions to the m/z = 74 ions. Absolute isotopic ratios are measured within seconds without the need for precalibration of the SIFT-MS instrument, currently to an accuracy of better than 2%. PMID:11014448

Spanel; Smith

2000-10-01

349

Measurement of Sulfur Isotopic Composition (?34S) by Multiple-Collector Thermal Ionization Mass Spectrometry (MC-TIMS) Using a 33S/36S Double Spike  

NASA Astrophysics Data System (ADS)

A new analytical technique for the determination of ?34S will be described. The technique is based on the production of singularly charged arsenic sulfide molecular ions (AsS+) by thermal ionization using silica gel as an emitter and combines multiple-collector thermal ionization mass spectrometry (MC-TIMS) with a 33S/36S double spike to correct instrumental fractionation. Because the double spike is added to the sample before chemical processing, both the isotopic composition and sulfur concentration are measured simultaneously. The accuracy and precision of the double spike technique is comparable to or better than modern gas source mass spectrometry, but requires about a factor of 10 less sample. ?33S effects can be determined directly in an unspiked sample without any assumptions about the value of k (mass dependent fractionation factor) which is currently required by gas source mass spectrometry. Three international sulfur standards (IAEA-S-1, IAEA-S-2, and IAEA-S-3) were measured to evaluate the precision and accuracy of the new technique and to evaluate the consensus values for these standards. Two different double spike preparations were used. The ?34S values (reported relative to Vienna Canyon Diablo Troilite (VCDT), (?34S () = 34S/32S)sample/(34S/32S)VCDT - 1) x 1000]), 34S/32SVCDT = 0.0441626) determined were -0.32 0.04 (1?, n=4) and -0.31 0.13 (1?, n=8) for IAEA-S-1, 22.65 0.04 (1?, n=7) and 22.60 0.06 (1?, n=5) for IAEA- S-2, and -32.47 0.07 (1?, n=8) for IAEA-S-3. The amount of natural sample used for these analyses ranged from 0.40 ?moles to 2.35 ?moles. Each standard showed less than 0.5 variability (IAEA-S-1 < 0.4, IAEA-S-2 < 0.2, and IAEA-S-3 < 0.2). Our values for S-1 and S-2 are in excellent agreement with the consensus values and the values reported by other laboratories using both SF6 and SO2. Our value for S-3 differs statistically from the Institute for Reference Materials and Measurement (IRMM) value and is slightly lower than the currently accepted consensus value (-32.3). Because the technique is based on thermal ionization of AsS+, and As is mononuclidic, corrections for interferences or for scale contraction/expansion are not required. The availability of MC-TIMS instruments in laboratories around the world makes this technique immediately available to a much larger scientific community who require highly accurate and precise measurements of sulfur.

Mann, J. L.; Kelly, W. R.

2006-05-01

350

Characterization of Diesel Fuel by Chemical Separation Combined with Capillary Gas Chromatography (GC) Isotope Ratio Mass Spectrometry (IRMS)  

SciTech Connect

The purpose of this study was to perform a preliminary investigation of compound-specific isotope analysis (CSIA) of diesel fuels to evaluate whether the technique could distinguish between the diesel samples from different sources/locations. The ability to differentiate or correlate diesel samples could be valuable for detecting fuel tax evasion schemes. Two fractionation techniques were used to isolate the n-alkanes from the fuel. Both ?13C and ?D values for the n-alkanes were then determined by CSIA in each sample. Plots of ?D versus ?13C with sample n-alkane points connected in order of increasing carbon number gave well separated clusters with characteristic shapes for each sample. Principal components analysis (PCA) with ?13C, ?D, or combined ?13C and ?D data on the yielded scores plots that could clearly differentiate the samples, thereby demonstrating the potential of this approach for fingerprinting fuel samples using the ?13C and ?D values.

Harvey, Scott D.; Jarman, Kristin H.; Moran, James J.; Sorensen, Christina M.; Wright, Bob W.

2011-09-15

351

Quantitation of orotic acid in urine using isotope dilution-selected ion gas chromatography-mass spectrometry.  

PubMed

The measurement of urinary orotic acid excretion is an important test for establishing a diagnosis of hereditary orotic aciduria, a genetic defect of pyrimidine biosynthesis. Measurement of secondary urinary orotic acid elevation is also an important clinical test for the differential diagnosis of hyperammonemia due to some of the primary disorders of the urea cycle including ornithine transcarbamylase (OTC) deficiency, and the hyperornithinemia-hyperammonemia-homocitrullinemia (HHH) syndrome. Low levels of orotic acid are observed in carbamylphosphate synthetase (CPS) defects. This method utilizes a stable-isotope labeled internal standard (1, 3-(15)N-orotic acid), which is added to the standards, controls, and patient samples prior to extraction. Interference from urea is removed by incubation of samples with urease and the orotic acid is derivatized by trimethylsilylation. Quantitation is made against an eight-point standard curve using specific selected ions from both the labeled and unlabeled orotic acid. PMID:20077096

Chen, Jie; Bennett, Michael J

2010-01-01

352

Screening multimycotoxins in food-grade gums by stable isotope dilution and liquid chromatography/tandem mass spectrometry.  

PubMed

Stable isotope dilution with LC/MSIMS was used to determine the following 11 mycotoxins in food grade gums: aflatoxins B1, B2, G1, and G2; deoxynivalenol; fumonisins B1, B2, and B3; ochratoxin A; T-2 toxin; and zearalenone. Samples were fortified with 11 [13C]-uniformly labeled internal standard ([13C]-IS) mycotoxins that corresponded to the 11 target mycotoxins and extracted by acetonitrile-water (4 + 1, v/v), followed by LC/MS/MS analysis. Mycotoxins were quantitated with the fortified [13C]-IS in each sample. The average recoveries of aflatoxins B1, B2, G1, and G2 (1, 5, and 25 microg/kg); deoxynivalenol and fumonisins B1, B2, and B3 (25, 100, and 500 microg/kg); and ochratoxin A, T-2 toxin, and zearalenone (10, 50, and 250 microg/kg) ranged from 84 to 117% with RSDs less than 20%. Method-dependent LOQs were from 0.1 (aflatoxin B1) to 25 microg/kg (fumonisin B3). Among 20 market samples, aflatoxin B1 (< LOQ) was detected in a Guar gum and a Tragacanth gum, and zearalenone (6 +/- 0.6 microg/kg) was detected in a Xanthan gum. The detected mycotoxins were further confirmed by comparing their enhanced product ion spectra to those of reference standards. The single laboratory validated stable isotope dilution and LC/MSIMS method provides sufficient selectivity, sensitivity, accuracy, and reproducibility with a simple sample preparation to screen the 11 mycotoxins in gums. PMID:25051639

Zhang, Kai; Wong, Jon W; Jia, Zhengwei; Vaclavikova, Marta; Trucksess, Mary W; Begley, Timothy H

2014-01-01

353

Determination of compound-specific Hg isotope ratios from transient signals using gas chromatography coupled to multicollector inductively coupled plasma mass spectrometry (MC-ICP/MS).  

PubMed

MeHg and inorganic Hg compounds were measured in aqueous media for isotope ratio analysis using aqueous phase derivatization, followed by purge-and-trap preconcentration. Compound-specific isotope ratio measurements were performed by gas chromatography interfaced to MC-ICP/MS. Several methods of calculating isotope ratios were evaluated for their precision and accuracy and compared with conventional continuous flow cold vapor measurements. An apparent fractionation of Hg isotopes was observed during the GC elution process for all isotope pairs, which necessitated integration of signals prior to the isotope ratio calculation. A newly developed average peak ratio method yielded the most accurate isotope ratio in relation to values obtained by a continuous flow technique and the best reproducibility. Compound-specific isotope ratios obtained after GC separation were statistically not different from ratios measured by continuous flow cold vapor measurements. Typical external uncertainties were 0.16 per thousand RSD (n = 8) for the (202)Hg(/198)Hg ratio of MeHg and 0.18 per thousand RSD for the same ratio in inorganic Hg using the optimized operating conditions. Using a newly developed reference standard addition method, the isotopic composition of inorganic Hg and MeHg synthesized from this inorganic Hg was measured in the same run, obtaining a value of delta (202)Hg = -1.49 +/- 0.47 (2SD; n = 10). For optimum performance a minimum mass of 2 ng per Hg species should be introduced onto the column. PMID:18488203

Dzurko, Mark; Foucher, Delphine; Hintelmann, Holger

2009-01-01

354

Ion trap mass spectrometry  

SciTech Connect

This paper reports on the quadrupole ion trap which is a mass spectrometer whose essential components can be held in one hand. But is has a mass range of about 10{sup 5} daltons per charge, provides molecular weight and structural information on biopolymers, and has the greatest sensitivity of all mass spectrometers. These features, however, has become available only within the past few years. They stem from an almost neglected 1958 invention, one in which interest was maintained by only a few research groups, notably those of John Todd at the University of Kent in England and Ray March at Trent University in Canada. Development of a new scanning method by George Stafford and his coworkers of Finnigan Corp. provided the impetus that led Finnigan to introduce a commercial ion trap in 1983. Since then, the device has been transformed from a simple gas chromatography detector to a high-performance mass spectrometer.

Cooks, R.G. (Purdue Univ. (US)); Glish, G.L.; Mc Luckey, S.A. (Oak Ridge National Lab. (US)); Kaiser, R.E. (Eli Lilly and Co. (US))

1991-03-25

355

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

PubMed

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

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

2014-07-01

356

Mass spectrometry of proteins of known mass Andrew D. Miranker*  

E-print Network

Commentary Mass spectrometry of proteins of known mass Andrew D. Miranker* Department of Molecular spectrometry. Most sci- entists' expectation of mass spectrome- try is that of determining the mass the gel and proteolysed, and the fragment masses determined by mass spectrometry. Given the specificity

Miranker, Andrew

357

Tandem Mass Spectrometry in Physiology  

NSDL National Science Digital Library

Tandem mass spectrometry coupled to liquid chromatography (LC-MS/MS) allows identification of proteins in a complex mixture without need for protein purification ("shotgun" proteomics). Recent progress in LC-MS/MS-based quantification, phosphoproteomic analysis, and targeted LC-MS/MS using multiple reaction monitoring (MRM) has made LC-MS/MS a powerful tool for the study of cell physiology.

2007-12-01

358

Open Mass Spectrometry Search Algorithm  

Microsoft Academic Search

Large numbers of MS\\/MS peptide spectra generated in proteomics experiments require efficient, sensitive and specific algorithms for peptide identification. In the Open Mass Spectrometry Search Algorithm [OMSSA], specificity is calculated by a classic probability score using an explicit model for matching experimental spectra to sequences. At default thresholds, OMSSA matches more spectra from a standard protein cocktail than a comparable

Lewis Y. Geer; Sanford P. Markey; Jeffrey A. Kowalak; Lukas Wagner; Ming Xu; Dawn M. Maynard; Xiaoyu Yang; Wenyao Shi; Stephen H. Bryant

2004-01-01

359

Adaptation of continuous-flow cavity ring-down spectroscopy for batch analysis of ?13C of CO2 and comparison with isotope ratio mass spectrometry.  

PubMed

Measurements of ?(13)C in CO(2) have traditionally relied on samples stored in sealed vessels and subsequently analyzed using magnetic sector isotope ratio mass spectrometry (IRMS), an accurate but expensive and high-maintenance analytical method. Recent developments in optical spectroscopy have yielded instruments that can measure ?(13)CO(2) in continuous streams of air with precision and accuracy approaching those of IRMS, but at a fraction of the cost. However, continuous sampling is unsuited for certain applications, creating a need for conversion of these instruments for batch operation. Here, we present a flask (syringe) adaptor that allows the collection and storage of small aliquots (20-30 mL air) for injection into the cavity ring-down spectroscopy (CRDS) instrument. We demonstrate that the adaptor's precision is similar to that of traditional IRMS (standard deviation of 0.3 for 385 ppm CO(2) standard gas). In addition, the concentration precision (0.3% of sample concentration) was higher for CRDS than for IRMS (7% of sample concentration). Using the adaptor in conjunction with CRDS, we sampled soil chambers and found that soil-respired ?(13)C varied between two different locations in a pion-juniper woodland. In a second experiment, we found no significant discrimination between the respiration of a small beetle (~5 mm) and its diet. Our work shows that the CRDS system is flexible enough to be used for the analysis of batch samples as well as for continuous sampling. This flexibility broadens the range of applications for which CRDS has the potential to replace magnetic sector IRMS. PMID:21766378

Berryman, E M; Marshall, J D; Rahn, T; Cook, S P; Litvak, M

2011-08-30

360

Determination of the H isotopic composition of individual components in fine-scale mixtures of organic matter and phyllosilicates with the nanoscale secondary ion mass spectrometry.  

PubMed

When organic matter is mixed on a nanometer scale with clay minerals, the individual D/H ratios of the two H-bearing phases cannot be directly measured even with the nominal spatial resolution of nanoscale secondary ion mass spectrometry (NanoSIMS, 50-100 nm). To overcome this limitation, a new analytical protocol is proposed based on the deconvolution of the D(-)/H(-) and (16)OD(-)/(16)OH(-) ionic ratios measured by NanoSIMS. Indeed, since the yields of H(-) and (16)OH(-) are different for organics and clays, it should be theoretically possible to determine the mixing ratio of these two components in the area analyzed by the ion probe. Using organics with different D/H ratios, the interdependence of the D(-)/H(-) and (16)OD(-)/(16)OH(-) ionic ratios was determined in pure samples. Then using the H(-) and (16)OH(-) yields and the isotopic ratios measured on pure organic matter and clays, the expected D(-)/H(-) and (16)OD(-)/(16)OH(-) variations as a function of the mixing proportions were determined. These numerical predictions are consistent with measurements on laboratory prepared mixtures of D-rich organic matter and D-poor phyllosilicates, validating both the proposed experimental protocol and its use for meteorites. With an improvement of the precision of the ionic ratios by a factor of 10, it should possible to expend this protocol to samples having natural terrestrial D/H variations. Such an improvement could be attainable with the development of synthetic deuterated reference samples. PMID:23121456

Piani, Laurette; Remusat, Laurent; Robert, Franois

2012-12-01

361

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

PubMed

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

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

2014-06-15

362

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

PubMed Central

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

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

2014-01-01

363

Quantitative analysis of penicillins in porcine tissues, milk and animal feed using derivatisation with piperidine and stable isotope dilution liquid chromatography tandem mass spectrometry.  

PubMed

Penicillins are used universally in both human and veterinary medicine. The European Union (EU) has established maximum residue levels (MRLs) for most ss-lactam antibiotics in milk and animal tissues and included them in the National Residue Monitoring Programs. In this study, a novel method is described for the determination and confirmation of eight penicillins in porcine tissues, milk and animal feed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). To prevent degradation of penicillin residues during workup, a derivatisation procedure was developed, by which penicillins were converted to stable piperidine derivatives. Deuterated piperidine derivatives were synthesised for all relevant penicillins, enabling the use of isotope dilution for accurate quantification. Penicillin residues were derivatised in the crude extract with piperidine and isolated using solid-phase extraction. The penicillin piperidine derivatives were determined by LC-MS/MS. The method was validated at the current MRLs, which range from 25-300 microg kg(-1) in muscle and kidney to 4-30 microg kg(-1) in milk as well as at the target value of 100 microg kg(-1) chosen for animal feed, according to the EU requirements for a quantitative confirmatory method. Accuracy ranged from 94-113% (muscle), 83-111% (kidney) and 87-103% (milk) to 88-116% (animal feed). Intra-day precision (relative standard deviation (RSD)(r)) ranged from 5-13% (muscle, n = 18), 4-17% (kidney, n = 7) and 5-18% (milk, n = 7) to 11-32% (animal feed, n = 18). Inter-day precision (RSD(RL), n = 18) ranged from 6-23% (muscle) to 11-36% (animal feed). From the results, it was concluded that the method was fit for purpose at the target MRLs in animal tissue and target levels for animal feed. PMID:20186537

van Holthoon, Frdrique; Mulder, Patrick P J; van Bennekom, Eric O; Heskamp, Henri; Zuidema, Tina; van Rhijn, Hans J A

2010-04-01

364

Determination of 17 illicit drugs in oral fluid using isotope dilution ultra-high performance liquid chromatography/tandem mass spectrometry with three atmospheric pressure ionizations.  

PubMed

The collection of oral fluid for drug testing is easy and non-invasive. This study developed a drug testing method using ultra-high performance liquid chromatography/tandem mass spectrometry (UHPLC-MS/MS) in selected-reaction monitoring (SRM) mode. We tested the method on the analysis of four opiates and their metabolites, five amphetamines, flunitrazepam and its two metabolites, and cocaine and its four metabolites in oral fluid. 100-?L samples of oral fluid were diluted with twice the amount of water then spiked with isotope-labeled internal standards. After the samples had undergone high-speed centrifugation for 20 min, we analyzed the supernatant. The recovery of the sample preparation ranged from 81 to 108%. We compared the performance of electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI). The ion suppression of most analytes on ESI (28-78%) was lower than that of APCI and APPI. A post-column flow split (5:1) did not reduce the matrix effect on ESI. Direct APPI performed better than dopant-assisted APPI using toluene. ESI, APCI and APPI limits of quantitation mostly ranged from 0.11 to 1.9 ng/mL, 0.02 to 2.2 ng/mL and 0.02 to 2.1 ng/mL, respectively, but were much higher on amphetamine and ecgonine methyl ester (about 2.7-4.7 ng/mL, 8.7-14 ng/mL, and 10-19 ng/mL, respectively). Most of the bias percentages (accuracy) and relative standard deviations (precision) on spiked samples were below 15%. This method greatly simplifies the process of sample preparation and shortens the chromatographic time to only 7.5 min per run and is able to detect analytes at sub-ppb levels. PMID:20951654

Wang, I-Ting; Feng, Yu-Ting; Chen, Chia-Yang

2010-11-15

365

Capillary electrophoresis-mass spectrometry  

Microsoft Academic Search

As an on-line separation method, capillary electrophoresis (CE)-mass spectrometry (MS) distinguishes analytes by both their differences in electrophoretic mobilities and structural information. CE-MS combines the advantages of CE and MS so that information on both high separation efficiency and molecular masses and\\/or fragmentation can be obtained in one analysis. During the past few years CE-MS has undergone significant development both

Jianyi Cai; Jack Henion

1995-01-01

366

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

PubMed

To assess food safety emergencies caused by highly hazardous chemical-tainted foods, simultaneous analysis of organophosphorus insecticides in fatty foods such as precooked foods was conducted using thin-layer chromatography/direct analysis in real time time-of-flight mass spectrometry (TLC/DART-TOFMS) and isotope dilution technique. Polar (methamidophos and acephate) and nonpolar organophosphorus insecticides (fenitrothion, diazinon, and EPN) were studied. Experiments to ascertain chromatographic patterns using TLC/DART-TOFMS reveal that it was more useful than GC/MS or GC/MS/MS for the simultaneous analyses of polar and nonpolar pesticides, while obviating the addition of a protective agent for tailing effects of polar pesticides. Lower helium gas temperature (260C) for DART-TOFMS was suitable for the simultaneous analysis of target pesticides. Linearities were achieved respectively at a lower standard concentration range (0.05-5 ?g) for diazinon and EPN and at a higher standard concentration range (2.5-25 ?g) for methamidophos, acephate, and fenitrothion. Their respective coefficients of determination were ? 0.9989 and ? 0.9959. A few higher repeatabilities (RSDs) for diazinon and EPN were found (>20%), although isotope dilution technique was used. Application to the HPTLC plate without an automatic TLC sampler might be inferred as a cause of their higher RSDs. Detection limits were estimated in the higher picogram range for diazinon and EPN, and in the lower nanogram range for methamidophos, acephate, and fenitrothion. Aside from methamidophos, recovery results (n=3) obtained using a highly insecticide-tainted fatty food (dumpling) and raw food (grapefruit) samples (10mg/kg) using TLC/DART-TOFMS with both complex and simpler cleanups were not as susceptible to matrix effects (95-121%; RSD, 1.3-14%) as those using GC/MS/MS (102-117%; RSD, 0.4-8.5%), although dumpling samples using GC/MS were remarkably susceptible to matrix effects. The coupled method of TLC with simpler cleanup and DART-TOFMS can be regarded as the same analytical tool as GC/MS/MS, which is useful to assess food safety emergencies caused by highly hazardous chemical-tainted foods. PMID:25454149

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

2014-11-28

367

Electrospray Ionization Mass Spectrometry  

SciTech Connect

Electrospray Ionization (ESI) is a process whereby gas phase ions are created from molecules in solution. As a solution exits a narrow tube in the presence of a strong electric field, an aerosol of charged droplets are is formed that produces gas phase ions as they it desolvates. ESI-MS comprises the creation of ions by ESI and the determination of their mass to charge ratio (m/z) by MS.

Kelly, Ryan T.; Marginean, Ioan; Tang, Keqi

2014-06-13

368

JOURNAL OF MASS SPECTROMETRY J. Mass Spectrom. 2003; 38: 277282  

E-print Network

JOURNAL OF MASS SPECTROMETRY J. Mass Spectrom. 2003; 38: 277­282 Published online 24 January 2003 A from Dictyostelium discoideum were analyzed using Q-TOF mass spectrometry. The accurate molecular mass could be identified as N-terminal acetylation by tandem mass spectrometry. Extracted ion chromatograms

Manstein, Dietmar J.

369

Two-dimensional heart-cut LC-LC improves accuracy of exact-matching double isotope dilution mass spectrometry measurements of aflatoxin B1 in cereal-based baby food, maize, and maize-based feed.  

PubMed

Aflatoxins, mycotoxins of fungi of the Aspergillus sp., pose a risk to consumer health and are, therefore, regulated by more than 100 countries. To facilitate method development and validation as well as assessment of measurement capabilities, availability of certified reference materials and proficiency testing schemes is important. For these purposes, highly accurate determinations of the aflatoxin content in the materials used are necessary. We describe here the use of two-dimensional heart-cut LC-LC in combination with exact-matching double isotope dilution mass spectrometry to determine the content of aflatoxin B1 in three materials used in a proficiency testing scheme. The serious reduction in ionization suppression afforded by the two-dimensional heart-cut LC-LC had a positive effect on the precision of the measured isotope ratios of the exact-matching double isotope dilution mass spectrometry. This is evidenced by the expanded measurement uncertainty (k?=?2) of 0.017?g/kg or 8.9% relative to a mass fraction of aflatoxin B1 in a cereal-based baby food of 0.197?g/kg. This value is in perfect agreement with the consensus value of this material from a proficiency test (PT) scheme for National Reference Laboratories executed by the European Reference Laboratory for Mycotoxins. The effort necessary to perform the described methodology precludes its frequent use but for specific applications we see it as a valuable tool. PMID:25015044

Breidbach, Andreas; Ulberth, Franz

2014-07-12

370

Computational mass spectrometry for small molecules  

PubMed Central

The identification of small molecules from mass spectrometry (MS) data remains a major challenge in the interpretation of MS data. This review covers the computational aspects of identifying small molecules, from the identification of a compound searching a reference spectral library, to the structural elucidation of unknowns. In detail, we describe the basic principles and pitfalls of searching mass spectral reference libraries. Determining the molecular formula of the compound can serve as a basis for subsequent structural elucidation; consequently, we cover different methods for molecular formula identification, focussing on isotope pattern analysis. We then discuss automated methods to deal with mass spectra of compounds that are not present in spectral libraries, and provide an insight into de novo analysis of fragmentation spectra using fragmentation trees. In addition, this review shortly covers the reconstruction of metabolic networks using MS data. Finally, we list available software for different steps of the analysis pipeline. PMID:23453222

2013-01-01

371

Mass spectrometry and renal calculi  

PubMed Central

The present review represents a concise and complete survey of the literature covering 20042009, concerning the mass spectrometric techniques involved in the structural investigation of renal calculi. After a short presentation of the fundamental mass spectrometric techniques (MALDITOF, QTOF, MSMS) as well as hyphenated methods (GCMS, LCMS, CEMS), an extensive study of the urinary proteome analysis as well as the detection and quantification by mass spectrometry of toxins, drugs and metabolites from renal calculi is presented. PMID:20968197

Purcarea, VL; Sisu, I; Sisu, E

2010-01-01

372

Mass spectrometry of aerospace materials  

NASA Technical Reports Server (NTRS)

Mass spectrometry is used for chemical analysis of aerospace materials and contaminants. Years of analytical aerospace experience have resulted in the development of specialized techniques of sampling and analysis which are required in order to optimize results. This work has resulted in the evolution of a hybrid method of indexing mass spectra which include both the largest peaks and the structurally significant peaks in a concise format. With this system, a library of mass spectra of aerospace materials was assembled, including the materials responsible for 80 to 90 percent of the contamination problems at Goddard Space Flight Center during the past several years.

Colony, J. A.

1976-01-01

373

Inductively coupled plasma mass spectrometry: Radiological challenges  

SciTech Connect

Inductively coupled plasma mass spectrometry (ICP/MS) is increasingly being applied to radionuclide determinations. Direct determination of Th, U, Np, Pu, and Am isotopes have provided the initial impetus to incorporate lCP/MS instrumentation into the radioanalytical laboratory. Isobaric and molecular ion interferences have limited the instrument`s application for directly measuring fission and activation produced isotopes, however. For example, separations of {sup 59,63}Ni from naturally occurring elements Co and Cu, {sup 99}Tc from {sup 99}Ru, {sup 107}Pd from {sup 107}Ag, and {sup 151}Sm from {sup 151}Eu are required to unequivocally determine these radioisotopes. Coupling the ICP/N4S with automated separation techniques such as high-pressure ion chromatography (HPIC), response signals differentiated by mass and time provide a superior means for measuring these man-made isotopes. In addition to ICP/MS detection, radiometric methods can decomplimentary data, particularly for shorter lived radionuclides. We will illustrate how an on-line solid state Y-glass {Beta} detector and an ICP/MS detector can be used together to characterize analytes radioactive samples such as Hanford tankwastes. Quantitation using time and mass separated signals obtained with varying eluant composition remains a major analytical challenge, and approaches to this problem will be discussed.

Smith, M.R.; Farmer, O.T. III; Koppenaal, D.W. [Pacific Northwest Lab., Richland, WA (United States)

1995-12-31

374

Author's personal copy Ambient mass spectrometry  

E-print Network

Author's personal copy Ambient mass spectrometry for in vivo local analysis and in situ molecular tissue imaging Peter Nemes, Akos Vertes Recent technical innovations in mass spectrometry (MS) have analysis; Mass spectrometry; Metabolomics; Molecular imaging; Peptidomics; Single-cell analysis; Tissue

Vertes, Akos

375

Towards single-molecule nanomechanical mass spectrometry  

E-print Network

Towards single-molecule nanomechanical mass spectrometry A. K. Naik1 , M. S. Hanay1 , W. K. Hiebert1,2 , X. L. Feng1 and M. L. Roukes1 * Mass spectrometry provides rapid and quantitative species in real time. Here, we report the first demonstration of mass spectrometry based on single

Roukes, Michael L.

376

Mass Spectrometry and Computational Proteomics Vineet Bafna  

E-print Network

Mass Spectrometry and Computational Proteomics Vineet Bafna Computer Science & Engineering, Univ Abstract Mass Spectrometry is the tool of choice for Proteomics, with applications to peptide sequencing of algorithms for interpreting mass spectrometry (MS) data is provided. This overview is not intended

Bafna, Vineet

377

ACCOUNT AND PERSPECTIVE Macromolecule Mass Spectrometry  

E-print Network

ACCOUNT AND PERSPECTIVE Macromolecule Mass Spectrometry: Citation Mining of User Documents Ronald N papers to Fenn's 1989 Science paper on Electrospray Ionization for Mass Spectrometry, and to the 400 first generation SCI citing papers to Tanaka's 1988 Rapid Communications in Mass Spectrometry paper

Karypis, George

378

Direct mass measurements on francium isotopes and deduced masses for odd-z neighbouring elements  

Microsoft Academic Search

The masses of 204-210, 212Fr and 224-228Fr have been determined with direct on-line mass spectrometry. From previously known Qa values, the masses of 28 isotopes of Pa, Ac, At, Bi and Tl are deduced. All these experimental masses are compared with the current mass predictions. Permanent address: II. Physikalisches Institt, 6300 Giessen Germany.

M. Epherre; G. Audi; C. Thibault; R. Klapisch; G. Huber; F. Touchard; H. Wollnik

1980-01-01

379

The use of Fluorinated Graphite Polymer in the Oxygen-Isotope Analysis of Silicates by Continuous Flow Isotope Ratio Mass Spectrometry (CF-IRMS)  

NASA Astrophysics Data System (ADS)

To date the majority of analytical procedures for ?18O analysis of silicates require relatively expensive apparatus involving the use of hazardous fluorine or halogen fluoride gases. Carbon reduction offers the potential to avoid the use of hazardous gases; however, it has been plagued by low yields and variable isotopic fractionation leading to significant differences in isotopic composition compared to conventional fluorination techniques (CFT). We adopt a carbon reduction method, which includes a fluorinated graphite polymer (F>60%) to help oxidize the silicate, thus increasing the percent yield as well as the precision of the analyses. Three silicate standards (NBS-28; UWG-2; GBW044190) were analyzed to compare this method against CFT. Silicate samples of 0.2mg are combined with 2mg of fluorinated graphite and sealed in a silver cup. The cups are then heated instantaneously to 1470C in a high temperature conversion elemental analyzer (TC/EA). The evolved oxygen reacts with carbon in the furnace resulting in carbon monoxide which is transported via a helium carrier gas to a series of chemical and cold traps prior to introduction into the gas chromatograph. An Ascarite II and Mg(ClO4)2 chemical trap removes acids (e.g. HF) and water, followed by an LN2 cold trap to remove SiF4. The He carrier gas flow is kept low (0.7bar) to maximize reaction time, whereas He flow to the open split is increased (0.7bar) in order to reduce peak tailing in the IRMS. Using this method individual analysis can be completed in ~7 minutes. Oxygen yields range from 54-92%; however reproducibility better than 0.5 is normally achievable. Measured values are consistently enriched in 18O compared with accepted values; however, this offset is systematic and can be corrected for using a linear correction factor. Corrected values are: 9.110.3, 5.950.5, and -1.780.4 for NBS-28, UWG-2, and GBW044190 respectively. As the number of laboratories with CF-IRMS and TC/EA apparatus increases the development of this method has the potential to make ?18O analysis of silicates more widely available.

Kingston, A. W.; Weis, D.; Francois, R.

2008-12-01

380

International Journal of Mass Spectrometry 229 (2003) 5560 High resolution mass spectrometry using a  

E-print Network

International Journal of Mass Spectrometry 229 (2003) 55­60 High resolution mass spectrometry using mass spectrometry; Linear electrostatic ion beam trap; Self-bunching; Fourier transformation 1. Introduction Mass spectrometry is one of the most common analyti- cal techniques in modern physical

Savin, Daniel Wolf

381

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

Microsoft Academic Search

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

Fluor Daniel Hanford

1997-01-01

382

Estradiol-17 beta quantified in serum by isotope dilution-gas chromatography-mass spectrometry: reversed-phase C18 high-performance liquid chromatography compared with immuno-affinity chromatography for sample pretreatment.  

PubMed

Here, isotope dilution-gas chromatography-mass spectometry is used as a reference technique for determining the concentration of estradiol-17 beta in candidate human serum Reference Material. The accuracy of assigned concentrations in biologic materials is not only determined by instrumental performance, it also depends greatly on the selectivity of the procedure for isolating the analyte from the biological matrix, an issue which we consider insufficiently addressed in the literature. We introduced reversed-phase C18 high-performance liquid chromatography as a fractionation procedure in addition to the commonly used solvent extraction and column chromatography on Sephadex LH-20. The validity of this approach as part of a Reference Method for measurement of estradiol-17 beta by isotope dilution-gas chromatography-mass spectrometry was investigated by comparison with immuno-affinity chromatography, which on theoretical grounds is generally considered as highly selective. PMID:3168218

Thienpont, L M; Verhaeghe, P G; Van Brussel, K A; De Leenheer, A P

1988-10-01

383

Mass spectrometry-based proteomics  

Microsoft Academic Search

Recent successes illustrate the role of mass spectrometry-based proteomics as an indispensable tool for molecular and cellular biology and for the emerging field of systems biology. These include the study of protein-protein interactions via affinity-based isolations on a small and proteome-wide scale, the mapping of numerous organelles, the concurrent description of the malaria parasite genome and proteome, and the generation

Ruedi Aebersold; Matthias Mann

2003-01-01

384

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

SciTech Connect

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

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

1983-01-01

385

JOURNAL OF MASS SPECTROMETRY J. Mass Spectrom. 2008; 43: 10531062  

E-print Network

JOURNAL OF MASS SPECTROMETRY J. Mass Spectrom. 2008; 43: 1053­1062 Published online 20 February-(2-chlorophenyl)propenoate by electron ionization mass spectrometry showed the distinct loss of an ortho chlorine; benzopyrylium cation; density functional theory calculations; electron ionization mass spectrometry INTRODUCTION

Hammock, Bruce D.

386

Mass spectrometry. [review of techniques  

NASA Technical Reports Server (NTRS)

Advances in mass spectrometry (MS) and its applications over the past decade are reviewed in depth, with annotated literature references. New instrumentation and techniques surveyed include: modulated-beam MS, chromatographic MS on-line computer techniques, digital computer-compatible quadrupole MS, selected ion monitoring (mass fragmentography), and computer-aided management of MS data and interpretation. Areas of application surveyed include: organic MS and electron impact MS, field ionization kinetics, appearance potentials, translational energy release, studies of metastable species, photoionization, calculations of molecular orbitals, chemical kinetics, field desorption MS, high pressure MS, ion cyclotron resonance, biochemistry, medical/clinical chemistry, pharmacology, and environmental chemistry and pollution studies.

Burlingame, A. L.; Kimble, B. J.; Derrick, P. J.

1976-01-01

387

Glycosaminoglycan Glycomics Using Mass Spectrometry*  

PubMed Central

The fact that sulfated glycosaminoglycans (GAGs) are necessary for the functioning of all animal physiological systems drives the need to understand their biology. This understanding is limited, however, by the heterogeneous nature of GAG chains and their dynamic spatial and temporal expression patterns. GAGs have a regulated structure overlaid by heterogeneity but lack the detail necessary to build structure/function relationships. In order to provide this information, we need glycomics platforms that are sensitive, robust, high throughput, and information rich. This review summarizes progress on mass-spectrometry-based GAG glycomics methods. The areas covered include disaccharide analysis, oligosaccharide profiling, and tandem mass spectrometric sequencing. PMID:23325770

Zaia, Joseph

2013-01-01

388

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

PubMed

A highly sensitive method for the determination of sulfur mustard (SM) metabolites thiodiglycol (TDG) and thiodiglycol sulfoxide (TDGO) in urine was established and validated using isotope-dilution negative-ion chemical ionization (NICI) gas chromatography-mass spectrometry (GC-MS). TDGO in the samples was reduced with TiCl3, and then determined together with TDG as a single analyte. The sample preparation procedures, including two solid-phase-extraction (SPE) clean-up steps, were optimized to improve the sensitivity of the method. The limits of detection (LOD) for both TDG and TDG plus TDGO (TDG + TDGO) were 0.1 ng mL(-1), and the limits of quantitation (LOQ) for both were 0.3 ng mL(-1). The method was used in a rabbit cutaneous SM exposure model. Domestic rabbits were exposed to neat liquid SM at three dosage levels (0.02, 0.05, and 0.15 LD50), and the urinary excretion of four species of hydrolysis metabolites, namely free TDG, free plus conjugated TDG (total TDG), free TDG + TDGO, and free plus conjugated TDG + TDGO (total TDG + TDGO), was evaluated to investigate the metabolic processes. The total urinary excretion profiles of the metabolites, including the peak time, time window, and dose-response and time-response relationships, were clarified. The results revealed that the concentrations of TDG and TDG + TDGO in the urine increased quickly and then decreased rapidly in the first two days after SM exposure. The cumulative amount of total TDG + TDGO excreted in urine during the first five days accounted for 0.5-1% of the applied dose of SM. It is also concluded that TDG and TDGO in urine existed mainly in free form, the levels of glucuronide and of sulfate conjugates of TDG or TDGO were very low, and most hydrolysis metabolites were present in the oxidized form (TDGO). The study indicates that the abnormal increase of TDG and TDGO excretion levels can be used as a diagnostic indicator and establishes a reference time-window for retrospective analysis and sampling after SM exposure. PMID:24924210

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

2014-08-01

389

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

PubMed Central

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants and are carcinogenic in multiple organs and species. Benzo[a]pyrene (B[a]P) is a representative PAH and has been studied extensively for its carcinogenicity and toxicity. B[a]P itself is chemically inert and requires metabolic activation to exhibit its toxicity and carcinogenicity. Three major metabolic pathways have been well documented. The signature metabolites generated from the radical cation (peroxidase or monooxygenase mediated) pathway are B[a]P-1,6-dione and B[a]P-3,6-dione, the signature metabolite generated from the diol-epoxide (P450 mediated) pathway is B[a]P-r-7,t-8,t-9,c-10-tetrahydrotetrol (B[a]P-tetrol-1) and the signature metabolite generated from the o-quinone (aldo-keto reductase mediated) pathway is B[a]P-7,8-dione. The contributions of these different metabolic pathways to cancer initiation and the exploitation of this information for cancer prevention are still under debate. With the availability of a library of [13C4]-labeled B[a]P metabolite internal standards, we developed a sensitive stable isotope dilution atmospheric pressure chemical ionization tandem mass spectrometry method to address this issue by quantitating B[a]P metabolites from each metabolic pathway in human lung cells. This analytical method represents a 500 fold increased sensitivity compared with a method using HPLC-radiometric detection. The limit of quantitation (LOQ) was determined to be 6 fmol on column for 3-hydroxybenzo[a]pyrene (3-OH-B[a]P), the generally accepted biomarker for B[a]P exposure. This high level of sensitivity and robustness of the method was demonstrated in a study of B[a]P metabolic profiles in human bronchoalveolar H358 cells induced or uninduced with the AhR ligand, 2,3,7,8-tetrachlorodibenzodioxin (TCDD). All the signature metabolites were detected and successfully quantitated. Our results suggest that all three metabolic pathways contribute equally in the overall metabolism of B[a]P in H358 cells with or without TCDD induction. The sensitivity of the method should permit the identification of cell-type differences in B[a]P activation and detoxication and could also be used for biomonitoring human exposure to PAH. PMID:21962213

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

2013-01-01

390

A mass spectrometry primer for mass spectrometry imaging  

PubMed Central

Mass spectrometry imaging (MSI), a rapidly growing subfield of chemical imaging, employs mass spectrometry (MS) technologies to create single- and multi-dimensional localization maps for a variety of atoms and molecules. Complimentary to other imaging approaches, MSI provides high chemical specificity and broad analyte coverage. This powerful analytical toolset is capable of measuring the distribution of many classes of inorganics, metabolites, proteins and pharmaceuticals in chemically and structurally complex biological specimens in vivo, in vitro, and in situ. The MSI approaches highlighted in this Methods in Molecular Biology volume provide flexibility of detection, characterization, and identification of multiple known and unknown analytes. The goal of this chapter is to introduce investigators who may be unfamiliar with MS to the basic principles of the mass spectrometric approaches as used in MSI. In addition to guidelines for choosing the most suitable MSI method for specific investigations, cross-references are provided to the chapters in this volume that describe the appropriate experimental protocols. PMID:20680583

Rubakhin, Stanislav S.; Sweedler, Jonathan V.

2011-01-01

391

Calculation of Transactinide Homolog Isotope Production Reactions Possible with the Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory  

SciTech Connect

The LLNL heavy element group has been investigating the chemical properties of the heaviest elements over the past several years. The properties of the transactinides (elements with Z > 103) are often unknown due to their low production rates and short half-lives, which require lengthy cyclotron irradiations in order to make enough atoms for statistically significant evaluations of their chemistry. In addition, automated chemical methods are often required to perform consistent and rapid chemical separations on the order of minutes for the duration of the experiment, which can last from weeks to months. Separation methods can include extraction chromatography, liquid-liquid extraction, or gas-phase chromatography. Before a lengthy transactinide experiment can be performed at an accelerator, a large amount of preparatory work must be done both to ensure the successful application of the chosen chemical system to the transactinide chemistry problem being addressed, and to evaluate the behavior of the lighter elemental homologs in the same chemical system. Since transactinide chemistry is literally performed on one single atom, its chemical properties cannot be determined from bulk chemical matrices, but instead must be inferred from the behavior of the lighter elements that occur in its chemical group and in those of its neighboring elements. By first studying the lighter group homologs in a particular chemical system, when the same system is applied to the transactinide element under investigation, its decay properties can be directly compared to those of the homologues, thereby allowing an inference of its own chemistry. The Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory (LLNL) includes a 1 MV Tandem accelerator, capable of accelerating light ions such as protons to energies of roughly 15 MeV. By using the CAMS beamline, tracers of transactinide homolog elements can be produced both for development of chemical systems and for evaluation of homolog chemical properties. CAMS also offers an environment for testing these systems 'online' by incorporating automated chemical systems into the beamline so that tracers can be created, transported, and chemically separated all on the shorter timescales required for transactinide experiments. Even though CAMS is limited in the types and energies of ions they can accelerate, there are still a wide variety of reactions that can be performed there with commercially available target materials. The half-lives of these isotopes vary over a range that could be used for both online chemistry (where shorter half-lives are required) and benchtop tracers studies (where longer lived isotopes are preferred). In this document, they present a summary of tracer production reactions that could be performed at CAMS, specifically for online, automated chemical studies. They are from chemical groups four through seven, 13, and 14, which would be appropriate for studies of elements 104-107, 113, and 114. Reactions were selected that had (a) commercially available target material, (b) half-lives long enough for transport from a target chamber to an automated chemistry system, and (c) cross-sections at CAMS available projectile energies that were large enough to produce enough atoms to result in a statistically relevant signal after losses for transport and chemistry were considered. In addition, the resulting product atoms had to decay with an observable gamma-ray using standard Ge gamma-ray detectors. The table includes calculations performed for both metal targets and their corresponding oxides.

Moody, K J; Shaughnessy, D A; Gostic, J M

2011-11-29

392

Diagnosing Prion Diseases: Mass Spectrometry-Based Approaches  

Technology Transfer Automated Retrieval System (TEKTRAN)

Mass spectrometry is an established means of quantitating the prions present in infected hamsters. Calibration curves relating the area ratios of the selected analyte peptides and their oxidized analogs to stable isotope labeled internal standards were prepared. The limit of detection (LOD) and limi...

393

Resonant Laser Ionization Mass Spectrometry: An Alternative to AMS?  

SciTech Connect

Resonant laser ionization mass spectrometry (RIMS) has developed into a versatile experimental method particularly concerning applications for highly selective ultratrace analaysis. Apart from providing nearly complete isobaric suspression and high overall efficiency, the possibolility for combining optical isotpic selectivity with that of hte mass spectrometer leads to remarkable specifications. The widespread analytical potential and applicability of different techniques based on resonant laser ionization is demonstrated in investigations on stable and radioactive ultratrace isotopes with the focus on applications which require high selectivity, concerning, e.g., the noble gas isotopes, 81,85KR, PU isotopes, 89,90SR, 99Tc and 41Ca. Selective ultratrace determination of these radioisotopes proved access to a variety of fundamental research problems in environmental sciences, geo- and cosmochemistry, archaeology, and biomedicine, which previously were often an exclusive domain for accelerator mass spectrometry (AMS).

Wendt, Klaus; Trautmann, N.; Bushaw, Bruce A.

2001-02-15

394

The utility of mass spectrometry for the analysis of proteins has grown enormously in the past decade. Significant advances in  

E-print Network

601 The utility of mass spectrometry for the analysis of proteins has grown enormously in the past include the combination of mass spectrometry with isotopic labeling, affinity labeling and genomic spectrometry MT metallothionein m/z mass/charge TOF time of flight Introduction A mass spectrometer can

Miranker, Andrew