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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

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

3

Separated Isotopes as Internal Standards in Spark Source Mass Spectrometry  

Microsoft Academic Search

The use of separated stable isotopes as internal standards in spark source mass spectrometry is described. This method is useful for solution samples and complements the more classical isotope dilution technique. For powdered or insoluble samples, the isotopes are dried onto a conducting matrix material-usually high purity silver powder-followed by homogenization of the sample with this «spiked’ matrix. The resulting

D. L. Donohue; J. A. Carter; J. C. Franklin

1977-01-01

4

USING ISOTOPE DILUTION MASS SPECTROMETRY TO DETERMINE AQUEOUS TRICHLOROACETIC ACID  

EPA Science Inventory

The development, verification, and application of a method based on isotope dilution gas chromatography-mass spectrometry to determine aqueous trichloroacetic acid (TCAA) at the micrograms per litre level are described. The simultaneous determination of aqueous chloroform is also...

5

Hydrogen isotope analysis by quadrupole mass spectrometry  

Microsoft Academic Search

The analysis of isotopes of hydrogen (H, D, T) and helium (³He, 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

6

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.

7

Resonance ionization mass spectrometry for precise measurements of isotope ratios  

NASA Astrophysics Data System (ADS)

Resonance ionization mass spectrometry offers extremely high sensitivity and elemental selectivity in microanalysis, but the isotopic precision attainable by this technique has been limited. Measured isotope ratios are sensitive to small fluctuations in the pointing, pulse timing, and wavelength of the resonance lasers. We show that, by minimizing these fluctuations using feedback controls and by power-broadening the optical transitions, we are able to measure chromium isotope ratios with statistics-limited precision better than 1%. Small additional improvements in reproducibility come from careful shaping of the electric field in the region where atoms are photoionized and from minimizing pulse-to-pulse variations in the time-of-flight mass spectrometer through which the photoions travel. The increased reproducibility of isotopic measurements on standard materials has enabled us to detect anomalous chromium isotopic abundances in presolar SiC grains extracted from primitive meteorites.

Levine, Jonathan; Savina, Michael R.; Stephan, Thomas; Dauphas, Nicolas; Davis, Andrew M.; Knight, Kim B.; Pellin, Michael J.

2009-12-01

8

High-precision continuous-flow isotope ratio mass spectrometry.  

PubMed

Although high-precision isotope determinations are routine in many areas of natural science, the instrument principles for their measurements have remained remarkably unchanged for four decades. The introduction of continuous-flow techniques to isotope ratio mass spectrometry (IRMS) instrumentation has precipitated a rapid expansion in capabilities for high-precision measurement of C, N, O, S, and H isotopes in the 1990s. Elemental analyzers, based on the flash combustion of solid organic samples, are interfaced to IRMS to facilitate routine C and N isotopic analysis of unprocessed samples. Gas/liquid equilibrators have automated O and H isotopic analysis of water in untreated aqueous fluids as complex as urine. Automated cryogenic concentrators permit analysis at part-per-million concentrations in environmental samples. Capillary gas chromatography interfaced to IRMS via on-line microchemistry facilitates compound-specific isotope analysis (CSIA) for purified organic analytes of 1 nmol of C, N, or O. GC-based CSIA for hydrogen and liquid chromatography-based interfaces to IRMS have both been demonstrated, and continuing progress promises to bring these advances to routine use. Automated position-specific isotope analysis (PSIA) using noncatalytic pyrolysis has been shown to produce fragments without appreciable carbon scrambling or major isotopic fractionation, and shows great promise for intramolecular isotope ratio analysis. Finally, IRMS notation and useful elementary isotopic relationships derived from the fundamental mass balance equation are presented. PMID:9538528

Brenna, J T; Corso, T N; Tobias, H J; Caimi, R J

1997-01-01

9

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

10

Improved Isotopic Measurement of Plutonium by Thermal Ionization Mass Spectrometry  

SciTech Connect

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

Shick, C. Jr.

2002-02-07

11

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

12

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.

Vogl, Jochen

2013-01-01

13

Quantitation of DNA adducts by stable isotope dilution mass spectrometry  

PubMed Central

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

Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

2012-01-01

14

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

15

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

16

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

PubMed

The key role of a forensic scientist is to assist in determining whether a crime has been committed, and if so, assist in the identification of the offender. Many people hold the belief that a particular item can be conclusively linked to a specific person, place or object. Unfortunately, this is often not achievable in forensic science. In performing their role, scientists develop and test hypotheses. The significance of those hypotheses that cannot be rejected upon completion of all available examinations/analyses is then evaluated. Although one can generally identify the substances present using available techniques, it is generally not possible to distinguish one source of the same substance from another. In such circumstances, although a particular hypothesis cannot be rejected, it cannot be conclusively proven, i.e. the samples could still have originated from different sources. This limitation of not being able to distinguish between sources currently extends to the analysis of other forensic samples including, but not limited to, ignitable liquids, paints, adhesives, textile fibres, plastics, and illicit drugs. Stable isotope ratio mass spectrometry (IRMS) is an additional technique that can be utilised to test a given hypothesis. This technique shows the potential to be able to individualise a range of materials of forensic interest. This paper provides a brief description of the technique, followed by a review of the various applications of IRMS in different scientific fields. The focus of this summary is on forensic applications of IRMS, in particular the analysis of explosives, ignitable liquids and illicit drugs. PMID:15919168

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

2006-02-10

17

Computer Analysis of Isotope Clusters in Mass Spectrometry  

ERIC Educational Resources Information Center

Describes the application of a computer program designed to produce a formula determination simultaneously accounting for both elemental composition and probable isotopic species for a measured ion mass. (SLH)

Bell, Harold M.

1974-01-01

18

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

Chloé Nadia Maréchal; Philippe Télouk; Francis Albarède

1999-01-01

19

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 Nâ and COâ 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

20

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

21

Photon burst mass spectrometry--ultrasensitive detection of rare isotopes  

SciTech Connect

Progress is reported on the development of a new technique for measurement of trace levels of radioisotopes which is based on fluorescence detection of output from a mass spectrometer. Significant achievements include the observation of fluorescence and burst signals from Kr isotopes, including enriched samples of {sup 85}Kr with a 4-collector system. An abundance sensitivity is demonstrated with {sup 83}Kr and {sup 85}Kr.

Hansen, C.S.; Pan, X.J.; Fairbank, W.M. Jr. [Colorado State Univ., Fort Collins, CO (United States). Physics Dept.; Oona, H.; Chamberlin, E.P.; Nogar, N.S.; Fearey, B.L. [Los Alamos National Lab., NM (United States)

1995-02-01

22

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

23

Liquid Chromatography Coupled to Isotope Ratio Mass Spectrometry:  A New Perspective on Honey Adulteration Detection  

Microsoft Academic Search

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 ‰13Choney ranged from -14.2 to -27.2‰, and ‰13Cprotein ranged from -23.6

Ana I. Cabañero; Jose L. Recio; MERCEDES RUPE Ä REZ

2006-01-01

24

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

25

Absolute quantification of peptides by isotope dilution liquid chromatography-inductively coupled plasma mass spectrometry and gas chromatography\\/mass spectrometry  

Microsoft Academic Search

Absolute quantitation of peptides\\/proteins in dilute calibration solutions used in various diagnostic settings is a major challenge. Here we report the absolute quantitation of peptides by non-species-specific isotope dilution liquid chromatography-inductively coupled plasma mass spectrometry (ID LC-ICPMS) based on stoichiometric Eu tagging. The method was validated by species-specific isotope dilution gas chromatography\\/mass spectrometry (GC\\/MS) analysis of constituent amino acids of

R. a b c Liu; X. b Hou; Y. b Lv; M. a McCooeye; L. a Yang; Z.a Mester

2013-01-01

26

Elemental fingerprint analysis of barley ( Hordeum vulgare ) using inductively coupled plasma mass spectrometry, isotope-ratio mass spectrometry, and multivariate statistics  

Microsoft Academic Search

Inductively coupled plasma mass spectrometry (ICP–MS) and isotope-ratio mass spectrometry (IR-MS) have been used to examine the multi-elemental composition and 15N\\/ 14N and 13C\\/ 12C isotope ratios of three spring barley ( Hordeum vulgare) genotypes (Orthega, Barke, and Bartok) grown in three typical Danish agricultural soils (North Jutland, West Jutland, and East Zealand) differing in soil fertility. The aim of

Søren Husted; Birgitte F. Mikkelsen; Jacob Jensen; NielsErik Nielsen

2004-01-01

27

New technologies for small sample stable isotope measurement: static vacuum gas source mass spectrometry, laser probes, ion probes and gas chromatography-isotope ratio mass spectrometry  

NASA Astrophysics Data System (ADS)

Since there are 83 natural elements, any review of the use of mass spectrometry for the study of abundance and isotopic compositions of individual species in a geological environment, including locations beyond the Earth, has of necessity to be selective. This paper will focus on the studies of the so-called "light elements": hydrogen, carbon, nitrogen, oxygen, silicon and sulphur and their isotope systems. Five of the elements chosen (H, C, O, N and si) are amongst the most abundant in the cosmos, four (H, C, O and N) contribute substantially to life processes and choosing either C or Si together with O would allow as to account for > 60% of virtually all rocks. To further restrict the subject matter, I intend to concentrate on advances in the techniques for measurement of these elements. Amongst the most important advances in technology are the following: (i) the reduction of sample requirements for gas source stable isotope mass spectrometry into the picomole range; (ii) the application of focussed lasers as a means of extracting gas for isotopic measurement; (iii) a demonstration of the abilities of the ion microprobe (SIMS) in producing isotope measurements; and (iv) coupling of gas chromatography to stable isotope mass spectrometers for compound specific isotope analysis of complex mixtures. Some of the scientific highlights which have been achieved by the above means are respectively: (i) the identification of individual silicon carbide minerals as grains of interstellar dust; (ii) the demonstration of growth effects in diamonds of terrestrial and extraterrestrial origin; (iii) mineral specific isotopic compositions for complex geological materials; and (iv) unravelling the origin of mixtures of biomarkers in sedimentary environments.

Pillinger, C. T.

1992-09-01

28

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.

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

2008-01-01

29

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

PubMed

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

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

2012-10-20

30

Experimental investigations of trimer ion contributions in the low resolution mass spectrometry of hydrogen isotope mixtures.  

PubMed

This paper reports on some preliminary experimental results of a work in progress regarding a problem involving the quantitative analysis of hydrogen isotopes by mass spectrometry of low resolution: the triatomic (trimer) ions interferences with the isotopic hydrogen species having the same mass/charge. These results indicate that, in complex mixtures of hydrogen isotopes, trimer ions are strongly affected by the presence of other species, and a new approach that takes into account the destruction mechanism of trimer ions is necessary for a proper determination of their contributions. PMID:23149602

Bidica, Nicolae

2012-01-01

31

Determination of germanium by isotope dilution-hydride generation inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Inorganic germanium in aqueous solution is determined by a combination of isotope dilution, hydride generation, and inductively-coupled plasma mass spectrometry (ID-HG-ICP-MS). Samples (5–20 ml) are spiked with an enriched stable isotope (70Ge). Germanic acid is reduced by sodium borohydride to germane (GeH4), stripped in He gas and collected on a liquid nitrogen trap. The hydrides are subsequently evaporated from the

Richard A. Mortlock; Philip. N. Froelich

1996-01-01

32

High-precision measurement of magnesium isotopes by multiple-collector inductively coupled plasma mass spectrometry  

Microsoft Academic Search

Multiple-collector inductively coupled plasma mass spectrometry has been used for the precise measurement of variations in the isotopic composition of Mg in a range of materials. The contributions of C?C, C?N, and Mg?H molecular species to the mass spectrum in the Mg mass region are minimised. Variations in sample 26Mg\\/24Mg and 25Mg\\/24Mg ratios are expressed as ?26Mg and ?25Mg units,

Albert Galy; Nick S. Belshaw; Ludwik Halicz; R. Keith O’Nions

2001-01-01

33

Current perspectives of 14 C-isotope measurement in biomedical accelerator mass spectrometry  

Microsoft Academic Search

Accelerator mass spectrometry (AMS) is an extremely sensitive nuclear physics technique developed in the mid-70’s for radiocarbon dating of historical artefacts. The technique centres round the use of a tandem Van de Graaff accelerator to generate the potential energy to permit separation of elemental isotopes at the single atom level. AMS was first used in the early 90’s for the

Graham Lappin; R. Colin Garner

2004-01-01

34

Plumbo-Isotopy: The Measurement of Lead Isotopes by Multi-Collector Inductively Coupled Mass Spectrometry.  

National Technical Information Service (NTIS)

This open-file report describes the analytical protocol for measurement of lead (Pb) isotope compositions using the Nu Plasma HR multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) facility in Building 20, Denver Federal Center, Denve...

W. I. Ridley

2005-01-01

35

Detection of counterfeit antiviral drug Heptodin™ and classification of counterfeits using isotope amount ratio measurements by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) and isotope ratio mass spectrometry (IRMS)  

Microsoft Academic Search

Isotope ratio mass spectrometry (IRMS) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) are highly important techniques that can provide forensic evidence that otherwise would not be available. MC-ICP-MS has proved to be a very powerful tool for measuring high precision and accuracy isotope amount ratios. In this work, the potential of combining isotope amount ratio measurements performed by MC-ICP-MS

Rebeca Santamaria-Fernandez; Ruth Hearn; Jean-Claude Wolff

2009-01-01

36

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

37

Application of high-precision isotope ratio monitoring mass spectrometry to identify the biosynthetic origins of proteins  

PubMed Central

Isotope ratio monitoring (IRM) mass spectrometry was used to measure the relative abundance of stable isotopes in several samples of adult human hemoglobin expressed in E. coli, yeast, and human blood. The results showed significant differences in the distribution of 15N and 13C isotopes among hemoglobin samples produced in these organisms. This indicates that IRM mass spectrometry can be used in forensic protein chemistry to identify the origin of protein expression.

Apostol, Izydor; Brooks, Paul D.; Mathews, Antony J.

2001-01-01

38

Determination of carbon isotope ratios of methanol and acetaldehyde in air samples by gas chromatography-isotope ratio mass spectrometry combined with headspace solid-phase microextraction  

Microsoft Academic Search

Isotopic signatures of atmospheric methanol and acetaldehyde have the potential to improve our ability to quantitatively assess their importance in atmospheric chemistry. However, isotopic measurements of atmospheric methanol and acetaldehyde and their individual source and sink processes have been limited. In this study, we examined gas chromatography-isotope ratio mass spectrometry combined with headspace solid-phase microextraction to measure the carbon isotope

Keita Yamada; Ryota Hattori; Yuji Ito; Hiroki Shibata; Naohiro Yoshida

2010-01-01

39

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

Microsoft Academic Search

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

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

2009-01-01

40

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

41

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

42

Measurement of trace isotopes by photon burst mass spectrometry.  

National Technical Information Service (NTIS)

Progress is reported on the development of a new laser- and mass spectrometer-based technique for measurement of trace levels of radioisotopes. Significant results to date include the demonstration of high efficiency and throughput in a mass spectrometer,...

W. M. Fairbank C. S. Hansen R. D. LaBelle X. J. Pan E. P. Chamberlin

1991-01-01

43

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

44

Determination of iron in serum and water by resonance ionization isotope dilution mass spectrometry  

Microsoft Academic Search

Resonance ionization mass spectrometry has been used in conjunction with isotope dilution to determine the iron content of SRM 909 (Human Serum) and SRM 1643b (Trace Elements in Water). Iron was thermally vaporized from a filament at 1250 K. A one-wavelength, two-photon ionization scheme was employed utilizing UV light at 283.6 nm provided by a Nd:YAG pumped dye laser with

J. D. Fassett; L. J. Powell; L. J. Moore

1984-01-01

45

Lead in prehistoric, historic and contemporary Japanese: stable isotopic study by ICP mass spectrometry  

Microsoft Academic Search

Lead concentration and isotopic composition of prehistoric (middle and latest Jomon era, 2000–4500BP, n=6), historic (Edo era, 130–400BP, n=10), and contemporary (died in 1987–88, n=15) Japanese bones, and deciduous teeth from contemporary Japanese children born during 1985–88 (n=17) were analyzed by inductively coupled plasma mass spectrometry. Lead concentration was lowest in Jomon bones and was higher in rural Edo, contemporary,

Jun Yoshinaga; Minoru Yoneda; Masatoshi Morita; Tsuguyoshi Suzuki

1998-01-01

46

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

Microsoft Academic Search

Growth retardation as well as the development of Cushingoid features in adrenally insufficient patients treated with the currently accepted replacement dose of cortisol (33-41 mumol\\/day.m2; 12-15 mg\\/m2.day) prompted us to reevaluate the cortisol production rate (FPR) in normal subjects and patients with Cushing's syndrome, using a recently developed thermospray liquid chromatography-mass spectrometry method. The stable isotope (9,12,12-2H3)cortisol was infused continuously

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

1991-01-01

47

Determination of atmospheric carbonyl sulfide by isotope dilution gas chromatography/mass spectrometry  

SciTech Connect

A gas chromatography/mass spectrometry (GB/MS) method for determining atmospheric carbonyl sulfide (OCS) with a precision better than 2% is reported. High precision and insensitivity to sample loss and changes in detector response were achieved by using isotopically labeled OCS as an internal standard. Tenax, Molecular Sieve 5A, Carbosieve B, and Carbosieve S were evaluated for collecting atmospheric OCS. Molecular Sieve 5A provided the best trapping and recovery efficiencies.

Lewin, E.E.; Taggart, R.L.; Lalevic, M.; Bandy, A.R.

1987-05-01

48

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

49

Calibration and Data Processing in Gas Chromatography Combustion Isotope Ratio Mass Spectrometry  

PubMed Central

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 (13C/12C). 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 ?13C = ?13CM – ?13CE difference measurements required for establishing adverse analytical findings for metabolites relative to endogenous reference compounds. Considerations for the anti-doping analyst are reviewed.

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

2013-01-01

50

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

51

Strong anion-exchange liquid chromatography coupled with isotope ratio mass spectrometry using a Liquiface interface.  

PubMed

The introduction of liquid chromatography coupled with isotope ratio mass spectrometry (LC/IRMS) as an analytical tool for the measurement of isotope ratios in non-volatile analytes has somewhat simplified the analytical cycle from sample collection to analysis mainly due to the avoidance of the extensive sample processing and derivatisation that were necessary for gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Here we test the performance of coupling strong anion exchange to IRMS using only the second commercially available interface; the Liquiface. The system was modified from installation specification to improve peak resolution in the interface and maintain peak separation from the column to the mass spectrometer. The system performance was assessed by the determination of sensitivity, accuracy and precision attained from carbohydrate separations. The system performed satisfactorily after modifications, resulting in maintenance of peak resolution from column to mass spectrometer. The sensitivity achieved suggested that approximately 150 ng carbon could be analysed with acceptable precision (<0.3 per thousand). Accuracy was maintained in the interface as determined by correlation with offline techniques, resulting in regression coefficient of r(2) = 0.98 and a slope of 0.99. The average precision achieved for the separation of seven monosaccharides was 0.36 per thousand. The integration of a carbonate removal device limited the effect of background carbon perturbations in the mass spectrometer associated with eluent gradients, and the coupling of strong anion-exchange chromatography with IRMS was successfully achieved using the Liquiface. PMID:20499320

Morrison, Douglas J; Taylor, Karen; Preston, Tom

2010-06-30

52

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

53

On the utility of isotopic fine structure mass spectrometry in protein identification.  

PubMed

Modern mass spectrometry (MS)-based protein identification and characterization relies upon accurate mass measurements of the (13)C isotopic distributions of the enzymatically produced peptides. Interestingly, obtaining peptide elemental composition information from its isotopic fine structure mass spectrum to increase the confidence in peptide and protein identification has not yet been developed into a bottom-up proteomics-grade analytical approach. Here, we discuss the possible utility and limitations of the isotopic fine structure MS for peptide and protein identification. First, we in silico identify the peptides from the E. coli tryptic digest and show the increased confidence in peptide identification by consideration of the isotopic fine structures of these peptides as a function of mass and abundance accuracies. In the following, we demonstrate that the state-of-the-art high magnetic field Fourier transform ion cyclotron resonance (FT-ICR) MS allows a routine acquisition of the isotopic fine structure information of a number of isobaric peptide pairs, including a pair of peptides originating from E. coli. Finally, we address the practical limitation of the isotopic fine structure MS implementation in the time-constraint experiments by applying an advanced signal processing technique, filter diagonalization method, to the experimental transients to overcome the resolution barrier set by the typically applied Fourier transformation. We thus demonstrate that the isotopic fine structures of peptides may indeed improve the peptide and possibly protein identification, can be produced in a routine experiment by the state-of-the-art high resolution mass spectrometers, and can be potentially obtained on a chromatographic time-scale of a typical bottom-up proteomics experiment. The latter one requires at least an order of magnitude increase in sensitivity of ion detection, which presumably can be realized using high-field Orbitrap FTMS and/or future generation of ultrahigh magnetic field FT-ICR MS equipped with harmonized ICR cells. PMID:22468966

Miladinovi?, Saša M; Kozhinov, Anton N; Gorshkov, Mikhail V; Tsybin, Yury O

2012-05-01

54

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

SciTech Connect

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 the sample surface by a beam of high-energy xenon atoms and detected with a high-resolution mass spectrometer. A data acquisition system has been developed to control the mass spectrometer and record the ion signals. Detailed analysis of potential sources of error indicates that the precision of the method is presently limited primarily by an isotope effect that occurs during ion desorption. Results presented here demonstrate that the relative abundances of calcium isotopes in urine can be determined with high precision (coefficient of variation < 0.2%) and that the method is a viable alternative to conventional thermal ionization mass spectrometry. The method is especially attractive because it uses a conventional high-resolution mass spectrometer which is routinely used for analysis of organic substances.

Jiang, X.; Smith, D.L.

1987-11-01

55

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

56

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

NASA Astrophysics Data System (ADS)

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.

2013-02-01

57

Chlorine Isotope Effects from Isotope Ratio Mass Spectrometry Suggest Intramolecular C-Cl Bond Competition in Trichloroethene (TCE) Reductive Dehalogenation.  

PubMed

Chlorinated ethenes are prevalent groundwater contaminants. To better constrain (bio)chemical reaction mechanisms of reductive dechlorination, the position-specificity of reductive trichloroethene (TCE) dehalogenation was investigated. Selective biotransformation reactions (i) of tetrachloroethene (PCE) to TCE in cultures of Desulfitobacterium sp. strain Viet1; and (ii) of TCE to cis-1,2-dichloroethene (cis-DCE) in cultures of Geobacter lovleyi strain SZ were investigated. Compound-average carbon isotope effects were -19.0‰ ± 0.9‰ (PCE) and -12.2‰ ± 1.0‰ (TCE) (95% confidence intervals). Using instrumental advances in chlorine isotope analysis by continuous flow isotope ratio mass spectrometry, compound-average chorine isotope effects were measured for PCE (-5.0‰ ± 0.1‰) and TCE (-3.6‰ ± 0.2‰). In addition, position-specific kinetic chlorine isotope effects were determined from fits of reactant and product isotope ratios. In PCE biodegradation, primary chlorine isotope effects were substantially larger (by -16.3‰ ± 1.4‰ (standard error)) than secondary. In TCE biodegradation, in contrast, the product cis-DCE reflected an average isotope effect of -2.4‰ ± 0.3‰ and the product chloride an isotope effect of -6.5‰ ± 2.5‰, in the original positions of TCE from which the products were formed (95% confidence intervals). A greater difference would be expected for a position-specific reaction (chloride would exclusively reflect a primary isotope effect). These results therefore suggest that both vicinal chlorine substituents of TCE were reactive (intramolecular competition). This finding puts new constraints on mechanistic scenarios and favours either nucleophilic addition by Co(I) or single electron transfer as reductive dehalogenation mechanisms. PMID:24853618

Cretnik, Stefan; Bernstein, Anat; Shouakar-Stash, Orfan; Löffler, Frank; Elsner, Martin

2014-01-01

58

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. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25044895

González-Antuña, Ana; Rodríguez-González, Pablo; García Alonso, J Ignacio

2014-08-01

59

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; Stöbener, N; Trautmann, N; Wendt, K

2012-11-01

60

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

USGS Publications Warehouse

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

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

1987-01-01

61

Quantitative proteome analysis by solid-phase isotope tagging and mass spectrometry.  

PubMed

The adaptation of sequences of chemical reactions to a solid-phase format has been essential to the automation, reproducibility, and efficiency of a number of biotechnological processes including peptide and oligonucleotide synthesis and sequencing. Here we describe a method for the site-specific, stable isotopic labeling of cysteinyl peptides in complex peptide mixtures through a solid-phase capture and release process, and the concomitant isolation of the labeled peptides. The recovered peptides were analyzed by microcapillary liquid chromatography and tandem mass spectrometry (microLC-MS/MS) to determine their sequences and relative quantities. The method was used to detect galactose-induced changes in protein abundance in the yeast Saccharomyces cerevisiae. A side-by-side comparison with the isotope-coded affinity tag (ICAT) method demonstrated that the solid-phase method for stable isotope tagging of peptides is comparatively simpler, more efficient, and more sensitive. PMID:11981568

Zhou, Huilin; Ranish, Jeffrey A; Watts, Julian D; Aebersold, Ruedi

2002-05-01

62

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

SciTech Connect

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

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

1985-11-15

63

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

PubMed

Methods have been developed for the simultaneous quantitative analysis of vitamin B6 forms in biological samples by isotope dilution mass spectrometry using deuterated forms of pyridoxine, pyridoxal, pyridoxamine, and pyridoxic acid. The biological fluid or tissue sample was homogenized and then treated with a cocktail containing appropriate amounts of each deuterated vitamer, as well as the deuterated, phosphorylated vitamer forms. The individual vitamers were isolated from the homogenate by a complex high-performance liquid chromatographic procedure that provided separate fractions for each of the six vitamers found in biological samples. Aldehydic B6 vitamers were reduced to the alcohol form prior to acetylation and analysis by gas chromatography/mass spectrometry (GC/MS). The three resulting vitamers were analyzed by electron ionization GC/MS using a silicone capillary column. The methods have been applied to analysis of vitamin B6 in liver, milk, urine, and feces at levels as low as 0.02 nmol/ml. PMID:4091275

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

1985-11-15

64

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

65

Rapid quality control analysis of (13)C-enriched substrate synthesis by isotope ratio mass spectrometry.  

PubMed

There is a growing interest in the use of (13)C-enriched substrates to investigate metabolic processes in humans. The non-invasive nature of (13)C breath tests makes them attractive to clinicians, particularly because they can be safely used in children. The availability of suitable (13)C-enriched substrates can limit the application of this biotechnology. We have used isotope ratio mass spectrometry to assay the chemical purity and isotopic enrichment of substrates that were synthesised to study gut transit and colonic fermentation. Lactose ureide and lactose [(13)C]ureide were synthesised by acid-catalysed condensation of lactose and urea or (13)C urea, respectively. Glucose ureide and glucose [(13)C]ureide were synthesised by similar methods but required an additional purification step to remove urea of crystallisation. Substrates were analysed by standard analytical techniques and combustion isotope ratio mass spectrometry for carbon and nitrogen content and (13)C-enrichment. Monitoring the C/N ratio proved to be a sensitive assay of chemical purity. Analysis of the percentage composition of C and N (and hence O + H) suggested that lactose ureide crystallises as the dihydrate. It was synthesised with approximately 99% chemical purity and with the theoretical enrichment. Glucose ureide was synthesised with approximately 98% chemical purity but with lower than theoretical enrichment. PMID:11466784

Morrison, D J; Dodson, B; Preston, T; Weaver, L T

2001-01-01

66

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

67

Isotope-selective laser photodetachment for 129I accelerator mass spectrometry  

NASA Astrophysics Data System (ADS)

A pulsed injection-locked Ti:Sapphire laser and a negative ion laser ablation source are developed for compact accelerator mass spectrometry assisted by isotope-selective laser photodetachment. An output of about 60 mW at a repetition rate of 1 kHz is available using intracavity second-harmonic generation with a bandwidth of 20 MHz. A negative iodine ion pulse with a width of 100 ns is obtained by laser ablation of a NH4I sample. The negative ion source and the injection-locked Ti:Sapphire laser are suitable for trace analysis of 129I.

Takahashi, Tone; Tomita, Hideki; Nakayama, Motoi; Adachi, Yoshitaka; Sonnenschein, Volker; Iguchi, Tetsuo; Wendt, Klaus

2013-04-01

68

Isotope dilution liquid chromatography-tandem mass spectrometry for quantitative amino acid analysis.  

PubMed

The role of amino acid analysis in bioanalysis has changed from a qualitative to a quantitative technique. With the discovery of both electrospray ionization and matrix-assisted laser desorption ionization in the early 1990s, the use of amino acid analysis for qualitative analysis of proteins and peptides has been replaced by mass spectrometry. Accurate measurement of the relative molecular masses of proteins and peptides, peptide mapping, and sequencing by tandem mass spectrometry provide significantly better qualitative information than can be achieved from amino acid analysis. At NIST, amino acid analysis is used to assign concentration values to protein and peptide standard reference materials (SRMs) which, subsequently, will be used in the calibration of a wide variety of protein and peptide assays, such as those used in clinical diagnostics. It is critical that the amino acid analysis method used at NIST for SRM measurement deliver the highest accuracy and precision possible. Therefore, we have developed an amino acid analysis method that uses isotope dilution LC-MS/MS - the analytical technique routinely used at NIST to certify analyte concentrations in SRMs for a wide variety of analytes. Amino acid analysis by isotope dilution LC-MS/MS was first used to measure the concentration of bovine serum albumin in NIST SRM 927d ("bovine serum albumin, 7% solution"). We have recently refined our isotope dilution LC-MS/MS amino acid analysis method to certify the concentration of 17 amino acids in NIST SRM 2389a ("amino acids in 0.1 mol/L hydrochloric acid"). We present here our most recent method for the quantification of amino acids using isotope dilution LC-MS/MS. PMID:22125133

Bunk, David M; Lowenthal, Mark S

2012-01-01

69

Advantages of isotopic depletion of proteins for hydrogen/deuterium exchange experiments monitored by mass spectrometry.  

PubMed

Solution-phase hydrogen/deuterium exchange (HDX) monitored by mass spectrometry is an excellent tool to study protein-protein interactions and conformational changes in biological systems, especially when traditional methods such as X-ray crystallography or nuclear magnetic resonance are not feasible. Peak overlap among the dozens of proteolytic fragments (including those from autolysis of the protease) can be severe, due to high protein molecular weight(s) and the broad isotopic distributions due to multiple deuterations of many peptides. In addition, different subunits of a protein complex can yield isomeric proteolytic fragments. Here, we show that depletion of (13)C and/or (15)N for one or more protein subunits of a complex can greatly simplify the mass spectra, increase the signal-to-noise ratio of the depleted fragment ions, and remove ambiguity in assignment of the m/z values to the correct isomeric peptides. Specifically, it becomes possible to monitor the exchange progress for two isobaric fragments originating from two or more different subunits within the complex, without having to resort to tandem mass spectrometry techniques that can lead to deuterium scrambling in the gas phase. Finally, because the isotopic distribution for a small to medium-size peptide is essentially just the monoisotopic species ((12)C(c)(1)H(h)(14)N(n)(16)O(o)(32)S(s)), it is not necessary to deconvolve the natural abundance distribution for each partially deuterated peptide during HDX data reduction. PMID:20337424

Bou-Assaf, George M; Chamoun, Jean E; Emmett, Mark R; Fajer, Piotr G; Marshall, Alan G

2010-04-15

70

Isolation and Puification of Uranium Isotopes for Measurement by Mass-Spectrometry (233, 234, 235, 236, 238U) and Alpha Spectrometry (232U)  

SciTech Connect

This report describes a standardized methodology used by researchers from the Center for Accelerator Mass Spectrometry (CAMS) (Energy and Environment Directorate) and the Environmental Radiochemistry Group (Chemistry and Materials Science Directorate) at the Lawrence Livermore National Laboratory (LLNL) for the full isotopic analysis of uranium from solution. The methodology has largely been developed for use in characterizing the uranium composition of selected nuclear materials but may also be applicable to environmental studies and assessments of public, military or occupational exposures to uranium using in-vitro bioassay monitoring techniques. Uranium isotope concentrations and isotopic ratios are measured using a combination of Multi Collector Inductively Coupled Plasma Mass Spectrometry (MC ICP-MS), Accelerator Mass Spectrometry (AMS) and Alpha Spectrometry.

Marinelli, R; Hamilton, T; Brown, T; Marchetti, A; Williams, R; Tumey, S

2006-05-30

71

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

72

Identification of ground water contaminations by landfills using precise boron isotope ratio measurements with negative thermal ionization mass spectrometry  

Microsoft Academic Search

Precise boron isotope ratio measurements with negative thermal ionization mass spectrometry were used for the identification\\u000a of ground water contaminations by leakages of landfills. BO-\\u000a 2thermal ions were produced to determine the 11B\\/10B isotope ratio, which was expressed as ?11B value in ‰ normalized to the standard reference material NIST SRM 951. For example, household waste influences the boron\\u000a isotope

S. Eisenhut; K. G. Heumann

1997-01-01

73

Quantitative protein analysis by solid phase isotope tagging and mass spectrometry.  

PubMed

Here we describe a method for stable isotope labeling and solid-phase capture of cysteinyl peptides from complex protein mixtures. Site-specific, quantitative labeling of cysteine residues with tags that differ in isotopic content enables quantification of relative peptide abundance between samples. Labeling on a solid phase provides for simultaneous simplification of a complex peptide mixture by isolating cysteinyl, and subsequently tagged, peptides. Peptides from proteolytic digests of protein samples are labeled in preparation for analysis by microcapillary liquid chromatography and tandem mass spectrometry (microLC-MS/MS) to determine their sequences and relative abundance between samples. This approach enables rapid identification and accurate quantification of relative abundance of individual proteins from different biological contexts. PMID:15064479

Zhou, Huilin; Boyle, Rosemary; Aebersold, Ruedi

2004-01-01

74

Isotope ratio mass spectrometry as a tool to determine aerosol yields in organic seed aerosols  

NASA Astrophysics Data System (ADS)

For long time it was thought that small hydrocarbons and carbonyls do not contribute to aerosol formation. However, it was recently found that oxidation of the C5-compound isoprene forms products of low enough volatility to partition into the particle phase. Moreover, there is strong evidence that the C2-carbonyl compound glyoxal can partition into the particle phase to a certain extent dependent on the particle phase composition. Due to the low aerosol yield of for instance isoprene it is quite difficult to determine its yield at a low precursor concentration. In addition, reactions in the particle phase like oligomerization, esterification, etc. may strongly influence the uptake of relatively volatile oxidation products. These reactions may be dependent on the chemical composition of the particle phase. Therefore, experiments should be performed with an organic seed aerosol. We have explored isotope labeling to determine the aerosol yield of isoprene (Dommen et al. ES&T, 43, 6697-6702 (2009)). The main bulk of the particle is formed from a high aerosol yield compound where the labeled oxidation products of the labeled precursors can partition into. Using a 13C-labeled isoprene we then could discriminate by isotope ratio mass spectrometry the amount of oxidation products from the labeled precursor partitioned into the bulk aerosol. We further improved the technique of isotope labeling in combination with isotope ratio mass spectrometry such that we are now able to use this method for aerosol concentrations below 10 ?g/m3, which is of most relevance for atmospheric conditions. This allows now to test aerosol yields in different types of organic seeds. The measurement technique will be presented and an example of the aerosol yield of a labeled short chain hydrocarbon will be shown.

Dommen, J.; Barmet, P.; Bianchi, F.; Pfaffenberger, L.; Decarlo, P. F.; Saurer, M.; Siegwolf, R. T.; Prevot, A. S.; Baltensperger, U.

2010-12-01

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.; Morré, Jeffrey T.; Bradford, C. Samuel; Beckman, Joseph S.

2013-01-01

76

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, Gérard; Fay, Laurent

2008-09-15

77

Calculation and mitigation of isotopic interferences in liquid chromatography-mass spectrometry/mass spectrometry assays and its application in supporting microdose absolute bioavailability studies.  

PubMed

A methodology for the accurate calculation and mitigation of isotopic interferences in liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) assays and its application in supporting microdose absolute bioavailability studies are reported for the first time. For simplicity, this calculation methodology and the strategy to minimize the isotopic interference are demonstrated using a simple molecule entity, then applied to actual development drugs. The exact isotopic interferences calculated with this methodology were often much less than the traditionally used, overestimated isotopic interferences simply based on the molecular isotope abundance. One application of the methodology is the selection of a stable isotopically labeled internal standard (SIL-IS) for an LC-MS/MS bioanalytical assay. The second application is the selection of an SIL analogue for use in intravenous (i.v.) microdosing for the determination of absolute bioavailability. In the case of microdosing, the traditional approach of calculating isotopic interferences can result in selecting a labeling scheme that overlabels the i.v.-dosed drug or leads to incorrect conclusions on the feasibility of using an SIL drug and analysis by LC-MS/MS. The methodology presented here can guide the synthesis by accurately calculating the isotopic interferences when labeling at different positions, using different selective reaction monitoring (SRM) transitions or adding more labeling positions. This methodology has been successfully applied to the selection of the labeled i.v.-dosed drugs for use in two microdose absolute bioavailability studies, before initiating the chemical synthesis. With this methodology, significant time and cost saving can be achieved in supporting microdose absolute bioavailability studies with stable labeled drugs. PMID:22540405

Gu, Huidong; Wang, Jian; Aubry, Anne-Françoise; Jiang, Hao; Zeng, Jianing; Easter, John; Wang, Jun-sheng; Dockens, Randy; Bifano, Marc; Burrell, Richard; Arnold, Mark E

2012-06-01

78

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

79

Calculation of partial isotope incorporation into peptides measured by mass spectrometry  

PubMed Central

Background Stable isotope probing (SIP) technique was developed to link function, structure and activity of microbial cultures metabolizing carbon and nitrogen containing substrates to synthesize their biomass. Currently, available methods are restricted solely to the estimation of fully saturated heavy stable isotope incorporation and convenient methods with sufficient accuracy are still missing. However in order to track carbon fluxes in microbial communities new methods are required that allow the calculation of partial incorporation into biomolecules. Results In this study, we use the characteristics of the so-called 'half decimal place rule' (HDPR) in order to accurately calculate the partial13C incorporation in peptides from enzymatic digested proteins. Due to the clade-crossing universality of proteins within bacteria, any available high-resolution mass spectrometry generated dataset consisting of tryptically-digested peptides can be used as reference. We used a freely available peptide mass dataset from Mycobacterium tuberculosis consisting of 315,579 entries. From this the error of estimated versus known heavy stable isotope incorporation from an increasing number of randomly drawn peptide sub-samples (100 times each; no repetition) was calculated. To acquire an estimated incorporation error of less than 5 atom %, about 100 peptide masses were needed. Finally, for testing the general applicability of our method, peptide masses of tryptically digested proteins from Pseudomonas putida ML2 grown on labeled substrate of various known concentrations were used and13C isotopic incorporation was successfully predicted. An easy-to-use script [1] was further developed to guide users through the calculation procedure for their own data series. Conclusion Our method is valuable for estimating13C incorporation into peptides/proteins accurately and with high sensitivity. Generally, our method holds promise for wider applications in qualitative and especially quantitative proteomics.

2010-01-01

80

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

PubMed

Thermal ionisation mass spectrometry (TIMS) method has been developed for the simultaneous detection of different cerium isotopes in biological samples (i.e., blood and urine) at very low concentrations. The work has been done in the frame of a biokinetic study, where different stable cerium isotopes have been administered orally and intravenously as tracers to the human body. In order to develop an appropriate detection method for the tracers in the biological samples, an optimum sample preparation technique has been set and adapted to the specific requirements of the analysis technique used, i.e., TIMS. For sample evaporation and ionisation, the double tantalum filament technique showed the best results. The ions produced were simultaneously collected on a secondary electron multiplier so that the isotopic ratios of the cerium isotopes in the biological samples could be measured. The technique has been optimised for the determination of cerium down to 1 ng loaded on the evaporation filament corresponding to cerium concentrations of down to 1 ng ml(-1) in the blood or urine samples. It has been shown that the technique is reliable in application and enables studies on cerium metabolism and biokinetics in humans without employing radioactive tracers. PMID:21644136

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

2011-06-01

81

Stable carbon isotopic analyses of lignin-derived CuO oxidation products by isotope ratio monitoring-gas chromatography-mass spectrometry (irm-GC-MS)  

Microsoft Academic Search

In this paper, we evaluate compound-specific isotope analyses of lignin reaction products through the combined application of alkaline CuO oxidation and isotope ratio monitoring-gas chromatography-mass spectrometry (irm-GC-MS). Analyses of phenol standards as trimethylsilyl ethers\\/esters by irm-GC-MS yield accurate (±0.5‰) estimates of their isotopic signatures after correcting for added derivative carbon with precisions ?1‰. CuO oxidation of purified lignin polymers yields

Miguel A. Goñi; Timothy I. Eglinton

1996-01-01

82

Quantitative cross-linking/mass spectrometry using isotope-labelled cross-linkers?  

PubMed Central

Dynamic proteins and multi-protein complexes govern most biological processes. Cross-linking/mass spectrometry (CLMS) is increasingly successful in providing residue-resolution data on static proteinaceous structures. Here we investigate the technical feasibility of recording dynamic processes using isotope-labelling for quantitation. We cross-linked human serum albumin (HSA) with the readily available cross-linker BS3-d0/4 in different heavy/light ratios. We found two limitations. First, isotope labelling reduced the number of identified cross-links. This is in line with similar findings when identifying proteins. Second, standard quantitative proteomics software was not suitable for work with cross-linking. To ameliorate this we wrote a basic open source application, XiQ. Using XiQ we could establish that quantitative CLMS was technically feasible. Biological significance Cross-linking/mass spectrometry (CLMS) has become a powerful tool for providing residue-resolution data on static proteinaceous structures. Adding quantitation to CLMS will extend its ability of recording dynamic processes. Here we introduce a cross-linking specific quantitation strategy by using isotope labelled cross-linkers. Using a model system, we demonstrate the principle and feasibility of quantifying cross-linking data and discuss challenges one may encounter while doing so. We then provide a basic open source application, XiQ, to carry out automated quantitation of CLMS data. Our work lays the foundations of studying the molecular details of biological processes at greater ease than this could be done so far. This article is part of a Special Issue entitled: New Horizons and Applications for Proteomics [EuPA 2012].

Fischer, Lutz; Chen, Zhuo Angel; Rappsilber, Juri

2013-01-01

83

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

SciTech Connect

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

Biegalski, S; Buchholz, B

2009-08-26

84

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

85

A stable-isotope mass spectrometry-based metabolic footprinting approach to analyze exudates from phytoplankton.  

PubMed

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 (13)C-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 (13)C-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

86

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

87

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

PubMed

Hydroponic isotope labeling of entire plants (HILEP) combines hydroponic plant cultivation and metabolic labeling with stable isotopes using (15)N-containing inorganic salts to label whole and mature plants. Employing (15)N salts as the sole nitrogen source for HILEP leads to the production of healthy-looking plants which contain (15)N proteins labeled to nearly 100%. Therefore, HILEP is suitable for quantitative plant proteomic analysis, where plants are grown in either (14)N- or (15)N-hydroponic media and pooled when the biological samples are collected for relative proteome quantitation. The pooled (14)N-/(15)N-protein extracts can be fractionated in any suitable way and digested with a protease for shotgun proteomics, using typically reverse phase liquid chromatography nanoelectrospray ionization tandem mass spectrometry (RPLC-nESI-MS/MS). Best results were obtained with a hybrid ion trap/FT-MS mass spectrometer, combining high mass accuracy and sensitivity for the MS data acquisition with speed and high-throughput MS/MS data acquisition, increasing the number of proteins identified and quantified and improving protein quantitation. Peak processing and picking from raw MS data files, protein identification, and quantitation were performed in a highly automated way using integrated MS data analysis software with minimum manual intervention, thus easing the analytical workflow. In this methodology paper, we describe how to grow Arabidopsis plants hydroponically for isotope labeling using (15)N salts and how to quantitate the resulting proteomes using a convenient workflow that does not require extensive bioinformatics skills. PMID:22665301

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

2012-01-01

88

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

89

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

90

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

PubMed

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

Perkola, Noora; Sainio, Pirjo

2014-01-01

91

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

92

Determination of part-per-trillion levels of atmosphere dimethyl sulfide by isotope dilution gas chromatography/mass spectrometry  

NASA Astrophysics Data System (ADS)

Stable isotopic dilution was applied to the determination of dimethyl sulfide (DMS) in ambient air at the low part-per-trillion by volume (pptrv) levels. Perdeuterated DMS was used as an internal standard in the gas chromatography/mass spectrometry determination. The isotopically labelled internal standard provided insensitivity to possible losses of DMS in sampling and analysis. The lower limit of detection (LLD) was 1 pptrv with a sample acquisition time of 2 min.

Thornton, Donald C.; Bandy, Alan R.; Ridgeway, Robert G.; Driedger, Arthur R., III; Lalevic, Marija

1990-11-01

93

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.

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

2008-01-01

94

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

95

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

PubMed

Polyamines are essential polycations, playing important roles in mammalian physiology. Theoretically, the involvement of homocysteine in polyamine synthesis via S-adenosylmethionine is possible; however, to our knowledge, it has not been established experimentally. Here, we propose an original approach for investigation of homocysteine metabolites in an animal model. The method is based on the combination of isotope-labeled homocysteine supplementation and high-resolution accurate mass spectrometry analysis. Structural identity of the isotope-labeled metabolites was confirmed by accurate mass measurements of molecular and fragment ions and comparison of the retention times and tandem mass spectrometry fragmentation patterns. Isotope-labeled methionine, spermidine, and spermine were detected in all investigated plasma and tissue samples. The induction of moderate hyperhomocysteinemia leads to an alteration in polyamine levels in a different manner. The involvement of homocysteine in polyamine synthesis and modulation of polyamine levels could contribute to a better understanding of the mechanisms connected with homocysteine toxicity. PMID:24736325

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

2014-07-15

96

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

97

Determination of B in body fluids by isotope dilution inductively coupled mass spectrometry with direct injection nebulization  

Microsoft Academic Search

The determination of B in small volumes of undigested blood plasma and urine by isotope dilution and high efficiency direct injection nebulization (DIN) inductively coupled plasma mass spectrometry (ICP-MS) is proposed. The C interference over 11B was removed by precipitating the samples proteins. Samples aliquots of 1 ml were spiked with an enriched 10B solution and shaken during 1 h

Ana Cláudia S Bellato; Maria Fernanda Giné; Amauri A Menegário

2004-01-01

98

Detection of counterfeit antiviral drug Heptodin and classification of counterfeits using isotope amount ratio measurements by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) and isotope ratio mass spectrometry (IRMS).  

PubMed

Isotope ratio mass spectrometry (IRMS) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) are highly important techniques that can provide forensic evidence that otherwise would not be available. MC-ICP-MS has proved to be a very powerful tool for measuring high precision and accuracy isotope amount ratios. In this work, the potential of combining isotope amount ratio measurements performed by MC-ICP-MS and IRMS for the detection of counterfeit pharmaceutical tablets has been investigated. An extensive study for the antiviral drug Heptodin has been performed for several isotopic ratios combining MC-ICP-MS and an elemental analyser EA-IRMS for stable isotope amount ratio measurements. The study has been carried out for 139 batches of the antiviral drug and analyses have been performed for C, S, N and Mg isotope ratios. Authenticity ranges have been obtained for each isotopic system and combined to generate a unique multi-isotopic pattern only present in the genuine tablets. Counterfeit tablets have then been identified as those tablets with an isotopic fingerprint outside the genuine isotopic range. The combination of those two techniques has therefore great potential for pharmaceutical counterfeit detection. A much greater power of discrimination is obtained when at least three isotopic systems are combined. The data from these studies could be presented as evidence in court and therefore methods need to be validated to support their credibility. It is also crucial to be able to produce uncertainty values associated to the isotope amount ratio measurements so that significant differences can be identified and the genuineness of a sample can be assessed. PMID:19606588

Santamaria-Fernandez, Rebeca; Hearn, Ruth; Wolff, Jean-Claude

2009-06-01

99

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

PubMed

A new method for bulk carbon isotope ratio determination of water-soluble samples is presented that is based on flow injection analysis-isotope ratio mass spectrometry (FIA-IRMS) using an LC IsoLink interface. Advantages of the method are that (i) only very small amounts of sample are required (2-5 microL of the sample for up to 200 possible injections), (ii) it avoids complex sample preparation procedures such as needed for EA-IRMS analysis (only sample dilution and injection,) and (iii) high throughput due to short analysis times is possible (approximately 15 min for five replicates). The method was first tested and evaluated as a fast screening method with industrially produced ethanol samples, and additionally the applicability was tested by the measurement of 81 alcoholic beverages, for example, whiskey, brandy, vodka, tequila, and others. The minimal sample concentration required for precise and reproducible measurements was around 50 microL L(-1) ethanol/water (1.71 mM carbon). The limit of repeatability was determined to be r=0.49%. FIA-IRMS represents a fast screening method for beverage authenticity control. Due to this, samples can be prescreened as a decisive criterion for more detailed investigations by HPLC-IRMS or multielement GC-IRMS measurements for a verification of adulteration. PMID:19856915

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

2009-11-25

100

Environmental Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Environmental mass spectrometry is an important branch of science because it provides many of the data that underlie policy decisions that can directly influence the health of people and ecosystems. Environmental mass spectrometry is currently undergoing rapid development. Among the most relevant directions are a significant broadening of the lists of formally targeted compounds; a parallel interest in nontarget chemicals; an increase in the reliability of analyses involving accurate mass measurements, tandem mass spectrometry, and isotopically labeled standards; and a shift toward faster high-throughput analysis, with minimal sample preparation, involving various approaches, including ambient ionization techniques and miniature instruments. A real revolution in analytical chemistry could be triggered with the appearance of robust, simple, and sensitive portable mass spectrometers that can utilize ambient ionization techniques. If the cost of such instruments is reduced to a reasonable level, mass spectrometers could become valuable household devices.

Lebedev, Albert T.

2013-06-01

101

Developing new isotope-coded mass spectrometry-cleavable cross-linkers for elucidating protein structures.  

PubMed

Structural characterization of protein complexes is essential for the understanding of their function and regulation. However, it remains challenging due to limitations in existing tools. With recent technological improvements, cross-linking mass spectrometry (XL-MS) has become a powerful strategy to define protein-protein interactions and elucidate structural topologies of protein complexes. To further advance XL-MS studies, we present here the development of new isotope-coded MS-cleavable homobifunctional cross-linkers: d0- and d10-labeled dimethyl disuccinimidyl sulfoxide (DMDSSO). Detailed characterization of DMDSSO cross-linked peptides further demonstrates that sulfoxide-containing MS-cleavable cross-linkers offer robust and predictable MS2 fragmentation of cross-linked peptides, permitting subsequent MS3 analysis for simplified, unambiguous identification. Concurrent usage of these reagents provides a characteristic doublet pattern of DMDSSO cross-linked peptides, thus aiding in the confidence of cross-link identification by MS(n) analysis. More importantly, the unique isotopic profile permits quantitative analysis of cross-linked peptides and therefore expands the capability of XL-MS strategies to analyze both static and dynamic protein interactions. Together, our work has established a new XL-MS workflow for future studies toward the understanding of structural dynamics of protein complexes. PMID:24471733

Yu, Clinton; Kandur, Wynne; Kao, Athit; Rychnovsky, Scott; Huang, Lan

2014-02-18

102

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

103

Thiol metabolomics of endothelial cells using capillary liquid chromatography mass spectrometry with isotope coded affinity tags.  

PubMed

Thiol and disulfide levels are critical to maintaining the redox potential of a cell. Perturbations of these levels are important in disease pathogenesis. To improve endogenous mammalian metabolome quantitation, thiol specific tagging, extraction and relative quantitation were undertaken. Reduced and oxidized thiol (disulfide) metabolites from endothelial cells were tagged and extracted using cleavable isotope coded affinity tags (cICAT). Extracted cICAT labeled thiols were analyzed using capillary reverse phase liquid chromatography coupled to mass spectrometry (capLC-MS) with positive mode electrospray ionization. Reactions between thiol metabolite standards and the reactive group of cICAT indicate completion by 8h at pH 9 with no apparent disulfide formation. cICAT labeled reduced thiols from endothelial cells showed 1-5% RSD using ratiometric quantitation of isotopes and 6-17% RSD based on signal intensity alone. Sample injection was optimized to 16 pmol. Using high mass accuracy MS, 75 putative thiol metabolites were detected in all experimental samples. Treatment of endothelial cells with 2,3-dimethoxy-5-methyl-1,4-benzoquinone (BQ) shows decreased levels in 28 putative reduced thiols and increased levels of 27 putative disulfides. Treatment of endothelial cells with 30 mM glucose resulted in 22 putative reduced thiols with decreased levels and 7 putative disulfides with increased concentration. Thiols were identified based on accurate mass within 3 ppm and analysis of fragmentation patterns. Using higher collision induced dissociation (HCD), shared product ions between different thiols led to the analysis of thiols from the cysteine-glutathione (Cys-GSH) pathway. Specific reduced thiols and disulfides in this pathway revealed changes different from the overall trends of thiols/disulfides. This suggests varying regulation of the Cys-GSH pathway distinct from other thiol-containing pathways and dependence on the type of environmental stimulus. These results indicate the utility of analyzing reduced thiols and disulfides in eukaryotic samples. PMID:21420094

Yuan, Wei; Edwards, James L

2011-05-01

104

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

PubMed

Cadmium was quantified at 80.15±0.86 ng/g (mean±95% expanded uncertainty) in NIST SRM 3280 Multivitamin/Multielement Tablets, using isotope dilution mass spectrometry. The method described utilized various precipitation and solid-phase extraction separation methodologies to isolate Cd from Sn and Mo, present respectively, at 11.1±0.9 mg/kg and 70.7±4.5 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

105

High-precision isotope ratio mass spectrometry and stable isotope precursors for tracer studies in cell culture.  

PubMed

The use of stable isotope-labeled tracers is demonstrated in an in vitro system with analysis by high-precision isotope ratio mass spectrometry (IRMS), using n-3 long-chain polyunsaturated fatty acid (LCP) biosynthesis from [U-(13)C]18:3n-3 (18:3n-3*) in Y79 human retinoblastoma cells as a model system. The cells were cultured as a suspension in RPMI 1640 medium supplemented with 15% fetal calf serum at 37 degrees C with 5% CO(2) in air. They were harvested by sedimentation and cell lipids were extracted to determine the presence of 18:3n-3* metabolites using gas chromatography-combustion (GCC)-IRMS. As the dose of 18:3n-3* was systematically increased from treatment to treatment, the atom percent excess and the amounts of biosynthesized LCP* increased, while the percentage dose in each n-3 LCP* remained constant. Cultures incubated with 0.5 micromol (10 microM) of albumin-bound 18:3n-3, composed of 18:3n-3* diluted 1/60 or 1/100 with natural abundance 18:3n-3, yielded products with enrichments about 1.5 at.% excess (delta(13)C(PDB) < 1500 per thousand), which is optimal for high-precision measurements. Kinetics in Y79 cells incubated with 18:3n-3* showed that n-3 LCP* incorporation increased over time; 18:3n-3*, 20:5n-3*, 22:5n-3*, and 22:6n-3* were detected at all time points with the 1/60 dilution. These data document experimental parameters for optimal stable isotope use and IRMS detection for in vitro tracer methodology. PMID:11078586

Huang, M C; Muddana, S; Horowitz, E N; McCormick, C C; Infante, J P; Brenna, J T

2000-12-01

106

Evaluation of an isotope dilution liquid chromatography tandem mass spectrometry method for pharmaceuticals in fish.  

PubMed

An isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was successfully developed and applied for analysis of 15 pharmaceuticals and 2 pharmaceutically active metabolites in fish tissues. This method relied on electrospray ionization (ESI), for which the influence of sample matrix on analyte ionization efficiencies remains a persistent challenge to environmental analysis. Statistically derived method detection limits (MDLs) for most analytes ranged from 1 to 10 ng/g, independent of sample matrix, and were as low as 0.04 ng/g for the most sensitive compounds in fillet tissue. MDLs for fish fillets were determined for both 10 ?L and 100 ?L injection volumes; however, results showed that detection limits did not scale linearly with injection volume. Direct comparison of spike recoveries from fish liver demonstrated that isotope dilution was superior to matrix-matched calibration in compensating for matrix interference. Spike recoveries for the isotope dilution approach generally ranged from 91 to 112%, independent of tissue (i.e., fillet or liver). The developed method was applied to examine target analytes in brown trout (Salmo trutta), collected upstream and downstream from a municipal effluent discharge to East Canyon Creek, Park City, UT, USA. Though no pharmaceuticals were detected in fish samples from the upstream location, 3 and 10 compounds (out of 17 target analytes) were detected in fish fillet and liver samples, respectively, from the downstream sampling site. Pharmaceuticals in fish fillets were observed at concentrations ranging from 0.14 to 12 ng/g, while levels were markedly higher in liver tissues (range: 0.27-600 ng/g). PMID:22840821

Du, B; Perez-Hurtado, P; Brooks, B W; Chambliss, C K

2012-08-31

107

Ultratrace-level radium-226 determination in seawater samples by isotope dilution inductively coupled plasma mass spectrometry  

Microsoft Academic Search

An improved and novel sample preparation method for 226Ra determination in liquid samples by isotope dilution inductively coupled plasma sector field mass spectrometry using laboratory-prepared\\u000a 228Ra tracer has been developed. The procedure involves a selective preconcentration achieved by applying laboratory-prepared\\u000a MnO2 resin followed by cation exchange chromatographic separation. In order to completely eliminate possible molecular interferences,\\u000a medium mass resolution (R?=?4,000)

Zsolt Varga

2008-01-01

108

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

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

109

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

110

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

111

An Improved Measurement of Isotopic Ratios by High Resolution Mass Spectrometry  

NASA Astrophysics Data System (ADS)

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 2H2O-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.

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

2013-02-01

112

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

113

Studies of lipid turnover in cells with stable isotope and gas chromatograph-mass spectrometry.  

PubMed

Phospholipids are major building blocks for biological membranes. In addition, metabolites derived from their degradation are important signals in major cellular events, such as proliferation and apoptosis. The concept of lipid signaling in cells is derived mainly from the measurement of change in the concentration of lipid molecules. However, these changes in concentration are only a small part of the underlying metabolic change induced by a perturbation in the cell. In contrast, metabolic kinetic studies documenting product-precursor relationships and turnover rates are useful in elucidating the responsible mechanisms. Historically, metabolic studies of phospholipids in cells have been carried out with pulse or pulse-chase methods using radioactive isotopes. While these studies provide valuable information, their scope is restricted by inherent limitations. In this paper we describe a method using [1,2,3,4-13C(4)]palmitate as the tracer for studying the metabolic kinetics of the molecular species of diacylglycerol, ceramide, phosphatidylcholine, and sphingomyelin. After growing cells in the presence of labeled palmitate complexed to serum albumin, the lipids are extracted and separated into lipid classes. After enzymatic hydrolysis, diacylglyerols and ceramides as bis-trimethylsilyl derivatives are determined quantitatively with capillary column gas chromatography. Internal standards for each lipid class are used in the procedure. In addition, the isotopic enrichments of the lipid molecular species are determined with gas chromatograph-mass spectrometry. We applied this method to the study of HL60 cells. Different turnover rates were found for various molecular species. In addition, the sn-1 and sn-2 acyl groups appear to be synthesized at different rates for different molecular species. Other information, such as chain elongation and desaturation, might also be derived through the use of this method. PMID:14751270

Tserng, Kou-Yi; Griffin, Ronda

2004-02-15

114

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.

Bluck, Les; Volmer, Dietrich A.

2013-01-01

115

[Honey adulteration detection using liquid chromatography/ elemental analysis-isotope ratio mass spectrometry].  

PubMed

A new method for honey adulteration detection using liquid chromatography/elemental analysis-isotope ratio mass spectrometry (LC/EA-IRMS) was developed. Based on the individual delta13C values detected for 38 authentic honey samples, the limits for the authentic honey samples were proposed: the delta13C difference between protein and honey (Deltadelta13C(P-H)) should be higher or equal to than -0.95 per thousand, the delta13C difference between fructose and glucose (Deltadelta13C(F-G)) should be from -0.64 per thousand to 0.53 per thousand, and the maximum difference of delta13C values between all the components (Deltadelta13Cmax) should be lower than 2.09 per thousand. Based on the above criteria, the 58 positive samples spiked with C4 or C3 plant sugar syrup were confirmed by LC/EA-IRMS method from 150 commercial honey samples, while only 7 samples spiked with C4 plant sugar syrup were confirmed by the official EA-IRMS method. The proposed method represents a significant improvement in comparing with the official EA-IRMS method. PMID:21574394

Fei, Xiaoqing; Wu, Bin; Sehn, Chongyu; Ding, Tao; Li, Lihua; Lu, Ying

2011-01-01

116

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

PubMed

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

Ohata, Masaki; Miura, Tsutomu

2014-07-21

117

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

PubMed

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

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

2010-05-01

118

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

PubMed Central

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

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

2011-01-01

119

Determination of trace iron in zirconium by isotope dilution-thermal ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

An isotope dilution-thermal ionization mass spectrometry method for the determination of parts-per-million levels of iron in zirconium is required for precise, accurate analyses in studies of the effects of iron on the irradiation deformation of nuclear alloys. A two-stage purification procedure was developed to avoid the signal suppression and interference caused by the zirconium matrix. After sample dissolution and spiking with 54Fe, the bulk of the zirconium is removed by ion exchange chromatography, and the eluted Fe(III) is further purified by micro-solvent extraction into tributyl phosphate-impregnated resin beads. The iron is back-extracted, submicrogram amounts are loaded onto previously outgassed zone-refined Re filaments, and 54/56 ratios are measured at 1170°C. A silica gel/boric acid ionization enhancer is used to obtain stable Fe+ currents as strong as 2 × 10-14. A from nanogram loadings of pure iron. The procedural blank of 20 ± 6 ng is sufficiently low to allow determination of ppm levels of iron in 0.1 g zirconium samples. The analyses of solution standards showed agreement within 2% between measured and expected values, and a good fit, r2 = 0.99997, to a linear regression. The analyses of metal standards exhibited a similar good fit to a linear regression of measured against expected values, and showed good agreement with other methods. The method meets the requirements for zirconium metallurgical studies, and may be extended to other applications.

Elliot, N. L.; Campbell, M. A.; Green, L. W.

1995-08-01

120

Measurement of trimethylamine-N-oxide by stable isotope dilution liquid chromatography tandem mass spectrometry.  

PubMed

Trimethylamine-N-oxide (TMAO) levels in blood predict future risk for major adverse cardiac events including myocardial infarction, stroke, and death. Thus, the rapid determination of circulating TMAO concentration is of clinical interest. Here we report a method to measure TMAO in biological matrices by stable isotope dilution liquid chromatography tandem mass spectrometry (LC/MS/MS) with lower and upper limits of quantification of 0.05 and >200?M, respectively. Spike and recovery studies demonstrate an accuracy at low (0.5?M), mid (5?M), and high (100?M) levels of 98.2, 97.3, and 101.6%, respectively. Additional assay performance metrics include intraday and interday coefficients of variance of <6.4 and <9.9%, respectively, across the range of TMAO levels. Stability studies reveal that TMAO in plasma is stable both during storage at -80°C for 5years and to multiple freeze thaw cycles. Fasting plasma normal range studies among apparently healthy subjects (n=349) show a range of 0.73-126?M, median (interquartile range) levels of 3.45 (2.25-5.79)?M, and increasing values with age. The LC/MS/MS-based assay reported should be of value for further studies evaluating TMAO as a risk marker and for examining the effect of dietary, pharmacologic, and environmental factors on TMAO levels. PMID:24704102

Wang, Zeneng; Levison, Bruce S; Hazen, Jennie E; Donahue, Lillian; Li, Xin-Min; Hazen, Stanley L

2014-06-15

121

Validation of pentaacetylaldononitrile derivative for dual 2H gas chromatography/mass spectrometry and 13C gas chromatography/combustion/isotope ratio mass spectrometry analysis of glucose.  

PubMed

A reference method to accurately define kinetics in response to the ingestion of glucose in terms of total, exogenous and endogenous glucose is to use stable-isotope-labelled compounds such as 2H and 13C glucose followed by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analysis. The use of the usual pentaacetyl (5Ac) derivative generates difficulties in obtaining accurate and reproducible results due to the two chromatographic peaks for the syn and anti isomers, and to the isotopic effect occurring during acetylation. Therefore, the pentaacetylaldononitrile derivative (Aldo) was validated for both isotopes, and compared with the 5Ac derivative. A correction factor including carbon atom dilution (stoichiometric equation) and the kinetic isotopic effect (KIE) was determined. Analytical validation results for the 2H GC/MS and 13C GC/C/IRMS measurements produced acceptable results with both derivatives. When 2H enrichments of plasma samples were < or = 1 mol % excess (MPE), the repeatability (RSD(Aldo Intra assay and Intra day) <0.94%, RSD(5Ac Intra assay and Intra day) <3.29%), accuracy (Aldo <3.4%, 5Ac <29.0%), and stability of the derivatized samples were significantly better when the Aldo derivatives of the plasma samples were used (p < 0.05). When the glucose kinetics were assessed in nine human subjects, after glucose ingestion, the plasma glucose 2H enrichments were identical with both derivatives, whereas the 13C enrichments needed a correction factor to fit together. Due to KIE variation, this correction factor was not constant and had to be calculated for each batch of analyses, to obtain satisfactory results. Mean quantities of exogenous glucose exhibit marked difference (20.9 +/- 1.3g (5Ac) vs. 26.7 +/- 2.5g (Aldo)) when calculated with stoichiometric correction, but fit perfectly when calculated after application of the correction factor (22.1 +/- 1.3g (5Ac) vs. 22.9 +/- 1.9g (Aldo)). Finally, the pentaacetylaldononitrile derivative, used here in GC/C/IRMS for the first time, enables measurement of 2H and 13C enrichments in plasma glucose with a single sample preparation. PMID:19904737

Sauvinet, Valérie; Gabert, Laure; Qin, Du; Louche-Pélissier, Corinne; Laville, Martine; Désage, Michel

2009-12-01

122

PALOMA : an isotope analyzer using static mass spectrometry, coupled with cryogenic and chemical trapping, for the MSL mission to Mars  

NASA Astrophysics Data System (ADS)

The technique of GCMS analysis has to be completed by static mass spectrometry for precise in-situ measurements of the isotopic composition of planetary atmospheres (noble gases, stable isotopes), and volatile outgassed products from solid sample pyrolysis. Static mass spectrometry, coupled with gas separation by cryo-separation and gettering, is commonly used in the laboratory to study volatiles extracted from terrestrial and meteoritic samples. Such an instrument (PALOMA) is presently developed in our laboratories, and it will be coupled with a Pyr-GCMS analyzer (MACE), built by a US consortium of science laboratories and industrials (University of Michigan, Southwest Research Institute, JPL, Ball Aerospace). The MACE/PALOMA experiment will be proposed on the NASA Mars Science Laboratory mission, planned to be launched in 2009. The scientific objectives of PALOMA, coupled with MACE, may be listed as follows : (i) search for isotopic signatures of past life in atmosphere, rock, dust and ice samples, with emphasis on carbon, nitrogen and hydrogen; (ii) accurately measure isotopic composition of atmospheric noble gases, and stable isotopes, in order to better constrain past escape, surface interaction, outgassing history and climate evolution; (iii) precisely measure diurnal/ seasonal variations of isotopic ratios of H2O, CO2, and N2, for improving our understanding of present and past climate, and of the role of water cycle. Main measurement objectives are : (i) C, H, O, N isotopic composition in both organic evolved samples (provided by MACE pyrolysis system) and atmosphere with high accuracy (a few per mil at 1-s level); (ii) noble gas (He, Ne, Ar, Kr, Xe) and stable (C, H, O, N) isotope composition in atmosphere with high accuracy (a few per mil at 1-s level); (iii) molecular and isotopic composition of inorganic evolved samples (salts, hydrates, nitrates, {ldots}), including ices; (iv) diurnal and seasonal monitoring of D/H in water vapor, and water ice.

Chassefiere, E.; Jambon, A.; Berthelier, J.-J.; Goulpeau, G.; Leblanc, F.; Montmessin, F.; Sarda, P.; Agrinier, P.; Fouchet, T.; Waite, H.

123

A guide through the computational analysis of isotope-labeled mass spectrometry-based quantitative proteomics data: an application study  

Microsoft Academic Search

Background  Mass spectrometry-based proteomics has reached a stage where it is possible to comprehensively analyze the whole proteome\\u000a of a cell in one experiment. Here, the employment of stable isotopes has become a standard technique to yield relative abundance\\u000a values of proteins. In recent times, more and more experiments are conducted that depict not only a static image of the up-

Stefan P Albaum; Hannes Hahne; Andreas Otto; Ute Haußmann; Dörte Becher; Ansgar Poetsch; Alexander Goesmann; Tim W Nattkemper

2011-01-01

124

Detection of exogenous hydrocortisone in horse urine by gas chromatography-combustion-carbon isotope ratio mass spectrometry.  

PubMed

A gas chromatography-combustion-isotope ratio mass spectrometry method for confirmation of hydrocortisone abuse in horseracing and equine sports is proposed. Urinary hydrocortisone was converted to a bismethylenedioxy derivative which presents good gas chromatographic properties and brings an extra carbon contribution of only two carbon atoms. Synthetic hydrocortisone has a different 13C abundance from that of natural urinary horse hydrocortisone and the difference is significant, therefore exogenous and endogenous hydrocortisone can be distinguished. PMID:9449559

Aguilera, R; Becchi, M; Mateus, L; Popot, M A; Bonnaire, Y; Casabianca, H; Hatton, C K

1997-11-21

125

Comparison of pneumatic nebulization and hydride generation inductively coupled plasma mass spectrometry for isotopic analysis of selenium  

Microsoft Academic Search

A comparative investigation between pneumatic nebulization and continuous hydride generation as sample introduction methods for inductively coupled plasma mass spectrometry was carried out for isotopic analysis of selenium in biological samples of interest to human metabolic studies. Experimental parameters known to affect the analytical performance of the system were evaluated: instrument operating parameters, analyte solution\\/NaBHâ flow rate, and NaBHâ concentration.

Morteza. Janghorbani; Bill T. G. Ting

1989-01-01

126

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

127

Pilot Study for the Standardization of Insulin Immunoassays with Isotope Dilution-Liquid Chromatography\\/Tandem Mass Spectrometry  

Microsoft Academic Search

Background: An international working group convened by the American Diabetes Association (ADA) called for a reference measurement procedure for use in a true- ness-based standardization project of insulin immuno- assays. In view of this demand, we conducted a pilot study to investigate the feasibility of such a standard- ization project with our isotope dilution-liquid chro- matography\\/tandem mass spectrometry (ID-LC\\/tandem MS)

Diego Rodriguez-Cabaleiro; Katleen Van Uytfanghe; Veronique Stove; Tom Fiers; Linda M. Thienpont

2007-01-01

128

Lead speciation in rainwater by isotope dilution-high performance liquid chromatography-inductively coupled plasma-mass spectrometry  

Microsoft Academic Search

A new method for lead speciation in rainwater by isotope dilution analysis (IDA) using directly coupled high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) is described and demonstrated. Samples containing trimethyllead (TML) chloride and triethyllead (TEL) chloride in the presence of large amounts of inorganic lead have been analysed by HPLC-ICP-MS using reverse phase ion-pairing chromatography. The detection limit for

Les Ebdon; Steve J. Hill; Cristina Rivas

1998-01-01

129

An Improved Measurement of Isotopic Ratios by High Resolution Mass Spectrometry  

PubMed Central

The study of protein kinetics requires an accurate measurement of isotopic ratios of peptides. Although Fourier transform-ion cyclotron resonance mass spectrometers (FT-ICR MS) yield accurate mass measurements of analytes, the isotopoloque ratios are consistently lower than predicted. Recently, we demonstrated that the magnitude of the spectral error in the FT-ICR MS 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 2H2O-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.

Ilchenko, S.; Previs, S.F.; Rachdaoui, N.; Willard, B.; McCullough, A.; Kasumov, T.

2013-01-01

130

Measurement of Th Isotopes in Volcanic Rocks by Plasma Ionization Multi-Collector Mass Spectrometry  

NASA Astrophysics Data System (ADS)

A technique is presented for the determination of 232Th/230Th in volcanic rocks by plasma ionization multi-collector mass spectrometry (PIMMS) utilizing the ThermoFinnigan Neptune. These analyses were made statically, measuring 232Th on a Faraday cup and 230Th on the RPQ channel using the SEM. Because of the large dynamic range in the 232Th/230Th of volcanic rocks (> 105), accurate and precise measurement of 232Th/230Th using PIMMS requires: 1) high abundance sensitivity to minimize tailing of 232Th onto 230Th, and 2) explicit knowledge of the instrumental mass bias and the gain calibration of the two detectors used for the measurement. Using the RPQ on the Finnigan Neptune, the abundance sensitivity at 90% transmission was ~25ppb over 2 amu. Using an exponential fit the resulting tail correction of 232Th on 230Th is 0.7% for ratios of 3x105 and 0.3% for ratios of 1.5x105. To correct for both instrumental mass fractionation between masses 230 and 232 and the relative difference in the efficiency of the Faraday and SEM detectors we evaluated using both: 1) a linear interpolation of the 238U/^{236}U measured in the NBS U010 interspersed between each sample, and normalized to its certified value (14,432 ±149), and 2) a linear interpolation of the 232Th/230Th measured in the UCSC ThA interspersed between each sample, and normalized to its nominal value (170,760±2,049). Our results show that, due to both differences in instrumental mass bias and differences of the ion energies through the RPQ filter of U and Th, U does not work as an adequate proxy for Th. Replicate measurements of 232Th/230Th in synthetic and rock Th isotopic standards provide an overall reproducibility on the 232Th/230Th of <1% (2?) and show excellent agreement with their `known` values established by other techniques within the reported errors, supporting the reliability and accuracy of this method. This PIMMS technique has considerable advantages over existing TIMS and SIMS techniques in terms of ionization efficiency and total sample consumption (and hence sample size requirement), as well as the rapidity of analysis.

Sims, K. W.; Ball, L.; Schwieters, J.

2006-12-01

131

The measurement of free thyroxine by isotope dilution tandem mass spectrometry  

PubMed Central

Background Most clinical chemistry laboratories measure free thyroxine (FT4) by an analogue (direct) method. Nevertheless, the validity of analogue FT4 immunoassays has been questioned and patient’s results using this approach frequently do not fit in with the clinical presentation. Because of these problems we routinely send out all direct free T4’s that are < 2.5th percentile and many that are > 97.5th percentile for measurement by equilibrium dialysis, the gold standard method. In approximately half of these cases, the FT4 by equilibrium dialysis was normal. We developed a rapid, reliable free T4 method employing isotope dilution tandem mass spectrometry and compared our results with both the analogue (direct) free T4 and equilibrium dialysis procedures. Methods An API-4000 tandem mass spectrometer (Sciex, Toronto, Canada) equipped with TurboIonSpray and Agilent HPLC system was used employing isotope dilution with deuterium labeled internal standard (IS=L-thyroxine-d2). Serum was filtered through the Centrifree YM-30 ultrafiltration device by centrifugation, IS added to the ultrafiltrate, and 400 ?L injected onto a C-18 column. After washing, the switch valve is activated and a methanol gradient allows for elution of both T4 and the IS into the LC/MS/MS system. Quantitation was by MRM analysis in the negative mode. Equilibrium dialysis was performed by the Nichols method and analogue free T4 results were obtained on the Dade Dimension RxL. Results The within-day and between-day CV’s were < 7.1% at all concentrations tested. The results correlated well with equilibrium dialysis (Eq Dial=0.971 MS+0.041, n =68, Syx=1.381, r =0.954). A poor correlation was found with the analogue (direct) free T4 method (IA=0.326 MS+6.27, n =154, Syx=1.96, r =0.459). Conclusions Samples can be processed in batches of 30. The free T4 tandem MS method has a rapid turn-around-time vs the equilibrium dialysis procedure, with a chromatographic run time of 8 min per sample.

Soldin, Steven J.; Soukhova, Nadia; Janicic, Natasa; Jonklaas, Jacqueline; Soldin, Offie P.

2013-01-01

132

Detailed assessment of isotope ratio infrared spectroscopy and isotope ratio mass spectrometry for the stable isotope analysis of plant and soil waters.  

PubMed

As an alternative to isotope ratio mass spectrometry (IRMS), the isotope ratio infrared spectroscopy (IRIS) approach has the advantage of low cost, continuous measurement and the capacity for field-based application for the analysis of the stable isotopes of water. Recent studies have indicated that there are potential issues of organic contamination of the spectral signal in the IRIS method, resulting in incorrect results for leaf samples. To gain a more thorough understanding of the effects of sample type (e.g., leaf, root, stem and soil), sample species, sampling time and climatic condition (dry vs. wet) on water isotope estimates using IRIS, we collected soil samples and plant components from a number of major species at a fine temporal resolution (every 2?h for 24-48?h) across three locations with different climatic conditions in the Heihe River Basin, China. The hydrogen and oxygen isotopic compositions of the extracted water from these samples were measured using both an IRMS and an IRIS instrument. The results show that the mean discrepancies between the IRMS and IRIS approaches for ?(18) O and ?D, respectively, were: -5.6‰ and -75.7‰ for leaf water; -4.0‰ and -23.3‰ for stem water; -3.4‰ and -28.2‰ for root water; -0.5‰ and -6.7‰ for xylem water; -0.06‰ and -0.3‰ for xylem flow; and -0.1‰ and 0.3‰ for soil water. The order of the discrepancy was: leaf > stem ? root > xylem > xylem flow ? soil. In general, species of the same functional types (e.g., woody vs. herbaceous) within similar habitats showed similar deviations. For different functional types, the differences were large. Sampling at nighttime did not remove the observed deviations. PMID:21953962

Zhao, Liangju; Xiao, Honglang; Zhou, Jian; Wang, Lixin; Cheng, Guodong; Zhou, Maoxian; Yin, Li; McCabe, Matthew F

2011-10-30

133

Detailed assessment of isotope ratio infrared spectroscopy and isotope ratio mass spectrometry for the stable isotope analysis of plant and soil waters  

NASA Astrophysics Data System (ADS)

As an alternative to isotope ratio mass spectrometry (IRMS) the isotope ratio infrared spectroscopy (IRIS) approach has the advantage of low cost, continuous measurement and capacity for field based application for the analysis of stable water isotopes. Recent studies have indicated that there are potential issues of organic contamination of the spectral signal in the IRIS method, resulting in errant readings for leaf samples. To gain a more thorough understanding of the effects of sample type (e.g., leaf, root, stem and soil), sample species, sampling time and climatic condition (dry vs. wet) on water isotope estimates using IRIS, we collected soil samples and plant components from a number of major species at a fine temporal resolution (every two hours for 24-48 hours) across three locations with different climatic conditions in the Heihe River Basin, China. The hydrogen and oxygen isotopic composition of the extracted water from these samples was measured using both an IRMS and IRIS instrument. Results show that the mean discrepancy between the IRMS and IRIS approach, for ?18O and ?D respectively, was: -5.6% and -75.7% for leaf water; -4.0% and -23.3% for stem water; -3.4% and -28.2% for root water; -6.7% and -0.5% for xylem water; -0.06% and -0.3% for xylem flow; and -0.1% and 0.3% for soil water. The order of the discrepancy followed: leaf > stem ? root > xylem > xylem flow ? soil. In general, species of the same functional types (e.g., woody vs. herbaceous) within similar habitats showed similar deviations. For different functional types, the differences were large. Sampling during the nighttime did not remove the observed deviations.

Zhao, L.; Xiao, H.; Zhou, J.; Wang, L.; Cheng, G.; Zhou, M.; Yin, L.; McCabe, M. F.

2011-12-01

134

Determination of methionine and selenomethionine in selenium-enriched yeast by species-specific isotope dilution with liquid chromatography-mass spectrometry and inductively coupled plasma mass spectrometry detection  

Microsoft Academic Search

Selenomethionine (SeMet) and methionine (Met), liberated by acid hydrolysis of selenium-enriched yeast, were quantified by liquid chromatography-mass spectrometry (LC\\/MS) using standard additions calibrations as well as isotope dilution (ID) based on species-specific 13C-enriched spikes. LC inductively coupled plasma mass spectrometry (ICPMS) was also employed for the quantification of SeMet, and 74Se-enriched SeMet was used for ID calibration. The results were

Shona McSheehy; Lu Yang; Ralph Sturgeon; Zoltan Mester

2005-01-01

135

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 1×10(6). Alpha spectrometry can also be applied so that the shorter-lived (238)Pu isotope can be measured successfully. (239) Pu, (242)Pu and (237)Np were measured by ICP-MS, while (236)Pu and (238)Pu were measured by alpha spectrometry. PMID:21056724

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

2010-12-01

136

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

137

Determination of radium isotope ratios and abundances in geologic samples by thermal ionization mass spectrometry.  

PubMed

We describe chemical separation and mass spectrometric procedures for the measurement of radium isotopes in geologic samples. These methods provide 226Ra/228Ra ratio measurements for 1 g or less of rock sample containing subpicogram amounts of radium with precision better than 1.5% (95% confidence level). Radium-226 concentrations were measured by isotope dilution for smaller sample sizes (100-500 mg) containing as little as 1-10 fg of total 226Ra with similar high precision. PMID:1858983

Volpe, A M; Olivares, J A; Murrell, M T

1991-05-01

138

Measurement of triglyceride synthesis in humans using deuterium oxide and isotope ratio mass spectrometry.  

PubMed

Short-term triglyceride (TG) synthesis was measured over 48 h in four healthy males from the incorporation rate of deuterium in body water into plasma TG. Subjects drank 0.7 g D2O kg-1 estimated body water (99.8 atom% excess), followed by water containing 1.4 g D2O kg-1 water to maintain plasma deuterium enrichment at plateau. Blood samples (20 ml) were obtained before dosing and every 4 h thereafter. Subjects self-selected three meals each day. TG from each time point were separated from plasma lipids by thin-layer chromatography and combusted to water and CO2. Combustion water was vacuum distilled into Zn-containing Pyrex tubes, reduced to hydrogen gas, and analyzed for deuterium enrichment by isotope ratio mass spectrometry. Deuterium enrichment of TG increased over the 48 h study period for all four subjects studied. Superimposed on this increase were short-term non-periodic fluctuations in enrichment reflecting dietary influx and intra-individual differences in TG metabolism. The TG fractional synthetic rate (FSR) was calculated using linear and mono-exponential models. Triglyceride FSR of the subjects over the first 24 h of the study was 0.0702 +/- 0.0048 day-1 (mean +/- SEM) by the linear model and 0.0728 +/- 0.0051 day-1 by the exponential model. Deuterium enrichment reached a plateau on day 2, indicative of continuing TG synthesis in a saturated body water pool. These results are consistent with the notion of meal-dependent variability in TG synthesis into a small rapid turnover plasma TG pool. PMID:1653617

Leitch, C A; Jones, P J

1991-06-01

139

Stable isotope liquid chromatography-tandem mass spectrometry assay for fatty acid amide hydrolase activity.  

PubMed

Fatty acid amide hydrolase (FAAH) is the main enzyme responsible for the hydrolysis of the endocannabinoid anandamide (arachidonoyl ethanolamide, AEA) to arachidonic acid (AA) and ethanolamine (EA). Published FAAH activity assays mostly employ radiolabeled anandamide or synthetic fluorogenic substrates. We report a stable isotope liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for specific, sensitive, and high-throughput capable FAAH activity measurements. The assay uses AEA labeled with deuterium on the EA moiety (d?-AEA) as substrate and measures the specific reaction product tetradeutero-EA (d?-EA) and the internal standard ¹³C?-EA. Selected reaction monitoring of m/z 66?m/z 48 (d?-EA) and m/z 64?m/z 46 (¹³C?-EA) in the positive electrospray ionization mode after liquid chromatographic separation on a HILIC (hydrophilic interaction liquid chromatography) column is performed. The assay was developed and thoroughly validated using recombinant human FAAH (rhFAAH) and then was applied to human blood and dog liver samples. rhFAAH-catalyzed d?-AEA hydrolysis obeyed Michaelis-Menten kinetics (K(M)=12.3 ?M, V(max)=27.6 nmol/min mg). Oleoyl oxazolopyridine (oloxa) was a potent, partial noncompetitive inhibitor of rhFAAH (IC??=24.3 nM). Substrate specificity of other fatty acid ethanolamides decreased with decreasing length, number of double bonds, and lipophilicity of the fatty acid skeleton. In human whole blood, we detected FAAH activity that was inhibited by oloxa. PMID:22146559

Rakers, Christin; Zoerner, Alexander A; Engeli, Stefan; Batkai, Sandor; Jordan, Jens; Tsikas, Dimitrios

2012-02-15

140

Rapid detection of antibiotic resistance based on mass spectrometry and stable isotopes.  

PubMed

With the emergence and growing complexity of bacterial drug resistance, rapid and reliable susceptibility testing has become a topical issue. Therefore, new technologies that assist in predicting the effectiveness of empiric antibiotic therapy are of great interest. Although the use of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) for the rapid detection of antibiotic resistance is an attractive option, the current methods for MALDI-TOF MS susceptibility testing are restricted to very limited conditions. Here, we describe a technique that may allow for rapid susceptibility testing to an extent that is comparable to phenotypic methods. The test was based on a stable isotope labelling by amino acids in cell culture (SILAC)-like approach. This technique was used to visualise the growth of bacteria in the presence of an antibiotic. Pseudomonas aeruginosa was chosen as the model organism, and strains were incubated in normal medium, medium supplemented with (13)C6-(15)?N2-labelled lysine and medium supplemented with labelled lysine and antibiotic. Peak shifts occurring due to the incorporation of the labelled amino acids were detected by MALDI-TOF MS. Three antibiotics with different mechanisms of action, meropenem, tobramycin and ciprofloxacin, were tested. A semi-automated algorithm was created to enable rapid and unbiased data evaluation. With the proposed test, a clear distinction between resistant and susceptible isolates was possible for all three antibiotics. The application of SILAC technology for the detection of antibiotic resistance may contribute to accelerated and reliable susceptibility testing. PMID:24338093

Jung, J S; Eberl, T; Sparbier, K; Lange, C; Kostrzewa, M; Schubert, S; Wieser, A

2014-06-01

141

Cellular Lipid Extraction for Targeted Stable Isotope Dilution Liquid Chromatography-Mass Spectrometry Analysis  

PubMed Central

The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including numerous stereoisomers1,2. 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 cancer3-7. 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) analysis9. After the extraction, derivatization with an electron capture (EC) reagent, pentafluorylbenzyl bromide (PFB) is employed to increase detection sensitivity10,11. 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 lipids12. 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 metabolites13. 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.

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

2011-01-01

142

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

143

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

144

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

145

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

146

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

147

Software for the calculation of isotope patterns in tandem mass spectrometry.  

PubMed

Software, available at no cost on the Internet, is described which uses polynomial expansion algorithms to calculate the isotope patterns for precursor ion, neutral loss, and MSn product ion tandem mass spectra. Such information is useful for determining product ion and neutral loss composition, identification of analytes in complex samples, deconvolution of overlapping spectra, and correction of peak heights or areas in quantitative analysis. The effect of less than unit mass resolution on the isotope patterns is described and experimental examples of the use of the software are presented. PMID:18677719

Ramaley, Louis; Herrera, Lisandra Cubero

2008-09-01

148

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 2–3 weeks.

Basu, Sankha S; Blair, Ian A

2013-01-01

149

Innovations in Mass Spectrometry for Precise and Accurate Isotope Ratio Determination from Very Small Analyte Quantities (Invited)  

NASA Astrophysics Data System (ADS)

This presentation describes progress in mass spectrometry for analysing very small analyte quantities, illustrated by example applications from nuclear forensics. In this challenging application, precise and accurate (‰) uranium isotope ratios are required from 1 - 2 µm diameter uranium oxide particles, which comprise less than 40 pg of uranium. Traditionally these are analysed using thermal ionisation mass spectrometry (TIMS), and more recently using secondary ionisation mass spectrometry (SIMS). Multicollector inductively-coupled plasma mass spectrometry (MC-ICP-MS) can offer higher productivity compared to these techniques, but is traditionally limited by low efficiency of analyte utilisation (sample through to ion detection). Samples can either be introduced as a solution, or sampled directly from solid using laser ablation. Large multi-isotope ratio datasets can help identify provenance and intended use of anthropogenic uranium and other nuclear materials [1]. The Thermo Scientific NEPTUNE Plus (Bremen, Germany) with ‘Jet Interface’ option offers unparalleled MC-ICP-MS sensitivity. An analyte utilisation of c. 4% has previously been reported for uranium [2]. This high-sensitivity configuration utilises a dry high-capacity (100 m3/h) interface pump, special skimmer and sampler cones and a desolvating nebuliser system. Coupled with new acquisition methodologies, this sensitivity enhancement makes possible the analysis of micro-particles and small sample volumes at higher precision levels than previously achieved. New, high-performance, full-size and compact discrete dynode secondary electron multipliers (SEM) exhibit excellent stability and linearity over a large dynamic range and can be configured to simultaneously measure all of the uranium isotopes. Options for high abundance-sensitivity filters on two ion beams are also available, e.g. for 236U and 234U. Additionally, amplifiers with high ohm (1012 - 1013) feedback resistors have been developed to optimise signal to noise ratios from low ion beam intensities on Faraday cups [2,3]. Data will be presented from the Thermo Scientific NEPTUNE Plus MC-ICP-MS, sampling sub-nanogram quantities of analyte from solution and by laser ablation. Faraday only measurements of sub-microgram analyte quantities will also be presented, using a 1012 ? amplifier for the minor isotope 234U. These data are compared to a dataset collected by a first generation MC-ICP-MS instrument, reported by Lloyd et al. [1]. [1] N. S. Lloyd, R. R. Parrish, M. S. A. Horstwood & S. R. N. Chenery, Journal of Analytical Atomic Spectrometry 24 (6), 752 (2009). [2] C. Bouman, J.B. Schwieters, M. Deerberg & D. Tuttas, Geochimica et Cosmochimica Acta 73 (13, Supplement 1) (2009). [3] D. Tuttas, J.B. Schwieters, & N.S. Lloyd, Geochimica et Cosmochimica Acta 74 (11, Supplement 1) (2010).

Lloyd, N. S.; Bouman, C.; Horstwood, M. S.; Parrish, R. R.; Schwieters, J. B.

2010-12-01

150

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

PubMed

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 ((44)Ca/(42)Ca and (44)Ca/(43)Ca) on a Neptune multiple collector inductively coupled plasma mass spectrometer (MC-ICPMS) in urine. Purification requirements for Sr, Ti, and K (Ca/Sr > 10?000; Ca/Ti > 10?000?000; 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 ?(44/42)Ca measurements of purified samples containing 25 ?g of Ca can be determined with typical errors less than ±0.2‰ (2?). PMID:21740001

Morgan, Jennifer L L; Gordon, Gwyneth W; Arrua, Ruth C; Skulan, Joseph L; Anbar, Ariel D; Bullen, Thomas D

2011-09-15

151

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

152

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

153

Stable Isotope- and Mass Spectrometry-based Metabolomics as Tools in Drug Metabolism: A Study Expanding Tempol Pharmacology  

PubMed Central

The application of mass spectrometry-based metabolomics in the field of drug metabolism has yielded important insights not only into the metabolic routes of drugs but has provided unbiased, global perspectives of the endogenous metabolome that can be useful for identifying biomarkers associated with mechanism of action, efficacy, and toxicity. In this report, a stable isotope- and mass spectrometry-based metabolomics approach that captures both drug metabolism and changes in the endogenous metabolome in a single experiment is described. Here the antioxidant drug tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) was chosen because its mechanism of action is not completely understood and its metabolic fate has not been studied extensively. Furthermore, its small size (MW = 172.2) and chemical composition (C9H18NO2) makes it challenging to distinguish from endogenous metabolites. In this study, mice were dosed with tempol or deuterated tempol (C9D17HNO2) and their urine profiled using ultraperformance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Principal component analysis of the urinary metabolomics data generated a Y-shaped scatter plot containing drug metabolites (protonated and deuterated) that were clearly distinct from the endogenous metabolites. Ten tempol drug metabolites, including eight novel metabolites, were identified. Phase II metabolism was the major metabolic pathway of tempol in vivo, including glucuronidation and glucosidation. Urinary endogenous metabolites significantly elevated by tempol treatment included 2,8-dihydroxyquinoline (8.0-fold, P<0.05) and 2,8-dihydroxyquinoline-?-D-glucuronide (6.8-fold, P<0.05). Urinary endogenous metabolites significantly attenuated by tempol treatment including pantothenic acid (1.3-fold, P<0.05) and isobutrylcarnitine (5.3-fold, P<0.01). This study underscores the power of a stable isotope- and mass spectrometry-based metabolomics in expanding the view of drug pharmacology.

Li, Fei; Pang, Xiaoyan; Krausz, Kristopher W.; Jiang, Changtao; Chen, Chi; Cook, John A.; Krishna, Murali C.; Mitchell, James B.; Gonzalez, Frank J.; Patterson, Andrew D.

2013-01-01

154

Determination of the Natural Abundances of Krypton and Xenon Isotopes Using Mass Spectrometry: A Demonstration of Isotopes and the Basis of Atomic Mass  

Microsoft Academic Search

This paper describes the use of a gas chromatograph-mass spectrometer to demonstrate the existence of isotopes to students in an introductory chemistry course. Fragmentation reactions are avoided through the use of a noble gas (krypton or xenon) as the analyte. Students are able to readily identify the naturally occurring isotopes of the noble gas, and the quantitative mass spectrometric data

David N. Blauch; Merlyn D. Schuh; Felix A. Carroll

2002-01-01

155

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

PubMed

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.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2149219

Houghton, E; Dumasia, M C; Teale, P; Smith, S J; Cox, J; Marshall, D; Gower, D B

1990-10-01

156

Isotope labelling - paired homologous double neutral loss scan-mass spectrometry for profiling of metabolites with a carboxyl group.  

PubMed

We developed a novel method for non-targeted screening of metabolites by high performance liquid chromatography-mass spectrometry with paired homologous double neutral loss scan mode after in vitro isotope labelling (IL-HPLC-PHDNL-MS). As a proof of concept, we investigated the carboxylic acid metabolite profiling in plant samples by the IL-HPLC-PHDNL-MS method. To this end, N,N-dimethylaminobutylamine (DMBA) and d(4)-N,N-dimethylaminobutylamine (d(4)-DMBA) were synthesized and utilized to label carboxylic acids. Our results show the MS response of carboxylic acids was enhanced by 20- to 40-fold after labelling. As for the IL-HPLC-PHDNL-MS analysis, DMBA and d(4)-DMBA labelled samples were mixed equally before MS analysis. Because the isotope labelled moieties (dimethylamino moiety, Me2N) of DMBA and d(4)-DMBA are easily ruptured and lost as neutral fragments (NL 45 and NL 49) under collision induced dissociation (CID), two neutral loss scans can be carried out simultaneously to record the signals of DMBA and d(4)-DMBA labelled samples, respectively. In this respect, the metabolites from two samples labelled with different isotope reagents are ionized at the same time but recorded separately by mass spectrometry, which can eliminate the MS response fluctuation and mutual interference. Using this method, six potential biomarkers involved in wounded tomato leaves were identified, and their structures were further elucidated by product ion scan and high resolution mass spectrometry analysis. Taken together, the IL-HPLC-PHDNL-MS method demonstrated good performance on the identification as well as relative quantification of metabolites with a carboxyl group in biological samples. PMID:24839964

Huang, Yun-Qing; Wang, Qiu-Yi; Liu, Jia-Qi; Hao, Yan-Hong; Yuan, Bi-Feng; Feng, Yu-Qi

2014-06-01

157

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

158

Segmentation of Multi-Isotope Imaging Mass Spectrometry Data for Semi-Automatic Detection of Regions of Interest  

PubMed Central

Multi-isotope imaging mass spectrometry (MIMS) associates secondary ion mass spectrometry (SIMS) with detection of several atomic masses, the use of stable isotopes as labels, and affiliated quantitative image-analysis software. By associating image and measure, MIMS allows one to obtain quantitative information about biological processes in sub-cellular domains. MIMS can be applied to a wide range of biomedical problems, in particular metabolism and cell fate [1], [2], [3]. In order to obtain morphologically pertinent data from MIMS images, we have to define regions of interest (ROIs). ROIs are drawn by hand, a tedious and time-consuming process. We have developed and successfully applied a support vector machine (SVM) for segmentation of MIMS images that allows fast, semi-automatic boundary detection of regions of interests. Using the SVM, high-quality ROIs (as compared to an expert's manual delineation) were obtained for 2 types of images derived from unrelated data sets. This automation simplifies, accelerates and improves the post-processing analysis of MIMS images. This approach has been integrated into “Open MIMS,” an ImageJ-plugin for comprehensive analysis of MIMS images that is available online at http://www.nrims.hms.harvard.edu/NRIMS_ImageJ.php.

Poczatek, J. Collin; Turck, Christoph W.; Lechene, Claude

2012-01-01

159

Quantification of immunoreactive viral influenza proteins by immunoaffinity capture and isotope-dilution liquid chromatography-tandem mass spectrometry.  

PubMed

An immunocapture isotope dilution mass spectrometry (IC-IDMS) method was developed to quantify antibody-bound influenza hemagglutinins (HA) in trivalent influenza vaccines (TIV). Currently, regulatory potency requirements for TIV require HA quantification based on the single radial immunodiffusion (SRID) assay, which is time-consuming, laborious, and requires production of large quantities of reagents globally. In IC-IDMS, antiserum to the HA of interest captured viral proteins that were in the correct conformation to be recognized by the antibodies. The captured proteins were digested, and evolutionarily conserved tryptic peptides were quantified using isotope-dilution liquid chromatography-tandem mass spectrometry. IC-IDMS relies on antibody-antigen binding similar to SRID but incorporates the accuracy and precision of IDMS. Polyclonal antibodies (pAb-H3) prepared by injection of sheep with purified H3 HA captured 82.9% (55.26 fmol/?L) of the total H3 HA (66.69 fmol/?L) from the commercial TIV and 93.6% (57.23 fmol/?L) of the total H3 HA (61.14 fmol/?L) in purified virus. While other HA (H1, B), neuraminidase (N1, N2, NB), viral matrix proteins, and nucleoproteins were also captured by this antiserum, our results were not affected due to the specificity of the mass spectrometer. IC-IDMS is an accurate, precise, sensitive, and selective method to measure antibody-bound HA in purified virus and commercial vaccines. PMID:21591780

Pierce, Carrie L; Williams, Tracie L; Moura, Hercules; Pirkle, James L; Cox, Nancy J; Stevens, James; Donis, Ruben O; Barr, John R

2011-06-15

160

Measurement of 13C/12C of chloroacetic acids by gas chromatography/combustion/isotope ratio mass spectrometry.  

PubMed

This paper describes a novel analytical methodology using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) to measure the 13C/12C ratios of chloroacetic acids (CAAs). CAAs are a major class of environmental pollutants that are widely distributed throughout the world, often at relatively high concentrations, and are of concern due to their toxic effects, particularly on plants. The 13C/12C of CAA reagents was measured by IRMS subsequent to offline combustion. Aqueous solutions of these CAAs were derivatized to the corresponding methyl chloroacetates (MCAAs) with acidic methanol with a known isotopic composition, extracted into pentane, and analyzed by GC/C/IRMS. Measured 13C/12C ratios of derivatized MCAAs were in agreement with calculated values within 1 per thousand for monochloroacetic acid and trichloroacetic acid and within 2 per thousand for dichloroacetic acid, suggesting that methylation and other analytical methodology steps do not isotopically fractionate derivatized MCAAs. 13C/12C ratios of reagent CAAs from different sources had varying isotopic signatures suggesting differences in source carbon and/or production methods. Our results underscore the potential of stable isotopes to serve as tracers of environmental sources of CAAs. PMID:12504128

Wong, Charles S; Muir, Derek C G; Mabury, Scott A

2003-02-01

161

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

162

Delta13C stable isotope analysis of atmospheric oxygenated volatile organic compounds by gas chromatography-isotope ratio mass spectrometry.  

PubMed

We present a new method for analyzing the delta(13)C isotopic composition of several oxygenated volatile organic compounds (OVOCs) from direct sources and ambient atmospheric samples. Guided by the requirements for analysis of trace components in air, a gas chromatograph isotope ratio mass spectrometer (GC-IRMS) system was developed with the goal of increasing sensitivity, reducing dead-volume and peak band broadening, optimizing combustion and water removal, and decreasing the split ratio to the isotope ratio mass spectrometer (IRMS). The technique relies on a two-stage preconcentration system, a low-volume capillary reactor and water trap, and a balanced reference gas delivery system. The instrument's measurement precision is 0.6 to 2.9 per thousand (1sigma), and results indicate that negligible sample fractionation occurs during gas sampling. Measured delta(13)C values have a minor dependence on sample size; linearity for acetone was 0.06 per thousand ng C(-1) and was best over 1-10 ng C. Sensitivity is approximately 10 times greater than similar instrumentation designs, incorporates the use of a diluted working reference gas (0.1% CO(2)), and requires collection of >0.7 ng C to produce accurate and precise results. With this detection limit, a 1.0 L sample of ambient air provides sufficient carbon for isotopic analysis. Emissions from vegetation and vehicle exhaust are compared and show clear differences in isotopic signatures. Ambient samples collected in metropolitan Miami and the Everglades National Park can be differentiated and reflect multiple sources and sinks affecting a single sampling location. Vehicle exhaust emissions of ethanol, and those collected in metropolitan Miami, have anomalously enriched delta(13)C values ranging from -5.0 to -17.2 per thousand; we attribute this result to ethanol's origin from corn and use as an additive in automotive fuels. PMID:20704369

Giebel, Brian M; Swart, Peter K; Riemer, Daniel D

2010-08-15

163

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

164

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

165

A high precision isotope ratio mass spectrometry method for measuring the O 2/N 2 ratio of air  

NASA Astrophysics Data System (ADS)

Studies of the distribution of O 2 in air will inform us about critical problems in the global carbon cycle which are not readily accessed by other measurements, including the rate of seasonal net production in the oceans on a hemispheric scale, the rate at which the oceans are taking up anthropogenic CO 2 and the net rate of change of the continental biomass. In this paper, we outline a method for measuring the O 2/N 2 ratio of air to a standard error of ± 6 per meg (± 0.006%.) for a sample analyzed in quadruplicate, corresponding to ± 1.2 ppm V O 2 in air out of 210,000. The method involves measuring the ratio of 16O 2 to 15N 14N by isotope ratio mass spectrometry. Potential and actual problems with this method include fractionation as sample and reference gases are introduced to the mass spectrometer, mass spectrometric nonlinearity, effects of imbalance of sample and reference ion currents on the measured isotopic ratio, isobaric interferences at masses 28 and 29 due to the formation of CO + from CO 2 in the source and zero enrichments. We discuss the magnitude of errors introduced by these factors and outline the relevant corrections. The ultimate mass spectrometric uncertainty is about ±2 per meg (±0.4 ppmV) for a 1 h instrumental analysis. Overall precision is currently limited by fractionation as sample and reference gases are introduced into the mass spectrometer. A considerable improvement in precision may be possible.

Bender, Michael L.; Tans, Pieter P.; Ellis, J. Taylor; Orchardo, Joseph; Habfast, Karleugen

1994-11-01

166

Split-field drift tube/mass spectrometry and isotopic labeling techniques for determination of single amino acid polymorphisms.  

PubMed

A combination of split-field drift tube/mass spectrometry and isotopic labeling techniques is evaluated as a means of identifying single amino acid polymorphisms (SAAPs) in proteins. The method is demonstrated using cytochromec (equine and bovine) and hemoglobin (bovine and sheep). For these studies, proteins from different species are digested with trypsin, and the peptides are labeled at primary amine groups [using either a light (H(3))- or heavy (D(3))-isotopic reagent]. SAAP analysis is carried out by mixing the light-labeled peptides of one species with the heavy-labeled peptides of the other and electrospraying the resulting mixture into a split-field drift tube/mass spectrometer. Peptides having the same sequence in both species appear as doublets in the mass spectrum [shifted in mass-to-charge (m/z) according to the number of incorporated labels]; additionally, these species have identical mobility distributions. Peptides having sequences that differ by one amino acid appear as peaks in the mass spectrum that are shifted in m/z according to the mass difference associated with the SAAP and the number of incorporated labels. The ion mobility distributions for these peptides (differing by only a single amino acid) can often be rationalized by their expected similarities or differences providing additional evidence that they are related. In all, 12 and 26 peptide variants (between species) corresponding to 5 and 11 amino acid polymorphisms have been identified for the cytochrome c and hemoglobin protein samples, respectively. PMID:16889409

Valentine, Stephen J; Sevugarajan, S; Kurulugama, Ruwan T; Koeniger, Stormy L; Merenbloom, Samuel I; Bohrer, Brian C; Clemmer, David E

2006-08-01

167

Evidence for a possible dietary effect on the isotopic composition of Zn in blood via isotopic analysis of food products by multi-collector ICP-mass spectrometry.  

PubMed

In this work, the hypothesis of a possible dietary effect on the isotopic composition of Zn in blood from populations with different feeding habits, i.e. lacto-ovo vegetarians and omnivores, was investigated through isotopic analysis of Zn in common food products by multi-collector ICP - mass spectrometry (MC-ICP-MS). Several certified reference materials (CRMs) were also included in the sample set for comparison purposes. For these CRMs, the isotopic composition of Zn is expressed as ?-values, calculated with respect to both IRMM-3702 and JMC-ZnLyon, as isotopic standards. The range of ?(66)Zn values observed in food products was approximately 1.9‰. In general, vegetables, cereals and derived products showed an enrichment of the heavier Zn isotopes, whereas a depletion was observed in products of animal origin (meat, fish, egg and semi-skimmed milk), relative to human blood samples. Mussel, however, showed a significant enrichment of the heavier isotopes, which is hypothetically attributed to its accumulation behaviour. Thus, the lower ?(66)Zn values found in food products of animal origin appear to be reflected in the lower ?(66)Zn value observed in blood from an omnivorous population compared to that for a vegetarian population. PMID:24196216

Costas-Rodríguez, Marta; Van Heghe, Lana; Vanhaecke, Frank

2014-01-01

168

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

169

Measurement of high-dynamic-range thorium isotopic ratios using continuous-wave resonance ionization mass spectrometry  

SciTech Connect

We have developed continuous-wave resonance ionization mass spectrometry (cw-RIMS) methods to measure [sup 230]Th/[sup 232]Th isotopic ratios. The overall Th ionization detection efficiency using a 1 + 1 RIMS process (narrow-band laser for the resonant step and a high-power ultraviolet- (UV-) Ar[sup +] laser for the ionization step) is 0.10%. Measurement of the [sup 230]Th/[sup 232]Th ratio (4.096 x 10[sup [minus]4]) of a laboratory standard shows that the cw-RIMS method has internal precision comparable to thermal ionization mass spectrometry measurements ([approximately] 0.5%, 2[sigma][sub m]), but introduces a small bias (2-4%), which is correctable by calibration with an isotopic standard. The bias is due to intrinsic laser-induced biases in the 1 + 1 RIMS process and in a nonresonant process due to the UV-Ar[sup +] laser alone, which contributes approximately 3% to the total Th[sup +] signal. Laser power dependence experiments show that neither the resonant nor the ionization step is entirely saturated; therefore, the isotopic bias is probably due to differences in the transition strengths of the isotopes. The reproducibility of the RIMS-induced bias is dependent on the reproducibility of the laser parameters, but can be kept within the precision of the measurements ([approximately] 0.5%). Ratio measurements of the 4.096 x 10[sup [minus]4] standard and of a sample of Table Mountain Latite demonstrates that cw-RIMS can accurately measure [sup 230]Th/[sup 232]Th ratios when the laser-induced biases are calibrated and kept constant. 41 refs.., 8 figs., 3 tabs.

Tissue, B.M. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)); Pickett, D.A.; Fearey, B.L. (Los Alamos National Lab., NM (United States))

1994-04-15

170

Isotopic Measurement of Lead in Nanogram Quantities on Multi-Collector Inductively Coupled Plasma Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Lead isotopes have been used as geochemical tracers in Earth Sciences, such as geochemistry, paleoclimatology and chronology, due to the diverse ratios and variable elemental abundance. Determination of Pb isotope ratios, with 2-sigma external precisions of 200 ppm for 207Pb/206Pb and 208Pb/206Pb and 800 ppm for for 206Pb/204Pb, can be performed with a Faraday-cup protocol in static mode on a multi-collector ICP-MS (MC-ICP-MS), Thermo Electron Neptune. The sample size is as low as 3 ng of Pb consumed per measurement. Lead blanks, from acid, labware, and airborne particulate, was effectively reduced to less than 10 pg, which causes an isotopic ratio bias of 30-50 ppm at most. Isobaric interference of 204Hg on 204Pb was corrected by monitoring the ion beam intensity of 202Hg. Mass dependant instrumental fractionation was normalized to 205Tl/203Tl value. A desolvation nebulization system, Cetac Aridus, and an X-skimmer cone were used to enhance signal intensity. With a sample uptake rate of 50 ? L/min, Pb concentration of 5-10 ng/ml offers an ion beam intensity of larger than 1 volt for 208Pb. The measured isotope ratios with 2-sigma external uncertainty of an international standard of NIST- Pb 981 are: 206Pb/204Pb= 16.9419 ± 0.012, 207Pb/206Pb= 0.91475 ± 0.0002 and 208Pb/206Pb= 2.1674 ± 0.00035. The key merit of this technique is to provide a possibility of analyzing Pb isotopic composition in trace-quantity of 1-10 ng, mainly for sample with limited Pb content.

Lo, Y.; Shen, C.; Gallet, S.

2007-12-01

171

Determination of rare earth elements, thorium and uranium by inductively coupled plasma mass spectrometry and strontium isotopes by thermal ionization mass spectrometry in soil samples of Bryansk region contaminated due to Chernobyl accident  

Microsoft Academic Search

The present paper describes the inductively coupled plasma mass spectrometric (ICP-MS) determination of rare earth elements (REEs), thorium and uranium in forest, pasture, field and kitchen garden soils from a Russian territory and in certified reference materials (JLK-1, JSD-2 and BCR-1). In addition to concentration data, strontium isotopic composition of the soil samples were measured by thermal ionization mass spectrometry.

S. K. Sahoo; H. Yonehara; K. Kurotaki; K. Shiraishi; V. Ramzaev; A. Barkovski

2001-01-01

172

Investigation of uranium isotopic signatures in real-life particles from a nuclear facility by thermal ionization mass spectrometry.  

PubMed

An improved method was recently developed for the isotopic analysis of single-reference uranium oxide particles for nuclear safeguards. This method is a combination of analytical tools including in situ SEM micromanipulation, filament carburization and multiple ion counting (MIC) detection, which is found to improve sensitivity for thermal ionization mass spectrometry (TIMS) isotope ratio analysis. The question was raised whether this method could be applied for the detection of nuclear signatures in real-life particles with unknown isotopic composition. Therefore, environmental dust was collected in different locations within a nuclear facility. The screening of the samples to find the uranium particles of interest was performed using a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray (EDX) detector. The comparison of the measurement results to reference data evaluated by international safeguards authorities was of key importance for data interpretation. For the majority of investigated particles, detection of uranium isotopic signatures provided information on current and past nuclear feed operations that compared well with facility declarations. PMID:21417310

Kraiem, Monia; Richter, Stephan; Kühn, Heinz; Stefaniak, Elzbieta A; Kerckhove, Giovani; Truyens, Jan; Aregbe, Yetunde

2011-04-15

173

Determination of lead in urine and whole blood by stable isotope dilution gas chromatography-mass spectrometry.  

PubMed

A stable isotope dilution gas chromatography-mass spectrometry (GC-MS) method is described for the determination of lead (Pb) in urine and whole blood. The use of lithium bis(trifluoroethyl)dithiocarbamate Pb(FDEDTC) as a chelating agent showed strong memory effect, restricting the range of Pb isotope ratios that can be measured in unknown samples. To overcome this carryover problem, we further derivatized the Pb(FDEDTC)2 chelate with 4-fluorophenyl magnesium bromide to form Pb(FC6H4)4. The sequential analyses of solutions of natural Pb and enriched 204Pb with Pb(FC6H4)4 chelate by GC-MS demonstrated no observable memory effect. Precision and accuracy of Pb isotope ratio measurements with Pb(FC6H4)4 were established, and the isotope dilution GC-MS method was validated by determining Pb concentrations in urine standards from the National Institute of Standards and Technology, urine and blood reference materials from the New York State Department of Health, and blood Pb survey samples from the College of American Pathologists. PMID:8044988

Aggarwal, S K; Kinter, M; Herold, D A

1994-08-01

174

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

175

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 1×10(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

176

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

177

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

PubMed

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

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

2001-08-01

178

On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion-isotope ratio mass spectrometry  

NASA Astrophysics Data System (ADS)

Stable carbon isotope analysis of methane (?13C of CH4) on atmospheric samples is one key method to constrain the current and past atmospheric CH4 budget. A frequently applied measurement technique is gas chromatography isotope ratio mass spectrometry coupled to a combustion-preconcentration unit. This report shows that the atmospheric trace gas krypton can severely interfere during the mass spectrometric measurement leading to significant biases in ?13C of CH4 if krypton is not sufficiently separated during the analysis. According to our experiments, the krypton interference is likely composed of two individual effects with the lateral tailing of the doubly charged 86Kr peak affecting the neighbouring m/z 44 and partially the m/z 45 Faraday cups. Additionally, a broad signal affecting m/z 45 and especially m/z 46 is assumed to result from scattered ions of singly charged krypton. The introduced bias in the measured isotope ratios is dependent on the chromatographic separation, the Kr to CH4 mixing ratio in the sample, the mass spectrometer source tuning as well as the detector configuration and can amount to up to several permil in ?13C. Apart from technical solutions to avoid this interference we present correction routines to a posteriori remove the bias.

Schmitt, Jochen; Seth, Barbara; Bock, Michael; van der Veen, Carina; Möller, Lars; Sapart, Celia; Prokopiou, Markella; Sowers, Todd; Röckmann, Thomas; Fischer, Hubertus

2014-05-01

179

On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion-isotope ratio mass spectrometry  

NASA Astrophysics Data System (ADS)

Stable carbon isotope analysis of methane (?13C of CH4) on atmospheric samples is one key method to constrain the current and past atmospheric CH4 budget. A frequently applied measurement technique is gas chromatography (GC) isotope ratio mass spectrometry (IRMS) coupled to a combustion-preconcentration unit. This report shows that the atmospheric trace gas krypton (Kr) can severely interfere during the mass spectrometric measurement, leading to significant biases in ?13C of CH4, if krypton is not sufficiently separated during the analysis. According to our experiments, the krypton interference is likely composed of two individual effects, with the lateral tailing of the doubly charged 86Kr peak affecting the neighbouring m/z 44 and partially the m/z 45 Faraday cups. Additionally, a broad signal affecting m/z 45 and especially m/z 46 is assumed to result from scattered ions of singly charged krypton. The introduced bias in the measured isotope ratios is dependent on the chromatographic separation, the krypton-to-CH4 mixing ratio in the sample, the focusing of the mass spectrometer as well as the detector configuration and can amount to up to several per mil in ?13C. Apart from technical solutions to avoid this interference, we present correction routines to a posteriori remove the bias.

Schmitt, J.; Seth, B.; Bock, M.; van der Veen, C.; Möller, L.; Sapart, C. J.; Prokopiou, M.; Sowers, T.; Röckmann, T.; Fischer, H.

2013-05-01

180

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

PubMed

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

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

2013-02-01

181

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

PubMed

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

Mestek, O; Komínková, J; Koplík, R; Suchánek, M

2001-06-21

182

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

183

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

PubMed

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

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

2014-07-15

184

A site-specific, multiplexed kinase activity assay using stable-isotope dilution and high-resolution mass spectrometry  

PubMed Central

Most kinases are capable of recognizing and phosphorylating peptides containing short, linear sequence motifs. To measure the activation state of many kinases from the same cell lysate, we created a multiplexed, mass-spectrometry-based in vitro kinase assay. Ninety chemically synthesized peptides derived from well-characterized peptide substrates and in vivo phosphorylation sites with either known or previously unidentified upstream kinases were reacted individually in a plate format with crude cell lysates and ATP. Phosphorylation rates were directly measured based on the addition of 90 same-sequence, site-specific phosphopeptides enriched in stable isotopes to act as ideal quantitative internal standards for analysis by liquid chromatography coupled to tandem mass spectrometry. This approach concurrently measured up to 90 site-specific peptide phosphorylation rates, reporting a diagnostic fingerprint for activated kinase pathways. We applied this unique kinome-activity profiling strategy in a variety of cellular settings, including mitogen stimulation, cell cycle, pharmacological inhibition of pathways, and to a panel of breast cancer cell lines. Finally, we identified the source of activity for a peptide (derived from a PI3K regulatory subunit) from our library. This peptide substrate demonstrated mitotic and tyrosine-specific phosphorylation, which was confirmed to be a novel Src family kinase site in vivo.

Yu, Yonghao; Anjum, Rana; Kubota, Kazuishi; Rush, John; Villen, Judit; Gygi, Steven P.

2009-01-01

185

Ultratrace-level radium-226 determination in seawater samples by isotope dilution inductively coupled plasma mass spectrometry.  

PubMed

An improved and novel sample preparation method for 226Ra determination in liquid samples by isotope dilution inductively coupled plasma sector field mass spectrometry using laboratory-prepared 228Ra tracer has been developed. The procedure involves a selective preconcentration achieved by applying laboratory-prepared MnO2 resin followed by cation exchange chromatographic separation. In order to completely eliminate possible molecular interferences, medium mass resolution (R = 4,000) combined with chemical separation was found to be a good compromise that enhanced the reliability of the method. The detection limit of 0.084 fg g(-1) (3.1 mBq kg(-1)) achieved is comparable to that of the emanation method or alpha spectrometry and is suitable for low-level environmental measurements. The chemical recovery of the sample preparation method ranged from 72 to 94%. The proposed method enables a rapid, accurate and less labor-intensive approach to routine environmental 226Ra determination than the radioanalytical techniques conventionally applied. PMID:17593357

Varga, Zsolt

2008-01-01

186

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

SciTech Connect

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

Huang, L.Q.

1989-03-01

187

Measurement of dialkyl phosphate metabolites of organophosphorus pesticides in human urine using lyophilization with gas chromatography-tandem mass spectrometry and isotope dilution quantification  

Microsoft Academic Search

Urinary dialkylphosphate (DAP) metabolites have been used to estimate human exposure to organophosphorus pesticides. We developed a method for quantifying the six DAP urinary metabolites of at least 28 organophosphorus pesticides using lyophilization and chemical derivatization followed by analysis using isotope-dilution gas chromatography–tandem mass spectrometry (GC–MS\\/MS). Urine samples were spiked with stable isotope analogues of the DAPs and the water

Roberto Bravo; Lisa M Caltabiano; Gayanga Weerasekera; Ralph D Whitehead; Carolina Fernandez; Larry L Needham; Asa Bradman; Dana B Barr

2004-01-01

188

Determination of serum uric acid using high-performance liquid chromatography (HPLC)\\/isotope dilution mass spectrometry (IDMS) as a candidate reference method  

Microsoft Academic Search

Uric acid is an important diagnostic marker of catabolism of the purine nucleosides, and accurate measurements of serum uric acid are necessary for proper diagnosis of gout or renal disease appearance. A candidate reference method involving isotope dilution coupled with liquid chromatography\\/mass spectrometry (LC\\/MS) has been described. An isotopically labeled internal standard, [1,3-15N2] uric acid, was added to serum, followed

Xinhua Dai; Xiang Fang; Chunmei Zhang; Ruifeng Xu; Bei Xu

2007-01-01

189

Gas chromatography–combustion–isotope ratio mass spectrometry analysis of 19-norsteroids: application to the detection of a nandrolone metabolite in urine  

Microsoft Academic Search

Determination of whether the major metabolite of nandrolone in urine, 19-norandrosterone (19-NA), is exogenous or endogenous in origin is one of the most exciting challenges for antidoping laboratories. Gas chromatography–combustion–isotope ratio mass spectrometry (GC–C–IRMS) can be used to differentiate these two origins by carbon isotopic ratio analysis. A complete method for purification of 19-NA in urine has been established. Acetylated

Jean-Charles Mathurin; Valérie Herrou; Emmanuel Bourgogne; Laurent Pascaud; Jacques de Ceaurriz

2001-01-01

190

Determination of 90Sr and Pu isotopes in contaminated groundwater samples by inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

A sensitive analytical method for determining the artificial radionuclides 90Sr, 239Pu and 240Pu at the ultratrace level in groundwater samples from the Semipalatinsk Test Site area in Kazakhstan by double-focusing sector field inductively coupled plasma mass spectrometry (ICP-SFMS) was developed. In order to avoid possible isobaric interferences at m/z 90 for 90Sr determination (e.g. 90Zr+, 40Ar50Cr+, 36Ar54Fe+, 58Ni16O2+, 180Hf2+, etc.), the measurements were performed at medium mass resolution under cold plasma conditions. Pu was separated from uranium by means of extraction chromatography using Eichrom TEVA resin with a recovery of 83%. The limits of detection for 90Sr, 239Pu and 240Pu in water samples were determined as 11, 0.12 and 0.1 fg ml-1, respectively. Concentrations of 90Sr and 239Pu in contaminated groundwater samples ranged from 18 to 32 and from 28 to 856 fg ml-1, respectively. The 240Pu/239Pu isotopic ratio in groundwater samples was measured as 0.17. This isotope ratio indicates that the most probable source of contamination of the investigated groundwater samples was the nuclear weapons tests at the Semipalatinsk Test Site conducted by the USSR in the 1960s.

Zoriy, Miroslav V.; Ostapczuk, Peter; Halicz, Ludwik; Hille, Ralf; Becker, J. Sabine

2005-04-01

191

[A novel method for absolute protein quantification using 18O isotope labeled concatamers of Q peptides combined with isotope dilution-multiple reaction monitoring mass spectrometry].  

PubMed

A method of concatamers of Q peptides (QconCATs) protein labeled with 18O-multiple reaction monitoring mass spectrometry for absolute quantification of proteins is established. The purity of the QconCAT recombinant protein was characterized by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), and its purity was above 99%. The relative molecular mass was approximately 63.4 kDa. The peptides digested from the QconCAT recombinant protein and the extract of Thermoanaerobacter tengcongensis (TTE) were analyzed by mass spectrometry. The raw data were processed by pFind and pLabel softwares. The results showed that the efficiencies of protein digestion and the 18O labeling efficiency were able to meet the need of the protein quantification. The performance of the method was evaluated. The absolute contents of the selected proteins in TTE were determined with the relative standard deviations of less than 20% and the accuracy is high. The method not only avoid using the expensive reagent of stable isotope labeling with amino acids in cell culture (SILAC), but also provides an alternative way for the accurately absolute quantification of proteins in biological samples for quantitative proteomic research. PMID:24063190

Li, Nannan; Zhou, Lianqi; Mao, Xinli; Zhang, Jiao; Wei, Junying; Lin, Hongjun; Li, Jiabin; Tian, Fang; Zhang, Yangjun; Qian, Xiaohong

2013-06-01

192

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

193

Isotope Label-Aided Mass Spectrometry Reveals the Influence of Environmental Factors on Metabolism in Single Eggs of Fruit Fly  

PubMed Central

In order to investigate the influence of light/dark cycle on the biosynthesis of metabolites during oogenesis, here we demonstrate a simple experimental protocol which combines in-vivo isotopic labeling of primary metabolites with mass spectrometric analysis of single eggs of fruit fly (Drosophila melanogaster). First, fruit flies were adapted to light/dark cycle using artificial white light. Second, female flies were incubated with an isotopically labeled sugar (13C6-glucose) for 12 h – either during the circadian day or the circadian night, at light or at dark. Third, eggs were obtained from the incubated female flies, and analyzed individually by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS): this yielded information about the extent of labeling with carbon-13. Since the incorporation of carbon-13 to uridine diphosphate glucose (UDP-glucose) in fruit fly eggs is very fast, the labeling of this metabolite was used as an indicator of the biosynthesis of metabolites flies/eggs during 12-h periods, which correspond to circadian day or circadian night. The results reveal that once the flies adapted to the 12-h-light/12-h-dark cycle, the incorporation of carbon-13 to UDP-glucose present in fruit fly eggs was not markedly altered by an acute perturbation to this cycle. This effect may be due to a relationship between biosynthesis of primary metabolites in developing eggs and an alteration to the intake of the labeled substrate – possibly related to the change of the feeding habit. Overall, the study shows the possibility of using MALDI-MS in conjunction with isotopic labeling of small metazoans to unravel the influence of environmental cues on primary metabolism.

Tseng, Te-Wei; Wu, June-Tai; Chen, Yu-Chie; Urban, Pawel L.

2012-01-01

194

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.

2012-09-21

195

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

196

Simultaneous assay of isotopic enrichment and concentration of guanidinoacetate and creatine by gas chromatography-mass spectrometry.  

PubMed

A gas chromatography-mass spectrometry (GC-MS) method for the simultaneous measurement of isotopic enrichment and concentration of guanidinoacetate (GAA) and creatine in plasma sample for kinetic studies is reported. The method, based on preparation of the bis(trifluoromethyl)pyrimidine methyl ester derivatives of GAA and creatine, is robust and sensitive. The lowest measurable m(1) and m(3) enrichment for GAA and creatine, respectively, was 0.3%. The calibration curves for measurements of concentration were linear over ranges of 0.5 to 250microM GAA and 2 to 500microM for creatine. The method was reliable for inter- and intraassay precision, accuracy, and linearity. The technique was applied in a healthy adult to determine the in vivo fractional synthesis rate of creatine using primed-constant rate infusion of [1-(13)C]glycine. It was found that isotopic enrichment of GAA reached a plateau by 30min of infusion of [1-(13)C]glycine, indicating either a small pool size or a rapid turnover rate (or both) of GAA. In contrast, the tracer appearance in creatine was slow (slope=0.00097), suggesting a large pool size and a slow rate of synthesis of creatine. This method can be used to estimate the rate of synthesis of creatine in vivo in human and animal studies. PMID:19646413

Kasumov, Takhar; Gruca, Lourdes L; Dasarathy, Srinivasan; Kalhan, Satish C

2009-12-01

197

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

PubMed

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

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

2012-09-15

198

Determination of total and isotopic uranium by inductively coupled plasma-mass spectrometry at the Fernald Environmental Management Project  

SciTech Connect

At the Fernald Environmental Management Project (FEMP) in southwestern Ohio, ICP-mass spectrometry (ICP-MS), with sample introduction by peristaltic pumping, is used to determine total and isotopic uranium (U-234, U-235, U-236 and U-238) in soil samples. These analyses are conducted in support of the environmental cleanup of the FEMP site. Various aspects of the sample preparation and instrumental analysis will be discussed. Initial sample preparation consists of oven drying to determine moisture content, and grinding and rolling to homogenize the sample. This is followed by a nitric/hydrofluoric acid digestion to bring the uranium in the sample into solution. Bismuth is added to the sample prior to digestion to monitor for losses. The total uranium (U-238) content of this solution and the U{sup 235}/U{sup 238} ratio are measured on the first pass through the ICP-MS. To determine the concentration of the less abundant U{sup 234} and U{sup 236} isotopes, the digestate is further concentrated by using Eichrom TRU-Spec extraction columns before the second pass through the ICP-MS. Quality controls for both the sample preparation and instrumental protocols will also be discussed. Finally, an explanation of the calculations used to report the data in either weight percent or activity units will be given.

Miller, F.L.; Bolin, R.N.; Feller, M.T.; Danahy, R.J.

1995-04-01

199

Diagnosis of inborn errors of metabolism using filter paper urine, urease treatment, isotope dilution and gas chromatography-mass spectrometry.  

PubMed

This review will be concerned primarily with a practical yet comprehensive diagnostic procedure for the diagnosis or even mass screening of a variety of metabolic disorders. This rapid, highly sensitive procedure offers possibilities for clinical chemistry laboratories to extend their diagnostic capacity to new areas of metabolic disorders. The diagnostic procedure consists of the use of urine or filter paper urine, preincubation of urine with urease, stable isotope dilution, and gas chromatography-mass spectrometry. Sample preparation from urine or filter paper urine, creatinine determination, stable isotope-labeled compounds used, and GC-MS measurement conditions are described. Not only organic acids or polar ones but also amino acids, sugars, polyols, purines, pyrimidines and other compounds are simultaneously analyzed and quantified. In this review, a pilot study for screening of 22 target diseases in newborns we are conducting in Japan is described. A neonate with presymptomatic propionic acidemia was detected among 10,000 neonates in the pilot study. The metabolic profiles of patients with ornithine carbamoyl transferase deficiency, fructose-1,6-bisphosphatase deficiency or succinic semialdehyde dehydrogenase deficiency obtained by this method are presented as examples. They were compared to those obtained by the conventional solvent extraction methods or by the tandem mass spectrometric method currently done with dried filter blood spots. The highly sensitive, specific and comprehensive features of our procedure are also demonstrated by its use in establishing the chemical diagnosis of pyrimidine degradation defects in order to prevent side effects of pyrimidine analogs such as 5-flurouracil, and the differential diagnosis of three types of homocystinuria, orotic aciduria, uraciluria and other urea cycle disorders. Evaluation of the effects of liver transplantation or nutritional conditions such as folate deficiency in patients with inborn errors of metabolism is also described. PMID:11482733

Kuhara, T

2001-07-01

200

Measurement of Muscle Protein Fractional Synthetic Rate by Capillary Gas Chromatography/Combustion Isotope Ratio Mass Spectrometry  

PubMed Central

The measurement of skeletal muscle protein fractional synthetic rate using an infusion of (1-13C)leucine and measuring the isotopic abundance of the tracer in skeletal muscle protein by preparative gas chromatography (GC)/ninhydrin isotope ratio mass spectrometry (IRMS) is laborious and subject to errors owing to contamination by 12C. The purpose of this study was to compare muscle (13C)leucine enrichment measured with the conventional preparative GC/ninhydrin IRMS approach to a new, continuous-flow technique using capillary GC/combustion IRMS. Quadriceps muscles were removed from four Sprague–Dawley rats after each was infused at a different rate with (1-13C)leucine for 6–8 h. Muscle leucine enrichment (at.% excess) measured by both methods differed by less than 4%, except at low (13C)leucine enrichments (<0.03 at.% excess). In addition, capillary GC/combustion IRMS was used to assess muscle (13C)leucine enrichment and fractional muscle protein synthesis rate in ten normal young men and women infused with (1,2-13C2)leucine for 12–14 h. This approach reduced the variability of the isotope abundance measure and gave estimates of muscle protein synthesis rate (0.050 ± 0.011% h?1 (mean ± SEM); range = 0.023–0.147% h?1) that agree with published values determined using the standard analytical approach. The measurement of (13C)leucine enrichment from skeletal muscle protein by capillary GC/combustion IRMS provides a simple, acceptable and practical alternative to preparative GC/ninhydrin IRMS.

Yarasheski, Kevin E.; Smith, Kenneth; Rennie, Michael J.; Bier, Dennis M.

2014-01-01

201

Measurements of natural uranium concentration and isotopic composition with permil-level precision by inductively coupled plasma–quadrupole mass spectrometry  

Microsoft Academic Search

A new analytical technique using inductively coupled plasma–quadrupole mass spectrometry (ICP-QMS) has been developed that produces permil-level precision in the measurement of uranium concentration ([U]) and isotopic composition (?234U) in natural materials. A 233U-236U double spike method was used to correct for mass fractionation during analysis. To correct for ratio drifting, samples were bracketed by uranium standard measurements. A sensitivity

Chuan-Chou Shen; Huei-Ting Lin; Mei-Fei Chu; Ein-Fen Yu; Xianfeng Wang; Jeffrey A. Dorale

2006-01-01

202

Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS)--part 1: instrument validation of the DELTAplusXP IRMS for bulk nitrogen isotope ratio measurements.  

PubMed

A significant amount of research has been conducted into the use of stable isotopes to assist in determining the origin of various materials. The research conducted in the forensic field shows the potential of isotope ratio mass spectrometry (IRMS) to provide a level of discrimination not achievable utilizing traditional forensic techniques. Despite the research there have been few, if any, publications addressing the validation and measurement uncertainty of the technique for forensic applications. This study, the first in a planned series, presents validation data for the measurement of bulk nitrogen isotope ratios in ammonium nitrate (AN) using the DELTA(plus)XP (Thermo Finnigan) IRMS instrument equipped with a ConFlo III interface and FlashEA 1112 elemental analyzer (EA). Appropriate laboratory standards, analytical methods and correction calculations were developed and evaluated. A validation protocol was developed in line with the guidelines provided by the National Association of Testing Authorities, Australia (NATA). Performance characteristics including: accuracy, precision/repeatability, reproducibility/ruggedness, robustness, linear range, and measurement uncertainty were evaluated for the measurement of nitrogen isotope ratios in AN. AN (99.5%) and ammonium thiocyanate (99.99+%) were determined to be the most suitable laboratory standards and were calibrated against international standards (certified reference materials). All performance characteristics were within an acceptable range when potential uncertainties, including the manufacturer's uncertainty of the technique and standards, were taken into account. The experiments described in this article could be used as a model for validation of other instruments for similar purposes. Later studies in this series will address the more general issue of demonstrating that the IRMS technique is scientifically sound and fit-for-purpose in the forensic explosives analysis field. PMID:20015166

Benson, Sarah J; Lennard, Christopher J; Hill, David M; Maynard, Philip; Roux, Claude

2010-01-01

203

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

204

Pathway of diethyl phthalate photolysis in sea-water determined by gas chromatography-mass spectrometry and compound-specific isotope analysis.  

PubMed

The degradation mechanism of diethyl phthalate (DEP) in natural seawater under UV irradiation was investigated using a combination of intermediates detection and determination of stable carbon isotopic fractionation. Typical intermediates identified with gas chromatography-mass spectrometry (GC-MS) were mono-ethyl phthalate (MEP) and phthalic anhydride. Stable carbon isotope signature was determined by gas chromatography coupled with isotope ratio mass spectrometry through a combustion interface (GC-C-IRMS). A profound (13)C enrichment, with a ?(13)C isotope shift of 12.3±0.3‰ (f=0.09) in residual DEP molecule, was clearly an indicator to its photolysis. The reactive position isotope enrichment factor (?(reactive position)) and apparent kinetic isotope effects (AKIE) were -35.25±2.26‰ and 1.075, respectively, indicating that the initial reaction step was cleavage of a CO bond in DEP photolysis. Based on these observations, a degradation pathway was proposed. First, a CO bond in DEP molecule was broken to form MEP. Then, MEP was further degraded to phthalic anhydride. Our work demonstrates that compound-specific isotope analysis (CSIA), when combined with intermediates analysis, is a reliable measure to deduce the mechanism of DEP photolysis. This approach might be extended as a reference for mechanism investigation in complicated environment systems. PMID:22883110

Peng, Xuewei; Feng, Lijuan; Li, Xianguo

2013-01-01

205

Simultaneous detection of multiple hydroxylated polychlorinated biphenyls from a complex tissue matrix using gas chromatography/isotope dilution mass spectrometry.  

PubMed

In this study, we developed a comprehensive, highly sensitive, and robust method for determining 53 congeners of three to eight chlorinated OH-PCBs in liver and brain samples by using isotope dilution gas chromatography (GC) coupled with electron capture negative ionization mass spectrometry (ECNI-MS). These results were compared with those from GC coupled with electron ionization high-resolution mass spectrometry (EI-HRMS). Clean-up procedures for analysis of OH-PCBs homologs in liver and brain samples involve a pretreatment step consisting of acetonitrile partition and 5% hydrated silica-gel chromatography before derivatization. Recovery rates of tri- and tetra-chlorinated OH-PCBs in the acetonitrile partition method followed by the 5% hydrated silica-gel column (82% and 91%) were higher than conventional sulfuric acid treatment (2.0% and 3.5%). The method detection limits of OH-PCBs for each matrix obtained by GC/ECNI-MS and GC/EI-HRMS were 0.58-2.6 pg g(-1) and 0.36-1.6 pg g(-1) wet wt, respectively. Recovery rates of OH-PCB congeners in spike tests using sample matrices (10 and 50 pg) were 64.7-117% (CV: 4.7-14%) and 70.4-120% (CV: 2.3-12%), respectively. This analytical method may enable the simultaneous detection of various OH-PCBs from complex tissue matrices. Furthermore, this method allows more comprehensive assessment of the biological effects of OH-PCB exposure on critical organs. PMID:24274296

Eguchi, Akifumi; Nomiyama, Kei; Ochiai, Mari; Mizukawa, Hazuki; Nagano, Yasuko; Nakagawa, Katsuhiro; Tanaka, Kouki; Miyagawa, Haruhiko; Tanabe, Shinsuke

2014-01-15

206

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

207

An online method combining a thermal conversion elemental analyzer with isotope ratio mass spectrometry for the determination of hydrogen isotope composition and water concentration in geological samples.  

PubMed

An online continuous-flow method, combining a thermal conversion elemental analyzer (TC/EA) with isotope ratio mass spectrometry (MS), is evaluated for the determination of both the hydrogen isotope composition and the water concentration of hydrous and nominally anhydrous minerals. The technique involves reduction of hydrous minerals or nominally anhydrous minerals by reaction with glassy carbon at 1450 degrees C in a helium stream. The product gases, H2 and CO, are separated on a gas chromatographic column prior to analysis in the mass spectrometer. Calibration curves for the H concentration analysis were generated from a standard of benzoic acid (C7H6O2) that has an H concentration of 5.0 wt%; the analytical uncertainties were better than +/-0.05% in our runs. Two standards of material with given D values, polyethylene IAEA-CH-7 and biotite NBS-30, were tested for the purpose of calibrating a natural garnet 04BXL02 representing nominally anhydrous minerals. Preheating at 90 degrees C for 12 h was found to be suitable for removing adsorption water on the sample surface. This results in constant D values and total H2O contents for the garnet, with weighted means of -94 +/- 1 and 522 +/- 11 ppm (wt), respectively. The TC/EA-MS technique allows routine analysis of sample sizes as small as 0.01 microL H2O. For natural minerals, absolute reproducibilities for D values are +/-0.5 to +/-2 (1) and relative uncertainties for total H2O concentrations are at levels of +/-1% to +/-3% (1). Therefore, this online method can be used for the quantitative determination of H isotope composition and H2O concentration of either hydrous or anhydrous minerals. PMID:17370247

Gong, Bing; Zheng, Yong-Fei; Chen, Ren-Xu

2007-01-01

208

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

PubMed

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

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

2005-03-01

209

Ultrasonic energy as a new tool for fast isotopic 18O labeling of proteins for mass spectrometry-based techniques: preliminary results.  

PubMed

Preliminary results regarding fast isotopic labeling of proteins with (18)O in conjunction with matrix assisted laser desorption ionization time of flight mass spectrometry technique are presented. Similar (16)O/(18)O isotopic labeling ratios were found for the overnight procedure (12h) and the new fast ultrasonic one (30 min) for the BSA, ovalbumin and alpha-lactalbumin proteins. The procedure, however, failed to promote double (18)O isotopic labeling for the proteins, ovalbumin and alpha-lactalbumin. Two different sonication frequencies, 35 and 130 kHz, were studied at two different sonication times of 15 and 30 min, being best results obtained with the procedure at 130 kHz of sonication frequency and 30 min of sonication time. For comparative purposes the overnight isotopic (18)O labeling procedure was done. In addition, the new fast isotopic labeling procedure was also studied without ultrasonication, in a water bath at 60 degrees C. PMID:18585297

Carreira, R J; Rial-Otero, R; López-Ferrer, D; Lodeiro, C; Capelo, J L

2008-07-15

210

Ultrasonic Energy as a New Tool for Fast Isotopic 18O Labeling of Proteins for Mass Spectrometry-Based Techniques: Preliminary Results  

SciTech Connect

Preliminary results regarding fast isotopic labeling of proteins with 18O in conjunction with matrix assisted laser desorption ionization time of flight mass spectrometry technique are presented. Similar 16O/18O isotopic labeling ratios were found for the overnight procedure (12 h) and the new fast ultrasonic one (30 min) for the BSA, ovalbumin and ?-lactalbumin proteins. The procedure, however, failed to promote double 18O isotopic labeling for the proteins ovalbumin and ?-lactalbumin. Two different sonication frequencies, 35 kHz and 130 kHz, were studied at two different sonication times of 15 min and 30 min, being best results obtained with the procedure at 130 kHz of sonication frequency and 30 min of sonication time. For comparative purposes the overnight isotopic 18O labeling procedure was done. In addition, the new fast isotopic labeling procedure was also studied without ultrasonication, in a water bath at 60 ºC.

Carreira, R.J.; Rial-Otero, R.; Lopez-Ferrer, Dani; Lodeiro, C.; Capelo, J.L.

2008-07-15

211

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

212

Transition of Iodine Analysis to Accelerator Mass Spectrometry.  

National Technical Information Service (NTIS)

Funding was received from NA-22 to investigate transitioning iodine isotopic analyses to an accelerator mass spectrometry (AMS) system. The present method uses gas-phase chemistry followed by thermal ionization mass spectrometry (TIMS). It was anticipated...

J. E. Delmore

2010-01-01

213

In-gel stable isotope labeling for relative quantification using mass spectrometry  

Microsoft Academic Search

Although differences in protein staining intensity can often be visualized by difference gel electrophoresis, abundant proteins can obscure less abundant proteins, and quantification of post-translational modifications is difficult. We present a protocol for quantifying changes in the abundance of a specific protein or changes in specific modifications of a protein using in-gel stable isotope labeling. In this protocol protein extracts

Xiang Zhang; Bin Zheng; Lisa A Maroney; Heather R Christofk; Ning Wu; Lewis C Cantley; John M Asara

2006-01-01

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

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

PubMed

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 50nm 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

2014-07-01

216

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

217

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

PubMed

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

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

2014-07-01

218

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

SciTech Connect

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

Lantto, O.

1982-05-01

219

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

220

Carbon isotope ratio analysis of organic moieties from fossil mummified wood: establishing optimum conditions for off-line pyrolysis extraction using gas chromatography/mass spectrometry.  

PubMed

Mummified fossil wood was studied using off-line pyrolysis-gas chromatography/mass spectrometry to reveal detailed insights into the pyrolysis conditions that are needed to obtain simultaneously sufficient amounts of both cellulose and lignin markers for stable carbon isotope analyses. The off-line pyrolysis was applied at a range of temperatures (200, 250 and 300 degrees C) and times (1 and 2 h) to determine the optimum temperature and time that yielded the highest quantity of true markers for lignin and cellulose. Increasing the time from 1 to 2 h had no effect whereas increasing the temperature led to large differences. The products released during the low-temperature pyrolysis were mostly related to thermally labile moieties. Only at 300 degrees C were sufficient amounts of products released that represent true cellulose and lignin building blocks and which could be studied using gas chromatography/combustion isotope ratio mass spectrometry. PMID:12362390

Poole, Imogen; van Bergen, Pim F

2002-01-01

221

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

222

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

Microsoft Academic Search

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

Laura Campo; Silvia Fustinoni; PierAlberto Bertazzi

223

Application of isotope dilution to the determination of methylmercury in fish tissue by solid-phase microextraction gas chromatography-mass spectrometry  

Microsoft Academic Search

Species-specific isotope dilution (ID) calibration using solid-phase microextraction (SPME) in combination with gas chromatography-mass spectrometry (GC-MS) for separation and detection of methylmercury (MeHg) in fish tissue is described. Samples were digested with methanolic potassium hydroxide. Analytes were propylated and headspace sampled with a polydimethylsiloxane-coated SPME fused-silica fiber. ID analysis was performed using a laboratory-synthesized 198Hg-enriched methylmercury (Me198Hg) spike. Using selective

Lu Yang; Vanessa Colombini; Paulette Maxwell; Zoltán Mester; Ralph E. Sturgeon

2003-01-01

224

The quantification of synthetic corticosteroids using isotope dilution gas chromatography negative chemical ionization mass spectrometry.  

PubMed

Prednisolone, dexamethasone and betamethasone were labelled with deuterium via a simple synthetic procedure and used as internal standards in the gas chromatographic/mass spectrometric analysis of the corresponding undeuterated compounds. The mass spectrometer was used in the negative chemical ionization mode, which gave fragmentation of the methoxime trimethylsilyl ether derivatives favourable for their quantification. The method was applicable to the quantification of synthetic corticosteroids contained in human aqueous humour in the 0.1-10-ng range. PMID:3382802

Midgley, J M; Watson, D G; Healey, T; Noble, M

1988-05-01

225

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

226

Percent cholesterol absorption in normal women and men quantified with dual stable isotopic tracers and negative ion mass spectrometry  

Microsoft Academic Search

Percent cholesterol absorption was measured in 94 normal subjects aged 17-80 years while consuming diets generally low in cholesterol (mean intake 5 226 6 126 mg\\/ day). A new dual stable isotope method was used where a cholesterol tracer containing 6 extra mass units was given in- travenously and another tracer with 5 extra mass units was given orally during

Matthew S. Bosner; Louis G. Lange; William F. Stenson; Richard E. Ostlund

227

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.

2011-06-13

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

2013-07-12

229

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

230

Analysis of exogenous nandrolone metabolite in horse urine by gas chromatography/combustion/carbon isotope ratio mass spectrometry.  

PubMed

Nandrolone (17beta-hydroxy-4-estren-3-one, NAD) is an endogenous steroid hormone; thus, the detection of its metabolites is not conclusive of NAD doping in racehorses. NAD doping control in male horses is based on the threshold, namely, the concentration ratio of 5alpha-estran-3beta,17alpha-diol (ETA) to 5(10)-estren-3beta,17alpha-diol (ETE). The ETA/ETE ratio of 1/1 was determined based on statistical data of authentic horses in International Federation of Horseracing Authorities. To individuals with complex metabolic disorders, however, such a threshold might not be applicable. The aim of this study was to establish an analytical method that discriminates endogenous steroids from exogenous ones in horse urine after NAD administration using gas chromatography/combustion/carbon isotope ratio mass spectrometry (GC/C/IRMS). Urine was sampled from NAD-administered and authentic horses. Ten millilitres of urine was hydrolyzed and subjected to liquid-liquid extraction and solid phase extraction. The residue of the extracts purified by HPLC was derivatized by acetylation. As a result of measurement of the (13)C/(12)C ratio (delta(13)C) by GC/C/IRMS, the delta(13)C values of ETA for NAD-administered and authentic horses were -32.20+/-0.35 per thousand and -27.85+/-0.75 per thousand (n=60), respectively. The detection limit of ETA in this GC/C/IRMS analysis was approximately 25 ng/ml. This study indicates that the measurement of delta(13)C by GC/C/IRMS enables us to discriminate exogenous ETA derived from NAD administration from endogenous ETA, proving that GC/C/IRMS is a useful technique to complement the ETA/ETE ratio. PMID:17714906

Yamada, Masayuki; Kinoshita, Kenji; Kurosawa, Masahiko; Saito, Koichi; Nakazawa, Hiroyuki

2007-11-30

231

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

PubMed

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

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

2014-02-01

232

Liquid chromatography/electrospray ionization/isotopic dilution mass spectrometry analysis of n-(phosphonomethyl) glycine and mass spectrometry analysis of aminomethyl phosphonic acid in environmental water and vegetation matrixes.  

PubMed

A liquid chromatography/electrospray/mass spectrometry (LC/ES/MS) method was developed for the analysis of glyphosate (n-phosphonomethyl glycine) and its metabolite, aminomethyl phosphonic acid (AMPA) using isotope-labelled glyphosate as a method surrogate. Optimized parameters were achieved to derivatize glyphosate and AMPA using 9-fluorenylmethyl chloroformate (FMOC-Cl) in borate buffer prior to a reversed-phase LC analysis. Method spike recovery data obtained using laboratory and real world sample matrixes indicated an excellent correlation between the recovery of the native and isotope-labelled glyphosate. Hence, the first performance-based, isotope dilution MS method with superior precision, accuracy, and data quality was developed for the analysis of glyphosate. There was, however, no observable correlation between the isotope-labelled glyphosate and AMPA. Thus, the use of this procedure for the accurate analysis of AMPA was not supported. Method detection limits established using standard U.S. Environmental Protection Agency protocol were 0.06 and 0.30 microg/L, respectively, for glyphosate and AMPA in water matrixes and 0.11 and 0.53 microg/g, respectively, in vegetation matrixes. Problems, solutions, and the method performance data related to the analysis of chlorine-treated drinking water samples are discussed. Applying this method to other environmental matrixes, e.g., soil, with minimum modifications is possible, assuring accurate, multimedia studies of glyphosate concentration in the environment and the delivery of useful multimedia information for regulatory applications. PMID:11767144

Grey, L; Nguyen, B; Yang, P

2001-01-01

233

Conceptual Study on New Isotope Analysis Technique with Resonance Ionization Mass Spectrometry Using Inductively Coupled Plasma as an Atomic Source (ICP-RIMS)  

NASA Astrophysics Data System (ADS)

We have proposed the novel isotope analysis technique with Resonance Ionization Mass Spectrometry using Inductively Coupled Plasma as an atomic source (ICP-RIMS). Each component of ICP-RIMS is conceptually designed. We conclude that the orthogonal acceleration time-of-flight mass spectrometer (oa-TOF-MS) driven by a high-repetition-rate pulsed laser would be suitable system for ICP-RIMS. We, additionally, suggest that the first vacuum stage of the vacuum interface, which is between the sampling and skimmer cones, is desired to maintain as low pressure as possible in order to suppress the Doppler broadening and to skim the supersonic jet effectively.

Watanabe, K.; Higuchi, Y.; Tomita, H.; Kawarabayashi, J.; Uritani, A.; Iguchi, T.

2009-03-01

234

Conceptual Study on New Isotope Analysis Technique with Resonance Ionization Mass Spectrometry Using Inductively Coupled Plasma as an Atomic Source (ICP-RIMS)  

SciTech Connect

We have proposed the novel isotope analysis technique with Resonance Ionization Mass Spectrometry using Inductively Coupled Plasma as an atomic source (ICP-RIMS). Each component of ICP-RIMS is conceptually designed. We conclude that the orthogonal acceleration time-of-flight mass spectrometer (oa-TOF-MS) driven by a high-repetition-rate pulsed laser would be suitable system for ICP-RIMS. We, additionally, suggest that the first vacuum stage of the vacuum interface, which is between the sampling and skimmer cones, is desired to maintain as low pressure as possible in order to suppress the Doppler broadening and to skim the supersonic jet effectively.

Watanabe, K.; Uritani, A. [Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan); Higuchi, Y.; Tomita, H.; Kawarabayashi, J.; Iguchi, T. [Department of Quantum Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)

2009-03-17

235

Nanopore Mass Spectrometry  

NASA Astrophysics Data System (ADS)

We describe a concept for single-DNA analysis called nanopore mass spectrometry, which seeks to combine the benefits of nanopores with the speed, sensitivity, and robustness of single base detection by mass spectrometry. The basic idea is to cleave the individual nucleotides from a DNA polymer as they transit a nanopore in sequence, and to identify each one by determining its charge-to-mass ratio in a mass spectrometer. We describe how nanopore mass spectrometry can addresse the challenges faced by other nanopore-based DNA analysis approaches. We also describe the design, construction, and testing of a prototype instrument that interfaces a nanopore ion source with a quadrupole mass filter and a single ion detector. We are using this new instrument to test the key scientific questions bearing on our analysis strategy: 1) Can DNA nucleotides be reliably transferred from their native liquid phase into the vacuum environment of a mass spectrometer? 2) Can nucleotides be detected with near 100% efficiency? 3) Can DNA polymers be controllably cleaved to isolate ionized bases or nucleotides in the mass spectrometer?

Stein, Derek; Bush, Joseph; Mihovilovic, Mirna; Maulbetsch, William; Moon, Wooyoung; Bazemore-Walker, Carthene; Weber, Peter

2012-02-01

236

Improvement in Thermal-Ionization Mass Spectrometry (TIMS) using Total Flash Evaporation (TFE) method for lanthanides isotope ratio measurements in transmutation targets  

SciTech Connect

The experiments involved in the PHENIX french nuclear reactor to obtain precise and accurate data on the total capture cross sections of the heavy isotopes and fission products require isotopic ratios measurements with uncertainty of a few per mil. These accurate isotopic ratio measurements are performed with mass spectrometer equipped with multi-collector system. The major difficulty for the analyses of these actinides and fission products is the low quantity of the initial powder enclosed in steel container (3 to 5 mg) and the very low quantities of products formed (several {mu}g) after irradiation. Specific analytical developments are performed by Thermal Ionization Mass Spectrometry (TIMS) to be able to analyse several nanograms of elements with this technique. A specific method of acquisition named Total Flash Evaporation was adapted in this study in the case of lanthanide measurements for quantity deposited on the filament in the order of 2 ng and applied on irradiated fuel. To validate the analytical approach and discuss about the accuracy of the data, the isotopic ratios obtained by TIMS are compared with other mass spectrometric techniques such as Multiple-Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). (authors)

Mialle, S.; Gourgiotis, A.; Aubert, M.; Stadelmann, G.; Gautier, C.; Isnard, H. [Commissariat a l'Energie Atomique, CEA Saclay, DEN/DPC/SECR/LANIE, 91191 Gif sur Yvette (France); Chartier, F. [Commissariat a l'Energie Atomique, CEA Saclay, DEN/DPC, 91191 Gif sur Yvette (France)

2011-07-01

237

Direct determination of urinary iodine by inductively coupled plasma mass spectrometry using isotope dilution with iodine-129  

Microsoft Academic Search

An inductively coupled mass spectrometric method was developed for the direct determination of iodine in urine. The application of isotope dilution analysis with added 129I offers new possibilities for automatic and accurate determinations. The sample preparation con- sists of dilution with an ammonia solution containing 129 I. The validation was made by comparison with the results obtained in another laboratory

Max Haldimann; Bernhard Zimmerli; Claudine Als; Hans Gerber

238

Trace determination of uranium, thorium, calcium, and other heavy metals in high-purity refractory metal silicides, niobium, and silicon dioxide with isotope dilution mass spectrometry  

SciTech Connect

A method for the determination of trace impurities (U, Th, Ca, Fe, Cr, Ni, Cu, and Cd) in silicides of refractory metals, in niobium, and in silicon dioxide with isotope dilution mass spectrometry (IDMS) has been developed. This method enables uranium and thorium analyses down to the lowest picogram per gram level with high precision and accuracy, which is especially important for the characterization of microelectronic devices. The other elements can be determined down to the low nanogram per gram level or - depending on the blank values - in some cases less. Selective chromatographic, extractive, and electrolytic procedures for the trace-matrix-separation were combined with positive thermal ionization mass spectrometry. Different samples of high-purity materials (metal and silicide powders, compact silicide, and silicon dioxide powder) for advanced technologies were analyzed.

Herzner, P.; Heumann, K.G. (Universitaet Regensburg (Germany))

1992-12-01

239

Comparison of water isotope-ratio determinations using two cavity ring-down instruments and classical mass spectrometry in continuous ice-core analysis.  

PubMed

We present a detailed comparison between subsequent versions of commercially available wavelength-scanned cavity ring-down water isotope analysers (L2120-i and L2130-i, Picarro Inc.). The analysers are used in parallel in a continuous mode by adaption of a low-volume flash evaporation module. Application of the analysers to ice-core analysis is assessed by comparison between continuous water isotope measurements of a glacial ice-core from Severnaya Zemlya with discrete isotope-ratio mass spectrometry measurements performed on parallel samples from the same ice-core. The great advances between instrument versions, particularly in the measurement of ?(2)H, allow the continuous technique to achieve the same high level of accuracy and precision obtained using traditional isotope spectrometry techniques in a fraction of the experiment time. However, when applied to continuous ice-core measurements, increased integration times result in a compromise of the achievable depth resolution of the ice-core records. PMID:23713832

Maselli, Olivia J; Fritzsche, Diedrich; Layman, Lawrence; McConnell, Joseph R; Meyer, Hanno

2013-01-01

240

Analytical mass spectrometry. Abstracts  

SciTech Connect

This 43rd Annual Summer Symposium on Analytical Chemistry was held July 24--27, 1990 at Oak Ridge, TN and contained sessions on the following topics: Fundamentals of Analytical Mass Spectrometry (MS), MS in the National Laboratories, Lasers and Fourier Transform Methods, Future of MS, New Ionization and LC/MS Methods, and an extra session. (WET)

Not Available

1990-12-31

241

Analytical mass spectrometry  

SciTech Connect

This 43rd Annual Summer Symposium on Analytical Chemistry was held July 24--27, 1990 at Oak Ridge, TN and contained sessions on the following topics: Fundamentals of Analytical Mass Spectrometry (MS), MS in the National Laboratories, Lasers and Fourier Transform Methods, Future of MS, New Ionization and LC/MS Methods, and an extra session. (WET)

Not Available

1990-01-01

242

Glow discharge mass spectrometry  

Microsoft Academic Search

Over the past twenty years or so, glow discharge mass spectrometry (GDMS) has become the industry standard for the analysis of trace elements in metals and semiconductors. A review of its history is followed by a picture of the present situation and a look to where the future may lie. Applications are summarised, including the ability of GDMS to offer depth-resolved

Volker Hoffmann; Martin Kasik; Peter K. Robinson; Cornel Venzago

2005-01-01

243

Steady-state kinetics of serum bile acids in healthy human subjects: single and dual isotope techniques using stable isotopes and mass spectrometry  

SciTech Connect

Techniques have been developed for the measurement of the complete steady-state kinetics of both chenodeoxycholic (CDCA) and cholic (CA) acid and the pool size of deoxycholic acid (DCA) from the serum of healthy subjects using stable isotopes and capillary gas-liquid chromatography-mass spectrometry (GLC-MS). Serum bile acids were purified by a method employing a C18 chromatographic cartridge, acid solvolysis, enzymic hydrolysis, methylation, a C8 chromatographic cartridge, and TMS-ether derivatization. Fifty mg each of (24-/sup 13/C)CDCA and (24-/sup 13/C)CA was given to five healthy subjects and kinetics were measured from serum and bile. In each case, the measurements from serum (S) equalled those from bile (B) (CDCA (S vs. B): fractional turnover rate (FTR) (d-1) 0.17 +/- 0.03 vs. 0.18 +/- 0.04; pool (g) 0.64 +/- 0.1 vs. 0.68 +/- 0.14, synthesis (g d-1) 0.12 +/- 0.03 vs. 0.1 +/- 0.03; CA (S vs. B): FTR (d-1) 0.28 +/- 0.05 vs. 0.29 +/- 0.07, pool (g) 0.84 +/- 0.29 vs. 0.82 +/- 0.29, synthesis (g d-1) 0.24 +/- 0.10 vs. 0.25 +/- 0.12). In addition, a dual isotope technique for measuring the steady-state kinetics of CDCA was developed using (11,12-2H)CDCA, (24-/sup 13/C)CDCA, and a single sample of serum. In ten subjects, the FTR, pool and synthesis of CDCA measured from serum was similar to that measured from bile. Finally, a technique for estimating the deoxycholic acid (DCA) pool from serum using the ratio of the 370 ion of DCA to that of CDCA was developed. In summary, these data demonstrate that the steady-state kinetics of CDCA and CA and the pool size of DCA can be measured from the serum of healthy subjects.

Everson, G.T.

1987-03-01

244

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

PubMed

A gas chromatographic (GC) method with mass spectrometry detection (MS) for the determination of eight polycyclic aromatic hydrocarbons (PAHs) in olive pomace oil has been developed. The oil was diluted with n-pentane and extracted by liquid-liquid partition with dimethyl sulphoxide (DMSO). After water addition and back-extraction with cyclohexane, a thin-layer chromatography on silica gel was performed as a further purification step. The PAHs spot was scraped off from the plate and the final extract was concentrated and analysed by GC-MS in full scan mode. The eight PAHs under investigation were determined in the presence of the corresponding labelled compounds added as internal standards to the sample at the beginning of the analytical process. The identified PAHs were then quantified by the isotope dilution methodology assuring the compensation of the concentration of each analyte for any variation in the sample preparation. The method precision was satisfactory with relative standard deviation (R.S.D.) values in the range 3.6-12.7% for all PAHs. The average recovery rates ranged from 69.0 to 97.5%. Accuracy was also calculated for benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene by analysing a certified reference material (CRM 458, coconut oil) with adequate results. All response curves exhibited a linear fit from 0.1 to 10 microg ml(-1) and the determination coefficients R2 were better than 0.9942. The limits of detection (0.1-0.4 microg kg(-1)) were acceptable when compared with the maximum permitted limit of 2 microg kg(-1) for each of the eight considered PAHs and 5 microg kg(-1) for the sum of the eight PAHs established by the Italian legislation. Measurement uncertainty was finally calculated identifying and quantifying the uncertainty components of the analytical process. The relative expanded uncertainties (Uc), expressed as percent values were in the range 8.5-11.4% thus appropriate for residues quantification in the range of concentrations considered in the present study. PMID:15679162

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

2005-01-14

245

Examination of the rate of peptide biosynthesis in neuroendocrine cell lines using a stable isotopic label and mass spectrometry.  

PubMed

The biosynthesis of neuroendocrine peptides is typically examined by following the rate of appearance of a radioactive amino acid into mature forms of peptides. In the present study, we labeled cell lines with L-leucine containing 10 deuterium residues (d(10)-Leu) and used mass spectrometry to measure the biosynthetic rate of gamma-lipotropin in the AtT-20 cell line and insulin in the INS-1 cell line. After 3 h of labeling, both peptides show detectable levels of the d-labeled form in the cells and media. The relative levels of the d-labeled forms are greater in the media than in the cells, consistent with previous studies that found that newly synthesized peptides are secreted at a higher rate than older peptides under basal conditions. When AtT-20 cells were stimulated with KCl or forskolin, the ratio of d- to H-labeled gamma-lipotropin in the medium decreased, suggesting that the older peptide was in a compartment that could be released upon the appropriate stimulation. Overexpression of proSAAS in AtT-20 cells reduced the ratio of d- to H-labeled gamma-lipotropin, consistent with the proposed role of proSAAS as an endogenous inhibitor of prohormone convertase-1. Labeling with d10-Leu was also used to test whether altering the pH of the secretory pathway with chloroquine affected the rate of peptide biosynthesis. In AtT-20 cells, 30 microm chloroquine for 3 or 6 h significantly reduced the rate of formation of gamma-lipotropin in both cells and media. Similarly, INS-1 cells treated with 10, 30, or 60 microm chloroquine for 6 h showed a significant decrease in the rate of formation of insulin in both cells and media. These results are consistent with the acidic pH optima for peptide processing enzymes. Stable isotopic labeling with d10-Leu provides a sensitive method to examine the rate of peptide formation in neuroendocrine cell lines. PMID:15255936

Che, Fa-Yun; Yuan, Quan; Kalinina, Elena; Fricker, Lloyd D

2004-08-01

246

Determination of serum uric acid using high-performance liquid chromatography (HPLC)/isotope dilution mass spectrometry (ID-MS) as a candidate reference method.  

PubMed

Uric acid is an important diagnostic marker of catabolism of the purine nucleosides, and accurate measurements of serum uric acid are necessary for proper diagnosis of gout or renal disease appearance. A candidate reference method involving isotope dilution coupled with liquid chromatography/mass spectrometry (LC/MS) has been described. An isotopically labeled internal standard, [1,3-(15)N(2)] uric acid, was added to serum, followed by equilibration and protein removal clean up to prepare samples for liquid chromatography/mass spectrometry electrospray ionization (LC/MS-ESI) analyses. (M-H)(-) ions at m/z 167 and 169 for uric acid and its labeled internal standard were monitored for LC/MS. The accuracy of the measurement was evaluated by a comparison of results of this candidate reference method on lyophilized human serum reference materials for uric acid (Standard Reference Materials SRM909b) with the certified values determined by gas chromatography/mass spectrometry reference methods and by a recovery study for the added uric acid. The method performed well against the established reference method of ion-exchange followed by derivatization isotope dilution (ID) gas chromatography mass spectrometry (ID-GC/MS). The results of this method for uric acid agreed well with the certified values and were within 0.10%. The amounts of uric acid recovered and added were in good agreement for the three concentrations. This method was applied to determine uric acid in samples of frozen serum pools. Excellent precision was obtained with within-set CVs of 0.08-0.18% and between-set CVs of 0.02-0.07% for LC/MS analyses. Liquid chromatography/tandem mass spectrometry electrospray ionization (LC/MS/MS-ESI) analysis was also performed. The LC/MS and LC/MS/MS results were in very good agreement (within 0.14%). This LC/MS method, which demonstrates good accuracy and precision, and is in the speed of analysis without the need for a derivatization stage, qualifies as a candidate reference method. This method can be used as an alternative reference method to provide an accuracy base to which the routine methods can be compared. PMID:17704012

Dai, Xinhua; Fang, Xiang; Zhang, Chunmei; Xu, Ruifeng; Xu, Bei

2007-10-01

247

Determination of Am and Cm in spent nuclear fuels by isotope dilution inductively coupled plasma mass spectrometry and isotope dilution thermal ionization mass spectrometry after separation by high-performance liquid chromatography  

Microsoft Academic Search

Elemental and isotopic determination of americium and curium in spent nuclear fuels is necessary to validate neutronic calculation\\u000a codes and for nuclear waste disposal purposes. Prior to mass spectrometric analysis, it is mandatory to perform separations\\u000a in order to eliminate isobaric interferences between U, Pu, Am and Cm. In the spent fuels samples analyzed, a separation of\\u000a U and Pu

Frédéric Chartier; Michel Aubert; Mireille Pilier

1999-01-01

248

Application of nanosecond-UV laser ablation-inductively coupled plasma mass spectrometry for the isotopic analysis of single submicrometer-size uranium particles.  

PubMed

For the first time, laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) was used to carry out isotopic measurement on single submicrometer-size uranium particles. The analytical procedure was applied on two particle-containing samples already analyzed in the same laboratory by established techniques for particle analysis: combination of the fission track technique with thermo-ionization mass spectrometry (FT-TIMS) and secondary ion mass spectrometry (SIMS). Particles were extracted from their initial matrix with ethanol and deposited on a polycarbonate disk where they were fixed in a layer of an organic compound (collodion). Prior to the isotopic analysis, particles were precisely located on the disk's surface by scanning electron microscopy (SEM) for one sample and using the fission track technique for the other sample. Most of the particles were smaller than 1 ?m, and their (235)U content was in the femtogram range. (235)U/(238)U ratios were successfully analyzed for all located particles using a nanosecond-UV laser (Cetac LSX 213 nm) coupled to a quadrupole-based ICPMS (Thermo "X-Series II"). LA-ICPMS results, although less precise and accurate (typically 10%) than the ones obtained by FT-TIMS and SIMS due to short (20-40 s), transient, and noisy signals, are in good agreement with the certified values or with the results obtained with other techniques. Thanks to good measurement efficiency (~6 × 10(-4)) and high signal/noise ratio during the analysis, LA-ICPMS can be considered a very promising technique for fast particle analysis, provided that uranium-bearing particles are fixed on the sample holder and located prior to isotope measurement. PMID:21875035

Pointurier, Fabien; Pottin, Anne-Claire; Hubert, Amélie

2011-10-15

249

Further development of IDGS: Isotope dilution gamma-ray spectrometry  

SciTech Connect

The isotope dilution gamma-ray spectrometry (IDGS) technique for determining the plutonium concentration and isotopic composition of highly radioactive spent-fuel dissolver solutions has been further developed. Both the sample preparation and the analysis have been improved. The plutonium isotopic analysis is based on high-resolution, low-energy gamma-ray spectrometry. The plutonium concentration in the dissolver solutions then is calculated from the measured isotopic differences among the spike, the dissolver solution, and the spiked dissolver solution. Plutonium concentrations and isotopic compositions of dissolver solutions analyzed from this study agree well with those obtained by traditional isotope dilution mass spectrometry (IDMS) and are consistent with the first IDGS experimental result. With the current detector efficiency, sample size, and a 100-min count time, the estimated precision is {approximately}0.5% for {sup 239}Pu and {sup 240}Pu isotopic analyses and {approximately}1% for the plutonium concentration analysis. 5 refs., 2 figs., 7 tabs.

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

1991-01-01

250

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.

2010-01-01

251

Non-linear signal response functions and their effects on the statistical and noise cancellation properties of isotope ratio measurements by multi-collector plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

A nebulizer-centric response function model of the analytical inductively coupled argon plasma ion source was used to investigate the statistical frequency distributions and noise reduction factors of simultaneously measured flicker noise limited isotope ion signals and their ratios. The response function model was extended by assuming i) a single gaussian distributed random noise source (nebulizer gas pressure fluctuations) and ii) the isotope ion signal response is a parabolic function of the nebulizer gas pressure. Model calculations of ion signal and signal ratio histograms were obtained by applying the statistical method of translation to the non-linear response function model of the plasma. Histograms of Ni, Cu, Pr, Tl and Pb isotope ion signals measured using a multi-collector plasma mass spectrometer were, without exception, negative skew. Histograms of the corresponding isotope ratios of Ni, Cu, Tl and Pb were either positive or negative skew. There was a complete agreement between the measured and model calculated histogram skew properties. The nebulizer-centric response function model was also used to investigate the effect of non-linear response functions on the effectiveness of noise cancellation by signal division. An alternative noise correction procedure suitable for parabolic signal response functions was derived and applied to measurements of isotope ratios of Cu, Ni, Pb and Tl. The largest noise reduction factors were always obtained when the non-linearity of the response functions was taken into account by the isotope ratio calculation. Possible applications of the nebulizer-centric response function model to other types of analytical instrumentation, large amplitude signal noise sources (e.g., lasers, pumped nebulizers) and analytical error in isotope ratio measurements by multi-collector plasma mass spectrometry are discussed.

Doherty, W.

2013-07-01

252

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

253

Assay of Low Deuterium Enrichment of Water by Isotopic Exchange with [U- 13C 3]Acetone and Gas Chromatography–Mass Spectrometry  

Microsoft Academic Search

A sensitive assay of the2H-enrichment of water based on the isotopic exchange between the hydrogens of water and of acetone in alkaline medium is described and validated. For low2H-enrichments (0.008 to 0.5%), the sample is spiked with [U-13C3]acetone and NaOH. After exchange,2H-enriched [U-13C3]acetone is extracted with chloroform and assayed by gas chromatography–mass spectrometry. With some instruments, ion–molecule reactions, resulting in

Dawei Yang; Frédérique Diraison; Michel Beylot; Daniel Z. Brunengraber; Mark A. Samols; Vernon E. Anderson; Henri Brunengraber

1998-01-01

254

Simultaneous quantification of G M1 and G M2 gangliosides by isotope dilution tandem mass spectrometry  

Microsoft Academic Search

ObjectivesGangliosides (GGs) are considered as diagnostic biomarkers and therapeutic targets and agents. The goal of this study was to develop a tandem mass spectrometry (MS\\/MS) method for the simultaneous measurement of both GM1 and GM2 gangliosides in human cerebrospinal fluid (CSF) samples in order to be able to determine their concentrations in patients with Tay-Sachs and Sandhoff disease and assess

Jianghong Gu; Cynthia J. Tifft; Steven J. Soldin

2008-01-01

255

Resonance ionization mass spectrometry of ion beam sputtered neutrals for element- and isotope-selective analysis of plutonium in micro-particles.  

PubMed

Micro-particles containing actinides are of interest for risk assessments of contaminated areas, nuclear forensic analyses, and IAEA as well as Euratom safeguards programs. For their analysis, secondary ion mass spectrometry (SIMS) has been established as the state-of-the-art standard technique. In the case of actinide mixtures within the particles, however, SIMS suffers from isobaric interferences (e.g., (238)U/(238)Pu, (241)Am/(241)Pu). This can be eliminated by applying resonance ionization mass spectrometry which is based on stepwise resonant excitation and ionization of atoms with laser light, followed by mass spectrometric detection of the produced ions, combining high elemental selectivity with the analysis of isotopic compositions. This paper describes the instrumental modifications for coupling a commercial time-of-flight (TOF)-SIMS apparatus with three-step resonant post-ionization of the sputtered neutrals using a high-repetition-rate (kHz) Nd:YAG laser pumped tunable titanium:sapphire laser system. Spatially resolved ion images obtained from actinide-containing particles in TOF-SIMS mode demonstrate the capability for isotopic and spatial resolution. Results from three-step resonant post-ionization of bulk Gd and Pu samples successfully demonstrate the high elemental selectivity of this process. PMID:19557397

Erdmann, N; Kratz, J-V; Trautmann, N; Passler, G

2009-11-01

256

MASS SPECTROMETRY IN ENVIRONMENTAL SCIENCES  

EPA Science Inventory

This review covers applications of mass spectrometry to the environmental sciences. From the early applications of mass spectrometry to environmental research in the 1960s and 1970s, mass spectrometry has played an important role in aiding our understanding of environmental poll...

257

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

258

Measurements of235U/238U isotopic ratio in the photoproduct UF5 by multiphoton ionization and time-of-flight mass spectrometry  

NASA Astrophysics Data System (ADS)

A MultiPhoton-Ionization Time-Of-Flight Mass Spectrometry (MPI/TOFMS) apparatus was developed for real-time measurement of the uranium isotopic ratio in nascent UF5 formed by the 266 nm photolysis of effusive UF6 ( < 300 K, ? 1.3 × 10-4 Pa). The UF5 was selectively and efficiently multiphoton ionized by 532 nm radiation at appreciably low fluences ( < 10 J/cm2). The main ions observed, U+ and U2+, were subsequently analyzed with a TOFMS with mass resolution of 1190 to separate235U n+ and238U n+ completely. The isotopic ratio measurements showed good precision resulting from the excellent agreement which was observed between the isotopic ratios in UF5 products and those in a parent UF6 sample. These results suggested that the MPI/TOFMS method can be applied to the real-time analysis of separation factors in the molecular laser isotope separation of uranium by ionization of UF5 following the infrared photodissociation of UF6.

Okada, Y.; Kato, S.; Satooka, S.; Takeuchi, K.

1996-05-01

259

Determination of tellurium in urine by isotope dilution gas chromatography/mass spectrometry using (4-fluorophenyl)magnesium bromide as a derivatizing agent and a comparison with electrothermal atomic absorption spectrometry.  

PubMed

The antitumor drug AS-101 [ammoniumtrichloro (dioxoethylene-O,O')tellurate(IV)] is the first tellurium-containing compound that has been identified as possessing immunomodulating properties and minimal toxicity. We have developed a stable isotope dilution gas chromatography/mass spectrometry method using 120Te as an internal standard and (4-fluorophenyl)magnesium bromide as a derivatizing agent for Te determination in urine. The urine samples were digested using HNO3 + H2O2 prior to derivatization with lithium bis(trifluoroethyl)dithiocarbamate at a pH of 3. The trifluorodiethyldithiocarbamate of tellurium was reacted with the Grignard reagent in anhydrous diethyl ether to obtain Te-(FC6H4)2 for GC/MS analysis. All isotope ratio measurements were made by selected ion monitoring with a Finnigan MAT 8230 organic mass spectrometer using a 10-m fused silica capillary column. Overall percision values for the five major Te isotopes relative to 130Te were 0.6-3.1% when 10-ng samples of chelated Te were analyzed. No appreciable memory or carry-over effect was observed when two synthetic mixtures differing in 120Te:130Te ratios by a factor of 50 were sequentially analyzed. The isotope dilution GC/MS method was validated by determining Te in urine samples and comparing the values with electrothermal atomic absorption spectrometry. Te concentrations were determined in the 100-500 micrograms/L range with CVs of 1-4%. PMID:8210046

Aggarwal, S K; Kinter, M; Nicholson, J; Herold, D A

1994-04-15

260

Determination of 11-deoxycortisol (Reichstein's compound S) in human plasma by clinical isotope dilution mass spectrometry using benchtop gas chromatography-mass selective detection.  

PubMed

A first assay based on stable isotope dilution/gas chromatography-mass spectrometry (ID/GC-MS) has been developed for plasma 11-deoxycortisol (Reichstein's compound S), the leading hormonal marker of 11beta-hydroxylase deficiency. A suitable internal standard being unavailable, we synthesized dideuterated 11-deoxycortisol according to a newly devised synthetic procedure. 17,21-Dihydroxy-pregna-1,4-diene-3,20-dione underwent selective deuteration using Wilkinson's catalyst. Our product [1alpha,2alpha-2H2]11-deoxycortisol was obtained in good yield (35.6%) and high isotopic purity (0.1% 2H0, 99.9% 2H2). Structural confirmation was done by MS and NMR. Our plasma work up consisted of equilibration of plasma with internal standard ([1alpha,2alpha-2H2]11-deoxycortisol), solid phase extraction with Extrelut NT columns, a clean up step using Sephadex LH-20 mini columns and preparation of heptafluorobutyrates as derivatives. Quantification was achieved by selected ion monitoring of m/z 465.40 (analyte) and m/z 467.40 (internal standard). One hundred twenty picograms of 11-deoxycortisol gave a signal to noise ratio of 10. Calibration plot was linear. Spiking experiments showed good accuracy with relative errors <3.0%. Intraassay precision CV was 4.78% and interassay precision CV was 4.56%. We succeeded in integrating our new analyte into our already existing multisteroid ID/GC-MS plasma assay, which now, in its expanded version, is capable of determining all major diagnostic steroids of androgen related disorders in a single profile: 11-deoxycortisol, 17alpha-hydroxyprogesterone, testosterone, 4-androstenedione, 17alpha-hydroxypregnenolone, dehydroepiandrosterone, androstanediol and 5alpha-dihydrotestosterone. The diagnostic potential of our multisteroid ID/GC-MS assay, the small amounts of plasma (0.5 ml) required, the rapid and convenient sample work up, the application of benchtop GC-MS instrumentation, and highest specificity offered by mass spectrometric detection prove our assay suitable for routine clinical use, especially in pediatric endocrinology. PMID:12231120

Wudy, Stefan A; Hartmann, Michaela; Homoki, Janos

2002-09-01

261

Biological Cluster Mass Spectrometry  

PubMed Central

This article reviews the new physics and new applications of secondary ion mass spectrometry using cluster ion probes. These probes, particularly C60, exhibit enhanced molecular desorption with improved sensitivity owing to the unique nature of the energy-deposition process. In addition, these projectiles are capable of eroding molecular solids while retaining the molecular specificity of mass spectrometry. When the beams are microfocused to a spot on the sample, bioimaging experiments in two and three dimensions are feasible. We describe emerging theoretical models that allow the energy-deposition process to be understood on an atomic and molecular basis. Moreover, experiments on model systems are described that allow protocols for imaging on biological materials to be implemented. Finally, we present recent applications of imaging to biological tissue and single cells to illustrate the future directions of this methodology.

Winograd, Nicholas; Garrison, Barbara J.

2010-01-01

262

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

PubMed

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

Kawaguchi, Migaku; Eyama, Sakae; Takatsu, Akiko

2014-08-01

263

?13C of volatile organic compounds (VOCS) in airborne samples by thermal desorption-gas chromatography-isotope ratio-mass spectrometry (TD-GC-IR-MS)  

NASA Astrophysics Data System (ADS)

This paper is a preliminary investigation into the use of a thermal desorption-gas chromatography-isotope ratio mass spectrometry (TD-GC-IR-MS) method to determine stable carbon isotopic compositions ( ?13C) of low molecular-weight volatile organic compounds (VOCs) in airborne samples (e.g. industrial and car exhaust emissions) as a means of differentiating their sources in the environment. A TD-GC-IR-MS method for obtaining ?13C of VOCs (benzene, toluene, chlorobenzene, ethylbenzene, m-xylene and propylbenzene) in air samples has been optimised, and is proven to be both reproducible and linear. The ?13C of the VOC standards was found to be comparable (within analytical error) to that obtained from direct GC-IR-MS analysis. This novel method of VOC analysis is valuable in environmental and forensic investigations.

Turner, Nicole; Jones, Mark; Grice, Kliti; Dawson, Daniel; Ioppolo-Armanios, Marisa; Fisher, Steven J.

264

Contents of selected B vitamins in NIST SRM 3280 multivitamin/multielement tablets by liquid chromatography isotope dilution mass spectrometry.  

PubMed

There is increased interest in accurately assessing the total dietary intake of vitamins from all sources, including foods and dietary supplements. Consequently, a Dietary Supplement Ingredient Database (DSID), based upon analytical values, is being established by USDA with support of the Office of Dietary Supplements (ODS), NIH. The DSID necessitated the development of a new SRM, 3280--Multivitamin/Multimineral Tablets, by the National Institute of Standards and Technology (NIST), with support from the ODS. As a continuation of a long-term project to develop and validate new methods of determining water-soluble B vitamins in foods and dietary supplements, and as part of a collaborative effort with NIST to characterize SRM 3280, values for the vitamin contents of SRM 3280 have been generated by a liquid chromatographic isotope dilution mass spectrometric (LC/IDMS) method. Isotope-labeled ((13)C and/or (2)H) B vitamins (B1-thiamine, B6-pyridoxine, B3-nicotinamide, and B5-pantothenic acid) were obtained from commercial sources, with the support of the ODS/NIH. Our LC/IDMS method uses a C18 reversed phase column, an Agilent 1100 HPLC system, and a Quattro Micro triple-quad mass spectrometer (MS). B vitamin determination was achieved using a gradient LC profile combined with MS/MS detection in multiple reaction monitoring mode. Stock solutions of the isotope-labeled vitamins were calibrated against USP standard solutions. The SRM tablets, with added amounts of the four isotope-labeled B vitamins, were extracted and the vitamins simultaneously determined in a single LC run, in contrast with the single-component determinations performed via IDMS. Unknown vitamin concentrations were calculated by comparing the ratios of the integrated LC peaks at the different masses of the unlabeled and labeled vitamins. PMID:17646973

Chen, Pei; Ozcan, Mustafa; Wolf, Wayne R

2007-09-01

265

Method development for the redox speciation analysis of iron by ion chromatography-inductively coupled plasma mass spectrometry and carryover assessment using isotopically labeled analyte analogues.  

PubMed

An ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) method was developed for the redox speciation analysis of iron (Fe) based on in-column complexation of Fe(2+) and Fe(3+) by dipicolinic acid (DPA). The effects of column type, mobile phase composition and molecular ion interference were studied in the method optimization. The carryover of the target species in the IC-ICP-MS method was uniquely and effectively evaluated using isotopically enriched analogues of the analytes ((54)Fe(2+) and (57)Fe(3+)). Standard solutions of the enriched standards were injected into the system following analysis of a sample, and the ratios of the isotopes of iron in the enriched standards were calculated based on the chromatographic peak areas. The concentrations of the analytes carried over from the sample to the enriched standards were determined using the quantitative relationship in isotope dilution mass spectrometry (IDMS). In contrast to the routine way of evaluating carryover effect by injecting a blank solution after sample analysis, the use of isotopically enriched standards identified significant analyte carryover in the present method. Extensive experiments were carried out to systematically identify the source of the carryover and to eliminate the problem; the separation column was found to be the exclusive source. More than 95% of the analyte carryover was eliminated by reducing the length of the column. The detection limit of the IC-ICP-MS method (MDL) for the iron species was 2ngg(-1). The method was used to determine Fe(2+) and Fe(3+) in synthetic aqueous standard solutions and a beverage sample. PMID:24819017

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

2014-06-20

266

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

267

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

268

A novel approach to measure isotope ratios via multi-collector-inductively coupled plasma-mass spectrometry based on sample mixing with a non-enriched standard.  

PubMed

In this work, a novel approach to measure isotope ratios via multi-collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) for low amounts of target element is proposed. The methodology is based on mixing of the sample (target element isolate) with a non-enriched in-house standard, previously characterized for its isotopic composition. This methodology has been applied to isotopic analysis of Cu and of Fe in whole blood samples. For this purpose, different mixtures of sample + in-house standard were prepared and adjusted to a final concentration of 500 ?g/L of the target elements for isotopic analysis. ?(65)Cu, ?(56)Fe, and ?(57)Fe varied linearly as a function of the amount of in-house standard (or of sample) present in the mixture. The isotopic composition of the sample was calculated considering the isotope ratios measured for (i) the mixture and (ii) the in-house standard and (iii) the relative concentrations of target element contributed by the sample and the standard to the mixture, respectively. For validation purposes, the isotopic analysis of whole blood Cu was carried out using both the conventional (using 2 mL of whole blood) and the newly developed approach (using 500 ?L of whole blood). The ?(65)Cu values obtained using mixtures containing 40 % (200 ?g/L) of Cu from the blood samples and 60 % (300 ?g/L) of Cu from the in-house standard were in good agreement with the ?(65)Cu value obtained using the conventional approach (bias ?0.15?‰). PMID:24828978

Costas-Rodríguez, Marta; Lobo, Lara; Vanhaecke, Frank

2014-07-01

269

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

270

Fingerprint analysis using mass spectrometry  

US Patent & Trademark Office Database

The present invention is directed to a method for determining the presence of a residue on or within a fingerprint using matrix-assisted mass spectrometric techniques. The matrix-assisted mass spectrometric technique can be selected from Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Time-Of-Flight Mass Spectrometry (MALDI-TOF-MS) and/or Surface Assisted Laser Desorption/Ionisation Time-Of-Flight Mass Spectrometry (SALDI-TOF-MS).

2011-04-12

271

Development of cadmium/silver/palladium separation by ion chromatography with quadrupole inductively coupled plasma mass spectrometry detection for off-line cadmium isotopic measurements.  

PubMed

A separation method was investigated to perform off-line cadmium isotopic measurements on a (109)Ag transmutation target. Ion chromatography (IC) with Q ICPMS detection (quadrupole inductively coupled plasma mass spectrometry detection) was chosen to separate cadmium from the isobarically interfering elements, silver and palladium, present in the sample. The optimization of chromatographic conditions was particularly studied. Several anion and cation columns (Dionex AG11(®), CS10(®) and CS12(®)) were compared with different mobile phases (HNO(3), HCl). The separation procedure was achieved with a carboxylate-functionalized cation exchange CS12 column using 0.5 M HNO(3) as eluent. The developed technique yielded satisfactory results in terms of separation factors (greater than 5) and provides an efficient solution to obtain rapidly purified cadmium fractions (decontamination factors higher 100,000 for silver and palladium) which can directly be analyzed by multi collection inductively coupled plasma mass spectrometry (MC ICPMS). By applying the proposed procedure, accurate and precise cadmium isotope ratios were determined for the irradiated (109)Ag transmutation target. PMID:21703628

Gautier, C; Bourgeois, M; Isnard, H; Nonell, A; Stadelmann, G; Goutelard, F

2011-08-01

272

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

SciTech Connect

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

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

1984-05-01

273

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.

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

2010-01-01

274

Relative quantitation of glycans using stable isotopic labels 1-(d0/d5) phenyl-3-methyl-5-pyrazolone by mass spectrometry.  

PubMed

A deuterium reagent, 1-(d5) phenyl-3-methyl-5-pyrazolone (d5-PMP), has been synthesized and used for relative quantitative analysis of oligosaccharides by mass spectrometry (MS) using d0/d5-PMP stable isotopic labeling. Previously reported permethylation-based isotopic labels generate variable mass differences, and reductive amination-based isotopic labels cause a loss of some acid-labile groups in carbohydrates. In contrast, d0/d5-PMP stable isotopic labeling is performed at the reducing end of glycans under basic conditions without desialylation, and the mass difference (?m=10 Da) between the heavy form (d5-PMP derivative) and light form (d0-PMP derivative) of each glycan is invariable. When the two derivative forms of a glycan are mixed in equimolar amounts, a pair of peaks with a 10-Da mass differences is observed in the MS profile. The difference at relative intensity between the d0- and d5-PMP derivatives reflects the difference in quantity of glycans in two samples, making it possible to carry out both qualitative and relative quantitative analyses of glycans in glycomic studies. Application of this method on DP(2) to DP(6) maltodextrin oligosaccharides and N-linked glycans released from ribonuclease B and bovine fetuin demonstrates a 10-fold relative quantitative dynamic range, a satisfying reproducibility (coefficient of variation [CV] ? 8.34%), and good accuracy (relative error [RE] ? 5.1%) of the method. The suggested technique has been successfully applied for comparative quantitative analysis of free oligosaccharides in human and bovine milk. PMID:21803021

Zhang, Ping; Zhang, Ying; Xue, Xiangdong; Wang, Chenjian; Wang, Zhongfu; Huang, Linjuan

2011-11-01

275

5-Diethylamino-naphthalene-1-sulfonyl chloride (DensCl): a novel triplex isotope labeling reagent for quantitative metabolome analysis by liquid chromatography mass spectrometry.  

PubMed

We describe a new set of isotope reagents, (12)C4-, (12)C2(13)C2-, and (13)C4-5-diethylamino-naphthalene-1-sulfonyl chloride (DensCl), in combination with liquid chromatography Fourier-transform ion cyclotron resonance mass spectrometry (LC-FTICR-MS), for improved analysis of the amine- and phenol-containing submetabolome. The synthesis of the reagents is reported, and an optimized derivatization protocol for labeling amines and phenols is described. To demonstrate the utility of the triplex reagents for metabolome profiling of biological samples, urine samples collected daily from a healthy volunteer over a period of 14 days were analyzed. The overall workflow is straightforward, including differential isotope labeling of individual samples and a pooled sample that serves a global internal standard, mixing of the isotope differentially labeled samples and LC-MS analysis for relative metabolome quantification. Comparing to the dansyl chloride (DnsCl) duplex isotope reagents, the new triplex DensCl reagents offer the advantages of improved metabolite detectability due to enhanced sensitivity (i.e., about 1000 peak pairs detected by DensCl labeling vs about 600 peak pairs detected by DnsCl labeling) and analysis speed (i.e., simultaneous analysis of two comparative samples by DensCl vs only one comparative sample analyzed by DnsCl). PMID:24200037

Zhou, Ruokun; Guo, Kevin; Li, Liang

2013-12-01

276

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.

2007-01-11

277

Identification of honokiol metabolites in rats by the method of stable isotope cluster technique and ultra-high performance liquid chromatography/quadrupole-time-of-flight mass spectrometry.  

PubMed

Honokiol, a natural molecule isolated from Magnolia officinalis Rehd. et Wils., is widely known as an antitumor agent. In present work, an analysis of in vivo biotransformation and metabolites of honokiol has been performed by a combined method based on stable isotope cluster technique with honokiol-[(13)C6]-labeled and ultra-high performance liquid chromatography/quadrupole-time-of-flight-mass spectrometry (UHPLC/Q-TOF-MS). The metabolites could be easily identified by the determination of a chromatographically co-eluted pair of isotopomers (MS doublet peaks) with similar peak intensities and mass difference corresponding to that between isotope-labeled and non-isotope-labeled honokiol. A total of eighteen metabolites were detected and tentatively identified, fourteen of which were reported for the first time. The results indicated that the main metabolic pathways of honokiol in rats were hydroxylation, methylation, sulfation and glucuronidation. This study provided the first essential information on biotransformation and metabolites of honokiol in rats, which was very useful for further pharmacological and clinical studies of honokiol as a potent drug candidate. PMID:23792368

Lai, Huijun; Tang, Minghai; Liu, Juan; Dong, Yinfeng; Qiu, Neng; Li, Shucai; Ma, Liang; Yang, Jianhong; Song, Hang; Zhang, Yongkui; Peng, Aihua; Chen, Lijuan

2013-07-15

278

Isotope cluster-based compound matching in gas chromatography/mass spectrometry for non-targeted metabolomics.  

PubMed

Gas chromatography coupled to mass spectrometry (GC/MS) has emerged as a powerful tool in metabolomics studies. A major bottleneck in current data analysis of GC/MS-based metabolomics studies is compound matching and identification, as current methods generate high rates of false positive and false-negative identifications. This is especially true for data sets containing a high amount of noise. In this work, a novel spectral similarity measure based on the specific fragmentation patterns of electron impact mass spectra is proposed. An important aspect of these algorithmic methods is the handling of noisy data. The performance of the proposed method compared to the dot product, the current gold standard, was evaluated on a complex biological data set. The analysis results showed significant improvements of the proposed method in compound matching and chromatogram alignment compared to the dot product. PMID:23514283

Wegner, André; Sapcariu, Sean C; Weindl, Daniel; Hiller, Karsten

2013-04-16

279

New even-parity high-lying levels of Sm I and measurement of isotope shifts by two-color resonance ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

In this work, we investigate the even-parity high-lying levels of Sm I in the energy region 33136-33960 cm-1 by performing two-color three-photon resonance ionization spectroscopy in an atomic beam coupled to a time-of-flight mass spectrometer using two tunable pulsed dye lasers. We observe twenty-one new and confirm eight previously reported even-parity energy levels of Sm I in this spectral region. Absolute energies of these levels are determined with an accuracy of ±0.3 cm-1. Using electric dipole selection rule, total angular momentum (J-value) of the most newly observed levels is assigned uniquely. Further, employing two-color three-step resonance ionization mass spectrometry, we measure the isotope shift between 154Sm and 144Sm of sixteen high-lying levels with a moderate accuracy of ±30 mK.

Seema, A. U.; Mandal, P. K.; Rath, Asawari D.; Dev, Vas

2014-09-01

280

Mass spectrometry of cannabinoids.  

PubMed

The mechanism of fragmentation of cannabinoids to fragments m/e 314, 299, 271, 258, 246, 243, and 231 is given. Cannabidiol cannabinoidiol, cannabinol, delta6- and delta1-tetrahydrocannabinol, cannabichromene, cannabicyclol, derivatives with pentyl, propyl, and methyl side chains, their methyl ethers, and cis-trans and ortho-para isomers were analyzed by GLC-mass spectrometry using different energies for fragmentation during GLC elution. The following mechanism was distinguished: loss of a methyl radical, ring closure and rotation, McLafferty rearrangement, retro Diels-Alder, internal protonation, isomerization and internal bond formation, and one-step fragmentation to m/e 231. PMID:925901

Vree, T B

1977-10-01

281

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.

Han, Liang; Costello, Catherine E.

2014-01-01

282

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

283

A gas chromatography/pyrolysis/isotope ratio mass spectrometry system for high-precision deltaD measurements of atmospheric methane extracted from ice cores.  

PubMed

Air enclosures in polar ice cores represent the only direct paleoatmospheric archive. Analysis of the entrapped air provides clues to the climate system of the past in decadal to centennial resolution. A wealth of information has been gained from measurements of concentrations of greenhouse gases; however, little is known about their isotopic composition. In particular, stable isotopologues (deltaD and delta(13)C) of methane (CH(4)) record valuable information on its global cycle as the different sources exhibit distinct carbon and hydrogen isotopic composition. However, CH(4) isotope analysis is limited by the large sample size required and the demanding analysis as high precision is required. Here we present a highly automated, high-precision online gas chromatography/pyrolysis/isotope ratio monitoring mass spectrometry (GC/P/irmMS) technique for the analysis of deltaD(CH(4)). It includes gas extraction from ice, preconcentration, gas chromatographic separation and pyrolysis of CH(4) from roughly 500 g of ice with CH(4) concentrations as low as 350 ppbv. Ice samples with approximately 40 mL air and only approximately 1 nmol CH(4) can be measured with a precision of 3.4 per thousand. The precision for 65 mL air samples with recent atmospheric concentration is 1.5 per thousand. The CH(4) concentration can be obtained along with isotope data which is crucial for reporting ice core data on matched time scales and enables us to detect flaws in the measurement procedure. Custom-made script-based processing of MS raw and peak data enhance the system's performance with respect to stability, peak size dependency, hence precision and accuracy and last but not least time requirement. PMID:20155754

Bock, Michael; Schmitt, Jochen; Behrens, Melanie; Möller, Lars; Schneider, Robert; Sapart, Celia; Fischer, Hubertus

2010-03-15

284

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

SciTech Connect

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

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

1985-12-01

285

Trace analysis of acidic pharmaceutical residues in waters with isotope dilution gas chromatography-mass spectrometry via methylation derivatization.  

PubMed

Acidic pharmaceutical residues are pollutants of emerging concern and are generally monitored by HPLC-MS/MS. However, due to the limited separation efficiency of HPLC column and lack of suitable mass transition for confirmation analysis, some interference may not be separated completely and differentiated from ibuprofen, which may cause the results with interference, especially in sample with complex matrix. The objective of this study is to develop a sensitive and reliable method for the determination of acidic pharmaceutical residues in water samples by GC-MS with better resolution by using methylation derivatization and isotope dilution techniques. TMSDM, a mild reagent, was used as the derivatization reagent coupling with the isotope dilution technique, for the first time, to improve the precision and accuracy of the analytical method to determine the pharmaceutical residues in water. The MDLs for the five acidic organic compounds: ibuprofen, gemfibrozil, naproxen, ketoprofen and diclofenac were from 0.7 to 1.1 ng/L, with recoveries ranging from 93 to 110%. Alternative to the HPLC-MS/MS method, the developed GC-MS protocols provides an additional option for the analysis of acidic pharmaceutical residues in water, with better separation efficiency in reducing interferences from complicated sample matrix, for determination of ibuprofen residues. PMID:21872014

Hu, Ruikang; Yang, Zhaoguang; Zhang, Lifeng

2011-09-30

286

Acetate, propionate and butyrate in plasma: determination of the concentration and isotopic enrichment by gas chromatography/mass spectrometry with positive chemical ionization.  

PubMed

This study describes a rapid and simple method to determine short-chain fatty acid (SCFA) concentrations and their isotopic enrichments (M(0) + 1 and M(0) + 2) in human plasma. Sample preparation involves SCFA extraction and derivatization with 1-(tert-butyldimethylsilyl)imidazole. Gas chromatography/mass spectrometry was performed using chemical ionization with ammonia as the reagent gas. Outstanding resolution, excellent linearity and good detection limits were obtained. Inter-assay and intra-assay repeatability was below 10% and 3% respectively for SCFA concentration. Inter-assay repeatability was below 5%, 4%, 6%, and 14% for isotopic enrichment determination of [1-(13)C]acetate and [1,2-(13)C(2)]acetate, [1-(13)C]propionate and [1-(13)C]butyrate respectively, with intra-assay being below 6%. Such SCFA concentrations and isotopic enrichments were determined in the plasma of rats infused with a (13)C-labeled SCFA. The turnovers of acetate, propionate and butyrate in rats were 19 micromol kg(-1) min(-1), 2.6 micromol kg(-1) min(-1), 0.3 micromol kg(-1) min(-1) respectively. PMID:11473403

Pouteau, E; Meirim, I; Métairon, S; Fay, L B

2001-07-01

287

Stable isotope labeling for matrix-assisted laser desorption/ionization mass spectrometry and post-source decay analysis of ribonucleic acids.  

PubMed

Matrix-assisted laser desorption/ionization mass spectrometry is a powerful analytical tool for the structural characterization of oligonucleotides and nucleic acids. Here we report the application of stable isotope labeling for the simplified characterization of ribonucleic acids (RNAs). An (18)O label is incorporated at the 3'-phosphate of oligoribonucleotides during the enzymatic processing of intact RNAs. As implemented, a buffer solution containing a 50 : 50 mixture of H(2)O and (18)O-labeled H(2)O is used during endonuclease digestion. Upon digestion, characteristic doublets representative of the isotopic distribution of oxygen are noted for those products that contain 3'-phosphate groups. This approach is used to distinguish readily endonuclease digestion products from incomplete digestion products and non-specific cleavage products. In addition, RNase digestion products containing the characteristic isotopic doublet can be selected for further characterization by post-source decay (PSD) analysis. PSD products carrying the 3'-phosphate group will appear as a doublet, thereby simplifying fragment ion assignment. PMID:12938108

Berhane, Beniam T; Limbach, Patrick A

2003-08-01

288

The forensic analysis of office paper using carbon isotope ratio mass spectrometry--part 2: method development, validation and sample handling.  

PubMed

This paper describes the development and validation of a method for the analysis of office papers by measuring carbon isotopes using isotope ratio mass spectrometry (IRMS). The method development phase included testing protocols for storage, sample materials, set-up of the analytical run; and examining the effects of other paper examination procedures on IRMS results. A method validation was performed so that the Delta(plus) XP IRMS instrument (Thermo Finnigan, Bremen, Germany) with Flash EA™ 1112 could be used to measure document paper samples for forensic casework. A validation protocol that would meet international standards for laboratory accreditation (international standard ISO 17025) was structured so that the instruments performance characteristics could be observed. All performance characteristics measured were found to be within an acceptable range and an expanded measurement uncertainty for the measurement of carbon isotopes in paper was calculated at 0.26‰, with a coverage factor of 2. This method was utilized in a large-scale study, published as part one of this series, that showed that IRMS of document papers is useful as a chemical comparison technique for 80 gsm white office papers. PMID:23810570

Jones, Kylie; Benson, Sarah; Roux, Claude

2013-09-10

289

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

290

?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

291

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

292

Isotope signatures allow identification of chemically cross-linked peptides by mass spectrometry: a novel method to determine interresidue distances in protein structures through cross-linking.  

PubMed

Knowledge of protein structures and protein-protein interactions is essential for understanding of biological processes. Recent advances in protein cross-linking and mass spectrometry (MS) have shown significant potential to contribute to this area. Here we report a novel method to rapidly and accurately identify cross-linked peptides based on their unique isotope signature when digested in the presence of H(2)(18)O. This method overcomes the need for specially synthesized cross-linkers and/or multiple MS runs required by other techniques. We validated our method by performing a "blind" analysis of 5 proteins/complexes of known structure. Side chain repacking calculations using Rosetta show that 17 of our 20 positively identified cross-links fit the published atomic structures. The remaining 3 cross-links are likely due to protein aggregation. The accuracy and rapid throughput of our workflow will advance the use of protein cross-linking in structural biology. PMID:20476776

Zelter, Alex; Hoopmann, Michael R; Vernon, Robert; Baker, David; MacCoss, Michael J; Davis, Trisha N

2010-07-01

293

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

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

294

Application of amino acid analysis using hydrophilic interaction liquid chromatography coupled with isotope dilution mass spectrometry for peptide and protein quantification.  

PubMed

Amino acid analysis that is based on the use of hydrophilic interaction liquid chromatography (HILIC) coupled with isotope dilution mass spectrometry (IDMS) has been developed for the accurate quantification of underivatized amino acids from hydrolyzed protein/peptide. Sufficient separation of amino acids on a zwitterion chromatography (ZIC)-HILIC column was achieved after removal of chloride ions in the hydrolyzate. The detection limits and quantification limits as concentration of the four amino acids ranged from 0.003 to 0.04pmol microL(-1) and from 0.01 to 0.1pmol microL(-1), respectively. The analytical results for the certified reference materials, angiotensin I and bovine serum albumin (BSA), were satisfactory. Furthermore, the quantitative results by this method were compared with those by the commercially available precolumn method, derivatizd with aminoquinolylhydroxysuccinimidyl carbamate (AQC method), and better recovery and more precise data were obtained with this method. PMID:19665950

Kato, Megumi; Kato, Hisashi; Eyama, Sakae; Takatsu, Akiko

2009-10-01

295

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

PubMed

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

Wang, Jian-Hua; Guo, Cui

2010-07-01

296

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

Microsoft Academic Search

Isotope ratio mass spectrometry online coupled with capillary gas chromatography (GC–Py–IRMS) 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; Hervé Casabianca; Marie-Florence Grenier-Loustalot

2006-01-01

297

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

PubMed Central

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

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

2012-01-01

298

Ion Drift-Chemical Ionization Mass Spectrometry.  

National Technical Information Service (NTIS)

A method and apparatus for conducting mass spectrometry. The mass spectrometry may be accomplished by ion drift-chemical ionization mass spectrometry. One embodiment includes a chemical ionization mass spectrometer comprising an ion drift zone having an i...

R. Zhang

2005-01-01

299

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

300

Determination of Rhenium and Platinum in Natural Waters and Sediments, and Iridium in Sediments by Flow Injection Isotope Dilution Inductively Coupled Plasma Mass Spectrometry. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Methods have been developed to measure Re, Ir, and Pt in natural waters and sediments by isotope dilution inductively coupled plasma mass spectrometry (ID-ICPMS). The techniques have been applied to determination of the three elements in sediments, Pt in ...

D. C. Colodner E. A. Boyle J. M. Edmond

1993-01-01

301

Collision-induced dissociation of the A + 2 isotope ion facilitates glucosinolates structure elucidation by electrospray ionization-tandem mass spectrometry with a linear quadrupole ion trap.  

PubMed

An approach is presented that can be of general applicability for structural elucidation of naturally occurring glucosinolates (GLSs) in crude plant extracts based on the fragmentation of isotopic A and A + 2 peaks. The most important fragmentation pathways were studied by tandem mass spectrometry (MS(n), n = 2, 3) using a linear quadrupole ion trap (LTQ) upon GLSs separation by optimized reversed-phase liquid chromatography (RPLC) and electrospray ionization (ESI) in negative ion mode. As the LTQ MS analyzer ensures high sensitivity and linearity, the fragmentation behavior under collision induced dissociation (CID) of the isotopic peaks A and A + 2 as precursor ions was carefully examined. All GLSs (R-C(7)H(11)O(9)NS(2)(-)) share a common structure with at least two sulfur atoms and significant isotopic abundance of (34)S. Thus, dissociation of the +2 Da isotopomeric ions results in several fragment ion doublets containing a combination of (32)S and (34)S. Accordingly, their relative abundances allow one to speed up the structural recognition of GLSs with great confidence, as it produces more structurally informative ions than conventional tandem MS performed on A ions. This approach has been validated on known GLSs bearing two, three, four, and six sulfur atoms by comparing expected and measured isotopic peak abundance ratios (I(A)/I(A)(+2)). Both group- and compound-specific fragments were observed; the predominant pathway of fragmentation of GLSs gives rise to species having the following m/z values, [M - SO(3) - H](-), [M - 196 - H](-), [M - 178 - H](-), and [M - 162 - H](-) after H rearrangement from the R- side chain. The present strategy was successfully applied to extracts of rocket salad leaves (Eruca sativa L.), which was sufficient for the chemical identification of a not already known 6-methylsulfonyl-3-oxohexyl-GLS, a long-chain-length aliphatic glucosinolate, which contains three sulfurs and exhibits a deprotonated molecular ion at m/z 494.1. PMID:20521824

Cataldi, Tommaso R I; Lelario, Filomena; Orlando, Donatella; Bufo, Sabino A

2010-07-01

302

Rapid determination of plutonium isotopes in environmental samples using sequential injection extraction chromatography and detection by inductively coupled plasma mass spectrometry.  

PubMed

This article presents an automated method for the rapid determination of 239Pu and 240Pu in various environmental samples. The analytical method involves the in-line separation of Pu isotopes using extraction chromatography (TEVA) implemented in a sequential injection (SI) network followed by detection of isolated analytes with inductively coupled plasma mass spectrometry (ICP-MS). The method has been devised for the determination of Pu isotopes at environmentally relevant concentrations, whereby it has been successfully applied to the analyses of large volumes/amounts of samples, for example, 100-200 g of soil and sediment, 20 g of seaweed, and 200 L of seawater following analyte preconcentration. The investigation of the separation capability of the assembled SI system revealed that up to 200 g of soil or sediment can be treated using a column containing about 0.70 g of TEVA resin. The analytical results of Pu isotopes in the reference materials showed good agreement with the certified or reference values at the 0.05 significance level. Chemical yields of Pu ranged from 80 to 105%, and the decontamination factors for uranium, thorium, mercury and lead were all above 10(4). The duration of the in-line extraction chromatographic run was <1.5 h, and the proposed setup was able to handle up to 20 samples (14 mL each) in a fully automated mode using a single chromatographic column. The SI manifold is thus suitable for rapid and automated determination of Pu isotopes in environmental risk assessment and emergency preparedness scenarios. PMID:19722516

Qiao, Jixin; Hou, Xiaolin; Roos, Per; Miró, Manuel

2009-10-01

303

Mass spectrometry in ionospheric research.  

PubMed

Mass spectrometry played a key role in the development of the understanding of the earth's ionosphere. Of primary importance was its use for in situ atmospheric measurements of the ion and neutral composition of the atmosphere. Mass spectrometry has also played an essential role in the laboratory measurement of critical ionospheric molecular processes. Examples of both are given. PMID:17099890

Ferguson, Eldon E

2007-01-01

304

Biomedical accelerator mass spectrometry  

NASA Astrophysics Data System (ADS)

Ultrasensitive SIMS with accelerator based spectrometers has recently begun to be applied to biomedical problems. Certain very long-lived radioisotopes of very low natural abundances can be used to trace metabolism at environmental dose levels ( [greater-or-equal, slanted] z mol in mg samples). 14C in particular can be employed to label a myriad of compounds. Competing technologies typically require super environmental doses that can perturb the system under investigation, followed by uncertain extrapolation to the low dose regime. 41Ca and 26Al are also used as elemental tracers. Given the sensitivity of the accelerator method, care must be taken to avoid contamination of the mass spectrometer and the apparatus employed in prior sample handling including chemical separation. This infant field comprises the efforts of a dozen accelerator laboratories. The Center for Accelerator Mass Spectrometry has been particularly active. In addition to collaborating with groups further afield, we are researching the kinematics and binding of genotoxins in-house, and we support innovative uses of our capability in the disciplines of chemistry, pharmacology, nutrition and physiology within the University of California. The field can be expected to grow further given the numerous potential applications and the efforts of several groups and companies to integrate more the accelerator technology into biomedical research programs; the development of miniaturized accelerator systems and ion sources capable of interfacing to conventional HPLC and GMC, etc. apparatus for complementary chemical analysis is anticipated for biomedical laboratories.

Freeman, Stewart P. H. T.; Vogel, John S.

1995-05-01

305

An inductively coupled plasma mass spectrometry method for the quantification of yttrium-antibody based drugs using stable isotope tracing.  

PubMed

Targeted radioimmunotherapy has been recently clinically validated and approved for the treatment of cancer by the US Food and Drug Administration. This therapeutic approach employs monoclonal antibodies directed to cancer-related, cell-surface antigens coupled to beta-emitting nuclides. 90Y is one of the most useful radioisotopes in the development of antibody based radioimmunotherapy and evaluation of the pharmacokinetic profile for 90Y-radiopharmaceuticals is usually performed by radiochemical methods. In this work we have developed an alternative radioactive-free approach to evaluate pharmacokinetic profiles based on the inductively coupled plasma mass spectrometric (ICP-MS) quantification of 89Y. A highly sensitive and rapid method for the determination of yttrium in urine is described and applied to evaluate the urinary clearance of antibody-based drugs labeled with the stable isotope of yttrium, 89Y. This approach overcomes some important limitations for pre-clinical radioanalytical methods such as radiation hazards and radioactive waste disposal. Method development was performed by determining detection and quantification limits, and precision as repeatability and trueness. These performance parameters fulfilled the acceptance criteria for bioanalytical methods. PMID:17590870

Ciavardelli, Domenico; D'Anniballe, Gaetano; Nano, Giuseppe; Martin, Franck; Federici, Giorgio; Sacchetta, Paolo; Di Ilio, Carmine; Urbani, Andrea

2007-01-01

306

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.

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

2013-01-01

307

Structural Analysis of Guanylyl Cyclase-Activating Protein-2 (GCAP-2) Homodimer by Stable Isotope-Labeling, Chemical Cross-Linking, and Mass Spectrometry  

NASA Astrophysics Data System (ADS)

The topology of the GCAP-2 homodimer was investigated by chemical cross-linking and high resolution mass spectrometry. Complementary conducted size-exclusion chromatography and analytical ultracentrifugation studies indicated that GCAP-2 forms a homodimer both in the absence and in the presence of Ca2+. In-depth MS and MS/MS analysis of the cross-linked products was aided by 15 N-labeled GCAP-2. The use of isotope-labeled protein delivered reliable structural information on the GCAP-2 homodimer, enabling an unambiguous discrimination between cross-links within one monomer (intramolecular) or between two subunits (intermolecular). The limited number of cross-links obtained in the Ca2+-bound state allowed us to deduce a defined homodimeric GCAP-2 structure by a docking and molecular dynamics approach. In the Ca2+-free state, GCAP-2 is more flexible as indicated by the higher number of cross-links. We consider stable isotope-labeling to be indispensable for deriving reliable structural information from chemical cross-linking data of multi-subunit protein assemblies.

Pettelkau, Jens; Thondorf, Iris; Theisgen, Stephan; Lilie, Hauke; Schröder, Thomas; Arlt, Christian; Ihling, Christian H.; Sinz, Andrea

2013-12-01

308

Determination of the natural abundance delta15N of nortropane alkaloids by gas chromatography-isotope ratio mass spectrometry of their ethylcarbamate esters.  

PubMed

An important route for the detoxification of tropane alkaloids involves N-demethylation to the nor-compounds followed by further degradation. In order to study the mechanisms of the pertinent reactions, a suitable means to determine the isotope ratios of the substrates and products is required. However, the polarity and functionality of the nortropane compounds makes their analysis as free bases difficult. A method is described which allows both the quantification of nortropane alkaloids and the determination of their natural abundance delta(15)N values. The protocol exploits the derivatisation of the alkaloids by reaction with ethyl chloroformate in aqueous medium and the quantitative extraction of the ensuing ethylcarbamate esters. The improved chromatographic properties of these derivatives gives ample separation of the isomeric nortropine and norpseudotropine for measurement of their delta(15)N (per thousand) values by isotope ratio mass spectrometry interfaced to gas chromatography. Adequate separation could not be achieved with the underivatised compounds. Repeatability and precision are sufficient to allow differences in the delta(15)N values (Deltadelta(15)N) > 0.8 per thousand to be measured, with a standard deviation routinely approximately 0.3 per thousand. The methodology has been tested by determining the changes in the delta(15)N values of nortropine and norpseudotropine during degradation by cell suspension cultures of a Pseudomonas strain expressing a specific capacity for tropine catabolism. The precision and reproducibility are shown sufficient to allow the evolution of the delta(15)N values to be followed during the fermentation. PMID:20024532

Kosieradzka, Katarzyna; Tea, Illa; Gentil, Emmanuel; Robins, Richard J

2010-02-01

309

Re-evaluation of interferences of doubly charged ions of heavy rare earth elements on Sr isotopic analysis using multi-collector inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

We re-evaluate the interference of doubly charged heavy rare earth elements during Sr isotopic analysis using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). A series of mixed solutions of standard reference material SRM 987, rare earth elements, and Sr separated from rock reference materials are measured to assess the influence of isobaric interferences on the MC-ICP-MS analysis of Sr isotopes. After sample dissolution, conventional cation-exchange chromatography is employed for Sr purification of rock reference materials prior to MC-ICP-MS measurement. It has been demonstrated that if the natural abundances of Er and Yb are used to correct for doubly charged ion interferences on Sr, an overcorrection results. In contrast, the use of measured doubly charged ion ratios results in an accurate and precise correction of isobaric interference. This finding is confirmed by analytical results for several certified reference materials from mafic (basaltic) to felsic (granitic) silicate rocks. It is noteworthy that, because Er is more prone to doubly charged ion formation, it dominates over Yb doubly charged ions as an interference source.

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

2014-07-01

310

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 µg/kg and those for phthalates were in the range of 4.6-10.0 µg/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 µg/kg. PMID:25029399

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

2014-09-01

311

Quantification of (15)N-nitrate in urine with gas chromatography combustion isotope ratio mass spectrometry to estimate endogenous NO production.  

PubMed

The use of stable isotope labeled substrates and subsequent analysis of urinary nitrate, forms a noninvasive test for evaluation of the in vivo NO metabolism. The present paper describes a new method for simultaneous quantification of (15)N-nitrate and total nitrate with gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS). Nitrate, isolated from urine with a nitrate selective resin, was reduced to nitrite using copperized cadmium. Subsequently, Sudan I was formed by diazotation. Sudan II was added as internal standard, and both molecules were analyzed with GC-C-IRMS as tert-butyldimethylsilyl derivatives. The accuracy was determined during a recovery study of two different known nitrate concentrations and two (15)N-enrichments. A recovery of 101.6% and 103.9% for total nitrate and 107.6% and 91.2% for (15)N-nitrate was obtained, respectively. The validated method was applied on complete 72 h urine collections after intravenous administration of (15)N-nitrate and (15)N-arginine in humans. On average, 51.8% (47.0-71.0%) of administered (15)N-nitrate was excreted, while 0.68% (0.44-1.17%) of (15)N-arginine was metabolized to nitrate. In conclusion, this method can be used for accurate simultaneous determination of (15)N-nitrate and total nitrate concentrations in urine and can be applied in clinical studies for noninvasive evaluation of NO metabolism in vivo. PMID:20000695

Houben, Els; Hamer, Henrike M; Luypaerts, Anja; De Preter, Vicky; Evenepoel, Pieter; Rutgeerts, Paul; Verbeke, Kristin

2010-01-15

312

Tracing Cationic Nutrients from Xylem into Stem Tissue of French Bean by Stable Isotope Tracers and Cryo-Secondary Ion Mass Spectrometry[W][OA  

PubMed Central

Fluxes of mineral nutrients in the xylem are strongly influenced by interactions with the surrounding stem tissues and are probably regulated by them. Toward a mechanistic understanding of these interactions, we applied stable isotope tracers of magnesium, potassium, and calcium continuously to the transpiration stream of cut bean (Phaseolus vulgaris) shoots to study their radial exchange at the cell and tissue level with stem tissues between pith and phloem. For isotope localization, we combined sample preparation with secondary ion mass spectrometry in a completely cryogenic workflow. After 20 min of application, tracers were readily detectable to various degrees in all tissues. The xylem parenchyma near the vessels exchanged freely with the vessels, its nutrient elements reaching a steady state of strong exchange with elements in the vessels within 20 min, mainly via apoplastic pathways. A slow exchange between vessels and cambium and phloem suggested that they are separated from the xylem, parenchyma, and pith, possibly by an apoplastic barrier to diffusion for nutrients (as for carbohydrates). There was little difference in these distributions when tracers were applied directly to intact xylem via a microcapillary, suggesting that xylem tension had little effect on radial exchange of these nutrients and that their movement was mainly diffusive.

Metzner, Ralf; Schneider, Heike Ursula; Breuer, Uwe; Thorpe, Michael Robert; Schurr, Ulrich; Schroeder, Walter Heinz

2010-01-01

313

Determination of very low stable isotope enrichments of [(2)H(5)]-phenylalanine in chicken liver using liquid chromatography-tandem mass spectrometry (LC-MS/MS).  

PubMed

Stable isotope labeled amino acids are frequently used to examine nutritive effects on protein synthesis. This technique is characterized by tracing the incorporation of the label into newly synthesized proteins. In the present investigation, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of very low enrichment of protein-bound l-[(2)H(5)]-phenylalanine ([(2)H(5)]-phe) in chicken liver. The LC-MS/MS measurements were carried out in positive atmospheric pressure chemical ionization (APCI) mode. Two mass transitions each for [(2)H(5)]-phe (171.1/125.1 and 171.1/106.1) and l-phenylalanine (phe) (166.1/91.1 and 166.1/93.1) were chosen for quantification and qualification. Due to the high excesses of phe, less sensitive transitions were chosen in the case of phe. The separation was carried out on a phenyl-hexyl column using 0.1% formic acid as eluent A and methanol as eluent B. The method was calibrated with calibration standard solutions in the range of 0.01-0.5 mole percent excess (MPE). Linear regression analysis led to coefficients of determination (r(2)) greater than 0.9995. The method was applied on liver samples from experiments investigating nutritive effects on tissue protein synthesis in broiler chickens. These samples were analyzed with a gas chromatography-mass spectrometry (GC-MS) method and reanalyzed with the developed LC-MS/MS method one year later. Compared to GC-MS, the main advantages of the LC-MS/MS method are its higher selectivity as well as the elimination of the need to convert and derivatize the samples prior to measuring. PMID:23217318

Wilkerling, Katrin; Valenta, Hana; Kersten, Susanne; Dänicke, Sven

2012-12-12

314

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

315

Measurement of 13C and 15N isotope labeling by gas chromatography/combustion/isotope ratio mass spectrometry to study amino acid fluxes in a plant-microbe symbiotic association.  

PubMed

We have developed a method based on a double labeling with stable isotopes and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) analyses to study amino acid exchange in a symbiotic plant-microbe association. Isotopic precision was studied for 21 standards including 15 amino acid derivatives, three N-protected amino acid methyl esters, three amines and one international standard. High correlations were observed between the ?(13)C and ?(15)N values obtained by GC/C/IRMS and those obtained by an elemental analyzer (EA) coupled to an isotope ratio mass spectrometer (R(2) = 0.9868 and 0.9992, respectively). The mean precision measured was 0.04‰ for ?(13)C and 0.28‰ for ?(15)N (n = 15). This method was applied in vivo to the symbiotic relationship between alfalfa (Medicago sativa L.) and N(2)-fixing bacteria. Plants were simultaneously labeled over 10 days with (13)C-depleted CO(2) ((12)CO(2)), which was assimilated through photosynthesis by leaves, and (15)N(2) fixed via nodules. Subsequently, the C and N isotope compositions (i.e. ?(13)C and ?(15)N) of free amino acids were analyzed in leaves and nodules by GC/C/IRMS. The method revealed the pattern of C and N exchange between leaves and nodules, highlighting that ?-aminobutanoic acid and glycine may represent an important form of C transport from leaves to the nodules. The results confirmed the validity, reliability and accuracy of the method for assessing C and N fluxes between plants and symbiotic bacteria and support the use of this technique in a broad range of metabolic and fluxomic studies. PMID:21290446

Molero, Gemma; Aranjuelo, Iker; Teixidor, Pilar; Araus, José Luis; Nogués, Salvador

2011-03-15

316

Automated high-speed analysis of selected organic compounds in urban air by on-line isotopic dilution cryofocusing gas chromatography/mass spectrometry.  

PubMed

An automated environmental air monitor has been developed to measure selected organic compounds in urban air. The instrument is based on a cryofocusing-thermal desorption gas chromatographic mass spectrometry technique where the mass spectrometer is a slightly modified residual gas analyzer (RGA). The RGA was chosen as a detector because the whole system must be robust for long periods, with 24-h continuous air monitoring. RCA are extremely simple and seemed the most reliable mass spectrometers for this purpose. Moreover, because they have no physically limited ion source, contamination is considerably reduced, so maintenance intervals are longer.The gas chromatograph is equipped with a computer-controlled six-way sampling valve, with a 100-mL sampling loop and thermal desorption cold trap injector. Environmental air is enriched with an isotopically labeled internal standard in the sampling line. This internal standard is added with a validated, custom-made, permeation tube device. The "on-line" internal standard provides for high quality quantitative data because all variations in instrument sensitivity in cryofocusing or in thermal desorption efficiency are taken into account. High repetition rates (down to 5 min for a full analytical cycle) are obtained with the use of an isothermal gas chromatography program, microbore capillary column, and environmental air sampling during the gas chromatography run. PMID:24226389

Davoli, E; Cappellini, L; Maggi, M; Fanelli, R

1994-11-01

317

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

318

Determination of cyclophosphamide and ifosfamide in sewage effluent by stable isotope-dilution liquid chromatography-tandem mass spectrometry.  

PubMed

A reliable and specific method was developed for the determination of the cytotoxic drugs cyclophosphamide and ifosfamide in sewage effluent. The most successful combination was found to be Strata-X solid-phase extraction followed by Florisil® clean-up with analysis by liquid chromatography-tandem mass spectrometry. Quantification by internal standardisation was achieved using custom synthesised d4-cyclophophosphamide. The mass spectrometer was operated in highly selective reaction monitoring (HSRM) mode, which significantly reduced matrix noise and improved sensitivity. Although it suffered from some ionisation suppression, electrospray ionisation (ESI) was found to give an order of magnitude better sensitivity in terms of limit of detection than atmospheric pressure chemical ionisation (APCI). Using final effluent from two different sewage treatment plants, the method was validated following official European guidelines and shown to be a high performance tool for routine analysis at the sub-nanogram per litre level. Depending on the matrix, the limit of detection for cyclophosphamide was between 0.03 ng/L and 0.12 ng/L and for ifosfamide between 0.05 ng/L and 0.09 ng/L. For cyclophosphamide the accuracy and precision, tested at 1.7 ng/L, were 98-109% and ? 13%, CV respectively. For ifosfamide the accuracy and precision, tested at 1.1 ng/L, were 98-113% and ? 15% CV, respectively. Depending on the sample matrix the absolute recovery of the internal standard was between 57% and 70%. The method was tested by analysis of spot samples taken from the final effluent discharges of two sewage treatment plants; the first using a conventional trickling filter treatment process and second employing activated sludge followed by ultra violet treatment. Cyclophosphamide was detected at 0.19 ng/L at the first plant and at the second detected at 3.7 ng/L and 3.5 ng/L, before and after the UV treatment process; ifosfamide was not detectable at either plant. PMID:22014384

Llewellyn, N; Lloyd, P; Jürgens, M D; Johnson, A C

2011-11-25

319

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

320

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

321

Quantification of serum C-peptide by isotope-dilution liquid chromatography-tandem mass spectrometry: enhanced detection using chemical modification and immunoaffinity purification.  

PubMed

A method was developed to quantify human serum C-peptide by isotope-dilution mass spectrometry (ID MS). This new approach used immunoaffinity purification and chemical modification to improve the sensitivity which covered the wide range of reference interval of serum C-peptide. The immunoaffinity purification was performed using monoclonal antibody against human C-peptide that was immobilized on magnetic beads, and the purified C-peptide was chemically modified using 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS). With this method, the LC-MS/MS peak area increased 23-fold compared with the conventional purification by solid-phase extraction and without chemical modification. The limit of quantification was estimated to be 0.003ng on column, which was lower than previously reported. The validation study showed that (1) the response in the 0.003-2.9ng range on column was linear (regression coefficient, r(2)=0.9994), (2) the relative standard deviation (RSD) within and between days was inferior to 4.0%, and (3) the spike and recovery test showed the mean recoveries ranging between 99% and 108%. Comparison with an established commercial immunoassay showed high correlation (r(2)=0.9994) at serum concentration of 0.19-8.49ng/mL. These assessments suggest that this ID MS-based approach can quantify human serum C-peptide with high sensitivity and precision in the reference interval and find a potential use in the reference measurement procedure of serum C-peptide, allowing traceable measurement. This method may also generally be applied to peptide quantification in biological fluids with high sensitivity. PMID:24607695

Kinumi, Tomoya; Mizuno, Ryoko; Takatsu, Akiko

2014-03-15

322

Continuous Simultaneous Detection in Mass Spectrometry  

SciTech Connect

In mass spectrometry, several advantages can be derived when multiple mass-to-charge values are detected simultaneously. One such advantage is an improved duty cycle, which leads to superior limits of detection, better precision, shorter analysis times, and reduced sample sizes. A second advantage is the ability to reduce correlated noise by taking the ratio of two or more simultaneously collected signals, enabling greatly enhanced isotope ratio data. A final advantage is the elimination of spectral skew, leading to more accurate transient signal analysis. Here, these advantages are demonstrated by means of a novel Faraday-strip array detector coupled to a Mattauch-Herzog mass spectrograph. The same system is used to monitor elemental fractionation phenomena in laser ablation inductively coupled plasma mass spectrometry.

Schilling, G. D.; Andrade, Francisco J.; Barnes IV., James H.; Sperline, Roger P.; Denton, M. Bonner; Barinaga, Charles J.; Koppenaal, David W.; Hieftje, Gary M.

2007-10-15

323

Direct determination of methylmercury and inorganic mercury in biological materials by solid sampling-electrothermal vaporization-inductively coupled plasma-isotope dilution-mass spectrometry.  

PubMed

This paper reports on the use of solid sampling-electrothermal vaporization-inductively coupled plasma mass spectrometry (SS-EIV-ICPMS) for the direct and simultaneous determination of methylmercury and inorganic mercury in biological materials. The main advantage of this fast and sensitive method is that no sample preparation is required. In this way, the sample throughput can be considerably increased, problems of contamination and analyte losses are kept to a minimum and, even more important, the original chemical form of the different analyte species in the solid samples is preserved. To achieve this goal, a solid sample is inserted into a graphite furnace of the boat-in-tube type and is subsequently submitted to an appropriate temperature program, leading to the separate vaporization of methylmercury and inorganic mercury, which are transported into the ICP by means of an argon carrier gas. The separation was accomplished within 75 s. For the quantification of the two peaks, species-unspecific isotope dilution was used. For this purpose, a stable flow of argon loaded with gaseous Hg isotopically enriched in 200Hg was generated using a permeation tube that was constructed in-house. Its emission rate was determined by collecting the mercury released during a given time interval on a gold-coated silica absorber, after which the amount collected was released by heating of the absorber and determined by cold vapor atomic absorption spectrometry (CVAAS) and cold vapor atomic fluorescence spectrometry (CVAFS). A reference material from the Canadian National Research Council (NRC) (TORT-2) was used to assess the accuracy of the method. For the application of the method to samples with diverse mercury contents, the spike/sample ratio can be optimized by varying the emission rate of the permeation tube simply by adapting its temperature. To prove the feasibility of this approach, two reference materials (BCR 463 and DORM-2) with a methylmercury content more than 10 times higher than that of TORT-2 were also analyzed. The detection limits obtained for 1 mg of sample (2 ng g(-1) and 6 ng g(-1) for methylmercury and inorganic mercury, respectively) were found to be sufficiently low for this kind of application and are competitive when compared to other techniques. PMID:12175173

Gelaude, I; Dams, R; Resano, M; Vanhaecke, F; Moens, L

2002-08-01

324

Mass spectrometry of nanodiamonds.  

PubMed

Detonation nanodiamonds (NDs) were studied by time-of-flight mass spectrometry (TOF MS). The formation of singly charged carbon clusters, C(n) (+), with groups of clusters at n = 1-35, n approximately 160-400 and clusters with n approximately 8000 was observed. On applying either high laser energy or ultrasound, the position and intensity of the maxima change and a new group of clusters at n approximately 70-80 is formed. High carbon clusters consist of an even number of carbons while the percentage of odd-numbered clusters is quite low (< or =5-10%). On increasing the laser energy, the maximum of ionization (at n approximately 200 carbons) is shifted towards the lower m/z values. It is suggested that this is mainly due to the disaggregation of the original NDs. However, the partial destruction of NDs is also possible. The carbon clusters (n approximately 2-35) are partially hydrogenated and the average value of the hydrogenation was 10-30%. Trace impurities in NDs like Li, B, Fe, and others were detected at high laser energy. Several matrices for ionizing NDs were examined and NDs themselves can also be used as a matrix for the ionization of various organic compounds. When NDs were used as a matrix for gold nanoparticles, the formation of various gold carbides Au(m)C(n) was detected and their stoichiometry was determined. It was demonstrated that TOF MS can be used advantageously to analyze NDs, characterize their size distribution, aggregation, presence of trace impurities and surface chemistry. PMID:19280609

Houska, Jan; Panyala, Nagender Reddy; Peña-Méndez, Eladia Maria; Havel, Josef

2009-04-01

325

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

326

Quantitative determination of chloramphenicol in milk powders by isotope dilution liquid chromatography coupled to tandem mass spectrometry.  

PubMed

A method is described for the determination of residues of the illegal antibiotic chloramphenicol (CAP) in milk powders. The analyte is quantified by liquid chromatography coupled to electrospray ionisation tandem mass spectrometry (LC-ESI-MS-MS) operating in negative ion multiple reaction monitoring mode (MRM) after a liquid-liquid extraction followed by a clean-up step on solid phase extraction (SPE) cartridge. Because of the presence of two chlorine atoms in the CAP molecule, four specific transition reactions of CAP were monitored by MS-MS in selecting m/z 321 --> 257, 321 --> 152 (35Cl2) and m/z 323 --> 257, 323 --> 152 (37Cl35Cl). Two calibration curves were constructed by plotting the area ratio of m/z 321 --> 152 versus 326 --> 157 and m/z 321 --> 257 versus 326 --> 262 against their corresponding amount ratio. Indeed, even if m/z 321 --> 152 was found to give a higher MS-MS response (calibration curve used by default), an interfering chemical substance was sometimes observed for some milk extracts and not for the transition m/z 321 --> 257. The quantitation method was validated according to the European Union (EU) criteria for the analysis of veterinary drug residues at 0.1, 0.2 and 0.5 microg/kg concentration levels using d5-CAP as internal standard. The decision limit (CCalpha) and detection capability (CCbeta) of CAP in milk were calculated for m/z 321 --> 152 at 0.02 microg/kg and 0.03 microg/kg, respectively, and for m/z 321 --> 257 at 0.02 microg/kg and 0.04 microg/kg, respectively. At the lowest fortification level (i.e. 0.1 microg/kg), repeatability and within-laboratory reproducibility were calculated for m/z 321 --> 257 both at 0.02 microg/kg and for m/z 321 --> 152 at 0.03 and 0.05 microg/kg, respectively. Moreover, the measurement of uncertainty of the analytical method was calculated at the same spiking levels and falls within the precision values of the within-laboratory reproducibility. This method can be applied to several types of milk powders (e.g. full cream, skim) and can serve as a monitoring tool to avoid that unacceptable levels of residues of CAP enter the food chain. PMID:15553164

Guy, Philippe A; Royer, Delphine; Mottier, Pascal; Gremaud, Eric; Perisset, Adrienne; Stadler, Richard H

2004-10-29

327

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 ?¹³C values for the endogenous and exogenous steroids as well as their chromatographic retention times. The certified ?¹³C values of the reference calibrators were plotted in relation to measured m/z ¹³CO?/¹²CO? (i.e. R(45/44)) mass spectrometric signals of each calibrator. ?¹³C values of the sample steroids were calculated from the least squares fit through the calibration curve. The effect of the external calibration on ?¹³C 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(?¹³C)=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

328

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

PubMed

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

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

2004-08-25

329

Effects of conventional heating on the stability of major olive oil phenolic compounds by tandem mass spectrometry and isotope dilution assay.  

PubMed

The quality of olive oils is sensorially tested by accurate and well established methods. It enables the classification of the pressed oils into the classes of extra virgin oil, virgin oil and lampant oil. Nonetheless, it would be convenient to have analytical methods for screening oils or supporting sensorial analysis using a reliable independent approach based on exploitation of mass spectrometric methodologies. A number of methods have been proposed to evaluate deficiencies of extra virgin olive oils resulting from inappropriate technological treatments, such as high or low temperature deodoration, and home cooking processes. The quality and nutraceutical value of extra virgin olive oil (EVOO) can be related to the antioxidant property of its phenolic compounds. Olive oil is a source of at least 30 phenolic compounds, such as oleuropein, oleocanthal, hydroxytyrosol, and tyrosol, all acting as strong antioxidants, radical scavengers and NSAI-like drugs. We now report the efficacy of MRM tandem mass spectrometry, assisted by the isotope dilution assay, in the evaluation of the thermal stability of selected active principles of extra virgin olive oil. PMID:21124271

Attya, Mohamed; Benabdelkamel, Hicham; Perri, Enzo; Russo, Anna; Sindona, Giovanni

2010-01-01

330

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 9.06±0.13 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; Nóbrega, Joaquim A; Christopher, Steven J

2014-01-01

331

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

332

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

333

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

334

Combined method for the determination of ?-aminobutyric and ?-alanine in cerebrospinal fluid by stable isotope dilution mass spectrometry  

Microsoft Academic Search

A previously described method for the determination of GABA in CSF has been expanded to include both GABA and ?-ALA, using a single GC–MS analysis. A stable isotope labelled internal standard for ?-ALA was synthesised to achieve accurate quantification. This new combined method expands the diagnostic power compared to an isolated GABA measurement. Control values for free and total GABA

E. A Struys; W. S Guérand; H. J ten Brink; C Jakobs

1999-01-01

335

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

336

Measurement of ?18O, ?17O, and 17O-excess in water by off-axis integrated cavity output spectroscopy and isotope ratio mass spectrometry.  

PubMed

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 (17)O isotope in addition to (2)H and (18)O. Off-axis integrated cavity output spectroscopy (OA-ICOS) is demonstrated for accurate and precise measurements ?(18)O, ?(17)O, and (17)O-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 Greenland Ice Sheet Precipitation (GISP) demonstrate the precision and accuracy of OA-ICOS: ?(18)OVSMOW-SLAP = -24.74 ± 0.07‰ (1?) and ?(17)OVSMOW-SLAP = -13.12 ± 0.05‰ (1?). For comparison, the International Atomic Energy Agency (IAEA) value for ?(18)OVSMOW-SLAP is -24.76 ± 0.09‰ (1?) and an average of previously reported values for ?(17)OVSMOW-SLAP is -13.12 ± 0.06‰ (1?). Multiple (26) high-precision measurements of GISP provide a (17)O-excessVSMOW-SLAP of 23 ± 10 per meg (1?); an average of previously reported values for (17)O-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 ?(18)O, ?(17)O, and (17)O-excess. The ability to measure accurately ?(18)O, ?(17)O, and (17)O-excess in liquid water inexpensively and without sample conversion is expected to increase vastly the application of ?(17)O and (17)O-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

2013-11-01

337

Mass spectrometry. [in organic chemistry  

NASA Technical Reports Server (NTRS)

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 gas-phase ion chemistry as electron-impact ionization and decomposition, photoionization, field ionization and desorption, high-pressure mass spectrometry, ion cyclotron resonance, and isomerization reactions of organic ions. Applications of mass spectrometry are examined with respect to bio-oligomers and their constituents, biomedically important substances, microbiology, environmental organic analysis, and organic geochemistry.

Burlingame, A. L.; Shackleton, C. H. L.; Howe, I.; Chizhov, O. S.

1978-01-01

338

Biochemical Fractionation and Stable Isotope Dilution Liquid Chromatography-mass Spectrometry for Targeted and Microdomain-specific Protein Quantification in Human Postmortem Brain Tissue*  

PubMed Central

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

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

2012-01-01

339

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, Frédérique; Martin, Gilles G

2004-01-01

340

Thiazolidinedione bioactivation: a comparison of the bioactivation potentials of troglitazone, rosiglitazone, and pioglitazone using stable isotope-labeled analogues and liquid chromatography tandem mass spectrometry.  

PubMed

Troglitazone, a thiazolidinedione (TZD) type insulin sensitizer for the treatment of diabetes, was withdrawn from the U.S. market after several fatal cases of hepatotoxicity. Although the mechanism(s) of these idiosyncratic adverse reactions are not completely understood, circumstantial evidence suggests at least a partial contribution of reactive metabolite formation. Despite isolated case reports of hepatotoxicity, the other TZD derivatives pioglitazone and rosiglitazone are comparatively safe. Herein, we report on the bioactivation potential of these drugs and their TZD ring isotope-labeled 2-(15)N-3,4,5-(13)C(3) analogues in rat and human liver microsomes supplemented with glutathione (GSH). Screening for GSH adducts as surrogate markers for reactive intermediate formation was performed by liquid chromatography tandem mass spectrometry. Chemical characterization of the GSH conjugates was conducted by acquisition of their respective product ion spectra and the comparison between unlabeled and stable isotope-labeled TZD derivatives. The data suggest that all drugs undergo bioactivation processes via a common metabolic activation on the TZD ring, yielding disulfide type GSH conjugates as evidenced by the loss of labeled positions in the TZD moiety. Additional bioactivation processes leading to GSH adducts not involving TZD ring scission were evident for troglitazone. In human liver microsomes at low substrate concentrations, only troglitazone yielded a predominant GSH adduct not involving TZD ring scission. This property may contribute, together with other factors such as the relatively high dose administered as well as its potential to induce hepatic cholestasis and oxidative stress, to the hepatotoxicity of this drug. PMID:16918252

Alvarez-Sanchez, Rubén; Montavon, François; Hartung, Thomas; Pähler, Axel

2006-08-01

341

Influence of relative abundance of isotopes on depth resolution for depth profiling of metal coatings by laser ablation inductively coupled plasma mass spectrometry.  

PubMed

A systematic study on the influence of relative abundance of isotopes of elements in the coating (A(c)) and in the substrate (A(s)) on both shape of time-resolved signals and depth resolution (Delta z) was performed for depth profile analysis of metal coatings on metal substrates by ultraviolet (266 nm) nanosecond laser ablation inductively coupled plasma quadrupole mass spectrometry. Five coated samples with coating thicknesses of the same order of magnitude (20-30 microm) were tested: nickel coating on aluminium, chromium and copper, and steel coated with copper and zinc. A laser repetition rate of 1 Hz and a laser fluence of 21 J cm(-2) were used. Five different depth profile types were established, which showed a clear dependence on A(c)/A(s) ratio. In general, depth profiles obtained for ratios above 1-10 could not be used to determine Delta z. We found that Delta z increased non-linearly with A(c)/A(s) ratio. The best depth profile types, leading to highest depth resolution and reproducibility, were attained in all cases by using the isotopes with low/medium A(c) values and with the highest A(s) values. In these conditions, an improvement of up to 4 times in Delta z values was achieved. The average ablation rates were in the range from 0.55 microm pulse(-1) for copper coating on steel to 0.83 microm pulse(-1) for zinc coating on steel, and the Delta z values were between 2.74 microm for nickel coating on chromium and 5.91 microm for nickel coating on copper, with RSD values about 5-8%. PMID:20188923

Fariñas, Juan C; Coedo, Aurora G; Dorado, Teresa

2010-04-15

342

Online gas chromatography combustion/pyrolysis-isotope ratio mass spectrometry (HRGC-C/P-IRMS) of (+/-)-Dihydroactinidiolide from tea ( Camellia sinensis ) and rooibos tea ( Aspalathus linearis ).  

PubMed

Online capillary gas chromatography-isotope ratio mass spectrometry in both the combustion and the pyrolysis modes (HRGC-C/P-IRMS) was employed to perform authentication studies of the flavoring agent (+/-)-dihydroactinidiolide. Thus, the delta(13)C(V-PDB) and delta(2)H(V-SMOW) values of synthetic (ex synthetic beta-ionone and natural beta-carotene) as well as enzymatically (ex synthetic and natural beta-carotene) produced references were studied in comparison with those of the natural substance isolated from black (n = 17) and green teas (n = 6) ( Camellia sinensis ) as well as Rooibos tea ( Aspalathus linearis ) (n = 7). The isotope values determined for both the synthetic and enzymatically produced samples of (+/-)-dihydroactinidiolide reflected the influence of the origin of their educts. Hence, in cases when synthetic educts were used, the delta(13)C(V-PDB) and delta(2)H(V-SMOW) values ranged from -27.0 to -28.4 per thousand and from -28 to -169 per thousand, respectively, whereas the use of natural educts led to ranges from -30.3 to -31.6 per thousand and from -154 to -228 per thousand, respectively. As to the tea samples, delta(13)C(V-PDB) and delta(2)H(V-SMOW) values ranging from -29.0 to -34.1 per thousand and from -153 to -274 per thousand, respectively, were recorded for (+/-)-dihydroactinidiolide from black and green teas, whereas that from Rooibos tea showed (2)H/(1)H ratios ranging from -189 to -210 per thousand as well as slightly enriched values in the (13)C/(12)C ratios ranging from -24.4 to -27.1 per thousand. PMID:19514730

del Mar Caja, María; Preston, Christina; Menzel, Michael; Kempf, Michael; Schreier, Peter

2009-07-01

343

Characterization of diesel fuel by chemical separation combined with capillary gas chromatography (GC) isotope ratio mass spectrometry (IRMS).  

PubMed

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 diesel samples from different sources/locations. The ability to differentiate or correlate diesel samples could be valuable for discovering fuel tax evasion schemes or for environmental forensic studies. Two urea adduction-based techniques were used to isolate the n-alkanes from the fuel. Both carbon isotope ratio (?(13)C) and hydrogen isotope ratio (?D) values for the n-alkanes were then determined by CSIA in each sample. The samples investigated had ?(13)C values that ranged from -30.1‰ to -26.8‰, whereas ?D values ranged from -83‰ to -156‰. Plots of ?D versus ?(13)C 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 ?(13)C, ?D, or combined ?(13)C and ?D data was applied to extract the maximum information content. PCA scores plots could clearly differentiate the samples, thereby demonstrating the potential of this approach for distinguishing (e.g., fingerprinting) fuel samples using ?(13)C and ?D values. PMID:22967550

Harvey, Scott D; Jarman, Kristin H; Moran, James J; Sorensen, Christina M; Wright, Bob W

2012-09-15

344

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

345

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

346

Solid sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the direct determination of Hg in different materials using isotope dilution with a gaseous phase for calibration  

NASA Astrophysics Data System (ADS)

This paper evaluates the potential of electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICPMS) for the direct determination of Hg in solid samples, using a 200Hg-enriched gaseous phase for calibration based on isotope dilution. Three different samples were studied, BCR CRM 320 River sediment, IAEA-086 Hair and a real (wet) freshwater fish sample (M1). The samples selected show important differences in their matrix composition, and especially the fish sample constitutes a challenge as a result of its high water content (?80%). The main conclusion of the work is that the calibration approach investigated succesfully corrects for all the matrix effects (suppression) observed during Hg vaporization, allowing accurate values to be obtained in all cases. Moreover, practically the same operating conditions could be used for all sample types. The method finally proposed presents interesting features for the direct determination of this challenging element in solid samples, such as: a low sample consumption (a few milligrams), a high sample throughput (10 min/sample), a low limit of detection (6 ng g -1) and a reduced risk of analyte losses or contamination. Precision values depend on the homogeneity of the sample studied, and are typically in the vicinity of 10% RSD, except for the more inhomogenous river sediment (18% RSD).

Resano, M.; Gelaude, I.; Dams, R.; Vanhaecke, F.

2005-03-01

347

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

PubMed

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

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

2014-08-01

348

Quantification of 2-acetyl-1-pyrroline in rice by stable isotope dilution assay through headspace solid-phase microextraction coupled to gas chromatography-tandem mass spectrometry.  

PubMed

A new and convenient synthesis of 2-acetyl-1-pyrroline (2AP), a potent flavor compound in rice, and its ring-deuterated analog, 2-acetyl-1-d(2)-pyrroline (2AP-d(2)), was reported. A stable isotope dilution assay (SIDA), involving headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-positive chemical ionization-ion trap-tandem mass spectrometry (GC-PCI-IT-MS-MS), was developed for 2AP quantification. A divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was used for HS-SPME procedure and parameters affecting analytes recovery, such as extraction time and temperature, pH and salt, were studied. The repeatability of the method (n=10) expressed as relative standard deviation (RSD) was 11.6%. A good linearity was observed from 5.9 to 779 ng of 2AP (r(2)=0.9989). Limits of detection (LOD) and quantification (LOQ) for 2AP were 0.1 and 0.4 ng g(-1) of rice, respectively. The recovery of spiked 2AP from rice matrix was almost complete. The developed method was applied to the quantification of 2AP in aerial parts and grains of scented and non-scented rice cultivars. PMID:20800726

Maraval, Isabelle; Sen, Kemal; Agrebi, Abdelhamid; Menut, Chantal; Morere, Alain; Boulanger, Renaud; Gay, Frédéric; Mestres, Christian; Gunata, Ziya

2010-08-24

349

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

PubMed Central

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

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

2014-01-01

350

Studies on the analysis of 25-hydroxyvitamin D(3) by isotope-dilution liquid chromatography-tandem mass spectrometry using enzyme-assisted derivatisation.  

PubMed

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-(2)H6]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 chromatography-tandem mass spectrometry. Recovery experiments for 25-hydroxyvitamin D3 performed on adult human serum give recovery of 102-106%. 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

2014-04-11

351

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

NASA Astrophysics Data System (ADS)

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

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

2004-10-01

352

Determination of bisphenol A, triclosan and their metabolites in human urine using isotope-dilution liquid chromatography-tandem mass spectrometry.  

PubMed

Bisphenol A (BPA) and triclosan (TCS) are ubiquitous environmental phenols exhibiting endocrine disrupting activities that may be involved in various health disorders in humans. There is a need to measure separately free forms and conjugated metabolites because only the former are biologically active. We have developed sensitive methods using isotope-dilution liquid chromatography-tandem mass spectrometry for individual measurements of free BPA and TCS as well as their metabolites, BPA glucuronide (BPAG), BPA monosulfate (BPAS), BPA disulfate (BPADS), TCS glucuronide (TCSG) and TCS sulfate (TCSS) in urine. Comparative analyses of urine samples from 46 volunteers living in the Quebec City area using the new methods and a GC-MS/MS method previously used in our laboratory revealed very strong correlations for total BPA (Spearman's rs=0.862, p<0.0001) and total TCS concentrations (rs=0.942, p<0.0001). Glucuronide metabolites were the most abundant BPA and TCS species in urine samples (>94% of total urinary concentrations). Unconjugated TCS concentrations represented a small proportion of total TCS species (median=1.6%) but its concentration was likely underestimated due to losses by adsorption to the surface of polypropylene tubes used for sample storage. To our knowledge, we are the first to report levels of free, sulfated and glucuronidated TCS levels in human urine. PMID:24835763

Provencher, Gilles; Bérubé, René; Dumas, Pierre; Bienvenu, Jean-François; Gaudreau, Eric; Bélanger, Patrick; Ayotte, Pierre

2014-06-27

353

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.

2011-05-25

354

Advances in structure elucidation of small molecules using mass spectrometry  

Microsoft Academic Search

The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and\\u000a bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern\\u000a mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage\\u000a MS(n) capability, as well as hybrid mass spectrometric and orthogonal

Tobias Kind; Oliver Fiehn

2010-01-01

355

Application of routine estimation of Pb isotopic ratios by inductively coupled plasma mass spectrometry for studying the Pb origin in hair of children living in polluted areas. A pilot study  

Microsoft Academic Search

The analysis of 204Pb, 206Pb, 207Pb and 208Pb isotope ratios for environmental Pb markers (leaded gasoline, air-borne particulate matter, house window dust) and hair of children was undertaken by the routine quadrupole inductively coupled argon plasma mass spectrometry (Q-ICP-MS). Hair samples collected from 10-year-old children living in Krakow in 1995 and 35 randomly selected children, aged 11, both sexes were

H. Barton; Z. Zachwieja; S. D'Ilio; S. Caroli

2000-01-01

356

Strategy combining separation of isotope-labeled unfolded proteins and matrix-assisted laser desorption\\/ionization mass spectrometry analysis enables quantification of a wide range of serum proteins  

Microsoft Academic Search

A novel strategy for the quantitative profiling of serum proteome is described. It includes an ammonium sulfate depletion of the serum, an affordable stable isotope labeling chemistry for samples with a large amount of protein, separation of the unfolded proteins, and relative quantification by matrix-assisted laser desorption\\/ionization (MALDI) mass spectrometry (MS). Labeling of unfolded proteins was performed using normal (D0)

Wei-Li Liao; Illarion V. Turko

2008-01-01

357

Producing SI-traceable reference values for Cd, Cr and Pb amount contents in polyethylene samples from the Polymer Elemental Reference Material (PERM) project using isotope dilution mass spectrometry  

Microsoft Academic Search

The present paper describes the certification of the amount content of Cd, Cr and Pb in two different polyethylene materials\\u000a within the third phase of the Polyethylene Elemental Reference Material (PERM) project. The analytical procedure to establish\\u000a the reference values for Cd, Cr and Pb amount contents in these materials is based on isotope dilution mass spectrometry used\\u000a as a

J. Vogl; D. Liesegang; M. Ostermann; J. Diemer; M. Berglund; C. R. Quétel; P. D. P. Taylor; K. G. Heumann

2000-01-01

358

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

359

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

PubMed Central

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

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

2011-01-01

360

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

361

Relative quantitation of protein nitration by liquid chromatography-mass spectrometry using isotope-coded dimethyl labeling and chemoprecipitation  

PubMed Central

Protein nitration has been recognized as an important biomarker for nitroxidative stress associated with various diseases. While identification of protein targets for nitration is important, its quantitative profiling also is necessary to understand the biological impact of this low-abundance posttranslational modification. We have previously reported an efficient and straightforward enrichment method for nitropeptides to reduce sample complexity and permit unambiguous site-specific identifications by LC–MS analyses. This approach relies on two chemical derivatization steps: specifically reductive methylation of aliphatic amines and, then, conversion of nitrotyrosines to the corresponding aminotyrosines before their selective capture by a solid-phase reagent we introduced previously. Hence, the method inherently offers the opportunity for relative quantitation of nitropeptides by using isotopic variants of formaldehyde for reductive methylation. This simple method was tested via LC–MS analyses of differently N-methylated nitropeptides and nitroubiquitin as a model nitroprotein enriched from human serum albumin digest and from human plasma, respectively.

Guo, Jia; Prokai-Tatrai, Katalin; Prokai, Laszlo

2012-01-01

362

Ion Trap Mass Spectrometry  

SciTech Connect

This chapter describes research conducted in a few research groups in the 1990s in which RF quadrupole ion trap mass spectrometers were coupled to a powerful atomic ion source, the inductively coupled plasma used in conventional ICP-MS instruments. Major section titles for this chapter are: RF Quadrupole Ion Traps Features of RF Quadrupole Ion Trap Mass Spectrometers Selective Ion Trapping methods Inductively Coupled Plasma Source Ion Trap Mass Spectrometers

Eiden, Greg C.

2005-09-01

363

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

364

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

365

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

366

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.

Watrous, Jeramie D.; Dorrestein, Pieter C.

2013-01-01

367

Application of mass spectrometry for metabolite identification.  

PubMed

Metabolism studies play a pivotal role in drug discovery and development. Characterization of metabolic "hot-spots" as well as reactive and pharmacologically active metabolites is critical to designing new drug candidates with improved metabolic stability, toxicological profile and efficacy. Metabolite identification in the preclinical species used for safety evaluation is required in order to determine whether human metabolites have been adequately tested during non-clinical safety assessment. From an instrumental standpoint, high performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) dominates all analytical tools used for metabolite identification. The general strategies employed for metabolite identification in both drug discovery and drug development settings together with sample preparation techniques are reviewed herein. These include a discussion of the various ionization methods, mass analyzers, and tandem mass spectrometry (MS/MS) techniques that are used for structural characterization in a modern drug metabolism laboratory. Mass spectrometry-based techniques, such as stable isotope labeling, on-line H/D exchange, accurate mass measurement to enhance metabolite identification and recent improvements in data acquisition and processing for accelerating metabolite identification are also described. Rounding out this review, we offer additional thoughts about the potential of alternative and less frequently used techniques such as LC-NMR/MS, CRIMS and ICPMS. PMID:16787159

Ma, Shuguang; Chowdhury, Swapan K; Alton, Kevin B

2006-06-01

368

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

Microsoft Academic Search

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

Pilar Montero; Fernando Bea

1998-01-01

369

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

370

UPb isotope geochronology of zircon: evaluation of the laser probe-inductively coupled plasma mass spectrometry technique  

Microsoft Academic Search

Using a laser ablation microprobe-inductively coupled plasma mass spectrometer (LP-ICPMS) we have determined 238U, 207Pb, 206Pb, and 204Pb abundances of several zircon populations whose ages have previously been measured by other techniques (principally ion microprobe). Ages of the samples range from 360–2800 Ma. A frequency quadrupled Nd-YAG UV laser (266 nm) which produces pit sizes of 10–15 ?m was used

Takafumi Hirata; Robert W. Nesbitt

1995-01-01

371

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

372

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 Institüt, 6300 Giessen Germany.

M. Epherre; G. Audi; C. Thibault; R. Klapisch; G. Huber; F. Touchard; H. Wollnik

1980-01-01

373

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.

Rubakhin, Stanislav S.; Sweedler, Jonathan V.

2011-01-01

374

Simultaneous quantification of S-adenosyl methionine and S-adenosyl homocysteine in human plasma by stable-isotope dilution ultra performance liquid chromatography tandem mass spectrometry.  

PubMed

S-adenosyl methionine (SAM) is an important methyl group donor that is formed from methionine. S-adenosyl homocysteine (SAH) is formed after demethylation of SAM and represents a potent inhibitor of many methyltransferases. We developed an improved stable-isotope dilution ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantification of SAM and SAH in biological samples. The method comprises a phenylboronic acid-containing solid-phase extraction procedure, serving for binding and clean-up of SAM and SAH. After extraction, samples were separated and detected using either a HPLC SymmetryShield RP(18) or an Acquity UPLC BEH C(18) column with a HPLC-MS/MS or an UPLC-MS/MS system. The best results were obtained by Acquity UPLC BEH C(18) column. In plasma samples, the estimated intraassay coefficients of variation (CVs) for SAM and SAH were 3.3% and 3.9%, respectively, the interassay CVs were 10.1% for SAM and 8.3% for SAH. Mean recovery of SAM and SAH at two different concentrations was 100.0% for SAM and 101.7% for SAH. The quantification limits were 0.5 and 0.7nmol/L for SAM and SAH, respectively. In 31 plasma samples, the mean concentrations (SD) were 85.5 (11.1)nmol/L for SAM and 13.3 (5.0)nmol/L for SAH with a SAM/SAH ratio of 7.0 (1.8). The new UPLC-MS/MS method showed very high sensitivity and selectivity for SAM and SAH, low CVs and fast sample preparation (40 samples in 60min) and analysis time (3min). This new assay can be used for large-scale clinical studies. PMID:19828381

Kirsch, Susanne H; Knapp, Jean-Pierre; Geisel, Jürgen; Herrmann, Wolfgang; Obeid, Rima

2009-11-15

375

Strong anion exchange liquid chromatographic separation of protein amino acids for natural 13C-abundance determination by isotope ratio mass spectrometry.  

PubMed

Amino acids are the building blocks of proteins and the analysis of their (13)C abundances is greatly simplified by the use of liquid chromatography (LC) systems coupled with isotope ratio mass spectrometry (IRMS) compared with gas chromatography (GC)-based methods. To date, various cation exchange chromatography columns have been employed for amino acid separation. Here, we report strong anion exchange chromatography (SAX) coupled to IRMS with a Liquiface interface for amino acid ?(13)C determination. Mixtures of underivatised amino acids (0.1-0.5 mM) and hydrolysates of representative proteins (prawns and bovine serum albumin) were resolved by LC/IRMS using a SAX column and inorganic eluents. Background inorganic carbon content was minimised through careful preparation of alkaline reagents and use of a pre-injector on-line carbonate removal device. SAX chromatography completely resolved 11 of the 16 expected protein amino acids following acid hydrolysis in underivatised form. Basic and neutral amino acids were resolved with 35 mM NaOH in isocratic mode. Elution of the aromatic and acidic amino acids required a higher hydroxide concentration (180 mM) and a counterion (NO?3-, 5-25 mM). The total run time was 70 min. The average ?(13)C precision of baseline-resolved peaks was 0.75‰ (range 0.04 to 1.06‰). SAX is a viable alternative to cation chromatography, especially where analysis of basic amino acids is important. The technology shows promise for (13)C amino acid analysis in ecology, archaeology, forensic science, nutrition and protein metabolism. PMID:21213362

Abaye, Daniel A; Morrison, Douglas J; Preston, Tom

2011-02-15

376

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

SciTech Connect

The antimicrobial compound triclocarban (TCC; 3,4,4'-trichlorocarbanilide; CAS-bar 101-20-2) is a high-production-volume chemical, recently suggested to cause widespread contamination of US water resources. To test this hypothesis, we developed an isotope dilution liquid chromatography