Sample records for isotope mass spectrometry

  1. Isotope Ratio Mass Spectrometry.

    PubMed

    Muccio, Zeland; Jackson, Glen P

    2009-02-01

    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

  2. Isotope dilution mass spectrometry

    Microsoft Academic Search

    Klaus G. Heumann

    1992-01-01

    In the past isotope dilution mass spectrometry (IDMS) has usually been applied using the formation of positive thermal ions of metals. Especially in calibrating other analytical methods and for the certification of standard reference materials this type of IDMS became a routine method. Today, the progress in this field lies in the determination of ultra trace amounts of elements, e.g.

  3. Isotope ratio mass spectrometry in nutrition research

    Microsoft Academic Search

    Luke

    1994-01-01

    Many of the biochemical pathways and processes that form the foundation of modern nutrition research was elucidated using stable isotopes as physiological tracers. Since the discovery of stable isotopes, improvements and innovations in mass spectrometry and chromatography have led to greatly expanded applications. This research project was designed to evaluate gas chromatography\\/combustion\\/isotope ratio mass spectrometry (GC\\/C\\/IRMS) as a tool for

  4. Accelerator mass spectrometry of plutonium isotopes

    Microsoft Academic Search

    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

    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

  5. Isotope ratio mass spectrometry in nutrition research

    SciTech Connect

    Luke, A.H.

    1994-12-31

    Many of the biochemical pathways and processes that form the foundation of modern nutrition research was elucidated using stable isotopes as physiological tracers. Since the discovery of stable isotopes, improvements and innovations in mass spectrometry and chromatography have led to greatly expanded applications. This research project was designed to evaluate gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) as a tool for isotopic tracer studies and to delineate the operational parameters for the analysis of {sup 13}C-labeled cholesterol, leucine and {alpha}-ketoisocaproate. The same isotope ratio mass spectrometer was then used as the base instrument for the ratio mass spectrometer was then used as the base instrument for the development of two additional inlet systems: a continuous-flow inlet for the analyses of {sup 13}C and {sup 18}O as CO{sub 2} and a filament inlet for on-line combustion and isotopic analysis of non-volatile organic compounds. Each of these three inlets was evaluated and their utility in nutrition research illustrated. GC/C/IRMS was used to analyze cholesterol, leucine and {alpha}-ketoisocaproate with good accuracy, precision and little isotopic memory. For all three compounds the detection limits achieved well surpassed currently used technologies. For compounds that can be well separated by GC, GC/C/IRMS is a valuable analytical tool. The continuous-flow inlet provided good accuracy and precision for measurements of {sup 13}CO{sub 2} from breath tests and {sup 18}O as CO{sub 2} from total energy expenditure tests. Most importantly, the continuous-flow inlet increased sample throughput by at least a factor of three over conventional analytical techniques. The filament inlet provided accurate and precise {sup 13}C ratio measurements of both natural abundance and enriched standards of non-volatile organic compounds of physiological interest.

  6. Calcium isotope analysis by mass spectrometry.

    PubMed

    Boulyga, Sergei F

    2010-01-01

    The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abundances in natural samples has challenged the analysts for more than three decades. Practically all Ca isotopes suffer from significant isobaric interferences, whereas low-abundant isotopes can be particularly affected by neighboring major isotopes. The extent of natural variations of stable isotopes appears to be relatively limited, and highly precise techniques are required to resolve isotopic effects. Isotope fractionation during sample preparation and measurements and instrumental mass bias can significantly exceed small isotope abundance variations in samples, which have to be investigated. Not surprisingly, a TIMS procedure developed by Russell et al. (Russell et al., 1978. Geochim Cosmochim Acta 42: 1075-1090) for Ca isotope measurements was considered as revolutionary for isotopic measurements in general, and that approach is used nowadays (with small modifications) for practically all isotopic systems and with different mass spectrometric techniques. Nevertheless, despite several decades of calcium research and corresponding development of mass spectrometers, the available precision and accuracy is still not always sufficient to achieve the challenging goals. The present article discusses figures of merits of presently used analytical methods and instrumentation, and attempts to critically assess their limitations. In Sections 2 and 3, mass spectrometric methods applied to precise stable isotope analysis and to the determination of (41)Ca are described. Section 4 contains a short summary of selected applications, and includes tracer experiments and the potential use of biological isotope fractionation in medical studies, paleoclimatic and paleoceanographic, and other terrestrial as well as extraterrestrial investigations. PMID:19551693

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

    NASA Astrophysics Data System (ADS)

    Betti, Maria

    2005-04-01

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

  8. Hydrogen isotope analysis by quadrupole mass spectrometry

    Microsoft Academic Search

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

    1981-01-01

    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 =

  9. Hydrogen isotope analysis by quadrupole mass spectrometry

    Microsoft Academic Search

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

    1981-01-01

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

  10. Calcium Isotope Analysis by Mass Spectrometry

    Microsoft Academic Search

    S. Boulyga; S. Richter

    2010-01-01

    The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abundances in natural samples has challenged the analysts

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

    NASA Astrophysics Data System (ADS)

    Ireland, Trevor R.

    2013-01-01

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

  12. High Precision Isotope Petrography by Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Yurimoto, H.

    2009-12-01

    Since Shimizu et al. (GCA 1978) have demonstrated that in-situ micro-scale analyses of isotopes and trace elements in minerals were succeeded by secondary ion mass spectrometry (SIMS), geochemists develop the SIMS methods towards isotope mapping with spatial resolution of electron microscopy level. At present, high spatial resolution imaging by SIMS has been succeeded by scanning methods using ion-probe and by projection methods using stigmatic secondary ion optics. For high precision isotope analysis with high spatial resolution, intense secondary ions are indispensable for each pixel in the image. However, one of the major instrumental problems is that there were no adequate detectors for this purpose. In order to solve the problem, we proposed a two-dimensional solid-state ion detector called SCAPS (Takayanagi et al., IEEE Trans. 2003). The development is still continued and performances of recent SCAPS detector is achieved to: (1) direct sensitive for ions from single ion, (2) no dead time, and (3) perfect linearity of five orders of magnitude dynamic range. Installing the SCAPS detector into a stigmatic SIMS of Cameca ims-1270, we obtained oxygen isotope (delta-O-17 and delta-O-18) images of about 100 micrometer field with ~500 nm resolution and ~5 permil precision. The performance of high precision isotope imaging have might not be matured, but overcome a hurdle towards isotope petrography (Isotopography). We apply this isotopography to research fields of (a) survey of isotope anomalous micrograins and (b) isotope micro-distribution in rocks and minerals. In the application (a), we found in-situ presolar grains in meteorites (Nagashima et al., Nature 2004) and cosmic symplectite (COS) from a meteorite (Sakamoto et al., Science 2007). In the application (b), we showed how distribute oxygen isotopic compositions in micro-scale within CAI minerals (Yurimoto et al., Rev. Mineral. 2008; Fagan et al., in prep.). In combination fields of (a) and (b), we demonstrated how preserves Martian water and how contaminates terrestrial water in Martian meteorites (Greenwood et al., GRL 2008). These new knowledge from isotopography provides novel perspective of earth and planetary sciences.

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

    E-print Network

    other isotope-ratio mass spectrometers in which LN2 is used as a moisture trap for gaseous hydrogen to a VG Micromass model 602 dual inlet isotope-ratio mass spectrometer.3,4,6 Gaseous hydrogenCaution on the Use of Liquid Nitrogen Traps in Stable Hydrogen Isotope-Ratio Mass Spectrometry

  14. Advances in Isotope Ratio Mass Spectrometry and Required Isotope Reference Materials

    PubMed Central

    Vogl, Jochen

    2013-01-01

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

  15. Efficient Analysis of Mass Spectrometry Data Using the Isotope Wavelet

    SciTech Connect

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

    2007-09-18

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

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

    PubMed Central

    Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

    2012-01-01

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

  17. Quantitating isotopic molecular labels with accelerator mass spectrometry.

    PubMed

    Vogel, John S; Love, Adam H

    2005-01-01

    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

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

    Microsoft Academic Search

    Matthew S. Fantle; Thomas D. Bullen

    2009-01-01

    The use of isotopes to understand the behavior of metals in geological, hydrological, and biological systems has rapidly expanded in recent years. One of the mass spectrometric techniques used to analyze metal isotopes is thermal ionization mass spectrometry, or TIMS. While TIMS has been a useful analytical technique for the measurement of isotopic composition for decades and TIMS instruments are

  19. Overcoming spectral overlap in isotopic analysis via single- and multi-collector ICP–mass spectrometry

    Microsoft Academic Search

    Frank Vanhaecke; Luc Moens

    2004-01-01

    For isotope ratio applications where an internal isotope ratio precision >0.05–0.1% relative standard deviation suffices, single-collector inductively coupled plasma mass spectrometry (ICPMS) is fit-for-purpose, but for detecting more subtle variations in the natural isotopic composition of a target element, only multi-collector ICPMS (MC-ICPMS) can compete with thermal ionization mass spectrometry (TIMS). While as a result of the extensive sample preparation

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

    PubMed

    Hilkert; Douthitt; Schlüter; Brand

    1999-07-01

    Of all the elements, hydrogen has the largest naturally occurring variations in the ratio of its stable isotopes (D/H). It is for this reason that there has been a strong desire to add hydrogen to the list of elements amenable to isotope ratio monitoring gas chromatography/mass spectrometry (irm-GC/MS). In irm-GC/MS the sample is entrained in helium as the carrier gas, which is also ionized and separated in the isotope ratio mass spectrometer (IRMS). Because of the low abundance of deuterium in nature, precise and accurate on-line monitoring of D/H ratios with an IRMS requires that low energy helium ions be kept out of the m/z 3 collector, which requires the use of an energy filter. A clean mass 3 (HD(+.)) signal which is independent of a large helium load in the electron impact ion source is essential in order to reach the sensitivity required for D/H analysis of capillary GC peaks. A new IRMS system, the DELTA(plus)XL(trade mark), has been designed for high precision, high accuracy measurements of transient signals of hydrogen gas. It incorporates a retardation lens integrated into the m/z 3 Faraday cup collector. Following GC separation, the hydrogen bound in organic compounds must be quantitatively converted into H(2) gas prior to analysis in the IRMS. Quantitative conversion is achieved by high temperature conversion (TC) at temperatures >1400 degrees C. Measurements of D/H ratios of individual organic compounds in complicated natural mixtures can now be made to a precision of 2 per thousand (delta notation) or, better, with typical sample amounts of approximately 200 ng per compound. Initial applications have focused on compounds of interest to petroleum research (biomarkers and natural gas components), food and flavor control (vanillin and ethanol), and metabolic studies (fatty acids and steroids). Copyright 1999 John Wiley & Sons, Ltd. PMID:10407302

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

    E-print Network

    Sessions, Alex L.

    Determination of the H3 Factor in Hydrogen Isotope Ratio Monitoring Mass Spectrometry Alex L spectrometer.1 Since H3 + is not resolved from HD+ by typical isotope ratio mass spectrometers, a correction, is a parameter required in high- precision, mass spectrometric analyses of hydrogen iso- topic abundances. When H

  2. High-precision gas chromatography-combustion isotope ratio mass spectrometry at low signal levels

    Microsoft Academic Search

    Keith J. Goodman; J. Thomas Brenna

    1995-01-01

    Precision and accuracy of gas chromatography-combustion isotope ratio mass spectrometry are investigated for sample levels down to about 5 pmol C in fatty acid methyl ester mixtures spanning 1000-fold in concentration. Precision and accuracy of isotope ratios diverge rapidly for conventional summation methods, and become unusable below 30 pmol material on column. At lower levels, mean isotope ratios were statistically

  3. Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS) — Preliminary study on TATP and PETN

    Microsoft Academic Search

    Sarah J. Benson; Christopher J. Lennard; Philip Maynard; David M. Hill; Anita S. Andrew; Claude Roux

    2009-01-01

    The application of isotopic techniques to investigations requiring the provision of evidence to a Court is limited. The objective of this research was to investigate the application of light stable isotopes and isotope ratio mass spectrometry (IRMS) to solve complex forensic cases by providing a level of discrimination not achievable utilising traditional forensic techniques.Due to the current threat of organic

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

    Microsoft Academic Search

    Chloé Nadia Maréchal; Philippe Télouk; Francis Albarède

    1999-01-01

    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

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

    E-print Network

    Hilscher, Larry Wayne

    1985-01-01

    of the requiremer ts for the degree of MASTEP. QF SCIENCE August 1985 Major Subject: Chemistry MEASUREMENT OF POSITIONAL ISOTOPE EXCHANGE RATES IN ENZYME CATALYZED REACTIONS BY FAST ATOM BOMBARDMENT MASS SPECTROMETRY A Thesis LARRY NAYNE HILSCHER Approved...MEASUREMENT OF POSITIONAL ISOTOPE EXCHANGE RATES IN ENZYME CATALYZED REACTIONS BY FAST ATOM BOMBARDMENT MASS SPECTROMETRY A Thesis by LARRY NAYNE HILSCHER Submitted to the Gradu te College of Texas A&M University in partial fulfil" mert...

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

    PubMed

    Ireland, Trevor R

    2013-01-01

    Mass spectrometry is fundamental to measurements of isotope ratios for applications in isotope geochemistry, geochronology, and cosmochemistry. Magnetic-sector mass spectrometers are most common because these provide the best precision in isotope ratio measurements. Where the highest precision is desired, chemical separation followed by mass spectrometric analysis is carried out with gas (noble gas and stable isotope mass spectrometry), liquid (inductively coupled plasma mass spectrometry), or solid (thermal ionization mass spectrometry) samples. Developments in in situ analysis, including ion microprobes and laser ablation inductively coupled plasma mass spectrometry, have opened up issues concerning homogeneity according to domain size, and allow ever smaller amounts of material to be analyzed. While mass spectrometry is built solidly on developments in the 20th century, there are new technologies that will push the limits in terms of precision, accuracy, and sample efficiency. Developments of new instruments based on time-of-flight mass spectrometers could open up the ultimate levels of sensitivity per sample atom. PMID:23387630

  7. Split-Field Drift Tube/Mass Spectrometry and Isotopic Labeling Techniques for Determination of Single Amino Acid Polymorphisms

    E-print Network

    Clemmer, David E.

    Split-Field Drift Tube/Mass Spectrometry and Isotopic Labeling Techniques for Determination/mass spectrometry and isotopic labeling techniques is evaluated as a means of identifying single amino acid, and the peptides are labeled at primary amine groups [using either a light (H3)- or heavy (D3)-isotopic reagent

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

    Microsoft Academic Search

    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

    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

  9. Characterization of tetramethylammonium hydroxide thermochemolysis products of near-shore marine sediments using gas chromatography\\/mass spectrometry and gas chromatography\\/combustion\\/isotope ratio mass spectrometry

    Microsoft Academic Search

    Jerry Pulchan; Teofilo A. Abrajano; Robert Helleur

    1997-01-01

    The study describes the application of gas chromatography\\/mass spectrometry (GC\\/MS) and gas chromatography\\/combustion\\/isotope ratio mass spectrometry (GC\\/C\\/IRMS) to characterize the molecular and compound-specific stable carbon isotope composition, respectively, of tetramethylammonium hydroxide (TMAH) thermochemolysis products of organic matter present in marine sediments. The objective of the study was to examine the usefulness of TMAH thermochemolysis products in identifying organic markers of

  10. Quantitation of metal isotope ratios by laser desorption time-of-flight mass spectrometry.

    PubMed

    Koumenis, I L; Vestal, M L; Yergey, A L; Abrams, S; Deming, S N; Hutchens, T W

    1995-12-15

    Laser desorption time-of-flight mass spectrometry (LD/TOF-MS) is evaluated for the determination of stable metal isotope ratios. The isotope ratios of five metal ions (Cu, Ca, Mg, Fe, Zn) in atomic absorption standard solutions and two metal ions (Ca, Mg) in human serum samples are determined. With an existing LD/TOF-MS instrument we show that the technique can overcome the difficulties of the most commonly used methods for measuring metal isotope ratios: (1) all metals are ionizable without surface treatment, thus overcoming the major drawback of thermal ionization mass spectrometry (TIMS); (2) there is no matrix involved to interfere with the metal ion detection, thus overcoming the major disadvantage of inductively coupled plasma mass spectrometry (ICPMS); (3) there is no interference from hydride ions, a major disadvantage of fast atom bombardment secondary ionization mass spectrometry; (4) a mixture of metals can be detected simultaneously using a single laser wavelength, overcoming the major disadvantage of resonance ionization mass spectrometry; (5) accuracy and precision comparable to ICPMS can be achieved with the current instrumentation; (6) precision comparable to TIMS is feasible; and most importantly (7) high precision can be achieved on very small quantities of material because the LD/TOF-MS instrument permits all masses to be monitored simultaneously and very small differences in isotope ratio can be detected. PMID:8633789

  11. Analytical techniques in biomedical stable isotope applications: (isotope ratio) mass spectrometry or infrared spectrometry?

    Microsoft Academic Search

    Frans Stellaard; Henk Elzinga

    2005-01-01

    An overview is presented of biomedical applications of stable isotopes in general, but mainly focused on the activities of the Center for Liver, Digestive and Metabolic Diseases of the University Medical Center Groningen. The aims of metabolic studies in the areas of glucose, fat, cholesterol and protein metabolism are briefly explained, as well as the principle of breath testing and

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

    PubMed

    Bidica, Nicolae

    2012-01-01

    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

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

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2005-01-01

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

  14. Microfabrication of high temperature micro-reactors for continuous flow isotope ratio mass spectrometry

    Microsoft Academic Search

    Herbert J. TobiasJ; J. Thomas Brenna

    2010-01-01

    Robust, high temperature micro-reactors for on-line conversion of organic compounds were microfabricated in high purity fused\\u000a silica to enable stable isotopic compositional analysis of individual compounds in mixtures using advanced gas chromatography\\u000a (GC) separation techniques, such as fast GC and comprehensive 2D GC, coupled to isotope ratio mass spectrometry (IRMS). These\\u000a micro-reactors could also be manufactured at larger channel dimensions

  15. Accuracy and long-term reproducibility of lead isotopic measurements by multiple-collector inductively coupled plasma mass spectrometry using an external method for correction of mass discrimination

    Microsoft Academic Search

    Mark Rehkämperab; Alex N. Halliday

    1998-01-01

    The precision of isotopic measurements of Pb by thermal ionization mass spectrometry (TIMS) is limited by the fact that this element does not possess an invariant isotope ratio that can be used for the correction of mass fractionation by internal normalization. Multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) can overcome this limitation, because with plasma ionization, elements with overlapping mass

  16. Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS) — Discrimination of ammonium nitrate sources

    Microsoft Academic Search

    Sarah J. Benson; Christopher J. Lennard; Philip Maynard; David M. Hill; Anita S. Andrew; Claude Roux

    2009-01-01

    An evaluation was undertaken to determine if isotope ratio mass spectrometry (IRMS) could assist in the investigation of complex forensic cases by providing a level of discrimination not achievable utilising traditional forensic techniques. The focus of the research was on ammonium nitrate (AN), a common oxidiser used in improvised explosive mixtures.The potential value of IRMS to attribute Australian AN samples

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  18. DETERMINATION OF NIACIN IN FOOD MATERIALS BY ISOTOPE DILUTION MASS SPECTROMETRY

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. Simultaneous stable carbon isotopic analysis of wine glycerol and ethanol by liquid chromatography coupled to isotope ratio mass spectrometry.

    PubMed

    Cabañero, Ana I; Recio, Jose L; Rupérez, Mercedes

    2010-01-27

    A novel procedure was established for the simultaneous characterization of wine glycerol and ethanol (13)C/(12)C isotope ratio, using liquid chromatography/isotope ratio mass spectrometry (LC-IRMS). Several parameters influencing separation of glycerol and ethanol from wine matrix were optimized. Results obtained for 35 Spanish samples exposed no significant differences and very strong correlations (r = 0.99) between the glycerol (13)C/(12)C ratios obtained by an alternative method (gas chromatography/isotope ratio mass spectrometry) and the proposed new methodology, and between the ethanol (13)C/(12)C ratios obtained by the official method (elemental analyzer/isotope ratio mass spectrometry) and the proposed new methodology. The accuracy of the proposed method varied from 0.01 to 0.19 per thousand, and the analytical precision was better than 0.25 per thousand. The new developed LC-IRMS method it is the first isotopic method that allows (13)C/(12)C determination of both analytes in the same run directly from a liquid sample with no previous glycerol or ethanol isolation, overcoming technical difficulties associated with complex sample treatment and improving in terms of simplicity and speed. PMID:20025274

  20. Profiling thiol redox proteome using isotope tagging mass spectrometry.

    PubMed

    Parker, Jennifer; Zhu, Ning; Zhu, Mengmeng; Chen, Sixue

    2012-01-01

    Pseudomonas syringae pv. tomato strain DC3000 not only causes bacterial speck disease in Solanum lycopersicum but also on Brassica species, as well as on Arabidopsis thaliana, a genetically tractable host plant(1,2). The accumulation of reactive oxygen species (ROS) in cotyledons inoculated with DC3000 indicates a role of ROS in modulating necrotic cell death during bacterial speck disease of tomato(3). Hydrogen peroxide, a component of ROS, is produced after inoculation of tomato plants with Pseudomonas(3). Hydrogen peroxide can be detected using a histochemical stain 3'-3' diaminobenzidine (DAB)(4). DAB staining reacts with hydrogen peroxide to produce a brown stain on the leaf tissue(4). ROS has a regulatory role of the cellular redox environment, which can change the redox status of certain proteins(5). Cysteine is an important amino acid sensitive to redox changes. Under mild oxidation, reversible oxidation of cysteine sulfhydryl groups serves as redox sensors and signal transducers that regulate a variety of physiological processes(6,7). Tandem mass tag (TMT) reagents enable concurrent identification and multiplexed quantitation of proteins in different samples using tandem mass spectrometry(8,9). The cysteine-reactive TMT (cysTMT) reagents enable selective labeling and relative quantitation of cysteine-containing peptides from up to six biological samples. Each isobaric cysTMT tag has the same nominal parent mass and is composed of a sulfhydryl-reactive group, a MS-neutral spacer arm and an MS/MS reporter(10). After labeling, the samples were subject to protease digestion. The cysteine-labeled peptides were enriched using a resin containing anti-TMT antibody. During MS/MS analysis, a series of reporter ions (i.e., 126-131 Da) emerge in the low mass region, providing information on relative quantitation. The workflow is effective for reducing sample complexity, improving dynamic range and studying cysteine modifications. Here we present redox proteomic analysis of the Pst DC3000 treated tomato (Rio Grande) leaves using cysTMT technology. This high-throughput method has the potential to be applied to studying other redox-regulated physiological processes. PMID:22472559

  1. Profiling Thiol Redox Proteome Using Isotope Tagging Mass Spectrometry

    PubMed Central

    Parker, Jennifer; Zhu, Ning; Zhu, Mengmeng; Chen, Sixue

    2012-01-01

    Pseudomonas syringae pv. tomato strain DC3000 not only causes bacterial speck disease in Solanum lycopersicum but also on Brassica species, as well as on Arabidopsis thaliana, a genetically tractable host plant1,2. The accumulation of reactive oxygen species (ROS) in cotyledons inoculated with DC3000 indicates a role of ROS in modulating necrotic cell death during bacterial speck disease of tomato3. Hydrogen peroxide, a component of ROS, is produced after inoculation of tomato plants with Pseudomonas3. Hydrogen peroxide can be detected using a histochemical stain 3'-3' diaminobenzidine (DAB)4. DAB staining reacts with hydrogen peroxide to produce a brown stain on the leaf tissue4. ROS has a regulatory role of the cellular redox environment, which can change the redox status of certain proteins5. Cysteine is an important amino acid sensitive to redox changes. Under mild oxidation, reversible oxidation of cysteine sulfhydryl groups serves as redox sensors and signal transducers that regulate a variety of physiological processes6,7. Tandem mass tag (TMT) reagents enable concurrent identification and multiplexed quantitation of proteins in different samples using tandem mass spectrometry8,9. The cysteine-reactive TMT (cysTMT) reagents enable selective labeling and relative quantitation of cysteine-containing peptides from up to six biological samples. Each isobaric cysTMT tag has the same nominal parent mass and is composed of a sulfhydryl-reactive group, a MS-neutral spacer arm and an MS/MS reporter10. After labeling, the samples were subject to protease digestion. The cysteine-labeled peptides were enriched using a resin containing anti-TMT antibody. During MS/MS analysis, a series of reporter ions (i.e., 126-131 Da) emerge in the low mass region, providing information on relative quantitation. The workflow is effective for reducing sample complexity, improving dynamic range and studying cysteine modifications. Here we present redox proteomic analysis of the Pst DC3000 treated tomato (Rio Grande) leaves using cysTMT technology. This high-throughput method has the potential to be applied to studying other redox-regulated physiological processes. PMID:22472559

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

    PubMed

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

    2015-06-01

    Isotope ratio mass spectrometry (IRMS) has been used in numerous fields of forensic science in a source inference perspective. This review compiles the studies published on the application of isotope ratio mass spectrometry (IRMS) to the traditional fields of forensic science so far. It completes the review of Benson et al. [1] and synthesises the extent of knowledge already gathered in the following fields: illicit drugs, flammable liquids, human provenancing, microtraces, explosives and other specific materials (packaging tapes, safety matches, plastics, etc.). For each field, a discussion assesses the state of science and highlights the relevance of the information in a forensic context. Through the different discussions which mark out the review, the potential and limitations of IRMS, as well as the needs and challenges of future studies are emphasized. The paper elicits the various dimensions of the source which can be obtained from the isotope information and demonstrates the transversal nature of IRMS as a tool for source inference. PMID:25909994

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

    NASA Astrophysics Data System (ADS)

    Suen, Timothy Wu

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

  4. Isotope ratio mass spectrometry coupled to liquid and gas chromatography for wine ethanol characterization.

    PubMed

    Cabañero, Ana I; Recio, Jose L; Rupérez, Mercedes

    2008-10-01

    Two new procedures for wine ethanol 13C/12C isotope ratio determination, using high-performance liquid chromatography and gas chromatography isotope ratio mass spectrometry (HPLC/IRMS and GC/IRMS), have been developed to improve isotopic methods dedicated to the study of wine authenticity. Parameters influencing separation of ethanol from wine matrix such as column, temperature, mobile phase, flow rates and injection mode were investigated. Twenty-three wine samples from various origins were analyzed for validation of the procedures. The analytical precision was better than 0.15 per thousand, and no significant isotopic fractionation was observed employing both separative techniques coupled to IRMS. No significant differences and a very strong correlation (r = 0.99) were observed between the 13C/12C ratios obtained by the official method (elemental analyzer/isotope ratio mass spectrometry) and the proposed new methodology. The potential advantages of the developed methods over the traditional one are speed (reducing time required from hours to minutes) and simplicity. In addition, these are the first isotopic methods that allow 13C/12C determination directly from a liquid sample with no previous ethanol isolation, overcoming technical difficulties associated with sample treatment. PMID:18798196

  5. Analysis of [U-13C6]glucose in human plasma using liquid chromatography/isotope ratio mass spectrometry compared with two other mass spectrometry techniques.

    PubMed

    Schierbeek, Henk; Moerdijk-Poortvliet, Tanja C W; van den Akker, Chris H P; te Braake, Frans W J; Boschker, Henricus T S; van Goudoever, Johannes B

    2009-12-01

    The use of stable isotope labelled glucose provides insight into glucose metabolism. The 13C-isotopic enrichment of glucose is usually measured by gas chromatography/mass spectrometry (GC/MS) or gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). However, in both techniques the samples must be derivatized prior to analysis, which makes sample preparation more labour-intensive and increases the uncertainty of the measured isotopic composition. A novel method for the determination of isotopic enrichment of glucose in human plasma using liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) has been developed. Using this technique, for which hardly any sample preparation is needed, we showed that both the enrichment and the concentration could be measured with very high precision using only 20 microL of plasma. In addition, a comparison with GC/MS and GC/IRMS showed that the best performance was achieved with the LC/IRMS method making it the method of choice for the measurement of 13C-isotopic enrichment in plasma samples. PMID:19902413

  6. In-Vivo Zinc Metabolism by Isotope Ratio Mass Spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The purpose of this chapter is to highlight some of the methodological and technical issues surrounding the in vivo use of stable isotopes and to provide examples of how such studies have advanced our knowledge of human zinc metabolism. The advantages and disadvantages of the currently available in...

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

    NASA Astrophysics Data System (ADS)

    Gilevska, Tetyana; Gehre, Matthias; Richnow, Hans

    2014-05-01

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

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

    Microsoft Academic Search

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

    1991-01-01

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

  9. Analysis of quantization error in high-precision continuous-flow isotope ratio mass spectrometry

    Microsoft Academic Search

    Gavin L. Sacks; Christopher J. Wolyniak; J. Thomas Brenna

    2003-01-01

    High-precision isotope ratio mass spectrometry (IRMS) systems are equipped with digitizers that deliver effective maximum digitization depths of 16 to 24bits; however, there are no analyses of the proper board depth required to retain high precision in continuous-flow techniques. We report an experimental and theoretical evaluation of quantization error in continuous-flow IRMS (CF-IRMS). CO2 samples (100pmol–30nmol) were injected into a

  10. Selective isotope determination of lanthanum by diode-laser-initiated resonance-ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Young, J. P.; Shaw, R. W.

    1995-08-01

    A diode-laser step has been incorporated into a resonance-ionization mass spectrometry optical excitation process to enhance the isotopic selectivity of the technique. Lanthanum isotope ratio enhancements as high as 103 were achieved by use of a single-frequency cw diode laser tuned to excite the first step of a three-step excitation-ionization optical process; the subsequent steps were excited by use of a pulsed dye laser. Applying the same optical technique, we measured atomic hyperfine constants for the high-lying even-parity 4D5/2 state of lanthanum at 30354 cm-1 . The general utility of this spectral approach is discussed.

  11. High-precision gas chromatography-combustion isotope ratio mass spectrometry at low signal levels.

    PubMed

    Goodman, K J; Brenna, J T

    1995-01-01

    Precision and accuracy of gas chromatography-combustion isotope ratio mass spectrometry are investigated for sample levels down to about 5 pmol C in fatty acid methyl ester mixtures spanning 1000-fold in concentration. Precision and accuracy of isotope ratios diverge rapidly for conventional summation methods, and become unusable below 30 pmol material on column. At lower levels, mean isotope ratios were statistically different from reference values indicating bias as well as poor precision. In contrast, curve fitting, using the exponentially modified Gaussian line shape, gives improved precision for most peaks and useful results down to 3 pmol. The curve-fitting algorithm was also less sensitive to signal integration time than the summation method. These data indicate that curve fitting may be the method of choice for integration of noisy data when high-precision isotope ratios are desired. PMID:7881535

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    PubMed Central

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

    2011-01-01

    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

  14. Measurement of trace isotopes by photon burst mass spectrometry

    SciTech Connect

    Fairbank, W.M. Jr.; Hansen, C.S.; LaBelle, R.D.; Pan, X.J. (Colorado State Univ., Fort Collins, CO (USA). Dept. of Physics); Chamberlin, E.P.; Fearcy, B.L.; Gritzo, R.E.; Keller, R.A.; Miller, C.M.; Oona, H. (Los Alamos National Lab., NM (USA))

    1991-01-01

    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, efficient production of metastable atoms from Ar{sup +} and Kr{sup +} beams, a demonstration of the photon burst detector principle with Mg{sup +} ions, and the verification of zero background in a two-detector system. 7 refs., 5 figs.

  15. Very high resolution saturation spectroscopy of lutetium isotopes via c-w single-frequency laser resonance ionization mass spectrometry

    SciTech Connect

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

    1987-01-01

    In this paper, we discuss the use of Resonance Ionization Mass Spectrometry (RIMS) to perform isotopically selective saturation spectroscopy of lutetium isotopes. Utilizing this technique, it is shown that accurate measurements of the relative frequencies of hyperfine (HF) components for different isotopes easily can be made without the need for an isotopically enriched sample. The precision with which the HF splitting constants can be determined is estimated to be approx.5 times greater than in previous work.

  16. Membrane permeation continuous-flow isotope ratio mass spectrometry for on-line carbon isotope ratio determination.

    PubMed

    Tremblay, Patrice; Savard, Martine M; Smirnoff, Anna; Paquin, Real

    2009-07-01

    Gaseous membrane permeation (MP) technologies have been combined with continuous-flow isotope ratio mass spectrometry for on-line delta13C measurements. The experimental setup of membrane permeation-gas chromatography/combustion/isotope ratio mass spectrometry (MP-GC/C/IRMS) quantitatively traps gas streams in membrane permeation experiments under steady-state conditions and performs on-line gas transfer into a GC/C/IRMS system. A commercial polydimethylsiloxane (PDMS) membrane sheet was used for the experiments. Laboratory tests using CO2 demonstrate that the whole process does not fractionate the C isotopes of CO2. Moreover, the delta13C values of CO2 permeated on-line give the same isotopic results as off-line static dual-inlet IRMS delta13C measurements. Formaldehyde generated from aqueous formaldehyde solutions has also been used as the feed gas for permeation experiments and on-line delta13C determination. The feed-formaldehyde delta13C value was pre-determined by sampling the headspace of the thermostated aqueous formaldehyde solution. Comparison of the results obtained by headspace with those from direct aqueous formaldehyde injection confirms that the headspace sampling does not generate isotopic fractionation, but the permeated formaldehyde analyzed on-line yields a 13C enrichment relative to the feed delta13C value, the isotopic fractionation being 1.0026 +/- 0.0003. The delta13C values have been normalized using an adapted two-point isotopic calibration for delta13C values ranging from -42 to -10 per thousand. The MP-GC/C/IRMS system allows the delta13C determination of formaldehyde without chemical derivatization or additional analytical imprecision. PMID:19533600

  17. Forensic analysis of explosives using isotope ratio mass spectrometry (IRMS)--discrimination of ammonium nitrate sources.

    PubMed

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

    2009-06-01

    An evaluation was undertaken to determine if isotope ratio mass spectrometry (IRMS) could assist in the investigation of complex forensic cases by providing a level of discrimination not achievable utilising traditional forensic techniques. The focus of the research was on ammonium nitrate (AN), a common oxidiser used in improvised explosive mixtures. The potential value of IRMS to attribute Australian AN samples to the manufacturing source was demonstrated through the development of a preliminary AN classification scheme based on nitrogen isotopes. Although the discrimination utilising nitrogen isotopes alone was limited and only relevant to samples from the three Australian manufacturers during the evaluated time period, the classification scheme has potential as an investigative aid. Combining oxygen and hydrogen stable isotope values permitted the differentiation of AN prills from three different Australian manufacturers. Samples from five different overseas sources could be differentiated utilising a combination of the nitrogen, oxygen and hydrogen isotope values. Limited differentiation between Australian and overseas prills was achieved for the samples analysed. The comparison of nitrogen isotope values from intact AN prill samples with those from post-blast AN prill residues highlighted that the nitrogen isotopic composition of the prills was not maintained post-blast; hence, limiting the technique to analysis of un-reacted explosive material. PMID:19606584

  18. Elemental analysis of complex organic aerosol using isotopic labeling and unit-resolution mass spectrometry.

    PubMed

    Hicks, Raea K; Day, Douglas A; Jimenez, Jose L; Tolbert, Margaret A

    2015-03-01

    Elemental analysis of unit-mass resolution (UMR) mass spectra is limited by the amount of information available to definitively elucidate the molecular formula of a molecule ionized by electron impact. The problem is compounded when a mixture of organic molecules (such as those found in organic aerosols) is analyzed without the benefit of prior separation. For this reason, quadrupole mass spectrometry is not usually suited to the elemental analysis of organic mixtures. Here, we present a mathematical method for the elemental analysis of UMR mass spectra of a complex organic aerosol through the use of isotopic labeling. Quadrupole aerosol mass spectrometry was used to obtain UMR data of (13)C-labeled and unlabeled aerosol generated by far ultraviolet (FUV) photochemistry of gas mixtures containing 0.1% of either CH4 or (13)CH4 in N2. In this method, the differences in the positions of ion groups in the resulting spectra are used to estimate the mass fraction of carbon in the aerosol, and estimation of the remaining elements follows. Analysis of the UMR data yields an elemental composition of 63 ± 7% C, 8 ± 1% H, and 29 ± 7% N by mass. Unlabeled aerosols formed under the same conditions are found by high-resolution time-of-flight aerosol mass spectrometry to have an elemental composition of 63 ± 3% C, 8 ± 1% H, 20 ± 4% N, and 9 ± 3% O by mass, in good agreement with the UMR method. This favorable comparison verifies the method, which expands the UMR mass spectrometry toolkit. PMID:25645140

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

    USGS Publications Warehouse

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

    1987-01-01

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

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

    PubMed Central

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

    2006-01-01

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

  1. Quantifying proteomes and their post-translational modifications by stable isotope label-based mass spectrometry

    PubMed Central

    Merrill, Anna E.; Coon, Joshua J.

    2013-01-01

    Stable isotope labeling coupled with mass spectrometry has revolutionized the scope and impact of protein expression studies. Label incorporation can occur metabolically or chemically, and each method bears specific strengths and weaknesses. Quantitative proteomics confidently identifies specific interactions between proteins and other biological species, such as nucleic acids and metabolites. Extending label-based methods to phosphorylation-modified forms of proteins enables the construction of signaling networks and their temporal responses to stimuli. The integration of multiple data types offers systems-level insight on coordinated biological processes. Finally, the development of methods applicable to tissue quantification suggests the emerging role of label-based, quantitative mass spectrometry in translational science. PMID:23835517

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

    PubMed

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

    2009-09-01

    The geochemistry of multiply substituted isotopologues ('clumped-isotope' geochemistry) examines the abundances in natural materials of molecules, formula units or moieties that contain more than one rare isotope (e.g. (13)C(18)O(16)O, (18)O(18)O, (15)N(2), (13)C(18)O(16)O(2) (2-)). Such species form the basis of carbonate clumped-isotope thermometry and undergo distinctive fractionations during a variety of natural processes, but initial reports have provided few details of their analysis. In this study, we present detailed data and arguments regarding the theoretical and practical limits of precision, methods of standardization, instrument linearity and related issues for clumped-isotope analysis by dual-inlet gas-source isotope ratio mass spectrometry (IRMS). We demonstrate long-term stability and subtenth per mil precision in 47/44 ratios for counting systems consisting of a Faraday cup registered through a 10(12) ohm resistor on three Thermo-Finnigan 253 IRMS systems. Based on the analyses of heated CO(2) gases, which have a stochastic distribution of isotopes among possible isotopologues, we document and correct for (1) isotopic exchange among analyte CO(2) molecules and (2) subtle nonlinearity in the relationship between actual and measured 47/44 ratios. External precisions of approximately 0.01 per thousand are routinely achieved for measurements of the mass-47 anomaly (a measure mostly of the abundance anomaly of (13)C-(18)O bonds) and follow counting statistics. The present technical limit to precision intrinsic to our methods and instrumentation is approximately 5 parts per million (ppm), whereas precisions of measurements of heterogeneous natural materials are more typically approximately 10 ppm (both 1 s.e.). These correspond to errors in carbonate clumped-isotope thermometry of +/-1.2 degrees C and +/-2.4 degrees C, respectively. PMID:19621330

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

    E-print Network

    Tian, Weidong

    isotopic label and mass spectrometry Fa-Yun Che,*,1 Quan Yuan,* ,1 Elena Kalinina* and Lloyd D. Fricker. These results are consistent with the acidic pH optima for peptide processing enzymes. Stable isotopic labeling of peptides. In the present study, we labeled cell lines with L-leucine containing 10 deuterium residues (d10

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

    The Low Energy Beam and Ion Trap (LEBIT) facility combines high precision Penning trap mass spectrometry with fast beam projectile fragmentation and high pressure gas stopping techniques. Advanced ion manipulation, such as high efficiency continuous mass selection in an ion-guide and radio-frequency ion accumulation and bunching, are used to purify, cool, and pulse the beam. Recent mass measurements include ^63-66Fe, ^66As, and ^32Si. The neutron-rich iron isotopes access the N = 40 subshell closure. The new significantly lower mass uncertainty makes ^66As a candidate to test the CVC hypothesis. ^32Si, member of the A = 32, T = 2 quintet, provides the most precise test of the isobaric multiplet mass equation . An overview of the various aspects of ion manipulation and some of the resulting measurements will be presented.

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    Penning trap mass spectrometry is presented as a complementary tool to nuclear spectroscopy experiments for the study of nuclear structure in the vicinity of N=40, Z=28. High-precision mass measurements of the Fe63-66 and Co64-67 isotopes have been carried out with the Low Energy Beam and Ion Trap (LEBIT) Penning trap mass spectrometer. The newly obtained mass values for Fe66 and Co67 are presented, together with the previously reported LEBIT mass measurements in this region. In the case of Fe65 the existence of a new isomer is reported, and an isomer recently discovered by decay spectroscopy in Co67 is confirmed. Relative mass uncertainties as low as 4×10-8 are obtained. All mass values are found to be in good agreement with previous experimental results with the exception of Co64, where a 5? deviation is observed. Using these data the two neutron separation energies S2n are calculated. However, the large error bars in the mass values of the neighbor Fe and Co isotopes with N>40 complicate the validation of a weak subshell closure at N=40 for the Co isotopes or the possible reduction in the neutron shell gap in the case of the Fe isotopes, in accordance with the theoretical predictions of an onset of deformation in the region.

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

    SciTech Connect

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

    2006-05-30

    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.

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

    PubMed

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

    2001-01-01

    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

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

    SciTech Connect

    Luong, E.

    1999-05-10

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

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

    USGS Publications Warehouse

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

    2009-01-01

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

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

    SciTech Connect

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

    2010-02-05

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

  12. Precise determination of lithium isotopic composition by thermal ionization mass spectrometry in natural samples such as seawater

    Microsoft Academic Search

    Sarata Kumar Sahoo; Akimasa Masuda

    1998-01-01

    The isotopic composition of lithium in an NIST SRM 924 Li2CO3, isotopically enriched 6Li2CO3 supplied by ORNL and in seawater has been determined by using thermal ionization mass spectrometry (TIMS) based on the use of lithium phosphate as the ion source. In order to minimize isotopic fractionation, the 6Li+\\/7Li+ ion ratio was measured by using a triple filament technique. The

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

    Microsoft Academic Search

    S. Eisenhut; K. G. Heumann

    1997-01-01

    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

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

    PubMed

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

    2010-04-15

    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

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

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.

    2007-12-01

    Secondary Ion Mass Spectrometry, SIMS or ion microprobe analysis, has become an important tool for geochemistry because of its ability study the distributions of elemental and isotopic abundances in situ on polished samples with high (typically a few microns to sub-micron) spatial resolution. In addition, SIMS exhibits high sensitivity for a wide range of elements (H to Pu) so that isotope analyses can sometimes be performed for elements that comprise only trace quantities of some mineral phase (e.g., Pb in zircon) or on major and/or minor elements in very small samples (e.g., presolar dust grains). Offsetting these positive attributes are analytical difficulties due to the complexity of the sputtering source of analyte ions: (1) relatively efficient production of molecular ion species (especially from a complex matrix such as most natural minerals) that cause interferences at the same nominal mass as atomic ions of interest, and (2) quantitation problems caused by variations in the ionization efficiencies of different elements and/or isotopes depending upon the chemical state of the sample surface during sputtering--the so-called "matrix effects". Despite the availability of high mass resolution instruments (e.g., SHRIMP II/RG, CAMECA 1270/1280/NanoSIMS), the molecular ion interferences effectively limit the region of the mass table that can be investigated in most samples to isotope systems at Ni or lighter or at Os or heavier. The matrix effects and the sensitivity of instrumental mass discrimination to the physical state of the sample surface can hamper reproducibility and have contributed to a view that SIMS analyses, especially for so- called stable isotopes, are most appropriate for extraterrestrial samples which are often small, rare, and can exhibit large magnitude isotopic effects. Recent improvements in instrumentation and technique have extended the scope of SIMS isotopic analyses and applications now range from geochronology to paleoclimatology to volcanology to biogeochemistry and cosmochemistry. Multiple collector (static magnetic field) measurements at high mass resolving power have enabled high precision (sub-permil) for several stable isotopes systems (e.g., C, O, Mg, S). Applied to geochronology, the multiple collector approach permits very rapid survey of zircon Pb-Pb ages to identify candidate Hadean grains for further detailed analysis. Ion imaging has been used to correlate isotope compositions with biochemistry (e.g., FISH-SIMS) or to search for especially rare samples among larger populations (e.g., supernova grains of Stardust). For favorable sample geometries with lateral homogeneity, SIMS isotope analyses may be conducted in depth-profiling mode which brings spatial resolution into the tens of nm range. Applications of this approach include experimental petrology, thermochronology, and isotopic analyses of shallowly-implanted solar wind ions. New approaches to removal of molecular ion interferences include reverse- geometry instrumentation and accelerator-based SIMS. There always exists trade-offs between microanalysis and trace analysis on the one hand, and high precision on the other. In this contribution, I will review current status for isotope precision and accuracy of SIMS for applications in stable and radiogenic isotopes as a function of spatial scale. A discussion of current limits and future prospects for improvement in understanding matrix effects will be given. Examples from ion imaging/ depth profiling/ geochronology and cosmochemistry will be provided.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    PubMed

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

    2015-04-01

    The identification of drug metabolites is very important in drug development. Nowadays, the most widely used methods are isotopes and mass spectrometry. However, the commercial isotopic labeled reagents are usually very expensive, and the rapid and convenient identification of metabolites is still difficult. In this paper, an (18)O isotope labeling strategy was developed and the isotopes were used as a tool to identify drug metabolites using mass spectrometry. Curcumin was selected as a model drug to evaluate the established method, and the (18)O labeled curcumin was successfully synthesized. The non-labeled and (18)O labeled curcumin were simultaneously metabolized in human liver microsomes (HLMs) and analyzed by liquid chromatography/mass spectrometry (LC-MS). The two groups of chromatograms obtained from metabolic reaction mixture with and without cofactors were compared and analyzed using Metabolynx software (Waters Corp., Milford, MA, USA). The mass spectra of the newly appearing chromatographic peaks in the experimental sample were further analyzed to find the metabolite candidates. Their chemical structures were confirmed by tandem mass spectrometry. Three metabolites, including two reduction products and a glucuronide conjugate, were successfully detected under their specific HLMs metabolic conditions, which were in accordance with the literature reported results. The results demonstrated that the developed isotope labeling method, together with post-acquisition data processing using Metabolynx software, could be used for fast identification of new drug metabolites. PMID:25592681

  19. Analysis of Isotopic Labeling in Peptide Fragments by Tandem Mass Spectrometry

    PubMed Central

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

    2014-01-01

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

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

    PubMed Central

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

    2013-01-01

    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]. PMID:23541715

  1. Profiling of aldehyde-containing compounds by stable isotope labelling-assisted mass spectrometry analysis.

    PubMed

    Yu, Lei; Liu, Ping; Wang, Ya-Lan; Yu, Qiong-Wei; Yuan, Bi-Feng; Feng, Yu-Qi

    2015-07-13

    We developed a strategy for non-targeted profiling of aldehyde-containing compounds by stable isotope labelling in combination with liquid chromatography-double neutral loss scan-mass spectrometry (SIL-LC-DNLS-MS) analysis. A pair of stable isotope labelling reagents (4-(2-(trimethylammonio)ethoxy)benzenaminium halide, 4-APC and d4-4-(2-(trimethylammonio)ethoxy)benzenaminium halide, 4-APC-d4) that can selectively label aldehyde-containing compounds were synthesized. The 4-APC and 4-APC-d4 labelled compounds were capable of generating two characteristic neutral fragments of 87 Da and 91 Da, respectively, under collision induced dissociation (CID). Therefore, double neutral loss scans were carried out simultaneously to record the signals of the potential aldehyde-containing compounds. In this respect, the aldehyde-containing compounds from two samples labelled with 4-APC and 4-APC-d4 were ionized at the same time but recorded separately by mass spectrometry. The peak pairs with characteristic mass differences (n × 4 Da) can be readily extracted from the DNLS spectra and assigned as potential aldehyde-containing candidates, which facilitates the identification of the target aldehydes. 4-APC and 4-APC-d4 labelling also dramatically increased detection sensitivities of the derivatives. Using the SIL-LC-DNLS-MS strategy, we successfully profiled the aldehyde-containing compounds in human urine and white wine. Our results showed that 16 and 19 potential aldehyde-containing compounds were discovered in human urine and white wine, respectively. In addition, 5 and 4 aldehyde-containing compounds in human urine and white wine were further identified by comparison with aldehyde standards. Altogether, SIL-LC-DNLS-MS demonstrated to be a promising approach in the identification and relative quantification of aldehyde-containing compounds from complex samples. PMID:26086784

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    Microsoft Academic Search

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

    2004-01-01

    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

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

    SciTech Connect

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

    1991-01-01

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

  6. Sampling systems for isotope-ratio mass spectrometry of atmospheric ammonia.

    PubMed

    Skinner, Richard; Ineson, Phil; Jones, Helen; Sleep, Daren; Theobald, Mark

    2006-01-01

    Passive and active ammonia (NH(3)) sampling devices have been tested for their nitrogen (N) capture potential and delta(15)N fractionation effects. Several sampling techniques produced significantly different delta(15)NH(3) signals when sampling the same NH(3) source released from field site fumigation campaigns. Conventional passive NH(3)-monitoring systems have shown to provide insufficient N for isotope-ratio mass spectrometry and various modified devices have been developed, based on existing diffusion tube designs, to overcome this problem. The final sampler design was then tested in a wind tunnel to verify that sampling NH(3) in different environmental conditions did not significantly fractionate the delta(15)N signal. PMID:16331745

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

    ERIC Educational Resources Information Center

    Sein, Lawrence T., Jr.

    2006-01-01

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

  8. Background effects on Faraday collectors in gas-source mass spectrometry and implications for clumped isotope measurements

    E-print Network

    Gilli, Adrian

    and measured isotope ratios. Here we show that negative backgrounds on the Faraday cups recording the minor ion can be performed accurately if the slit width of the m/z 44 Faraday cup significantly exceedsBackground effects on Faraday collectors in gas-source mass spectrometry and implications

  9. Determination of nitrogen-15 isotope fractionation in tropine: evaluation of extraction protocols for isotope ratio measurement by isotope ratio mass spectrometry.

    PubMed

    Molinié, Roland; Kwiecie?, Renata A; Silvestre, Virginie; Robins, Richard J

    2009-12-01

    N-Demethylation of tropine is an important step in the degradation of this compound and related metabolites. With the purpose of understanding the reaction mechanism(s) involved, it is desirable to measure the 15N kinetic isotope effects (KIEs), which can be accessed through the 15N isotope shift (Deltadelta15N) during the reaction. To measure the isotope fractionation in 15N during tropine degradation necessitates the extraction of the residual substrate from dilute aqueous solution without introducing artefactual isotope fractionation. Three protocols have been compared for the extraction and measurement of the 15N/14N ratio of tropine from aqueous medium, involving liquid-liquid phase partitioning or silica-C18 solid-phase extraction. Quantification was by gas chromatography (GC) on the recovered organic phase and delta15N values were obtained by isotope ratio measurement mass spectrometry (irm-MS). Although all the protocols used can provide satisfactory data and both irm-EA-MS and irm-GC-MS can be used to obtain the delta15N values, the most convenient method is liquid-liquid extraction from a reduced aqueous volume combined with irm-GC-MS. The protocols are applied to the measurement of 15N isotope shifts during growth of a Pseudomonas strain that uses tropane alkaloids as sole source of carbon and nitrogen. The accuracy of the determination of the 15N/14N ratio is sufficient to be used for the determination of 15N-KIEs. PMID:19924779

  10. Forensic Mass Spectrometry.

    PubMed

    Hoffmann, William D; Jackson, Glen P

    2015-07-22

    Developments in forensic mass spectrometry tend to follow, rather than lead, the developments in other disciplines. Examples of techniques having forensic potential born independently of forensic applications include ambient ionization, imaging mass spectrometry, isotope ratio mass spectrometry, portable mass spectrometers, and hyphenated chromatography-mass spectrometry instruments, to name a few. Forensic science has the potential to benefit enormously from developments that are funded by other means, if only the infrastructure and personnel existed to adopt, validate, and implement the new technologies into casework. Perhaps one unique area in which forensic science is at the cutting edge is in the area of chemometrics and the determination of likelihood ratios for the evaluation of the weight of evidence. Such statistical techniques have been developed most extensively for ignitable-liquid residue analyses and isotope ratio analysis. This review attempts to capture the trends, motivating forces, and likely impact of developing areas of forensic mass spectrometry, with the caveat that none of this research is likely to have any real impact in the forensic community unless: (a) The instruments developed are turned into robust black boxes with red and green lights for positives and negatives, respectively, or (b) there are PhD graduates in the workforce who can help adopt these sophisticated techniques. PMID:26070716

  11. Developing New Isotope-Coded Mass Spectrometry-Cleavable Cross-Linkers for Elucidating Protein Structures

    PubMed Central

    2015-01-01

    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 MSn 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

  12. Quantitative analysis of WRN exonuclease activity by isotope dilution mass spectrometry.

    PubMed

    Mangerich, Aswin; Veith, Sebastian; Popp, Oliver; Fahrer, Jörg; Martello, Rita; Bohr, Vilhelm A; Bürkle, Alexander

    2012-08-01

    Werner syndrome is a disorder characterized by a premature aging phenotype. The disease is caused by mutations in the WRN gene which encodes a DNA helicase/exonuclease which is involved in multiple aspects of DNA metabolism. Current methods mostly rely on radiometric techniques to assess WRN exonuclease activity. Here we present an alternative, quantitative approach based on non-radioactive isotope dilution mass spectrometry (LC-MS/MS). A oligoduplex substrate mimicking the telomeric sequence was used for method development. Released nucleotides, which correlate with the degree of oligoduplex degradation, were dephosphorylated, purified, and quantified by LC-MS/MS. Heavy-isotope-labeled internal standards were used to account for technical variability. The method was validated in terms of reproducibility, time-course and concentration-dependency of the reaction. As shown in this study, the LC-MS/MS method can assess exonuclease activity of WRN mutants, WRN's substrate and strand specificity, and modulatory effects of WRN interaction partners and posttranslational modifications. Moreover, it can be used to analyze the selectivity and processivity of WRN exonuclease and allows the screening of small molecules for WRN exonuclease inhibitors. Importantly, this approach can easily be adapted to study nucleases other than WRN. This is of general interest, because exonucleases are key players in DNA metabolism and aging mechanisms. PMID:22766507

  13. Determination of Phytochelatins in Rice by Stable Isotope Labeling Coupled with Liquid Chromatography-Mass Spectrometry.

    PubMed

    Liu, Ping; Cai, Wen-Jing; Yu, Lei; Yuan, Bi-Feng; Feng, Yu-Qi

    2015-07-01

    A highly sensitive method was developed for the detection of phytochelatins (PCs) in rice by stable isotope labeling coupled with liquid chromatography-electrospray ionization-tandem mass spectrometry (IL-LC-ESI-MS/MS) analysis. A pair of isotope-labeling reagents [?-bromoacetonylquinolinium bromide (BQB) and BQB-d(7)] were used to label PCs in plant sample and standard PCs, respectively, and then combined prior to LC/MS analysis. The heavy labeled standards were used as the internal standards for quantitation to minimize the matrix and ion suppression effects in MS analysis. In addition, the ionization efficiency of PCs was greatly enhanced through the introduction of a permanent charged moiety of quaternary ammonium of BQB into PCs. The detection sensitivities of PCs upon BQB labeling improved by 14-750-fold, and therefore, PCs can be quantitated using only 5 mg of plant tissue. Furthermore, under cadmium (Cd) stress, we found that the contents of PCs in rice dramatically increased with the increased concentrations and treatment time of Cd. It was worth noting that PC5 was first identified and quantitated in rice tissues under Cd stress in the current study. Taken together, this IL-LC-ESI-MS/MS method demonstrated to be a promising strategy in detection of PCs in plants with high sensitivity and reliability. PMID:26073168

  14. Ultratrace analysis of calcium with high isotopic selectivity by diodelaser resonance ionisation mass spectrometry

    Microsoft Academic Search

    K. Wendt; K. Blaum; B. A. Bushaw; F. Juston; W. Nörtershäuser; N. Trautmann; B. Wiche

    1997-01-01

    A resonance ionisation mass spectrometer for the ultratrace determination of calcium isotopes is presented. It achieves high\\u000a overall efficiency, ultra-high isotopic abundance sensitivity of more than 1010 and complete suppression of isobars. The system can be used for isotope ratio studies on stable and long-lived trace isotopes\\u000a with the final goal of radiodating via 41Ca-determination. For the different applications optical

  15. Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Smith, J. Scott; Thakur, Rohan A.

    Mass spectrometry (MS) is unique among the various spectroscopy techniques in both theory and instrumentation. As you may recall, spectroscopy involves the interaction of electromagnetic radiation or some form of energy with molecules. The molecules absorb the radiation and produce a spectrum either during the absorption process or as the excited molecules return to the ground state. MS works by placing a charge on a molecule, thereby converting it to an ion in a process called ionization. The generated ions are then resolved according to their mass-to-charge ratio (m/z) by subjecting them to electrostatic fields (mass analyzer) and finally detected. An additional stage of ion fragmentation may be included before detection to elicit structural information in a technique known as tandem MS. The result of ion generation, separation, fragmentation, and detection is manifested as a mass spectrum that can be interpreted to yield molecular weight or structural information. The uniqueness of this process allows the method to be used for both detection and identification of an unknown compound.

  16. Quantitative Metabolome Analysis Based on Chromatographic Peak Reconstruction in Chemical Isotope Labeling Liquid Chromatography Mass Spectrometry.

    PubMed

    Huan, Tao; Li, Liang

    2015-07-21

    Generating precise and accurate quantitative information on metabolomic changes in comparative samples is important for metabolomics research where technical variations in the metabolomic data should be minimized in order to reveal biological changes. We report a method and software program, IsoMS-Quant, for extracting quantitative information from a metabolomic data set generated by chemical isotope labeling (CIL) liquid chromatography mass spectrometry (LC-MS). Unlike previous work of relying on mass spectral peak ratio of the highest intensity peak pair to measure relative quantity difference of a differentially labeled metabolite, this new program reconstructs the chromatographic peaks of the light- and heavy-labeled metabolite pair and then calculates the ratio of their peak areas to represent the relative concentration difference in two comparative samples. Using chromatographic peaks to perform relative quantification is shown to be more precise and accurate. IsoMS-Quant is integrated with IsoMS for picking peak pairs and Zero-fill for retrieving missing peak pairs in the initial peak pairs table generated by IsoMS to form a complete tool for processing CIL LC-MS data. This program can be freely downloaded from the www.MyCompoundID.org web site for noncommercial use. PMID:26086729

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    PubMed

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

    2004-01-01

    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

  19. Improvements on high-precision measurement of bromine isotope ratios by multicollector inductively coupled plasma mass spectrometry.

    PubMed

    Wei, Hai-Zhen; Jiang, Shao-Yong; Zhu, Zhi-Yong; Yang, Tao; Yang, Jing-Hong; Yan, Xiong; Wu, He-Pin; Yang, Tang-Li

    2015-10-01

    A new, feasible procedure for high-precision bromine isotope analysis using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) is described. With a combination of HR mass resolution mode and accurate optimization of the Zoom Optics parameters (Focus Quad: -1.30; Zoom Quad: 0.00), the challenging problem of the isobaric interferences ((40)Ar(38)ArH(+) and (40)Ar(40)ArH(+)) in the measurement of bromine isotopes ((79)Br(+), (81)Br(+)) has been effectively solved. The external reproducibility of the measured (81)Br/(79)Br ratios in the selected standard reference materials ranged from ±0.03‰ to ±0.14‰, which is superior to or equivalent to the best results from previous contributions. The effect of counter cations on the Br(+) signal intensity and the instrumental-induced mass bias was evaluated as the loss of HBr aerosol in nebulizer and potential diffusive isotope fractionations. PMID:26078163

  20. Isotope Ratio Mass Spectrometry and Shale Gas - What Is Possible with Current Technology?

    NASA Astrophysics Data System (ADS)

    Barrie, C. D.; Kasson, A.

    2014-12-01

    With ever increasing exploration and exploitation of 'unconventional' hydrocarbon resources, the drive to understand the origins, history and importance of these resources and their effects on the surrounding environment (i.e. ground waters) has never been more important. High-throughput, high-precision isotopic measurements are therefore a key tool in this industry to both understand the gas generated and monitor the development and stability of wells through time. With the advent of cavity ringdown spectroscopy (CRDS) instrumentation, there has been a push in some applications - environmental & atmospheric - to gather more and more data directly at the location of collection or at dedicated field stations. Furthermore, CRDS has resulted in users seeking greater autonomy of instrumentation and so-called black box technology. Traditionally IRMS technology has not met any of these demands, requiring very specific and extensive footprint, power and environmental requirements. This has meant that the 'Oil & Gas' sector, which for natural gases measurements requires GC-IRMS technology - not possible via CRDS - loses time, money and manpower as samples get sent to central facility or contract labs with potentially long lee times. However, recent developments in technology mean that IRMS systems exist which are benchtop, have much lower power requirements, standard power connections and as long as housed in a temperature controlled field stations can be deployed anywhere. Furthermore, with advances in electronics and software IRMS systems are approaching the black box level of newer instrumentation while maintaining the flexibility and abilities of isotope ratio mass spectrometry. This presentation will outline changes in IRMS technology applicable to the Oil & Gas industry, discuss the feasibility of true 'field' deployability and present results from a range of Oil & Gas samples.

  1. Mass Spectrometry

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed Central

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

    2014-01-01

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

  3. The determination of uranium in urine by isotope dilution mass spectrometry using resin bead loading

    SciTech Connect

    May, M.P.; Walker, R.L.; Scott, T.G.; Dyer, F.F.; Stokely, J.R.

    1983-01-01

    Ion exchange separations are coupled with isotope dilution mass spectrometry to provide a highly sensitive method for the determination of uranium in urine. This method was examined for its sensitivity, practicality, reproducibility, and accuracy. Our goal was to measure uranium at the 0.1 ng/ml +- 0.01 ng/ml level for 10 mL aliquots of urine. The ability to measure this low concentration of uranium can be limited by both instrumental background and contamination from working environment, reagents, and labware in the procedure. Initially, high blank levels of uranium were observed so much emphasis was placed upon lowering the procedural blank. To achieve a 10% uncertainty, this blank must remain low and be reproducible throughout all determinations. The validity of the method was tested by analyzing an artificial urine spiked with a known concentration of uranium and several human urine samples analyzed by an independent method. Details and results of the method plus its possible bioassay applications are presented. 1 tab.

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

    PubMed

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

    2013-02-01

    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

  5. Accurate and precise lithium isotopic determinations of igneous rock samples using multi-collector inductively coupled plasma mass spectrometry

    Microsoft Academic Search

    Yoshiro Nishio; Shun’ichi Nakai

    2002-01-01

    A second-generation multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) was applied to lithium isotopic measurements. The high sensitivity of the ICP-MS enabled high precision (±0.82‰, 2?) analyses with small amount of Li (?45ng Li). A single-step column separation protocol was established with which rapid purification of lithium from rock solutions can be carried out with reduced blank (<10pg). The influence

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

    Microsoft Academic Search

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

    2003-01-01

    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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  8. In-Gel Stable-Isotope Labeling (ISIL): a strategy for mass spectrometry-based relative quantification.

    PubMed

    Asara, John M; Zhang, Xiang; Zheng, Bin; Christofk, Heather H; Wu, Ning; Cantley, Lewis C

    2006-01-01

    Most proteomics approaches for relative quantification of protein expression use a combination of stable-isotope labeling and mass spectrometry. Traditionally, researchers have used difference gel electrophoresis (DIGE) from stained 1D and 2D gels for relative quantification. While differences in protein staining intensity can often be visualized, abundant proteins can obscure less abundant proteins, and quantification of post-translational modifications is difficult. A method is presented for quantifying changes in the abundance of a specific protein or changes in specific modifications of a protein using In-gel Stable-Isotope Labeling (ISIL). Proteins extracted from any source (tissue, cell line, immunoprecipitate, etc.), treated under two experimental conditions, are resolved in separate lanes by gel electrophoresis. The regions of interest (visualized by staining) are reacted separately with light versus heavy isotope-labeled reagents, and the gel slices are then mixed and digested with proteases. The resulting peptides are then analyzed by LC-MS to determine relative abundance of light/heavy isotope pairs and analyzed by LC-MS/MS for identification of sequence and modifications. The strategy compares well with other relative quantification strategies, and in silico calculations reveal its effectiveness as a global relative quantification strategy. An advantage of ISIL is that visualization of gel differences can be used as a first quantification step followed by accurate and sensitive protein level stable-isotope labeling and mass spectrometry-based relative quantification. PMID:16396506

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

    SciTech Connect

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

    2011-08-01

    The identification of peptides that result from post-translational modifications is critical for understanding normal pathways of cellular regulation as well as identifying damage from, or exposures to xenobiotics, i.e. the exposome. However, because of their low abundance in proteomes, effective detection of modified peptides by mass spectrometry (MS) typically requires enrichment to eliminate false identifications. We present a new method for confidently identifying peptides with mercury (Hg)-containing adducts that is based on the influence of mercury’s seven stable isotopes on peptide isotope distributions detected by high-resolution MS. Using a pure protein and E. coli cultures exposed to phenyl mercuric acetate, we show the pattern of peak heights in isotope distributions from primary MS single scans efficiently identified Hg adducts in data from chromatographic separation coupled with tandem mass spectrometry with sensitivity and specificity greater than 90%. Isotope distributions are independent of peptide identifications based on peptide fragmentation (e.g. by SEQUEST), so both methods can be combined to eliminate false positives. Summing peptide isotope distributions across multiple scans improved specificity to 99.4% and sensitivity above 95%, affording identification of an unexpected Hg modification. We also illustrate the theoretical applicability of the method for detection of several less common elements including the essential element, selenium, as selenocysteine in peptides.

  10. Influence of recent vegetation on labile and recalcitrant carbon soil pools in central Queensland, Australia: evidence from thermal analysis-quadrupole mass spectrometry-isotope ratio mass spectrometry.

    PubMed

    Lopez-Capel, Elisa; Krull, Evelyn S; Bol, Roland; Manning, David A C

    2008-06-01

    The effect of a recent vegetation change (<100 years) from C(4) grassland to C(3) woodland in central Queensland, Australia, on soil organic matter (SOM) composition and SOM dynamics has been investigated using a novel coupled thermogravimetry-differential scanning calorimetry-quadrupole.mass spectrometry-isotope ratio mass spectrometry (TG-DSC-QMS-IRMS) system. TG-DSC-QMS-IRMS distinguishes the C isotope composition of discrete SOM pools, showing changes in labile, recalcitrant and refractory carbon in the bulk soil and particle size fractions which track the vegetation changes. Analysis of evolved gases (by QMS) from thermal decomposition, rather than observed weight loss, proved essential in determining the temperature at which SOM decomposes, because smectite and kaolinite clays contribute to observed weight losses. The delta(13)C analyses of the CO(2) evolved at different temperatures for bulk soil and particle size-separates showed that most of the labile SOM under the more recent woody vegetation was C(3)-derived carbon whereas the delta(13)C values in the recalcitrant SOM showed greater C(4) contributions. This indicated a shift from grass (C(4))- to tree (C(3))-derived carbon in the woodland, which was also supported by the two-phase (13)C enrichment with depth, i.e. C(3) vegetation dominated the top soil (0-10 cm), but the C(4) contribution increased with depth (more gradual). This is perturbed by the inclusion of charcoal from forest fires ((14)C age incursions) and by the deep incorporation of C(3) carbon due to root penetration. PMID:18446757

  11. 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

    Shona McSheehy; Lu Yang; Ralph Sturgeon; Zoltan Mester

    2005-01-01

    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

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

    PubMed

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

    2005-12-01

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

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

    PubMed

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

    2011-10-30

    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

  14. 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)

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

    2011-12-01

    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.

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

    PubMed

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

    2013-01-01

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

  16. Analysis of quantization error in high-precision continuous-flow isotope ratio mass spectrometry.

    PubMed

    Sacks, Gavin L; Wolyniak, Christopher J; Brenna, J Thomas

    2003-12-12

    High-precision isotope ratio mass spectrometry (IRMS) systems are equipped with digitizers that deliver effective maximum digitization depths of 16 to 24 bits; however, there are no analyses of the proper board depth required to retain high precision in continuous-flow techniques. We report an experimental and theoretical evaluation of quantization error in continuous-flow IRMS (CF-IRMS). CO2 samples (100 pmol-30 nmol) were injected into a gas chromatography combustion IRMS system (GC-CIRMS). The analog signal was digitized by high precision, 24-bit ADC boards at 10 Hz, and was post-processed to simulate 12, 14, and 16-bit data sets. Delta13Cpdh values were calculated for all data sets by the conventional "summation" method or by curve-fitting the chromatographic peaks to the exponentially modified Gaussian (EMG) function. Benchmarks of S.D.(delta13Cpdh) = 0.3, 0.6, and 1.0/1000 were considered to assess precision. In the presence of significant quantization noise, curve-fitting required several-fold less CO2 than the summation method to reach a given benchmark. We derived an equation to describe the theoretical limitations of precision for the summation method as a function of CO2 admitted to the source and the step size of the boards. Theory was in close agreement with the observed lower limit of precision for the simulated 16-bit data set. Curve-fitting achieved a precision of S.D. <0.3/1000 for injections 20-fold smaller than summation for CO2 samples collected on an IRMS with 16-bit resolution. By mitigating the impact of quantization noise, curve-fitting expands the dynamic range within a single run to include lower analyte levels, and effectively reduces the need for high pumping capacities and high precision ADC boards. PMID:14661751

  17. Multi-isotope imaging mass spectrometry reveals slow protein turnover in hair-cell stereocilia.

    PubMed

    Zhang, Duan-Sun; Piazza, Valeria; Perrin, Benjamin J; Rzadzinska, Agnieszka K; Poczatek, J Collin; Wang, Mei; Prosser, Haydn M; Ervasti, James M; Corey, David P; Lechene, Claude P

    2012-01-26

    Hair cells of the inner ear are not normally replaced during an animal's life, and must continually renew components of their various organelles. Among these are the stereocilia, each with a core of several hundred actin filaments that arise from their apical surfaces and that bear the mechanotransduction apparatus at their tips. Actin turnover in stereocilia has previously been studied by transfecting neonatal rat hair cells in culture with a ?-actin-GFP fusion, and evidence was found that actin is replaced, from the top down, in 2-3 days. Overexpression of the actin-binding protein espin causes elongation of stereocilia within 12-24 hours, also suggesting rapid regulation of stereocilia lengths. Similarly, the mechanosensory 'tip links' are replaced in 5-10 hours after cleavage in chicken and mammalian hair cells. In contrast, turnover in chick stereocilia in vivo is much slower. It might be that only certain components of stereocilia turn over quickly, that rapid turnover occurs only in neonatal animals, only in culture, or only in response to a challenge like breakage or actin overexpression. Here we quantify protein turnover by feeding animals with a (15)N-labelled precursor amino acid and using multi-isotope imaging mass spectrometry to measure appearance of new protein. Surprisingly, in adult frogs and mice and in neonatal mice, in vivo and in vitro, the stereocilia were remarkably stable, incorporating newly synthesized protein at <10% per day. Only stereocilia tips had rapid turnover and no treadmilling was observed. Other methods confirmed this: in hair cells expressing ?-actin-GFP we bleached fiducial lines across hair bundles, but they did not move in 6 days. When we stopped expression of ?- or ?-actin with tamoxifen-inducible recombination, neither actin isoform left the stereocilia, except at the tips. Thus, rapid turnover in stereocilia occurs only at the tips and not by a treadmilling process. PMID:22246323

  18. Ultratrace analysis of calcium with high isotopic selectivity by diode laser resonance ionization mass spectrometry

    Microsoft Academic Search

    Karen M. Wendt; K. Blaum; Bruce A. Bushaw; P. Mueller; W. Noertershaeuser; A. Schmitt; N. Trautmann; B. Wiche

    1998-01-01

    A refined diode laser based resonance ionization mass spectrometer for highly selective ultratrace analysis is presented, which combines coherent narrow-band multistep resonance excitation and ionization with a compact quadruple mass spectrometer. The widespread analytical potential and applicability of this system is demonstrated in the determination of calcium trace and ultratrace isotopes for cosmochemical studies, medical investigations and radiodating. For a

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

    USGS Publications Warehouse

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

    2003-01-01

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

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

    PubMed

    Coplen, Tyler B; Qi, Haiping

    2010-09-15

    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

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

    USGS Publications Warehouse

    Coplen, Tyler B.; Qi, Haiping

    2010-01-01

    An anomalous stable hydrogen isotopic fractionation of 4 ‰ in gaseous hydrogen has been correlated with the process of adding liquid nitrogen (LN2) to top off the dewar of a stainless-steel water trap on a gaseous hydrogen-water platinum equilibration system. Although the cause of this isotopic fractionation is unknown, its effect can be mitigated by (1) increasing the capacity of any dewars so that they do not need to be filled during a daily analytic run, (2) interspersing isotopic reference waters among unknowns, and (3) applying a linear drift correction and linear normalization to isotopic results with a program such as Laboratory Information Management System (LIMS) for Light Stable Isotopes. With adoption of the above guidelines, measurement uncertainty can be substantially improved. For example, the long-term (months to years) ?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

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

    USGS Publications Warehouse

    Coplen, T.B.; Qi, H.

    2010-01-01

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

  3. 87Sr/86Sr Isotope Ratio Measurements of Calcium-rich matrices by (Laser Ablation)-Multiple Collector Inductively Coupled Plasma Mass Spectrometry: A Survey on Mass Discrimination and Matrix-Induced Interferences

    NASA Astrophysics Data System (ADS)

    Irrgeher, J.; Galler, P.; Zitek, A.; Teschler-Nicola, M.; Prohaska, T.

    2012-04-01

    87Sr/86Sr Isotope Ratio Measurements of Calcium-rich matrices by (Laser Ablation)-Multiple Collector Inductively Coupled Plasma Mass Spectrometry: A Survey on Mass Discrimination and Matrix-Induced Interferences

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    PubMed Central

    Basu, Sankha S; Blair, Ian A

    2013-01-01

    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. PMID:22157971

  6. Studies of corrosion in power plant boiler tubes by measurement of oxygen isotopes and trace elements using secondary-ion mass spectrometry

    Microsoft Academic Search

    David R. Cole; Lee R. Riciputi; David J. Wesolowski; Bruce A. Paterson; Steven M. Fortier

    1997-01-01

    Recent advances in secondary ionization mass spectrometry (SIMS) techniques allow the resolution of differences in the natural abundances of the isotopes of 18O and 16O, and their ratio in both conducting and insulating materials. These techniques have been used in this study to measure the oxygen isotope signatures and their spatial distribution in corrosion products formed during high-temperature oxidation of

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

    SciTech Connect

    Isselhardt, B H

    2011-09-06

    Resonance Ionization Mass Spectrometry (RIMS) has been developed as a method to measure relative uranium isotope abundances. In this approach, RIMS is used as an element-selective ionization process to provide a distinction between uranium atoms and potential isobars without the aid of chemical purification and separation. We explore the laser parameters critical to the ionization process and their effects on the measured isotope ratio. Specifically, the use of broad bandwidth lasers with automated feedback control of wavelength was applied to the measurement of {sup 235}U/{sup 238}U ratios to decrease laser-induced isotopic fractionation. By broadening the bandwidth of the first laser in a 3-color, 3-photon ionization process from a bandwidth of 1.8 GHz to about 10 GHz, the variation in sequential relative isotope abundance measurements decreased from >10% to less than 0.5%. This procedure was demonstrated for the direct interrogation of uranium oxide targets with essentially no sample preparation. A rate equation model for predicting the relative ionization probability has been developed to study the effect of variation in laser parameters on the measured isotope ratio. This work demonstrates that RIMS can be used for the robust measurement of uranium isotope ratios.

  8. Analyzing Nuclear Fuel Cycles from Isotopic Ratios of Waste Products Applicable to Measurement by Accelerator Mass Spectrometry

    SciTech Connect

    Biegalski, S R; Whitney, S M; Buchholz, B

    2005-08-24

    An extensive study was conducted to determine isotopic ratios of nuclides in spent fuel that may be utilized to reveal historical characteristics of a nuclear reactor cycle. This forensic information is important to determine the origin of unknown nuclear waste. The distribution of isotopes in waste products provides information about a nuclear fuel cycle, even when the isotopes of uranium and plutonium are removed through chemical processing. Several different reactor cycles of the PWR, BWR, CANDU, and LMFBR were simulated for this work with the ORIGEN-ARP and ORIGEN 2.2 codes. The spent fuel nuclide concentrations of these reactors were analyzed to find the most informative isotopic ratios indicative of irradiation cycle length and reactor design. Special focus was given to long-lived and stable fission products that would be present many years after their creation. For such nuclides, mass spectrometry analysis methods often have better detection limits than classic gamma-ray spectroscopy. The isotopic ratios {sup 151}Sm/{sup 146}Sm, {sup 149}Sm/{sup 146}Sm, and {sup 244}Cm/{sup 246}Cm were found to be good indicators of fuel cycle length and are well suited for analysis by accelerator mass spectroscopy.

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

    USGS Publications Warehouse

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

    2011-01-01

    We describe a new chemical separation method to isolate Ca from other matrix elements in biological samples, developed with the long-term goal of making high-precision measurement of natural stable Ca isotope variations a clinically applicable tool to assess bone mineral balance. A new two-column procedure utilizing HBr achieves the purity required to accurately and precisely measure two Ca isotope ratios (44Ca/42Ca and 44Ca/43Ca) on a Neptune multiple collector inductively coupled plasma mass spectrometer (MC-ICPMS) in urine. Purification requirements for Sr, Ti, and K (Ca/Sr > 10000; Ca/Ti > 10000000; and Ca/K > 10) were determined by addition of these elements to Ca standards of known isotopic composition. Accuracy was determined by (1) comparing Ca isotope results for samples and standards to published data obtained using thermal ionization mass spectrometry (TIMS), (2) adding a Ca standard of known isotopic composition to a urine sample purified of Ca, and (3) analyzing mixtures of urine samples and standards in varying proportions. The accuracy and precision of ?44/42Ca measurements of purified samples containing 25 ?g of Ca can be determined with typical errors less than ±0.2‰ (2?).

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

    PubMed

    Liu, Rui; Hou, Xiandeng; Lv, Yi; McCooeye, Margaret; Yang, Lu; Mester, Zoltán

    2013-04-16

    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 the target peptide. Quantitative labeling of bradykinin peptide was accomplished with a commercially available 2',2?-(10-(2-((2,5-dioxopyrrolidin-1-yl)oxy)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (DOTA-NHS-ester) and subsequently tagged with Eu. A (151)Eu-enriched spike was used for the non-species-specific ID LC-ICPMS determination of bradykinin. The non-species-specific ID LC-ICPMS method was cross-validated by a species-specific ID GC/MS approach, which is based on the determination of phenylalanine in bradykinin to derive the concentration of the peptide in the sample. The hydrolysis of the peptide into amino acids was achieved by microwave digestion with 4 M methanesulfonic acid, and derivatization of phenylalanine with methyl chloroformate (MCF) was performed prior to its detection by GC/MS based on a (13)C-enriched phenylalanine spike. The accuracy of the method was confirmed at various concentration levels with a typical precision of better than 5% relative standard deviation (RSD) at 20 pmol for non-species-specific ID LC-ICPMS and 500 pmol for species-specific ID GC/MS. A detection limit (3 SD) of 7.2 fmol estimated for ID LC-ICPMS with a 10 ?L injection volume from three procedure blanks was obtained for bradykinin, confirming the suitability of the method for the direct determination of peptides at trace levels. To the best of our knowledge, the proposed method is the first ICPMS peptide quantification strategy which employs an independent validation strategy using species-specific ID GC/MS for amino acid quantitation. PMID:23489086

  11. Calibration strategies for the determination of stable carbon absolute isotope ratios in a glycine candidate reference material by elemental analyser-isotope ratio mass spectrometry.

    PubMed

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

    2015-04-01

    We report a methodology for the determination of the stable carbon absolute isotope ratio of a glycine candidate reference material with natural carbon isotopic composition using EA-IRMS. For the first time, stable carbon absolute isotope ratios have been reported using continuous flow rather than dual inlet isotope ratio mass spectrometry. Also for the first time, a calibration strategy based on the use of synthetic mixtures gravimetrically prepared from well characterised, highly (13)C-enriched and (13)C-depleted glycines was developed for EA-IRMS calibration and generation of absolute carbon isotope ratio values traceable to the SI through calibration standards of known purity. A second calibration strategy based on converting the more typically determined delta values on the Vienna PeeDee Belemnite (VPDB) scale using literature values for the absolute carbon isotope ratio of VPDB itself was used for comparison. Both calibration approaches provided results consistent with those previously reported for the same natural glycine using MC-ICP-MS; absolute carbon ratios of 10,649?×?10(-6) with an expanded uncertainty (k?=?2) of 24?×?10(-6) and 10,646?×?10(-6) with an expanded uncertainty (k?=?2) of 88?×?10(-6) were obtained, respectively. The absolute carbon isotope ratio of the VPDB standard was found to be 11,115?×?10(-6) with an expanded uncertainty (k?=?2) of 27?×?10(-6), which is in excellent agreement with previously published values. PMID:24908413

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

    NASA Astrophysics Data System (ADS)

    Cavazzini, Giancarlo

    2005-01-01

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

  13. Comparative quantification and identification of phosphoproteins using stable isotope labeling and liquid chromatography\\/mass spectrometry

    Microsoft Academic Search

    Wolfram Weckwerth; Lothar Willmitzer; Oliver Fiehn

    2000-01-01

    A new liquid chromatography\\/mass spectrometry (LC\\/MS) method is described for relative quantification of phosphoproteins to simultaneously compare the phosphorylation status of proteins under two different conditions. Quantification was achieved by b-elimination of phosphate from phospho-Ser\\/Thr followed by Micheal addition of ethanethiol and\\/or ethane-d5-thiol selectively at the vinyl moiety of dehydroalanine and dehydroamino-2-butyric acid. The method was evaluated using the model

  14. Quantitative biomedical mass spectrometry

    NASA Astrophysics Data System (ADS)

    de Leenheer, Andrép; Thienpont, Linda M.

    1992-09-01

    The scope of this contribution is an illustration of the capabilities of isotope dilution mass spectrometry (IDMS) for quantification of target substances in the biomedical field. After a brief discussion of the general principles of quantitative MS in biological samples, special attention will be paid to new technological developments or trends in IDMS from selected examples from the literature. The final section will deal with the use of IDMS for accuracy assessment in clinical chemistry. Methodological aspects considered crucial for avoiding sources of error will be discussed.

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

    Microsoft Academic Search

    J. F. Cotte; H. Casabianca; J. Lhéritier; C. Perrucchietti; C. Sanglar; H. Waton; M. F. Grenier-Loustalot

    2007-01-01

    Honey samples were analyzed by stable carbon isotopic ratio analysis by mass spectrometry (SCIRA-MS) and site-specific natural isotopic fractionation measured by nuclear magnetic resonance (SNIF-NMR) to first determine their potentials for characterizing the substance and then to combat adulteration. Honey samples from several geographic and botanical origins were analyzed. The ?13C parameter was not significant for characterizing an origin, while

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

    PubMed

    Fernández, Beatriz; Rodríguez-González, Pablo; García Alonso, J Ignacio; Malherbe, Julien; García-Fonseca, Sergio; Pereiro, Rosario; Sanz-Medel, Alfredo

    2014-12-01

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

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

    SciTech Connect

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

    2004-01-01

    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.

  18. Accelerator mass spectrometry.

    PubMed

    Hellborg, Ragnar; Skog, Göran

    2008-01-01

    In this overview the technique of accelerator mass spectrometry (AMS) and its use are described. AMS is a highly sensitive method of counting atoms. It is used to detect very low concentrations of natural isotopic abundances (typically in the range between 10(-12) and 10(-16)) of both radionuclides and stable nuclides. The main advantages of AMS compared to conventional radiometric methods are the use of smaller samples (mg and even sub-mg size) and shorter measuring times (less than 1 hr). The equipment used for AMS is almost exclusively based on the electrostatic tandem accelerator, although some of the newest systems are based on a slightly different principle. Dedicated accelerators as well as older "nuclear physics machines" can be found in the 80 or so AMS laboratories in existence today. The most widely used isotope studied with AMS is 14C. Besides radiocarbon dating this isotope is used in climate studies, biomedicine applications and many other fields. More than 100,000 14C samples are measured per year. Other isotopes studied include 10Be, 26Al, 36Cl, 41Ca, 59Ni, 129I, U, and Pu. Although these measurements are important, the number of samples of these other isotopes measured each year is estimated to be less than 10% of the number of 14C samples. PMID:18470926

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

    Microsoft Academic Search

    Mark D Schmitz; Samuel A Bowring; Trevor R Ireland

    2003-01-01

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

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

    Microsoft Academic Search

    D. M. Beals

    1996-01-01

    An isotope dilution\\/inductively coupled plasma mass spectrometric method (ID\\/ICP-MS) for measuring the concentration of technetium-99 in aqueous samples was developed at the Savannah River Technology Center (SRTC). The procedure is faster than radiometric tecniques, is less subject to interferences, and has equal or better detection limits. It is currently being used to measure the concentration of99Tc in samples of Savannah

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

    Microsoft Academic Search

    Beals

    1992-01-01

    An isotope dilution\\/inductively coupled plasma mass spectrometric method (ID\\/ICP-MS) for measuring the concentration of technetium-99 in aqueous samples was developed at the Savannah River Technology Center (SRTC). The procedure is faster than radiometric techniques, is also less subject to interferences, and has equal or better detection limits. It is currently being used to measure the concentration of ⁹⁹Tc in samples

  2. Isotopic analysis of calcium in blood plasma and bone from mouse samples by multiple collector-ICP-mass spectrometry.

    PubMed

    Hirata, Takafumi; Tanoshima, Mina; Suga, Akinobu; Tanaka, Yu-ki; Nagata, Yuichi; Shinohara, Atsuko; Chiba, Momoko

    2008-01-01

    The biological processing of Ca produces significant stable isotope fractionation. The level of isotopic fractionation can provide key information about the variation in dietary consumption or Ca metabolism. To investigate this, we measured the 43Ca/42Ca and 44Ca/42Ca ratios for bone and blood plasma samples collected from mice of various ages using multiple collector-ICP-mass spectrometry (MC-ICP-MS). The 44Ca/42Ca ratio in bones was significantly (0.44-0.84 per thousand) lower than the corresponding ratios in the diet, suggesting that Ca was isotopically fractionated during Ca metabolism for bone formation. The resulting 44Ca/42Ca ratios for blood plasma showed almost identical, or slightly higher, values (0.03-0.2 per thousand) than found in a corresponding diet. This indicates that a significant amount of Ca in the blood plasma was from dietary sources. Unlike that discovered for Fe, there were no significant differences in the measured 44Ca/42Ca ratios between female and male specimens (for either bone or blood plasma samples). Similarity, the 44Ca/42Ca ratios suggests that there were no significant differences in Ca dietary consumption or Ca metabolism between female and male specimens. In contrast, the 44Ca/42Ca ratios of blood plasma from mother mice during the lactation period were significantly higher than those for all other adult specimens. This suggests that Ca supplied to infants through lactation was isotopically lighter, and the preferential supply of isotopically lighter Ca resulted in isotopically heavier Ca in blood plasma of mother mice during the lactation period. The data obtained here clearly demonstrate that the Ca isotopic ratio has a potential to become a new tool for evaluating changes in dietary consumption, or Ca metabolism of animals. PMID:18997383

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

    PubMed

    Leckrone, K J; Hayes, J M

    1998-07-01

    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

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

    USGS Publications Warehouse

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

    1989-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

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

    PubMed

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

    1995-07-15

    Conditions and systems for on-line combustion of effluents from capillary gas chromatographic columns and for removal of water vapor from product streams were tested. Organic carbon in gas chromatographic peaks 15 s wide and containing up to 30 nanomoles of carbon was quantitatively converted to CO2 by tubular combustion reactors, 200 x 0.5 mm, packed with CuO or NiO. No auxiliary source of O2 was required because oxygen was supplied by metal oxides. Spontaneous degradation of CuO limited the life of CuO reactors at T > 850 degrees C. Since NiO does not spontaneously degrade, its use might be favored, but Ni-bound carbon phases form and lead to inaccurate isotopic results at T < 1050 degrees C if gas-phase O2 is not added. For all compounds tested except CH4, equivalent isotopic results are provided by CuO at 850 degrees C, NiO + O2 (gas-phase mole fraction, 10(-3)) at 1050 degrees C and NiO at 1150 degrees C. The combustion interface did not contribute additional analytical uncertainty, thus observed standard deviations of 13C/12C ratios were within a factor of 2 of shot-noise limits. For combustion and isotopic analyses of CH4, in which quantitative combustion required T approximately 950 degrees C, NiO-based systems are preferred, and precision is approximately 2 times lower than that observed for other analytes. Water must be removed from the gas stream transmitted to the mass spectrometer or else protonation of CO2 will lead to inaccuracy in isotopic analyses. Although thresholds for this effect vary between mass spectrometers, differential permeation of H2O through Nafion tubing was effective in both cases tested, but the required length of the Nafion membrane was 4 times greater for the more sensitive mass spectrometer. PMID:11536720

  7. Determination of Mineral-Specific Clumped Isotope Acid Digestion Fractionation Factors Using Heating Experiments and Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Henry, D.; Tang, J.; Mosenfelder, J. L.; Eagle, R.; Tripati, A.

    2014-12-01

    Clumped isotope thermometry involves the determination of formation temperatures of carbonates from the fraction of isotopologues containing multiple rare isotopes (oxygen-18 and carbon-13). At high temperatures, the abundance of these isotopologues should be stochastic. At lower temperatures, there is a tendency for heavy isotopes to form bonds with each other. However, spectroscopic determination of isotope ratios with high precision is difficult in solids, and so 13C-18O bond abundance is not measured in the solid phase. Instead, analysis of carbonates is performed using gas source mass spectrometry, by reacting the carbonate samples with phosphoric acid and measuring the evolved CO2 gas. As an oxygen atom is lost during the conversion of CO32- groups to CO2, this reaction is hypothesized to result in mineral and acid digestion temperature-dependent fractionation. In order to quantify this fractionation between CO32- and CO2, this experiment seeks to determine acid fractionation factors for carbonate samples of varying composition by randomizing samples through intense heating and comparing analyte CO2 measured composition to the expected composition for a stochastically distributed sample. From this analysis, future carbonate measurements can be calibrated to account for acid digestion fractionation.

  8. Curve fitting for restoration of accuracy for overlapping peaks in gas chromatography/combustion isotope ratio mass spectrometry.

    PubMed

    Goodman, K J; Brenna, J T

    1994-04-15

    The effect of graded degrees of overlap on high-precision and -accuracy carbon isotope ratios determined by gas chromatography/combustion isotope ratio mass spectrometry (GCC/IRMS) is reported. Overlapping peaks of closely matched isotope ratio (difference delta 13CPDB < 1%) were analyzed by the conventional vertical drop summation algorithm and by curve fitting using the Levenberg-Marquardt algorithm. The conventional algorithm resulted in systematic bias related to degree of overlap even though precision was not noticeably affected. The exponentially modified Gaussian (EMG) and HaarhoffVanderLinde (HVL) functions were found to model GCC/IRMS peaks satisfactorily. Useful models over a wide range of overlap were obtained by applying consecutive HVL/HVL or HVL/EMG functions to overlapping peaks. Accuracy was improved in most cases and was never degraded. This study demonstrates the presence of subtle bias in isotope ratio determinations of overlapping peaks and the ability of automated curve fitting to compensate for these biases. PMID:8210045

  9. Discrimination of geographical origin of lentils (Lens culinaris Medik.) using isotope ratio mass spectrometry combined with chemometrics.

    PubMed

    Longobardi, F; Casiello, G; Cortese, M; Perini, M; Camin, F; Catucci, L; Agostiano, A

    2015-12-01

    The aim of this study was to predict the geographic origin of lentils by using isotope ratio mass spectrometry (IRMS) in combination with chemometrics. Lentil samples from two origins, i.e. Italy and Canada, were analysed obtaining the stable isotope ratios of ?(13)C, ?(15)N, ?(2)H, ?(18)O, and ?(34)S. A comparison between median values (U-test) highlighted statistically significant differences (p<0.05) for all isotopic parameters between the lentils produced in these two different geographic areas, except for ?(15)N. Applying principal component analysis, grouping of samples was observed on the basis of origin but with overlapping zones; consequently, two supervised discriminant techniques, i.e. partial least squares discriminant analysis and k-nearest neighbours algorithm were used. Both models showed good performances with external prediction abilities of about 93% demonstrating the suitability of the methods developed. Subsequently, isotopic determinations were also performed on the protein and starch fractions and the relevant results are reported. PMID:26041202

  10. Determination of cadmium, mercury and lead in seawater by electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Liu, Hung-Wei; Jiang, Shiuh-Jen; Liu, Shin-Hung

    1999-09-01

    Electrothermal vaporization isotope dilution inductively coupled plasma mass spectrometry (ETV-ID-ICP-MS) has been applied to the determination of Cd, Hg and Pb in seawater samples. The isotope ratios of the elements studied in each analytical run were calculated from the peak areas of each isotope. Various modifiers were tested for the best signal of these elements. After preliminary studies, 0.15% m/v TAC and 4% v/v HCl were added to the sample solution to work as the modifier. The ETV-ID-ICP-MS method has been applied to the determination of Cd, Hg and Pb in NASS-4 and CASS-3 reference seawater samples and seawater samples collected from Kaohsiung area. The results for reference sample NASS-4 and CASS-3 agreed satisfactorily with the reference values. Results for other samples determined by isotope dilution and method of standard additions agreed satisfactorily. Detection limits were approximately 0.002, 0.005 and 0.001 ng ml -1 for Cd, Hg and Pb in seawater, respectively, with the ETV-ICP-MS method. Precision between sample replicates was better than 20% for most of the determinations.

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

    PubMed

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

    2014-08-01

    The performance of liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) for polar halogenated compounds was evaluated. Oxidation capacity of the system was tested with halogenated acetic acids and halogenated aromatic compounds. Acetic acid (AA) was selected as a reference compound for complete oxidation and compared on the molar basis to the oxidation of other analytes. The isotope values were proofed with calibrated ?(13)C values obtained with an elemental analyzer (EA). Correct isotope values were obtained for mono- and dichlorinated, fluorinated, and tribrominated acetic acids and also for aniline, phenol, benzene, bromobenzene, chlorobenzene, 1,2-dichlorobenzene, 2,4,6-trichlorophenol, pentafluorophenol, and nitrobenzene. Incomplete oxidation of trichloroacetic acid (TCA) and trifluoroacetic acid (TFA) resulted in lower recovery compared to AA (37% and 24%, respectively) and in isotopic shift compared to values obtained with EA (TCA ??(13)C(EA/LC-IRMS) = 8.8‰, TFA ??(13)C(EA/LC-IRMS) = 6.0‰). Improvement of oxidation by longer reaction time in the reactor and increase in the concentration of sulfate radicals did not lead to complete combustion of TCA and TFA needed for ?(13)C analysis. To the best of our knowledge, this is the first time such highly chlorinated compounds were studied with the LC-IRMS system. This work provides information for method development of LC-IRMS methods for halogenated contaminants that are known as potential threats to public health and the environment. PMID:24975492

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

    NASA Astrophysics Data System (ADS)

    Dwyer, G. S.; Vengosh, A.

    2012-12-01

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

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

    PubMed

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

    2014-09-24

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

  14. Deletion of Genes Encoding Arginase Improves Use of “Heavy” Isotope-Labeled Arginine for Mass Spectrometry in Fission Yeast

    PubMed Central

    Borek, Weronika E.; Zou, Juan; Rappsilber, Juri; Sawin, Kenneth E.

    2015-01-01

    The use of “heavy” isotope-labeled arginine for stable isotope labeling by amino acids in cell culture (SILAC) mass spectrometry in the fission yeast Schizosaccharomyces pombe is hindered by the fact that under normal conditions, arginine is extensively catabolized in vivo, resulting in the appearance of “heavy”-isotope label in several other amino acids, most notably proline, but also glutamate, glutamine and lysine. This “arginine conversion problem” significantly impairs quantification of mass spectra. Previously, we developed a method to prevent arginine conversion in fission yeast SILAC, based on deletion of genes involved in arginine catabolism. Here we show that although this method is indeed successful when 13C6-arginine (Arg-6) is used for labeling, it is less successful when 13C615N4-arginine (Arg-10), a theoretically preferable label, is used. In particular, we find that with this method, “heavy”-isotope label derived from Arg-10 is observed in amino acids other than arginine, indicating metabolic conversion of Arg-10. Arg-10 conversion, which severely complicates both MS and MS/MS analysis, is further confirmed by the presence of 13C515N2-arginine (Arg-7) in arginine-containing peptides from Arg-10-labeled cells. We describe how all of the problems associated with the use of Arg-10 can be overcome by a simple modification of our original method. We show that simultaneous deletion of the fission yeast arginase genes car1+ and aru1+ prevents virtually all of the arginine conversion that would otherwise result from the use of Arg-10. This solution should enable a wider use of heavy isotope-labeled amino acids in fission yeast SILAC. PMID:26075619

  15. Deletion of Genes Encoding Arginase Improves Use of "Heavy" Isotope-Labeled Arginine for Mass Spectrometry in Fission Yeast.

    PubMed

    Borek, Weronika E; Zou, Juan; Rappsilber, Juri; Sawin, Kenneth E

    2015-01-01

    The use of "heavy" isotope-labeled arginine for stable isotope labeling by amino acids in cell culture (SILAC) mass spectrometry in the fission yeast Schizosaccharomyces pombe is hindered by the fact that under normal conditions, arginine is extensively catabolized in vivo, resulting in the appearance of "heavy"-isotope label in several other amino acids, most notably proline, but also glutamate, glutamine and lysine. This "arginine conversion problem" significantly impairs quantification of mass spectra. Previously, we developed a method to prevent arginine conversion in fission yeast SILAC, based on deletion of genes involved in arginine catabolism. Here we show that although this method is indeed successful when 13C6-arginine (Arg-6) is used for labeling, it is less successful when 13C615N4-arginine (Arg-10), a theoretically preferable label, is used. In particular, we find that with this method, "heavy"-isotope label derived from Arg-10 is observed in amino acids other than arginine, indicating metabolic conversion of Arg-10. Arg-10 conversion, which severely complicates both MS and MS/MS analysis, is further confirmed by the presence of 13C515N2-arginine (Arg-7) in arginine-containing peptides from Arg-10-labeled cells. We describe how all of the problems associated with the use of Arg-10 can be overcome by a simple modification of our original method. We show that simultaneous deletion of the fission yeast arginase genes car1+ and aru1+ prevents virtually all of the arginine conversion that would otherwise result from the use of Arg-10. This solution should enable a wider use of heavy isotope-labeled amino acids in fission yeast SILAC. PMID:26075619

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

    PubMed Central

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

    2012-01-01

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

  17. Isotope dilution gas chromatography/mass spectrometry method for the determination of methionine sulfoxide in protein.

    PubMed

    Sochaski, M A; Jenkins, A J; Lyons, T J; Thorpe, S R; Baynes, J W

    2001-10-01

    We have developed a new technique for quantifying methionine sulfoxide (MetSO) in protein to assess levels of oxidative stress in physiological systems. In this procedure, samples are hydrolyzed with methanesulfonic acid (MSA) in order to avoid the conversion of MetSO to methionine (Met) that occurs during hydrolysis of protein in HCl. The hydrolysate is fractionated on a cation exchange column to remove the nonvolatile MSA from amino acids, and the amino acids are then derivatized as their trimethylsilyl esters for analysis by selected ion monitoring-gas chromatography/mass spectrometry. The limit of detection of the assay is 200 pmol of MetSO per analysis, and the interassay coefficient of variation is 5.8%. Compared to current methods, the SIM-GC/MS assay avoids the potential for conversion of Met to MetSO during sample preparation, requires less sample preparation time, has lower variability, and uses mass spectrometry for sensitive and specific analyte detection. PMID:11605844

  18. Simultaneous determination of creatinine and creatine in human serum by double-spike isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS).

    PubMed

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

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

    PubMed

    Merritt, D A; Hayes, J M

    1994-07-15

    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. PMID:11536639

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

    PubMed

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

    2013-04-16

    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

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

    PubMed

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

    2013-02-01

    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

  4. Measurement of very low stable isotope enrichments by gas chromatography/mass spectrometry: application to measurement of muscle protein synthesis.

    PubMed

    Patterson, B W; Zhang, X J; Chen, Y; Klein, S; Wolfe, R R

    1997-08-01

    Measurement of muscle protein synthesis using stable isotopically labeled tracers usually requires isotope ratio mass spectrometry (IRMS) because of the need to measure very low enrichments of stable isotopically labeled tracers (tracer to tracee ratio [TTR], 0.005% to 0.10%). This approach is laborious, requiring purification of the metabolite of interest and combustion to a gas for IRMS analysis, and is best suited for use with 13C tracers. We have developed an approach whereby low enrichments can be conveniently measured by a conventional gas chromatography/mass spectrometry (GC/MS) instrument. The approach includes three critical elements: (1) use of a highly substituted tracer containing three or more labeled atoms, to measure enrichment above a very low natural abundance of highly substituted isotopomers; (2) use of a highly substituted natural abundance isotopomer as a base ion for comparison rather than the most abundant m + 0 isotopomer, to reduce the dynamic range of the isotopomer ratio measurement; and (3) a sensitive mass spectrometric analysis that measures the natural abundance of the isotopomer used as a tracer with a high signal to noise ratio (> 100:1). This approach was used to measure the rate of synthesis of muscle protein following a primed continuous infusion of L-[13C6]-phenylalanine (PHE) in eight fasted dogs and L-[2H3]-leucine in five fasted human subjects. Values for [13C6]-PHE enrichment by GC/MS rates were virtually identical to those obtained by a conventional approach using high-performance liquid chromatography (HPLC) to isolate PHE, combustion to CO2, and measurement of 13CO2 enrichment by IRMS (IRMS enrichment = 0.9988 x GC/MS enrichment, R2 = .891), resulting in identical values for muscle fractional synthesis rates ([FSRs] mean +/- SEM: 2.7 +/- 0.2 and 2.5 +/- 0.2%/d for GC/MS and IRMS, respectively). Human muscle synthesis rates measured by GC/MS analysis of [2H3]-leucine enrichment (1.90 +/- 0.17%/d) were similar to published values based on IRMS analysis using a 1- 13C-leucine tracer. We conclude that compared with the IRMS approach, the GC/MS approach offers faster throughput, has a lower sample requirement, and is suitable for a wider variety of tracers such as 2H. The principles outlined here should be applicable to the measurement of low enrichments by GC/MS in a wide variety of stable isotope tracer applications. PMID:9258279

  5. 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

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

    2004-01-01

    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

  6. Development of an on-line isotope dilution laser ablation inductively coupled plasma mass spectrometry (LA–ICP-MS) method for determination of boron in silicon wafers

    Microsoft Academic Search

    Chao-Kai Yang; Po-Hsiang Chi; Yong-Chine Lin; Yuh-Chang Sun; Mo-Hsiung Yang

    2010-01-01

    A method has been developed based on an on-line isotope dilution technique couple with laser ablation\\/inductively coupled plasma mass spectrometry (LA–ICP-MS), for the determination of boron in p-type silicon wafers. The laser-ablated sample aerosol was mixed on-line with an enriched boron aerosol supplied continuously using a conventional nebulization system. Upon mixing the two aerosol streams, the isotope ratio of boron

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

    PubMed

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

    2013-12-01

    A procedure to detect whether carbon dioxide was added to French ciders has been developed. For this purpose, an optimised and simplified method is proposed to determine (13)C/(12)C isotope ratio of carbon dioxide (?(13)C) in ciders. Three critical steps were checked: (1) influence of atmospheric CO2 remaining in the loaded vial, (2) impact of helium flush, (3) sampling speed. This study showed that atmospheric CO2 does not impact the measurement, that helium flush can lead to isotopic fractionation and finally, that a fractionation occurs only 5h after bottle opening. The method, without any other preparation, consists in sampling 0.2 mL of cold (4 °C) cider in a vial that is passed in an ultrasonic bath for 10 min at room temperature to enhance cider de-carbonation. The headspace CO2 is then analysed using the link Multiflow®-isotope ratio mass spectrometer. Each year, a data bank is developed by fermenting authentic apples juices in order to control cider authenticity. Over a four year span (2008-2011), the CO2 produced during the fermentation step was studied. This set of 61 authentic ciders, from various French production areas, was used to determine a ?(13)C value range of -22.59±0.92‰ for authentic ciders CO2 bubbles. 75 commercial ciders were analysed with this method. Most of the samples analysed present a gas ?(13)C value in the expected range. Nevertheless, some ciders have ?(13)C values outside the 3? limit, revealing carbonation by technical CO2. This practice is not allowed for organic, "Controlled Appellation of Origin" ciders and ciders specifying natural carbonation on the label. PMID:23870934

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

    PubMed Central

    2015-01-01

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

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

    PubMed

    Varga, Zsolt

    2008-01-01

    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

  10. Accuracy of some routine method used in clinical chemistry as judged by isotope dilution-mass spectrometry

    SciTech Connect

    Bjoerkhem, I.; Bergman, A.; Falk, O.; Kallner, A.; Lantto, O.; Svensson, L.; Akerloef, E.; Blomstrand, R.

    1981-05-01

    Serum from patients was pooled, filtered, dispensed, and frozen. This pooled specimen was used for accuracy control in 64 participating laboratories in Sweden. Mean values (state-of-the-art values) were obtained for creatinine, cholesterol, glucose, urea, uric acid, and cortisol. These values were compared with values obtained with highly accurate reference methods based on isotope dilution-mass spectrometry. Differences were marked in the case of determination of creatinine and cortisol. Concerning the other components, the differences between the state-of-the-art value and the values obtained with the reference methods were negligible. Moreover, the glucose oxidase and the oxime methods for determination of glucose and urea were found to give significantly lower values than the hexokinase and urease methods, respectively. Researchers conclude that methods with a higher degree of accuracy are required for routine determination of creatinine and cortisol.

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

    PubMed

    Huang, L Q

    1989-01-01

    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 15N,13C-alachlor and 2H5-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. PMID:2651394

  12. Application of speciated isotope dilution mass spectrometry to evaluate extraction methods for determining mercury speciation in soils and sediments.

    PubMed

    Rahman, G M Mizanur; Kingston, H M Skip

    2004-07-01

    Extraction techniques commonly used to extract methylmercury or mercury species from various matrixes have been evaluated regarding their potential to transform inorganic mercury to methylmercury, or vice versa, during sample preparation steps by applying speciated isotope dilution mass spectrometry. Two of the five tested methods were highly prone to form inorganic mercury from methylmercury. Some published methods converted methylmercury to inorganic mercury approximately 100% (including the spiked CH(3)(201)Hg(+)). In other methods, as much as 45% of methylmercury was converted to inorganic mercury during extraction. The methods evaluated included cold acid extraction and sonication. Other methods, such as the proposed EPA RCRA Draft Method 3200, microwave-assisted extraction, and another sonication-based methods induced very little or no methylmercury transformation to inorganic mercury. Among these three methods, the proposed Draft EPA Method 3200 was found to be the most efficient. PMID:15228324

  13. Effect of H/D isotopomerization in the assay of resveratrol by tandem mass spectrometry and isotope dilution method.

    PubMed

    Di Donna, Leonardo; Mazzotti, Fabio; Benabdelkamel, Hicham; Gabriele, Bartolo; Plastina, Pierluigi; Sindona, Giovanni

    2009-10-15

    Resveratrol is a phytoalexin found in several plant tissues and present in wines, which is supplied as a nutritional supplement. Different studies have revealed its beneficial effects as anticancer, antiviral, neuroprotective, antiaging, and anti-inflammatory natural active principle. The assaying of resveratrol by mass spectrometry and isotope dilution method, using a stable [(2)H(4)] analogue, has required a full elucidation of its gas-phase H/D isotopomerization. Either selected ion monitoring (SIM) or multiple reaction monitoring (MRM) methods have been used for the evaluation of the amount of resveratrol present in wine and plasma samples in the negative ionization mode. In all instances the acquired accuracy, limit of quantitation (LOQ), and limit of detection (LOD) are fit for the intended purpose of the assay. PMID:19769389

  14. DETERMINATION OF 5-METHYLTETRAHYDROFOLIC ACID IN HUMAN SERUM BY STABLE-ISOTOPE DILUTION HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This report describes a stable isotope liquid chromatography-mass spectrometry (LC-MS) method that was developed for the quantitative determination of 5-methyltetrahydrofolic acid (5-MTHFA) and folic acid in a variety of citrus juices. Folates were extracted from juices and the polyglutamyl side ch...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  16. The use of total evaporation method using Channeltron electron multipliers by thermal ionization mass spectrometry for europium isotope ratio measurements on picogram sample amounts

    Microsoft Academic Search

    S. Mialle; A. Quémet; A. Ponvienne; A. Gourgiotis; M. Aubert; H. Isnard; F. Chartier

    Thermal ionization mass spectrometry (TIMS) is a well established instrumental technique for providing accurate and precise isotope ratio measurements for elements with low first ionization potential. In the nuclear domain, particularly for the study of spent nuclear fuel sample solutions, the reduction of quantities is an important issue in order to decrease the analyst exposition to the radioactive samples. This

  17. Achieving traceable chemical measurements: inter-laboratory evaluation of a simplified technique for isotope dilution mass spectrometry. Part 2. Methodology for high accuracy analysis of organic analytes

    Microsoft Academic Search

    Mike Sargent; Gerry Newman; Ken Webb

    2004-01-01

    A high accuracy measurement procedure developed and validated at LGC has been transferred to a number of expert UK laboratories, and their experience in applying the technique has been evaluated by inter-laboratory comparisons. It is an “exact matching” calibration procedure for analysis of organic analytes using isotope dilution mass spectrometry (IDMS). This calibration procedure uses a calibration blend and a

  18. Measurement of Niacin in a Variety of Food Samples by High Performance Liquid Chromatography-Stable Isotope Dilution Mass Spectrometry (Experimental Biology, April, 2007, Washington, D.C.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. Metal Oxide-Based Selective Enrichment Combined with Stable Isotope Labeling-Mass Spectrometry Analysis for Profiling of Ribose Conjugates.

    PubMed

    Chu, Jie-Mei; Qi, Chu-Bo; Huang, Yun-Qing; Jiang, Han-Peng; Hao, Yan-Hong; Yuan, Bi-Feng; Feng, Yu-Qi

    2015-07-21

    Some modified ribonucleosides in biological fluids have been evaluated as cancer-related metabolites. Detection of endogenous modified ribonucleosides in biological fluids may serve as a noninvasive cancers diagnostic method. However, determination of modified ribonucleosides is still challenging because of their low abundance and serious matrix interferences in biological fluids. Here, we developed a novel strategy for comprehensive profiling of ribose conjugates from biological fluids using metal oxide-based dispersive solid-phase extraction (DSPE) followed with in vitro stable isotope labeling and double neutral loss scan-mass spectrometry analysis (DSPE-SIL-LC-DNLS-MS). Cerium dioxide (CeO2) was used to selectively recognize and capture ribose conjugates from complex biological samples under basic environment. The enriched ribose conjugates were subsequently labeled with a pair of isotope labeling reagents (acetone and acetone-d6). The glucosidic bond of acetone labeled ribose conjugates is readily ruptured, and the generated ribose that carries an isotope tag can be lost as a neutral fragment under collision induced dissociation (CID). Since the light (acetone) and heavy (acetone-d6) labeled compounds have the same chemical structures and can generate different neutral loss fragments (NL 172 and 178 Da), it is therefore highly convenient to profile ribose conjugates by double neutral loss scan mode in mass spectrometry analysis. In this respect, the light and heavy labeled compounds were ionized at the same condition but recorded separately on MS spectra, which can significantly improve the detection specificity and facilitate the identification of ribose conjugates. Using the developed DSPE-SIL-LC-DNLS-MS strategy, we profiled the ribose conjugates in human urine, and 49 ribose conjugates were readily identified, among which 7 ribose conjugates exhibited significant contents change between healthy controls and lymphoma patients. The DSPE-SIL-LC-DNLS-MS strategy combines the selective enrichment, stable isotope labeling, and double neutral loss scan - MS analysis, which therefore can efficiently minimize false positive results, facilitate the relative quantification, and notably increase the numbers of identified ribose conjugates in biological fluids samples. Taken together, this study established a promising strategy for the effective profiling of urinary modified ribonucleosides, and simultaneous evaluation of the contents change of multiple modified ribonucleosides should provide more accurate and conclusive results for the use of urinary modified ribonucleosides as indicators of cancers. PMID:26086917

  20. What is Mass Spectrometry?

    NSDL National Science Digital Library

    Chiu, Chia M.

    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?"

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

    PubMed

    Guyon, Francois; Gaillard, Laetitia; Brault, Audrey; Gaultier, Nicolas; Salagoïty, Marie-Hélène; Médina, Bernard

    2013-12-27

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

  2. Development of versatile isotopic labeling reagents for profiling the amine submetabolome by liquid chromatography-mass spectrometry.

    PubMed

    Zhou, Ruokun; Huan, Tao; Li, Liang

    2015-06-30

    Metabolomic profiling involves relative quantification of metabolites in comparative samples and identification of the significant metabolites that differentiate different groups (e.g., diseased vs. controls). Chemical isotope labeling (CIL) liquid chromatography-mass spectrometry (LC-MS) is an enabling technique that can provide improved metabolome coverage and metabolite quantification. However, chemical identification of labeled metabolites can still be a challenge. In this work, a new set of isotopic labeling reagents offering versatile properties to enhance both detection and identification are described. They were prepared by a glycine molecule (or its isotopic counterpart) and an aromatic acid with varying structures through a simple three-step synthesis route. In addition to relatively low costs of synthesizing the reagents, this reaction route allows adjusting reagent property in accordance with the desired application objective. To date, two isotopic reagents, 4-dimethylaminobenzoylamido acetic acid N-hydroxylsuccinimide ester (DBAA-NHS) and 4-methoxybenzoylamido acetic acid N-hydroxylsuccinimide ester (MBAA-NHS), for labeling the amine-containing metabolites (i.e., amine submetabolome) have been synthesized. The labeling conditions and the related LC-MS method have been optimized. We demonstrate that DBAA labeling can increase the metabolite detectability because of the presence of an electrospray ionization (ESI)-active dimethylaminobenzoyl group. On the other hand, MBAA labeled metabolites can be fragmented in MS/MS and pseudo MS(3) experiments to provide structural information on metabolites of interest. Thus, these reagents can be tailored to quantitative profiling of the amine submetabolome as well as metabolite identification in metabolomics applications. PMID:26041526

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

    Microsoft Academic Search

    Sankha S Basu; Ian A Blair

    2011-01-01

    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

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

    PubMed

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

    2014-01-01

    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

  5. Stable isotopic analysis of pyrogenic organic matter in soils by liquid chromatography-isotope-ratio mass spectrometry of benzene polycarboxylic acids.

    PubMed

    Yarnes, Christopher; Santos, Fernanda; Singh, Nimisha; Abiven, Samuel; Schmidt, Michael W I; Bird, Jeffrey A

    2011-12-30

    Pyrogenic organic matter (PyOM), the incomplete combustion product of organic materials, is considered stable in soils and represents a potentially important terrestrial sink for atmospheric carbon dioxide. One well-established method of measuring PyOM in the environment is as benzene polycarboxylic acids (BPCAs), a compound-specific method, which allows both qualitative and quantitative estimation of PyOM. Until now, stable isotope measurement of PyOM carbon involved measurement of the trimethylsilyl (TMS) or methyl (Me) polycarboxylic acid derivatives by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). However, BPCA derivatives can contain as much as 150% derivative carbon, necessitating post-analysis correction for the accurate measurement of ?¹³C values, leading to increased measurement error. Here, we describe a method for ?¹³C isotope ratio measurement and quantification of BPCAs from soil-derived PyOM, based on ion-exchange chromatography (IEC-IRMS). The reproducibility of the ?¹³C measurement of individual BPCAs by IEC-IRMS was better than 0.35‰ (1?). The ?¹³C-BPCA analysis of PyOM in soils, including at natural and artificially enriched ¹³C-abundance, produced accurate and precise ?¹³C measurements. Analysis of samples that differed in ?¹³C by as much as 900‰ revealed carryover of <1‰ between samples. The weighted sum of individual ?¹³C-BPCA measurements was correlated with previous isotopic measurements of whole PyOM, providing complementary information for bulk isotopic measurements. We discuss potential applications of ?¹³C-BPCA measurements, including the study of turnover rates of PyOM in soils and the partitioning of PyOM sources based on photosynthetic pathways. PMID:22468329

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

    NASA Astrophysics Data System (ADS)

    Kawashima, Hiroto; Murakami, Mai

    2014-06-01

    The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular of their stable carbon isotope ratio (?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.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-05-01

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

  9. Analysis of organophosphate flame retardants and plasticisers in water by isotope dilution gas chromatography-electron ionisation tandem mass spectrometry.

    PubMed

    Teo, Tiffany L L; McDonald, James A; Coleman, Heather M; Khan, Stuart J

    2015-10-01

    The widespread use of organophosphate flame retardants (PFRs) in commercial products have led to their increased presence in the environment. In this study, a rapid and reliable analytical method was developed for the analysis of five PFRs in water using gas chromatography tandem mass spectrometry (GC-MS/MS) with electron ionisation (EI) and a run time of 13min. The PFRs investigated were tributyl phosphate (TBP), tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), tris(1,3-dichloro-2-propyl) phosphate (TDCP) and triphenyl phosphate (TPP). Solid phase extraction (SPE) was undertaken to extract and concentrate target analytes from aqueous matrices. All water samples were extracted from a volume of 500mL. Isotopically labelled compounds were used to account for analytical variability and for accurate quantification by isotope dilution. Method recoveries for all compounds were above 80% in all tested water samples. Method detection limits for all target analytes ranged from 0.3 to 24ng/L in ultrapure water, tap water, seawater, surface water, secondary effluent and swimming pool water. Validation of this method confirmed satisfactory method stability with less than 1% coefficients of variation, verifying that this approach produced good reproducibility. PMID:26078137

  10. Fast and accurate procedure for the determination of Cr(VI) in solid samples by isotope dilution mass spectrometry.

    PubMed

    Fabregat-Cabello, Neus; Rodríguez-González, Pablo; Castillo, Ángel; Malherbe, Julien; Roig-Navarro, Antoni F; Long, Stephen E; García Alonso, J Ignacio

    2012-11-20

    We present here a new environmental measurement method for the rapid extraction and accurate quantification of Cr(VI) in solid samples. The quantitative extraction of Cr(VI) is achieved in 10 minutes by means of focused microwave assisted extraction using 50 mmol/L Ethylendiamintetraacetic acid (EDTA) at pH 10 as extractant. In addition, it enables the separation of Cr species by anion exchange chromatography using a mobile phase which is a 1:10 dilution of the extracting solution. Thus, neutralization or acidification steps which are prone to cause interconversion of Cr species are not needed. Another benefit of using EDTA is that it allows to measure Cr(III)-EDTA complex and Cr(VI) simultaneously in an alkaline extraction solution. The application of a 10 minutes focused microwave assisted extraction (5 min at 90 °C plus 5 min at 110 °C) has been shown to quantitatively extract all forms of hexavalent chromium from the standard reference materials (SRM) candidate NIST 2700 and NIST 2701. A double spike isotope dilution mass spectrometry (IDMS) procedure was employed to study chromium interconversion reactions. It was observed that the formation of a Cr(III)-EDTA complex avoided Cr(III) oxidation for these two reference materials. Thus, the use of a double spiking strategy for quantification is not required and a single spike IDMS procedure using isotopically enriched Cr(VI) provided accurate results. PMID:23092182

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

    SciTech Connect

    Beals, D.M.

    1992-09-01

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

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

    SciTech Connect

    Beals, D.M.

    1992-01-01

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

  13. Determination of cadmium in oyster tissue using isotope dilution inductively coupled plasma mass spectrometry: comparison of results obtained in the standard and He\\/H 2 cell modes

    Microsoft Academic Search

    Yiu-chung Yip; Hei-shing Chu; Kwok-chu Chan; Kam-kit Chan; Ping-yuk Cheung; Wing-cheong Sham

    2006-01-01

    An inductively coupled plasma quadrupole mass spectrometer equipped with an octopole collision\\/reaction cell was used for\\u000a the determination of cadmium in oyster tissue samples using isotope dilution inductively coupled plasma mass spectrometry.\\u000a The oyster samples in question were found to contain Mo and Zr. In our feasibility study on a Cd standard solution (10 ?g\\u000a L?1) containing a matrix of Mo

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

    PubMed

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

    2015-04-01

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

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

    PubMed

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

    2014-01-01

    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

  16. Accurate measurement of uranium isotope ratios in soil samples using thermal ionization mass spectrometry equipped with a warp energy filter

    Microsoft Academic Search

    Sarata Kumar Sahoo; Yuji Nakamura; Kunio Shiraishi; Akimasa Masuda

    2004-01-01

    A chemical and mass-spectrometric procedure for uranium isotopic analysis using a thermal ionisation mass spectrometer equipped with a Wide Aperture Retardation Potential energy filter has been developed and applied to uranium isotopic measurements for various soil samples. Soil samples were digested using a microwave digestor. Uranium was isolated from soil samples by the chemical separation procedure based on the use

  17. Quantitative proteomic approaches in mouse: stable isotope incorporation by metabolic (SILAC) or chemical labeling (reductive dimethylation) combined with high-resolution mass spectrometry.

    PubMed

    Billing, Anja M; Ben Hamidane, Hisham; Graumann, Johannes

    2015-01-01

    Mass spectrometry-based quantitative proteomics is a powerful method for in-depth exploration of protein expression, allowing researchers to probe its regulation and study signal-transduction networks, protein turnover, secretion, and spatial distribution, as well as post-translational modification and protein-protein interaction, on a large scale. Precise protein quantitation may be achieved by incorporation of stable isotopes, which introduce a mass shift detectable by mass spectrometry, allowing multiplexing of several samples and therefore relative quantification. Stable isotope incorporation into proteins or peptides can be attained either by metabolic labeling (e.g., SILAC) or by chemical labeling (e.g., reductive dimethylation). Both labeling approaches are presented here. They are straightforward and robust and can be applied to murine samples. While both SILAC and reductive dimethylation offer similar multiplexing capabilities and quantitative accuracy, reductive dimethylation is more versatile and can be used with any sample type. PMID:25727197

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

    NASA Astrophysics Data System (ADS)

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

    2001-09-01

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

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

    SciTech Connect

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

    2008-07-15

    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.

  20. Kinetics of intestinal calcium absorption in humans measured using stable isotopes and high-precision thermal ionization mass spectrometry.

    PubMed

    Price, R I; Kent, G N; Rosman, K J; Gutteridge, D H; Reeve, J; Allen, J P; Stuckey, B G; Smith, M; Guelfi, G; Hickling, C J

    1990-06-01

    Oral (44Ca: 0.13-0.20 mmol) and intravenous (42Ca: 0.02-0.037 mmol) isotopically enriched stable calcium (Ca) tracers were given together with an oral dose of 2.5 mmol of natural Ca to normal subjects. Blood and urine samples were collected up to 24 h after the tracer doses and atom fractions (AFs) of these tracers (relative to natural Ca) were measured by high-precision thermal ionization mass spectrometry (TIMS). The time-dependent fractional rate of oral dose absorbed and true fractional intestinal Ca absorption (alpha) were derived from the Afs by mathematical deconvolution. After 6 h, the ratio AF oral tracer/AF intravenous tracer in blood equalled that in urine and did not change thereafter. Reproducibility of the combination of chemical precipitation of Ca (from a urine standard) and subsequent TIMS measurements, in nine runs over 13 months, was 1.2% (coefficient of variation). This was in accord with the within-run reproducibility. An estimate of alpha derived from a single blood or urine measurement was 6-10% higher than the reference value obtained by deconvolution. This discrepancy could be explained by a correction factor depending, in part, on the elapsed time for peak Ca intestinal absorption rate. Instrumentally induced mass fractionation, as well as contributions from radiogenic Ca, had a significant effect on the accuracy and reproducibility of the ratio of AFs of tracers in blood and urine. PMID:2357488

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

    USGS Publications Warehouse

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

    2009-01-01

    Accurate determinations of stable isotope ratios require a calibration using at least two reference materials with different isotopic compositions to anchor the isotopic scale and compensate for differences in machine slope. Ideally, the 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.

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

    PubMed Central

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

    2014-01-01

    RATIONALE We describe an analytical procedure that allows sample collection and measurement of carbon isotopic composition (?13CV-PDB value) and dissolved inorganic carbon concentration, [DIC], in aqueous samples without further manipulation post field collection. By comparing outputs from two different mass spectrometers, we quantify with the statistical rigour uncertainty associated with the estimation of an unknown measurement. This is rarely undertaken, but it is needed to understand the significance of field data and to interpret quality assurance exercises. METHODS Immediate acidification of field samples during collection in evacuated, pre-acidified vials removed the need for toxic chemicals to inhibit continued bacterial activity that might compromise isotopic and concentration measurements. Aqueous standards mimicked the sample matrix and avoided headspace fractionation corrections. Samples were analysed using continuous-flow isotope-ratio mass spectrometry, but for low DIC concentration the mass spectrometer response could be non-linear. This had to be corrected for. RESULTS Mass spectrometer non-linearity exists. Rather than estimating precision as the repeat analysis of an internal standard, we have adopted inverse linear calibrations to quantify the precision and 95% confidence intervals (CI) of the ?13CDIC values. The response for [DIC] estimation was always linear. For 0.05–0.5 mM DIC internal standards, however, changes in mass spectrometer linearity resulted in estimations of the precision in the ?13CVPDB value of an unknown ranging from ± 0.44‰ to ± 1.33‰ (mean values) and a mean 95% CI half-width of ±1.1–3.1‰. CONCLUSIONS Mass spectrometer non-linearity should be considered in estimating uncertainty in measurement. Similarly, statistically robust estimates of precision and accuracy should also be adopted. Such estimations do not inhibit research advances: our consideration of small-scale spatial variability at two points on a small order river system demonstrates field data ranges larger than the precision and uncertainties. However, without such statistical quantification, exercises such as inter-lab calibrations are less meaningful. PMID:24711275

  3. Mass spectrometry of long-lived radionuclides

    NASA Astrophysics Data System (ADS)

    Becker, Johanna Sabine

    2003-10-01

    The capability of determining element concentrations at the trace and ultratrace level and isotope ratios is a main feature of inorganic mass spectrometry. The precise and accurate determination of isotope ratios of long-lived natural and artificial radionuclides is required, e.g. for their environmental monitoring and health control, for studying radionuclide migration, for age dating, for determining isotope ratios of radiogenic elements in the nuclear industry, for quality assurance and determination of the burn-up of fuel material in a nuclear power plant, for reprocessing plants, nuclear material accounting and radioactive waste control. Inorganic mass spectrometry, especially inductively coupled plasma mass spectrometry (ICP-MS) as the most important inorganic mass spectrometric technique today, possesses excellent sensitivity, precision and good accuracy for isotope ratio measurements and practically no restriction with respect to the ionization potential of the element investigated—therefore, thermal ionization mass spectrometry (TIMS), which has been used as the dominant analytical technique for precise isotope ratio measurements of long-lived radionuclides for many decades, is being replaced increasingly by ICP-MS. In the last few years instrumental progress in improving figures of merit for the determination of isotope ratio measurements of long-lived radionuclides in ICP-MS has been achieved by the application of a multiple ion collector device (MC-ICP-MS) and the introduction of the collision cell interface in order to dissociate disturbing argon-based molecular ions, to reduce the kinetic energy of ions and neutralize the disturbing noble gas ions (e.g. of 129Xe + for the determination of 129I). The review describes the state of the art and the progress of different inorganic mass spectrometric techniques such as ICP-MS, laser ablation ICP-MS vs. TIMS, glow discharge mass spectrometry, secondary ion mass spectrometry, resonance ionization mass spectrometry and accelerator mass spectrometry for the determination of long-lived radionuclides in quite different materials.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  5. Heart-cutting two-dimensional gas chromatography in combination with isotope ratio mass spectrometry for the characterization of the wax fraction in plant material.

    PubMed

    Dumont, Emmie; Tienpont, Bart; Higashi, Nobukazu; Mitsui, Kazuhisa; Ochiai, Nobuo; Kanda, Hirooki; David, Frank; Sandra, Pat

    2013-11-22

    Gas chromatography coupled to isotope ratio mass spectrometry after on-line combustion (GC-C-IRMS) and high temperature conversion (GC-HTC-IRMS) is used for compound specific isotope ratio determination. This determination can only be performed successfully if the target solutes are fully resolved from other compounds. A new instrumental set-up consisting of heart-cutting two-dimensional GC based on capillary flow technology and a low thermal mass GC oven in combination with an isotope ratio mass spectrometer is presented. Capillary flow technology was also used in all column and interface connections for robust and leak-free operation. The new configuration was applied to the characterization of wax compounds in tobacco leaf and corresponding smoke samples. It is demonstrated that high accuracy is obtained, both in the determination of ?(13)C and ?(2)H values, allowing the study of biosynthesis and delivery mechanisms of naturally occurring compounds in tobacco. PMID:23721809

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

    E-print Network

    Suen, Timothy Wu

    2012-01-01

    chemical reactions during laser ablation. Contents Acknowledgments iii Introduction and Background 1.1 Nuclear Safeguards and Nuclear Forensics . . . . . . . . . . . . . .and forensics [20], however, isotopic analysis plays a critical role, providing information about intended use, reactor conditions, age, and chemicalforensics, on the other hand, makes use of a much broader array of analytical techniques, from trace chemical

  7. Isolation of bicarbonate from equine urine for isotope ratio mass spectrometry.

    PubMed

    Hülsemann, Frank; Flenker, Ulrich; Machnik, Marc; Schänzer, Wilhelm

    2007-12-01

    Sodium bicarbonate administration to horses prior to competition in order to enhance the buffer capacity of the organism is considered as a doping offence. The analysis of the isotopic composition of urinary bicarbonate/CO(2) (TCO(2)) may help to identify an exogenous bicarbonate source, as technical sodium bicarbonate exhibits elevated delta(13)C values compared with urinary total carbon. The isolation of TCO(2) from 60 equine urine samples as BaCO(3) followed by an isotopic analysis shows a significant variability of delta(13)C for TCO(2) of more than 10 per thousand. The delta(13)C of total carbon and TCO(2) seem to reflect different proportions of C3 and C4 plant material in the diet. The isotopic analysis of different mixtures of technical NaHCO(3) and equine urine shows that TCO(2) can be easily isolated without major isotopic fractionation; however, attention has to be paid to the storage time of urine samples, as a shift of delta(13)C of TCO(2) to lower values may occur. PMID:18041617

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

    PubMed

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

    2015-04-01

    Polyethylene is probably the most used plastic material in daily life and its accurate analysis is of importance. In this communication the chemical structure of polyethylenes is studied in detail using conventional analytical pyrolysis (Py-GC/MS), bulk stable isotopic analysis (IRMS) and pyrolysis compound specific stable isotopic analysis (Py-CSIA) to measure stable isotope proportions (?(13)C, ?(15)N and ?D) of polyethylene pyrolysis compounds. Polyethylene pyrolysis yields triplet peaks of n-alkanes, ?-alkenes and ?,?-alkanedienes. No differences were found for bulk ?(13)C among different polyethylene types. However, conspicuous differences in ?D were evident. It was possible to assign structure ?(13)C and ?D values to specific polyethylene pyrolysis products in the range 12-18 carbon chain length. Conspicuous differences were found for the pyrolysis products with unsaturated moieties showing significant higher ?D values than saturated chains (alkanes) that were deuterium depleted. In addition, a full isotopic fingerprinting (?(13)C, ?(15)N and ?D) for a dye (o-chloroaniline) contained in a polyethylene is reported. To the best of our knowledge this is the first application Py-CSIA to the study of a synthetic polymer. This hyphenated analytical technique is a promising tool to study synthetic materials, providing not only a fingerprinting, but also allowing the traceability of the polymerization process and the origin of the materials. PMID:25725959

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

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

    PubMed

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

    2013-01-01

    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

  11. Fourier transform mass spectrometry.

    PubMed

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

    2011-07-01

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

  12. Determination of 3-quinuclidinyl benzilate (QNB) and its major metabolites in urine by isotope dilution gas chromatography/mass spectrometry.

    PubMed

    Byrd, G D; Paule, R C; Sander, L C; Sniegoski, L T; White, E; Bausum, H T

    1992-01-01

    In response to the scheduled destruction of U.S. military stockpiles of the hallucinogenic agent 3-quinuclidinyl benzilate (QNB), a specific confirmatory test for human exposure to QNB was developed. The amount of the parent compound in the urine as well as the two major metabolites, 3-quinuclidinol (Q) and benzilic acid (BA), was determined because the relationship between QNB dose and levels of QNB and its metabolites in human urine is not known. QNB was determined in urine samples spiked at a target level of 0.5 ng/mL, and the metabolites BA and Q were determined at a target level of 5 ng/mL. The method uses solid-phase extraction to isolate each analyte from the urine and isotope dilution gas chromatography/mass spectrometry for quantitation. Each analyte is converted to its trimethylsilyl derivative for analysis. The analytical method was tested on eight different urine samples spiked with known amounts of the analytes near the target levels, at 10 times the target levels, and blank (unspiked) urine samples. The variabilities in the method are for the most part evenly distributed between three imprecision categories: GC/MS measurement, sample preparation, and the urine samples. The total imprecision (1 standard deviation) of a single measurement is about 15% of the value for each analyte. PMID:1522714

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

    SciTech Connect

    Lantto, O.

    1982-05-01

    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.

  14. Tracing nitrogenous disinfection byproducts after medium pressure UV water treatment by stable isotope labeling and high resolution mass spectrometry.

    PubMed

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

    2015-04-01

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

  15. Determining mycotoxins in baby foods and animal feeds using stable isotope dilution and liquid chromatography tandem mass spectrometry.

    PubMed

    Zhang, Kai; Wong, Jon W; Krynitsky, Alexander J; Trucksess, Mary W

    2014-09-10

    We developed a stable isotope dilution assay with liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine multiple mycotoxins in baby foods and animal feeds. Samples were fortified with [(13)C]-uniformly labeled mycotoxins as internal standards ([(13)C]-IS) and prepared by solvent extraction (50% acetonitrile in water) and filtration, followed by LC-MS/MS analysis. Mycotoxins in each sample were quantitated with the corresponding [(13)C]-IS. In general, recoveries of aflatoxins (2-100 ng/g), deoxynivalenol, fumonisins (50-2000 ng/g), ochratoxin A (20-1000 ng/kg), T-2 toxin, and zearalenone (40-2000 ng/g) in tested matrices (grain/rice/oatmeal-based formula, animal feed, dry cat/dog food) ranged from 70 to 120% with relative standard deviations (RSDs) <20%. The method provides sufficient selectivity, sensitivity, accuracy, and reproducibility to screen for aflatoxins at ng/g concentrations and deoxynivalenol and fumonisins at low ?g/g concentrations in baby foods and animal feeds, without using conventional standard addition or matrix-matched calibration standards to correct for matrix effects. PMID:25153173

  16. Isotope dilution gas chromatography-mass spectrometry in the determination of benzene, toluene, styrene and acrylonitrile in mainstream cigarette smoke.

    PubMed

    Byrd, G D; Fowler, K W; Hicks, R D; Lovette, M E; Borgerding, M F

    1990-03-23

    A cryogenic trapping method with isotope dilution gas chromatography-mass spectrometry analysis has been developed for the determination of benzene, toluene, styrene and acrylonitrile in mainstream vapor phase cigarette smoke. The method is simple, direct, and quantitative. Vapor phase samples are collected cryogenically in a series of four traps following removal of the particulate phase with a Cambridge filter pad. For all four analytes, 75-85% of the total amounts recovered were found in the initial trap and less than 1% in the final trap. Assessment of instrumental precision by multiple injections of a sample gave relative standard deviations of less than 2%. Linear calibration for all analytes over the analysis range gave an r2 value greater than 0.99 with average relative standard deviations at the mean ranging from 1.4 to 8.2%. The cigarettes analyzed include a reference cigarette (Kentucky 1R4F), a commercial ultra-low "tar" mentholated cigarette, and two cigarettes that heat but do not burn tobacco. The values determined for the four analytes in the 1R4F samples are comparable to reported values of similar cigarettes. The cigarettes which heat rather than burn tobacco yield less of all four analytes compared to the other cigarettes in the study. PMID:2185256

  17. Liquid chromatography with isotope-dilution mass spectrometry for determination of water-soluble vitamins in foods.

    PubMed

    Phillips, Melissa M

    2015-04-01

    Vitamins are essential for improving and maintaining human health, and the main source of vitamins is the diet. Measurement of the quantities of water-soluble vitamins in common food materials is important to understand the impact of vitamin intake on human health, and also to provide necessary information for regulators to determine adequate intakes. Liquid chromatography (LC) and mass spectrometry (MS) based methods for water-soluble vitamin analysis are abundant in the literature, but most focus on only fortified foods or dietary supplements or allow determination of only a single vitamin. In this work, a method based on LC/MS and LC/MS/MS has been developed to allow simultaneous quantitation of eight water-soluble vitamins, including multiple forms of vitamins B3 and B6, in a variety of fortified and unfortified food-matrix Standard Reference Materials (SRMs). Optimization of extraction of unbound vitamin forms and confirmation using data from external laboratories ensured accuracy in the assigned values, and addition of stable isotope labeled internal standards for each of the vitamins allowed for increased precision. PMID:25433686

  18. Isotope dilution liquid chromatography - mass spectrometry methods for fat- and water-soluble vitamins in nutritional formulations.

    PubMed

    Phinney, Karen W; Rimmer, Catherine A; Thomas, Jeanice Brown; Sander, Lane C; Sharpless, Katherine E; Wise, Stephen A

    2011-01-01

    Vitamins are essential to human health, and dietary supplements containing vitamins are widely used by individuals hoping to ensure they have adequate intake of these important nutrients. Measurement of vitamins in nutritional formulations is necessary to monitor regulatory compliance and in studies examining the nutrient intake of specific populations. Liquid chromatographic methods, primarily with UV absorbance detection, are well established for both fat- and water-soluble measurements, but they do have limitations for certain analytes and may suffer from a lack of specificity in complex matrices. Liquid chromatography-mass spectrometry (LC-MS) provides both sensitivity and specificity for the determination of vitamins in these matrices, and simultaneous analysis of multiple vitamins in a single analysis is often possible. In this work, LC-MS methods were developed for both fat- and water-soluble vitamins and applied to the measurement of these analytes in two NIST Standard Reference Materials. When possible, stable isotope labeled internal standards were employed for quantification. PMID:21117618

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

    Microsoft Academic Search

    Amir Sapkota; Jochen Heidler; Rolf U.. Halden

    2007-01-01

    The antimicrobial compound triclocarban (TCC; 3,4,4?-trichlorocarbanilide; CAS? 101-20-2) is a high-production-volume chemical, recently suggested to cause widespread contamination of US water resources. To test this hypothesis, we developed an isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry method for ultratrace analysis of TCC (0.9ng\\/L detection limit) and analyzed low-volume water samples (200mL) along with primary sludge samples from across

  20. Detrital, metamorphic and metasomatic tourmaline in high-pressure metasediments from Syros (Greece): intra-grain boron isotope patterns determined by secondary-ion mass spectrometry

    Microsoft Academic Search

    Horst R. Marschall; Rainer Altherr; Angelika Kalt; Thomas Ludwig

    2008-01-01

    The boron isotopic composition of zoned tourmaline in two metasediments from the island of Syros, determined by secondary-ion\\u000a mass spectrometry (SIMS), reflects the sedimentary and metamorphic record of the rocks. Tourmaline from a silicate-bearing\\u000a marble contains small (?20 ?m) detrital cores with highly variable ?\\u000a 11B values (?10.7 to +3.6‰), pointing to a heterogeneous protolith derived from multiple sources. The sedimentary

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

    E-print Network

    Paris-Sud XI, Université de

    with a stable isotope (D-glucose-1-13C, 99 atom % enrichment) for a period of approximately 24 h. A control cage workers were kept in each of four small cages without food for a period of 6 h. Female mites removed from in three of the four cages were then allowed to feed on a glucose solution (1:1by volume) labeled

  2. In situ hafnium isotope ratio analysis of zircon by inductively coupled plasma multiple collector mass spectrometry

    Microsoft Academic Search

    Matthew F. Thirlwall; Andrew J. Walder

    1995-01-01

    Hf isotopic data are reported for ten ?0.01-mm2 subareas of a zircon crystal separated from the ? 318-Ma diatreme of Elie Ness, Fife, Scotland. In situ analysis was achieved by ablation sampling with a Nd:YAG laser into an inductively-coupled plasma, with ions dispersed by a sector magnet and integrated in a 7-Faraday multicollector array. Despite large interferences from Yb (16%

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

    PubMed Central

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

    2014-01-01

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

  4. The use of an enriched isotope as an on-line internal standard in inductively coupled plasma mass spectrometry: a reference method for a proposed deter

    NASA Astrophysics Data System (ADS)

    Klinkenberg, Huub; Beeren, Ton; Van Borm, Werner; Van Der Linden, Fons; Raets, Mich

    1993-04-01

    The continuous addition of a solution of an enriched Te isotope ( 125Te) as internal standard results in an on-line isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) analysis for the determination of tellurium in industrial waste water. The described method combines ease and speed of operation with the precision and accuracy attainable with isotope dilution. In order to check for possible polyatomic interferences, two analyte isotopes ( 128Te and 130Te) were used. Isotopic ratios were converted into calibration graphs that are curved for both analyte isotopes. A formula is presented with which the shape of a calibration graph can be calculated beforehand. ICP-MS has been used as a reference method for a proposed graphite furnace atomic absorption spectrometry (GFAAS) procedure that uses the combination of palladium, Triton X-100 and hydrogen as matrix modifier. Only Triton X-100 could assure the uniform atomization of tellurium. Obviously the particle size distribution of palladium is much more important than the dispersion of palladium particles in the graphite furnace. Forty-eight waste water samples were analysed. The GFAAS and ICP-MS results were compared as paired samples using a t-test on their differences. At a confidence level of 0.05, both methods gave identical results.

  5. Development of a simple, fast, and accurate method for the direct quantification of selective estrogen receptor modulators using stable isotope dilution mass spectrometry.

    PubMed

    Yerramsetty, Vamsidhar; Roe, Mikel; Cohen, Jerry; Hegeman, Adrian; Ismail, Baraem

    2013-07-24

    A rapid analytical procedure was developed to quantify major selective estrogen receptor modulators (SERMs) simultaneously using stable isotope dilution mass spectrometry (SID-LCMS). Two novel isotopically labeled (SIL) analogues of natural SERMs, genistein and daidzein, were synthesized using a H/D exchange reaction mechanism. Computational chemistry coupled with MS and NMR data confirmed the site and mechanism of deuteration. The SIL analogues, which were mono- and dideutero substituted at the ortho positions, exhibited minimal deuterium isotope effects and were stable under the employed sample preparation protocol and MS analysis. An isotopic overlap correction was successfully employed to improve the accuracy and precision of the analytical method. The developed method, which was found to be sensitive, selective, precise and accurate, could be a valuable tool for research focused on determining the bioavailability of individual SERMs. PMID:23805827

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    As metagenomics increases our insight into microbial community diversity and metabolic potential, new approaches are required to determine the biogeochemical expression of this potential within ecosystems. Because stable isotopic analysis of the major bioactive elements (C, N) has been used historically to map flows of substrates and energy among macroscopic food webs, similar principles may apply to microbes. To address this challenge, we have developed a new analytical approach called Protein Stable Isotope Fingerprinting (P-SIF). P-SIF generates natural stable isotopic fingerprints of microbial individual or community proteomes. The main advantage of P-SIF is the potential to bridge the gap between diversity and function, thereby providing a window into the "black box" of environmental microbiology and helping to decipher the roles of uncultivated species. Our method implements a three-way, orthogonal scheme to separate mixtures of whole proteins into subfractions dominated by single or closely-related proteins. Protein extracts first are isoelectrically focused in a gel-free technique that yields 12 fractions separated over a gradient of pH 3-10. Each fraction then is separated by size-exclusion chromatography into 20 pools, ranging from >100kD to ~10kD. Finally, each of these pools is subjected to HPLC and collected in 40 time-slices based on protein hydrophobicity. Theoretical calculation reveals that the true chromatographic resolution of the total scheme is 5000, somewhat less than the 9600 resulting fractions. High-yielding fractions are subjected to ?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.

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

    PubMed

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

    2012-11-01

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

  8. Quantitative, Multiplexed Assays for Low Abundance Proteins in Plasma by Targeted Mass Spectrometry and Stable Isotope Dilution*S

    PubMed Central

    Keshishian, Hasmik; Addona, Terri; Burgess, Michael; Kuhn, Eric; Carr, Steven A.

    2008-01-01

    Biomarker discovery produces lists of candidate markers whose presence and level must be subsequently verified in serum or plasma. Verification represents a paradigm shift from unbiased discovery approaches to targeted, hypothesis-driven methods and relies upon specific, quantitative assays optimized for the selective detection of target proteins. Many protein biomarkers of clinical currency are present at or below the nanogram/milliliter range in plasma and have been inaccessible to date by MS-based methods. Using multiple reaction monitoring coupled with stable isotope dilution mass spectrometry, we describe here the development of quantitative, multiplexed assays for six proteins in plasma that achieve limits of quantitation in the 1–10 ng/ml range with percent coefficients of variation from 3 to 15% without immunoaffinity enrichment of either proteins or peptides. Sample processing methods with sufficient throughput, recovery, and reproducibility to enable robust detection and quantitation of candidate biomarker proteins were developed and optimized by addition of exogenous proteins to immunoaffinity depleted plasma from a healthy donor. Quantitative multiple reaction monitoring assays were designed and optimized for signature peptides derived from the test proteins. Based upon calibration curves using known concentrations of spiked protein in plasma, we determined that each target protein had at least one signature peptide with a limit of quantitation in the 1–10 ng/ml range and linearity typically over 2 orders of magnitude in the measurement range of interest. Limits of detection were frequently in the high picogram/milliliter range. These levels of assay performance represent up to a 1000-fold improvement compared with direct analysis of proteins in plasma by MS and were achieved by simple, robust sample processing involving abundant protein depletion and minimal fractionation by strong cation exchange chromatography at the peptide level prior to LC-multiple reaction monitoring/MS. The methods presented here provide a solid basis for developing quantitative MS-based assays of low level proteins in blood. PMID:17939991

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

    Microsoft Academic Search

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

    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

  10. Understanding Chemistry: Mass Spectrometry

    NSDL National Science Digital Library

    Clark, Jim

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

  11. Accuracy in the isotope dilution mass spectrometry of uranium in rubidium uranium sulphate Rb[sub 2]U(SO[sub 4])[sub 3

    SciTech Connect

    Ramakumar, K.L.; Jeyakumar, S.; Raman, V.A.; Gnanayyan, L.; Rao, R.; Saxena, M.K.; Kavimandan, V.D.; Jain, H.C. (Bhabha Atomic Research Centre, Bombay (India))

    1993-05-01

    Problems encountered in the determination of uranium in rubidium uranium sulphate (Rb[sub 2]U(SO[sub 4])[sub 3]) employing isotope dilution thermal ionization mass spectrometry (ID-TIMS) are discussed. The positive bias of 0.2 to 0.3% in the determination of uranium in Rb[sub 2]U(SO[sub 4])[sub 3] by ID-TIMS with respect to the stoichiometric composition has been resolved by modifying the chemical exchange procedures. The concentration of uranium in Rb[sub 2]U(SO[sub 4])[sub 3] could be determined with an accuracy better than 0.1% employing the HClO[sub 4] treatment for proper isotopic exchange between the spike and sample isotopes. 12 refs., 1 fig., 5 tabs.

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

    SciTech Connect

    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

    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)

  13. Analytical mass spectrometry. Abstracts

    SciTech Connect

    Not Available

    1990-12-31

    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)

  14. Analytical mass spectrometry

    SciTech Connect

    Not Available

    1990-01-01

    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)

  15. A novel quantification strategy of transferrin and albumin in human serum by species-unspecific isotope dilution laser ablation inductively coupled plasma mass spectrometry (ICP-MS).

    PubMed

    Feng, Liuxing; Zhang, Dan; Wang, Jun; Shen, Dairui; Li, Hongmei

    2015-07-16

    Species-specific (SS) isotope dilution analysis with gel electrophoresis (GE)-laser ablation (LA)-ICP-MS is a promising technique for the quantification of particular metal-binding proteins in biological samples. However, unavailable isotopically enriched spike and metal losses in GE separation are main limitations for SS-isotope dilution PAGE-LA-ICP-MS. In this study, we report for the first time the absolute quantification of transferrin (Tf) and albumin (Alb) in human serum by non-denaturing (native) GE combined with species-unspecific isotope dilution mass spectrometry (IDMS). In order to achieve a homogeneous distribution of both protein and isotope-enriched spike (simulated isotope equilibration), immersing the protein strips with (34)S spike solution after gel electrophoresis was demonstrated to be an effective way of spike addition. Furthermore, effects of immersion time and (34)S spike concentration were investigated to obtain optimal conditions of the post-electrophoresis isotope dilution method. The relative mass of spike and ablated sample (msp/msam) in IDMS equation was calculated by standard Tf and Alb proteins, which could be applied to the quantification of Tf and Alb in ERM-DA470k/IFCC for method confirmation. The results were in agreement with the certified value with good precision and small uncertainty (1.5-3%). In this method, species-specific spike protein is not necessary and the integrity of the heteroatom-protein could be maintained in sample preparation process. Moreover, the application of species-unspecific isotope dilution GE-LA-ICP-MS has the potential to offer reliable, direct and simultaneous quantification of proteins after conventional 1D and 2D gel electrophoretic separations. PMID:26073803

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

    PubMed

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

    2013-11-27

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

  17. VMSL: Virtual Mass Spectrometry Laboratory

    NSDL National Science Digital Library

    2011-07-05

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

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

    Microsoft Academic Search

    Max Haldimann; Bernhard Zimmerli; Claudine Als; Hans Gerber

    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

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

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

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

  20. Multi-Isotope Secondary Ion Mass Spectrometry Combining Heavy Water 2H with 15N Labeling As Complementary Tracers for Metabolic Heterogeneity at the Single-Cell Level

    NASA Astrophysics Data System (ADS)

    Kopf, S.; McGlynn, S.; Cowley, E.; Green, A.; Newman, D. K.; Orphan, V. J.

    2014-12-01

    Metabolic rates of microbial communities constitute a key physiological parameter for understanding the in situ growth constraints for life in any environment. Isotope labeling techniques provide a powerful approach for measuring such biological activity, due to the use of isotopically enriched substrate tracers whose incorporation into biological materials can be detected with high sensitivity by isotope-ratio mass spectrometry. Nano-meter scale secondary ion mass spectrometry (NanoSIMS) combined with stable isotope labeling provides a unique tool for studying the spatiometabolic activity of microbial populations at the single cell level in order to assess both community structure and population diversity. However, assessing the distribution and range of microbial activity in complex environmental systems with slow-growing organisms, diverse carbon and nitrogen sources, or heterotrophic subpopulations poses a tremendous technical challenge because the introduction of isotopically labeled substrates frequently changes the nutrient availability and can inflate or bias measures of activity. Here, we present the use of hydrogen isotope labeling with deuterated water as an important new addition to the isotopic toolkit and apply it for the determination of single cell microbial activities by NanoSIMS imaging. This tool provides a labeling technique that minimally alters any aquatic chemical environment, can be administered with strong labels even in minimal addition (natural background is very low), is an equally universal substrate for all forms of life even in complex, carbon and nitrogen saturated systems, and can be combined with other isotopic tracers. The combination of heavy water labeling with the most commonly used NanoSIMS tracer, 15N, is technically challenging but opens up a powerful new set of multi-tracer experiments for the study of microbial activity in complex communities. We present the first truly simultaneous single cell triple isotope system measurements of 2H/1H, 13C/12C and 15N/14N and apply it to study of microbial metabolic heterogeneity and nitrogen metabolism in a continuous culture case study. Our data provide insight into both the diversity of microbial activity rates, as well as patterns of ammonium utilization at the single cell level.

  1. Mass Spectrometry and Glycomics

    PubMed Central

    2010-01-01

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

  2. Development of a new method for the determination of thyroxine in serum based on isotope dilution gas chromatography mass spectrometry.

    PubMed

    Thienpont, L M; De Brabandere, V I; Stöckl, D; De Leenheer, A P

    1994-08-01

    A new gas chromatographic/mass spectrometric method in combination with isotope dilution for the determination of thyroxine in serum is described. Special attention was paid to the methylation step of thyroxine, which was investigated using methanolic HCl, dimethylformamide/dimethylacetal and diazomethane, the latter giving the best results in terms of reproducible isotope ratios. For internal standardization, (13C6)-thyroxine was dissolved in fraction V human albumin solution (70 g l-1). The internal standard-in-albumin solution was mixed with known amounts of thyroxine standard, dissolved in 0.05 M Na2HPO4 buffer at pH 11.6, to give isotope ratios of 0.75, 1.00 and 1.25. The same internal standard solution was also used for isotope dilution of the unknown serum samples. The volume of serum was adapted to give a 1:1 isotope ratio. Sample pretreatment consisted of protein precipitation and a two-step liquid/liquid extraction procedure. After methylation of unlabelled and labelled thyroxine with diazomethane and perfluoroacylation with pentafluoropropionic anhydride and heptafluorobutyric anhydride, respectively, mass spectrometric monitoring was done at m/z 951/957 and 1001/1007. Quantitative determination of thyroxine in five serum samples in duplicate, during three consecutive days, showed a mean overall imprecision of 1.0% and a deviation of +0.4% from the target value as determined by a definitive method. PMID:7918690

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

    PubMed

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

    2005-01-14

    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

  4. Determination of paraffin and aromatic hydrocarbon type chemicals in liquid distillates produced from the pyrolysis process of waste plastics by isotope-dilution mass spectrometry

    Microsoft Academic Search

    Young-Hwa Seo; Dae-Hyun Shin

    2002-01-01

    Isotope dilution mass spectrometry was developed for the determination of composition of paraffins, olefins, naphthenes and aromatics in distilled oil produced from the pyrolysis reaction of mixed waste plastics using labeled hydrocarbon internal standards including octane-d18, dodecane-d26, hexadecane-d34, benzene-d6, toluene-d8, ethylbenzene-d10, 1,3,5-trimethylbenzene-d12 and naphthalene-d8. This technique made it possible to thoroughly quantify more than three hundred peaks in plastic-derived pyrolysis

  5. Quantitation of cortisol and related 3-oxo-4-ene steroids in urine using gas chromatography\\/mass spectrometry with stable isotope-labeled internal standards

    Microsoft Academic Search

    Mario Palermo; Celso Gomez-Sanchez; Esther Roitman; Cedric H. L. Shackleton

    1996-01-01

    A method for the profiling of several important 3-oxo-4-ene urinary steroids is reported. The methodology is combined gas chromatography\\/mass spectrometry (GC\\/MS) utilizing stable isotope-labeled internal standards. The following standards were obtained or easily synthesized: [9,11,12,12-2H4]cortisol, [1,2-2H2] and [9,12,12-2H2]cortisone, [1,2-2H2]6?-hydroxycortisol, and [1,2-2H2]18-hydroxycortisol. We found the following excretions of free steroids for normal adult males and females: cortisol (males mean ± SD,

  6. Determination of uranium isotopic ratios in biological samples using laser ablation inductively coupled plasma double focusing sector field mass spectrometry with cooled ablation chamber

    NASA Astrophysics Data System (ADS)

    Zoriy, M. V.; Kayser, M.; Izmer, A.; Pickhardt, C.; Becker, J. S.

    2005-04-01

    An analytical procedure has been proposed for the determination of precise uranium isotope ratios in a thin uranium layer on a biological surface by laser ablation inductively coupled plasma sector field mass spectrometry (LA-ICP-MS). A cooled laser ablation chamber using a Peltier element was developed in order to analyze element distribution in thin cross-sections of frozen tissues with a lateral resolution in the [mu]m range. In order to study the figures of merit of LA-ICP-MS with the cooled laser ablation chamber, one drop (20 [mu]L, U concentration 200 ng mL-1), each of the certified isotope reference materials NIST U350 and NIST U930, the uranium isotopic standard CCLU-500 and also a drop of uranium with a natural isotopic pattern was deposited and analyzed on the biological surface (flower leaf). The precision and accuracy of isotope ratio measurements are significantly improved using cooled laser ablation chamber in comparison to non-cooled chamber. The precision of the measurements of isotope ratios in the range of 2.0-1.6% for 234U/238U, 1.3-0.4% for 235U/238U and 2.1-1.0% for 236U/238U in selected uranium isotopic standards reference material were determined by microlocal analysis (diameter of laser ablation crater: 15, 25 and 50 [mu]m) using LA-ICP-MS with a cooled laser ablation chamber. The accuracy of 234U/238U, 235U/238U and 236U/238U isotope ratio measurements varied in the range of 4.2-1.1%, 2.4-0.5% and 4.8-1.1%, respectively, and were dependent on the diameter of the laser beam used.

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

    Microsoft Academic Search

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

    2005-01-01

    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

  8. Determination of melamine and its analogues in egg by gas chromatography-tandem mass spectrometry using an isotope dilution technique

    Microsoft Academic Search

    H. Miao; S. Fan; P. P. Zhou; L. Zhang; Y. F. Zhao; Y. N. Wu

    2010-01-01

    A method was developed for the simultaneous determination of melamine, ammeline, ammelide, and cyanuric acid in egg using gas chromatography-tandem mass spectrometry (GC-MS\\/MS). The samples were first extracted by the solution of diethylamine–water–acetonitrile (10:40:50, v\\/v\\/v). Clean-up employed an ‘On Guard II’ RP cartridge, and the dried elute was derivatised using bis-(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS). Derivatised samples were analysed

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

    Microsoft Academic Search

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

    2008-01-01

    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

  10. Sensitive, Efficient Quantitation of 13C-Enriched Nucleic Acids via Ultrahigh-Performance Liquid Chromatography–Tandem Mass Spectrometry for Applications in Stable Isotope Probing

    PubMed Central

    Wilhelm, Roland; Szeitz, András; Klassen, Tara L.

    2014-01-01

    Stable isotope probing (SIP) of nucleic acids is a powerful tool for studying the functional traits of microbial populations within complex communities, but SIP involves a number of technical challenges. Many of the difficulties in DNA-SIP and RNA-SIP experiments can be effectively overcome with an efficient, sensitive method for quantitating the isotopic enrichment of nucleic acids. Here, we present a sensitive method for quantitating 13C enrichment of nucleic acids, requiring a few nanograms of sample, and we demonstrate its utility in typical DNA-SIP and RNA-SIP experiments. All five nucleobases (adenine, guanine, cytosine, thymine, and uracil) were separated and detected by using ultrahigh-performance liquid chromatography–tandem mass spectrometry. We detected all isotopic species in samples with as low as 1.5 atom% 13C above natural abundance, using 1-ng loadings. Quantitation was used to characterize the isotopic enrichment kinetics of cellulose- and lignin-based microcosm experiments and to optimize the recovery of enriched nucleic acids. Application of our method will minimize the quantity of expensive isotopically labeled substrates required and reduce the risk of failed experiments due to insufficient recovery of labeled nucleic acids for sequencing library preparation. PMID:25217022

  11. Sensitive, Efficient Quantitation of 13C-Enriched Nucleic Acids via Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry for Applications in Stable Isotope Probing.

    PubMed

    Wilhelm, Roland; Szeitz, András; Klassen, Tara L; Mohn, William W

    2014-12-01

    Stable isotope probing (SIP) of nucleic acids is a powerful tool for studying the functional traits of microbial populations within complex communities, but SIP involves a number of technical challenges. Many of the difficulties in DNA-SIP and RNA-SIP experiments can be effectively overcome with an efficient, sensitive method for quantitating the isotopic enrichment of nucleic acids. Here, we present a sensitive method for quantitating (13)C enrichment of nucleic acids, requiring a few nanograms of sample, and we demonstrate its utility in typical DNA-SIP and RNA-SIP experiments. All five nucleobases (adenine, guanine, cytosine, thymine, and uracil) were separated and detected by using ultrahigh-performance liquid chromatography-tandem mass spectrometry. We detected all isotopic species in samples with as low as 1.5 atom% (13)C above natural abundance, using 1-ng loadings. Quantitation was used to characterize the isotopic enrichment kinetics of cellulose- and lignin-based microcosm experiments and to optimize the recovery of enriched nucleic acids. Application of our method will minimize the quantity of expensive isotopically labeled substrates required and reduce the risk of failed experiments due to insufficient recovery of labeled nucleic acids for sequencing library preparation. PMID:25217022

  12. Biological Cluster Mass Spectrometry

    PubMed Central

    Winograd, Nicholas; Garrison, Barbara J.

    2010-01-01

    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. PMID:20055679

  13. Mass Spectrometry and Glycomics

    Microsoft Academic Search

    Jasna Peter-Katalinic

    Mass spectrometry (MS) in biochemical and biophysical research of complex carbohydrates has to meet a number of challenges\\u000a if compared to other biomacromolecules, like proteins and nucleic acids. MS, as an universal and indispensible tool for analysis\\u000a of biological samples after introduction of soft ionization techniques, like Fast Atom Bombardment (FAB), electrospray (ESI)\\u000a and matrix-assisted laser desorption ionization (MALDI), allows

  14. Easy Extraction Method To Evaluate ?(13)C Vanillin by Liquid Chromatography-Isotopic Ratio Mass Spectrometry in Chocolate Bars and Chocolate Snack Foods.

    PubMed

    Bononi, Monica; Quaglia, Giancarlo; Tateo, Fernando

    2015-05-20

    An easy extraction method that permits the use of a liquid chromatography-isotopic ratio mass spectrometry (LC-IRMS) system to evaluate ?(13)C of vanillin in chocolate products and industrial flavorings is presented. The method applies the determination of stable isotopes of carbon to discriminate between natural vanillin from vanilla beans and vanillin from other sources (mixtures from beans, synthesis, or biotechnology). A series of 13 chocolate bars and chocolate snack foods available on the Italian market and 8 vanilla flavorings derived from industrial quality control processes were analyzed. Only 30% of products considered in this work that declared "vanilla" on the label showed data that permitted the declaration "vanilla" according to European Union (EU) Regulation 1334/2008. All samples not citing "vanilla" or "natural flavoring" on the label gave the correct declaration. The extraction method is presented with data useful for statistical evaluation. PMID:25965784

  15. 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

    Kawaguchi, Migaku; Eyama, Sakae; Takatsu, Akiko

    2014-08-01

    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

  16. Determination of uranium isotopic composition and 236U content of soil samples and hot particles using inductively coupled plasma mass spectrometry.

    PubMed

    Boulyga, S F; Becker, J S

    2001-07-01

    As a result of the accident at the Chernobyl nuclear power plant (NPP) the environment was contaminated with spent nuclear fuel. The 236U isotope was used in this study to monitor the spent uranium from nuclear fallout in soil samples collected in the vicinity of the Chernobyl NPP. Nuclear track radiography was applied for the identification and extraction of hot radioactive particles from soil samples. A rapid and sensitive analytical procedure was developed for uranium isotopic ratio measurement in environmental samples based on double-focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) with a MicroMist nebulizer and a direct injection high-efficiency nebulizer (DIHEN). The performance of the DF-ICP-MS with a quartz DIHEN and plasma shielded torch was studied. Overall detection efficiencies of 4 x 10(-4) and 10(-3) counts per atom were achieved for 238U in DF-ICP-QMS with the MicroMist nebulizer and DIHEN, respectively. The rate of formation of uranium hydride ions UH+/U+ was 1.2 x 10(-4) and 1.4 x 10(-4), respectively. The precision of short-term measurements of uranium isotopic ratios (n = 5) in 1 microg L(-1) NBS U-020 standard solution was 0.11% (238U/235U) and 1.4% (236U/238U) using a MicroMist nebulizer and 0.25% (235U/238U) and 1.9% (236U/P38U) using a DIHEN. The isotopic composition of all investigated Chernobyl soil samples differed from those of natural uranium; i.e. in these samples the 236U/238U ratio ranged from 10(-5) to 10(-3). Results obtained with ICP-MS, alpha- and gamma-spectrometry showed differences in the migration properties of spent uranium, plutonium, and americium. The isotopic ratio of uranium was also measured in hot particles extracted from soil samples. PMID:11496994

  17. 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

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

    2014-07-01

    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

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

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2005-01-01

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

  19. Nuclear applications of inorganic mass spectrometry.

    PubMed

    De Laeter, John

    2010-01-01

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

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

    SciTech Connect

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

    1984-05-01

    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.

  1. Laser probe mass spectrometry

    NASA Astrophysics Data System (ADS)

    Campana, Joseph E.

    1991-04-01

    Fourier transform mass spectrometry (FT/MSR) has been recognized as a powerful analytical technique for the determination of elemental compositions and the molecular structure of materials. The simultaneous measurement of all species, produced in a single event, in a Fourier transform mass spectrometer provides a natural combination with pulsed lasers, where the pulsed laser is used to ablate and ionize a portion of a sample. This unique combination of lasers with FTMS provides elemental and molecular information from inorganic and organic materials and from surface layers and from bulk materials. Microanalysis of materials, allowing spatially-resolved high-resolution mass spectra to be obtained, is possible with small laser spot sizes and optical systems for viewing samples inside the mass spectrometer. The advantages of FTMS are reviewed, and several examples of laser probe FTMS are illustrated to demonstrate applications of the technique to industrial problem solving.

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

    SciTech Connect

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

    2012-01-15

    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.

  3. 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.

  4. Effectiveness of isotopically labelled and non-isotopically labelled internal standards in the gas chromatography/mass spectrometry analysis of sulfur compounds in wines: use of a statistically based matrix comprehensive approach.

    PubMed

    Lavagnini, Irma; Fedrizzi, Bruno; Versini, Giuseppe; Magno, Franco

    2009-04-01

    The effectiveness of isotopically and non-isotopically labelled internal standards in reducing matrix-induced effects is evaluated. The question is addressed in the quantitative analysis by gas chromatography/mass spectrometry (GC/MS) of dimethyl sulphide, chosen as a typical example of volatile sulphur compounds, in wine matrices. When matrix/run effects are not cancelled out the use of a variance component model (VCM) to handle the linear calibrations obtained by regression technique is successful. The method implies the estimation of an overall calibration straight line, which properly takes into account the uncertainty due to different matrices, the calibration run and the measurement error, making the use of an isotopically labelled internal standard not necessary. The obtained results show that the benefits of lowering times and costs for routine analyses compensate for the small increase in uncertainty in the concentration values obtained in the regression analysis and the slight increase in the detection limit. PMID:19291680

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

    Microsoft Academic Search

    Norbert Stoll; Enrico Schmidt; Kerstin Thurow

    2006-01-01

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

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

    PubMed

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

    2011-11-01

    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

  7. Quantitative determination of 8-hydroxy-2?-deoxyguanosine in human urine by isotope dilution mass spectrometry: normal levels in hemochromatosis

    Microsoft Academic Search

    Inger Holmberg; Per Stål; Mats Hamberg

    1999-01-01

    A previously developed method for quantitative determination of 8-hydroxyguanine by gas chromatography-mass spectrometry was modified to allow measurement of 8-hydroxy-2?-deoxyguanosine in human urine. [4,5,6,8-13C4]8-Hydroxy-2?-deoxyguanosine was prepared by enzymatic coupling of [4,5,6,8-13C4]8-hydroxyguanine to deoxyribose-1-phosphate. Samples of human urine (2 ml) were spiked with the labeled nucleoside (13 nmol) and subjected to solid phase extraction and reversed phase high performance liquid chromatography.

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

    USGS Publications Warehouse

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

    2010-01-01

    Measurements of ?(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.

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

    PubMed

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

    2007-01-16

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

  10. 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

    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

    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

  11. Exploring the limits of robust detection of incorporation of 13C by mass spectrometry in protein-based stable isotope probing (protein-SIP).

    PubMed

    Taubert, Martin; Baumann, Sven; von Bergen, Martin; Seifert, Jana

    2011-10-01

    One of the features of protein-based stable isotope probing is the parallel identification of differentially labeled peptide forms and the accurate calculation of their relative isotope abundances. The level of incorporation is informative of the metabolic activity of the species that synthesized the said protein and peptide. To model the carbon flux in a microbial community, an accurate assessment is crucial. Since the initial processes in carbon consumption are one of the most interesting objectives in microbial ecology, the methodology to detect low amounts of incorporation was tuned, and the limits of robust detection were analyzed. For this, Pseudomonas fluorescens DSM 50090T was grown on galactose using different ratios of (12)C/(13)C galactose from 10% down to 0.1% labeled galactose. After prolonged cultivation to ensure complete labeling, protein samples were separated by one-dimensional gel electrophoresis, subsequently tryptically digested and analyzed by ultra-performance liquid chromatography (UPLC) Orbitrap tandem mass spectrometry (MS/MS) measurements. The isotopic patterns from identified peptides in the mass spectra were used to calculate the (13)C relative isotope abundance (RIA) in the respective peptides. The statistic distribution of the RIA values in dependence of the number of analyzed peptides was compared between the different ratios of unlabeled/labeled substrate. The acquired data showed that the applied method is capable of detecting a difference in (13)C incorporation of ±0.1% RIA based on at least 20 peptides. This sensitivity makes protein-stable isotope probing a valuable method for quantitative assessment of species specific metabolic activity in metaproteomics. PMID:21822970

  12. High-Resolution Twin-Ion Metabolite Extraction (HiTIME) Mass Spectrometry: Nontargeted Detection of Unknown Drug Metabolites by Isotope Labeling, Liquid Chromatography Mass Spectrometry, and Automated High-Performance Computing.

    PubMed

    Leeming, Michael G; Isaac, Andrew P; Pope, Bernard J; Cranswick, Noel; Wright, Christine E; Ziogas, James; O'Hair, Richard A J; Donald, William A

    2015-04-21

    The metabolic fate of a compound can often determine the success of a new drug lead. Thus, significant effort is directed toward identifying the metabolites formed from a given molecule. Here, an automated and nontargeted procedure is introduced for detecting drug metabolites without authentic metabolite standards via the use of stable isotope labeling, liquid chromatography mass spectrometry (LC/MS), and high-performance computing. LC/MS of blood plasma extracts from rats that were administered a 1:1 mixture of acetaminophen (APAP) and (13)C6-APAP resulted in mass spectra that contained "twin" ions for drug metabolites that were not detected in control spectra (i.e., no APAP administered). Because of the development of a program (high-resolution twin-ion metabolite extraction; HiTIME) that can identify twin-ions in high-resolution mass spectra without centroiding (i.e., reduction of mass spectral peaks to single data points), 9 doublets corresponding to APAP metabolites were identified. This is nearly twice that obtained by use of existing programs that make use of centroiding to reduce computational cost under these conditions with a quadrupole time-of-flight mass spectrometer. By a manual search for all reported APAP metabolite ions, no additional twin-ion signals were assigned. These data indicate that all the major metabolites of APAP and multiple low-abundance metabolites (e.g., acetaminophen hydroxy- and methoxysulfate) that are rarely reported were detected. This methodology can be used to detect drug metabolites without prior knowledge of their identity. HiTIME is freely available from https://github.com/bjpop/HiTIME . PMID:25818563

  13. 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

    Hattori, M; Hirata, T

    2001-06-01

    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

  14. Mass spectrometry of priority pollutants

    SciTech Connect

    Middleditch, B.S.; Hines, H.B.; Missler, S.R.

    1981-01-01

    This book presents information on the following subjects: anintroduction to gas chromatography; mass spectrometry; review of available methods for comparing spectra; selective ion monitoring; problems associated with the analysis of volatile samples and problems of data processing; use of mass spectrometry in environmental science, cosmo-chemistry, geochemistry, and the pharmaceutical and petrochemical industries; and modern mass spectrometers.

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

    PubMed

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

    2014-09-16

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

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

    PubMed

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

    2014-12-01

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

  17. Dual element ((15)N/ (14)N, (13)C/ (12)C) isotope analysis of glyphosate and AMPA by derivatization-gas chromatography isotope ratio mass spectrometry (GC/IRMS) combined with LC/IRMS.

    PubMed

    Mogusu, Emmanuel O; Wolbert, J Benjamin; Kujawinski, Dorothea M; Jochmann, Maik A; Elsner, Martin

    2015-07-01

    To assess sources and degradation of the herbicide glyphosate [N-(phosphonomethyl) glycine] and its metabolite AMPA (aminomethylphosphonic acid), concentration measurements are often inconclusive and even (13)C/(12)C analysis alone may give limited information. To advance isotope ratio analysis of an additional element, we present compound-specific (15)N/(14)N analysis of glyphosate and AMPA by a two step derivatization in combination with gas chromatography/isotope ratio mass spectrometry (GC/IRMS). The N-H group was derivatized with isopropyl chloroformate (iso-PCF), and remaining acidic groups were subsequently methylated with trimethylsilyldiazomethane (TMSD). Iso-PCF treatment at pH <10 gave too low (15)N/(14)N ratios indicating an incomplete derivatization; in contrast, too high (15)N/(14)N ratios at pH >10 indicated decomposition of the derivative. At pH 10, and with an excess of iso-PCF by 10-24, greatest yields and accurate (15)N/(14)N ratios were obtained (deviation from elemental analyzer-IRMS: -0.2?±?0.9 % for glyphosate; -0.4?±?0.7 % for AMPA). Limits for accurate ?(15)N analysis of glyphosate and AMPA were 150 and 250 ng injected, respectively. A combination of ?(15)N and ?(13)C analysis by liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) (1) enabled an improved distinction of commercial glyphosate products and (2) showed that glyphosate isotope values during degradation by MnO2 clearly fell outside the commercial product range. This highlights the potential of combined carbon and nitrogen isotopes analysis to trace sources and degradation of glyphosate. PMID:25967147

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

    PubMed

    Rossier, Joël S; Maury, Valérie; de Voogd, Blaise; Pfammatter, Elmar

    2014-10-01

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

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

    USGS Publications Warehouse

    Matsumoto, A.; Hinkley, T.K.

    1997-01-01

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

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

    PubMed Central

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

    2010-01-01

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

  1. Iron absorption in man calculated from erythrocyte incorporation of the stable isotope iron-54 determined by fast atom bombardment mass spectrometry

    SciTech Connect

    Lehmann, W.D.; Fischer, R.; Heinrich, H.C.

    1988-07-01

    The methodology of precise isotope abundance determinations of erythrocyte iron by fast atom bombardment mass spectrometry and signal averaging is established. For the determination of the 54Fe/56Fe ratio a relative precision of 0.5% and an absolute precision of 0.03% is achieved. After oral loading with 54Fe-enriched samples in the range between 5 and 25 mg per subject, the 14-day erythrocyte incorporation of 54Fe has been determined in five individuals, namely, two adults, two children, and one infant. In the two adults, the oral dose of 54Fe was simultaneously labeled with a trace amount of carrier-free 59Fe. In these double-isotope loading tests, a good agreement was observed between the absorption data determined on the basis of whole body retention of 59Fe and on the basis of the 54Fe erythrocyte incorporation. The stable isotope methodology applied allows measurement of the iron absorption using highly enriched 54Fe at a dose of 25 mg for an adult or at a dose of 5 mg for infants of about 1 year of age.

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

    PubMed

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

    2013-09-01

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

  3. 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

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

    2009-01-01

    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.

  4. A high precision isotope ratio mass spectrometry method for measuring the O{sub 2}/N{sub 2} ratio of air

    SciTech Connect

    Bender, M.L.; Ellis, J.T.; Orchardo, J. [Univ. of Rhode Island, Kingston, RI (United States)] [Univ. of Rhode Island, Kingston, RI (United States); Tans, P.P. [National Oceanic and Atmospheric Administration, Boulder, CO (United States)] [National Oceanic and Atmospheric Administration, Boulder, CO (United States); Habfast, K. [Finnigan MAT GmbH, Bremen (Germany)] [Finnigan MAT GmbH, Bremen (Germany)

    1994-11-01

    Studies of the distribution of O{sub 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{sub 2}, and the net of change of the continental biomass. In this paper, we outline a method for measuring the O{sub 2}/N{sub 2} ratio of air to a standard error of {+-}6 per meg ({+-}0.006{per_thousand}) for a sample analyzed in quadruplicate, corresponding to {+-}1.2 ppmV O{sub 2} in air out of 210,000. The method involves measuring the ratio of {sup 16}O{sub 2} to {sup 15}N{sup 14}N 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{sup +} from CO{sub 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.

  5. Absolute quantification of protein NP24 in tomato fruit by liquid chromatography/tandem mass spectrometry using stable isotope-labelled tryptic peptide standard.

    PubMed

    Ippoushi, Katsunari; Sasanuma, Motoe; Oike, Hideaki; Kobori, Masuko; Maeda-Yamamoto, Mari

    2015-04-15

    Protein NP24 is a thaumatin-like protein contained in tomato (Lycopersicon esculentum Mill.). This protein is reported to be a putative tomato allergen and is listed as a food allergen in Structural Database of Allergenic Proteins (SDAP). In this research, we developed the quantitative analysis of NP24 by employing the protein absolute quantification (AQUA) technology composed of stable isotope-labelled internal standard (SIIS) peptide (GQTWVINAPR[(13)C6,(15)N4]) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). A linear relationship (r(2)>0.99) was found throughout the concentration range (2.0-500 fmol/?L). The coefficients of variation (CVs) measured on each of the five days when NP24 contained in the tomato skin was analysed did not exceed 13%. Our developed assay of NP24 will contribute to the allergological examination of tomato and its derived products. PMID:25466018

  6. Mass spectrometry of oligosaccharides.

    PubMed

    Zaia, Joseph

    2004-01-01

    Glycosylation is a common post-translational modification to cell surface and extracellular matrix (ECM) proteins as well as to lipids. As a result, cells carry a dense coat of carbohydrates on their surfaces that mediates a wide variety of cell-cell and cell-matrix interactions that are crucial to development and function. Because of the historical difficulties with the analysis of complex carbohydrate structures, a detailed understanding of their roles in biology has been slow to develop. Just as mass spectrometry has proven to be the core technology behind proteomics, it stands to play a similar role in the study of functional implications of carbohydrate expression, known as glycomics. This review summarizes the state of knowledge for the mass spectrometric analysis of oligosaccharides with regard to neutral, sialylated, and sulfated compound classes. Mass spectrometric techniques for the ionization and fragmentation of oligosaccharides are discussed so as to give the reader the background to make informed decisions to solve structure-activity relations in glycomics. PMID:14966796

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

    PubMed

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

    2010-04-01

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

  8. 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

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

    2012-04-01

    Carbonyl compounds are common byproducts of many metabolic processes. These volatile chemicals 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 (15)N(4)-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 1.5h resulted in 2.6 ± 0.5 ?g TFAA-DNPH, corresponding to 9.3 ± 1.7 nmol TFAA, captured by the cartridge. PMID:22342210

  9. Accelerator Mass Spectrometry of Actinides in Ground- and Seawater: An Innovative Method Allowing for the Simultaneous Analysis of U, Np, Pu, Am, and Cm Isotopes below ppq Levels.

    PubMed

    Quinto, Francesca; Golser, Robin; Lagos, Markus; Plaschke, Markus; Schäfer, Thorsten; Steier, Peter; Geckeis, Horst

    2015-06-01

    (236)U, (237)Np, and Pu isotopes and (243)Am were determined in ground- and seawater samples at levels below ppq (fg/g) with a maximum sample size of 250 g. Such high sensitivity was possible by using accelerator mass spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA) with extreme selectivity and recently improved efficiency and a significantly simplified separation chemistry. The use of nonisotopic tracers was investigated in order to allow for the determination of (237)Np and (243)Am, for which isotopic tracers either are rarely available or suffer from various isobaric mass interferences. In the present study, actinides were concentrated from the sample matrix via iron hydroxide coprecipitation and measured sequentially without previous chemical separation from each other. The analytical method was validated by the analysis of the Reference Material IAEA 443 and was applied to groundwater samples from the Colloid Formation and Migration (CFM) project at the deep underground rock laboratory of the Grimsel Test Site (GTS) and to natural water samples affected solely by global fallout. While the precision of the presented analytical method is somewhat limited by the use of nonisotopic spikes, the sensitivity allows for the determination of ?10(5) atoms in a sample. This provides, e.g., the capability to study the long-term release and retention of actinide tracers in field experiments as well as the transport of actinides in a variety of environmental systems by tracing contamination from global fallout. PMID:25938849

  10. Mass spectrometry in ionospheric research.

    PubMed

    Ferguson, Eldon E

    2007-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  12. Simultaneous determination of two major snow crab aeroallergens in processing plants by use of isotopic dilution tandem mass spectrometry.

    PubMed

    Abdel Rahman, Anas M; Gagné, Sébastien; Helleur, Robert J

    2012-05-01

    Snow crab is a major fishery in the North Atlantic region. During crab processing the proteins are aerosolized and some are responsible for development of occupational asthma. Tropomyosin and arginine kinase have recently been reported as major snow crab allergens. A liquid chromatographic tandem mass spectrometric method has been developed for simultaneous analysis of these two proteins in air samples collected from processing plants. These proteins were initially isolated then characterized by use of mass spectrometry to determine their primary structure and signature peptides. The signature peptides were chemically synthesized in light and heavy forms and used as standards for developing the multiple-reaction monitoring transitions to monitor allergen levels. A validation study was performed; precision and accuracy were 1.8-8% and 91-104%, respectively. Replicate air samples were collected on air filters from two crab-processing plants in Newfoundland and Labrador (NL) and four located in Quebec. In NL, measured levels of both tropomyosin and arginine kinase were between 1 and 20 ng m(-3). In Quebec plants, however, levels were found to be much higher at 2-2400 ng m(-3). Significant differences were also observed among the plants and individual processing workstations. For the first time arginine kinase has been detected in its aerosolized form in processing plants. In general, levels of the allergens were highest in the butchering and cooking areas; plant design can, however, have a significant effect on levels of the allergens. PMID:22392376

  13. Method development for the determination of cadmium, copper, lead, selenium and thallium in sediments by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry and isotopic dilution calibration

    NASA Astrophysics Data System (ADS)

    Dias, Lúcia Felicidade; Miranda, Gilson R.; Saint'Pierre, Tatiana D.; Maia, Sandra M.; Frescura, Vera L. A.; Curtius, Adilson J.

    2005-01-01

    A procedure for the determination of Cd, Cu, Pb, Se and Tl by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) with calibration by isotopic dilution is proposed. The slurry is prepared by mixing the sample with diluted nitric and hydrofluoric acids in an ultrasonic bath and then in a water bath at 60 °C for 120 min. The slurries were let to stand at least for 12 h, manually shaken before poured into the autosampler cups and homogenized by passing through an argon flow, just before pipetting it into the furnace. The analytes were determined in two groups, according to their thermal behaviors. The furnace temperature program was optimized and the selected compromised pyrolysis temperatures were: 400 °C for Cd, Se and Tl and 700 °C for Cu and Pb. The vaporization temperature was 2300 °C. The analyses were carried out without modifier as no significant effect was observed for different tested modifiers. Different sample particle sizes did not affect the sensitivity significantly, then a particle size ?50 ?m was adopted. The accuracy was checked by analyzing five certified reference sediments, with analytes concentrations from sub-?g g -1 to a few hundreds ?g g -1. The great majority of the obtained concentrations were in agreement with the certified values. The detection limits, determined for the MESS-2 certified sediment, were, in ?g g -1: 0.01 for Cd; 0.8 for Cu; 0.4 for Pb; 0.4 for Se and 0.06 for Tl. The precision was adequate with relative standard deviations lower than 12%. Isotopic dilution showed to be an efficient calibration technique for slurry, as the extraction of the analyte to the liquid phase of the slurry and the reactions in the vaporizer must help the equilibration between the added isotope and the isotope in the sample.

  14. Quantification of Sulforaphane Mercapturic Acid Pathway Conjugates in Human Urine by High-Performance Liquid Chromatography and Isotope-Dilution Tandem Mass Spectrometry

    PubMed Central

    Egner, Patricia A.; Kensler, Thomas W.; Chen, Jian-Guo; Gange, Stephen J.; Groopman, John D.; Friesen, Marlin D.

    2011-01-01

    We report validation of the first high-pressure liquid chromatography isotope-dilution mass spectrometry method to measure sulforaphane (SFN) and its glutathione-derived conjugates in human urine. As epidemiological evidence continues to mount that the consumption of a diet rich in cruciferous vegetables may reduce the risk of certain cancers, the development of analytical methodologies to accurately measure isothiocyanates (ITCs) and their subsequent metabolic products becomes paramount. SFN, the principal ITC produced by broccoli, is an effective chemopreventive agent with multiple modes of action. SFN and SFN conjugates have often been measured collectively utilizing a cyclocondensation assay with 1,2-benzenedithiol. More recently, some of the major SFN conjugates have been determined using mass spectrometry. Here, triple-quadrupole mass spectrometry has been coupled with the use of stable isotope-labeled internal standards of D8-SFN and all four D8-SFN mercapturic acid pathway conjugates to provide an accurate, precise, sensitive, and specific method for analysis of these compounds. Using urine samples collected during an earlier intervention with broccoli sprouts, the concentrations of SFN, SFN-cysteine, and the mercapturic acid SFN-N-acetylcysteine were sufficiently high such that as little as 50 nL of urine was required for analysis. Although each study participant received an equivalent dose of broccoli sprout preparation, the interindividual conversion of the precursor glucosinolate to SFN varied over 100-fold. These 98 urines provided an ideal sample set for examining the robustness of the assay. The mean urinary concentrations ± standard deviations in overnight voids following ingestion of the first dose were 4.7 ± 5.1, 0.03 ± 0.05, 0.06 ± 0.06, 18 ± 15, and 42 ± 23 nmol/mg creatinine for SFN, SFN-glutathione, SFN-cysteine-glycine, SFN-cysteine, and SFN-N-acetylcysteine, respectively. This method determines SFN and all four SFN glutathione-derived metabolites with minimal sample preparation and will be extremely useful in understanding the role of SFN-rich foods in preventing cancer and other chronic diseases. PMID:18729326

  15. Separating Autotrophic and Heterotrophic Contributions to Soil Respiration in Maize-Based Agroecosystems Using Stable Carbon Isotope Ratio Mass Spectrometry.

    NASA Astrophysics Data System (ADS)

    Amos, B.; Walters, D. T.; Madhavan, S.; Arkebauer, T. J.; Scoby, D. L.

    2005-12-01

    Any effort to establish a carbon budget for a growing crop by means of a thorough accounting of all C sources and sinks will require the ability to discriminate between autotrophic and heterotrophic contributions to soil surface CO2 flux. Autotrophic soil respiration (Ra) is defined as combined root respiration and the respiration of soil microorganisms residing in the rhizosphere and using root-derived carbohydrates as an energy source, while heterotrophic respiration (Rh) is defined as the respiration of soil microorganisms and macroorganisms not directly under the influence of the live root system and using SOM as an energy source. We partition soil surface CO2 flux into its autotrophic and heterotrophic components by combining root exclusion with stable carbon isotope techniques in production scale (~65 ha) maize-based agroecosystems. After flux measurements, small chambers are placed on collars in both root excluded shields and in non-root excluded soil, ambient headspace CO2 is removed using a soda lime trap, and soil-respired C is allowed to collect in the chambers. Soil respiration samples are then collected in 12mL evacuated exetainers and analyzed for ?13C by means of a Finnigan Delta-S isotope ratio mass spectrometer interfaced with a Thermo Finnigan GasBench II and a cryogenic trap to increase CO2 concentration. These ?13C measurements were made throughout the 2005 growing season in maize fields representing three agroecosystems: irrigated continuous maize, irrigated maize-soybean rotation, and rainfed maize soybean rotation. Estimates of autotrophic and heterotrophic soil respiration along with other results of this study will be presented.

  16. [International comparison APMP. QM-S6: determination of clenbuterol in porcine meat by isotopic dilution mass spectrometry].

    PubMed

    Xu, Sen; Li, Xiuqin; Luo, Ximing; Zhang, Qinghe

    2014-10-01

    A method was developed for the determination of clenbuterol in porcine meat by iso- topic dilution mass spectrometry (IDMS). National Institute of Metrology of China (NIM) par- ticipated in the international comparison activity organized by Asia Pacific Metrology (APMP) and got an international mutual recognition result using this method. The important factors of the method, such as the spray voltage, mobile phase, chromatographic column, extraction, purification and filtration conditions were investigated to acquire optimum conditions. The opti- mization results showed that the composition and pH value of the mobile phase had effects on the response of the mass spectrum of clenbuterol and the optimal value of the spray voltage. The solvent of sample had influences on the chromatographic retention behavior of clenbuterol. It was found that methanol caused a serious solvent effect, even made chromatographic peak split. Since clenbuterol was easily adsorbed on hydrophilic filter membranes and solid phase extraction columns, there were interference suppressions for the quantification of clenbuterol because of the eluate of the solid phase extraction columns. The homogenate method with extraction solvent of 0.1% (v/v) formic acid in acetonitrile had the highest extraction efficiency. The limit of the detection (LOD, S/N > 3) of the method was 0.2 ?g/kg. The determination results of clenbuterol in the porcine meat by this method were 5.18 ?g/kg ± 0.50 ?g/kg (k = 2). This method is accurate, reliable, reproducible, and suitable for the determination of clenbuterol with trace quantity in porcine meat. PMID:25739271

  17. Mass Spectrometry and Protein Analysis

    NSDL National Science Digital Library

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

    2006-04-14

    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 spectrometryâ??based analytical platforms and experimental strategies have emerged. Here we review recent advances in mass spectrometry instrumentation in the context of current and emerging research strategies in protein science.

  18. Quantitative detection of trichloroacetic acid in human urine using isotope dilution high-performance liquid chromatography-electrospray ionization tandem mass spectrometry.

    PubMed

    Kuklenyik, Zsuzsanna; Ashley, David L; Calafat, Antonia M

    2002-05-01

    The chemical disinfection of drinking water to control microbial contaminants results in the formation of disinfection byproducts (DBPs). The volatile trihalomethanes and the nonvolatile haloacetic acids (HAAs) are the most prevalent DBPs. It is important to monitor human exposure to HAAs because of their potential adversehealth effects, such as cancer. Among the HAAs, urinary trichloroacetic acid (TCAA) is a potential valid biomarker for assessing chronic ingestion exposure to HAAs from drinking water. We have developed a rugged, high-throughput, sensitive, accurate, and precise assay for the measurement of trace levels of TCAA in human urine using a simple solid-phase extraction (SPE) cleanup followed by isotope dilution high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). TCAA is extracted from the urine using SPE, separated from other extract components by reversed-phase HPLC, and analyzed by negative ion electrospray ionization-isotope dilution-MS/MS using a multiple reaction monitoring experiment. The method is simple and fast and is not labor intensive (sample preparation and analysis can be performed in approximately 15 min) with a limit of detection of 0.5 ng/mL in 1 mL of urine. PMID:12033307

  19. Measurements of water vapor isotope ratios with wavelength-scanned cavity ring-down spectroscopy technology: new insights and important caveats for deuterium excess measurements in tropical areas in comparison with isotope-ratio mass spectrometry.

    PubMed

    Tremoy, Guillaume; Vimeux, Françoise; Cattani, Olivier; Mayaki, Salla; Souley, Ide; Favreau, Guillaume

    2011-12-15

    The new infrared laser spectroscopic techniques enable us to measure the isotopic composition (?(18)O and ?(2)H) of atmospheric water vapor. With the objective of monitoring the isotopic composition of tropical water vapor (West Africa, South America), and to discuss deuterium excess variability (d=?(2)H - 8?(18)O) with an accuracy similar to measurements arising from isotope-ratio mass spectrometry (IRMS), we have conducted a number of tests and calibrations using a wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) technique. We focus in this paper on four main aspects regarding (1) the tubing material, (2) the humidity calibration of the instrument, (3) the water vapor concentration effects on ?, and (4) the isotopic calibration of the instrument. First, we show that Synflex tubing strongly affects ?(2)H measurements and thus leads to unusable d values. Second, we show that the mixing ratio as measured by WS-CRDS has to be calibrated versus atmospheric mixing ratio measurements and we also suggest possible non-linear effects over the whole mixing ratio range (~2 to 20 g/kg). Third, we show that significant non-linear effects are induced by water vapor concentration variations on ? measurements, especially for mixing ratios lower than ~5 g/kg. This effect induces a 5 to 10‰ error in deuterium excess and is instrument-dependent. Finally, we show that an isotopic calibration (comparison between measured and true values of isotopic water standards) is needed to avoid errors on deuterium excess that can attain ~10‰. PMID:22095494

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

    PubMed

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

    2014-09-01

    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 [C3H6NH·H](+) and [TATP·NH4](+), 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

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

    SciTech Connect

    Bürger, Stefan [New Brunswick Laboratory, Argonne, IL; Riciputi, Lee R [Los Alamos National Laboratory (LANL); Bostick, Debra A [ORNL; Turgeon, Steven [University of Alberta, Edmondton, Canada; McBay, Eddie H [ORNL; Lavelle, Mark [ORNL

    2009-01-01

    A ThermoFisher 'Triton' multi-collector thermal ionization mass spectrometer (MC-TIMS) was evaluated for trace and ultra-trace level isotoperatioanalysis of actinides (uranium, plutonium, and americium), fission products and geolocators (strontium, cesium, and neodymium). Total efficiencies (atoms loaded to ions detected) of up to 0.5-2% for U, Pu, and Am, and 1-30% for Sr, Cs, and Nd can be reported employing resin bead load techniques onto flat ribbon Re filaments or resin beads loaded into a millimeter-sized cavity drilled into a Re rod. This results in detection limits of <0.1 fg (10{sup 4} atoms to 10{sup 5} atoms) for {sup 239-242+244}Pu, {sup 233+236}U, {sup 241-243}Am, {sup 89,90}Sr, and {sup 134,135,137}Cs, and {le} 1 pg for natural Nd isotopes (limited by the chemical processing blank) using a secondary electron multiplier (SEM) or multiple-ion counters (MICs). Relative standard deviations (RSD) as small as 0.1% and abundance sensitivities of 1 x 10{sup 6} or better using a SEM are reported here. Precisions of RSD {approx} 0.01-0.001% using a multi-collector Faraday cup array can be achieved at sub-nanogram concentrations for strontium and neodymium and are suitable to gain crucial geolocation information. The analytical protocols reported herein are of particular value for nuclear forensic and nuclear safeguard applications.

  2. Development and co-validation of porcine insulin certified reference material by high-performance liquid chromatography-isotope dilution mass spectrometry.

    PubMed

    Wu, Liqing; Takatsu, Akiko; Park, Sang-Ryoul; Yang, Bin; Yang, Huaxin; Kinumi, Tomoya; Wang, Jing; Bi, Jiaming; Wang, Yang

    2015-04-01

    This article concerns the development and co-validation of a porcine insulin (pINS) certified reference material (CRM) produced by the National Institute of Metrology, People's Republic of China. Each CRM unit contained about 15 mg of purified solid pINS. The moisture content, amount of ignition residue, molecular mass, and purity of the pINS were measured. Both high-performance liquid chromatography-isotope dilution mass spectrometry and a purity deduction method were used to determine the mass fraction of the pINS. Fifteen units were selected to study the between-bottle homogeneity, and no inhomogeneity was observed. A stability study concluded that the CRM was stable for at least 12 months at -20 °C. The certified value of the CRM was (0.892?±?0.036) g/g. A co-validation of the CRM was performed among Chinese, Japanese, and Korean laboratories under the framework of the Asian Collaboration on Reference Materials. The co-validation results agreed well with the certified value of the CRM. Consequently, the pINS CRM may be used as a calibration material or as a validation standard for pharmaceutical purposes to improve the quality of pharmaceutical products. PMID:25534116

  3. Accelerator mass spectrometry as a bioanalytical tool for nutritional research

    SciTech Connect

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

    1997-09-01

    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.

  4. Compact hydrogen\\/helium isotope mass spectrometer

    Microsoft Academic Search

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

    1996-01-01

    The compact hydrogen and helium isotope mass spectrometer of the present invention combines low mass-resolution ion mass spectrometry and beam-foil interaction technology to unambiguously detect and quantify deuterium (D), tritium (T), hydrogen molecule (H.sub.2, HD, D.sub.2, HT, DT, and T.sub.2), .sup.3 He, and .sup.4 He concentrations and concentration variations. The spectrometer provides real-time, high sensitivity, and high accuracy measurements. Currently,

  5. Mass Spectrometry & Proteomics Services Unit

    E-print Network

    Graham, Nick

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

  6. Linear electric field mass spectrometry

    DOEpatents

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

    1992-12-01

    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.

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

    SciTech Connect

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

    2009-06-08

    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.

  8. Validation of the determination of the B isotopic composition in Roman glasses with laser ablation multi-collector inductively coupled plasma-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Devulder, Veerle; Gerdes, Axel; Vanhaecke, Frank; Degryse, Patrick

    2015-03-01

    The applicability of laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) for the determination of the B isotopic composition in Roman glasses was investigated. The ?11B values thus obtained provide information on the natron flux used during the glass-making process. The glass samples used for this purpose were previously characterized using pneumatic nebulization (PN) MC-ICP-MS. Unfortunately, this method is time-consuming and labor-intensive and consumes some 100 mg of sample, which is a rather high amount for ancient materials. Therefore, the use of the less invasive and faster LA-MC-ICP-MS approach was explored. In this work, the results for 29 Roman glasses and 4 home-made glasses obtained using both techniques were compared to assess the suitability of LA-MC-ICP-MS in this context. The results are in excellent agreement within experimental uncertainty. No difference in overall mass discrimination was observed between the Roman glasses, NIST SRM 610 reference glass and B6 obsidian. The expanded uncertainty of the LA-MC-ICP-MS approach was estimated to be < 2‰, which is similar to that obtained upon sample digestion and PN-MC-ICP-MS measurement.

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

    PubMed

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

    2010-01-01

    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

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

    PubMed

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

    2014-01-01

    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

  11. Simultaneous determination of water-soluble vitamins in SRM 1849 Infant/Adult Nutritional Formula powder by liquid chromatography-isotope dilution mass spectrometry.

    PubMed

    Goldschmidt, Robert J; Wolf, Wayne R

    2010-05-01

    Assessing dietary intake of vitamins from all sources, including foods, dietary supplements, and fortified foods, would be aided considerably by having analytical methodologies that are capable of simultaneous determination of several vitamins. Vitamins naturally present in foods may occur in different chemical forms, with levels ranging over several orders of magnitude. Vitamins in dietary supplements and fortified foods, however, are typically added in a single chemical form, and matrix issues are usually not as complex. These sources should thus be relatively amenable to approaches that aim for simultaneous determination of multiple vitamins. Our recent work has focused on development of liquid chromatography (LC)-UV/fluorescence and LC-tandem mass spectrometry methods for the simultaneous determination of water-soluble vitamins (thiamine, niacin, pyridoxine, pantothenic acid, folic acid, biotin, and riboflavin) in dietary supplement tablets and fortified foods, such as formula powders and breakfast cereals. As part of the validation of our methods and collaboration in characterization of a new NIST SRM 1849 Infant/Adult Nutritional Formula powder, we report data on SRM 1849 using isotope dilution mass spectrometric methods. Use of available NIST Standard Reference Materials(R) as test matrices in our method development and validation gives a benchmark for future application of these methods. We compare three chromatographic approaches and provide data on stability of vitamin standard solutions for LC-based multiple vitamin determinations. PMID:20063152

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

    Microsoft Academic Search

    Viorica. Lopez-Avila; Pat. Hirata; Susan. Kraska; Michael. Flanagan; John H. Taylor; Stephen C. Hern

    1985-01-01

    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-dâ, lindane-dâ, pentachlorophenol-¹³Câ, and diazinon-dââ 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

  13. Pitfalls encountered during quantitative determination of 3-alkyl-2-methoxypyrazines in grape must and wine using gas chromatography-mass spectrometry with stable isotope dilution analysis. Comprehensive two-dimensional gas chromatography-mass spectrometry and on-line liquid chromatography-multidimensional gas chromatography-mass spectrometry as potential loopholes.

    PubMed

    Schmarr, Hans-Georg; Ganss, Sebastian; Koschinski, Stefan; Fischer, Ulrich; Riehle, Carmen; Kinnart, Julian; Potouridis, Theodoros; Kutyrev, Maria

    2010-10-22

    The analysis of 3-alkyl-2-methoxypyrazines in Vitis vinifera grape must or wine at the low nanogram per liter level failed in several situations when applying a one-dimensional gas chromatographic analysis with mass spectrometric detection (GC-MS). Sample preparation methods such as headspace solid phase microextraction or solid phase extraction were convenient procedures, however lacking extraction selectivity for complex matrices. Analysis by comprehensive two-dimensional gas chromatography with mass spectrometric detection clearly demonstrated the potential for co-elution in such matrices and the risk for erroneous results when applying one-dimensional GC-MS. In one example, matrix problems would have been a challenge even for a comprehensive two-dimensional chromatographic approach with MS detection (GC×GC-MS). A solution to matrix problems was found by protonating the 3-alkyl-2-methoxypyrazines in acidic pH and sample clean-up using solid phase extraction with a mixed-mode polymeric cation-exchange sorbent. Quantification was performed by a stable isotope dilution assay, following analysis by on-line coupled high performance liquid chromatography with multidimensional gas chromatography and detection with mass spectrometry (on-line LC-MDGC-MS). This new approach allowed trace-level analysis of 3-alkyl-2-methoxypyrazines in grape musts and wines and is described for V. vinifera Sauvignon blanc, following 3-alkyl-2-methoxypyrazines concentrations during ripening and in the processed wines. PMID:20637469

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

    NASA Astrophysics Data System (ADS)

    Schmitz, Mark D.; Bowring, Samuel A.; Ireland, Trevor R.

    2003-10-01

    U-Pb zircon geochronology is increasingly called upon to achieve the resolution of absolute time at the 0.1% to 1% level for rocks of Phanerozoic to Hadean age. Doing so requires accurate calibration of the several methods (conventional isotope dilution thermal ionization mass spectrometry [ID-TIMS], Pb evaporation, high-resolution ion microprobe [e.g. SHRIMP], and laser ablation inductively coupled plasma mass spectrometry [LA-ICPMS]) currently in use, in numerous laboratories, for the analysis of U and Pb isotopes in accessory minerals. Toward this end, the geochronological community would benefit from the establishment, distribution and widespread analysis of one or more standard reference materials. Among the candidates is natural zircon from the Duluth Complex anorthositic series of the Midcontinent Rift system of North America. These zircons, first dated by conventional ID-TIMS at 1099.1 ± 0.5 Ma, have been subsequently adopted as a geochronological standard by a number of high resolution ion microprobe facilities. A new and independent analysis of the systematics of a large set of single zircons (n = 27) from the same mineral separate yields indistinguishable 207Pb/ 206Pb, upper intercept, and U-Pb concordia dates for the AS3 zircons. The concordia date, based on a subset of 12 concordant and equivalent zircons, of 1099.1 ± 0.2 Ma (±1.2 Ma considering systematic uncertainties in Pb/U tracer calibration and U decay constants) is indistinguishable from previously published results. We further document the absence of inherited Pb in the AS3 zircons, and discuss strategies for avoiding certain domains within the AS3 zircons exhibiting small amounts of radiation-induced, surface and fracture-correlated, recent Pb loss. Although the AS3 zircons do not represent the ideal (and elusive) homogeneous closed U-Pb system, we conclude that these and similar zircons from the Duluth Complex anorthositic series can provide a suitable geochronological reference standard for numerous U-Pb zircon analytical methods, given appropriate preparation guided by the results of this study. Our high-precision data set also serves as a useful confirmatory test of the currently accepted U decay constants.

  15. Mass Spectrometry in the Postgenomic Era

    E-print Network

    Chait, Brian T.

    Mass Spectrometry in the Postgenomic Era Brian T. Chait Laboratory for Mass Spectrometry reserved 0066-4154/11/0707-0239$20.00 Keywords cellular systems, proteomics, protein complexes, native mass spectrometry, lipidomics Abstract Mass spectrometry (MS) is rapidly becoming an essential tool for bi- ologists

  16. Mass spectrometry. [in organic chemistry

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

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

    PubMed

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

    2013-11-01

    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

  18. Femtosecond laser ablation molecular isotopic spectrometry for zirconium isotope analysis.

    PubMed

    Hou, Huaming; Chan, George C-Y; Mao, Xianglei; Zorba, Vassilia; Zheng, Ronger; Russo, Richard E

    2015-05-01

    Laser ablation molecular isotopic spectrometry (LAMIS) for rapid isotopic analysis of zirconium at atmospheric pressure was studied with a femtosecond-laser system operated under high repetition rate (1 kHz) and low pulse energy (160 ?J). The temporal evolution of zirconium neutral-atomic and ionic lines, as well as zirconium oxide molecular bands, were studied. Six molecular bands, belonging to the d(3)?-a(3)? (i.e., the ? system) and E(1)?(+)-X(1)?(+) transitions, were observed with appreciable isotopic shifts. The assignments of the isotopic bandheads were first based on theoretical predictions of the band origins and the associated isotopic shifts of various dipole-allowed ZrO electronic transitions, followed by an experimental confirmation with a (94)Zr-enriched ZrO2 sample. In this work, the ?(0,1) band from the d(3)?3-a(3)?3 subsystem was utilized for Zr isotope analysis based on a compromise between the magnitude of isotopic shifts in emission wavelengths, emission strengths, signal-to-background ratios, and spectral interferences. The analysis was performed in a standardless calibration approach; the isotopic information was extracted from the experimentally measured molecular spectra through theoretical spectral fitting. The results demonstrate the feasibility to obtain isotopic information for a spectrally complicated element like zirconium, without the need to use isotopically labeled calibration standards. The availability of comprehensive molecular constants will further improve the analytical accuracy of this standardless calibration approach. PMID:25821993

  19. Quantitation of changes in protein phosphorylation: A simple method based on stable isotope labeling and mass spectrometry

    Microsoft Academic Search

    Débora Bonenfant; Tobias Schmelzle; Estela Jacinto; José L. Crespo; Thierry Mini; Michael N. Hall; Paul Jenoe

    2003-01-01

    Reversible protein phosphorylation plays an important role in many cellular processes. However, a simple and reliable method to measure changes in the extent of phosphorylation is lacking. Here, we present a method to quantitate the changes in phosphorylation occurring in a protein in response to a stimulus. The method consists of three steps: (i) enzymatic digestion in H216O or isotopically

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

    PubMed

    Campo, Laura; Fustinoni, Silvia; Bertazzi, Pieralberto

    2011-08-01

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

  1. Validation of an isotope dilution gas chromatography-mass spectrometry method for combined analysis of oxysterols and oxyphytosterols in serum samples.

    PubMed

    Schött, Hans-Frieder; Lütjohann, Dieter

    2015-07-01

    We describe the validation of a method for the analysis of oxysterols, i.e. oxycholesterols and oxyphytosterols, in human serum using gas chromatography-mass spectrometry selected ion monitoring (GC-MS-SIM). Concentrations of 7?- and 7?-hydroxy-, and 7oxo-cholesterol, -campesterol, and -sitosterol as well as 4?-hydroxycholesterol and side-chain oxygenated 24S-, 25-, and 27-hydroxycholesterol were determined by isotope dilution methodology. After saponification at room temperature the oxysterols were extracted, separated from their substrates, cholesterol, campesterol, and sitosterol, by solid phase extraction, and subsequently derivatised to their corresponding trimethylsilyl-ethers prior to GC-MS-SIM. In order to prevent artificial autoxidation butylated hydroxytoluene and ethylenediaminetetraacetic acid were added. The validation of the method was performed according to the International Conference on Harmonisation guidance, including limits of detection and quantification, ranges, recovery and precision. Due to improved instrumental settings and work-up procedure, limits of detection and quantification ranged between 8.0-202.0pg/mL and 28.0-674pg/mL, respectively. Recovery data in five calibration points varied between 91.9% and 116.8% and in serum samples between 93.1% and 118.1%. The mean coefficient of variation (CV) for the recovery of all compounds was <10%. Well satisfying CVs for within-day precision (2.1-10.8%) and for between-day precision (2.3-12.1%) were obtained. More than 20 samples could be processed in a single routine day and test series of about 300 samples can be realised without impairment of the validation parameters during a sequence. Comparison of oxysterol and oxyphytosterol content in serum and plasma revealed no difference. A fully validated isotope dilution methodology for the quantification of oxycholesterols and oxyphytosterols from human serum or plasma is presented. PMID:25701095

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

    PubMed

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

    2010-04-15

    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

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

    PubMed

    Jamin, Eric; Martin, Frédérique; Martin, Gilles G

    2004-01-01

    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

  4. Protein Quantitation Using Mass Spectrometry

    PubMed Central

    Zhang, Guoan; Ueberheide, Beatrix M.; Waldemarson, Sofia; Myung, Sunnie; Molloy, Kelly; Eriksson, Jan; Chait, Brian T.; Neubert, Thomas A.; Fenyö, David

    2013-01-01

    Mass spectrometry is a method of choice for quantifying low-abundance proteins and peptides in many biological studies. Here, we describe a range of computational aspects of protein and peptide quantitation, including methods for finding and integrating mass spectrometric peptide peaks, and detecting interference to obtain a robust measure of the amount of proteins present in samples. PMID:20835801

  5. A Glossary for Mass Spectrometry

    NSDL National Science Digital Library

    Busch, Kenneth L.

    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.

  6. Studies on the analysis of 25-hydroxyvitamin D3 by isotope-dilution liquid chromatography–tandem mass spectrometry using enzyme-assisted derivatisation

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-12-01

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

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

    PubMed

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

    2013-11-01

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

  9. Gas chromatography flow rates for determining deuterium/hydrogen ratios of natural gas by gas chromatography/high-temperature conversion/isotope ratio mass spectrometry.

    PubMed

    Jia, Wanglu; Peng, Ping'an; Liu, Jinzhong

    2008-08-01

    The effects of the gas chromatography flow rate on the determination of the deuterium/hydrogen (D/H) ratios of natural gas utilising gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/TC/IRMS) have been evaluated. In general, the measured deltaD values of methane, ethane and propane decrease with increase in column flow rate. When the column flow rate is 1 mL/min or higher, which is commonly used for the determination of D/H ratios of natural gas, the organic H in gas compounds may not be completely converted into hydrogen gas. Based on the results of experiments conducted on a GC column with an i.d. of 0.32 mm, a GC flow rate of 0.6 mL/min is proposed for determining the D/H ratios of natural gas by GC/TC/IRMS. Although this value may be dependent on the instrument conditions used in this work, we believe that correct deltaD values of organic compounds with a few carbon atoms are obtained only when relatively low GC flow rates are used for D/H analysis by GC/TC/IRMS. Moreover, as the presence of trace water could significantly affect the determination of D/H ratios, a newly designed inlet liner was used to remove trace water contained in some gas samples. PMID:18636428

  10. [Simultaneous determination of delta13C values of glycerol and ethanol in wine by liquid chromatography coupled with isotope ratio mass spectrometry].

    PubMed

    Li, Xuemin; Jia, Guangqun; Cao, Yanzhong; Zhang, Jinjie; Wang, Lei; Sun, Huiyuan

    2013-12-01

    A novel procedure was established for the characterization of delta13C values of glycerol and ethanol in wine by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). Several parameters influencing the separation of glycerol and ethanol from wine matrix were optimized. The precision and accuracy of the proposed method were 0.15 per thousand to 0.26 per thousand and 0.11 per thousand to 0.28 per thousand, respectively. The results obtained for 40 wine samples displayed that the delta13C value of glycerol ranged from--26.87 per thousand to--32.96 per thousand and that of ethanol ranged from--24.06 per thousand to--28.29 per thousand. Close correlations (R = 0.82) were obtained between the delta13C values of glycerol and ethanol. The proposed method didn't need complex sample treatment, and the delta13C values of glycerol and ethanol in wine can be simultaneously determined, thus improving the method in terms of simplicity and speed compared with traditional methods. PMID:24669712

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

    SciTech Connect

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

    2009-09-04

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

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

    USGS Publications Warehouse

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

    2001-01-01

    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.

  13. Detection of FGF15 in Plasma by Stable Isotope Standards and Capture by Anti-peptide Antibodies and Targeted Mass Spectrometry.

    PubMed

    Katafuchi, Takeshi; Esterházy, Daria; Lemoff, Andrew; Ding, Xunshan; Sondhi, Varun; Kliewer, Steven A; Mirzaei, Hamid; Mangelsdorf, David J

    2015-06-01

    Fibroblast growth factor 15 (FGF15) has been proposed as a postprandial hormone that signals from intestine to liver to regulate bile acid and carbohydrate homeostasis. However, detecting FGF15 in blood using conventional techniques has proven difficult. Here, we describe a stable isotope standards and capture by anti-peptide antibodies (SISCAPA) assay that combines immuno-enrichment with selected reaction monitoring (SRM) mass spectrometry to overcome this issue. Using this assay, we show that FGF15 circulates in plasma in an FXR and circadian rhythm-dependent manner at concentrations that activate its receptor. Consistent with the proposed endocrine role for FGF15 in liver, mice lacking hepatocyte expression of the obligate FGF15 co-receptor, ?-Klotho, have increased bile acid synthesis and reduced glycogen storage despite having supraphysiological plasma FGF15 concentrations. Collectively, these data demonstrate that FGF15 functions as a hormone and highlight the utility of SISCAPA-SRM as a sensitive assay for detecting low-abundance proteins in plasma. PMID:26039452

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

    NASA Astrophysics Data System (ADS)

    Guo, Kevin; Bamforth, Fiona; Li, Liang

    2011-02-01

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

  15. Recent advances in biomedical applications of accelerator mass spectrometry

    Microsoft Academic Search

    Sang Soo Hah

    2009-01-01

    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

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

    PubMed

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

    2012-09-15

    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

  17. Symposium on accelerator mass spectrometry

    SciTech Connect

    None

    1981-01-01

    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.

  18. Digital Imaging Mass Spectrometry

    Microsoft Academic Search

    Casimir Bamberger; Uwe Renz; Andreas Bamberger

    2011-01-01

    Methods to visualize the two-dimensional (2D) distribution of molecules by mass spectrometric imaging evolve rapidly and yield\\u000a novel applications in biology, medicine, and material surface sciences. Most mass spectrometric imagers acquire high mass\\u000a resolution spectra spot-by-spot and thereby scan the object’s surface. Thus, imaging is slow and image reconstruction remains\\u000a cumbersome. Here we describe an imaging mass spectrometer that exploits

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  20. Digital Imaging Mass Spectrometry

    E-print Network

    Bamberger, Casimir; Bamberger, Andreas

    2011-01-01

    Methods to visualize the two-dimensional 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 MALDI directly from the target sample onto the detector. This imaging mass spectrometer has a spatial resolving power at the specimen of (84\\pm35) \\mu m with a mass resolution of 45 and locates atoms or organic compounds on a surface area up to ~2 cm2. Extended laser spots of ~5 mm2 on structured specimens allowed parallel imaging of s...

  1. Establishing a chromium-reactor design for measuring delta2H values of solid polyhalogenated compounds using direct elemental analysis and stable isotope ratio mass spectrometry.

    PubMed

    Armbruster, Wolfgang; Lehnert, Katja; Vetter, Walter

    2006-01-01

    2H/1H isotope ratios of polyhalogenated compounds were determined by elemental analysis and isotope ratio mass spectrometry (EA-IRMS). Initial measurements with standard EA-IRMS equipment, which used high-temperature pyrolysis to convert the organic compounds into hydrogen, did not achieve significant signals for polychlorinated pesticides and related compounds, presumably due to the formation of HCl instead of hydrogen. To reverse this problematic reaction, a chromium reactor was incorporated into the element analyzer system, which scavenged Cl, forming chromium chloride and releasing hydrogen again in the form of H2. The optimized system therefore allowed the delta2H values of polyhalogenated compounds to be determined. A quality assurance program was developed based on several parameters. (i) Each compound was analyzed using a sequence of five injections, where the first measurement was discarded. (ii) Recovery of H (when calculated relative to acetanilide) had to be >90% for all replicates in a sequence. (iii) All delta-values within a sequence had to vary by less than 10/1000. (iv) Results had to be reproducible on another day with a different sample scheme. Once this reproducibility had been established, variabilities in the delta2H values of organohalogen standards were investigated using the technique. The highest delta2H value of +75/1000 was found for o,p'-DDD, whereas the strongest depletion in deuterium was found for Melipax (-181/1000). The most important results for comparable compounds were as follows. DDT-related compounds gave delta2H values of between +59 and +75/1000 (technical DDT, o,p'- and p,p'-DDD) or in the range of approximately -1/1000, indicative of the different sources/methods of producing this compound. Four HCH isomers from the same supplier showed relatively similar hydrogen isotope distributions, whereas two lindane (gamma-HCH) standards from other sources had 39/1000 less deuterium. This difference is likely due to different purification steps during the isolation of pure lindane from the technical HCH mixture. An even greater difference was observed between the delta2H values of Toxaphene (US product dating from 1978) and Melipax (product from the former East Germany, dating from 1979), which gave delta2H values of -101/1000 and -181/1000, respectively, meaning that both products were easily distinguished via delta2H-IRMS. Fractioning of hydrogen isotopes in the atmospheric water cycle was suggested as one reason for the different values. In this theory, the water (which had different delta2H values depending on where it was taken from) was incorporated during the biosynthesis of camphene, which is the natural product used to produce both products. These results indicate that hydrogen isotope-specific analysis can be a valuable tool for tracing the origins of a compound in certain cases. PMID:16283262

  2. High-precision measurements of uranium and thorium isotopic ratios by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS)

    NASA Astrophysics Data System (ADS)

    Wang, Lisheng; Ma, Zhibang; Duan, Wuhui

    2015-04-01

    Isotopic compositions of U-Th and 230Th dating have been widely used in earth sciences, such as chronology, geochemistry, oceanography and hydrology. In this study, five ages of different carbonate samples were measured using 230Th dating technique with U-Th high-precision isotopic measurements by multi-collector inductively coupled plasma mass spectrometry, in Uranium-series Chronology Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences.In this study, the precision and accuracy of uranium isotopic composition were estimated by measuring the uranium ratios of NBS-CRM 112A, NBS-CRM U500 and HU-1. The mean measured ratios, 234U/238U = 52.86 (±0.04) × 10-6 and ?234U = -38.36 (±0.77) × 10-3 for NBS-CRM 112A, 234U/238U = 10.4184 (±0.0001) × 10-3, 236U/238U = 15.43 (±0.01) × 10-4 and 238U/235U = 1.00021 (±0.00002) for NBS-CRM U500, 234U/238U = 54.911 (±0.007) and ?234U = -1.04 (±0.13) × 10-3 for HU-1 (95% confidence levels). The U isotope data for standard reference materials are in excellent agreement with previous studies, further highlighting the reliability and analytical capabilities of our technique. We measured the thorium isotopic ratios of three different thorium standards by MC-ICPMS. The three standards (Th-1, Th-2 and Th-3) were mixed by HU-1 and NBS 232Th standard, with the 230Th/232Th ratios from 10-4 to 10-6. The mean measured atomic ratios, 230Th/232Th = 2.1227 (±0.0024) × 10-6, 2.7246 (±0.0026) × 10-5, and 2.8358 (±0.0007) × 10-4 for Th-1, Th-2 and Th-3 (95% confidence levels), respectively. Using this technique, the following standard samples were dated by MC-ICPMS. Sample RKM-4, collected from Babardos Kendal Hill terrace, was used during the first stage of the Uranium-Series Intercomparison Project (USIP-I). Samples 76001, RKM-5 and RKM-6 were studied during the second stage of the USIP program (USIP-II). Sample 76001 is a laminated flowstone, collected from Sumidero Terejapa, Chiapas, Mexico, and samples RKM-5 and RKM-6 are from the Babardos III terrace and the lower terrace (6 to 10m) of Curacao, respectively. China RCM GBW04412 was also analyzed. The ages of the five standard samples mentioned above are 197970±1590 yr BP, 47520±220 yr BP, 129300±650 yr BP, 130830±550 yr BP, and 86940±300 yr BP for samples RKM-4, 76001, RKM-5, RKM-6 and GBW04412, respectively. The results are consistent with the data of the same samples analyzed in Institute of Global Environmental Change, Xi'an Jiaotong University and Department of Earth Sciences, University of Minnesota, USA within errors, which suggests that the technique in our lab is reliable.

  3. Determination of 4(5)-methylimidazole in carbonated beverages by isotope-dilution liquid chromatography-tandem mass spectrometry.

    PubMed

    Ratnayake, Geemitha; Halldorson, Thor; Bestvater, Lianna; Tomy, Gregg T

    2015-07-01

    The purpose of this study was to develop a method to quantify 4(5)-methylimidazole (4-MEI), a suspected carcinogen, in carbonated beverages by simple sample dilution and isotope-dilution reverse-phase LC-MS/MS. Isotope dilution using hexa-deuterated methylimidazole (d6-4-MEI) was used to quantify native 4-MEI and to assess matrix effects quantitatively. The accuracy of the method was assessed by intentionally fortifying a negative control sample at three doses: low, medium and high (replicates of n = 5 each) with a known amount of 4-MEI. The respective absolute error in each case was 18.7 ± 0.7%, 14.6 ± 2.8% and 21.1 ± 9.7%. Within-day (intra-) and day-to-day (inter-) repeatability, determined as the relative standard deviation by fortifying a negative control sample (n = 5), were 9.5% and 15.4%, respectively. Average ion suppression of d6-4-MEI in beer was 63.9 ± 3.2%, while no suppression or enhancement was seen in non-alcoholic samples. The instrument and method limit of detection were calculated as 0.6 and 5.8 ng ml(-1), respectively. 4(5)-Methylimidazole was quantified in a variety of store-bought consumer beverages and it was found that in many of the samples tested consuming a single can of beer would result in intake levels of 4-MEI that exceed the no significant risk guideline of 29 µg day(-1). Conversely, 4-MEI in the samples was orders of magnitude smaller than the European Food Safety Authority acceptable daily intake threshold value of 100 mg kg(-1) bw day(-1). PMID:25994392

  4. Tandem Mass Spectrometry in Physiology

    NSDL National Science Digital Library

    2007-12-01

    Tandem mass spectrometry coupled to liquid chromatography (LC-MS/MS) allows identification of proteins in a complex mixture without need for protein purification ("shotgun" proteomics). Recent progress in LC-MS/MS-based quantification, phosphoproteomic analysis, and targeted LC-MS/MS using multiple reaction monitoring (MRM) has made LC-MS/MS a powerful tool for the study of cell physiology.

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

    SciTech Connect

    Sapkota, Amir [Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Johns Hopkins University Center for Water and Health, Baltimore, MD 21205-2103 (United States); Heidler, Jochen [Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Johns Hopkins University Center for Water and Health, Baltimore, MD 21205-2103 (United States); Halden, Rolf U. [Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Johns Hopkins University Center for Water and Health, Baltimore, MD 21205-2103 (United States)]. E-mail: rhalden@jhsph.edu

    2007-01-15

    The antimicrobial compound triclocarban (TCC; 3,4,4'-trichlorocarbanilide; CAS-bar 101-20-2) is a high-production-volume chemical, recently suggested to cause widespread contamination of US water resources. To test this hypothesis, we developed an isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry method for ultratrace analysis of TCC (0.9ng/L detection limit) and analyzed low-volume water samples (200mL) along with primary sludge samples from across the United States. All river water samples (100%) collected downstream of wastewater treatment plants had detectable levels of TCC, as compared to 56% of those taken upstream. Concentrations of TCC (mean+/-standard deviation) downstream of sewage treatment plants (84+/-110ng/L) were significantly higher (P<0.05; Wilcoxon rank sum test) than those of samples taken upstream (12+/-15ng/L). Compared to surface water, mean TCC concentrations found in dried, primary sludge obtained from municipal sewage treatment plants in five states were six orders of magnitude greater (19,300+/-7100{mu}g/kg). Several river samples contained a co-contaminant, identified based on its chromatographic retention time, molecular base ion, and MS/MS fragmentation behavior as 4,4'-dichlorocarbanilide (DCC; CAS-bar 1219-99-4). In addition to TCC and DCC, municipal sludge contained a second co-contaminant, 3,3',4,4'-tetrachlorocarbanilide (TetraCC; CAS-bar 4300-43-0). Both newly detected compounds were present as impurities (0.2%{sub w/w} each) in technical grade TCC (99%). Application of the new method for chlorocarbanilide analysis yielded TCC occurrence data for 13 US states, confirmed the role of sewage treatment plants as environmental inputs of TCC, and identified DCC and TetraCC as previously unrecognized pollutants released into the environment alongside TCC.

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

    PubMed

    Sapkota, Amir; Heidler, Jochen; Halden, Rolf U

    2007-01-01

    The antimicrobial compound triclocarban (TCC; 3,4,4'-trichlorocarbanilide; CAS# 101-20-2) is a high-production-volume chemical, recently suggested to cause widespread contamination of US water resources. To test this hypothesis, we developed an isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry method for ultratrace analysis of TCC (0.9 ng/L detection limit) and analyzed low-volume water samples (200 mL) along with primary sludge samples from across the United States. All river water samples (100%) collected downstream of wastewater treatment plants had detectable levels of TCC, as compared to 56% of those taken upstream. Concentrations of TCC (mean+/-standard deviation) downstream of sewage treatment plants (84+/-110 ng/L) were significantly higher (P<0.05; Wilcoxon rank sum test) than those of samples taken upstream (12+/-15 ng/L). Compared to surface water, mean TCC concentrations found in dried, primary sludge obtained from municipal sewage treatment plants in five states were six orders of magnitude greater (19,300+/-7100 microg/kg). Several river samples contained a co-contaminant, identified based on its chromatographic retention time, molecular base ion, and MS/MS fragmentation behavior as 4,4'-dichlorocarbanilide (DCC; CAS# 1219-99-4). In addition to TCC and DCC, municipal sludge contained a second co-contaminant, 3,3',4,4'-tetrachlorocarbanilide (TetraCC; CAS# 4300-43-0). Both newly detected compounds were present as impurities (0.2%(w/w) each) in technical grade TCC (99%). Application of the new method for chlorocarbanilide analysis yielded TCC occurrence data for 13 US states, confirmed the role of sewage treatment plants as environmental inputs of TCC, and identified DCC and TetraCC as previously unrecognized pollutants released into the environment alongside TCC. PMID:16678153

  7. Determination of agmatine using isotope dilution UPLC-tandem mass spectrometry: application to the characterization of the arginine decarboxylase pathway in Pseudomonas aeruginosa.

    PubMed

    Dalluge, Joseph J; McCurtain, Jennifer L; Gilbertsen, Adam J; Kalstabakken, Kyle A; Williams, Bryan J

    2015-07-01

    A method has been developed for the direct determination of agmatine in bacterial culture supernatants using isotope dilution ultra performance liquid chromatography (UPLC)-tandem mass spectrometry (UPLC-MS/MS). Agmatine determination in bacterial supernatants is comprised of spiking culture or isolate supernatants with a fixed concentration of uniformly labeled (13)C5,(15)N4-agmatine (synthesized by decarboxylation of uniformly labeled (13)C6,(15)N4-arginine using arginine decarboxylase from Pseudomonas aeruginosa) as an internal standard, followed by derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBDF) to improve the reversed-phase chromatographic retention characteristics of agmatine, as well as the selectivity and sensitivity of UPLC-MS/MS detection of this amine in complex biologically derived mixtures. Intrasample precisions for measurement of agmatine in culture supernatants average 4.1 % (relative standard deviation). Calibration curves are linear over the range 5 nM to 10 ?M, and the detection limit is estimated at 1.5 nM. To demonstrate the utility of the method, agmatine levels in supernatants of overnight cultures of wild-type (UCBPP-PA14), as well as arginine decarboxylase and agmatine deiminase mutant strains of P. aeruginosa strain UCBPP-PA14 were measured. This method verified that the mutant strains are lacking the specific metabolic capabilities to produce and metabolize agmatine. In addition, measurement of agmatine in supernatants of a panel of clinical isolates from patients with cystic fibrosis revealed that three of the P. aeruginosa isolates hyper-secreted agmatine into the supernatant, hypothesized to be a result of a mutation in the aguA gene. Because agmatine has potential inflammatory activities in the lung, this phenotype may be a virulence factor for P. aeruginosa in the lung environment of cystic fibrosis patients. PMID:25957842

  8. Simplified method for microlitre deuterium measurements in water and urine by gas chromatography-high-temperature conversion-isotope ratio mass spectrometry.

    PubMed

    Gucciardi, Antonina; Cogo, Paola E; Traldi, Umberto; Eaton, Simon; Darch, Tegan; Simonato, Manuela; Ori, Carlo; Carnielli, Virgilio P

    2008-07-01

    Deuterium (2H) in water and urine can be measured by off-line and, more recently, on-line techniques using isotope ratio mass spectrometry (IRMS). We describe a new simple on-line pyrolysis method for the analysis of 2H/1H in water and urine samples by continuous flow IRMS, normally used for 2H/1H measurements in organic compounds. A deactivated column connected the split injector to a high-temperature conversion reactor (TC HD), and 0.5 microL of sample was injected. Accuracy and precision were determined with Vienna Standard Mean Ocean Water (VSMOW), Standard Light Antarctic Precipitation (SLAP), and Greenland Ice Sheet Precipitation (GISP). The range of linearity was measured with a calibration curve of enriched water from 0 up to 0.1 atom percent excess (APE) (i.e. -72 up to 6323 delta per mil (deltaD per thousand)) with a precision of <5 per thousand and accuracy ranging between 1 and 55 per thousand. Blinded reanalysis of urine samples by an equilibration device (Gas Bench) and by a dedicated pyrolysis system (TC/EA) was performed and results compared by the Bland-Altman test. Enrichments ranged between 600 and 2400 per thousand deltaD(VSMOW) with a precision of +/-5 per thousand. Urine enrichments described by our method were strongly correlated with values obtained by Gas Bench and TC/EA (p < 0.0001). There was a significant memory effect that was reduced by injecting the sample 15 times and discarding the first 10 injections, together with accurate furnace conditioning and appropriate cleaning of the syringe. Data indicate that the method is accurate, and that it can be used for water and urine deuterium determination when a Gas Bench or TC/EA instrument is not available and the amount of sample is limited. PMID:18512843

  9. Quantification of key red blood cell folates from subjects with defined MTHFR 677C>T genotypes using stable isotope dilution liquid chromatography/mass spectrometry

    PubMed Central

    Huang, Yuehua; Khartulyari, Stefanie; Morales, Megan E.; Stanislawska-Sachadyn, Anna; Von Feldt, Joan M.; Whitehead, Alexander S.; Blair, Ian A.

    2014-01-01

    Red blood cell (RBC) folate levels are established at the time of erythropoiesis and therefore provide a surrogate biomarker for the average folate status of an individual over the preceding four months. Folates are present as folylpolyglutamates, highly polar molecules that cannot be secreted from the RBCs, and must be converted into their monoglutamate forms prior to analysis. This was accomplished using an individual’s plasma pteroylpolyglutamate hydrolase by lysing the RBCs in whole blood at pH 5 in the presence of ascorbic acid. Quantitative conversion of formylated tetrahydrofolate derivatives into the stable 5,10-methenyltetrahydrofolate (5,10-MTHF) form was conducted at pH 1.5 in the presence of [13C5]-5-formyltetrahydrofolate. The resulting [13C5]-5,10-MTHF was then used as an internal standard for the formylated forms of tetrahydrofolate that had been converted into 5,10-MTHF as well any 5,10-MTHF that had been present in the original sample. A stable isotope dilution liquid chromatography-multiple reaction monitoring/mass spectrometry method was validated and then used for the accurate and precise quantification of RBC folic acid, 5-methyltetrahydrofolate (5-MTHF), tetrahydrofolate (THF), and 5,10-MTHF. The method was sensitive and robust and was used to assess the relationship between different methylenetetrahydrofolate reductase (MTHFR) 677C>T genotypes and RBC folate phenotypes. Four distinct RBC folate phenotypes could be identified. These were classified according to the relative amounts of individual RBC folates as type I (5-MTHF >95%; THF <5%; 5,10-MTHF <5%), type II (5-MTHF <95%; THF 5% to 20%; 5,10-MTHF <5%), type III (5-MTHF >55%; THF >20%; 5,10-MTHF >5%), and type IV (5-MTHF <55%; THF >20%; 5,10-MTHF >5%). PMID:18634122

  10. Analysis of LDEF experiment AO187-2 chemical and isotopic measurements of micrometeoroids by secondary ion mass spectrometry. Final report

    SciTech Connect

    Zinner, E.

    1995-11-01

    Experiment AO187-2, that was flown on board the Long Duration Exposure Facility (LDEF), was designed to measure the chemical and isotopic compositions of interplanetary dust impinging on the spacecraft from outer space. Information on the nature and composition of orbital debris was also anticipated. The spacecraft maintained a constant orientation with respect to its velocity vector thereby defining leading and trailing edges that faced respectively into and away from the direction of motion. Arrays of individual capture cells each 80.8 sq cm in size and totaling 237 in number were exposed on both the leading and trailing edges of LDEF. Each cell consisted of a pure Ge target surface slightly separated from a thin (2.5 micrometers) metallized plastic `entrance foil.` The basic concept was that incoming projectiles would penetrate the foil, strike the Ge target plate at high velocity producing a vapor-liquid cloud that would re-deposit material on the underside of the plastic foil. This material would then be analyzed using the sensitive surface analysis technique of Secondary Ion Mass Spectrometry (SIMS). In practice, most of the plastic entrance foils failed during the extended period of orbital exposure probably due to a combination of UV embrittlement, large densities of impact events and (for the leading edge) the effects of atomic oxygen erosion in orbit. However the foils failed gradually and most remained in place on the capture cells for a significant fraction of the duration of the flight. Because most of the impactors were small (less than 10 micrometers) they were heated and dispersed in traversing the entrance foils producing clouds of molten droplets and vapor that produced easily identifiable `extended impacts` on the Ge target plates.

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

    Microsoft Academic Search

    Takafumi Hirata; Robert W. Nesbitt

    1995-01-01

    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

  12. Ambient Ionization Mass Spectrometry

    Microsoft Academic Search

    Min-Zong Huang; Cheng-Hui Yuan; Sy-Chyi Cheng; Yi-Tzu Cho; Jentaie Shiea

    2010-01-01

    Mass spectrometric ionization methods that operate under ambient conditions and require minimal or no sample pretreatment have attracted much attention in such fields as biomedicine, food safety, antiterrorism, pharmaceuticals, and environmental pollution. These technologies usually involve separate ionization and sample-introduction events, allowing independent control over each set of conditions. Ionization is typically performed under ambient conditions through use of existing

  13. THERMOSPRAY MASS SPECTROMETRY AND THERMOSPRAY MASS SPECTROMETRY/MASS SPECTROMETRY OF TWO DEOXYGUANOSINE CARCINOGEN ADDUCTS

    EPA Science Inventory

    Analysis of N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-C8-AAF) and N-(deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF) by thermospray mass spectrometry (TSP/MS) provided (MH)+ ions. TSP/MS/MS of the (MH)+ ions produced (BH2)+ ions....

  14. Electrospray Ionization Mass Spectrometry

    SciTech Connect

    Kelly, Ryan T.; Marginean, Ioan; Tang, Keqi

    2014-06-13

    Electrospray Ionization (ESI) is a process whereby gas phase ions are created from molecules in solution. As a solution exits a narrow tube in the presence of a strong electric field, an aerosol of charged droplets are is formed that produces gas phase ions as they it desolvates. ESI-MS comprises the creation of ions by ESI and the determination of their mass to charge ratio (m/z) by MS.

  15. Sulfur Isotope Variation in Basaltic Melt Inclusions from Krakatau Revealed by a Newly Developed Secondary Ion Mass Spectrometry Technique for Silicate Glasses

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    Sulfur is a ubiquitous element with variable valance states (S2-, S0, S4+, S6+) allowing for its participation in a wide variety of chemical and biogeochemical processes. However, its potential as an isotopic tracer in magmatic processes has not been fully developed and is crucial to understanding of sulfur recycling in subduction zones and between Earth's major reservoirs, mantle, lithosphere and coupled hydrosphere-atmosphere. Previous studies of silicate glasses and melt inclusions have been hampered by lack of an in situ isotopic measurement technique with spatial resolution of 10 to 100 microns. We have developed a new secondary ion mass spectrometry (SIMS) analytical technique for measurement of 34S/32S ratios in silicate glasses utilizing the IMS 1280 at Woods Hole Oceanographic Institution. A beam of 133Cs+ ions with 13 keV energy and current of 1-2 nA is focused onto a 10 micron spot and rastered over 30 × 30 microns. A Normal Incidence Electron Gun was used to compensate excess charge. The rastered beam is then centered to the optical axis of the machine, and a mechanical aperture is placed on the image plane to limit the area of analysis to the central 15 × 15 microns. The energy slit width was adjusted to 50 eV. A mass resolving power of 5500 was sufficient for eliminating mass interferences. A suite of synthetic and natural glasses with ?34SVCDT values spanning from - 5.6‰ to 18.5‰ with SiO2 from 44-72 weight % were measured. Magnitude of the instrumental mass fractionation (?) for 34S/32S ratios is 0.991 and is constant for all the glasses measured despite their compositions. Precision of individual measurements of 34S/32S ratios is 0.4 ‰, or better. Preliminary ?34S measurements of olivine-hosted basaltic melt inclusions in pre- 1883 basaltic scoria from Krakatau volcano Indonesia vary from -5.6 to 7.9‰ with sulfur concentrations from 490 to 2170 ppm, respectively. Host olivines are Fo77-80 and inclusions generally need minor to no post-entrapment corrections using KDFe-MgOl-liquid = 0.30. Most inclusions are basaltic though a few range up to basaltic andesite. Sulfur X-ray wavelength scans of melt inclusions indicates 60% of dissolved sulfur present as SO4. Dissolved H2O (by FTIR) ranges from 2.7 to 4.1 weight %, and CO2 concentrations are currently being determined. Dissolved Cl in melt inclusions ranges from 600 to 1100 ppm. Possible correlations of ?34S values with dissolved volatiles (by SIMS, and FTIR), and trace element concentrations are being evaluated.

  16. Computational mass spectrometry for small molecules

    PubMed Central

    2013-01-01

    The identification of small molecules from mass spectrometry (MS) data remains a major challenge in the interpretation of MS data. This review covers the computational aspects of identifying small molecules, from the identification of a compound searching a reference spectral library, to the structural elucidation of unknowns. In detail, we describe the basic principles and pitfalls of searching mass spectral reference libraries. Determining the molecular formula of the compound can serve as a basis for subsequent structural elucidation; consequently, we cover different methods for molecular formula identification, focussing on isotope pattern analysis. We then discuss automated methods to deal with mass spectra of compounds that are not present in spectral libraries, and provide an insight into de novo analysis of fragmentation spectra using fragmentation trees. In addition, this review shortly covers the reconstruction of metabolic networks using MS data. Finally, we list available software for different steps of the analysis pipeline. PMID:23453222

  17. Computational mass spectrometry for small molecules.

    PubMed

    Scheubert, Kerstin; Hufsky, Franziska; Böcker, Sebastian

    2013-01-01

    : The identification of small molecules from mass spectrometry (MS) data remains a major challenge in the interpretation of MS data. This review covers the computational aspects of identifying small molecules, from the identification of a compound searching a reference spectral library, to the structural elucidation of unknowns. In detail, we describe the basic principles and pitfalls of searching mass spectral reference libraries. Determining the molecular formula of the compound can serve as a basis for subsequent structural elucidation; consequently, we cover different methods for molecular formula identification, focussing on isotope pattern analysis. We then discuss automated methods to deal with mass spectra of compounds that are not present in spectral libraries, and provide an insight into de novo analysis of fragmentation spectra using fragmentation trees. In addition, this review shortly covers the reconstruction of metabolic networks using MS data. Finally, we list available software for different steps of the analysis pipeline. PMID:23453222

  18. Mass Spectrometry and Computational Proteomics Vineet Bafna

    E-print Network

    Bafna, Vineet

    Mass Spectrometry and Computational Proteomics Vineet Bafna Computer Science & Engineering, Univ Abstract Mass Spectrometry is the tool of choice for Proteomics, with applications to peptide sequencing of algorithms for interpreting mass spectrometry (MS) data is provided. This overview is not intended

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

    Microsoft Academic Search

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

    1994-01-01

    An automated environmental air monitor has been developed to measure selected organic compounds in urban air. The instrument\\u000a is based on a cryofocusing-thermal desorption gas chromatographic mass spectrometry technique where the mass spectrometer\\u000a is a slightly modified residual gas analyzer (RGA). The RGA was chosen as a detector because the whole system must be robust\\u000a for long periods, with 24-h

  20. Mass-independent isotope effects.

    PubMed

    Buchachenko, Anatoly L

    2013-02-28

    Three fundamental properties of atomic nuclei-mass, spin (and related magnetic moment), and volume-are the source of isotope effects. The mostly deserved and popular, with almost hundred-year history, is the mass-dependent isotope effect. The first mass-independent isotope effect which chemically discriminates isotopes by their nuclear spins and nuclear magnetic moments rather than by their masses was detected in 1976. It was named as the magnetic isotope effect because it is controlled by magnetic interaction, i.e., electron-nuclear hyperfine coupling in the paramagnetic species, the reaction intermediates. The effect follows from the universal physical property of chemical reactions to conserve angular momentum (spin) of electrons and nuclei. It is now detected for oxygen, silicon, sulfur, germanium, tin, mercury, magnesium, calcium, zinc, and uranium in a great variety of chemical and biochemical reactions including those of medical and ecological importance. Another mass-independent isotope effect was detected in 1983 as a deviation of isotopic distribution in reaction products from that which would be expected from the mass-dependent isotope effect. On the physical basis, it is in fact a mass-dependent effect, but it surprisingly results in isotope fractionation which is incompatible with that predicted by traditional mass-dependent effects. It is supposed to be a function of dynamic parameters of reaction and energy relaxation in excited states of products. The third, nuclear volume mass-independent isotope effect is detected in the high-resolution atomic and molecular spectra and in the extraction processes, but there are no unambiguous indications of its importance as an isotope fractionation factor in chemical reactions. PMID:23301791

  1. Mass spectrometry-based proteomics

    Microsoft Academic Search

    Ruedi Aebersold; Matthias Mann

    2003-01-01

    Recent successes illustrate the role of mass spectrometry-based proteomics as an indispensable tool for molecular and cellular biology and for the emerging field of systems biology. These include the study of protein-protein interactions via affinity-based isolations on a small and proteome-wide scale, the mapping of numerous organelles, the concurrent description of the malaria parasite genome and proteome, and the generation

  2. Visualizing life with ambient mass spectrometry.

    PubMed

    Hsu, Cheng-Chih; Dorrestein, Pieter C

    2015-02-01

    Since the development of desorption electrospray ionization (DESI), many other ionization methods for ambient and atmospheric pressure mass spectrometry have been developed. Ambient ionization mass spectrometry has now been used for a wide variety of biological applications, including plant science, microbiology, neuroscience, and cancer pathology. Multimodal integration of atmospheric ionization sources with the other biotechnologies, as well as high performance computational methods for mass spectrometry data processing is one of the major emerging area's for ambient mass spectrometry. In this opinion article, we will highlight some of the most influential technological advances of ambient mass spectrometry in recent years and their applications to the life sciences. PMID:25146170

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

    Microsoft Academic Search

    Fluor Daniel Hanford

    1997-01-01

    Suitable analytical methods must be tested and developed for monitoring the individual process steps within the fuel cycle of a fusion reactor and for tritium accountability. The utility of laser-Raman spectroscopy accompanied by mass spectrometry with an Omegatron was investigated using the analysis of all hydrogen isotopes and isotopically labeled methanes as an example. The Omegatron is useful for analyzing

  4. Standard test method for analysis of total and isotopic uranium and total thorium in soils by inductively coupled plasma-mass spectrometry

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This test method covers the measurement of total uranium (U) and thorium (Th) concentrations in soils, as well as the determination of the isotopic weight percentages of 234U, 235U, 236U, and 238U, thereby allowing for the calculation of individual isotopic uranium activity or total uranium activity. This inductively coupled plasma-mass spectroscopy (ICP-MS) method is intended as an alternative analysis to methods such as alpha spectroscopy or thermal ionization mass spectroscopy (TIMS). Also, while this test method covers only those isotopes listed above, the instrumental technique may be expanded to cover other long-lived radioisotopes since the preparation technique includes the preconcentration of the actinide series of elements. The resultant sample volume can be further reduced for introduction into the ICP-MS via an electrothermal vaporization (ETV) unit or other sample introduction device, even though the standard peristaltic pump introduction is applied for this test method. The sample preparatio...

  5. Isotopic Analysis of OS and RE with Negative Thermal Ion Mass Spectrometry and Application to the Age and Evolution of Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Creaser, R. A.; Papanastassiou, D. A.; Wasserburg, G. J.

    1992-07-01

    The ^187Re-^187Os isotope system has long been recognized as a method by which the age of iron meteorites can be directly determined (Herr et al., 1961). Pioneering work by Luck and Allegre (1983) established a whole-rock isochron for iron meteorites and the results, were used to determine indirectly the half-life of ^187Re. We have developed: a) high ionization efficiency mass spectrometry techniques for platinum group elements, including both Re and Os separated from iron meteorites (Creaser et al., 1991, 1992); b) low filament loading blanks for both Re and Os (<0.1 picogram, each); c) high yield and low blanks for the chemical separation techniques (yields 70-80%; blanks 1 pg for Os, <10 pg for Re). We have developed a new method for the rapid, clean and efficient separation of Os and Re from 10^-2 g samples of iron meteorites. This will permit taking advantage of variations of Re/Os on a small scale. The chemical separation scheme involves acid dissolution, preconcentration of Os and Re from Fe-Ni, oxidative solvent extraction of Os and ion exchange chromatography to recover Re. We have established that Os and Re thus chemically separated from iron meteorites show the same ionization efficiency as Os and Re from standard solutions, namely ~20% for each element. Of primary importance is the degree of isotope exchange and equilibration between sample and spike for Os. By analyzing the isotopic composition of Os at different stages of the chemical separation we are able to demonstrate that isotopic equilibration can be achieved to the level of +-1o/oo. However, this is not yet a routinely resolved issue. We believe, based on experience during the development of this technique, that isotope equilibration for Os prior to chemical separation is a critical issue that needs further attention. The results we have obtained so far from iron meteorites are given in Table 1. We have started analyses of the large magmatic group of IIA irons, which are little shocked and little metamorphosed, in order to attempt to establish a high precision isochron for these objects. For two samples, where we have high precision data for both Os and Re, the slope indicated is 0.077, which yields an age of 4530 Ma using the best estimate of the ^187Re half-life by direct measurement (Lindner et al., 1989). These results are in close agreement with the revised data of Horan et al. (1992) but markedly different from published iron meteorite data using the lower precision techniques where slopes of 0.070-0.074 indicate apparent ages of 4150-4350 Ma. We believe that previously reported data, including the data on the half-life of ^187Re, require confirmation using the current high-precision and high- sensitivity techniques, before the reliability and utility of the Re-Os technique can be ascertained. Acknowledgement. This work was supported by NASA, Grant NAG 943. Contribution No. 779. References Creaser, R. A., Papanastassiou, D. A., and Wasserburg, G. J. (1991a) Geochim. Cosmochim. Acta 55, 397-401. Creaser, R. A., Papanastassiou, D. A., and Wasserburg, G. J. (1992) Lunar Planet. Sci. XXIII (abstract), 255-256. Herr, W., Hoffmeister, W., Hirt, B., Geiss, J., and Houtermans, F. G. (1961) Z. Naturforsch. 16a, 1053-1058. Horan, M. F., Morgan, J. W., Walker, R. J., and Grossman, J. N. (1992) Science 255, 1118-1121. Lindner, M., Leich, D. A., Russ, G. P., Bazan, J. M., and Borg, R. J. (1989) Geochim. Cosmochim. Acta 53, 1597-1606. Luck, J. M. and Allegre, C. J. (1983) Nature 302, 130-132. Table 1. Re-Os isotopic data from iron meteorites. Os ppm Re ppb 187Os/188Os 187Re/188Os Bennett County IIA 59.6+-0.1 0.12503+-5 Coahuila IIA 9.87+-0.02 0.14158+-7 Tocopilla IIA 1.062+-0.002 207.9 0.16913+-15 0.9451 Negrillos IIA 69.4+-0.1 5022.7 0.12315+-2 0.3497 Cape York IIIA 0.13374+-9 Canyon Diablo IA 0.13464+-11 Tlacotepc IVB 0.12068+-8 Osmium standard (NHr)2OsCl6 0.14911+-3

  6. Mass spectrometry. [review of techniques

    NASA Technical Reports Server (NTRS)

    Burlingame, A. L.; Kimble, B. J.; Derrick, P. J.

    1976-01-01

    Advances in mass spectrometry (MS) and its applications over the past decade are reviewed in depth, with annotated literature references. New instrumentation and techniques surveyed include: modulated-beam MS, chromatographic MS on-line computer techniques, digital computer-compatible quadrupole MS, selected ion monitoring (mass fragmentography), and computer-aided management of MS data and interpretation. Areas of application surveyed include: organic MS and electron impact MS, field ionization kinetics, appearance potentials, translational energy release, studies of metastable species, photoionization, calculations of molecular orbitals, chemical kinetics, field desorption MS, high pressure MS, ion cyclotron resonance, biochemistry, medical/clinical chemistry, pharmacology, and environmental chemistry and pollution studies.

  7. Developments in ion mobility spectrometry-mass spectrometry

    Microsoft Academic Search

    D. Collins; M. Lee

    2002-01-01

    Ion mobility spectrometry (IMS) has been used for over 30 years as a sensitive detector of organic compounds. The following is a brief review of IMS and its principles with an emphasis on its usage when coupled to mass spectrometry. Since its inception, IMS has been interfaced with quadrupole, time-of-flight, and Fourier-transform ion cyclotron resonance mass spectrometry. These hybrid instruments

  8. Diagnosing Prion Diseases: Mass Spectrometry-Based Approaches

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mass spectrometry is an established means of quantitating the prions present in infected hamsters. Calibration curves relating the area ratios of the selected analyte peptides and their oxidized analogs to stable isotope labeled internal standards were prepared. The limit of detection (LOD) and limi...

  9. An optimized method for the accurate determination of patulin in apple products by isotope dilution-liquid chromatography/mass spectrometry.

    PubMed

    Seo, Miyeong; Kim, Byungjoo; Baek, Song-Yee

    2015-07-01

    Patulin, a mycotoxin produced by several molds in fruits, has been frequently detected in apple products. Therefore, regulatory bodies have established recommended maximum permitted patulin concentrations for each type of apple product. Although several analytical methods have been adopted to determine patulin in food, quality control of patulin analysis is not easy, as reliable certified reference materials (CRMs) are not available. In this study, as a part of a project for developing CRMs for patulin analysis, we developed isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC/MS/MS) as a higher-order reference method for the accurate value-assignment of CRMs. (13)C7-patulin was used as internal standard. Samples were extracted with ethyl acetate to improve recovery. For further sample cleanup with solid-phase extraction (SPE), the HLB SPE cartridge was chosen after comparing with several other types of SPE cartridges. High-performance liquid chromatography was performed on a multimode column for proper retention and separation of highly polar and water-soluble patulin from sample interferences. Sample extracts were analyzed by LC/MS/MS with electrospray ionization in negative ion mode with selected reaction monitoring of patulin and (13)C7-patulin at m/z 153?m/z 109 and m/z 160?m/z 115, respectively. The validity of the method was tested by measuring gravimetrically fortified samples of various apple products. In addition, the repeatability and the reproducibility of the method were tested to evaluate the performance of the method. The method was shown to provide accurate measurements in the 3-40 ?g/kg range with a relative expanded uncertainty of around 1 %. Graphical Abstract SRM chromatograms of patulin in blank apple concentrate and fortified apple concentrate (10 ?g/kg patulin), presenting the retention and separation of patulin from matrix interferences with a multi-mode column (Scherzo SM-C18, 250 mm length, 4.6 mm i.d., 3 ?m particle size, from Imtakt) under various LC mobile phase compositions. PMID:25925860

  10. Comparison of extraction methods for quantitation of methionine and selenomethionine in yeast by species specific isotope dilution gas chromatography-mass spectrometry.

    PubMed

    Yang, Lu; Sturgeon, Ralph E; McSheehy, Shona; Mester, Zoltán

    2004-11-01

    Fourteen extraction methods commonly cited in the literature were evaluated for the quantitation of methionine (Met) and selenomethionine (SeMet) in a yeast candidate certified reference material (CRM). Species specific isotope dilution (ID) gas chromatography-mass spectrometry (GC-MS) was utilized to effectively compensate for potential errors, such as losses during derivatization and clean up steps. Despite different extraction methods, the same derivatization procedure using methyl chloroformate was applied with a single exception, which was based on digestion with cyanogen bromide with 2% SnCl2 in 0.1 M HCl. Significant differences in measured Met and SeMet concentrations were obtained when different extraction methods were used. A 4 M methanesulfonic acid reflux digestion was found to be the most efficient for both analytes. Digestion with CNBr with 2% SnCl2 in 0.1 M HCl for the determination of SeMet showed the second highest extraction efficiency. Despite frequent use of enzymatic hydrolysis for the extraction of SeMet from yeast, very low extraction efficiencies for both analytes were obtained for four of eight tested methods. Among these, the highest extraction efficiencies for both analytes were obtained using 20mg pronase and 10mg lipase with incubation at 37 degrees C for 24 h. However, recoveries remained nearly 30 and 50% lower for Met and SeMet, respectively, compared to extraction with methanesulfonic acid. Lowest extraction efficiencies for both analytes were obtained when HCl or tetramethylammonium hydroxide (TMAH) digestions were used. Efficient extraction was also achieved using 200 mg (or 400 mg) of protease XIV with incubation at 37 degrees C for 72 h (or 24 h). Concentrations of 3331+/-45 and 3334+/-39 microg g(-1) (mean and one standard deviation, n = 4) for SeMet were obtained using 200 mg (72 h incubation) and 400 mg (24 h incubation) of protease XIV, respectively, in agreement with a value of 3404+/-38 microg g(-1) obtained using a methanesulfonic acid reflux. PMID:15560494

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

    PubMed Central

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

    2013-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants and are carcinogenic in multiple organs and species. Benzo[a]pyrene (B[a]P) is a representative PAH and has been studied extensively for its carcinogenicity and toxicity. B[a]P itself is chemically inert and requires metabolic activation to exhibit its toxicity and carcinogenicity. Three major metabolic pathways have been well documented. The signature metabolites generated from the radical cation (peroxidase or monooxygenase mediated) pathway are B[a]P-1,6-dione and B[a]P-3,6-dione, the signature metabolite generated from the diol-epoxide (P450 mediated) pathway is B[a]P-r-7,t-8,t-9,c-10-tetrahydrotetrol (B[a]P-tetrol-1) and the signature metabolite generated from the o-quinone (aldo-keto reductase mediated) pathway is B[a]P-7,8-dione. The contributions of these different metabolic pathways to cancer initiation and the exploitation of this information for cancer prevention are still under debate. With the availability of a library of [13C4]-labeled B[a]P metabolite internal standards, we developed a sensitive stable isotope dilution atmospheric pressure chemical ionization tandem mass spectrometry method to address this issue by quantitating B[a]P metabolites from each metabolic pathway in human lung cells. This analytical method represents a 500 fold increased sensitivity compared with a method using HPLC-radiometric detection. The limit of quantitation (LOQ) was determined to be 6 fmol on column for 3-hydroxybenzo[a]pyrene (3-OH-B[a]P), the generally accepted biomarker for B[a]P exposure. This high level of sensitivity and robustness of the method was demonstrated in a study of B[a]P metabolic profiles in human bronchoalveolar H358 cells induced or uninduced with the AhR ligand, 2,3,7,8-tetrachlorodibenzodioxin (TCDD). All the signature metabolites were detected and successfully quantitated. Our results suggest that all three metabolic pathways contribute equally in the overall metabolism of B[a]P in H358 cells with or without TCDD induction. The sensitivity of the method should permit the identification of cell-type differences in B[a]P activation and detoxication and could also be used for biomonitoring human exposure to PAH. PMID:21962213

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

    PubMed

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

    2013-07-01

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

  13. Comparison of high-temperature conversion and equilibration methods for the determination of d31-palmitic acid oxidation in man using continuous-flow isotope ratio mass spectrometry.

    PubMed

    Sauvinet, Valérie; Gabert, Laure; Alligier, Maud; Normand, Sylvie; Roth, Hubert; Laville, Martine; Désage, Michel

    2011-10-15

    During nutritional interventions, the ingestion of d(31)-palmitic acid and H(2)(18)O allows the assessment of dietary fatty acid oxidation from cumulative (2)H recovery in urine and the estimation of the total body water pool (TBW) from (18)O dilution. Continuous-flow isotope ratio mass spectrometry (CF-IRMS) coupled to either equilibration or high-temperature conversion (HTC) techniques permits (2)H- and (18)O-enrichment measurements in biological fluids. Thus it was of great interest to compare these methods applied to the determination of dietary fatty acid oxidation. The linearity, accuracy and correlation between CF-equilibration and CF-HTC were first checked using (2)H- and (18)O-enriched water and urine samples. Urine samples from 14 subjects were then measured with both methods. The (2)H and (18)O raw data were normalised against calibration lines. The final aim was to study the impact of the normalised raw results on physiological data (i.e. TBW and d(31)-palmitate recovery). No significant difference was observed between the (18)O- and (2)H-enrichment measurements depending on the analytical method used. The TBW volumes calculated from the (18)O enrichments measured either with CF-equilibration or CF-HTC were not significantly different: respectively, 45.1 ± 1.0 L or 45.7 ± 1.0 L (mean ± sem, p = 0.09). The palmitic acid oxidation results obtained from the (2)H-enrichment measurements and the TBW from CF-equilibration vs. CF-HTC were not significantly different (p ? 0.26): with ?(2)H values of, respectively, 16.2 ± 1.6% vs. 16.2 ± 1.1% at 8 h, 18.7 ± 2.0% vs. 17.6 ± 1.3% at 12 h and 21.7 ± 1.9% vs. 21.5 ± 1.3% at 3 days post-dose (mean ± sem). Thus, even if CF-HTC was preferred because it was more practical to carry out, both methods allow the study of dietary lipid oxidation in man and generate similar results. PMID:21913252

  14. On-line monitoring of benzene air concentrations while driving in traffic by means of isotopic dilution gas chromatography/mass spectrometry.

    PubMed

    Davoli, E; Cappellini, L; Moggi, M; Ferrari, S; Fanelli, R

    1996-01-01

    There is no shortage of information about the average benzene concentrations in urban air, but there is very little about microenvironmental exposure, such as in-vehicle concentrations while driving in various traffic conditions, while refuelling, or while in a parking garage. The main reason for this lack of data is that no analytical instrumentation has been available to measure on-line trace amounts of benzene in such situations. We have recently proposed a highly accurate, high-speed cryofocusing gas chromatography/mass spectrometry (GC/MS) system for monitoring benzene concentrations in air. Accuracy of the analytical data is achieved by enrichment of the air sample before trapping, with a stable isotope permeation tube system. The same principles have been applied to a new instrument, specifically designed for operation on an electric vehicle (Ducato Elettra, Fiat). The zero emission vehicle and the fully transportable, battery-operated GC/MS system provide a unique possibility of monitoring benzene exposure in real everyday situations such as while driving, refuelling, or repairing a car. All power consumptions have been reduced so as to achieve a battery-operated GC/MS system. Liquid nitrogen cryofocusing has been replaced by a packed, inductively heated, graphitized charcoal microtrap. The instrument has been mounted on shock absorbers and installed in the van. The whole system has been tested in both fixed and mobile conditions. The maximum monitoring period without external power supply is 6 h. The full analytical cycle is 4 min, allowing close to real-time monitoring, and the minimum detectable level is 1 microgram/m3 for benzene. In-vehicle monitoring showed that, when recirculation was off and ventilation on, i.e., air from outside the vehicle was blown inside, concentrations varied widely in different driving conditions: moving from a parking lot into normal traffic on an urban traffic condition roadway yielded an increase in benzene concentration from 17 to 62.3 micrograms/m3 even if the actual distance was small. A larger increase was observed when a car was left with the engine running at a distance 2 m from the zero emission vehicle: We measured an increment of benzene concentrations from 15.2 to 174.4 micrograms/m3 with a car equipped with a catalytic converter, and from 19.1 to 386.3 micrograms/m3 with a car without such a converter. PMID:8738357

  15. Mass independent bias in W isotopes in MC-ICP-MS instruments Naoki Shiraiab

    E-print Network

    Weston, Ken

    Mass independent bias in W isotopes in MC-ICP-MS instruments Naoki Shiraiab and Munir Humayun of natural mass independent isotope variations by precise isotopic measurements of elements by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) requires a detailed understanding of the instrumental

  16. Backbone cleavages and sequential loss of carbon monoxide and ammonia from protonated AGG: A combined tandem mass spectrometry, isotope labeling, and theoretical study

    Microsoft Academic Search

    Benjamin J. Bythell; Douglas F. Barofsky; Francesco Pingitore; Michael J. Polce; Ping Wang; Chrys Wesdemiotis; Béla Paizs

    2007-01-01

    The fragmentation characteristics of protonated alanylglycylglycine, [AGG+H]+, were investigated by tandem mass spectrometry in MALDI-TOF\\/TOF, ion trap, and hybrid sector instruments. b2 is the most abundant fragment ion in MALDI-TOF\\/TOF, ion trap, and hybrid sector metastable ion (MI) experiments, while y2 is slightly more abundant than b2 in collision activated dissociation (CAD) performed in the sector instrument. The A-G amide

  17. Electrophoresis-mass spectrometry probe

    DOEpatents

    Andresen, B.D.; Fought, E.R.

    1987-11-10

    The invention involves a new technique for the separation of complex mixtures of chemicals, which utilizes a unique interface probe for conventional mass spectrometers which allows the electrophoretically separated compounds to be analyzed in real-time by a mass spectrometer. This new chemical analysis interface, which couples electrophoresis with mass spectrometry, allows complex mixtures to be analyzed very rapidly, with much greater specificity, and with greater sensitivity. The interface or probe provides a means whereby large and/or polar molecules in complex mixtures to be completely characterized. The preferred embodiment of the probe utilizes a double capillary tip which allows the probe tip to be continually wetted by the buffer, which provides for increased heat dissipation, and results in a continually operating interface which is more durable and electronically stable than the illustrated single capillary tip probe interface. 8 figs.

  18. Electrophoresis-mass spectrometry probe

    DOEpatents

    Andresen, Brian D. (Pleasanton, CA); Fought, Eric R. (Livermore, CA)

    1987-01-01

    The invention involves a new technique for the separation of complex mixtures of chemicals, which utilizes a unique interface probe for conventional mass spectrometers which allows the electrophoretically separated compounds to be analyzed in real-time by a mass spectrometer. This new chemical analysis interface, which couples electrophoresis with mass spectrometry, allows complex mixtures to be analyzed very rapidly, with much greater specificity, and with greater sensitivity. The interface or probe provides a means whereby large and/or polar molecules in complex mixtures to be completely characterized. The preferred embodiment of the probe utilizes a double capillary tip which allows the probe tip to be continually wetted by the buffer, which provides for increased heat dissipation, and results in a continually operating interface which is more durable and electronically stable than the illustrated single capillary tip probe interface.

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

    NASA Astrophysics Data System (ADS)

    Costas-Rodríguez, M.; Lavilla, Isela; Bendicho, Carlos

    2011-06-01

    In this work, ultrasound-assisted extraction (UAE) was evaluated as a sample preparation procedure for lead isotope ratio measurements in marine biological tissues by multicollector inductively coupled plasma-mass spectrometry. 20 mg of marine biological tissue and 1 mL of acid extractant were sonicated for 3 min at 60% ultrasound amplitude. Matrix separation was performed in the supernatant using a chromatographic exchange resin (Sr-Spec™). Total elimination of organic matter was achieved during the separation step. Microwave-assisted digestion and dry-ashing were used for comparative purposes. No significant differences were found in lead isotope ratios at 95% of confidence level. UAE emerges as an advantageous alternative to classical methods for sample preparation owing to its simplicity and rapidity ( i.e. operation steps were reduced), low reagent consumption and low contamination risks.

  20. Qupe -a Rich Internet Application to take a Step Forward in the Analysis of Mass Spectrometry-Based Quantitative

    E-print Network

    Will, Sebastian

    Qupe - a Rich Internet Application to take a Step Forward in the Analysis of Mass Spectrometry of Technology, Bielefeld University 5 Biomolecular Mass Spectrometry, Department of Analytical Chemistry, Ruhr in this field of study is proteomics where tandem mass spectrometry (LC-MS/MS) in combination with isotopic

  1. Mass spectrometry of fluoroalkyl substituted fullerenes

    SciTech Connect

    McEwen, C.N.; Krusic, P.J.; Fagan, P.J. [E.I. du Pont de Nemours & Co., Wilmington, DE (United States)

    1994-12-31

    Mass spectrometry has played a significant role in the discovery of fullerenes and in the analysis of their chemical derivatives. Because these electron deficient spherical polyene structures readily attach electrons to produce stable anions, negative ionization methods are frequently used in the analysis of these materials by mass spectrometry. Addition of electron withdrawing substituents to buckminsterfullerene should increase the cross-section for electron attachment and make these compounds even more susceptible to analysis by negative ion mass spectrometry.

  2. Analysis of household ignitable liquids and their post-combustion weathered residues using compound-specific gas chromatography-combustion-isotope ratio mass spectrometry.

    PubMed

    Schwartz, Zeland; An, Yan; Konstantynova, Kateryna I; Jackson, Glen P

    2013-12-10

    The continuing rise in home and vehicular arson cases involving the use of ignitable liquids continues to be an area of concern for criminal and civil investigators. In this study, the compound-specific ?(13)C values of various components of four flammable household chemicals were measured using a single quadrupole mass spectrometer and an isotope ratio mass spectrometer as simultaneous detectors for a gas chromatograph. Whereas compound-specific carbon isotope ratios were able to discriminate between different sources of neat (pre-combustion) ignitable liquids, analyses of the post-combustion residues were problematic. Weathering caused by combustion resulted in a significant increase in the (13)C content of specific peaks relative to the neat liquids (i.e. less negative delta values) such that the isotopic comparison of pre- and post-combustion residues resulted in fractionation ranging from 0 to +10‰. Because of the current lack of understanding of isotopic fractionation during combustion, and because of problems encountered with co-elution in the more complex samples, compound-specific IRMS does not appear to be suitable for fire debris analysis. The comparison of non-combusted or non-weathered ignitable liquids is much more reliable, especially for relatively simple mixtures, and is best suited for exclusionary purposes until such time as a comprehensive database of samples is developed. Without a measure of the population variance, one cannot presently predict the false positive identification rate for the comparison of two ignitable liquids; i.e. the probability that two random ignitable liquid samples have indistinguishable isotope ratios. PMID:24314542

  3. ACCOUNT AND PERSPECTIVE Macromolecule Mass Spectrometry

    E-print Network

    Karypis, George

    ACCOUNT AND PERSPECTIVE Macromolecule Mass Spectrometry: Citation Mining of User Documents Ronald N the identification and structural analysis of biological macromolecules. In particular, Fenn and Tanaka focused

  4. Measurement of selected polybrominated diphenyl ethers, polybrominated and polychlorinated biphenyls, and organochlorine pesticides in human serum and milk using comprehensive two-dimensional gas chromatography isotope dilution time-of-flight mass spectrometry.

    PubMed

    Focant, Jean-François; Sjödin, Andreas; Turner, Wayman E; Patterson, Donald G

    2004-11-01

    A new method using comprehensive two-dimensional gas chromatography and isotope dilution time-of-flight mass spectrometry (GCxGC-IDTOFMS) for the simultaneous measurement of selected polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and brominated flame retardants is presented. In contrast to the reference methods based on classical GC/MS, a single injection of the extract containing all compounds of interest results in accurate identification and quantification. Using GCxGC ensures the chromatographic separation of most compounds, and TOFMS allows mass spectral deconvolution of coeluting compounds as well as the use of (13)C-labeled internal standards for quantification. Isotope ratio measurements of the most intense ions for both native and labels ensure the required specificity. The use of this new method with an automated sample preparation procedure developed at the Centers for Disease Control and Prevention (CDC) for the analysis of human serum and milk compared favorably to conventional isotope-dilution one-dimensional gas chromatography-high-resolution mass spectrometry (GC-IDHRMS) for the different human serum and milk pools tested. The instrumental detection limits ranged between 0.5 pg/microL and 10 pg/microL and the method detection limits ranged between 1 and 15 pg/microL (N = 59 analytes). The reproducibility of the method was almost as good as with GC-IDHRMS, the relative standard deviations ranging between 1 and 11% for OCPs measured in human serum. OCP, PBDE, and PCB levels measured using the two methods were highly correlated, and the deviations between the two methods were below 20% for most analytes with concentrations above 1 ng/g milk lipids. PMID:15516123

  5. Development of a novel method for unraveling the origin of natron flux used in Roman glass production based on B isotopic analysis via multicollector inductively coupled plasma mass spectrometry.

    PubMed

    Devulder, Veerle; Degryse, Patrick; Vanhaecke, Frank

    2013-12-17

    The provenance of the flux raw material used in the manufacturing of Roman glass is an understudied topic in archaeology. Whether one or multiple sources of natron mineral salts were exploited during this period is still open for debate, largely because of the lack of a good provenance indicator. The flux is the major source of B in Roman glass. Therefore, B isotopic analysis of a sufficiently large collection and variety (origin and age) of such glass samples might give an indication of the number of flux sources used. For this purpose, a method based on acid digestion, chromatographic B isolation and B isotopic analysis using multicollector inductively coupled plasma mass spectrometry was developed. B isolation was accomplished using a combination of strong cation exchange and strong anion exchange chromatography. Although the B fraction was not completely matrix-free, the remaining Sb was shown not to affect the ?(11)B result. The method was validated using obsidian and archaeological glass samples that were stripped of their B content, after which an isotopic reference material with known B isotopic composition was added. Absence of artificial B isotope fractionation was demonstrated, and the total uncertainty was shown to be <2‰. A proof-of-concept application to natron glass samples showed a narrow range of ?(11)B, whereas first results for natron salt samples do show a larger difference in ?(11)B. These results suggest the use of only one natron source or of several sources with similar ?(11)B. This indicates that B isotopic analysis is a promising tool for the provenance determination of this flux raw material. PMID:24279483

  6. Treatise on the Measurement of Molecular Masses with Ion Mobility Spectrometry

    E-print Network

    Clemmer, David E.

    Treatise on the Measurement of Molecular Masses with Ion Mobility Spectrometry Stephen J. Valentine 47405 The ability to separate isotopes by high-resolution ion mobility spectrometry techniques) by utilizing heavy collision gases and high-resolution ion mobility analyzers. The mass accuracy associated

  7. Compact hydrogen/helium isotope mass spectrometer

    DOEpatents

    Funsten, Herbert O. (Los Alamos, NM); McComas, David J. (Los Alamos, NM); Scime, Earl E. (Morgantown, WV)

    1996-01-01

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

  8. S1 certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate certified reference material (organochlorine pesticides in tea) by isotope dilution gas chromatography-mass spectrometry.

    PubMed

    Sin, Della Wai-Mei; Wong, Yee-Lok; Cheng, Eddie Chung-Chin; Lo, Man-Fung; Ho, Clare; Mok, Chuen-Shing; Wong, Siu-Kay

    2015-04-01

    This paper presents the certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate tea certified reference material (code: GLHK-11-03) according to the requirements of the ISO Guide 30 series. Certification of GLHK-11-03 was based on an analytical method purposely developed for the accurate measurement of the mass fraction of the target analytes in the material. An isotope dilution mass spectrometry (IDMS) method involving determination by (i) gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) and (ii) gas chromatography-electron ionization-high-resolution mass spectrometry (GC-EI-HRMS) techniques was employed. The performance of the described method was demonstrated through participation in the key comparison CCQM-K95 "Mid-Polarity Analytes in Food Matrix: Mid-Polarity Pesticides in Tea" organized by the Consultative Committee for Amount of Substance-Metrology in Chemistry in 2012, where the study material was the same as the certified reference material (CRM). The values reported by using the developed method were in good agreement with the key comparison reference value (KCRV) assigned for beta-endosulfan (727?±?14 ?g kg(-1)) and endosulfan sulfate (505?±?11 ?g kg(-1)), where the degree of equivalence (DoE) values were 0.41 and 0.40, respectively. The certified values of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in dry mass fraction in GLHK-11-03 were 350, 730, and 502 ?g kg(-1), respectively, and the respective expanded uncertainties, due to sample inhomogeneity, long-term and short-term stability, and variability in the characterization procedure, were 27 ?g kg(-1) (7.8 %), 48 ?g kg(-1) (6.6 %), and 33 ?g kg(-1) (6.6 %). PMID:25619984

  9. Statistical characterization of multiple-reaction monitoring mass spectrometry (MRM-MS) assays for quantitative proteomics

    E-print Network

    Mani, D R

    Multiple reaction monitoring mass spectrometry (MRM-MS) with stable isotope dilution (SID) is increasingly becoming a widely accepted assay for the quantification of proteins and peptides. These assays have shown great ...

  10. Stopped-Flow Kinetic Analysis Using Hadamard Transform Time-of-Flight Mass Spectrometry

    E-print Network

    Zare, Richard N.

    of the 30S ribosomal subunit with pulse-chase analysis coupled to MALDI mass spectrometry where the pulse was composed of 15 N-containing proteins that were extracted from bacteria cultured in isotopically enriched

  11. Four decades of joy in mass spectrometry.

    PubMed

    Nibbering, Nico M M

    2006-01-01

    Tremendous developments in mass spectrometry have taken place in the last 40 years. This holds for both the science and the instrumental revolutions in this field. In chemistry the research was heavily focused on organic molecules that upon electron ionization fragmented via complex mechanistic pathways as shown by isotopic labeling experiments. These studies, including ion structure determinations, were performed with use of double focusing mass spectrometers of both conventional and reversed geometry, and equipped with various types of metastable ion scanning and collision-induced dissociation techniques developed by physical and analytical chemists. Time-resolved mass spectrometry by use of the field ionization kinetics method, developed by physical chemists, was another powerful way to unravel details of unimolecular gas phase ion dissociations. Then the development of new ionization methods, such as desorption chemical ionization, field desorption, and fast atom bombardment permitted not only to analyze unvolatile, thermally labile and higher molecular weight compounds, but also to study their chemical behavior in the gas phase, initially with use of double focusing instruments and later on with multisector and hybrid mass spectrometers. These ionization methods also enabled to study organometallic compounds and increasingly the field of medium-sized to large biomolecules, the latter being exploded in the last decade by the development of electrospray- and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry. Another area of research concerned the bimolecular chemistry of organic ions with organic molecules in the gas phase. Initially this was performed with use of among others drift-cell ion cyclotron resonance spectroscopy, that later on was replaced by the developed method of ion trapping and Fourier transform ion cyclotron resonance. Combination of the latter with the afore-mentioned ionization methods has shifted also in this case the research on organic molecules to organometallic/inorganic systems, and predominantly to biomolecules in the last decade. This invited review will describe the research efforts made by the author's group over the last 40 years together with some personal experiences during his career. PMID:16736509

  12. Atmospheric Pressure Mass Spectrometry: A New Analytical

    E-print Network

    Seitzinger, Sybil

    Atmospheric Pressure Mass Spectrometry: A New Analytical Chemical Characterization Method climate, air quality, and ecosystem processes. Atmospheric pressure electrospray ionization mass, Piscataway, New Jersey 08854-8058 The complex mixture of organic compounds in the atmosphere influences

  13. Pushing the Limits of Accelerator Mass Spectrometry

    SciTech Connect

    Galindo-Uribarri, Alfredo {nmn} [ORNL; Beene, James R [ORNL; Danchev, M. [University of Tennessee, Knoxville (UTK); Doupe, J. [University of Toronto; Fuentes Madariaga, Beatriz E [ORNL; Gomez Del Campo, Jorge [ORNL; Hausladen, Paul [ORNL; Juras, Raymond C [ORNL; Liang, J Felix [ORNL; Litherland, Albert E [ORNL; Liu, Yuan [ORNL; Meigs, Martha J [ORNL; Mills, Gerald D [ORNL; Mueller, Paul Edward [ORNL; Padilla-Rodal, Elizabeth [ORNL; Pavan, John R [ORNL; Sinclair IV, John W [ORNL; Stracener, Daniel W [ORNL

    2007-01-01

    A renewed interest in Accelerator Mass Spectrometry (AMS) from nuclear physics laboratories is emerging in connection with Radioactive Ion Beams (RIBs). At the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL) we are exploring the AMS capabilities of the 25-MV Tandem acclerator. Behind this effort is the realization that two fields of research - AMS and RIBs - complement each other in techniques. Development of effective and efficient beam purification techniques is of common interest to both AMS and the RIB program. Two main characteristics of the 25-MV Tandem provide unique opportunities for performing the highest sensitivity measurements of AMS; namely i) the highest operating voltage in the world, and ii) a folded geometry which involves a 180 degree magnet in the terminal. For the RIB program, we have used AMS techniques to improve the sensitivity of detection of some radioactive species in the measurement of unknown massses of n-rich nuclei. For AMS, we have concentrated in exploring two important isotopes, 14C and 36Cl, for applications that require the highest sensitivity. We have successfully measured 36Cl/Cl ratios as low as a few times 10-16 in seawater samples demonstrating that our set has the highest sensitivity for this isotope and proving that 36Cl can be measured at the levels required for a tracer in oceanography.

  14. Evolution and revolution in instrumentation for plasma-source mass spectrometry

    Microsoft Academic Search

    Gary M. Hieftje; James H. Barnes; Ole A. Grøn; Andrew M. Leach; Denise M. McClenathan; Steven J. Ray; David A. Solyom; William C. Wetzel; M. Bonner Denton; David W. Koppenaal

    2001-01-01

    Plasma-source mass spectrometry, usually in the form of inductively coupled plas- ma mass spectrometry (ICP-MS), has matured into a widely accepted method for ultra-trace multielemental analysis. However, the method exhibits shortcomings. For example, it does not provide adequate precision for isotope ratio measurements if many isotopes are to be determined. Moreover, isobaric overlaps (spectral interferences) can be very troublesome in

  15. Mass-Dependent and Mass-Independent Isotope Effects of Zinc in a Redox Reaction

    Microsoft Academic Search

    Toshiyuki Fujii; Fre?de?ric Moynier; Akihiro Uehara; Minori Abe; Qing-Zhu Yin; Takayuki Nagai; Hajimu Yamana

    2009-01-01

    We report the isotope fractionation of zinc (Zn) associated with a redox reaction between Zn0 and Zn(II). Zn isotopes were found fractionated in pyrometallurgical biphase extraction between liquid zinc and molten chloride. The isotopic composition of Zn in the molten chloride phase was analyzed by multiple collector inductively coupled plasma mass spectrometry and reported as mZn\\/64Zn (m = 66, 67,

  16. Standard test method for analysis of isotopic composition of uranium in nuclear-grade fuel material by quadrupole inductively coupled plasma-mass spectrometry

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This test method is applicable to the determination of the isotopic composition of uranium (U) in nuclear-grade fuel material. The following isotopic weight percentages are determined using a quadrupole inductively coupled plasma-mass spectrometer (Q-ICP-MS): 233U, 234U, 235U, 236U, and 238U. The analysis can be performed on various material matrices after acid dissolution and sample dilution into water or dilute nitric (HNO3) acid. These materials include: fuel product, uranium oxide, uranium oxide alloys, uranyl nitrate (UNH) crystals, and solutions. The sample preparation discussed in this test method focuses on fuel product material but may be used for uranium oxide or a uranium oxide alloy. Other preparation techniques may be used and some references are given. Purification of the uranium by anion-exchange extraction is not required for this test method, as it is required by other test methods such as radiochemistry and thermal ionization mass spectroscopy (TIMS). This test method is also described i...

  17. Mass Spectrometry-Based Approaches Toward Absolute Quantitative Proteomics

    PubMed Central

    Kito, Keiji; Ito, Takashi

    2008-01-01

    Mass spectrometry has served as a major tool for the discipline of proteomics to catalogue proteins in an unprecedented scale. With chemical and metabolic techniques for stable isotope labeling developed over the past decade, it is now routinely used as a method for relative quantification to provide valuable information on alteration of protein abundance in a proteome-wide scale. More recently, absolute or stoichiometric quantification of proteome is becoming feasible, in particular, with the development of strategies with isotope-labeled standards composed of concatenated peptides. On the other hand, remarkable progress has been also made in label-free quantification methods based on the number of identified peptides. Here we review these mass spectrometry-based approaches for absolute quantification of proteome and discuss their implications. PMID:19452043

  18. Development of isotope dilution gamma-ray spectrometry for plutonium analysis

    SciTech Connect

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

    1991-01-01

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

  19. Characterization of metabolic profile of honokiol in rat feces using liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry and (13)C stable isotope labeling.

    PubMed

    Dong, Yinfeng; Tang, Minghai; Song, Hang; Li, Rong; Wang, Chunyu; Ye, Haoyu; Qiu, Neng; Zhang, Yongkui; Chen, Lijuan; Wei, Yuquan

    2014-03-15

    As fecal excretion is one of important routes of elimination of drugs and their metabolites, it is indispensable to investigate the metabolites in feces for more comprehensive information on biotransformation in vivo. In this study, a sensitive and reliable approach based on ultra-performance liquid chromatography/quadrupole-time-of-flight-mass spectrometry (UHPLC-Q-TOF-MS) was applied to characterize the metabolic profile of honokiol in rat feces after the administration of an equimolar mixture of honokiol and [(13)C6]-labeled honokiol. Totally 42 metabolites were discovered and tentatively identified in rat feces samples, 26 metabolites were first reported, including two novel classes of metabolites, methylated and dimeric metabolites of honokiol. Moreover, this study provided basic comparative data on the metabolites in rat plasma, feces and urine, which gave better understanding of the metabolic fate of honokiol in vivo. PMID:24566334

  20. Theoretical investigation of isotope absorption spectrometry: computer simulations

    SciTech Connect

    Pathiratne, S.

    1987-01-01

    A computer model that can calculate absorbances for atomic absorption spectrometry involving multi-isotopic elements is presented. The validity of the model calculations is verified by close matching of calculated absorbances with independently measured experimental absorbances aimed to determine isotope abundances of Li. The model is able to reveal behavior of atomic absorption experimental systems which are difficult to observe directly unless the experiments are performed with extreme care. The significance of the dependence of isotope shifts and hyperfine and fine structure separations of spectral lines on the sensitivity of isotope abundance determinations using flame atomic absorption spectrometry are demonstrated. Further, the effects of concentrations of all isotopes and the flame parameters (line broadening parameter and collisional shift of absorption lines) on the ability to discriminate among isotopes for a given experimental system are shown. For four selected elements (Ga, Cu, Pb and Hg), with different hyperfine structures, isotope shifts and number of isotopes, the optimum experimental conditions and the strategies to be used for isotope abundance determinations using flame atomic absorption spectrometry are delineated. For the four selected elements, the experimental conditions (the elemental concentrations and the type of the flame absorption cell) which do not introduce errors into analyses are presented. For the four elements referred to above, the magnitude of analytical error and the maximum absorbance that do not introduce error into analysis are also determined for several analyte isotopic compositions, elemental concentrations and different experimental conditions.

  1. Broadband Analysis of Bioagents by Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Fenselau, Catherine; Wynne, Colin; Edwards, Nathan

    Mass spectrometry was first reported to provide analysis of intact metabolite biomarkers from whole cells in 1975.1 Since then advances in ionization techniques have extended our capabilities to polar lipids and, eventually, to proteins.2, 3 Mass spectrometry provides a broadband detection system, which, however, has great specificity. Bioinformatics plays an important role in providing flexible and rapid characterization of species, based on protein and peptide mass spectra collected in the field.

  2. Data mining in proteomic mass spectrometry

    Microsoft Academic Search

    Asha Thomas; Georgia D. Tourassi; Adel S. Elmaghraby; Roland Valdes; Saeed A. Jortani

    2006-01-01

    Data mining application to proteomic data from mass spectrometry has gained much interest in recent years. Advances made in\\u000a proteomics and mass spectrometry have resulted in considerable amount of data that cannot be easily visualized or interpreted.\\u000a Mass spectral proteomic datasets are typically high dimensional but with small sample size. Consequently, advanced artificial\\u000a intelligence and machine learning algorithms are increasingly

  3. Injection optics for fast mass switching for accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    Weisser, D. C.; Fifield, L. K.; De Cesare, M.; Tims, S. G.; Lobanov, N. R.; Crook, G. G.; Tsifakis, D.; Tunningley, T. B.

    2013-04-01

    Accelerator Mass Spectrometry (AMS) measures the ratio of extremely small amounts of a radioactive isotope in the presence of ˜ 1015 times more stable ones. The isotopes are injected sequentially over a repeated period and observed at the exit of the accelerator. so any fluctuations in ion source output or transmission through the accelerator over a time comparable to the measurement time, will reduce the accuracy of such measurements. This compromise in accuracy can be lessened by reducing the switching time between isotopes from several seconds to a few milli-seconds. New AMS systems accomplish fast switching by modifying the beam energy though the 90 injection magnet by pulsing the voltage by several kV on the flight tube in the magnet. That requires that the flight tube be electrically insulated which competes with having the flight tube as large as possible. At the ANU, insulating the magnet flight tube would not only have reduced the acceptance of the injection system, but conflicted with a beam chopper attached to the flight tube, that would also have had to be insulated from the ground. This was not practical so the novel alternative of pulsing the voltage on the high voltage ion source deck is being implemented. Beam optics calculations have been performed and beam tests conducted that demonstrated that, in addition to pulsing the voltage on the 150 kV ion source deck, a pulsed Einzel lens in front of the following electrostatic quadrupole triplet lens is required to maintain isotope-independent transmission through the 14UD Pelletron accelerator. The high voltage rise time performance of the components of the system has been shown to be satisfactory.

  4. Cross contamination in dual inlet isotope ratio mass spectrometers

    Microsoft Academic Search

    H. A. J. Meijer; R. E. M. Neubert; G. H. Visser

    2000-01-01

    Since the early days of geochemical isotope ratio mass spectrometry there has always been the problem of cross contamination, i.e. the contamination of the sample gas with traces of reference gas (and vice versa) in a dual inlet system and the analyzer itself. This was attributable to valve leakages and could be corrected for. In modern leak-free machines this problem

  5. I-Mass: International Mass Spectrometry Web Resource

    NSDL National Science Digital Library

    Coined as "Mass Spectroscopy's Web Address," this is a site with information for and about mass spectrometry. It features news and articles related to mass spectrometry, gleans important updates from scientific journals on mass spectroscopy, and provides conference and career links. The page also features links to classic articles, definitions, history, Nobel Prizes, protocols, resources, techniques, troubleshooting and tutorials. A link to a repository for jobs involving mass spectroscopy is also given.

  6. Quantification of N?-(2-Furoylmethyl)-l-lysine (furosine), N?-(Carboxymethyl)-l-lysine (CML), N?-(Carboxyethyl)-l-lysine (CEL) and total lysine through stable isotope dilution assay and tandem mass spectrometry.

    PubMed

    Troise, Antonio Dario; Fiore, Alberto; Wiltafsky, Markus; Fogliano, Vincenzo

    2015-12-01

    The control of Maillard reaction (MR) is a key point to ensure processed foods quality. Due to the presence of a primary amino group on its side chain, lysine is particularly prone to chemical modifications with the formation of Amadori products (AP), N?-(Carboxymethyl)-l-lysine (CML), N?-(Carboxyethyl)-l-lysine (CEL). A new analytical strategy was proposed which allowed to simultaneously quantify lysine, CML, CEL and the N?-(2-Furoylmethyl)-l-lysine (furosine), the indirect marker of AP. The procedure is based on stable isotope dilution assay followed by liquid chromatography tandem mass spectrometry. It showed high sensitivity and good reproducibility and repeatability in different foods. The limit of detection and the RSD% were lower than 5ppb and below 8%, respectively. Results obtained with the new procedure not only improved the knowledge about the reliability of thermal treatment markers, but also defined new insights in the relationship between Maillard reaction products and their precursors. PMID:26041204

  7. Accurate and precise determination of boron isotopic ratios at low concentration by positive thermal ionization mass spectrometry using static multicollection of Cs2BO2+ ions.

    PubMed

    He, Mao-yong; Xiao, Ying-kai; Jin, Zhang-dong; Ma, Yun-qi; Xiao, Jun; Zhang, Yan-ling; Luo, Chong-guang; Zhang, Fei

    2013-07-01

    A static double-collector system for accurate, precise, and rapid boron isotope analysis has been established by employing a newly fixed Faraday H3 and H4 cup enabling simultaneously collected Cs2BO2(+) ion beams (m/z = 308 and 309) on a Finnigan-MAT Triton thermal ionization mass spectrometer of boron (Triton B). The experimental result indicated that Cs2BO2(+) ion beams (m/z = 308 and 309) were simultaneously collected using a fixed Faraday H3 and H4 cup without using the "Zoom Quad" function and reduced accelerating voltage. Furthermore, the method enabled the measurement of samples containing as little as 20 ng of boron. An analysis of the National Institute of Standards and Technology standard reference material (NIST SRM) 951 standard showed external reproducibility (2RSD) of ±0.013‰, ± 0.013‰, and ±0.019‰ for 100, 50, and 20 ng of boron, respectively. The present method of static multicollection of Cs2BO2(+) ions is applicable to a wide field of boron isotopic research that requires high precision and accuracy to analyze samples with low boron concentrations, including pore fluids, foraminifera, rivers, rainwater, and other natural samples. PMID:23718810

  8. Quantitation of resveratrol in red wines by means of stable isotope dilution analysis-ultra-performance liquid chromatography-Quan-time-of-flight mass spectrometry and cross validation.

    PubMed

    Stark, Timo; Wollmann, Nadine; Lösch, Sofie; Hofmann, Thomas

    2011-05-01

    A stable isotope dilution analysis (SIDA) was developed for the quantitative analysis of the health-promoting phytoalexin (E)-resveratrol in red wines by means of UPLC-QuanTOF-MS. After hemisynthetic preparation of (E)-3,5,4'-trihydroxy-2,4,6-trideuterostilbene ((E)-[(2)H(3)]-resveratrol) as the stable isotope labeled internal standard, validation experiments revealed recovery rate of 96.2 ± 0.8% RSD, thus demonstrating the robustness and accuracy of the SIDA-UPLC-QuanTOF-MS method. Repeatability and reproducibility expressed as RSD showed excellent values of 3.0% and 4.0% for (E)-[(2)H(3)]-resveratrol. Cross validation against a SIDA-HPLC-MS/MS analysis using a triple quadrupole mass spectrometer revealed comparable data, but the SIDA-UPLC-QuanTOF-MS was four times faster, thus making the latter method preferential for an accurate high-throughput analysis of wine samples. Comparison of the SIDA data to those obtained by quantitation using a standard addition method and external calibration, respectively, revealed 97.7% and 32.4% of the resveratrol concentration determined by means of SIDA-UPLC-QuanTOF-MS and 101.0% and 12.7% of the resveratrol levels found by using SIDA-HPLC-MS/MS. PMID:21438545

  9. Derivatization in mass spectrometry --7. On-line derivatisation/degradation.

    PubMed

    Halket, John M; Zaikin, Vladimir G

    2006-01-01

    The review describes on-line derivatization/degradation methods employed in mass spectrometry to solve some structural and analytical problems. Advantages and applications of various positions of reaction systems connected mainly to a mass spectrometer or a gas chromatograph/mass spectrometer are considered. Among these are reaction systems connected directly to the mass spectrometer (reaction mass spectrometry, pyrolysis-mass spectrometry or direct pyrolysis-mass spectrometry); flash-heaters as reactors in gas chromatography/mass spectrometry (GC/MS); in-line chemical reactors located before the chromatographic column [pre-column derivatization/degradation with the use of catalytic reactions, pyrolysis (pyrolysis-GC/MS), degradation in elemental analyzers-isotope ratio mass pectrometry (EA-IRMS)]; on-column derivatization and deuteration; reactor located between the chromatographic column and a mass spectrometer [post-column catalytic derivatization, gas chromatograph-combustion-isotope ratio mass spectrometer (GC-c-IRMS)]. Post-column derivatization in high performance liquid chromatography/mass spectro-metry is briefly mentioned. Application of such on-line methodology to structure elucidation of low molecular mass compounds and polymers, to the determination of isotope ratios of the most common elements, to the investigation of catalytic reactions is discussed.. PMID:16531644

  10. The utility of mass spectrometry for the analysis of proteins has grown enormously in the past decade. Significant advances in

    E-print Network

    Miranker, Andrew

    include the combination of mass spectrometry with isotopic labeling, affinity labeling and genomic electrospray ionization FWHM full width at half maximum IAPP islet amyloid polypeptide ICAT isotope as mass divided by full width at half maximum (FWHM). This is sufficient to resolve isotopic peaks

  11. Standard test method for analysis of urine for uranium-235 and uranium-238 isotopes by inductively coupled plasma-mass spectrometry

    E-print Network

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This test method covers the determination of the concentration of uranium-235 and uranium-238 in urine using Inductively Coupled Plasma-Mass Spectrometry. This test method can be used to support uranium facility bioassay programs. 1.2 This method detection limits for 235U and 238U are 6 ng/L. To meet the requirements of ANSI N13.30, the minimum detectable activity (MDA) of each radionuclide measured must be at least 0.1 pCi/L (0.0037 Bq/L). The MDA translates to 47 ng/L for 235U and 300 ng/L for 238U. Uranium– 234 cannot be determined at the MDA with this test method because of its low mass concentration level equivalent to 0.1 pCi/L. 1.3 The digestion and anion separation of urine may not be necessary when uranium concentrations of more than 100 ng/L are present. 1.4 Units—The values stated in picoCurie per liter units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1....

  12. Glycoprotein profiling by electrospray mass spectrometry

    E-print Network

    Jiang, Hui; Desaire, Heather; Butnev, V. Y.; Bousfield, George R.

    2004-05-01

    This work compares several different methods of site-specific analysis of glycoproteins using electrospray mass spectrometry. The glycoprotein, oLHalpha (ovine luteinizing hormone, a-subunit) was chosen as an appropriate example protein...

  13. Certification of the Cu and Cd amount contents in artificial food digest using isotope dilution inductively coupled plasma mass spectrometry for Pilot Study 13 of the Comité Consultatif pour la Quantité de Matière

    NASA Astrophysics Data System (ADS)

    Vassileva, E.; Quétel, C. R.; Petrov, I.

    2003-08-01

    The Comité Consultatif pour la Quantité de Matière (CCQM) launched the Pilot Study 13, an interlaboratory comparison between the metrological organizations worldwide on the determination of Ca, Cu and Cd in artificial food digests. These samples (available in 7% HNO 3 and with a salinity evaluated around 370 mg kg -1, including approx. 30 mg Na kg -1) were prepared by gravimetrical mixing, and thus reference values traceable to the Kg for the three elements were available eventually. This paper describes the contribution of IRMM for the certification of the Cu and the Cd amount contents. The analytical protocol developed was based on isotope dilution associated to inductively coupled plasma mass spectrometry (ID-ICP-MS). The Cu measurements required 125-fold dilution of the initial sample solution. An interference of 23Na 40Ar + on 63Cu + was identified but, since the ratio between both species was over 1000, it was successfully overcome by the calculation of a correction factor for its effect on the Cu amount content directly. Dilution of the sample was not possible for Cd only present at the low ng g -1 level. Up to 1% difference was observed on Cd isotope ratio results between measurements performed directly or after matrix separation. This is rarely shown. As similar results could be obtained either way after the necessary corrections, the direct measurements approach associated to a correction for mass discrimination effects using the CCQM-P13 sample itself (and the IUPAC table values as reference for the natural Cd isotopic composition) was preferred as it was the easiest. SI traceable values were obtained for Cu and Cd with less than 1 and 1.5% combined uncertainty, respectively (6 995±55 ( k=2) nmol kg -1 and 45.53±0.64 ( k=2) nmol kg -1). The excellent agreement between these results and the reference values (less than 0.6 and 0.08% difference) further validated the analytical protocols developed.

  14. Determination of Sr isotopes in calcium phosphates using laser ablation inductively coupled plasma mass spectrometry and their application to archaeological tooth enamel

    NASA Astrophysics Data System (ADS)

    Horstwood, M. S. A.; Evans, J. A.; Montgomery, J.

    2008-12-01

    The determination of accurate Sr isotope ratios in calcium phosphate matrices by laser ablation multi-collector ICP-MS is demonstrated as possible even with low Sr concentration archaeological material. Multiple on-line interference correction routines for doubly-charged REE, Ca dimers and Rb with additional calibration against TIMS-characterised materials are required to achieve this. The calibration strategy proposed uses both inorganic and biogenic apatite matrices to monitor and correct for a 40Ca- 31P- 16O polyatomic present at levels of 0.3-1% of the non-oxide peak, which interferes on 87Sr causing inaccuracies of 0.03-0.4% in the 87Sr/ 86Sr isotope ratio. The possibility also exists for synthetic materials to be used in this calibration. After correction for interferences total combined uncertainties of 0.04-0.15% (2SD) are achieved for analyses of 13-24 ?g of archaeological tooth enamel with Sr concentrations of ca. 100-500 ppm using MC-ICP-MS. In particular, for samples containing >300 ppm Sr, total uncertainties of ˜0.05% are possible utilising 7-12 ng Sr. Data quality is monitored by determination of 84Sr/ 86Sr ratios. When applied to an archaeological cattle tooth this approach shows Sr-isotope variations along the length of the tooth in agreement with independent TIMS data. The 40Ca- 31P- 16O polyatomic interference is the root cause of the bias at mass 87 during laser ablation ICP-MS analysis of inorganic and biogenic calcium phosphate (apatite) matrices. This results in inaccurate 87Sr/ 86Sr ratios even after correction of Ca dimers and doubly charged rare earth elements. This interference is essentially constant at specific ablation conditions and therefore the effect on 87Sr/ 86Sr data varies in proportion to changes in the Sr concentration of the ablated material. Complete elimination of this interference is unlikely through normal analytical mechanisms and therefore represents a limitation on the achievable accuracy of LA-(MC-)ICP-MS 87Sr/ 86Sr data without rigorous calibration to known reference materials.

  15. Mass spectrometry of proteins of known mass Andrew D. Miranker*

    E-print Network

    Miranker, Andrew

    Commentary Mass spectrometry of proteins of known mass Andrew D. Miranker* Department of Molecular measurements in biochemistry are as fundamental as mass. Whereas the mass of a macromolecule is often in- ferred by its migration through polymer gels, direct measure may only be deter- mined by mass

  16. Mass-Dependent and Mass-Independent Isotope Effects of Zinc in a Redox Reaction

    NASA Astrophysics Data System (ADS)

    Fujii, Toshiyuki; Moynier, Frédéric; Uehara, Akihiro; Abe, Minori; Yin, Qing-Zhu; Nagai, Takayuki; Yamana, Hajimu

    2009-10-01

    We report the isotope fractionation of zinc (Zn) associated with a redox reaction between Zn0 and Zn(II). Zn isotopes were found fractionated in pyrometallurgical biphase extraction between liquid zinc and molten chloride. The isotopic composition of Zn in the molten chloride phase was analyzed by multiple collector inductively coupled plasma mass spectrometry and reported as mZn/64Zn (m = 66, 67, and 68) ratios. The observed isotope fractionation consists of the mass-dependent and mass-independent isotope effects. The contributions of the nuclear mass and the nuclear volume to the overall isotope effect were evaluated by employing first-principles quantum calculations and using reported isotope shifts in atomic spectra. The magnitude of the mass-dependent isotope effect was explained by the sum of the isotope effect via intramolecular vibrations and the correction to the Born-Oppenheimer electronic energy. The mass-independent isotope effect was correlated with the Gibbs free energy change in the redox reaction.

  17. Methods for recalibration of mass spectrometry data

    DOEpatents

    Tolmachev, Aleksey V. (Richland, WA); Smith, Richard D. (Richland, WA)

    2009-03-03

    Disclosed are methods for recalibrating mass spectrometry data that provide improvement in both mass accuracy and precision by adjusting for experimental variance in parameters that have a substantial impact on mass measurement accuracy. Optimal coefficients are determined using correlated pairs of mass values compiled by matching sets of measured and putative mass values that minimize overall effective mass error and mass error spread. Coefficients are subsequently used to correct mass values for peaks detected in the measured dataset, providing recalibration thereof. Sub-ppm mass measurement accuracy has been demonstrated on a complex fungal proteome after recalibration, providing improved confidence for peptide identifications.

  18. 1912: a Titanic year for mass spectrometry.

    PubMed

    Downard, Kevin M

    2012-08-01

    The 1912 sinking of the Titanic continues to capture the imagination and fascination of the general public. The year coincides with the birth of mass spectrometry that began with the cathode ray experiments performed by Joseph John (J. J.) Thomson in Cambridge. Modifications made to Thomson's cathode ray apparatus by Francis William Aston, resulted in an increase in the brightness of the positive rays that aided their detection. This led to the discovery of heavy isotopes for many of the chemical elements in the ensuing decades. As the discovery of (22) Ne was reported in 1913, another of Thomson's students was taking part in an expedition to help save future ocean liners from the fate of the Titanic. Geoffrey Ingram Taylor took part in the first ice patrol of the North Atlantic in 1913 aboard the SS Scotia to investigate the formation and position of icebergs. This article, 100?years on, describes Taylor's work and its impact on safe ocean passage across the Atlantic. PMID:22899512

  19. Cortisol production rates measured by liquid chromatography/mass spectrometry

    SciTech Connect

    Esteban, N.V.; Yergey, A.L. (National Institute of Child Health and Human Development, Bethesda, MD (USA))

    1990-04-01

    Cortisol production rates (FPRs) in physiologic and pathologic states in humans have been investigated over the past 30 years. However, there has been conflicting evidence concerning the validity of the currently accepted value of FPRs in humans (12 to 15 mg/m2/d) as determined by radiotracer methodology. The present study reviews previous methods proposed for the measurement of FPRs in humans and discusses the applications of the first method for the direct determination of 24-hour plasma FPRs during continuous administration of a stable isotope, using a thermospray high-pressure liquid chromatography-mass spectrometry technique. The technique is fast, sensitive, and, unlike gas chromatography-mass spectrometry methods, does not require derivatization, allowing on-line detection and quantification of plasma cortisol after a simple extraction procedure. The results of determination of plasma FPRs by stable tracer/mass spectrometry are directly in units of mass/time and, unlike radiotracer methods, are independent of any determination of volume of distribution or cortisol concentration. Our methodology offers distinct advantages over radiotracer techniques in simplicity and reliability since only single measurements of isotope ratios are required. The technique was validated in adrenalectomized patients. Circadian variations in daily FRPs were observed in normal volunteers, and, to date, results suggest a lower FRP in normal children and adults than previously believed. 88 references.

  20. Simultaneous determination of 11 ?-agonists in human urine using high-performance liquid chromatography/tandem mass spectrometry with isotope dilution.

    PubMed

    Wang, Xiaoli; Guo, Tao; Wang, Shanshan; Yuan, Jinpeng; Zhao, Rusong

    2015-04-01

    The misuse of ?-agonists constitutes a potential risk to public health and has been forbidden in many countries. In this study, we describe a method for specific, sensitive and rapid detection of ?-agonists in human urine. Urine samples were extracted with ethyl acetate, without any additional purification step, and analyzed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) with Clenbuterol-D9 and Salbuterol-D3 as internal standards. The intra- and interday precision values of the method were all <5.60% and the accuracy ranged from 94.5 to 109%. Extraction recovery for 11 ?-agonists varied from 66.7 to 108%. One UPLC-MS-MS analysis could be completed within 12 min and the limits of detection for 11 ?-agonists were 0.1 ng/mL in the experiment. ?-Agonists in human urines from 24 volunteers were analyzed by our validated method and 1.70 ng/mL salbutamol was detected in one volunteer. The application of UPLC-MS-MS method in ?-agonists detection of human urine will be helpful in veterinary control of ?-agonists and for studying the effect of ?-agonists on human health. PMID:25542892

  1. Improvements in 230Th dating, 230Th and 234U half-life values, and U-Th isotopic measurements by multi-collector inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Cheng, Hai; Lawrence Edwards, R.; Shen, Chuan-Chou; Polyak, Victor J.; Asmerom, Yemane; Woodhead, Jon; Hellstrom, John; Wang, Yongjin; Kong, Xinggong; Spötl, Christoph; Wang, Xianfeng; Calvin Alexander, E.

    2013-06-01

    We have developed techniques for measuring 234U and 230Th on Faraday cups with precisions of 1-3 epsilon units (1 ?-unit=1 part in 104) using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Using a Thermo-Scientific Neptune with desolvation nebulization, we obtained ionization/transmission efficiencies of 1-2% for both U and Th. We set up protocols to correct for tailing, prepared U and Th gravimetric standards, tested a Th mass fractionation correction procedure based on U isotopes, and identified natural calcite samples likely to be in U-Th isotopic secular equilibrium. The measured atomic ratios, 234U/238U=54.970 (±0.019)×10-6 and 230Th/238U=16.916 (±0.018)×10-6, for these calcite samples were identical within errors (quoted 2? uncertainties calculated combining all sources of error). Half-life values calculated from these ratios are consistent with previous values, but have much smaller errors: 245,620±260 a for 234U and 75,584±110 a for 230Th (quoted 2? uncertainties calculated using all sources of error). In calculating a 230Th age, some of the systematic errors included in estimating the full error in the half-lives effectively cancel. Removing these uncertainties (uncertainty in the 238U half-life value, uncertainty in our gravimetric uranium and thorium standards, and uncertainty in the absolute isotopic composition of the uranium standard), yields effective uncertainties for the purposes of 230Th dating of ±70 a for the 234U half-life value and ±30 a for the 230Th half-life value. Under ideal circumstances, with our methods, the 2? uncertainty in age, including uncertainty in half-life values is ±10 a at 10 ka, ±100 a at 130 ka, ±300 a at 200 ka, ±1 ka at 300 ka, ±2 ka at 400 ka, ±6 ka at 500 ka, and ±12 ka at 600 ka. The isotopic composition of a sample with an age <800 ka can clearly be resolved from the isotopic composition of a sample in secular equilibrium, assuming closed system behavior. Using these techniques, we analyzed a Sanbao Cave (Hubei, China) stalagmite that formed between 510 and 640 ka ago. As the half-life values were determined independent of the Sanbao Cave ages, the observed co-variation between stalagmite ?18O and Northern Hemisphere summer insolation is consistent with accurate ages and half-life values.

  2. Precise Measurement of Phenylalanine ?15N Values via Elemental Analysis-Isotope Ratio Mass Spectrometry Following Purification with High-Pressure Liquid Chromatography: A New Tool for Fine-Scale Paleo-Nitrogen Cycle Reconstructions

    NASA Astrophysics Data System (ADS)

    Broek, T.; Walker, B. D.; Batista, F. C.; Andreasen, D.; Hill, T. M.; Guilderson, T. P.; McCarthy, M.

    2012-12-01

    Compound specific isotope analysis of individual amino acids (CSI-AA) in organic paleoarchives is emerging as a powerful tool for reconstructing the paleo-nitrogen (N) cycle. Because the ?15N of phenylalanine (Phe) remains almost unchanged with diagenesis or trophic transfer it has been demonstrated to be the most promising AA proxy for the ?15N of primary production. However, the precise measurement of AA ?15N values is currently limited by the standard gas chromatography-isotope ratio mass spectrometer (GC-IRMS) approach. The key problem with this approach is that GC-IRMS ?15N precision (±1‰) is almost an order of magnitude lower than typical bulk ?15N measurements (±0.1‰), posing a significant problem for assessing fine scale changes within paleo-climate records. Additionally, required instrumentation is both expensive, and not widely available. Here we present an offline approach in which Phe is purified via high-pressure liquid chromatography (HPLC), using an analytical scale, mixed-phase column and automated fraction collection. ?13C and ?15N values of the fractions are then determined via standard elemental analysis-isotope ratio mass spectrometry (EA-IRMS). We evaluate the precision of this HPLC-EA-IRMS method vs. traditional GC-IRMS for Phe ?15N values of isotopic AA standards and various proteinaceous marine samples (marine coral, sediment, and cyanobacteria). Typical HPLC-EA-IRMS ?15N precision is ±0.1‰ for isotopic AA standards and ±0.5‰ for marine coral, sediment, and cyanobacteria samples compared to ±0.5‰ and ±1.0‰ for AA standards and samples analyzed by GC-IRMS. In order to demonstrate the viability of our approach, we present a comparison of a Phe ?15N record produced from a deep-sea bamboo coral specimen from Monterey Bay, CA, using our offline HPLC-EA-IRMS method vs. standard GC-IRMS. Each method produced equivalent Phe ?15N values within error, however, the HPLC-EA-IRMS method produced Phe ?15N values with over twice the precision of the traditional GC-IRMS method (HPLC-EA-IRMS standard deviation = 0.27‰ ± 0.14‰, GC-IRMS standard deviation = 0.60‰ ± 0.20‰). Our results suggest that this HPLC-EA-IRMS method represents a powerful, yet widely available tool for reconstructing fine scale N-cycling processes within paleoceanographic records.

  3. Fatty acid composition and ?13 C of bulk and individual fatty acids as marker for authenticating Italian PDO/PGI extra virgin olive oils by means of isotopic ratio mass spectrometry.

    PubMed

    Faberi, Angelo; Marianella, Rosa Maria; Fuselli, Fabio; La Mantia, Alessandro; Ciardiello, Felice; Montesano, Camilla; Mascini, Marcello; Sergi, Manuel; Compagnone, Dario

    2014-09-01

    European Regulation (EEC) 2568/91 has been setting the minimum requirements in order to allow labeling of oil as extra virgin. These general requirements, are based on physical-chemical and organoleptic parameters directly linked to the freshness and quality of the product. Isotope ratio mass spectrometry (IRMS) was demonstrated to be a useful tool for the discrimination of the origin of unknown samples, because the obtained data are practically independent of the cultivar employed and the production technique. In this work, the evaluation of the composition of fatty acid methyl esters (FAME) alongside with the determination of stable isotope ratio of C in bulk oils and in main FAME constituents have been investigated as a tool to improve geographical discrimination of Italian Protected Designation of Origin/Protected Geographical Indication (PDO/PGI) samples. For this purpose, authentic PDO/PGI extra virgin olive oils were sampled at oil mills and grouped into different sets according to their areas of provenience. The use of principal component analysis and partial least squares discriminant analysis multivariate analysis techniques demonstrated that discrimination of olive oil samples can be done using geographical and pedoclimatic parameters predominantly by using ?(13) C results of bulk and individual fatty acids. Results showed that ?(13) C values are a more reliable marker of origin with respect to fatty acid composition. PMID:25230181

  4. Direct High-Precision Measurements of the (87)Sr/(86)Sr Isotope Ratio in Natural Water without Chemical Separation Using Thermal Ionization Mass Spectrometry Equipped with 10(12) ? Resistors.

    PubMed

    Li, Chao-Feng; Guo, Jing-Hui; Chu, Zhu-Yin; Feng, Lian-Jun; Wang, Xuan-Ce

    2015-07-21

    Thermal ionization mass spectrometry (TIMS) allows excellent precision for determining Sr isotope ratios in natural water samples. Traditionally, a chemical separation procedure using cation exchange resin has been employed to obtain a high purity Sr fraction from natural water, which makes sample preparation time-consuming. In this study, we present a rapid and precise method for the direct determination of the Sr isotope ratio of natural water using TIMS equipped with amplifiers with two 10(12) ? resistors. To eliminate the (87)Rb isobaric interference, Re ribbons are used as filaments, providing a significant advantage over W ribbons in the inhibition of Rb(+) emission, based on systematically examining a series of NIST SRM987 standard doping with various amounts of Rb using Re and W ribbons. To validate the applicability of our method, twenty-two natural water samples, including different water types (rain, snow, river, lake and drinking water), that show a large range in Sr content variations (2.54-922.8 ppb), were collected and analyzed from North and South China. Analytical results show good precision (0.003-0.005%, 2 RSE) and the method was further validated by comparative analysis of the same water with and without chemical separation. The method is simple and rapid, eliminates sample preparation time, and prevents potential contamination during complicated sample-preparation procedures. Therefore, a high sample throughput inherent to the TIMS can be fully utilized. PMID:26105121

  5. Performance evaluation of elemental analysis/isotope ratio mass spectrometry methods for the determination of the D/H ratio in tetramethylurea and other compounds--results of a laboratory inter-comparison.

    PubMed

    Bréas, Olivier; Thomas, Freddy; Zeleny, Reinhard; Calderone, Giovanni; Jamin, Eric; Guillou, Claude

    2007-01-01

    Tetramethylurea (TMU) with a certified D/H ratio is the internal standard for Site-specific Natural Isotope Fractionation measured by Nuclear Magnetic Resonance (SNIF-NMR) analysis of wine ethanol for detection of possible adulterations (Commission Regulation 2676/90). A new batch of a TMU certified reference material (CRM) is currently being prepared. Whereas SNIF-NMR has been employed up to now, Elemental Analysis/Isotope Ratio Mass Spectrometry ((2)H-EA-IRMS) was envisaged as the method of choice for value assignment of the new CRM, as more precise (better repeatable) data might be obtained, resulting in lower uncertainty of the certified value. In order to evaluate the accuracy and intra- and inter-laboratory reproducibility of (2)H-EA-IRMS methods, a laboratory inter-comparison was carried out by analysing TMU and other organic compounds, as well as some waters. The results revealed that experienced laboratories are capable of generating robust and well comparable data, which highlights the emerging potential of IRMS in food authenticity testing. However, a systematic bias between IRMS and SNIF-NMR reference data was observed for TMU; this lack of data consistency rules out the (2)H-IRMS technique for the characterisation measurement of the new TMU CRM. PMID:17428013

  6. ?13C and ?18O isotopic composition of CaCO3 measured by continuous flow isotope ratio mass spectrometry: statistical evaluation and verification by application to Devils Hole core DH-11 calcite

    USGS Publications Warehouse

    Revesz, Kinga M.; Landwehr, Jurate M.

    2002-01-01

    A new method was developed to analyze the stable carbon and oxygen isotope ratios of small samples (400?±?20?µg) of calcium carbonate. This new method streamlines the classical phosphoric acid/calcium carbonate (H3PO4/CaCO3) reaction method by making use of a recently available Thermoquest-Finnigan GasBench II preparation device and a Delta Plus XL continuous flow isotope ratio mass spectrometer. Conditions for which the H3PO4/CaCO3 reaction produced reproducible and accurate results with minimal error had to be determined. When the acid/carbonate reaction temperature was kept at 26?°C and the reaction time was between 24 and 54?h, the precision of the carbon and oxygen isotope ratios for pooled samples from three reference standard materials was ?0.1 and ?0.2 per mill or ‰, respectively, although later analysis showed that materials from one specific standard required reaction time between 34 and 54?h for ?18O to achieve this level of precision. Aliquot screening methods were shown to further minimize the total error. The accuracy and precision of the new method were analyzed and confirmed by statistical analysis. The utility of the method was verified by analyzing calcite from Devils Hole, Nevada, for which isotope-ratio values had previously been obtained by the classical method. Devils Hole core DH-11 recently had been re-cut and re-sampled, and isotope-ratio values were obtained using the new method. The results were comparable with those obtained by the classical method with correlation?=?+0.96 for both isotope ratios. The consistency of the isotopic results is such that an alignment offset could be identified in the re-sampled core material, and two cutting errors that occurred during re-sampling then were confirmed independently. This result indicates that the new method is a viable alternative to the classical reaction method. In particular, the new method requires less sample material permitting finer resolution and allows automation of some processes resulting in considerable time savings. 

  7. Endogenous lithium determination in blood plasma and urine by isotope dilution mass spectrometry and preliminary isolation of lithium fraction using paper chromatography.

    PubMed

    Fleishman, D G; Nikiforov, V A; Saulus, A A

    1992-02-01

    A version of isotope dilution mass spectrometric technique elaborated for measuring endogenous lithium concentrations in human blood plasma and urine (10(-7) M region) and applicable in clinical practice is described. A tracer solution of lithium (LiCl) enriched in 6Li (with abundances 6Li 92%, 7Li 8%) is added to a certain volume of human plasma (0.2-0.4 ml) or urine (0.05-0.1 ml) and dried under an infrared lamp. Thereupon a soluble part extracted from dried plasma with the aid of 0.1 N HCl is dried as well. Dry extracts from plasma and dried samples of urine are processed by 30% H2O2 and subsequently subjected to paper chromatography (with ethanol as a solvent). Such processing of samples is simple and short (about an hour, 3 min of chromatographic process inclusive), achieving a good separation from organic matrix and interfering macroelements. Contamination of sample in processing is about 2-5 pmol; routine control of contamination and account of their influence are accomplished by measuring two different volumes of each sample. Measurements are made with high precision: cyclic repeated scanning of 7Li and 6Li peaks have a standard deviation of 7Li/6Li ratio no more than 0.7%. The method described was used to determine endogenous lithium clearance of hypertensive patients and patients with transplanted kidney. PMID:1606185

  8. Treatise on the Measurement of Molecular Masses with Ion Mobility Spectrometry

    PubMed Central

    Valentine, Stephen J.; Clemmer, David E.

    2009-01-01

    The ability to separate isotopes by high-resolution ion mobility spectrometry techniques is considered as a direct means for determining mass at ambient pressures. Calculations of peak shapes from the transport equation show that it should be possible to separate isotopes for low mass ions (<200) by utilizing heavy collision gasses and high resolution ion mobility analyzers. The mass accuracy associated with this isotopic separation approach based on ion mobility separation is considered. Finally, we predict several isotopes that should be separable. PMID:19548697

  9. Molecularly imprinted solid phase extraction using stable isotope labeled compounds as template and liquid chromatography–mass spectrometry for trace analysis of bisphenol A in water sample

    Microsoft Academic Search

    Migaku Kawaguchi; Yoshio Hayatsu; Hisao Nakata; Yumiko Ishii; Rie Ito; Koichi Saito; Hiroyuki Nakazawa

    2005-01-01

    We have developed a molecularly imprinted polymer (MIP) using a stable isotope labeled compound as the template molecule and called it the “isotope molecularly imprinted polymer” (IMIP). In this study, bisphenol A (BPA) was used as the model compound. None imprinted polymer (NIP), MIP, dummy molecularly imprinted polymer (DMIP) and IMIP were prepared by the suspension polymerization method using without

  10. MAPPING HUMAN MOVEMENT USING STABLE OXYGEN ISOTOPIC RATIO MASS SPECTROMETRY: POTENTIAL APPLICATION TO FORENSIC SCIENCE DEMONSTRATED BY A MODERN HORSE-HUMAN STUDY

    Microsoft Academic Search

    L. S. BELL; J. A LEE-THORP; K. DOBNEY

    The utility of stable oxygen isotope analysis for demonstrating human migration has been developed and demonstrated on archaeological human populations. The application of this approach to tracking human movement has seldom been applied within forensic science. This paper gives results from a stable oxygen isotope assessment of extant modern human and horse enamel ? 18O values recovered from tooth enamel.

  11. Determination of Selected B-complex Vitamins in the NIST Multivitamin Reference Standard Material by Stable Isotope Dilution Mass Spectrometry (Experimental Biology, April, 2007, Washington, D.C.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  12. Mass spectrometry: playing catch up Mass spectrometry is more than ever at the forefront of functional proteomics research. The

    E-print Network

    Cai, Long

    Mass spectrometry: playing catch up Mass spectrometry is more than ever at the forefront of Munster. John Yates of the Scripps Research Institute views mass spectrometry as basically evolving: consis- tent improvements in mass spectrometry instruments over the past decade have been enabling

  13. Quantitative analysis of N-glycans from human alfa-acid-glycoprotein using stable isotope labeling and zwitterionic hydrophilic interaction capillary liquid chromatography electrospray mass spectrometry as tool for pancreatic disease diagnosis.

    PubMed

    Giménez, Estela; Balmaña, Meritxell; Figueras, Joan; Fort, Esther; de Bolós, Carme; Sanz-Nebot, Victòria; Peracaula, Rosa; Rizzi, Andreas

    2015-03-25

    In this work we demonstrate the potential of glycan reductive isotope labeling (GRIL) using [(12)C]- and [(13)C]-coded aniline and zwitterionic hydrophilic interaction capillary liquid chromatography electrospray mass spectrometry (?ZIC-HILIC-ESI-MS) for relative quantitation of glycosylation variants in selected glycoproteins present in samples from cancer patients. Human ?1-acid-glycoprotein (hAGP) is an acute phase serum glycoprotein whose glycosylation has been described to be altered in cancer and chronic inflammation. However, it is not clear yet whether some particular glycans in hAGP can be used as biomarker for differentiating between these two pathologies. In this work, hAGP was isolated by immunoaffinity chromatography (IAC) from serum samples of healthy individuals and from those suffering chronic pancreatitis and different stages of pancreatic cancer, respectively. After de-N-glycosylation, relative quantitation of the hAGP glycans was carried out using stable isotope labeling and ?ZIC-HILIC-ESI-MS analysis. First, protein denaturing conditions prior to PNGase F digestion were optimized to achieve quantitative digestion yields, and the reproducibility of the established methodology was evaluated with standard hAGP. Then, the proposed method was applied to the analysis of the clinical samples (control vs. pathological). Pancreatic cancer samples clearly showed an increase in the abundance of fucosylated glycans as the stage of the disease increases and this was unlike to samples from chronic pancreatitis. The results gained here indicate the mentioned glycan in hAGP as a candidate structure worth to be corroborated by an extended study including more clinical cases; especially those with chronic pancreatitis and initial stages of pancreatic cancer. Importantly, the results demonstrate that the presented methodology combining an enrichment of a target protein by IAC with isotope coded relative quantitation of N-glycans can be successfully used for targeted glycomics studies. The methodology is assumed being suitable as well for other such studies aimed at finding novel cancer associated glycoprotein biomarkers. PMID:25732693

  14. Extracting cluster distributions from mass spectra: IsotopeFit

    PubMed Central

    Ralser, Stefan; Postler, Johannes; Harnisch, Martina; Ellis, Andrew M.; Scheier, Paul

    2015-01-01

    The availability of high resolution mass spectrometry in the study of atomic and molecular clusters opens up challenges for the interpretation of the data. In complex systems each resolved mass peak may contain contributions from multiple species because of the isotope structure of constituent elements and because a multitude of different types of clusters with different compositions are present. A computational procedure which can help to identify a specific cluster from this complex dataset and quantify its relative abundance would be extremely helpful to many who work in this field. Here some new software designed for this purpose, known as IsotopeFit, is described.

  15. Secondary-Ion Mass Spectrometry of Genetically Encoded Targets**

    PubMed Central

    Vreja, Ingrid C; Kabatas, Selda; Saka, Sinem K; Kröhnert, Katharina; Höschen, Carmen; Opazo, Felipe; Diederichsen, Ulf; Rizzoli, Silvio O

    2015-01-01

    Secondary ion mass spectrometry (SIMS) is generally used in imaging the isotopic composition of various materials. It is becoming increasingly popular in biology, especially for investigations of cellular metabolism. However, individual proteins are difficult to identify in SIMS, which limits the ability of this technology to study individual compartments or protein complexes. We present a method for specific protein isotopic and fluorescence labeling (SPILL), based on a novel click reaction with isotopic probes. Using this method, we added 19F-enriched labels to different proteins, and visualized them by NanoSIMS and fluorescence microscopy. The 19F signal allowed the precise visualization of the protein of interest, with minimal background, and enabled correlative studies of protein distribution and cellular metabolism or composition. SPILL can be applied to biological systems suitable for click chemistry, which include most cell-culture systems, as well as small model organisms. PMID:25783034

  16. Secondary-ion mass spectrometry of genetically encoded targets.

    PubMed

    Vreja, Ingrid C; Kabatas, Selda; Saka, Sinem K; Kröhnert, Katharina; Höschen, Carmen; Opazo, Felipe; Diederichsen, Ulf; Rizzoli, Silvio O

    2015-05-01

    Secondary ion mass spectrometry (SIMS) is generally used in imaging the isotopic composition of various materials. It is becoming increasingly popular in biology, especially for investigations of cellular metabolism. However, individual proteins are difficult to identify in SIMS, which limits the ability of this technology to study individual compartments or protein complexes. We present a method for specific protein isotopic and fluorescence labeling (SPILL), based on a novel click reaction with isotopic probes. Using this method, we added (19) F-enriched labels to different proteins, and visualized them by NanoSIMS and fluorescence microscopy. The (19) F signal allowed the precise visualization of the protein of interest, with minimal background, and enabled correlative studies of protein distribution and cellular metabolism or composition. SPILL can be applied to biological systems suitable for click chemistry, which include most cell-culture systems, as well as small model organisms. PMID:25783034

  17. STRUCTURAL CHARACTERIZATION OF SULFONATED AZO DYES USING LIQUID SECONDARY ION MASS SPECTROMETRY/TANDEM MASS SPECTROMETRY

    EPA Science Inventory

    Eight monosulfonated and disulfonated azo dyes were analyzed using liquid secondary ion mass spectrometry/tandem mass spectrometry, in the negative ion mode, under low-energy conditions (110-150 eV). any structurally characteristic fragment ions were obtained, several of which ha...

  18. STRUCTURAL CHARACTERIZATION OF REACTIVE DYES USING SECONDARY ION MASS SPECTROMETRY/TANDEM MASS SPECTROMETRY

    EPA Science Inventory

    Reactive Blue 19 (RB 19), its reactive form (RB 19-VS) and its hydrolyzed form, (RB 19-OH) were examined using liquid secondary ion mass spectrometry/tandem mass spectrometry (LSIMS/MS/MS) in the negative-ion mode under low-energy collision conditions (240-300 eV). tructurally ch...

  19. CHARACTERIZATION OF DOXYLAMINE AND PYRILAMINE METABOLITES VIA THERMOSPRAY/MASS SPECTROMETRY AND TANDEM MASS SPECTROMETRY

    EPA Science Inventory

    Analysis of doxylamine N-oxide and pyrilamine N-oxide as synthetic standards and biologically derived metabolites by thermospray mass spectrometry (TSP/MS) provided (M + H)+ ions for each metabolite. TSP/tandem mass spectrometry (TSP/MS/MS) of the (M + H)+ ions provided fragment ...

  20. Mass Spectrometry of Intact Membrane Protein Complexes

    PubMed Central

    Laganowsky, Arthur; Reading, Eamonn; Hopper, Jonathan T.S.; Robinson, Carol V.

    2014-01-01

    Mass spectrometry of intact soluble protein complexes has emerged as a powerful technique to study the stoichiometry, structure-function and dynamics of protein assemblies. Recent developments have extended this technique to the study of membrane protein complexes where it has already revealed subunit stoichiometries and specific phospholipid interactions. Here, we describe a protocol for mass spectrometry of membrane protein complexes. The protocol begins with preparation of the membrane protein complex enabling not only the direct assessment of stoichiometry, delipidation, and quality of the target complex, but also evaluation of the purification strategy. A detailed list of compatible non-ionic detergents is included, along with a protocol for screening detergents to find an optimal one for mass spectrometry, biochemical and structural studies. This protocol also covers the preparation of lipids for protein-lipid binding studies and includes detailed settings for a Q-ToF mass spectrometer after introduction of complexes from gold-coated nanoflow capillaries. PMID:23471109

  1. Development, validation and application of a stable isotope dilution liquid chromatography electrospray ionization/selected reaction monitoring/mass spectrometry (SID-LC/ESI/SRM/MS) method for quantification of keto-androgens in human serum?, ??

    PubMed Central

    Tamae, Daniel; Byrns, Michael; Marck, Brett; Mostaghel, Elahe A.; Nelson, Peter S.; Lange, Paul; Lin, Daniel; Taplin, Mary-Ellen; Balk, Steven; Ellis, William; True, Larry; Vessella, Robert; Montgomery, Bruce; Blair, Ian A.; Penning, Trevor M.

    2013-01-01

    Prostate cancer is the most frequently diagnosed form of cancer in males in the United States. The disease is androgen driven and the use of orchiectomy or chemical castration, known as androgen deprivation therapy (ADT) has been employed for the treatment of advanced prostate cancer for over 70 years. Agents such as GnRH agonists and non-steroidal androgen receptor antagonists are routinely used in the clinic, but eventually relapse occurs due to the emergence of castration-resistant prostate cancer. With the appreciation that androgen signaling still persists in these patients and the development of new therapies such as abiraterone and enzalutamide that further suppresses androgen synthesis or signaling, there is a renewed need for sensitive and specific methods to quantify androgen precursor and metabolite levels to assess drug efficacy. We describe the development, validation and application of a stable isotope dilution liquid chromatography electrospray ionization selected reaction monitoring mass spectrometry (SID-LC/ESI/SRM/MS) method for quantification of serum keto-androgens and their sulfate and glucuronide conjugates using Girard-T oxime derivatives. The method is robust down to 0.2–4 pg on column, depending on the androgen metabolite quantified, and can also quantify dehydroepiandrosterone sulfate (DHEA-S) in only 1 ?L of serum. The clinical utility of this method was demonstrated by analyzing serum androgens from patients enrolled in a clinical trial assessing combinations of pharmacological agents to maximally suppress gonadal and adrenal androgens (Targeted Androgen Pathway Suppression, TAPS clinical trial). The method was validated by correlating the results obtained with a hydroxylamine derivatization procedure coupled with tandem mass spectrometry using selected reaction monitoring that was conducted in an independent laboratory. PMID:23851165

  2. Identification and Quantification of DNA Repair Protein Apurinic/Apyrimidinic Endonuclease 1 (APE1) in Human Cells by Liquid Chromatography/Isotope-Dilution Tandem Mass Spectrometry

    PubMed Central

    Kirkali, Güldal; Jaruga, Pawel; Reddy, Prasad T.; Tona, Alessandro; Nelson, Bryant C.; Li, Mengxia; Wilson, David M.; Dizdaroglu, Miral

    2013-01-01

    Unless repaired, DNA damage can drive mutagenesis or cell death. DNA repair proteins may therefore be used as biomarkers in disease etiology or therapeutic response prediction. Thus, the accurate determination of DNA repair protein expression and genotype is of fundamental importance. Among DNA repair proteins involved in base excision repair, apurinic/apyrimidinic endonuclease 1 (APE1) is the major endonuclease in mammals and plays important roles in transcriptional regulation and modulating stress responses. Here, we present a novel approach involving LC-MS/MS with isotope-dilution to positively identify and accurately quantify APE1 in human cells and mouse tissue. A completely 15N-labeled full-length human APE1 was produced and used as an internal standard. Fourteen tryptic peptides of both human APE1 (hAPE1) and 15N-labeled hAPE1 were identified following trypsin digestion. These peptides matched the theoretical peptides expected from trypsin digestion and provided a statistically significant protein score that would unequivocally identify hAPE1. Using the developed methodology, APE1 was positively identified and quantified in nuclear and cytoplasmic extracts of multiple human cell lines and mouse liver using selected-reaction monitoring of typical mass transitions of the tryptic peptides. We also show that the methodology can be applied to the identification of hAPE1 variants found in the human population. The results describe a novel approach for the accurate measurement of wild-type and variant forms of hAPE1 in vivo, and ultimately for defining the role of this protein in disease development and treatment responses. PMID:23922845

  3. Analysis of bioactive eicosanoids in equine plasma by stable isotope dilution reversed-phase liquid chromatography/multiple reaction monitoring mass spectrometry.

    PubMed

    Mangal, Dipti; Uboh, Cornelius E; Soma, Lawrence R

    2011-03-15

    Oxidative metabolites of arachidonic acid (AA) are implicated in inflammation. Thus, we evaluated cycloxygenases (COXs) and lipoxygenases (LOs) mediated metabolism of AA to eicosanoids in equine plasma. Eicosanoids were extracted from plasma by two liquid-liquid extraction (LLE) steps; first was by chloroform/isopropanol and second by methyl-tert-butyl ether. For identification and quantification of 25 eicosanoids, a highly specific, selective and sensitive stable isotope dilution liquid chromatography (LC) multiple reaction monitoring (MRM) mass spectrometric (MS) method was developed. To avoid artifact formation of eicosanoids, deferoxamine was added to plasma to chelate residual transition metal ions. The calibration curve showed excellent linearity within 0.1 to 10 ng/mL. Slopes of the calibration curves generated by adding known quantities of eicosanoids in plasma were higher than those prepared in methanol/mobile phase A. Addition of deferoxamine decreased the slope of calibration curves generated using plasma. Limit of detection (LOD) was 1-10 pg on-column for 25 different eicosanoids. Inter-day accuracy was 86-111%, whereas intra-day accuracy was from 88-110%, and precision did not exceed 15% for all quality control (QC) samples. To evaluate the formation of eicosanoids, AA was exogenously added or endogenous AA was released from esterified lipids by calcium ionophore (CI) A23187 treatment of equine whole blood. Pre-treatment of equine whole blood with dexamethasone (DEX) significantly inhibited AA or CI A23187- mediated formation of eicosanoids. The validated method is now employed in studies undertaken to better understand the mechanism of action and pharmacokinetics/pharmacodynamics of eicosanoids after administration of glucocorticoids to horses. This method is reliably reproducible. PMID:21290445

  4. Algorithms for Peptide Mass Spectrometry

    E-print Network

    Spang, Rainer

    ) then continue box else open new box surrounding the isotopic peaks. fi done #12;Wavelet-based pattern detection + - - = transformed signal signal mother wavelet #12;Wavelet-based pattern detection non-peptidic compound peptide with charge 3 noise peaks Scoring of intervals in wavelet transform based on mean intensity and (local

  5. Accelerator mass spectrometry at LLNL: Plans for the near-term future

    SciTech Connect

    McAninch, J.E.; Roberts, M.L.; Caffee, M.W.; Hainsworth, C.L. [Lawrence Livermore National Lab., CA (United States)] [and others

    1996-10-01

    The Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory currently performs routine measurements of most of the usual AMS isotopes at naturally occurring levels. We believe that planned upgrades of our facility and advances in detection techniques will allow us to extend AMS to other long-lived isotopes throughout the periodic table. We will summarize our current capabilities and discuss our plans for developing new isotopes, with examples and their intended applications in safeguards and security.

  6. Current Status and Advances in Quantitative Proteomic Mass Spectrometry

    PubMed Central

    Wasinger, Valerie C.; Zeng, Ming; Yau, Yunki

    2013-01-01

    The accurate quantitation of proteins and peptides in complex biological systems is one of the most challenging areas of proteomics. Mass spectrometry-based approaches have forged significant in-roads allowing accurate and sensitive quantitation and the ability to multiplex vastly complex samples through the application of robust bioinformatic tools. These relative and absolute quantitative measures using label-free, tags, or stable isotope labelling have their own strengths and limitations. The continuous development of these methods is vital for increasing reproducibility in the rapidly expanding application of quantitative proteomics in biomarker discovery and validation. This paper provides a critical overview of the primary mass spectrometry-based quantitative approaches and the current status of quantitative proteomics in biomedical research. PMID:23533757

  7. Measurement of 151Sm with the HI13 accelerator mass spectrometry system

    Microsoft Academic Search

    Xinyi Yin; Ming He; Kejun Dong; Shaoyong Wu; Jinsong Zhang; Jilong Zhang; Tongxin Wang; Anzhi Cui; Yinggen Ouyang; Zhiyong Zhang; Jian Yuan; Shan Jiang

    2010-01-01

    151Sm is an interesting nuclide in many research fields. Measurement methods of the long-lived 151Sm with accelerator mass spectrometry have been developed at China Institute of Atomic Energy. The chemical form of samples was Sm2O3 and the extracted ion was SmO?. To date, the sensitivity, that is, the isotopic ratio, of 151Sm measured using accelerator mass spectrometry is about 10?8.

  8. MALDI Imaging Mass Spectrometry – Painting Molecular Pictures

    PubMed Central

    Schwamborn, Kristina; Caprioli, Richard M.

    2010-01-01

    MALDI Imaging Mass Spectrometry is a molecular analytical technology capable of simultaneously measuring multiple analytes directly from intact tissue sections. Histological features within the sample can be correlated with molecular species without the need for target-specific reagents such as antibodies. Several studies have demonstrated the strength of the technology for uncovering new markers that correlate with disease severity as well as prognosis and therapeutic response. This review describes technological aspects of imaging mass spectrometry together with applications in cancer research. PMID:20965799

  9. Advanced Mass Spectrometers for Hydrogen Isotope Analyses

    SciTech Connect

    Chastagner, P.

    2001-08-01

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

  10. Advanced Mass Spectrometers for Hydrogen Isotope Analyses

    Microsoft Academic Search

    Chastagner

    2001-01-01

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

  11. Advantages of N2 and Ar as reaction gases for measurement of multiple Se isotopes using inductively coupled plasma-mass spectrometry with a collision/reaction cell

    NASA Astrophysics Data System (ADS)

    Olesik, John W.; Gray, Patrick J.

    2014-10-01

    Thirteen collision/reaction gases (CH4, O2, H2, CH3F, C2H6, N2O, NH3, SF6, Xe, Ne, N2, CO and Ar) were investigated to reduce the ArAr+, Ar2H+, Ar2H2+, SeH+, BrH+ and ArCl+ overlaps on Se+ isotopes. N2 and Ar had particular advantages for the measurement of multiple Se isotopes compared to the other gases. Experiments using CH4 and CD4 determined that H-atom transfer from CH4 to Se+ resulted in the formation of SeH+.

  12. Introductory Tutorial to Mass Spectrometry

    NSDL National Science Digital Library

    Breci, L.

    An introduction to GC-MS for beginning students in analytical or organic chemistry lab. The site includes discussion of quadrupole mass analyzers, ionization, detection, and interpretation of mass spectra. One of the best features of this site is a series of on-line quizzes on the interpretation of EI mass spectra that includes hints as well as explanations of why the answers are right or wrong.

  13. Determination of 1-methyl-1H-1,2,4-triazole in soils contaminated by rocket fuel using solid-phase microextraction, isotope dilution and gas chromatography-mass spectrometry.

    PubMed

    Yegemova, Saltanat; Bakaikina, Nadezhda V; Kenessov, Bulat; Koziel, Jacek A; Nauryzbayev, Mikhail

    2015-10-01

    Environmental monitoring of Central Kazakhstan territories where heavy space booster rockets land requires fast, efficient, and inexpensive analytical methods. The goal of this study was to develop a method for quantitation of the most stable transformation product of rocket fuel, i.e., highly toxic unsymmetrical dimethylhydrazine - 1-methyl-1H-1,2,4-triazole (MTA) in soils using solid-phase microextraction (SPME) in combination with gas chromatography-mass spectrometry. Quantitation of organic compounds in soil samples by SPME is complicated by a matrix effect. Thus, an isotope dilution method was chosen using deuterated analyte (1-(trideuteromethyl)-1H-1,2,4-triazole; MTA-d3) for matrix effect control. The work included study of the matrix effect, optimization of a sample equilibration stage (time and temperature) after spiking MTA-d3 and validation of the developed method. Soils of different type and water content showed an order of magnitude difference in SPME effectiveness of the analyte. Isotope dilution minimized matrix effects. However, proper equilibration of MTA-d3 in soil was required. Complete MTA-d3 equilibration at temperatures below 40°C was not observed. Increase of temperature to 60°C and 80°C enhanced equilibration reaching theoretical MTA/MTA-d3 response ratios after 13 and 3h, respectively. Recoveries of MTA depended on concentrations of spiked MTA-d3 during method validation. Lowest spiked MTA-d3 concentration (0.24mgkg(-1)) provided best MTA recoveries (91-121%). Addition of excess water to soil sample prior to SPME increased equilibration rate, but it also decreased method sensitivity. Method detection limit depended on soil type, water content, and was always below 1mgkg(-1). The newly developed method is fully automated, and requires much lower time, labor and financial resources compared to known methods. PMID:26078153

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

    PubMed

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

    2013-10-01

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

  15. Automated on-line column-switching high performance liquid chromatography isotope dilution tandem mass spectrometry method for the quantification of bisphenol A, bisphenol F, bisphenol S, and 11 other phenols in urine.

    PubMed

    Zhou, Xiaoliu; Kramer, Joshua P; Calafat, Antonia M; Ye, Xiaoyun

    2014-01-01

    Human exposure to bisphenol A (BPA) is widespread. However, in recent years, bisphenol analogs such as bisphenol S (BPS) and bisphenol F (BPF) are replacing BPA in the production of some consumer products. Because human exposure to these alternative bisphenols may occur, biomonitoring of these bisphenol analogs is warranted. In the present study, we developed and validated a sensitive and selective method that uses on-line solid phase extraction coupled to high performance liquid chromatography-isotope dilution tandem mass spectrometry with peak focusing to measure BPA, BPF, BPS, and 11 other environmental phenols in urine. The method required a small amount of sample (100?L) and minimal sample pretreatment. The limits of detection were 0.03ng/mL (BPS), 0.06ng/mL (BPF), 0.10ng/mL (BPA), and ranged from 0.1ng/mL to 1.0ng/mL for the other 11 phenols. In 100 urine samples collected in 2009-2012 from a convenience group of anonymous adults in the United States, of the three bisphenols, we detected BPA at the highest frequency and median concentrations (95%, 0.72ng/mL), followed by BPS (78%, 0.13ng/mL) and BPF (55%, 0.08ng/mL). This sensitive, rugged, and labor and cost-effective method could be used for the analysis of large number of samples for epidemiologic studies. PMID:24316527

  16. Mass spectrometry–based proteomics turns quantitative

    Microsoft Academic Search

    Shao-En Ong; Matthias Mann

    2005-01-01

    The field of proteomics is built on technologies to analyze large numbers of proteins—ideally the entire proteome—in the same experiment. Mass spectrometry (MS) has been successfully used to characterize proteins in complex mixtures, but results so far have largely been qualitative. Two recently developed methodologies offer the opportunity to obtain quantitative proteomic information. Comparing the signals from the same peptide

  17. ANALYSIS BY ION TRAP MASS SPECTROMETRY

    Microsoft Academic Search

    David G. Kakhniashvili; Lee A. Bulla; Steven R. Goodman

    This report describes an analysis of the red blood cell proteome by ion trap tandem mass spectrometry in line with liquid chromatography. Mature red blood cells lack all internal cell structures and consist of cytoplasm within a plasma membrane envelope. To maximize outcome, total red blood cell protein was divided into two fractions of membrane-associated proteins and cytoplasmic pro- teins.

  18. MALDI Imaging Mass Spectrometry – Painting Molecular Pictures

    Microsoft Academic Search

    Kristina Schwamborn; Richard M. Caprioli

    2010-01-01

    MALDI Imaging Mass Spectrometry is a molecular analytical technology capable of simultaneously measuring multiple analytes directly from intact tissue sections. Histological features within the sample can be correlated with molecular species without the need for target-specific reagents such as antibodies. Several studies have demonstrated the strength of the technology for uncovering new markers that correlate with disease severity as well

  19. Targeted Quantitation of Proteins by Mass Spectrometry

    PubMed Central

    2013-01-01

    Quantitative measurement of proteins is one of the most fundamental analytical tasks in a biochemistry laboratory, but widely used immunochemical methods often have limited specificity and high measurement variation. In this review, we discuss applications of multiple-reaction monitoring (MRM) mass spectrometry, which allows sensitive, precise quantitative analyses of peptides and the proteins from which they are derived. Systematic development of MRM assays is permitted by databases of peptide mass spectra and sequences, software tools for analysis design and data analysis, and rapid evolution of tandem mass spectrometer technology. Key advantages of MRM assays are the ability to target specific peptide sequences, including variants and modified forms, and the capacity for multiplexing that allows analysis of dozens to hundreds of peptides. Different quantitative standardization methods provide options that balance precision, sensitivity, and assay cost. Targeted protein quantitation by MRM and related mass spectrometry methods can advance biochemistry by transforming approaches to protein measurement. PMID:23517332

  20. Accelerator mass spectrometry for measurement of long-lived radioisotopes.

    PubMed

    Elmore, D; Phillips, F M

    1987-05-01

    Particle accelerators, such as those built for research in nuclear physics, can also be used together with magnetic and electrostatic mass analyzers to measure rare isotopes at very low abundance ratios. All molecular ions can be eliminated when accelerated to energies of millions of electron volts. Some atomic isobars can be eliminated with the use of negative ions; others can be separated at high energies by measuring their rate of energy loss in a detector. The long-lived radioisotopes (10)Be, (14)C,(26)A1, 36Cl, and (129)1 can now be measured in small natural samples having isotopic abundances in the range 10(-12) to 10(- 5) and as few as 10(5) atoms. In the past few years, research applications of accelerator mass spectrometry have been concentrated in the earth sciences (climatology, cosmochemistry, environmental chemistry, geochronology, glaciology, hydrology, igneous petrogenesis, minerals exploration, sedimentology, and volcanology), in anthropology and archeology (radiocarbon dating), and in physics (searches for exotic particles and measurement of halflives). In addition, accelerator mass spectrometry may become an important tool for the materials and biological sciences. PMID:17740475

  1. Peak capacity of ion mobility mass spectrometry

    Microsoft Academic Search

    Brandon T. Ruotolo; Kent J. Gillig; Earle G. Stone; David H. Russell

    2002-01-01

    Advances in the field of proteomics depend upon the development of high-throughput separation methods. Ion mobility-mass spectrometry is a fast separation method (separations on the millisecond time-scale), which has potential for peptide complex mixture analysis. Possible disadvantages of this technique center around the lack of orthogonality between separation based on ion mobility and separation based on mass. In order to

  2. MATRIX-ASSISTED LASER DESORPTION MASS SPECTROMETRY

    Microsoft Academic Search

    Michael J. Stump; Richard C. Fleming; Wei-Hong Gong; Arwah J. Jaber; Jeffrey J. Jones; Charles W. Surber; Charles L. Wilkins

    2002-01-01

    Matrix-assisted laser desorption\\/ionization (MALDI) mass spectrometry is a technique that has attracted widespread interest since its introduction in 1988. It is primarily implemented using time-of-flight or trapped ion mass analyzers and greatly facilitates determination of molecular weights for biomolecules, polymers, and natural products. Numerous publications on these and related applications have appeared during the past ten years. The present brief

  3. Determination of Sr isotopes in calcium phosphates using laser ablation inductively coupled plasma mass spectrometry and their application to archaeological tooth enamel

    Microsoft Academic Search

    M. S. A. Horstwood; J. A. Evans; J. Montgomery

    2008-01-01

    The determination of accurate Sr isotope ratios in calcium phosphate matrices by laser ablation multi-collector ICP-MS is demonstrated as possible even with low Sr concentration archaeological material. Multiple on-line interference correction routines for doubly-charged REE, Ca dimers and Rb with additional calibration against TIMS-characterised materials are required to achieve this. The calibration strategy proposed uses both inorganic and biogenic apatite

  4. Analysis of trace metals (Cu, Cd, Pb, and Fe) in seawater using single batch nitrilotriacetate resin extraction and isotope dilution inductively coupled plasma mass spectrometry

    Microsoft Academic Search

    Jong-Mi Lee; Edward A. Boyle; Yolanda Echegoyen-Sanz; Jessica N. Fitzsimmons; Ruifeng Zhang; Richard A. Kayser

    2011-01-01

    A simple and accurate low-blank method has been developed for the analysis of total dissolved copper, cadmium, lead, and iron in a small volume (1.3–1.5mL per element) of seawater. Pre-concentration and salt-separation of a stable isotope spiked sample are achieved by single batch extraction onto nitrilotriacetate (NTA)-type Superflow® chelating resin beads (100–2400 beads depending on the element). Metals are released

  5. Isotopic Effect on Ion Mobility and Separation of Isotopomers by High-Field Ion Mobility Spectrometry

    SciTech Connect

    Shvartsburg, Alexandre A.; Clemmer, David E.; Smith, Richard D.

    2010-10-01

    Since early 1900-s, when vacuum techniques and ion detectors first enabled investigations of gas-phase ions, two approaches to their separation and characterization have emerged - mass spectrometry (MS) and ion mobility spectrometry (IMS).1,2 Though both exploit that distinct charged species move in electric fields differently, MS is performed in vacuum and is based only on the ion mass/charge (m/q) ratio while IMS involves sufficiently dense buffer gases and relies on ion transport properties. The first major discovery enabled by MS was the existence of isotopes by Thomson and Aston,3 and isotopic analyses have since been integral to MS. In particular, the preparative separation of U isotopes using Lawrence’s Calutron was the first industrial application of MS,4 and isotopic labeling is key to MS quantification methods. With IMS, the issue of isotopes was largely ignored as the resolving power (R) was generally too low for their separation. Here, we demonstrate that recently developed high-resolution differential IMS can separate isotopic molecular ions, including nominal isobars with different isotopic content and isotopomers. This capability may enable a new method for isotope separation in a small-scale format at ambient pressure and aid localization of labeled sites in various molecules. Perhaps most importantly, the isotopic shifts depend on the labeled atom position and thus may contain the kind of detailed structural information that is available in solution or solid state using tools such as NMR but has not generally been obtainable for gas-phase ions.

  6. High-precision analysis on annual variations of heavy metals, lead isotopes and rare earth elements in mangrove tree rings by inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Yu, Ke-Fu; Kamber, Balz S.; Lawrence, Michael G.; Greig, Alan; Zhao, Jian-Xin

    2007-02-01

    Annual variations from 1982 to 1999 of a wide range of trace elements and reconnaissance Pb isotopes ( 207Pb/ 206Pb and 208Pb/ 206Pb) were analyzed by solution ICP-MS on digested ash from mangrove Rhizophora apiculata, obtained from Leizhou Peninsula, along northern coast of South China Sea. The concentrations of the majority of elements show a weak declining trend with growth from 1982 to 1999, punctuated by several high concentration spikes. The declining trends are positively correlated with ring width and negatively correlated with inferred water-use efficiency, suggesting a physiological control over metal-uptake in this species. The episodic metal concentration-peaks cannot be interpreted with lateral movement or growth activities and appear to be related to environmental pollution events. Pb isotope ratios for most samples plot along the 'Chinese Pb line' and clearly document the importance of gasoline Pb as a source of contaminant. Shale-normalised REE + Y patterns are relatively flat and consistent across the growth period, with all patterns showing a positive Ce anomaly and elevated Y/Ho ratio. The positive Ce anomaly is observed regardless of the choice of normaliser, in contrast to previously reported REE patterns for terrestrial and marine plants. This pilot study of trace element, REE + Y and Pb isotope distribution in mangrove tree rings indicates the potential use of mangroves as monitors of historical environmental change.

  7. Spatial Querying of Imaging Mass Spectrometry Data for the Biochemical Characterization of Anatomical Regions in Tissue

    E-print Network

    Imaging Mass Spectrometry MALDI-based imaging mass spectrometry [13] uses the molecular specificitySpatial Querying of Imaging Mass Spectrometry Data for the Biochemical Characterization Leuven, Belgium. Abstract. Imaging mass spectrometry or mass spectral imaging (MSI) is a technology

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

    NASA Astrophysics Data System (ADS)

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

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

  9. Advances in structure elucidation of small molecules using mass spectrometry

    PubMed Central

    Fiehn, Oliver

    2010-01-01

    The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules. Electronic supplementary material The online version of this article (doi:10.1007/s12566-010-0015-9) contains supplementary material, which is available to authorized users. PMID:21289855

  10. Linking Mass Spectrometry with Toxicology for Emerging Water Contaminants

    EPA Science Inventory

    This overview presentation will discuss the benefits of combining mass spectrometry with toxicology. These benefits will be described for 3 main areas: (1) Toxicity assays used to test new environmental contaminants previously identified using mass spectrometry, such that furth...

  11. STANDARDISATION & GUIDELINES Recommendations for mass spectrometry data quality

    E-print Network

    STANDARDISATION & GUIDELINES Recommendations for mass spectrometry data quality metrics for open) an evolving list of comprehensive quality metrics and (ii) standards accompanied by software analytics for open access proteomic data, particularly concerning tandem mass spectrometry data used to identify

  12. Trends in biochemical and biomedical applications of mass spectrometry

    NASA Astrophysics Data System (ADS)

    Gelpi, Emilio

    1992-09-01

    This review attempts an in-depth evaluation of progress and achievements made since the last 11th International Mass Spectrometry Conference in the application of mass spectrometric techniques to biochemistry and biomedicine. For this purpose, scientific contributions in this field at major international meetings have been monitored, together with an extensive appraisal of literature data covering the period from 1988 to 1991. A bibliometric evaluation of the MEDLINE database for this period provides a total of almost 4000 entries for mass spectrometry. This allows a detailed study of literature and geographical sources of the most frequent applications, of disciplines where mass spectrometry is most active and of types of sample and instrumentation most commonly used. In this regard major efforts according to number of publications (over 100 literature reports) are concentrated in countries like Canada, France, Germany, Italy, Japan, Sweden, UK and the USA. Also, most of the work using mass spectrometry in biochemistry and biomedicine is centred on studies on biotransformation, metabolism, pharmacology, pharmacokinetics and toxicology, which have been carried out on samples of blood, urine, plasma and tissue, by order of frequency of use. Human and animal studies appear to be evenly distributed in terms of the number of reports published in the literature in which the authors make use of experimental animals or describe work on human samples. Along these lines, special attention is given to the real usefulness of mass spectrometry (MS) technology in routine medical practice. Thus the review concentrates on evaluating the progress made in disease diagnosis and overall patient care. As regards prevailing techniques, GCMS continues to be the mainstay of the state of the art methods for multicomponent analysis, stable isotope tracer studies and metabolic profiling, while HPLC--MS and tandem MS are becoming increasingly important in biomedical research. However, despite the relatively large number of mass spectrometry reports in the biomedical sciences very few true routine applications are described, and recent technological innovations in instrumentation such as FABMS, electrospray, plasma or laser desorption have contributed relatively much more to structural biology, especially in biopolymer studies of macromolecules rather than to real life biomedical applications on patients and clinical problems.

  13. Analysis of trace metals (Cu, Cd, Pb, and Fe) in seawater using single batch nitrilotriacetate resin extraction and isotope dilution inductively coupled plasma mass spectrometry.

    PubMed

    Lee, Jong-Mi; Boyle, Edward A; Echegoyen-Sanz, Yolanda; Fitzsimmons, Jessica N; Zhang, Ruifeng; Kayser, Richard A

    2011-02-01

    A simple and accurate low-blank method has been developed for the analysis of total dissolved copper, cadmium, lead, and iron in a small volume (1.3-1.5 mL per element) of seawater. Pre-concentration and salt-separation of a stable isotope spiked sample are achieved by single batch extraction onto nitrilotriacetate (NTA)-type Superflow(®) chelating resin beads (100-2400 beads depending on the element). Metals are released into 0.1-0.5 M HNO(3), and trace metal isotope ratios are determined by ICPMS. The benefit of this method compared to our previous Mg(OH)(2) coprecipitation method is that the final matrix is very dilute so cone-clogging and matrix sensitivity suppression are minimal, while still retaining the high accuracy of the isotope dilution technique. Recovery efficiencies are sensitive to sample pH, number of resin beads added, and the length of time allowed for sample-resin binding and elution; these factors are optimized for each element to yield the highest recovery. The method has a low procedural blank and high sensitivity sufficient for the analysis of pM-nM open-ocean trace metal concentrations. Application of this method to samples from the Bermuda Atlantic Time-Series Study station provides oceanographically consistent Cu, Cd, Pb, and Fe profiles that are in good agreement with other reliable data for this site. In addition, the method can potentially be modified for the simultaneous analysis of multiple elements, which will be beneficial for the analysis of large number of samples. PMID:21237313

  14. Analysis of urinary 8-isoprostane as an oxidative stress biomarker by stable isotope dilution using automated online in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry.

    PubMed

    Mizuno, Keisuke; Kataoka, Hiroyuki

    2015-08-10

    We have developed a simple and sensitive method for the determination of the oxidative stress biomarker 8-isoprostane (8-IP) in human urine by automated online in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a Zorbax Eclipse XDB-8 column and 0.1% formic acid/methanol (25/75, v/v) as a mobile phase. Electrospray MS/MS for 8-IP was performed on an API 4000 triple quadruple mass spectrometer in negative ion mode. The optimum in-tube SPME conditions were 20 draw/eject cycles with a sample size of 40?L using a Carboxen 1006 PLOT capillary column for the extraction. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Total analysis time of this method including online extraction and analysis was about 30min for each sample. The in-tube SPME LC-MS/MS method showed good linearity in the concentration range of 20-1000pg/mL with a correlation coefficient r=0.9999 for 8-IP using a stable isotope-labeled internal standard, 8-IP-d4. The detection limit of 8-IP was 3.3pg/mL and the proposed method showed 42-fold higher sensitivity than the direct injection method. The intra-day and inter-day precisions (relative standard deviations) were below 5.0% and 8.5% (n=5), respectively. This method was applied successfully to the analysis of urine samples without pretreatment or interference peaks. The recovery rates of 8-IP spiked into urine samples were above 92%. This method is useful for assessing the effects of oxidative stress and antioxidant intake. PMID:25956225

  15. Accelerating Mass Spectrometry-Based Protein Identification , Leihao Xia 1

    E-print Network

    Chu, Xiaowen

    Accelerating Mass Spectrometry-Based Protein Identification Using GPUs You Li 1 , Leihao Xia 1@jdl.ac.cn); XC (chxw@comp.hkbu.edu.hk) Tandem mass spectrometry-based database searching is currently significantly improve the speed of the scoring module in mass spectrometry-based protein identification

  16. Tandem mass spectrometry in the clinical chemistry laboratory

    Microsoft Academic Search

    Kent C. Dooley

    2003-01-01

    Tandem mass spectrometry is becoming an increasingly important analytical technology in the clinical laboratory environment. Applications in toxicology and therapeutic drug monitoring have opened the door for tandem mass spectrometry and now we are seeing a vast array of new applications being developed. It has been the combination of tandem mass spectrometry with sample introduction techniques employing atomospheric pressure ionization

  17. Mass Spectrometry Facility University of Connecticut, BiotechnologyBioservices Center

    E-print Network

    Holsinger, Kent

    Mass Spectrometry Facility University of Connecticut, Biotechnology·Bioservices Center Chemistry) 486-4265 dennis.hill@uconn.edu "The mission of the Mass Spectrometry Facility is to serve.biotech.uconn.edu/msf The Biotechnology·Bioservices Center Welcomes New Mass Spectrometry Facility Scientist Dr. You-Jun Fu. Facility

  18. Mass spectrometry tools for the classification and identification of bacteria

    Microsoft Academic Search

    Magdalena Kliem; Sascha Sauer

    2010-01-01

    Mass spectrometry has become an important analytical tool in biology in the past two decades. In principle, mass spectrometry offers high-throughput, sensitive and specific analysis for many applications in microbiology, including clinical diagnostics and environmental research. Recently, several mass spectrometry methods for the classification and identification of bacteria and other microorganisms, as well as new software analysis tools, have been

  19. Analysis of long-lived isotopes by liquid scintillation spectrometry

    SciTech Connect

    Bowers, D.L.; Greenwood, L.R.

    1987-01-01

    Neutron production cross sections are reported for reactions leading to long-lived isotopes in fusion reactor materials. Pure elements and separated isotopes were irradiated with 14.6 to 14.8 MeV neutron fluences up to 10 Y n/cmS. Undesired activities were chemically separated and the long-lived activities were measured using both liquid scintillation and x-ray spectrometry. Results are presented for the reactions VWFe(n,2n)VVFe (2.73 y), WUNi(n,2n)WTNi (100 y), WTCu(n,P)WTNi, and WNi(n,2n)VZNi (76,000 y).

  20. Initial results of positron ionization mass spectrometry

    NASA Technical Reports Server (NTRS)

    Donohue, D. L.; Hulett, L. D., Jr.; Mcluckey, S. A.; Glish, G. L.; Eckenrode, B. A.

    1990-01-01

    The use of monoenergetic positrons for the ionization of organic molecules in the gas phase is described. The ionic products are analyzed with a time-of-flight mass spectrometer and detected to produce a mass spectrum. The ionization mechanisms which can be studied in this way include positron impact at energies above the ionization limit of the target molecules, positronium formation in the Ore gap energy range, and positron attachment at energies less than 1eV. The technique of positron ionization mass spectrometry (PIMS) may have analytical utility in that chemical selectivity is observed for one or more of these processes.

  1. Cometary and interstellar dust grains - Analysis by ion microprobe mass spectrometry and other techniques

    NASA Astrophysics Data System (ADS)

    Zinner, E.

    1991-04-01

    A survey of microanalytical measurements on interplanetary dust particles (IDPs) and interstellar dust grains from primitive meteorites is presented. Ion-microprobe mass spectrometry with its capability to determine isotopic compositions of many elements on a micron spatial scale has played a special role. Examples are measurements of H, N, and O isotopes and refractory trace elements in IDPs; C, N, Mg, and Si isotopes in interstellar SiC grains; and C and N isotopes and H, N, Al, and Si concentrations in interstellar graphite grains.

  2. Characterization of protein glycosylation by mass spectrometry.

    PubMed

    Burlingame, A L

    1996-02-01

    Electrospray ionization, a natural interface with microbore and capillary high-pressure liquid chromatography, has become the method of choice for the reliable structural characterization of protein glycosylation by mass spectrometry at the picomole level. Its advantages include inherent sensitivity in the femtomole range, compatibility with collisional activation methods that both permit the detection and monitoring of structurally specific ions and enable the induction of glycopeptide fragmentation that facilitates determination of glycoform sequence and branching. Developments in high-performance electrospray mass spectrometry include sample introduction at nanoliter flow rates, tandem magnetic sector/orthogonal time-of-flight instruments, Fourier transform instruments, and new ion optical strategies, including ion traps. Although a sensitive and important complementary technique, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry suffers from matrix-dependent deposition of excess internal energies, which produce extensive metastable fragmentation and (photo)adduct formation. These metastable fragments may be focused into a mass spectrum by employing an ion mirror (reflectron) in time-of-flight instrumentation. In favorable cases, structural information may be obtained. PMID:8742373

  3. Mass spectrometry imaging under ambient conditions.

    PubMed

    Wu, Chunping; Dill, Allison L; Eberlin, Livia S; Cooks, R Graham; Ifa, Demian R

    2013-01-01

    Mass spectrometry imaging (MSI) has emerged as an important tool in the last decade and it is beginning to show potential to provide new information in many fields owing to its unique ability to acquire molecularly specific images and to provide multiplexed information, without the need for labeling or staining. In MSI, the chemical identity of molecules present on a surface is investigated as a function of spatial distribution. In addition to now standard methods involving MSI in vacuum, recently developed ambient ionization techniques allow MSI to be performed under atmospheric pressure on untreated samples outside the mass spectrometer. Here we review recent developments and applications of MSI emphasizing the ambient ionization techniques of desorption electrospray ionization (DESI), laser ablation electrospray ionization (LAESI), probe electrospray ionization (PESI), desorption atmospheric pressure photoionization (DAPPI), femtosecond laser desorption ionization (fs-LDI), laser electrospray mass spectrometry (LEMS), infrared laser ablation metastable-induced chemical ionization (IR-LAMICI), liquid microjunction surface sampling probe mass spectrometry (LMJ-SSP MS), nanospray desorption electrospray ionization (nano-DESI), and plasma sources such as the low temperature plasma (LTP) probe and laser ablation coupled to flowing atmospheric-pressure afterglow (LA-FAPA). Included are discussions of some of the features of ambient MSI for example the ability to implement chemical reactions with the goal of providing high abundance ions characteristic of specific compounds of interest and the use of tandem mass spectrometry to either map the distribution of targeted molecules with high specificity or to provide additional MS information on the structural identification of compounds. We also describe the role of bioinformatics in acquiring and interpreting the chemical and spatial information obtained through MSI, especially in biological applications for tissue diagnostic purposes. Finally, we discuss the challenges in ambient MSI and include perspectives on the future of the field. PMID:22996621

  4. Mass Spectrometry Imaging under Ambient Conditions

    PubMed Central

    Wu, Chunping; Dill, Allison L.; Eberlin, Livia S.; Cooks, R. Graham; Ifa, Demian R.

    2012-01-01

    Mass spectrometry imaging (MSI) has emerged as an important tool in the last decade and it is beginning to show potential to provide new information in many fields owing to its unique ability to acquire molecularly specific images and to provide multiplexed information, without the need for labeling or staining. In MSI, the chemical identity of molecules present on a surface is investigated as a function of spatial distribution. In addition to now standard methods involving MSI in vacuum, recently developed ambient ionization techniques allow MSI to be performed under atmospheric pressure on untreated samples outside the mass spectrometer. Here we review recent developments and applications of MSI emphasizing the ambient ionization techniques of desorption electrospray ionization (DESI), laser ablation electrospray ionization (LAESI), probe electrospray ionization (PESI), desorption atmospheric pressure photoionization (DAPPI), femtosecond laser desorption ionization (fs-LDI), laser electrospray mass spectrometry (LEMS), infrared laser ablation metastable-induced chemical ionization (IR-LAMICI), liquid microjunction surface sampling probe mass spectrometry (LMJ-SSP MS), nanospray desorption electrospray ionization (nano-DESI), and plasma sources such as the low temperature plasma (LTP) probe and laser ablation coupled to flowing atmospheric-pressure afterglow (LA-FAPA). Included are discussions of some of the features of ambient MSI including the ability to implement chemical reactions with the goal of providing high abundance ions characteristic of specific compounds of interest and the use of tandem mass spectrometry to either map the distribution of targeted molecules with high specificity or to provide additional MS information in the structural identification of compounds. We also describe the role of bioinformatics in acquiring and interpreting the chemical and spatial information obtained through MSI, especially in biological applications for tissue diagnostic purposes. Finally, we discuss the challenges in ambient MSI and include perspectives on the future of the field. PMID:22996621

  5. Matrix effects in plasma desorption mass spectrometry

    Microsoft Academic Search

    Stephane Bouchonnet; Yannik Hoppilliard; Christine Mauriac

    1993-01-01

    In Plasma Desorption (PD) Mass Spectrometry, valine\\/matrix mixtures have been studied in order to specify the influence of a matrix during the desorption-ionization (DI) of volume. The different matrices used were carboxylic acids (barbituric acid, 2-chloronicotinic acid, 3-chloropropionic acid, cysteine, pentafluorobenzoic acid, picric acid, sinapinic acid) and CsI, an inorganic salt. Three effects are proposed to explain the influence of

  6. Monolithic multinozzle emitters for nanoelectrospray mass spectrometry

    DOEpatents

    Wang, Daojing (Daly City, CA); Yang, Peidong (Kensington, CA); Kim, Woong (Seoul, KR); Fan, Rong (Pasadena, CA)

    2011-09-20

    Novel and significantly simplified procedures for fabrication of fully integrated nanoelectrospray emitters have been described. For nanofabricated monolithic multinozzle emitters (NM.sup.2 emitters), a bottom up approach using silicon nanowires on a silicon sliver is used. For microfabricated monolithic multinozzle emitters (M.sup.3 emitters), a top down approach using MEMS techniques on silicon wafers is used. The emitters have performance comparable to that of commercially-available silica capillary emitters for nanoelectrospray mass spectrometry.

  7. Miniaturization of Electrospray Ionization Mass Spectrometry

    Microsoft Academic Search

    Troy D. Wood; Marie A. Moy; Anthony R. Dolan; Paul M. Bigwarfe Jr; Thomas P. White; Douglas R. Smith; Daniel J. Higbee

    2003-01-01

    The development of electrospray ionization (ESI) has proved an enormous breakthrough in structural biology because it provides a means for transferring large biological molecules into the gas-phase as intact charged ions. In the post-genomics era, increased attention has been focused on mass spectrometry techniques capable of providing structural information for biological molecules—especially proteins—with minimal sample consumption. Miniaturized ESI, known as

  8. Disease Classification from Capillary Electrophoresis: Mass Spectrometry

    Microsoft Academic Search

    Simon Rogers; Mark Girolami; Ronald Krebs; Harald Mischak

    2005-01-01

    \\u000a We investigate the possibility of using pattern recognition techniques to classify various disease types using data produced\\u000a by a new form of rapid Mass Spectrometry. The data format has several advantages over other high-throughput technologies and\\u000a as such could become a useful diagnostic tool. We investigate the binary and multi-class performances obtained using standard\\u000a classifiers as the number of features

  9. Electrospray Ionization Mass Spectrometry of Tetrodotoxin and Its Analogs: Liquid Chromatography\\/Mass Spectrometry, Tandem Mass Spectrometry, and Liquid Chromatography\\/Tandem Mass Spectrometry

    Microsoft Academic Search

    Yuki Shoji; Mari Yotsu-Yamashita; Teruo Miyazawa; Takeshi Yasumoto

    2001-01-01

    Tetrodotoxin (TTX), a powerful sodium channel blocker, usually exists as a mixture of its analogs (TTXs) in natural sources. Due to the structural variation, some analogs are difficult to detect using the postcolumn liquid chromatography-fluorescent detection (LC-FLD) system. Liquid chromatography\\/electrospray ionization mass spectrometry (LC\\/ESI-MS) analysis of TTXs can be achieved by a combination of chromatography on a reversed-phase column with

  10. Innovative method for determination of 19 polycyclic aromatic hydrocarbons in food and oil samples using gas chromatography coupled to tandem mass spectrometry based on an isotope dilution approach.

    PubMed

    Veyrand, Bruno; Brosseaud, Aline; Sarcher, Ludovic; Varlet, Vincent; Monteau, Fabrice; Marchand, Philippe; Andre, François; Le Bizec, Bruno

    2007-05-18

    An efficient and selective analytical method for the determination and the quantification of 19 polycyclic aromatic hydrocarbons (PAHs) in food and oil has been developed. This method includes the monitoring of 15 PAHs stated as a priority by the EU in their 2005/108 recommendation. The samples were extracted according to a selective extraction step using pressurized liquid extraction followed by a purification with polystyrene-divinylbenzene SPE. Identification and quantification were performed using GC-MS/MS, with an isotope dilution approach using (13)C-labelled PAHs. The novel combination of selective extraction followed by purification provides highly purified analytes combined to a fast and automated method. The advantages of GC-MS/MS as compared to other detection methods are tremendous in terms of sensitivity, selectivity and interpretation facilities. Limits of detection varied between 0.008 and 0.15 microg kg(-1), limits of quantification between 0.025 and 0.915 microg kg(-1) for PAHs in food. The calibration curves showed a good linearity for all PAHs (R(2)>0.99) and precision and recovery were fit for purpose. Trueness of the method was carried out using the US National Institute of Standards and Technology SRM 2977 reference material. PMID:17395191

  11. Gas chromatography-combustion-mass spectrometry with postcolumn isotope dilution for compound-independent quantification: its potential to assess HS-SPME procedures.

    PubMed

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

    2010-08-15

    A quadrupole GC-MS instrument with an electron ionization (EI) source has been modified to enable application of postcolumn isotope dilution analysis for the standardless quantification of organic compounds injected in the gas chromatograph. Instrumental modifications included the quantitative conversion of the separated compounds into CO(2), using a postcolumn combustion furnace, and the subsequent mixing of the gas with a constant flow of (13)CO(2) diluted in helium. The online measurement of the (12)CO(2)/(13)CO(2) (44/45) ratio in the EI-MS allowed us to obtain quantitative data without resorting to compound-specific standards. Validation of the procedure involved the analysis of standard solutions containing different families of organic compounds (C(9)-C(20) linear hydrocarbons, BTEX and esters) obtaining satisfactory results in all cases in terms of absolute errors (<6%) and precision (<4% RSD). The developed procedure showed excellent linearity over the range assayed (2 orders of magnitude) and adequate detection limits for carbon containing compounds (0.8 pg C s(-1)). The generic value of this compound-independent calibration approach was assessed by studying the quantitative performance of Head Space-Solid Phase Microextraction (HS-SPME). The proposed compound-independent quantification by EI-MS permits comparison of the performance of different fibers by assessing analyte recoveries with extreme robustness, simplicity, and precision. PMID:20704376

  12. Body fluid identification by mass spectrometry.

    PubMed

    Yang, Heyi; Zhou, Bo; Deng, Haiteng; Prinz, Mechthild; Siegel, Donald

    2013-11-01

    Standard methods for body fluid identification typically rely on detection of the functional proteins specific to or enriched in them, such as hemoglobin in blood, alkaline phosphatase and PSA in semen, or ?-amylase in saliva. While these markers can be relatively specific, the multiple methods used to identify them frequently rely on nonspecific chemical, enzymatic, or antibody reactions that usually require the structural integrity of the markers and are not confirmatory because other proteins or substances can also give positive test results. Recent advances in proteomics and mass spectrometry offer the ability to simultaneously detect multiple body fluid protein markers in a single, confirmatory test. Here, multiple markers for blood, saliva, and semen are identified by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Data demonstrate the ability to detect these body fluids at nanoliter to subnanoliter levels and to distinguish mixtures. Protein stability of mock samples assayed after 16 months showed no diminution of signal. Because multiple peptides from multiple protein markers are detected and effectively sequenced by MALDI MS/MS, the assay is confirmatory. As mass spectrometry detects whatever peptides are present in a sample, no a priori knowledge of an unknown stain is necessary to perform the test. PMID:23525663

  13. [Sample preparation and bioanalysis in mass spectrometry].

    PubMed

    Bourgogne, Emmanuel; Wagner, Michel

    2015-01-01

    The quantitative analysis of compounds of clinical interest of low molecular weight (<1000 Da) in biological fluids is currently in most cases performed by liquid chromatography-mass spectrometry (LC-MS). Analysis of these compounds in biological fluids (plasma, urine, saliva, hair...) is a difficult task requiring a sample preparation. Sample preparation is a crucial part of chemical/biological analysis and in a sense is considered the bottleneck of the whole analytical process. The main objectives of sam