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Isotope Ratio Mass Spectrometry (isotope + ratio_mass_spectrometry)

Distribution by Scientific Domains

Chemistry	97%

Selected Abstracts

The application of carbon isotope ratio mass spectrometry to doping control

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2008
Adam T. Cawley
Abstract The administration of synthetic steroid copies is one of the most important issues facing sports. Doping control laboratories accredited by the World Anti-Doping Agency (WADA) require methods of analysis that allow endogenous steroids to be distinguished from their synthetic analogs in urine. The ability to measure isotope distribution at natural abundance with high accuracy and precision has increased the application of Gas Chromatography,Combustion,Isotope Ratio Mass Spectrometry (GC,C,IRMS) to doping control in recent years. GC,C,IRMS is capable of measuring the carbon isotope ratio (,13C) of urinary steroids and confirm their synthetic origin based on the abnormal 13C content. This tutorial describes some of the complexities encountered by obtaining valid ,13C measurements from GC,C,IRMS and the need for careful interpretation of all relevant information concerning an individual's metabolism in order to make an informed decision with respect to a doping violation. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Liquid chromatography combined with mass spectrometry for 13C isotopic analysis in life science research

MASS SPECTROMETRY REVIEWS, Issue 6 2007
Jean-Philippe Godin
Abstract Among the different disciplines covered by mass spectrometry, measurement of 13C/12C isotopic ratio crosses a large section of disciplines from a tool revealing the origin of compounds to more recent approaches such as metabolomics and proteomics. Isotope ratio mass spectrometry (IRMS) and molecular mass spectrometry (MS) are the two most mature techniques for 13C isotopic analysis of compounds, respectively, for high and low-isotopic precision. For the sample introduction, the coupling of gas chromatography (GC) to either IRMS or MS is state of the art technique for targeted isotopic analysis of volatile analytes. However, liquid chromatography (LC) also needs to be considered as a tool for the sample introduction into IRMS or MS for 13C isotopic analyses of non-volatile analytes at natural abundance as well as for 13C-labeled compounds. This review presents the past and the current processes used to perform 13C isotopic analysis in combination with LC. It gives particular attention to the combination of LC with IRMS which started in the 1990's with the moving wire transport, then subsequently moved to the chemical reaction interface (CRI) and was made commercially available in 2004 with the wet chemical oxidation interface (LC-IRMS). The LC-IRMS method development is also discussed in this review, including the possible approaches for increasing selectivity and efficiency, for example, using a 100% aqueous mobile phase for the LC separation. In addition, applications for measuring 13C isotopic enrichments using atmospheric pressure LC-MS instruments with a quadrupole, a time-of-flight, and an ion trap analyzer are also discussed as well as a LC-ICPMS using a prototype instrument with two quadrupoles. © 2007 Wiley Periodicals, Inc., Mass Spec Rev 26:751,774, 2007 [source]

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

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2008
Ana I. Cabañero
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,, 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. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Stable isotope analysis of safety matches using isotope ratio mass spectrometry,a forensic case study,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2005
N. L. Farmer
Isotope ratio mass spectrometry (IRMS) was used to assess what contribution the technique could make towards the comparative analysis of matchstick samples within the ,normal' framework of a forensic investigation. A method was developed to allow the comparison of samples submitted as a result of an investigation, with the added advantage of rapid sample turn-around expected within this field. To the best of our knowledge this is the first time that wooden safety matches have been analysed using IRMS. In this particular case, bulk stable isotope analysis carrried out on a ,like-for-like' basis could demonstrate conclusively that matches seized from a suspect were different from those collected at the scene of crime. The maximum ,13C variability observed within one box was 2.5,, which, in conjunction with the error of measurement, was regarded to yield too wide an error margin as to permit differentiation of matchsticks based on 13C isotopic composition alone given that the ,natural' 13C abundance in wood ranges from ,20 to ,30,. However, from the ,2H values obtained for crime scene matches and seized matches of ,114.5, and ,65,, respectively, it was concluded that the matches seized were distinctly different from those collected at the crime scene. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Technical considerations for RNA-based stable isotope probing: an approach to associating microbial diversity with microbial community function,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2002
Mike Manefield
An ongoing challenge within microbial ecology is the development of methodologies that attribute microbial community functions to microbial diversity. One approach, involving the incorporation of stable isotopes from labelled tracer compounds into biological signature molecules (biomarkers), may overcome this current limitation. To examine the potential of RNA as the biomarker in stable isotope probing we have generated a series of atom % 13C-enriched RNA samples through exploitation of the anabolic abilities of a phenol-degrading environmental isolate. Isotope ratio mass spectrometry was used to determine the atom % 13C of each RNA sample (ca. 1,100%). The corresponding buoyant density (1.755,1.795,g,mL,1) was determined by equilibrium density gradient centrifugation and agarose gel electrophoresis. This empirically defined relationship between the atom % 13C of RNA and its buoyant density suggests ribonucleic acids with atom % 13C enrichments greater than 10% can be isolated by equilibrium density centrifugation. The processing and analysis of isolated RNA by reverse transcription polymerase chain reaction, denaturing gradient gel electrophoresis, cloning and sequencing are discussed. The RNA-based stable isotope probing protocol presented here will find particular utility in assessing the roles of microbial community members in the biodegradation of natural and anthropogenic xenobiotic compounds. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Sulfur isotope analysis of cinnabar from Roman wall paintings by elemental analysis/isotope ratio mass spectrometry , tracking the origin of archaeological red pigments and their authenticity

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2010
Jorge E. Spangenberg
The most valuable pigment of the Roman wall paintings was the red color obtained from powdered cinnabar (Minium Cinnabaris pigment), the red mercury sulfide (HgS), which was brought from mercury (Hg) deposits in the Roman Empire. To address the question of whether sulfur isotope signatures can serve as a rapid method to establish the provenance of the red pigment in Roman frescoes, we have measured the sulfur isotope composition (,34S value in , VCDT) in samples of wall painting from the Roman city Aventicum (Avenches, Vaud, Switzerland) and compared them with values from cinnabar from European mercury deposits (Almadén in Spain, Idria in Slovenia, Monte Amiata in Italy, Moschellandsberg in Germany, and Genepy in France). Our study shows that the ,34S values of cinnabar from the studied Roman wall paintings fall within or near to the composition of Almadén cinnabar; thus, the provenance of the raw material may be deduced. This approach may provide information on provenance and authenticity in archaeological, restoration and forensic studies of Roman and Greek frescoes. Copyright © 2010 John Wiley & Sons, Ltd. [source]

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

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2009
Arndt Schimmelmann
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 , values of these reference materials should bracket the isotopic range of samples with unknown , 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 ,15N, 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,, ,13Cnicotine ,30.05 to +7.72,, ,15Nnicotine ,6.03 to +33.62,; ,15Nacetanilide +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 ,15N 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. Published in 2009 by John Wiley & Sons, Ltd. [source]

Carbon isotope determination for separate components of heterogeneous materials using coupled thermogravimetric analysis/isotope ratio mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2008
David A. C. Manning
A gas-tight thermal analysis system (Netzsch STA 449C Jupiter) has been connected to an isotope ratio mass spectrometer (PDZ Europa 20-20) via an interface containing an oxidizing furnace, water trap, and gas-sampling valve. Using this system, ,13C has been measured for CO2 derived from the thermal decomposition of carbonate and oxalate minerals and organic materials at temperatures that correspond to different decomposition events. There is close agreement between measured and published ,13C values for carbonate and oxalate minerals, which have simple decarbonation reactions on heating. Cellulose and lignin-rich materials show much more complex thermal decomposition, reflecting differences in their purity and structure, and measured ,13C values vary with the temperature of gas sampling. Provided that measurements are made at temperatures that correspond to the decomposition of cellulose and lignin (indicated by maximum weight loss), internally consistent data can be obtained. However, measurements for cellulose and lignin are systematically enriched in ,13C (by up to 1.4,) with respect to those reported for reference materials, possibly due to the slower combustion kinetics (compared with EA-IRMS). Thermogravimetric analysis/isotope ratio mass spectrometry (TG-IRMS) is ideal for materials and samples for which it is not possible to use other isotopic measurement techniques, for example because of sample heterogeneity. Copyright © 2008 John Wiley & Sons, Ltd. [source]

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

Treatment methods for the determination of ,2H and ,18O of hair keratin by continuous-flow isotope-ratio mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2005
Gabriel J. Bowen
The structural proteins that comprise ,90% of animal hair have the potential to record environmentally and physiologically determined variation in ,2H and ,18O values of body water. Broad, systematic, geospatial variation in stable hydrogen and oxygen isotopes of environmental water and the capacity for rapid, precise measurement via methods such as high-temperature conversion elemental analyzer/isotope ratio mass spectrometry (TC/EA-IRMS) make these isotope systems particularly well suited for applications requiring the geolocation of hair samples. In order for such applications to be successful, however, methods must exist for the accurate determination of hair ,2H and ,18O values reflecting the primary products of biosynthesis. Here, we present the results of experiments designed to examine two potential inaccuracies affecting ,2H and ,18O measurements of hair: the contribution of non-biologic hydrogen and oxygen to samples in the form of sorbed molecular water, and the exchange of hydroxyl-bound hydrogen between hair keratin and ambient water vapor. We show that rapid sorption of molecular water from the atmosphere can have a substantial effect on measured ,2H and ,18O values of hair (comprising ,7.7% of the measured isotopic signal for H and up to ,10.6% for O), but that this contribution can be effectively removed through vacuum-drying of samples for 6 days. Hydrogen exchange between hair keratin and ambient vapor is also rapid (reaching equilibrium within 3,4 days), with 9,16% of the total hydrogen available for exchange at room temperature. Based on the results of these experiments, we outline a recommended sample treatment procedure for routine measurement of ,2H and ,18O in mammal hair. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Continuous flow isotope ratio mass spectrometry for the measurement of nanomole amounts of 13CO2 by a reverse isotope dilution method

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2002
J. Guitton
Abstract A simple method for the determination of nanomole amounts of 13CO2 generated from an in vitro reaction is reported. The incubation medium contains a known amount of unlabeled sodium bicarbonate and the gaseous 13CO2 enriches the atmosphere upon which a measurement of the isotopic enrichment (13CO2/12CO2) is made corresponding to a reverse isotope dilution. The quantification of the 13CO2 was performed by gas chromatography/isotope ratio mass spectrometry. This assay was validated in terms of linearity, accuracy and precision using three different substrates which produce 13CO2 either by enzymatic reaction [13C]urea, sodium [13C]formate) or by chemical reaction (sodium [13C]bicarbonate). Four calibration curves were tested for each 13C-labeled substrate, allowing the quantification of 13CO2 from 25 pmol to 150 nmol. The dynamics of the assay were obtained as a function of the quantity of unlabeled sodium bicarbonate added to each sample. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Mixed-mode chromatography/isotope ratio mass spectrometry,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2010
James S. O. McCullagh
Liquid chromatography coupled to molecular mass spectrometry (LC/MS) has been a standard technique since the early 1970s but liquid chromatography coupled to high-precision isotope ratio mass spectrometry (LC/IRMS) has only been available commercially since 2004. This development has, for the first time, enabled natural abundance and low enrichment ,13C measurements to be applied to individual analytes in aqueous mixtures creating new opportunities for IRMS applications, particularly for the isotopic study of biological molecules. A growing number of applications have been published in a range of areas including amino acid metabolism, carbohydrates studies, quantification of cellular and plasma metabolites, dietary tracer and nucleic acid studies. There is strong potential to extend these to new compounds and complex matrices but several challenges face the development of LC/IRMS methods. To achieve accurate isotopic measurements, HPLC separations must provide baseline-resolution between analyte peaks; however, the design of current liquid interfaces places severe restrictions on compatible flow rates and in particular mobile phase compositions. These create a significant challenge on which reports associated with LC/IRMS have not previously focused. Accordingly, this paper will address aspects of chromatography in the context of LC/IRMS, in particular focusing on mixed-mode separations and their benefits in light of these restrictions. It aims to provide an overview of mixed-mode stationary phases and of ways to improve high aqueous separations through manipulation of parameters such as column length, temperature and mobile phase pH. The results of several practical experiments are given using proteogenic amino acids and nucleosides both of which are of noted importance in the LC/IRMS literature. This communication aims to demonstrate that mixed-mode stationary phases provide a flexible approach given the constraints of LC/IRMS interface design and acts as a practical guide for the development of new chromatographic methods compatible with LC/IRMS applications. Copyright © 2010 John Wiley & Sons, Ltd. [source]

A versatile method for stable carbon isotope analysis of carbohydrates by high-performance liquid chromatography/isotope ratio mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008
H. T. S. Boschker
We have developed a method to analyze stable carbon isotope (13C/12C) ratios in a variety of carbohydrates using high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS). The chromatography is based on strong anion-exchange columns with low strength NaOH eluents. An eluent concentration of 1,mM resulted in low background signals and good separation of most of the typical plant neutral carbohydrates. We also show that more strongly bound carbohydrates such as acidic carbohydrates can be separated by inclusion of NO as an inorganic pusher ion in the eluent. Analyses of neutral carbohydrate concentrations and their stable carbon isotope ratios are shown for plant materials and marine sediment samples both at natural abundance and for 13C-enriched samples. The main advantage of HPLC/IRMS analysis over traditional gas chromatography based methods is that no derivatization is needed resulting in simple sample treatment and improved accuracy and reproducibility. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A new approach to determine method detection limits for compound-specific isotope analysis of volatile organic compounds

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2006
Maik A. Jochmann
Compound-specific isotope analysis (CSIA) has been established as a useful tool in the field of environmental science, in particular in the assessment of contaminated sites. What limits the use of gas chromatography/isotope ratio mass spectrometry (GC/IRMS) is the low sensitivity of the method compared with GC/MS analysis; however, the development of suitable extraction and enrichment techniques for important groundwater contaminants will extend the fields of application for GC/IRMS. So far, purge and trap (P&T) is the most effective, known preconcentration technique for on-line CSIA with the lowest reported method detection limits (MDLs in the low,µg/L range). With the goal of improving the sensitivity of a fully automated GC/IRMS analysis method, a commercially available P&T system was modified. The method was evaluated for ten monoaromatic compounds (benzene, toluene, para -xylene, ethylbenzene, propylbenzene, isopropylbenzene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, fluorobenzene) and ten halogenated volatile organic compounds (VOCs) (dichloromethane, cis -1,2-dichloroethene, trans -1,2-dichloroethene, carbon tetrachloride, chloroform, 1,2-dichloroethane, trichloroethene, tetrachlorethene, 1,2-dibromoethane, bromoform). The influence of method parameters, including purge gas flow rates and purge times, on ,13C values of target compounds was evaluated. The P&T method showed good reproducibility, high linearity and small isotopic fractionation. MDLs were determined by consecutive calculation of the ,13C mean values. The last concentration for which the ,13C value was within this iterative interval and for which the standard deviation was lower than ±0.5, for triplicate measurements was defined as the MDL. MDLs for monoaromatic compounds between 0.07 and 0.35,µg/L are the lowest values reported so far for continuous-flow isotope ratio measurements using an automated system. MDLs for halogenated hydrocarbons were between 0.76 and 27,µg/L. The environmental applicability of the P&T-GC/IRMS method in the low-µg/L range was demonstrated in a case study on groundwater samples from a former military air field contaminated with VOCs. Copyright © 2006 John Wiley & Sons, Ltd. [source]

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

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2008
Wanglu Jia
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 ,D 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 ,D 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. Copyright © 2008 John Wiley & Sons, Ltd. [source]

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

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2008
Jean-Philippe Godin
Abstract On-line gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) is commonly used to measure isotopic ratios at natural abundance as well as for tracer studies in nutritional and medical research. However, high-precision 13C isotopic enrichment can also be measured by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). Indeed, LC-IRMS can be used, as shown by the new method reported here, to obtain a baseline separation and to measure 13C isotopic enrichment of underivatised amino acids (Asp, Thr,Ser, Glu, Pro, Gly, Ala, Cys and Val). In case of Val, at natural abundance, the SD(,13C) reported with this method was found to be below 1, . Another key feature of the new LC-IRMS method reported in this paper is the comparison of the LC-IRMS approach with the conventional GC-C-IRMS determination. To perform this comparative study, isotopic enrichments were measured from underivatised Val and its N(O, S)-ethoxycarbonyl ethyl ester derivative. Between 0.0 and 1.0 molar percent excess (MPE) (,13C = , 12.3 to 150.8,), the calculated root-mean-square (rms) of SD was 0.38 and 0.46, and the calculated rms of accuracy was 0.023 and 0.005 MPE, respectively, for GC-C-IRMS and LC-IRMS. Both systems measured accurately low isotopic enrichments (0.002 atom percent excess (APE)) with an SD (APE) of 0.0004. To correlate the relative (,13C) and absolute (atom%, APE and MPE) isotopic enrichment of Val measured by the GC-C-IRMS and LC-IRMS devices, mathematical equations showing the slope and intercept of the curves were established and validated with experimental data between 0.0 to 2.3 MPE. Finally, both GC-C-IRMS and LC-IRMS instruments were also used to assess isotopic enrichment of protein-bound 13C,Val in tibial epiphysis in a tracer study performed in rats. Isotopic enrichments measured by LC-IRMS and GC-C-IRMS were not statistically different (p > 0.05). The results of this work indicate that the LC-IRMS was successful for high-precision 13C isotopic measurements in tracer studies giving 13C isotopic enrichment similar to the GC-C-IRMS but without the step of GC derivatisation. Therefore, for clinical studies requiring high-precision isotopic measurement, the LC-IRMS is the method of choice to measure the isotopic ratio. Copyright © 2008 John Wiley & Sons, Ltd. [source]

The application of carbon isotope ratio mass spectrometry to doping control

Continuous flow isotope ratio mass spectrometry for the measurement of nanomole amounts of 13CO2 by a reverse isotope dilution method

Cometary glycine detected in samples returned by Stardust

METEORITICS & PLANETARY SCIENCE, Issue 9 2009
Jamie E. Elsila
Here, we present the stable carbon isotopic ratios of glycine and ,-amino- n -caproic acid (EACA), the two most abundant amino acids identified in Stardust-returned foil samples measured by gas chromatography-mass spectrometry coupled with isotope ratio mass spectrometry. The ,13C value for glycine of +29 ± 6, strongly suggests an extraterrestrial origin for glycine, while the ,13C value for EACA of ,25 ± 2, indicates terrestrial contamination by Nylon-6 during curation. This represents the first detection of a cometary amino acid. [source]

Comparison of secondary ion mass spectrometry and micromilling/continuous flow isotope ratio mass spectrometry techniques used to acquire intra-otolith ,18O values of wild Atlantic salmon (Salmo salar)

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2010
N. N. Hanson
The chemical signals in the sequential layers of fish otoliths have the potential to provide fisheries biologists with temporal and spatial details of migration which are difficult to obtain without expensive tracking methods. Signal resolution depends, however, on the extraction technique used. We compared the use of mechanical micromilling and continuous flow isotope ratio mass spectrometry (CF-IRMS) methods with secondary ion mass spectrometry (SIMS) to obtain ,18O profiles from otoliths of wild Atlantic salmon (Salmo salar) and used these to corroborate the time of freshwater emigration of the juvenile with macroscopic patterns within the otolith. Both techniques showed the transition occurring at the same visible feature on the otolith, allowing future analyses to easily identify the juvenile (freshwater) versus adult (marine) life-stages. However, SIMS showed a rapid and abrupt transition whereas micromilling provided a less distinct signal. The number of samples that could be obtained per unit area sampled using SIMS was 2 to 3 times greater than that when using micromilling/CF-IRMS although the ,18O values and analytical precisions (,0.2,) of the two methods were comparable. In addition, SIMS ,18O results were used to compare otolith aragonite values with predicted values calculated using various isotope fractionation equations. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Discrepancies between isotope ratio infrared spectroscopy and isotope ratio mass spectrometry for the stable isotope analysis of plant and soil waters

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2010
Adam G. West
The use of isotope ratio infrared spectroscopy (IRIS) for the stable hydrogen and oxygen isotope analysis of water is increasing. While IRIS has many advantages over traditional isotope ratio mass spectrometry (IRMS), it may also be prone to errors that do not impact upon IRMS analyses. Of particular concern is the potential for contaminants in the water sample to interfere with the spectroscopy, thus leading to erroneous stable isotope data. Water extracted from plant and soil samples may often contain organic contaminants. The extent to which contaminants may interfere with IRIS and thus impact upon data quality is presently unknown. We tested the performance of IRIS relative to IRMS for water extracted from 11 plant species and one organic soil horizon. IRIS deviated considerably from IRMS for over half of the samples tested, with deviations as large as 46, (,2H) and 15.4, (,18O) being measured. This effect was reduced somewhat by using activated charcoal to remove organics from the water; however, deviations as large as 35, (,2H) and 11.8, (,18O) were still measured for these cleaned samples. Interestingly, the use of activated charcoal to clean water samples had less effect than previously thought for IRMS analyses. Our data show that extreme caution is required when using IRIS to analyse water samples that may contain organic contaminants. We suggest that the development of new cleaning techniques for removing organic contaminants together with instrument-based software to flag potentially problematic samples are necessary to ensure accurate plant and soil water analyses using IRIS. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Mixed-mode chromatography/isotope ratio mass spectrometry,

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

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2009
Roland Molinié
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 (,,15N) 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 ,15N 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 ,15N 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. Copyright © 2009 John Wiley & Sons, Ltd. [source]

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

Effects of active silicon uptake by rice on 29Si fractionation in various plant parts,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009
Jan Reent Köster
Rice (Oryza sativa L.) accumulates large amounts of silicon which improves its growth and health due to enhanced resistance to biotic and abiotic stresses. Silicon uptake and loading to xylem in rice are predominantly active processes performed by transporters encoded by the recently identified genes Lsi1 (Si influx transporter gene) and Lsi2 (Si efflux transporter gene). Silicon deposition in rice during translocation to upper plant tissues is known to discriminate against the heavier isotopes 29Si and 30Si, resulting in isotope fractionation within the plant. We analyzed straw and husk samples of rice mutants defective in Lsi1, Lsi2 or both for silicon content and ,29Si using isotope ratio mass spectrometry (IRMS) and compared these results with those for the corresponding wild-type varieties (WT). The silicon content was higher in husk than in straw. All the mutant rice lines showed clearly lower silicon content than the WT lines (4,23% Si of WT). The ,29Si was lower in straw and husk for the uptake defective mutant (lsi1) than for WT, albeit ,29Si was 0.3, higher in husk than in straw in both lines. The effect of defective efflux (lsi2) differed for straw and husk with higher ,29Si in straw, but lower ,29Si in husk while WT showed similar ,29Si in both fractions. These initial results show the potential of Si isotopes to enlighten the influence of active uptake on translocation and deposition processes in the plant. Copyright © 2009 John Wiley & Sons, Ltd. [source]

,13C, ,15N and ,2H isotope ratio mass spectrometry of ephedrine and pseudoephedrine: application to methylamphetamine profiling

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2009
Michael Collins
Conventional chemical profiling of methylamphetamine has been used for many years to determine the synthetic route employed and where possible to identify the precursor chemicals used. In this study stable isotope ratio analysis was investigated as a means of determining the origin of the methylamphetamine precursors, ephedrine and pseudoephedrine. Ephedrine and pseudoephedrine may be prepared industrially by several routes. Results are presented for the stable isotope ratios of carbon (,13C), nitrogen (,15N) and hydrogen (,2H) measured in methylamphetamine samples synthesized from ephedrine and pseudoephedrine of known provenance. It is clear from the results that measurement of the ,13C, ,15N and ,2H stable isotope ratios by elemental analyzer/thermal conversion isotope ratio mass spectrometry (EA/TC-IRMS) in high-purity methylamphetamine samples will allow determination of the synthetic source of the ephedrine or pseudoephedrine precursor as being either of a natural, semi-synthetic, or fully synthetic origin. Copyright © 2009 Commonwealth of Australia. Published by John Wiley & Sons, Ltd. [source]

Revised ,34S reference values for IAEA sulfur isotope reference materials S-2 and S-3,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2009
Jacqueline L. Mann
Revised ,34S reference values with associated expanded uncertainties (95% confidence interval (C.I.)) are presented for the sulfur isotope reference materials IAEA-S-2 (22.62,±,0.16,) and IAEA-S-3 (,32.49,±,0.16,). These revised values are determined using two relative-difference measurement techniques, gas source isotope ratio mass spectrometry (GIRMS) and double-spike multi-collector thermal ionization mass spectrometry (MC-TIMS). Gas analyses have traditionally been considered the most robust for relative isotopic difference measurements of sulfur. The double-spike MC-TIMS technique provides an independent method for value-assignment validation and produces revised values that are both unbiased and more precise than previous value assignments. Unbiased ,34S values are required to anchor the positive and negative end members of the sulfur delta (,) scale because they are the basis for reporting both ,34S values and the derived mass-independent ,33S and ,36S values. Published in 2009 by John Wiley & Sons, Ltd. [source]

New isotope ratio mass spectrometric method of precise ,37Cl determinations

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2009
Stanislaw Halas
The most precise method of chlorine isotope analysis described to date is based on the isotope ratio mass spectrometry (IRMS) of chlorine quantitatively converted into chloromethane, CH3Cl. This gas can be produced from several chlorine-containing compounds and analyzed by IRMS. However, the mass spectrum of chloromethane is rather complicated and the ratio of the most abundant ions (mass-52/mass-50) differs from the 37Cl/35Cl isotope ratio. This difference becomes significant when the , exceeds 10,. Moreover, the electron ionization source yields approximately 80% of all the ionic species at the useful masses 50 and 52. To overcome these drawbacks, we have devised a negative ion mass spectrometer which retains all the best features of IRMS, including a dual-inlet system with changeover valve, dual collector assembly and CH3Cl gas as analyte. In the modified ion source we have replaced the ionization chamber with an electron beam by a metal tube with a hot metal filament inside it. Within this tube the 35Cl, and 37Cl, ions are produced with an efficiency dependent on the filament material and its temperature. No other ionic species were found in the mass spectrum except of traces at masses 26 and 28 at ppm levels, probably due to the formation of CN, and CO,. The minimal amount of Cl used in our method is of the order of 5,µmol (3,mg AgCl) and the precision is better than 0.005, (1,). Copyright © 2009 John Wiley & Sons, Ltd. [source]

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

Uncertainties in the oxygen isotopic composition of barium sulfate induced by coprecipitation of nitrate

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2008
Greg Michalski
Coprecipitation of nitrate and sulfate by barium has probably resulted in significant error in numerous studies dealing with the oxygen isotopic composition of natural sulfates using chemical/thermal conversion of BaSO4 and analysis by isotope ratio mass spectrometry. In solutions where NO/SO molar ratios are above 2 the amount of nitrate coprecipitated with BaSO4 reaches a maximum of approximately 7% and decreases roughly linearly as the molar ratio decreases. The fraction of coprecipitated nitrate appears to increase with decreasing pH and is also affected by the nature of the cations in the precipitating solution. The size of the oxygen isotope artifact in sulfate depends both on the amount of coprecipitated nitrate and the ,18O and ,17O values of the nitrate, both of which can be highly variable. The oxygen isotopic composition of sulfate extracted from atmospheric aerosols or rain waters are probably severely biased because photochemical nitrate is usually also present and it is highly enriched in 18O (,18O ,50,90,) and has a large mass-independent isotopic composition (,17O ,20,32,). The sulfate ,18O error can be 2,5, with ,17O artifacts reaching as high as 4.0,. Copyright © 2008 John Wiley & Sons, Ltd. [source]