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Krauß S, Vetter W. Geographical and Species Differentiation of Truffles ( Tuber spp.) by Means of Stable Isotope Ratio Analysis of Light Elements (H, C, and N). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:14386-14392. [PMID: 32378890 DOI: 10.1021/acs.jafc.0c01051] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Truffles (Tuber spp.) are considered the most expensive edible fungi and, therefore, are highly prone to food fraud. In this study, authentic truffles from different countries of origin and species were characterized by the determination of their stable carbon, nitrogen, and hydrogen isotope ratios (bulk δ2H, δ13C, and δ15N values). Chinese truffles from Yunnan or related provinces (n = 19) could be well-separated from all European samples (eight countries; n = 105) by means of their significantly (p < 0.05) more negative δ2H values. Furthermore, samples of the second most expensive European species Tuber magnatum were both more enriched in 15N and more depleted in 13C compared to the remaining samples, which allowed for an unequivocal differentiation. Hence, stable isotope ratio analysis could be of high value in terms of authentication of truffles.
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Affiliation(s)
- Stephanie Krauß
- Institute of Food Chemistry (170b), University of Hohenheim, Garbenstraße 28, D-70599 Stuttgart, Germany
| | - Walter Vetter
- Institute of Food Chemistry (170b), University of Hohenheim, Garbenstraße 28, D-70599 Stuttgart, Germany
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2
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Lee DH, Kim H, Yun HY, Park M, Choe S, In S, Kim E, Han E, Shin KH. Complementary approach for accurate determination of carbon isotopic compositions in γ-hydroxybutyric acid using gas chromatography/combustion-isotope ratio mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33:1434-1439. [PMID: 31070267 DOI: 10.1002/rcm.8481] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 05/03/2019] [Accepted: 05/03/2019] [Indexed: 06/09/2023]
Abstract
RATIONALE γ-Hydroxybutyric acid (GHB) is a naturally endogenous neurotransmitter that is popular as a recreational drug due to its sedative, hypnotic, and euphoric effects. GHB derived from endogenous production or exogenous ingestion has been effectively discriminated by carbon isotopic compositions (δ13 C values) through gas chromatography/combustion-isotope ratio mass spectrometry (GC/C-IRMS). However, an unintended uncertainty of isotopic signatures caused by a wide range of GHB quantities remains unsolved when using only single-isotope corrections of the di-TMS derivative. METHODS The δ13 C values of the original GHB standard were first determined by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). The δ13 C values of silylated GHB in concentrations from 10 to 500 ppm were determined by GC/C-IRMS. With respect to the silylated reaction products, the correction of δ13 C values for the introduced carbons was calculated from a stoichiometric mass balance equation. RESULTS The results showed a significant quantity-dependent trend in δ13 C values of introduced carbon (δ13 Cdi-TMS values) with increased GHB standard concentrations (r2 = 0.70, p <0.05). We applied a logarithmic equation to determine isotopic data in low-GHB urine specimens from five healthy female volunteers. The δ13 CGHB values in urine samples corrected with quantity-dependent δ13 Cdi-TMS values were different by an average of 2.7‰ from those corrected with single δ13 Cdi-TMS values (p <0.05). CONCLUSIONS Our results suggest that the overall residual amount-dependent isotope fractionation should be mathematically corrected by the logarithmic function and this may improve the reliability of isotopic analysis to evaluate the origin of GHB before applying the approach to routine toxicological and forensic studies.
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Affiliation(s)
- Dong-Hun Lee
- Hanyang University, 55 Hanyangdaehak-ro, Sangrok-gu, Ansan, 15588, Republic of Korea
| | - Hyojeong Kim
- College of Pharmacy, Duksung Women's University, 144 Samyang-ro, Dobong-gu, Seoul, 01369, Republic of Korea
- Innovative Drug Center, Duksung Women's University, Seoul, South Korea
| | - Hee Young Yun
- Hanyang University, 55 Hanyangdaehak-ro, Sangrok-gu, Ansan, 15588, Republic of Korea
| | | | | | - Sanghwan In
- National Forensic Service, Republic of Korea
| | - Eunmi Kim
- National Forensic Service, Republic of Korea
| | - Eunyoung Han
- College of Pharmacy, Duksung Women's University, 144 Samyang-ro, Dobong-gu, Seoul, 01369, Republic of Korea
- Innovative Drug Center, Duksung Women's University, Seoul, South Korea
| | - Kyung-Hoon Shin
- Hanyang University, 55 Hanyangdaehak-ro, Sangrok-gu, Ansan, 15588, Republic of Korea
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Analysis of household ignitable liquids and their post-combustion weathered residues using compound-specific gas chromatography-combustion-isotope ratio mass spectrometry. Forensic Sci Int 2013; 233:365-73. [DOI: 10.1016/j.forsciint.2013.10.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 10/09/2013] [Accepted: 10/12/2013] [Indexed: 11/23/2022]
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4
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Zech M, Saurer M, Tuthorn M, Rinne K, Werner RA, Siegwolf R, Glaser B, Juchelka D. A novel methodological approach for δ(18)O analysis of sugars using gas chromatography-pyrolysis-isotope ratio mass spectrometry. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2013; 49:492-502. [PMID: 24313371 DOI: 10.1080/10256016.2013.824875] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Although the instrumental coupling of gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) for compound-specific δ(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 δ(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 δ(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 δ(18)O analysis for sucrose from needle extract (soluble carbohydrate) samples. The obtained δ(18)Osucrose/ Vienna Standard Mean Ocean Water (VSMOW) values are more positive and vary in a wider range (32.1-40.1 ‰) than the δ(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 δ(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 δ(18)Osucrose analysis for plant physiology and paleoclimate studies.
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Affiliation(s)
- Michael Zech
- a Department of Soil Physics and Chair of Geomorphology , University of Bayreuth , Bayreuth , Germany
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5
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Janssens G, Courtheyn D, Mangelinckx S, Prévost S, Bichon E, Monteau F, De Poorter G, De Kimpe N, Le Bizec B. Use of isotope ratio mass spectrometry to differentiate between endogenous steroids and synthetic homologues in cattle: a review. Anal Chim Acta 2012; 772:1-15. [PMID: 23540242 DOI: 10.1016/j.aca.2012.12.035] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 12/18/2012] [Accepted: 12/21/2012] [Indexed: 11/16/2022]
Abstract
Although substantial technical advances have been achieved during the past decades to extend and facilitate the analysis of growth promoters in cattle, the detection of abuse of synthetic analogs of naturally occurring hormones has remained a challenging issue. When it became clear that the exogenous origin of steroid hormones could be traced based on the (13)C/(12)C isotope ratio of the substances, GC/C/IRMS has been successfully implemented to this aim since the end of the past century. However, due to the costly character of the instrumental setup, the susceptibility of the equipment to errors and the complex and time consuming sample preparation, this method is up until now only applied by a limited number of laboratories. In this review, the general principles as well as the practical application of GC/C/IRMS to differentiate between endogenous steroids and exogenously synthesized homologous compounds in cattle will be discussed in detail, and will be placed next to other existing and to be developed methods based on isotope ratio mass spectrometry. Finally, the link will be made with the field of sports doping, where GC/C/IRMS has been established within the World Anti-Doping Agency (WADA) approved methods as the official technique to differentiate between exogenous and endogenous steroids over the past few years.
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Affiliation(s)
- Geert Janssens
- Federal Agency for the Safety of the Food Chain, Directorate General Laboratories, Brussels, Belgium.
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Liu W, Wang Z, Cui L, Sauer PE, Cao Y. Variation of compound-specific hydrogen isotope ratios under changing temperature program in gas chromatography/thermal conversion/isotope ratio mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:1746-1752. [PMID: 22777775 DOI: 10.1002/rcm.6283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
RATIONALE In recent experiments, we found that compound-specific δ(2)H values can vary as a result of changing the gas chromatography temperature program under common pyrolysis conditions. To achieve better precision, it is necessary to examine the details and find a solution to this problem when using gas chromatography/thermal conversion/isotope ratio mass spectrometry (GC-TC-IRMS) for hydrogen isotope analysis. METHODS A test was designed to find the possible temperature effect under four different GC temperature ramp rates using n-alkanes (n-C(21), n-C(27), and n-C(31)) and fatty acids (n-C(12), n-C(18), and n-C(24)). The common 'hexane' method was used initially to condition the pyrolysis reactor. Experiments were then carried out using the 'methane condition' method because it was considered to improve pyrolysis efficiency. RESULTS Under the 'hexane condition' the measured hydrogen isotope ratios of the n-alkanes and n-fatty acids became more positive with increasing GC temperature ramp rate. The ion current intensity of hydrogen also generally increased. However, when the 'methane condition' method was used, the measured δ(2)H values of the n-alkanes and n-fatty acids showed little change under different GC temperature ramp rates. CONCLUSIONS Higher pyrolysis efficiency could reduce the tailing of the H(2) peak and the related isotopic variations at increased GC temperature ramp rates. In addition, too slow a temperature ramp rate could broaden the peak width and thus increase the background effect and possible isotopic fractionations in the split interface; this could also influence the hydrogen isotope values. We therefore suggest that the appropriate temperature ramp rate is an important factor in improving the precision in analyzing compound-specific hydrogen isotopes.
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Affiliation(s)
- Weiguo Liu
- State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi'an, 710075, PR China.
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Elsner M, Jochmann MA, Hofstetter TB, Hunkeler D, Bernstein A, Schmidt TC, Schimmelmann A. Current challenges in compound-specific stable isotope analysis of environmental organic contaminants. Anal Bioanal Chem 2012; 403:2471-91. [DOI: 10.1007/s00216-011-5683-y] [Citation(s) in RCA: 202] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 12/15/2011] [Accepted: 12/18/2011] [Indexed: 11/30/2022]
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8
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Recent developments in the use of isotope ratio mass spectrometry in sports drug testing. Anal Bioanal Chem 2011; 401:433-47. [DOI: 10.1007/s00216-011-4886-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 03/03/2011] [Accepted: 03/08/2011] [Indexed: 10/18/2022]
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9
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Piper T, Opfermann G, Thevis M, Schänzer W. Determination of (13)C/(12)C ratios of endogenous urinary steroids excreted as sulpho conjugates. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:3171-3181. [PMID: 20941765 DOI: 10.1002/rcm.4762] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The application of a comprehensive gas chromatography/combustion/isotope ratio mass spectrometry-based method for the measurement of stable carbon isotopes of endogenous urinary steroids excreted as sulphates is presented. The key element in sample preparation is the consecutive cleanup with high-performance liquid chromatography of underivatized and acetylated steroids, which allows the isolation of seven analytes (pregn-5-ene-3β,17α,20α-triol, etiocholanolone, androsterone, epiandrosterone, dehydroepiandrosterone (DHEA), androst-5-ene-3β,17β-diol and androst-5-ene-3β,17α-diol) from a single urine specimen. These steroids are of particular importance to doping controls as they should enable the sensitive and retrospective detection of DHEA abuse by athletes.Depending on the biological background, the determination limit for all steroids ranges from 5 to 10 ng/mL for a 10 mL specimen. The method is validated by means of linear mixing models for each steroid, which covers the items, repeatability and reproducibility. The specificity was further demonstrated by gas chromatography/mass spectrometry for each analyte, and no influence of the sample preparation or the quantity of analyte on carbon isotope ratios was observed. In order to determine naturally occurring (13)C/(12)C ratios and urinary concentrations of all implemented steroids, a reference population of n = 67 subjects was measured to enable the calculation of reference limits for all relevant steroidal Δ values.The applicability of the developed method was tested by means of a DHEA excretion study. Despite the fact that orally ingested DHEA is preferentially converted into sulphated metabolites and that the renal clearance of sulphated steroids is slow, only the (13)C/(12)C ratio of EpiA demonstrated the potential to prolong the detection time for DHEA misuse.
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Affiliation(s)
- Thomas Piper
- German Sport University Cologne, Institute of Biochemistry, Am Sportpark Müngersdorf 6, 50933 Cologne, Germany.
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10
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Muccio Z, Jackson GP. Simultaneous Identification and δ13C Classification of Drugs Using GC with Concurrent Single Quadrupole and Isotope Ratio Mass Spectrometers*. J Forensic Sci 2010; 56 Suppl 1:S203-9. [DOI: 10.1111/j.1556-4029.2010.01594.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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11
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Bock M, Schmitt J, Behrens M, Möller L, Schneider R, Sapart C, Fischer H. A gas chromatography/pyrolysis/isotope ratio mass spectrometry system for high-precision deltaD measurements of atmospheric methane extracted from ice cores. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:621-633. [PMID: 20155754 DOI: 10.1002/rcm.4429] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Air enclosures in polar ice cores represent the only direct paleoatmospheric archive. Analysis of the entrapped air provides clues to the climate system of the past in decadal to centennial resolution. A wealth of information has been gained from measurements of concentrations of greenhouse gases; however, little is known about their isotopic composition. In particular, stable isotopologues (deltaD and delta(13)C) of methane (CH(4)) record valuable information on its global cycle as the different sources exhibit distinct carbon and hydrogen isotopic composition. However, CH(4) isotope analysis is limited by the large sample size required and the demanding analysis as high precision is required. Here we present a highly automated, high-precision online gas chromatography/pyrolysis/isotope ratio monitoring mass spectrometry (GC/P/irmMS) technique for the analysis of deltaD(CH(4)). It includes gas extraction from ice, preconcentration, gas chromatographic separation and pyrolysis of CH(4) from roughly 500 g of ice with CH(4) concentrations as low as 350 ppbv. Ice samples with approximately 40 mL air and only approximately 1 nmol CH(4) can be measured with a precision of 3.4 per thousand. The precision for 65 mL air samples with recent atmospheric concentration is 1.5 per thousand. The CH(4) concentration can be obtained along with isotope data which is crucial for reporting ice core data on matched time scales and enables us to detect flaws in the measurement procedure. Custom-made script-based processing of MS raw and peak data enhance the system's performance with respect to stability, peak size dependency, hence precision and accuracy and last but not least time requirement.
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Affiliation(s)
- Michael Bock
- Climate and Environmental Physics and Oeschger Centre for Climate Change Research, University of Bern, Switzerland.
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12
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Zech M, Glaser B. Compound-specific delta18O analyses of neutral sugars in soils using gas chromatography-pyrolysis-isotope ratio mass spectrometry: problems, possible solutions and a first application. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2009; 23:3522-3532. [PMID: 19844972 DOI: 10.1002/rcm.4278] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Although gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IRMS) has allowed us to make online compound-specific delta18O measurements for about the last ten years, this technique has hardly been applied. We tested different pyrolysis reactor designs using standards (vanillin, ethylvanillin, a fatty acid methyl ester and alkanes) in order to optimize the GC-Py-IRMS delta18O measurements. The method was then applied to methylboronic acid (MBA) sugar derivatives (pentoses, 6-deoxyhexoses and hexoses). Plant- and microbial-derived monosaccharides were extracted hydrolytically from litter and topsoils before derivatization. The measured delta18O values of samples and co-analyzed reference material were first drift-corrected by use of regularly discharged pulses of CO reference gas. Secondly, they were corrected for the amount dependence of the delta18O values. Thirdly, the delta18O values were calibrated using the reference material (principle of 'Identical Treatment'), and, finally, a correction was applied by taking the hydrolytically introduced and water-exchangeable oxygen atoms into account. Our results suggest that the delta18O values of plant-derived monosaccharides in litter reflect the climatic conditions of the last year, whereas delta18O values of the respective topsoils reflect the averaged climate signal of the last decades or even centuries. This demonstrates the high potential of the method for palaeoclimate reconstructions.
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Affiliation(s)
- Michael Zech
- Chair of Geomorphology, University of Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany.
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Gauchotte C, O'Sullivan G, Davis S, Kalin RM. Development of an advanced on-line position-specific stable carbon isotope system and application to methyl tert-butyl ether. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2009; 23:3183-3193. [PMID: 19725079 DOI: 10.1002/rcm.4222] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present an advanced system for on-line position-specific carbon isotope analysis. The main limitation of on-line intramolecular isotope ratio measurements has been that optimal pyrolytic fragments are obtained mostly at temperatures where the analyte has not completely reacted. As a result of undetermined isotopic fractionation, the isotopic signatures of the pyrolysis products are not strictly equal to these of the equivalent moieties in the parent molecule. We designed a pyrolytic unit in which both temperature and reaction time are variable parameters, enabling determination of the enrichment factor of the pyrolysis at optimal temperature by construction of a Rayleigh plot. In the case of methyl tert-butyl ether (MTBE) presented here, a 'pre-pyrolysis' fractionation of MTBE leading to a depletion of 0.9 per thousand was discovered and the enrichment factor of the optimal pyrolysis reaction was determined at -1.7 per thousand. Absolute delta(13)C values of two functional groups of MTBE - the methoxy group and the 2-methylpropane group - could be determined with 95% confidence intervals of 0.4 per thousand and 0.5 per thousand, respectively.
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Affiliation(s)
- Caroline Gauchotte
- Department of Civil Engineering, University of Strathclyde, John Anderson Building, Glasgow G4 0NG, UK.
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Piper T, Mareck U, Geyer H, Flenker U, Thevis M, Platen P, Schänzer W. Determination of 13C/12C ratios of endogenous urinary steroids: method validation, reference population and application to doping control purposes. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2008; 22:2161-2175. [PMID: 18536069 DOI: 10.1002/rcm.3601] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The application of a comprehensive gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS)-based method for stable carbon isotopes of endogenous urinary steroids is presented. The key element in sample preparation is the consecutive cleanup with high-performance liquid chromatography (HPLC) of underivatized and acetylated steroids, which allows the isolation of ten analytes (11beta-hydroxyandrosterone, 5alpha-androst-16-en-3beta-ol, pregnanediol, androsterone, etiocholanolone, testosterone, epitestosterone, 5alpha-androstane-3alpha,17beta-diol, 5beta-androstane-3alpha,17beta-diol and dehydroepiandrosterone) from a single urine specimen. These steroids are of particular importance to doping controls as they enable the sensitive and retrospective detection of steroid abuse by athletes. Depending on the biological background, the determination limit for all steroids ranges from 5 to 10 ng/mL for a 10 mL specimen. The method is validated by means of linear mixing models for each steroid, which covers repeatability and reproducibility. Specificity was further demonstrated by gas chromatography/mass spectrometry (GC/MS) for each analyte, and no influence of the sample preparation or the quantity of analyte on carbon isotope ratios was observed. In order to determine naturally occurring (13)C/(12)C ratios of all implemented steroids, a reference population of n = 61 subjects was measured to enable the calculation of reference limits for all relevant steroidal Delta values.
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Affiliation(s)
- Thomas Piper
- Institute of Biochemistry, German Sport University Cologne, Carl-Diem-Weg 6, 50933 Köln, Germany.
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15
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Zech M, Glaser B. Improved compound-specific delta13C analysis of n-alkanes for application in palaeoenvironmental studies. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2008; 22:135-142. [PMID: 18059042 DOI: 10.1002/rcm.3342] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We present an optimized method for compound-specific stable carbon isotope (delta(13)C) analysis of n-alkanes. For sample preparation, the traditionally used Soxhlet extraction was replaced by accelerated solvent extraction (ASE). delta(13)C values of individual n-alkanes--measured using gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS)--were first drift-corrected with regularly discharged pure CO(2) pulses as reference gas and, secondly, corrected for the amount dependence of the delta(13)C values by co-analyzing standards with varying analyte concentrations. Finally, the delta(13)C values were calibrated against two internal standards. The improved method was applied to selected sediment samples from a palaeoenvironmental study in subtropical NE Argentina. The measured delta(13)C values of all long-chain n-alkanes (nC(27), nC(29), nC(31) and nC(33)), representing biomarkers for terrestrial plants, correlate significantly with the delta(13)C of bulk organic matter (delta(13)C(TOC)). The latter is hence corroborated as a proxy for C3-C4 vegetation changes. Furthermore, the delta(13)C variations reveal higher amplitudes for nC(31) and nC(33) than for nC(27) and nC(29), indicating that the former n-alkanes mainly derive from C3 and/or C4 grasses, whereas the latter homologues mainly derive from C3 plants (trees and shrubs). Except for the lowermost part of the sediment core, the delta(13)C values of the mid-chain alkanes nC(23) and nC(25) do not reflect the terrestrial delta(13)C pattern, thus indicating that they are probably mainly of lacustrine origin.
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Affiliation(s)
- Michael Zech
- Institute of Soil Science and Soil Geography, University of Bayreuth, D-95445 Bayreuth, Germany.
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16
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Blessing M, Jochmann MA, Schmidt TC. Pitfalls in compound-specific isotope analysis of environmental samples. Anal Bioanal Chem 2007; 390:591-603. [PMID: 17901949 DOI: 10.1007/s00216-007-1588-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Revised: 08/27/2007] [Accepted: 08/29/2007] [Indexed: 11/25/2022]
Abstract
In the last decade compound-specific stable isotope analysis (CSIA) has evolved as a valuable technique in the field of environmental science, especially in contaminated site assessment. Instrumentation and methods exist for highly precise measurements of the isotopic composition of organic contaminants even in a very low concentration range. Nevertheless, the determination of precise and accurate isotope data of environmental samples can be a challenge. Since CSIA is gaining more and more popularity in the assessment of in situ biodegradation of organic contaminants, an increasing number of authorities and environmental consulting offices are interested in the application of the method for contaminated site remediation. Because of this, it is important to demonstrate the problems and limitations associated with compound-specific isotope measurements of environmental samples. In this review, potential pitfalls of the analytical procedure are critically discussed and strategies to avoid possible sources of error are provided. In order to maintain the analytical quality and to ensure the basis for reliable stable isotope data, recommendations on groundwater sampling, and sample preservation and storage are given. Important aspects of sample preparation and preconcentration techniques to improve sensitivity are highlighted. Problems related to chromatographic resolution and matrix interference are discussed that have to be considered in order to achieve accurate gas chromatography/isotope ratio mass spectrometry measurements. As a result, the need for a thorough investigation of compound-specific isotope fractionation effects introduced by any step of the overall analytical method by standards with known isotopic composition is emphasized. Finally, we address some important points that have to be considered when interpreting data from field investigations.
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Affiliation(s)
- Michaela Blessing
- Center for Applied Geoscience (ZAG), Eberhard Karls University of Tuebingen, Sigwartstr. 10, 72076, Tuebingen, Germany
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Goldstein AH, Shaw SL. Isotopes of Volatile Organic Compounds: An Emerging Approach for Studying Atmospheric Budgets and Chemistry. Chem Rev 2003; 103:5025-48. [PMID: 14664642 DOI: 10.1021/cr0206566] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Allen H Goldstein
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720, USA.
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Schüth C, Bill M, Barth JAC, Slater GF, Kalin RM. Carbon isotope fractionation during reductive dechlorination of TCE in batch experiments with iron samples from reactive barriers. JOURNAL OF CONTAMINANT HYDROLOGY 2003; 66:25-37. [PMID: 14516939 DOI: 10.1016/s0169-7722(03)00026-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Reductive dechlorination of trichloroethene (TCE) by zero-valent iron produces a systematic enrichment of 13C in the remaining substrate that can be described using a Rayleigh model. In this study, fractionation factors for TCE dechlorination with iron samples from two permeable reactive barriers (PRBs) were established in batch experiments. Samples included original unused iron as well as material from a barrier in Belfast after almost 4 years of operation. Despite the variety of samples, carbon isotope fractionations of TCE were remarkably similar and seemed to be independent of iron origin, reaction rate, and formation of precipitates on the iron surfaces. The average enrichment factor for all experiments was -10.1 per thousand (+/- 0.4 per thousand). These results indicate that the enrichment factor provides a powerful tool to monitor the reaction progress, and thus the performance, of an iron-reactive barrier over time. The strong fractionation observed may also serve as a tool to distinguish between insufficient residence time in the wall and a possible bypassing of the wall by the plume, which should result in an unchanged isotopic signature of the TCE. Although further work is necessary to apply this stable isotope method in the field, it has potential to serve as a unique monitoring tool for PRBs based on zero-valent iron.
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Affiliation(s)
- Christoph Schüth
- Applied Geology Group, Department of Applied Geology, Geological Institute, University of Tübingen, Sigwartstr. 10, Tübingen D-72076, Germany.
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Norlin E, Irgum K, Ohlsson KEA. Nitrogen isotope analysis of ammonium in aqueous solutions using a perfluorosulfonated ionomer membrane for solid-phase microextraction. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2003; 17:936-942. [PMID: 12717766 DOI: 10.1002/rcm.993] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The use of custom-made solid-phase microextraction (SPME) fibers coated with a perfluorosulfonated ionomer, Nafion, was investigated for nitrogen isotopic analysis of ammonium in aqueous solutions. Aqueous ammonium was converted to ammonia by addition of a base, followed by absorption from the headspace, desorption in the injection port of a gas chromatograph, and analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Fibers coated with a Nafion tubing were chosen due to a higher fiber-gas distribution constant and a higher Nafion thickness than fibers coated with Nafion solution, both leading to a higher amount of ammonia absorbed at equilibrium. The Nafion membrane-coated fiber absorbed approximately 20 times more than a commercial polydimethylsiloxane (PDMS) fiber. The isotopic fractionation between fiber and gas was 1.0117 +/- 0.0009 (standard deviation, SD, of all measurements) at an initial ammonia gas concentration of 21-210 microM. At 390 microM initial gas concentration it was slightly lower. When sampling from liquid samples, an ammonium concentration of 10 mM was needed to obtain a sufficient amount of ammonia absorbed. Modeling of the absorption at different temperatures showed that the absorption was approximately constant in the temperature range suitable for SPME experiments. Absorption at room temperature was therefore used for simplicity. A pilot study was conducted in which absorption was achieved from a single 9 microL droplet of sample. The preliminary results showed that delta(15)N analysis was possible for only 0.4-0.5 micromol of ammonium with a SD of 0.8 per thousand (n = 5).
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Affiliation(s)
- Elin Norlin
- Swedish University of Agricultural Sciences, Department of Forest Ecology, Section of Soil Science, SE-901 83 Umeå, Sweden.
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Schmitt J, Glaser B, Zech W. Amount-dependent isotopic fractionation during compound-specific isotope analysis. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2003; 17:970-977. [PMID: 12717771 DOI: 10.1002/rcm.1009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The performance of a gas chromatography-combustion-isotope ratio mass spectrometry system (GC-C-IRMS) with respect to the dependence of delta(13)C values on the amount of sample is presented. Particular attention is paid to the localization of the amount-dependent isotopic fractionation within the system. Injection experiments with varying amounts of gases (CO(2), n-hexane, and toluene) revealed that neither the detector unit nor the combustion reactor, but rather the conditions in the split/splitless injector, contributed to this effect. Although optimization of injector parameters was performed and a reduction of this adverse effect from 3 to 1 per thousand was achieved, it was not possible to eliminate isotopic fractionation completely. Consequently, additional injector parameters have to be considered and adjusted to achieve injection conditions free of fractionation. For routine analysis of the compound-specific delta(13)C analysis of different biomarkers in many environmental samples, perfect optimization may not always be reached. Therefore, in order to prevent systematic errors in the measured delta(13)C values due to different sample concentrations, it is suggested that correction for the remaining unknown amount-dependent fractionation can be made by means of co-analyzing standards of varying analyte concentrations and known delta(13)C values. Residual overall amount-dependent isotope-fractionation can thus be corrected mathematically.
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Affiliation(s)
- Jochen Schmitt
- Institute of Soil Science and Soil Geography, University of Bayreuth, D-95440 Bayreuth, Germany.
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21
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Meier-Augenstein W. Stable isotope analysis of fatty acids by gas chromatography–isotope ratio mass spectrometry. Anal Chim Acta 2002. [DOI: 10.1016/s0003-2670(02)00194-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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22
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Mathurin JC, Herrou V, Bourgogne E, Pascaud L, de Ceaurriz J. Gas chromatography-combustion-isotope ratio mass spectrometry analysis of 19-norsteroids: application to the detection of a nandrolone metabolite in urine. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 2001; 759:267-75. [PMID: 11499480 DOI: 10.1016/s0378-4347(01)00241-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Determination of whether the major metabolite of nandrolone in urine, 19-norandrosterone (19-NA), is exogenous or endogenous in origin is one of the most exciting challenges for antidoping laboratories. Gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) can be used to differentiate these two origins by carbon isotopic ratio analysis. A complete method for purification of 19-NA in urine has been established. Acetylated ketosteroids, and in particular 19-NA, are isolated from the urine matrix before analysis after hydrolysis and purification of urine by reversed-phase and normal solid-phase extraction. The limit of detection for 19-NA was about 60 ng with recoveries of 54-60%. Evidence of exogenous administration of 19-NA may be established from isotope ratio determination from the 13C/12C ratios of several synthetic 19-norsteroids compared to those obtained for endogenous steroids.
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Affiliation(s)
- J C Mathurin
- Laboratoire National de Dépistage du Dopage, CREPS, Chatenay Malabry, France.
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Bill M, Schüth C, Barth JA, Kalin RM. Carbon isotope fractionation during abiotic reductive dehalogenation of trichloroethene (TCE). CHEMOSPHERE 2001; 44:1281-1286. [PMID: 11513419 DOI: 10.1016/s0045-6535(00)00274-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Dehalogenation of trichloroethene (TCE) in the aqueous phase, either on palladium catalysts with hydrogen as the reductant or on metallic iron, was associated with strong changes in delta13C. In general, the delta13C of product phases were more negative than those of the parent compound and were enriched with time and fraction of TCE remaining. For dehalogenation with iron, the delta13C of TCE and products varied from -42/1000 to +5/1000. For the palladium experiments, the final product, ethane, reached the initial delta13C of TCE at completion of the dehalogenation reaction. During dehalogenation, the carbon isotope fractionation between TCE and product phases was not constant. The variation in delta13C of TCE and products offers a new monitoring tool that operates independently of the initial concentration of pollutants for abiotic degradation processes of TCE in the subsurface, and may be useful for evaluation of remediation efficiency.
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Affiliation(s)
- M Bill
- Applied Geology Group, Geological Institute, University of Tübingen, Germany
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Kalin RM, Hamilton JT, Harper DB, Miller LG, Lamb C, Kennedy JT, Downey A, McCauley S, Goldstein AH. Continuous flow stable isotope methods for study of delta(13)C fractionation during halomethane production and degradation. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2001; 15:357-363. [PMID: 11241767 DOI: 10.1002/rcm.219] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Gas chromatography/mass spectrometry/isotope ratio mass spectrometry (GC/MS/IRMS) methods for delta(13)C measurement of the halomethanes CH(3)Cl, CH(3)Br, CH(3)I and methanethiol (CH(3)SH) during studies of their biological production, biological degradation, and abiotic reactions are presented. Optimisation of gas chromatographic parameters allowed the identification and quantification of CO(2), O(2), CH(3)Cl, CH(3)Br, CH(3)I and CH(3)SH from a single sample, and also the concurrent measurement of delta(13)C for each of the halomethanes and methanethiol. Precision of delta(13)C measurements for halomethane standards decreased (+/-0.3, +/-0.5 and +/-1.3 per thousand) with increasing mass (CH(3)Cl, CH(3)Br, CH(3)I, respectively). Given that carbon isotope effects during biological production, biological degradation and some chemical (abiotic) reactions can be as much as 100 per thousand, stable isotope analysis offers a precise method to study the global sources and sinks of these halogenated compounds that are of considerable importance to our understanding of stratospheric ozone destruction.
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Affiliation(s)
- R M Kalin
- Environmental Engineering Research Centre, School of Civil Engineering, The Queen's University of Belfast, Belfast BT9 5AG, UK.
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Barth JA, Kalin RM, Larkin MJ, Hall JA, Fitzgerald U. Isotopic composition of inorganic carbon as an indicator of benzoate degradation by pseudomonas putida: temperature, growth rate and pH effects. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2000; 14:1316-1320. [PMID: 10920348 DOI: 10.1002/1097-0231(20000815)14:15<1316::aid-rcm933>3.0.co;2-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Degradation experiments of benzoate by Pseudomonas putida resulted in enzymatic carbon isotope fractionations. However, isotopic temperature effects between experiments at 20 and 30 degrees C were minor. Averages of the last three values of the CO(2) isotopic composition (delta(13)C(CO2(g))) were more negative than the initial benzoate delta(13)C value (-26.2 per thousand Vienna Pee Dee Belenite (VPDB)) by 3.8, 3.4 and 3.2 per thousand at 20, 25 and 30 degrees C, respectively. Although the maximum isotopic temperature difference found was only 0.6 per thousand, more extreme temperature variations may cause larger isotope effects. In order to understand the isotope effects on the total inorganic carbon (TIC), a better measure is to calculate the proportions of the inorganic carbon species (CO(2)(g), CO(2)(aq) and HCO(3)(-)) and to determine their cumulative delta(13)C(TIC). In all three experiments delta(13)C(TIC) was more positive than the initial isotopic composition of the benzoate at a pH of 7. This suggests an uptake of (12)C in the biomass in order to match the carbon balance of these closed system experiments.
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Affiliation(s)
- J A Barth
- Environmental Engineering Research and QUESTOR Centre, The Queen's University Belfast, David Keir Building, Stranmillis Rd, Belfast BT9 5AG, N. Ireland, UK.
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