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Rapid Commun Mass Spectrom

Title:		Determination of the delta(2) H values of high molecular weight lipids by high-temperature gas chromatography coupled to isotope ratio mass spectrometry
Author(s):		Lengger SK; Weber Y; Taylor KWR; Kopf SH; Berstan R; Bull ID; Mayser JP; Leavitt WD; Blewett J; Pearson A; Pancost RD;
Address:		"Organic Geochemistry Unit, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK. Biogeochemistry Research Centre, School of Geography, Earth and Environmental Science, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK. Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St, Cambridge, MA, 02138, USA. Elementar UK Ltd, Earl Road, Cheadle Hulme, Stockport, SK8 6PT, UK. Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, USA. Department of Earth Science, Department of Chemistry, Department of Biological Sciences, Dartmouth College, Hanover, NH, USA. School of Earth Sciences and Cabot Institute for the Environment, University of Bristol, Queens Road, Bristol, BS8 1RL, UK"
Journal Title:		Rapid Commun Mass Spectrom
Year:		2021
Volume:		35
Issue:		4
Page Number:		e8983 -
DOI:		10.1002/rcm.8983
ISSN/ISBN:		1097-0231 (Electronic) 0951-4198 (Linking)
Abstract:		"RATIONALE: The hydrogen isotopic composition of lipids (delta(2) H(lipid) ) is widely used in food science and as a proxy for past hydrological conditions. Determining the delta(2) H values of large, well-preserved triacylglycerides and other microbial lipids, such as glycerol dialkyl glycerol tetraether (GDGT) lipids, is thus of widespread interest but has so far not been possible due to their low volatility which prohibits analysis by traditional gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC/P/IRMS). METHODS: We determined the delta(2) H values of large, polar molecules and applied high-temperature gas chromatography (HTGC) methods on a modified GC/P/IRMS system. The system used a high-temperature 7-m GC column, and a glass Y-splitter for low thermal mass. Methods were validated using authentic standards of large, functionalised molecules (triacylglycerides, TGs), purified standards of GDGTs. The results were compared with delta(2) H values determined by high-temperature elemental analyser/pyrolysis/isotope ratio mass spectrometry (HTEA/P/IRMS), and subsequently applied to the analysis of GDGTs in a sample from a methane seep and a Welsh peat. RESULTS: The delta(2) H values of TGs agreed within error between HTGC/P/IRMS and HTEA/IRMS, with HTGC/P/IRMS showing larger errors. Archaeal lipid GDGTs with up to three cyclisations could be analysed: the delta(2) H values were not significantly different between methods with standard deviations of 5 to 6 per thousand. When environmental samples were analysed, the delta(2) H values of isoGDGTs were 50 per thousand more negative than those of terrestrial brGDGTs. CONCLUSIONS: Our results indicate that the HTGC/P/IRMS method developed here is appropriate to determine the delta(2) H values of TGs, GDGTs with up to two cyclisations, and potentially other high molecular weight compounds. The methodology will widen the current analytical window for biomarker and food light stable isotope analyses. Moreover, our initial measurements suggest that bacterial and archaeal GDGT delta(2) H values can record environmental and ecological conditions"
Keywords:		Archaea/chemistry Bacteria/chemistry Deuterium/*analysis Gas Chromatography-Mass Spectrometry/*methods Lipids/*chemistry Molecular Weight Soil/chemistry Temperature;
Notes:		"MedlineLengger, Sabine K Weber, Yuki Taylor, Kyle W R Kopf, Sebastian H Berstan, Robert Bull, Ian D Mayser, Jan-Peter Leavitt, William D Blewett, Jerome Pearson, Ann Pancost, Richard D eng 825.14.014/Netherlands Organisation for Scientific Research/ Rubicon/ Evaluation Study England 2020/10/18 Rapid Commun Mass Spectrom. 2021 Feb 28; 35(4):e8983. doi: 10.1002/rcm.8983"