Determination of the δ 2 H values of high molecular weight lipids by high temperature GC coupled to isotope ratio mass spectrometry
Determination of the δ 2 H values of high molecular weight lipids by high temperature GC coupled to isotope ratio mass spectrometry
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高温 GC 联用同位素比质谱法测定高分子量脂质的 δ 2 H 值
DOI：
10.1002/rcm.8983
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发表时间：
2020
影响因子：
2
通讯作者：
Pearson, Ann
中科院分区：
文献类型：
--
作者：
Lengger, 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
基本原理 脂质的氢同位素组成 (d2Hlipid) 广泛应用于食品科学，并可作为过去水文条件的代表。因此，测定大的、保存良好的三酰甘油酯和其他微生物脂质（例如甘油二烷基甘油四醚 (GDGT) 脂质）的 d2H 值受到广泛关注，但由于其挥发性低，无法使用传统气相色谱/热解/同位素比质谱 (GC/P/IRMS) 进行分析，因此迄今为止还无法实现。方法 我们测定了大极性分子的 d2H 值，并在改进的 GC/P/IRMS 系统上应用高温气相色谱 (HTGC) 方法。该系统使用高温 7 米 GC 色谱柱和玻璃 Y 型分流器以实现低热质量。使用大的功能化分子（三酰甘油酯，TG）的真实标准品、GDGT 的纯化标准品对方法进行了验证。将结果与高温元素分析仪/热解/同位素比质谱 (HTEA/P/IRMS) 测定的 d2H 值进行比较，随后应用于甲烷渗漏和威尔士泥炭样品中 GDGT 的分析。结果 HTGC/P/IRMS 和 HTEA/IRMS TG 的 d2H 值在误差范围内一致，其中 HTGC/P/IRMS 误差较大。可以分析最多具有三个环化的古菌脂质 GDGT：d2H 值在标准偏差为 5 至 6‰的方法之间没有显着差异。分析环境样本时，isoGDGT 的 d2H 值比陆地 brGDGT 的负值低 50‰。结论 我们的结果表明，本文开发的 HTGC/P/IRMS 方法适合测定 TG、最多两次环化的 GDGT 以及其他潜在高分子量化合物的 d2H 值。该方法将拓宽当前生物标志物和食品光稳定同位素分析的分析窗口。此外，我们的初步测量表明细菌和古细菌的 GDGT d2H 值可以记录环境和生态条件。
Rationale The hydrogen isotopic composition of lipids (d2Hlipid) is widely used in food science and as a proxy for past hydrological conditions. Determining the d2H 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 d2H 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 d2H 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 d2H 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 d2H values were not significantly different between methods with standard deviations of 5 to 6‰. When environmental samples were analysed, the d2H values of isoGDGTs were 50‰ more negative than those of terrestrial brGDGTs. Conclusions Our results indicate that the HTGC/P/IRMS method developed here is appropriate to determine the d2H 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 d2H values can record environmental and ecological conditions.