Swiss Federal Institute of Aquatic Science and Technology, 8600 Dubendorf, Switzerland.
Environ Sci Technol. 2010 Feb 1;44(3):1023-9. doi: 10.1021/es901760q.
We developed a method for the vacuum extraction (VacEx) of volatile organic compounds (VOCs) from water samples for ultratrace determinations of carbon isotopic signatures. Our method permits compound-specific stable carbon isotope analysis (CSIA) at VOC concentrations as low as 0.03-1.34 microg/L. VacEx was developed to extract and preconcentrate VOCs for subsequent carbon-CSIA by the standard technique purge-and-trap (P&T) coupled to an isotope-ratio mass spectrometer (IRMS). Even without complete extraction, the delta(13)C signatures of VOCs determined by VacEx-P&T-IRMS were in good agreement (deviation <1 per thousand) with signatures determined by P&T-IRMS. This indicates that VacEx does not cause isotopic discrimination. Limits of quantification (LOQs) for delta(13)C analysis were: 0.03-0.06 microg/L for benzene, toluene, o-xylene, m-p-xylene and ethylbenzene, 0.09 microg/L for methyl tert-butyl ether (MTBE), and 0.18-0.27 microg/L for trans-DCE, cis-DCE, TCE and PCE. These are the lowest LOQs reported to date for continuous-flow isotope-ratio determinations using a commercially available and automated system. To our knowledge, analytical protocols adopted from noble gas analysis in water were applied for the first time to determine the isotope composition of organic contaminants. We applied VacEx in a field study to illustrate how the determination of VOC isotopic signatures at very low concentrations opens new avenues in the in situ assessment of these priority groundwater pollutants.
我们开发了一种从水样中真空提取（VacEx）挥发性有机化合物（VOCs）的方法，用于痕量碳同位素特征的超痕量测定。我们的方法允许在 0.03-1.34μg/L 的 VOC 浓度下进行化合物特异性稳定碳同位素分析（CSIA）。VacEx 是为了提取和浓缩 VOC，以便随后通过与同位素质谱仪（IRMS）耦合的标准吹扫捕集（P&T）技术进行碳-CSIA。即使没有完全提取，通过 VacEx-P&T-IRMS 测定的 VOC 的 δ13C 特征与通过 P&T-IRMS 测定的特征非常吻合（偏差<1‰）。这表明 VacEx 不会引起同位素歧视。δ13C 分析的定量限（LOQ）为：苯、甲苯、邻二甲苯、间二甲苯和乙苯为 0.03-0.06μg/L，甲基叔丁基醚（MTBE）为 0.09μg/L，反式-DCE、顺式-DCE、TCE 和 PCE 为 0.18-0.27μg/L。这是迄今为止使用市售和自动化系统进行连续流动同位素比测定报告的最低 LOQ。据我们所知，从水中的稀有气体分析中采用的分析方案首次应用于确定有机污染物的同位素组成。我们在野外研究中应用了 VacEx，以说明在非常低的浓度下测定 VOC 同位素特征如何为这些优先地下水污染物的原位评估开辟新途径。
Zotero 插件