水体中痕量挥发性有机物单体碳同位素组成分析

将固相微萃取(SPME)技术与冷阱富集系统相结合,对水体中痕量挥发性有机物进行了单体碳同位素分析,方法检测限较常规SPME提高了一个数量级。在优化的条件下,对20 μg/L的三氯乙烯/四氯乙烯和10 μg/L的苯/甲苯水溶液进行了单体碳同位素分析,相比于纯溶剂(液相)碳同位素值,顶空(气相)同位素分析误差不超过0.5‰,而样本标准偏差为0.3‰。对某受四氯乙烯污染的北京地下水进行了同位素测定,近污染源点(B408)与远污染源点(B230)四氯乙烯的碳同位素值(δ13C)分别为 -37.8‰和-34.45‰

Analysis of Compound-Specific Carbon Isotopic Compositions of Trace-Level Volatile Organic Compounds in Aqueous Phases

A method combining solid phase microextraction (SPME) with cryofocus technique was developed for the compound-specific carbon isotope analysis of volatile organic compounds in aqueous phase. The detection limit was 10 times better than the conventional SPME method. Under the optimized analytical conditions, aqueous samples of trichloroethylene/perchloroethylene (TCE/PCE) (20 microg/L) and benzene/toluene (10 microg/L) were analyzed. The delta 13C fractionation compared to pure-phase and headspace analysis was less than 0.5 per thousand. The standard deviation was 0.3 per thousand. The method was applied to the delta 13C analysis of PCE in a contaminated groundwater in Beijing. The delta 13C values of PCE on site B408 (source area) and site B230 (spilled area) were -37.8 per thousand and -34.45 per thousand, respectively. The enriched delta 13C value on site B230 may be caused by biodegradation or chemical reaction in groundwater. The tested delta 13C value of benzene, toluene, trichloroethylene and perchloroethylene from different manufacturers were different, indicating that carbon isotope analysis is a useful method to distinguish the sources of contaminants in the environment. This method is simple, easy to use and highly sensitive. It is suitable for the compound-specific carbon isotope analysis of volatile organic compounds in aqueous phase.