正己烷萃取-气相色谱法测定地下水中5种挥发性氯代烃的方法优化

摘要

通过优化传统液-液萃取方法及气相色谱检测条件,建立了一种同时测定地下水中四氯乙烯、三氯乙烯、四氯化碳、三氯甲烷及1,2-二氯乙烷5种混合挥发性氯代烃的方法.结果表明:在萃取剂正己烷与待测样品体积比为5∶1的情况下,涡旋3min后各污染物质一次萃取率最高;在该最优条件下进行方法优化,表明四氯乙烯、三氯乙烯、四氯化碳、三氯甲烷及1,2-二氯乙烷的检出限分别为2.6、3.0、2.5、3.8、35.9μg/L,空白加标回收率为97.3%~114.6%,低浓度与高浓度样品加标回收率分别为90.8%~113.3%、107.4%~114.5%.该优化方法缩短了传统液-液萃取方法的萃取时间,提高了污染物的一次回收率,对取自于代表场地的地下水样品中5种挥发性氯代烃浓度检测结果与吹扫-捕集气相色谱法检测结果基本一致.%This study optimized the traditional liquid-liquid extraction method and the detection conditions of the hexane extraction-gas chromatography (HE-GC) method, and developed a method for simultaneously determining five types of volatile chlorinated hydrocarbons (VCHs), including tetrachloroethylene, trichloroethylene, carbon tetrachloride, chloroform, and 1,2-dichloroethane in groundwater.The results show that the highest extraction efficiency can be achieved with a hexane-to-sample volume ratio of 5∶1 after three minutes of vortex rotation.The optimization results show that the detection limits for tetrachloroethylene, trichloroethylene, carbon tetrachloride, chloroform, and 1,2-dichloroethane were 2.6, 3.0, 2.5, 3.8, and 35.9 μg/L, respectively.The recovery rates of the five types of VCHs in blank samples with standard solutions added were between 97.3% and 114.6%.The recovery rates for low-and high-concentration samples ranged from 90.8% to 113.3%, and from 107.4% to 114.5%, respectively.The optimized method has shortened the time of extraction compared with the traditional method and improved the efficiency of pollutant recovery.The detected concentrations of the five types of VCHs in groundwater samples collected from a representative site using the optimized method were consistent with those using the purge-and-trap gas chromatography method.