Study on a Pretreatment Method for Volatile Organic Compounds in Standard Soil Samples

Volatile organic compounds (VOCs) have low concentrations and are readily volatile in soil samples. Therefore, it is very important to choose the appropriate extraction method. A method for the extraction of 53 kinds of VOCs in standard soil samples was established in this paper, including halogenated alkanes, halogenated alkenes and benzenes. After comparing the influence of pH with the concentration and volume of extract solvent, the method of Headspace-Gas Chromatography-Mass Spectrometry (GC-MS) was established to analyze volatile organic compounds by using 4 mL 100% methanol without acidification. Except for 1,1,2,2-tetrachloroethane and trichloroethylene, the average recoveries of 53 VOCs and 2 surrogates were between 40.45%-119.73% with 0.10 μg/g internal standard, and the relative standard deviations (RSD) for all the compounds ranged from 1.26% to 9.14%. The abnormal 1,1,2,2-tetrachloroethane and trichloroethylene was mainly caused by the decomposition of 1,1,2,2-tetrachloroethane in alkaline soil. This method was fast, simple, and effective in extraction. More research is necessary to address the problems of low recovery rate of alkenes for soil Standard Reference Sample CRM 628-030 and the decomposition of 1,1,2,2-tetrachloroethane.