A Porous Membrane Extraction and Microtrap System for On-line Monitoring of Volatile Organic Compounds in Water

Based on the membrane pervaporation extraction and microtrap process, a sample pretreatment device for volatile organic compounds in water was constructed and evaluated systematically. The volatile organic compounds (VOCs) in water samples could be extracted, preconcentrated, desorbed thermally, and then injected directly into gas chromatography automatically and continuously. Two kinds of membrane materials, polydimethylsiloxane (PDMS) and polyvinylidene fluoride (PVDF), extraction temperature, extraction time, and carrier gas flow rate were investigated with nine model compounds, chloroform, 1,2-dichloroethane, carbon tetrachloride, trichloroethylene, tetrachloroethylene, toluene, ethylbenzene, styrene, chlorobenzene. Using this membrane extraction/microtrap device combined with gas chromatography and a flame ionization detector, under the conditions of 60 degrees C extraction temperature, 30 min concentration time and 8 mL/min carrier gas flow, the detection limits of chlorinated hydrocarbons were in the range of 0. 003-0. 041 mu g/L. The RSDs between 2. 7% and 13. 0% were obtained. Coefficients of correlation were all above 0. 9936. This result demonstrated that this device was very useful for monitoring volatile organic compounds in water.