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 method, a sample pretreatment device for volatile organic compounds in water was constructed and evaluated. The volatile organic compounds (VOCs) in water samples could be extracted, preconcentrated, desorbed thermally, and injected directly into a gas chromatograph automatically. Two kinds of porous hollow fiber membrane materials, polydimethylsiloxane (PDMS) and polyvinylidene fluoride (PVDF), were examined. Extraction parameters, such as extraction temperature, extraction time, and carrier gas flow rate, were investigated by using nine model compounds, including chloroform, 1,2-dichloroethane, carbon tetrachloride, trichloroethylene, tetrachloroethylene, toluene, ethylbenzene, styrene and chlorobenzene. Under the optimum conditions (extraction temperature of 60 °C and concentration time of 30 min with purge gas flow of 8 mL min−1), the detection limits of chlorinated hydrocarbons were in the range of 0.003–0.041 μg L−1, with RSD of 2.7% and 13.0%, using a flame ionization detector. Coefficients of correlation were all above 0.9936. This result demonstrated that this device was feasible for monitoring volatile organic compounds in water.

With the membrane pervaporation extraction and microtrap device, the volatile organic compounds (VOCs) in water samples could diffuse spontaneously through hollow fiber membrane, be taken away by carrier gas, and then were extracted and preconcentrated by microtrap. These adsorbed VOCs could be desorbed thermally, injected directly into a gas chromatograph, and quantified precisely.Figure optionsDownload as PowerPoint slide