Trace analysis of BTEX compounds in water with a membrane interfaced ion mobility spectrometer

A tubular silicone membrane interface has been developed for trace detection of benzene, toluene, ethyl benzene, and xylene (BTEX) compounds in water with a portable ion mobility spectrometer. Effects of flow rate, membrane length and stirring conditions on the IMS signals have been systematically investigated. Besides conventional dynamic mode operation, static mode sampling has been demonstrated for the first time and high sensitivities were achieved by sampling of BTEX contaminated water with static mode operation. A toluene concentration of 0.101 mg l(-1) in purified water, corresponding to a headspace concentration of 2.75 (mug m(-3)), was determined by static mode sampling. Headspace sampling without the membrane interface could not detect toluene at this concentration. This method has high sensitivity for trace concentrations of gasoline components in river water with a response time of several seconds. The apparatus developed is portable and can be used for sensitive detection of organic contaminants in water, with improved performance compared to conventional modes of IMS sampling.