Continuous monitoring of volatile organic compounds in water using on-line membrane extraction and microtrap gas chromatography system

A method for continuous monitoring of volatile organic compounds (VOCs) in water is presented. The aqueous sample containing VOCs is passed through a hollow fiber membrane. The VOCs selectively migrate across the membrane into an inert gas stream. The VOCs are trapped and concentrated by a microtrap in front of the GC column. The retained VOCs are desorbed from the microtrap by an electrically generated temperature pulse. Rapid heating generates a concentration pulse of analytes which serves as an injection for chromatographic separation. Continuous monitoring is achieved by making a series of pulses (or injections) and corresponding to each pulse a chromatogram is obtained. This system showed excellent results for VOCs monitoring at trace levels. Detection limits for most VOCs were at the low ppb (μg/1) level.