Continuous monitoring of volatile organic compounds in air emissions using an on-line membrane extraction-microtrap-gas chromatographic system

A method for the continuous monitoring of volatile organic compounds (VOCs) in air using on-line membrane extraction followed by gas chromatographic analysis is presented. The air is passed through one or more hollow-fiber membranes and the VOCs selectively permeate across the membrane into a flow of inert gas such as nitrogen. Before entering the GC column, the VOCs are trapped and concentrated by a microtrap. A concentration pulse of the trapped VOCs is generated by direct electrical heating of the microtrap, which serves as injection for GC separation. Continuous monitoring is done by making injections at fixed intervals of time while the air stream flows continuously through the membrane module.