CONTINUOUS MONITORING OF VOLATILE ORGANIC-COMPOUNDS IN AIR EMISSIONS USING AN ONLINE 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 chromat ographic analysis is presented. The air is passed through one or more hollow-fiber membranes and the VOCs selectively permeate across the me mbrane into a flow of inert gas such as nitrogen. Before entering the GC column, the VOCs are trapped and concentrated by a microtrap. A con centration 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 interval s of time while the air stream flows continuously through the membrane module.