On-line monitoring of trihalomethanes in drinking water using continuous-flow purge and cryofocusing gas chromatography-mass spectrometry

A continuous-flow purge-and-trap-GC-MS system was developed for on-line mon itoring of THMs (trihalomethanes) in drinking water. Three systems with dif ferent traps and purging flow-rates are discussed. In order to minimize int erference from water vapor, total purge gas volume and injection temperatur e were controlled during analysis. Shorter sample concentration time and GC separation time reduced total cycle time to less than 5 min. The detection limits of the system could be lowered to 10 ppt, 25 ppt, 40 ppt, and 50 pp t (w/w) for CHCl3, CHCl2Br, CHClBr2, and CHBr3, respectively. This system c ould detect changes in sample concentration when applied to the on-line mon itoring of THMs in drinking water. (C) 2001 Published by Elsevier Science B .V.