DETERMINATION OF PHENYLUREA HERBICIDES IN WATER SAMPLES USING ONLINE SORPTIVE PRECONCENTRATION AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH UV OF ELECTROSPRAY MASS-SPECTROMETRIC DETECTION

A recently developed method for the extraction of organic micropolluta nts from aqueous samples based on sorptive enrichment in columns packe d with 100% polydimethylsiloxane (PDMS) particles was coupled on-line with HPLC analysis. The sorptive enrichment procedure originally devel oped for relatively nonpolar analytes was used to preconcentrate polar phenylurea herbicides from aqueous samples. PDMS extraction columns o f 5, 10 and 25 cm were used to extract the herbicides from distilled, tap and river water samples. A model that allows prediction of retenti on and breakthrough volumes is presented. Despite the essentially apol ar nature of the PDMS material, it is possible to concentrate sample v olumes up to 10 ml on PDMS cartridges without losses of the most polar analyte under investigation, fenuron. For less polar analytes signifi cantly larger sample volumes can be applied. Since standard UV detecti on does not profiles ide adequate selectivity for river water samples, an electrospray (ES)-MS instrument was used to determine phenylurea h erbicides in a water sample from the river Dommel, Methoxuron was pres ent at a level of 80 ng/l. The detection limit of the current set-up, using 10 mi water samples and ES-MS detection is 10 ng/l in river wate r samples. Strategies for further improvement of the detection limits are identified. (C) 1998 Elsevier Science B.V.