Determination of phenylurea herbicides in natural waters at concentrationsbelow 1 ng 1(-1) using solid-phase extraction, derivatization, and solid-phase microextraction gas chromatography mass spectrometry

A procedure is presented which allows the ultratrace level determination of phenylurea herbicides (PUHs) in natural waters. Samples were enriched by s olid-phase extraction (SPE) on Carbopack B and alkylated with iodoethane an d sodium hydride to yield thermostable products. After derivatization, the aqueous samples were extracted and injected by SPME. The use of iodoethane instead of iodomethane allowed the differentiation between parent compounds and the N-demethylated metabolites. Limits of detection were between 0.3 a nd 1.0 ng/l for the parent compounds. Standard deviations below 10% were ac hieved for samples containing more than 4 ng/l in very different matrices i ncluding Nanopure water, lake water, and waste water treatment plant (WWTP) effluent. Moreover, the para-hydroxylated metabolite of diuron could be qu antified with the same procedure. The presence of further metabolites was a ssessed qualitatively. Chromatography was stable over a large number of mea surements even with dirty samples from WWTP effluent. The precision and sen sitivity of the developed analytical method allowed the investigation of th e fate of PUHs in lakes, their degradation during drinking water treatment and their transport within the North Sea. (C) 2001 Elsevier Science B.V. Al l rights reserved.