Detection and identification of the herbicide isoproturon and its metabolites in field samples after a heavy rainfall event

The occurence of isoproturon [N-(4-isopropylphenyl)-N`, N`-dimethyl urea] and its metabolites was investigated in soil solution, runoff and creek water from a farm in Scheyern (Bavaria, FRG) after a heavy rainfall event following the application in spring 1994. The analytical procedure included enrichment by C 18 solid-phase extraction and reversed-phase HPLC with diode army detection. The major degradation product in most of the samples was identified as 2-hydroxy-isoproturon [N-(4-(2-hydroxyisopropyl)-phenyl)-N`, N`-dimethyl urea] using the authentic compound. The latter has been isolated from wheat cell culture medium and its structure elucidated by NMR and MS. Furthermore, the polar metabolites monodesmethyl-isoproturon [N-(4-Isopropylphenyl)-N`-T-methyl urea] and 2-hydroxy-monodesmethyl-isoproturon [N-(4-Isopropylphenyl)-N'-methyl urea] and 2-hydroxy-monodesmethyl-isoproturon [N-(4-(2-hydroxyisopropyl)-phenyl)-N'-methyl urea] were identified by comparison of their retention times and DAD-UV spectra with reference compounds. The detection of isoproturon in soil solution down to 170 cm depth and in creek water in concentrations exceeding 4 mu g/l and also of the polar metabolites in concentrations up to 0,9 mu g/l indicated the mobility of this phenylurea herbicide and its degradation products. Therefore the metabolites should be considered in studies on the migration of isoproturon and in the ecotoxicological evaluation.