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 array 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′-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 μg/1 and also of the polar metabolites in concentrations up to 0,9 μg/1 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.