Quantification of the urea herbicide, diuron, in water by enzyme immunoassay

Surface and subsurface waters taken from agricultural lands were analysed for diuron by gas chromatography-mass spectrometry, high performance liquid chromatography and enzyme-linked immunosorbent assay (ELISA). The last method used sheep polyclonal antibodies to chlortoluron. Antibody binding was revealed by the colour developer 3,3',5,5'-tetramethylbenzidine-hydrogen peroxide. The colour, measured at 450 nm, was inversely related to the concentration of diuron. The detection limit in pure water was 0.01 ppb and the quantitative range was 0.05-1 ppb. The method detected urea herbicides with 3 or 4 substituted phenyl groups provided they were not larger than 4 atoms. The results obtained by ELISA showed good correlation with those obtained by instrumental methods. The ELISA results were slightly lower in surface waters and higher in subsurface waters. There was no need for extraction, clean-up or concentration before analysis.