ELISA determination of the sulfonylurea herbicide metsulfuron-methyl in different water types

Sulfonylurea herbicides efficiently control broad-leafed weeds and some grasses in cereals. They are typically applied at rates of <100 g/ha. The application of a recently developed competitive enzyme-linked immunosorbent assay (ELISA) for metsulfuron-methyl to spiked real-world water samples such as tap water, surface water from lakes and rivers, municipal wastewater, and landfill leachate is described. With pure water samples the IC₅₀ value for the target analyte is 1.4 μg/L with the LOD being 40 ng/L. Determination of tap water and surface water was possible without any sample preparation such as filtration, extraction, pH adjustment, or dilution. On the contrary, with wastewater and leachate strong matrix interferences were observed, and, therefore, filtration and dilution of these samples prior to the immunochemical determination was necessary. Whereas with wastewater a 100- fold dilution was sufficient to ensure accurate herbicide quantification, even with a 500-fold dilution of leachate a positive bias of the method at lower concentrations (<1 μg/L) was observed. Determination of samples spiked with commercial metsulfuron-methyl formulation (GROPPER) showed no interference due to matrix in the immunological method.