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

Sulfonylurea herbicides efficiently control broad-leafed weeds and some gra sses in cereals. They are typically applied at rates of <100 g/ha. The appl ication of a recently developed competitive enzyme-linked immunosorbent ass ay (ELISA) for metsulfuron-methyl to spiked real-world water samples such a s 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 mu g/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 contrar y, with wastewater and leachate strong matrix interferences were observed, and, therefore, filtration and dilution of these samples prior to the immun ochemical determination was necessary. Whereas with wastewater a 100-fold d ilution was sufficient to ensure accurate herbicide quantification, even wi th a 500-fold dilution of leachate a positive bias of the method at lower c oncentrations (<1 mu g/L) was observed. Determination of samples spiked wit h commercial metsulfuron-methyl formulation (GROPPER) showed no interferenc e due to matrix in the immunological method.