Development of a polarization fluoroimmunoassay for the herbicide metsulfuron-methyl

A polarization fluoroimmunoassay (PFIA) based on previously raised rabbit polyclonal antibodies was developed for detection and quantification of the sulfonylurea herbicide metsulfuron-methyl (MSM) in surface water samples. A 'restricted' hapten, consisting of only phenylsulfonamide moiety of MSM molecule was used to synthesize a fluorescein-labelled derivative of MSM (tracer). The limited assay cross-reactivity was observed towards most of sulfonylurea herbicides, with exception of primisulfuron-methyl and chlorimuron-ethyl. The optimized MSM PFIA had a dynamic range from 30 to 1000 μg l^-1 with an IC₅₀ value of 123 μg l^-1 and a lower detection limit of 5 μg l^-1 Intra- and inter-assay precision over the of MSM calibration curve dynamic range were 0.9 and 7.1%, respectively. Influence of several organic solvents on MSM PFIA performance was investigated, and the assay was found to tolerate up to 10% v/v of methanol, DMSO and acetone. Application of MSM PFIA technique to the analysis of surface water samples taken from lakes and rivers in Bavaria, and spiked with MSM at concentration of 50μg l^-1, gave mean MSM recoveries of 108.6-110.8%.