Analysis of sulfonylurea herbicides by gas-liquid chromatography. 2. Determination of chlorsulfuron and metsulfuron-methyl in soil and water samples

Sulfonylureas are extracted from water samples using solid-phase extraction (SPE) with C18-silica) Teflon disks. Soil samples are extracted with 0.1 M sodium hydrogen carbonate, and the acidified extracts are processed as for water samples. The concentrated eluents are treated with diazomethane in ethyl acetate, which forms the thermally stable N,N'-dimethyl derivatives of the herbicides. Residues are screened by capillary GC using effluent splitting to electron rupture and nitrogen-phosphorus detectors. Residues are confirmed by GC-MS using selected ion monitoring