MICROWAVE-ASSISTED SOLVENT-EXTRACTION AND REVERSED-PHASE LIQUID-CHROMATOGRAPHY UV DETECTION FOR SCREENING SOILS FOR SULFONYLUREA HERBICIDES

A multi-residue method for the rapid assay of cinosulfuron, thifensulf uron-methyl, metsulfuron-methyl, sulfometuron-methyl and chlorsulfuron in soil samples has been developed. The method involves microwave-ass isted solvent extraction (MASE) prior to analysis by reversed-phase li quid chromatography (RPLC) and UV detection at 226 nm. MASE conditions were established providing efficient extraction without degradation o f the analytes, furthermore selectivity can be enhanced by limiting th e coextraction of interferences. Selected MASE conditions, including d ichloromethane-methanol (90:10,v/v) as the extraction solvent, provide d, in 10 min, a complete extraction of the analytes from soil samples. The extracts obtained with the developed MASE procedure are analysed by RPLC-UV in less than 15 min without additional cleanup; the overall procedure allows the determination of the analytes in soils to a leve l of at least 5 mu g/kg. Method validation was performed by analysing freshly spiked sail samples and samples with aged residues at levels b etween 20 and 1000 mu g/kg. Depending on the spiked level and the type of spiked sample recoveries were obtained between 70-100% with R.S.D. s between 1-10%. (C) 1998 Elsevier Science B.V.