Trace-Level Quantitation of Sulfonylurea Herbicides in Natural Water

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Abstract
A novel gas chromatographic/electron capture detection (GC/ECD) technique is described for quantitation of trace sulfonylurea herbicide residues in natural water. In this method, the parent sulfonylurea herbicides are isolated from their aryl sulfonamide metabolites by Florisil chromatography, and the acidic aqueous hydrolysis products of the parent compounds are then quantitated. The method has been validated for both metsulfuron methyl (MET; methyl 2-{[(4-methoxy-6-methyl-1,3,5-triazin- 2-yl)aminocarbonyl] aminosulfonyl} benzoate), and chlorsulfuron [CHLOR; 2-chloro-A/-(4-methoxy-6- methyl-1,3,5-triazin-2-yl)-aminocarbonyl benzenesulfonamide]. Acidic hydrolysis of the isolated parent compounds MET and CHLOR produced a high yield of the corresponding aryl sulfonamides, methyl 2-(aminosulfonyl)benzoate and 2- chlorobenzenesulfonamide, as confirmed by mass spectral analysis. In-house validation studies confirmed excellent chromatographic behavior, high recovery efficiency (>80%), and generally good precision (<12% coefficient of variation) for quantitation of MET and CHLOR in fortified natural water samples over a wide range of concentrations (50 ppb, 500 ppt, and 50 ppt). Validated limits of quantitation were 50 ppt, with minimum limits of detection conservatively estimated as 10 ppt.

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