MULTIRESIDUE ANALYSIS OF PESTICIDES IN WINES BY SOLID-PHASE EXTRACTION

A method is described for screening wine for 74 pesticide residues. Al iquots of wine (10 mL) are extracted with 500 mg C-18-silica solid-pha se extraction (SPE) columns after addition of carbophenothion internal standard at 0.1 mg/L. The column is washed with 20% ethanol-water (4 mL), and pesticide residues are eluted with 1 mL ethyl acetate. The ex tract is made up to 2 mL final volume with isooctane for screening by gas-liquid chromatography (GC) using a narrow-bore FSOT column (5% phe nyl-95% methyl-silicone bonded phase) with effluent splitting to elect ron capture (ECD) and nitrogen-phosphorus (NPD) detectors. A second GC system, using a 50% phenyl-50% methyl-silicone FSOT column with efflu ent splitting to ECD and flame photometric detector (P mode), is used for confirmation. The SPE method was rapid, robust, and reproducible R ecovery of pesticides added at 0.2 mg/L were 70-110% for the majority of pesticides, with standard deviations (SDs) of 1-18%. Some highly po lar pesticides gave low recoveries. At a fortification level of 1 mg/L in wine, 13 fungicides gave recoveries of 80-118%, with SDs of 2-14%. At 0.02 mg/L, some less stable pesticides exhibited enhanced recoveri es due to the protective effects of coextractives during GC. Detection limits were 0.01-0.02 mg/L with no major interferences observed from a range of wines. The multiple GC column and detector combinations and the internal standard provided a high degree of assurance in the iden tification of residues in wine.