Multiresidue Analysis of Pesticides in Wines by Solid-Phase Extraction

Abstract

Abstract A method is described for screening wine for 74 pesticide residues. Aliquots of wine (10 mL) are extracted with 500 mg C18–silica solid-phase extraction (SPE) columns after addition of carbophe-nothion 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 extract is made up to 2 mL final volume with isooctane for screening by gas–liquid chromatography (GC) using a narrow-bore FSOT column (5% phenyl–95% methyl-silicone bonded phase) with effluent splitting to electron capture (ECD) and nitrogen–phosphorus (NPD) detectors. A second GC system, using a 50% phenyl–50% methyl-silicone FSOT column with effluent splitting to ECD and flame photometric detector (P mode), is used for confirmation. The SPE method was rapid, robust, and reproducible. Recovery 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 polar 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 recoveries 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 identification of residues in wine.