Gas Chromatographic Determination of Cypermethrin and Fenvalerate Residues in Wheat and Milled Fractions

A method to determine cypermethrin and fenvalerate residues in wheat and milled fractions was developed. The method involved extraction of residues with acetone-hexane and partitioning residues into hexane using aqueous sodium chloride solution. After concentrating hexane extracts, column chromatography cleanup was performed on Pasteur pipette micro columns containing Florisil, using benzene as the elution solvent, and packed column electron-capture GC was used for analysis. The limits of detection with this method were 0.02mgkg−1 for cypermethrin and 0.04mgkg−1 for fenvalerate. Average recoveries of 82 to 98% of cypermethrin and 80-86% of fenvalerate were obtained from wheat and milled fractions fortified at 0.41 to 3.80 mg kg−1. No interference was observed from co-extractives.