Column switching and liquid chromatographic technique for the rapid determination of fenoxycarb insecticide residues in apples

Fenoxycarb residues are analyzed by column switching and reversed-phase hig h performance liquid chromatography (RP-HPLC). The active ingredient is ext racted from apples on a silica gel column using a n-hexane - diethyl ether mixture. The eluate is evaporated, dry residue dissolved in acetonitrile-de ionized water, and injected into the liquid chromatograph with a column swi tching system (C8 columns), and a UV-photodiode array detector (UV - PDA). The analyte is quantified by the external standard method. The average reco veries of the active ingredient from the spiked sample are 81.3 +/- 3.2% an d 80.3 +/- 5.8%, the coefficients of variation are 3.9% and 7.2% for fortif ication levels 0.1 mg/kg and 0.05 mg/kg, respectively, and the limit of qua ntification at lambda = 228 nm is 0.05 mg/kg. Labor and organic solvent use s are greatly reduced in comparison to the existing methods. The overall pr ocedure allows a sample throughput of up to 30 samples per day. The method was applied to the determination of fenoxycarb residue in apples from treat ed orchards.