Column Extraction of Chlorpyrifos from Contaminated Fish

A method for measuring chlorpyrifos in fish, which combines extraction, filtration, and cleanup in one step, is described. Minced fish samples were mixed with potassium dihydrogen phosphate and disodium hydrogen phosphate, ground with anhydrous sodium sulfate, and eluted from a prepacked chromatographic column containing silica gel. The endogenous coextractives were retained by the column while chlorpyrifos was quantitatively eluted with 40 mL of 5% ether in hexane. Recoveries averaged 86.8% for unexposed fish fortified with 2-12 ppm of chlorpyrifos. The method was applied to the analysis of fish from a lagoon contaminated with chlorpyrifos by a spray treatment of a wooden bridge for termites.