Optimization of sweep codistillation apparatus for determination of coumaphos and other organophosphorus pesticide residues in animal fat.

Optimum conditions have been developed for the quantitative recovery of coumaphos from animal fat by using a commercial sweep codistillation unit. Under the conditions specified (255 degrees C distillation temperature, 250 mL/min of nitrogen, 60 min sweep time) and using Florisil trapping, the mean recovery of coumaphos was 91% with a coefficient of variation of 6%. Other organophosphorus pesticides recovered include diazinon, chlorpyrifos, ethion, and bromophos-ethyl with recoveries ranging from 90 to 96% and coefficients of variation ranging between 4 and 6%.