Determination of acephate and methamidophos in foods using super-absorbent polymer

The water-soluble pesticides acephate and methamidophos were extracted from comminuted vegetables after their juice was absorbed by super-absorbent polymer particles. Food homogenate (10 g) was mixed with 5 g of polymer, and the mixture was extracted with 75 mi of ethyl acetate using a high speed homogenizer, The extracts were cleaned up by a silica gel mini-column and determination was by GC-FPD. This extraction procedure was compared with the Japanese official method in which samples were dehydrated with 75 g of anhydrous Na2SO4 and extracted with ethyl acetate, Unlike that of anhydrous Na2SO4 our mixture of sample and polymer was not bulky, nor did it harden. Recovery tests in seven vegetables at the 0.1 ppm level showed that recovery rates with polymer dehydration were usually more than 80% for both pesticides with <10% precision, The two extraction procedures detected similar pesticide levels in pesticide-containing vegetables. These findings revealed that the inexpensive super-absorbent polymer can be used in residual analysis of acephate and methamidophos in foods in place of bulky anhydrous Na2SO4.