Simple Analytical Method for Organophosphorus Pesticide Determination in Unpolished Rice, Using Removal of Fats by Zinc Acetate

Open Access
Publisher Website
Google Scholar
Abstract
A rapid and simple method is developed for the determination of organophosphorus pesticides in unpolished rice. The new method incorporated acetonitrile-water (1 + 1) extraction, removal of fats by zinc acetate, and further cleanup on an activated charcoal chromatographic column. The higher fatty acids in the extract react rapidly with zinc acetate to form insoluble zinc carboxylates, which precipitate. Additional interferences were cleaned up on an activated charcoal chromatographic column, and organophosphorus pesticides adsorbed on the activated charcoal were eluted with acetone-hexane. Dimethoate is not retained on the activated charcoal and must be extracted with dichloromethane from the first acetonitrile-water eluate. Pesticides are measured by flame photometric gas chromatography. Recoveries from 50 g unpolished rice samples fortified with 5-50 μg diazinon, 6-30 μg parathion, 8-40 μg fenitrothion and IBP, 10-50 μg dimethoate and fenthoate, 20-100 μg malathion, or 40-200 μg EPN ranged from 75.7 to 95.8%.