Small-scale multi-residue method for the determination of organochlorine and pyrethroid pesticides in vegetables

Abstract

A simple and inexpensive multi-residue method is described for the determination of organochlorine and pyrethroid pesticides in vegetables. Pesticides in vegetables were extracted with ethanol and partitioned into toluene. A mini-column packed with 0.5 g of Florisil was used for further clean-up prior to gas chromatographic determination. The detection limits were 0.02–0.05 μg/g without concentrating the extract, which are below the maximum residue limits set by the Singapore government. The recoveries of the pesticides from fortified samples were 65–97% at the 0.1 μg/g level and 87–114% at the 0.5 μg/g level. The amounts of the reagents required for analysing one sample are only 100 ml of ethanol, 6 ml of toluene and 0.5 g of Florisil. Among fifteen vegetable samples collected from the Singapore local market and were analysed by this method, five were found to contain detectable amount of organochlorine pesticides. One sample contained 22 μg/g of endosulfan but the residue levels in other four samples were below 1 μg/g.