SMALL-SCALE MULTI-RESIDUE METHOD FOR THE DETERMINATION OF ORGANOCHLORINE AND PYRETHROID PESTICIDES IN VEGETABLES

A simple and inexpensive multi-residue method is described for the det ermination of organochlorine and pyrethroid pesticides in vegetables. Pesticides in vegetables were extracted with ethanol and partitioned i nto toluene. A mini-column packed with 0.5 g of Florisil was used for further clean-up prior to gas chromatographic determination. The detec tion limits were 0.02-0.05 mu g/g without concentrating the extract, w hich are below the maximum residue limits set by the Singapore governm ent. The recoveries of the pesticides from fortified samples were 65-9 7% at the 0.1 mu g/g level and 87-114% at the 0.5 mu g/g level. The am ounts of the reagents required for analysing one sample are only 100 m l of ethanol, 6 ml of toluene and 0.5 g of Florisil. Among fifteen veg etable samples collected from the Singapore local market and were anal ysed by this method, five were found to contain detectable amount of o rganochlorine pesticides. One sample contained 22 mu g/g of endosulfan but the residue levels in other four samples were below 1 mu g/g.