GAS-CHROMATOGRAPHIC DETERMINATION OF ORGANOCHLORINE AND PYRETHROID PESTICIDES OF HORTICULTURAL CONCERN

An optimized gas chromatographic method is described for the determination of thirteen organochlorine and pyrethroid pesticides currently applied to vegetable and fruit crops. The selected pesticides are extracted with ethyl acetate-sodium sulphate and an aliquot is evaporated to dryness and reconstituted in 10 mi of light petroleum. Sample clean-up is accomplished by aspirating 2 ml of the light petroleum extract through a silica gel solid-phase disposable cartridge. Following aspiration, the sample is eluted with 2 mi of diethyl ether-light petroleum (50:50) and is ready for GC with electron-capture detection. The method provides an excellent clean-up for all matrices studied. The recoveries varied from 73 to 106%, except for captan (51%), with relative standard deviations from 3.5 to 20.4% in all instances. Detection limits of less than 0.01 mg/kg were obtained. The sample throughput is ca. 51 per 24 h. These results were confirmed by GC-MS. Results are also presented for extracts of four different food product types fortified with the target pesticides. Data for real residues of these pesticides found in vegetables during 1 year routinely applying the multi-residue method are also presented.