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

An optimized gas chromatographic method is described for the determina tion of thirteen organochlorine and pyrethroid pesticides currently ap plied to vegetable and fruit crops. The selected pesticides are extrac ted with ethyl acetate-sodium sulphate and an aliquot is evaporated to dryness and reconstituted in 10 mi of light petroleum. Sample clean-u p is accomplished by aspirating 2 ml of the light petroleum extract th rough a silica gel solid-phase disposable cartridge. Following aspirat ion, 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 recoveri es varied from 73 to 106%, except for captan (51%), with relative stan dard deviations from 3.5 to 20.4% in all instances. Detection limits o f 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 pres ented for extracts of four different food product types fortified with the target pesticides. Data for real residues of these pesticides fou nd in vegetables during 1 year routinely applying the multi-residue me thod are also presented.