EVALUATION OF THE DECAY OF MALATHION, DICHLOFLUANID AND FENITROTHION PESTICIDES IN APPLE SAMPLES, USING GAS-CHROMATOGRAPHY

In this paper an analytical study of the decay, both in the laboratory and on the trees of malathion, fenitrothion and dichlofluanid pestici des in apple samples is reported. 'Safety periods' (time which must el apse between pesticide spraying and consumption of the fruit), their p enetration inside the fruit in each situation and the main reasons of the decay are evaluated. Studies were independently performed on each pesticide. To undertake the study in the laboratory, the apple samples were previously sprayed with an aqueous suspension of commercial pest icides and apples were periodically taken. Afterwards, apples were sub jected to extraction by Soxhlet using ethyl acetate as solvent and the pesticides were determined by gas chromatography (using a capillary c olumn and NPD detector). The results showed a poor decay of fenitrothi on after 2 months of treatment and a logarithmic decay for the other t wo pesticides. The study on the trees was performed following a simila r analytical methodology. In this case, the three compounds showed log arithmic decay curves, indicating more rapid decay than in the laborat ory. In no case was any pesticide observed to penetrate inside the app le (under the peeling).