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 pesticides in apple samples is reported. 'Safety periods' (time which must elapse between pesticide spraying and consumption of the fruit), their penetration 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 pesticides and apples were periodically taken. Afterwards, apples were subjected to extraction by Soxhlet using ethyl acetate as solvent and the pesticides were determined by gas chromatography (using a capillary column and NPD detector). The results showed a poor decay of fenitrothion after 2 months of treatment and a logarithmic decay for the other two pesticides. The study on the trees was performed following a similar analytical methodology. In this case, the three compounds showed logarithmic decay curves, indicating more rapid decay than in the laboratory. In no case was any pesticide observed to penetrate inside the apple (under the peeling).