DECAY OF FENTHION IN GREEN TABLE OLIVES

The period needed for fenthion, an insecticide frequently used in sout hern Italy against the olive fly, to decline to safety levels was asse ssed by developing a method for extraction and gas-liquid chromatograp hy with nitrogen-phosphorus detection, and measuring fenthion persiste nce in green table olives after treatments in two periods of the year when the insect is particularly active. High overall recovery (90-100% ), satisfactory linearity (r(2) = 0.998) and precision (4-5%) in the u seful working range 0.03-3.962 ppm, and a low detection limit of the a ctive ingredient (0.004 mg/kg) were obtained. The investigation on two olive cultivars showed swift degradation of fenthion in July, accordi ng to the first-order kinetic model with a half-life of about 1 day, w hile in September the decay seemed to be the result of two processes, the slower of which had a half-life ranging from 3 to 7 days. The meth od was used to evaluate the effect of sweetening olives with 2% alkali ne solution on fenthion content, and a decrease in the pesticide conce ntration of 7-10% was found.