Degradation of azinphos-ethyl in apples stored in different conditions

Residual levels of the pesticide azinphos-ethyl were studied in an experiment on field-sprayed Grand-Smith apples. The pesticide was applied according to manufacturer recommendations. Apples received a single spraying at a rate of application of 60 g of active ingredient/100 L. Residues were determined with a simple gas chromatographic method using a 30 m glass capillary column and an NP detector. The recovery of azinphos-ethyl was 87-123%, and the limit of determination was 0.005 mg/kg. The decomposition of azinphos-ethyl was studied in apples remaining on the trees after spraying and in apples harvested and stored under ambient temperature conditions, in refrigerated rooms, and in controlled atmosphere (CA) rooms. The results show that there exists a delayed residue decline during postharvest storage compared to that for apples remaining on the trees. From the experimental results, best fit curves were determined and kinetic equations, rate constants, and half-lives were Calculated. Half-lives and times to reach the legal limit (0.05 mg/kg) were, respectively, 10 and 62 days for apples on the trees, 83 and 447 days for apples stored at ambient conditions, 91 and 507 days for apples stored in CA rooms, and 136 and 749 days for apples stored in refrigerated rooms.