DOI: 10.36347/sajb.2016.v04i05.014

Pages: 432-443

The photolysis of Chlorpyrifos technical was assessed by following the OECD guideline 316. The Tier 1: Theoretical screen of photolysis test for Chlorpyrifos technical was conducted to determine the approximate half-life by taking a single UV-Visible absorption spectrum for Chlorpyrifos technical in sterile pH 4 buffer solutions from 250nm to 800nm. Based on tier 1- theoretical screen study approximate half-life value obtained less than 30 days. The tier 2- experimental study was conducted at 25± 2°C under direct Sunlight. The percent degradation, half-life and rate constant data calculated following Tier 2 study. Based on the Tier 2 study the results, the direct photolysis rate constant (Kd) of Chlorpyrifos technical was 0.07119 day-1 and Half-life (t1/2) value was 9.73 days. The fortified samples showed an average recovery of 96.88% in pH 4 buffer solution. LC-MS analysis was done to identify the degradation product of Chlorpyrifos Technical in both, irradiated and non-irradiated samples on day 0, 3, 7, 10, 15, 20, and 30. The degradation products identified in the irradiated samples are O, O-diethyl hydrogen phosphorothioate, O-(amino methyl) O, O-diethyl phosphorothioate, and O-ethyl O-methyl O-(3, 5, 6-trichloropyridin-2-yl) phosphorothioate on day 3, day 7, and day 10 in Chlorpyrifos Technical. No degradation product was identified in the dark control Chlorpyrifos Technical samples. On the basis of these results, aqueous abiotic photolysis is expected to contribute significantly to the degradation of Chlorpyrifos technical. Direct photolysis is expected to be a major route of degradation of Chlorpyrifos in the environment as evidenced by the absorbance of Chlorpyrifos in UV/VISIBLE at the wavelength > 290 nm.