EPA 8270 analytical standard of organophosphorus pesticides containing a mix of O,O,O – triethylphosphorothioate, sulfotep, phorate, methyl parathion, parathion and famphur in hexane:acetone (80:20 v/v) was obtained from Supelco (Bellefonte, USA) at a concentration of 2000 mg L−1. Analytical standard of organochlorine pesticides containing a mix of alpha-BHC, gamma-BHC, beta-BHC, heptachlor, delta-BHC, heptachlor epoxide isomer B, endosulfan I (alpha), 4,4-DDE, dieldrin, endrin, 4,4-DDD,