Jornal de Técnicas Analíticas e Bioanalíticas

Abstrato

Analysis of Pesticides in Water Samples and Removal of Monocrotophos by γ-Irradiation

Ismail M, Murtaza Sayed, Hasan M Khan and William J Cooper

The analysis of 20 organochlorine pesticides has been carried out in surface water samples collected from Peshawar, KPK, Pakistan, using SPME-GC-ECD method. This method showed good liner response with R² values in the range of 0.9933 to 0.9999 for all pesticides. Percent recoveries at 1 μg L^-1 for all the pesticides ranged from 89.9 to 106.1%. A total of 59 surface water samples were tasted for 20 organochlorin pesticides residues, of which, 37 samples were found contaminated with γ-BHC, 12 samples with β-BHC, 25 samples with heptachlor and 25 samples with aldrin with a maximum concentration of 0.092, 0.053, 0.089 and 0.036 μg L^-1, respectively. However other pesticides were found in lesser no. of water samples. The Gamma irradiation decomposition of monocrotophos aqueous solution at various concentrations (60-150 mg L^-1) was carried out and their removal efficiency was investigated. Gamma irradiation showed 100% degradation for a 60 mg L-1 solution at an absorbed dose of 1200 Gy. The dose constants investigated in this study ranged from 1.4×10-³ to 3.0×10^-3 Gy^-1. The effect of saturated solutions of N₂ and N₂O, and radical scavengers such as tert-butanol and iso-propanol, on the degradation of monocrotophos were also studied. The results showed that degradation of monocrotophos mainly proceeded through oxidative •OH radical. The inorganic by-products NO₃-, NH₄+ and PO₄^3- were quantitatively determined by ion chromatography. A detail mechanism pathway of monocrotophos degradation by irradition has been developed.