Development of multi-residue method for determination of pesticides in river, ground and lake water in delhi using gas chromatography

A method for determination of selected pesticides in water and their distribution in surface, ground and lake water was developed. The methodology includes improved extraction, cleanup and determination of pesticides by using gas chromatography-electron capture detector (GLC-ECD). The pesticides alachlor, metolachlor, chlorpyriphos, fipronil, α-endosulfan, p,p’ -DDE, β-endosulfan, endosulfan sulfate and p,p’ -DDT were extracted using liquid-liquid partitioning, extract cleaned by adsorption column cleanup using florisil as adsorbent and analyzed by GLC-ECD. Under optimized conditions, GLC-ECD was found to be highly sensitive for the selected pesticides. Among the solvents used for extraction, dichloromethane gave highest recovery followed by hexane and ethyl acetate. The standardized cleanup procedure was found suitable analysis of pesticides in water as there was no matrix interference. The method was found to be accurate with recoveries ranging from 81.7–96.8%, repeatable (4.76- 7.48%), reproducible (RSD 4.41–7.03%) and sensitive (LOD 0.03–0.3 μg L⁻¹ and LOQ 0.1–0.6 μg L⁻¹). The residues of the selected pesticides were monitored in water of Yamuna River, a nearby Lake and ground water at Okhla and Wazirabad areas of Delhi. The pesticides detected in water samples of Yamuna river were β-endosulfan, β-endosulfan, p,p’ -DDE and p,p’ -DDT (traces to 0.324 μg L⁻¹). No residue of pesticides were found in ground and lake water except p,p’ -DDT (traces) in ground water at Okhla. The method developed is practical, efficient and reliable for the determination of the selected group of pesticides in the water samples.