Analytical method for the determination of pesticides in soil by thin layer chromatography

Abstract

The term pesticide as used throughout this report refers to chemical substances (i.e. conventional pesticides) that are biologically active and interfere with the normal biological processes of living organisms deemed to be pests, whether these are noxious plants or weeds, insects, mould or fungi. Monocrotophos is an organophosphorus insecticide with systemic activity and is used for the control of a wide range of chewing, sucking and boring pests. Chloropyrofus is a crystalline organophosphate insecticide that inhibits acetyl cholinesterase and is used to control insect pests. Acephate is an organophosphate foliar insecticide, is used primarily for control of aphids. Accurately weighed 10g of spiked soil and transfer in to 50ml volumetric flask and add 20ml of methanol then kept in ultrasonicator for 20min for efficient extraction. The above extracts were filtered through whatman filter paper. The filtrates were evaporated on a heating mantle at 40°C to dryness. The residue was dissolved in 1ml of Methanol. The type of pesticide present in the soil sample was determined TLC method by using Methanol–water (8:2, v/v) as a mobile phase. The R_f value of test sample (1) and standard sample (1) Monocrotophos are 0.92 and 0.88 respectively, the spots are identified under the short U.V light and the spot colour is blue in colour. Other test samples did not produce any spots, it indicates the absence of Chloropyrofus, Quinolphos and Acephate in the soil sample.