Determination of Selected Organophosphorus Insecticides and Their Oxides in Tea and Soil by HPTLC

Abstract

A determination method of selected organophosphorus insecticides and their oxides (Parathion- methyl and Dimethyl- paraoxon; Parathion and Paraoxon; Chlorpyrifos and Chlorpyrifos-oxon.) in tea and soil was developed with high performance thin-layer chromatography (HPTLC). The acetonitrile was applied to extract tea sample and the tandem column of solid-phase extraction was to clean samples up. The soil sample was extracted with ethyl acetate and not to be clean-up. The processed samples were directly applied as bands to glass-backed silica gel 60F254 HPTLC plates. The plates were developed by AMD with 7-step for tea samples and 2-step for soil samples. Evaluation of the developed HPTLC plates was performed densitometrically. Three fortification levels of the samples were conducted in the test. In this method, the detection limits of parathion-methyl, dimethyl-paraoxon, parathion, paraoxon and chlorpyrifos-oxon were from 3.0×10–9 g to 1.0×10–8 g in different development systems. The chlorpyrifos was from 7.0×10–9 g to 2.0×10–8 g. Recoveries of the pesticides residues from tea were 68.98-116.73%, and the soil were 69.44 –120.00 % except the chlorpyrifos. The relative standard deviations were 4.02–17.50 % for tea, and 3.11–14.20 % for soil except the chlorpyrifos. The Rf value and the validation data were given. The development by AMD in this method was discussed.