A Simple Method for Screening of Soil Samples for Organochlorine Insecticide Residues by Thin-Layer Chromatography

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Abstract
A simple, rapid and sensitive screening procedure requiring no costly equipment is described for the estimation of chlorinated hydrocarbon insecticide residues in soil samples by semi-quantitative TLC. Three published insecticide residue extraction procedures were evaluated for the recovery of spiked as well as field-acquired and naturally weathered residues from soil samples. Extraction of soils with methanol-water (2:1, v/v) and partitioning of extracts with n-hexane, followed by TLC on alumina G plates gave minimum interference of co-extractives and complete recovery of the residues. The average recoveries of dieldrin and p,p′-DDT as determined by GC for the validation of the method were 93 and 110%, respectively. Additional column chromatographic clean-up on alumina neutral was necessary for soil samples rich in organic matter. Insecticide residues could be estimated down to 0.02μg g−1; the procedure has been used for the determination of organochlorine residues in more than 100 soil samples.