Simplified determination of combined residues of lindane and other HCH isomers in vegetables, fruits, wheat, pulses and medicinal plants by matrix solid-phase dispersion (MSPD) followed by GC-ECD

A fast, simple and inexpensive sample preparation method based on matrix solid-phase dispersion (MSPD) technique is proposed for the isolation of combined residues of hexachlorocyclohexane isomers from fruits, vegetables, grains, pulses and medicinal plants. Both extraction and clean-up were carried out in a single step and target compounds were determined by gas chromatography coupled with electron capture detection (GC-Ni-63 ECD). The major factors affecting extraction yield and sensitivity, such as type of dispersant material and extraction solvent, were evaluated and optimised. Under optimised conditions, 5 g of sample matrix was dispersed with 500 mg of Florisil and blended with 1 g of anhydrous magnesium sulphate and 500 mg of sodium chloride, and transferred into a glass column containing neutral alumina (2 g) and anhydrous sodium sulphate (500 mg). The dispersed sample matrix was then eluted with 10 ml of n-hexane-ethyl acetate mixture (70:30, v/v) and repeated with another 10 ml of same solvent mixture. Recoveries of the proposed method for the spiked samples ranged from 93% to 103% and the day-to-day variability remained between 5% and 10%. The limit of detection (LOD) of alpha-, beta-, gamma- and delta- HCH was 3, 6, 4 and 5 ng g(-1), respectively. Satisfactory results were obtained in the routine analysis of real samples, confirming the reliability and efficacy of this method for the analysis of HCH residues in food matrices and medicinal plants. (C) 2008 Elsevier Ltd. All rights reserved.