Matrix solid-phase dispersion extraction versus solid-phase extraction in the analysis of combined residues of...

This paper describes a method based on matrix solid-phase dispersion (MSPD) to determine the presence of combined residues of hexachlorocyclohexane (HCH) isomers (alpha-, beta-, gamma- and delta-) in various plant matrices including vegetables, fruits, leaves, grains and roots, by gas chromatography with (63)Ni electron-capture detection. The MSPD method consists of sample homogenization, cellular disruption, exhaustive extraction, fractionation and clean up by simple processes in which a small amount of sample (5 g) was blended with Florisil and the mixture passed into a small chromatographic column and eluted with 10 ml of n-hexane-ethyl acetate solvent mixture (70:30; v/v) and repeated with another 10 ml of the same solvent mixture. A comparison with classical solid-phase extraction (SPE) showed MSPD to be efficient, fast, simple and easy to perform. The detection limit of various HCH isomers was found to be in the range of 2.15-5.68 ng and method detection limit varied from 0.465 to 1.136 ng g(-1). Mean recoveries were found in the range of 91-98%. Till date, there are no official methods or standards by Central Pollution Control Board or Bureau of Indian standards that take into account India's real life conditions in the analysis of pesticide residues in plant matrices and the MSPD method described herein has proved to be a feasible one for the analysis of combined residues of HCH isomers in various plant materials.