Ultrasonic-assisted matrix solid-phase dispersion as an improved methodology for the determination of pesticides in fruits

An Ultrasonic-assisted matrix solid-phase dispersion (UA-MSPD) method has been developed for extracting and cleaning-up 15 organophosphorus pesticides (OPPs) and 9 triazines in fruits. Using reversed phase octasilyl-derivatised silica (C8) as dispersant and ethyl acetate as extraction solvent two sonica, tion devices, an ultrasonic bath and a sonoreactor, were tested for speeding and increasing the efficiency of the MSPD process. A standard MSPD and a heating-assisted MSPD procedure were also done. Gas chromatography-mass spectrometry was used for analyte determination. 1-min sonication with the sonoreactor at 50% amplitude provided the best results, with reproducibilities below 15% for the pesticides studied. The general low detection limits (1-42 mu g kg(-1))ensure proper determination at maximum allowed residue levels set in Current legislations, except for dimethoate and disulfuton. The analytical performance of the method was evaluated for apples. pear and apricot, showing little or no matrix effect. (C) 2008 Elsevier B.V. All rights reserved.