Comparison of octadecylsilica and graphitized carbon black as materials for solid-phase extraction of fungicide and insecticide residues from fruit and vegetables

Methods for the determination of thirteen fungicide and insecticide residues by solid-phase extraction with C-18 and graphitized carbon black (GCB) were evaluated. The extraction of the residues was achieved by using matrix solid-phase dispersion (MSPD) and more conventional polar solvent extraction followed by liquid-solid phase partitioning. Determination was carried out by capillary gas chromatography with electron-capture and mass spectrometry detectors. The recoveries were determined by fortifying six different crops (apples, oranges, pears, tomatoes, lettuces and paprikas) with the pesticides studied (bromopropylate, chlorpyrifos methyl, cypermethryn, deltamethryn, fenarimol, fenvalerate, imazalil, lindane, permethryn, phentoate, procymidone, propiconazole and vinclozoline). Although, the data showed that the two extraction methods and both sorbents were able to isolate the pesticide residues from fruit and vegetables, the best results were obtained using MSPD with C-18 which gave recoveries ranging from 70 to 105% and practical detection limits between 5.0 and 50.0 mu g/kg for all the compounds. Ten of these pesticides have been detected in samples taken from Valencia markets, at levels of 0.02-20.50 mg/kg using the described methodology. (C) 1997 Elsevier Science B.V.