Determination of fungicide residues in white grapes for winemaking by gas chromatography with mass spectrometric detection and assessment of matrix effects.

A new analytical method, based on organic solvent extraction with dichloromethane-acetone (75 + 25, v/v) followed by gas chromatography with mass spectrometric detection, is presented for the determination of residues of 10 fungicides in white grapes for vinification. Some of them (cyprodinil, fludioxonil, and pyrimethanil) have been used for only 2-3 years and, therefore, no methods are available in the scientific literature for such a screening. Quality parameters yielded good precision (relative standard deviation of <10%) and detection limits (ranging between 1 and 18 microg/kg) that are lower than the maximum residue limits (MRLs) set by the 76/895/European Economic Community (EEC) and 90/642/EEC Directives. The applicability of the method was evaluated by analysis of 5 different white grapes produced in the Rías Baixas area in Galicia (northwestern Spain) for vinification. The method showed good performance in analyses of real samples to determine whether the concentrations of the fungicides used exceeded their MRLs. The method of standard additions was found to be necessary to avoid matrix effects in the quantification of fungicide residues. Results showed that concentrations of the fungicides identified in grapes were lower than the MRLs established by the European legislation.