Determination of pesticide residues in wine by solid-phase extraction on-line combined with liquid chromatography tandem mass spectrometry

Liquid chromatography tandem mass spectrometry (LC-MS/MS) has been combined with different sample preparation strategies to determine potential pesticide residues existing in wine. Herein, we propose the on-line coupling between solid-phase extraction (SPE), based on a reversed-phase polystyrene-divinyl benzene (PS-DVB) sorbent, and LC-MS/MS for the automated monitoring of a selection of 48 pesticides (37 fungicides and 11 insecticides) in this beverage. Parameters affecting the sensitivity, selectivity, accuracy and robustness of the method are evaluated as function of sample volume, clean-up conditions, and number of extraction-desorption cycles performed with the same SPE cartridge. Considering a sample volume of 3 mu L, the on-line SPE LC-MS/MS method was free of MEs, attaining LOQs below 2.5 mu g L-1, and providing recoveries in the range from 70 to 120 % for 90 % of investigated compounds. Increasing the volume of sample loaded in the on-line SPE cartridge to 25 mu L permitted a further reduction of LOQs, with a linear response range (0.1-25 mu g L-1), covering the analysis of low residue samples. Twelve out of 48 investigated compounds were noticed at individual concentrations above 10 mu g L-1 in at least one out of 30 processed wines. In white wines, the sum of concentrations for iprovalicarb, fenhexamide and metalaxyl represented more than 50 % of total residues. As regards red wines, tebuconazole, cyprodinil and metalaxyl were the predominant species.