Pressurised liquid extraction and capillary electrophoresis–mass spectrometry for the analysis of pesticide residues in fruits from Valencian markets, Spain

A procedure based in capillary electrophoresis–mass spectrometry (CE–MS) for the analysis of seven pesticides (flutolanil, simazine, haloxyfop, acifluorfen, dinoseb, picloram, and ioxynil) in four Mediterranean summer fruits with high water content (peaches, melon, watermelon, and apricot) is developed. Several conditions were studied for the optimisation of both, the separation and the electrospray (ESI) connection. The best results were obtained using 35 mM ammonium formiate (pH 9.7) as separation buffer, 20 °C as capillary temperature and 23 kV as applied voltage in an uncoated fused-silica capillary with 50 cm total length, 25 cm thermostated length, 25 cm at room temperature length, connected to an MS detector by an ESI sprayer kit. The appropriate sheath liquid was ammonium formiate with 10% of formic acid at 5 μL min−1. Separation time for all pesticides was achieved in 12 min. Extraction was carried out by pressurised liquid extraction (PLE) in an ASE® 200 system from Dionex using hot water at 60 °C and 1500 psi, followed by a solid-phase extraction (SPE) clean-up step using StrataX cartridges. Recoveries ranged from 58% to 88% and the relative standard deviations (RSDs) were 9–19%. The limits of detection (LODs) and quantification (LOQs) were in all cases lower than the MRLs, 0.01 and 0.05 mg kg−1, respectively. The potential of the method was demonstrated by analysing summer fruits taken from agricultural Mediterranean zone cooperatives.