Multiple pesticide analysis in wine by MEKC combined with solid-phase microextraction and sample stacking

In this work, a new method for the determination in white wines of 12 pesticides widely used in vine cultivars (namely, carbendazim, pirimicarb, metalaxyl, pyrimethanil, procymidone, nuarimol, azoxystrobin, tebufenozide, fenarimol, benalaxyl, penconazole, and tetradifon) using solid-phase microextraction (SPME) and MEKC with diode-array detection (DAD) was developed. The MEKC buffer consisted of 100 mM sodium tetraborate and 30 mM SDS at pH 8.5 with 6% v/v 1-propanol. Reversed-electrode polarity stacking mode (REPSM) was applied as on-line preconcentration strategy. In order to carry out an effective and sensitive determination of these pesticides in wine samples, an off-line SPME procedure was optimized by means of an experimental design. After studying the extraction performance of different SPME coatings, PDMS/divinylbenzene (PDMS/DVB) fibers were found the most appropriate for the extraction of most of these pesticides. Carbendazim and metalaxyl could not be extracted from wine samples. Calibration curves for extracted standards and fortified white wines were studied in order to determine the presence of a matrix effect. The combination of both preconcentration procedures (SPME and REPSM) allowed the determination of ten of these pesticides in white wines at concentrations between 0.054 and 0.113 mg/L. (i.e., levels well below the maximum residue limits (MRLs) allowed for these compounds in wine grapes). Ten homemade wines were they analyzed with the optimized method demonstrating the usefulness of the proposed procedure.