Capillary zone electrophoresis for the determination of thiabendazole, prochloraz and procymidone in grapes.

Capillary zone electrophoresis with UV detection was applied to the simultaneous determination of thiabendazole, prochloraz and procymidone in grapes. Electrolyte conditions such as pH, composition and concentration of the buffer, addition of organic solvent and working voltage were checked to obtain a high-performance separation of the three fungicides (by measurement of separation efficiency and resolution). The most critical parameter was the pH of the running buffer. The best separation was achieved in 4 mM phosphate solution at pH 3.5. The repeatability of the migration times, expressed as RSD, was < 0.44%. The three peaks were completely resolved with a separation efficiency up to 100,000 theoretical plates. Solid-phase extraction was used for the isolation and preconcentration of the fungicides, which provided a concentration factor of 10:1 and limits of detection lower than the maximum residue limits. The mean recoveries of the fungicides were 73.75% for thiabendazole, 41.70% for prochloraz and 92.23% for procymidone. This method was used to determine these compounds in 20 real samples taken from a local market.