Analysis of polyphenols using capillary zone electrophoresis – Determination of the most effective wine sample pre‐treatment method

A simple CZE method has been developed for the simultaneous determination of eight polyphenolic compounds. The influence of several experimental conditions such as buffer (concentration and pH) and temperature were studied. Optimum separation was achieved in less than 25 min by using a BGE of 50 mM Na(2)B(4)O(7) and 10 mM Na(2)HPO(4) at pH 9.6, a temperature of 25°C and an applied voltage of 25 kV. Good linearities for all eight analytes were obtained with correlation coefficients higher than 0.99. The LODs were between 0.03 and 5.05 μg/mL and the RSD values of the migration times were found to be less than 1%. The optimal separation conditions were then used for the identification and the quantitation of polyphenolic compounds in Cypriot wine samples using six different sample preparation procedures. In particular, two direct injection methods (without any extraction step), three different liquid-liquid extraction procedures and an SPE procedure were examined. These sample pre-treatment methods were also compared in order to determine the one that is the most effective, in regard to analyte recovery, time, difficulty, and reproducibility. Liquid-liquid extraction using diethyl ether as the organic solvent proved to be the most effective.