Development and validation of a capillary zone electrophoresis method for the quantitative determination of anthocyanins in wine.

A capillary zone electrophoresis (CZE) method is proposed for the quantitative determination of anthocyanins in wine as an alternative to high-performance liquid chromatography. The CZE separation was carried out using a 46 cm (effective length) x 75 microm I.D. fused-silica capillary at 10 degrees C and a 50 mM sodium tetraborate buffer at pH 8.4 with 15% of methanol as modifier. A voltage of 25 kV and a hydrodynamic injection of 300 mbar s were used. The electropherograms were recorded at 599 nm. It was found that SO2 (antibacterial and antioxidant agent added to wine during its production) increased the absorbance of anthocyanins at 599 nm in a basic medium. Therefore, a concentration of 250 mg/l of SO2 was added to the samples and the calibration solution before the analysis in order to avoid errors by this matrix effect. The analytical response was linear (R=0.998) between 10 and 700 microg/ml of malvidin-3-O-glucoside. The limit of detection and the reproducibility (as a relative standard deviation, n=11) were 1 microg/ml and 1.5%, respectively. Finally, the CZE method was validated by the analysis of synthetic wine samples (errors less than 8%) and by the comparison of the results obtained in the analysis of different monovarietal wines by CZE with those obtained by the standard HPLC method. In this comparison, a good correlation (R=0.998) with a slope of 1.005+/-0.044 and an intercept of -0.752+/-6.690 was obtained for malvidin-3-O-glucoside.