Determination of flavonoids by high-performance liquid chromatography and capillary electrophoresis.

The compounds of flavonoid, an important group in nature, can prevent coronary heart disease and anticancer by virtue of the characteristics of antioxidation. Nine flavonoids most often seen in grape wine, namely apigenin, baicalein, naringenin, luteolin, hesperetin, galangin, kaempferol, quercetin, and myricetine, were determined by means of high-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE) in this work. A successful resolution was obtained from an unusual additive of tetrahydrofuran in mobile phase by HPLC. One notable thing is that the mixture of luteolin and quercetin could be separated for the first time by HPLC. In addition, the better detection limit was still attainable even with the use of tetrahydrofuran. The detection limits of CZE performed in borate buffer were hundreds-fold better than in previous reports. Furthermore, the retention and migration behavior of the analytes studied were discussed. As the result of this study, the elution order of flavone and flavonone was reversed to the contention proposed by Wulf et al. It was predictable from the interaction with tetrahydrofuran. Consequently, the extracts from grape wine with solid-phase extraction were analyzed by developing methods of HPLC and CZE. The obtained recoveries ranged from 90 to 107% and the relative standard deviations were under 6.3%.