SEPARATION OF FLAVONES BY CAPILLARY ELECTROPHORESIS - THE INFLUENCE OF PKA ON ELECTROPHORETIC MOBILITY

In order to evaluate the influence of pKa on electrophoretic mobility (EM), two novel series of synthetic flavonoids comprising eight monohy droxyflavones and four tri-O-methylluteolins were studied. In this way the effect of varying molecular size on EM was eliminated in each ser ies. A linear relationship between EM and pKa is demonstrated for both series, with the parallel slope for the luteolins being at lower aver age EM due to their larger molecular size relative to the monohydroxyf lavones. In an extension of these studies, the EM of a series of dihyd roxyflavones was also determined. It is shown that the relative EM of a dihydroxyflavone is determined primarily by the pKa of its most acid ic hydroxyl group, unless complexation with berate in the electrophore sis buffer occurs. A rationalization of the differences in EM values b etween the mono- and di-hydroxy series has provided an insight into th e relative importance of effects such as molecular size, pKa and berat e complexing on EM.