Optimization of separation selectivity in capillary electrophoresis of flavonoids

The migration behaviour of selected flavonoids differing in their degree of hydroxylation was investigated. The influence of the solvent in the injected sample, the surfactant [sodium dodecyl sulphate (SDS)] and pH on the separation selectivity was studied. The organic solvent (methanol or 2-propanol) modifies the interaction between micelles and analytes, thus reducing migration times and resolution. SDS improves the separation at pH 8.3, whereas it has less or no effect at higher pH. At pH 10.5 the separation is mainly regulated by ionization of the hydroxyl groups and borate complexation of the carbohydrate residues.