Determination of Dissociation Constants of Cumarins by Capillary Zone Electrophoresis

Capillary zone electrophoresis(CZE) is applied to the determination of dissociation constants of coumarin derivatives (daphnin, daphnetin and umbelliferone). Capillary electrophoresis is an attractive method for pKa measurements, which is based on the migration time or mobilities of ionic species over a range of pH values. The pKa values of three cumarins is 7.43(7-HC), 6.91(DN) and 6.86(DP). The method was validated by the comparison of results obtained by a traditional method, UV spectroscopy. No distinct difference was observed between the two methods. The CZE-UV method for pKa measurement shows good repeatability and reliability.