Effect of surfactants on the dissociation constants of ascorbic and maleic acids

The dissociation equilibria of ascorbic and maleic acids have been studied in certain cationic, anionic and non-ionic micellar media and their pKa values have been evaluated by the potentiometric, conductometric and spectrophotometric techniques. These pKa values have been found to shift in micellar media as compared to those in pure water. The differences in the values have been attributed to the solvent properties of the interfacial and bulk phases involving contribution from the micellar surface potential in the case of charged micelles. The values of the limiting molar conductance of the acids have been determined in the various surfactants and were found to be different in different surfactants. In case of the cationic surfactants the limiting molar conductance was found to increase with increase in surfactant concentration.