Determination of Dissociation Constants of (5,6-Dioxo-3-sulfoquinoline-7-yloxy)acetic Acid in Aqueous Solution at 25°C by Potentiometric Titration

The thermodynamic dissociation constants of (5,6-dioxo-3-sulfoquinoline-7-yloxy)acetic acid in aqueous solution at 25.0 ± 0.1°C were firstly determined using an improved potentiometric titration method. Based on the data of the potentiometric titrations and the least-square method, the values of p K a of this acid were calculated and the p K a1 = 1.795 ± 0.005 was assigned to quinoline ring and the p K a2 = 3.368 ± 0.010 for carboxyl group. The obtained results were analyzed in detail and compared with some similar known structures in order to conclude the accuracy and reliability of the improved potentiometric titration method.