Determination of the dissociation constants of polyepoxysuccinic acid

The dissociation constants of polyepoxysuccinic acid (PESA) were investigated in this study. Based on the potentiometric titration and the BEST program, the dissociation constants of PESA were determined. Considering the complexity of the dissociation of PESA in aqueous solution, several models were constructed to simulate the dissociation process of PESA. By comparison, the dissociation constants of PESA were obtained with model 4. The species distribution of PESA in aqueous solution as a function of pH was also presented according to the experimental and calculation results. It showed that the H 2L model with five basic structure units to describe the dissociation of PESA was reasonable, and the relevant constants had less error and better matching between the experimental and calculation data. The corresponding values of pK ai were 4.68 and 4.92, respectively, for H2L at 35°C with ionic strength of 0.1 mol/L. © 2008 Higher Education Press and Springer-Verlag GmbH.