Solid-liquid equilibrium of l-alanyl-l-glutamine form II in methanol + water and isopropanol + water systems

Abstract

Solid–liquid equilibrium data of L-alanyl-L-glutamine (Ala-Gln) are important for development of industrial crystallization technology of Ala-Gln. In this paper, the solubility data of one polymorph of Ala-Gln (form II) in binary methanol+water and isopropanol+water solvents mixtures from 278.15 to 313.15K were determined by using a dynamic method under atmospheric pressure. The modified Apelblat equation, the van't Hoff equation, the modified CNIBS/R-K model and the modified Jouyban–Acree model were used to correlate the experimental solubility data, respectively. Computational results showed that the Jouyban–Acree model has the lowest AIC (Akaike's Information Criterion) value in both binary solvents mixtures, which means that the Jouyban–Acree model is better for correlating the experimental solubility data. In addition, the thermodynamic properties of the dissolution process, including the standard Gibbs energy change, the standard enthalpy and standard entropy of dissolution of Ala-Gln form II, were also calculated by the van't Hoff equation.