Solubility of l-phenylalanine in water and different binary mixtures from 288.15 to 318.15 K

The solubility of l-phenylalanine in water and binary mixtures (methanol + water and ethanol + water) at temperatures ranging from 288.15 to 318.15 K was investigated. The results obtained from these measurements were correlated with the temperature and the molar fraction of water by the combined nearly ideal binary solvent (CNIBS)/Redlich–Kister(R–K) model and the semiempirical Apelblat model. Both of the models demonstrated good fitting with the experimental data, while the CNIBS/R–K model gave a more accurate prediction. In addition, the thermodynamic properties of the solution process, including the Gibbs energy, enthalpy, and entropy, were obtained using the van’t Hoff equation and the Gibbs equation. The experimental results showed that water was a better solvent for l-phenylalanine than methanol and ethanol, which could thus be used as effective anti-solvents in the crystallization process. For all the cases studied, the values of both the standard molar enthalpy change and standard molar Gibbs energy change of solution were positive, which indicated that the process was endothermic and not spontaneous.