Measurement and thermodynamic functions of solid–liquid phase equilibrium of d-(−)-quinic acid in H2O, methanol, ethanol and (H2O + methanol), (H2O + ethanol) binary solvent mixtures

• Solubility of d-(−)-quinic acid in pure and binary solvents was determined.
• The solubility data were fitted using four models.
• Good correlation was existed between experimental and calculated solubilities.
• Results showed that the Apelblat model superior to the λh, Wilson and NRTL model.
• The Gibbs free energy, enthalpy, entropy were calculated by the van’t Hoff analysis.

The solubility of d-(−)-quinic acid in H2O, methanol, ethanol and (H2O + methanol), (H2O + ethanol) binary solvent mixtures was measured at temperatures from (298.15 to 328.15 or 348.15) K by using the HPLC method under atmospheric pressure. The experimental values indicate that the solubility of d-(−)-quinic acid in the binary mixed solvents increases with the increasing temperature and decreases with the rise of molar concentration of organic solvents. The Apelblat model, λh model, Wilson model and NRTL model were used to correlate the experimental results and the relative average deviation (RAD) between the experimental and calculated values is less than 0.0358, 0.0421, 0.0359 and 0.0397 for the Apelblat model, λh model, Wilson model and NRTL model, respectively. Furthermore, thermodynamic properties of the solution process, including the Gibbs energy, enthalpy, and entropy were also calculated and analyzed.

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