Measurement and Correlation of Solubility and Thermodynamic Properties of Vinpocetine in Nine Pure Solvents and (Ethanol plus Water) Binary Solvent

The solid-liquid equilibrium data of vinpocetine in nine pure solvents and ethanol-water binary system at temperatures ranging from 283.15 to 323.15 K was experimentally measured by gravimetric method under atmospheric pressure. For the different types of investigated solvent, the solid-liquid equilibrium solubility of vinpocetine increased with augmented temperature. Experimental solubility was fitted with several thermodynamic models including the modified Apelblat model, lambda h model, and nonrandom two-liquid (NRTL) model, as well as the combined nearly ideal binary solvent/Redlich-Kister model. All the fitted values were in satisfactory agreement with the experimental results. The thermodynamic parameters were calculated by the activity coefficients of vinpocetine in different solvents, which were obtained by NRTL model. The results demonstrated that the mixing process of vinpocetine with experimental solvents was spontaneous and entropy-driven.