Equilibrium Solubility of 18β-Glycyrrhetinic Acid in 12 Pure Solvents: Determination, Correlation, and Hansen Solubility Parameter

In this study, the solubility data of 18β-glycyrrhetinic acid (GA) in 12 neat solvents were determined by the static equilibrium method at a temperature range of 278.15–323.15 K under a pressure of 0.1 MPa. These selected solvents were methanol, ethanol, n-propanol, isopropanol, methyl acetate, propyl acetate, butyl acetate, isobutyl acetate, acetone, 1,4-dioxane, N,N-dimethylformamide (DMF), and tetrahydrofuran (THF). The experimental results showed that the solubility of GA was positively correlated with temperature and was correlated using thermodynamic models. Activity coefficient models such as the NRTL model, Wilson model, Margules model, and van Laar model were applied to fit the experimental solubility of GA. A good relevance can be obtained for data fitting using these models, and the best fitting effect was achieved with the Wilson equation from ARD and R2. The Hansen solubility parameter was applied to explain the GA solubility phenomenon in pure solvents. These study results contribute to crystallization operation of GA for purification and separation.