Solubility of Gastrodin in Pure and Mixed Solvents at 273.15-313.15 K and Its Correlation with Different Thermodynamic Models

The solubility of gastrodin in pure and mixed solvents was determined by using the isothermal saturation method at temperatures ranging from 273.15 to 313.15 K under 101.0 kPa. At all studied temperature, the solubility data obey the following order: 1,4-dioxane > ethyl acetate > toluene > cyclohexanone > isopropanol > acetone > ethanol > n-propanol > acetonitrile > 1-butanol > cyclohexane. In the mixture of ethyl acetate + ethanol, the solubility increases to the maximum at around w = 0.8 with the increasing content fraction of cosolvent and then decreases. The composition dependence of the solubility has a. The solubility data in pure and mixed solvents were correlated by the modified Apelblat equation, lambda h equation, Jouyban-Acree model, and CNIBS/R-K model. In the pure solvent, the largest root mean square deviation (RMSD) value is 5.7 x 10(-5), which is obtained in the lambda h equation, and the relative average deviation (RAD) values are all less than 6.77%. In mixed solvents, the RAD data obtained using the Jouyban-Acree model is a little larger, 5.27%, and the RMSD value is 3.22 x 10(-4). However, the maximum RAD and RMSD values for the CNIBS/R-K model are 2.68% and 7.1 x 10(-5), respectively. Hence, the CNIBS/R-K model is shown to be better than the Jouyban-Acree model in this work.