Solubility measurement, Hansen solubility parameter and thermodynamic modeling of etodolac in four binary solvents from 278.15 K to 323.15 K

Abstract

In this study, the laser monitoring method was used to measure the solubility of etodolac in four binary mixtures ((n-propanol, methyl acetate, n-butyl acetate and acetone) + n-hexane) at 278.15 K–323.15 K. The results show that under a certain solvent composition, the solubility of etodolac increases with the increase of temperature. Except for the mixture of acetone + n-hexane, the solubility of etodolac in the other three mixing systems increases with the increase of the mass fraction of the co-solvent (n-propanol, methyl acetate and n-butyl acetate) at a certain temperature. For the acetone + n-hexane system, the order of solubility is: acetone > acetone (ω1 = 0.6000) + n-hexane > acetone (ω1 = 0.8000) + n-hexane > acetone (ω1 = 0.4000) + n-hexane > acetone (ω1 = 0.2001) + n-hexane, indicating that a co-dissolution phenomenon may occur when the mass fraction of acetone is 0.6000. The Hansen solubility parameter was used to explain the solubility order of etodolac in four binary mixed solvents. At the same time, five models (modified Apelblat model, Buchowski-Ksiazaczak λh model, Wilson model, Three-Suffix Margules model and Uniquac model) were used to correlate the solubility data, which shows that all the five models have a good correlation. Through the comparison of ARD and RMSD, it was found that the modified Apelblat model can get more satisfactory results.