Solid-liquid phase equilibrium of 2, 4-epibrassinolide in binary mixed solvents: Solubility determination, model correlation, preferential solvation and thermodynamic properties

Abstract

The solubility of 2, 4-epibrassinolide in four binary mixed solvents including (ethanol + water, isopropanol + water, acetone + water, and acetonitrile + water) with numerous compositions was determined at temperature of 283.15 K to 323.15 K by a laser dynamic method. The solubility of 2, 4-epibrassinolide in all four binary solvent mixtures increases with increasing temperature. At a given temperature, it shows a trend of increasing and then decreasing with increasing mole fraction of water. In the same solvent composition, the order of solubility is isopropanol + water > ethanol + water > acetone + water > acetonitrile + water. The experimental solubility data of 2, 4-epibrassinolide was correlated with the modified Apelblat, Van’t Hoff, NRTL, Wilson, and three-suffix Margules model. The preferential solvation mechanism of 2, 4-epibrassinolide in four aqueous solutions was also discussed by IKBI method. Furthermore, the Wilson model was worked to analyze the thermodynamic mixing properties of the solutions, including ΔmixG, ΔmixH and ΔmixS. All ΔmixG values are negative indicating that the mixing process of 2, 4-epibrassinolide in these solvents is spontaneous.