Investigation of solid–liquid equilibrium of stevioside in different pure and binary mix solvents at various temperatures

Abstract

The solubility of stevioside (a natural sweetener) in 12 pure solvents (methanol, 1-propanol, 2-propanol, 1-buthanol, 2-buthanol, 1-pentanol, 2-pentanol, 2-ethoxyethanol, 2-propoxyethanol, 2-buthoxyethanol, water, and acetone) and in binary mixed solvents (2-ethoxyethanol + water) have been determined using high performance liquid chromatography (HPLC) method at temperatures ranging from 288.15 to 328.15 K and atmospheric pressure. From the experimental data, it was found that the solubility increased with the rising temperature in all selected solvents. The experimental data for the solubility of stevioside were correlated with Apelblat and non-random two-liquid (NRTL) models. It was found that the Apelblat model has the better quality in fitting the solubility data. Also, thermodynamic functions of dissolution, mixing and transfer process were calculated by the van’t Hoff equation. Furthermore, the crystal habits of stevioside in selected solvents were studied.