Experimental solid–liquid phase equilibria of {cholesterol + binary solvent mixture: 1-Alcohol (C 4–C 10) + cyclohexane}

Abstract

Solid–liquid phase diagrams (SLE) have been determined for {cholesterol + 1-alcohol (1-heptanol, 1-octanol, 1-nonanol, 1-decanol}, or binary solvent mixture {1-alcohol (1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol) + cyclohexane} using a dynamic method at ambient pressure. Simple eutectic systems with complete miscibility in the liquid phase were observed. The solubility increases with an increase in the number of carbon atoms in the 1-alcohol chain length. The temperature of the eutectic points shifts to the lower cholesterol mole fractions as the alkyl chain length of the 1-alcohol decreases. The higher cross-intermolecular interaction was observed for the longer length of an alcohol, especially with 1-decanol. The solubility data in 1-alcohols were compared with values calculated by means of the Wilson, UNIQUAC and UNIQUAC ASM equations utilizing parameters derived from the SLE results. The existence of a solid–solid first order phase transition in cholesterol has been taken into consideration in calculations. The average root–mean–square deviation for the correlation of the solubility data in alcohols and cyclohexane has been on the level of σ T = 2.8 K. Solid–liquid equilibria, for the ternary systems (cholesterol + binary solvent) have been discussed as a function of the mole fraction of a second named component in the solute-free mixed solvent ( x C 0 ). The experimental results have shown the influence of the solvent or binary solvent mixture on the temperature of the solid–solid phase transition ( T tr). The addition of cyclohexane to the binary solvent mixture causes in general an increasing the solid–solid phase transition temperature of the cholesterol. The synergistic effect of solubility was observed in binary solvent mixtures with maximum at x C 0 = 0.6 – 0.8 . Isotherms reveal decreasing effect of the enhanced solubility with an increase in temperature. SLE curves for two ternary systems were correlated with the Wilson model as an example.