Solubility of L-tyrosine in aqueous solutions of methanol, ethanol, n-propanol and dimethyl sulfoxide: Experimental determination and preferential solvation analysis

The equilibrium solubility of L-tyrosine in solvent mixtures of methanol (1) + water (2), ethanol (1) + water (2), n-propanol (1) + water (2) and dimethyl sulfoxide (DMSO, 1) + water (2) were determined experimentally by using isothermal dissolution equilibrium method within the temperature range from 283.15 to 323.15 K under atmospheric pressure (101.1 kPa). At the same temperature and mass fraction of methanol (ethanol, n-propanol or DMSO), the mole fraction solubility of L-tyrosine was greater in (DMSO + water) than in the other three solvent mixtures. The solvent effect was explained in terms of solute-solvent and solvent-solvent interactions. The preferential solvation parameters were derived from their thermodynamic solution properties by means of the inverse Kirkwood-Buff integrals method. The preferential solvation parameters (delta chi(1,3)) for methanol, ethanol, n-propanol or DMSO were negative in the methanol (1) + water (2), ethanol (1) + water (2), n-propanol (1) + water (2) mixtures with a very wide compositions, which indicated that L-tyrosine was preferentially solvated by water. While L-tyrosine was preferentially solvated neither by water nor by DMSO for the DMSO (1) + water (2) mixtures. Temperature has a little effect on the preferential solvation magnitudes for the studied solutions. The higher solvation by water could be explained in terms of the higher acidic behavior of the solvent interacting with the Lewis basic groups of the L-tyrosine. In addition, the drugs' solubility was mathematically represented by using the Jouyban-Acree model, van't Hoff-Jouyban-Acree model and Apelblat-Jouyban-Acree model obtaining average relative deviations lower than 1.47% for correlative studies. It is noteworthy that the solubility data presented in this work contribute to the expansion of the physicochemical information about the solubility of drugs in binary solvent mixtures and also allows the thermodynamic analysis of the respective dissolution and specific solvation process. (C) 2018 Elsevier Ltd.