Preferential solvation of dehydroepiandrosterone acetate in (co-solvent + ethyl acetate) mixtures according to the inverse Kirkwood–Buff integrals method

Abstract

The preferential solvation parameters (δx1,3) of dehydroepiandrosterone acetate (DHEA acetate) in three co-solvent mixtures of methanol (1)+ethyl acetate (2), ethanol (1)+ethyl acetate (2), and isopropanol (1)+ethyl acetate (2) were derived from their available solubility data by means of the inverse Kirkwood–Buff integrals method. The values of δx1,3 vary non-linearly with the co-solvent (1) proportion in all the co-solvent mixtures. For the studied systems, the values of δx1,3 are negative in alcohol-rich mixtures, but positive in ethyl acetate-rich mixtures. The preferential solvation magnitude of DHEA acetate by the ethyl acetate is highest in {methanol (1)+ethyl acetate (2)} mixtures at 293.15K and 303.15K. While at 313.15K, it is highest in {isopropanol (1)+ethyl acetate (2)} mixtures. The δx1,3 values are positive indicating that DHEA acetate is preferentially solvated by ethyl acetate. The co-solvent action may be related to the disordered structure of ethyl acetate molecules around the non-polar moieties of DHEA acetate which increases the solvation having maximum values near to x1=0.25–0.35 for the three co-solvent mixtures.