Abstract

DELGADO, Daniel Ricardo; PENA, Maria Angeles  and  MARTINEZ, Feming. Preferential solvation of acetaminophen in ethanol + water solvent mixtures according to the inverse Kirkwood-Buff integrals method. Rev. colomb. cienc. quim. farm. [online]. 2013, vol.42, n.2, pp.298-314. ISSN 0034-7418.

The preferential solvation parameters, i.e., the differences between the local mole fraction of solvents around the solute and those for the bulk co-solvent mixtures in solutions of acetaminophen in ethanol + water binary mixtures were derived from their thermodynamic properties by means of the inverse Kirkwood-Buff integrals (IKBI) method. It is found that acetaminophen is sensitive to solvation effects, so the preferential solvation parameter δx_E,A, is negative in water-rich and ethanol-rich mixtures but positive in co-solvent compositions from 0.24 to 0.73 in mole fraction of ethanol. It is conjecturable that in water-rich mixtures the hydrophobic hydration around the aromatic ring and methyl group present in the drug plays a relevant role in the solvation. The more solvation by ethanol in mixtures of similar co-solvent compositions could be due mainly to polarity effects. Finally, the preference of this drug for water in ethanol-rich mixtures could be explained in terms of the bigger acidic behavior of water molecules interacting with the hydrogen-acceptor groups present in acetaminophen such as the carbonyl group.

Keywords : acetaminophen; ethanol; solubility; inverse Kirkwood-Buff integrals; IKBI; preferential solvation.

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