Journal of the Brazilian Chemical Society
Print version ISSN 0103-5053
JIMENEZ, Jackson A. and MARTINEZ, Fleming. Thermodynamic study of the solubility of acetaminophen in propylene glycol + water cosolvent mixtures. J. Braz. Chem. Soc. [online]. 2006, vol.17, n.1, pp. 125-134. ISSN 0103-5053. http://dx.doi.org/10.1590/S0103-50532006000100018.
Based on van't Hoff and Gibbs equations the thermodynamic functions Gibbs energy, enthalpy, and entropy of solution, mixing and solvation of acetaminophen in propylene glycol + water (PG + W) cosolvent mixtures, were evaluated from solubility data determined at several temperatures. The solubility was greater at 100% of PG at all temperatures studied. The solvation of this drug in the mixtures increases as the PG proportion is also increased founding a maximum at 70% of PG. From 10% up to 20% of PG and from 70% up to 100% of PG, entropy driving was found, while from pure water up to 10% of PG and from 20% up to 70% of PG, enthalpy driving was found. These facts can be explained in terms of water-structure loss, and a diminishing in the energy required for cavity formation in the solvent, for mixtures from 30% up to 70% of PG.
Keywords : acetaminophen; solubility; solution thermodynamics; activity coefficients.