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Thermodynamic study of the solubility of acetaminophen in propylene glycol + water cosolvent mixtures

2006; Brazilian Chemical Society; Volume: 17; Issue: 1 Linguagem: Inglês

10.1590/s0103-50532006000100018

1678-4790

Jackson Jiménez, Fleming Martínez,

Chemical and Physical Properties in Aqueous Solutions

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.