Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Trimethoprim (TMP) is an important antibacterial synergist in human and veterinary medicine. In this work, the solubilities of TMP in five pure solvents (ethanol, water, ethyl acetate, acetonitrile, and 2-propanol) and two binary mixtures (ethanol + water and 2-propanol + water) were measured by an equilibrium method over the temperature range from (293.15 to 322.65) K under atmospheric pressure. The experimental results show that in the pure solvents the solubility of TMP increases with increasing temperature, and the solubility decreases in the following order: ethanol greater than acetonitrile greater than 2-propanol greater than ethyl acetate greater than water. In the mixed solvents, the solubility of TMP increases with increasing temperature and mass fraction of the organic solvent. The mole-fraction solubility of TMP was observed to be the highest in the mixed solvent 50% ethanol/2-propanol, and the lowest mole-fraction solubility of TMP was found in water. Three correlating models (the modified Apelblat equation, the h equation, and the ideal model) were used to correlate the experimental solubility values in the pure solvents, and four models (the modified Apelblat equation, the h equation, the ideal model, and the CNIBS/R-K model) were applied to correlate the experimental solubilities in the mixed solvents. All of these thermodynamic models gave satisfactory correlation results, with the modified Apelblat equation showing better fitting degree than the other three equations. Furthermore, the standard molar enthalpy of the TMP during the dissolving process (Hsoldeg ) was also determined in this work, and the results show that the dissolution process is endothermic.