Estimating the solubility and solution thermodynamics parameters of aliskiren hemifumarate (AHF) in three different room temperature ionic liquids (RTILs), Transcutol-HP (THP) and water are interesting as there is no solubility data available in the literature. In the current study, the solubility and solution thermodynamics of AHF in three different RTILs, THP and water at the temperature range from 298.2 to 318.2 K under air pressure 0.1 MP were evaluated. The solid phase evaluation by Differential Scanning Calorimetry (DSC) and Powder X-ray Diffraction (PXRD) indicated no conversion of AHF into polymorph. The mole fraction solubility of AHF was found to be highest in 1-hexyl-3-methylimidazolium hexafluorophosphate (HMMHFP) ionic liquid (7.46 × 10-2) at 318.2 K. The obtained solubility values of AHF was regressed by the Apelblat and van't Hoff models with overall root mean square deviations (RMSD) of 0.62% and 1.42%, respectively. The ideal solubility of AHF was higher compared to experimental solubility values at different temperatures. The lowest activity coefficient was found in HMMHFP, which confirmed highest molecular interaction between AHF-HMMHFP. The estimated thermodynamic parameters confirmed endothermic and entropy driven dissolution of AHF in different RTILs, THP, and water.
Keywords: entropy; ionic liquids; molecular interaction; solubility; thermodynamics.