Molecular Interactions of Ketorolac Tromethamine with Protic Ionic Liquids: Combined Volumetric and Spectroscopic Studies

The density and speed of sound of ketorolac tromethamine (KT) in aqueous protic ionic liquid (PIL) solutions were systematically measured over a range of concentrations and temperatures between 298.15 to 313.15 K at atmospheric pressure. These experimental measurements enabled the determination of apparent molar volume (V2,ϕ) and apparent isentropic compressibility (Ks,2,ϕ), which were further used to calculate the partial molar volume (V2°) and partial molar isentropic compressibility (Ks,2°) at infinite dilution through appropriate data-fitting techniques. Thus, the estimated thermodynamic parameters are of utmost importance concerning the solvation phenomenon and interactions at the molecular level between the solvents and drug molecules, regarding the structural modifications caused by PILs. Investigations using UV–visible spectroscopy showed hyperchromic shifts with increased PIL concentrations, indicating marked changes in electronic transitions related to specific solvation effects. Increasing the anionic chain length of PILs also exhibited an effect; its influence was critical for modifying drug solubility and stability, and such studies would lead to novel insights in designing PIL-based pharmaceutical formulations. This highlights the potential of PILs in modulating physicochemical properties through controlled solvation interactions to act as novel excipients to improve drug delivery and bioavailability.