Volumetric Studies\nof Theophylline-PEGylated Deep\nEutectic Solvents in Aqueous Solution

Deep eutectic solvents (DESs) have garnered significant\nattention\nas eco-friendly alternatives to conventional solvents. Understanding\nthe solution chemistry of DES is crucial for green chemistry processes\nin pharmaceutical formulations. This study presents a comprehensive\nvolumetric investigation to elucidate the molecular interactions and\nthermodynamic properties of theophylline in aqueous DES environments.\nA DES composed of PEG-400 and citric acid/ascorbic acid was tailored\nto study the theophylline–DES interactions. Measurements of\ndensity and speed of sound were conducted within the range of 293.15–318.15\nK and 0.1 MPa. Analysis of apparent molar volumes, infinite dilution\npartial molar volumes, and volumetric transfer parameters provided\nthe plausible theophylline–DES–water interactions. The\nfindings indicate a complex interplay of interactions among DES components\nand theophylline, with notable observations on the dimerization of\ntheophylline leading to a reduction in the transfer volume. This study\nsheds light on DES-mediated drug–water interactions, which\noffer valuable implications for pharmaceutical applications.