Thermodynamic and spectroscopic study of solutions of therapeutic deep eutectic solvents (THEDES) in supercritical CO2

Abstract

The solubilities of the Deep Eutectic Solvents (DES) ibuprofen:thymol and ibuprofen:L-menthol in supercritical CO2 were determined up to 250 bar at 40, 50 and 60 °C using a variable volume view cell. The solubility of DES at different compositions was compared to that of the individual components showing little deviation from the linear trend. The vapour-phase compositions for some conditions were also determined by 1H NMR showing that the CO2 preferentially extracts the most volatile component. A FTIR spectroscopic study of the DES at room pressure and the DES dissolved in CO2 was also conducted. At room temperature, ibuprofen was present either forming a dimer or bonded to the terpene. When the DES was dissolved in CO2, significant amounts of free ibuprofen were also found. A simple association model was proposed and some thermodynamic magnitudes were determined. The spectroscopic information is consistent with the thermodynamic data.