Solubilities of pharmaceutical and bioactive compounds in trihexyl(tetradecyl)phosphonium chloride ionic liquid

The solubility of pharmaceutical and bioactive compounds, such as N-acetyl-l-cysteine, isoniazid, pyrazine-2-carboxamide, coumarin, 4-hydroxycoumarin, 4'-isobutylacetophenone, ibuprofen and thymoquinone, was tested in trihexyl(tetradecyl)phosphonium chloride. Hydrophobicity/hydrophilicity feature and melting point affected the solubility of the solutes in [P_6,6,6,14][Cl]. 4'-Isobutylacetophenone, thymoquinone, coumarin and ibuprofen exhibited the best solubility in the IL due to their hydrophobicity. Then, N-acetyl-l-cysteine was found to be less soluble, and later on isoniazid, 4-hydroxycoumarin and pyrazinecarboxamide showed limited solubility in IL. The solid-liquid phase equilibria of all investigated systems were described using the six different correlation equations. Considering the correlation of the phase equilibrium data, the satisfactory results which revealed a good description with an acceptable standard deviation temperature range were collected for systems with: N-acetyl-l-cysteine, coumarin, thymoquinone and ibuprofen. The solubilities of the studied compounds were approximately 2 times higher in trihexyl(tetradecyl)phosphonium chloride than in trihexyl(tetradecyl)phosphonium bis[(trifluoromethyl)sulfonyl]amide ionic liquid.