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

• Solubility of trihexyl(tetradecyl)phosphonium chloride ionic liquid and pharmaceutical compounds.
• Solubility of trihexyl(tetradecyl)phosphonium chloride ionic liquid and bioactive compounds.
• Dependence between hydrophobicity and melting point directs the solubility.
• Solubility of antituberculosis drugs in [P6,6,6,14][Cl].
• Solubility in trihexyl(tetradecyl)phosphonium chloride is better than in bis[(trifluoromethyl)sulfonyl]amide.

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 [P6,6,6,14][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.

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