Equilibrium Solubility of Loxoprofen in 14 Monosolvents: Determination, Correlation, and Hansen Solubility Parameter

The mole fraction solubility of loxoprofen was investigated by the gravimetric static method in 14 monosolvents of methanol, ethanol, n-propanol, iso-propanol, methyl acetate, ethyl acetate, n-propyl acetate, iso-propyl acetate, iso-amyl acetate, iso-butyl acetate, butyl acetate, ethyl orthosilicate, acetonitrile, and 1,4-dioxane in the temperature range of 283.15–328.15 K under 0.1 MPa. Experiment results demonstrated that loxoprofen solubility increased positively with increasing temperature. Among 14 monosolvents, the mole fraction solubility of loxoprofen at 298.15 K followed this order: 1,4-dioxane (0.2143) > methanol (0.1185) > iso-propanol (0.09662) ≈ ethanol (0.09431) > n-propanol (0.09045) > methyl acetate (0.08949) > ethyl acetate (0.08475) > n-propyl acetate (0.06314) > iso-propyl acetate (0.0560) > butyl acetate (0.05270) > iso-butyl acetate (0.0451) ≈ iso-amyl acetate (0.04484) > acetonitrile (0.04193) > ethyl orthosilicate (0.03648). The four usually thermodynamic models including the modified Apelblat model, the Yaws model, the Van’t Hoff model, and the λh model were applied to correlate solubility data, and the Yaws model obtained a relatively accurate correlation result by values of RAD and RMSD. Hansen solubility parameters of solvents were quoted to explain the dissolving behavior of loxoprofen in 14 monosolvents.