Thermodynamic modelling, Hansen solubility parameter and solvent effect of oxaprozin in thirteen pure solvents at different temperatures

The solubility of oxaprozin in thirteen organic solvents (methanol (MeOH), ethanol (EtOH), n-propanol (n-PrOH), n-butanol (n-BuOH), n-pentanol (n-PeOH), methyl acetate (MeAC), ethyl acetate (EtAC), n-propyl acetate (n-PrAC), n-butyl acetate (n-BuAC), n-amyl acetate (n-AmAC), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO)) was determined using a laser monitoring method at atmospheric pressure in this work. The measured temperature range for all selected solvents is 278.15 K to 323.15 K except DMSO 293.15 K to 323.15 K. Through the entire studied temperature range, the results turned out that oxaprozin solubility in selected solvents has a positive correlation with temperature variation. Four mathematical models were employed to correlate the solubility data including two empirical models (modified Apelblat model, λh model) and two activity coefficient models (UNIQUAC model, NRTL model), with the modified Apelblat model giving the best regression. Solubility order of oxaprozin in thirteen solvents was analysed by using the Hansen solubility parameter (HSP) and the solvent effect (solvent interaction) was investigated through correlating oxaprozin solubility in selected solvents based on KAT-LSER model. Moreover, according to van’t Hoff equation, thermodynamic properties including apparent standard molar enthalpy change (Δ sol H ° ), apparent standard molar Gibbs energy change (Δ sol G° ) and apparent standard molar entropy change (Δ sol S ) of the dissolution process of oxaprozin were also calculated and discussed.