Solubility and preferential solvation of nimodipine and azlocillin drug compounds in (ethanol + ethyl acetate) mixtures

This research focuses explicitly on the solubility of azlocillin and nimodipine in mixed binary solvents. This is relevant for pharmaceutical companies involved in developing and formulating these drugs. At a constant pressure of 101.2 kPa and temperatures ranging from 283.15 K to 323.15 K, the mole fraction equilibrium solubility of nimodipine and azlocillin in binary solvents (ethanol + ethyl acetate) was determined experimentally by gravimetric method. The results demonstrated that azlocillin and nimodipine solubility improved with higher ethanol mole fractions in mixed solvent systems. Among the three thermodynamic models, the experimental solubility data was best explained by the van't Hoff-Jouyban-Acree (V-J-A) model, followed by the Jouyban-Acree (J-A) model. The greatest RAD and RMSD values occur when two variables are compared to one another (RMSD) were 4.96 × 10⁻² and 10.62 × 10⁻⁴ for azlocillin and 1.463 × 10⁻² and 2.393 × 10⁻⁴ for nimodipine, respectively. The preferential solvation parameter \({\delta x}_{1,drug}\) ${\delta x}_{1,drug}$ is more significant than zero for nimodipine and azlocillin in the respective ranges of 0.60 < x_E < 1 and 0.60 − 0.65 < x_E < 1. This indicates that these two studied drug compounds prefer solvated by ethanol over ethyl acetate under these conditions. These results offer valuable perspectives for researchers in the pharmaceutical sciences, especially regarding the comprehension of drug compound solubility and solvation behavior in mixed solvent systems.