Solubility of meloxicam in aqueous binary mixtures of formamide, N-methylformamide and N,N-dimethylformamide: Determination, correlation, thermodynamics and preferential solvation

Abstract

In this research the experimental solubility of meloxicam (MLX) in {formamide (FM) + water}, {N-methylformamide (NMF) + water} and {N,N-dimethylformamide (DMF) + water} mixtures were determined at five temperatures, 293.15 K, 298.15 K, 303.15 K, 308.15 K and 313.15 K. MLX solubility increases with the cosolvent proportion in the mixtures and with temperature arising. Experimental solubility of MLX was modelled by using three well-known cosolvency models, namely the combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K), Modified-Wilson model and Jouyban-Acree model. The mean relative deviation (MPD%), in the accuracy of each mathematical model in relation to experimental solubility, shown CNIBS/R-K model is better in contrast to the other models. The model results were below of 3.21% for (FM + water) mixtures, to each temperature in the study. Furthermore, these were below of 1.72% for (NMF + water) mixtures and below of 1.70% for (DMF + water) mixtures, respectively. Apparent thermodynamic quantities of dissolution and mixing, as well as the preferential solvation parameters of MLX were calculated. Gibbs energies and enthalpies of dissolution were positive whereas the respective entropies were negative. MLX is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by cosolvent molecules in mixtures of cosolvent-rich mixtures.