Solubility and preferential solvation of meloxicam in methanol + water mixtures at 298.15 K

Abstract

The equilibrium solubility of meloxicam in methanol+water binary mixtures at 298.15K was determined and the preferential solvation parameters were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals method. From solvent effect studies, it is found that this drug is sensitive to specific solvation effects. The preferential solvation parameter by methanol δx1,3, is negative in water-rich mixtures but positive in compositions from 0.30 in mole fraction of methanol to pure methanol. It is conjecturable that in the former case the hydrophobic hydration around aromatic rings and/or methyl groups plays a relevant role in the solvation. The more solvation by methanol in mixtures of similar co-solvent compositions and in methanol-rich mixtures could be explained in terms of the bigger basic behavior of the co-solvent interacting with hydrogen-donor groups of the drug.