Dissolution thermodynamics and preferential solvation of meloxicam in (acetonitrile + water) mixtures

ABSTRACT

Solubility of meloxicam in {acetonitrile + water} mixtures at five temperatures from 293.15 K to 313.15 K has been determined and correlated by means of the Jouyban-Acree model. By using the van’t Hoff and Gibbs equations the respective apparent thermodynamic quantities for the dissolution and mixing processes, namely Gibbs energy, enthalpy, and entropy, were calculated. Non-linear enthalpy–entropy relationship was observed in the plot of enthalpy vs. Gibbs energy exhibiting negative slope in the composition region 0.00 < x₁ < 0.20 and variant slopes in the other mixtures. Based on the inverse Kirkwood-Buff integrals it follows that meloxicam is preferentially solvated by water molecules in water-rich and acetonitrile-rich mixtures but preferentially solvated by acetonitrile molecules in mixtures 0.26 < x₁ < 0.60.

KEYWORDS:

• Meloxicam
• {acetonitrile (1) + water (2)} mixtures
• cosolvency
• dissolution thermodynamics
• Jouyban-Acree model
• preferential solvation
• IKBI

Acknowledgements

We thank the Departments of Pharmacy and Physics of the Universidad Nacional de Colombia for facilitating the equipment and laboratories used. Colciencias’ financial support is highly appreciated. Partial financial support of Tabriz University of Medical Sciences under grant number of 62733 is acknowledged.

Disclosure statement

The authors claim that there is no conflict of interest.

Additional information

Funding

This work was supported by the Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS) [Convocatoria doctorado 785-2017]; Tabriz University of Medical Sciences [62733].