Solubility of meloxicam in ethylene glycol-water and propylene glycol-ethanol mixtures: Experimental determination and thermodynamic analysis

The solubility profile of meloxicam in ethylene glycol (EG)-water and propylene glycol (PG)–ethanol mixtures at five temperatures in the range of 288.15–308.15 K under atmospheric pressure are determined and related by means of the Jouyban-Acree model. Experimental results show that solubility always increases as temperature increases; and, when the composition of ethylene glycol increased in the first mixture, while in the second one is maximum, in the region $0.4 < X_{\text{PG}} < 0.8$. The thermodynamic parameters (Gibbs energy, enthalpy and entropy) of meloxicam in both systems are also calculated by using vańt Hoff and Gibbs equations. Both Gibbs energy and enthalpy of solution are positive in the mixture under analysis. As far as, dissolution entropy is negative in all proportion of EG except for neat ethanol; in PG mixture is positive when $0.1 > X_{\text{PG}}$ and the range $0.4 < X_{\text{PG}} < 0.6$. For ethylene glycol–water mixtures, enthalpy-driving is the main contributing force to the Gibbs energy. Conversely, in propylene glycol systems, the entropic contribution is higher.