Solubility measurement and thermodynamic modeling of Doxycycline Hyclate two binary solvent systems at 276.95–323.75 K

The solubility values of Doxycycline Hyclate (DH) in water + methanol (or +ethanol and n-propanol) mixture solvents were measured and correlated from 276.95 K to 323.75 K. Experiment results indicated that solubility data in four pure solvents followed this order: methanol> ethanol≈water>n-propanol, and solubility data increased with increasing temperature in all selected solvents. In mixture solvents, the solubility data of Doxycycline Hyclate reached a minimum at x c  = 0.75 in water( x c ) + methanol(1- x c ), a maximum at x c  = 0.75 in water(x c ) + ethanol(1- x c ) and a maximum at x c  = 0.8 in water( x c ) + n-propanol(1- x c ). Moreover, Experimental solubility data was well-correlated with the modified Apelblat model, the Apelblat-Jouyban Acree model and Van't Hoff-Jouyban Acree model, respectively. Correlation coefficient values and relative average deviation values showed these models were very consistent with the experimental values. Furthermore, thermodynamic properties of Doxycycline Hyclate in dissolution process were calculated and discussed from the experimental solubility and parameters of modified Apelblat model.