Solubility and Thermodynamic Model Correlation of Zonisamide in Different Pure Solvents from T = (273.15 to 313.15) K

Zonisamide is moderately soluble in water with a reported solubility of 0.8 mg.mol(-1) (6.78 x 10(-5) in mole fraction). The objective is to study the solubility of zonisamide in methanol, ethanol, n-propanol, isopropanol, 1-butanol, acetonitrile, ethyl acetate, toluene, 2-butanone, cyclohexanone, 1,4-dioxane, and N,N-dimethylformamide (DMF) at the temperature range from 273.15 to 313.15 K, which was measured using the isothermal dissolution equilibrium method under the pressure of 101.2 kPa. The largest solubility value was found in DMF followed by 1,4-dioxane > 2-butanone > cyclohexanone > acetonitrile > ethyl acetate > methanol > ethanol > isopropanol > n-propanol > 1-butanol > toluene. It could be found that the solubility in organic solvent was much higher than that in water. The solubility result in different solvents was correlated by the modified Apelblat equation and lambda h equation nonrandom two-liquid (NRTL) model. In the modified Apelblat equation, the maximum data is 1.57%. However, the largest relative average deviation (RAD) of lambda h equation and NRTL model was obtained in 1-butanol and was more than 5%. All RAD values in the modified Apelblat equation are smaller than those in lambda h equation and NRTL model. Therefore, the modified Apelblat equation is more suitable to correlate the solubility data of zonisamide in all selected solvents.