Solubility of sulphadiazine in (acetonitrile plus water) mixtures: measurement, correlation, thermodynamics and preferential solvation

The equilibrium solubility at temperatures from (293.15 to 313.15) K, dissolution thermodynamics and preferential solvation of sulphadiazine (SD) in {acetonitrile (ACN) (1) + water (2)} mixtures is reported. Mole fraction solubility of SD (x(3)) increases when temperature arises and also increases with the ACN proportion increasing. It varies from 4.81 x 10(-6) in neat water to 6.02 x 10(-4) in neat ACN at 298.15 K. Solubility behaviour was adequately correlated by Jouyban-Acree, modified Wilson and non-linear (proposed by Machatha et al.) models and the obtained mean percentage deviations (MPD) are 4.1%, 2.3% and 2.3%, respectively. The comparison of the MPD shows that the prediction using Jouyban-Acree model is more accurate than Jouyban-Acree-Abraham equation for solubility prediction of SD in {ACN (1) + water (2)}. From the variation of solubility with temperature the apparent thermodynamic analysis of dissolution was performed in all the mixtures and neat solvents. Based on the inverse Kirkwood-Buff integrals preferential solvation parameters were calculated. SD is preferentially solvated by water in water-rich mixtures (0.00 x(1) < 0.26) but preferentially solvated by ACN in the interval (0.26 x(1) < 0.65). In ACN-rich mixtures the behaviour is not well defined.