Thermodynamic study and preferential solvation of sulfamerazine in acetonitrile + methanol cosolvent mixtures at different temperatures

Abstract

This paper discusses sulfamerazine (SMR) solubility in Acetonitrile (MeCN) + Methanol (MeOH) cosolvents at nine temperatures (278.15–318.15 K). Herein, the maximum SMR solubility was reached in a cosolvent mixture at the highest studied temperature, and the minimum SMR solubility was reached in neat methanol at the lowest studied temperature. Using experimental data, thermodynamic functions were calculated for both the solution and mixture using the Gibbs and van’t Hoff equations, thus determining that the solution process is endothermic with entropic favoring. In addition, the preferential solvation parameters (δx3,1), calculated using the inverse Kirkwood-Buff integrals (IKBI) method, are reported; SMR is preferentially solvated by MeOH in MeOH-rich mixtures, and in intermediate and MeCN-rich mixtures, the δx3,1 values indicate that SMR is not preferentially solvated by any of the two solvents in the mixture (MeCN + MeOH). Finally, eight models were assessed (Apelblat, van’t Hoff, Yaws, λh, Weibull, NRTL, Wilson, and Wilson modified), with all presenting mean relative deviation percentages (MRD%) under 6%, which indicates a good correlation with the experimental data.