Solubility of 5-aminosalicylic acid in {N-methyl-2-pyrrolidone + ethanol} mixtures at T = (293.2 to 313.2) K

Abstract

The solubility determination of 5-aminosalicylic acid (mesalazine) in the N-methyl-2-pyrrolidone (NMP)/ethanol mixtures was carried out at T = (293.2 to 313.2) K. The solubility data were represented by the Jouyban-Acree, NRTL and UNIQUAC models. Apparent thermodynamic quantities for mesalazine dissolved in NMP/ethanol mixtures were determined. To discuss solute-solvent interactions in the present system, the activity coefficient values for mesalazine were computed. The results revealed that the solubility increases by addition of NMP and reaches a maximum value at neat NMP which is consistent with the minimum values of both Gibbs free energy of dissolution and mesalazine activity coefficient observed at neat NMP. Moreover, this drug is preferentially solvated by ethanol in ethanol-rich mixtures but preferential solvation by NMP in NMP-rich mixtures is observed.