The dissolution behaviour and thermodynamic properties calculation of praziquantel in pure and mixed organic solvents

The purpose is to study the dissolution behaviour for praziquantel in different solvent. The dissolution capacity within the temperature range from 273.15 K to 313.15 K was researched by using the isothermal equilibrium method and evaluated with the modified Apelblat equation, λh equation and Jouyban-Acree model. In pure solvents, the largest values were found in N-methyl pyrrolidone (NMP, 8.106 × 10−2 in mole fraction) at 313.15 K, and followed by cyclohexanone (5.964 × 10−2), toluene (3.842 × 10−2), acetonitrile (3.519 × 10−2), acetone (3.001 × 10−2), ethyl acetate (2.896 × 10−2), n-octanol (2.715 × 10−2), isopropanol (1.882 × 10−2) and n-hexane (4.379 × 10−2). While in mixtures of (NMP + isopropanol), the solubility capacity increased monotonically with the increase of temperature and NMP mass fraction. KAT-LSER method was applied to analyse the effect of solute–solvent intermolecular interactions on the solubility in pure solvents. More importantly, the selection of appropriate solvents for praziquantel dissolution is important to its application. Moreover, the effect of the solute–solvent intermolecular interactions on the solubility in pure and mixed solvents was discussed as well. In the following, the analysis of apparent thermodynamic analysis indicates that the dissolution is an endothermic, spontaneous and entropy driven process.