Thermal analyses (TGA and DSC) of some spironolactone solvates

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies have been performed on a commercial preparation of spironolactone and on five solvates (acetonitrile, ethyl acetate, ethanol, methanol, and benzene) prepared from it by recrystallization at room temperature. The results of these studies are discussed and compared with those recently reported in the literature for similar preparations. The variable behaviour of these solvates in their release (and partial retention) of solvent before the onset of melting, meant that their stoichiometry had to be measured by elemental microanalyses. Solvent loss from solvate decomposition was followed by thermogravimetric analysis (TGA). Solvate decomposition and spironolactone melting temperatures and enthalpies were determined by differential scanning calorimetry (DSC). The parent substance and two of the solvates (methanol and ethanol) exhibited small exotherms in addition to the expected endotherms.