The use of thermal analysis and mass spectrometry to study the solid state behavior in pharmaceutical tablet mixtures

The behavior of aspirin in the presence of tablet excipients and in the presence and absence of moisture was investigated. The methods used for investigation were differential thermal analysis (DTA), thermogravimetry (TG), and direct ionization probe mass spectrometry (DIP-MS). In addition, the degradation of aspirin in the absence of moisture was investigated by TG, and the residue after the first decomposition on the TG curve was subjected to DIP-MS. A degradation mechanism for dry aspirin is postulated. Aspirin in tablet form was shown to be stabilized in the presence of increasing amounts of corn starch. These and related studies on the shelf-life of pharmaceutical products indicate possible interactions between the active ingredient and other ingredients of product formulations.