Compositional Analysis of Drugs and Injectable Biological Products by Thermogravimetry

Abstract

Thermogravimetry (TG) is specified in the U.S. Pharmacopeia for the compositional analysis of certain drugs. It is specified for use in determining the percentage of volatile substances in drugs such as vincristine sulfate and vinblastine sulfate. TG reveals interactions between a controlled atmosphere and a drug and between an active substance and excipients. TG is used in the compositional analysis of injectable biological products in various ways. For pneumococcal, Haemophilus b, and meningococcal bulk polysaccharides that are used in vaccine production, TG is used to determine the moisture content (approximately 5 to 25 percent) so that the content of protein, nucleic acid, phosphorus, and other constituents may be accurately determined on a dry weight basis to demonstrate that a sample meets the specifications for the product. TG is also used to determine residual moisture in freeze-dried final container biological products such as Blood Grouping Sera and Antibody to Hepatitis B Surface Antigen. TG is used to confirm or supplement information obtained from Karl Fischer or gravimetric (loss on drying) moisture analysis techniques. TG has been combined with mass spectrometry to verify moisture data for group Y meningococcal poly-saccharide and freeze-dried antibody to hepatitis B surface antigen and to identify an impurity in a Haemophilus b polysaccharide.