THERMAL-ANALYSIS OF PROTEINS OF PHARMACEUTICAL INTEREST

Four major methods for the thermal analysis of proteins are reviewed. Thermogravimetric analysis (TGA) is commonly used for moisture content measurements in raw materials and lyophilized protein products. Diffe rential scanning calorimetry (DSC) can detect and quantitate changes i n the transition temperature and enthalpy due to formulation variables such as pH, ionic strength, and stabilizers. DSC is also used to dete ct the glass transition temperature T(g) in protein solutions and lyop hilized products. The determination of T(g) is necessary in defining a freeze-drying cycle and storage temperature for the lyophilized produ cts. Thermomechanical analysis (TMA) is used to detect T(g) and is mor e sensitive than DSC. Electrical resistance measurement has been used to detect eutectic temperature and thermal expansion events but its ap plication in detecting T(g) requires further investigation.