Thermal analysis

Thermal analysis is closely related to microcalorimetry, in that some thermal analysis techniques also measure enthalpy or heat capacity changes. However, thermal analysis is broadly defined as techniques that characterize materials based on measurement of the changes that occur in one or more properties of the material when it is subjected to a controlled temperature change program. The Victorian College of Pharmacy is equipped with two major thermal analysis techniques, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The first of these measures the change in heat capacity of the sample as its temperature is increased or decreased. If the sample passes through a phase transition, e.g., melting, then there is a substantial change in the heat capacity as a function of temperature. This data allows determination of the enthalpy change for the phase change, which in turn is a significant factor in describing the intermolecular forces in the sample. TGA measures the change in mass of a sample as a function of temperature, by weighing it with a seven figure microbalance that has a precision-controlled furnace surrounding the sample pan. Losses in mass can be attributed to vaporization of volatile materials (such as adsorbed surface water, or internal solvent of crystallization), sublimation or to decomposition of the compound. Moisture loss can be corroborated by Karl Fischer analysis.