In the pharmaceutical industry thermal analysis has been used in development, production, and quality control settings. Over the years, constantly improving instrumentation has led to advanced characterization methods. MPS uses state-of-the-art TGA and DSC instruments to provide our customers with the best data possible and the most information available from these techniques.
In general, thermal analysis employs a linear temperature ramp with time. As temperature increases, signals which might include sample mass or heat flux are recorded. Isothermal studies are also sometimes used.
Techniques available from MPS include the following:
TGA: Thermal gravimetric analysis measures the sample mass as temperature is increased. Decomposition, loss of water, or other solvents are frequent causes for mass loss.
DSC: Differential scanning calorimetry compares the power required to keep a sample container and a reference container increasing in temperature at the same selected heating rate. From the power difference, the net heat flux into the sample is determined and recorded. The recorded heat flux is proportional to the sample apparent heat capacity. This heat capacity includes the heat capacity of the sample materials plus any heat generated by a phase transition or decomposition. Both exothermic and endothermic events can be recorded. DSC is commonly used to determine the temperatures where phase transitions occur. In addition to the transition temperature, it is possible to determine the enthalpy of the transition. Because glass transitions are accompanied by a change in heat capacity, glass transition temperatures may also be determined. Isothermal studies are also possible using DSC equipment. DSC is used frequently to determine melting points, enthalpies of fusion, solid phase transitions, and glass transition temperatures.
MDSC: Modulated DSC differs from standard DSC in that the standard linear heat rate is modulated with a sinusoidal heating rate. The modulation of the linear heating rate with the sinusoidal heating rate allows one to separate reversible and kinetic (nonreversing) phenomena. Examples of reversible events include glass transitions and melting. Nonreversing events include enthalpic relaxation, evaporation, crystallization, decomposition, and cure. A MDSC report includes a standard DSC (reversing + nonreversing), reversing, and nonreversing plots.