Simultaneous Thermal Analysis (STA) is a combination of two related techniques that measure thermal properties. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) are among the most commonly used thermal analysis techniques. They can be used in concert with STA to provide more information about samples than either one could provide alone.

In DSC, the thermal response of the sample is compared to the response from a standard reference sample. Both are held at the same temperature, and as the temperature is gradually changed, the heat-flow into the sample is measured. Particular changes in the heat flow curves from the DSC indicate phase transitions and provide insight into sample stability, kinetics, water distribution and other material properties of interest. A closely related technique is Differential Thermal Analysis (DTA) in which the heat flow is held constant while fluctuations in temperature are measured. Even in standalone systems, DTA and DSC are commonly carried out on the same apparatus.

As in DSC, TGA involves ramping up the temperature of the sample. In TGA, the dependent variable being measured is the mass of the sample. As a sample is heated, it may give off gases, water or other volatile compounds. TGA provides complimentary information to the information derived from DSC. The measured weight loss can indicate transitions in the material, as well as decomposition, solvent loss and even corrosion of materials.

STA provides simultaneous DSC/TGA analysis in a single run, which is an advantage over performing separate analyses and matching their curves. The combined analysis has applications as varied as measuring the phase transitions in polymers, the stability of pharmaceutical preparations, or textural changes in food that may occur during processing.

STA instruments have varied specifications. Although most basic systems have a maximum temperature of about 1000°C, different furnace types allow the instruments to reach maximum temperatures in excess of 2000°C. The other major distinguishing feature is the sensitivity of the TGA microbalance and the DSC temperature and heat sensors. Yet more complementary information can be obtained by augmenting STA with chemical analysis of the evolved gases liberated during the run. Many suppliers offer options to combine STA with infrared spectroscopy or MS.

Since DSC and TGA are the most prominent thermal analysis techniques, all of the top suppliers in thermal analysis offer both techniques separately and combined in STA instruments. In addition to the STA market leaders, significant vendors include PerkinElmer, SII Nanotechnology, Mettler-Toledo and Setaram. Smaller STA suppliers include Bähr Thermoanalyse and Instrument Specialists. The total market for STA, including aftermarket and service, was about $58 million in 2008.

Simultaneous Thermal Analysis at a Glance:

Leading Suppliers

• Waters

• Shimadzu

• Netzsch AG

Largest Markets

• Polymers

• Pharmaceuticals

• Food

Instrument Cost

• $35,000–$100,000