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Evolved gas analysis by thermogravimetry-differential thermal analysis-mass spectrometry (TG-DTA-MS) technique

Winter 2011, Volume 27, No. 1
Kazuko Motomura and Lani Llego Celiz

The thermogravimetry-differential thermal analysis (TG-DTA) is a simultaneous measurement technique where the material’s mass changes as well as energy changes are measured during heating and the macroinformation on the physico-chemical changes of the material can be concluded from the obtained data.  However, in order to fully understand the reactions that have occurred, it has to depend on the information obtained from other measurement techniques. Such as in TG-DTA where a mass loss is associated with an endothermic reaction, then we can conclude that reactions such as dehydration, evaporation, sublimation, degradation or reduction have occurred. Although we can conclude the kind of reactions that have occurred if the information on the material’s structural formula, degradation temperature or water adsorption percentages are present, but on the contrary, it is difficult to draw conclusions if the material is unknown. In this case, combining TG-DTA with other measurement techniques is helpful in understanding the structural changes in the material and if the volatilized chemical species are known, then the chemical reaction process that can be derived will be a useful information. The combination of TG-DTA and evolved gas analysis is one of the complex measurements. Evolved gas analysis (EGA) is defined as a measurement technique where the gases which evolved from the sample upon heating are qualitatively and quantitatively measured as a function of temperature. It is often combined with other thermal analysis techniques rather than used as a stand-alone module.

Examples of EGA detection analyzers are mass spectrometer (MS), thermal conductivity detector (TCD), flame ionization detector (FID) and infrared spectrometer (IR). Among these, the MS is characterized as highly sensitive and can perform measurements rapidly. During the recent years, the TG-DTA-MS is a combination of MS and TG-DTA where it can also be used as a standard module.


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