The pyrolysis or oxidative degradation of organic matter, and the decomposition of inorganic materials during thermoanalytical experiments result in the evolution of many volatile components. Thermogravimetric analysis (TGA) is well introduced in this field of compositional analysis, however showing only the integral weight change for the complex processes. The on-line detection and identification of all volatiles in suitable gas analyzers is necessary to understand the nature, chemistry and mechanism of the involved processes. Mainly mass spectrometry (MS) and Fourier-transform infrared spectroscopy (FTIR) are established methods for a continuous gas analysis combined with TGA.

All considerations about coupling of gas analyzers with thermobalances or other thermal analysis instruments have to start with the study of the gas flow conditions around the sample and the further gas flow path to the coupling interface and the detectors.

Only when combined with thermal analysis in a perfect coupling system does mass spectrometry exhibit its extremely high sensitivity and its universal function for all kinds of volatile matter. The Skimmer^® coupling will be described as such an ideal system for coupling with TG-DTA/DSC, in the comparison with the more frequently used capillary couplings.

Fourier-transform infrared spectroscopy (FTIR) is well established for the identification of organic structures in the solid phase, and it is therefore sometimes also favored for the identification of volatiles during decomposition of organic materials. The gas transfer system must ensure also here the complete and undelayed transport of all evolved species from the thermobalance into the gas-measuring cell of the FTIR.

The novel pulse thermal analysis technique (PulseTA^®) for improvements of the quantitative information from coupled gas analysis methods and for more detailed studies of solid-gas reactions will be discussed with typical application results.

In the comparison of TG-MS and TG-FTIR applications, the specific advantages of both methods, depending on the purpose of the application, will be worked out.

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