Evolved gas analysis


Evolved gas analysis is a method used to study the gas evolved from a heated sample that undergoes decomposition or desorption. It is either possible just to detect evolved gases using evolved gas detection or to analyse explicitly which gases evolved using evolved gas analysis. Therefore different analytical methods can be employed such as mass spectrometry, Fourier transform spectroscopy, gas chromatography, or optical in-situ evolved gas analysis.
By coupling the thermal analysis instrument, e. g. TGA or DSC, with a fast Quadrupole Mass Spectrometer the detection of gas separation and identification of the separated components are possible in exact time correlation with the other thermal analysis signals. DSC/TGA-QMS or TGA-QMS yields information on the composition of the evolved gases. It allows fast and easy interpretation of atomic/inorganic vapors and standard gases like H2, H2O, CO2, etc. Fragmentation, interpretation of organic molecules is sometimes difficult.
The combination with an FTIR has become popular, especially in the polymer producing, chemical and pharmaceutical industry. DSC/TGA-FTIR or TGA-FTIR yields information on the composition of the evolved gases. The advantage is an easy interpretation of organic vapors without fragmentation. Symmetrical molecules can not be detected.
An EGA instrument named the Thermal and Evolved-Gas Analyzer was flown on the Phoenix Lander probe that reached Mars in May 2008. Its purpose was to study Martian soil samples.