Evolved gas analysis (EGA) is a method used to study the gas evolved from a heated sample that undergoes decomposition or

desorption Desorption is the physical process where a previously adsorbed substance is released from a surface. This happens when a molecule gains enough energy to overcome the activation barrier of the bounding energy that keeps it in the surface. There ...

. It is either possible just to detect evolved gases using evolved gas detection (EGD) or to analyse explicitly which gases evolved using evolved gas analysis (EGA). Therefore different analytical methods can be employed such as

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...

Fourier transform spectroscopy Fourier-transform spectroscopy is a measurement technique whereby spectra are collected based on measurements of the coherence of a radiative source, using time-domain or space-domain measurements of the radiation, electromagnetic or not. It ca ...

gas chromatography Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, ...

, or optical in-situ evolved gas analysis. By coupling the thermal analysis instrument, e. g. TGA (

thermogravimetry Thermogravimetric analysis or thermal gravimetric analysis (TGA) is a method of thermal analysis in which the mass of a sample is measured over time as the temperature changes. This measurement provides information about physical phenomena, such ...

) or DSC (

differential scanning calorimetry Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature. Both the sample and ref ...

), with a fast Quadrupole Mass Spectrometer (QMS) 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 (mass numbers of elements and molecules) 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 (Fourier transform infrared spectrometer) has become popular, especially in the polymer producing, chemical and pharmaceutical industry. DSC/TGA-FTIR or TGA-FTIR yields information on the composition (absorption bands) of the evolved gases (bonding conditions). The advantage is an easy interpretation (spectra data bases) 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 ''Phoenix'' was an uncrewed space probe that landed on the surface of Mars on May 25, 2008, and operated until November 2, 2008. ''Phoenix'' was operational on Mars for Timekeeping on Mars#Sols, sols ( days). Its instruments were used to asse ...

probe that reached Mars in May 2008. Its purpose was to study Martian soil samples. An EGA instrument was contained within th
Sample Analysis at Mars (SAM) instrument suite
onboard Curiosity Rover which landed on Mars in 2012. The instrument's goal was to understand the habitability and past climates of Mars. SA
detected complex organic carbon on the surface of Mars
at Gale Crater in a 3.5 billion year old mudstone. Pia19808-main tight crop-monday

References

Instrumental analysis {{chem-stub