Evolved gas analysis

What is EGA used for?

EGA is used to identify the gases a material releases when it is heated, along with the temperatures at which decomposition occurs. The method has applications in the development of new materials, including semiconductors, catalysts, and polymers. It can, for example, be used to determine the extent to which harmful compounds, such as phthalates or bisphenols, are released from plastics upon heating.

Evolved gas analysis can also be used in pharmaceutical industry product development to assess the effects of temperature changes on the stability of new drugs. Similarly, in the fuel industry, EGA can help determine the conditions where fuel quality starts to degrade and the gases that are released when this happens. In environmental analysis, EGA can be used to detect contaminants in soil in trace quantities.

EGA can be performed on a variety of solid and liquid sample types, and a relatively small quantity of the sample material is required (usually ≤ 1g).

How does evolved gas analysis work?

Evolved gas analysis begins by heating the sample to the point where it starts to undergo thermal decomposition. This is done thermogravimetrically, which means that the sample is gradually heated while the changes in its mass are monitored.

As gases are released by the sample, they are collected and moved to a coupled analyzer, such as FTIR or MS, which will provide information about the chemical nature of the gases. The information regarding temperature, change in mass, and detection of gases can then be compiled to create an accurate profile of the changes the material undergoes upon heating.

EGA techniques: TGA-FTIR, TGA-MS & TGA-GC-MS

The main types of analyzers that can be connected to a TGA instrument to perform EGA are the Fourier transform infrared spectroscope (FTIR), the mass spectrometer (MS), and the gas chromatograph-mass spectrometer (GC-MS). 

TGA-FTIR can be used to identify evolved gases by comparison to spectral libraries of IR-active compounds. It is well-suited for identifying gases originating from polymeric materials but cannot detect noble or diatomic gases.

TGA-MS offers higher sensitivity and can identify trace amounts of contaminants released by materials including pharmaceuticals and soil. It can also be used to analyze metallic compounds that FTIR cannot capture due to them not absorbing infrared light. Using a TGA-GC-MS setup further improves the separation and therefore identification of volatile and semi-volatile components in complex organic matrices.