Evolved Gas Analysis

Couplings / Evolved Gas Analysis (EGA)

By integrating a Thermal Analyzer (such as TGA, STA, or DIL) with a thermal and evolved gas analyzer like FTIR (Fourier-transform infrared spectroscopy) or QMS (Quadrupole-Mass-Spectrometer), a potent coupling is established. This synergy provides concurrent and correlated information from both gas analysis instruments.

Moreover, the optional Pulse Analysis feature introduces a precisely predetermined quantity of gas into the Thermobalance (TGA) or Simultaneous Thermal Analyzer (STA), significantly expanding the range of measurement capabilities.


The combination of a Linseis Thermal Analyzer with a FTIR is especially interesting in fields such as polymers, chemical and pharmaceutical industry. For interpretation different libraries are available.


The QMS – quadrupole mass spectrometer coupling device is a state of the art mass spectrometer with a heated inlet system. The QMS is used for the analysis of volatile decompositions.


By coupling a TGA or a STA with a (GC-MS) gas chromatography–mass spectrometry which is an analytical method that combines the features of gas chromatography and mass spectrometry, one can combine the strength on these two tools.

EGA Optical In Situ

An optical In-Situ evolved gas analysis offers many advantages such as: no Cooling / Modification of the measuring gas (for example no out-condensation, no transition reaction and no equilibrium shift).

Typical pairings for simultaneous measurements encompass:

TG-DSC-MS (Thermogravimetry, Differential Scanning Calorimetry, Mass Spectrometer): This combination enables the concurrent examination of thermal and mass properties.

TGA-MS (Thermal Balance coupled with Mass Spectrometer): Joining a thermal balance with a Mass Spectrometer offers comprehensive insights into material characteristics.

TG-DSC-GC/MS (Thermogravity, Differential Scanning Calorimetry, Gas Chromatography / Mass Spectrometry): This coupling integrates multiple techniques for a thorough understanding of materials’ thermal and gas-related behavior.

Analytical methods utilized for these couplings encompass:
  • FT-IR Spectroscopy: Employing Fourier-transform infrared spectroscopy for detailed gas analysis.
  • Quadrupole Mass Spectrometry (QMS): Utilizing QMS for precise mass analysis.
  • ELIF Spectroscopy (Excimer Laser Induced Fragmentation Fluorescence): Employing ELIF spectroscopy for detailed insight into sample behavior.
  • Gas Chromatography: Aiding in the separation and analysis of gas components.
The integration of thermal analyzers with spectrometers or chromatographs can be achieved through various methods, including:
  • Heated Transfer Capillaries (for FTIR, GCMS, GC, MS).
  • Sniffer Coupling (for GCMS, GC, MS).
  • Optical In Situ Observation (for ELIF), providing real-time insight into samples.

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Heated transfer capillary

The most straightforward method of coupling involves a heated capillary. Here, a heated capillary conduit channels the evolved gases from the thermobalance to the spectrometer or chromatograph. In the case of EGA MS coupling, the internal diameter of the capillary is typically less than 0.1 mm. The capillary is maintained at a temperature of 200-300°C, which can pose a potential risk of outgassing condensation during transfer and potential capillary blockages.

Sniffer coupling

This technique is primarily employed for mass spectrometer coupling. It involves the passage of gases through a tiny EGA (Evolved Gas Analysis) port located in close proximity to the sample within the furnace. These gases are then transferred through a vacuum line to the mass spectrometer. By doing so, gases are sampled at a high concentration in close proximity to the sample, even at elevated temperatures, and are directly transported into an ultra-high vacuum environment. This approach effectively eliminates any potential risk of condensation during the transfer process from the thermobalance to the mass spectrometer.

Optical in situ observation

In this scenario, optical windows are seamlessly integrated into the thermobalances. During the heating process, samples often undergo phase transitions or experience weight changes attributed to solvent evaporation and chemical reactions. These alterations can be effectively detected through thermal analysis techniques: calorimetric methods (DTA and DSC) provide insights into the heat involved in these processes, while thermogravimetry (TG) reveals changes in weight.

Weight changes may manifest as an increase due to oxidation reactions or a decrease due to decomposition with the release of volatile compounds. To gain a deeper understanding of sample composition and the pathways of decomposition, the analysis of these evolved gases proves to be invaluable.

Since thermal analysis alone does not provide information about the nature of these evolved gases, coupling with spectrometers or chromatographs emerges as a valuable tool for Evolved Gas Analysis (EGA).

Infrared spectroscopy

Infrared light possesses the capability to stimulate molecular vibrations within molecules. To be responsive to IR-spectroscopy, a molecule must undergo a change in its dipolar momentum during excitation. Gases such as CO2, CO, hydrocarbons, and water vapor exhibit IR-active vibration modes, while gases like N2 and O2 lack detectable IR activity.

The resulting IR spectra offer a means of identifying components through distinctive vibrations. These vibrations can either be characteristic of a specific functional group (e.g., CO, COOR) or unique to a particular compound. The spectral region spanning from 1500 to 500 cm-1, often referred to as the “fingerprint region,” is particularly valuable for compound identification. Spectral libraries are valuable tools for interpreting these spectra.

Coupling IR-spectroscopy with TGA and STA proves especially beneficial in evolved gas analysis of organic compounds, such as polymers, enhancing the understanding of their decomposition processes.

Mass spectroscopy

Mass spectrometry is a technique that segregates molecules based on their molecular weight relative to their electrical charge (m/e). In quadrupole mass spectrometry (QMS), molecules are directed into a magnetic quadrupole field after acceleration in a static electric field. Within this field, molecules and their fragments are precisely sorted by their masses, facilitating their identification. Mass spectrometry proves highly valuable for determining the molecular weight of outgassing products and analyzing gases that may not exhibit IR-spectroscopy activity (e.g., N2, O2, CO, etc.).

Mass spectrometry has the remarkable capability to detect nearly all molecules, including the fragments of larger molecules. These fragments often carry characteristic signatures indicative of specific compounds or functional groups. This method is widely employed across various disciplines, encompassing polymer and organic Evolved Gas Analysis (EGA), as well as applications in forensic science, medicine, biology, and material science.

Furthermore, mass spectrometry can be seamlessly combined with a Gas Chromatography (GC) method, which provides insights into the purity of substances analyzed by the mass spectrometer. This combined approach, known as GC-MS, offers a comprehensive understanding of both purity and the molecular weight of the substrates under examination.

ELIF spectroscopy

ELIF, which stands for Excimer Laser Induced Fragmentation Fluorescence, is a specialized technique employed for the analysis of alkali metal compounds. Its fundamental measuring principle revolves around the simultaneous breaking of molecules and exciting the respective alkali atom through a VUV-laser (Vacuum Ultraviolet). Subsequently, when the excited atom returns to its original state, it emits a photon with a characteristic wavelength. The intensity of this “fluorescent signal” serves as a quantitative measure of the concentration of the specific compound under investigation.

ELIF spectroscopy is an invaluable tool for characterizing alkali metal compounds like NaCl, KCl, NaOH, and others. It should be noted that the utilization of ELIF spectroscopy necessitates optical in-situ coupling.

Gas chromatography

The evolved gases often form a complex mixture of compounds. To analyze them effectively, column chromatography is employed to separate these compounds before subjecting them to various analytical techniques. The selection of the chromatographic separation column depends on the nature of the molecules to be separated, considering their polarity or lack thereof.

Commonly employed detection techniques include flame ionization detectors (FID) and thermal conductivity detectors (TCD). These detectors play a crucial role in identifying and quantifying the individual components within the complex gas mixture.


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