Evolved Gas Analysis (EGA) is “a technique in which the nature and/or amount of volatile product released by a substance subjected to a controlled temperature program is determined”, this is the definition given from the IUPAC Compendium of Chemical Terminology…
Thermo-analytical instruments: thermo balances (TGA), differential thermal analysers, or calorimeters (STA, DSC, but sometimes also simpler reactors), are the most commonly used to start study the sample evolution. Thermogravimetry is useful for the quantification of each single gaseous evolution process as the results of an increasing thermal ramp or a defined isothermal temperature.
The combination of a thermogravimetry with other analytical devices (FTIR and/or GC/MS) lead to achieve interesting result on the nature of the released gases or vapors, allowing also to prove a supposed reaction under heating or isothermal conditions.
TGA-IR and TGA-IR-GC/MS Combinations
Coupling with FTIR has become popular, especially for polymer, chemical, pharmaceutical industries, environment and quality control. TGA-FTIR (or TG-IR) is an online, continuous and fast analysis which gives useful information on the composition (absorption bands) of the evolved gases (bonding conditions), with a fast and easy interpretation without fragmentation (based on spectra that can be compared to spectral reference database for identifying the chemical class or family of the unknowns).
Other combinations like TGA-GC/MS and TGA-FTIR-GC/MS – or only MS – add the detection of gas separation and identification of single components with an exact time correlation with the other thermal analysis signal. These techniques are more sensitive with higher performances, providing more complete results useful for reverse engineering, R&D, microplastics analysis & polymers in general, and unknown mixtures which need to be identified.
Active Vs Passive EGA Approach
Our approach for Evolved Gas Analysis is to couple instruments with thermostatted gas transfer lines which connects inline TGA with FTIR and/or GC/MS maintaining the TGA pressure constant when temperature is increasing during the experiment. RedShift acts differently from passive system which uses the native pressure generated in the TGA furnace during the experiment to push the evolved gases through the path. Passive system destroys precious results that cannot be seen in the FTIR and/or GC/MS analysis.
We named RedShift state-or-art technology: Balanced Flow Technique with an active gas sampling system which do not affect flow rate, temperature and internal pressure of the TGA. It eliminates gas mixture and cross interference between flows, decreasing also bad effects of TGA dead volume, thanks to specifically designed TGA adapters available for the most known TGAs in the market. Gases and vapours reach FTIR and/or GCMS for the analysis with a constant speed, providing accurate and repeatable analysis with qualitative and quantitative results.
To learn more about Balance Flow Technique, please contact us!