Couplings / Evolved Gas Analysis
Thermogravimetry (TG) or Thermogravimetric Analysis (TGA) measure the mass loss or gain of a sample of material as a function of time or temperature when it is heated or cooled under a certain temperature profile. Simultaneous thermal analysis (TG-DTA or TG-DSC) additionally allows qualifying or quantifying the corresponding heat effects.
The contribution of hyphenated techniques, also known as Evolved Gas Analysis (EGA) have proved particularly interesting for the investigation of the chemistry of a reaction or thermal decomposition owing to the identification of the evolved species.
Mass spectrometry identifies the evolved molecules after their ionization based on the m/z ratio of the main ions and their fragments. Coupling can be achieved thanks to the heated capillary or supersonic methods.
– Features: best limit of detection, fast transfer time
– Benefits: applicable to small mass variations, easy to setup, detection of heavy molecules (with Supersonic System)
Chemical functions of the evolved molecules are identified according to their specific absorption of IR light wavelengths.
– Features: Chemical function specific signals
– Benefits: Applicable to the detection of families of substances in complex gas blends evolved from decomposition of organic samples
TG-GC/MS is becoming increasingly popular, as gas chromatography allows a first separation of the evolved species, before their identification by the mass spectrometer.
– Features: Best gaseous molecules separation and identification
– Benefits: Applicable to the identification of substances in complex gas blends evolved from decomposition of organic samples