Highest resolution in Evolved Gas Analysis (EGA)

TG-GC-MS Coupling

 

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The primary scope of TG-GC-MS coupling is to detect, separate and analyze organic components. It is also possible to use the coupled GC-MS for detailed gas analysis to further improve the temperature-programmed pyrolysis of organic materials, biomass, renewable solid fuels, carbonaceous materials, and polymers in the TG/STA. The volatile products emitted during combustion processes can be determined with high sensitivity and resolution at various oxygen content levels.

The highly sensitive GC-MS gas detection and identification capabilities allow for improved analysis of additives, stabilizers, and residual solvents in food, pharmaceuticals, cosmetics, and polymers.

TG-DTG-TIC plot of non-vulcanized Natural Rubber (NR), 3.36 mg, N2, continuous injection of the evolved gases at 1-min intervals. A constant high temperature is maintained in the GC column to allow the gas mixture to pass quickly and separate into its main components.

At the onset of the NR decomposition (32 min., 346.3°C), the primary volatile products are isoprene C5H8 (peak 1 in TIC chromatogram) and 1-methyl-4-(1-methylethenyl)-cyclohexene C10H16 (peak 2).

This continuous GC-MS mode shows the gas evolution as a function of temperature and time and allows for the selection of individual mass numbers (m/z) for continuous plotting as a function of temperature (single ion monitoring, SIM).

The second stage of the NR decomposition (onset at 38 min., 406.2°C) is characterized by the evolution of products in addition to isoprene and substituted cyclohexene (as shown above). These can be identified as 5,5-dimethyl-1,3-cyclopentadiene (C7H10, 94 m/z), 1-methylene-2-vinylcyclopentane (C8H12, 108 m/z) and beta-humulene (C15H24, 204 m/z).

TG-DTG-T plot of oak wood, 4.37 mg, N2, event-controlled triggering of the GC-MS run at 291°C and at 347°C (DTG threshold 8 %/min; temperature stops until GC-MS run is finished). Detailed analysis of the gas composition is achieved by the GC furnace program: isothermal 60°C for 0.5 min, linear heating to 310°C at 25 K/min.

Total Ion Chromatogram for the first step of oak wood pyrolysis, with library search result for the main peaks (table listed in ascending order of retention times (RT/min)).

RT	Area%		Best hit (NIST/Wiley)
1.157	2.27		6H,8H-Benzopyrano[3,4-b]benzopyran
1.356	8.96		Acetic acid
1.398	2.24		1-Penten-3-ol
2.253	26.67		Furfural
2.551	1.65		Thiazole
3.018	1.96		1-methyl-1-silacyclohexane
3.243	14.86		3-Methyl Hydantoin
6.881	1.70		Benzenamine, N-methyl-N-phenyl-
9.156	16.97		2-Isopropyl-10-methylphenanthrene
9.209	9.01		Phenanthrene, 1-methyl-7-(1-methylethyl)-
9.298	1.42		Benzene, 1-methyl-4-[(4-propylphenyl)ethynyl]-

Total Ion Chromatogram for the second step of oak wood pyrolysis, with library search result for the main peaks (table listed in ascending order of retention times (RT/min)).

RT	Area / %		Best hit (NIST/Wiley)
1.157	7.72		[2-(4-Dimethylaminocinnamoyl)-5-me thylphenoxy]difluoroborane
1.408	6.83		Furan, 2-methyl-
1.681	1.70		Furan, 2,5-dimethyl-
2.258	21.28		Furfural
2.357	7.37		2-Furanmethanol
3.033	7.80		2-Furancarboxaldehyde, 5-methyl-
3.128	2.91		2-Amino-3-hydroxypyridine
3.820	2.81		Phenol, 2-methoxy-
3.972	2.19		Levoglucosenone
4.444	1.63		2-Methoxy-5-methylphenol
5.335	3.73		Phenol, 2,6-dimethoxy-
6.897	2.03		Benzenamine, 4-(phenylmethyl)-
9.209	12.26		Phenanthrene, 1-methyl-7-(1-methylethyl)-
9.340	2.72		Benzene, 1-methyl-4-[(4-propylphenyl)ethynyl]-