There are some polymers which on pyrolytic decomposition produce several gases like CO2, CO, H2, CxHy, PH3, NH3 etc. along with several organic fragments. TGA coupled with Evolved Gas Analysis can give idea about the stepwise decomposition products. In the above specific case, which type of EGA technique will be most suitable for qualitative and quantitative determination of the evolved gases/byproducts? Please rate them as per decreasing order of sensitivity with reason: TGA-FTIR, TGA-MS, TGA-GC MS, TGA-MS MS
It is difficult to rate four EGA techniques for me simply because we do not have access to all techniques.
In our labs two systems are available: TGA-FTIR and TG-GC/MS. Sensitivity must be seen for each instrument separately. We have two different TGAs connected. Our GC/MS TGA is one order of magnitude more sensitive than the FTIR one. FTIR is usually used as qualitative analysis in most of our applications. Detection sensitivity of FTIR also depends on the gas flow rate for the transfer line. With standard flow rates samples are too highly diluted in the FTIR chamber - therefore no detection is possible.
Deeper analysis in our applications is done with TGA-GC/MS which allows identification of molecules and/or substances. Usually, the sample is less diluted, but has to pass the oven controlled column to reach the MS system. You need to be aware about the interactions between sample and column (separation processes) if you do not have a good idea what degradation products can be expected.
Kind regards
Peter
Thank you Peter for your nice answer. In my case I have idea about the decomposition products. But I want to evaluate them quantitatively and also qualitatively at each step of decomposition. In this case do you think TGA-GC MS will be more efficient rather than TGA - FTIR? We can't afford both TGA-GC MS and TGA-FTIR due to budget issue.
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