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| TGA - High Pressure/High Temperature/High Mass |
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Thermogravimetric Analysis (TGA)
In Thermogravimetry (TG) and TG/FTIR systems, there are many variables that can affect the detection limit of the system. It is demonstrated in this paper that the larger the sample size, the better the detection limit. For TG/FTIR, with a certain kind of TG/FTIR interface, the detection limit is dependent upon the sample holder volume of the TG system. It is proved that, for a sample mixture, the ratio of balance sensitivity to standard sample holder volume should be used to characterize the detection limit of TG, while the standard sample holder volume of the TG system should be used to characterize that of TG/FTIR.
Thermogravimetry (TG) has widely been used as a tool to detect material composition. i,ii When the sample’s evolved gases are also of interest, an evolved gas analyzer (EGA) unit will be utilized. Among the options for EGA, Fourier Transform Infra-Red spectroscopy (FTIR) and Mass Spectroscopy (MS) are two techniques often used. Between TG/FTIR and TG/MS, TG/FTIR is the more common combination because of the relatively simple coupling technique involved.
In a TG system, the important measured parameters are weight, temperature and time. Weight is the signal which is the most important of these, and much is made (correctly) of capacity and sensitivity of the balance used in the TG system. In FTIR, besides the accuracy of the wavenumber, another important feature is the signal to noise ratio or sensitivity.
To measure small amounts of a component in a sample, the detection limit will ultimately decide if the measurement can be made. The detection limit is defined as the smallest concentration or percentage of a components which can be detected. Such a definition has been widely used for various analytical instrumentation, and in general, the higher sensitivity, the better the detection limits. However, this term has not been applied to TG or TG/FTIR, because sample size will decide the amount of evolved gases and sample weight loss/gain, and eventually the detection limit for a sample. |
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