Sample application pyrolyzers

The presence of water as a reaction product from the pyrolytic processes or as adsorbed water on the material to be pyrolyzed is not unusual. However, in analytical pyrolysis, water is not commonly added to the sample. During some pyrolytic processes with industrial applications such as wood pyrolysis, water is sometimes added intentionally. The main effect of water during pyrolysis is hydrolysis. This takes place as the temperature elevates and can be seen in the modification of the yields of different final pyrolysis products. Therefore, the reproducibility in analytical pyrolysis may be influenced by the variability of water content of the initial sample [31]. 

Laser pyrolyzers are practically the only type of radiative heating pyrolyzer with certain applicability. Attempts were made in the past to use a strong light/heat source and focus the beam with lenses [20] to achieve the desired power output. However, the laser as a radiative energy source is much more convenient. The laser beam can be focused onto a small spot of a sample to deliver the radiative energy. This provides a special way to pyrolyze only a small portion of a sample. A variety of laser types were used for pyrolysis purposes normal pulsed, Q-switched, or continuous wave (cw) [21], at different energy levels. More common are the normal pulsed high-power lasers. 

Infrared (IR) techniques are reported in literature to be used in combination with different thermal experiments as a convenient tool of analysis. For example, IR-EGA (infrared evolved gas analysis) was used for obtaining information on different thermal and combustion processes [19]. A simple IR attachment where the sample can be pyrolyzed close to the IR beam is also commercially available (Pyroscan/IR from CDS Analytical). Although the IR detectors are by far not as popular as the MS, pyrolysis-gas chromatography/Fourier transform IR (Py-GC/FTIR) occasionally has been used in polymer analysis. Such applications have been commonly related to the analysis of certain gases such as CO2, CO, CH4, NH3, etc., where the MS analysis is less successful [20, 21]. 

Besides derivatization or selective analysis using SPME, off-line pyrolysis before a chromatographic analysis can be used for various other purposes. One such purpose is the use in the pyrolyzer of larger samples, which would not be appropriate to send directly into a GC instrument. Larger sample must be used in specific applications, for example in the analysis of trace components in pyrolysates. Another application of offline systems Is found when a dedicated GC or GC-MS instrument cannot be afforded only for pyrolysate analysis. 

In recent years, the development of soft desorption-ionization methods has allowed the application of mass spectrometry to the characterization of polymers [7]. Using these new direct introduction methods the sample is admitted in the condensed phase and subsequently vaporized, pyrolyzed or bombarded so as to emit useful intact ions. 

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