Py-MS technique

Some MS systems have, besides a temperature controlled probe, a heated-filament probe. This type of probe allows a more direct heating of the sample when it is deposited directly on the filament [48]. However, most of these probes still operate within common values for the current intensity and voltage and have a TRT that is longer than those used for flash pyrolysis. True flash pyrolysis using a resistively heated filament requires boosted current or boosted voltage for achieving a rapid heating (see Section 4.3), and such systems are commercially available. 

The volatile components or the labile groups from a polymer will be released at lower temperatures (or at the beginning of the heating time), while the polymer backbone will decompose at higher temperatures. Each point in the total ion trace (TIT) has an associated mass spectrum that allows the characterization of this process. Thermal analysis (TA) associated with the MS analysis of the evolving pyrolysates is a useful tool for polymer analysis, but the main focus in this process is not relat to an actual pyrolysis. 

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The Py-MS technique has been used extensively to characterize synthetic polymers, biopolymers, and fossil fuels (5-8,10, 11). In this work the technique has been modified by using a mass spectrometer which provides precise mass measurements directly upon pyrolysis. The advantage of this approach is two... 

This study has demonstrated that the Py-MS technique using precise mass measurements can be useful for characterizing macerals. Furthermore, the information derived from the... 

The degree of methylation (DM) of pectin [60] can be estimated using a Py-MS technique. The application of principal component analysis and canonical variate analysis to the Py-MS data (see Section 5.5) showed a linear relationship between DM and the first canonical variate score of the data as shown in Figure 7.5.3. 

Py-MS Pyrolysis is the thermal degradation of a compound in an inert atmosphere or vacuum. The two py-MS techniques are py-(GC-MS), in which the complex thermal degradation products are separated by the gas chromatograph prior to analysis by the mass spectrometer, and DP-MS technique, in which thermal degradation occurs inside the mass spectrometer close to the ionization source. 

Py/GC/MS. pyrolysis, gas chromatography, and mass spectrometry used as a combined technique Py/MS. pyrolysis and mass spectrometry used as a combined technique oa-TOF. orthogonally accelerated time of flight Q. quadrupole field or instrument... 

Furthermore, the major disadvantages encountered in GC/MS, i.e. undetectability of synthetic polymers and unpredictable interferences due to their presence, may be avoided using the Py-GC/MS technique. All these aspects strongly suggest how useful, and in some cases fundamental, analytical pyrolysis is in the analysis of complex samples, such as those collected from works of art, to implement and support results obtained with wet chemical pretreatment followed by GC/MS analysis. 

As an alternative, a two-step Py-GC/MS technique can be applied allowing the identification of volatile diterpenoids in the first step and of the polymeric fraction in the second step [33]. The procedure involves an on-line derivatization at 250°C with TMAH, followed by the pyrolysis of the remaining high molecular weight fraction. 

Techniques are available to quantify the generation of smoke, toxic and corrosive fire products using the NBS Smoke Chamber (15), pyrolysis-gas chromatography/mass spectrometry (PY-GC-MS) (J 6), FMRC Flammability Apparatus (2,3,5,17,18), OSU Heat Release Rate Apparatus (13) and the NIST Cone Calorimeter (JJO. Techniques are also available to assess generation of 1) toxic compounds in terms of animal response (19), and 2) corrosive compounds in terms of metal corrosion (J 7). In the study, FMRC techniques and AMTL PY-GC-MS techniques were used. 

The total number of compounds identified using the PY-GC-MS technique varied from 19 for MTL 5 to 39 for MTL 2. 

Li XH, Meng YZ, Zhu Q, Tjong SC (2003) Thermal decomposition characteristics of poly (propylene carbonate) using TG/fR and Py-GC/MS techniques. Polym Degrad Stab 81 157-165... 

Another rapid technique for characterizing non-volatile materials which has been applied to coal macerals is pyrolysis mass spectrometry (Py-MS) (82-84). The evaluation of the complex data produced by this technique has been aided by the use of statistical analysis. Homologous series of molecules can be identified and variation between the various maceral groups is quite evident. 

Pyrolysis-mas spectrometry (Py-MS) A pyrolysis technique in which the volatile pyrolysates are analysed by mass spectrometry. 

For ail the classes of compounds discussed above, it is possible to trace similarities between pyrolysis fragmentations and mass spectral fragmentations. However, it is not always simple to predict the result of each of the two processes. This adds supplementary complications for the interpretation of the data in the Py-MS analytical technique where the two processes are combined (see Sections 5.4 and 5.5). 

Besides simple similarity comparisons, more elaborate comparisons were also performed on Py-GC data [1]. Some of the techniques utilized to compare Py-GC data are similar to those used for the processing of Py-MS results that will be discussed in Section 5.5. 

In order to obtain even simpler MS spectra that will counteract a number of drawbacks in the common El ionization procedures applied in Py-EI MS, several special ionization techniques were applied. One of them is Cl ionization, but also field ionization (FI), field desorption (FD), and photoionization (PI) were utilized to obtain simplified mass spectra for pyrolysates. Also, MS/MS techniques were utilized for the analysis in attempts to substitute at least in part for the need of a separation. 

Lasers have been used as a source of energy for pyrolysis, and several experimental systems were described in Section 4.5. The main use of lasers in mass spectral analysis is associated with several desorption techniques where the pyrolysis is an undesired process. However, laser pyrolysis is also used in direct coupling with an MS system, and a schematic diagram of a laser Py-MS system is shown in Figure 5.4.5. 

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