Pyrolysis - mass spectrometry technique direct

In addition to GC/MS, high performance liquid chromatography (HPLC/MS) has been used to analyse natural resins in ancient samples, particularly for paint varnishes containing mastic and dammar resins [34]. A partial limitation of chromatographic techniques is that they do not permit the analysis of the polymeric fraction or insoluble fraction that may be present in the native resins or formed in the course of ageing. Techniques based on the direct introduction of the sample in the mass spectrometer such as direct temperature resolved mass spectrometry (DTMS), direct exposure mass spectrometry (DE-MS) and direct inlet mass spectrometry (DI-MS), and on analytical pyrolysis (Py-GC/MS), have been employed as complementary techniques to obtain preliminary information on the... 

Qian, K. Killinger, W.E. Casey, M. Nicol, G.R. Rapid Polymer Identification by In-Source Direct Pyrolysis Mass Spectrometry and Library Searching Techniques. Anal. Chem. 1996, 68, 1019-1027. 

In pyrolysis-mass spectrometry (Py-MS) the pyrolysate is directly transferred to a mass spectrometer and analyzed, generating a complex spectrum. The sample introduction can be done using various techniques. One simple technique is the direct insertion probe (DIP) where the sample is deposited on an insert that has the capability of heating the sample and of introducing the pyrolysate directly into the ion source of the mass spectrometer (see e.g. [1]). Another technique is the Curie point Py-MS where an attachment to the mass spectrometer allows the sample to be placed in a radio frequency (RF) region continued by an expansion chamber connected to the ion source. The sample is pyrolyzed and the pyrolysate ionized and analyzed in the MS instrument. A schematic diagram of a Curie point Py-MS system is shown in Figure 3.3.2. 

The low volatility of macromolecules initially precluded the widespread application of MS analysis to polymer systems. Nevertheless, meaningful structural information can be extracted from the mass spectra of unvolatile macromolecules by El, Cl, and FI techniques, and this is due to the considerable attention that has been focused on the methods of characterization of polymers by Direct Pyrolysis Mass Spectrometry (UPMS). " ... 

K. Qian, W. Killinger, and M. Casey, Rapid polymer identification by in-source direct pyrolysis mass spectrometry and library searching techniques. Anal. Chem., 68 1019-1027 (1996). 

Thermal analysis of PS, poly-p-methylstyrene and polyalpha-methylstyrene was carried out using evolved-gas analysis by IR and mass spectrometry and direct-pyrolysis analysis by mass spectrometric techniques. Evolved-gas analysis, both by IR and mass spectrometry, revealed features due mainly to the corresponding monomers or stable, volatile and low relative molec.wt. degradation products. In direct-pyrolysis mass spectrometry, however, primary decomposition products and heavier fragments such as dimers and trimers could also be detected. The ion-temp, profiles of the corresponding monomer ions revealed information about the thermal stability of the polymers. 25 refs. (XXVIII Colloquium Spectroscopicum Internationale, York, UK, June/July 1993)... 

Direct temperature-resolved pyrolysis-mass spectrometry (DT-MS or TPPy-MS) performed close to the ion source is another rapid and sensitive technique in the characterisation of involatile... 

Qian et al carried out a rapid identification of polymers using a technique based on ion source direct pyrolysis mass spectrometry and library searching. Polymers were pyrolysed using a coiled filament designed for desorption chemical ionization/desorption electron ionization applications. Pyrolysis products were ionized at 70 ev electron impact. This yielded highly reproducible spectra characteristic of the polymer. Using these techniques and library searching a comprehensive library of 150 polymers was developed. 

Direct pyrolysis-mass spectrometry (Py-MS) is applied to determine the primary structure of macromolecules and to investigate selective thermal degradation mechanisms. This technique allows the thermal decomposition products of the polymer sample to be observed directly in the ion source of the mass spectrometer, so that the evolving products are ionised and continuously detected by repetitive mass scans almost simultaneously with their formation 805917 757742. Since pyrolysis is accomplished under high vacuum, the thermal fragments are readily removed from the hot zone, and because of the low probability of molecular collisions and fast detection the occurrence of secondary reactions... 

Non-volatile organic compounds can be characterized by c.g.c. if pyrolyzed directly into the injector chamber of a g.c. [56, 57 ]. It has been shown that size exlusion chromatography and gel permeation chromatography are adequate techniques for fractionation of non-volatile components from water samples. The fractions are then to pyrolysis-g.c.— mass spectrometry for the characterization of humic acid and fulvic acids, sugars, and proteins [57 ]. ... 

Another MS technique used in connection to pyrolysis is MIMS (membrane introduction mass spectrometry). MIMS is in fact a special inlet for the mass spectrometer, where a membrane (usually silicone, non-polar) lets only certain molecule types enter the Ionization chamber of the MS. This allows, for example, direct analysis of certain volatile organic compounds from air. The system makes possible the coupling of atmospheric pyrolysis to a mass spectrometer [61a] allowing direct sampling of the pyrolysate. Other parts of the mass spectrometer do not need to be changed when using MIMS. 

Pyrolysis-direct chemical ionization mass spectrometry ( r-DCI-MS) was recently introduced as a pyrolysis technique for the characterization of complex macromolecular samples and for the analysis of biopolymers. This technique does not require special pyrolysis equipment and can be performed with an instrument which is equipped with a chemical ionization source and a standard DCI probe, which consists of an extended wire used to introduce the sample material directly into the chemical ionization plasma. An important characteristic of this technique is the pyrolysis... 

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