Laser micropyrolysis

Vastola, F. J., and A. J. Pirone Use of the Laser-Micropyrolysis-Mass-Spectro-meter in Studying the Pyrolysis of Coal. Prep. Div. Fuel Chem. Am. Chem, Soc. 70(2), C 53/C 58 (1966). 

Figure 4.5.2. Simplified diagrams of two laser micropyrolysis setups A cw laser with a microscope, B pulse laser with alignment low power laser.

Figure 4.7.1. The variation in chromatographic peak heights for n-alkanes generated from torbanite pyrolysed by several techniques [35] A - laser micropyrolysis, B - sealed vessel microscale furnace pyrolysis, C - resistiveiy heated pyrolysis (HP 18580 A Pyroprobe), and D - microfurnace pyrolysis (SGE Pyrojector).

Laser micropyrolysis gas chromatography-mass spectrometry A laser microprobe is used to target selectively microscopic samples of toner, for subsequently GC-MS detection. Fused toners are directly analyzed in situ avoiding the traditional separation of toner from the paper substrate. This method offers a high spatial resolution and selectivity but further studies may be necessary to improve its reproducibility. 

It would be an advantage to be able to analyze the chemical composition of individual oil inclusions. FTIR spectroscopy enables this to be partly achieved, but to provide the molecular detail needed for source and maturity assessment, an MS method is required. Advances in laser micropyrolysis GC-MS design mean that this is beginning to become possible. TOF-SIMS already shows great promise for chemical mapping of organic compounds in fluid inclusions and, in conjunction with laser ablation, may offer the best way to obtain chemical compositions of individual oil inclusions in the future. However, these techniques are unlikely to replace the power of detailed GC-MS with off-line crushing and will probably evolve as complementary techniques. 

Greenwood, P.F., George, S.C., Wilson, M.A., Hall, K.X. (1996) A new apparatus for laser micropyrolysis-gas chromatography/mass spectrometry. Journal of Analytical and Applied Pyrolysis, 38,101-118. 

Greenwood,P.F.,George,S.C.,Hall,K. (1998)Apphcations of laser micropyrolysis gas chromatography mass spectrometry. Organic Geochemistry, 29,1075-1089. 

Mass spectrometry using alternative ionization and sample preparation methods are employed in ink and paint analysis. The oldest of these techniques is based on pjnrolysis of the sample (typically, a paint) prior to its introduction into the GC. Detectors for PyGC are and FID. Pyrolysis patterns can be examined in the same way accelerant patterns are (Chapter 10), but increasingly, GCMS is preferred over FID. Pyrolysis is, by definition, destructive, but the sample size is reasonably small, and recently a micropyrolysis GCMS has been developed and applied to photocopier toners and paint. A laser is focused on the sample through a microscope, and the pyrolysis vapor product is directed into the GCMS system. The pattern of the pyrolyzates and chemical composition... 

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