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The time- and space-resolved chemical signatures of gases and vapours formed in solid-state combustion processes are difficult to examine using recent analytical techniques. A machine-smoked cigarette represents a very reproducible model system for dynamic solid-state combustion. By using a special sampling system (microprobe unit) that extracts the formed gases from inside of the burning cigarette, which is coupled to a photoionisation mass spectrometer, it was possible to study the evolution of organic gases during a 2-s cigarette puff. The concentrations of various pyrolysis and combustion products such as 1,3-butadiene, toluene, acetaldehyde and phenol were monitored on-line at different sampling points within cigarettes. A near-microscopic-scale spatial resolution and a 200-ms time resolution were achieved. Finally, the recorded information was combined to generate time-resolved concentration maps, showing the formation and destruction zones of the investigated compounds in the burning cigarette. The combustion zone at the tip of cigarette, where e.g. 1,3-butadiene is predominately formed, was clearly separable from the pyrolysis zones. Depending on the stability of the precursor (e.g. lignin or cellulose), the position of pyrolytic formation varies. In conclusion, it was demonstrated that soft photoionisation mass spectrometry in conjunction with a microprobe sampling device can be used for time- and space-resolved analysis of combustion and pyrolysis reactions. In addition to studies on the model cigarette, further model systems may be studied with this approach. This may include further studies on the combustion of biomass or coal chunks, on heterogeneously catalysed reactions or on spray, dust and gas combustion processes. [ABSTRACT FROM AUTHOR]

Abstract: Three different tobacco samples (Burley, Virginia, and Oriental) were thermally desorbed at varying temperatures (190, 250, and 310°C) and the evolved gas phase at every temperature step has been analyzed applying single photon ionisation (SPI)-time-of-flight mass spectrometry (TOFMS) and resonance enhanced multiphoton ionisation (REMPI)-time-of-flight mass spectrometry. These soft and selective ionisation techniques allow fast and comprehensive on-line monitoring of a large variety of aliphatic and aromatic substances with almost no fragmentation of molecular ions. Many oxygen containing compounds could be detected such as phenol, hydroquinone, and (vinyl)guiacol along with unsaturated hydrocarbons and nicotine. In addition, with REMPI a large variety of PAH are accessible. Different tobacco types yield slightly distinguished mass spectra. By utilizing statistical tools (Fisher criterion and PCA) the three tobaccos can be discerned rather rapidly from each other and possible marker compounds for a given tobacco can be identified. Extension of this newly conceived method to other biomass material and potential coupling to other methods of thermal analysis seems feasible in the future. [Copyright &y& Elsevier]

Abstract: PVC and tobacco samples were pyrolyzed in a rotary furnace at different temperatures and reaction gas compositions. Released gaseous products were analyzed using single photon ionization (SPI)/resonance enhanced multiphoton ionization (REMPI)–time-of-flight mass spectrometry (TOFMS). These soft and selective ionization techniques allow fast and comprehensive on-line monitoring of a large variety of aliphatic and aromatic substances without fragmentation of the molecular ions. The thermal decomposition of PVC led to the appearance of chlorinated aromatic compounds at trace levels, which could be detected with SPI–TOFMS. Polycyclic aromatic hydrocarbons (PAH) were simultaneously accessible by REMPI–TOFMS. Different tobacco types can be distinguished by photoionization mass spectrometry of their gaseous pyrolysis products. In addition, pyrolysis products can be classified in three groups depending on their behaviour at different pyrolysis temperatures, which might help to unravel formation mechanisms and chemical pathways of hazardous substances. [Copyright &y& Elsevier]