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CORESTA Congress, Quebec, 2014, Smoke Science/Product Technology Groups, ST 85

Highly time-resolved two-dimensional mapping of molecular combustion and pyrolysis product concentrations: looking into a burning cigarette during puffing

ZIMMERMANN R.(1); HERTZ-SCHÜNEMANN R.(1); EHLERT S.(1); LIU C.(2); McADAM K.G.(2); BAKER R.R.(2)†; COBURN S.(2); STREIBEL T.(1)
(1) University of Rostock, Chair of Analytical Chemistry, Rostock, Germany; (2) British American Tobacco, Group R&D, Southampton, U.K.; (†) Deceased

Combustion and pyrolysis are complex and dynamic chemical processes that are by far not fully understood. This is in particular true when the highly dynamic cigarettes smoking process is considered. The gas phase chemistry of tobacco combustion in its voids and pores is extremely difficult to address by conventional analytical methods. In the last years, photo ionisation mass spectrometry (PIMS) was established as a fast on-line analytical technique to analyse the chemical signature of highly dynamic combustion and pyrolysis processes in cigarettes during puffing[1]. Recently a new combination of PIMS (laser based single photon ionisation, 118 nm) and a capillary microprobe sampling system (µ-probe) was developed, allowing direct examination of the composition of organic vapours even in the centre of the cigarette’s combustion zone[2]. This µ-probe-PIMS approach now is further developed to a spatial- and temporal resolving mapping method. Repetitive smoking experiments with a reproducible smoke machine and standard reference cigarettes were performed and different sampling positions in the cigarette rod were multiply addressed by µ-probe PIMS measurements. The time resolved PIMS sequences were later combined to spatially resolved, time-dependent “maps” for the different compounds. This new imaging technique was used to measure quantitative distributions of e.g. nitrogen monoxide, benzene and oxygen in the burning tip of a cigarette during a 2 second lasting puff (~200 ms time resolution). The different formation and destruction zones of the investigated compounds in the reaction region and their dynamic changes were observed during the puff, and space-resolved kinetic data was obtained. For example, the classical formation and destruction mechanisms of NO during the puff (fuel-NO formation and re-burn in hydrocarbon rich zones) could be observed in a space- and time-resolved manner. In addition applications of the PIMS technology to better understand heat-not burn or e-cigarette devices are discussed.

[1] Adam, T. et al., Analytica Chimica Acta, 657 (2010) 36-44;
[2] Hertz, R., et al., Analytica Chimica Acta, 714 (2012) 104-113