Discrimination of three tobacco types by application of Thermal Desorption/Photo Ionisation Time-of-Flight Mass Spectrometry as well as investigation of sidestream smoke using Single Photon Ionisation/Time-of-Flight Mass Spectrometry
Recently, Pyrolysis Single Photon Ionisation/Time-of-Flight Mass spectrometry (Py-SPI-TOFMS) has been applied to differentiate between three major tobacco types, Burley, Virginia, and Oriental, respectively. In doing so, tobacco samples have been pyrolyzed at 800 °C in nitrogen atmosphere. In addition, this approach has been extended by replacing the harsh pyrolysis conditions with Thermal Desorption/Photo Ionisation Mass Spectrometry (TD/PI-MS) applying much milder thermal conditions. The soft resonance-enhanced multiphoton ionisation (REMPI) as well as single photon ionisation (SPI) are applied, which in combination with time-of-flight mass spectrometry (TOFMS) are well suited for the sensitive and fragmentationless detection of polycyclic aromatic hydrocarbons (PAH), aliphatic and oxygenated hydrocarbons. Tobacco samples are heated sequentially to 190, 250, and 310 °C. Evolved gases are guided via a heated deactivated quartz capillary into the ion source of the mass spectrometer. TOFMS spectra are recorded as long as evaporated compounds are visible before moving on to the next temperature. The spectra that can be allocated to each temperature are summed. The mass spectra obtained have been analyzed by Principal Component Analysis (PCA) to distinguish between different tobacco types. Prior variable reduction of the data set was carried out by calculation of the Fisher-Ratios. Recognition of different tobacco types is possible by analyzing only a few key substances. Secondly, the same statistical approach was applied to the on-line analysis of sidestream smoke from cigarettes containing the aforementioned pure tobaccos. Although the mass spectra obtained looked very similar to each other, a clear distinction is possible without much effort using the statistical tools. Further improvements of the ionisation technique such as the development of electron-beam pumped rare-gas excimer VUV-lamp systems for SPI could lead to a rapid widely applicable technique for identifying distinct tobaccos.