Pyrolysis single-photon ionisation time-of-flight mass spectrometry (Py-SPI-TOFMS) for the discrimination of three tobacco types
Pyrolysis single photon ionisation/time-of-flight mass spectrometry (Py-SPI-TOFMS) has been applied to differentiate between three major tobacco types, viz Burley, Virginia, and Oriental, respectively. SPI is known as a soft ionisation technique that allows fast and comprehensive on-line monitoring of a large variety of aliphatic and aromatic substances with no or only few fragmentation of the molecule ions. Tobacco samples were pyrolyzed at 800°C in a nitrogen atmosphere. The resulting pyrolysis off-gas contained signals from more than 70 masses in a mass range between 5 m/z and 170 m/z. Mass spectra obtained were analyzed by Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) to distinguish between different tobacco types. Prior variable reduction of the data set was carried out by calculation of the Fisher-Ratios. Results achieved give information about chemical composition and characteristics of the pyrolysis gas from each tobacco type and enable conclusions on plant cultivation. Based on LDA, a model for tobacco type recognition of unknown samples was established, which was cross-checked by additional measurements of each tobacco type. Furthermore, first results on the recognition of tobacco mixtures based on Principal Component Regression (PCR) are presented. Recognition of different tobacco types is possible by only analyzing a few key substances without prior treatment of the samples. First measurements of tobacco mixtures provided promising results and reveal the potential of Py-SPI-MS for applications in various fields. Latest improvements of the ionisation technique such as the development of electron-beam pumped rare-gas excimer VUV-lamp systems for SPI, which replace costly laser instruments; incorporation of quadrupole mass spectrometers, and commercially available pyrolyzer devices including automated sampling systems would lead to a wide applicable technique, whose operation requires a minimum of expenditure of time.