Photoionization time-of-flight mass spectrometry as a tool for the identification of selected isomers in the gas phase of mainstream cigarette smoke
To identify selected isomers in the gas phase of mainstream cigarette smoke, an on-line measurement system with a photoionization unit was built. With this instrument, photoionization efficiency (PIE) curves for constituents in the gas phase of mainstream cigarette smoke were established. The before mentioned system is set up as follows: single-port smoking machine, three-port injector and synchrotron radiation vacuum ultraviolet single photon ionization time-of-flight mass spectrometry. The PIE curves of a calibration gas containing 1,3-butadiene, 1,2-butadiene and 1-butyne as well as the gas phase constituents in mainstream cigarette smoke derived under the ISO (International Organization for Standardization) smoking regime were separately determined between 8.0 and 10.6 eV. The isomers of the earlier mentioned three compounds in the calibration gas and the gas phase constituents in mainstream cigarette smoke were characterized by experimental PIE curves and multiple linear regression (MLR) method. Our results showed that PIE curves combined with the MLR method were not only capable to provide a substantial and accurate characterization of the isomers in the gas phase of mainstream cigarette smoke, but also to determine the mole percentages of each isomer at the same mass-to-charge ratio. These results can be used as the basis for further qualitative and quantitative analysis of gas-phase constituents in mainstream smoke by applying on-line and real-time analysis with soft ionization mass spectrometry, especially synchrotron radiation photoionization mass spectrometry.