Application of laser ionization mass spectrometry for on-line characterization of organic compounds in main- and sidestream smoke
Tobacco smoke is a fast changing and extremely complex mixture containing thousands of compounds. Consequently, to account for the dynamic smoke composition analytical techniques exhibiting a very high time resolution are required. The measurement technique used in the framework of this study is a laser-based ionisation method coupled to time-of-flight mass spectrometry (TOF-MS). Most organic compounds as well as some inorganic species are ionized by the soft single photon ionisation (SPI) achieved by vacuum ultraviolet (VUV) laser pulses. SPI produces almost no fragments in the mass spectrum and offers selectivity by means of the ionisation potential of the target compounds. For puff-by-puff resolved measurements of mainstream and sidestream smoke the measurement system is connected to a Borgwaldt single port smoking machine, which has been slightly modified to reduce memory effects caused inside the machine during the real time investigation. For sidestream measurements, a fishtail device was utilized as a sampling tool. Either way, a heated fused silica capillary serving as transfer line was applied to extract a small portion of main- or sidestream smoke, which was subsequently carried to the ion source of the mass spectrometer. Main- and sidestream smoke of different cigarette types have been compared on a puff-by-puff basis. Thereby, various characteristic trends in concentration could be observed during the course of the smoking process. For instance, some compounds such as butadiene exhibit their highest mainstream concentration in the first puff. As for the sidestream behaviour, there are species which show distinct concentration maxima immediately after a puff, then again the concentration of other compounds is increasing during and after the first puff and remains unchanged for the remainder of the cigarette.