Simultaneous on-line analysis of gas phase and particulate phase of cigarette mainstream smoke
Tobacco smoke is a complex and dynamic matrix consisting of gaseous and particulate material, in which about 4800 constituents have been identified. The chemical composition and partition between phases of the smoke can change continuously and is strongly influenced by time, temperature, chemistry and dilution of smoke. We present an experimental set-up consisting of gas phase and particulate phase on-line instrumentation for comprehensive analysis of mainstream tobacco smoke. Cigarettes comprising Burley, Virginia or Oriental tobacco at 3 filter ventilation levels were smoked, with particle diameter and concentration measured by electrical mobility (Model DMS-500, Cambustion, Cambridge, UK). Chemical composition was characterised on-line by two soft photoionisation techniques; resonance-enhanced multi-photon ionisation (REMPI) and single photon ionisation (SPI) techniques, both coupled to time-of-flight mass spectrometry (TOFMS). Count median diameter (CMD) averaged over the cigarette varied from 182 - 260 nm and increased with increasing filter ventilation and lower puff flow rates; a consequence of increasing smoke residence time and coagulation within the rod. Puff-by-puff data showed increasing particle concentration and decreasing diameter as the tobacco was consumed and the coagulation period decreased. Mass spectrometry data show that most smoke constituents feature a continuous increase from the first to the last puff. However, there are some substances, in particular unsaturated hydrocarbons e.g. butadiene, isoprene, and propyne, which show a completely different behaviour by having the highest amounts in the first puff. This is likely to be related to the different combustion and pyrolysis conditions when the cigarette is lit.