Integration of time and spatially resolved in-situ temperature and pressure measurements with soft ionisation mass spectrometry inside a burning superslim cigarette

Abstract Background Accurate diagnostics of key thermophysical and thermochemical parameters in multi-phased combustion phenomena is essential for understanding formation mechanisms of reaction products. Aim To combine simultaneous temperature and pressure measurements with fast in-situ chemical sampling techniques within a superslim cigarette to: (1) obtain detailed physical and chemical information from this dynamic combustion system in response to an externally applied air flow, and (2) demonstrate the comprehensive capabilities of the approach in deducing mechanistic information about complex chemical reactions. Methods A micrometre sampling stage was used to accurately position the in-situ sampling probes for insertion into the cigarette. An array of 0.254-mm thermocouples (for gas-phase temperature) and multiple 0.35-mm diameter quartz tubes connected to transducers (to measure pressure), were inserted into the superslim cigarette. For chemical analysis, a single heated 0.5-mm chemical sampling microprobe was also inserted, and coupled to a single-photon soft ionisation (SPI) mass spectrometer through a heated transfer line. The different measurement techniques were synchronised by mapping two probes at a time (e.g. temperature/pressure or temperature/chemistry); the physical and chemical events were visualised and mapped using dedicated software to integrate the various data sets. Results The highly heterogeneous combustion system was characterised using a series of temperature, gas flow velocity maps. The complex and dynamic variations in thermochemical events occurring within the cigarettes were monitored by following three marker compounds, NH 3 , indole and nicotine. The time- and spatially resolved formation maps for these compounds illustrated the operation of thermal desorption, pyrolysis and combustion-led processes within the cigarette, following application of an externally applied air flow. Conclusion By integrating two physical sensors with fast chemical sampling, the burning of a superslim cigarette has studied in-situ in unparalleled detail. The experimental setup enabled complex combustion diagnostics within a confined but dynamic geometry.