Louise Bishop

The pyrolysis of tobacco ingredients

Relationships between tobacco components and smoke products are complex and often difficult to unravel. Pyrolysis experiments have commonly been used to establish such relationships. However, unless they are performed under dynamic conditions that are relevant to those that occur during tobacco burning, results can be obtained which have little resemblance to those obtained during cigarette smoking. The relevance of pyrolysis experiments to the behaviour of tobacco ingredients in a burning cigarette is considered. Based on the temperature, heating rate, oxygen levels and gas flow conditions that occur inside the burning zone of a cigarette, together with a review of relevant pyrolysis and smoking experiments, a set of pyrolysis conditions has been developed that approximates those occurring in the pyrolysis region of the burning cigarette. The conditions include heating the sample at 30 ◦ Cs −1 from 300 to 900 ◦ C under a flow of 9% oxygen in nitrogen. Experiments on the pyrolytic behaviour of eleven relatively volatile substances under these conditions give results that are in good agreement with results from thirteen published studies in which cigarettes incorporating labelled versions of the substances were smoked. Subsequently, 291 single-compound tobacco ingredients have been pyrolysed under this set of conditions, most of which are relatively volatile. This enables the behaviour of these ingredients in a burning cigarette to be estimated in terms of intact transfer to mainstream smoke versus pyrolytic decomposition. It is predicted that almost a third of the substances would transfer to mainstream smoke at least 99% intact, and almost two-thirds would transfer 95% intact. Where pyrolytic decomposition does occur, the products are listed together with an estimate of the levels in smoke that would arise from the ingredient.

Multivariate analysis of mainstream tobacco smoke particulate phase by headspace solid-phase micro extraction coupled with comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry

A method involving headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography (GC×GC) coupled to time-of-flight mass spectrometry (TOFMS) was developed and applied to evaluate profiles of volatile compounds present in mainstream tobacco smoke particulate matter trapped on glass fiber filters. Six SPME fibers were tested for the extraction capacities toward selected compounds, showing the best results for the polyacrylate fiber. The optimization of the extraction conditions was carried out using multivariate response surface methodology. Two cigarette types differing in a filter design were analyzed using optimized conditions. A template was built in order to generate comprehensive chemical information, which conceded obtaining consistent information across 24 chromatograms. Principal component analysis (PCA) allowed a clear differentiation of the studied cigarette types. Fisher ratio analysis allowed identification of compounds responsible for the chemical differences between the cigarette samples. Of the selected 143 most important ones, 134 analytes were reduced by the active carbon filter, while for nine, classical cellulose acetate filter was more efficient.

Analysis of mainstream tobacco smoke particulate phase using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry.

Comprehensive 2D GC coupled to time-of-flight mass spectrometry was applied for the characterization of the particulate phase of mainstream tobacco smoke particulate. Five 3R4F research cigarettes were smoked on a rotary smoking machine under standardized conditions, total particular matter was collected on Cambridge filter pads and extracted using methanol-based liquid extraction and dynamic headspace (DHS) approaches. Automated peak finding and mass spectral deconvolution combined with scripting and manual revision of library hits were used to evaluate the library search results. The revised peak table contained nearly 1800 individual compounds for the DHS sample and over 900 for the solvent extracted sample. These methods of extraction were shown to be complementary, leading to only 11% of repeated analytes, and their combination gave rise to a list of almost 2500 individual compounds.

The Pyrolysis of (−)-(S)-Nicotine: Racemization and Decomposition

The pyrolytic behaviour of (−)-(S)-nicotine in methanol was investigated using on-line pyrolysis GC/MS to establish whether racemization to the R(+) antipode occurs and to identify other products of pyrolysis. The conditions used included pyrolysing the sample for 15 seconds in an atmosphere of 9% oxygen in nitrogen (275ml/min total flow) across the temperature range of 200°C–1000°C. A chiral Cyclodex-B analytical column (30m × 0.25mm i.d. × 0.25 μm film thickness) was used to separate the enantiomers of nicotine, although the two enantiomer peaks were not baseline resolved. The results of the experiment shows that there is no increase in (+)-(R)-nicotine levels across a wide temperature range. This suggests that the elevated levels of (+)-R-nicotine observed in tobacco smoke (compared to tobacco leaf material) are not due to the pyrolytic auto-racemization of (−)-(S)-nicotine but are a result of more complex interactions between (−)-(S)-nicotine and other smoke components. The pyrolysis of isotopically labelled nicotine established that nicotine undergoes thermal decomposition to β-nicotyrine which in turn may decompose to other products. Chirality 2010.

Using altmetrics and citation counts to assess the social and academic impact of Medecins Sans Frontieres publications

• Online attention tends to be low across all article types for MSF publications; nearly all of the attention comes from Twitter. • Non-research articles tend to be tweeted by a higher average number of people than research articles. • The number of articles mentioned online at least once increased in 2012 but was still only just over 50%. • Citations are slower to accrue, reaching 60% for 2011 research articles but only around 20% for 2012 equivalents.