Search Results

1 - 3 of 3 items

  • Author: Kevin G. McAdam x
Clear All Modify Search

Summary

A previously established method based on headspace solidphase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography (GC×GC) coupled to time-of-flight mass spectrometry (TOFMS) has been used to evaluate and compare the profiles of semi-volatile compounds present in mainstream tobacco smoke particulate matter trapped on glass fibre filters for two types of cigarettes differing only in filter design. In the first cigarette, the filter cavity contained approximately 60 mg of a weakly basic macroporous polystyrene resin cross-linked with divinyl benzene and with surface amine functionality (CR20), whereas in the second cigarette, it was empty.

Relative quantitative analysis, chemical identification, and chemical grouping allowed the use of both parametric and non-parametric analyses to identify differences in the chemical composition of the smokes from these cigarettes. The analysis demonstrated that in addition to the selective partial removal of volatile carbonyls and HCN demonstrated previously, CR20 selectively, but incompletely removed 316 compounds from the particulate phase of cigarette smoke, mainly aryl and aromatic hydrocarbons as well as other more volatile species. In contrast, the relative proportion of amines, hydroxylated aromatic compounds and less volatile species was increased in the smoke from the cigarette containing CR20 in the filter.

Our findings show that high resolution GC techniques combined with mass spectrometry and chemometric approaches are powerful tools for deconvoluting the complexity of combustion aerosols, as well as helping to identify changes in chemical composition resulting from modifications to cigarette designs. [Beitr. Tabakforsch. Int. 28 (2019) 231–249]

Abstract

Accurate measurements of cigarette coal temperature are essential to understand the thermophysical and thermo-chemical processes in a burning cigarette. The last system-atic studies of cigarette burning temperature measurements were conducted in the mid-1970s. Contemporary cigarettes have evolved in design features and multiple standard machine-smoking regimes have also become available, hence there is a need to re-examine cigarette combustion. In this work, we performed systematic measurements on gas-phase temperature of burning cigarettes using an improved fine thermocouple technique. The effects of machine-smoking parameters (puff volume and puff duration) and filter ventilation levels were studied with high spatial and time resolutions during single puffs. The experimental results were presented in a number of differ-ent ways to highlight the dynamic and complex thermal processes inside a burning coal. A mathematical distribution equation was used to fit the experimental temperature data. Extracting and plotting the distribution parameters against puffing time revealed complex temperature profiles under different coal volume as a function of puffing intensities or filter ventilation levels. By dividing the coal volume prior to puffing into three temperature ranges (low-temperature from 200 to 400 °C, medium-temperature from 400 to 600 °C, and high-temperature volume above 600 °C) by following their development at different smoking regimes, useful mechanistic details were obtained. Finally, direct visualisation of the gas-phase temperature through detailed temperature and temperature gradient contour maps provided further insights into the complex thermo-physics of the burning coal. [Beitr. Tabakforsch. Int. 26 (2014) 191-203]

Summary

A diffusion denuder apparatus has been used to investigate the gas-particle partitioning of formaldehyde, acetaldehyde, acrolein and crotonaldehyde in cigarette mainstream smoke (MS), compounds that are of interest owing to their toxicity and near quantitative retention in the body during cigarette smoking. Formaldehyde showed the best performance in denuder experiments with simple aldehyde-air mixtures owing to the relatively fast rate of the heterogeneous reaction formaldehyde(g) + dinitrophenylhydrazine(s) 6 hydrazone(s). Analysis with the GORMLEY-KENNEDY equation revealed that formaldehyde denuder removal approached, but did not attain, complete efficiency even under optimized operational conditions. Acetaldehyde, acrolein and crotonaldehyde were trapped with considerably lower efficiency than formaldehyde under the denuder conditions used, and more effective denuder wall coatings would be required to examine gas-particle partitioning of these other carbonyls. The proportion of form-aldehyde in the smoke particulate phase initially entering the denuder was > 99%, but loss of formaldehyde from the smoke particles was relatively rapid leading to 35%–61% deposition over the denuder length. The temperature dependence of formaldehyde deposition in the denuder was well predicted using Henry’s law constant for aqueous formaldehyde solutions. These observed properties of form-aldehyde are primarily due to reversible reactions of formaldehyde with water in cigarette smoke leading to the much less volatile species methanediol, its oligomers and hydrate. These data suggest that cigarette smoke inhalation is likely to expose the deeper-lung generations of smokers to greater relative formaldehyde exposure, and greater genotoxic risk at those generations than might occur through inhalation of formaldehyde vapour alone.

Risk assessments of formaldehyde in cigarette smoke should be updated to recognise this modified risk profile. [Beitr. Tabakforsch. Int. 29 (2020) 2–20]