- Dettagli della rivista
- Pubblicato per la prima volta
- 01 Jan 1992
- Periodo di pubblicazione
- 4 volte all'anno
- Accesso libero
Pagine: 53 - 57
By means of the dispersion quotient method, the aerosol properties of freshly produced sidestream smoke were measured during the puff and subsequent interpuff period. These measurements were made on short time scales and at high aerosol concentrations. Examples are presented, which show the influence of different combustion conditions during the puff (resulting from different degrees of ventilation and different types of tobacco) on the emission of sidestream particles during the interpuff period. The ratio of the volume concentrations of the particles before and during a puff is reduced by ventilation and is nearly unchanged by the variation of the tobacco type.
- Accesso libero
An Application of Fourier Transform Infra-red (FT-IR) Microspectroscopy to the Study of Cigarette Manufacturing Defects
Pagine: 59 - 64
FT-IR microspectroscopy was used to investigate a common type of cigarette defect in which the filter separates from the tobacco rod. Infra-red imagings of the adhesive located at this junction on the tipping papers from both defective and acceptable cigarettes were obtained. A comparison of these data revealed that although adhesive was present in the seam area of the defective cigarettes, the amount of adhesive was significantly less and its distribution was not uniform.
- Accesso libero
Relative Positions of the Thermal Convection Column and Smoke Plume Generated from a Smoldering Cigarette
Pagine: 65 - 74
The relative positions of the thermal convection column and the smoke plume from a variety of smoldering cigarettes were measured using a combination of schlieren and visual optical systems. The schlieren technique is an optical method used to observe refractive index gradients in gases and other clear media. The refractive index gradients can be caused by variations in pressure, composition or temperature. The convection column of heated air and combustion gases rising from a cigarette coal was observed with a two mirror schlieren system. A video camera was used as the observing device rather than the usual photographic camera. A second video camera was arranged to view the smoke plume rising from the coal region. The two video images were combined with a video special effects generator and were viewed on a single monitor. The behaviour and relative positions of both columns were thus observed in real time with two non-invasive optical methods. The schlieren images of the convection column were compared to those of model systems such as a heated cylinder and a small flame. Results for experimental cigarettes with paper porosities of 12 cm/min to 48 cm/min (Coresta) during smolder showed that the thermal convection column was centered 2 mm to 3 mm in front of the paper char line directly over the hottest part of the coal as determined by infra-red imaging. The smoke plume was centered 2 mm behind the paper char line and the position did not change with paper porosity. Results for experimental cigarettes made with a commercially available low sidestream paper showed that the position of the convection column did not change. However, the position of the smoke plume changed considerably. In addition to being markedly decreased in visibility, the plume now appeared to be centered directly over the paper char line. This change in position provides a valuable insight into the mechanism of smoke reduction. The low sidestream papers seem to work by preventing the escape of smoke forming condensibles through the paper behind the paper char line. The condensibles are therefore forced to escape at the paper char line and undergo increased combustion and pyrolysis. As a result, some are converted to lower molecular weight materials and are unable to condense as readily to form the smoke. In addition, the remaining condensibles are released into a hotter and faster rising gas stream. This serves to reduce smoke formation by suppressing condensation and increasing dilution.
- Accesso libero
Pagine: 75 - 86
Time-resolved measurements of intrapuff nicotine yield in mainstream smoke have been performed with a specially designed intrapuff smoking apparatus (IPSA). The IPSA-filter traversing mechanism collects mainstream particles on a rectangular filter pad which moves at a constant velocity perpendicular to the direction of smoke flow at the mouthend of the cigarette. Filter pads were assayed by two analytical techniques. Standard gas chromatographic (GC) methodology was used to quantify nicotine mass in five equal time segments per puff. A second method, using a Berthold TLC-Linear Analyser, measured total radioactivity across the pad for samples from [2'-14C]-nicotine labelled cigarettes. Intrapuff nicotine concentrations were determined from measured puff flow-rate profiles and the collected masses of nicotine on the filters. GC nicotine concentration measurements correlated well with total activity from the scanner measurements. Studies carried out with filtered full-flavour cigarettes revealed that nicotine concentrations in the smoke vary significantly during a puff. This work provides a new technique for studying time-resolved yields of mainstream smoke components. It may potentially be used to elucidate mechanisms controlling the yield of nicotine and other mainstream smoke components.
- Accesso libero
Pagine: 87 - 92
A bright and a Burley tobacco were grown at four fertilization rates and each tobacco was then both flue-cured and air-cured. Levels of alkaloids and nitrosamines were found to increase with increasing fertilization levels. Levels of alkaloids, N-nitrosonornicotine (NNN), and other tobacco-specific nitrosamines (TSNA) were consistently higher in the Burley tobacco than in the bright tobacco, regardless of curing method. In comparing the effects of curing, it was found that NNN and total TSNA levels were higher in the midrib than in the lamina of the air-cured samples, while just the opposite was found for the flue-cured samples. Flue-curing bright tobacco produced three times the level of TSNA vs air-curing the same tobacco. On the other hand, flue-curing Burley tobacco reduced the alkaloids, but greatly increased the TSNA in the lamina. As midribs from the air-cured Burley leaves had three times the TSNA concentration of the lamina, the use of air-cured midribs in tobacco products should be avoided. It was concluded that lower fertilization levels and careful manipulations of curing parameters could lower nitrosamine levels in cured tobacco.