- Dettagli della rivista
- Formato
- Rivista
- eISSN
- 2719-9509
- Pubblicato per la prima volta
- 01 Jan 1992
- Periodo di pubblicazione
- 4 volte all'anno
- Lingue
- Inglese
Cerca
- Accesso libero
Formation and Reduction of Carbon Monoxide
Pagine: 439 - 447
Astratto
The total amounts of carbon monoxide (CO) and carbon dioxide (CO2) in the mainstream smoke of a burning cigarette during a steady draw were measured by a non-dispersive infrared (IR) technique for a variety of flow rates. The temperature profiles in the cigarette were also measured under the same flow conditions. The data were used in a diffusion model to estimate the concentrations of these gases downstream of the pyrolysis zone. The contribution of pyrolysis in the generation of these gases was calculated using a kinetic model. The remaining CO and CO2 are attributed to processes occurring in the combustion zone. The calculated mean concentrations of carbon oxides behind the pyrolysis zone are in reasonable agreement with the experimental data. The contributions of pyrolysis and combustion to the formation of CO were found to be approximately 1/3 and 2/3 respectively. The results show that the peak temperature rises with an increase in the mainstream flow rate in the limited range of 0 to 200 mL/min. As a result, the concentrations of carbon oxides behind the pyrolysis zone also increase with the flow rate and reach plateaus at higher flow rates.
- Accesso libero
Mainstream Smoke Chemical Analyses for 2R4F Kentucky Reference Cigarette
Pagine: 448 - 458
Astratto
A new reference cigarette, 2R4F, has been designed to replace the 1R4F Kentucky reference cigarette. This new cigarette has virtually the same blend composition as the 1R4F cigarette. However, the 1R4F cigarette was made in 1983 and the variation in the tobacco from crop year to crop year as well as the difference in the age of the two cigarettes were expected to generate differences in the smoke chemistry. A study done for the quantitation of more than 44 analytes in smoke, including most compounds considered as biologically active, is presented in this report. The analyses were performed by six independent laboratories using a variety of analytical techniques. The smoking was performed using International Standard (ISO) recommendations. The results showed only small differences between the two cigarettes regarding ‘tar', nicotine and carbon monoxide (CO), as well as for aminonaphthalenes, resorcinol, and some aldehydes. Although the two reference cigarettes were made as close as possible, the concentrations of a significant number of analytes in the smoke differed between 10% to 30%. Specific trace compounds in the blend such as metals and tobacco specific nitrosamines (TSNA), which may influence the smoke composition, were also different between the two cigarettes. The level of lead, in particular, was very different in tobacco between 1983 and 2002.
- Accesso libero
Changes in Levels of Amino Acids and Basic Components in Burley Tobacco Produced by Roasting
Pagine: 459 - 466
Astratto
Three burley tobacco samples from three different areas in China and Brazil were roasted under three processing conditions. The amino acids and basic components of the burley tobacco samples were determined before and after roasting. Routine tobacco variables (reducing sugars, total water-soluble sugars, total nitrogen, total alkaloids, total volatile bases, and pH) were determined according to the Chinese National Standard Methods (CNSM). Free amino acids were determined by high performance liquid chromatography (HPLC). The basic compounds were isolated by use of simultaneous distillation and extraction (SDE) equipment. Their levels were determined qualitatively and quantitatively on a) a gas chromatograph (GC) equipped with a nitrogen-phosphorus detector (NPD) and b) by gas chromatography mass spectrometry (GC-MS). The results indicated that the chemical changes occurring during roasting have a significant impact on burley tobacco quality. Roasting decreased the tobacco pH value and the levels of total nitrogen, reducing sugars, free amino acids, and other nitrogenous substances, such as amines and alkaloids. The latter are usually related to the irritancy and sharp taste of burley tobacco smoke. In contrast, the levels of pyrazines, important contributors to the characteristic burley flavor, increased.
- Accesso libero
Role of Oxides of Nitrogen in Tobacco-Specific Nitrosamine Formation in Flue-Cured Tobacco
Pagine: 467 - 475
Astratto
Tobacco is known to contain a class of nitrosamines known as tobacco-specific nitrosamines or TSNA. Nitrosation of naturally occurring tobacco alkaloids is commonly accepted as the mechanism of TSNA formation in tobacco. Because green and freshly harvested tobaccos are virtually free of TSNA, formation and accumulation of TSNA are generally considered to occur during the curing process. Most recent hypotheses have focused on microbial reduction of nitrate to nitrite and other oxides of nitrogen (NOcompounds) that react with tobacco alkaloids to form TSNA during curing. This natural microbial process remains the prevalent hypothesis for TSNA formation in burley and other air-cured tobaccos. However, a different mechanism for the formation of TSNA in flue-cured tobacco, independent of microbial activity, is documented in this paper. It is common practice to flue-cure Virginia or blonde tobacco in bulk barns that incorporate forced air ventilation and temperature control. For the last thirty-five years, many modern bulk barns in North America generally have used liquid propane gas (LPG) with direct-fired burners that exhaust combustion gases directly into the barn where the tobacco is exposed to those gases. Our studies indicate that LPG combustion by-products in the exhaust stream, namely NO, react with naturally occurring tobacco alkaloids to form TSNA. Heat exchange curing methods preclude exposure of the tobacco to combustion gases and by-products, thereby eliminating this significant source of TSNA formation, without degrading leaf quality or smoking character. Research findings from 1998 and 1999 are presented to demonstrate the role of NOgases in TSNA formation and the significance of direct-fired curing as a primary source of TSNA formation in flue-cured tobacco. Also, data from an extensive barn conversion program in 2000, which resulted in a 94% average reduction in TSNA levels in cured flue-cured leaf, are presented.
- Accesso libero
Cigarette Mouth Insertion Depths Among Chinese Smokers
Pagine: 476 - 480
Astratto
Vent blocking - where filter ventilation holes are intentionally or unintentionally, partly or completely covered by smokers’ lips during smoking - is an aspect of smoking behavior which can alter mainstream smoke yields. This study was designed to determine if, and to what extent ventilation holes were blocked by smokers’ lips in two cohorts of Chinese smokers. In this study, two groups of samples were collected. One group (1742 butts) was collected randomly from public places in six chosen cities. Another (1037 butts) was obtained by collecting the butts from identified smokers in Kunming. In this paper, the mouth insertion depth among Chinese smokers was studied for the first time by a staining method employing ninhydrin in ethanol. The results indicate that Chinese smokers exhibit a mouth insertion depth ranging from 1 to 17 mm with an average value of 7.5 AA± 2 mm. In this study, 95% of the ventilated filters examined showed that the vent zone was neither completely nor partially covered by smokers’ lips.