A microwave generator and a closed-circuit wind tunnel were used to measure the thermal diffusivity of tobacco (Nicotianatabacum L.) stems in vivo by the unsteady-state method. A simple mathematical model for heat flow, based on Fourier's heat-conduction equation and Newton's law of cooling, was used in this study. The microwave method was found to be relatively rapid as both heating and cooling of a cylindrical stem in an air stream could be completed in approximately 30 minutes for thermal-diffusivity determinations. Thermal-diffusivity value of the tobacco stems, containing 94 % moisture and a mean stem temperature of 30°C, was found to be (1.38 ± 0.06) × 10-7 m2 s-1. The coefficient of variation for the measurements did not exceed 1.4 % as determined through the analysis of cooling curves for five different air-flow rates over the stems. This study showed that the microwave technique could be effectively used to determine both accurately and reliably the thermal diffusivity of tobacco stems in vivo.
Near infra-red (NIR) reflectance spectroscopy has been used for rapidly and reproducibly measuring the NIR spectra of mainstream smoke collected on Cambridge filter pads and quantifying the chemical composition from the spectral data. This technique has four main advantages: speed, simplicity of sample preparation, multiple analytes from one scan of a sample, and non-destruction of the sample. The study has been conducted in our research laboratory to define the possible use of NIRA (Near Infra-red Reflectance Analysis) as an instrumental screening tool for analysing mainstream smoke collected on Cambridge Filter pads. A major advantage of this method is that it eliminates the use of dangerous chemicals such as cyanogen bromide or chloride involved with some standard assays. Using specific wavelengths, we are able to determine with acceptable accuracy water, nicotine and tar. Correlation coefficients of NIRA results compared with those obtained by standard methods are better than 0.9 for all analyses. NIRA cannot replace ISO standard methods, flow analysis or chromatography, but as a reliable screening analysis, it could reduce the routine work load by 80 %. These savings could be achieved by prescreening samples with NIRA and analysing only suspect samples by distillation or continuous flow analysis.
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.
A gas chromatographic method is described which is suitable for the quantitative routine determination of CO in tobacco smoke. The CO is separated from other gases on a moderately activated molecular sieve column and is quantitatively determined after hydrogenation on a nickel-contact at 290°C with a flame ionisation detector. The method is characterized by high sensitivity and great stability of the separation column. A comparison of a "constant flow" smoking machine and a smoking machine operated by pistons, in the course of which a container filled with a saturated solution of sodium chloride or a polyvinylchloride bag was employed for gas storing, led to comparable results. The addition of NaNO3 (8 %) reduced the CO value by 30 %. Filters have no influence on the CO yield
An investigation was performed to determine optimum conditions for the generation and collection of particulate matter and carbon oxides in sidestream smoke with a cylindrical chamber of 80 mm internal diameter. The most adequate conditions were found to be 50 cm distance between the burning cone and the Cambridge filter pad and 10 l/ min air flow rate through the chamber. Under these conditions, the static burn rate was virtually the same as that without the chamber and almost constant values for condensate were obtained by replicate measurements. Furthermore, the concentration of carbon monoxide delivered to a room could be estimated by this method. But, it was not possible to estimate the concentration of smoke particles in a room by use of sidestream measurements.
The results of this analysis suggest that a filter geometry which will allow smoke to pass at a Iower than normal velocity is desirable to improve filter efficiency. This improved efficiency is due to the major contribution of the diffusion mechanism and the insignificant contribution of the impaction mechanism to the filtration process. Lower than normal velocities wilI also reduce the pressure drop. If a filter can be designed to operate at a lower velocity, and therefore at a lower pressure drop, it is desirable to have the acetate filaments oriented perpendicularly to the flow direction of the smoke. This geometry gives higher removal per unit weight of acetate than the geometry of a conventional filter.
The collection of sidestream smoke (SSS) using the “BAT fishtail chimney” method became the accepted standard, but following the harmonisation of linear and rotary smoking machines it is no longer possible to observe all parameters of the method as published. A prerequisite of any SSS collection method is that mainstream smoke (MSS) yields should not be affected. Additionally all the standard features and parameters of normal MSS collection should as far as possible remain unchanged. The previously published method and current harmonised MSS collection are not compatible mainly due to the significant increase in air-flow rate over the cigarettes that is now necessary. This study describes the use of a modified chimney that incorporates an airtight insert causing a reduction in aperture size leading to a local increase in airflow over the cigarette. The method optimises SSS collection whilst maintaining full compliance with the current International Organisation for Standardisation (ISO) Standards for MSS collection.
Nitric oxide in cigarette smoke was conveniently determined by non-dispersive infrared analysis (NDIR). Recoveries of 95 % were obtained with standard gas-air mixtures but recoveries from smoke increased from 87% for high-yield to 91 % for low-yield cigarettes. Relative error was about 4 %. A reduction in the dead volume of Cambridge filter cassettes, to reduce the amount of NO reacted between puffs, increased NO deliveries of cigarettes by 4%. Deliveries of NO were estimated to average 4 % lower due to oxidation, but reaction with other smoke components reduced them further depending upon concentrations. The NO deliveries of cigarettes increased as blend nitrate increased and as the flow of air around cigarettes decreased. Nitric oxide in smoke and in standard gas-air mixtures, determined by non-dispersive infrared (NDIR) spectroscopy, was substantiated by an automated colorimetric analysis. Interfering smoke species were determined and circumvented in both methods.
Based on the unique temperature and oxygen profiles in a burning cigarette, a novel approach is proposed in this paper to use a single oxidant/catalyst in the cigarette filler for simultaneous removal of carbon monoxide (CO) and nitric oxide (NO) in mainstream smoke. A nanoparticle iron oxide is identified as a very active material for this application due to its multiple functions as a CO catalyst, as a CO oxidant, and in its reduced forms as a NO catalyst. The multiple functions of the nanoparticle iron oxide are characterized in a flow tube reactor and the working mechanisms of these multiple functions for CO and NO removal in a burning cigarette are explained. The effect of smoke condensate on the catalyst are examined and discussed. The advantage of in situ generation of the catalyst during the cigarette burning process is illustrated. The test results of nanoparticle iron oxide for CO and NO removal in cigarettes are presented.
A device for measuring the flow, duration and volume characteristics of human puffing behaviour when smoking cigarettes is described. Cigarettes are smoked through a holder comprising a measured pressure drop across a critical orifice. The holder also contains a Light Emitting Diode (LED) and photodetector that measures light obscuration in order to estimate nicotine-free dry particulate matter (NFDPM, “tar”) delivery. All data are recorded on a puff-by-puff basis and displayed in real time. These NFDPM estimates are known as optical “tar” (OT), and are derived from the calibration of the OT measurement versus gravimetric NFDPM yields of cigarettes under a range of smoking regimes. In a test study, puff volumes from 20-80 mL were recorded to ± 6.0% of a pre-set volume, with an absolute error of 4.7 mL for an 80 mL volume drawn on a lit cigarette, and an average error of less than 2.0 mL across the range 20-80 mL. The relationship between NFDPM and OT was linear (R2 = 0.99) and accurate to ± 1.3 mg per cigarette over the range 1-23 mg per cigarette. The device provides an alternative to the widely used part filter methodology for estimating mouth level exposure with an added benefit that no further laboratory smoking replication or analysis is required. When used in conjunction with the part filter methodology, the puffing behaviour recorded can explain anomalies in the data while providing a second independent estimate.