The filtration and retention characteristics of nicotine, phenol, benzo[a]pyrene (B[a]P), 4-(methylnitrosamino)-1- (3-pyridyl)-1-butanone (NNK), crotonaldehyde, hydrogen cyanide (HCN) and ammonia in conventional cellulose acetate fiber filters were investigated. By quantitatively analyzing their contents released in mainstream smoke and retained in filters, their filtration efficiencies, taken as the ratio of filter retention content to total yield, were determined under both International Organization for Standardization (ISO) and Health Canadian Intense (HCI) smoking regimes. Using a precision laser cutter, the filters were either cut transversely into 5-7 segments for longitudinal distribution pattern study, or cut transversely into 3 segments firstly and then each segment was cut concentrically into 3 concentric segments for spatial distribution pattern study. Contents of the named smoke components retained in these filter segments were quantitatively analyzed. The data were calibrated and then processed with interpolation analysis and polynomial fitting. The longitudinal distribution patterns for all components mentioned above, as well as spatial distribution patterns for nicotine, phenol, HCN, ammonia and crotonaldehyde, were obtained. The filtration efficiencies of different smoke components varied between 24% and 15% for HCN, 87% and 92% for phenol under ISO and HCI smoking regimes respectively. The filtration efficiencies of all the studied components under HCI smoking were lower than under ISO smoking to different extents except phenol which showed the opposite trend. Different mainstream smoke components have their own retention behavior and distribution characteristics which are determined by the physical and chemical properties of the component and its interaction with cellulose acetate fiber and the glycerol triacetate within the filter. The diversity of retention distribution patterns of different components shows the high complexity of cigarette smoke filtration in filters. [Beitr. Tabakforsch Int. 26 (2014) 121-131]
A home-made electrostatic force microscopy (EFM) system is described which is directed toward assessment of the microscopic geometry of the surface of specimens made of non-conductive material with a large thickness. This system is based on the variation in the electrostatic force between the conductive probe and the non-conductive specimen in order to get its surface morphology. First, based on the principle of dielectric polarization, the variation rules of the electrostatic force between the charged probe and the non-conductive specimen were studied. Later, a special tuning fork resonant probe unit made of quartz crystal was fabricated for measurement of the electrostatic force, and the scanning probe microscopic system in the constant force mode was constructed to characterize the three-dimensional micro-topography of the surface of the specimen. Finally, this system was used to perform scanning measurement experiments on the indented surface of the specimen made of the polyvinyl chloride (PVC) material with thickness 3 mm. In the present experimental system, when the external voltage was 100 V and the distance from the probe tip to the specimen surface approximately 100 nm, the variance in the resonant frequency of the probe unit was around 0.5 Hz. These results indicate that this home-made EFM system can effectively characterize the micro-topography of the non-conductive specimen with very large thickness which is above several millimeters.
An improved theoretical model was presented to predict the filtration efficiency of cigarette filters. Filtration equations of single fibers considering the interference of neighboring fibers were applied in the model. Cellulose acetate fibers in cigarette filters were approximated as cylinders. The fiber size was adjusted by its size projected on the flow field. The solid fraction of fibers in cigarette filters was recalculated using the size of the virtual cylinders. The varying flow velocity during smoking was taken into account when calculating the filtration efficiency. The effective hydrodynamic particle diameter of cigarette smoke was estimated to be 0.44 μm by the difference of filtration efficiencies under ISO and Health Canada Intense (HCI) smoking regimes. Filtration contributions due to diffusion, interception and inertial impaction were 62%, 32% and 6%, respectively, at a flow velocity of 0.38 m/s for particles of 0.44 μm diameter. The effect of inertial impaction was insignificant but not negligible under ISO smoking regime. The measured and predicted efficiencies of two cigarette samples were compared and satisfactory agreement was obtained. [Beitr. Tabakforsch. Int. 26 (2015) 232-240]