Volume 3 (1965): Issue 3 (August 1965)

A method is described for the study of the abilities of different substances to r~move phenol from a gas stream, with application to the selective filtration of tobacco smoke in mind. Use was made .of ,gas chromatography, measuring the retention time of phenol on columns containing different materials. Differences in the mechanism through which phenol is retained by pure and plasticized cellulose acetates became apparent. A number of substances expected to give hydrogen bonding with phenol were added to the usual cigarette filter materials. Considerable increase in phenol retention was only found in the cases of urea and nicotinamide

Any smoke component is distributed over both the particulate and the gaseaus phases. The distribution is determined by a) the vapour pressure of the considered substance, b) its concentration in the smoke, and c) its physico-chemical affinity for the particulate phase. The availability of a substance in the gaseaus state, i. e. the condition for its selective removal by an appropriate filter, is therefore dependent on these factors. The experiments designed to study these relationships are based on three variables held each at several Ievels: :1. Test substances distinguishing themselves by the factors a), b), and c): Carbon monoxide, crude (moist) smoke condensate, total water, pyridine, total alkaloids, volatile phenols, catechol, and scopoletin. 2. These substances are determined in the smoke trapped separately per individual puffs. The composition of the smoke leaving the cigarette depends on the puff number, according to the factors a), b), and c). 3· Use of four different smoke filtration devices permitting the study of the availability of a given test substance or of its affinity to the filter material. The following expressions are used for the interpretation of the experimental results: The ratio of the yield of test substance to the yield of crude condensate; the coefficients of filtration of the test substance in both the tobacco rod and the experimental filter; the coefflcient of selectivity, defined as the difference between the respective coefficients of filtration for the crude condensate and for the test .substance. The results of the experimentation tend to confirm the initial hypothesis and give ,sufficient detailed information to permit the tentative establishment of a general scheme which allows to predict the selective behaviour of a particular ·smoke component, if its concentration in the smoke, its vapour pressure and its presumable affinity towards a given filter material are known. lt is further shown that a mathematical expression for the yield of a particular smoke component, as a function of the puff number, can be established on an empirical basis for carbon monoxide, · crude condensate, total alkaloids, catechol and scopoletin. The increase in the yield of carbon monoxide with the puff number is shown to be due to a CO loss through the permeable paper wrapper of the cigarette, this loss being smaller as the butt becomes shorter

A rational definition for characterizing the capacity of a cigarette filter to selectively modify the chemical composition of mainstream smoke is presented. The definition is related to the concept of separation factor as defined in chemical engineering and applied in the description of various unit processes. A number of numerical values for a wide range of cigarette filters currently found in the world market place are presented. The relative independence of the selectivity as defined in this paper upon tobacco types is demonstrated. Using a fixed filter construction in terms of amount and type of cellulose acetate fiber and plasticizer content, selectivity values are presented as a function of cigarette length and relative proportion of the cigarette which is allotted to the filter. Further, it is shown that selectivity appears to increase with length for given filter construction parameters. A limited amount of data regarding selectivity for weak acid components of mainstream smoke and certain gas phase components is presented as a characterization of dual filters currently on the US market

The authors present the basic analytical values for, and the calculation of CORESTA efficiency indices E_i related to some chemical items (phenols, polyphenols, Ehrlich-positive compounds, hetero-N compounds, indole) in the smoke of filter cigarettes (dark air cured type, two types of filter tips of the acetate group, with and without activated carbon additive). The calculation presented for proposed "selectivity indices" E_i / E_G confirms factually the high grade of selectivity for phenols and some hetero-N compounds in the experimented systems; some critical facts are called to the attention concerning the role played by the activated carbon additive

With reference to recently acquired knowledge of the behaviour of cigarette smoke the author proposes definitions of the various smoke streams of a cigarette, of the smoke yield, of selectivity, and of the selective filtration. The choice of an appropriate smoke component upon which the definition of selectivity could be based is discussed

Einleitung Absorptionseffekte Konzentrationsverschiebung Ausbeuteänderungen Literatur

Data are presented for the retentions and selectivity factors of a variety of filters, and a method of calculation of the resultant values for dual filters made up from these materials is described

One of the best known ways of modifying cigarette smoke is by the use of cigarette filters of various types. Filters are now being made from a variety of materials and, of recent years, have become more complex in structure and function. The authors consider the different ways in which different types of filters modify the chemical composition of the smoke showing some typical results. A new method of studying the range of higher boiling compounds in the smoke based on the volatilization of compounds trapped on a Cambridge Filter is discussed and information which this provides with different filter types is presented. Having shown the different action of the available range of filters as individuals, the possibilities of combining these in different ways to produce multiple filters and the degree of control of the smoke composition made possible as a result are discussed. If one examines the efficiency of any type of filter towards the whole range of substances in tobacco smoke from the permanent gases up to the high boiling compounds such as nicotine, one finds that the efficiency of the same filter varies widely according to the compound considered. Further, one finds that the pattern of efficiencies over the range of compounds is quite different between one filter and another. If, in the design of a filter cigarette, one wishes to emphasize or reduce various portions of the smoke it is possible to exercise a considerable degree of control by the use of suitable types of filter or combinations of filters. In addition to removing smoke constituents to varying degrees it is also possible to add desirable constituents to the smoke such as flavours by means of filters and the analytical technique mentioned above is very suitable for assessing the amount of such flavouring material which is actually present in the cigarette smoke