- Dettagli della rivista
- Pubblicato per la prima volta
- 01 Jan 1992
- Periodo di pubblicazione
- 4 volte all'anno
- Accesso libero
Pyrolytic Disintegration of Selected Tobacco Constituents and Pyrosynthetic Formation of Aromatic Hydrocarbons from Cleavage Products Formed by Pyrolysis
Pagine: 1 - 9
A rapid pyrolysis technique, combined with gas chromatographic separation and interpretation of mass spectra obtained from the resulting pyrolysispyrosynthesis products, has been used in the study of three different compounds present in processed tobacco: n-C25 alkane, neophytadiene and phytol. The compounds are representative for a homologous series of n-alkanes and for a series of branched-chain compounds including neophytadiene, phytol, solanesol and esters of solanesol (tobacco constituents). At temperatures below 600°C the pyrolysis in the absence of oxygen, but in a helium flow gives only slight aromatisation when n-alkanes are treated. For the isoprenoid compounds neophytadiene and phytol aromatisation starts between 500 and 600°C. The products formed tend to develop more-condensed ring structures at increasing temperature, although benzene and toluene are dominating even at temperatures as high as 800 to 900°C. Aromatisation leading to relatively less methyl substitution results with increasing temperature. Previous pyrolysis work and recent interpretations point to the formation of structures such as acenaphthylene, acenaphthene, cyclopenta[cd]pyrene, 3,4-dihydrocyclopenta[cd]pyrene and probably similar structures derived from three and four-membered condensed ring structures produced.
- Accesso libero
Pagine: 11 - 16
A procedure has been developed for filter analysis whereby the cellulose acetate is dissolved in acetonitrile to release any trapped nicotine. Dissolving the filter eliminates time consuming steam distillation or solvent extraction steps and assures that the recovery of nicotine is complete. After the filter is dissolved, the cellulose acetate is precipitated by addition of an amine-phosphate buffer and an aliquot of the filtered solution is analysed by high-pressure liquid chromatography (HPLC). Two methods of HPLC analysis are described. In both cases the separation is achieved on a cyano-bonded silica column and detection is by ultra-violet absorption at 254 nm. Different mobile phases are used in the two methods. In the first procedure, a diethylamine-phosphate buffer at pH 7.56 is used while in the second procedure, a dimethylamine-phosphate buffer at pH 3.00 is used. Analytical results are equivalent for both chromatographic methods, but the second procedure may offer extended analytical column life. Results of a study relating the structure of the amine in the mobile phase to nicotine retention are presented. The amount of nicotine trapped on cellulose acetate filters during smoking was determined with increasing intervals between smoking and analysis. These results demonstrate that nicotine is stable on filters and previous problems of analysis were caused by difficulty in removal from aged filters.
- Accesso libero
Pagine: 17 - 27
The role of calcium in plants has been the subject of research for many years. Calcium has been postulated to cover a wide variety of functions which have major and minor influences on the plant's metabolism. Calcium interaction with pectin has been postulated as a major source of cell wall stability, however, no direct measurements of this interaction have been made. In this study, a sequential extraction method has been utilized to fractionate the various forms of calcium present in cured bright and Burley tobacco. The extraction method uses water, potassium chloride, lanthanum chloride and hydrochloric acid with emphasis on the lanthanum chloride extraction which appears to preferentially replace the structural calcium. Extraction data in conjunction with light microscopy (LM) and transmission electron microscopy (TEM) data have been used to predict the role of structural calcium in the cell wall. Oxalate and calcium analyses have been made at each of the extraction steps for bright tobacco. It is shown that the major portion of calcium extracted is not associated with oxalate except for the hydrochloric acid step. The data show that approximately 20 % of the calcium is structurally related and that calcium oxalate utilizes a maximum of another 20 % of the total calcium. The remaining 60 % is non-structural and non-oxalate and is probably inorganic salts and salts of organic acids. Combining these two techniques provides a means of obtaining quantitative information that either technique used independently could not provide. The techniques used in this study are applicable to the investigation of other plant types and may be useful in furthering the general knowledge of the role of calcium in plant materials.
- Accesso libero
Pagine: 29 - 36
One sample each of aged uncased, cured bright lamina, bright stems, Burley lamina and Burley stems were examined by a variety of general analytical methods and then characterized by our standard fractionation procedure. These tobacco samples were chosen to be reasonably representative of the tobaccos used in current commercial cigarette products. Although for a given variety of tobacco the concentrations of chemical constituents may vary as a function of stalk position, cultural management, geographic origin or crop year, we believe that the following conclusions based on these samples are generally valid:  levels of ethanol solubles, total reducing sugars and starch are much higher in bright than in Burley,  concentrations of soluble ammonia and nitrate are greater in Burley than in bright,  total alkaloid and protein concentrations are higher in lamina than in stems,  cellulose, potassium and chloride concentrations are much greater in stems than in lamina,  concentrations of pectin, lignin and soluble hemicellulose do not vary greatly from one type of tobacco to another,  Burley lamina has greater concentrations of protein and acid detergent solubles than do the other types of tobaccos, and  bright lamina has a much lower level of total ash than do the other types of tobaccos. An examination of some of the components in ash led to the following conclusions:  total ash values are reasonable relative indicators of the level of non-nitrate inorganics,  a good estimate of the total contents of potassium, calcium, chloride, sulfate, phosphorus, silicon and magnesium may be obtained by multiplying the total ash value by 0.612, and  it is likely that most of the potassium and calcium in total ash is actually present as carbonates rather than oxides. The significantly higher levels of both protein and acid detergent solubles found in Burley lamina are thought to indicate that this protein may be unique in terms of its carbohydrate content or in terms of the nature or extent of its cross linkage.
- Accesso libero
Chronic Inhalation Studies in Mice: I. Facilities and Equipment for “Nose-Only” Exposure to Cigarette Smoke
Pagine: 37 - 53
Facilities and equipment are described for large-scale, long-term “nose-only” inhalation exposure of mice to whole cigarette smoke. Experimental procedures and equipment were designed to provide the mice with exposure conditions where  the lung was the major target organ for the smoke,  large quantities of fresh, whole cigarette smoke could be generated,  large numbers of animals could be exposed at one time,  routine, daily exposures could be given over a major portion of the lifetime of the animal,  monitoring and documentation of the quantity of smoke presented to the animals was provided during each exposure session,  safety systems were provided that assured exposure of the animals to smoke only under pre-set exposure conditions, and  cigarette smoke was generated under conditions where factors, such as cigarette type, smoke aerosol concentration and smoke particle size, were controlled.
- Accesso libero
Pagine: 55 - 58
Data from experiments conducted at one location in 1980 and two in 1981 showed that MH residues were greater on flue-cured tobacco after application of a K-MH (potassium salt of MH) formulation than of a DEA-MH (diethanolamine salt of MH) formulation at the same rate of active ingredient. On cured lamina mean residue values from K-MH for the two locations in 1981 were 48 % and 61 % greater than those for DEA-MH. There was no apparent loss of residue for either formulation during the curing process. Sucker control was less efficient with the DEA-MH than with the K-MH formulation and was associated with the level of residue in the leaf.