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Copyright of Tobacco Science & Technology is the property of Tobacco Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to accurately determine pyrazines and pyridines in saliva of tobacco smokers, a method of gas chromatography-positive chemical ionization-time of flight mass spectrometry (GC-PCI-TOF MS) was developed. The pre-treatment method of sample, chromatogphic condition and MS condition were optimized. Saliva samples were extracted with dichloromethane by vortex mixing and cleaned up by primary secondary amine (PSA), then detected by GC-PCI-TOF MS. Retention time, precise mass data of characteristic ions and fragmentation patterns of characteristic fragment ions were employed to qualitative identification, external standard method was used for quantitative determination. The results showed that: 1) The average of extraction yield of 11 pyrazines and pyridines was 97.7% when 5 mL saliva sample was extracted by dichloromethane two times. 2) The matrix effects were studied by comparing the pyrazines and pyridines peak response in matrix standard solution and matrix-free standard solution, which performed with no significance. 3) Mass number of characteristic ions measured was in good agreement with predicted value, and the error was less than 3.12×10-6. Besides, predominant molecular ion and adduct molecular ion peak were obtained in PCI mode with less fragment ions formation. The mass spectrum was simple and clear, which was easy to identify. Given the above, the accuracy of qualitative analysis for low concentrations of pyrazines and pyridines in saliva could be significantly improved. 4) The linear correlation coefficients were above 0.999 1, the limits of detection (LODs) ranged from 0.9 μg/L to 2.4 μg/L, the limits of quantitation (LOQs) ranged from 3.0 μg/L to 7.9 μg/L, and the recoveries ranged from 85% to 104% at three spiked levels. The quantitative method was proved to be high accuracy and high sensitivity. 5) The detection results of saliva of tobacco smokers showed that the main pyrazines and pyridines in smokers’ saliva were pyridine, 2-methylpyrazine and dimethylpyrazines, and the contents of pyridine and 2-methylpyrazine in smokers’ saliva was differed by cigarette type. Low concentration of trimethylpyrazine and tetramethylpyrazine were detected in specific saliva samples of tobacco smokers. 3-Ethylpyridine and 5-ethyl-2-methylpyridine were not found in experimental tobacco smokers’ saliva sample. 6) Pyrazines and pyridines’ contents in different smokers’ saliva of 6 kind cigarettes were analyzed using principal component analysis which can distinguish different types of cigarette. Further analysis indicated that there was a significant variance-(P<0.05) between the pyrazines and pyridines in saliva among the 6 different kinds of cigarette, which might be a significantly characteristic of cigarette type. The method is simple, rapid and accuracy, which is superior in analyzing low level of pyrazines and pyridines in saliva of tobacco smokers and similar complex matrix. The study result will also offer accurate and scientific reference on cigarette product development. [ABSTRACT FROM AUTHOR]

With tobacco samples from the lower part of Henan production area as raw materials, the conventional chemical components and volatile aroma components in different microwave pretreated flue-cured tobacco leaves were analyzed by continuous flow analysis, high performance liquid chromatography and gas chromatography-ion mobility spectrometry (GC-IMS), etc. The results showed that microwave hydrothermal treatment could reduce the contents of water-soluble sugar, reducing sugar, plant alkaloid and phenolic substances in flue-cured tobacco leaves. Microwave hydrothermal treatment could increase the contents of total nitrogen and petroleum ether extract, and significantly increase the nitrogen-alkali ratio of flue-cured tobacco leaves (P≤0.05). The nitrogen-base ratio in the microwave hydrothermal 700 W-6 min treatment group was as high as 1.65. After microwave drying, the conventional chemical components in flue-cured tobacco leaves were still in the category of high-quality tobacco leaves, and the volatile alkali content increased significantly (P≤0.05). In addition, a total of 56 volatile aroma components were identified by GC-IMS, and the fresh aroma of flue-cured tobacco leaves could be increased by microwave water heat treatment, while the sweet flavor of flue-cured tobacco leaves could be increased by microwave drying treatment. [ABSTRACT FROM AUTHOR]

To investigate the influence of heating temperature on the evolution of physical and chemical structures of thermal interpreted emissions and solid phase residues in tobacco under low-oxygen atmosphere, a tubular furnace reactor was used to capture the smoke components of reconstituted tobacco leaves at different heating temperatures under low oxygen concentration and prepare solid phase residues. Representative smoke components were detected by GC-MS, and various analysis and characterization techniques were used to detect the microstructure and chemical composition of solid phase residues. The results showed that during the heating process of reconstituted tobacco leaves, the basic substances such as glycerol, propylene glycol, and nicotine were mostly directly transferred to the smoke aerosol after being heated. The release of crotonaldehyde, hydroxyacetone, isoprene, and benzene derivatives increased with increasing temperature, while the release of naphthalene decreased with increasing temperature. Phenolic ketone components such as guaiacol, cresol, phenol, 2,3-butanedione, 1-hydroxy-2-butanone, and 2 (5H)-furanone exhibited fluctuations with temperature changes; The representative volatile compounds represented by low-temperature cracking of isoprene in flue gas increase with the increase of temperature; The degree of ashing of the solid residue fiber skeleton increases with the increase of temperature; Before 370 °C, the reconstituted tobacco leaves were mainly characterized by volatilization, distillation, and the dehydroxylation/decarboxylation of hemicellulose and cellulose. With the increase of temperature, there was an oxidation reaction in the pyrolysis process, and the proportion of more stable oxygen containing functional groups on the surface of the reconstituted tobacco leaves increased sharply. [ABSTRACT FROM AUTHOR]