气相色谱-正化学电离源-飞行时间质谱法测定烟草吸食者唾液中的吡嗪和吡啶类物质

建立了气相色谱-正化学电离源-飞行时间质谱法（GC-PCI-TOF MS）测定烟草吸食者唾液中9种吡嗪和吡啶类物质。样品经二氯甲烷溶剂萃取，N-丙基乙二胺（PSA）吸附剂分散固相萃取净化后，进行GC-PCI-TOF MS检测。结合特征离子的保留时间、精确质量数、裂解规律对目标物进行定性分析，以外标法定量。结果表明：9种吡嗪和吡啶类物质的线性相关系数R²均大于0.999 1，定量限为3.0～7.9 μg/L，回收率在85%~104%之间；烟草吸食者唾液中含量较高的吡嗪和吡啶类物质为吡啶、2-甲基吡嗪，二甲基吡嗪类有少量检出；不同卷烟样品吸食者唾液中吡啶和2-甲基吡嗪的含量存在明显差异。对不同类型卷烟样品吸食者唾液中吡嗪和吡啶类物质含量进行主成分分析，发现同种卷烟中二者含量能很好地聚类，不同卷烟中二者含量存在显著性差异（P<0.05），因此可以按吸食者唾液中吡嗪和吡啶类含量对卷烟进行分类。

Determination of Pyrazines and Pyridines in Saliva of Tobacco Smokers by Gas Chromatography-Positive Chemical Ionization-Time of Flight Mass Spectrometry

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.