光电离质谱技术在线监测不同部位烟草裂解产物

On-line Monitoring of Tobacco Pyrolysis Products in Different Parts by Photoionization Mass Spectrometry

为了实时、在线研究烟草原料烟丝的热裂解产物,本工作搭建了一套热裂解光电离质谱装置。利用真空紫外光电离飞行时间质谱装置研究烤烟烟丝不同部位(上-B2F、中-C3F和下-X2F)分别在300、400、500、600和700℃热裂解时的产物,在线获得3个部位烟丝一系列热解产物的光电离质谱图,比较不同裂解温度下热解产物的变化规律。实验进一步分析了500℃下热解产物,如乙烯胺(m/z 43)、异戊二烯(m/z 68)和二甲基呋喃(m/z 96)等信号强度随时间的动态变化曲线,掌握裂解反应的动态变化过程。通过主成分分析(PCA)法对裂解产物质谱图进行统计分析,得到不同部位烟丝化学成分的差异。其中,m/z 58、96、110组分为下部烟(X2F)热解的标志性产物,m/z 43、126组分为中部烟(C3F)的代表性产物,上部烟(B2F)的主要代表性产物为m/z 84组分。结果表明,光电离质谱技术是一种研究烟草热解产物动态变化的重要手段,可通过评估裂解产物中主要成分及相对含量快速区分不同部位烟草样品。

An on-line pyrolysis-vacuum ultraviolet photoionization mass spectrometer was built for the analysis of pyrolysis products of tobacco.Vacuum ultraviolet photoionization is a“soft”ionization method producing few or no fragments of molecular ions,and identifing the complex pyrolysis products in real time.In this work,the pyrolysis of tobacco leaves from various stalk positions(B2F,C3F and X2F)at 300,400,500,600 and 700℃,and the effects of reaction temperature on the pyrolysis products intensity were studied.A series of mass spectra of pyrolysis products were obtained,and the changes of products at different pyrolysis temperatures were compared.The analysis results of products at different pyrolysis temperatures were helpful to reveal the formation mechanism of compounds in different parts of cut tobacco during pyrolysis/combustion.The dynamic curves of pyrolysis products such as vinylamine(m/z 43),isoprene(m/z 68)and dimethylfuran(m/z 96)with time were further observed at 500℃,so as to master the dynamic change process of pyrolysis reaction.It was found that the increase of temperature can dramatically shorten the reaction time.Generally,the primary products will be formed at the medium cracking temperature,and gradually pyrolyzed into secondary products with the increase of temperature,the secondary products will be accompanied by higher temperature cracking and thermal synthesis to form tertiary products.In order to quickly screen and identify different parts of tobacco,principal component analysis(PCA)was used to analyze the mass spectra of pyrolysis products,and the differences of chemical components in different parts of tobacco were identified.Then,the components with m/z 58,96,110 were the typical products of X2F,the components with m/z 43,126 were the representative products of C3F,and the main representative product of B2F was the component with m/z 84.Based on the above results,photoionization mass spectrometry was important to study the dynamic changes of tobacco pyrolysis products,the pyrolysis products of different parts of tobacco were quickly identified at 300-700℃,and the main pyrolysis products were summarized.By comprehensively evaluating the main components and relative content of pyrolysis products,tobacco samples from different parts can be quickly distinguished.