微量气体超高灵敏度四极质谱检测分析

发布时间：2018-03-05 14:44

本文选题：微量气体分析　切入点：四极质谱法　出处：《东南大学》2016年硕士论文　论文类型：学位论文

【摘要】：微量气体分析是气体分析的重要组成部分,在工业生产及日常生活中都有着十分广泛的应用。总得来说,微量气体分析主要有两层含义：对总气体量很大的微量或超低微量杂质分析和对总气体量很小的分析对象的气体检测。论文阐述并比较了四极质谱法、气相色谱法、光谱法等常见的微量气体检测方法。在对总气体量很小的微量气体分析中,四极质谱的灵敏度最高。论文针对四极质谱分析法中的开放式离子源和封闭式离子源对痕量灵敏度的影响进行了分析,结果表明传统的开放式离子源不能满足微量气体样品分析所需的痕量灵敏度,而封闭式离子源不仅保持电离空间内外较高的压强差,提高了微量气体在电离空间的含量,而且能较好抑制离子源的本底干扰。因此,在对微量气体样品做痕量分析时采用封闭式离子源结构。同时,论文理论分析并对比了微量气体样品总气体量的非破坏性和破坏性测量方法。通过对比发现,破坏性测量中的压力计测量法作为绝对测量法,其准确度最高。论文针对封闭式离子源的性能参数会对微量气体四极质谱分析的灵敏度产生重要的影响开展了理论研究。在封闭式离子源的性能参数中,电子的入射孔径不仅影响着电离空间内的压强,而且决定着灯丝发射的电子进入电离空间的效率。采用COMSOL Multiphysics5.0和CST DESIGN ENVIRONMENT分别对封闭式离子源的电场分布和电子轨迹进行了研究。初步的模拟结果表明,随着电子入射孔的半径的增大,电离室内的压强越低,但电子入射效率增大。当电子入射孔的半径为1.8mm左右时,电子入射效率和封闭式离子源电离空间内压强的乘积达到最大。实验装置采用机械泵、分子泵组成的动态真空系统,质谱分析室内的极限真空为3.44×10-4Pa。实验中采用封闭离子源,配合17级铍铜电子倍增器和大极杆的四极杆匹配可以实现微量气体的超高灵敏度(PPM级)和高分辨率分析。实验针对直径为531.1μ m，壁厚3.96μm的空心小球内部的气体成分进行了分析,并取得了实验数据。
[Abstract]:Trace gas analysis is an important part of gas analysis. It is widely used in industrial production and daily life. Trace gas analysis has two main meanings: trace or ultralow trace impurity analysis with large total gas content and gas detection with very small total gas content. In the analysis of trace gases with a very small amount of total gas, The sensitivity of quadrupole mass spectrometry is the highest. The influence of open ion source and closed ion source on trace sensitivity in quadrupole mass spectrometry is analyzed in this paper. The results show that the traditional open ion source can not meet the trace sensitivity required for the analysis of trace gas samples, but the closed ion source not only keeps the high pressure difference inside and outside the ionization space, but also increases the content of trace gas in the ionization space. And it can restrain the background interference of ion source. Therefore, the closed ion source structure is used in trace analysis of trace gas samples. This paper theoretically analyses and compares the nondestructive and destructive measurement methods for the total gas quantity of trace gas samples. Through comparison, it is found that the pressure gauge method is used as the absolute measurement method in destructive measurement. The performance parameters of closed ion source have important influence on the sensitivity of trace gas quadrupole mass spectrometry. The incident aperture of electrons not only affects the pressure in ionization space, Moreover, the efficiency of electrons emitted by filament into ionization space is determined. The electric field distribution and electron trajectory of closed ion source are studied by COMSOL Multiphysics5.0 and CST DESIGN ENVIRONMENT, respectively. The preliminary simulation results show that, With the increase of the radius of the electron incident hole, the pressure in the ionization chamber is lower, but the incident efficiency of the electron is increased. When the radius of the electron incident hole is about 1.8 mm, The electron incidence efficiency and the product of the pressure in the ionization space of the closed ion source reach the maximum. The experimental device is a dynamic vacuum system composed of mechanical pump and molecular pump. The limit vacuum in the mass spectrometric analysis room is 3.44 脳 10 ~ (-4) Pa. the closed ion source is used in the experiment. The high sensitivity PPM and high resolution analysis of trace gas can be realized by matching the quadrupole rod with 17 grade beryllium copper electron multiplier and large pole rod. The gas composition inside the hollow sphere with a diameter of 531.1 渭 m and a wall thickness of 3.96 渭 m is analyzed experimentally. The experimental data are obtained.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O657.63

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