School or Earth, Atmospheric and Environment Science, University of Manchester, UK.
Photon Science Institute, University of Manchester, UK.
Analyst. 2017 Oct 7;142(19):3666-3673. doi: 10.1039/c7an01161j. Epub 2017 Sep 7.
Lithium ion attachment mass spectrometry provides a non-specific, non-fragmenting, sensitive and robust method for the detection of volatile species in the gas phase. The design, manufacture and results of lithium based ion attachment ionisation sources for two different mass spectrometry systems are presented. In this study trace gas analysis is investigated using a modified Chemical Ionization Mass Spectrometer (CIMS) and vapour pressure measurements are made using a modified Knudsen Effusion Mass Spectrometer (KEMS). In the Li CIMS, where the Li ionization acts a soft and unselective ionization source, limits of detection of 0.2 ppt for formic acid, 15 ppt for nitric acid and 120 ppt for ammonia were achieved, allowing for ambient measurements of such species at atmospherically relevant concentrations. In the first application of Lithium ion attachment in ultra-high vacuum (UHV), vapor pressures of various atmospherically relevant species were measured with the adapted KEMS, giving measured values equivalent to previous results from electron impact KEMS. In the Li KEMS vapour pressures <10 mbar can be measured without any fragmentation, as is seen with the initial electron impact (EI) set up, allowing the vapor pressure of individual components within mixtures to be determined.
锂离子附着质谱提供了一种非特异性、无碎片、灵敏且强大的方法，用于检测气相中的挥发性物质。本文介绍了两种不同质谱系统中基于锂的离子附着离子源的设计、制造和结果。在这项研究中，使用改进的化学电离质谱仪（CIMS）研究痕量气体分析，并使用改进的克努森扩散质谱仪（KEMS）进行蒸气压测量。在 Li CIMS 中，Li 离子化作用是一种软而非选择性的离子源，实现了对甲酸的检测限为 0.2 ppt，对硝酸的检测限为 15 ppt，对氨的检测限为 120 ppt，从而可以在大气相关浓度下进行这些物质的环境测量。在超高真空（UHV）中锂离子附着的首次应用中，使用改进的 KEMS 测量了各种与大气相关的物质的蒸气压，得到的测量值与先前电子碰撞 KEMS 的结果相当。在 Li KEMS 中，无需任何碎片就可以测量<10 mbar 的蒸气压，这与初始电子碰撞（EI）装置相同，从而可以确定混合物中各个成分的蒸气压。
