The development of a Lithium-attachment chemical ionization mass spectrometer for studies in the atmosphere

Lead Research Organisation: University of Manchester
Department Name: Earth Atmospheric and Env Sciences


This research project will develop a state-of-the-art ionization source that can be used for laboratory studies and as a field instrument for the detection and quantification of both gas-phase and aerosol-phase analytes. A novel adaptation of Li+-attachment chemical ionization mass spectrometry will be used as a detection system for various species present in the atmosphere. By realizing the innovations within this project, Li+-attachment has the potential to be a universal detection system that can ionize practically any component of the air and is therefore diverse with respect to the chemical systems that it can monitor as well as the conditions in which it can be employed. This project will demonstrate the capability of this ionization scheme via three proof-of-principle projects, namely the detection of BVOCs, detection and speciation of organic aerosols and the development of Knudsen effusion mass spectrometry to determine organic activity coefficients.


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Description The aim of the project was to build and develop a ground breaking high intensity Li+-attachment source to function as a universal detector for applications in both the laboratory and field measurements. This Source would then be used for; A new refinement of Li+-attachment chemical ionization mass spectrometry (CIMS), a Li+-attachment Knudsen effusion mass spectrometer (KEMS) and a Li+-attachment aerosol mass spectrometer.(Li-AMS).

Initially a single spiral wire filament coated with lithium bearing _-eucryptite was produced. This formed the basis of a source used for use in the CIMS. Once the ion optics had been adjusted sufficiently to allow transmission of primary ions from the source it was then calibrated using acetone perm sources in a nitrogen bath gas giving an mda of 8 ppb. The filament was then improved by using a Pt:Ir mesh and an improved _-eucryptite synthesis method. This lead to a factor 500 improvement in primary ion current, with a corresponding improvement in the mda. Detection limits using our improved source are 4 ppt for acetone. 0.2 ppt for formic acid, 15 ppt for nitric acid and 120 ppt for ammonia. These measurements of both an acid and a base with high sensitivities are first for our CIMS. Proxy reactions for VOC degredation were also studied and a wide range of reaction products were observed. In spite of improvements made to the manufacturing and operation of the filaments, the problem of burnout (from uneven heating and melting) remained persistent.

The source was successfully miniaturized for mounting on our KEMS. The small size of the opening on our crossbeam ion source meant there was no improvement from using a mesh over a wire. We successfully detected effused species adducts under UHV conditions with no fragmentation. The source was sufficiently sensitive to see traces of vacuum contamination in the system. In principle the source can be mounted on a quad-AMS although there are issues with mounting on a ToF-AMS due to the very large number of primary ions the source emits.

The manufacturing and design, as we as these initial results are to be submitted Atmospheric measurement techniques (Booth 2013). The initial results from the KEMS work have led to further funding from NERC (grant NE/J009202/1) to use this technique to investigate thermodynamic activities and vapour pressures of mixtures.
Exploitation Route n/a the research could lead to development of novel ionisation sources in mass spectrometry
Sectors Chemicals,Energy,Environment

Description so far our results have not been used by Mass Spec companies
First Year Of Impact 2014
Sector Environment,Pharmaceuticals and Medical Biotechnology
Impact Types Economic