Fundamental investigations of ion mobility and separation of isomers by high resolution ion mobility spectrometry

• Applicant: Professor Dr.-Ing. Stefan Zimmermann
• Subject Area: Analytical Chemistry ; Measurement Systems
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263334553

The main objective of the proposed research project is the development of a compact high-resolution ion mobility spectrometer (IMS) with a resolving power of R > 300, detection limits down to ppt-levels and fast response times of less than a second while different non-radioactive ion sources can be easily coupled to the IMS depending on the application. The main technical challenges are designing such a compact IMS that meets all the analytical requirements mentioned above and the development of complex electronics required for operating the system. This includes the development of a low-noise, high-gain amplifier with 1 GV/A at 150 kHz and the possibility to easily adjust the bandwidth with respect to the achieved resolving power, fast high-voltage switches for operating the ion shutter and a compact high-voltage cascade circuit for a direct low-power supply of the drift ring electrodes. In order to optimize the IMS design a detailed experimental characterization is needed. Furthermore, analytical and numerical models considering all relevant effects on the analytical performance will be developed and experimentally validated. In particular, the ion transport inside the IMS from the ionization region to the detector plate will be numerically simulated. However, for feasible simulations the transient electrical field inhomogeneities mainly caused by the ion shutter and moving ion clouds, ion discharge effects at metallic surfaces, diffusion and convective transport phenomena of ions and neutrals as well as the ionization properties of different ion sources have to be carefully considered. In addition, the ion density and ion distribution generated inside the ionization region by different ion sources will be measured at the moment of ion injection through the shutter and used as feasible initial conditions for the numerical simulations. This research project concentrates on a non-radioactive electron emitter, a weak x-ray source and a photoionization source for ion generation. After successive optimization cycles both an experimentally validated theoretical model describing all relevant effects on the analytical performance and a compact high-resolution IMS with exchangeable ion sources will be available at the end of the project. A possible project extension would concentrate on application-oriented system optimization with a focus on breath analysis and bioprocess monitoring. Furthermore, a nano-electrospray ionization source will be coupled to the IMS for fast analysis of liquids.

• DFG Programme: Research Grants