Integration of Ion Mobility Analysis in a Linear Quadrupole Ion Trap for Enhanced Analytical Capability

• Applicant: Dr.-Ing. Christoph Schäfer
• Subject Area: Analytical Chemistry ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566668822

The accurate identification and quantification of volatile organic compounds (VOCs) in complex chemical environments requires a highly sensitive, selective and reliable real-time analytical technique. Although mass spectrometry (MS) fundamentally meets these requirements, it faces challenges in distinguishing isobaric and isomeric ions in complex samples, as they have the same m/z values. Techniques like coupling MS with gas chromatography (GC) or ion mobility spectrometry (IMS), as well as using tandem-MS can improve the separation of these ions. However, GC-MS results in longer analysis times and is therefore unsuitable for real-time applications, while tandem-MS and IMS-MS increase instrumental complexity. Current research at the J. Heyrovský Institute of Physical Chemistry in Prague aims to develop a new generation of mass spectrometry for trace gas and VOC vapor analysis, using a linear quadrupole ion trap (LQIT). This integrated platform combines chemical ionization, m/z analysis, and optional collision-induced dissociation of mass-selected parent ions within a single ion trap, resulting in high analytical performance and simultaneously reducing instrumental complexity by eliminating additional separation stages and replacing multiple mass analyzers with a single LQIT. The primary objective of this project is to integrate ion mobility analysis as an additional separation dimension into the LQIT, enabling more reliable identification of VOCs and untargeted quantification in complex mixtures. Here, the time at which the ions are emitted at resonance excitation, influenced by collisions with neutral gas particles, is used to determine the ion mobility. The ion motion within the ion trap can be described as that of a damped harmonic oscillator, with the relationship between the damping constant and the ion mobility still unclear. A central challenge of this project is thus the development of a theoretical foundation for precisely deriving ion mobility from experimental data. To validate this approach, reference values of ion mobility will be established using an appropriate reference platform, such as the selected ion flow-drift tube MS, at various operating pressures. Experimental validation is conducted by comparing the ion mobilities determined in the LQIT with these reference values. Additionally, it is investigated whether the field dependence of ion mobility and unwanted fragmentations known from the literature occur during ion mobility analysis. Finally, the improved separation capability of the modified LQIT will be demonstrated with mixtures of isomeric and isobaric ions.

• DFG Programme: WBP Fellowship
• International Connection: Czech Republic
• Host: Professor Dr. Patrick Spanel