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M. Antoniadou:
"Development and evaluation of a fast multiplexing injector for GC analysis. Application to the analysis of lithium ion battery volatiles.";
Supervisor, Reviewer: E. Rosenberg, J. Fleig, G. Zachariadis; Institut für Chemische Technologien und Analytik, 2021; oral examination: 2021-04-08.

The aim of this PhD thesis is to develop and evaluate a novel type of multiplex injector for gas chromatography. Multiplex sampling has been combined previously with various analytical techniques like ion mobility spectrometry, capillary electrophoresis and chromatography for the modulated introduction of the sample into the analytical system. So far, the motivation to use the multiplex sampling was the signal to noise ratio improvement and potential for high-throughput analysis. For achieving the signal to noise ratio improvement, the same sample is introduced into the analytical system according to a specific pseudorandom binary sequence. The output of the analytical system includes many sample injections in a single run and with the help of a mathematical process the single/averaged chromatogram with improved single to noise ratio is obtained.

The resulting graph (convoluted or multiplexed graph) contains the superimposed information on the various sample injections performed during one run. This creates the basis for another application of the multiplex sampling which is the monitoring of different processes in which the concentrations of analytes within the sample change within an experiment (one single run). The advantage of this form of multiplex sample introduction and subsequent data evaluation is that processes can be monitored whose timescales of change are much quicker than the runtime of a single chromatographic run. This application can be highly useful for the study of electrolyte degradation processes in the lithium ion battery which can be relatively fast so that conventional chromatographic methods are no longer suitable in terms of time resolution when requiring more information on the formed degradation products.

Our study aims at the development and investigation of different multiplex injection configurations which will be tested for their efficiency and accuracy on achieving fast sample injections. The most appropriate configuration will be used for the analysis of volatile compounds evolving from lithium ion batteries under abuse conditions (overcharging). Additionally, the data processing needed for extracting each time-resolved chromatogram will be established and examined. By the end of the study, we should be able to successfully apply the multiplex sampling for the monitoring of the state-of-health of a lithium ion battery during overcharge experiments and draw conclusions on the potential health or chemical hazard of the volatile compounds being formed in the degradation of lithium ion battery electrolytes.

Unsere Studie zielt auf die Entwicklung und Untersuchung verschiedener Multiplex-Injektionskonfigurationen ab. Die am besten geeignete Konfiguration soll bei der Analyse flüchtiger Verbindungen verwendet werden. Zusätzlich werden verschiedene für die Extraktion jedes zeitaufgelösten Chromatogramms erforderliche Datenverarbeitungsalgorithmen entwickelt und untersucht. Am Ende der Studie soll der Sicherheitsstatus einer Lithium-Ionen-Batterie während eines Überladungsexperiments untersucht werden, was anhand des Abbaus des Elektrolyten dieser Lithium-Ionen-Batterie beurteilt werden kann.

multiplexing / fast GC / lithium ion battery / electrolyte degradation