Session 10

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Gas chromatography is the most powerful technique to separate mixtures of volatile compounds; however, doing so normally requires a significant amount of time, and imposes thus limitation to the speed and the time resolution that can be achieved with chromatographic measurements. Many technologically relevant processes do, however, require measurements with a time resolution that is at the scale of one minute, or potentially even less. From the van Deemter equation it is obvious that it is impossible to maximise separation speed beyond the optimum separation velocity without losing efficiency [1]. A closer inspection of this equation reveals, however, various possibilities to gain separation speed.
We will discuss various approaches to speed up chromatographic separation and to gain time resolution between measurements that we have developed and applied in response to the need of monitoring the volatile compounds formed by the degradation of the organic electrolyte of lithium ion batteries during various use conditions. As extreme operation conditions or misuse can lead to catastrophic degradation of the electrolyte in the lithium ion battery, fast responding chromatographic techniques are required [2]. These include the use of vacuum outlet conditions, multiplexing, and of fast (positive or negative) thermal gradients. Their individual benefits and limitations will be presented and critically discussed here, with a particular view to their practical applicability.

Acknowledgements
The authors gratefully acknowledge financial support of this work by the Austrian Research Promotion Agency (FFG) under Project numbers 835790 (“SiLithium”), 858298 (“DianaBatt”) and 879613 (“OPERION”).

References
[1]  J.J. van Deemter, F.J. Zuiderweg, A. Klinkenberg, Chem. Eng. Sci. 5 (1956) 271-289.
[2]  Y.P. Stenzel, F. Horsthemke, M. Winter, S. Nowak, Separations 6 (2019) 26.