The CO signal shows a strong drift and noise and is additionally also strongly influenced by traces of N2 as a background gas. Fortunately, with the exception of the nitrogen background, the inclusion of CO does not significantly affect the calculated amounts of the other gases formed. In other words, for the quantification of the other gases it does not matter whether CO is present or just an artefact. The strong drift of the CO signal is found for both cells with different solvents. This shows that, at least in our measurement setup, the amount of CO is not easily determined even when using the MCD algorithm approach. CO is therefore not easily distinguished from measurement artefacts and other methods such as IR spectroscopy should be used in parallel .