In this work, we studied the electrochemical properties of different batches of [MPPip][TFSI] with Au(111). It was shown that the reproducibility of the results strongly depends on the manufacturer, purchase date and pre-treatment of the IL. We were able to categorise the ILs into two distinctly different electrochemical behaviours, which are likely a result of specific types of still unknown impurities. It seems that one of the impurities can be removed to some extend by a molecular sieve. This procedure, however, also seems to introduce Na as another impurity in the system. In contrast to the common understanding, water that is discussed to be a native impurity in ILs, does not seem to have a significant impact on the electrochemical properties. The changes observed upon addition of water were attributed to residual O 2 , which has been introduced into the system along with the water. The unknown impurities in turn have an impact on the potential region, where water and O 2 are catalytically converted. The magnitude of the currents for these conversion reactions strongly depends on the water/O 2 ratio. An important aspect is also that it takes quite some time for O 2 to be released from the IL in the glove box, and hence the reproducibility also strongly depends on the time of preparation and measurement. In total our work illustrates the complexity in studying the redox properties of ILs especially with welldefined electrodes, which are, however, mandatory to derive a clearer picture of interfacial processes.