We recommend that attention be given to the possibility of sample contamination in trace level electrochemical experiments when classical aqueous oxygen scrubbers are used. Although fresh electrolyte or water pre-saturators can be used to minimize ion carryover by aerosol spray, mercury vapor is still present in the gas stream. Many electrochemists now use solid catalysts (such as BASF R3-11, Badische Anilin and Soda-Fabrik), and their use, or that of pre-purified gases, are recommended to avoid such problems with purge gases in trace electroanalyses.