Electrogeneration of superoxide ion at mercury electrodes with a hydrophobic adsorption film in aqueous media

The electrogeneration of superoxide ion (O-2(-)) by the one-electron reduction of O-2 in alkaline aqueous media has been examined using the hanging mercury drop electrode in the presence of several surfactants of the quinoline groups. Based on the superoxide dismutase (SOD)-catalyzed disproportionation behavior of O-2(-) on the cyclic voltammograms, new surfactants, in the presence of which O-2(-) was actually electrogenerated, could be searched: 2-, 4-, 6-, 7- and 8-methylquinolines (3, 4, 5, 6 and 7), and 2-phenyl and 5,6-benzoquinolines (8 and 9). It was found that the effectiveness for the electrogeneration of O-2(-) largely depends on the surfactant and decreases in the order of quinoline (1), isoquinoline (2) > 5, 6, 7 > 3, 4 > 8 > triphenylphosphine oxide (10) > 9. In addition. a brief discussion on the structure and physicochemical properties of the surfactant film desirable for the effective O-2(-) electrogeneration in aqueous media is given.