To get a reproducible signal over time, the electrode surfaces should be cleaned periodically by a potential pulse or by mechanically polishing the electrode surfaces 18,19. With pulsed amperometry 20,21, applying far positive and far negative potentials in each cycle at the electrode polarizes the electrode to renew the electrode surface, which results in very reproducible current shape and magnitude. The potentials and delay times of oxidation and reduction steps were determined by a series of separate experiments.