7. Ma et al. studied the electrochemistry of dopamine in the presence of ascorbic acid at a recessed ring-disk electrode array. The electrode array consisted of 2000 individual nanopores with a single disk electrode in the bottom of each pore and a cylindrical ring electrode guarding the disk (as shown in the SEM image below). Riring=+0.5Vfloi The right figure shows cyclic voltammograms acquired by sweeping the disk electrode while either allowing the ring electrode to float, (a), or holding it at an oxidizing potential, (b). The different colors represent different concentrations of ascorbic acid in the presence of the 100M dopamine analyte. Clearly when the ring is allowed to float the ascorbic acid peak (E0.05V) interferes with the dopamine peak of interest at E+0.2V, especially when the ascorbic acid (10 mM) is present in excess relative to the dopamine (100M). However, when the ring potential is fixed at Ering=+0.5V, all of the dopamine results collapse to a single curve independent of the ascorbic acid concentration. Posit a reasonable electrochemical explanation for this observation. Hint: Carefully compare the positive and negative going waves in (a)