For the first set, the conversion of DHA to DHAQ was measured at different initial concentrations of DHA. The oxidation of DHA and cycling of the formed DHAQ were performed under conditions similar to those described in Figure . In 2.0 M OH -, when the DHA initial concentration is reduced from 50 mM to 2.5 mM, the conversion efficiency changes only from 88% to 85%. This change, however, is not significant because of the uncertainties involved in measuring transferred charges in the experiment. Therefore, the conversion efficiency appears to be essentially independent of the DHA concentration present in the electrolyte.