The key new observation of our study is that ferricyanide losses were exacerbated by both phenazine and quinone anolytes possessing hydroxyl groups. The two anolytes that did not possess strong coordinating groups, 2,7-AQDS and 2,6-DPPAQ, were found to have minimal interactions with ferricyanide. Though direct coordination to form a solid initially appears to be a simple explanation for this phenomenon, on-line NMR simulated-crossover experiments show that the rate of ferricyanide loss was nearly two orders of magnitude higher than the rate of 2,6-DHAQ loss. Furthermore, no direct evidence was found that indicated that 2,6-DHAQ was present in the precipitates formed when the anolyte and catholyte are mixed. This could be explained by strong interactions between the coordinated 2,6-DHAQ and paramagnetic Fe 3+ , leading to paramagnetic quenching of the 1 H NMR signal. However, the losses of ferricyanide and 2,6-DHAQ still cannot be explained fully by the small quantity of solid precipitates obtained, which was just ~18 mg from a 500 mL solution containing 2402 mg of 2,6-DHAQ (Methods S8). To explain the full an 80% loss of 2,6-DHAQ, the solid precipitates would need to contain at least 1922 mg of 2,6-DHAQ.