Quantitative ex situ 1 H NMR spectra were obtained for each solution within 1 h of preparation, and again 1 week later (Figure ). Remarkably, an (84 ± 12)% decrease in 2,6-DHAQ and (20.1 ± 0.3)% decrease in ferricyanide concentration was observed after one week (Figure ). For comparison, no significant change in 2,6-DHAQ concentration was measured in the 2,6-DHAQspiked ferrocyanide electrolyte (i.e., discharged catholyte, Fe(II) oxidation state) after one week of aging (Figure ). Importantly, in a control experiment where a solution of 0.29 M ferricyanide was aged in the absence of 2,6-DHAQ, ferricyanide losses were minimal, at just (0.7 ± 0.2)% (Figure ). This shows that ferricyanide losses are enhanced in the presence of 2,6-DHAQ, and vice versa.