Ionic Liquid Reference Electrodes With a Well-Controlled Co(II)/Co(III) Redox Buffer as Solid Contact

Solid-contact reference electrodes that comprise a polymeric reference membrane doped with an ionic liquid are an alternative to conventional reference electrodes with a salt bridge. To enhance the electrode-to-electrode reproducibility of solid-contact reference electrodes, a hydrophobic redox buffer consisting of the Co(III) and Co(II) complexes of 1,10-phenanthroline ([Co(phen)₃]^3+/2+) was incorporated into these reference membranes, providing redox buffer capacity at the interface of the reference membrane and the underlying solid electron conductor. As required for proper functioning, the E° of these reference electrodes is not sample dependent and exhibits a good electrode-to-electrode reproducibility, with a standard deviation as low as 2.1mV.