A Reference Electrode for Electrochemical and Cryoelectrochemical Use in Tetrahydrofuran Solvent

We report a reference electrode for direct use in tetrahydrofuran (THF) at low temperatures. A reference solution containing equimolar amounts of ferrocene/ferrocenium hexafluorophosphate (Fc/Fc + ) are prepared to give a 4 mM solution in THF that contains tetrabutylammonium hexafluorophosphate (TBAF) supporting electrolyte thus, minimizing liquid junction potentials. The reference solution is added to a sealed glass tube with a porous frit at one end, and a platinum wire is inserted into the tube. The reference electrode assembly is then inserted into a THF test solution. Potentiometric measurements show that the system responds in the expected Nernstian fashion over the concentration and temperature ranges, 4 mM to 40 μM and 20 °C to −45 °C respectively. In addition, it is shown by steady–state cyclic voltammetry at a platinum microelectrode that the chemical reactivity of ferrocenium hexafluorophosphate (Fc + ) otherwise seen in THF is suppressed by ion‐pairing with PF $\rm{ {_{6}^{-}}}$ using tetrabutylammonium hexafluorophosphate (TBAF) as the supporting electrolyte.