Self-driven coulometry without an external electric source

Abstract

During the usual electrolysis, an electric power supply is needed to transfer electrons between the electroactive species and an electrode. If the substance in the sample solution is to be oxidized (reduced) without an external electric power supply, the potential of the half-cell containing the sample solution must be sufficiently lower (higher) than that of the half-cell in which the counter electrode is placed. If on short-circuiting both half-cells electrolysis in the sample-containing half-cell occurs spontaneously, i.e., without external power supply, the cell is so-called self-driven. This concept has been used in a coulometric cell with a carbon felt electrode impregnated with electrolyte not containing an electroactive species and a carbon felt counter electrode impregnated with hexacyanoferrate(III) solution. Determinations of l-ascorbic acid and NADH carried out with nearly 100% discharging efficiencies and it was demonstrated that self-driven coulometry exhibited the same properties as conventional electrolytic coulometry using an external electric power supply.