Application of the oxidation reaction of a ferrocene derivative (FcSQC6) as driving force for the transfer of hydrophilic sulfate anions at a three-phase electrode

Studies at three-phase electrodes (TPE, glassy carbon electrode, an aqueous and organic solution) are often performed to detect organic and inorganic anions. However, it is difficult to find a redox probe or ionophore that would allow the transfer of highly hydrophilic sulphate ions. Recently, TPE studies of ion pair receptors consisting of a crown ether cation-binding site and a squaramide anion-binding domain have emerged, offering the ability to extract extremely hydrophilic sulphate salts. In this article, we show that we can induce sulphate anion transfer in a three-phase electrode system using the controlled oxidation reaction ferrocene grafted to a squaramide-based ion receptor in the organic phase. We evaluate this receptor for the transfer of sulphate ions and its selectivity towards other anions. The effect of the cation bound by the crown ether on the ion transfer potential to transfer across phase boundaries is shown. These measurements demonstrate the potential of applying ferrocene derivatives in ion-transfer voltammetry for the transfer and detection of highly hydrophilic anions.