Chromate and dichromate electro-insertion processes into a N,N,N′,N′-tetraoctylphenylenediamine redox liquid

Ion transfer processes across aqueous | organic phase boundaries are of considerable importance in biological and analytical chemistry. When driven by a potential applied to the liquid | liquid interface the ion transfer may be detected as voltammetric response. Here, a potential applied to the electrode | aqueous electrolyte | organic oil (N,N,N′,N′-tetraoctylphenylenediamine, TOPD) triple interface is employed to drive anion transfer. Upon oxidation of TOPD deposited in the form of microdroplets onto the electrode and immersed in aqueous media, the transfer of monovalent anions (perchlorate) and divalent anions (sulfate, chromate, dichromate) occurs to maintain charge neutrality in the organic oil phase. Sulfate (0.1 M) as a very hydrophilic anion undergoes transfer into the organic phase at a potential positive of 0.4 V (vs. Ag/AgCl) and may be employed as an 'inert' background electrolyte. Chromate is shown to undergo electro-insertion at low concentrations down to 10 μM. Within the oil phase chromate is undergoing condensation to the more stable dichromate.