Trifluoromethanesulphonate-selective liquid membrane electrode

Abstract

A liquid membrane electrode that is sensitive to trifluoromethanesulphonate (triflate) ions has been developed. It incorporates the ion-exchanging compound, Ni(bphen)₃²⁺·2(CF₃SO₃^–)(bphen = 4,7-diphenyl-1,10-phenanthroline), dissolved in the organic solvent 2-nitro-p-cymene. The electrode exhibits a near-Nernstian response for triflate concentrations greater than 1 × 10^–4 mol dm^–3, with a slope of 59.5 mV per concentration decade at 25 °C. The limit of detection is 1.5 × 10^–4 mol dm^–3 triflate. The response time is about 5 s and the working pH is in the range 4–9. The electrode has a reasonably high selectivity towards the triflate ion relative to other common organic and inorganic ions. It can be used for the potentiometric determination of triflate. The triflate anion is a useful alternative to perchlorate in studies of monovalent ligands with poor coordination properties.