Triphenyllead Chloride as a New Ionophore for an Iodide-Selective Membrane Electrode

ABSTRACT

Triphenyllead chloride was found to act as an ionophore for iodide. An electrode constructed using this ionophore and tris(2-ethylhexyl) phosphate as a membrane solvent in a poly(vinyl chloride) membrane matrix exhibited a near-Nernstian response to iodide in the concentration range 1x10⁻⁵-1x10⁻² M with a slope of-56 mV per concentration decade. The lower limit of detection was around 3 μM. The electrode displayed the following selectivity sequence: Γ > salicylate > SCN⁻ ∼ Br⁻ > Cl⁻ > ClO₄ ⁻ > CH₃COO⁻ > NO₃ ⁻ > SO₄ ²⁻ ∼ HPO₄ ²⁻ > HCO₃ ⁻, which largely deviates from the Hofmeister sequence and also is not in accordance with the selectivity sequence of an electrode based on triphenyltin chloride. The pH dependence of the electrode response was not significant in the pH range 2-7. Diphenyllead dichloride also exhibited a similar selectivity sequence as triphenyllead chloride, but sensitivity to iodide was much lower than for triphenyllead chloride.

Keywords::

• Ion-selective electrode
• Iodide ionophore
• Selectivity
• Organolead compound
• Triphenyllead chloride