Ionophore/ionomer films on glassy carbon electrodes for accumulation voltammetry. Investigation of a lead(II) ionophore

Abstract

The use of ionophores in voltammetry with modified glassy carbon (GC) electrodes is described. A lead(II) ionophore, methylenebis (N, N-diisobutyldithiocarbamate) was dissolved in a solution containing 0.1% Nafion, and this mixture was applied to the GC electrode. Solvent evaporation gave the GC–Nafion–ionophore modified electrode. The composition of the film coating was studied with respect to the mass of Nafion and amount of ionophore; the best composition was found to comprise 20 µg Nafion and 10 nmol ionophore. Accumulation of lead(II) from 0.1 mol l^–1 acetate buffer (pH 4) followed by voltammetry gave a quasi-reversible reduction peak at about –0.85 V (versus SCE), with halfwave potential, E_1/2=–0.57 V and peak-to-peak separation, ΔE_p= 0.51 V. This reduction potential is 0.25 V more negative than the reduction potential in the absence of the ionophore where E_1/2=–0.48 V and ΔE_p= 0.14 V. Accumulation of 1 × 10^–5 mol l^–1 lead(II) for 60 s at the GC–Nafion–ionophore modified electrode gave a lead(II) surface coverage of 1.3 × 10^–9 mol cm^–2. The film exhibited thin-film voltammetric behaviour. Detection of lead(II) down to 1 × 10^–7 mol l^–1 with a 600 s accumulation time was possible. The effects of preconcentration time and solution composition were evaluated. The accumulation process appears to consist of two steps: ion exchange followed by complexation in the film.