Ex situ prepared nafion-coated antimony film electrode for adsorptive stripping voltammetry of model metal ions in the presence of pyrogallol red

A nafion-coated antimony film electrode (NSbFE) was prepared ex situ and applied to the model metal ions Pb(II) and Cd(II) by adsorptive stripping voltammetry in the presence of pyrogallol red (PGR). To enhance the electroanalytical performance of the NSbFE, we optimized several operational parameters, including antimony concentration, deposition potential and time used in the preparation of the electrode, and effect of pH, ligand concentration (C_PGR), adsorptive potential, and time (E_ads, t _ads). The NSbFE exhibited well developed signals for the reduction of the adsorbed complexes at -0.63 and -0.92 V for Pb-PGR and Cd-PGR, respectively, with higher current compared to unmodified electrodes. The optimum parameters for NSbFE preparation consisting of 100 mg L^-1 Sb(III), 0.5 mol L^-1 HCl at -1.5 V (150 s) and for the determination of Pb(II) and Cd(II) were pH = 4.5 (acetate buffer); C_PGR = 2.8 μmol L ^-1; E_ads = -0.40 V and t_ads = 100 s. The electrode presents good linear behavior in the examined concentration range from 0.9 to 12.0 μg L^-1 for both metal ions, with a limit of detection (3σ) of 0.4 and 0.9 μg L^-1 for Pb(II) and 0.5 and 1.0 μg L^-1 for Cd(II) using 2-mm and 3-mm diameter glassy carbon electrodes, respectively. The relative standard deviation for a Pb(II) a Cd(II) solution (9.8 μg L^-1) was 2.0% for six successive assays. The method was validated using certified reference water for trace elements (TMDA-61) with satisfactory results. Finally, the method was applied to the determination of Pb(II) and Cd(II) in tap and mineral water.