Abstract: The over-oxidized poly-(N-acetylaniline) modified glassy carbon electrode with in-situ deposited bismuth film (Bi/over-oxidized PNAANI/GCE) was employed for simultaneous determination of trace Cd(Ⅱ) and Pb(Ⅱ) in edible salts with square wave anodic stripping voltammetry. Such an over-oxidized PNAANI film possesses excellent cation permselectivity, and can remarkably increase the sensitivity and selectivity of the modified electrode. The in-situ deposited bismuth film was used as an alternative to mercury to improve the preconcentration ability for Cd(Ⅱ) and Pb(Ⅱ). The calibration curves for Cd(Ⅱ) and Pb(Ⅱ) both covered two linear ranges, 0.2~3.0 μg·L-1 and 3.0~33 μg·L-1. The detection limits of Cd(Ⅱ) and Pb(Ⅱ) were 0.015 μg·L-1 and 0.029 μg·L-1 respectively with a deposition time of 300 s. Moreover, this as-prepared electrode has high stability and anti-interference capability. The proposed method was successfully applied to the determination of cadmium and lead in edible salt samples.

Key words: over-oxidized poly (N-acetylaniline), bismuth film, modified electrode, anodic stripping voltammetry, cadmium, lead