Determination of lead and cadmium in rice samples by sequential injection/anodic stripping voltammetry using a bismuth film/crown ether/Nafion modified screen-printed carbon electrode

A highly sensitive automated method for the determination of Pb2+ and Cd2+ by sequential injection/anodic stripping voltammetry using a crown ether/Nafion modified screen-printed carbon electrode coated with a bismuth film was developed. The bismuth film was prepared by in situ depositing of Bi3+ simultaneously with the analyte metal ions on the modified electrode at −1.2 V vs. Ag/AgCl reference electrode for 180 s, using hydrochloric acid as a supporting electrolyte. Under the optimal conditions, estimated from sequential univariate analysis of each of the parameters, a linear detection range of 0.5–60 μg dm−3 for both metal ions was found, with a LOD (3Sb/S) of 0.11 μg dm−3 for Pb2+ and 0.27 μg dm−3 for Cd2+. This method shows good reproducibility and stability and was successfully applied to measure Pb2+ and Cd2+ levels in rice and rice product samples, with good agreement with those obtained by the standard ICP-OES method.