A study of Nafion-coated bismuth-film electrodes for the determination of trace metals by anodic stripping voltammetry

Abstract

This work reports on the fabrication, characterization and applications of Nafion-coated bismuth-film electrodes (NCBFE's) for the determination of trace metals by anodic stripping voltammetry (ASV). A NCBFE was typically prepared by first applying a 5 microl drop of a 1% Nafion solution onto the surface of a glassy-carbon rotating-disk electrode. After evaporation of the solvent, the Bi film was plated on the electrode in situ(i.e. by spiking the sample with 1000 microg l(-1) of Bi(iii) and simultaneous electrolytic deposition of the metal ions and bismuth film on the electrode surface at -1.4 V) or ex-situ(i.e. by electrolytic deposition of the bismuth film in a separate solution containing 1000 microg l(-1) of Bi(iii), followed by the ASV measurement step in the sample solution). Various fabrication and operational parameters were thoroughly investigated and discussed in terms of their effect on the ASV signals. It was found that this voltammetric sensor was suitable for the determination of metals at trace levels by square-wave ASV (SWASV) due to its multi-element detection potential, improved analytical sensitivity, high resistance to surfactants, low cost, ease of fabrication, robustness, speed of analysis and low toxicity (as compared to traditional mercury electrodes). In the presence of 4 mg l(-1) of Triton X-100, the NCBFE afforded a 10-fold peak height enhancement for the Pb peak and a 14-fold enhancement for the Cd peak over a bare BFE while the determination of Zn was feasible only on the NCBFE. The limits of detection (at a signal-to-noise ratio of 3) were 0.1 microg l(-1) for Cd and Pb and 0.4 microg l(-1) for Zn for a deposition time of 10 min. Finally, the electrode was applied to different real samples (tap-water, urine and wine) for the analysis of trace metals with satisfactory results.