Nafion-coated bismuth film electrodes on pyrolyzed photoresist/alumina supports for analysis of trace heavy metals

Novel pyrolyzed photoresist film (PPF) electrodes for application in electroanalysis have been prepared by pyrolysis of various photoresists on alumina substrates and characterized for their electrical, microstructural and electrochemical properties. As a support, the PPF electrodes were successfully applied for the determination of heavy metals (Pb, Cd and Zn) in an aqueous solution by square wave anodic stripping voltammetry (SWASV) on in situ formed bismuth film electrodes (BiFEs) with or without Nafion-coating. Selected parameters of Nafion film preparation (thickness, curing temperature) on the analytical performance of Nafion-coated BiFEs were investigated. Since the concentration of Bi(III) used for formation of the bismuth film influences the height of the stripping peaks, the bismuth to target metals concentration ratio had to be optimized in the range from 1 to 50. 2 × 10−6 mol/L concentration of Bi(III) was chosen for the target metals concentration range of 1 × 10−8–1 × 10−7 mol/L. By using the bare and the Nafion-coated BiFEs in simultaneous determination of target metals it has been found that the analytical sensitivities for Pb(II) and Cd(II) were 2 times higher in comparison with non-coated BiFEs due to the synergistic effect of redox cycling and non-faradic cation-exchanging preconcentration in the Nafion film. In the best case, the detection limits were estimated as 3 × 10−9, 6 × 10−9 and 2.4 × 10−8 mol/L for Pb(II), Cd(II) and Zn(II), respectively.