Bismuth film electrodes for heavy metals determination

Abstract

Bismuth film electrodes (BiFEs) have a potential to replace toxic mercury used most frequently for determination of heavy metals (Cd, Pb, Zn) by anodic stripping voltammetry. We prepared a graphite disc electrode (0.5 mm in diameter) from a pencil-lead rod and developed a nitrogen doped diamond-like carbon (NDLC) microelectrode array consisting of 50 625 microdiscs with 3 &mgr;m in diameter and interelectrode distances of 20 &mgr;m on a highly conductive silicon substrate as a support for BiFEs. The disc graphite BiFE was used for simultaneous determination of Pb(II), Cd(II) and Zn(II) by square wave voltammetry (SWV) in an aqueous solution. We found the optimum bismuth-to-metal concentration ratio in the solution to be 20. The dependence of the stripping responses on the concentration of target metals was linear in the range from 1×10^-8 to 1.2×10^-7 mol/L. Detection limits 2.4×10^-9 mol/L for Pb(II), 2.9×10^-9 mol/L for Cd(II) and 1.2×10^-8 mol/L for Zn(II) were estimated. A bismuth-plated NDLC microelectrode array was used for Pb(II) determination by differential pulse voltammetry (DPV) in an aqueous solution. We found that the stripping current for bismuth-plated NDLC array was linear in the concentration range of Pb(II) from 2×10^-8 to 1.2×10^-7 mol/L. The detection limit 2.2×10^-8 mol/L was estimated from a calibration plot.