Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode

Abstract

An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L⁻¹ HCl solution containing 0.02 mol L⁻¹ KI, Hg²⁺ was firstly preconcentrated at the MWNT film and then reduced at −0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about −0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I⁻ remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg²⁺ at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg²⁺ over the range 8×10⁻¹⁰–5×10⁻⁷ mol L⁻¹. The lowest detectable concentration of Hg²⁺ is 2×10⁻¹⁰ mol L⁻¹ at 5 min accumulation. The relative standard deviation (RSD) at 1×10⁻⁸ mol L⁻¹ Hg²⁺ was about 6% (n=10). By using this proposed method, Hg²⁺ in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis.