Nafion-Graphene Nanocomposite in situ Plated Bismuth-film Electrodes on Pencil Graphite Substrates for the Determination of Trace Heavy Metals by Anodic Stripping Voltammetry

Abstract

The use of disposable and inexpensive pencil graphite rods, modified with a Nafion-graphene nanocomposite, in conjunction with an in situ plated bismuth-film is reported as electrochemical sensor for the determination of trace amounts of Zn2+, Cd2+ and Pb2+ in tap water samples. Synthesised graphene was characterised using electron microscopy, FTIR and Raman spectroscopy. The Nafion- graphene nanocomposite pencil graphite bismuth-film electrode (NG-PG-BiE) exhibited superior detection capabilities as a result of increased surface area, electron conductivity and binding properties of the NG-Bi film. The instrumental parameters associated with the simultaneous determination of target metals namely, bismuth-film concentration, deposition potential, deposition time and rotation speed were investigated and optimized. Relative standard deviation (RSD %) for the oxidation peaks were calculated to be within the 1.5 - 3.3 % range of for all three target metal ions. The NG-PG-BiE showed detection limits of 0.17 μg L-1, 0.09 μg L-1 and 0.13 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively, at a deposition time of 120 seconds. Finally, the electroanalytical sensor was successfully applied towards the determination of target metal ions in tap water samples below the USEPA standards of 5 mg L-1, 5 μg L-1 and 15 μg L-1 for Zn2+, Cd2+ and Pb2+ respectively.