The voltammetric behaviour of lead at a hand drawn pencil electrode and its trace determination in water by stripping voltammetry

Abstract

This is the first reported proof of concept application of pencil drawn electrodes (PDEs) for anodic stripping voltammetric determination of Pb²⁺ or any metal ion. PDEs offer advantages of economics, simplicity and rapid fabrication, affording a green alternative for the development of new devices. Cyclic voltammetric investigations of Pb²⁺ at these electrodes in 0.30 M acetic acid were characterised by a cathodic reduction peak on the initial negative scan resulting from the reduction of Pb²⁺ ions to Pb⁰. Anodic peaks obtained on the return positive scan showed that Pb had been deposited as a thin film on the PDE surface. The addition of Cl⁻ ions to this electrolyte improved the voltammetric behaviour and a supporting electrolyte of 0.30 M acetic acid containing 0.25 M KCl was found to be optimum. Investigations were made into the possibility of determining trace levels of Pb²⁺ by differential pulse anodic stripping voltammetry. The effect of accumulation potential and time were investigated and optimised. Three anodic stripping peaks were recorded resulting from the heterogeneous nature of the electrode surface. Using an accumulation potential of −1.1 V and an accumulation time of 200 s a bimodal calibration curve was recorded, with linear ranges between 80 to 330 ng mL⁻¹ and 330 to 915 ng mL⁻¹. The theoretical detection limit (3σ) was calculated as 9.5 ng mL⁻¹. Pb²⁺ determinations on a drainage water sample gave a mean recovery of 100.9% (CV% = 5.7%) at a concentration of 166.1 ng mL⁻¹ indicating the method holds promise for the determination of Pb²⁺ in such samples.