Voltammetric Determination of Hg²⁺, Zn²⁺, and Pb²⁺ Ions Using a PEDOT/NTA-Modified Electrode

A novel electrochemical sensor for determining trace levels of Hg²⁺, Pb²⁺, and Zn²⁺ ions in water using square wave voltammetry (SWV) is reported. The sensor is based on a platinum electrode (Pt) modified by poly(3,4-ethylenedioxythiophene) and N _α,N _α-bis-(carboxymethyl)-l-lysine hydrate (NTA lysine) PEDOT/NTA. The modified electrode surface (PEDOT/NTA) was prepared via the introduction of the lysine-NTA group to a PEDOT/N-hydroxyphthalimide NHP electrode. The (PEDOT/NTA) was characterized via cyclic voltammetry (CV), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The effects of scan rates on the electrochemical properties of the polymer electrode were also investigated. The electrochemical results were used to estimate the coverage of the electrode polymer surface and its electrostability in background electrolyte solutions. Several analytical parameters, such as polymer film thickness, metal deposition time, and pH of the electrolyte, were examined. Linear responses to Hg²⁺, Pb²⁺, and Zn²⁺ ions in the concentration range of 5-100 μg L^-1 were obtained. The limits of detection (LODs) for the determination of Hg²⁺, Pb²⁺, and Zn²⁺ ions were 1.73, 2.33, and 1.99 μg L^-1, respectively. These promising results revealed that modified PEDOT/NTA films might well represent an important addition to existing electrochemical sensor technologies.