Electrochemical sensor based on a thin film of organokaolinite material modified glassy carbon electrode (GCE) and application to the simultaneous sensitive detection of Pb2+ and Cu2+ ions in contaminated water

A pure natural kaolinite (K) was modified by intercalation and grafting into the interlayer space of 1-(2-hydroxyethyl)piperazine (HEP). The resulting organo-inorganic hybrid material (referred as KHEP) was characterised using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and 29Si nuclear magnetic resonance (NMR) techniques. The electrochemical characterisation of K and KHEP materials was carried out by studying the electrochemical behaviour using cyclic voltammetry of [Fe(CN)6]3− ions on the surface of a glassy carbon electrode (GCE) modified with a film of each of these materials (GCE/K and GCE/KHEP). The GCE/KHEP organokaolinite film electrode was successfully applied for the simultaneous detection of Pb(II) and Cu(II) in contaminated media. The peak currents of Pb(II) and Cu(II) obtained under the same optimal conditions on GCE/KHEP were much more intense than those obtained on GCE/K and bare GCE. Under optimal conditions, the influence of the concentration of Cu2+ and Pb2+ ions on the peak currents was studied for several concentration ranges. The obtained linear calibration curves were then used to calculate the different limits of detection (LOD) on the basis of a signal-to-noise ratio of 3. Thus, in simultaneous detection and for the concentration range from 0.02 to 0.12 µmol L−1 (pH accumulation medium 5.0) and for each of the ions analysed, LODs of 1.942 nmol L−1 for Cu(II) and a LOD of 1.072 nmol L−1 for Pb(II) were obtained. The GCE/KHEP sensor developed in this work was successfully applied for the simultaneous detection of Pb(II) and Cu(II) in real samples. ASSWV signal corresponding to the simultaneous detection of Pb2+ and Cu2+ ions recorded on unmodified GCE (black curve), GCE/K; (red curve) and GCE/KHEP (blue curve) in 0.2 mol L−1 NaNO3 (with pH adjusted at 2.5) after 7 min of accumulation in aqueous medium (pH 5.0) of each ion at the concentration at 2.0 µmol L−1. Other experimental conditions are as follows: telec: 80 s, Eelec: − 0.90 V, Potential amplitude: 0.05 V, Step potential (V): 0.005 V and Frequency: 50 Hz.