Characterization and theoretical studies of synthesized (E)-2((3-methylbenzilidene) amino) phenol complexes for the fabrication of novel electrochemical sensor for determination of Pb²⁺ and Hg²⁺ ions

A Schiff base (E)-2((3-methylbenzilidene) amino) phenol (EMBAP)/multi-walled carbon nanotube modified carbon paste electrode was applied to the selective and accurate determination of Hg²⁺ and Pb²⁺ ions by voltammetric methods. The morphology of electrodes surface was characterized, and a density functional theory (DFT) based on the interaction of target ions with EMBAP was investigated. The theoretical binding energies, entropies, free energies and formation constants were calculated. The results indicated that complexes are stable, and formation is spontaneous. The synergistic advantages of EMBAP and MWNTs caused higher sensitivity, fast electron transfer, well reproducibility, long time stability, and well anti-interference capability. The theoretical studies showed that the most important interaction is the electron-donating O lone pair to the contacting LP* of metal ions. Under optimum conditions, the peak current was linear in 0.1–200 μmol L⁻¹ and 0.1–250 μmol L⁻¹ concentration of Hg²⁺ and Pb²⁺ with limits of detection (S/N = 3) of 28 nmol L⁻¹ and 41 nmol L⁻¹ for Hg²⁺ and Pb²⁺, respectively. The current method was applied for the simultaneous determination of Hg²⁺ and Pb²⁺ in algae samples with comparable accuracy and precision respect to reference methods.