Thiacalix[4]arene-based complex with Co(II) ions as electrode modifier for simultaneous electrochemical determination of Cd(II), Pb(II), and Cu(II)

Abstract

A complex [Co₄(TCTA)₂(H₂O)₈]∙10H₂O (Co-TCTA) based on thiacalix[4]arene derivative has been synthesized for the first time using the solvothermal method. The glassy carbon electrode (GCE) modified with Co-TCTA (Co-TCTA/GCE) could simultaneously determine Cd²⁺, Pb²⁺, and Cu²⁺ at around - 0.75 V, - 0.60 V, and - 0.10 V (vs. ref. Ag/AgCl) and had good stability, selectivity, and reproducibility with relative standard deviation (RSD) of 4.4% for Cd²⁺, 1.4% for Pb²⁺, and 5.4% for Cu²⁺. Co-TCTA/GCE showed wide linear range of 0.4-8.0 μM for Cd²⁺, 0.4-7.0 μM for Pb²⁺, and 0.6-6.0 μM for Cu²⁺ when three ions were determined simultaneously. The limits of detection (LODs) of Cd²⁺, Pb²⁺, and Cu²⁺ were 0.071 μM, 0.022 μM, and 0.021 μM, respectively. Moreover, the sensor was used to determine three ions in lake water sample with satisfactory recoveries of 93.6-93.8% for Cd²⁺, 93.8-103.3% for Pb²⁺ and 94.6-95.3% for Cu²⁺. The good adsorption capacity of Co-TCTA and Co(II)/Co(0) circular mechanism on the surface of the electrode were proposed to enhance the electrochemical signals. This work enriched the theoretical research on the complexes for the determination of heavy metal ions.

Keywords: Co(II)/Co(0) circular mechanism; Electrochemical sensor; Heavy metal ions; Thiacalix[4]arene-based complex.