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

A complex [Co(TCTA)(HO)]∙10HO (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 Cd, Pb, and Cu 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 Cd, 1.4% for Pb, and 5.4% for Cu. Co-TCTA/GCE showed wide linear range of 0.4-8.0 μM for Cd, 0.4-7.0 μM for Pb, and 0.6-6.0 μM for Cu when three ions were determined simultaneously. The limits of detection (LODs) of Cd, Pb, and Cu 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 Cd, 93.8-103.3% for Pb and 94.6-95.3% for Cu. 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.