Simultaneous electrochemical sensing of heavy metal ions (Zn2+, Cd2+, Pb2+, and Hg2+) in food samples using a covalent organic framework/carbon black modified glassy carbon electrode

•The COF was synthesized by a mild and facile modification method.•CB-COF/GCE was used to detect Zn2+, Cd2+, Pb2+, and Hg2+ for the first time.•The modified GCE shows satisfactory performance in the analysis of ions by DPASV.•The sensor was employed to determine Zn2+, Cd2+, Pb2+, and Hg2+ in food samples.•To validate, a comparison of the electroanalytical method versus AAS was made. In this study, for the first time, a selective electrochemical sensor by glassy carbon electrode (GCE) modified with the covalent organic framework (COF) and carbon black (CB) was introduced and applied to simultaneous sensing of Zn2+, Cd2+, Pb2+, and Hg2+ via differential pulse anodic stripping voltammetry (DPASV). The COF is supplied through a condensation reaction between melamine and trimesic acid. The COF and CB, which are used to modify the GCE surface, increase electrochemical activity. The linearity to determine ions was achieved as Zn2+: 0.009–1100 nM, Cd2+: 0.005–1100 nM, Pb2+: 0.003–1100 nM, and Hg2+: 0.001–1100 nM. Besides, the detection limits for Zn2+, Cd2+, Pb2+, and Hg2+ have obtained 0.003, 0.002, 0.001 and 0.0003 nM, respectively. The CB-COF/GCE was applied to simultaneously measure the ions in food samples. For validation, atomic absorption spectrometry (AAS) was applied to measure the amount of target metal ions as a standard method in real samples.