Simultaneous determination of Pb and Hg at food specimens by a Melamine-based covalent organic framework modified glassy carbon electrode.

Heavy metals determination is of great importance. In this respect, a recently synthesized melamine-based covalent organic framework (Schiff base network (SNW)) was used in this research as a novel modifier to alter a glassy carbon electrode for the simultaneous anodic stripping square wave voltammetric measurement of Pb and Hg ions. At first, the complexation of SNW with Pb and Hg ions were evaluated by density functional theory calculations. Afterward, the modified electrode was characterized by various techniques including Fourier-transform infrared spectroscopy, Scanning electron microscopy, energy dispersive X-ray analysis, cyclic voltammetry, and electrochemical impedance spectroscopy. Then, all of the effective experimental factors including pH, supporting electrolyte type, and instrumental parameters were optimized. Under optimized conditions (pH = 2.0, deposition time = 150 S, accumulation potential = -1000 (mV), pulse amplitude = 40 mV, frequency = 50 Hz, and voltage step = 7 mV) the designed sensor showed a linear response over the concentration ranges of 0.01-0.3 and 0.05-0.3 µmol/L for Pb and Hg respectively with a detection limit of 0.00072 and 0.01211 µmol/L. In the end, the designed electrochemical sensor was successfully employed for simultaneous measurement of Pb and Hg at different edible samples.