Simultaneous determination of Pb²⁺ and Hg²⁺ at food specimens by a Melamine-based covalent organic framework modified...

Heavy metals determination is of great importance. In this respect, a recently synthesized melamine-based covalent organic framework (Schiff base network₁ (SNW₁)) 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 Pb²⁺ and Hg²⁺ ions. At first, the complexation of SNW₁ with Pb²⁺ and Hg²⁺ 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 Pb²⁺ and Hg²⁺ 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 Pb²⁺ and Hg²⁺ at different edible samples.