Thiol-based chemically modified carbon screen-printed electrode for simultaneous quantification of trace level Pb(II) and Cd(II)

Present work reports, the development of a novel electrochemical sensor based on a diazonium-coupling reaction and covalent attachment of the –NH₂ group of cysteamine (Cyst) on screen-printed carbon electrode (SPCE), for simultaneous determination of Pb(II) and Cd(II). Initially, the in-situ generated 4-carboxyphenyl (4-CP) diazonium salt was electro-grafted to generate 4-CP/SPCE, followed by covalent bonding of terminal carboxylic group of 4-CP with –NH₂ group of Cyst to give Cyst/4-CP/SPCE. The modified electrode showed an enhanced selectivity and sensitivity toward the quantification of Pb(II) and Cd(II) using square wave anodic stripping voltammetry (SWASV) without mutual interference. Under optimal experimental conditions, the newly designed sensor showed a wide linear range of 0.01 µM to 0.7 µM. The limit of detection (LOD) obtained was 0.882 nM (0.09 ppb) and 0.65 nM (0.134 ppb) for Cd(II) and Pb(II), respectively. The modified SPCE exhibited good stability, selectivity, and reproducibility. Furthermore, the sensor was successfully applied for the determination of Pb(II) and Cd(II) ions in water samples which illustrated excellent recoveries in different spiked samples and the results were in line with the standard ICP-AES analysis.

A thiol-based disposable electrochemical sensor was developed via electro grafting of diazonium salt on SPCE followed by covalent immobilization of cysteamine for quantification of Pb(II) and Cd(II) in water samples.