Application of carbon sensors for potentiometric determination of copper(II) in water and biological fluids of Wilson disease patients. Studying the surface reaction using SEM, EDX, IR and DFT

The performance characteristics of a new selective and sensitive modified screen printed electrode (MSPE; electrode I) and carbon paste electrode (MCPE; electrode II) based on 2-N, N-dimethylcarbamimidoyl (metformin) as modifier for the potentiometric determination of copper (II) in water sample, serum and urine samples of Wilson disease patients have been optimized. The chemical reaction which happens between Cu (II) and the modifier on the surface of the sensors was investigated with scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), IR spectra measurement and computational calculations at DFT/B3LYP. The sensors showed perfect potentiometric response for Cu (II) over concentration range of 1.0 × 10−6 - 1.0 × 10−2 and 1.0 × 10−6 - 5.0 × 10−2 mol L−1 with a detection limit of 1.0 × 10−6 mol L−1with divalent slope value 30.2 and 31.8 mV decade−1 over the pH range of 2-6 for MCPE and MSPE, respectively. MSPE was stable with repeatable potential over period of 37 days and exhibits fast response time of 6 and 10 s for MSPE and MCPE, respectively. Also, these sensors exhibited good selectivity towards Cu(II) with respect to other metal ions and have higher antibacterial activity against Staphylococcus aureus as Gram-positive bacteria and Escherichia coli as Gram-negative bacteria. The obtained results using the sensors were in agreement with those obtained using the reported method.