A modified hybrid silsesquioxane/histidine composite for copper and zinc adsorption and it behavior in the electro-oxidation of ascorbic acid.

Octa-(3-chloropropryl)silsesquioxane was chemically modified with histidine (SSQ-H) and characterized by spectroscopy in the infrared region (FT-IR), X-ray diffraction (XRD), X-ray Dispersive Energy Spectroscopy (EDX), Scanning Electron Microscopy (SEM). The analytical properties of SSQ-H were tested regarding of Cu2+ and Zn2+ adsorption and as an electrochemical sensor for the detection of ascorbic acid. The metal sorption results indicate that maximum amount of Cu2+ and Zn2+ adsorbed (Nfmax) were 1.58 × 10-3 and 5.67 × 10-4 mol g-1, respectively. After Cu2+ and Zn2+ ion adsorption and interaction with potassium hexacyanoferrate (III), the investigated materials displayed electroactivity for ascorbic acid detection. The anodic peak currents responses of a graphite paste electrode containing CuHCFSSQ-H presented a linear response in the concentration range of 4.0 × 10-4 to 4.0 × 10-3 mol L-1 for ascorbic acid detection. The limit of detection was of 2.99 × 10-4 mol L-1, with an amperometric sensitivity of 1.69 μA/mol L-1. The intensity of the anodic peak currents of the graphite paste electrode containing ZnHCFSSQ-H in the concentration range of 9.0 × 10-5 to 9.0 × 10-4 mol L-1 also displayed a linear response. The limit of detection was of 6.76 × 10-5 mol L-1, with an amperometric sensitivity of 0.0206 A/mol L-1.