Electrochemical detection of copper(II) at an electrode modified by a carnosine - Silica hybrid material

Abstract

A new solid-phase extractant based on carnosine moieties covalently attached to a silica backbone (S-Car) was introduced into a carbon paste electrode (CPE), and the resulting modified electrode (S-Car-MCPE) was applied to the preconcentration and subsequent voltammetric quantification of copper(II). The electrode modifier was a solid organic-inorganic hybrid prepared by co-condensation of tetraethoxysilane with an organotri-ethoxysilane containing a carnosine dipeptide (β-alanyl-1-histidine) derivative. This hybrid material has propensity for binding CuII species from aqueous solutions. The basic voltammetric characterization of S-Car-MCPE, previously loaded with CuII, indicates clearly that its electrochemical activity requires desorption of the analyte out of the solid material prior to undergoing charge transfer. A two-step analytical procedure was then applied, involving the sequence "accumulation at open-circuit - voltammetric detection by anodic stripping differential pulse voltammetry". Both these steps have been optimized with respect to various experimental parameters (electrode composition, pH and composition of both detection and accumulation media, preconcentration time, detection mode, presence of interference). Linear response to copper(II) was found in the 5 × 10-8 M to 10-6 M concentration range, with a detection limit estimated at 4 × 10-9 M (0.06 ppb). This new immobilization approach for peptide-based materials on electrode surfaces is promising for further developments of organic-inorganic hybrids in electroanalysis.