Voltammetric detection of copper(II) at a carbon paste electrode containing an organically modified silica

Abstract

A carbon paste electrode modified with aminopropyl-grafted silica gel (APS) was evaluated as an electrochemical sensor for copper species in aqueous medium. The overall analysis involved a two-step procedure: an accumulation step at open circuit, followed by medium exchange to a pure electrolyte solution for the voltammetric quantification. During the preconcentration step, copper(II) was accumulated on the APS surface by complexation with the amine groups. In the detection step, copper(II) was desorbed in acidic medium, then cathodically electrolyzed at −0.5 V for 60 s, and detected by anodic stripping square wave voltammetry. The influence of various experimental parameters on the sensor response was investigated (i.e. pH of the detection and accumulation media, electrolysis time, carbon paste composition, silica gel porosity, accumulation time). Reproducible results were obtained, giving after optimization a linear calibration in the 5×10 −8–2×10 −7 M concentration range, with a detection limit of 3×10 −9 M. This new sensor was applied to copper analysis in laboratory tap water.