Selective monitoring of Cu(II) species using a silica modified carbon paste electrode Original Research Article

The incorporation of silica particles within carbon paste leads to improved amperometric detection of copper(II) in ammoniacal medium. The enhanced sensitivity was attributed to the accumulation of copper(II) by adsorption on the ionised surface silanol groups of silica. The sensor was found to be highly selective to copper(II) with respect to alkali and alkaline earth metal cations and transition metal–ammonia complex species. The improved selectivity was explained by the strong silanolate–copper interactions, leading to appreciable accumulation even in high ionic strength media, as ascertained by measurements performed in synthetic ground and sea waters. Moreover, cyclic voltammetry using the silica modified carbon paste electrode was applied to the in situ investigation of copper(II) sorption processes on silica. Various silica-based materials were used to shed useful insights into these sorption processes, in relation to their capacity for copper(II) as well as their specific surface area and porosity.