Determination of free metal ion concentrations using screen-printed electrodes and AGNES with the charge as response function

Abstract

AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) has been implemented with screen-printed electrodes (SPE) for the determination of the free concentration of Zn2+, Cd2+ and Pb2+. For SPE, the stripped charge is a suitable response function which does not require the second stage of AGNES to be under diffusion limited conditions. This property can be used in the avoiding of the interference of Pb on [Cd2+] determination. The proportionality factor between stripped charge and concentration of amalgamated metal depends on the volume of mercury and opens the way to a future calibrationless strategy. Zn and Cd complexation with oxalate at various pH-values confirms the suitability of the developed methodology, which compares favourable with the standard one based on the Hanging Mercury Drop Electrode.

The authors acknowledge support of this research from the Communauté d'Agglomération de Pau Pyrénées (CDAPP), from the Spanish Ministerio de Ciencia e Innovación (CTQ2009-07831 and CTQ2009-14612), from the European Community EFA15/08 (PyrMet) and from the Comissionat d’Universitats i Recerca de la Generalitat de Catalunya (2009SGR00465).