Simultaneous determination and speciation of zinc, cadmium, lead, and copper in natural water with minimum handling and artifacts, by voltammetry on a gel-integrated microelectrode array

The paper reports a new approach based on a gel-integrated Hg-plated-Ir-bas ed microelectrode array (GIME), for measuring Cu, Pb, Cd, and Zn speciation fin natural waters. This paper focuses on the quantitative discrimination between mobile and colloidal metal species (size limit of a few nanometers) , for which most classical separation techniques present severe drawbacks. Previous papers have shown qualitatively that GIME combined with square wav e anodic stripping voltammetry (SWASV) has the basic characteristics requir ed to discriminate between these two fractions directly on the unperturbed sample. In addition, because of the large sensitivity provided by GIME, com plexation parameters (equilibrium constants and site concentrations) can be determined in little-perturbed samples, particularly without metal additio n or with small addition compared with natural concentrations. The advantag es of this procedure are exemplified and the possible artifacts occurring w hen titrating the sample with metals, in particular intermetallic compound formation and other problems, are discussed in detail. The present paper sh ows that the characteristics of GIME make it a unique tool to get quantitat ive information on metal speciation at nanomolar or even subnanomolar Bevel s, with only minor sample handling.