Voltammetric Quantification of Zn and Cu, Together with Hg and Pb, Based on a Gold Microwire Electrode, in a Wider Spectrum of Surface Waters

摘要

The simultaneous determination of Zn and Cu by anodic stripping voltammetry (ASV) is prone to errors due to the formation of Cu-Zn intermetallic compounds. The main aim of this work was to study the possibility of simultaneous determination of Zn and Cu, together with Hg and Pb, using a mercury-free solid gold microwire electrode. The multi-element detection was carried out by differential pulse anodic stripping voltammetry (DPASV), in a chloride medium (0.5M NaCl) under moderate acid conditions (HCl 1.0mM) in the presence of oxygen, where the gold microwire electrode was used as stationary or vibrating working electrode during the deposition step. Under these conditions, no formation of Cu-Zn intermetallic compounds were found for concentrations usually determined in surface waters. In addition, quantification of Zn and Cu, together with Hg and Pb, can be performed in a wide range of concentrations (about two orders of magnitude) using the same sample, in a very short period of time. The detection limits for Cu, Hg, Pb and Zn, using a vibrating electrode and 30s of deposition time, were 0.2μgL~(-1) for Hg, 0.3μgL~(-1) for Pb and 0.4μgL~(-1) for Zn and Cu, respectively. The proposed DPASV methods were successfully applied to the determination of Cu, Hg, Pb, and Zn in a certified reference fresh water, river, tap and coastal sea waters. These results proved the applicability and versatility of the proposed methods for the analysis of different water matrices and showed that a gold microwire electrode is a suitable choice to determine simultaneously Zn and Cu.