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

Abstract

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 (0.5 M NaCl) under moderate acid conditions (HCl 1.0 mM) 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 30 s of deposition time, were 0.2 mg L À1 for Hg, 0.3 mg L À1 for Pb and 0.4 mg L À1 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.

Electrochemical determination of inorganic mercury and arsenic—A review

“…Hg(II) was successfully determined in tap, river and sea water with detection limit of 0.2 µg/L using 30 s deposition time and showed linearity over concentration range of 0.2-20 µg/L (Alves et al 2013). Hot gold microwave A sensitivity of 0.08 µg/L was achieved for Hg(II) detection in river water using hot gold micro-wire (Wang et al 1999).…”

Electroanalysis in environmental monitoring: Tracking trace metals—A mini review

“…An initially excellent performance of Au microwire with LOD of 6 and 25 pM for Hg and Cu in model solutions [32] was further improved by using it as a vibrating Au microwire electrode (VGME) [33]. Microwire electrodes of different sizes (5, 10 or 25 µm) were used for determination of traces of Zn, Cd, Pb, Cu, Hg, As, Sb in various environmental samples [19,[34][35][36][37]. Using VGME with optimized voltammetric procedure (LOD below 0.1 nM), Salaün et al were able to measure As(III) and Sb(III) at nM level in seawater samples [38].…”

Simultaneous Anodic Stripping Voltammetric Determination of Pb and Cd, Using a Vibrating Gold Microwire Electrode, Assisted by Chemometric Techniques

“…According to the described above, it is obvious that anodic stripping voltammetric analysis, based on gold electrodes, seems not to be the best option for the simultaneous determination of Pb and Cd. On the other hand, as it was demonstrated in our previous work 2, a gold microwire electrode is a good choice to quantify simultaneously Zn, Cu, Hg and Pb under a wide range of concentrations in different types (saline or fresh) of surface waters without the formation of Cu‐Zn intermetallic compounds. Thus, in this case, there is a great interest to explore the possibility to determine Cd together with Pb, using the previously developed analytical procedure 2, as it will allow determining simultaneously a total of five metal ions (Zn, Cu, Hg, Pb and Cd, respectively) in a single scan quickly.…”

“…On the other hand, as it was demonstrated in our previous work 2, a gold microwire electrode is a good choice to quantify simultaneously Zn, Cu, Hg and Pb under a wide range of concentrations in different types (saline or fresh) of surface waters without the formation of Cu‐Zn intermetallic compounds. Thus, in this case, there is a great interest to explore the possibility to determine Cd together with Pb, using the previously developed analytical procedure 2, as it will allow determining simultaneously a total of five metal ions (Zn, Cu, Hg, Pb and Cd, respectively) in a single scan quickly. The development of this multi‐element analysis, through the use of a non‐toxic gold microwire electrode and a simple stripping voltammetric procedure, enables a profitable work in an effective way and ensures to save material, reagents, time and energy.…”

“…We have recently reported the excellent characteristics of gold microwire electrodes for simultaneous anodic stripping voltammetric determination of Cu, Hg, Pb and As 1 or Zn 2 metal ions in surface waters. Simultaneous metals determination was achieved, without removing oxygen, through the application of a subtractive anodic stripping procedure (background correction) using an automatic, simple and quick sequence 1, 2. However, as a result of the strongly overlapped peaks, this electrode and unmodified gold electrodes 1–3 are, in general, unsuitable to determine simultaneously mixtures of Pb and Cd.…”