Hg(II) trace electrochemical detection on gold electrode: Evidence for chloride adsorption as the responsible for the broad baseline

Abstract

Investigations were performed in order to clarify the origin of the broad baseline observed during Hg(II) trace electrochemical detection on gold electrode in the presence of Cl À anions. The influence of Cl À concentration on the shape of the voltammograms was studied in the presence and in the absence of Bovine Serum Albumin (BSA) in order to bring out adsorption/desorption processes. On the basis of these experiments, and contrary to what has been proposed by several authors in the literature, it was proved that the broad baseline does not result from calomel (Hg 2 Cl 2) formation but is rather related to an interaction between Cl À and polycrystalline Au electrode surface. The evolution of the shape of the baseline was also studied in the presence of other halide anions, namely F À , Br À , and I À. The latter two were found to induce a broad baseline similar to that recorded in the presence of Cl À. Finally, it was shown that BSA addition is not suitable for Hg(II) detection since it prevents Hg(0) deposition onto the electrode surface.

Mercury(II) trace detection by a gold nanoparticle-modified glassy carbon electrode using square-wave anodic stripping voltammetry including a chloride desorption step

“…The amperometric response towards Hg(II) was found to be dependent on AuNPs size and density [49] and was hampered by a broad baseline due to chloride anions contribution. We proved that this was rather due to Cl -adsorption onto the Au surface than to calomel formation [50], contrary to what has been reported previously in the literature [51].…”

“…Indeed, once the analytical blank subtraction operated (see Experimental Section for details), the resulting peak current (i p ) was nearly twice when using the chloride desorption step, suggesting an improved sensitivity of the AuNPs toward Hg(II). Applying a negative desorption potential also induced simultaneously a slight decrease in the broad amperometric signal observed in the potential range 0.2 -0.4 V, which was proved to result from Cl -adsorption [50]. Consequently, this additional desorption step clearly modified the overall shape of the voltammogram by reducing the broad baseline and by improving the amperometric response with respect to Hg(II) detection.…”

Highly Sensitive and Selective Detection of Arsenic Using Electrogenerated Nanotextured Gold Assemblage

“…The stripping of arsenic in HCl generates a peak in the vicinity of 0.16 V Ag/AgCl , which can be ascribed to the electrooxidation of arsenic. 46 However, an additional peak was also observed at a slightly more positive potential, thereby masking the electrochemical response from arsenic stripping at an ultralow concentration (Figure S12). This behavior was also observed previously for arsenic sensing in HCl.…”

“…SWASV response for arsenic reveals that the magnitude of the current response due to the stripping of arsenic is strongly dependent on the choice of the supporting electrolyte (Figures and S13). The stripping of arsenic in HCl generates a peak in the vicinity of 0.16 V Ag/AgCl , which can be ascribed to the electrooxidation of arsenic . However, an additional peak was also observed at a slightly more positive potential, thereby masking the electrochemical response from arsenic stripping at an ultralow concentration (Figure S12).…”

Ultrasensitive detection of mercury(ii) ions on a hybrid film of a graphene and gold nanoparticle-modified electrode

“…23,24 Gold (Au) has been classified as a privileged metal for mercury electroreduction due to the specific affinity between these two metals. 25 However, the amalgam formation will cause permanent structural damage to the bare Au electrode and affect its service time. Besides, nanosized Au particles are difficult to disperse uniformly on a bare and smooth electrode surface.…”