The effect of composition of solid silver amalgam electrodes on their electrochemical response |
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Authors: | Djenaine De Souza Lucia Helena Mascaro and Orlando Fatibello-Filho |
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Institution: | (1) Departamento de Qu?mica Anal?tica e F?sico-Qu?mica, Centro de Ci?ncias, Universidade Federal d’o Cear?, Bloco 940 Campus do Pici, 60455-970 Fortaleza, CE, Brazil;(2) Departamento de Qu?mica, Universidade Federal de S?o Carlos, Rodovia Washington Luis (SP 310) Km 235, 13565-905 S?o Carlos, S?o Paulo, Brazil |
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Abstract: | The main purpose of this work was to evaluate the effect of the silver to mercury ratio on the voltammetric responses of silver
solid amalgam electrodes (AgSAE’s). For this, the AgSAE were prepared by mechanical mixing the metals in the following mass
ratios of silver to mercury: 30/70, 40/60, 50/50, 60/40, and 70/30. The resulting AgSAE’s were physically characterized by
energy dispersive X-ray analysis, X-ray diffraction and scanning electron microscopy, confirming the mass percentages of the
silver and mercury, the total absence of liquid mercury and a globular structure of all AgSAE’s. Furthermore, it was observed
that the AgSAE 30/70 contained only one single phase (Ag2Hg3), and no metallic silver or mercury oxides. Additionally, the resulting AgSAE’s were chemically characterized with respect
to the influence of the electrode composition on the reproducibility and electrochemical signals of a hexamine-ruthenium (III)
chloride solution by use of electrochemical impedance spectroscopy and cyclic voltammetry. The separation between anodic and
cathodic peaks, and consequently, the charge transfer resistance across the electrode/solution interface, and the electroactive
area were calculated demonstrating that the 30/70 composition is the best surface for practical applications. Finally, square-wave
voltammetry experiments were performed in 4-nitrophenol solution, with a previous optimization of the experimental and voltammetric
parameters. The calculated detection limit shows that the AgSAE 30/70 is suitable for determining any contamination by p-nitrophenol, minimizing the toxic residues in case of using liquid mercury electrodes. |
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