Effect of supporting electrolytes on voltammetry with manual staircase voltage scan

Résumé

The minimal instrumentation voltammetry with manual staircase voltage scan allows to obtain electrochemical results with non-commercial equipment. Several researches have demonstrated its analytical and metrological validity; however, some variables have not been studied in this kind of methods, such as the effect of the supporting electrolyte on the repeatability of the voltammograms. In this paper, a study is presented about the effect of KNO₃, KCl, KClO₄, K₂SO₄ and Na₂SO₃ as supporting electrolytes on the voltammograms obtained for the oxidation of KI and succinic acid, both at 0,1 mol/L; ascorbic acid 0,01 mol/L and potassium hexacyanoferrate (II) 0,08 mol/L, all of them as an analytical model. A graphite microdisc was used as working electrode; a bar of the same material was used as the auxiliary electrode. A silver electrode was used as the reference electrode. The Analysis of Variance was the statistical tool for the comparison of the voltammetric currents. A Multiple Range Contrast by a Fisher's LSD Test was used to identify the groups with statistical differences. There were statistical differences between the currents obtained with different supporting electrolytes for all the electroactive species studied. The best voltammetric results were obtained using KCl and KNO₃ as supporting electrolytes.