Potentiometric stripping analysis vs. differential pulse anodic stripping voltammetry for copper(II) analysis at relatively positive deposition potential

Abstract

A comparative study of potentiometric stripping analysis (PSA) and differential pulse anodic stripping voltammetry (DPASV) for copper analysis at relatively positive deposition potential, E d = −0.3 V vs. Ag AgCl(s) , 3 mol/l KCl, was carried out both in 0.01 mol/l KNO 3, pH 6.5, and in a saline water (ionic strength ca. 0.5 mol/l, pH 7.5). A deposition time of 3 min was used. When a static mercury drop electrode was used as working electrode, PSA allowed determinations of copper in both media with the following limits of detection (LOD): 0.15 μmol/l, for 0.01 M KNO 3, and 0.28 μmol/l for saline water. DPASV allowed copper determination in 0.01 M KNO 3 with LOD = 0.18 μmol/l, but not in the saline water, because the baseline was not well-defined. When a thin mercury film was used as the working electrode, the DPASV defection capability improved markedly in 0.01 M KNO 3, LOD = 0.018 μmol/l, but the determination of copper in the saline water was still unfeasible at E d = − 0.3 V. These results indicate that PSA can be applied to copper analysis in saline waters at more positive deposition potentials than DPASV, but the LOD of PSA was too high to allow copper speciation in natural waters. In addition, it was verified that the presence in the solution of organic matter (humic acids 0.12 or 0.30 mg C/l), adsorbable at the working electrode, had no effect on the PSA signal, but markedly interfered in the DPASV response.