APPLICATION OF POTENTIOMETRIC STRIPPING ANALYSIS FOR SPECIATION OF COPPER-COMPLEXES WITH A NON-ADSORBABLE LIGAND ON A MERCURY-ELECTRODE

Potentiometric stripping analysis (PSA) was used for determination of conditional stability constants (beta') of copper(II) complexes. Glyci ne was used as a model of a non-adsorbable ligand on the mercury elect rode that forms well defined 1:1 and 1:2 copper(II)-glycine complexes, which are labile within the time scale of the analytical technique. T he calculations were performed by the DeFord-Hume method, which was ap plied to the shifts in peak potential (dt/dE vs. E) provoked by the pr esence of different concentration of the ligand in the metal solution. For comparison purposes, the study was also carried out by differenti al pulse anodic stripping voltammetry (DPASV). The results obtained by PSA both L at pH 6.0, log beta(1)' = 5.0 +/- 0.2 and log beta(2)' = 7 .6 +/- 0.2, and at pH 6.5, log beta(1)' = 5.7 +/- 0.6 and log beta(2) = 8.5 +/- 0.4 (standard deviations are given), were in agreement with those obtained by DPASV and from the literature, which indicates that PSA is suitable for this type of study.