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Original scientific paper

Voltammetric Determination of Stability Constants of Lead Complexes with Vitamin C

Gina Branica
Mirjana Metikoš-Huković
Dario Omanović

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page 77-83

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Interactions between lead and ascorbic acid were investigated by polarography and voltammetry. The following techniques were applied: sampled polarography, differential pulse anodic stripping voltammetry, and square-wave voltammetry. Measurements were performed in perchlorate aqueous solutions under physiological ionic strength (0.15 mol dm–3). Electrochemical reaction of the lead(II) ascorbate complex was studied in various electrolyte compositions to find the optimal measurement conditions for determination of the corresponding stability constants ([Pb2+]= 4 ×10–7 mol dm–3, pH = 5.5; total concentration of ascorbic acid between 10–5 and 10–1 mol dm–3). Determination of stability constants of labile lead(II) ascorbate complexes was based on the DeFord-Hume methodology, and they were calculated from the dependence of the shift of PbII peak potential on the free ascorbate ion concentration. The computed stability constants were: log β1 = 9.3 ±0.2 and log β2 = 18.0±0.1.


lead, L-ascorbic acid, voltammetry, stability constants

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