engleski

Research of interactions between lead and ascorbic acid in aqueous solutions by voltammetry

Interactions between lead and ascorbic acid were investigated by polarography and voltammetry. Applied techniques were: sampled polarography, differential pulse anodic stripping voltammetry, cyclic voltammetry and square-wave voltammetry. The measurements were performed in perchlorate aqueous solutions under physiological ionic strength 0.15 mol/L. The system is electrochemically reversible (without adsorption effects or interactions of other lead complexes e.g. hydroxides) under following conditions: [Pb2+] = 4×10-7 mol/L and pH = 5.5. Ascorbic acid was gradually added in the concentration range between 10-5 and 10-1 mol/L. After each increment the signal of lead was recorded by square wave voltammetry. Stability constants were computed from the data obtained (free ascorbinat concentration, shift of peak potential) by applying a non-linear regression of the DeFord-Hume F0 function after Levenberg-Marquardt fit implemented in the software Sigma Plot. Computations of the apparent stability constants, under the assumption of a series of mononuclear complexes (MLn, n = 1, 2...) yielded the values for lead ascorbinato complexes: logβ 1 = 9.3 and logβ 2 = 18.0.

C-vitamine; lead; voltammetry

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