Voltammetric behaviour at gold electrodes immersed in the bcr sequential extraction scheme media aplication o underpotential deposition-stripping voltammetry to determination of copper in soil extracts

摘要

The development of mercury-free electroanalytical systems for in-field analysis of pollutants reguires a foundation on the electrochemical behaviur of the chosen electrode naterial in the target sample materies,in this work,the vehaviour of gold working electrodes in the media employed in the bcr sequential extraction protocol,for the fractionation of metals in solid environmental matrices,is reported.All three of the BCR sequential extractin media are redox active,on the basis of acidity and oxygen content as well as the inherent reducting or oxidsing nature of some of the reagents comployed:0.11 M acetic acid,0.1 M hydrocylammonium chloride (adjusted to pH 2) and 1M ammonium acetate (adjusted to pH 2)with added trace hydrogen perixide.The available potential ranges to gether with the demonstrated detectin of target metals in these media are presented.Stripping voltammetry of coppor or lead in the BCR extract media solutions reveal a multi-peak behaviour due to the stripping of both bulk methal and underpotential metal deposits.A precedure based on underpotential deposition-stripping voltammetry (UPD-SV)was evaluated for application ot determinatin of copper in 0.11 m acetic acid soil extracts.A preliminary screening step in which diferent deposition times are applied to the sample enables a deposition time commensurate with upd-sv to be selected so that on bulk deposition or stripping ocdurs thus simplifying the shape and features of the resulting voltammograms.Choice of the suitable deposition time is then followed by standards addition calibration.The method was validated by the analysis of a number of BCR 0.11 M acetic acid soil extracts.Good agreement was obtained been the upd-sv method and atomic spectroscopic results.