Determination of Lead and Copper in Wine by Anodic Stripping Voltammetry With Mercury Microelectrodes: Assessment of the Influence of Sample Pretreatment Procedures

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Abstract
The results obtained using different pretreatment procedures for determining total lead and copper in wine by anodic stripping voltammetry were compared. The measurements were performed by employing mercury microelectrodes as the working electrode and linear sweep voltammetry as the voltammetric technique in the oxidation step. The pretreatments considered were (A) wine plus concentrated HCl to pH 1.5; (B) wine plus 30% m/m H 2 O 2 (2.5:1 v/v) and UV irradiation for 2 h; and (C) wine plus concentrated HCl to pH 1.5 and UV irradiation for 4 h. The three procedures gave different results, and the efficiency of the different procedures in releasing the cations from inorganic and organic complexes can be ranked as B > C > A. Moreover, data obtained with procedure B agreed within 15% with the values found by AAS measurements. For the quantification of the metal ions, both the multiple standard addition method, based on current or charge versus concentration graphs, and an absolute method, based on the charge involved in the stripping peak, were employed. The latter procedure allowed measurements to be carried out even when the calibration plots were not linear. When all the quantitative methods could be applied, data agreement within 5% was found.

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