Multiple standard addition with latent variables (MSALV): Application to the determination of copper in wine by using differential-pulse anodic stripping voltammetry

Abstract

MSALV, multiple standard addition with latent variables, is a new method designed to overcome the difficulties presented by the determination of an analyte in a complex sample in which equilibria exist whose displacement may alter the response of the sensors when the analyte is added in a multiple addition. MSALV has been used to quantify the Cu content in samples of wine using differential-pulse anodic stripping voltammetry (DPASV) with a mercury electrode and ethylenediaminetetraacetic acid (EDTA) and KCl as complexing agents. The existence of the EDTA-Cu(II) complex and Cu(I)-chloride complex intermediate leads to a change in the sensibility of the sensors when Cu(II) is added, which must be born in mind during construction of the multiple addition model. The use of latent variables calculated by partial least squares (PLS) provides a solution which is both quantitatively adequate and chemically interpretable. The results of four repeated determinations of Cu in samples of red wine are shown. In each case the latent variables were calculated from the intensities recorded at fifteen potentials in eight voltammograms corresponding to the successive additions of wine and/or copper.