Determination of some inorganic anions and heavy metals in D.O.C. Golden and Amber Marsala wines: statistical study of the influence of ageing period, colour and sugar content

The purpose of this paper was to determine the concentration of inorganic anions (chloride, nitrate, sulphate) and trace metal cations (cadmium, copper, lead, zinc) in different types of Marsala wines produced in the D.O.C. zone of Marsala (West Sicily), and to study the correlation between the content of these elements and the characteristics of the wines as the age, the colour, and the sugar content. The quantification of inorganic ions was executed by ion exchange chromatography with a conductivity detector and 8 mM phtalic acid, 2% acetonitile, pH 4 Tris buffer as the mobile phase, which allowed to separate sulphates from tartrates. Cadmium, copper, lead and zinc were simultaneously determined by derivative anodic stripping chronopotentiometry. The obtained results provided evidence that the concentrations of all the studied anions and cations were lower than the law limits. The analysis of variance (ANOVA) showed that ageing in wooden barrels has significantly influenced the concentration of inorganic ions (Cd2+,Cl-,NO3-,Pb2+,SO42-,Zn2+); these relations have been further studied using multivariate statistical methods such as the principal component analysis (PCA) and the linear discriminant analysis (LDA). Finally, in order to create the model that connects the age of the wine to the concentration of some inorganic ions a multiple linear regression analysis was used. In Marsala wines, other factors, such as the sugar content and the colour did not show any influence on the concentration of the studied inorganic elements.