Preliminary estimates of lactic and malic acid in wine using electrodes printed from inks containing sol–gel precursors

Two enzymes, lactate oxidase and malate dehydrogenase, were used in the construction of working electrodes for the amperometric determination of lactic and malic acid in wine. Preparation of the enzyme matrices had to satisfy two technologies: thick-film printing and sol–gels. The matrices were thus complex printing inks, consisting principally of gel precursors, graphite, cellulosic binder and enzyme. After mixing, the inks were printed before gel formation. The electrodes responded to standard solutions of lactic and malic acids. In combination with the method of standard addition, the electrodes were able to provide estimates of the concentrations of lactic and malic acids in some white wines.