Simultaneous amperometric determination of malic and gluconic acids in wine using screen-printed carbon electrodes

The selective and simultaneous amperometric determination of malic and gluconic acids was carried out using a screen-printed design with two working carbon electrodes. One of the two working electrodes was modified with gold nanoparticles, tetrathiafulvalene (TTF) and malate quinone oxido-reductase enzyme for the sensitive detection of malic acid. Analogously, the other working electrode was modified with TTF and gluconate dehydrogenase enzyme for the sensitive detection of gluconic acid. The array of biosensors responds to gluconic and malic acids giving each anodic currents (+100 mV and pH 6.5), with detection capabilities of 1.89 μM (α = β = 0.05) and 0.79 μM to malic and gluconic acids, respectively, at room temperature. The method has been applied to the determination of both analytes in wine, obtaining successful results.