Determination of the total acid content in wine based on the voltammetric reduction of quinone

Voltammetric determination of the total acid content of wine was made by me asuring the reduction prepeak current of 3,5-di-t-butyl-1,2-benzoquinone (D BBQ) due to the presence of acids in unbuffered ethanol medium. DBBQ was fo und to be a suitable quinone reagent for this determination with respect to its reduction potential, stability, and solubility in ethanol containing o rganic acids. On the voltammogram of DBBQ obtained with organic acids such as tartaric, citric. and malic acids. using a beaker-type cell and a plasti c formed carbon working electrode, a well-defined single prepeak appeared w hose height was proportional to the total acid concentration. at 0.1 V (vs. a saturated calomel electrode. SCE) during the cathodic potential scan. Th e values of the total acid content of 23 wine samples determined by the pre sent method were compared with those of titratable acidity obtained by the conventional potentiometric titration method. A good correlation was obtain ed between the results by both methods with a correlation coefficient of 0. 966. The present method is superior in sensitivity and requires only one tw entieth the volume of wine sample compared to the titration method.