Modulated Interactions between the Electrochemical Label and Liquor Compounds: Differentiating between Aging Times of Typical Chinese Liquors

We carried out thorough cyclic voltammetric (CV) studies to evaluate the intermolecular interactions between the electrochemical label and the liquor compounds. In the cyclic voltammograms, both the anodic and cathodic peak potential of FcCH2OH were positively shifted, resulting from the formation of hydrogen bonding between FcCH2OH and C2H5OH. Only the anodic peak potential of FcCH2OH was positively shifted, resulting from the formation of ion-pair between the oxidized form (Fc+CH2OH) and the negatively charged carboxylate (RCOO−). Combining cyclic voltammetry and gas chromatography, the result shows an evident correlation between peak potential and the content of the negatively charged ions present in the liquor (e.g., 1 mM sodium acetate with the potential shift of +40 ± 5 mV; 1 mM sodium citrate with the potential shift of +38 ± 4 mV). Further, a fast approach (total scanning time: 56 s), which is complementary to the conventional chromatographic and mass spectrographic characterizations, has been developed for differentiating aging times (1, 2, 3, 4, 5 and 10 years) of typical Chinese liquors.