Quantitative Determination of Acetic Acid and Ethanol in Vinegar Using Proton Nuclear Magnetic Resonance

This study explores the application of proton nuclear magnetic resonance (1H NMR) spectroscopy for the simultaneous determination of acetic acid and ethanol concentrations in commercial vinegar samples, eliminating the need for prior separation procedures. The method demonstrated an average error of 10.53% for acetic acid and between 3.63 and 5.68% for ethanol, depending on the spectral peak analyzed. Inter-day analysis over a week yielded average relative standard deviations of 0.81% for acetic acid and 1.53 to 2.36% for ethanol, indicating high precision. Notably, the results revealed significant adulteration in the vinegar industry, with only 5 out of 12 samples meeting acceptable acetic acid concentrations (5–8%), while nearly half of the samples contained ethanol levels exceeding the maximum allowable concentration. This study underscores the efficacy of 1H NMR spectroscopy as a reliable technique for quality control in vinegar analysis.