A Green Approach to Multi-Element Analysis of Vinegars by ICP-OES Using Diluted Acid Digestion

Vinegar is a widely used condiment, consisting essentially of acetic acid and water. This study developed a microwave-assisted digestion method using diluted nitric acid and hydrogen peroxide to determine Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Zn in various vinegars by ICP-OES, and K and Na by flame photometry. Sixteen vinegar samples (alcohol, balsamic, apple, and red wine) were analyzed. A 2³ factorial design optimized the digestion procedure, yielding the best conditions with 1.0 g of sample, 7 mL of 0.3 mol L⁻¹ nitric acid, and 1 mL H₂O₂, for 45 min at 200 °C. Detection limits ranged from 0.015 to 10.5 µg g⁻¹. PCA explained 90% of data variance, revealing that balsamic vinegars had higher concentrations of Cu, K, and Zn, distinguishing them from alcohol and wine vinegars.