Determination of Acetic Acid in Vinegar Using High-Performance Liquid Chromatography with Fluorescence Detection

Abstract

Acetic acid is a major organic acid in vinegar, and monitoring its concentration during fermentation is important for process control and quality assessment. However, high-performance liquid chromatography (HPLC) with ultraviolet detection is often affected by interference from coexisting components. In this study, an HPLC with fluorescence detection (HPLC-FLD) method was developed for the determination of acetic acid in vinegar. Acetic acid was derivatized with 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ), a fluorescence derivatization reagent that reacts with carboxy groups. A weakly alkaline reaction medium was selected for the derivatization, and the mobile phase composition was optimized to achieve sufficient chromatographic separation from coexisting compounds. The developed method showed sufficient linearity (r² > 0.999), precision (RSD ≤ 11.0 %), and accuracy (recovery: 94.6–113.7 %). The method was successfully applied to the determination of acetic acid in commercial vinegar, yielding a concentration of 158.0 ± 9.2 mM. The satisfactory analytical performance is attributed to the high selectivity of fluorescence detection for NBD-PZ-labeled compounds and the enhanced chromatographic retention of the derivatized acetic acid under reversed-phase chromatographic conditions, which reduced interference from coexisting components. This method provides an alternative analytical approach for the determination of acetic acid in vinegar by HPLC-FLD.