Validation of an HPLC-UV Method for Simultaneous Analysis of Ascorbic and Oxalic Acids in Beverages

A reversed-phase high-performance liquid chromatography (RP/HPLC-UV) method was developed for the rapid and simultaneous analysis of ascorbic and oxalic acids in both industrial and freshly squeezed beverages. Due to the rapid degradation of ascorbic acid, its stability was also investigated. The analysis was performed using an Inertsil ODS-3 column with a mobile phase consisting of 0.01 mol L⁻¹ KH₂PO₄ phosphate buffer at pH 2.3. Detection wavelengths were set at 245 nm for ascorbic acid and 205 nm for oxalic acid. The limits of detection (LOD) were 1.4 mg L⁻¹ for ascorbic acid and 1.3 mg L⁻¹ for oxalic acid. After 48 hours of opening an industrial fruit juice package, an 18.5% reduction in ascorbic acid content was found. The method demonstrated within-day repeatability (n = 3) of 4.1% for ascorbic acid and 4.6% for oxalic acid. Between-day precision, expressed as relative standard deviation (RSD), was 3.85% for ascorbic acid and 4.33% for oxalic acid, based on 10 replicates (n= 10). The accuracy of the method was validated with an average recovery rate ranging from 93% to 104%.