Determination of Preservative Benzoic Acid by Catalytic Oxidation Fluorometry

Based on the catalytic effect of cobalt (II) on the oxidation of benzoic acid by potassium bromate in NaH2PO4Na2HPO4 buffer solution at the condition of pH 8, a new catalytic oxidation fluorometry method was proposed for the indirect determination of benzoic acid. Under optimal determination conditions, an excellent linear relationship between benzoic acid concentration within a range of 5 × 10-7 3 × 10-5 g/mL and fluorescence intensity was observed. The detection limit of this established method was 2×10-8 g/mL. The reproducibility experiments revealed the relative standard deviation (RSD) of 1.9% for benzoic acid solution at the concentration of 1 × 10-6 g/mL. This established method has been applied for the detection of benzoic acid in vinegar and sauce. The recovery rates were in the range of 95.7% 101.6% with satisfactory results.