Determination of Synthetic Food Colorants in Water-Soluble Beverages Individually by HPLC and Totally by Ce(IV)-Oxidative Spectrophotometry

Food colorants are an important class of food additives that give the first impression to consumers about the quality of food. Ce(IV)-reducing antioxidant capacity assay originally developed in our laboratories was adapted to the determination of synthetic food colorants for the first time. This method allowing for total antioxidant capacity assay of dietary polyphenols, flavonoids, and ascorbic acid in plant extracts is based on the room temperature oxidation of antioxidant compounds with Ce(IV) sulfate in dilute H₂SO₄ solution and measurement of the absorbance of unreacted Ce(IV) at 320?nm. The results of the proposed method were correlated with high-performance liquid chromatography (HPLC) findings. Individual standard solutions, synthetic mixtures of synthetic colorants, and colorant extracts were identified and quantified with HPLC on a C₁₈ column equipped with a diode array detector, and slight modifications on the existing HPLC method were made to analyze synthetic colorant mixtures. This work proposes Ce(IV)-oxidative spectrophotometry as a complementary technique to HPLC in the analysis of food colorants.