Automated High Performance Liquid Chromatographic Determination of Intermediates and Side Reaction Products in FD&C Red No. 3

Abstract

Abstract A rapid, sensitive, reproducible method that uses high performance liquid chromatography in the reverse phase mode is described for the determination of intermediates and side reaction products in FD&C Red No. 3. With this method, 2 intermediates, phthalic acid and resorcinol, and 2 side reaction products, 2-(2',4'-dihydroxybenzoyl)benzoic acid and 2-(2',4'-dihydroxy-3',5'-diiodobenzoyl)benzoic acid, are eluted in a reproducible pattern as a gradient increases the organic nature of the buffered mobile phase. Fhthalic acid and the 2 side reaction products are quantitated. The intermediate resorcinol is detected but not quantitated. Recoveries averaged 99.4-102.8% for phthalic acid and the 2 side reaction products added to samples of FD&C Red No. 3 at levels ranging from 0.02 to 0.22%.