Determination of 2,4,6-triiodoresorcinol and other side reaction products and intermediates in the colour additive FD&C Red No. 3 (erythrosine) using high-performance liquid chromatography.

An HPLC method was developed for the quantitative determination of 2,4,6-triiodoresorcinol (I3R), 2-(2',4'-dihydroxy-3',5'-diiodobenzoyl)benzoic acid, resorcinol, phthalic acid, and sodium iodide in the colour additive FD&C Red No. 3 (erythrosine) (R3). Due to the fast decomposition of I3R in aqueous solutions, the dye portions analysed were dissolved in methanol and the determinations were performed in the freshly-made solutions.

Identification of the decarboxylated analog of tetrabromotetrachloro-fluorescein and its quantification in the color additives D&C Red Nos. 27 and 28 (phloxine B) using high-performance liquid chromatography.

The present work describes (a) the identification and characterization of an impurity, 2,4,5,7-tetrabromo-6-hydroxy-9-(2,3,4,5-tetrachlorophenyl)-3H-xanthen-3-one (BCPX), in the color additives D&C Red Nos. 27 and 28 (phloxine B) and (b) the determination of the extent and level of BCPX contamination in certified lots of these colors. For these purposes, BCPX (a compound not previously reported in the literature) was synthetically prepared.