Extraction and TLC separation of food, drug, and cosmetic dyes from tablet-coating formulations

A rapid method for extraction of dyes from tablet-coating formulations is described. The dyes were released from their lakes by treatment with concentrated phosphoric acid and dissolved in methanol. After being made alkaline with ammonium hydroxide, the mixture was centrifuged to obtain a clear supernate for application to the TLC plate. With ethyl acetate--methanol--water--concentrated ammonium hydroxide (150:40:35:5) on silica gel, 20 dyes were separated sufficiently to confirm their presence in the coating formulation.