Simultaneous determination of eleven dyes and their aluminum lakes in drugs.

A 3-step extraction method was developed for the simultaneous determination of 11 dyes and their aluminum lakes in drugs. The dyes were first extracted with warm water (approximately 60°C) and were cleaned up by solid-phase extraction with a tC 18 cartridge. Aluminum lake dyes that remained in the precipitate were extracted with 0.02M NaOH. Aluminum in the dye lakes was reextracted into the organic layer with acetylacetone-butyl acetate (1 + 9, v/v), as an acetylacetone chelate, and was quantified by atomic absorption spectrometry. The dye portions of the aluminum lakes remained in the aqueous layer and were cleaned up in the same way as the dyes. The dyes and the dye portions of the aluminum lakes were quantified by ion-pair liquid chromatography with a photodiode array detector within 20 min. The recoveries of dyes from drug fortified at 10 μg of each dye per pill were 87.0-102.2%, and the recoveries of dyes from drugs fortified at 50 μg of each dye lake per pill were 82.9-101.6%, except for recoveries of indigo carmine. In 40 ethical and over-the-counter drugs, dyes that were not indicated in the package insert information for drugs were detected in 5 samples. The highest amount of dye found in a drug was 1169.5 μg erythrosine, which was detected in a capsule of antibiotic. Aluminum lake dyes were detected in 8 samples of various dosage forms.