Determination of synthetic food dyes in food by capillary electrophoresis

A method for the determination of 12 synthetic food dyes (Amaranth, Erythrosine, Allura Red AC, New Coccine, Phloxine, Rose Bengal, Acid Red, Tartrazine, Sunset Yellow FCF, Fast Green FCF, Brilliant Blue FCF, Indigo Carmine) in food was developed using capillary electrophoresis (CE) with photodiode array detection. The dyes were extracted with water and 0.5% ammonia-ethanol (1 : 1) mixture, and cleaned up using solid-phase extraction (Sep-Pak Plus tC 18). The dyes were eluted with methanol from the cartridge. The dyes were separated by CE on a bubble cell fused-silica capillary (72 cm to the detector, 75 gm i.d.) using 20% acetonitrile in a mixture of 10 mmol/L potassium phosphate, monobasic and 5 mmol/L sodium carbonate (pH 10.0) as the running buffer. Identifications of the dyes were performed on the basis of the migration time and the absorbance spectrum of each peak. The coefficients of variation of the migration times and the peak areas were 0.28-0.62% and 1.84-4.30%, respectively (n=5). The identification limits using the absorbance spectra of the dyes were 10 mug/mL for Brilliant Blue FCF and Fast Green FCF, and 5 mug/mL for the other 10 dyes. The recoveries of the 12 dyes from pickles, soft drinks and candies at the level of 10 mug/g were 70.0-101.5%. The method was applied to the analysis of dyes in foods. The dyes detected by CE were in agreement with those detected by paper chromatography.