Simultaneous determination of food coal-tar dyes by ion-pair high performance liquid chromatography

A method of isocratic high performance liquid chromatography (HPLC) using an ion-pair partition system was established for simultaneous determination of 11 food coal-tar dyes (FD: including Amaranth, R-2; Erythrosine, R-3; New Coccine, R-102; Phloxine, R-104; Rose Bengal, R-105; Acid Red, R-106; Tartrazine, Y-4; Sunset Yellow FCF, Y-5; Fast Green FCF, G-3; Brilliant Blue FCF, B-1 and Indigo Carmine, B-2). Conditions for HPLC analysis were as follows: column, Develosil ODS-5 (5μm, 4.6mm i. d. ×250mm); mobile phase, acetonitrile-0.05M sodium dihydrogen phosphate (3:2) containing 0.002M cetyltrimethylammonium chloride and 0.003M tetra-n-hexylammonium bromide, pH adjusted to 3.0 with phosphoric acid; column temperature, 50°C; flow rate, 1ml/min; detection wavelength, 254nm. Soft drinks were pretreated with polyamide column chromatography prior to HPLC analysis for FD. Recoveries of FD from soft drinks were over 89.0%. The detection limits were 0.05μg/g for R-106, B-2, Y-4 and Y-5, 0.10μg/g for B-1, R-2, R-3, R-102 and R-104, and 0.20μg/g for G-3 and R-105. This method is considered to be applicable for routine analysis of food coal-tar dyes.