Analytical Method of 21 Coal Tar Dyes in Foods by HPLC

A method of analysis of 21 coal tar dyes in foods by HPLC was developed. After adjustment of the pH to 3.5-4.0 with acetic acid, the dye solution was applied to a Sep-pak Vac C18 cartridge, and the cartridge was washed with water. The cartridge was eluted with 50% methanol (fraction A), and then with methanol (fraction B). The dyes in each eluate were determined by high performance liquid chromatograph with a UV-VIS detector. The HPLC separation was carried out on a COSMOSIL 5C18-AR column using 0.025M ammonium acetate (containing 0.01M tetrabutylammonium bromide (TBA))-acetonitrile-methanol (62:28:10) as a mobile phase for fraction A, and 0.025M ammonium acetate (containing 0.01M TBA)-acetonitrile-methanol (50:40:10) as a mobile phase for fraction B. Recoveries of dyes added to a soft drink, a jelly and a candy at 10μg/g were 85-103%, 76-99%, and 73-103%, respectively. Recovery of dyes added to pickles was 64-99%, except for Black PN. The detection limits of dyes were 0.1-0.5μ/ml.