Analytical Method of 21 Coal-Tar Dyes in Protein-rich Foods by Solid-phase Extraction and HPLC

Abstract

A method of cleaning up coal-tar dyes in protein-rich foods, e.g. processed fish and meat, was investigated.
The dyes were extracted with 4 mol/L urea and with a mixture of 28% ammonia solution-methanol-4 mol/L urea (7 : 80 : 20) from foods, and cleaned with a Sep-Pak Vac C₁₈ cartridge in the ion-pair mode. The dyes were eluted with 0.025 mol/L ammonium acetate (containing 0.01 mol/L tetrabutylammonium bromide (TBA))-acetonitrile (1 : 1) 2 mL and ammonium acetate (containing TBA)-2-propanol (1 : 1) 2 mL from the cartridge. The eluate was adjusted with 0.1 mol/L TBA to 5 mL and analyzed by isocratic HPLC with a photo- diode array detector.
The recoveries of dyes from boiled fish paste, ham and cod roe at 10 μg/g were more than 91.0, 85.5 and 85.4%, respectively, except for green S (GS), erythrosine (R3) and phloxine (R104). Using the proposed method, these dyes were detected in commercial foods.