Hygienic Study of Coal-Tar Dyes Used in Drugs and Cosmetics. I. Separation of Cosmetic Azo Dyes by Reversed-phase High Performance Liquid Chromatography and Determination of Pure Dye Content in Commercial Dyes

Abstract

Separation and determination of twenty kinds of cosmetic azo dyes permitted in Japan were studied by reversed-phase high performance liquid chromatography. For identification and determination of the tested dyes, the system of Nucleosil 5C₁₈ column and acidic mobile phase was very useful. The used mobile phases were CH₃CN-THF-H₂O (pH 3.2, H₃PO₄) for oil-soluble dyes, and CH₃CN-THF-H₂O (pH2.0, HClO₄) for water-soluble dyes, Ca-lakes and Ba-lakes, respectively. This method was applied on 93 samples of commercial cosmetic azo dyes for the determination of "pure dye content." Data obtained by this method agreed well with those by the recommended official methods such as titanous chloride titration and spectrophotometric determination. Comparing with the official method, advantage of this method was to prevent the influences of contaminated other dyes, subsidiary dyes and impurities.