The contemporary impurity tests are not effective for the detection and determination of starting materials, uncombined intermediates of organic synthesis as well as subsidiary dyes contained in cosmetic coal-tar dyes.
A systematic detection and determination method of them in 14 kinds of xanthene dyes was established with the aid of HPLC. The following operation conditions were chosen; “Zorbax C-8” (reversed phase resin) column, gradient elution system of ammonium chloride (pH 8.0) solution and a mixture of methanol and acetonitrile (4:1) with UV detection system at the wavelength of 230nm.
By use of the proposed method actual survey was carried out on 39 commercial xanthene coaltar dyes for cosmetic use. More than 3 kinds of subsidiary dyes were found from all the samples. The amounts of starting materials and uncombined intermediates of organic synthesis contained in the samples were relatively low compared with those of subsidiary dyes.