Abstract
Red No. 204 (Lake Red CBA) has been widely used for make-up products including lipstick. It is an extremely important red pigment, but a contact sensitivity of Lake Red CBA has been reported by Sugai et al. (Contact Dermatitis 3, 249, 1977), and was also confirmed in our laboratory by modified guinea pig maximization test.
By analyzing Lake Red CBA, many organic impurities were detected therein. These impurities were isolated by HPLC and their structural formulae were confirmed by various analytical methods. As a result, many kinds of aromatic azo compounds (subsidiary colors) were found. The subsidiary colors which the structural formulae were confirmed were eleven kinds in which Sudan I (1-phenylazo-2-naphthol) previously reported as a strong sensitizer was included. Then, these confirmed subsidiary colors and the related compounds were synthesized for uses as the standard samples. And the subsidiary colors in Lake Red CBA were quantitatively analyzed and tested for the contact sensitivity. The subsidiary colors were contained in all of eight Lake Red CBA. From the results of the modified guinea pig maximization test of the synthesized subsidiary colors, it was found that each of them was a contact sensitizer, while Lake Red CBA itself was not.
Accordingly, Lake Red CBA free from subsidiary color was investigated. As an analytical result of C acid (2-Amino-5-chloro-p-toluene-sulfonic acid), a raw material for the synthesis, many kinds of aromatic amines which produce the subsidiary colors contained in Lake Red CBA were detected. It was confirmed that Lake Red CBA synthesized with C acid from which aromatic amines were removed as completely as possible contains no subsidiary color. Then, Lake fed CBA was synthesized with the purified C acid to which three types of the typical aromatic amines were added in the fixed quantity. As a result, it was found that the corresponding aromatic azo compounds are produced in proportion to the added amounts of aromatic amines.
Based on the results mentioned above, the manufacturing process of Lake Red CBA free from subsidiary colors was able to be applied for cosmetics.
This concept has been successfully applied to other impartant colors such as Sudan III, Orange II, Quinoline Yellow WS, Quinizarin Green SS, etc. and these purified colors free from contact sensitive impurities have been commercially produced for our use in cosmetic products.
