Abstract:

Chemical properties of hair dye ingredients are unstable, and the reproducibility of analysis is poor. According to the “safety technical specification for cosmetics”, the chemical standards of prohibited or restricted ingredients in hair dyes could be maintained in solution for 48 hours at most. Thus, it is difficult to conduct analysis on a large number of samples. In order to maintain the chemical stability of standards, benzyl bromide, a nucleophilic substitution reagent with a simple structure and high reactivity, was used to introduce benzyl groups to seven aniline-type hair dye molecules （i.e. 2-nitro-p-phenylenediamine, 4-nitro-o-phenylenediamine, p-aminophenol, 4-amino-m-cresol, 2-amino-3-hydroxypyridine, 2,3-hydroxypyridine）, to obtain derivatives with stable chemical properties and improve the accuracy and sensitivity of the analytical results. The results show that the derivatives of 7 hair dyes are stable within 10 days. This project provides a new idea for the analysis of chemical labile components, which are banned or restricted in chemical products.

Key words: hair dye, dyestuffs for restricted use, benzyl bromide, derivatives, isotopic labeling, LC-MS