Abstract: An analytical method was developed for the simultaneous determination of 11 aminophenols in direct and oxidized hair dyes by high performance liquid chromatography (HPLC). The samples were extracted with methanol using sodium bisulfite for anti-oxidation. The purification was carried out with the high speed frozen centrifugation. The separation was performed on an Agilent Zorbax SB C18 column with the mobile phases of acetonitrile and an ion pair system of sodium heptanesulfonate and phosphate under a gradient elution. The analytes were detected at three different wavelengths of 230, 270 and 400 nm. In the concentration range of 0.05~500 mg/L, the correlation coefficients for the 11 aminophenols were not less than 0.9992. The limits of quantification including 4-amino-3-nitrophenol, 2-amino-5-nitrophenol, and 4-(2-hydroxyethyl)amino-3-nitrophenol were 5 mg/kg. Other aminophenols including 4-aminophenol, 4-methyl aminophenol, 3-aminophenol, 2-aminophenol, 5-amino-o-cresol, 4-amino-3-methylphenol, 5-(2-hydroxyethyl)amino-o-cresol and 2-amino-4-nitrophenol were 20 mg/kg. The recoveries of the aminophenols spiked at different levels ranged from 88.5% to 109.5% with the relative standard deviations (RSDs) within the range of 2.2%~8.3%. The commercially available hair dye samples were analyzed for the aminophenols and the results showed that the method was suitable for the determination of the 11 aminophenols in direct and oxidized hair dyes.

Key words: aminophenols, frozen centrifugation, hair dye, multi-wavelength, high performance liquid chromatography (HPLC)