Abstract:

A high performance liquid chromatography using diode array detector （HPLC-DAD） technique was developed for the simultaneous determination of 45 dyes in oxidative hair dye products. The sample pretreatment method was as follow: weighed 0.5 g sample accurately, added 10 mL 2 g/L sodium bisulfite solution containing 70% methanol, extracted by ice bath ultrasonication for 15 min, and passed through a 0.45 μm filter membrane as the solution to be measured. The analytes were separated on a CAPCELL PAK MGⅡ-C₁₈ （4.6 mm×250 mm, 5 μm） by gradient elution using phosphate buffer-methanol-acetonitrile and phosphate buffer-methanol as mobile phases. The dyes were detected at two different wavelengths of 240 nm and 280 nm using a diode array detector. The results show that the 45 dyes can be separated well. All dyes have good linearity with the correlation coefficients greater than 0.998 4. The limits of detection （LODs） of the 45 dyes range from 1 to 34 μg/g, and the limits of quantification （LOQs） range from 2 to 113 μg/g. Recoveries range from 81.9% to 114.3% at three different concentration levels, with the RSDs less than 5.4%. Compared with the standard method of Safety and Technical Standards for Cosmetics （2015 edition）, this established method replenishes 13 permitted hair dyes, adds antioxidants and optimizes extraction solvent to improve the filtration effect during sample pretreatment, and optimizes gradient elution procedure. It is efficient, accurate, reproducible and suitable for detecting various hair dyes in oxidative hair dye products.

Key words: high performance liquid chromatography, dyes, oxidative hair dye product