Abstract:

A method for the simultaneous determination of 10 fluorescent colorants （fluorescein, sodium fluorescein, dibromofluorescein, diiodofluorescein, disodium diiodofluorescein, tetrabromofluorescein, disodium tetrabromofluorescein, tetrachloro-tetrabromofluorescein, disodium tetrachloro-tetrabromofluorescein and rhodamine B） in cosmetics by high performance liquid chromatography with fluorescence detection was established. This method was used to monitor the risk for more than 30 products including eyebrow pencils, lipsticks, eye shadows and blushers. The effects of extraction solvents on the fluorescent colorants were explored, and it is found that when the extraction solvent is methanol, the recovery rate of various fluorescent colorants can reach the best level. Meanwhile, to obtain higher sensitivity, the alkaline mobile phase glycine-methanol system was used to separate the fluorescent colorants. The effects of pH and concentration of glycine buffer solutions on the resolution and fluorescence intensity of the ten fluorescent colorants were also studied. It is found that when the pH is 9.0 and the concentration is 10 mmol/L, the resolution and fluorescence intensity of the 10 fluorescent colorants can achieve the best results. Finally, the fluorescent colorants were separated by Waters XBridge C₁₈ （5 μm×4.6 mm×250 mm）column using 10 mmol/L glycine-methanol as the mobile phase, and qualitative and quantitative analysis was performed by high performance liquid chromatography with a fluorescence detector. The results show that there is a good linear relationship between concentration and peak area with R² no less than 0.998. The limits of detection for diiodofluorescein and disodium diiodofluorescein are 1 μg/g and the limits of quantification are 3 μg/g, while the limits of detection for other fluorescent colorants are 0.2 μg/g and the limits of quantification are 0.5 μg/g. The average recoveries are from 88.7% to 118.5%, with relative standard deviations are in the range of 1.8%-8.2% （n=6）. This method has advantages such as simple pretreatment, high sensitivity and almost little interference from matrix. It is suitable for the simultaneous determination of the 10 fluorescent colorants in cosmetics. The method is expected to fill the gap in current detection methods and provide strong technical support for the quality monitoring and residue analysis of fluorescent colorants in cosmetics.

Key words: cosmetic, fluorescent color additive, high performance liquid chromatography