Abstract:

Attenuated total reflection Fourier transform infrared spectroscopy （ATR-FTIR） was used to differentiate sunscreen cosmetics with different formulations and track their quality changes. The results show that the integrity and fingerprint of the infrared spectrum of single and mixed emulsions are similar because of the same matrixes. However, the second-order derivation of the spectrum can magnify the difference between the fingerprint intervals of each spectrum, and can be used to differentiate sunscreen lotions with small differences in composition. During the 6-month accelerated experiment, the infrared spectrum experience obvious changes, with significant reducing or disappearing peak intensity and changing peak positions. Besides, the degree of change gradually increases with the acceleration time. According to the changing conditions of spectrum and correlation coefficient of the blank emulsion during acceleration, the correlation coefficient value of 0.980 0 is determined as the critical value of the overall quality change of such cosmetics during infrared detection. That is, when the correlation coefficient of the spectrum decreases to 0.980 0, the overall quality of the cosmetic has changed and reached the end of its shelf-life. It can be seen that ATR-FTIR is a direct way to reflect the overall quality change of the product during its storage period, and proved to be a rapid and scientific method for the overall quality inspection of cosmetic.

Key words: cosmetics, ATR-FTIR, identification, quality variation