[Determination of 13 sunscreen agents in cosmetics by gas chromatography-mass spectrometry]

Sunscreens can be categorized as physical and chemical types. Chemical sunscreens are widely used in cosmetics, and hence, their concentration in the desired products should be strictly monitored. Gas chromatography-mass spectrometry (GC-MS) is widely used for the analysis of cosmetics as it does not require organic mobile phases and allows for accurate qualitative and quantitative analyses. In this study, a method based on GC-MS was established for the determination of 13 sunscreen agents in cosmetics: ethylhexyl salicylate, homosalate, 4-methylbenzylidene camphor, ethylhexyl dimethyl para-aminobenzoic acid, ethylhexyl methoxycinnamate, octocrylene, butyl methoxydibenzoylmethane, diethylamino hydroxybenzoyl hexyl benzoate, 3-benzylidene camphor, benzophenone-3, camphor benzalkonium methosulfate, drometrizole trisiloxane, and isopentyl-4-methoxycinnamate. Accordingly, 0.5 g of the cosmetic product was dissolved in dichloromethane in a 50 mL volumetric flask and extracted ultrasonically for 15 min. Then, 1.0 mL of the extracting solution was withdrawn and diluted to 50.0 mL with dichloromethane. The mixture was filtered through a 0.22-μm membrane. A 1 μL aliquot of the dichloromethane solution was introduced onto the HP-5ms chromatographic column (30 m×250 μm×0.25 μm). The 13 components were separated under programed temperature elevation in the interval from 150 ℃ to 290 ℃. These components could be analyzed within 30 min after being ionized by the EI source, and their determination was achieved in selected ion monitoring (SIM) mode. The external standard method was employed for quantitative determination. Linear equations, linear correlation coefficients, and linear ranges were obtained by analyzing a series of mixed standard working solutions. The limits of detection (LODs, S/N=3) and limits of quantification (LOQs, S/N=10) of the 13 sunscreen agents were determined. The matrix effect and average recoveries of the 13 agents with six extraction solvents (dichloromethane, tetrahydrofuran, methanol, acetonitrile, n-hexane, and acetone) were compared. Among these, dichloromethane showed a weak matrix effect and high average recovery. The matrix effect of dichloromethane was 90.1%-100.5%, and the average recovery was 96.3%. All the 13 sunscreen agents showed good linearity in their corresponding ranges. The correlation coefficients (r ²) were higher than 0.998. The LODs and LOQs were in the ranges of 0.04 to 0.63 mg/g and 0.12 to 2.10 mg/g, respectively. Two types of cosmetics were selected to verify the accuracy and precision of the method at three levels. The average spiked recoveries of the 13 sunscreen agents in cream and lotion were 88.7%-103.6%, and 88.4%-102.3%, respectively; the corresponding relative standard deviations (RSDs, n=6) were 1.7%-4.9% and 1.2%-3.9%. Whitening cosmetics are frequently added with sunscreen agents, which is a regulatory blind spot. Five batches of skin whitening products containing sunscreen agents were detected using this method. The contents of five sunscreen agents in skin whitening cosmetics ranged from 0.8% to 5.2%, which were lower than the relevant limits in China. Owing to its advantages of simple operation, high sensitivity, and good recovery, the proposed method is suitable for the qualitative and quantitative determination of 13 sunscreen agents in cosmetics. This method provides technical support for market supervision and laboratory testing.