Abstract:

Organic solvents can be used to dissolve and disperse flavors, bactericides, preservatives, surfactants, oils, and coloring agents during the production of cosmetics. However, harmful chlorinated hydrocarbon organic solvents are found in cosmetics such as manicure products, anti-acne products, and perfumes. Long-term contact with such cosmetics will have an adverse effect on the consumers’ health. Past research has focused on very few chlorinated hydrocarbon organic solvents in cosmetics. Most organic solvents with low boiling points are typically determined by headspace-gas chromatography-mass spectrometry. In this study, a high-boiling-point solvent was used as the injection solvent, and the solvent delay time was cancelled. The compounds that could only peak during the solvent delay time were effectively separated. A method coupling sample pretreatment with gas chromatography-mass spectrometry (GC-MS) was developed for the simultaneous determination of 18 chlorinated hydrocarbon organic solvents in cosmetics: vinylidene chloride, dichloromethane, trans-1,2-dichloroethylene, 1,1-dichloroethane, cis-1,2-dichloroethylene, chloroform, 1,1,1-trichloroethane, carbon tetrachloride, 1,2-dichloroethane, trichloroethylene, 1,1,2-trichloroethane, tetrachloroethylene, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, 1,2,3-trichloropropane, pentachloroethane, hexachloroethane, and hexachloro-1,3-butadiene. These 18 solvents have a wide range of polarities and a notable difference in volatilities, in addition to many isomers and structural analogs, which renders their separation difficult. Therefore, the separation effect of three kinds of GC columns with different polarities was compared. n-Tetradecane, an injection solvent with good solubility, was selected as the extraction solvent. An organic solvent with high polarity has low extraction rate because of its weak polarity. Adding sodium chloride solution to the sample to induce the “salting out” effect could change the partition coefficient of the components, thereby improving the extraction rate. Therefore, the concentration of the sodium chloride solution added to the sample was optimized. In this work, liquid-liquid extraction was the main extraction process, so the effects of different shaking times, temperatures, and frequencies on the extraction rate were discussed. The optimized results are as follows: at normal temperature, the sample dispersed or dissolved in saturated sodium chloride solution was extracted by n-tetradecane at an oscillating speed of 100 r/min for 20 min. Separation was performed on an Agilent J&W DB-624 column (30 m×0.25 mm×1.4 μm) by GC-MS with an electrospray ionization (EI) source in the selected ion monitoring (SIM) mode. The external standard method was used for quantitative determination. The 18 compounds could be analyzed within 19 min. The 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 18 components were determined. The negative lipstick (solid) and mouthwash (liquid) samples were used as the spiked sample matrix at three levels, and the recoveries and precisions were calculated. The calibration curves showed good linearities for the 18 chlorinated hydrocarbon organic solvents in range of 0.2-100 mg/L, with correlation coefficients (R²) not less than 0.9992. The LODs and LOQs were in the range of 0.033-0.049 mg/L and 0.10-0.15 mg/L, respectively. The average recoveries of the 18 chlorinated hydrocarbon organic solvents in lipstick (solid) and mouthwash (liquid) were 92.4%-103.1% and 93.3%-102.4% respectively; the corresponding relative standard deviations (RSDs) were 3.1%-5.3% and 2.8%-5.4% (n=6). This method was used to determine 115 different types of cosmetics, and tetrachloroethylene was detected in three nail polishes. With its advantages of high sensitivity, good precision, and accuracy, the developed method is suitable for the quantitative analysis of the aforesaid 18 compounds in all kinds of cosmetics. The study findings would serve as a reference for the quality and safety monitoring of cosmetics.

Key words: gas chromatography-mass spectrometry (GC-MS), chlorinated hydrocarbon organic solvents, cosmetics