Determination of 10 Synthetic Musks in Cosmetics by Isotope Dilution-GC-MS/MS

As the cheap substitutes of natural musks, large quantities of synthetic musks (SMs) were manufactured and added in a wide variety of cosmetics for the distinct flavor as well as their abilities to improve the fixation of compounds and to round off fragrance compositions. However, with the in-depth research on synthetic musks, these compounds have been described as a new group of bioaccumulative and persistent xenobiotics. Much attention has been given to the level of synthetic musks in daily cosmetic products. In this study, a comprehensive analytical method based on isotope dilution-gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was developed and optimised for simultaneous determination of ten kinds of SMs in cosmetics. Cosmetic samples were spiked with deuterium-labeled isotope internal standards (d₃-AHTN and d₁₅-MX). Then 1.0 mL saturated sodium chloride and 2.0 mL n-hexane were added to the above sample to extract the target compounds. Ultrasonic extraction (20 min at 40 ℃) was chosen as the sample pretreatment method according to the results of the optimization experiments. The solution was centrifugated at 8 000 r/min for 3 min. The upper layer extraction solution was transfered and the remaining sample solution was cleaned twice with 2.0 mL n-hexane, respectively. After combining all the supernatant, the collected solution was evaporated with nitrogen and determined by GC-MS/MS. The conditions of GC-MS/MS were developed for simultaneous determination of ten SMs in cosmetic samples under the MRM mode. All compounds were separated by VF-WAXms capillary column, with which all targets could be detected with a clear baseline separation. Quantitative analysis was carried out using internal standard correction standard curve calibration. The results showed that ten SMs could reach a good linear relationship with the concentration range of 1.0-100.0 μg/L and the correlation coefficients were all more than 0.99. The limits of quantitation (LOQs) of SMs were 1.0-8.0 μg/kg. The recoveries were found to be from 92.5% to 102.0% with all relative standard deviation (RSD) lower than 5%. The proposed method was applied to the analysis of 100 cosmetic samples with the intention of demonstrating method adequacy for the detection of variety of SMs in common cosmetics such as lotions, emulsions and creams. 43 batches of samples were confirmed to contain SMs. The most frequently found compounds were galaxolide (HHCB) and tonalide (AHTN) with detection rate was 36% and 27%, respectively. The highest content of HHCB found in a moisturizing mask was up to 499.9 mg/kg and the concentrations of AHTN were between 0.1 and 119.2 mg/kg. Cashmeran (DPMI) and traseolide (ATII) were detected in 6 and 4 batches, separately with a range of 3.2-225.8 mg/kg and 0.2-24.0 mg/kg. Celestolide (ADBI), phantolide (AHMI), and musk ketone (MK) were detected at low levels in only one batch of sample, respectively. The banned substances (Chinese regulation “Safety and Technical Standards for Cosmetics” and GB/T 22731—2017 Fragrance Compound) such as musk tibetene (MT) and musk xylene (MX) were not found in all of samples. But the forbidden musk ambrette (MA) was confirmed in one sample at concentration of 92.1 mg/kg. All the experimental data showed that the method of this study is accurate, sensitive, convenient and rapid, and is adapted to the inspection of ten synthetic musks in cosmetics.