Abstract: A comprehensive analytical method based on isotope dilution-liquid chromatography-tandem mass spectrometry has been developed for the determination of N-nitrosodiethanolamine in cosmetics. Water-soluble cosmetic samples were extracted with water. The extract was centrifuged, then the upper solution was cleaned up by an Oasis HLB solid phase extraction cartridge. Oil-soluble cosmetic samples were extracted by liquid-liquid partition with dichloromethane and water. Qualitative and quantitative analyses were carried out for the analyte under the multiple reaction monitoring (MRM) mode after the chromatographic separation on a Waters Atlantis T3 column (150 mm×2.1 mm, 3 μm ). The quantitation was performed with deuterated N-nitrosodiethanolamine as internal standard. The limit of quantitation (LOQ) for N-nitrosodiethanolamine was 50 μg/kg. The mean recoveries were 89.1%~98.2% at the spiked levels of 50~250 μg/kg, with the intra-day precision less than 9% and the inter-day precision less than 11%. The method is suitable for the determination of NDELA in cosmetics.

Key words: cosmetics , liquid chromatography-tandem mass spectrometry, N-nitrosodiethanolamine, isotope dilution