Determination of N-nitrosamines in cosmetic products by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and liquid chromatography with mass spectrometry.

A new analytical method for the simultaneous determination of trace levels of seven prohibited N-nitrosamines (N-nitrosodimethylamine, N-nitrosoethylmethylamine, N-nitrosopyrrolidine, N-nitrosodiethylamine, N-nitrosopiperidine, N-nitrosomorpholine, and N-nitrosodiethanolamine) in cosmetic products has been developed. The method is based on vortex-assisted reversed-phase dispersive liquid-liquid microextraction, which allows the extraction of highly polar compounds, followed by liquid chromatography with mass spectrometry. The variables involved in the extraction process were studied to obtain the highest enrichment factor. Under the selected conditions, 75 μL of water as extraction solvent was added to 5 mL of n-hexane sample solution and assisted by vortex mixing during 30 s to form the cloudy solution. The method was successfully validated showing good linearity (0.5-50 ng/mL), enrichment factors up to 65 depending on the target compound, limits of detection values of 1.8-50 ng/g, and good repeatability (RSD < 9.8%). Finally, the proposed method was applied to different cosmetic samples. Quantitative relative recovery values (80-113%) were obtained, thus showing that matrix effects were negligible. The achieved analytical features of the proposed method, besides of its simplicity and affordability, make it useful to perform the quality control of cosmetic products to ensure the safety of consumers.