Simultaneous determination of preservatives and synthetic dyes in cosmetics by single-step vortex extraction and clean-up followed by liquid chromatography coupled to tandem mass spectrometry.

A simple methodology based on vortex extraction (VE) followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) has been developed for the simultaneous analysis of 22 regulated preservatives and synthetic dyes in cosmetics. The extraction procedure was performed in an Eppendorf tube allowing both extraction and clean-up in a single step, reducing sample and reagents consumption, and resulting in an effective and quick extraction. The method exhibited good linearity (R2 ≥ 0.9918) and intra and inter-day precision (%RSD ≤ 13) with LOQs lower than 0.587 µg g-1 for preservatives and 3.437 µg g-1 for synthetic dyes. Quantitative recoveries were obtained at four concentration levels in the range 2-100 µg g-1 in the cosmetic matrices. The method was successfully applied to a broad range of cosmetics, including both leave-on and rinse-off products in which 13 of the target compounds could be quantified at concentrations ranging from 0.39 to 442 µg g-1 in the case of dyes, and from 1.89 to 1335 µg g-1 for the preservatives. It can be highlighted the presence of parabens in 24 out of the 35 analyzed samples at concentrations higher than 1000 µg g-1 in a toothpaste.