Oak (Quercus spp.) acorns are used in animal feed and in the treatment of specific diseases due to their nutritional value and high content of bioactive compounds.

The increasing use of natural ingredients such as essential oils (EOs) and natural extracts (NEs) in cosmetics is an analytical and legislative challenge due to their complex composition, which includes recognized allergenic compounds. In this work, 17 EOs and NEs have been characterized by gas chromatography coupled to mass spectrometry (GC-MS) of dilutions of the original samples. Additionally, solid phase microextraction (SPME) was applied for the analysis of volatile components. The results obtained allowed the identification of more than 90 compounds, including 20 allergens, in the analyzed samples and the study of potential phytomarkers of the addition of EOs and ENs in cosmetics.

The wide range and complexity of cosmetic formulations currently available on the market poses a challenge from an analytical point of view. In addition, during cosmetics manufacture, impurities coming from raw materials or formed by reaction of different organic compounds present in the formulation may be present. Their identification is mandatory to assure product quality and consumer health. In this work, micro-matrix solid-phase dispersion (μMSPD) is proposed as a multi-target sample preparation strategy to analyze a wide number of unexpected families of compounds including polycyclic aromatic hydrocarbons (PAHs), pesticides, plasticizers, nitrosamines, alkylphenols (APs), and alkylphenol ethoxylates (APEOs). Analytical determination was performed by gas chromatography-mass spectrometry (GC-MS) for the determination of 51 target compounds in a single run, whereas liquid chromatography tandem mass spectrometry (LC-MS/MS) was employed for the analysis of six APs and APEOs. Both methodologies were successfully validated in terms of linearity, accuracy, and precision in leave-on and rinse-off cosmetics. Limits of detection (LODs) were calculated in the low ng g⁻¹, showing their suitability to determine trace levels of impurities and banned compounds with different chemical natures, providing useful tools to cosmetic control laboratories and companies.