Magnetic solid phase extraction with CoFe2O4/oleic acid nanoparticles coupled to gas chromatography-mass spectrometry for the determination of alkylphenols in baby foods

•In situ acetylation of the alkylphenols provided a good GC separation.•Magnetic nanoparticles functionalized with oleic acid efficiently preconcentrate the APs.•Most of the baby food samples analyzed were free from the studied APs.

Magnetic solid phase extraction (MSPE) with cobalt ferrite nanoparticles coated with oleic acid is described for the determination of alkylphenols (APs), 4-tert-butylphenol (TBP), 4-pentylphenol (PP), 4-hexylphenol (HP), 4-tert-octylphenol (TOP), 4-n-octylphenol (OP) and 4-nonylphenol (NP) in baby foods using gas chromatography with mass spectrometry (GC-MS). Prior to MSPE, the sample was treated with trichloroacetic acid, and the APs derivatized with acetic anhydride. Parameters affecting the extraction efficiency: amount of magnetic nanoparticles, extraction time and desorption conditions, were optimized. The enriched phase obtained was evaporated to dryness and the residue reconstituted in 50 μL of methanol, 1 μL of which was injected into the GC-MS. Samples were quantified applying matrix-matched calibration and using 2-chloro-5-bromoanisole as surrogate standard. The analysis of 0.5 g of sample provided detection limits in the 0.4-1.7 ng g−1 range. Some samples contained APs at levels of between 3 ng g−1 for HP and 122 ng g−1 for TOP.