Magnetic Solid-Phase Extraction Followed by HPLC–DAD for Highly Sensitive Determination of Phthalate Esters in Edible Vegetable Oils

Phthalate esters (PAEs) are prone to migrate from the plastic containers into oil during production and storage process. Owing to the trace amount of PAEs and complex sample matrix, it is of great importance to explore a facile and sensitive way to extract and detect PAEs from oil samples. In this work, magnetic covalent organic framework nanospheres (Fe3O4@COF(TbBD)) were fabricated by the aldehyde-amine condensation between benzidine (BD) and 1,3,5-triformylbenzene (Tb) on the surface of Fe3O4 nanoparticles with the help of ultrasonic treatment. The new type nanomaterials were firstly used to the magnetic solid-phase extraction (MSPE) of seven PAEs in edible vegetable oils prior to high performance liquid chromatography coupled with a diode array detector (HPLC–DAD). In order to achieve the best extraction efficiency, several key parameters were optimized. Under optimal conditions, the proposed Fe3O4@COF(TbBD)-MSPE-HPLC–DAD method possessed high sensitivity (0.55–0.95 µg/kg for LODs and 1.80–3.10 µg/kg for LOQs), good linearity (R2 ≥ 0.9983), and satisfactory recoveries (80.2–102.9%). The RSDs for intra-day was less than 6.1%, and inter-day was less than 7.9%. This work not only proposed a rapid and reliable approach for determining PAEs in edible vegetable oils but also broadened the application of magnetic COFs in food determination.