Facile synthesis of trifluoromethyl covalent organic framework for the efficient microextraction of per-and polyfluorinated alkyl substances from milk products

Trifluoromethyl covalent organic framework (CF 3 -COF) is facilely synthesized at room temperature using for solid-phase microextraction (SPME). The CF 3 -COF coating displays an improved extraction performance for per- and polyfluorinated alkyl substances (PFASs) comparing to amorphous polymer coating, non-contained fluorine covalent organic framework coating and commercially available SPME coating. The fluorine affinity of trifluoromethyl in CF 3 -COF for PFASs is demonstrated using the density functional theory calculation. Following the microextraction with CF 3 -COF-coated fiber, the targeted PFASs are eluted with 1 mL acetonitrile and quantified by ultrahigh performance liquid chromatography tandem mass spectrometry. The low limits of detection are 0.1–0.7 pg g −1 for milk and 0.2–0.8 pg g −1 for milk powder, suggesting the outstanding sensitivity. The precision for the method ranges between 2.9 and 9.9%. The fiber-to-fiber repeatability is in the range of 4.2–9.5%. Under the optimum conditions, the relative recoveries are 91.0–110% with RSDs ≤ 10% for milk and 89.8–111% with RSDs ≤ 10% for milk powder.