Metal organic framework/covalent organic framework composite for solid-phase microextraction of polycyclic aromatic hydrocarbons in milk samples

Based on the excellent physicochemical properties of metal organic framework (MOF) and covalent organic framework (COF), a novel MOF/COF composite was designed and prepared as coating fiber for headspace solid-phase microextraction (HS-SPME). Based on the amino group on the surface of as-synthesized UiO-66-NH2, porphyrin-based COF was covalently grown on the MOF surface by using tetra(4-aminophenyl)porphyrin and 4,4′-biphenyldicarboxaldehyde as building blocks to fabricate a novel MOF/COF composite. Subsequently, the composite was physically coated on the surface of polished stainless-steel wire for HS-SPME of polycyclic aromatic hydrocarbons (PAHs) by gas chromatography-flame ionization detection (GC-FID) determination. The morphology and structure of the MOF/COF composite was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and N2 adsorption–desorption. Influential adsorption and desorption parameters were optimized and the extraction mechanism was also discussed. Under optimal conditions, an HS-SPME/GC-FID method based on MOF/COF composite coated fiber was established for the analysis of PAHs in milk samples. The linear ranges of this method were 0.2–50.0 ng mL−1 (R2 > 0.9908), and the limits of detection and quantitation were in the range of 0.02–0.07 ng mL−1 and 0.07–0.24 ng mL−1, respectively. The relative standard deviations (RSDs) for PAHs were all less than 7.05 %, which indicated eminent repeatability and reproducibility of the established method. Besides, the enrichment factors for PAHs were relatively high in the range of 2003 to 7763, and the recoveries for milk samples were ranged from 85.43 % to 115.8 % with satisfactory RSDs of 0.92–9.00 %.