Fabrication of highly fluorinated porphyrin-based covalent organic frameworks decorated FeO nanospheres for magnetic solid phase extraction of fluoroquinolones.

A highly fluorinated porphyrin-based covalent organic frameworks magnetic adsorbent (FPy-COF@PDA@FeO) was fabricated by using polydopamine (PDA) grafting FeO nanospheres as magnetic core and FPy-COF as shell for magnetic solid phase extraction (MSPE) of fluoroquinolones (FQs). FPy-COF was constructed by using 5,15-bis(4-aminophenyl)-10,20-bis(perfluorophenyl)porphyrin and 4,4'-biphenyldicarboxaldehyde as two building blocks. PDA as a bridge grafting on the surface of FeO nanospheres facilitated the growth of FPy-COF. The morphology and structure of FPy-COF@PDA@FeO adsorbent were characterized in detail. The prepared magnetic adsorbent exhibited good extraction capability to amphiphilic FQs due to their superior chemical affinities such as fluorophilic interaction and hydrogen-bond interaction from nitrogen-rich skeleton. Under the optimized conditions, the MSPE method combined with high performance liquid chromatography with ultraviolet detection (HPLC-UV) was developed to sensitively quantify trace level of six FQs in milk samples. The developed MSPE-HPLC method showed good linearity with wide concentration range, precision, and low limits of detection (S/N = 3) for six FQs as low as 2.3 ngꞏmL in milk. The extraction recoveries of different spiked concentrations were in the range 77.8-110.4% for milk samples with RSD less than 9.7%.