Diverse pore-sized sulfonic acid covalent organic frameworks for solid-phase extraction of fluoroquinolones in food...

Tuning the pore size of covalent organic frameworks (COFs) to achieve maximum adsorption performance is an effective way for promoting the enrichment of trace fluoroquinolones (FQs) in food, but it remains challenging. Herein, we prepare three pore-sized sulfonic acid functionalized COFs (SF-COFs), named TPS, TBS, and TSS, to investigate the effect of pore size on the adsorption efficiency of FQs. These three SF-COFs exhibit excellent adsorption capacities for FQs including enrofloxacin (ENR), norfloxacin (NOR), and ciprofloxacin (CIP). Notably, TBS achieves a maximum adsorption capacity of 627.3 mg g^-1 for NOR, resulting from its suitable pore size (1.6 times larger than the size of FQs). Accordingly, we further develop a novel TBS based solid-phase extraction to couple with high-performance liquid chromatography for determination of FQs in various foods, which achieves rapid extraction (10 min), low detection limits (0.007-0.01 ng mL^-1), wide linear range (0.1-1000 ng mL^-1), and good recoveries (83.7%-105.2%).