Spherical covalent organic frameworks as advanced adsorbents for preconcentration and separation of phenolic...

As a promising generation of porous micro-materials, covalent organic frameworks (COFs) have great potentials for applications in separation and adsorption. In the present study, an advanced food-safety inspection method involving COFs as the adsorbents of solid phase extraction (SPE) is proposed for sensitive and accurate determination of target hazardous substances. Typical spherical TpBD COFs with large surface area and superior chemical stability were utilized as adsorbents for the preconcentration of phenolic endocrine disruptors (PEDs), followed by high performance liquid chromatography (HPLC) analysis. The well-prepared TpBD COFs were encapsulated in SPE cartridges and applied in food research, namely, for the separation and enrichment of four target endocrine disruptors in food samples. The possible factors influencing the SPE performance including the composition of the sample solvent, sample solution pH, sample flow rate, composition of the eluent, and the volume of the eluent were investigated and optimized. Due to the porous architecture and superior surface area of spherical TpBD, the enrichment of analytes via a COF-filled SPE column gave extremely low detection limits of 0.056-0.123 μg L^-1 along with a wide linear range of 0.5-100 μg L^-1 for all the analytes. Nine parallel determinations of the mixed standard with a concentration of 10 μg L^-1 produced the relative standard deviations of 2.23-3.08%, indicating the excellent repeatability of the COF-SPE assay. This study can open up a new route for the employment of COFs as efficient SPE adsorbents for the enrichment and quantification of trace/ultra-trace hazardous materials in complex food samples.