[Research advance of solid-phase microextraction based on covalent organic framework materials]

Solid-phase microextraction (SPME) is a fast and simple sample preparation technique that enables the enrichment of analytes, and it is used in combination with other detection techniques to provide accurate and sensitive analytical methods. SPME is widely used in environmental monitoring, food safety, life analysis, biomedicine, and other applications. The extractive coating is the core of the SPME technique, and the properties of the extractive coating greatly influence extraction selectivity and efficiency, as well as the enrichment effect. Therefore, the development of new and efficient extractive coating materials remains a hot topic in the analytical chemistry and sample preparation fields. Covalent organic frameworks (COFs) are a kind of porous crystalline network polymer materials formed by covalent bonds. Owing to the advantages of large specific surface area, high porosity, good stability, high designability, simple synthesis and post-modification, etc., it has been widely used in gas adsorption, catalysis, sensing and drug delivery. In recent years, COFs have attracted much attention in the field of sample preparation. A variety of novel COF-based SPME materials had been developed for extracting and enriching various types of analytes through π-π interaction, hydrophilic/hydrophobic interaction, electrostatic adsorption, and hydrogen-bonding, as well as pore effects. In this paper, the research advances of COFs for using in fiber-, in tube-, and membrane-based SPME over the past three years were discussed. Fiber surfaces had been modified with functionalized COFs or COF-hybrid materials for use in SPME through physical coating, in-situ growth, and chemical-bonding approaches. The combination of SPME fiber and chromatographic analysis can be used to detect a variety of analytes such as polycyclic aromatic hydrocarbons, phthalates, polychlorinated biphenyls, and pesticides in environmental and food samples, with good enrichment effects, wide linear ranges, and high sensitivity. Based on in tube-SPME, COFs-based monolithic column and fiber-filled tube as the extraction tubes were combined with high performance liquid chromatography online to develop highly sensitive detection methods for synthetic phenolic antioxidants and bisphenol compounds, respectively. In addition, COFs had also been used in membrane SPME technique, showing high efficiency in the extraction of trace polychlorinated biphenyls in environmental water. Finally, the development trends of COFs in the field of SPME was prospected.