Facile room-temperature synthesis of a spherical mesoporous covalent organic framework for ultrasensitive solid-phase microextraction of phenols prior to gas chromatography-tandem mass spectrometry

High-performance extraction of polar phenols from aqueous samples is challenging because of their hydrophilicity, extremely low concentration, and complicated matrices. Covalent organic frameworks (COFs) are new types of porous organic materials. In this work, spherical TPB-DMTP-COF was fabricated via a simple room-temperature solution-phase approach. The material exhibited high acid/base stability, remarkable thermostability, high crystallinity, and large surface area of 1560 m2 g−1 and thus could be an excellent coating for solid-phase microextraction (SPME) of phenols. This coating provided superior adsorption affinity toward phenols over commercial coatings. TPB-DMTP-coated fiber showed high enhancement factors (EFs, 1741–4265), and EFs increased with the number of chlorine or methyl substituents and high hydrophobicity of phenols. Hence, the strong adsorption affinity could be derived from hydrophobic and steric hindrance effects together with π−π affinity, H-bonding, van der Waals forces, and size-matching effect. The proposed approach based on TPB-DMTP-COF-coated fiber and gas chromatography-tandem mass spectrometry achieved low limits of detection (0.0048–0.015 ng L−1), wide linearity (0.05–1000 ng L−1), good precision (<8.87%), and reproducibility (<10.0%). The actual amounts of phenols ranged from 0.6 ng L−1 to 22.7 ng L−1 in underground water and reservoir water. The satisfactory recoveries (81.3–116.3%) for simultaneous analysis of five phenols were obtained. Therefore, TPB-DMTP-COF coating could be an excellent alternative for sensitive analysis of phenols at ultra-trace level in complex samples.