Covalent organic frameworks as a novel fiber coating for solid-phase microextraction of volatile benzene homologues

Covalent organic frameworks (COFs) have attracted great research interest due to their fascinating structures and potential applications in various fields. Here, the COF-SCU1 (SCU for Sichuan University) coated solid-phase microextraction (SPME) fibers were fabricated by coating it on prior functionalized stainless steel wires via a simple physical coating method, and applied to extract some volatile benzene homologues from indoor air samples. The main experimental parameters affecting the extraction efficiency were optimized, including extraction temperature, extraction time, and desorption time. The developed method, which combined the COF-SCU1 coated fiber-based SPME with gas chromatography-mass spectrometric detection, gave large enrichment factors (276-887), low limits of detection (0.03-0.15 ng L^-1), and good linearity (0.10-20 ng L^-1) for the determination of gaseous benzene homologues from three different indoor air samples. The precision (expressed as the relative standard deviations, RSDs) for six replicate determinations of the analytes at 10 ng L^-1 each of the analytes using the same COF-SCU1 coated fiber ranged from 5.8 to 8.9%. The fiber-to-fiber reproducibility for three parallel COF-SCU1 coated fibers varied from 6.9 to 10.7%. The recoveries of the analytes for the method for the spiked indoor air samples with the benzene homologues at the two concentrations of 1 and 10 ng L^-1 were in the range of 88.6-101.5% and 87.9-103.4% with the RSDs ranging from 3.9 to 10.3% and 3.4 to 8.5%, respectively. Graphical Abstract The covalent organic frameworks were applied as a novel fiber coating material for the solid-phase microextraction of volatile benzene homologues.