Layer‐by‐layer self‐assembly of a novel covalent organic frameworks microextraction coating for analyzing polycyclic aromatic hydrocarbons from aqueous solutions via gas chromatography

In this study, a new covalent organic framework, consisting of tetra(4-aminophenyl)porphyrin and tris(4-formyl phenyl)amine, was layer-by-layer immobilized on stainless-steel wire as a coating for microextraction. The fabrication process was easy and controllable under mild conditions. The as-grown fiber was applied to extract polycyclic aromatic hydrocarbons in aqueous solution via head-space solid-phase microextraction. Furthermore, it was analyzed by gas chromatography with a flame ionization detector. A wide linear range (0.1-50 microg/L), low limits of detection (0.006-0.024 microg/L, signal-to-noise ratio = 3), good repeatability (intra-fiber, n = 6, 3.1-8.50%), and reproducibility (fiber to fiber; n = 3, 5.79-9.98%), expressed as relative standard deviations, demonstrate the applicability of the newly developed coating. This new material was successfully utilized in real sample extraction with a satisfactory result. Potential parameters affecting the extraction efficiency, including extraction temperature and extraction time, salt concentration, agitation speed, sample volume, desorption temperature, and time, were also optimized and discussed.