Hydrophilic Chitosan/Covalent Organic Framework Composites for Efficient Solid-Phase Microextraction of Polar Phenolic Compounds Prior to Gas Chromatography: Mass Spectrometry Analysis

Covalent organic frameworks (COFs) have been widely used to prepare solid-phase microextraction (SPME) coatings due to their large specific surface area and adjustable pore size. However, the weak inherent hydrophilicity of COFs restricts their extraction performance for polar phenolic compounds. In this work, COFs were combined with chitosan (CS) via Schiff base reaction to prepare novel SPME coating materials. The incorporation of CS, which contains abundant hydrophilic functional groups, effectively enhanced the hydrophilicity of the CS/COF composite, thus boosting its interaction affinity towards polar phenols. In combination with gas chromatography—mass spectrometry (GC–MS), an efficient and sensitive analytical method was established. Under optimal conditions, the developed method demonstrated a broad linear range (5.0–1.0 × 10⁴ ng/L, R² > 0.9972), low detection limits (0.78–1.3 ng/L), good reproducibility (relative standard deviations (RSDs) < 8.8%), and excellent enrichment factors (5993–41,441). Moreover, the established method was successfully applied to quantify phenolic compounds in grapes, and the recoveries ranged from 92.2% to 111% with RSDs of 2.3%–7.8%, meeting practical application requirements. This study provides valuable insights into the efficient analysis and determination of trace polar contaminants in real samples.