Bipyridine-functionalized Covalent Organic Framework as a Reusable Adsorbent for Trace BTEX Detection in Water Samples.

Benzene, toluene, ethylbenzene, and xylenes (BTEX) are hazardous volatile organic compounds frequently detected in environmental waters, posing serious risks to human health and ecosystems. Therefore, sensitive and reliable analytical methods for trace BTEX monitoring are urgently needed. In this work, a novel imine-linked covalent organic framework (TAPB-Bpy) containing bipyridine units was synthesized via Schiff-base reaction and applied as a dispersive solid-phase extraction (d-SPE) adsorbent for the preconcentration of BTEX coupled with gas chromatography-flame ionization detection (GC-FID). Benefiting from its highly ordered porous structure, good thermal stability and abundant π-electron-rich sites, TAPB-Bpy exerts strong π-π stacking and weak C-H···N hydrogen bonding interactions with BTEX molecules, as verified by XPS analysis. Under optimized conditions, the method achieved a linear range of 0.003-10 µg L- 1, limits of detection (LODs) of 0.001 µg L- 1 for all four analytes, and good reproducibility with relative standard deviations (RSDs) below 8.1%. The adsorbent retained stable extraction efficiency after at least 30 reuse cycles, showing favorable cost-effectiveness. Compared with recently reported SPE/SPME methods for BTEX determination, our approach provides 2-10-fold lower LODs, a broader linear range, and superior reusability. When applied to real water samples including tap water, river water, rainwater, and industrial wastewater, satisfactory recoveries ranging from 90.9% to 109.6% were obtained, with RSDs between 1.0% and 9.0%. These results indicate that TAPB-Bpy is a promising d-SPE adsorbent for trace BTEX analysis in complex environmental matrices.