Cationic Covalent Organic Frameworks as a Solid-phase Microextraction Fiber Coating for the Rapid and Sensitive Determination of Legacy and Emerging Brominated Flame Retardants in Water

Legacy and emerging brominated flame retardants (BFRs) occur in environmental waters at trace to ultratrace levels and exhibit high structural diversity, posing significant challenges for sample pretreatment and analysis. Herein, by coupling solid-phase microextraction (SPME) with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS), we developed a rapid, comprehensive, and sensitive method for the determination of structurally diverse BFRs in water. A cationic covalent organic framework, Tp-DB-DMTF, was synthesized and prepared as an SPME fiber coating to achieve simultaneous enrichment of 13 legacy and emerging BFRs. Owing to the size-matched porosity and multiple cooperative interactions, the Tp-DB-DMTF-coated SPME fiber exhibited outstanding extraction performance with enrichment factors exceeding 6.0 × 103 and extraction capacities being 10.1–1608.5 times higher than those of commercial SPME fibers. Benefiting from solvent-free pretreatment and direct thermal desorption, the workflow required only 60 min while enabling exceptional sensitivity with method detection limits of 0.0017–0.60 ng L–1, outperforming previously reported methods. In addition, this method demonstrated a wide linear range of 0.01–200 ng L–1 (R2 ranging from 0.9927 to 0.9995), good precision (relative standard deviations of repeatability/reproducibility ≤ 14.0%), acceptable durability (≥90% efficiency after 60 reuses), and satisfactory recoveries (79.4–121.1%). Application to multiple types of environmental waters confirmed the feasibility of the method and revealed the co-occurrence of legacy and emerging BFRs. This work provides a practical and effective solution for determining BFRs in water, which is promising to address the needs for large-scale and longitudinal monitoring.