Triazine-Based Porous Organic Cage-Coated Fiber for Cold-Assisted Headspace SPME-GC-MS: Ultratrace Detection of Semivolatile Liquid Crystal Monomers in Human Urine

Liquid crystal monomers (LCMs), which are key components of electronic displays, are emerging environmental contaminants owing to their persistence, bioaccumulation, and potential toxicity. To address the challenge of their ultratrace detection in complex biological matrices, we developed a novel analytical platform that integrates cold-assisted headspace solid-phase microextraction (CA-HS-SPME) with gas chromatography–mass spectrometry using a triazine-based porous organic cage (T-POC) as the fiber coating. T-POC exhibits high thermal stability (>300 °C), strong hydrophobicity, and dual-mode mass-transfer channels, enabling efficient adsorption, reduced water interference, and accelerated analyte diffusion. Systematic optimization of the extraction and desorption conditions, combined with a circulating cooling module, enhanced the extraction efficiency by 6%–52% compared to that of conventional HS-SPME. The developed method exhibited excellent performance, with enrichment factors of 2.911 × 103–5.537 × 103, recoveries of 78.5–105.7%, relative standard deviations ≤10.3%, and ultralow limits of quantification (1.5–8.9 pg mL–1), exceeding those of previously reported methods by 2–4 orders of magnitude. This work demonstrates a powerful strategy for the ultrasensitive and reliable determination of semivolatile LCMs in human urine, offering a valuable tool for exposure assessment and toxicological studies while showcasing the promising application of porous organic cages in advanced sample pretreatment techniques.