Polybenzimidazole-based magnetic solid-phase extraction coupled with gas chromatography-mass spectrometry for the...

A novel Fe₃O₄/polybenzimidazole (Fe₃O₄/PBI) nanocomposite was synthesized by a facile phase inversion method and used as a magnetic solid-phase extraction (MSPE) adsorbent for the determination of eight triazine herbicides (THs) in environmental waters prior to gas chromatography-mass spectrometry (GC-MS). The Fe₃O₄/PBI nanocomposite combined the strong magnetism of Fe₃O₄ with the abundant functional groups and good chemical stability of PBI, providing multiple interaction sites for THs. Characterization results demonstrated the high magnetic strength (40.8 emu/g) and large specific surface area (90.5 m²/g) of the Fe₃O₄/PBI nanocomposite. Key MSPE parameters, including the amount of adsorbent, extraction and desorption times, ionic strength, sample pH, desorption solvent type and volume, were systematically optimized to achieve efficient extraction and desorption. Under optimal conditions, the proposed MSPE/GC-MS method based on the Fe₃O₄/PBI nanocomposite exhibited excellent analytical performance for eight THs, with wide linear ranges (0.1-100, 0.2-100, or 0.5-100 μg/L), low limits of detection (0.040-0.182 μg/L) and limits of quantification (0.133-0.606 μg/L), and satisfactory precision (relative standard deviations (RSDs) of 0.5-11.7%, n = 3). With 10 mg of adsorbent, extraction recoveries of the target THs ranged from 73.1% to 86.9% within 5 min. The Fe₃O₄/PBI nanocomposite showed good reusability, maintaining nearly constant peak areas over at least 10 consecutive extraction-desorption cycles, indicating high stability in high‑salinity matrix and organic solvents. The applicability of the method was further demonstrated by the analysis of THs in tap water, river water, and pond water samples, yielding relative recoveries of 80.8-118.8% with RSDs of 0.1-8.7%. These results demonstrate that the Fe₃O₄/PBI nanocomposite is a promising adsorbent for MSPE, and the developed MSPE/GC-MS method is suitable for the reliable determination of trace THs in environmental waters.