Enrichment and determination of polybrominated diphenyl ethers in environmental water samples by magnetic solid-phase extraction with core-shell magnetic carbon microspheres before gas chromatography with mass spectrometry

Core-shell structured Fe2O3/CeO2@MnO2 microspheres with abundant surface oxygen for sensitive solid-phase microextraction of polycyclic aromatic hydrocarbons from water

Core-shell structured Fe₂O₃/CeO₂@MnO₂ microspheres were fabricated and used as solid-phase microextraction coating for determination of polycyclic aromatic hydrocarbons (PAHs) in water samples. XPS spectra demonstrated the generation of abundant surface oxygen on Fe₂O₃/CeO₂@MnO₂ microspheres, which provided binding sites for enhancement of analyte extraction. Under optimized conditions, the proposed method presented good linearity in the concentration range 0.04-100 ng mL^-1, with low limits of detection varying from 0.38 to 3.57 ng L^-1 for eight PAHs. Relative standard deviations for a single fiber and five batches of fibers were in the ranges of 4.1-8.2% and 7.1-11.4%, respectively. The proposed method was successfully used for determination of PAHs in real river water samples with recoveries ranging from 87.1 to 115.9%. The proposed method using as-prepared Fe₂O₃/CeO₂@MnO₂ microspheres as SPME coating exhibit significant potential for real sample analysis due to its excellent reproducibility, high sensitivity, and good linearity.

High crystalline magnetic covalent organic framework with three-dimensional grapevine structure for ultrasensitive extraction of nitro-polycyclic aromatic hydrocarbons in food and environmental samples

Developing and establishing an efficient pre-treatment approach for the precise extraction of nitrated-polycyclic aromatic hydrocarbons (N-PAHs) from real-life samples is critical for ensuring their safety. In this study, a novel crystalline magnetic covalent organic framework with a grapevine structure not a single core-shell, Fe₃O₄@TAPT-DMTA-COF, was fabricated via chemical bonding. Unchanging the reticulated structure and high crystallinity of TAPT-DMTA-COF, the combination made this material possess not only simple operation via magnetic decantation but also remarkable chemical stability. Fe₃O₄@TAPT-DMTA-COF had a large surface area (1578.45 m²/g), and rich electronegative triazine-groups, which makes it become a superior magnetic enrichment material for trace N-PAHs. For N-PAHs analysis, low limits of detection (LODs) (1.43-17.24 ng/L), excellent relative standard deviations (RSDs ≤ 11.52%), and wide linearity (10-5000 ng/L) were obtained. Real-life applications based on this composite have been successfully explored by capturing the N-PAHs emitted from food and environmental samples.

Effective enrichment and detection of trace polybrominated diphenyl ethers in water samples based on magnetic covalent organic framework nanospheres coupled with chromatography-mass spectrometry

Novel core shell structured magnetic covalent organic frameworks were synthesized at room temperature and first applied in water samples for the enrichment of trace polybrominated diphenyl ethers (PBDEs) through magnetic solid-phase extraction. The prepared materials were characterized through transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer and X-ray photoelectron spectroscopy. During adsorption, the parameters affecting extraction and desorption efficiency were further optimized. Combined gas chromatography and mass spectrometry (GC/MS) revealed that high enrichment factors (275-292), low limits of detection (0.12-0.38 ng·L-1), wide linear ranges (0.5-1000 ng·L-1), and good reproducibility (intra-day 1.40%-4.31% and inter-day 5.14%-9.12%) were obtained under optimal conditions. The method successfully detected PBDEs in different water samples.

Facile synthesis of tubular magnetic fluorinated covalent organic frameworks for efficient enrichment of ultratrace polybrominated diphenyl ethers from environmental samples

Polybrominated diphenyl ethers (PBDEs), known as the most widely used brominated flame retardant, have received great public concern due to its hidden environment and health problems. Development of highly selective and sensitive analytical approaches for enrichment and detection of ultratrace PBDEs are in high demand. Conventional sample pretreatment techniques usually require tedious procedures, long time, and excessive consumption of solvent and sample, thus hindering ultrasensitive detection of PBDEs. To address this issue, we first reported a simple room-temperature approach for synthesis of tubular magnetic fluorinated covalent organic frameworks (MCNT@TAPB-TFTA). The introduction of fluorine atoms played multiple roles in improving the frameworks' hydrophobicity and the adsorption capabilities for PBDEs. Combined with atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS), several crucial parameters of magnetic solid-phase extraction (MSPE) including adsorbent dosage, adsorption time, pH, ion strength, the eluent, elution time and elution frequencies were examined in detail. The optimal method exhibited wide linear ranges (0.01-500 ng/L), low limit of detections (LODs, 0.0045-0.018 ng/L), good correlation coefficients (r ≥ 0.9977), and high enrichment factors (EFs, 1425-1886 folds) for eight PBDEs. Furthermore, this proposed method could be successfully applied to sensitive determination of ultratrace PBDEs in environmental samples, demonstrating the promising potential of the MCNT@TPAB-TFTA as an adsorbent in sample pretreatment.

Rapid magnetic solid-phase extraction of Congo Red and Basic Red 2 from aqueous solution by ZIF-8@CoFe2 O4 hybrid composites

Core-shell metal-organic framework materials have attracted considerable attention mainly due to their enhanced or new physicochemical properties compared with their single-component counterparts. In this work, a core-shell heterostructure of CoFe2 O4 -Zeolitic Imidazolate Framework-8 (ZIF-8@CoFe2 O4 ) is successfully fabricated and used as an solid-phase extraction adsorbent to efficiently extract Congo Red and Basic Red 2 dyes from contaminated aqueous solution. Vibrating sample magnetometry indicates that the saturated magnetization of ZIF-8@CoFe2 O4 is 3.3 emu/g, which is large enough for magnetic separation. The obtained hybrid magnetic metal-organic framework based material ZIF-8@CoFe2 O4 can remove the investigated dyes very fast within 1 min of the contact time. The adsorbent ZIF-8@CoFe2 O4 also shows a good reusability. After regeneration, the adsorbent can still exhibit high removal efficiency (∼97%) toward Congo Red for five cycles of desorption-adsorption. This work reveals the great potential of core-shell ZIF-8@CoFe2 O4 sorbents for the fast separation and preconcentration of organic pollutants in aqueous solution before high-performance liquid chromatography analysis.