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.

Room-temperature synthesis of magnetic covalent organic frameworks for analyzing trace benzoylurea insecticide residue in tea beverages.

A novel magnetic covalent organic framework (NH2-Fe3O4@COF) was prepared using a simple room-temperature synthesis in this study. These magnetic particles exhibited high adsorption performance with short adsorption time (10 min) for six benzoylurea insecticides (BUs) as magnetic solid-phase extraction (MSPE) adsorbents. Quantum chemistry calculation demonstrated that adsorption mechanism was primarily attributed to strong halogen bonds between electronegative O atoms of COF and electropositive F atoms of BUs as well as potential hydrophobic effect. Wide linearities (10-1000 ng·L-1) and low limits of detection (0.06-1.65 ng·L-1) for six analytes were obtained via liquid chromatography-tandem mass spectrometry. Applicability of the proposed method was further evaluated by analyzing four kinds of original tea beverages. Recoveries of six BUs in spiked samples ranged from 80.1% to 108.4%.

Facile synthesis of gold@graphitized mesoporous silica nanocomposite and its surface-assisted laser desorption/ionization for time-of-flight mass spectroscopy.

In this work, a novel core-shell structured gold@graphitized mesoporous silica nanocomposite (Au@GMSN) was synthesized by in situ graphitization of template within the mesochannels of mesoporous silica shell on gold core and demonstrated to be promising nanomaterials for surface-assisted laser desorption/ionization time-of-flight mass spectroscopy (SALDI-TOF MS). The integration of the graphitized mesoporous silica with the gold nanoparticles endowed Au@GMSN with large surface areas of graphitic structure, good dispersibility, and strong ultraviolet (UV) absorption. Au@GMSN exerted the synergistic effect on the efficient detection of small-molecular-weight analytes including amino acids, neutral saccharides, peptides, and traditional Chinese medicine. The Au@GMSN-assisted laser desorption/ionization exhibited the following superiorities: high ionization efficiency, low fragmentation interference, favorable salt tolerance, and good reproducibility. Moreover, because of the large hydrophobic inner surface area of the graphitized mesoporous silica shell, the Au@GMSN demonstrated its promising capacity in the pre-enrichment of aromatic analytes prior to SALDI-TOF MS, which favored rapid and sensitive detection.