Novel Fe3O4@metal-organic framework@polymer core-shell-shell nanospheres for fast extraction and specific preconcentration of nine organophosphorus pesticides from complex matrices.

Herein, a novel core-shell-shell magnetic nanosphere denoted as Fe3O4@ZIF-8@polymer was fabricated by sequential in situ self-assembly and precipitation polymerization for effective magnetic solid-phase extraction of nine organophosphorus pesticides (OPPs) from river water, pear, and cabbage samples. The integrated Fe3O4@ZIF-8@polymer featured convenient magnetic separation property and excellent multi-target binding ability. More importantly, the functional polymer coating greatly improved the extraction performance of Fe3O4@ZIF-8 for OPPs, thus facilitating the simultaneous determination of trace OPP residues in real samples. The developed MPSE-LC-MS/MS method exhibited good linearity (R2 ≥ 0.9991) over the concentration range of 0.2-200 µg L-1, low limits of detection of 0.0002-0.005 µg L-1 for river water and 0.006-0.185 µg kg-1 for pear and cabbage, satisfactory precision with relative standard deviations ≤ 9.7% and accuracy with recoveries of 69.5-94.3%. These results highlight that the combination of polymers with MOFs has great potential to fabricate excellent adsorbents for high-throughput analysis of various contaminants in complex matrices.

A "half" core-shell magnetic nanohybrid composed of zeolitic imidazolate framework and graphitic carbon nitride for magnetic solid-phase extraction of sulfonylurea herbicides from water samples followed by LC-MS/MS detection.

A "half" core-shell g-C3N4/Fe3O4@ZIF-8 nanohybrid, in which Fe3O4 and zeolite imidazolate framework-8 (ZIF-8) constructed the core-shell structure, was successfully fabricated via a versatile in situ growth strategy. This nanohybrid was employed for simultaneous magnetic solid-phase extraction (MSPE) of trace levels of fifteen target sulfonylurea herbicides (SUHs) in environmental water samples followed by LC-MS/MS detection. C3N4 nanosheets were first prepared by liquid exfoliation of bulk g-C3N4, after which Fe3O4 nanoparticles were uniformly deposited onto the surface of C3N4 nanosheets, and ZIF-8 nanoparticles were grown on the surface of g-C3N4/Fe3O4 by anchoring Zn2+ on g-C3N4/Fe3O4. Owing to the synergistic effect, the hybridization of C3N4 and ZIF-8 endowed the nanohybrid with higher multi-target adsorption ability for SUHs compared to pure C3N4 or ZIF-8. The separation as well as the enrichment processes were facilitated using Fe3O4 as a magnetic core. The influence of various parameters on MSPE efficiency, including adsorbent dosage, extraction time, solution pH, and desorption solvent and its volume, was investigated in detail. Under optimal conditions, the MSPE coupled with LC-MS/MS exhibited good linearity ranging from 0.5 to 100 µg L-1 with correlation coefficients (R2) ≥ 0.9919, high sensitivity with low limits of detection (LODs) of 0.005-0.141 µg L-1 and satisfactory recoveries of 67.4-105.5% with relative standard deviations (RSDs) < 9.8%. These results indicate that this method is reliable for the determination of SUHs in different matrices and the in situ growth strategy is a promising approach for constructing effective adsorbents. Graphical abstract Schematic representation of a "half" core-shell magnetic nanohybrid composed of zeolitic imidazolate framework (ZIF-8) and graphitic carbon nitride (g-C3N4) for magnetic solid-phase extraction (MSPE) of trace level determination of fifteen sulfonylurea herbicides (SUHs) in environmental water samples using LC-MS/MS detection.