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Enhanced adsorption/extraction of bisphenols by pyrrolic N-based 3D magnetic carbon nanocomposites for effervescence-assisted solid-phase microextraction of bisphenols from juices and the underlying interaction mechanisms


Herein, we fabricated a magnetic 3D nanocomposite based on Co,Ni-codoped and N-modified carbon nanotubes and reduced graphene (CoNi-N-CNTs/rGO). This nanomaterial possessed strong magnetism due to the presence of Co-Ni alloy, abundant defect sites owing to N doping, and a 3D multi-porous structure resulting from CNT in-situ growth on the graphene surface. Based on DFT calculations, H-bonding, hydrophobic and π-π conjugation were inferred to facilitate bisphenol adsorption by nanocomposites, among which π-π interactions provided the greatest adsorption contribution within a given N-doping type. By employing BPM as model compound, the adsorption energies (ΔEa) for π-π conjugation were −1.80, −1.59 and −2.08 eV for graphitic-N, pyridinic-N, and pyrrolic-N, respectively. This infers that pyrrolic-N sites form the strongest BP sorption bonds with the nanocomposite. The nanocomposites were utilized as an extractant in an effervescence tablet-assisted magnetic solid-phase microextraction (ET-MSPE) procedure that was optimized using Plackett-Burman design (PBD) and central composite design (CCD). Under optimized conditions, the ET-MSPE/HPLC-FLD method provided strong analytical performance for quantification of six BPs in juice with limits of detection of 0.06–0.20 μg/L, recoveries of 82.4–103.7 % and RSDs of 1.2–5.3 %. The particular novelty of this study lies in demonstrating the enhancement of adsorption/extraction efficiencies for BPs by nanocomposites resulting from N doping to generate the superior adsorption properties associated with the pyrrolic-N structure. These findings provide a theoretical foundation to inform the rational design of N-doped adsorbents/extractants based on a rigorus understanding of the molecular interactions occurring between carbon-based nanocomposites and BP analogues.

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