Controllable synthesis of magnetic nanoporous carbon with tunable porosity for the efficient cleanup of vegetable samples

Highly graphitic nanoporous carbon (NPC) was obtained from an agricultural waste-citrus peel at optimum condition. Then, a low-cost and pore size-controlled magnetic graphitic nanoporous carbon (MNPC) with ultrahigh specific surface area (1064 m(2) g(-1)) was successfully fabricated by coprecipitation of Fe3O4 particles onto NPC. The prepared MNPC was characterized by Brunauer-Emmett-Teller (BET), Raman spectrum, scanning electron microscope (SEM) and Fourier transform infrared spectrometry (FT-IR). BET results showed a significant increase in the micropores volume and specific surface area of MNPCs following the increase of carbonization temperature, which implied that highly efficient carbonization made NPC an excellent active phase for MNPC. Besides, the adsorption mechanism was investigated and turned out that pi-pi interactions between interfering substances and MNPC were considered to be the major driving force for the adsorption process. The experimental parameters affecting the cleanup efficiency was optimized through Response surface methodology (RSM) in detail. Under the optimal cleanup condition, the MNPC was applied for determination of 16 insecticides in vegetables coupled with gas chromatography-mass spectrometry (GC-MS), a satisfactory performance was obtained. Good linearity was observed in the investigated concentration range of 1-100 mg kg(-1) with correlation coefficients (r(2)) between 0.9963 and 0.9999. The limits of detection (LODs) were in the range of 0.03-0.33 mg kg(-1). The recoveries ranged from 81.9 to 112.3% with relative standard deviations (RSDs) less than 10.9%. To summary up, the MNPC could potentially be used as a super adsorbent to efficiently remove pigments from vegetables, so that the proposed method was an efficient cleanup and enrichment procedure. (C) 2018 Elsevier B.V. All rights reserved.