▎ 摘　　要

In this work, ultrathin magnetic nitrogen doped graphene tube (mNi@N-GrT) is synthetized via a template free graphitization process. The mNi@N-GrT as magnetic solid phase extraction adsorbent is used to extract three tetracyclines (TCs), showing the best extraction ability and adsorption capacity than graphene, MWCNT and magnetic MWCNT (NiFe2O4/MWCNT). The tubular structure of mNi@N-GrT can avoid the aggregation problem, provide higher active surface area and larger conjugated system. The doping of N atom will generate structural defects which will be adsorption sites for three TCs. Furthermore, the mNi@N-GrT with magnetic properties is beneficial to the recovery and recycle. The limits of detections (LODs) (S/N = 3:1) are in the range of 1.29-2.31 ng mL(-1) with average recoveries from 91.6 to 109.7% in milk samples. The results demonstrate that the mNi@N-GrT is a hopeful adsorbent in the MSPE of TCs in real samples. (C) 2018 Elsevier B.V. All rights reserved.