Self-assembled flower-like carbon nanosheets for magnetic solid-phase extraction of microcystins from aquatic organism.

Adsorbents with good dispersibility and high efficiency are crucial for magnetic solid-phase extraction (MSPE). In this study, flower-like magnetic nanomaterials (F-Ni@NiO@ZnO-C) were successfully prepared by calcination of metal-organic framework (MOF) precursors that was stacked by two-dimensional (2D) nanosheet. The synthesized F-Ni@NiO@ZnO-C has a flower-like layered structure with a large amount of pore space, promoting the rapid diffusion of targets. In addition, Zn doped in MOF precursors was still retained that further produced strong metal chelation with targets. The unique structure of F-Ni@NiO@ZnO-C was used as MSPE adsorbent, and combined with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for extraction of three microcystins (MCs) detection, including microcystin-LR (MC-LR), microcystin-RR (MC-RR), microcystin-YR (MC-YR). The resulting method has a detection limit of 0.2-1.0 pg mL, a linear dynamic range of 0.6-500.0 pg mL and has good linearity (R ≥ 0.9996). Finally, the established method was applied to the highly selective enrichment of MCs in biological samples, successfully detecting trace amounts of MCs (8.4-15.0 pg mL) with satisfactory recovery rates (83.7-103.1 %). The results indicated that flower-like magnetic F-Ni@NiO@ZnO-C was a promising adsorbent, providing great potential for the determination of trace amounts of MCs in biological samples.