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@ZnO₂-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@ZnO₂-C has a flower-like layered structure with a large amount of pore space, promoting the rapid diffusion of targets. In addition, Zn²⁺ doped in MOF precursors was still retained that further produced strong metal chelation with targets. The unique structure of F-Ni@NiO@ZnO₂-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⁻¹, a linear dynamic range of 0.6–500.0 pg mL⁻¹ 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⁻¹) with satisfactory recovery rates (83.7–103.1 %). The results indicated that flower-like magnetic F-Ni@NiO@ZnO₂-C was a promising adsorbent, providing great potential for the determination of trace amounts of MCs in biological samples.