An agaric-like covalent organic framework composite for efficient extraction of trace cytokinins in plant samples

Covalent organic framework composites have received great interest and regarded as new-generation porous materials in application of sample preparation. In this work, an agaric-like graphene oxide @ covalent organic framework (AGO@COF) composite was first synthesized and used as an ideal adsorbent for enrichment of trace cytokinins (CKs) due to its large specific surface area, rich in micro-mesopore and organic functional groups. The contact areas between AGO@COF composite and CKs were greatly increased due to the special agaric-like morphology, which would further improve the extraction efficiency. Hence, a rapid, simple and efficient AGO@COF-based dispersive solid-phase extraction method for detecting four CKs (N⁶-(delta 2-isopentenyl)-adenine, kinetin, DL-dihydrozeatin and 6-benzylaminopurine) was successfully established. The proposed method had low limits of detection (0.1-2.0 pg mL^-1), good reproducibility (RSDs≤3.9%, n=5) and high recoveries (84.4-107.7%). With this method, N⁶-(delta 2-isopentenyl)-adenine and 6-benzylaminopurine in plants were successfully detected and quantified. Results showed that the developed AGO@COF composite possessed superior extraction performance and potential application in enrichment of trace targets from complex plant samples.