Preparations And Applications Of Magnetic Nitrogen-doped Graphene And Immobilized Metal Affinity Magnetic Adsorbent

Sorbents are an important part of sample preparation.Among many sample preparation methods,magnetic solid phase extraction（MSPE）using magnetic particles as the adsorbent has been favored because of its fast mass transfer kinetics and easy and fast operation.Therefore,the development of new magnetic sorbents has become one of the hot topics in current analytical chemistry research.In recent years,graphene,as a hot material,has been widely used in various chemical research fields.However,graphene is prone to irreversible aggregation,which limits its development.Therefore,various modification methods have been developed to improve the adsorption performance of graphene.In this paper,two magnetic adsorbents were synthesized by heteroatom doping and surface modification,and they were applied to the detection of environmental pollutants and plant hormones,respectively.The main contents are as follows:（1）A one-step hydrothermal method was used to efficiently synthesize a magnetic nitrogen doped graphene（mag NG）,and then applied it to the study of adsorption of non-steroidal anti-inflammatory drugs（NSAIDs）.Since graphene has large specific surface area,after doping with nitrogen,a good adsorption effect can be obtained through strong hydrophobic force,π-πinteraction,and hydrogen bonding.Transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,infrared spectroscopy（FT-IR）,elemental analyzer,X-ray photoelectron spectroscopy（XPS）,superconducting quantum interference magnetic measurement system（SQUID）were used to characterize morphology,chemical composition and magnetic properties of the prepared adsorbent.After optimizing the parameters affecting extraction efficiency in detail,we used mag NG for enrichment and detection of NSAIDs in environmental samples.The detection limit range was 1.07-1.53 ng/ml,the spiked recovery was between 81.2 to 121.5%,and the relative standard deviations within and between days were less than 10.8%.In general,the analytical method established in this paper was an effective pretreatment and enrichment method,with an efficient extraction process,a wide linear range,and high precision.（2）After rapid deposition of stable polydopamine（PDA）and polyethyleneimine（PEI）layers on the surface of magnetic graphene（mag GO）,Glycidyl methacrylate（GMA）was grafted onto the surface to form a main chain by the surface-initiated atom transfer radical polymerization method（SI-ATRP）technique,and then ring-opening reaction was used to graft iminodiacetic acid（IDA）to the GMA chain.Finally,Cu²⁺was fixed on the carboxyl group of IDA.The coordination effect of Cu²⁺and N achieved selective adsorption of cytokinins（CKs）.The morphology,chemical structure and other properties of mag GO@PDA/PEI@GMA@IDA-Cu²⁺were characterized and used for the analysis and detection of cytokinins in plant samples.After optimizing the extraction conditions,we used it for the analysis and detection of cytokinin in plant samples.The recovery rate of the obtained samples was between 84.2%to 120%,and the relative standard deviations within and between days were less than 11.0%.Therefore,we believe that this analytical method has the ability to detect trace amounts of CKs in plants,and the extraction process is fast and efficient.