Boron Nitride Nanosheets-based Magnetic Solid Phase Extraction For Analysis Of Plant Growth Regulators And Phenoxyacid Herbicide Residues In The Environment

Excessive application of pesticides will not only cause environmental pollution problems,but also threaten food safety.Therefore,it is necessary to analyze and detect pesticide residue pollutants in the environment.However,the content of pesticide residue contaminants is usually at a trace level,and the sample matrix is complicated,so it becomes difficult to analyze.Magnetic solid phase extraction（MSPE）,as a new solid phase extraction technology,is widely used due to its simple operation and high extraction efficiency.In MSPE,magnetic adsorbents are a key factor affecting extraction efficiency and selectivity.The development of new adsorbents with excellent adsorption performance is currently a hot research area.Boron nitride nanosheets（BNNSs）,which has a structure similar to graphene,has gradually attracted attention in the field of adsorption due to high specific surface area,high oxidation resistance,and high chemical stability.In this paper,plant growth regulators（PGRs）and phenoxyacid herbicides（POAs）were selected as targets.Boron nitride nanosheets-based magnetic nanomaterials that are magnetic boron nitride nanosheets（Fe₃O₄@BNNSs）nanomaterial and polypyrrole modified magnetic boron nitride nanosheets（Fe₃O₄@BNNSs@PPy）nanomaterial were prepared and used as MSPE absorbents.Combined with HPLC-MS/MS technique,the Fe₃O₄@BNNSs nanomaterial was applied for the detection of PGRs in tomatoes and POAs in water,respectively.Meanwhile,the Fe₃O₄@BNNSs@PPy nanomaterial was used for the adsorption of4-chlorophenoxyacetic acid（4-CPA）and adsorption performance was studied.in detail.The main outlines are listed as follows:1.Novel Fe₃O₄@BNNSs nanocomposite was synthesized by chemical co-precipitation and characterized by SEM,FT-IR,XPS,XRD and VSM.Combined with HPLC-MS/MS technique,it was used as MSPE adsorbent for the determination of six PGRs in tomatoes.Several parameters affecting the extraction efficiencies were optimized.With the best factors,the method obtained low detection limits(0.002-0.010ng g^-1),good linear range(0.05-10 ng g^-1)and satisfactory precision（intra-day:1.2%-3.9%,inter-day:2.1%-6.9%）.Meanwhile,the established method was successfully employed to extract and determine PGRs in tomatoes with spiked recoveries of 85.2-109.0%.2.Novel Fe₃O₄@BNNSs nanocomposite was synthesized using chemical co-precipitation and characterized by SEM,FT-IR,XPS,XRD and VSM.Combined with HPLC-MS/MS technique,it was used as MSPE adsorbent to analyze five POAs in water.The extraction conditions were optimized.With the best factors,the method obtained low detection limits(7.6-30 ng L^-1),good linear range(20-10000 ng L^-1)and satisfactory precision（intra-day:1.1%-4.6%,inter-day:4.3%-6.8%）.Meanwhile,established approach was successfully employed to extract and determine POAs in three water samples（pond water,tap water and groundwater）with the spiked recoveries of76.6-107.2%.3.Fe₃O₄@BNNSs@PPy was successfully prepared by in-situ polymerization method with the aid of ferric chloride.The material was characterized by SEM,XRD,FT-IR,XPS and VSM.At the same time,it was used as MSPE adsorbent to remove4-CPA in water,and its adsorption performance and adsorption mechanism were studied.Studies have shown that the adsorption of 4-CPA by Fe₃O₄@BNNSs@PPy followed the Langmuir isotherm,which is a monolayer adsorption.The results of the adsorption kinetics showed that Fe₃O₄@BNNSs@PPy can quickly adsorb 4-CPA,and the adsorption kinetics conformed to the pseudo-second-order kinetics.Adsorption thermodynamics showed that the adsorption reaction is endothermic and the degree of disorder at the solid/liquid interface increases with increasing temperature.The adsorption capacity of 4-CPA was 105.75 mg g^-1.