| Although pesticides play a vital role in agriculture,it can also cause more or less adverse effects on the ecological environment and human health through various ways.Because pesticides have long half-life,high toxicity and easy residue in different nodes in the biological chain,it is of great significance to detect pesticide residues in various complex substrates.Owing to the matrix interference and insufficient instrumental detection limit for trace levels of analyte in real samples,direct chromatographic separation and determination of the species is difficult.Therefore,it is necessary to separate and enrich the analytes from the samples by combining appropriate sample pretreatment technology with modern analytical instruments,and establish fast,efficient and convenient methods for pesticide residue analysis.In this thesis,four magnetic adsorption materials were successfully prepared with iron-based nanomaterials as the magnetic core.These nanomaterials were adopted as the adsorbents,which,for the extraction and determination of pesticide residues combined with high performance liquid chromatography in various samples（fruits,vegetables,edible fungi,and environmental water）.The main contents of this thesis are as follows:（1）Magnetic graphene oxide（MGO）was synthesized by a green and rapid mechanochemical method,and it was adopted as magnetic solid phase extraction（MSPE）adsorbent for the separation of chlorpyrifos and imidacloprid in vegetable samples.The magnesium oxide was characterized by transmission electron microscopy（TEM）,Fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,Zeta potential measurement and vibrating sample magnetometer（VSM）.After optimizing the influencing factors of magnetic solid phase extraction（MSPE）,the optimal extraction conditions were determined.Under the optimum extraction conditions,a new method for the separation and analysis of chlorpyrifos and imidacloprid combined with high performance liquid chromatography with UV detector（HPLC-UV）was established.The experimental results showed that good linearity of chlorpyrifos and imidacloprid was obtained in the range of 2.0×10-3-10.0μg/m L,and the detection limits（LOD）and quantification limits（LDQ）were 1.5-4.9μg/L and 4.9-11.3μg/L,respectively.This proposed method successfully applied to the detection of chlorpyrifos and imidacloprid in vegetable samples with recoveries of 79.1-94.5%and the relative standard deviation（RSD）range was 3.3-6.7%.（2）Magnetic graphene oxide chitosan composite（MGO-CS）was successfully prepared and used as a magnetic adsorbent for the separation and determination of Lambda-Cyhalothrin combined with HPLC-UV.MGO-CS was prepared by a mechanochemical method,and the structures and properties were characterized by scanning electron microscope（SEM）,XRD,FTIR,VSM and thermogravimetric analyzer（TGA）.Several experimental factors affecting the extraction efficiency were optimized by single factor test.Under the optimal conditions,the method achieved a wide linear range(2.5×10-2-0.5μg/m L),low detection limit and quantification limit（LOD=4.2μg/L,LOQ=15.0μg/L）,satisfactory recovery（70.2-98.2%）and good reproducibility（RSD=2.1-7.1%）.The experimental results showed that the proposed method has been successful applied for the separation and analysis of Lambda-Cyhalothrin in vegetables.（3）A new MSPE-HPLC-UV method adopting magnetic ZIF-8（M-ZIF-8）was established for the separation and determination of carbendazim in edible fungi samples.The morphology and structure of M-ZIF-8 were characterized by SEM,FT-IR,XRD,TGA,N2 adsorption and VSM,and the factors affecting the extraction efficiency were optimized by single factor method.Under the optimal MSPE conditions,the proposed method displayed a good linear range(3.0×10-3-3.0μg/m L)with coefficients of determination（R2）of 0.9991.The LOD and LOQ were0.9μg/L and 2.6μg/L,respectively.The results of standard addition experiments showed that the average recovery was 80.1-96.6%,and the RSD was 1.5-4.6%.The results showed that the method had the advantages of high sensitivity,simple operation,environment friendly,and wide linear range,and is suitable for the detection of edible fungi samples.（4）The modified magnetic graphene oxide/ZIF-8 ternary composite（MGO-ZIF-8）was successfully fabricated by chemical co-precipitation method,and used for the co-extraction of acetamiprid and imidacloprid before HPLC-UV analysis.The MGO-ZIF-8 composites was characterized by SEM,XRD,FT-IR,TGA and VSM.Through single factor experiment,the best extraction conditions of MSPE were optimized.Under the optimal experimental conditions,the linear range of acetamiprid and imidacloprid was 3.0×10-3-2.0μg/m L,the LOD was 1.2-1.5μg/L,the LOQ was 4.1-4.9μg/L,and the enrichment factor was 15 times.This method could be used for the determination of acetamiprid and imidacloprid in tea samples,and actual spiked recovery was between 74.9-96.7%,and the RSD was 2.1-8.8%.There are 79 pictures,24 tables and 190 references in this thesis. |
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