Preparation Of Porous Composite Materials And Its Applications In The Determination Of Some Pesticide Residues

With a growing emphasis on the issue of food safety,various countries and regional organizations in the world have stipulated the maximum allowed residues for agricultural and veterinary drugs in foods.However,due to the complex matrix of food samples and the very low level of the residues of agricultural and veterinary drugs,it is impossible to directly detect them with the commonly used lab instruments.Therefore,the sample preparation process for the purpose of enriching the analytes and reducing the matrix effect has become a necessary step before the instrument detection.With the continuous development and application of new sample pretreatment technologies,solid phase extraction(SPE)and magnetic solid phase extraction(MSPE)technologies have been increasingly used in the field of food analysis.Compared with traditional liquid-liquid extraction sample preparation method,these two technologies have the advantages of simple operation and less consumption of organic solvents.Since the adsorbents are the core part of SPE and MSPE,the development of the adsorbents with good stability,high selectivity and strong adsorption capacity has become the main focus of the scientists from both materials science and analytical chemistry circles.After systematically reviewing the relevant literature,the author of this thesis prepared and synthesized three different porous composite materials and used them as the adsorbents for SPE or MSPE,respectively.To evaluate their adsorption properties,they were used to enrich some pesticides(carbamate pesticides,phenylurea herbicides,and phenylurea pesticides)residues in different samples.With the help of high performance liquid chromatographic detection,the new methods for the determination of different pesticide residues in food and environmental samples were established.The main research work is as follows:1.A graphene oxide-based composite(DABP-GO)was synthesized by using a simple diazonium salt method.The DABP-GO composite was characterized by scanning electron microscopy,infrared spectroscopy and nitrogen adsorption-desorption.The DABP-GO showed to be an effective solid-phase extraction(SPE)adsorbent for some carbamate pesticides.A SPE method with the DABP-GO as the adsorbent combined with high-performance liquid chromatography with ultraviolet detection was established to determine trace carbamate residues in vegetable samples(benincasahispida and pakchoi).Under the optimal conditions,the linear range was from 1.0 to 40.0 ng/g.The limits of detection and limits of quantitation for the six carbamates(metolcarb,arprocarb,carbaryl,isoprocarb,fenobcarb and diethofencarb)were 0.3?0.5 ng/g and 0.9?1.5 ng/g for benincasahispida sample and 0.5?1.0 ng/g and 1.5?3.0 ng/g for pakchoi sample,respectively.The relative standard deviations(RSDs)for the intra-day precision at the analyte concentration of 40 ng/g are from 2.3 to 8.2%(n=5)and the inter-day RSDs(n=5)are from 4.5 to 9.2%.2.A magnetic hyper-cross-linked polymer composite(Fe3O4/KAPs)wasprepared by using Friedel-Crafts reaction with triphenylphosphine and benzene as structural units and Fe3O4 as magnetic source.The resulting Fe3O4/KAP was shown to be an effective magnetic sorbent for the phenylurea herbicides(PUHs),including metoxuron,monuron,chlortoluron,monolinuron and buturon,and also for some phthalates,polycyclic aromatic hydrocarbons and chlorophenols.The Fe3O4/KAP was characterized by means of Brunauer-Emmett-Teller surface area measurements,Fourier-transform infrared spectroscopy,thermogravimetry,X-ray diffraction,scanning electron microscopy and transmission electron microscopy.After the desorption with acetonitrile,the analytes were quantified by HPLC with UV detection.The effects of adsorbent dosage,extraction time,sample solution pH,ionic strength,desorption solvent and desorption time were optimized for the PUHs.Under the optimaized conditions,the response is linear from 0.5?1.0 up to 50 ng/mL for the five PUHs.The limits of detection range between 0.05 and 0.30 ng/mL.Other figures of merit include(a)high enrichment factors(60?297),(b)good recoveries(91.8?106.5%),and(c)relative standard deviations of<8.4%.The method was successfully applied to the analysis of the PUHs in real bottled mixed juice milk and soymilk samples.The results indicate that the Fe3O4/KAPs have a wide application scope for the use as an adsorbent in magnetic solid phase extraction.3.An imine-linked porous organic framework synthesized from diaminobenzidine and terephthalaldehyde was covalently bonded to the surface of the amino-modified Fe3O4 to form a magnetic porous organic framework.The prepared magnetic porous organic framework(labeled as Fe3O4@DABPa)was characterized by nitrogen adsorption isotherm,Fourier-transform infrared spectroscopy,thermogravimetry,X-ray diffraction,scanning electron microscopy,and transmission electron microscopy.This Fe3O4@DABPa showed high adsorption ability for some benzoylurea insecticides including diflubenzuron,triflumuron,hexaflumuron,teflubenzuron,flufenoxuron and chlorfluazuron.By coupling the Fe3O4@DABPa based magnetic solid-phase extraction with high performance liquid-phase chromatographic detection,a sensitive method was developed for the determination of some benzoylurea insecticides from real water and bottled peach flavor drink samples with good linearity(r>0.9900),low detection limits(0.05?0.2 ng/mL)and satisfactory reproducibility(RSDs<9.55%).The method recoveries for the analytes from the spiked real samples were in the range of 90.31?110.76%.The results demonstrate that the method has a good sensitivity and accuracy for the determination of benzoylurea insecticides from some real samples.