The Preparation Of Porous Nano-materials And Their Applications In The Determination Of Some Pesticide Residues

The pesticide residue of the food samples cannot be directly analyzed by available analytical instruments because of the low concentration level of the target analytes and the complexity of the sample matrix.Therefore,a preliminary step called sample pretreatment for the isolation or enrichment of the analytes is an indispensable step in the whole extraction process.In recent years,solid-phase extraction and magnetic solid-phase extraction are commonly employed in sample preparations.Compared to traditional extraction technologies,they have advantages including easy operation,short extraction time,low comsumption of organic solvents and so on.In SPE and MSPE,adsorbent plays a dominant role for the efficient extraction of target analytes.Thus,the development of efficient adsorbents with high stability,high selectivity,and high adsorption performance for the adsorption of target analytes has become research hotspot.In this work,two kinds of porous nanomaterials were successfully synthesized and employed as both SPE and MSPE adsorbents.In combination of SPE and MSPE with high performanceliquidchromatography?HPLC?andhighperformanceliquid chromatography-mass spectrometry?HPLC-MS?,the methods for the determination of pesticide residue in food samples were established.The main research content was as follows:1.Magnetic spherical carbon was synthesized by a facile hydrothermal carbonization procedure with biomass glucose as the carbon precursor and nanoclusters iron colloid as magnetic precursor.The textures of the as-prepared magnetic spherical carbon were characterized by nitrogen adsorption-desorption isotherms,X-ray diffraction,transmission electron microscopy,scanning electron microscopy and vibration sample magnetometry.Results indicated that the magnetic spherical carbon possessed high surface area as well as strong magnetism,which endows the material with good adsorption capability and easy separation property.To assess its absorption performance,the magnetic spherical carbon was employed as adsorbent for the extraction and preconcentration of phthalate esters from lake water and milk samples prior to high performance liquid chromatographic analysis.Under the optimum extraction conditions,a good linearity was achieved with the linear correlation coefficients higher than 0.9973.The limits of detection?S/N=3?were 0.05ng/mL⁰.08 ng/mL for lake water and 0.1 ng/mL⁰.2 ng/mL for milk samples,respectively.The recoveries of the analytes for the method were in the range from 80.1%to112.6%.2.To further explore its adsorption performance,magnetic spherical carbon was applied to pre-concentrate carbamates in cabbage and environment water samples prior to determination by high performance liquid chromatographic.During the experiments,several experimental parameters possible influencing the extraction efficiency were optimized and researched.This extraction method showed a good linearity for the three carbamates in the concentration range from 0.1 to 80.0 ng/mL for water samples and from2.0 ng/g to 160.0 ng/g for cabbage sample with the correlation coefficients?r?higher than0.9987.The limits of detection?S/N=3?were 0.02 ng/mL⁰.03 ng/mL for water samples,and 0.2 ng/g⁰.4 ng/g for cabbage samples.The recoveries of the analytes for the method from spiked samples fell in the range from 84.7%to 107.7%.3.A hypercrosslinked organic polymer material?named as PTPA?was prepared by a simple one-step self-polycondensation of triphenylamine.A series of characterization experiments,including nitrogen adsorption,scanning electron microscopy,X-ray diffraction,Fourier transform infrared spectra,and thermogravimetric analysis,were carried out to evaluate the morphology,structure and other intrinsic properties of the PTPA.To investigate its adsorption performance,the PTPA was used as the solid-phase extraction adsorbent for the extraction of phenylurea herbicides from water,milk and tomato juice samples followed by high-performance liquid chromatographic analysis.Under optimum conditions,good linearity for the analytes was observed in the range of 0.05 ng/mL⁴0.0ng/mL,0.1 ng/mL⁴0.0 ng/mL and 0.5 ng/mL⁴0.0 ng/mL for water,milk and tomato juice samples,respectively.The established method also showed low limits of detection?S/N=3?in the range of 0.008 ng/mL⁰.01 ng/mL,0.01 ng/mL⁰.03 ng/mL and 0.05ng/mL⁰.1 ng/mL for water,milk and tomato juice samples,respectively.The possible adsorption mechanism of the PTPA towards the analytes was investigated,and the results demonstrated that the hydrogen bonding was the main interaction force between the PTPA and the analytes.It suggested that the PTPA can serve as a promising adsorbent for the efficient pre-enrichment of organic compounds with more hydrogen-bonding donor sites.4.To further broaden the application of PTPA,a magnetic polytriphenylamine porous organic polymer?MPTPA?was prepared by co-precipitation PTPA with Fe²⁺and Fe³⁺.The MPTPA was employed as the adsorbent for the magnetic solid phase extraction of the benzoylurea insecticides from tomato,cucumber and watermelon samples prior to their high performance liquid chromatography-mass spectral detection.Under the optimized conditions,the developed method gave a low limit of detection in the range from 0.05 ng/g to 0.1 ng/g and a good linear response in the range from 0.2 ng/g to 40.0 ng/g with coefficients of determination greater than 0.99.The method recoveries for spiked analytes at the concentrations of 3.0 ng/g and 15.0 ng/g in real samples were in the range of87.7%¹06.7%with the relative standard deviations less than 6.4%.The results showed that the MPTPA has a good adsorption capability toward the target analytes.The possible adsorption force of the MPTPA towards the analytes can be mainly attributed to the hydrogen bond and?-stacking interactions.The MPTPA showed great potential in efficient extraction of more organic compounds from real samples.