Preparation Of Metal-Organic Frameworks Hybrid Material For Application In Analysis Of Sulfonylurea Herbicides Residues

Sulfonylurea herbicides are widely used in agriculture,which could promote the stable production and increased production of crops.However,sulfonylurea herbicides have received widespread attention due to their long-term application and increasing usage in agricultural fields.They have presented adverse environmental problems and pesticide residues,which are harmful for microorganism and human.Owing to the low concentration of sulfonylurea herbicides in sample and complexity of sample matrices,it is urgent to establish a simple,rapid,highly sensitive and low detection limit sample enrichment and analysis method.Metal-organic frameworks（MOFs）,as a new type of organic-inorganic doped porous solid material which emerged in the 1990s,have displayed great application potential as sorbents in analytical fields owing to their unique pore structure,large surface area,diverse pore size,and good adsorption affinity.MOFs have been either directly used or engineered to meet the demands of sample collection,preconcentration,extraction and chromatographic separation.Based on numerous previous reports,MOFs composites were prepared and applied in solid phase microextraction,stirring bar adsorption extraction,dispersed solid phase extraction and magnetic solid phase extraction according to the physical and chemical properties of sulfonylurea herbicides and the unique features of MOFs materials.Moreover,these developed composites were used to enrich trace sulfonylurea herbicides in complicated samples.The main contributions are collected as follows:1 A novel polymerized monolith doped with metal-organic frameworks（UIO-66（Zr）-NH₂）was developed in a quartz capillary with microwave irradiation method.The fabricated monolith was examined by SEM.It had a uniform porous and continuous 3-dimensional network structure.The optimization of different parameters affecting solid-phase microextraction procedure were carried out including the pH value of the extraction solution,extraction time,salt concentration,desorption solvent and desorption time.The proposed hybrid monolith extraction method exhibited wide linear range（10-700μg/L）,low detection limits（0.19-1.79μg/L）.The enrichment factors（EFs）were in the range of 3.0-5.1-fold（theoretical enrichment factor was 20-fold）.Under the optimum experimental conditions,the resultant monolith was applied to extract four sulfonylurea herbicides from real soil and water samples before analysis with high-performance liquid chromatography.Satisfactory recoveries of four sulfonylurea herbicides were obtained with spiked real samples in the range of 75.7%-95.3%.RSD was less than 11.3%.The established method had the advantages of fast preparation and high sensitivity in the detection of sulfonylurea herbicides,and it is suitable for the separation and determination of trace polar analytes from soil and water samples in real environment.2 A SBSE-HPLC method was established for the determination of five sulfonylurea herbicides in enviromental samples（water and soil）.A magnetic MOFs hybrid monolithic stir bar was prepared by thermal polymerization in one step using neodymium supermagnetic(Nd₂Fe₁₄B)powders modified by 3-methacryloxypropyltrimethoxysilane as the component substrates.The factors affecting the extraction and desorption performance of the prepared materials on sulfonylurea herbicides,such as the pH value of extraction solvent,salt concentration,extraction time,desorption time and desorption solvent,were evaluated in detail.Under the optimal experimental conditions,the linear range was 10-700μg/L for TIM,MSM and AS,and 10-800μg/L for other two sulfonylurea herbicides.With enrichment factors 10.6-to 19.5-fold（theoretical EF,25-fold）,the limits of detection（S/N=3）were found to be 0.04-0.84μg/L.Satisfactory recoveries of sulfonylurea herbicides were obtained with spiked water and soil samples in the range of 68.8%-98.1%.It was proved that the MOFs hybrid stir bar was feasible to extract polar substances in complex matrices,which was potentially an optimal adsorbent for environmental analysis.3 SiO₂-UIO-66（Zr）-NH₂ composites were prepared by solvothermal method in one step and employed to extract five sulfonylurea herbicides by dispersed solid phase extraction（DSPE）coupled with high performance liquid chromatography（HPLC）.Several important experimental factors influencing the performance of extraction were optimized in detail,such as the mass of composites,extraction solvent,extraction time,desorption solvent and desorption time.Under the optimal conditions,the linear ranges were 10-400μg/L for five analytes,The limits of detection（S/N=3）of the developed method were 1.29-5.82μg/L.Finally,a method of DSPE-HPLC for determination of sulfonylurea herbicides in real soil samples was established with satisfactory recovery ranging from 80.81%to 92.17%.The developed method is simple,sensitive and applicable for the analysis of trace sulfonylurea herbicides in real soil samples.4 The core-shell Fe₃O₄@MOFs magnetic particles were synthesized by layer-by-layer encapsulation method and characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,vibrating sample magnetometer,X-ray diffraction and infrared spectroscopy（FTIR）.Five sulfonylurea herbicides,namely,amidosulfuron,thifensulfuron-methyl,sulfosulfuron,metsulfuron-methyl,tribenuron-methyl were selected as target analytes for MSPE.Under the optimum conditions,five target analytes had a good linear relationship at 5-200μg/L,and the detection limits varied in the range of 0.19-1.79μg/L.The established method was successfully applied to enrich and determine five sulfonylurea herbicides from actual pear sample.The satisfying recoveries of the spiked pear sample were from 75.36%to 91.58%.The resultant material possessed both magnetic performance of Fe₃O₄ and adsorption capability of IRMOF-3,therefore,the magnetic Fe₃O₄@MOFs particles based MSPE provided a promising alternative in sample pretreatment.