Synthesis And Application Of Novel Magnetic Solid-Phase-extraction Microspheres

Organic micropollutants(OMPs),including pesticides,endocrine-disrupting compounds,pharmaceutical products and personal care products,are ubiquitous in the aquatic environment with the concentration of μg/L or ng/L.Recently,OMPs have been found in surface water and drinking water worldwide,which have shown significant negative influences on the ecosystem and human health.Thus,the determination of OMPs in the aquatic environment and the evaluation of water quality safety have attracted increasing attentions.However,the concentration of OMPs in the aquatic environment is very low,which can hardly be analyzed by the analytical instruments,such as high performance liquid chromatography(HPLC),gas chromatograph(GC),and/or coupled with mass spectrometry(MS).Therefore,the preconcentration before instrumental analysis is very important for raising the concentration of OMPs and reducing the potential source of error.Compared with the other sample preconcentration methods,the solid phase extraction(SPE),characterized by rapid and efficient enrichment,low cost,and low organic solvent consumption,has become the most pervasive method for the enrichment of aquatic samples.However,some unavoidable difficulties would be encountered when the SPE method is applied to extract trace OMPs from large-volume aquatic samples.A large amount of time would be consumed when an SPE cartridge is used for the preconcentration because of the high backpressure.Recently,magnetic solid phase extraction(MSPE)has been developed,which provides a possible method to overcome the problems associated with the SPE cartridges.And some new magnetic sorbents have been prepared for SPE applications.These magnetic sorbents can be evenly dispersed in a large-volume water sample and can be quickly separated by a magnet after extraction.This process greatly shortens the preconcentration time and improves the extraction efficiency.Up to now,numerous MSPE materials have been developed for the extraction of OMPs.However,these materials have primarily emphasized on the selective extraction for a specific compound instead of all of the OMPs in water samples simultaneously.Hence,the MSPE is still at the stage of laboratory research.Based on the above-mentioned background,this work focused on the preparation of novel magnetic SPE microspheres with high surface area,which can be applied to the simultaneous extraction of various types of OMPs from aquatic samples.The main research contents and conclusions are as follows.(1)The recipe of the novel magnetic SPE microspheres with high surface area,comprising of bilayer-OA-coated Fe3O4 nanoparticles and divinylbenzene,was established through the optimization of modifying agent and monomer.Then,the magnetic microspheres were prepared via membrane emulsification,suspension polymerization,and post-crosslinking reaction.The new magnetic SPE microspheres were characterized by uniform distribution of particle size(6-9 μm),high specific surface area(>1000 m2/g),super paramagnetic,and high specific saturation magnetization(2.53 emu/g).The nanoparticles were nearly uniformly distributed in the microsphere matrix,which can guarantee the uniform behaviors of magnetic microspheres in solutiort under a magnetic field.Meanwhile,the pore structure,particles size and specific surface area of the magnetic microspheres were easy to control.(2)The influences of the physicochemical properties of the magnetic microspheres,including pore size,particle size and specific surface area,on the extraction processes were investigated.The results indicated that larger pore structures could reduce the intra-particle diffusion resistance of the target molecules,thereby accelerating the extraction process and reducing the extraction time.The diminution of the particle size could improve the specific surface area and increase the contact surface between the microspheres and the solution,resulting in the reduce of extraction time.High specific area signified more adsorrption sites,which could reduce the site competition between target molecules and result in decreasing the amount of microspheres and extraction time.(3)The extraction performance of the novel magnetic microspheres was evaluated through the extraction of polycyclic aromatic hydrocarbons(PAHs),phthalic acid esters(PAEs),and triazines pesticides from large-volume water samples.Orthogonal design and single factor experiments were applied to optimize the enrichment conditions.In conventional application range,the solution volume(0.5-7.5 L),salinity(0-2%),and humic acid(0-40 mg/L)had no significant influence on the efficiency of MSPE based on the novel magnetic microspheres,which was attributed to the high specific surface area and the small particle size.Due to the hydrophobic skeleton of the novel magnetic microspheres,the extraction behaviors would not be affected by the competition of adsorption sites between HA and target molecules.Moreover,the amount of magnetic microspheres and the extraction time had remarkable influences on the extraction performance.Determined by the MSPE-HPLC method under the optimized conditions,the limit of detection(LOD)for PAHs,PAEs,and Triazines was L76-19.55 ng/L,and the limit of quantification(LOQ)was 5.71-65.16 ng/L.(4)A rapid and efficient MSPE-GC/MS method,based on the novel magnetic microspheres,was established for the analysis of OMPs from aquatic samples.Analyzed by the proposed method,about 20 kinds OMPs were found from the Huaihe River samples,including PAHs,PAEs,Polychlorinated biphenyls(PCBs),pesticides,chlorobenzenes,and organic ketones.The extraction efficiencies were made a comparation between MSPE and Water oasis HLB,C18 cartridges,which are employed by the EPA(US)and National Standard(PRC)methods respectively.And the extraction efficiencie of MSPE based on the novel magnetic microspheres was superior to that of Waters Oasis HLB and C18 cartridge.It was indicated that the MSPE based on the novel magnetic microspheres had broad applicability for the extraction of OMPs from aquatic samples.