Study On Preparation Of Magnetic Composites And Its Application In Environmental Samples Preconcentration

With the development of modern analytical instruments,our environmental pollutants detection capability is more and more strong.But it is still very difficult to direct analysis of trace or ultra trace pollutants in complex samples,because the content of pollutants in the environment is extremely low,a large number of complex substrate may interfere the determination of the analyte.Therefore,prior to measurement,sample preconcentration is very necessary and extremely important.Solid phase extraction(SPE)is one of the most commonly used pre-treatment and pre-concentration techniques for the analysis of pollutants in environmental and biological samples.However,it is still tedious,time consuming,relatively expensive and labor intensive.To address these limitations,a new SPE technique called magnetic solid-phase extraction(MSPE),based on the use of magnetic or magnetically modified adsorbents,was developed and applied to bioseparation and chemical analysis.In MSPE procedures,the magnetic adsorbents are exposed in the sample solution to adsorb the analytes and then collect the analytes by an external magnetic field,which greatly simplifies the SPE procedure and enhances extraction efficiency.In addtion,the dispersion extraction mode increase the contact area between the adsorbent and the analyte,and magnetic adsorbent can be easily reused.MSPE shows the advantages of simple,easy and labour saving,it has become a forward-looking sample pretreatment technology.This thesis has investigated the synthesis and application of MSPE material.Three magnetic composites synthesized via self-assembly and chemical modification were used to develop high sensitive magnetic solid-phase extraction method.Combined with high performance liquid chromatography(HPLC),this new method has been successfully applied to investigate environmental water samples.The main contents are shown below:Part I.Graphene magnetic composites(Fe3O4@G)have been synthesized based on the click reaction between vinyl modified Fe3O4 and thiol modified graphene.Scanning electron microscopy(SEM),Transimission electron microscopy(TEM),infrared spectroscopy and raman spectroscopy demonstrated that Fe3O4@G have been successfully prepared.The extraction performance of Fe3O4@G was evaluated by using four PAHs,anthracene(AnT),pyrene(Pyr),benzo(a)anthracene(BaA)and benzo(a)pyrene(BaP)as model analytes.Under the optimum conditions,detection limits in the range of 0.1-0.5 ng/L were obtained by high performance liquid chromatography-fluorescence detection(HPLC-FLD).This method has been successfully applied for the determination of PAHs in environmental water samples by using the MSPE-HPLC-FLD.The recoveries for the four PAHs tested in spiked real water samples were in the range of 83.2-103.0%with relative standard deviations ranging from 2.3%～5.2%.Part II.Fe3O4@ionic liquid@pontamine sky blue nanoparticles(Fe3O4@IL@PSB NPs)and Fe3O4@ionic liquid@eriochrome black T nanoparticles(Fe3O4@IL@EBT NPs)were synthesized by self-assembly of the ionic liquid 1-octadecyl-3-methylimidazolium bromide(C18mimBr)and pontamine sky blue(PSB),eriochrome black T(EBT)onto the surface of Fe3O4 silica magnetic nanoparticles,as confirmed by infrared spectroscopy,ultraviolet-visible spectroscopy and superconducting quantum interface device magnetometer.Three chlorophenols including 2,4,6-trichlorophenol(2,4,6-TCP),2,3,4,6-tetrachlorophenoxide(2,3,4,6-TeCP)and pentachlorophenol(PCP)were chosed as model analytes,compared with the enrichment effects of the Fe3O4@IL@PSB and Fe3O4@IL@EBT,the results show that Fe3O4@IL@PSB has strong enrichment capability.Under the optimal conditions,the limit of detection(S/N=3)of 2,4,6-TCP,2,3,4,6-TeCP and PCP were 0.1 ug/L,0.05 ug/L,0.03 ug/L,which obtained by high performance liquid chromatography-ultraviolet detection(HPLC-UVD).The recoveries for the four CPs tested in spiked real water samples were in the range of 81.6-95.7.%with relative standard deviations ranging from 2.7%～5.3%.The method precented was simple and low cost,and Fe3O4@IL@PSB NPs can be reused for many times for the determination CPs in the environmental water samples.Part III.Fe3O4@vinyl phosphonic acid@octadecanethiol(Fe3O4@VPA@C18)have been synthesized based on the click reaction between vinyl phosphonic acid modified Fe3O4 and octadecanethiol.Scanning electron microscopy(SEM),Transimission electron microscopy(TEM)and infrared spectroscopy demonstrated that Fe3O4@VPA@C18 have been successfully prepared.The extraction performance of Fe3O4@VPA@C18was evaluated by using four OPPs,parathion-methyl(Methyl),phentriazophos(Tria),parathion(Para)and phoxim(Phox)as model analytes.Under the optimal conditions,the limit of detection(S/N=3)of Methyl,Tria,Para and PCP were 0.02 ug/L,0.02 ug/L,0.01 ug/L and 0.05ug/L,which were obtained by high performance liquid chromatography-ultraviolet detection(HPLC-UVD).This method has been successfully applied for the determination of OPPs in environmental water samples.The recoveries for the four OPPs tested in spiked real water samples were in the range of 81.7-92.8%with relative standard deviations ranging from 2.8%～5.3%.In addition,we compared with the enrichment effects of the Fe3O4@VPA@C18 and commercial Fe3O4@SiO2@C18,the results show that Fe3O4@VPA@C18 has stronger enrichment capability to OPPs.