| To study the relationship between environment and population health,it is necessary to accurately and timely obtain the exposure level of environmental organic pollutants.In the whole research system,the primary task is to effectively detect and monitor the concentration level of environmental organic pollutants.However,the concentration of organic pollutants in the environment is usually at the trace level,and the matrix is relatively complex,so efficient sample pretreatment techniques is the key point to achieve the removal of matrix interference effect,purification and enrichment of the target analytes,accurate qualitative and quantitative analysis.With the continuous development of green chemistry,how to develop and use the materials and methods with green chemistry characteristics is one of the research hotspots in the analysis of environmental pollutants.Among the emerging new materials and methods,magnetic nanomaterials and effervescent microextraction techniques have stood out due to their high efficiency and specificity and green economic characteristics,respectively.In this dissertation,two major types of daily contact environmental endocrine disruptors,polybrominated diphenyl ether and bisphenol analogs,were analyzed.Based on the effervescent microextraction with“green chemistry”characteristics,combined the synthesized functional material with the dispersive microextraction techniques,we established the following four trace analysis techniques of?magnetic?effervescent microextraction for the above-mentioned analytes in environmental water,food and human body fluid samples.It will provide a reliable and sensitive analytical method for the determination of environmental organic pollutants,and then provides accurate data support for the assessment of human exposure and the evaluation of population health risks.The main researches are as follows:Chapter ? Magnetic effervescent tablet-microextraction of polybrominated diphenyl ethers in liquid matrix samplesObjective:Herein,the magnetic Fe3S4 nanosheet was synthesized and introduced into the ionic liquid-based dispersible liquid-liquid microextraction techniques?META-IL-DLLME?assisted by magnetic efferent tablets,which was used in conjunction with HPLC/DAD to construct the method for the extraction and analysis of trace residues polybrominated biphenyl ether from liquid matrix samples.Methods:In this proposed method,a magnetic effervescent tablet,containing CO2sources,ionic liquids and magnetic Fe3S4 nanosheet,realize extractant dispersion and magnetic recovery into one-step.Fe3S4 was synthesized through solvothermal method,characterized by XRD,SEM,magnetic property,FT-IR,zeta potential and N2adsorption-desorption isotherms,and applied it for the first time to the newly developed method.Some important parameters were rigorously optimized,such as kinds of magnetic nanoparticles,effervescent agents,extraction solvents and their volumes,elution solvents,extraction temperature and salt addition.Results:Under the optimized conditions,the extraction recoveries?ERs?of Fe3S4for PBDEs were 20.8%-32.0%higher than those of conventional Fe3O4.The linear ranges of different PBDEs were 0.1/0.5-100?g L-11 with correlation coefficients of>0.9990.The ERs ranged from 80.7%to 99.3%,and the limits of detection and quantitation were 0.012-0.078?g L-11 and 0.04-0.26?g L-1,respectively.The intra-and inter-day precisions,expressed as relative standard deviations?RSD,n=6?,were1.32%-4.83%and 1.99%-4.25%,respectively.To evaluate its matrix effect,tap and river water,skim and whole milk,pregnant women and normal female serum were selected as the actual samples,the relative recoveries of PBDEs from the above-mentioned samples at three fortification levels(2.0,5.0 and 20.0?g L-1)were in the range of 77.3%-106.7%.Conclusions:The commonly used magnetic Fe3O4 can only achieve magnetic separation in the microextraction procedures,while magnetic Fe3S4 is more efficient in adsorption and extraction of organic analytes in addition to facilitating magnetic separation.Therefore,the results of this chapter provide an alternative to traditional magnetic separation and adsorbents.The results of mechanism analysis showed that the high extraction efficiency of PBDEs with Fe3S4 was attributed to its large specific surface area and pore size.In addition,the new combined techniques constructed in this chapter has great application potential in trace monitoring of environmental water bodies,liquid food and human serum samples.Chapter ? Development of magnetic effervescent tablets based on g-C3N4/NiFe2O4-ILs and its application in detection of trace bisphenols in human body fluidsObjective:A novel magnetic nanocomposite of g-C3N4/NiFe2O4 was prepared.It was mixed g-C3N4/NiFe2O4 with ILs to develop the magnetic effervescent tablets and combined with the dispersive liquid-liquid microextraction for the extraction and detection of trace bisphenols in human blood and urine samples.Methods:In this developed method,a magnetic effervescent tablet,containing CO2sources,ionic liquids and g-C3N4/NiFe2O4 magnetic nanocomposite,combines extractant dispersion and magnetic recovery into one-step.g-C3N4/NiFe2O4 was synthesized,a series of characterization?XRD,SEM,magnetic property,FT-IR,zeta potential and N2 adsorption-desorption isotherms?were performed and applied it for the first time to the newly developed method.Some important parameters were carefully optimized,such as pressed or unpressed effervescent tablet,kinds and weight of magnetic nanoparticles,effervescent agents,extraction solvents and their volumes,elution solvents,extraction temperature,pH and salt addition.Results:In the extraction system,the extraction recovery of pressed effervescent tablets was 17.2%-23.4%higher than that of unpressed effervescent tablets.Compared with the extraction efficiency of using ionic liquid individually,g-C3N4/NiFe2O4 offered32.02%-43.10%of contribution rate in the microextraction process.And what's more,explored the underlying reasons for the contribution rate.According to the characterization results,the extraction efficiency was greatly improved due to its large specific surface area(38.9m2 g-1),pore volume and pore diameter?0.24m3 g-11 and 23.4nm,respectively?.Under the optimized conditions,the META-IL-DLLME method combined with HPLC/FLD analysis gave the linear ranges of 0.05-100?g L-11 with correlation coefficients of 0.9991-0.9998.The limits of detection and quantitation were0.006-0.031?g L-11 and 0.020-0.010?g L-1,respectively.The intra-and inter-day precisions,expressed as relative standard deviations?RSD,n=6?,were 1.92%-3.90%and 2.93%-5.88%,respectively.To evaluate its matrix effect,male,female,pregnant urine and male,female,pregnant serum samples were selected as the actual samples,the relative recoveries of BPs from the above-mentioned samples at three fortification levels(1.0,10.0 and 100.0?g L-1)were in the range of 78.32%-104.06%.Conclusions:In short,whether to pressed effervescent tablets were compared,and the contribution rate of magnetic nanocomposite and ILs were calculated in the extraction process,and were preliminary discussed intrinsic properties on the g-C3N4/NiFe2O4 through a series of characterization.It is finally established magnetic effervescent tablets microextraction based on g-C3N4/NiFe2O4 magnetic nanocomposite,and successfully applied it for the extraction and detection of trace bisphenols in human blood and urine samples.Therefore,the results obtained in this study provide a superior alternative for the conventional magnetic separation and adsorbent material.Also,this newly developed method has a great potential in trace monitoring of environmental estrogens in human body fluids.Chapter ? Development of effervescent assisted switchable-hydrophilicity solvent microextraction and its application in the analysis of polybrominated diphenyl ethers in water and dairy milk samplesObjective:We prospectively constructed a novel method,effervescent assisted switchable-hydrophilicity solvent based on salting-out enhanced microextraction?EA-SHS-SAME?,for extraction and preconcentration of polybrominated diphenyl ethers?PBDEs?in dairy milk and water samples.Methods:In this proposed method,a kind of sodium carbonate solution containing carbon dioxide source was used to change the fatty acid from hydrophobicity to hydrophilic soluble salt.When sufficient amount of sulfuric acid solution was added to change soluble salt into hydrophobic fatty acid state,the target analytes in the solution were extracted to the upper fatty acid phase.At this time,the excessive salt solution was added into the oversaturated state,which is conducive to more target analytes entering the fatty acid phase and improving extraction efficiency.Some important parameters were rigorously optimized,such as the type and volume of fatty acid,the volume of sodium carbonate solution,the volume of sulfuric acid solution,the type of salting-out agent,etc.Results:Under the dispersing effect of inorganic acid and basic salt,it was avoided using the traditional organic dispersing solvent in the developed EA-SHS-SAME method,and making it more efficient and environmentally friendly.Under the optimized conditions,the EA-SHS-SAME method combined with HPLC-DAD analysis gave the linear ranges of 0.2-50?g L-11 with correlation coefficients of>0.9990.The limits of detection and quantitation were 0.026-0.085?g L-11 and 0.087-0.28?g L-1,respectively.The intra-and inter-day precisions,expressed as relative standard deviations?RSD,n=6?,were 2.48%-4.78%and 3.00%-6.75%,respectively.To evaluate its matrix effect,the relative recoveries of PBDEs from tap and river water,lowfat and whole milk samples at three fortification levels(1.0,10.0and 40.0?g L-1)were in the range of 78.06%-103.07%.Conclusions:In a word,an attractive new method of effervescent assisted switchable-hydrophilicity solvent based on salting-out enhanced microextraction combined with HPLC/DAD was proposed and successfully applied to the determination of trace PBDEs in water and dairy milk samples.The newly developed EA-SHS-SAME method,with the assistance of inorganic acids and basic salts,avoids using of traditional organic dispersing solvents,and making the method more simple,green efficient and environmentally friendly.In addition,it has great potential of the new constructed technique in trace monitoring of environmental water and liquid food samples.Chapter ? Preparation of NiFe2O4@SiO2@VA magnetic nanocomposites and its application in magnetic effervescent dispersion microextractionObjective:A novel magnetic nanocomposites of NiFe2O4@SiO2@VA were successfully developed,which were introduced as an adsorbent into the magnetic effervescent microextraction techniques combined with HPLC/FLD for determination of trace bisphenols in different types of water and dairy milk samples.Methods:The NiFe2O4@SiO2@VA magnetic nanocomposites were prepared and characterized by SEM,TEM,XRD,FT-IR,Zeta potential,hysteresis loop and nitrogen adsorption stripping curve,etc.Then,it was used as high adsorbent and strong magnetic separator in the magnetic effervescent microextraction techniques.Some important parameters in the process of extraction and the detailed optimization,such as whether to suppress effervescent tablets agent,kinds of magnetic materials and quality,eluant type,pH,salt effect,extraction and extraction time,etc.Some important parameters were carefully optimized,such as pressed or unpressed effervescent tablet,kinds and weight of magnetic nanoparticles,effervescent agents,elution solvents,pH,salt addition,extraction temperature and time.Results:In the extraction system,the extraction recovery of pressed effervescent tablets was 14.93%-20.17%higher than that of unpressed effervescent tablets.According to the characterization results,NiFe2O4@SiO2@VA magnetic nanocomposites has a larger specific surface area(88.8 m2 g-1),which is 9.25,2.64 and2.28 times of synthesized Fe3O4,Fe3S4,g-C3N4/NiFe2O4 in the previous chapters,respectively.Under the optimized conditions,the developed method combined with HPLC/FLD analysis gave the linear ranges of 0.01-100?g L-11 with correlation coefficients of 0.9990-0.9999.The limits of detection and quantitation were 0.010-0.088?g L-11 and 0.035-0.29?g L-1,respectively.The intra-and inter-day precisions,expressed as relative standard deviations?RSD,n=6?,were 2.23%-4.07%and1.91%-5.26%,respectively.To evaluate its matrix effect,the relative recoveries of BPs from tap water,drinking water,sewage inlet and outlet water samples and lowfat milk,baby milk,breast milk samples at three fortification levels(1.0,5.0 and 20.0?g L-1)were in the range of 77.30%-110.48%.Conclusions:In this article,the utilization of NiFe2O4@SiO2@VA in microextraction procedures can not only provide the simple,convenient and quick magnetic separation,but also enhance greatly the extraction efficiency owing to its larger specific surface area and pore size.So it can be used as an independent adsorbent without additional auxiliary extractant to achieve satisfactory extraction efficiency.Therefore,NiFe2O4@SiO2@VA can be used as a promising alternative for conventional magnetic separation and adsorbent material such as Fe3O4.The newly developed method,with the assistance of special magnetic effervescent tablets,avoids the utilization of traditional organic dispersive solvents,thereby reducing the pretreatment time and making this method more environmental benign.Overall,this developed method was proved to be simple,inexpensive,sensitive and environmentally friendly,and thus has a great potential application value in routine water/milk samples monitoring of trace-level BPs-like pollutants.Furthermore,the effervescent tablets could be easily prepared in advance and used as needed,which is suitable for on-site detection in the field investigation or developed automation of solvent extraction/microextraction and is thus a promising method. |
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