Novel Solid Phase Extraction Materials And Their Application To Trace/Ultra Trace Elements Analysis

Inductively coupled plasma-optical emission spectrometry/mass spectrometry(ICP-OES/MS),with the merit of multi-elemental analysis capability;large dynamic linear range;low detection limits;has gained strong recognition in trace metals analysis.Despite the aforementioned advantages,direct determination of metal ions in real sample is still limited,because the concentration of some metal ions are relatively low,even lower than the LODs,the complex sample matrix will influence the accuracy of the method,and sometimes the sample can not be directively introduced in detectors for analysis.Thus,sample pretreatment techniques are required in order to enrich the target metal ions and separate them from the complex sample matrix.Solid phase extraction(SPE)has become one of the most popular sample pretreatment approaches for metals ions due to the following advantages:high preconcentration factor;low solvent consumption;simplicity;high recovery efficiency;no emulsification phenomenon;easy automation.At present,the development of SPE is concentrated in the following respects:(1)exploration of new types of extraction material for SPE;(2)development of new kinds of SPE technique(including SPE automization);(3)the combination of SPE with other sample preparation techniques.Based on these,the objective of the dissertation is:(1)preparation,applying new kinds of extraction material for SPE analysis of trace metal ions in environmental samples and investigation of the adsorption mechanism;exploitation of ion imprinted-restricted accessed polymer for the direction analysis of trace metal ions in biological samples;(2)combination of ionic liquids with magnetic solid phase extraction for the analysis of trace elements in biological samples.The research contents of the dissertation include the following six parts:(1)Chitosan-modified magnetic nanoparticles were synthesized by emulsion method and were characterized by transmission electron microscopy(TEM),fourier transform infrared spectroscopy(FT-IR)and X-ray diffraction(XRD).With the use of the prepared chitosan-modified magnetic nanoparticals as extraction material,a new method of magnetic solid phase extraction(MSPE)combined with ICP-?ES was developed for the speciation of Cr(?)and Cr(?)in environmetal water samples.The parameters affected extraction and desorption of the target analytes,such as pH,extraction time,sedimentation time and sample volume etc,were investigated and the optimized conditions were established.With a preconcentration factor of 100,the detection limits(LODs)of Cr(?)and Cr(total)were 0.02 and 0.03 ng mL-1,respectively,and the relative standard deviations(RSDs)were 4.8 and 5.6%(n=7,c=1 ng mL-1),respectively.The method was successfully applied to analyze East Lake water samples(Wuhan)and rain water at campus of Wuhan University.In order to validate the accuracy of the proposed method,certified reference materials(GSBZ50009-88)were analyzed and the determined values were in good agreement with the certified values.The proposed method,with the merit of simple,rapid,high enrichment factor and low LODs,is suitable for large volume water sample analysis.(2)?-mercaptopropyltrimethoxysilane(?-MPTS)coated stir-bar was prepared by sol-gel method and a new method of stir-bar sorptive extraction(SBSE)combined with ICP-MS for the determination of Cu,Cd and Hg in environmental water samples was established.The stir bar coating was characterized by FT-IR and scanning electron microscopy(SEM).The parameters that affected the extraction efficiency of SBSE including pH,stirring rate,extraction time and desorption time were optimized.Under the optimal conditions,figure merit of the method was investigated.The limits of detection(LODs)of Cu,Cd and Hg were 0.098,0.048 and 0.063 ng mL-1,respectively,and the relative standard deviations(RSDs)were verying from 6.1 to 10.5%(n=7,c=1 ng mL-1).The preparation reproducibility for the prepared ?-MPTS coated stir-bar was within 7-10%(n=7,c=1 ng mL-1)in one batch,and from 11.7%to 13.8%(n=7,c=1 ng mL-1)with different batches.The method was applied to analyze Yangtze River,East Lake water samples(Wuhan)and rain water at campus of Wuhan University.In order to validate the accuracy of the proposed method,certified reference materials(GSBZ50009-88,GSBZ50016-90)environmental waters were analyzed and the determined values were in good agreement with the certified values.The established method was high sensitivity and environment benign.(3)A novel alumina hollow fiber was synthesized by sol-gel template method and was characterized by SEM,N2 adsorption technique and XRD.With the use of prepared alumina hollow fiber as extraction membrane,a new method of flow injection(F?)-membrane solid phase microextraction(MSPME)on-line coupled with ICP-OES was developed for simultaneous determination of trace metals(Cu,Mn and Ni)in environmental water samples.The adsorption capacities of the alumina hollowfiber for Cu,Mn and Ni were found to be 6.6,8.7 and 13.3mg g-1,respectively.With a preconcentration factor of 10,the limits of detection(LODs)for Cu,Mn and Ni were found to be 0.88,0.61 and 0.38 ng mL-1,respectively,and the relative standard deviations(RSDs)were ranging from 6.2 to 7.9%(n=7,c=10 ng mL-1).To validate the accuracy,the proposed method was applied to the analysis of certified reference material GSBZ50009-88 environmental water and the determined values are in good agreement with the certified values.The developed method was also employed for the analysis of Yangtze River water and East Lake water,and the recoveries for the spiked samples were in the range of 87.4-110.2%.How to improve the mechanical strength of the alumina hollow fiber is crucial for its development and applications.(4)The self-prepared Ti-containing mesoporous silica was characterized by SEM,TEM,FT-IR,XRD,ultravoilet spectrometer(UV)and N2 adsorption technique.The adsorption behaviour of Cr,Cu,Cd and Pb on Ti-containing mesoporous silica was studied and the adsorption mechanism was also investigated by FT-?R and X-ray photoelectron spectroscopy(XPS).With the Ti-containing mesoporous silica as adsorbent material,a new method of SPE combined with ICP-MS for the determination of Cr,Cu,Cd and Pb in environmental water and soil samples was established.The parameters affected extraction and desorption of the target analytes,such as pH,sample flow rate,desorption reagent,desorption flow rate and sample volume etc,were investigated.Under the optimized operating conditions,the limits of detection(LODs)of Cr,Cu,Cd and Pb were 4.3,2.4,8.9 and 2.3 pg mL-1 with a preconcentration factor of 10,respectively,and the relative standard deviations(RSDs)were varied from 6.1 to 7.3%(n=7,c=1 ng mL-1).The prepared material could be used more than 50 times.The method was applied to analyze East Lake water samples(Wuhan),soil and rain water at campus of Wuhan University.In order to validate the accuracy of the proposed method,certified reference materials(GSBZ50009-88,GBW07429(GSS-15))were analyzed and the determined values were in good agreement with the certified values.The proposed method had the advantages of low LODs and strong anti-interference ability.(5)A novel restricted accessed material(RAM)-Cu ion imprinted polymer(?P)of poly methyl methacrylate-polyethylene glycol was synthesized by surface imprinted-emulsion method and characterized by FT-IR,TEM and N2 adsorption technique.The results obtained by UV showed that the synthesized materials had good exclusion property for macromolecules.The synthesized RAM-?P materials were employed for microcolumn SPE of Cu(?)in biological fluids followed by ICP-?ES detection without other pretreatment steps.The experimental parameters including sample solution pH,sample flow rate,elution conditions and interfering ions were investigated and the optimal experimental conditions were established.Under the optimized operating conditions,the adsorption capacity of the prepared RAM-?P for Cu(?)was found to be 15.9 mg g-1.With a preconcentration factor of 30,the limits of detection(LODs)for Cu(?)was found to be 0.17 ng mL-1,and the relative standard deviations(RSDs)was 2.2%(n=7,c=1 ng mL-1).The developed method was employed for the direct analysis of human urine and serum samples,and the recoveries of Cu(?)for the spiked samples were between 90%and 108%.The determined values of Cu(?)in urine and serum samples obtained by direct SPE-ICP-OES without sample digestion were much less than those obtained by SPE-ICP-OES after digestion,indicating that Cu(?)is mainly coordinated with macromoleculars in these biological samples.From this point of view,the developed method of RAM-?P SPE-ICP-OES can not only be used for trace metal analysis,but also exhibits application potential in fractionation of free metal ions and metallic complex molecules(6)Ionic liquid-methyltrioctylammonium chloride coated magnetic nanoparticles were prepared,and a new method of MSPE combined with ICP-OES for the determination of Cu,Zn and Cd in human hair and urine samples was established.The pH on the extraction of Cu,Zn and Cd was investigated and the results showed that ionic liquid played a key role in extraction of target analytes,while the magnetic nanoparticles were as the carrier of ionic liquid and also as the base of magnetic separation.The parameters affected extraction and desorption of the target analytes,such as extraction time,desorption reagent and the amount of the ionic liquid etc,were investigated and the optimized conditions were established.Under the optimized conditions,the detection limits(LODs)of Cu,Zn and Cd were 0.54,0.56 and 0.33 ng mL-1,respectively,and the relative standard deviations(RSDs)were 4.9(c=2 ng mL-1,n=7),3.7(c=2 ng mL-1,n=7)and 5.1%(c=1 ng mL-1,n=7),respectively.To validate the accuracy,the proposed method was applied to the analysis of certified reference material(GBW07601 human hair,GBW09103 human urine)and the determined values are in good agreement with the certified values.The developed method was also employed for the analysis of human hair and urine,and the recoveries for the spiked samples were in the range of 89.1-120%.The developed method was simple,high sensitive,no organic solvents and chelation reagent required,and was a green analytical technique.