Synthesis Of Functionalized Monolithic Capillaries And Their Applications In Trace Elements Analysis And Speciation

The physiological activity and toxicity of trace elements are not only dependent on the concentration of the elements but also closely related to their physical and chemical species(such as free form,complexing form,oxidized form,reduced form,and nanoparticle species).Hence,it is of great importance to analyze trace elements and their species in real-world samples for assessing environmental pollution risk and protecting human health.Inductively coupled plasma mass spectrometry(ICP-MS)featuring with low limits of detection(LODs),wide linear range and fast analysis speed,is one of the most commonly used elemental specific detection techniques.However,some problems still exist in the direct ICP-MS determination of trace elements and their species in real-world samples.For example,the concentration levels of target elements or their species may be lower than the LODs of the ICP-MS instruments;the interference including mass interference and matrix effect in real-world sample analysis may affect the accuracy of the analytical results;common ICP-MS cannot recognize different species of a specific element.An appropriate sample pretreatment technique prior to ICP-MS determination can concentrate target elements,eliminate or decrease the matrix interference in real-world sample analysis and sometimes can realize the separation of different species.Monolithic capillary microextraction(CME)as a kind of miniaturized sample pretreatment technique,has the merits of low sample consumption,fast analysis speed,high adsorption capacity and ease to on-line combine with versatile detection techniques.For monolithic CME,adsorption materials play great role in the analytical performance including selectivity,sample throughput and so on.So far,three types of monolithic columns have been used in CME,including organic,inorganic and hybrid monolithic column.Among them,organic monolithic column has attracted great interests owing to its unique advantages of easy preparation,resistance to acid/base conditions,plenty of monomers available and so on,and has been widely applied to the analysis of organic substances.However,the application of organic monolithic CME to trace elements analysis is relatively rare,mainly due to the limited organic monolithic materials which are suitable for trace elements and their species analysis.The aim of this dissertation is to prepare functionalized organic monolithic columns with improved selectivity and specific surface area,and to apply them for the analysis of trace elements,elemental species and metal-containing nanoparticles(NPs)in real-world samples.The major contents of this dissertation are described as follows:(1)Poly(glycidyl methacrylate-ethylene dimethacrylate)(poly(GMA-EDMA))monolith was prepared and functionalized with mercapto groups,and a novel method of on-line polymer monolithic CME-ICP-MS was developed for the determination of trace Au and Pd in biological samples.The prepared monolith exhibited good selectivity to Au and Pd,and good resistance to strong acid with a long life span.Factors affecting the extraction efficiency of CME,such as sample acidity,sample flow rate,eluent conditions and coexisting ion interference were investigated in detail.Under the optimal conditions,the LODs(3a)were 5.9 ng L-1 for Au and 8.3 ng L-1 for Pd,and the relative standard deviations(RSDs,c=50 ng L-1,n=7)were 6.5%for Au and 1.1%for Pd,respectively.The developed method was successfully applied to the determination of Au and Pd in human urine and serum samples with the recoveries in the range of 84-118%for spiked samples.The developed on-line polymer monolithic CME-ICP-MS method has the advantages of rapidity,simplicity,low sample/reagent consumption,high sensitivity and is suitable for the determination of trace Au and Pd in biological samples with limited sample amount available and complex matrix.(2)A novel method of TiO2 NPs functionalized monolithic CME on-line coupling with ICP-MS was developed for the sequential determination of Gd3+ and Gd-based contrast agents in human urine samples.The monolithic capillary was prepared by embedding anatase TiO2 NPs in the poly(methacrylic acid-ethylene glycol dimethacrylate)(poly(MAA-EDMA))framework.By employing PO43-as bridge for the adsorption,the GdU+ and Gd-based contrast agents(such as gadolinium-diethylene triamine pentaacetic acid(Gd-DTPA)and Gd-DTPA-bismethylamide(Gd-DTPA-BMA))displayed different adsorption behaviors on the prepared TiO2 NPs functionalized poly(MAA-EDMA)monolithic capillary.Under the optimized conditions,the LODs were found to be 3.6,3.2,and 4.5 ng L-1 for Gd3+,Gd-DTPA,and Gd-DTPA-BMA,respectively,which are the lowest for Gd speciation up to date.The enrichment factor was 25-fold with the sample throughput of 5 h-1.The proposed method was validated by the analysis of Gd3+ and Gd-DTPA in the healthy human urine samples as well as Gd3+ and Gd-DTPA-BMA in patient urine samples.The method is simple,sensitive,rapid,and requires no oxidation/reduction or subtraction,which is suitable for the speciation of Gd3+ and Gd-based contrast agents in urine samples.(3)An on-line hydrophilic polymer monolithic CME-ICP-MS analytical system was developed for the size-based analysis of Au NPs in the range of 3-40 nm.Au NPs with different particle sizes which retained on the poly(acrylamide-vinylpyridine-methylene bis(acrylamide))(poly(AA-VP-Bis))monolithic capillary showed different elution behavior when cysteamine was used as the eluent,and the napierian logarithm of the critical eluent concentration(lnC(cysteamine))was linearly dependent on the particle size of Au NPs.It means that the unknown particle size of Au NPs can be deduced based on their critical eluent concentrations.The separation resolution of the developed method for Au NPs was about 20 nm,and developed method was successfully used for the baseline separation and quantification of 3 and 20 nm Au NPs,as well as 10 and 30 nm Au NPs.Compared with chromatographic-based methods for the size analysis of Au NPs,the developed on-line poly(AA-VP-Bis)monolithic CME-ICP-MS method features with the ability of simultaneous separation and enrichment of Au NPs,simple operation,low cost,high analytical speed,and high adsorption capacity.(4)With the existence of citric acid,TiO2 NPs can be selectively adsorbed on the poly(AA-VP-Bis)monolithic column at pH 1,whereas Ti ions cannot be adsorbed.Based on it,an on-line monolithic CME-ICP-MS method was developed for the analysis of TiO2 NPs in environmental water samples.Under the optimum conditions,an LOD of 0.63 μg L-1 for TiO2 NPs and a sample throughput of 6 h-1 were achieved.The method can be applied to the analysis of TiO2 NPs in the size range of 5-100 nm.The developed method was then applied to the analysis of TiO2 NPs in the East Lake water and Yangtze River water with the recoveries of 84-109%for spiked samples.Compared with othe reported methods for the analysis of TiO2 NPs,the developed on-line monolithic CME-ICP-MS has the merits of simple operation,low sample consumption,high throughput and no need for digestion before ICP-MS detection.(5)Metal organic frameworks(MOFs)were introduced to the synthesis of polymer based monolithic capillary by using the organic ligands of MOFs as functional monomers,and a monolithic CME-ICP-MS method was developed for on-line analysis of rare earth elements(REEs)in human urine and serum samples.Double bond-containing ligand was introduced into the synthesis of MOFs,and the ligand in MOFs was taken as functional organic monomer in the preparation of polymer based monolith.Taking advantages of the poor resistance to acid/base of MOFs,the central metal ions and ligand which were not polymerized in the monolithic column were flushed out easily,maintaining the porous structure and increasing the specific surface area and permeability of the polymer based monolith.The prepared monolithic column showed high adsorption capacity for REEs and the developed monolithic CME-ICP-MS method can be applied to the analysis of REEs in biological samples with complex matrix.