| With the rapid development of science technology and the enhancement of people’s safety consciousness, trace elements and their species analysis have been paid great attention in environmental pollution monitoring, food safety control and the potential risk assessment of human health. Among various elemental specific detection techniques, inductively coupled plasma mass spectrometry (ICP-MS) possesses distinct advantages including high sensitivity, low detection limits, wide linear range and fast analysis as well as the capability of multi-element detection and isotope analysis. Despite the advantages mentioned above, there are still some common problems when ICP-MS is used for direct analysis of real-word samples:(1) the concentration of the target analytes may be lower than the quantification limit of the instrument;(2) the interference (including mass interference and matrix effect) caused by complex samples may severely affect the accuracy of the analytical results;(3) ICP-MS can not recognize the different species of the same element. Therefore, suitable sample pretreatment techniques are usually required to reduce matrix effect as well as separate and enrich the target analytes prior to the ICP-MS analysis.Capillary microextraction (CME) technique, which was developed based on solid phase extraction (SPE), is a kind of miniaturized sample pretreatment technique. CME demonstrates the virtues of low cost and sample/solvent consumption, simple operation and easy automation by online coupling with different analytical instruments. Similar to solid phase (micro) extraction, the properties of extraction materials greatly determine the performances of CME such as extraction selectivity, the adsorption/desorption kinetics and adsorption capacity. Therefore, the development of novel capillary extraction materials and establishment of analytical method possessing the properties of low sample consumption, high throughput and suitability for real world sample analysis is of great significance. Monolithic material possesses relatively large specific surface area and quick mass transfer due to the micron grade throughpore and nanometer grade micropore. And monolith has shown great application potential in the field of separation and analysis. Compared with CME methods based on packed column and open tubular column, monolithic column based CME method possesses the advantages of high extraction capacity and low transfer resistance. Currently, monolithic CME has been coupled with various analytical instruments, such as high performance liquid chromatography (HPLC), capillary electrophoresis (CE) and capillary electrochromatography (CEC), for the analysis of biomacromolecule and organic small molecule. While the application of monolithic CME in the analysis of trace elements and their species is relatively rare up to now.The aim of this dissertation is to design and prepare different kinds of monolithic capillary for trace elements and their species analysis, to investigate the adsorption behaviors of target analytes on the monolithic capillary and to establish new methods based on monolithic CME-ICP-MS for the determination of trace elements and their species in environmental and biological samples. The main research works in this dissertation are described as follows:(1)3-aminopropyltriethoxysilane (APTES)-silica hybrid monolithic capillary was prepared by sol-gel method. This monolithic column showed the advantages of easy preparation, large adsorption capacity and easy regeneration. A method based on APTES-silica hybrid monolithic CME-ICP-MS was developed for the analysis of trace heavy metal elements including Mn、Co、Ni、Cu、Cd and Pb in human hair and urine samples. The limits of detection (LODs) of this method for the target elements were6.2ng L-1(Mn),1.5ng L-1(Co),5.2ng L-1(Ni),6.3ng L-1(Cu),1.2ng L-1(Cd) and14ng L-1(Pb), respectively. The relative standard deviations (RSDs) were less than5.1%(c=1μg L-1,n=7). This method has the virtues of good selectivity, strong resistance to matrix interference and low sample consumption, and is suitable for trace/ultratrace analysis of heavy metal elements in complex samples with limited amount.(2) Based on the strong acid-resistant ability of polymer monolithic column and strong affinity between iminodiacetic acid (IDA) and rare earth elements (REEs), an IDA modified glycidyl methacrylate (GMA)-based polymer monolithic column (poly(IDA-GMA-TRIM)) was prepared for the extraction of REEs. The monolithic column demonstrated the advantages of easy preparation, good reproducibility and long lifetime (it can be reused above100times). By coupling this monolithic column to a micro concentric nebulizer (MCN), a new on-line CME-MCN-ICP-MS method was developed for the analysis of trace REEs in human serum and urine samples. This method provided LODs less than1ng L-1for target REEs and a sample throughput of8.5h-1. In the analysis of15REEs in human urine and hair samples, the recoveries were in the range of82%-105%.(3) Using surface imprinting technique, silica monolithic capillary modified with Cd(Ⅱ) imprinted polymer was prepared and employed for CME of trace Cd from human serum and urine samples, followed by ICP-MS detection. Taking Mn(Ⅱ), Cu(Ⅱ) and Zn(Ⅱ) as competing ions, the extraction rate, distribution ratio and selectivity of this Cd(Ⅱ) imprinted monolithic capillary was investigated and it was found that the relative selectivity coefficients of this Cd(Ⅱ) imprinted monolithic capillary towards Mn(Ⅱ), Cu(II) and Zn(Ⅱ) were3.8,2.2and2.2respectively. Compared with non-imprinted monolithic capillary, the Cd(Ⅱ) imprinted monolithic capillary presented larger adsorption capacity (6μg m-1over4.2μg m-1). Compared with other reported methods involving Cd(Ⅱ) imprinted materials, this method is featured with easy removement of template Cd(Ⅱ), good selectivity, strong interference resistance, low sample consumption and easy regeneration. Therefore, this method is suitable for the separation and enrichment of trace Cd(Ⅱ) in micro-samples with complex matrix.(4) A poly(acrylamide-vinyl pyridine-methylene bisacrylamide)(poly(AA-VP-Bis)) monolithic capillary was designed and prepared for the separation and enrichment of gold nanoparticles. The extraction mechanism is based on the static electrical and hydrogen bond interactions between the citrate stabilizer on the surface of gold nanoparticles and pyridine/amide groups on the surface of monolith. The proposed method showed excellent selectivity and strong interference resistance, and the original morphology of gold nanoparticles could be maintained during the extraction process, making this method very suitable for the separation and enrichment of gold nanoparticles with carboxyl as stabilizer. Citrate stabilized gold nanoparticles with a size about3nm were taken as target analyte and the proposed on-line CME-ICP-MS method presented a detection limit of1.17fM and a sample throughput of6h-1. Compared with the method described in references, this method showed the advantages of low detection limit and sample consumption, fast extraction/desorption kinetics, wide linear range, high throughput as well as no requirement of digestion. This method was applied to the quantification of gold nanoparticles in tap water, Yangtze River water and East Lake water with recoveries in the range of77-103%.(5) Based on good extraction ability of poly(IDA-GMA-TRIM) towards Gd3+and the relatively strong interaction between carboxyl group and poly(AA-VP-Bis) monolithic column, a new method combining the two monolithic capillaries mentioned above with ICP-MS detection was developed for simultaneous extraction/enrichment of free Gd3+and Gadolinium acid Magnevist (Gd-DTPA). The LODs of this method towards Gd3+and Gd-DTPA were both lower than2ng L-1, offering an potential application of the proposed method in the quantification of Gd in environmental water samples. The total amount of free Gd3+and carboxyl-containing Gd-complex in East Lake and Yangtze River water samples were analyzed and the recoveries for Gd3+and Gd-DTPA were in the range of86%-104%. Compared with the method described in references for the analysis of Gd-DTPA, the use of strong acid (6mol L-1HNO3) for desorption of target analyte and the tedious operation of acid evaportion/desolvation was avoided in this method, demonstrating the characteristics of easy operation and instrument eco-friendly. |
