| Water is one of the most basic material of Earth humans and other creatures on which lives and breeds. With the great progress of modern human society and the rapid development of modern industry and agriculture, the environmental pollution and ecological destruction has become governments and scholars focus on the important issues, especially the water resources and water security. Generally, the environmental water samples are source diversity, complex matrix and huge span of concentration ranges, and the contention of the impact on the environment elements are very low. Therefore, to establish methods which are accurate, convenient and economical for the determination of trace elements in environmental water has been an important research topic in the field of analytical chemistry.Compared with various kinds of instrumental analysis methods, X ray fluorescence(XRF) analysis technology has absolute advantage in the long-term stability, automatic degree, analysis cost, impact on environmental and direct analysis of solid samples etc. However, because of its own defects of detection limit is not low enough, the matrix effects is very serious, the accuracy of analysis depend on standard material seriously, its excellent performance and great potential is not given full play, and the application fields are quite limited. Therefore, to make full use of the advantage of analytical instruments, develop its huge potential analysis abilities, improve the efficiency of the large analysis instrument, is an important research topic in Earth Science, Environmental Science, Analytical Chemistry and other fields. In this research, a novel methods are carried out by different types of sample enrichment technology (solid phase extraction and/or electrochemical deposition) combined with XRF for determination of trace element in environmental water samples. It has important academic significance and realistic significance in the following aspects. First, the use of these preconcentration procedures leads to solid thin targets loaded with the analytes, which are ideal samples to analyze by conventional XRF systems. Matrix and thickness-effect corrections can therefore be avoided and the XRF signal can be directly related to the element concentration. So the lack of the same type of standard material problem is easy to solve in the XRF analysis. Another advantage of these analytical strategies is the great improvement in the sensitivity compared with the direct analysis of the liquid sample by XRF spectrometry. Third, the analytes do not have to be eluted from enrichment carrier before XRF measurement, thus the risk of contamination which is caused by the elution reagent and the loss of analytes are reduced to the minimum. Fourth, in the field of miniaturization it is also important to note the possible use of micro sample in the dispersive micro solid-phase extraction(DMSPE) or electrodeposition(ED) technology. Last, but not least, is the low consumption of reagents in these preconcentration procedures. So it is a kind of green analysis method. In order to develop analysis methods of trace elements in water samples based XRF, the main research contents of this thesis are as follows:1. A novel, simple and sensitive method was developed for preconcentration and determination of trace amounts of Co2+, Ni2+, Pb2+ and Cd2+ using dithizone non-covalent functionalized graphene as solid sorbent of DMSPE in combination with XRF technology. The characterization of dithizone functionalized graphene was investigated by UV-Vis and FT-IR. With the novel solid sorbent, excellent enrichment factors about 1000 were obtained for Co2+, Ni2+, Pb2+ and Cd+ Parameters of affecting the extraction process (pH of the analyte solution, stirring time, the volume of the sample, complexing agent, adsorption capacity), and the effect of foreign metals were evaluated. Under the optimum conditions, the calibration graphs were linear in the range of 0.01 μg mL-1 to 3.0 μg mL-1 with a correlation coefficients better than 0.99, detection limits of Co2+, Ni2+, Pb2+ and Cd2+ were 1.3 ng mL-1,1.1 ng mL-1,2.0 ng mL-1, and 6.1 ng mL-1, respectively. The proposed method were successfully applied to measure the trace of Co2+, Ni2+, Pb2+ and Cd2+ in different types of environmental waters, and the recoveries were 95.2-112.2, respectively.2. A rapid and sensitive method was developed for the determination of trace amounts of Pb2+, Mn2+, Cu2+ and Zn2+ in aqueous solution using H2SO4/HNO3 covalent functionalized modified graphene as solid sorbent of DMSPE in combination with XRF technology. The characterization of covalent functionalized graphene was investigated by FT-IR and XRD. The main factors influencing the preconcentration and extraction of the metal ions, pH of the analyte solution, stirring time, the volume of the sample, adsorption capacity, were investigated, and the effect of foreign metals were evaluated. Under the optimized conditions, excellent enrichment factors about 900 were obtained for Pb2+, Mn2+, Cu2+ and Zn2+, and the calibration graphs were linear in the range of 0.01 μg mL-1 to 3.0 μg mL-1 with a correlation coefficients better than 0.99, detection limits were 1.8 ng mL-1,0.7 ng mL-1,0.5 ng mL-1, and 0.5 ng mL-1, respectively. The proposed method were successfully applied to measure the trace of Pb2+, Mn2+, Cu2+ and Zn2+ in different types of environmental waters, and the recoveries were 95.7～104.0, respectively.3. A preconcentration method by electrodeposition on a cathode of aluminum sheet was developed for determination trace amounts of Mn2+, Cu2+, Cr3+, Pb2+, Zn2+ and Cd2+ in the environmental waters, followed by conventional XRF. The influence of parameters such as pretreatment of aluminum plates, voltage, pH value and time on the deposition were investigated. Under the optimum experimental conditions, the detection limits for measurement of Mn2+, Cu2+, Cr3+, Pb2+, Zn2+ and Cd2+were 5.0 ng·mL-1,5.5 ng·mL-1,1.9 ng·mL-1,9.9 ng·mL-1,7.3 ng·mL-1 and 24.8 ng·mL-1, respectively. The proposed method has been applied to the determination of trace Mn2+, Cu2+, Cr3+, Pb2+, Zn2+ and Cd2+ in water samples with satisfactory results, and the recoveries were 94.4%-103.0%, respectively.4. An analytical method for the preconcentration and determination of Se in water samples in combination with conventional XRF by synergistic electrodeposition effect has been developed. The synergistic electrodeposition effect of Se with Pb2+ or Cu2+ was investigated. The experimental parameters, such as solution pH, deposition voltage, deposition time, supporting electrolyte, were optimized for the preconcentration. Under the optimum experimental conditions, the detection limit for measurement of Se was 1.2 ng·mL-1. The proposed method has been applied to the determination of trace Se in certified reference materials sample (GBW(E)080233) and actual environmental samples with satisfactory results, and the recoveries were better than 96%. |
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