Nano-TiO2 Solid-phase Extraction/Separation Coupled with Flow Injection－Atomic Absorption Spectrometer for Heavy Metal Speciation and Its Biomedical and Environmental Applications
| Autor: | Cheng-Fa Lee, 李正發 |
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| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 This study describes the development of analytical methods that used nano-TiO2 solid-phase extraction/separation coupled with flow injection (FI)－atomic absorption spectrometry (AAS) for heavy metal speciation. The proposed nano-TiO2 solid-phase extraction/separation－FI－AAS system was validated and applied to the detection of heavy metal species in human urine and environmental water samples. Three methods are presented in this study. Firstly, an on-line nano-TiO2 solid-phase extraction/separation coupled with FI－electrothermal AAS (ETAAS) system was developed for the separation of Se(IV) and Se(VI) in urine samples. The 0.02 M NaOH solution was used to elute the Se(IV) and Se(VI) species from the surface of nano-TiO2 film reactor and the eluent was introduced into the graphite tube by a flow injection system. The detection limits was 0.31 μg L-1 and 0.25 μg L-1 for Se(IV) and Se(VI), respectively. The precisions of the developed method for Se(IV) and Se(VI) were in the rages of 2.1 - 7.4%. The recoveries of Se(IV) and Se(VI) in urine samples were in the rages of 93.9 - 112.2%. The average concentrations of Se(IV) and Se(VI) in urine of patients with diabetes mellitus were found to be 5.7 and 10.5μg L-1, respectively. In subsequent part, an on-line nano-TiO2 photocatalysis reduction device coupled with FI-ETAAS was developed for chromium speciation. The process of chromium speciation in urine was based on the adsorption of Cr(III) and Cr(VI) on this photocatalysis reduction device. The absorbed Cr(VI) was photoreduced to Cr(III), and Cr(III) was eluted using 1.0 M formic acid. The detection limit for Cr(III) and Cr(VI) using this analytical method was 0.08 and 0.13 μg L-1, respectively. The precisions for the analysis of Cr(III) and Cr(VI) were in the range of 4.0 - 6.2%. The spiked recoveries were in the range of 96.0 - 98.3% for the determination of Cr(III) and Cr(VI). This analytical method was applied to the determination of Cr(III) and Cr(VI) in urine samples of human volunteers, during which samples were taken before and after the volunteers’ diets supplemented with chromium picolinate. Lastly, due to the complexity for separating the four arsenic speciesof interest, an analytical method was developed for the determination of them in environmental water samples using a nano-TiO2 solid-phase extraction/separation coupled with atomic absorption spectrometry. The separation of the four arsenic species was based on the selective adsorption of arsenic species onto the surface of TiO2 film at pH 3 or 10 and their subsequent selective desorption through elution with 50 mM NH4H2PO4, 50 mM (NH4)2C2O4 and 50 mM CH3COONH4 solution. The detection limits for As(III), As(V), MMA, and DMA was 0.17, 0.18, 0.14, and 0.11 μg L–1, respectively. The precisions of this analytical method for four arsenic species were in the range of 0.7 - 8.1%. The recoveries for As(III), As(V), MMA, and DMA spiked in water samples were in range of 90.4 - 107.3%. This proposed method was successfully applied for the speciation of four arsenic species in well water samples. In summary, the results of this study confirmed that a nano-TiO2 solid-phase extraction/separation coupled with atomic absorption spectrometry would be a novel and foresighted method for trace metal speciation and could benefit the exploration of trace heavy metals in biomedicial and environmental sciences. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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