| Summary: | 碩士 === 國立清華大學 === 生醫工程與環境科學系 === 98 === Since it has been widely recognized that the toxicological behaviors and the biochemical functions of trace elements are highly dependent on chemical forms, to date, the information on selenium speciation has been considered indispensable for the risk assessment and better understanding of its biological behavior. Nowadays, the coupling of HPLC with different on-line detection systems by chemical hydride generation device has been proven very useful for the speciation of trace elements. However, in view of converting Se(VI) into gaseous hydride by traditional methods is limited by its high oxidation potential, a new on-line vapor generation technique permitting rapid and effective formation of hydride species from Se(VI) is still necessary for the construction of an adequate hyphenated system for the speciation of selenium species.
Recently, an on-line HPLC-UV/nano-TiO2-ICP-MS system for the determination of inorganic selenium species was reported. Toward the goals of improvement of photocatalytical efficiency and reduction in sample consumption, we intended to develop a poly(methyl methacrylate) (PMMA) chip-based photo-reactor as an interfacing device resulting from the specific properties of microspace, and to combine HPLC and ICP-MS for the determination of Se(IV) and Se(VI) in aqueous samples. Meanwhile, to attain low per-unit manufacturing cost and rapid prototyping, a simple CO2 laser engraving technique was employed to fabricate the photo-reactor. Furthermore, to reduce the consumption of nano-TiO2 photocatalyst, we utilized a polyelectrolyte－poly(diallyldimethylammonium chloride) (PDADMAC) to assist the immobilization of nano-TiO2 particles onto the channel surface. Based on our experimental results, the device presented a greater stability in vaporization efficiency and lower baseline noise. Under the optimized condition, it merely needed 15s to transform inorganic selenium into gaseous selenide. The limit of detection of Se(IV) and Se(VI) were 0.043 and 0.042 μg L-1, respectively. For the analysis of irrigation water, the concentration of Se(IV) and Se(VI) were 0.109±0.019 and 0.090±0.013 μg L-1. Through a series of validation by analyzing 1643e Standard Reference Material and natural waters, it indicated that the proposed methods can be applied satisfactorily to the determination of inorganic selenium species in water samples. Based on the achieved analytical results, it also indicated that our developed on-line system is a fast, simple, low cost, low reagent consumption and high sample transportation efficiency method.
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