| Summary: | 碩士 === 國立清華大學 === 生醫工程與環境科學系 === 96 === Selenium is of considerable interest in human nutrition and health because of its dual role as toxicant and essential trace nutrient. The bioavalibility and toxicity of selenium is highly dependent on its chemical forms and concentration. Therefore, it is of great important to develop a method which is able to determine the concentration of different selenium species in biological fluid. Considering the demand on the high sensitive method, up to now, hydride generation (HG) is the most common technique to interface chromatography and spectrometers. However, in view of the inferior vaporization in converting Se(VI) and organoselenium species provided by conventional chemical HG method, in this study, we reformed our pervious design and process1 by integrating the alternative photooxidation characteristic of nano-TiO2 into the interfacing device to convert both inorganic and organic selenium-containing species to gaseous products that are favor for ICP-MS determination. To enable the applicability of our proposed method in the metabolism of selenium, three common-seen selenium containing species, named selenite(Se(IV)), selenate(Se(VI)) and selenomethionine(SeMet), were selected as target species in this study. To separate the analyte species, an anion-exchange column was employed, with the mobile phase of 50 mM carbonate buffer at pH 7 and flow-rate of 1 mL/min. After the chromatographic separation, the effluent was first on-line mixing with a 1 g/L TiO2 suspension and irradiating UV through a 2 m long coil at pH 3 to oxidize three selenium species into Se(VI). Subsequently, a 100 mM HCCOH was injected into the sample stream which serves as hole scavenger to reduce Se(VI) into volatile hydride species accompanying with the UV irradiating at pH 3 through another 2 m long photoreduction coil. Under the optimized conditions described above, the detection limits of Se(IV), Se(VI) and SeMet are 0.0039, 0.0072 and 0.0083 μg/L, respectively. The application of the established method in neat urine sample has found SeMet present as 5.9-7.2 μg/L and neither Se(IV) nor Se(VI) appear in the tested samples. Based on the achieved analytical results, it indicated that our developed HPLC- Photocatalyst-Assisted Digestion and Vaporization Device -ICPMS system is a fast, simple and high sample transportation efficiency method, and has the ability to determine different metabolic selenium species in human urine.
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