由於硒同時具有毒性元素與微量必需元素之雙重角色,因而引起人們廣泛的注意。然而,硒之生物有效性和毒性與其存在之化學形態及濃度有著密切的關係,因此發展可同時測定生物樣品中不同微量硒物種的分析方法,對硒的毒理及藥理研究十分重要。氫化物生成系統是目前最常使用於串聯層析系統與偵測器之界面,然而傳統使用化學試劑進行氫化並無法有效地將Se(VI)及有機硒物種轉化成氣態物種。為解決此問題,本研究藉由整合奈米級二氧化鈦同時具有氧化及還原能力的特性,發展出一套可有效地將無機與有機硒物種轉換成氣態物種之分析方法。本研究在層析系統中,使用陰離子交換管柱搭配碳酸緩衝溶液為動相進行分離。在完成後,先線上混流二氧化鈦懸浮溶液,再照射UV光使所有的硒物種氧化成Se(VI);接著注入做為電洞捕捉劑的甲酸,並照射UV光使Se(VI)還原成氣態物種以進行後續偵測。實驗結果顯示,Se(IV)、Se(VI)及SeMet三物種其偵測極限分別可低達0.0039、0.0072及0.0083 μg/L。最後應用於測定人體尿液樣品,可發現SeMet濃度約為5.9-7.2 μg/L且並無發現Se(IV)及Se(VI)的存在。綜上所述,本研究建立之HPLC-Photocatalyst-Assisted Digestion and Vaporization Device-ICPMS連線系統具有快速、簡單且樣品傳輸效率高等優點,並可應用於人體尿液中代謝硒物種的研究。
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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