- 學位論文
以離子層析結合魯米諾-雜多酸系統同時偵測三價與五價砷
Simultaneous Determination of Arsenite and Arsenate by Ion Chromatogray with Luminol-Heteropoly Acid
摘要
砷是大自然中常見的一種元素，普遍被視為一種類金屬，常以砷酸鹽類的型態存在於自然界中，常見的氧化態為 +3、+5。隨著人類生活水準的提高，砷酸鹽類的使用量日益增加，而砷對環境的汙染也隨著用途的增加，而不容再忽視。 本研究是利用離子層析法分離水溶液中的三價砷和五價砷，以魯米諾-雜多酸為反應基礎進行化學放光並結合流動注射法來進行水溶液中三價與五價砷的同時分析檢測。 本研究所利用的離子層析法的分離機制主要是根據離子排斥層析管柱的Donnan排斥來進行分離。完全解離的酸不被固定相保留，而酸所解離的陰離子受Donnan排斥，未解離的化合物則不受Donnan排斥，能進入樹酯的內微孔，分離是基於溶質和固定相之間的非離子性相互作用。 五價砷與雜多酸形成鉬釩砷三元雜多酸的錯合物，該錯合物再與放光試劑進行催化反應而產生放光，但三價砷在此反應中對於放光試劑並不具有催化的能力，所以必須先將其氧化成五價砷才能進行分析偵測。而利用過錳酸鉀作為氧化劑進行線上氧化的方式，可在短時間內有效的將三價砷氧化成五價砷。 在池水、地下水、水溝水的實際樣品的檢測分析上，可以發現As(V)和As(III)的添加回收率，可達到85 ~ 98%之間。五價砷及三價砷的檢量線結果均在100～2000 μg/L 的範圍內，R2分別為0.9981和0.9989，分法偵測極限則分別為39 μg/L和45 μg/L。 在其他金屬干擾檢測上，添加相當於分析樣品濃度100倍的 Zn、Co、Cu、Pb、Cd、Cr及Fe於三價及五價砷樣品中，對於三價及五價砷的偵測並無明顯的影響。 本研究所建立之離子層析結合魯米諾-雜多酸系統可以同時偵測到低濃度的三價砷與五價砷並分離可能影響分析物之干擾物，而且分析時間短，價格相對上較便宜，以及無須太繁瑣的前處理過程，可避免樣品污染的問題。
並列摘要
Arsenic is an element found in the nature and commonly known as a metalloid element. Its common form in the nature is salts with oxidation states of +3 and +5. Despite its toxicity, arsenic is an essential element in our body, whereas in the environment, arsenic is considered a toxic metal and its presence, especially in drinking water, is closely monitored via methods such as inductively-coupled plasma — mass spectrometry detection (ICP-MSD) or atomic absorption spectroscopy (AAS) with hydride generation detection. The goal of this research is to develop a simple and rapid method for simultaneous arsenic speciation in aqueous samples based on ion chromatography combined with heteropoly acid — luminol chemiluminescence detection (CLD). As(III) and As(V) are first separated by an anionic exchange column before reacting with the post-column reagent. The reaction between luminol and vanadomolybdoarsenate heteropoly acid (VMoAs-HPA) in basic solution produces light given off as chemiluminescence in the blue region. The As(V) could be specifically integrated with VMoAs-HPA complex by the addition of ammonium molybdate and ammonium vanadium solution to react with the arsenate in acidic medium. CL was performed by the reaction between the complex and alkaline luminol. The detection limit (3 × standard deviation of blank ) for As(V)and As(III) is 39 μg/L and 45 μg/L respectively. The calibration curve is linear over a range of 100 to 2000 μg/L for As(V) (R2 = 0.9981) and As(III) ( R2= 0.9989 ). Based on the results of these experiments, it can be concluded that IC-CLD with luminol-heteropoly acid system of As(V) to As(III) is a viable technique for the speciation of arsenic. This method has high selectivity and requires little sample preparation, short analysis time, and inexpensive instrumentation to achieve low-level arsenic speciation.