A Mg(OH)2 preconcentration/matrix reduction method for the determination of rare earth elements in environmental water sample by laser ablation inductively coupled plasma mass spectrometry

以Mg(OH)2共沉澱法結合LA-ICP-MS分析環境樣品中的稀土元素

陳逸翔(Yi-Hsiang Chen)

指導教授 ： 王竹方

國立清華大學/原子科學院/生醫工程與環境科學系/碩士(2008年)

摘要

Abstract
Laser ablation is most frequently applied to the analysis of solid sample. A combination of laser ablation (LA) with inductively coupled plasma mass spectrometry (ICP-MS) is one of the most powerful analytical techniques. LA-ICP-MS is advantageous because of its direct solid sampling capability, high sensitivity, fast analysis, microanalysis, and depth profiling capabilities. In this study, it was to evaluate the determination of rare earth elements as well as trace elements in water samples based on preconcentration with magnesium hydroxide prior to their determination by LA-ICP-MS. Dried microdroplets of sample, as well as standard solution previously mixed with methylene blue (MB), were prepared on a PTFE filter and ablated by LA-ICP-MS. MB was used as a matrix modifier to enhance the sample transport efficiency in LA-ICP-MS. Another advantage of MB toward this experiment is the absorption ability of UV light at 213nm. The influences of various analytical parameters for the quantitative recoveries of REEs, such as type of Mg carriers, quantity of Mg(OH)2 precipitated, pH effect, reaction time, absorption efficiencies of Mg(NO3)2, Ba2+ removal efficiency and repetitive co-precipitation process have been thoroughly investigated. Both the external standard and internal standard were applied for quantification by LA-ICP-MS. A good precision (RSD<10%) and high recovery (95~105%) result can be obtained in this research. The high correlation coefficients (0.998~0.999) and low detection limits for most elements of interest showed that this method would be useful for future quantification in any kind of liquid samples. The proposed method was applied to real environmental samples, such as bottled water, tap water, swimming pool water, lake water and simulated seawater.

關鍵字

氫氧化鎂 ； 微量金屬 ； 稀土元素 ； 雷射剝蝕 ； 雷射剝蝕感應耦合電漿質譜儀

並列摘要

摘要
雷射剝蝕技術常應用於固體樣品分析，雷射剝蝕結合感應耦合電漿質譜儀(LA-ICP-MS)為一極具發展潛力的分析技術。LA-ICP-MS的優點包括：可以直接分析固體樣品、具有高靈敏度、樣品分析速度快、可進行微區分析和縱深分析。本研究利用結合氫氧化鎂前處理方法與LA-ICP-MS的技術，分析水樣中的稀土元素和微量元素。將液體樣品預先與亞甲基藍(Methylene blue)混合，定體積的樣品滴於鐵氟龍濾紙上，並將其乾燥後，以LA-ICP-MS進行定量分析。亞甲基藍可當作基質修飾劑並增加樣品傳輸到LA-ICP-MS的速率，另一個優點是可以在213 nm吸收UV光而當作顯示劑。在氫氧化鎂前處的方法中，探討參數的最佳化，包含鎂化合物的選擇、鎂離子的沉澱量、酸鹼度影響、反應時間、吸附能力、干擾的去除和重複沉澱實驗等。研究過程中將利用外標法和內標法來達到LA-ICP-MS定量分析研究的準確性。研究結果顯示，此方法可以得到很好的精密度 (RSD <10%) 和高的回收率 (95~105%)，且具有很高的檢量線線性相關係數(0.998~ 0.999)和很低的偵測極限，因此可以應用於任何液體樣品的定量分析。本研究亦針對真實環境樣品進行採樣分析，包括瓶裝水、自來水、游泳池水、湖水和模擬海水，實驗結果顯示，此方法具有極高的可信度。

並列關鍵字

Mg(OH)2 ； Rare earth elements ； Trace elements ； LA-ICP-MS ； HASH(0x1c92aac0)

參考文獻

Ammann, A. A. (2007). "Inductively coupled plasma mass spectrometry (ICP MS): a versatile tool." Journal of mass spectrometry 42: 419-427.

Bahramifar, N. and Y. Yamini (2005). "On-line preconcentration of some rare earth elements in water samples using C-18-cartridge modified with 1-(2-pyridylazo) 2-naphtol (PAN) prior to simultaneous determination by inductively coupled plasma optical emission spectrometry (ICP-OES)." Analytica Chimica Acta 540(2): 325-332.

Becker, J. S., C. Pickhardt, et al. (2004). "Determination of Ag, Tl, and Pb in few milligrams of platinum nanoclusters by on-line isotope dilution in laser ablation inductively coupled plasma mass spectrometry." International Journal of Mass Spectrometry 237(1): 13-17.

Boulyga, S. F., D. Desideri, et al. (2003). "Plutonium and americium determination in mosses by laser ablation ICP-MS combined with isotope dilution technique." International Journal of Mass Spectrometry 226(3): 329-339.

Chen, Z., M. Megharaj, et al. (2007). "Removal of interferences in the speciation of chromium using an octopole reaction system in ion chromatography with inductively coupled plasma mass spectrometry." Talanta 73: 948-952.