改善吹氣捕捉系統搭配離子層析儀量測高鹽度樣品中的銨離子

Improvement of Purge-and-Trap Ion Chromatography on the Determination of Ammonium Ion in High-Salinity Samples

陳鴻震(Hung-Jhen Chen)

指導教授 ： 吳劍侯

國立清華大學/原子科學院/生醫工程與環境科學系/碩士(2007年)

https://doi.org/10.6843/NTHU.2007.00621

摘要

離子層析法是目前相當廣泛被用來量測銨離子的一種分析方法，但是要利用此方法來量測在高濃度鈉離子干擾之下微量的銨離子並不容易。使用一套簡單的吹氣捕捉前處理系統，並利用銨離子 (NH4+) 與氨（NH3）在水中的分佈隨著pH值變化的性質，將銨離子從複雜基質中分離，再以離子層析儀 (Ion Chromatography, IC) 進行銨離子定量分析。本論文主要目的為改善銨離子分離前處理系統穩定性與提升系統吹除效率。為了進一步了解氨在此吹氣捕捉系統中的傳輸行為，以兩層膜理論為基礎提出一適合此前處理系統的理論模型。此外，藉由改變前處理系統的實驗參數並利用所建立之理論模型，可求得銨離子在此系統中之亨利常數。影響前處理系統吹除效率主要因素有：吹除瓶中液面的高低、N2吹除氣體的流速、吹除的時間、加入的氫氧化鈉溶液濃度與控制整個吹除系統的溫度。此改良後之前處理系統不但可以準確地定量銨離子，還可藉由改變不同體積之吸附液來達到樣品前濃縮，提升訊號強度及保護分析管柱等優點。

關鍵字

銨離子 ； 亨利常數 ； 吹氣捕捉

並列摘要

Ion chromatography (IC) is widely used for the quantification of ammonium ion at the mg/L level. However, it is extremely difficult to analyze samples of very dissimilar concentration ratios of Na+/NH4+, such as seawater. P&T system utilized the characteristics of ammonium ion under alkaline environment can further convert ammonium to ammonia and prevent from the interference of high concentration of salt.

In this study, we improve the stability and efficiency of the P&T system. To better understand the kinetic of ammonia in the P&T system, a theoretical model is developed based on the mass balance and two film theory. System parameters, including the height of liquid in the purging bottle, temperature, N2 flow rate, purge time, concentration of sodium hydroxide were discussed. To increase the system stability by reducing the temperature variation, concentrated NaOH solution was used instead of solid particle of NaOH. The system efficiency was enhanced by increasing the height of purge tube.

並列關鍵字

Ammonium ion ； P&T system ； efficiency ； two film theory

參考文獻

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