利用電位滴定法檢測飲料中氯離子(Cl^-)之含量

Potentiometric Titration of Chloride in Beverages

傅冠儒(Bohr K. Fuh) ； 傅冠親(Gene K. Fuh) ； 蔡惠燕(Hwei-Yan Tsai)

《化學》 67卷4期 (2009/12) Pp. 413-420

https://doi.org/10.6623/chem.2009041

摘要

化學與日常生活息息相關，分析化學更是為我們健康把關的重要技藝 (techniques)，但中學生總是感受不到他的重要，以為化學只是一堆背誦與計算，作者希望透過簡易的實驗原理與操作，設計與日常生活相關的實驗讓中學生對分析化學有初步的認識，並引起中學生對分析化學的興趣。利用電位滴定法檢測飲料中氯離子 (Cl-) 含量是一個貼近日常生活的實驗，操作簡單，藥品危險性低，透過實驗結果數據處理，體會計算的意義，過程中有疑問也可學習設計實驗或找文獻解答疑問。本研究結果顯示利用硝酸銀水溶液標定飲料中之氯離子，以銀電極監測滴定過程之電位變化 (即銀離子濃度變化)，再利用二次微分法求得當量點體積，計算飲料中之氯離子含量。此方法不受飲料顏色或果渣的干擾，再現性 (RSD% ＜1.5%) 與準確度 (97.4~100.4%) 均很好。

關鍵字

電位滴定法 ； 氯離子分析

並列摘要

Chemistry is closely with the daily life. Analytical chemistry is especially important for examining the quality of products and clinical assays. However, the high-school students always feel that chemistry is only a lot of recitations and calculations. The authors tried to design an experiment with simple procedures relating to daily life. The high school students will have preliminary understanding about analytical chemistry via the experiment. The students will bring about interest in analytical chemistry too. The potentiometric titration of chloride (Cl^-) in beverages is related to daily life. The experimental procedures are simple and reagents used for the experiment are safe. Students can understand the meaning of calculation via processing the experimental results. Students can also lean how to search literatures to explain confused results. Silver nitrate solution was used as titrant reagent for chloride determination. Silver electrode was used to monitor the potential during the titrating process. The results were processed with secondary differentiation to obtain the equivalent-point volume. The color of beverages or fleshes of fruits do not interfere with the potentiometric titration. The reproducibility (RSD% ＜ 1.5%) and the accuracy (97.4~100.4%) are excellent.

並列關鍵字

Potentiometric titration ； Chloride analysis