製備鉍薄膜電極應用於微分脈衝剝除法中以偵測重金屬濃度

Electrochemical Detection of Heavy Metals by Differential Pulse Anodic Stripping Voltammetry on Bismuth Thin Film Electrodes

邱義琦(Yi-Chi Chiu)

指導教授 ： 顏溪成

國立臺灣大學/工學院/化學工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702879

摘要

電化學偵測方法相較於光譜法提供較方便且便宜的偵測條件，其費用及設備需求較低。於電化學偵測重金屬中，汞薄膜電極及懸汞電極有極低的偵測極限。然而，鉍金屬其毒性較汞金屬低，且能夠被人體所代謝，屬於對自然危害較低的金屬，近年來鉍薄膜電極已漸漸取代汞薄膜電極。
於本論文研究中，以含40ppm鉍離子之0.1M醋酸與醋酸鈉緩衝液將鉍金屬電沉積於玻璃碳電極上製備鉍薄膜電極，並以微分脈衝剝除法偵測溶液中的鎘離子濃度。在不改變脈衝波形的情況下，探討其沉積條件、待測液中的鉍離子濃度及旋轉對偵測結果之影響，並嘗試增加其有效反應面積及省去預沉積步驟以找到最佳的偵測效果及最方便的偵測方法。
實驗結果發現，在玻璃碳電極的前處理中，以0.5M硫酸作為洗液並以循環伏安法活化後之電極表面其有效反應面積提升了約原有的76%。在待測液方面，於含1ppm鉍離子之醋酸與醋酸鈉緩衝液中在偵測各濃度之鎘離子皆比其他濃度的鉍離子溶液來的好，而在線性表現方面於100ppb的鉍離子溶液中表現較好，其R-square值為0.998，因此可以推斷鎘濃度於10ppb至120ppb下，100ppb的鉍離子待測液為最佳偵測溶液。於氧氣敏感性探討中，在未除去氧氣的溶液中偵測重金屬溶液，於低掃描速率的條件下，鉍薄膜電極依舊能保有其效果。在沉積電位方面，本研究探討出其沉積電位窗口於-0.87V至-1.1V(vs Ag/AgCl/KCl)，若沉積電位於-1.2V以下，其剝除時產生的氫氣會附著於電極上，導致電極有效反面積下降，而造成電流峰值降低。為了簡化偵測流程，本研究探討鉍薄膜電極預沉積的必要性，結果發現於預濃縮時一同將鉍與鎘沉積在玻璃碳電極上能夠簡化操作流程，並避免電極於更換電沉積液及待測液時可能造成電極的汙染。而在電極部分，發現於剝除中不旋轉能獲得較穩定的偵測曲線，也能維持較厚的質傳邊界層。結合本實驗測試之結果測試於最佳條件中對於溶液中之鎘離子之偵測極限為0.2ppb。

關鍵字

陽極剝除伏安法 ； 微分脈衝法 ； 鉍薄膜電極

並列摘要

For trace metal analysis, electroanalytical methods offer several advantages over spectroscopies: simplicity, low cost and possibility of in-field application. Although the mercury thin film electrode and hanging mercury drop electrode are highly sensitive and selective, mercury is a highly toxic metal. Bismuth has been known as an environmentally friendly material which can be metabolized by human body, so nowadays bismuth thin film electrodes have become alternative material for electrochemical analysis. In this study, bismuth thin film electrodes were fabricated by electroplating bismuth on the glassy carbon electrode(GCE) in 0.1M acetate buffer solution (pH=4) containing 40ppm of Bi(III), and used in measuring of the concentration of Cd(II) by differential pulse anodic stripping voltammetry(DPASV). The effects of pre-electrodeposition potential, the concentration of Bi(III) in the analyte solution, and rotation of the working electrode have been investaged.
The experimental results showed that the sensitivity of the electrode was increased about 76% with the pretreatment of glassy carbon electrodes by applying cyclic potential scans in 0.5M H2SO4. It was found that DPASV provided better Cd(II) detection in the analyte solution containing 1000ppb of Bi(III), and the best linear plot based on peak area in determination of 10 to 120ppb of Cd(II) occurred in the analyte solution containing 100ppb of Bi(III). The Bi thin film electrode on GCE offered good detection, even in non-deaerated solutions. From the investigation of pre-electrodeposition potential in DPASV, the maximum peak current was obtained at -1.1V (vs Ag/AgCl/KCl). It has been found in the experimental results that the preparation of Bi thin film electrode before anodic stripping voltammetry has been found unnecessarily, which can simplify the detection procedures. In the anodic stripping step, the electrode without rotation could keep the more stable current peaks than the electrode with rotation. The detection limit of Cd2+ is 0.2ppb.

並列關鍵字

Differential pulse voltammetry ； Bismuth film electrodes ； Anodic stripping voltammetry ； Cd ion detection

參考文獻

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