重金屬砷是一種威脅人類健康的水中污染物，其中無機砷具有高毒性，它包含三價砷和五價砷，若是長期攝入，可能導致末梢組織壞死，以及增加罹患腎臟疾病、皮膚病、癌症等風險。傳統分析技術無法立即反映水質中的砷含量，且操作耗時；然而，近年來電化學技術逐漸受到關注，常被運用於快速偵測水質，其中包含無機砷的分析。目前僅少數文獻針對五價砷進行研究，原因是五價砷為電惰性，利用電化學技術不易直接測得。 本研究開發金-錳氧化物/氧化石墨烯-單壁奈米碳管修飾玻璃碳電極，在最佳的電極製備條件（電鍍電位-0.1 V、電鍍時間30秒）及最佳的操作條件（電解液為pH 2的0.2 M Clark-Lubs緩衝液、沉積電位-0.5 V、沉積時間300秒）下，使用方波陽極析出伏安法測量水中五價砷。而此修飾電極會進行循環伏安法和電化學阻抗圖譜分析。根據研究結果顯示，五價砷的訊號值與濃度之間具有良好的線性關係，偵測極限為0.90 µg L-1，遠低於國內飲用水標準(10 µg L-1)和2021年放流水標準(0.25 mg L-1)。在分析過程中，溶液中的三價砷會先被氧化成五價砷，再於電極表面上還原成金屬砷，原因與電解液中大量的氯離子有關。此外，本研究開發的修飾電極不會受到水中六價鉻及鐵離子的影響，並且能夠運用在自來水及飲用水的測量。因此，此修飾電極在水質監測方面具有良好的潛力。;Arsenic is one of the water contaminants which threats to human health. Total inorganic arsenic comprises arsenite (As(III)) and arsenate (As(V)) which are highly toxic. Long-term ingestion may lead to cancer, gangrene, disease of kidney, skin, etc. Commonly used method for arsenic determination is spectrophotometry which cannot reflect water quality immediately; however, electrochemical techniques have been noticed that can detect inorganic arsenic rapidly. But most of electrochemical techniques only developed for measurement of As(III) because As(V) species are hardly detected which due to its electro-inactive property. In this research, the gold and manganese oxide/ graphene oxide and single-walled carbon nanotubes modified glassy carbon electrode (Au-MnOx/GO-SWCNTs/GCE) was developed. Under the optimal preparation conditions (30 s electroplating at -0.1 V) and the optimal operation conditions (300 s deposition at -0.5 V), it was used to directly evaluate As(V) in water samples by square wave anodic stripping voltammetry (SWASV). The modified electrodes were performed by cyclic voltammetry and electrochemical impedance spectroscopy. Preconcentration of As(V) to As(0) on the Au-MnOx/GO-SWCNTs/GCE surface was associated with abundant Cl- ions in 0.2 M Clark-Lubs buffer (pH 2). The stripping current was found at -0.1 to 0.2 V which is proportional to the concentration of As(V) in the range from 5 to 100 μg L-1, and the detection limit is 0.90 μg L-1. It is lower than limited values of Drinking Water Quality Standard (10 μg L-1) and Effluent Standard (0.25 mg L-1) in 2021. Repeatability of As(V) for nine times analysis exhibits good with a relative standard deviation (RSD) of 4.59%. The modified electrode developed in this work is free from the interference of Cr(VI) and Fe(III). This modified electrode was successfully applied to the determination of As(V) in tap water and drinking water.
