| 摘要: | 重金屬鉻，為工業製程中常見的物質，最主要存在的型態為三價鉻(Cr(III))及六價鉻(Cr(VI))。其中，Cr(III)的毒性低於Cr(VI)，並且在生物過程中起著至關重要的作用，Cr(VI)則具有高毒性及致癌性，攝入過量將導致細胞癌、小腸癌及腸胃的刺激或潰瘍。目前工業處理Cr(VI)的主要方式為將其還原成Cr(III)再進行沉澱去除，因此，準確地測量鉻離子為一個重要的議題。現今常見的分析方式大多耗時長，需要複雜的前處理，無法即時測量，並且無法直接區分Cr(III)及Cr(VI)。電化學伏安法為一興新的分析技術，具有簡單、快速、靈敏、選擇性強、可小型化和便攜性等優點而受到重視。
本研究利用金奈米粒子/還原石墨烯/單壁奈米碳管複合材料修飾玻璃碳電極(Au/rGO/SWCNT/GCE)進行水中鉻物種之線性伏安法分析。首先選定適宜的伏安法分析，再進行材料的選擇及分析測試，經過金奈米粒子的沉積及伏安法分析條件的最佳化選擇，探討電極對水中鉻物種之穩定性、再現性及選擇性等性能分析。結果顯示，Au/rGO/SWCNT/GCE在不同電解液條件下可辨別Cr(III)及Cr(VI)，兩者濃度與電流值皆達到良好的線性關係，其中，Cr(VI)的線性範圍為 50–1500 µg L-1，R2為0.999，LOD為34.58 µg L-1，而Cr(III) 的線性範圍為 100–1500 µg L-1，R2為0.997，LOD為77.59 µg L-1，另外，電極擁有良好的重複性及再現性，相對標準偏差分別為2.8%和3.0%，並且水樣存在As(III)、Zn(II)、Cu(II)、Pb(II)、Fe(II)時無干擾現象。另外，在Cr(III)及Cr(VI)相互的干擾測試中，可知電極進行Cr(III)的分析時不會受到Cr(VI)干擾，但反之則會受到干擾。因此，為了確保分析的準確性，本研究提出了一種Au/rGO/SWCNT/GCE檢測Cr的程序，當水樣需分析時，必須先進行Cr(III)的檢測，若沒有檢測到Cr(III)，再進行Cr(VI)的檢測。最後，本研究在環境水體中進行鉻物種的分析，證實了在自來水及地下水中皆有良好的回收率。
;Chromium is commonly used in industrial processes, and its two most stable oxidation states are trivalent chromium Cr(III) and hexavalent chromium Cr(VI). Among them, Cr(III) is less toxic than Cr(VI) and plays an essential role in biological processes; Cr(VI) is more toxic due to its carcinogenic and mutagenic properties. Excessive intake of Cr(VI) will cause cell cancer, small intestine cancer, and gastrointestinal tract irritation or ulceration. At present, the main method of industrially treating of Cr(VI) is to reduce to Cr(III) and then remove by precipitation. Therefore, accurate measurement of both Cr(III) and Cr(VI) are important. The common analysis methods of heavy metals are usually time-consuming, complicated pre-processing, cannot be measured on-site, and difficult to directly distinguish Cr(III) and Cr(VI). Electrochemical voltammetry is a promising analytical technique, which has the advantages of simple, fast, sensitivity, selectivity, and possibilities for miniaturization and portability.
In this study, linear sweep voltammetry analysis of chromium was performed by gold nanoparticles/reduced graphene oxide/single walled carbon nanotubes modified glassy carbon electrode (Au/rGO/SWCNT/GCE). First, the appropriate voltammetry was selected, then the ratio of rGO and SWCNT was determined. After the investigation of parameter optimization of the deposition of gold nanoparticles and the voltammetry analysis, the repeatability, reproducibility, stability, and selective have been performed. The results show that Cr(III) and Cr(VI) could be distinguished by Au/rGO/SWCNT/GCE with different electrolytes condition. For Cr(VI), the dynamic range was 50–1500 µg L-1 (R2=0.999), and LOD=77.59 µg L-1. For Cr(III), the dynamic range was 100–1500 µg L-1 (R2=0.997), and LOD=34.58 µg L-1. The Au/rGO/SWCNT/GCE also had good selectivity (RSD, 2.87%) and reproducibility (RSD, 3.01%). In addition, high concentration of Cd(II), As(III), Zn(II), Cu(II), Pb(II) and Fe(II) would not cause interference. Moreover, mutual interference of Cr(III) and Cr(VI) was performed and it was found that the analysis of Cr(III) would not be interfered by Cr(VI), but not vice versa. Therefore, to ensure accuracy, this study proposed a procedure for detection of Cr by Au/rGO/SWCNT/GCE. That is, perform detection of Cr(III) first. If there is no Cr(III), then Cr(VI) can be determined without interference of Cr(III). Finally, the analysis of Cr(III) and Cr(VI) confirmed the good recovery in tap water and groundwater. |
