| dc.description.abstract | 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.
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