In situ detection of intermediates from the interaction of dissolved sulfide and manganese oxides with a platinum electrode in aqueous systems

2017 ◽  
Vol 14 (3) ◽  
pp. 178 ◽  
Author(s):  
Yao Luo ◽  
Yougang Shen ◽  
Lihu Liu ◽  
Jun Hong ◽  
Guohong Qiu ◽  
...  

Environmental contextDissolved sulfide results in soil acidification and subsequent contaminant leaching via oxidation processes, usually involving manganese oxides. In this work, redox processes were monitored in situ by cyclic voltammetry and HS– concentrations were semi-quantitatively determined. The method provides qualitative and semi-quantitative assessment for dissolved sulfide and its oxidation intermediates in aqueous systems. AbstractDissolved sulfide can be oxidised by manganese oxides in supergene environments, while the intermediates including S0, S2O32– and SO32– are easily oxidised by oxygen in air, resulting in some experimental errors in conventional analyses. In this work, the electrochemical behaviours of HS–, S2O32– and SO32– on a platinum electrode were studied by cyclic voltammetry and constant potential electrolysis, and in situ detection of the intermediates was conducted in aqueous systems of HS– and manganese oxides. The results showed that HS– was first oxidised to S0, and then transformed to SO42–. The peak current for the oxidation of HS– to S0 had a positive linear correlation with the used starting HS– concentration. S2O32– and SO32– were directly electrochemically oxidised to SO42–. The oxidation current peak potentials at 0, 0.45 and 0.7V were respectively observed for HS–, S2O32– and SO32– at pH 12.0. Cyclic voltammetry was conducted to monitor the redox processes of HS– and manganese oxides. The oxidation peak current of HS– to S0 decreased, and that of S2O32– to SO42– was observed to increase as the reaction proceeded. The rate of the decrease of the oxidation peak current of HS– indicated that the oxidation activity followed the order of birnessite>todorokite>manganite.

2013 ◽  
Vol 785-786 ◽  
pp. 527-532 ◽  
Author(s):  
Li Qing Ye ◽  
Yan Zheng ◽  
Li Li Yan ◽  
Yun Tao Gao

Inlaid multi-wall carbon nanotubes modified graphite electrode (MWCNTs-GE) was fabricated, combined with Reline Ionic Liquids which possess high conductivity and wide electrochemical window, the electrochemical behavior and determination of Rutin was investigated by cyclic voltammetry and differential pulse stripping voltammetry. The result shows that the oxidation peak current of rutin increased obviously at the inlaid multi-wall carbon nanotubes modified graphite lectrode and in the Reline Ionic Liquids compared to that at the bare graphiteelectrode (GE). In phosphate buffer solution (pH=6.3), one pair of redox peak of rutin was obtained by cyclic voltammetry with 0.32 V of Epaand 0.24 V of Epc. The oxidation peak current value was linearly related to the concentration of rutin in the range of 2×10-6~3×10-5mol·L-1and the detection limit was 9.4×10-7mol·L-1. The average RSD of rutin was 4.0%. The average recovery was 100.2%. The inlaid multi-wall carbon nanotubes modified graphite electrode and the Reline Ionic Liquids had the function of electrocatalysis to oxidation of rutin obviously.This method is reliable, fast and convenient, sensitive and can be used for the determination of the content of rutin.


2020 ◽  
Vol 18 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Ping Tang ◽  
Xiaosheng Tang ◽  
Shiyong Mei ◽  
Yixi Xie ◽  
Liangliang Liu ◽  
...  

AbstractIn this study, an electrochemical biosensor based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE) was developed and employed for antioxidant screening and antioxidant capacity evaluation. The oxidation peak current of guanine was improved and nearly tripled after modifications of chitosan and MoS2 nanosheet. The immobilized guanine could be damaged by hydroxyl radicals generated in Fenton solution. However, in the presence of antioxidants, the guanine was protected and the oxidation peak current of guanine increased. This process mimics the mechanism of antioxidant protection in human body. The factors affecting preparation of sensor and detection of antioxidant capacity were optimized. At the optimum conditions, the guanine/CS/MoS2/GCE showed wide linear range, low detection limit, satisfactory reproducibility and stability for detection. Ascorbic acid was used as a model antioxidant to evaluate the antioxidant capacity. A good linearity was observed with a correlation coefficient of 0.9959 in the concentrations between 0.5 and 4.0 mg L-1. The antioxidant capacities of three flavonoids were also tested and the rank of antioxidant capacities was ascorbic acid (51.84%), quercetin (45.82%), fisetin (34.39%) and catechin (16.99%). Due to the rapid measurement and low cost, this sensor could provide an available sensing platform for antioxidant screening and evaluation.


2012 ◽  
Vol 554-556 ◽  
pp. 440-444
Author(s):  
He Zhen Wu ◽  
Aie Cao ◽  
Di Lou Xu ◽  
Dao Bao Chu

Electrocatalytic oxidation of multi-nanostructured active electrode modified by platinum nanoparticles on glucose was examined. Based on 0.5mol/L KOH solution, we see a sensitive and good-shaped oxidation peak current near -0.77V (VS, SCE) by using differential pulse voltammetry method to scan in the range of -0.9~0.4V.The peak is regarded as the quantitative peak. There is a good linear relationship between glucose concentration and the peak current in the range of 1.0×10-2~1.0×10-5 mol/L. The linear correlation coefficient is 0.99864.The detection limit is 1.0×10-6mol/L. If added 0.06 m mol/L ascorbic acid or 0.3m mol/L uric acid (simulating human blood components), the determination of glucose is not interfered with. Results of the determination of glucose concentration in the blood are satisfactory.


2002 ◽  
Vol 57 (1) ◽  
pp. 92-98 ◽  
Author(s):  
Şeniz Özalp Yaman ◽  
Emren Esentürk ◽  
Ceyhan Kayran ◽  
Ahmet M. Önal

The electrochemical behaviour of pentacarbonyl(pyrazine)metal(0) complexes of the group 6 elements was studied by cyclic voltammetry in dichloromethane-(n-Bu)4NBF4 solventelectrolyte couple at -20°C vs. Ag/Ag+ or SCE reference electrode. Constant potential electrolyses of the complexes were carried out at their first oxidation peak potentials and monitored in situ by UV-Vis spectrometry. Electrolysis of W(CO)5pz produces [W(CO)5pz]+ and a similar electrochemical mechanism is expected both for Cr(CO)5pz and Mo(CO)5pz complexes. In situ low temperature constant current ESR electrolysis also confirmed the production of [W(CO)5pz]+ after the electron transfer.


2022 ◽  
Vol 905 ◽  
pp. 204-209
Author(s):  
Nan Dong ◽  
Ke Cao ◽  
Chen Xi Si ◽  
Dan Zheng

In this work, core–shell structured nanocomposites consisting of Pd doped Ag@C were synthesized by impregnation–reduction method. Then, sensing electrodes were fabricated by modifying Pd/Ag@C core-shell nanoparticles on screen-printed electrodes (SPE) for electrochemical determination of bisphenol A (BPA). The composition and morphology of nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, X ray diffraction and energy-dispersive X-ray spectroscopy. The electrochemical response characteristics of nanocomposites to BPA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results indicated that, compared with Ag@C and Pd/C, Pd/Ag@C nanocomposite shows greater catalytic activity to the oxidation of BPA due to the synergistic effect of Pd and Ag. Among the four synthesized Pd/Ag@C-x (x=1-4) nanomaterials, the Pd/Ag@C-3 exhibits the best sensing performance toward the sensitive detection of BPA. The linear range for BPA determination was from 8.0×10-8 M to 1.5×10-5M with a detection limit of 1.0×10-8 M. A less than 9% oxidation peak current change was observed on the determination of BPA using Pd/Ag@C-3/SPE when added different interfering species into the BPA solution. The oxidation peak current attenuation of BPA on Pd/Ag@C-3/SPE within five weeks was found to be less than 3.6%.


Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 669 ◽  
Author(s):  
Changzheng Wang ◽  
Fengnan Yang ◽  
Li Gao ◽  
Shoufang Xu ◽  
Louzhen Fan ◽  
...  

AuPt nanoparticles clusters (NPCs) were electrodeposited on multiwalled carbon nanotubes (MWCNTs). The as-prepared AuPt NPCs@MWCNTs nanocomposites exhibited considerably enhanced electrocatalytic activity than Pt NPs@MWCNTs for methanol oxidation in acid medium. In comparison with Pt NPs@MWCNTs, a remarkable resistance to CO poisoning and a higher If/Ib value (the ratio of the forward scan oxidation peak current (If) and reverse scan oxidation peak current (Ib)) was achieved by AuPt NPCs@MWCNTs electrocatalyst, which is attributable to the unique NPCs nanostructure with enlarged electrochemical active surface areas. These results demonstrated the potential of AuPt NPCs@MWCNTs, which can be considered as an efficient electrocatalyst for methanol oxidation in direct methanol fuel cells.


Nanomaterials ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 125 ◽  
Author(s):  
Quanguo He ◽  
Jun Liu ◽  
Jinxia Feng ◽  
Yiyong Wu ◽  
Yaling Tian ◽  
...  

In this paper, an electrochemical method for the measurement of tryptophan (Trp) was developed based on a glassy carbon electrode modified with polyvinylpyrrolidonefunctionalized graphene (PVP-GR)/glassy carbon electrode (GCE). In 0.1 M phosphate buffer solution (PBS, pH = 2.2), compared with bare GCE, PVP/GCE, and GR/GCE, the oxidation peak current of Trp increased dramatically at PVP-GR/GCE. The oxidation mechanism of Trp on the PVP-GR/GCE was discussed and the experimental conditions were optimized. Under the best experimental conditions, the oxidation peak current of Trp was proportional to its concentration in the range of 0.06 µM–10.0 µM and 10.0–100.0 µM, and the limit of detection (LOD) was 0.01 µM (S/N = 3). The target modified electrode with excellent repeatability, stability and selectivity, was successfully applied to detectTrp in drugs and biological samples.


2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
Weili Zhang ◽  
Xueliang Niu ◽  
Hua Zhang ◽  
Qingqing Jiang ◽  
Pingping Zhang

The interaction of protionamide with alizarin red S (ARS) and its analytical application were carefully investigated in this contribution. The interaction conditions were carefully studied and optimized by cyclic voltammetry. Under the optimum conditions, the cyclic voltammetry curve of ARS showed an oxidation peak with the peak potential of 0.57 V. After the addition of protionamide to the ARS solution, the peak potential was negatively moved, and meanwhile the oxidation peak current decreased apparently to the concentration of protionamide and then a new method for the protionamide determination was established. The linear equation between the decreasing current (Δip) and protionamide concentration was got as Δip (μA) = 0.01514C(mg/L) −0.01553  (n=9; r=0.991)with the linear range of 10.0~50.0 mg/L, and the detection limit (3σ) was got as 8.25 μg/mL. The effects of coexisting substances on the determination were carefully investigated and the protionamide artificial and tablet samples were detected with satisfactory results.


2013 ◽  
Vol 2 (2) ◽  
pp. 157-164 ◽  
Author(s):  
A. Zuzuarregui ◽  
S. Arana ◽  
E. Pérez-Lorenzo ◽  
S. Sánchez-Gómez ◽  
G. Martínez de Tejada ◽  
...  

Abstract. In this paper an electrochemical endotoxin biosensor consisting of an immobilized lipopolysaccharide (LPS) ligand, polymyxin B (PmB), is presented. Several parameters involved both in the device fabrication and in the detection process were analyzed to optimize the ligand immobilization and the interaction between PmB and LPS, aiming at increasing the sensitivity of the sensor. Different electrochemical pre-treatment procedures as well as the functionalization methods were studied and evaluated. The use of a SAM (self-assembled monolayer) to immobilize PmB and the quantification of the interactions via cyclic voltammetry allowed the development of a robust and simple device for in situ detection of LPS. Thus, the biosensor proposed in this work intends an approach to the demanding needs of the market for an integrated, portable and simple instrument for endotoxin detection.


Author(s):  
Manjunatha Jg

Objective: A new carbon nanotube (CNT)-graphite mixture paste electrode modified by Sodium dodecyl sulfate (SDS) surfactant (SDSMCNTGMPE) was prepared and applied for sensitive electrochemical determination of resorcinol (RS).Method: Cyclic voltammetry, variable pressure scanning electron microscopy, and differential voltammetry were employed for the surface analysis of the bare CNT-graphite mixture paste electrode and SDSMCNTGMPE. Comparison between the unmodified electrode and modified electrode, the modified electrode oxidation peak current significantly improved. The effects of the pH, scan rate, and concentration of RS on the peak current were investigated.Results: Results indicated that the peak current of RS is highest in 0.2 M pH 7.0 phosphate buffer solutions and that the electrode reaction corresponds to a rate controlled process. Under optimized experimental conditions, the oxidation peak current of RS was linear over a concentration range of 2×10−6 to 1.0×10−3 M with a detection limit of 5.8×10−6 M and quantification limit of 19×10−6 M.Conclusion: The prepared sensor also shows other features such as good stability, reproducibility and repeatability. The proposed sensor exhibits good application toward the detection of RS in commercial RS lotion samples.


Sign in / Sign up

Export Citation Format

Share Document