scholarly journals Electrochemical oxidation of methylthiomethyleneisoquinolinium chloride — the first water soluble alkylthiomethylene substituted ammonium salt

2011 ◽  
Vol 9 (5) ◽  
pp. 840-845 ◽  
Author(s):  
Sylwia Smarzewska ◽  
Sławomira Skrzypek ◽  
Barbara Bachowska ◽  
Piotr Bałczewski ◽  
Witold Ciesielski
Keyword(s):  
Electrochemical Oxidation ◽  
Ammonium Salt ◽  
Glassy Carbon ◽  
Spectroscopic Method ◽  
Water Soluble ◽  
Carbon Electrode ◽  
Oxidation Peak ◽  
Citrate Buffer ◽  
Step Potential ◽  
Oxidation Peak Current

AbstractElectrochemical oxidation of methylthiomethyleneisoquinolinium chloride (MTMIQ), the first alkylthiomethyl substituted ammonium salt, which is fully miscible with water has been investigated by voltammetric (SWV) method using glassy carbon electrode. On the electrode, MTMIQ undergoes oxidation at the potential near Ep = 0.07V (vs. Ag/AgCl/3 M KCl). The influence of the pH of buffers, amplitude, frequency, step potential on the received signal was studied. The best results were obtained with a citrate buffer at a pH of 5. The oxidation peak current used for MTMIQ voltammetric determination was in the range of 2–8×10−5 mol L−1, LOD = 3.7×10−6, LOQ = 1.2×10−5. The product of the oxidation was accumulated at the working electrode and was investigated by spectroscopic method. Mechanistic pathways of the oxidation have been proposed.

scholarly journals Electrochemical antioxidant screening and evaluation based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE)

2020 ◽  
Vol 18 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Ping Tang ◽  
Xiaosheng Tang ◽  
Shiyong Mei ◽  
Yixi Xie ◽  
Liangliang Liu ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Antioxidant Capacity ◽  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Carbon Electrode ◽  
Oxidation Peak ◽  
Modified Glassy Carbon Electrode ◽  
Peak Current ◽  
Oxidation Peak Current ◽  
Antioxidant Capacities

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.

scholarly journals Sensitive Voltammetric Sensor for Tryptophan Detection by Using Polyvinylpyrrolidone Functionalized Graphene/GCE

Nanomaterials ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 125 ◽  
Author(s):  
Quanguo He ◽  
Jun Liu ◽  
Jinxia Feng ◽  
Yiyong Wu ◽  
Yaling Tian ◽  
...  
Keyword(s):  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Limit Of Detection ◽  
Phosphate Buffer Solution ◽  
Oxidation Mechanism ◽  
Carbon Electrode ◽  
Oxidation Peak ◽  
Experimental Conditions ◽  
Peak Current ◽  
Oxidation Peak Current

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.

Electrochemical evaluation of the antioxidant capacity of natural compounds on glassy carbon electrode modified with guanine-, polythionine-, and nitrogen-doped graphene

2020 ◽  
Vol 18 (1) ◽  
pp. 1054-1063
Author(s):  
Yafen Fu ◽  
Zongyi You ◽  
Aiping Xiao ◽  
Liangliang Liu ◽  
Weien Zhou
Keyword(s):  
Antioxidant Capacity ◽  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Carbon Electrode ◽  
Oxidation Peak ◽  
Nitrogen Doped ◽  
Oxidation Peak Current ◽  
Capacity Evaluation ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene

AbstractAn electrochemical sensor based on guanine-, polythionine-, and nitrogen-doped graphene modified glassy carbon electrode (G/PTH/NG/GCE) was fabricated and applied for antioxidant capacity evaluation of natural compounds and complexes in electrochemical method since natural sources of active compounds exhibited various antioxidant activities. When the antioxidants existed in the system, the generated hydroxyl radicals were scavenged and the damage to guanine immobilized on the electrode was reduced less resulting in the oxidation peak current increased in square wave voltammetry. After the modifications of polythionine- and nitrogen-doped graphene, the oxidation peak current was improved. The effects of pH, incubation time, and concentrations of guanine and Fe2+ ions on the performances of the electrode were investigated and optimized. The G/PTH/NG/GCE showed good linearity, reproducibility, and storage stability for antioxidant capacity evaluation of ascorbic acid at the optimum conditions. The antioxidant capacities of three flavonoids and three plant extracts were measured using the G/PTH/NG/GCE and DPPH methods. Myricetin showed the highest antioxidant capacity in both electrochemical and DPPH methods. The proposed G/PTH/NG/GCE exhibited easy fabrication procedure, rapid detection time, and low cost for the detection of antioxidant activity for various kinds of samples.

Nitrite Sensors Based on Gold Particles and Polyaniline Modified Electrodes

2011 ◽  
Vol 239-242 ◽  
pp. 2466-2469
Author(s):  
Yu Cui Hao ◽  
Yan Juan Liu ◽  
Bin Hao
Keyword(s):  
Electrochemical Method ◽  
Electrocatalytic Oxidation ◽  
Modified Electrodes ◽  
High Sensitivity ◽  
Carbon Electrode ◽  
Oxidation Peak ◽  
Modified Glassy Carbon Electrode ◽  
Gold Particles ◽  
Oxidation Peak Current ◽  
Experimental Parameters

A nitrite sensor based on a gold particles/polyaniline modified glassy carbon electrode (Au/PAni/GCE) was devoped by electrochemical method. The electrocatalytic oxidation of nitrite at Au/PAni/GCE was studied by cyclic voltammetry. The experimental parameters were optimized, and a voltammetric method for determining nitrite was developed. In phosphate buffered solution(PBS) of pH 3.0, the oxidation peak current of nitrite is proportional to the concentration of nitrite over the range of 4.0×10-7～5.0×10-3mol/L with the detection limit of 2.0×10-7mol/L (r=0.9992). The presented methods of determing nitrite exhibited high sensitivity and good reproducibility.

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