scholarly journals Electrochemical Behavior of Quinoxalin-2-one Derivatives at Mercury Electrodes and Its Analytical Use

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Milan Zimpl ◽  
Jana Skopalova ◽  
David Jirovsky ◽  
Petr Bartak ◽  
Tomas Navratil ◽  
...  
Keyword(s):  
Electrochemical Behavior ◽  
Reduction Process ◽  
Differential Pulse ◽  
Point Of View ◽  
Semiquinone Radical ◽  
Mesomeric Effect ◽  
Radical Intermediate ◽  
Mercury Electrodes ◽  
Electron Reduction

Derivatives of quinoxalin-2-one are interesting compounds with potential pharmacological activity. From this point of view, understanding of their electrochemical behavior is of great importance. In the present paper, a mechanism of electrochemical reduction of quinoxalin-2-one derivatives at mercury dropping electrode was proposed. Pyrazine ring was found to be the main electroactive center undergoing a pH-dependent two-electron reduction process. The molecule protonization of nitrogen in the position 4 precedes the electron acceptance forming a semiquinone radical intermediate which is relatively stable in acidic solutions. Its further reduction is manifested by separated current signal. A positive mesomeric effect of the nonprotonized amino group in the position 7 of the derivative III accelerates the semiquinone reduction yielding a single current wave. The suggested reaction mechanism was verified by means of direct current polarography, differential pulse, cyclic and elimination voltammetry, and coulometry with subsequent GC/MS analysis. The understanding of the mechanism was applied in developing of analytical method for the determination of the studied compounds.

scholarly journals The effect of tamoxifen on the electrochemical behavior of Bi+3/Bi on the glassy carbon electrode and its determination via differential pulse anodic stripping voltammetry

2019 ◽  
Vol 63 (1) ◽  
Author(s):  
Mehdi Jalali ◽  
Zeinab Deris Falahieh ◽  
Mohammad Alimoradi ◽  
Jalal Albadi ◽  
Ali Niazi
Keyword(s):  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Electrochemical Behavior ◽  
Electrochemical Impedance ◽  
Anodic Stripping Voltammetry ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Peak Height ◽  
Carbon Electrode

The electrochemical behavior of Bi+3 ions on the surface of a glassy carbon electrode, in acidic media and in the presence of tamoxifen, was investigated. Cyclic voltammetry, chronoamperometry, differential pulse voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy were used to find the probable mechanism contributing to the reduction of the peak height of bismuth oxidation with an increase in the concentration of tamoxifen. The obtained results show a slight interaction between the bismuth species and tamoxifen which co-deposit on the surface of glassy carbon electrode. Therefore, the reduction in the peak height of bismuth oxidation as a function of tamoxifen concentration was used to develop a new differential pulse anodic striping voltammetry method for determination of trace amount of tamoxifen. The effects of experimental parameters on the in situ DPASV of Bi+3 ions in the presence of tamoxifen shown the optimal conditions as: 2 mol L-1 H2SO4 (1% v v-1 MeOH), a deposition potential of -0.5 V, a deposition time of 60 s, and a glassy carbon electrode rotation rate of 300 rpm. The calibration curve was plotted in the range of 0.5 to 6 µg mL-1 and the limits of detection and quantitation were calculated to be 3.1 × 10-5 µg mL-1 and 1.0 × 10-4 µg mL-1, respectively. The mean, RSD, and relative bias for 0.5 µg mL-1 (n=5) were found to be 0.49 µg mL-1, 0.3%, and 2%, respectively. Finally, the proposed method was successfully used for the determination of tamoxifen in serum and pharmaceutical samples.

The production of reactive oxygen species enhanced with the reduction of menadione by active thioredoxin reductase

Metallomics ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1490-1497 ◽  
Author(s):  
Jing Li ◽  
Xin Zuo ◽  
Ping Cheng ◽  
Xiaoyuan Ren ◽  
Shibo Sun ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Molecular Oxygen ◽  
Thioredoxin Reductase ◽  
Reactive Oxygen ◽  
Semiquinone Radical ◽  
Ros Production ◽  
Oxygen Species ◽  
Reduction Mechanism ◽  
Radical Intermediate ◽  
Electron Reduction

TXNRD1 participates in the ROS production with menadione by a one-electron reduction mechanism. TXNRD1 transfers electrons from NADPH to menadione to yield a semiquinone radical intermediate, which reacts with molecular oxygen to generate ROS.

scholarly journals Electrochemical Behavior and Voltammetric Determination of a Manganese(II) Complex at a Carbon Paste Electrode

2016 ◽  
Vol 11 ◽  
pp. ACI.S32150 ◽  
Author(s):  
Sophia Karastogianni ◽  
Stella Girousi
Keyword(s):  
Carboxylic Acid ◽  
Differential Pulse Voltammetry ◽  
Carbon Paste Electrode ◽  
Electrochemical Behavior ◽  
Differential Pulse ◽  
Carbon Paste ◽  
Oxidation Reduction ◽  
Pulse Voltammetry ◽  
Paste Electrode

Investigation of the electrochemical behavior using cyclic voltammetry and detection of [Mn2+(thiophenyl-2-carboxylic acid)2 (triethanolamine)] with adsorptive stripping differential pulse voltammetry. The electrochemical behavior of a manganese(II) complex [Mn2+(thiophenyl-2-carboxylic acid)2(triethanolamine)] (A) was investigated using cyclic and differential pulse voltammetry in an acetate buffer of pH 4.6 at a carbon paste electrode. Further, an oxidation-reduction mechanism was proposed. Meanwhile, an adsorptive stripping differential pulse voltammetric method was developed for the determination of manganese(II) complex.

Electrochemical behavior and voltammetric determination of the herbicide metribuzin at mercury electrodes

2001 ◽  
Vol 370 (7) ◽  
pp. 963-969 ◽  
Author(s):  
J. Skopalová ◽  
K. Lemr ◽  
M. Kotouček ◽  
L. Čáp ◽  
P. Barták
Keyword(s):  
Electrochemical Behavior ◽  
Voltammetric Determination ◽  
Mercury Electrodes

Polarographic and voltammetric determination of genotoxic 2-aminofluoren-9-one at mercury electrodes

2011 ◽  
Vol 76 (12) ◽  
pp. 1775-1790 ◽  
Author(s):  
Andrea Hájková ◽  
Vlastimil Vyskočil ◽  
Aleš Daňhel ◽  
Joseph Wang ◽  
Jiří Barek
Keyword(s):  
Differential Pulse Voltammetry ◽  
Mercury Electrode ◽  
Direct Determination ◽  
Differential Pulse ◽  
Differential Pulse Polarography ◽  
Limit Of Quantification ◽  
Dropping Mercury Electrode ◽  
Pulse Voltammetry ◽  
Mercury Electrodes

Electrochemical behavior of genotoxic 2-aminofluoren-9-one (2-AFN) was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a classical dropping mercury electrode (DME), and by DC voltammetry (DCV), differential pulse voltammetry (DPV), and adsorptive stripping differential pulse voltammetry (AdSDPV), all at a miniaturized hanging mercury drop minielectrode (HMDmE), in buffered aqueous-methanolic solutions. Optimum conditions were found for the determination of 2-AFN by DCTP at DME in the concentration range from 1 × 10–6to 1 × 10–4mol l–1(with a limit of quantification (LQ) of 5 × 10–7mol l–1), by DPP at DME (from 1 × 10–7to 1 × 10–4mol l–1;LQ ≈ 1 × 10–7mol l–1), by DCV and DPV at HMDmE (both from 1 × 10–7to 1 × 10–4mol l–1;LQs ≈ 2 × 10–7and 1 × 10–7mol l–1for DCV and DPV, respectively), and by AdSDPV at HMDmE (from 2 × 10–9to 1 × 10–7mol l–1;LQ ≈ 4 × 10–9mol l–1). Practical applicability of the developed methods was verified on the direct determination of 2-AFN in model samples of drinking and river water in nanomolar to micromolar concentrations.

scholarly journals Electrochemical behavior and differential pulse voltammetric determination of ceftazidime, cefuroxime-axetil and ceftriaxone

2013 ◽  
Vol 11 (1) ◽  
pp. 55-66 ◽  
Author(s):  
Mara Aleksic ◽  
Nikola Lijeskic ◽  
Jelena Pantic ◽  
Vera Kapetanovic
Keyword(s):  
Reduction Process ◽  
Differential Pulse ◽  
Cefuroxime Axetil ◽  
Pharmaceutical Dosage Forms ◽  
Diffusion Controlled ◽  
Voltammetric Behavior ◽  
Pulse Voltammetry ◽  
Ph Range ◽  
Linear Concentration

The voltammetric behavior of three cephalosporins: ceftazidime, cefuroxime-axetil and ceftriaxone has been examined in pH range 2.0-8.0 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), using a hanging mercury drop electrode (HMDE). The effect of pH of the electrolyte solution and scan rate on the peak currents and peak potentials was examined. The nature of the electrode reduction process in acid solution was found to be diffusion controlled for ceftazidime and cefuroxime-axetil, but strongly influenced by adsorption in the case of ceftriaxone reduction. The adsorption and reorientation of the ceftriaxone molecule at the electrode surface caused instability of the voltammetric signal and disabled its determination in the acid medium. Ceftriaxone adsorption decreased with the increase of pH, and at pH>7 the reduction process became diffusion controlled. Based on this study, DPV method was developed, validated and suggested for determination of ceftazidime at pH 2.0, cefuroxime-axetil at pH 3.5 and for ceftriaxone at pH 8.0. Linear concentration ranges, limits of detection (LOD) and quantification (LOQ) were determined. The method was applied for determination of cephalosporins in pharmaceutical dosage forms: Ceftazidime powder, Ceroxim tablets and Longaceph powder for injection solution.

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