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Oxidation Mechanism of Rhamnetin, a Bioflavonoid Compound
Ramešová, Šárka; Sokolová, Romana; Degano, I.
2016 - English
The natural flavonoid rhamnetin (2-(3,4-dihydroxyfenyl)-3,5-dihydroxy-7-methoxychromen-4-one) is important bioactive compound. Rhamnetin was studied in aqueous solution by electrochemical methods. The oxidation mechanism proceeds in sequential steps, which correspond to the hydroxyl oxidation of groups in the three aromatic rings. The study is based on in situ spectroelectrochemistry and identification of products by HPLC-DAD and HPLC–ESI MS/MS.
Keywords:
flavonoids; electrochemistry; oxidation mechanism
Available at various institutes of the ASCR
Oxidation Mechanism of Rhamnetin, a Bioflavonoid Compound
The natural flavonoid rhamnetin (2-(3,4-dihydroxyfenyl)-3,5-dihydroxy-7-methoxychromen-4-one) is important bioactive compound. Rhamnetin was studied in aqueous solution by electrochemical methods. The ...
Poly(Methylene Blue) Modified Carbon-based Electrodes for Electrochemical Detection of Hydrogen Sulfide
Zlámalová, Magda; Janda, Pavel; Nesměrák, K.
2016 - English
A comparative electrochemical study has been carried out of the electropolymerization of phenothiazine derivative, methylene blue (MB). Electrochemical properties of resulting electrocatalytically active methylene blue polymer (pMB) have been studied on three various carbon-based substrates: basal plane of highly oriented pyrolytic graphite (HOPG), pencil-graphite electrode (PGE) and carbon fibre micro electrode (CFE). Electrodes modified with the polymer (HOPG/pMB, PGE/pMB and CFE/pMB) have been prepared by potential cycling in aqueous electrolyte solution containing dissolved monomeric methylene blue. Electrocatalytic activity of three developed electrode systems towards hydrogen sulphide has been compared. Developed electrodes have been further investigated as potential sensors for sulfhydryl-containing compounds.
Keywords:
CFE; HOPG; electropolymerization
Available at various institutes of the ASCR
Poly(Methylene Blue) Modified Carbon-based Electrodes for Electrochemical Detection of Hydrogen Sulfide
A comparative electrochemical study has been carried out of the electropolymerization of phenothiazine derivative, methylene blue (MB). Electrochemical properties of resulting electrocatalytically ...
Poly(methylene blue) modified carbon based electrodes for the determination of sulfhydryl-containing compounds
Zlámalová, Magda; Janda, Pavel; Nesměrák, K.
2016 - English
This research presents the study of electrochemical polymerization of phenothiazine derivative, methylene blue (MB). Electrochemical pro perties and analytical application of resulting electrocatalytically active poly(methylene blue) (pMB) have been investigated. Three various carbon-based substrates: basal plane of highly oriented pyro lytic graphite (HOPG), pencil graphite electrode (PGE) and carbon fibre micro electrode (CFE) have been used. Aforementioned electrodes modified with the polymer (HOPG/pMB, PGE/pMB and CFE/pMB) have been prepared by potential cycling in aqueous electrolyte solution containing dissolved monomeric methylene blue. Electrocatalytic activity of three developed electrode systems towards hydrogen sulphide has been compared. Developed electrodes have been further investigated as potential sensors for sulfhydryl-containing compounds.
Keywords:
carbon-based electrodes; electropolymerization; hydrogen sulphide
Available at various institutes of the ASCR
Poly(methylene blue) modified carbon based electrodes for the determination of sulfhydryl-containing compounds
This research presents the study of electrochemical polymerization of phenothiazine derivative, methylene blue (MB). Electrochemical pro perties and analytical application of resulting ...
Role of Intramolecular Electron Interactions in Cathodic Reduction of Three Isomeric Benzenedialdehydes in Non-aqueous Media – a (Spectro)Electrochemical Study
Kantnerová, Kristýna; Klíma, Jiří; Ludvík, Jiří
2016 - English
This contribution is focused on cathodic reduction of three isomeric benzenedialdehydes – orthophthalaldehyde (OPA), isophthalaldehyde (IPA) and terephthalaldehyde (TPA) – in non-aqueous acetonitrile and dimethylformamide. Although their electrochemical behavior in aqueous solutions has been published several times, their investigation in organic aprotic solvents is lacking. Using DC-polarography, cyclic voltammetry, preparative electrolyses, coulometry and UV/Vis spectroelectro-chemistry their reduction was described and in the case of OPA and TPA, stable radical anions were characterized by EPR spectroscopy. The role of intramolecular electron interactions in their cathodic reduction is discussed.
Keywords:
Orthophthalaldehyde; OPA; IPA
Available at various institutes of the ASCR
Role of Intramolecular Electron Interactions in Cathodic Reduction of Three Isomeric Benzenedialdehydes in Non-aqueous Media – a (Spectro)Electrochemical Study
This contribution is focused on cathodic reduction of three isomeric benzenedialdehydes – orthophthalaldehyde (OPA), isophthalaldehyde (IPA) and terephthalaldehyde (TPA) – in non-aqueous acetonitrile ...
Electrochemical Impedence Spectroscopy and Steady-State Voltammetry at the Micro- between Two Immiscible Electrolyte Solution
Silver, Barry Richard; Holub, Karel; Mareček, Vladimír
2016 - English
The kinetic data of simple tetraethylammonium ion transfer across the water/1,2-DCE interface obtained by electrochemical impedance spectroscopy and steady-state voltammetry are compared. It is shown that the geometry of the microcapillary tip region is of critical importance to obtain reliable kinetic data. Quasi-reversible behavior of the ion transfer reaction, corresponding to an apparent standard rate constant of about 0.2 cm s-1, is observed with both experimental methods.\n
Keywords:
liquid-liquid interface; ion transport; AC impedance
Available at various institutes of the ASCR
Electrochemical Impedence Spectroscopy and Steady-State Voltammetry at the Micro- between Two Immiscible Electrolyte Solution
The kinetic data of simple tetraethylammonium ion transfer across the water/1,2-DCE interface obtained by electrochemical impedance spectroscopy and steady-state voltammetry are compared. It is shown ...
Study of 2-Nitrofluorene Interaction with DNA at a Glassy Carbon Electrode
Skalová, Štěpánka; Stávková, K.; Vyskočil, V.; Barek, J.
2016 - English
2-Nitrofluorene (2-NF) is a nitrated polycyclic aromatic hydrocarbon (NPAH) which occurs as the environmental pollutant. It is a potential carcinogen and mutagen. Interaction of deoxyribonucleic acid (DNA) with 2-NF was monitored using an electrochemical DNA biosensor prepared from a glassy carbon electrode (GCE) and low-molecular-weight DNA by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square-wave voltammetry (SWV).\nThere were no damaging interactions observed between DNA and 2-NF using EIS. However, CV shows intercalation of this substance into the DNA structure to form the complex 2-NF–DNA. Intercalation was also observed by SWV, confirming intercalation to reduce the number of electroactive sites and thus reducing the peak heights of adenosine and guanosine.
Keywords:
DNA biosensor; glassy carbon electrode; voltammetry
Available at various institutes of the ASCR
Study of 2-Nitrofluorene Interaction with DNA at a Glassy Carbon Electrode
2-Nitrofluorene (2-NF) is a nitrated polycyclic aromatic hydrocarbon (NPAH) which occurs as the environmental pollutant. It is a potential carcinogen and mutagen. Interaction of deoxyribonucleic acid ...
Structural, Redox and Spectrometric Characterization of Energetic Material FOX-7 (2,2-dinitroethene-1,1-diamine) in Solution
Šimková, Ludmila; Ludvík, Jiří
2016 - English
The investigation of energetic materials, especially organic nitro-amino-derivatives, always has attracted attention of physical chemists. However, published articles demonstrate lack of systematic study of molecules based on aliphatic backbones, rather than aromatic structures. This work represents the first systematic electrochemical and spectrometric characterization of 2,2-dinitroethene-1,1-diamine (FOX-7) in aqueous and aprotic solvent. Based on the results obtained from combination of electrochemistry with spectrometric methods, the actual structure of FOX-7 in various media was revealed, its reducibility described and radical intermediates as well as products were intercepted, isolated and characterized.
Keywords:
FOX-7; 2,2-dinitroethene-1,1-diamine; structure
Available at various institutes of the ASCR
Structural, Redox and Spectrometric Characterization of Energetic Material FOX-7 (2,2-dinitroethene-1,1-diamine) in Solution
The investigation of energetic materials, especially organic nitro-amino-derivatives, always has attracted attention of physical chemists. However, published articles demonstrate lack of systematic ...
Voltammetric determination of cancer biomarker 5-hydroxyindole-3-acetic acid at screen-printed carbon electrodes
Makrlíková, Anna; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
2016 - English
Tumor biomarker 5-hydroxyindole-3-acetic acid (5-HIAA) is a breakdown product of serotonin; level of this neurotransmitter can predict carcinoid tumors. 5-HIAA has been determined at screen-printed carbpon electrodes in the iptimum medium found: Britton-Robinson buffer (0.04 mol l-1, pH=3.0). Dependence of the peak current on the concentration of 5-HIAA was linear in the concentration region from 0.1 to 100 micromol l-1, with the limit of qiantification of 0.2 micromol l-1.
Keywords:
differential pulse voltammetry; tumor biomarker; screen-printed carbon electrodes
Available at various institutes of the ASCR
Voltammetric determination of cancer biomarker 5-hydroxyindole-3-acetic acid at screen-printed carbon electrodes
Tumor biomarker 5-hydroxyindole-3-acetic acid (5-HIAA) is a breakdown product of serotonin; level of this neurotransmitter can predict carcinoid tumors. 5-HIAA has been determined at screen-printed ...
Noise Analysis of Ion Transfer Kinetics at the Micro Liquid/Liquid Interface
Josypčuk, Oksana; Holub, Karel; Mareček, Vladimír
2015 - English
Fluctuation analysis was utilized to determine the TEA ion transfer kinetics across the water/1,2-dichloroethane interface. The average value ks = 0.34 cm s-1 is comparable with the previously reported value ks = 0.2 cm s-1, derived from electrochemical impedance spectroscopy experiments. The experimental approach utilizing a thick wall glass microcapillary to fix the interface exhibits a very small stray capacitance value, proving this system to be suitable for determining the kinetics of the fast ion transfer across a liquid/ liquid interface. Application of a method employing a small perturbation signal prevents polarization of the inner capillary surface by current flowing through the cell. The induced polarization of the capillary can affect ion concentration at the interface due to electroosmosis and thus make the kinetics data evaluation difficult or erroneous.
Keywords:
noise analysis; liquid/liquid interface; ion transfer kinetics
Available at various institutes of the ASCR
Noise Analysis of Ion Transfer Kinetics at the Micro Liquid/Liquid Interface
Fluctuation analysis was utilized to determine the TEA ion transfer kinetics across the water/1,2-dichloroethane interface. The average value ks = 0.34 cm s-1 is comparable with the previously ...
Influence of Electrode Preparation on Electrocatalytic Activity of Tetrapyridinoporphyrazinato Cobalt(II) Complex to Propylene
Klusáčková, Monika; Janda, Pavel; Tarábková, Hana
2015 - English
The water-soluble complex N ,N' ,N' ',N' "-Tetramethyl-tetra-3,4-pyridinoporphyrazinocobalt (CoTmt-3,4-ppa) has been deposited by different techniques on two substrate. Electrochemical deposition, spontaneous adsorption, and spin coating have been used to the modification of two electrode material: annealed gold as hydrophilic substrate and highly oriented pyrolytic graphite as hydrophobic substrate. The modified electrodes have been characterized using cyclic voltammetry, backscattering VIS spectroscopy and atomic force microscopy. The influence of substrate material and modification techniques on electrocatalytic activity of CoTmt-3,4-ppa modified electrodes for propylene oxidation has been studied.
Keywords:
water-soluble phthalcyanine; electrocatalysis; propylene
Available at various institutes of the ASCR
Influence of Electrode Preparation on Electrocatalytic Activity of Tetrapyridinoporphyrazinato Cobalt(II) Complex to Propylene
The water-soluble complex N ,N' ,N' ',N' "-Tetramethyl-tetra-3,4-pyridinoporphyrazinocobalt (CoTmt-3,4-ppa) has been deposited by different techniques on two substrate. Electrochemical deposition, ...
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