National Repository of Grey Literature 155 records found  beginprevious125 - 134nextend  jump to record: Search took 0.01 seconds. 
Electrochemical study of degradation of natural dyes used in artworks
Sokolová, Romana ; Degano, I. ; Hromadová, Magdaléna
This work is focused on the electrochemical study of natural flavonoid dyes used in artworks. Electrochemical behaviour of hematoxylin was studied in 0.1 M KCl, phosphate buffers of pH 5 – 12 and in acetonitrile. The mechanism of oxidation and the stability of intermediates as a function of pH are discussed. The electrochemical techniques are combined with spectrophotometry, LC/DAD and GC-MS analysis in order to identify the degradation products.
Electrochemical nitrogen fixation in the presence of fullerene -.gamma.-cyclodextrin complex
Kocábová, Jana ; Gál, Miroslav ; Hromadová, Magdaléna ; Pospíšil, Lubomír
We report on the electrochemical conversion of dinitrogen to ammonia at ambient pressure and 60oC mediated by reduced fullerene (C60) inside a molecular cavity of .gamma.-cyclodextrin (.gamma.-CD) in aqueous solution.
Electrochemical investigation of intramolecular electronic interactions in substituted nitrobenzens
Liška, A. ; Ludvík, Jiří
This research represents the first part of the electrochemical study of nitrocalixarenes. The title compounds represent thus the "monomeric" fragments and their models. The electrochemical reduction of aromatic nitrocompounds in non-aqueous media proceeds generally in two steps: one-electron reversible formation of radical anion and three-electron reduction to the hydroxylamine. In this work, however, four other different mechanisms of electroreduction of aromatic nitrocompounds are presented and the influence od p-substituents on the reduction pattern are discussed.
Six-membered nitrogen heterocycles - aromaticity and electron delocalization
Ludvík, Jiří ; Fábry, Jan
All six membered nitrogen heterocycles are generally considered as delocalized systems with high extent of aromaticity. However, in our investigations we observed that the heterocycles bearing the azine grouping C=N-N=C (1,2,4-triazines and pyridazines) exhibit lower aromaticity, the N-N bond has a rather single-bond character and partly blocks the delocalization.
Participation of electrochemistry in the studies of human metabolism
Navrátil, Tomáš ; Šenholdová, Z. ; Přistoupilová, K. ; Přistoupil, T. I. ; Heyrovský, Michael ; Pelclová, D. ; Žák, J.
The contribution deals with explanation of metabolism of long term supplemented creatine in human organism. This process differs from metabolism of natural endogenous creatine, which is excreted in form of creatinine. Exogenous creatine induces increase of peptide formation, of body mass, and of intracellular fluid.
Determination of herbicide dinoseb with amalgam and carbon electrodes
Fischer, J. ; Barek, J. ; Pecková, K. ; Zima, J. ; Kücükkolbasi, S. ; Ersöz, M. ; Kara, H. ; Josypčuk, Bohdan ; Navrátil, Tomáš
Dinoseb, systematically 2-(1-methylpropyl)-4,6-dinitro-phenol, is phenolic, commonly used herbicide and insecticide. Dinoseb has two very easy reducible nitro-groups in its structure and one electrochemically oxidizable hydroxy group. Differential pulse voltammetry was applied for its determination in water. The nitro group reduction was used for voltammetric determination with hanging mercury electrode (HMDE), mercury film electrode (MFE) and modified carbon paste electrode (MCPE) and carbon paste electrode (CPE) as well as meniscus modified silver solid amalgam electrode (m-AgSAE).
Speciation of lead in soil solution using anodic stripping voltammetry and diffusive gradient in thin film technique
Dytrtová, J. ; Šestáková, Ivana ; Jakl, M. ; Tlustoš, P.
Soil solution was obtained from pot experiments, where plant Thlaspi caerulescens Presl was grown on two different types of soil. Values for free lead ions in soil solution, determined with anodic stripping voltammetry are much smaller then values of "plant available lead", obtained from DGT technique.
Anodic stripping voltammetry application for the detection of copper in the presence of oxalic acid
Fenclová, K. ; Dytrtová, J. ; Jakl, M. ; Šestáková, Ivana ; Opekar, F.
Model solutions, prepared from cupric ions and different oxalic acid concentrations were studied with anodic stripping voltammetry. Signals of three different copper complexes were recognized.
Working amalgam paste electrodes
Josypčuk, Bohdan
Working amalgam paste electrodes.
The role of current magnitude in stripping chronopotentiommetry
Šestáková, Ivana
As a function of stripping current magnitude, regime of semi-infinite linear diffusion or complete depletion are characterized. Examples of different behaviour of system of metallothionein and cadmium ions in the dependence on value of stripping current are shown.

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