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Voltammetric measurement of H.sub.2./sub.O.sub.2./sub. concentration in aqua-organic solutions
Kurc, L. ; Floriš, T. ; Josypčuk, Bohdan
In this work was tested the applicability of voltammetry and of meniscus silver solid amalgam electrode for determination H2O2 in presence of organic species (solvent, substrate or product of Baeyer-Villiger oxidation of cycloketones to lactones). Hydrogen peroxide can be measured in its wide concentration interval in different aqua-organic solutions. The slope of H.sub.2./sub.O.sub.2./sub. concentration dependence decreases with increasing 1,4-dioxane concentration. 1,4-dioxane in mixture with water can be used up to its concentration 80 vol. %. Model species, which represent reactants and products of Baeyer-Villiger oxidation, influence calibration dependence individually and their effect is not possible to estimate. Hence, quantitative hydrogen peroxide determination in probes of reactive mixture, which have different composition, should be carried out by standard addition method.
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The Application of Silver Amalgam Electrode in Voltammetric Determination of Cd, Pb and Cu in Reference Materials of Plant Origin
Čížková, P. ; Šestáková, Ivana ; Josypčuk, Bohdan
Silver solid amalgam electrode, combined with PC-controlled regeneration of its surface, was successful in voltammetric analysis of Cd, Pb and Cu in certified reference materials BCR (Rye Gras) , 679 White Cabbage and other two candidate materials. Results were compared and statistically evaluated with those obtained by voltammetry on HMDE and ETA-AAS determination. Silver solid amalgam electrode, combined with PC-controlled regeneration of its surface, was successful in voltammetric analysis of Cd, Pb and Cu in certified reference materials BCR (Rye Gras) , 679 White Cabbage and other two candidate materials. Results were compared and statistically evaluated with those obtained by voltammetry on HMDE and ETA-AAS determination.
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Změny koncentrace TDGA v moči jako možný marker metabolismu thiosloučenin
Přistoupilová, K. ; Přistoupil, T. I. ; Šenholdová, Z. ; Navrátil, Tomáš ; Heyrovský, Michael ; Fenclová, Z.
The new simple voltammetric method we described recently, proved already to be useful in determining thiodiglycolic acid (TDGA) levels in urine samples of people influenced by some chemicals, victuals and pharmaceuticals. The present pilot study is a continuation of our previous work devoted to test general feasibility of the method. We concentrated upon time dependent quantitative changes of TDGA excretion into urine of selected volunteers. The TDGA level in all morning samples was the highest in comparison with samples collected during the day. The TDGA level was dependent on the health condition of each person involved. However, a further marked increase of TDGA in the morning urine was observed individually, in general when vitamin B12 had been administered in the evening the day before. Vitamin B12 is known to play an important role in the metabolism of one- and two-carbon units, of homocysteine and of sulfhydryls in general. Certain differences in excretion course of TDGA.
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Ink Films from Carbon Powders on Conventional Solid Electrodes as Alternative Disposable Sensors
Josypčuk, Bohdan ; Barek, J. ; Novotný, Ladislav
Rozšíření rozsahu pracovních potenciálů pevných elektrod bylo docíleno jejich pokrytím filmem z polymeru obsahujícího vodivé částice (grafitu, skelného uhlíku, nanotub aj.). Takový film může obsahovat 70 - 90% skelného uhlíku a 30 - 10% polystyrenu (procenta hmotnostní). Film se 70 % skelného uhlíku se chová více jako soubor mikroelektrod; s 90 % - spíše jako klasická elektroda ze skelného uhlíku. S takovým filmem lze pracovat i celý den; pro odstranění filmu stačí otřít ho o filtrační papír. Pro oxidaci ferocenu, adeninu, guaninu a jiných látek byly použity filmy s různým obsahem skelného uhlíku na podložkách ze stříbrného pevného amalgamu, zlata a platiny.
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Voltammetric Behavior of the Heterogeneous Graphite Composite
Šebková, Světlana
Graphite composite electrodes offer high chemical inertness, which is accompanied by a wide range of working potentials (the widest range of potentials was obtained using CE30 in borax buffer - almost 4 000 mV). Graphite composite electrodes find the field of application mostly in the work in the area of considerably positive potentials (e.g. oxidation of adenine, guanine, aminonaphtalene, etc.), and they offer unique possibilities analytical measurements.
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Phytochelatins as Cadmium and Zinc Ligands in Study Using Voltammetric Methods
Šestáková, Ivana ; Navrátil, Tomáš
Complexation of synthetically prepared phytochelatin PC3 was studied using differential pulse voltammetry on HMDE. This method allows to measure reduction peak of mercury compound of original peptide simultaneously with the reduction peaks of formed cadmium or zinc complexes. Elimination voltammetry with linear scan was used at selected stoichiometric ratio to characterise diffusion current of complexes formed. Substantial differences were found between Cd and Zn complexes, both in formation and behaviour.
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