Paste electrode with paste amalgam as an active electrode material is described here for the firs... more Paste electrode with paste amalgam as an active electrode material is described here for the first time. Designed electrode from silver paste amalgam (AgA‐PE) is solely metallic and does not contain any organic binder. Mechanical surface regeneration of AgA‐PE is performed in the same way as for classical carbon paste electrodes and reproducibility of such regeneration is about 10%. Electrochemical surface regeneration appeared very efficient for most measurements. In dependence on paste metal content, the electrode surface can be liquid (resembling a film) or rather solid. The hydrogen overvoltage on AgA‐PE is high, and the electrode allows measurements at highly negative potentials. AgA‐PE is well suited for study of reduction or oxidation processes without an accumulation step. Anodic stripping voltammetry of some metals tested on the electrode is influenced by formation of intermetallic compounds. The measurement based on cathodic stripping voltammetry (adenine, cysteine) and on catalytic processes from adsorbed state (complex of osmium tetroxide with 2,2′‐bipyridine) can be performed on AgA‐PE practically under the same conditions as found earlier for HMDE and for silver solid amalgam electrode. The working electrode from paste amalgam combines the advantages of paste and metal electrodes.
Rabbit liver Cd-metallothionein (CdMT) and Cd-complex of synthetically prepared pentapeptide (gam... more Rabbit liver Cd-metallothionein (CdMT) and Cd-complex of synthetically prepared pentapeptide (gamma-Glu-Cys)2-Gly were studied as examples of animal and plant metallothioneins. Using hanging mercury electrode, cathodic stripping voltammetry after adsorptive accumulation of the Cd(II)-SR complex at different potentials, is suitable for estimating changes occurring in metal coordination due to the presence of metal ions such as Zn2+, Cu2+, Hg2+ or excessive Cd2+. Conditions under which similar behaviour can be observed for both CdMT and Cd-pentapeptide complex are specified. On carbon electrodes, detailed study of reduction processes of Cd(II)-SR complexes is prevented by occurrence of a large catalytic current; oxidation processes are more suitable for study at these electrodes. Carbon composite paste electrode (10% SiO2) allows deposition of Cd(II)-SR complex during its reduction, as was demonstrated with Cd-cysteine, CdMT or Cd-pentapeptide complex. After deposition, oxidation peak of the uncomplexed Cd2+ ions and one or two oxidation peaks corresponding to a formation of the RS-Cd(II) complex are observed. Also, similarly as on Hg electrode, it was observed that excessive Cd2+ or Zn2+ ions influence oxidation peaks of the RS-Cd(II) complex formation. Combination of measurements on mercury electrode and composite paste electrode is recommended for studies of metallothionein interactions with metal ions or other metal complexes.
The study is focused on the silver solid amalgam electrode modified by mercury meniscus (m‐AgSAE)... more The study is focused on the silver solid amalgam electrode modified by mercury meniscus (m‐AgSAE). After its successful application for determination of heavy metals by differential pulse anodic stripping voltammetry (DPASV) in aqueous solutions, its use in more complicated matrices has followed. Four different reference materials of plant origin were used – White Cabbage, Rye Grass, Aubergine and Lucerne, and the obtained results of Cd, Cu and Pb contents were compared both with (certified) reference values and with results obtained by DPASV with HMDE and by AAS. Statistical evaluation confirmed good correlation between results of all three methods used and as well as with reference values.
Bioelectrochemistry and Bioenergetics, Aug 1, 1996
Compact triphenylphosphine oxide or tripiperidinophosphine oxide films formed at Hg surfaces are ... more Compact triphenylphosphine oxide or tripiperidinophosphine oxide films formed at Hg surfaces are shown to increase Cd, Zn-metal-lothionenin (MT) adsorptivity at the polarized electrode/solution interface. Interactions of the polar P= O group of these adsorbates with the hydrophilic centers located on the metalloprotein exterior are suggested as being responsible for this phenomenon. The resulting cathodic current (ic) due to the reduction of coordinated Cd (II) in Cd, Zn-MT increases more than seven times in the presence of 1.0× ...
The triphenylmethyl cation in aqueous sulphuric acid is reduced at the dropping mercury electrode... more The triphenylmethyl cation in aqueous sulphuric acid is reduced at the dropping mercury electrode to triphenylmethane in a reversible two-electron step, if the protonation of the radical formed by the first one-electron uptake is sufficiently fast. ([H2SO4] > ca. 23N). When it is not ([H2SO4] < ca. 20N), the radical can be reduced further to triphenylmethane in a second one-electron step at more negative potentials. The triphenylmethane, formed by either route, can be reoxidised to the original cation. Dimerization of radicals competes with their protonation or reduction. Interpretation of the polarograms is complicated by maxima. Reversibility of the reductions was proved by the commutator method.
The polarographic reduction of the following organic cations in aqueous sulphuric and in pure and... more The polarographic reduction of the following organic cations in aqueous sulphuric and in pure and aqueous methanesulphonic acids has been studied: triphenylmethyl, tri-p-tolymethyl, diphenylmethyl, 1,1-diphenylethyl, 1,1-diphenyl-n-butyl, 3-methyl-1-phenylindanyl.For most of the observed reduction waves the number of electrons and the reversibility (or lack thereof) could be established. The reaction scheme which accounted for our observations on the triphenyl carbonium ion in sulphuric acid was found adequate to explain the present results, except that for the tri-p-tolyl carbonium ion in aqueous acids an additional reaction, reduction of the hydrated ion, is also involved.
Adsorptive stripping voltammetry was combined with separation of the surfactants by gel chromatog... more Adsorptive stripping voltammetry was combined with separation of the surfactants by gel chromatography or solvent extraction for determination of the growth promotor, cyadox, and its metabolites in the plasma from pig blood. The procedure permits determination of the substance at concentrations from units to hundreds of ng per ml of plasma. The accuracy of the results was checked by comparison with radiochemical measurements.
Paste electrode with paste amalgam as an active electrode material is described here for the firs... more Paste electrode with paste amalgam as an active electrode material is described here for the first time. Designed electrode from silver paste amalgam (AgA‐PE) is solely metallic and does not contain any organic binder. Mechanical surface regeneration of AgA‐PE is performed in the same way as for classical carbon paste electrodes and reproducibility of such regeneration is about 10%. Electrochemical surface regeneration appeared very efficient for most measurements. In dependence on paste metal content, the electrode surface can be liquid (resembling a film) or rather solid. The hydrogen overvoltage on AgA‐PE is high, and the electrode allows measurements at highly negative potentials. AgA‐PE is well suited for study of reduction or oxidation processes without an accumulation step. Anodic stripping voltammetry of some metals tested on the electrode is influenced by formation of intermetallic compounds. The measurement based on cathodic stripping voltammetry (adenine, cysteine) and on catalytic processes from adsorbed state (complex of osmium tetroxide with 2,2′‐bipyridine) can be performed on AgA‐PE practically under the same conditions as found earlier for HMDE and for silver solid amalgam electrode. The working electrode from paste amalgam combines the advantages of paste and metal electrodes.
Rabbit liver Cd-metallothionein (CdMT) and Cd-complex of synthetically prepared pentapeptide (gam... more Rabbit liver Cd-metallothionein (CdMT) and Cd-complex of synthetically prepared pentapeptide (gamma-Glu-Cys)2-Gly were studied as examples of animal and plant metallothioneins. Using hanging mercury electrode, cathodic stripping voltammetry after adsorptive accumulation of the Cd(II)-SR complex at different potentials, is suitable for estimating changes occurring in metal coordination due to the presence of metal ions such as Zn2+, Cu2+, Hg2+ or excessive Cd2+. Conditions under which similar behaviour can be observed for both CdMT and Cd-pentapeptide complex are specified. On carbon electrodes, detailed study of reduction processes of Cd(II)-SR complexes is prevented by occurrence of a large catalytic current; oxidation processes are more suitable for study at these electrodes. Carbon composite paste electrode (10% SiO2) allows deposition of Cd(II)-SR complex during its reduction, as was demonstrated with Cd-cysteine, CdMT or Cd-pentapeptide complex. After deposition, oxidation peak of the uncomplexed Cd2+ ions and one or two oxidation peaks corresponding to a formation of the RS-Cd(II) complex are observed. Also, similarly as on Hg electrode, it was observed that excessive Cd2+ or Zn2+ ions influence oxidation peaks of the RS-Cd(II) complex formation. Combination of measurements on mercury electrode and composite paste electrode is recommended for studies of metallothionein interactions with metal ions or other metal complexes.
The study is focused on the silver solid amalgam electrode modified by mercury meniscus (m‐AgSAE)... more The study is focused on the silver solid amalgam electrode modified by mercury meniscus (m‐AgSAE). After its successful application for determination of heavy metals by differential pulse anodic stripping voltammetry (DPASV) in aqueous solutions, its use in more complicated matrices has followed. Four different reference materials of plant origin were used – White Cabbage, Rye Grass, Aubergine and Lucerne, and the obtained results of Cd, Cu and Pb contents were compared both with (certified) reference values and with results obtained by DPASV with HMDE and by AAS. Statistical evaluation confirmed good correlation between results of all three methods used and as well as with reference values.
Bioelectrochemistry and Bioenergetics, Aug 1, 1996
Compact triphenylphosphine oxide or tripiperidinophosphine oxide films formed at Hg surfaces are ... more Compact triphenylphosphine oxide or tripiperidinophosphine oxide films formed at Hg surfaces are shown to increase Cd, Zn-metal-lothionenin (MT) adsorptivity at the polarized electrode/solution interface. Interactions of the polar P= O group of these adsorbates with the hydrophilic centers located on the metalloprotein exterior are suggested as being responsible for this phenomenon. The resulting cathodic current (ic) due to the reduction of coordinated Cd (II) in Cd, Zn-MT increases more than seven times in the presence of 1.0× ...
The triphenylmethyl cation in aqueous sulphuric acid is reduced at the dropping mercury electrode... more The triphenylmethyl cation in aqueous sulphuric acid is reduced at the dropping mercury electrode to triphenylmethane in a reversible two-electron step, if the protonation of the radical formed by the first one-electron uptake is sufficiently fast. ([H2SO4] > ca. 23N). When it is not ([H2SO4] < ca. 20N), the radical can be reduced further to triphenylmethane in a second one-electron step at more negative potentials. The triphenylmethane, formed by either route, can be reoxidised to the original cation. Dimerization of radicals competes with their protonation or reduction. Interpretation of the polarograms is complicated by maxima. Reversibility of the reductions was proved by the commutator method.
The polarographic reduction of the following organic cations in aqueous sulphuric and in pure and... more The polarographic reduction of the following organic cations in aqueous sulphuric and in pure and aqueous methanesulphonic acids has been studied: triphenylmethyl, tri-p-tolymethyl, diphenylmethyl, 1,1-diphenylethyl, 1,1-diphenyl-n-butyl, 3-methyl-1-phenylindanyl.For most of the observed reduction waves the number of electrons and the reversibility (or lack thereof) could be established. The reaction scheme which accounted for our observations on the triphenyl carbonium ion in sulphuric acid was found adequate to explain the present results, except that for the tri-p-tolyl carbonium ion in aqueous acids an additional reaction, reduction of the hydrated ion, is also involved.
Adsorptive stripping voltammetry was combined with separation of the surfactants by gel chromatog... more Adsorptive stripping voltammetry was combined with separation of the surfactants by gel chromatography or solvent extraction for determination of the growth promotor, cyadox, and its metabolites in the plasma from pig blood. The procedure permits determination of the substance at concentrations from units to hundreds of ng per ml of plasma. The accuracy of the results was checked by comparison with radiochemical measurements.
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