National Repository of Grey Literature 18 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Silver amalgam electrodes in electroanalysis of selected agrochemicals
Daňhel, Aleš
Development and testing of novel non-toxic electrode materials, detection arrangements and analytical methods applicable in determination of selected agrochemicals is the main aim of this Ph.D. Thesis. New working electrodes based on silver solid amalgam paste (AgSA-PE) with organic pasting liquid and other based on crystallic silver amalgam (CAgAE) were developed, their electrochemical behaviour investigated and further used in voltammetric determination of widespread and toxic environmental pollutant 4-nitrophenol (4-NP). This analyte could be determined by DPV at AgSA-PE with limit of detection (LD) 1×10−6 mol l−1 and using CAgAE with LD 4×10−7 mol l−1 , both in 0.2 mol l−1 acetate buffer pH 4.8. Attempts to decrease LDs by utilization of adsorptive stripping voltammetry were not successful in either case. Crystallic silver amalgam was also successfully used for construction of microcylindric flow-through cell and tested for amperometric determination of nitrophenol mixture in HPLC-ED system. Both novel electrodes were found to be suitable alternatives to toxic mercury electrodes and the CAgAE seems to be promising working electrode for flowing systems. Method for sample preparation and voltammetric determination of broad-spectrum herbicide Glyphosate in contaminated soil samples was also...
Utilization of Catalytic Hydrogen Evolution in Electrochemical Analysis of Nucleic Acids
Fojta, Miroslav ; Daňhel, Aleš ; Špaček, Jan ; Havran, Luděk ; Šebest, Peter ; Orság, Petr ; Pivoňková, Hana ; Vosáhlová, J. ; Schwarzová-Pecková, K.
Catalysis of hydrogen evolution (CHE) at mercury in the presence of proteins was discoverd shortly after the introduction of polarography. In contrast, unmodified nucleic acids have not been reported to produce distinct signals due to the CHE to date. Chemically modified nucleic acids bearing certain extrinsic groups produce analytically useful signals due to hydrogen evloution catalyzed by the respective modifications. These species include (a) transition metal complexes, and (b) non-metal catalytically active organic moieties. In addition, the CHE has been reported to be invoved in guanine reduction process at the mercury-based electrodes.
Electrochemical Reduction and Oxidation of Nucleic Acids Bases and their Analogues: a Brief Overview
Fojta, Miroslav ; Špaček, Jan ; Dudová, Zdenka ; Pivoňková, Hana ; Daňhel, Aleš ; Fojt, Lukáš ; Havran, Luděk
Nucleic acids are known as electroactive biomacromolecules containing electrochemically reducible or oxidizable constituents. Nucleobases cytosine, 5-methylcytosine, adenine and guanine can be reduced in aqueous media on mercury or silver amalgam electrodes. Oxidation of all natural nucleic acids bases (in addition to the above mentioned ones, also uracil and thymine) was demonstrated using various types of carbon electrodes. Some of synthetic nucleobases or nucleotide analogues (e g., 7-deazapurines, cytidine analogues used as epigenetic modulators, etc.) exhibit specific electrochemical properties that differ from those of the parent bases and can be utilized to determine the given substance in the presence of natural nucleic acids or their components.
Electrodeposited Coatings at ITO/FTO Enhancing their Applicability in Electroanalysis
Daňhel, Aleš ; Fojta, Miroslav
Recent possibilities of modification of transparent electrodes based on indium-tin oxide and/or fluorine doped tin oxide by electrodeposited coatings enhancing their electrochemical applicability in electroanalysis are discussed in this work. Ordered mesoporous silica and/or chemically functionalized mesoporous silica thin films may serve, among the common utilization in solid phase extraction, as protective layer of the electrode surface against its fouling and/or as molecular sieve permeable for small molecules and blocking large ones (DNA, proteins, etc.). Furthermore an electrodeposition of organic modifiers and/or metal (nano) particles inside of the ordered silica nanochanels together with direct electrodeposition of selected metal (nano) particles onto selected conductive transparent supports are presented here as well.
Amalgam Electrodes Pretreatment and Electrochemical Analysis of DNA
Daňhel, Aleš ; Fojta, Miroslav
Mercury meniscus silver solid amalgam electode (m-AgSAE) represents the most suitable and perspective alternative to mercury electrodes which excel in sensitivity to biopolymers and their structural changes. This work briefly summarizes factors influencing electrochemical analysis of DNA at mercury and amalgam electrodes and it is mainly devoted to development of suitable pretreatment procedure, which could securte repeatable and reliable measurements of DNA at m-AgSAes. The results are essential for further utilization of amalgam electrodes in developement of biosensors, since DNA samples are very strongly adsorbed at the electrodes, and none pretreatment procedure was found to be successful in their complete desorption.
Limitations and Possibilities of Nanostructurized Silver Amalgam
Daňhel, Aleš ; Šebest, Peter ; Vidláková, Pavlína ; Ligmajer, Filip
Variability of silver amalgam offers a row of opportunities for its application in electrochemical and spectroelectrochemical methods, thanks to its chemical, mechanical, electrochemical and spectrometric properties. This work briefly revews preparation possibilities and limitations of nanostructurized crystalas and nanopartices pf silver amalgam at different forms of carbon metals (Ag, Au, Pt) and transparent materials (ITO, FTO). These detection sysytems are in the scope of ongoing systematics research with the potential to indevelopment of novel working (micro)electrodes and spectroelectrochemical cells, potentially utilizable in modern (bio)analytical applictions.
Reduction of the DNA at a Pyrolytic Graphite Electrode:Opening of the Second Half of the Potential Window
Špaček, Jan ; Daňhel, Aleš ; Hasoň, Stanislav ; Hejduková, M. ; Fojta, Miroslav
The pyrolytic graphite electrode (PGE) can be used at highly negative potentials, providing reduction signals known from mercury-based electrodes. Use of the negative part of the potential window more than doubled the number of analytically useful signals provided by unlabelled DNA on PGE. It enables selective analysis of all canonical DNA bases,5-methylcytosine and uracil It also allows for distinction of overlapping signals cathodic polarization can selectively ´switch off´ DNA anodic signals and rice versa. Newly observed signals corresponding to oxidation of reduced bases and reduction of oxidized bases are also described.
Electrochemical Deposition of Silver Amalgam Particles on Pyrolitic Graphite Electrode
Šebest, Peter ; Havranová-Vidláková, Pavlína ; Ligmajer, Filip ; Fojta, Miroslav ; Daňhel, Aleš
Silver solid amalgam represents suitable alternative electrode material to metallic mercury, Controlled electrodeposition of variable silver amalgam particles (AgAP) on the surface of pyrolitic graphite electrode from an electrolyte containing Agt It and Hg(II) ions is reported as a novel method suitable lot preparation of perspective supporting materials Scanning electron microscopy including energy-disperse X-ray spectrometer and image processing software were used for analysis of composition and morphology of AgAP on POE A model electrochemically reducible 4-niirophenol was used to test a potential applicability of AgAp-PGE in electroanalytical methods.
Preparation and Characterization of Silver Amalgam Particles on Gold Electrode Surface
Havranová-Vidláková, Pavlína ; Šebest, Peter ; Ligmajer, Filip ; Fojta, Miroslav ; Daňhel, Aleš
This work is focused on the preparation of silver amalgam particles by its direct electrodeposition on gold surfaces using double pulse chronoamperometry from solution containing soluble Ag+ and Hg2+ ionts. During the electrodepositions of silver amalgam particles, different: i) parameters of chronoamperometry, ii) Ag/Hg ratio in solution and iii) gold electrodes were studied. All the prepared amalgam particles were characterized by scanning electron microscope with energy dispersive X-ray spectroscopy and electrochemical methods. Voltammetric application of the gold electrodes decorated by sliver amalgam particles was confirmed by analysis of model organic nitrocompound using cyclic voltammetry.

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