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Study of redox and adsorption features of bile acids on hanging mercury drop electrode
Yershova, Polina ; Schwarzová, Karolina (advisor) ; Gajdár, Július (referee)
Bile acids are the end products of cholesterol metabolism and are important biological surfactants. The curved shape of their chains allows the cyclization of molecules, and the formation of a supramolecular structure. The goal of this thesis was to study the electrochemical and adsorption behavior of selected bile acids: lithocholic, deoxycholic and cholic acids. The measurements were carried out in the medium Brittonův-Robinson buffer:methanol in the ratio 9:1 using cyclic voltammetry and AC voltammetry methods and measuring the dependence of the differential capacitance Cd on the applied potential E. A hanging mercury drop electrode was used as a working electrode. The measurements showed that bile acids are adsorbed on the surface of the electrode and organizing themselves in self assembled monolayers (SAM). In our case we have observed formation of 2D condensed layers as specific form of SAM. Transfer techniques were used to demonstrate bile acid adsorption. A study of the behavior of lithocholic acid as a function of different pH values showed that only at pH 10.0 to 12.0 2D 2D condensation occurs, i. e. that at pH values in the range of 2.0 to 9.0 it is another type of adsorption. On AC voltammograms, there are a maximum of two areas in which peaks occur: the first is around -0.2 V and the...
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Development of electrochemical methods for study of antibacterial compounds in small volumes
Gajdár, Július ; Barek, Jiří (advisor) ; Šiškanova, Tatiana (referee) ; Labuda, Ján (referee)
Main goal of this Ph.D. thesis is to develop voltammetric methods for the electrochemical study of novel antimycobacterial compounds hydroxynaphthalene- carboxamides. Firstly, this study was focused on the miniaturization of voltammetric methods and construction of an electrochemical microcell due to usually small volume of samples that are associated with an analysis of biologically active compounds in biological matrices. Therefore, all aspects of the voltammetric procedure were studied in a relation to miniaturization. Microcells were based on commercially available electrodes: glassy carbon electrode as a reliable electrode material with well-described characteristics and a novel silver solid amalgam electrode. This study was carried out with analytes 4-nitrophenol, pesticide difenzoquat, and 1-hydroxy-N-(4-nitrophenyl)naphthalene-2-carboxamide. Attention was paid especially to the optimization of oxygen removal procedures in the drop of a solution. Developed miniaturized methods had the same parameters for the determination of studied compounds as in bigger volumes. The proposed electrochemical microcell can be generally used for voltammetric analysis of those samples of biological or environmental origin that are usually available in very limited volumes. Second part of the thesis was focused...
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Development of electrochemical methods for study of antibacterial compounds in small volumes
Gajdár, Július
Main goal of this Ph.D. thesis is to develop voltammetric methods for the electrochemical study of novel antimycobacterial compounds hydroxynaphthalene- carboxamides. Firstly, this study was focused on the miniaturization of voltammetric methods and construction of an electrochemical microcell due to usually small volume of samples that are associated with an analysis of biologically active compounds in biological matrices. Therefore, all aspects of the voltammetric procedure were studied in a relation to miniaturization. Microcells were based on commercially available electrodes: glassy carbon electrode as a reliable electrode material with well-described characteristics and a novel silver solid amalgam electrode. This study was carried out with analytes 4-nitrophenol, pesticide difenzoquat, and 1-hydroxy-N-(4-nitrophenyl)naphthalene-2-carboxamide. Attention was paid especially to the optimization of oxygen removal procedures in the drop of a solution. Developed miniaturized methods had the same parameters for the determination of studied compounds as in bigger volumes. The proposed electrochemical microcell can be generally used for voltammetric analysis of those samples of biological or environmental origin that are usually available in very limited volumes. Second part of the thesis was focused...
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Study of redox and adsorption features of bile acids on hanging mercury drop electrode
Yershova, Polina ; Schwarzová, Karolina (advisor) ; Gajdár, Július (referee)
Bile acids are the end products of cholesterol metabolism and are important biological surfactants. The curved shape of their chains allows the cyclization of molecules, and the formation of a supramolecular structure. The goal of this thesis was to study the electrochemical and adsorption behavior of selected bile acids: lithocholic, deoxycholic and cholic acids. The measurements were carried out in the medium Brittonův-Robinson buffer:methanol in the ratio 9:1 using cyclic voltammetry and AC voltammetry methods and measuring the dependence of the differential capacitance Cd on the applied potential E. A hanging mercury drop electrode was used as a working electrode. The measurements showed that bile acids are adsorbed on the surface of the electrode and organizing themselves in self assembled monolayers (SAM). In our case we have observed formation of 2D condensed layers as specific form of SAM. Transfer techniques were used to demonstrate bile acid adsorption. A study of the behavior of lithocholic acid as a function of different pH values showed that only at pH 10.0 to 12.0 2D 2D condensation occurs, i. e. that at pH values in the range of 2.0 to 9.0 it is another type of adsorption. On AC voltammograms, there are a maximum of two areas in which peaks occur: the first is around -0.2 V and the...
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Development of electrochemical methods for study of antibacterial compounds in small volumes
Gajdár, Július
Main goal of this Ph.D. thesis is to develop voltammetric methods for the electrochemical study of novel antimycobacterial compounds hydroxynaphthalene- carboxamides. Firstly, this study was focused on the miniaturization of voltammetric methods and construction of an electrochemical microcell due to usually small volume of samples that are associated with an analysis of biologically active compounds in biological matrices. Therefore, all aspects of the voltammetric procedure were studied in a relation to miniaturization. Microcells were based on commercially available electrodes: glassy carbon electrode as a reliable electrode material with well-described characteristics and a novel silver solid amalgam electrode. This study was carried out with analytes 4-nitrophenol, pesticide difenzoquat, and 1-hydroxy-N-(4-nitrophenyl)naphthalene-2-carboxamide. Attention was paid especially to the optimization of oxygen removal procedures in the drop of a solution. Developed miniaturized methods had the same parameters for the determination of studied compounds as in bigger volumes. The proposed electrochemical microcell can be generally used for voltammetric analysis of those samples of biological or environmental origin that are usually available in very limited volumes. Second part of the thesis was focused...
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Development of electrochemical methods for study of antibacterial compounds in small volumes
Gajdár, Július ; Barek, Jiří (advisor) ; Šiškanova, Tatiana (referee) ; Labuda, Ján (referee)
Main goal of this Ph.D. thesis is to develop voltammetric methods for the electrochemical study of novel antimycobacterial compounds hydroxynaphthalene- carboxamides. Firstly, this study was focused on the miniaturization of voltammetric methods and construction of an electrochemical microcell due to usually small volume of samples that are associated with an analysis of biologically active compounds in biological matrices. Therefore, all aspects of the voltammetric procedure were studied in a relation to miniaturization. Microcells were based on commercially available electrodes: glassy carbon electrode as a reliable electrode material with well-described characteristics and a novel silver solid amalgam electrode. This study was carried out with analytes 4-nitrophenol, pesticide difenzoquat, and 1-hydroxy-N-(4-nitrophenyl)naphthalene-2-carboxamide. Attention was paid especially to the optimization of oxygen removal procedures in the drop of a solution. Developed miniaturized methods had the same parameters for the determination of studied compounds as in bigger volumes. The proposed electrochemical microcell can be generally used for voltammetric analysis of those samples of biological or environmental origin that are usually available in very limited volumes. Second part of the thesis was focused...
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Application of Antimony Film Electrodes for Determination of Pesticide Trifluralin
Gajdár, Július ; Fischer, Jan (advisor) ; Vyskočil, Vlastimil (referee)
Antimony film electrode was studied for the use in a voltammetric analysis of organic compounds. The substance chosen as an analyte was trifluralin, which is used as a pesticide. The comparison of different substrate electrodes was carried out between five electrodes, which were gold, silver, copper, polished amalgam and glassy carbon electrode (GCE). Best performance was observed on antimony film glassy carbon electrode (SbFGCE). It provided higher sensitivity and lower limit of quantification in comparison with bare GCE. The antimony film was stable and it provided good reproducibility (RSD = 5.2 %). Parameters of an electrochemical preparation of SbFGCE were optimized. Conditions for determination of concentration of trifluralin were optimized on newly prepared SbFGCE. The best conditions were in a solution of methanol and 0.1 M hydrochloric acid in 1:1 ratio measured by differential pulse voltammetry. The limit of quantification was determined as 1.2·10-6 mol·l-1 . A direct voltammetric measurement on SbFGCE was carried out in a model river sample. Lower limits of quantification were achieved with solid phase extraction (SPE). Recovery values were 86 ± 8 % in deionized water with a preconcentration factor of 125. The limit of quantification was lowered to value 1.1·10-8 mol·l-1 . The extraction...
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Voltammetric determination of pesticides using meniscus modified silver solid amalgam electrode
Gajdár, Július ; Fischer, Jan (advisor) ; Dejmková, Hana (referee)
The aim of this bachelor thesis is to find the optimal conditions for voltammetric determination of pesticides cypermethrin, deltamethrin and difenzoquat on meniscus modified silver solid amalgam electrode using differential pulse voltammetry. Conditions under which cypermethrin and deltamethrin could be determinated were found in previously published works. These conditions were reproduced. Substances were studied in methanol and dimethylformamide solutions. The optimal conditions for determination of these two substances were not found. Voltammetric behaviour of difenzoquat was studied in different pH using Britton-Robinson buffer. The optimal pH 11 was chosen. The reproducibility of measurement was studied at concentration 1·10-4 mol·l-1 , peak was stable (RSD = 3%). Sharp maxima were found at high concentrations of analyte, addition of gelatine led to one well- defined peak. Peak potencial was - 1,4 V. Calibration dependences were measured at concentrations 2·10-7 mol·l-1 - 1·10-4 mol·l-1 . Limit of determination was 6,1·10-7 mol·l-1 . Linear dynamic range of this method was found between concentrations 6,1·10-7 - 2·10-5 mol·l-1 . Difenzoquat was determined in model samples of drinking and river water. Limits of detemination were achieved at concentrations 3,4·10-7 mol·l-1 in drinking water and...
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