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The use of carbon-based electrodes for the development of new electrochemical methods for the determination of aminonitrophenols
Dejmková, Hana ; Zima, Jiří (advisor) ; Ludvík, Jiří (referee) ; Vytřas, Karel (referee)
4 ABSTRACT Methods for the determination of five isomers of aminonitrophenol were developed, based on the technique of differential pulse voltammetry (DPV) and HPLC with amperometric detection. As the working electrodes, boron-doped diamond film electrode (BDDFE) and glassy carvon paste electrode (GCPE) were employed. Preliminary electrode testing was performed by cyclic voltammetry. The methods were aimed to the determination of all five aminonitrophenol isomers in hair dyes and to the determination of 2-amino-4- nitrophenol and 4-amino-2-nitrophenol in body fluids after solid phase extraction. From the voltammetric methods, the one using BDDFE for the cathodic determination in hair dyes exhibits sufficient selectivity. The performance of chromatographic methods was found suitable for the determination of aminonitrophenols in both observed matrices. The applicability of the developed methods was successfully confirmed by the determination of tested analyted in real samples of hair dyes and spiked samples of urine. Preceding measurements are described, dealing with the determination of other oxidizable compounds, containing phenolic or aniline moieties on BDDFE. The obtained results confirm that in some cases, BDDFE shows more resistance to fouling than other carbon-based electrodes, but in most cases, the...
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Electrochemical studies of the analytical utilization of self-assembled monolayers of calix[4]arene on the surface of polycrystalline gold electrode
Hrdlička, Vojtěch ; Navrátil, Tomáš (advisor) ; Ludvík, Jiří (referee)
This MSc. Thesis deals with electrochemical studies of the analytical utilization of self-assembled monolayers of thiolated calix[4]arene (C4A) and/or undecanthiole (C11SH) on the surface of a polycrystalline gold electrode. Hydroquinone, nitrobenzene, 2-nitrophenole and 4-nitrophenole have been used as tested model compounds. The real surface area of the electrode was determined using these two methods: From the charge of desorption peak of α-gold oxides (5.72±0.48 mm2 ) and using the Randles- Ševčík equation. (6.14±0.59 mm2 ). The preparation of the electrode consisted of polishing on alumina, immersing into piranha solution and cyclic voltammetry. The area of electrode surface was well reproducible. Stability of thiol monolayer in the area of negative potentials was tested. The C11SH layer is very stable; the desorption peak was recorded in basic solutions only (at −1.3 V vs. 3M Ag/AgCl). The position of the desorption peak of C4A is more pH dependent and it was recorded at −1.08 V at pH 13. The properties of the electrode modified by C11SH and or C4A were investigated using the model compound hydroquinone. It is assumed that the oxidation of the hydroquinone does not take place inside the C4A cavity; hence the hydroquinone molecule is too big to pass through the cavity. C11SH and C4 + C11SH act...
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Electrochemistry of Calixarenes
Liška, Alan ; Ludvík, Jiří (advisor) ; Zima, Jiří (referee) ; Cibulka, Radek (referee)
In the present thesis, both the published and the "ready-to-be-submitted" results concerning electrochemistry of calixarenes are summarized. The main focus is given to the detailed interpretation of experimental data, acquired during a systematic study of electroactive calixarene derivatives. The experiments were conducted under aprotic conditions (DMF) on mercury electrodes (mainly cyclic voltammetry and DC-polarography). It is demonstrated that electrochemistry should not serve only for redox characterization of studied compounds, but it offers a great number of other valuable information. The subject matter of the study are the calix[4]arenes (prevalently in the cone-conformation) which bear one to four reducible or oxidizable substituents ("redox probes") at various positions in order to be electrochemically investigable. Nitro- and nitroso compounds together with aldehydes, ketones, nitriles, aldoximes, carboxylic acids and corresponding esters, sulphones and esters of sulphonic acids are the most discussed compound series. Their relationship between structure and electrochemical response is presented in new connections ("stereoelectrochemistry"), in other words, how the redox probe position on the benzene ring (para-/meta-), bridging groups, or adjacent vs. opposite aromatic units...
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New Electrochemical Methods for Determination of Nitro and Oxo Derivatives of Fluorene
Vyskočil, Vlastimil ; Barek, Jiří (advisor) ; Ludvík, Jiří (referee) ; Heyrovský, Michal (referee)
4. Conclusion This Thesis represents a contribution to the search for new analytical methods applicable on environmental and biological samples. The current state- of-art concerning the formation, occurrence, and biological activity of fluorene and its nitro and oxo derivatives was summarized in Chapter 1. Further experimental work was focused on assessment of new approaches in the detection of the studied compounds. Attention was paid mainly to nitrofluorenes, fluorenone and nitrofluorenones, namely 2-nitrofluorene, 2,7-dinitrofluorene, 9-fluorenone, 2-nitro-9-fluorenone, and 2,7-dinitro-9- fluorenone and the possibilities of their determination using polarographic and voltammetric methods. Interactions of calf thymus dsDNA with 2-nitrofluorene and 2,7-dinitrofluorene at the DNA/SPCPE were investigated and subtle DNA damage under conditions of direct DNA-analyte interaction at room temperature and damage to DNA bases under condition of electrogeneration of short-lived radicals of nitrofluorenes at human body temperature were found. The obtained results can be summarized as follows: ● Modern polarographic and voltammetric methods at mercury electrodes developed for determination of trace amounts of 9-fluorenone and 2,7-dinitro-9-fluorenone (and other NPAHs generally) in concentration ranges from 2×10-8 to...
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Possibilities of Electrochemical Analysis Using a System of Electrodes With Non-Specific Response
Ederer, Jakub ; Nesměrák, Karel (advisor) ; Ludvík, Jiří (referee)
The master thesis present the possibilities of processing of electrochemical data from a group of four electrodes with non-selective response (simple sensor array) for electrochemical analysis with potential application of the results achieved in the construction of the sensor field type "electronic tongue". This simple system was applied to the sample simulating the food product. Electrochemical data were processed through mathematical operations such as Gaussian approximation, deconvolution or using basic mathematical operations.
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Electrochemical Biosensors and Detectors Based on Silver Solid Amalgam for Analysis in Flow Systems
Josypčuk, Oksana ; Barek, Jiří (advisor) ; Vytřas, Karel (referee) ; Ludvík, Jiří (referee)
In this Ph.D. thesis new possibilities of using amalgam electrodes are presented. First of all, the tubular detector based on silver solid amalgam (TD-AgSA) was designed for determination of reducible compounds in flow systems. It was tested on model solutions of Cd2+ , Zn2+ and 4-nitrophenol in amperometric mode under conditions of flow injection analysis. Results have shown that developed tubular detector is simple and low cost device suitable for detection of reducible compounds with good sensitivity, repeatability and long-term stability (at least 2 years) with possibility to work at potentials up to 2 V in aqueous solutions. Afterwards, this newly developed detector was successfully used for the determination of an active ingredient lomustine in pharmaceutical preparation CeeNU® Lomustine by non-stop-flow differential pulse voltammetry based on reduction of present nitroso group. For measurements in the flow system miniature reference electrodes saturated calomel electrode, mercury-mercurous sulfate, and mercury-mercuric oxide electrode based on paste silver solid amalgam were fabricated and tested for 14 months. The calomel electrode based on paste silver amalgam proved to be the most resistant to polarization and it was used in all experiments in this thesis. Next, the electrochemical...
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The Use of New Types of Carbon Electrodes for Voltammetric Determination of Organic Compounds
Birhanzlová, Tereza ; Barek, Jiří (advisor) ; Labuda, Ján (referee) ; Ludvík, Jiří (referee)
This Ph.D. thesis is focused on the use of a new type of non-toxic electrode (carbon film electrode - CFE) for voltammetric determination of environmental organic pollutants and on the development and use of a new type of solid electrode modified with carbon nanotubes for the determination of 2-nitrophenol (2-NP) and 8-nitroquinoline (8-NQ). The work is a continuation of the previous study of 5- nitroquinoline (5-NQ) using CFE in author's bachelor and diploma thesis. The determination of 5-NQ based on anodic oxidation is not possible at CFE and thus 2-NP was chosen as a model substance for voltammetric determination in both regions of potential window (cathodic and anodic). Further attention was paid to the development of a new type of carbon electrode with surface containing carbon nanotubes and its application for the determination of 8-NQ using differential pulse voltammetry (DPV) based on cathodic reduction of present nitro group. Silver solid electrode (AgE) as a substrate electrode for following modification was used. At first, the AgE itself was used for determination of 8-NQ in deionized water and in model samples of drinking and river water. Then the possibility of electrode surface modification using different type of carbon nanotubes was investigated. The AgE modified with carboxylated...
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The Use of New Types of Carbon Electrodes for Voltammetric Determination of Organic Compounds
Birhanzlová, Tereza ; Barek, Jiří (advisor) ; Labuda, Ján (referee) ; Ludvík, Jiří (referee)
This Ph.D. thesis is focused on the use of a new type of non-toxic electrode (carbon film electrode - CFE) for voltammetric determination of environmental organic pollutants and on the development and use of a new type of solid electrode modified with carbon nanotubes for the determination of 2-nitrophenol (2-NP) and 8-nitroquinoline (8-NQ). The work is a continuation of the previous study of 5- nitroquinoline (5-NQ) using CFE in author's bachelor and diploma thesis. The determination of 5-NQ based on anodic oxidation is not possible at CFE and thus 2-NP was chosen as a model substance for voltammetric determination in both regions of potential window (cathodic and anodic). Further attention was paid to the development of a new type of carbon electrode with surface containing carbon nanotubes and its application for the determination of 8-NQ using differential pulse voltammetry (DPV) based on cathodic reduction of present nitro group. Silver solid electrode (AgE) as a substrate electrode for following modification was used. At first, the AgE itself was used for determination of 8-NQ in deionized water and in model samples of drinking and river water. Then the possibility of electrode surface modification using different type of carbon nanotubes was investigated. The AgE modified with carboxylated...
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Redox Properties of Fluorinated Derivativers of 1,3-Diphenylisobenzofuran-Chromophores for Singlet Fission
Šimková, Ludmila ; Ludvík, Jiří
Derivatives of 1,3-diphenylisobenzofuran attract interest because they should be efficient as the molecules for singlet fission. The understanding of singlet fission in isolated molecules might be advantageous for use as solar cell sensitizers. This study is focused on fluorinated derivatives of 1,3-diphenylisobenzofuran and the effect of the position of fluorine atoms on their redox properties. For characterization of the redox properties standard electrochemical methods, and in situ UV-vis and EPR spectroscopy techniques were used.
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