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Time-resolved potentiometry on liquid-liquid interface
Mansfeldová, Věra
MSc. Věra Mansfeldová Dissertation thesis: Time-resolved potentiometry on liquid-liquid interface Abstract The aim of this work is to explore the method of temporal resolution in potentiometry as a new prospective electrochemical analytical technique. In connection with interface of two immiscible electrolyte solutions (ITIES) it may find utilization in analytical chemistry. This technique up to my knowledge has not been published yet. Potential response of analyte on liquid/liquid interface includes both distribution processes, their temporal resolution and redox processes, which specificity can modified by changing the composition of individual phases. Unlike "classic" potentiometric techniques, limited just to potential determination, this method, which I have given the working name "time resolved potentiometry at liquid-liquid interface" utilizes time development of potential response, which was found to be an analyte-specific function. The time resolved potentiometry presented in this work includes time course of potential response to analytical parameters specific for particular analyte. It brings series of data characterizing the analyte in given environment in a similar manner as spectra and may allow creating analyte-specific data package - fingerprint. Combination with ITIES allows, unlike...
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Thermodynamic modelling of hydrogen fuel cells
Nováček, Marek ; Pavelka, Michal (advisor) ; Němec, Tomáš (referee)
In this thesis, proton exchange membrane fuel cells are studied. At the beginning, the ideas underlying their function are exposed and some possibilities of usage are pre- sented. Thereafter, we aim to describe the processes inside the fuel cells with the aid of thermodynamics and in agreement with constitutive relations that have been obtained experimentally. Namely, we are interested in the fluxes of water and protons inside the membrane, where they are acted upon by thermodynamic forces, and the electrochemical reactions at the electrodes, which can be described by the Butler-Volmer equations. Also do we study the efficiency of the fuel cell by evaluating the production of entropy due to the diverse processes that take place in the fuel cell. It is the goal of the computational part of this thesis to propose a zero-dimensional model and compare it with the results provided in the supervisor's doctoral thesis. 1
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Izolace, separace a studium významných kov-vazných proteinů
Skaličková, Sylvie
The metal binding proteins are important group of biomolecules effects in living organisms. They represent series of vital important functions such as homeostasis of essential metals, they are involved in heavy metals detoxification, helps antioxidant system with free radical neutralization to prevent oxidation stress. Lot of them belongs to group of important enzymes catalyzing biochemical reactions. Last, but not least they are part of innate immunity system against pathogenes and could be utilized as a carrier cages in target drug therapy due to their unique transporter properties. A number of methods have been developed to study and observe the interactions between metalloproteins and specific biomolecules. First of all, the liquid chromatography enables isolation of required proteins from biological matrices. Further experiments utilized immunochemical, spectrophotometrical and electrochemical methods to clarify their properties and behaviour in various environments. The aim of the thesis was optimized analytical methods for separation and studying of the metal binding proteins.
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Utilization of Working Silver Solid Electrode for Voltammetric Determination of Drug Metronidazole
Mráček, Ondřej ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
This Bachelor thesis discusses the electrochemical behavior of metronidazole and seeks to find optimal conditions for the drug's voltammetric determination at a working silver solid electrode (AgSE) using differential pulse voltammetry (DPV). The voltammetric behavior of the drug was investigated, where the dependent variable was the pH of a water medium Britton-Robinson buffer (BRB). The optimum medium for voltammetric determination of metronidazole at a AgSE is a region of cathodic potential chosen to be the Britton-Robinson buffer, where the sodium hydroxide alkaline component (Na-BRB) has a pH of 10.0, and then measured further at voltammetric cell (volume of 10 ml) at concentration dependencies in the range of (1-1000)×10−6 mol/l. The limit of quantification (LOQ) and the limit of detection (LOD) were found to be 1.8×10−6 mol/l and 5.5×10−7 mol/l, respectively. In addition, the metronidazole was studied for the effect of electrochemical regeneration at the AgSE, where the parameters were: Nr = 150, Ein_r = 0 mV, Tin_r = 0.1 s, Efin_r = −1500 mV, Tfin_r = 0.1 s. The next section studies the electrochemical activity of the AgSE, which is not entirely ideal. The newly developed method might be applicable in the future for determining metronidazole through differential pulse voltammetry (DPV) to...
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Voltammetry with Preliminary Extraction as a New Approach for Rapid Determination of Formaldehyde in Wood-Based Products
Dvořák, Pavel ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
The aim of the presented Diploma Thesis was to develop a new method for the indirect determination of formaldehyde in wood-based products using gas-diffusion microextraction coupled with electrochemical detection on unmodified screen-printed electrodes (MLEM-SPCE). Formaldehyde released from the sample is derivatized using an acetylacetone reagent present in an acceptor solution. The product of derivatization of formaldehyde with acetylacetone is 3,5-diacetyl-1,4-dihydrolutidine (DDL) which forms a selective oxidation voltammetric peak at a potential of 0.4 V. Detection and quantification limits of 0.57 mg kg−1 and 1.89 mg kg−1 , respectively, were obtained, together with intra- and inter-day precision below 10% (as relative standard deviation, RSD). The developed methodology was applied to determine formaldehyde content in seven samples. Similar results were obtained from the European standard method EN 717-3 with a significant reduction of total analysis time. The developed method MLEM-SPCE, which combines the use of a new sample preparation procedure for volatile compounds with the firstly introduced determination of formaldehyde (as the derivative product DDL) on unmodified SPCEs, proves to be a promising alternative for the determination of formaldehyde in wood-based products and other samples.
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New Strategies in Electrochemical Detection of DNA Damage Induced by Interaction with UV radiation
Přibylová, Monika ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
V této bakalářské práci byl zkoumán netradiční redoxní indikátor 5-nitro-1,10-fenantrolin jako možný ukazatel poškození DNA. Měření probíhalo elektrochemicky technikou diferenční pulzní voltametrie v tříelektrodovém zapojení. Jako pracovní elektroda byla použita elektroda z ultračistého grafitu, která byla modifikována nízkomolekulární DNA z lososích spermií. Poškození DNA probíhalo pomocí UVC záření o vlnové délce 254 nm. Byl studován rozdíl výšky voltametrických signálů 5-nitro-1,10-fenantrolinu mezi nepoškozenou a poškozenou DNA. Nově vyvinuté metody se ukázaly jako slibné pro detekci míry poškození DNA v závislosti na čase ozařování a v závislosti na vzdálenosti od zdroje ozařování. Poškození DNA bylo rozsáhlejší u obou studovaných faktorů v závislosti na jejich rostoucích hodnotách. Klíčová slova Elektrochemie DNA biosenzory Netradiční elektrodové materiály Poškození DNA Biologicky aktivní látky Záření
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Characterization of electronic properties of nanowires for electrochemistry
Kovařík, Martin ; Čech, Vladimír (referee) ; Kolíbal, Miroslav (advisor)
Elektrochemické metody nacházejí využití v mnoha aplikacích (např. senzorice, skladování el. energie nebo katalýze). Jejich nespornou výhodou je nízká finanční náročnost na přístrojové vybavení. Abychom lépe porozuměli procesům probíhajícím na elektrodách, je dobré znát elektronickou pásovou strukturu materiálu elektrody. Úkolem této práce je vyhodnotit výstupní práci a pozici hrany valenčního pásu nových materiálů pro elektrody, konkrétně cínem dopovaného oxidu india pokrytého nanotrubicemi sulfidu wolframičitého. Ultrafialová fotoelektronová spektroskopie a Kelvinova silová mikroskopie jsou metody použité pro tuto analýzu. Zvláštní důraz je kladen na přípravu vzorků elektrod pro měření, aby nedošlo k nesprávné interpretaci výsledků vlivem vnějších efektů jako je např. kontaminace nebo modifikace povrchu.
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Observation of lead electrode surface by atomic force microscope AFM
Bouška, Marek ; Máca, Josef (referee) ; Bača, Petr (advisor)
This master's thesis is focused on in situ observation of the negative electrode of the lead acid accumulator using atomic force microscopy AFM. Discussed topics are lead acid accumulator, atomic force microscopy, cyclic voltammetry and current knowledge of the in situ observation of the lead acid accumulator using AFM. The main task of this project is assembling the experimental cells, make in situ observation of the negative electrode surface of the lead acid accumulator. In the end evaluate if this method is suitable for the lead acid battery observation.
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Thermodynamic analysis of solid oxide cells
Vágner, Petr ; Maršík, František (advisor) ; Grmela, Miroslav (referee) ; Pekař, Miloslav (referee)
Thermodynamic analysis of solid oxide cells Petr Vágner The thesis deals with continuum thermodynamic modeling and analysis of phe- nomena in solid oxide electrochemical cells. A general description of the evo- lution of charged mixtures using partial mass densities, momentum density, entropy density, electric induction, magnetic field, polarization, and magnetiza- tion based on the GENERIC framework is formulated. The formulation is used to recover the Landau-Lifshitz magnetization relaxation model, the Single Re- laxation Time model for dielectrics, and the generalized Poisson-Nernst-Planck model. The latter model is consequently linked to the second part, where a novel double layer model of an yttria-stabilized zirconia interface is formulated within non-equilibrium thermodynamics. The model is solved for numerically in the time domain, and cyclic voltammetry of the system is analyzed. The last part of the thesis demonstrates the limits of Exergy Analysis on a simple solid oxide hydrogen fuel cell model with non-isothermal boundary. It is demon- strated that the minimization of entropy production does not necessarily lead to the maximization of the electric power for certain optimization scenarios. The thesis consists of a compilation of published and unpublished results of the author.
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New redox labels for DNA
Simonova, Anna ; Hocek, Michal (advisor) ; Urban, Milan (referee) ; Vyskočil, Vlastimil (referee)
The aim of my thesis was the synthesis of the modified 2'-deoxyribonucleoside triphosphates (dNTPs) bearing electrochemically oxidizable labels and their incorporation into DNA for the application in bioanalysis. In the first part of my thesis, I developed the synthesis of modified dNTPs bearing 2,3- dihydrobenzofuran (DHB) or 2-methoxyphenol (MOP) labels at 5-position of 2'- deoxycytidine 5'-O-triphosphate and at the 7-position of 7-deaza-2'-deoxyadenosine 5'-O- triphosphate by Suzuki-Miyaura cross-coupling reactions. Then modified dNTPs were used as substrates for DNA polymerases in enzymatic synthesis of modified DNA by PCR and primer extension. Electrochemical properties of the DHB and MOP-labeled nucleosides, dNTPs and DNA were studied by using of a square-wave voltammetry (SWV) at the pyrolytic graphite electrode (PGE) giving signals of MOP oxidation around 0.5 V and DHB oxidation around 0.85 V. The use of DHB group in combination with other electrochemical active labels was limited by close position of its oxidation peak to the signals of oxidation of natural nucleobases, whereas MOP moiety was successfully used for redox coding of nucleobases in combination with aminophenyl or benzofurazane label giving two independently readable redox signals in each case. In the second part of this...
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