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Electrochemical detection of n-propanol on Au and Pt electrodes modified with polyaniline-based composites
Pejzlová, Michaela ; Fischer, Jan (advisor) ; Vyskočil, Vlastimil (referee)
The electrochemical oxidation of aliphatic alcohols is problematic on conventional electrode materials and to develop methods for their detection, the catalytic properties of electrode surfaces need to be exploited. This thesis is concerned with the study of the electrochemical deposition of polyaniline (PANI) in acidic media on three different electrodes, platinum, gold and glassy carbon electrode. The properties of the PANI modified electrodes were tested in comparison to the unmodified electrodes. The electrooxidation of aliphatic alcohols n-propanol and 2-propanol in alkaline medium was studied by cyclic voltammetry. Subsequently, the effect of electrodeposited noble metals (palladium and gold) on the surfaces of unmodified and PANI modified electrodes on the electrooxidation of propanol was investigated by using the same procedures. From the linear part of the concentration dependence of n-propanol on the chosen electrodes, the limit of detection was determined. The lowest value was calculated for the platinum electrode with electrodeposited gold (LOD = 0.2 mmol l−1 ). PANI modified electrodes showed wider linear dynamic range than electrodes without this modification. Keywords: cyclic voltammetry, electrooxidation, glassy carbon electrode, gold electrode, metal electrodeposition, n-propanol,...
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Development of voltammetric methods for detection of phytosterols on carbon-based electrodes
Zelenský, Michal ; Schwarzová, Karolina (advisor) ; Fischer, Jan (referee)
The aim of this diploma thesis was to develop an electrochemical method for three phytosterols, namely stigmasterol β-sitosterol and ergosterol using voltammetry techniques on glassy carbon electrode and boron doped diamond electrode. The work builds on previous results, where it was shown that the electrochemical oxidation of phytosterols requires perchloric acid in acetonitrile. When this acid is used, a dehydration reaction occurs. Calibration dependences were measured here for all phytosterols in an environment with a water content of 0.43%. The stability of the signal with increasing distilled water content was further investigated. Then the calibration dependences in the increased water content were measured again. If we want to use HPLC-type separation techniques, we must first find out how the phytosterols will behave in this environment, and therefore the signal stability on the buffer content was investigated. The buffers used were phosphate and acetate buffer. Subsequently, the concentration dependence was measured in an environment with a higher content of phosphate buffer. Furthermore, the possibility of detecting two phytosterols at once was investigated. Key words: dehydration, glassy carbon electrode, boron doped diamond electrode, oxidation, phytosterols, voltammetry
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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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Electrochemical properties of synthetic drugs 3-fluorophenmetrazine and 4-methylpentedrone
Jiroušková, Eliška ; Schwarzová, Karolina (advisor) ; Dejmková, Hana (referee)
The aim of this Thesis was to clarify electrochemical properties of two new psychoactive substances. These substances are an alternative to classical drugs because they are not controlled by current legislation. It is important to determine the metabolites of these substances to be able to detect them in organism. Their electrochemical properties could explain the process of the first phase of biotransformation in human organism. Two synthetic stimulants were studied - 3-fluorophenmetrazine and 4-methylpentedrone, used as substitutes for cocaine or ecstasy. The purity of substances was controlled by HPLC with UV/Vis diode array detector and the stability was verified by UV/Vis spectrophotometry. Electrochemical properties were studied in phosphate buffer using cyclic voltammetry. For both substances was calculated theoretical HOMO and LUMO spatial distribution. This information was important to estimate parts of molecules, that can be reduced or oxidised. The analytical method was developed on glassy carbon electrode using differential pulse voltammetry. Substance 3-fluorophenmetrazine was determined in phosphate buffer pH 9,0 with limit of detection of 5,1 µmol l-1 . The linear range of calibration curve is from 7,0 to 107,0 µmol/l, R = 0,9988. 4-methylpentedrone was determined in phosphate...
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Novel Approaches in Electrochemical Determination of Xenobiotic Compounds and in Study of Their Interaction with DNA
Hájková, Andrea ; Vyskočil, Vlastimil (advisor) ; Trnková, Libuše (referee) ; Labuda, Ján (referee)
Presented Ph.D. Thesis is focused on the development of analytical methods applicable for determination of selected xenobiotic compounds and for monitoring DNA damage they can induce. The main attention has been paid to the development and testing of non-toxic electrode materials for preparation of miniaturized electrochemical devices and novel electrochemical DNA biosensors. 2-Aminofluoren-9-one (2-AFN) was selected as a model environmental pollutant, which belongs to the group of hazardous genotoxic substances. Its carcinogenic and mutagenic effects may represent a risk to living and working environment. 2-AFN has one oxo group, where the cathodic reduction occurs, and one amino group, where the anodic oxidation occurs. The voltammetric behavior of 2-AFN in the negative potential region was investigated at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) representing a non-toxic and more mechanically robust alternative to mercury electrodes. This working electrode was subsequently used for the development of a newly designed miniaturized electrode system (MES), which has many benefits as the possibility of simple field measurements, easy portability, and the measurement in sample volume 100 µL. Moreover, a glassy carbon electrode (GCE) was used for further investigation of...
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Voltammetric Determination of 5-Nitrobenzimidazole Using Non-Traditional Electrode Materials
Chládková, Barbora ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
5 Abstract This Diploma Thesis is targeted on the determination of 5-nitrobenzimidazole (5-NBIA) using following techniques: DC voltammetry (DCV) and differential pulse voltammetry (DPV). As working electrodes, a silver amalgam paste electrode (AgA-PE), which was constructed for this determination in the form of a new prototype, a bismuth film electrode (BiFE), at which the optimum conditions for the deposition of the bismuth film at a suitable substrate (glassy carbon electrode and gold electrode were tested for this purpose) were initially optimized, and a glassy carbon electrode (GCE) were used. The optimum conditions for the voltammetric determination of 5-NBIA at the AgA-PE (in a medium of Britton-Robinson buffer (BR-buffer) of pH 7.0 for both DCV and DPV), at the BiFE with gold substrate (BR-buffer of pH 9.0 for both DCV and DPV; the film was deposited "ex situ" in a stirred plating solution (1000 mg L-1 Bi(III) solution in 0.1 mol L-1 acetate buffer of pH 4.5) for 300 s), and at the GCE (BR-buffer of pH 5,0 for both DCV and DPV). Under these conditions, calibration dependences were measured in the concentration ranges of 0.1 - 100 µmol L-1 (pro DCV a DPV na AgA-PE) and 1 - 100 µmol L-1 (pro DCV a DPV na BiFE a GCE), and the limits of quantification (LQs) were calculated for particular methods: LQ ≈...
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Development of Novel Electrochemical Methods Using Various Membrane Materials for Monitoring of Selected Anticancer Drugs and Phytochelatins
Skalová, Štěpánka ; Barek, Jiří (advisor) ; Labuda, Ján (referee) ; Trnková, Libuše (referee)
Present Ph.D. Thesis is focused on the development of electrochemical methods for determination of anticancer drugs using various types of membranes for their preliminary separation. Furthermore, this Thesis reports the study of transport mechanisms of heavy metals in the presence of phytochelatins across biological membranes. Sodium anthraquinone-2-sulphonate (AQS) was used as a model compound for its similar structure with anthraquinone-based (AQ-based) anticancer drugs (doxo/daunorubicin) and also due to its better availability. All these compounds can be easily electrochemically oxidized and/or reduced. Redox behaviour of AQS was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in a cathodic region on mercury meniscus modified (m-AgSAE) and polished silver solid amalgam (p-AgSAE) electrodes, Obtained results were used for the development of a micro-volume voltammetric cell (MVVC). Its applicability for voltammetric determination of anticancer drugs was verified by using doxorubicin (DX) as a model substance. The second part of this Thesis deals with therapeutic monitoring of anticancer drugs in the blood circulation of the patients. For pilot experiments, a liquid-flow system with dialysis catheter and amperometric detection was used. The flow rate of carrier...
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Utilization of potential programs in flow electrochemical determination of biologically active organic compounds
Bavol, Dmytro ; Dejmková, Hana (advisor) ; Josypčuk, Bohdan (referee) ; Metelka, Radovan (referee)
9 Abstract In this Ph.D. thesis possibilities of using our proposed potential programs for a multiple-pulse amperometry and a fast scan differential pulse voltammetry in combination with flow systems are presented. The development of new sensitive amperometric and voltammetric methods for the determination of oxidisable biologically active organic compounds is another aim of this work. In the first part of the work, the flow injection system and multiple-pulse amperometric detection were employed to develop and optimize a simple, low-cost, and rapid method for the simultaneous determination of natural and synthetic antioxidants. This technique involves the application of an appropriate potential waveform consisting of a suitable sequence of pulses on a single working electrode, thus allowing distinguish the analytes in a mixture with no need of separation. Conditions for the determination of antioxidants and modelling of the potential program were tested and studied, respectively. Second part of the work describes and characterizes the application of the fast scan differential pulse voltammetry (FSDPV) in combination with the flow systems. FSDPV is the electroanalytical technique that use high scan rate to record voltammograms within several milliseconds and ensures high temporal resolution. This technique...
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Utilization of potential programs in flow electrochemical determination of biologically active organic compounds
Bavol, Dmytro
9 Abstract In this Ph.D. thesis possibilities of using our proposed potential programs for a multiple-pulse amperometry and a fast scan differential pulse voltammetry in combination with flow systems are presented. The development of new sensitive amperometric and voltammetric methods for the determination of oxidisable biologically active organic compounds is another aim of this work. In the first part of the work, the flow injection system and multiple-pulse amperometric detection were employed to develop and optimize a simple, low-cost, and rapid method for the simultaneous determination of natural and synthetic antioxidants. This technique involves the application of an appropriate potential waveform consisting of a suitable sequence of pulses on a single working electrode, thus allowing distinguish the analytes in a mixture with no need of separation. Conditions for the determination of antioxidants and modelling of the potential program were tested and studied, respectively. Second part of the work describes and characterizes the application of the fast scan differential pulse voltammetry (FSDPV) in combination with the flow systems. FSDPV is the electroanalytical technique that use high scan rate to record voltammograms within several milliseconds and ensures high temporal resolution. This technique...
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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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