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Development of electroanalytical methods for detection of cholesterol, 7-dehydrocholesterol and cholecalciferol
Benešová, Lenka ; Schwarzová, Karolina (advisor) ; Navrátil, Tomáš (referee) ; Šelešovská, Renáta (referee)
Steroidival substances are an integral part of the human organism, such as bile acids, steroid hormones, vitamins. The most important sterol in whole organism is cholesterol, which is cornerstone of the all cell membranes. It is involved in important processes in the body, but its storage in blood vessels in the formo f low-density lipoprotein (LDL) is crucial of reason serious health diseases as atherosclerosis, myocardial infarction and others. 7-dehydrocholesterol is a precursor of cholesterol and another sterol compound studied by me, cholekalciferol, also known as a vitamin D3. Deficiency of 7-dehydrocholesterol reductase is the main indicatior of the possible genesis of Smith-Lemli-Opitz syndrome. One of the goals of this thesis was developed a suitable electrochemical method to facilitate the diagnosis of this syndrome from plasma and amniotic fluid in the prenatal and postnatal phases of pregnancy. Within the framework of this thesis were developer electrochemical methods in a batch and flow arrangement for detection of the above-mentioned sterols, namely cholesterol, 7-dehydrocholesterol and cholekalciferol. It was wokered in the medium contain perchloric acid or its salt sodium perchlorate in acetonitrile as supporting electrolyte. It was worked in the wide range of working disc...
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Electrochemical Techniques in Monitoring of Nervous System Drugs
Choińska-Mlynarczyk, Marta ; Hrdlička, Vojtěch ; Skopalová, J. ; Šelešovská, R. ; Kolivoška, Viliam ; Navrátil, Tomáš
Drugs of the nervous system (ATC group N) belong generally to the most commonly (mis)used substances worldwide. Their determination and monitoring of these drugs and their metabolites in various body fluids or environmental matrices represent a challenge for analytical chemists. Our research is focused on the application of electrochemical methods in the monitoring of the most frequently prescribed and the newly introduced nervous system drugs of precisely specified structures and/or of defined properties. For toxicological and pharmacokinetic reasons, emphasis has been placed on investigating the reaction mechanisms of their metabolite formation. New or alternative to commonly used electroanalytical methods applicable for monitoring and characterization of target compounds in their pure state, in body fluids, wastewaters, and other environmental matrices, has been developed. To improve the chemometric parameters and sensing characteristics, attention was paid to the construction of new electrochemical sensors, detectors (e.g. screen-printed, 3D printed), or cells, based on (modified/unmodified) traditional or nontraditional materials, preferably usable at the point-of-care.
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Porous Boron-Doped Diamond Electrodes: Characterisation and Application for Electroanalysis
Baluchová, Simona ; Schwarzová, Karolina (advisor) ; Navrátil, Tomáš (referee) ; Šelešovská, Renáta (referee)
This dissertation thesis presents newly developed electrode materials based on porous boron- doped diamond (BDDporous) and their potential applications in electroanalysis. Particularly, these novel BDDporous electrodes (twelve in total) were thoroughly electrochemically characterised and compared, and the ones with the most promising properties were selected to develop reliable voltammetric methods for detecting the neurotransmitter dopamine. Initially, the impact of selected fabrication parameters on the final properties and electrochemical behaviour of novel BDDporous electrodes was clarified; the following factors were specifically studied: (1) deposition template used, (2) boron-doping level, (3) growth time of the individual layers (i.e., porosity), (4) number of deposited layers (i.e., thickness), and (5) content of non-diamond (sp2 ) carbon impurities. Alterations in deposition conditions naturally resulted in BDDporous electrodes with diverse (i) structural and morphological features, which were investigated by scanning electron microscopy and Raman spectroscopy, and (ii) physical and electrochemical characteristics, examined by cyclic voltammetry. Besides, to assess the suitability of selected BDDporous electrodes for dopamine detection, other parameters, such as susceptibility to...
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Boron doped diamond and its utilization in electroanalysis of derivatives of aromatic compounds
Zavázalová, Jaroslava ; Schwarzová, Karolina (advisor) ; Šelešovská, Renáta (referee) ; Navrátil, Tomáš (referee)
This work is devoted to the study of boron doped diamond as electrode material, its properties and use in electroanalytical methods - in voltammetric and subsequently amperometric methods in combination with high performance liquid chromatography. The series of boron doped diamond films was tested with respect to the effect of boron concentration on their morphology, quality, electrochemical and spectral properties using scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and cyclic voltammetry and differential pulse voltammetry. Further, the effect of boron concentration on the determination of selected substances was investigated, both for their oxidation (2-aminobiphenyl, benzophenone-3) and for their reduction (5-nitroquinoline). Furthermore, a voltammetric and amperometric method was developed for the determination of a mixture of aminobiphenyls and aminonaphthalenes using a boron doped diamond electrode. The effects of activation cleaning programs on the signal of benzophenone-3 were investigated using a boron doped diamond electrode, and the determination of benzophenone-3 on boron doped diamond electrode in the presence of the selected surfactant was studied. Boron doped diamond as carbon-based material was compared with other selected carbon materials such as glassy...
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Voltammetric and Amperometric Determination of Nitrophenols Using Boron-Doped Diamond Film Electrode
Karaová, Jana ; Barek, Jiří (advisor) ; Šelešovská, Renáta (referee) ; Jaklová Dytrtová, Jana (referee)
Presented Ph.D. Thesis is focused on the use of the boron-doped diamond (BDD) electrodes for voltammetric and amperometric determination of selected nitrophenols: 2-nitrophenol (2NP), 4-nitrophenol (4NP), and 2,4-dinitrophenol (2,4DNP). These compounds are listed as "priority pollutants" by United States Environmental Protection Agency (US EPA) due to their negative impact on living organisms and are mainly used in agriculture as plant growth stimulators. BDD electrodes are used for determination of wide range of electrochemically both reducible and oxidisable organic compounds and have become a popular electrode material thanks to its commercial availability and excellent mechanical and electrochemical properties. A differential pulse voltammetric method was developed for the determination of 2NP, 4NP and 2,4DNP at a BDD film electrode using electrochemical reduction and of 4NP and 2,4DNP using electrochemical oxidation. The method was successfully applied for the direct determination of these compounds in drinking and river water in the concentration range from 4×10-7 to 2×10-5 mol.L-1 . To improve the limit of quantification, a preconcentration by solid phase extraction from 100 mL (drinking and river water) and 1000 mL (drinking water) of water samples was used with limit of determination...
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Testing of new electrode arrangements for monitoring of electrochemically oxidisable biologically active organic compounds
Libánský, Milan ; Zima, Jiří (advisor) ; Navrátil, Tomáš (referee) ; Šelešovská, Renáta (referee)
Submitted Ph.D. Thesis is focused on the electrochemical characterization and testing of recently developed working electrodes made from pure gold or graphitic carbon particles and electrochemical arrangements. These electrodes are suitable for large screening measurements of various organic compounds. The development of new sensitive voltammetric methods for determination of oxidisable biologically active organic compounds is another aim of this work. To verify its applicability, the array of carbon composite film electrodes integrated in measuring cell system was selected for the development of voltammetric methods for determination of homovanillic acid, vanillylmandelic acid, and indoxyl sulphate. These analytes, which belong to the group of biomarkers of human diseases, were selected for increasing interest in their determination in medical laboratories. Moreover, determination of indoxyl sulphate was coupled to its solid phase extraction from human urine prior to voltammetric determination. Obtained results were compared with measurements of standards with well-established carbon paste electrode. Sputtered (physical vapour deposition method) gold nanostructured film electrodes on treated PTFE substrates and gold nanostructured film electrodes modified with various functional groups on the...
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Using Voltammetric Method for Monitoring of Antioxidant Content in Biofuels
Tomášková, M. ; Chýlková, J. ; Navrátil, Tomáš ; Šelešovská, R.
The simple and fast method for analysis of Propyl gallate (PG) in biofuels was proposed in this paper. Voltammograms of antioxidant under study were recorded using linear sweep voltammetry method at a gold disc electrode in supporting electrolyte containing 0.18 mol L-1 H2SO4 and 10 % ethanol. For purposes to monitor effects on fuel quality caused by oxidative degradation, the proposed method was applied to samples of biodiesel and Ekodiesel® (the blend of biodiesel with fuel diesel). The analysis of PG can be performed without pretreatment of Ekodiesel samples, and after extraction using distilled water in case of biodiesel samples.
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Lab-made Sensors Based on Boron-doped Diamond for Determination of Herbicide Linuron
Štěpánková, M. ; Šelešovská, R. ; Janíková, L. ; Vojs, M. ; Marton, M. ; Behúl, M. ; Nováková, Kateřina ; Chýlková, J.
Voltammetric behaviour of substituted urea herbicide linuron (LIN) was investigated using two types of boron-doped diamond electrodes (BDDE): commercial BDDE and lab-made sensors based on boron-doped diamond (LM-BDDE). Various methods like cyclic voltammetry (CV), direct current voltammetry (DCV) and differential pulse voltammetry (DPV) were examined. It was found that LIN provides one oxidation peak using all of the tested working electrodes and the highest current response was recorded in the acidic media. Thus, Britton-Robinson (B-R) buffer of pH 2 was used as a supporting electrolyte. Parameters of DPV were optimized and the low limits of detection (LOD) were reached 1.41×10−7 M for commercial boron-doped diamond electrode and 8.81×10−9 M, respectively, which represents the lowest LOD obtained for lab-made boron-doped diamond electrodes.
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Voltammetric Behavior of Folates and Related Substances Using Silver Solid Amalgam Electrode
Bandžuchová, L. ; Šelešovská, R. ; Navrátil, Tomáš ; Chýlková, J.
The possibility of application of silver solid amalgam electrode in voltammetric analysis of compounds with folate structure (folic acid, methotrexate, leucovorin) and substances, which play an important role in its metabolism (riboflavin, hydroxocobalamin) has been investigated. Cyclic voltammetry, DC voltammetry and Elimination voltammetry with linear scan has been used for study of voltammetric behavior of mentioned substances and for elucidation of electrochemical reactions. Differential pulse voltammetry has been applied for development of sensitive methods of determination for investigated electroactive compounds. The proposed methods were successfully applied for real samples analysis. Obtained results have been compared with those achieved using HMDE.
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