National Repository of Grey Literature 199 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Study of redox reactions and adsorption of 4-nitrophenyl triazole labeled nucleosides and cresols on boron doped diamond electrodes for development of electroanalytical methods
Vosáhlová, Jana ; Schwarzová, Karolina (advisor) ; Havran, Luděk (referee) ; Navrátil, Tomáš (referee)
In this work, the application of boron-doped diamond electrodes with various surface pre- treatment were tested on selected oxidizable and reducible model compounds, specifically para and ortho cresols and 2'-deoxycytidine and 7-deazaadenosine labeled by 4-nitrophenyl triazole. The aim of the study was the investigation of electrochemical and adsorptive processes with respect to the development of electroanalytical methods of detection of the selected compounds, or utilization of boron-doped diamond electrodes as detectors in liquid-flow systems. Cresols were used as the model oxidizable compound. On O-terminated and polished boron- doped diamond electrodes, cresols provide oxidation signal owing to their oxidation to methylphenoxy radical at comparable potentials as on other carbon-based electrodes used as a reference in this work, i.e., glassy carbon electrode, pyrolytic graphite electrode, and carbon paste electrode. These carbon electrode materials show relatively high propensity to adsorption of reaction products, while such adsorption is minimal on boron-doped diamond. In situ anodic activation allows for a rapid regeneration of boron-doped diamond surface prior to each scan. A differential pulse voltammetric method that was developed with a detection limit of 0.61 mol∙l-1 to 2.97 mol∙l-1...
Studium vlivu vybraných podmínek prostředí na klíčení semen plevelů
Navrátil, Tomáš
The aim of this thesis was to find out the influence of temperature on germination of Tripleurospermum inodorum seeds. Seed germination took place in laboratory conditions. This thesis is based on two laboratory experiments. During the first experiment, the effect of different temperatures on the germination of Tripleurospermum inodorum seeds was observed. During the second experiment, it was observed how would the Tripleurospermum inodorum seed germinate if it was exposed to freezing temperatures for various periods of time. The seeds germinated best at 20 °C. At this temperature, germination was 92.5%. During the second experiment, the best germination was 74.5%. It was with seeds that had been exposed to frost for thirty days. Results have been written to the tables and processed to graphs. In addition, germination results were compared to other weed species. Evaluation of the thesis is given in the discussion.
Miniaturized boron doped diamond film electrode for neuroblastoma biomarkers determination
Hrdlička, Vojtěch ; Barek, J. ; Navrátil, Tomáš ; Taylor, Andrew
Cathodically pretreated miniaturized boron doped diamond film electrodewas successfully tested for the purposes of in-situ determination of neuroblastoma biomarkers after hollow-fibre based microextraction. Electrode was tested using K-3[Fe(CN)(6)] and vanillyl-mandelic acid as model substances. Limits of detection and determination are 2.2 and 6.6 mu mol L-1, respectively. Linear range was 2.2-100 mu molL(-1), repeatability 1.34% (n = 10).
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...
Voltammetry at Silica Gel-Modified Carbon Paste Electrode
Šestáková, Ivana ; Navrátil, Tomáš
Voltammetry using silica gel modified carbon paste electrode (SiO2-CPE) for oxidation of selected flavonoid showed better sensitivity and reproducibility than oxidation using glassy carbon or unmodified carbon paste electrode. Only SiO2-CPE is useful for study of cadmium complexation with cysteine containing ligand as phytochelatin or metallothionein. Voltammetry on boron doped diamond electrode showed only peak of sulfur compound oxidation, which decreased with the addition of cadmium ions.
Voltammetric Determination of Chili Peppers Pungency using Phospholipid Modified Glassy Carbon Electrode\n
Skopalová, J. ; Rajcová, A. ; Vokounová, D. ; Navrátil, Tomáš
The aim of this study was to develop a simple method for evaluation of the pungency in chili peppers with a glassy carbon electrode modified using phospholipid membrane prepared from asolectin. For these purposes cyclic voltammetry (CV) and differential pulse voltammetry (DPV) have been used. A few different methods have been tested: direct method, transfer method on unmodified and modified electrode, using standard addition method as well as calibration curve method. A statistically significant correlations with the results of the reference HPLC method have been found in case of voltammetric methods, especially in DPV with asolectin modified electrode.
Voltammetric Determination of Tumor Biomarkers using Flow Injection Analysis with Amperometric Detection
Němečková-Makrlíková, Anna ; Matysik, F.-M. ; Navrátil, Tomáš ; Barek, J. ; Vyskočil, V.
Three tumor biomarkers (homovanillic acid, vanillylmandelic acid, and 5-hydroxyindole-3-acetic acid) have been determined by flow injection analysis with amperometric detection at screen-printed carbon electrodes in optimum medium of Britton-Robinson buffer (0.04 mol l(-1), pH = 2.0). Dependences of the peaks current on the concentration of biomarkers were linear in the tested concentration region from 0.05 to 100 mu mol l(-1), with the limits of detection of 0.065 mu mol l(-1) for homovanillic acid, 0.053 mu mol l(-1) for vanillylmandelic acid, and 0.033 mu mol l(-1) for 5-hydroxyindole-3-acetic acid (calculated from heights), and 0.024 mu mol l(-1) for homovanillic acid, 0.020 mu mol l(-1) for vanillylmandelic acid, and 0.012 mu mol l(-1) for 5-hydroxyindole-3-acetic acid (calculated fromareas), respectively.
HPLC-ED/UV for determination of vanillylmandelic acid in human urine after solid phase extraction
Němečková-Makrlíková, Anna ; Dejmková, H. ; Navrátil, Tomáš ; Barek, J. ; Vyskočil, V.
HPLC with electrochemical and spectrophotometric detection (ED/UV) after solid phase extraction (SPE) was used for determination of vanillylmandelic acid in human urine. HPLC-ED was performed at a glassy carbon electrode in a “wall-jet” arrangement in acetate-phosphate buffer at pH = 2.5 and gradient elution (increasing content of\nacetonitrile from 5 to 25% in 10 minutes) was used. Optimized parameters were following: flow rate of mobile phase 1 mL min−1, detection potential +1.1 V, detection wavelength 279 nm, injected volume 20 μL. Dependence of the peak current on the analyte concentration was linear in the concentration range from 10 to 150 μmol L−1, with obtained limits of detection 2.6 μmol L−1 (calculated from peak height) and 1.9 μmol L−1 (calculated from peak area) for HPLC-ED, and 11.0 μmol L−1 (calculated from peak height) and 9.8 μmol L−1 (calculated from peak area) for HPLC-UV.

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1 Navrátil, T.
1 Navrátil, Tadeáš
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