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Voltammetric Determination of 4-Nitrobiphenyl at a Mercury Meniscus Modified Silver Solid Amalgam Electrode
Horáková, Eva ; Barek, Jiří (advisor) ; Schwarzová, Karolina (referee)
The presented bachelor thesis is devoted to study of electrochemical behavior of 4-nitrobiphenyl (4-NBP) and to finding of optimum conditions for its' determination using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE). The aim was to achieve the lowest possible limit of determination and to verify the applicability of the newly developed method for determination of 4-NBP in model samples of drinking water. Methanol-acetate buffer pH 4,8 (3:7) was found as an optimum medium for the determination of 4 NBP at a m-AgSAE in deionized water. During DCV it is not necessary to apply electrochemical regeneration of the working electrode, during DPV it is proper to apply following regeneration potentials: Ereg,1 = 0 mV, Ereg,2 = -1300 mV. The concentration dependence of the peak current was found to be linear for both methods for 10-5, 10-6 and 10-7 mol∙l-1 concentration ranges. The limit of determination of 4-NBP both by DCV and by DPV is 2∙10-7 mol∙l-1. The optimum medium for the determination of 4-NBP in drinking water is the mixture of the sample and acetate buffer pH 4,8 in the 9:1 ratio.. During DCV regeneration was not applied, during DPV it was applied with the following regeneration potentials: Ereg,1...
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Voltammetric Determination of Diafenthiurone Using Carbon Paste Electrode
Markvart, Jan ; Barek, Jiří (advisor) ; Zima, Jiří (referee)
In this bachelor thesis voltammetric behavior of Diafenthiuron using carbon paste electrode was investigated. Methodes used in this thesis were differential pulse voltammetry, cyclic voltammetry and DC voltammetry. Britton-Robinson buffer of optimal pH in mixture with methanol was used as a base electrolyte. Optimal pH of Britton-Robinson buffer was pH 3 for DC voltammetry and cyclic voltammetry and pH 5 for differential pulse voltammetry. Under optimal conditions limit of detection and limit of quantification for differential pulse voltammetry and DC voltammetry in 50% methanol were estimated. For differential pulse voltammetry detection limit was found to be 1,5* 10-5 mol/l and quantification limit was found to be 5* 10-5 mol/l. For DC voltammetry the detection limit was 1,7* 10-5 mol/l and quantification limit was 5,8* 10-5 mol/l.
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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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Voltammetric Determination of Metronidazol at a Polished Silver Solid Amalgam Composite Electrode
Škvorová, Lucie ; Barek, Jiří (advisor) ; Zima, Jiří (referee)
The aim of this work was to find out the optimal conditions for voltammetric determination of metronidazole, which is used as an anti-tumor drug. The stability of stock solution of metronidazole in deionized water was monitored using UV-VIS absorption spectrophotometry. Optimum conditions for voltammetric determination of metronidazole at a polished silver solid amalgam composite electrode (p-AgSA-CE) have been investigated. The dependence of voltammetric behavior of metronidazole (1∙10-4 mol/L) on pH of analyzed solution has been investigated using DC voltammetry (DCV) and differential pulse voltammetry (DPV) in the pH range 2,1 - 12,1 in aqueous media of Britton- Robinson (BR) buffer. For electrochemically reducible nitro group of metronidazole, the mechanism of voltammetric reduction at p-AgSA-CE was proposed. The optimum medium of aqueous BR buffer pH 4.0 was chosen for measuring the concentration dependences for both voltammetric techniques. The concentration range 2∙10-6 - 1∙10-4 mol/L of metronidazole was measured using DCV and DPV at p-AgSA-CE with reached limits of quantification (LQs) 2∙10-6 mol/L and 4∙10-6 mol/L for DCV and DPV, respectively. For comparison of used voltammetric techniques with supplemental analytical method, the concentration range 2∙10-6 - 1∙10-4 mol/L of metronidazole...
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