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Determination of arbutin using carbon paste electrode
Libánský, Milan ; Zima, Jiří (advisor) ; Navrátil, Tomáš (referee)
This bachelor thesis concerns to the optimization of the conditions for the determination of hydroquinone-β-D-glucopyranoside (arbutin) by the differential pulse voltammetry on carbon paste electrode. From the dependence of peak heights on the pH, buffer of pH 2 was selected as the optimum medium. In this media, concentration dependences were measured and detection limit and quantification limit of 0.73×10-6 mol/l and 2.42×10-6 mol/l, respectively, were obtained. The possibility of further increase of the sensitivity of determination by the accumulation step was studied, but the accumulation of arbutin was not observed even after ten minutes. The developed method for the determination of arbutin was verified by its determination in the real sample of the cosmetic cream. Results of extraction of arbutin to methanolic and aqueous solution were studied. Concentration of the analyte was determined by standard addition method. In the case of methanolic solution, very good repeatability of the measurements and agreement of the determined and declared content of arbutin in the cream was found. In the aqueous solution much lower amount of arbutin was found, probably due to incomplete extraction of the analyte.
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Silver Amalgam Electrodes in Electroanalysis of Selected Agrochemicals
Daňhel, Aleš ; Barek, Jiří (advisor) ; Vytřas, Karel (referee) ; Ludvík, Jiří (referee)
4 ABSTRACT Development and testing of novel non-toxic electrode materials, detection arrangements and analytical methods applicable in determination of selected agrochemicals is the main aim of this Ph.D. Thesis. New working electrodes based on silver solid amalgam paste (AgSA-PE) with organic pasting liquid and other based on crystallic silver amalgam (CAgAE) were developed, their electrochemical behaviour investigated and further used in voltammetric determination of widespread and toxic environmental pollutant 4-nitrophenol (4-NP). This analyte could be determined by DPV at AgSA-PE with limit of detection (LD) 1×10í6 mol lí1 and using CAgAE with LD 4×10í7 mol lí1 , both in 0.2 mol lí1 acetate buffer pH 4.8. Attempts to decrease LDs by utilization of adsorptive stripping voltammetry were not successful in either case. Crystallic silver amalgam was also successfully used for construction of microcylindric flow-through cell and tested for amperometric determination of nitrophenol mixture in HPLC-ED system. Both novel electrodes were found to be suitable alternatives to toxic mercury electrodes and the CAgAE seems to be promising working electrode for flowing systems. Method for sample preparation and voltammetric determination of broad-spectrum herbicide Glyphosate in contaminated soil samples was also...
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Novel Electrochemical Biosensor for the Detection of DNA Damage Caused by Chemical Carcinogens
Blašková, Marta ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
Presented Bachelor Thesis is focused on the development and utilization of a simple and inexpensive electrochemical DNA biosensor for the detection of DNA damage caused by chemical carcinogens. A glassy carbon electrode (GCE), having several advantages such as broad potential window and well-renewable surface, was used for its preparation. A low- molecular-weight DNA isolated from salmon sperm was used. The initial part of the work is devoted to the optimization of the biosensor preparation and to its characterization, which was performed using several electrochemical techniques - cyclic voltammetry (CV), square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). The influence of the DNA immobilization type on the quality of the biosensor response was also investigated. Two approaches were tested: (i) spontaneous adsorption of DNA by leaving the DNA stock solution to dry on the GCE surface and (ii) adsorptive accumulation of DNA on the GCE surface from the solution (selected as the optimum one). The second part of this Thesis deals with the detection of DNA damage by various chemical carcinogens. Four model substances were tested: flutamide (an antiandrogen antitumor drug), 4-nitro-3-(trifluoromethyl)aniline (NTMA; a metabolite of flutamide), 2-aminoanthracene (a genotoxic...
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Voltammetric Determination of 5-Nitrobenzimidazole at a Silver Amalgam Paste Electrode
Chládková, Barbora ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
This bachelor's thesis concerns the determination of 5-nitrobenzimidazole (5-NBIA) by the methods DC voltammetry (DCV) and differential pulse voltammetry (DPV). A silver amalgam paste electrode (AgA-PE), which was prepared for this determination in the laboratory, was used as a working electrode. The optimum conditions for voltammetric determination of 5-NBIA were found and under these conditions, concentration dependences were measured and the limits of quantification (LQ) were calculated for each method. The media of BR-buffer pH 7.0 and pH 5.0 were chosen as optimum for DCV determination of 5-NBIA at AgA-PE and DPV determination of 5-NBIA at AgA-PE, respectively. For both DCV and DPV, the linear concentration dependences were obtained in concentration ranges of 5-NBIA from 2 × 10-7 mol/l to 1 × 10-4 mol/l. The attained LQ were found to be 6 × 10-7 mol/l (for DCV at AgA-PE) and 2 × 10-7 mol/l (for DPV at AgA-PE).
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Voltammetric determination of drugs doxycycline and dimenhydrinate using carbon film electrode
Humpolíková, Jiřina ; Fischer, Jan (advisor) ; Dejmková, Hana (referee)
This bachelor's thesis concerns the determination of doxycycline (DX) and dimenhydrinate (DMH) by the methods DC voltammetry (DCV) and differential pulse voltammetry (DPV) on a carbon film electrode (CFE). The optimum conditions for voltammetric determination of DX and DMH were found and under these conditions, concentration dependences were measured and the limits of quantification (LOQ) were calculated for each method. The media of BR-buffer pH 12.0 was chosen as optimum for DCV and DPV determination of DX at CFE. For both DCV and DPV, the linear concentration dependences were obtained in concentration ranges of DX from 20 µmol·l-1 to 100 µmol·l-1 with LOQ 15,4 µmol·l-1 for DCV and 15,2 µmol·l-1 for DPV. DX was determined in drug using DCV under optimized conditions and for comparison of used voltammetric method DX in drug was determined also using UV-VIS spectrophotometry with consistent results. The optimum medium of BR buffer pH 3.0 was chosen for determination of DMH by DCV and pH 2.0 for DPV. The calibration range 2,0 - 10,0 µmol·l-1 of DMH was received using DCV and 0,2 - 1,0 µmol·l-1 of DMH was recevied using DPV at CFE with reached LOQ 0,08 µmol·l-1 for DCV and 0,02 µmol·l-1 for DPV. DMH was determined in comertional drugs using DCV on founded conditions. The stability of stock solution...
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Voltammetric Determination of Genotoxic 4-Nitroindane at Mercury and Silver Amalgam Electrodes
Burdová, Vendula ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
Presented Diploma Thesis is focused on electroanalytical determination of genotoxic 4-nitroindane, one of the nitrated polycyclic aromatic hydrocarbons (NPAHs). A hydrocarbon indane (a component of petrol) is a precursor of 4-nitroindane. NPAHs are produced all above by combustion processes in gasoline and diesel engines. It has been shown that NPAHs can be many times more mutagenic or carcinogenic than their parent PAHs, so the analysis of these dangerous pollutants becomes important for modern environmental analytical chemistry. Optimal conditions for determination of 4-nitroindane have been investigated in buffered water-methanolic solutions and electrochemical transformations of 4-nitroindane have been studied by DC voltammetry (DCV), differential pulse voltammetry (DPV) and cyclic voltammetry at a hanging mercury drop electrode (HMDE) and at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE). For voltammetric determination of 4-nitroindane, the following techniques were used: DCV (limit of quantification (LQ) ~ 7. 10-8 mol. l-1 ), DPV (LQ ~ 1. 10-7 mol. l-1 ) and adsorptive stripping voltammetry (AdSV; LQ ~ 7. 10-9 mol. l-1 ) at HMDE, and DCV (LQ ~ 1. 10-7 mol. l-1 ) and DPV (LQ ~ 1. 10-7 mol l-1 ) at m-AgSAE. The applicability of the newly developed...
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Voltammetric Determination of 4-Nitrobiphenyl at a Mercury Meniscus Modified Silver Solid Amalgam Electrode
Horáková, Eva ; Schwarzová, Karolina (referee) ; Barek, Jiří (advisor)
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 Flutamide at Screen-Printed Carbon Electrodes
Škvarla, Juraj ; Fischer, Jan (referee) ; Vyskočil, Vlastimil (advisor)
The paper deals with the electrochemical behaviour of flutamide at screen-printed carbon electrodes (SPCE) with the aim of optimizing conditions for their practical use in the in situ analyses. A stability of stock solution was verified and confirmed primarily. Then, an influence of pH, stirring time and flutamide concentration in the analyzed solution on the voltammetric behavior of flutamide were systematically studied using DC voltammetry and differential pulse voltammetry at SPCE. One well-developed voltammetric peak of flutamide was detected in the whole pH region investigated. The time of stirring appears to be of crucial importance for the result of measurements at all pHs. The longer time of stirring of the solution prior to measurements, the higher is the flutamide peak. Therefore, the time of stirring was set constant for the rest of measurements. The optimum conditions for voltammetric determination have been found in Britton-Robinson buffer pH 7.0 - methanol (9:1) for both DCV and DPV at SPCE. Concentration dependences were found to be linear for the range 1·10-6 - 1·10-4 mol·dm-3 and evaluable (but not reliable) up to 1·10-7 mol·dm-3 . Reached limits of quantification were 6·10-7 mol·dm-3 for DCV at SPCE and 8·10-7 mol·dm-3 for DPV at SPCE. The determination of flutamide in...
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Voltammetric Determination of Metronidazol at a Polished Silver Solid Amalgam Composite Electrode
Škvorová, Lucie ; Zima, Jiří (referee) ; Barek, Jiří (advisor)
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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