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Contribution to the use of new types of carbon paste and fiber electrodes for voltammetric and amperometric determination of 5-amino-6-nitroquinoline and resveratrol
Němcová, Lenka ; Zima, Jiří (advisor) ; Vytřas, Karel (referee) ; Navrátil, Tomáš (referee)
7 ABSTRACT (EN) This dissertation thesis is focused on the study of electrochemical properties of new types of carbon paste electrodes (CPE) and carbon fiber rod electrodes (CFRE), which were used for the development of new highly sensitive and selective voltammetric and amperometric methods for the determination of 5-amino-6-nitroquinoline and trans- and cis- isomers of resveratrol. The carbon paste electrodes were compared in terms of size of the microparticles of glassy carbon contained in the paste (diameters 0.4 - 12 µm; 10 - 20 µm; 20 - 50 µm) in comparison with carbon paste electrode consisting of crystalline graphite and solid glassy carbon electrode. The electrochemical properties were tested using potassium hexacyanoferrate in an aqueous supporting electrolyte and 5-amino-6-nitroquinoline (5A6NQ) in a mixed methanol-water supporting electrolyte. The carbon paste electrode was further used in an amperometric detector of a wall-jet type connected in series with a spectrophotometric detector for the development of a new HPLC method with electrochemical detection and spectrophotometric detection for the determination of trans-resveratrol and cis-resveratrol in samples of grains, hulls and leaves of common and tartary buckwheat. The method was optimized and used for the determination of resveratrol in...
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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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Voltammetric Determination of 5-Nitroindazole Using Hanging Mercury Drop Electrode Different Electrode and Polished Silver Solid Amalgam Electrode
Hrdlička, Vojtěch ; Navrátil, Tomáš (advisor) ; Zima, Jiří (referee)
The presented Bachelor Thesis deals with a study of electrochemical behavior of 5-nitroindazole (5-NI) with the search of optimal conditions for its determination using tech- niques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) at hanging mer- cury drop electrode (HMDE) and polished silver solid amalgam electrode (p-AgSAE), and with the comparison of reached limits of quantification (LQ ). The optimal conditions found for determination of 5-NI in deionized water using DPV at HDME were as follows: Britton-Robinson (BR) buffer of pH 8.0 and inital potential of +100 mV. The calibration dependences were measured in the concentration range from 1·10-7 to 1·10-5 mol·dm-3 with the LQ of 1.8·10-7 mol·dm-3 . Moreover, the posibility of using adsorbtion stirring voltametry (AdSV) for determination of 5-NI in BR buffer of pH 8 was investigated. The method was ineffective due to rising base- line. The mechanism of electrochemical reduction and oxidation in BR buffer of pH 8 at HMDE was investigated. It was found that the reduction of 5-NI was controlled by diffusion and the following oxidation was controlled by adsorbtion. For determination of 5-NI in deionized water using DVP at p-AgSAE, optimal conditions seemed to be as follows: BR buffer of pH 8.0 and initial potential of +100 mV....
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Electrochemical determination of 6-thioguanine at boron doped diamond film electrod
Humpolíková, Jiřina ; Fischer, Jan (advisor) ; Schwarzová, Karolina (referee)
This master's thesis is focused on the determination of 6-thioguanine (6-T) by DC voltammetry (DCV), differential pulse voltammetry (DPV) and flow injection analysis with electrochemical detection (FIA-ED) on a boron doped diamond electrode (BDDFE). The optimum conditions for determination of 6-T were found and under these conditions, concentration dependences were measured and the limits of quantification (LOQ) were calculated for each method. Medium of 60% methanol and phosphate buffer (PB) pH 2,0 was chosen as optimum for DCV and DPV determination of 6-T at BDDFE. For both DCV and DPV, the linear concentration dependences were obtained in concentration ranges of 6-T from 2 µmol·l-1 to 10 µmol·l-1 with LOQ 0,9 µmol·l-1 for DCV and 1,5 µmol·l-1 for DPV. Lower LOQ was achieved in PB pH 2,0, where LOQ was 0,6 µmol·l-1 for both DCV and DPV, but the problem was lower repeatability. In PB pH 2 6-T was determined by DCV in drinking and river water with LOQ 1,3 µmol·l-1 in both drinking and river water. The possibility of solid phase extraction was investigated as a method for preliminary separation of 6-T from urine. For FIA under optimized conditions (polarization potential 1300 mV, flow rate 5 ml·min1 and sample volume 50 µl) the linear concentrations dependences were obtained in concentration ranges...
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Electrolytes characterization based on mixtures of ionic liquids and aprotic solvents
Šašek, Martin ; Libich, Jiří (referee) ; Máca, Josef (advisor)
The thesis deals with liquid aprotic electrolytes based on mixtures of ionic liquid and solvent. EmimBF4, namely 1-ethyl-3-ethylimidazolium tetrafluoroborate, was used as the starting ionic liquid. A mixture of propylene carbonate, ethylene carbonate and dimethyl carbonate was used as solvents. Electrolytes were enriched with two electrolyte salts LiBF4 and NaBF4 from the resulting mixtures selected the most suitable electrolytes for Li-ion and Na-ion accumulators. Electrolytes were selected taking into account the required properties: the width of the potential window, the measured electrical conductivity and, last but not least, the safety.
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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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Determination of sulfamethizole using carbon paste electrodes
Mikeš, Miroslav ; Zima, Jiří (advisor) ; Vyskočil, Vlastimil (referee)
The proposed Thesis deals with the electrochemical behavior of sulfamethizole on carbon paste electrodes. Sulfamethizole is a sulfonamide antibiotic effective against a number of gram-positive and gram-negative bacteria. In human medicine, the most frequent application is for the treatment of urinary tract. In veterinary medicine, it is used for the and preventive treatment of both aquatic and terrestic animals. Due to the wide utilization and low metabolization, it also presents an environmental burden. The development of quick and sensitive methods for the determination in both biological and pharmaceutical matrices is therefore important. This Thesis deals with the search of optimum conditions for differential pulse voltammetric determination of sulfamethizole in tablets Micturol sedante, used for the treatment of urinary tract. The method uses Britton-Robinson (B-R) buffer pH 7 and reaches detection limit 0,39 µmol·l-1 . Results of the method complied with the manufacturer's information and with the results of spectrophotometric determination. In the other part of the work, conditions for the determination of sulfamethizole determination in urine samples. Fonund conditions were: Lichrospher® RP-18, 100 (5 µm), 125×4 mm, (LichroCART) column, mobile phase B-R buffer pH 3 : methanol (7:3, v/v) and...
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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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