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The Use of Silver Rotating Disk Electrode to Suppress Passivation During Voltammetric Determination of 4-Nitrophenol
Pitřinec, Jakub ; Fischer, Jan (advisor) ; Vyskočil, Vlastimil (referee)
In this bachelor's thesis results of the optimization of the measurement of 4-nitrophenol (1·10-4 mol·l-1 ) in the Britton-Robinson (BR) buffer medium on the silver rotating disk electrode are presented with the aim of suppressing the passivation of the electrode surface. The parameters of the differential pulse voltammetry (DPV) technique were optimized for the analytical use of the rotating disk electrode. In BR buffer pH 4,0 and at the electrode rotation speed of 250 rpm calibration dependences of 4-nitrophenol was obtained in the range of (1-10) ·10-5 mol·l-1 under selected optimal conditions and different methods of electrode surface pretreatment. The limit of quantification (LOQ) achieved with polishing before each measurement was 1,7·10-6 mol·l-1 and with polishing only before the concentration change was 8,8·10-6 mol·l-1 .
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Voltametric Determination of 4-Nitrophenol at a Bismuth Film Electrode
Hausner, Jiří ; Barek, Jiří (advisor) ; Dejmková, Hana (referee)
This Bachelor Thesis is focussed on the study of electrochemical behaviour of 4-nitrophenol (4-NP) and the search for optimal conditions for its voltammetric determination at a bismuth film-modified gold electrode (BiF-AuE). Voltammetric behaviour of 4-NP (c = 1×10-4 mol L-1 ) was investigated using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) in dependence on the pH of the medium used (Britton-Robinson buffers). For both techniques, Britton-Robinson buffer of pH 7.0 was chosen as the optimum medium. Repeatability of the determination of 4-NP (c = 1×10-4 mol L-1 ) was 0.6 % and 0.9 % for DCV and DPV, respectively. Calibration dependences of 4-NP were measured in the concentration range from 1×10-6 to 1×10-4 mol L-1 under the optimum conditions. Attained limits of quantification (LQs) were 7.6×10-7 mol L-1 and 1.5×10-6 mol L-1 for DCV and DPV, respectively. The applicability of the newly developed voltammetric methods for the determination of 4-NP was verified on model samples of drinking water with LQ 7.5×10-6 mol L-1 for DCV at the BiF-AuE and 1.4×10-6 mol L-1 for DPV at the BiF-AuE.
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Large-Surface Carbon Film Electrode - A Novel Sensor for Voltammetric Determination of Electrochemically Oxidizable Organic Compounds
Šmejkalová, Hana ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
of the Diploma Thesis In this Diploma Thesis, the electrochemical behavior of 4-nitrophenol (4-NP) was studied at a newly prepared large-surface carbon film electrode (ls-CFE) using techniques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) with the aim to develop sensitive analytical methods for its determination. Voltammetric behavior of 4-NP was investigated in the region of anodic potentials, in dependence on the pH of the medium used (realized using Britton-Robinson buffer). The optimum pH values for the determination of 4-NP were chosen as follows: pH 3.0 (for DCV) and pH 7.0 (for DPV). During anodic oxidation of 4-NP on the ls-CFE at the concentration of the analyte of 1·10-4 mol/l, the passivation of the electrode surface occurred. Thus, it was decided to record series of measurements always at a new carbon film. Using the sample of 4-NP (at the concentration of 1·10-4 mol/l), the repeatability of the application of individual carbon films was tested, with obtained RSD values of 3.7% and 3.6% for DCV and DPV, respectively. Under optimum conditions, the calibration dependences of 4-NP were measured in the concentration range from 1·10-6 to 1·10-4 mol/l, with the limits of quantification (LQs) of 1.5·10-6 mol/l (for DCV at the ls-CFE) and 4.6·10-7 mol/l (for DPV at the...
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New Methods of Oxygen Removal from Analyzed Solutions in Voltammetric Determination of Organic Compounds
Batěk, Jan ; Vyskočil, Vlastimil (advisor) ; Schwarzová, Karolina (referee)
The aim of this Bachelor Thesis was to verify new methods of oxygen removal from analyzed solutions in voltammetric determination of organic compounds. A method of chemical reduction was chosen to remove dissolved oxygen. Carbohydrazide, N,N-diethylhydroxylamine and 2-butanone oxime were used for removal of dissolved oxygen. These substances are used to remove oxygen from boiler systems. The last agent used to remove oxygen was sodium sulfite. Differential pulse voltammetry (DPV) was used to monitored the ability of oxygen scavengers. The effect of pH of the solution (Britton-Robinson buffer) on oxygen removal was also investigated. A solution of 4-nitrophenol at a concentration of 1∙10−4 mol∙l−1 was used as a model substance in these assays. We have found that carbohydrazide had no effect to remove oxygen in the whole pH range. Using sodium sulphite, oxygen was removed from the analyzed solution at pH 8, 10 and 12. Determination of 4-nitrophenol was thus possible. Using N,N-diethylhydroxylamine at pH 10 and 12 and 2-butanone oxime at pH 8, 10 and 12, oxygen was removed from the analyzed solutions. However, these substances are unsuitable for the determination of 4-nitrophenol.
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Large-Surface Carbon Film Electrode - A Novel Sensor for Voltammetric Determination of Electrochemically Oxidizable Organic Compounds
Šmejkalová, Hana ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
of the Diploma Thesis In this Diploma Thesis, the electrochemical behavior of 4-nitrophenol (4-NP) was studied at a newly prepared large-surface carbon film electrode (ls-CFE) using techniques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) with the aim to develop sensitive analytical methods for its determination. Voltammetric behavior of 4-NP was investigated in the region of anodic potentials, in dependence on the pH of the medium used (realized using Britton-Robinson buffer). The optimum pH values for the determination of 4-NP were chosen as follows: pH 3.0 (for DCV) and pH 7.0 (for DPV). During anodic oxidation of 4-NP on the ls-CFE at the concentration of the analyte of 1·10-4 mol/l, the passivation of the electrode surface occurred. Thus, it was decided to record series of measurements always at a new carbon film. Using the sample of 4-NP (at the concentration of 1·10-4 mol/l), the repeatability of the application of individual carbon films was tested, with obtained RSD values of 3.7% and 3.6% for DCV and DPV, respectively. Under optimum conditions, the calibration dependences of 4-NP were measured in the concentration range from 1·10-6 to 1·10-4 mol/l, with the limits of quantification (LQs) of 1.5·10-6 mol/l (for DCV at the ls-CFE) and 4.6·10-7 mol/l (for DPV at the...
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Voltametric Determination of 4-Nitrophenol at a Bismuth Film Electrode
Hausner, Jiří ; Barek, Jiří (advisor) ; Dejmková, Hana (referee)
This Bachelor Thesis is focussed on the study of electrochemical behaviour of 4-nitrophenol (4-NP) and the search for optimal conditions for its voltammetric determination at a bismuth film-modified gold electrode (BiF-AuE). Voltammetric behaviour of 4-NP (c = 1×10-4 mol L-1 ) was investigated using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) in dependence on the pH of the medium used (Britton-Robinson buffers). For both techniques, Britton-Robinson buffer of pH 7.0 was chosen as the optimum medium. Repeatability of the determination of 4-NP (c = 1×10-4 mol L-1 ) was 0.6 % and 0.9 % for DCV and DPV, respectively. Calibration dependences of 4-NP were measured in the concentration range from 1×10-6 to 1×10-4 mol L-1 under the optimum conditions. Attained limits of quantification (LQs) were 7.6×10-7 mol L-1 and 1.5×10-6 mol L-1 for DCV and DPV, respectively. The applicability of the newly developed voltammetric methods for the determination of 4-NP was verified on model samples of drinking water with LQ 7.5×10-6 mol L-1 for DCV at the BiF-AuE and 1.4×10-6 mol L-1 for DPV at the BiF-AuE.
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Voltammetric Determination of 4-Nitrophenol at a Large-Surface Carbon Film Electrode
Šmejkalová, Hana ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
The aim of presented Bachelor Thesis was to study an electrochemical behavior of 4-nitrophenol (4-NP) resulting in the founding of optimum conditions for its determination at newly prepared large-surface carbon film electrode (ls-CFE) using DC voltametry (DCV) and differential pulse voltammetry (DPV). Voltammetic behavior of 4-NP was investigated in dependence on the pH of the medium (realized using Britton-Robinson buffer). As optimum pH values for voltammetric determination of 4-NP at ls-CFE in cathodic potentials region, the pH values 6.0 (for DCV) and 7.0 (for DPV) were chosen. The determinations of 4-NP at ls-CFE (at a concentration of the analyte of 1·10-4 mol/l) showed a good repeatability for both voltammetric techniques used (2.2 % for DCV and 0.4 % for DPV). Therefore, the possibility of an electrochemical regeneration of the electrode surface has not been further investigated. Under optimum conditions, the calibration dependences of 4-NP were measured in the concentration range from 2·10-6 to 1·10-4 mol/l, with limits of quantification (LQ) of 2.3·10-6 mol/l (for DCV at ls-CFE) and 1.8·10-6 mol/l (for DPV at ls-CFE). The applicability of the newly developed methods of the determination of 4-NP was verified on the model samples of drinking water, with LQ of 1.0·10-6 mol/l (for DCV at...
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