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The use of mercury-based electrode materials for the study of electrochemical reduction of selected bile acids
Hulová, Dagmar ; Schwarzová, Karolina (advisor) ; Navrátil, Tomáš (referee)
The electrochemic's behaviour of the bile acids (cholic, glycocholic, deoxycholic, ursodeoxycholic and lithocholic acid) was studied on the meniscus-modified silver solid amalgam electrode (m-AgSAE) by differential pulse voltammery. Bile acids provide in the solution of the Britton - Robinson buffer and methanol (9:1) in the pH range 3.0 to 12.0 a cathodal signal in the high negative potentials: cholic acid, deoxycholic acid, ursodeoxycholic acid and lithocholic acid about −1400 mV and glycocholic acid, which alone is the conjugate with glycine, about −1500 mV. Cholic acid, glycocholic acid, deoxycholic acid and ursodeoxycholic acid provide the highest peaks to pH 5.0, approximately in their pKa values. Lithocholic acid provides peaks from pH 7.0. It was demonstrated by the cyclic voltammetry that the electrochemical behavior is influenced by the adsorption of the bile acids to the electrode; presumed reaction at the working electrode - a reduction of a proton of a carboxylic group, is controlled by the diffusion and the process is quasireversible. Utilization of the electrochemical reduction of bile acids for the voltammetric determination does not seem very suitable. It has been proven that the presence of the methanol deteriorates the measuring results for glycocholic acid. In the presence of...
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Determination of Lead Using FIA Technique with Spectrophotometric and Electrochemical Detection
Hála, Petr ; Vyskočil, Vlastimil (advisor) ; Rychlovský, Petr (referee)
The aim of this thesis was the determination of lead in water samples using complexating reaction with 4-(2-pyridylazo)-resorcinol in medium of 2-amino-2- hydroxymethyl-propan-1,3-diol hydrochloride buffer (Tris·HCl). Firstly, for the determination was chosen UV/VIS molecular spectrometry in a static arrangement. Subsequently, the method was performed in flow injection arrangement. The calibration was performed under optimal experimental conditions. The limits of detection for static and flow injection arrangements were 0.097 mol dm-3 and 0.27 mol dm-3 , respectively. Secondly, the determination of lead by differential pulse voltammetry was performed. The electrochemical properties of lead complex were investigated. During these experiments it was found out that small amount of this complex was adsorbed on the surface of silver solid amalgam electrode. The calibration was performed, the limit of detection was 0.020 mol dm-3 . Keywords Lead, 4-(2-pyridylazo)-resorcinol, flow injection analysis, UV/VIS molecular spectrometry, differential pulse voltammetry, silver solid amalgam electrode.
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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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Voltammetric Determination of 5-Nitroimidazole - The Structural Unit of Nitroimidazole Drugs
Šmídková, Monika ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
Presented Diploma Thesis deals with the study of electrochemical behavior of 5-nitroimidazole (5-NI), with the search for optimal conditions for its determination using techniques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) and at a boron-doped diamond film electrode (BDDFE), and with the comparison of reached limits of quantification (LQs). The optimal conditions found for measuring calibration dependences of 5-NI at the m-AgSAE in deionized water were as follows: Britton-Robinson buffer of pH 7.0 and 10.0 for DCV and DPV, respectively. At both thechniques, it is advisable to use an electrochemical regeneration of the electrode surface by the application of a couple of regeneration potentials Ereg,1 = 0 mV and Ereg,2 = −800 mV. The calibration dependences were measured in the concentration range from 1·10−6 to 1·10−4 mol·l−1 , with the LQs of 1.0·10−6 mol·l−1 for DCV at the m-AgSAE and 1.5·10−6 mol·l−1 for DPV at the m-AgSAE. The concentration dependences of 5-NI at the BDDFE were measured using the DCV technique in the BR buffer of pH 3.0. For the DPV technique, the optimal medium seemed to be the BR buffer of pH 2.0, however, because of the presence of an interfering peak in the supporting electrolyte,...
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Voltammetric Determination of Genotoxic Nitrobiphenyls
Horáková, Eva ; Vyskočil, Vlastimil (advisor) ; Navrátil, Tomáš (referee)
The presented diploma thesis is devoted to study of determination of 4-nitrobiphenyl (4-NBP) in model river water by DC voltammetry (DCV) and differential pulse voltammetry (DPV) at m-AgSAE (diploma thesis relates to bachelor thesis, in it DCV and DPV methods for determination of 4-NBP in deionized water were developed). Limit of determination (LOD) is 2·10-7 mol·l-1 by DCV and 4·10-7 mol·l-1 by DPV. The adsorptive stripping DPV (AdSDPV) technique was tested to archive lower LOD the AdSDPV, optimal conditions were not found. Electrochemical behavior of 2-nitrobiphenyl (2-NBP) at m-AgSAE was studied. Optimal conditions for its determination by both techniques DCV and DPV were found in methanol-0,01 mol·l-1 LiOH (1:9) and in this medium peak current dependence in 1·10-7 mol·l-1 to 1·10-4 mol·l-1 2-NBP (LOD ≈ 2·10-7 mol·l-1 by DCV and 1·10-7 mol·l-1 by DPV) concentration range was measured. Developed methods were successfully tested for determination of 2-NBP in drinking and river water samples. For both mediums obtained LODs were 2·10-7 mol·l-1 by DCV and 1·10-7 mol·l-1 by DPV. AdSDPV technique was unsuccessfully tested to achieve lower LOD. Optimal conditions for simultaneous determination of 4-NBP and 2-NBP by DPV technique at m-AgSAE were found: methanol-0,25 mol·l-1 acetate buffer (pH = 6,0) 3:7....
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Voltammetric Determination of Genotoxic 6-Nitrochrysene at a Mercury Meniscus Modified Silver Solid Amalgam Electrode
Šmídková, Monika ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
This Bachelor Thesis is devoted to the study of electrochemical behavior of 6-nitrochrysene (6-NCH) and to the finding of the 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). For measuring the concentration dependences of 6-NCH, the optimum medium methanol - BR buffer pH 9.0 (1:1) and the proper regeneration potentials Ereg,1 = 0 mV, Ereg,2 = -600 mV have been chosen for DCV at m-AgSAE and the medium methanol - BR buffer pH 10.0 (1:1) and the proper regeneration potentials Ereg,1 = 0 mV, Ereg,2 = -750 mV have been chosen for DPV at m-AgSAE. The concentration dependence was found to be linear only for the lowest concentration range of 10-7 mol·l-1 . In the concentration range of 10-6 mol·l-1 , the concentration dependences observed were polynomial. This result indicates a possible adsorption of 6-NCH on the surface of working electrode. Reached limits of quantification (LQ) were 1·10-7 mol·l-1 for DCV at m-AgSAE and 5·10-8 mol·l-1 for DPV at m-AgSAE. For comparison, the concentration dependence of 6-NCH was measured in methanol using UV-VIS spectrophotometry. Reached LQ ~ 1·10-7 mol·l-1 is comparable with LQs reached using DCV and DPV techniques.
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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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Use of the Silver Solid Amalgam Electrode for Determination of 5-Nitroindazole
Nováková, Kateřina ; Navrátil, Tomáš ; Hrdlička, V. ; Vyskočil, V. ; Barek, J. ; Chýlková, J.
The voltammetric behavior of 5- nitroindazole (5-NI) has been investigated using mercury meniscus modified (m-AgSAE) silver solid amalgam electrode (inner diameter 0.5 mm). Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were used for study of electrochemical behavior of 5-NI. Britton-Robinson buffer was found to be the best available supporting electrolyte for 5-NI determination. The reaction mechanism was investigated by CV and by elimination voltammetry with linear scan (EVLS). DPV with optimized working parameters was applied for analysis of model solutions containing 5-NI. The limit of detection was calculated as 0.14 mol L for m-AgSAE. Proposed method was successfully tested for analysis of real water samples spiked by 5-NI.
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Voltammetric Behavior of Folates and Related Substances Using Silver Solid Amalgam Electrode
Bandžuchová, L. ; Šelešovská, R. ; Navrátil, Tomáš ; Chýlková, J.
The possibility of application of silver solid amalgam electrode in voltammetric analysis of compounds with folate structure (folic acid, methotrexate, leucovorin) and substances, which play an important role in its metabolism (riboflavin, hydroxocobalamin) has been investigated. Cyclic voltammetry, DC voltammetry and Elimination voltammetry with linear scan has been used for study of voltammetric behavior of mentioned substances and for elucidation of electrochemical reactions. Differential pulse voltammetry has been applied for development of sensitive methods of determination for investigated electroactive compounds. The proposed methods were successfully applied for real samples analysis. Obtained results have been compared with those achieved using HMDE.
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