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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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Study of electrochemical behaviour of tauroursodeoxycholic acid at mercury-based electrodes
Pišnová, Kateřina ; Schwarzová, Karolina (advisor) ; Navrátil, Tomáš (referee)
This thesis deals with electrochemical behaviour of tauroursodeoxycholic acid (TUDCA) at silver solid amalgam electrode modified by mercury meniscus (m-AgSAE), polished silver solid amalgam electrode (p-AgSAE) and hanging mercury dropping electrode (HMDE). This thesis is a part of a bigger scientific research that deals with synthesis and characterization of supramolecular systems based on natural steroid compounds and its conjugates. TUDCA offers one reduction peak at m-AgSAE in the environment of Britton - Robinson buffer in range of pH 6.0 - 13.0. The potential of this peak is around −1200 mV. Using cyclic voltammetry was determined that the process on the electrode surface is quasireversible, the reduction is controlled by diffusion and the anodic process is controlled by adsorption. Concentration dependence measured at HMDE by direct current voltammetry in 0.04 mol∙l-1 borat buffer (pH 9.1) is linear in two concentration intervals - 1∙10-3 - 2∙10-4 mol∙l-1 and 1∙10-4 - 8∙10-6 mol∙l-1 of TUDCA. There was no linear dependence between the increase of concentration of TUDCA and the height of the peak obtained on amalgam electrodes by methods DC, DP, cyclic and "square-wave" voltammetry. On HMDE was in several short concentration intervals measured by a CV method a linear dependence of cathodic and...
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Electrochemical reduction of dehydrocholic and chenodeoxycholic acid at stationary mercury and amalgam electrodes
Patáková, Adéla ; Schwarzová, Karolina (advisor) ; Vyskočil, Vlastimil (referee)
This thesis deals with the study of electrochemical behaviour of dehydrocholic and chenodeoxycholic acid at stationary mercury-based electrodes - hanging mercury dropping electrode and silver solid amalgam electrode modified by a mercury meniscus. This is the first study of electrochemical behaviour of dehydrocholic acid which offers tree peaks with potentials around -1270 mV, -1450 mV and -1800 mV. The last one with the potential -1800 mV is probably the main peak given by reduction of carboxylic group of side chain of steroid skeleton. By cyclic voltammetry was determined that the process is quasireversible and is strongly influenced by adsorption of DHCA on the electrode surface and also by the pH which determines dissociation degree of carboxylic group. In the environment of BR buffer (pH 7.0) - methanol (9:1) was measured concentration dependence by DC, DP and "square-wave" voltammetry. By neither one of these methods have been reached satisfying limits of detection and wide linear dynamic ranges. However, the repeatable signals in wide range of pH can be used for electrochemical characterization of DHCA. CDCA offers in environment 0,04 mol·l-1 borat buffer (pH 9.1) - methanol (9:1) one signal with potential around -1350 mV. Position of this peak on the potential axe and also its height are...
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Electrochemical reduction of dehydrocholic and chenodeoxycholic acid at stationary mercury and amalgam electrodes
Patáková, Adéla ; Schwarzová, Karolina (advisor) ; Vyskočil, Vlastimil (referee)
This thesis deals with the study of electrochemical behaviour of dehydrocholic and chenodeoxycholic acid at stationary mercury-based electrodes - hanging mercury dropping electrode and silver solid amalgam electrode modified by a mercury meniscus. This is the first study of electrochemical behaviour of dehydrocholic acid which offers tree peaks with potentials around -1270 mV, -1450 mV and -1800 mV. The last one with the potential -1800 mV is probably the main peak given by reduction of carboxylic group of side chain of steroid skeleton. By cyclic voltammetry was determined that the process is quasireversible and is strongly influenced by adsorption of DHCA on the electrode surface and also by the pH which determines dissociation degree of carboxylic group. In the environment of BR buffer (pH 7.0) - methanol (9:1) was measured concentration dependence by DC, DP and "square-wave" voltammetry. By neither one of these methods have been reached satisfying limits of detection and wide linear dynamic ranges. However, the repeatable signals in wide range of pH can be used for electrochemical characterization of DHCA. CDCA offers in environment 0,04 mol·l-1 borat buffer (pH 9.1) - methanol (9:1) one signal with potential around -1350 mV. Position of this peak on the potential axe and also its height are...
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Study of electrochemical behaviour of tauroursodeoxycholic acid at mercury-based electrodes
Pišnová, Kateřina ; Schwarzová, Karolina (advisor) ; Navrátil, Tomáš (referee)
This thesis deals with electrochemical behaviour of tauroursodeoxycholic acid (TUDCA) at silver solid amalgam electrode modified by mercury meniscus (m-AgSAE), polished silver solid amalgam electrode (p-AgSAE) and hanging mercury dropping electrode (HMDE). This thesis is a part of a bigger scientific research that deals with synthesis and characterization of supramolecular systems based on natural steroid compounds and its conjugates. TUDCA offers one reduction peak at m-AgSAE in the environment of Britton - Robinson buffer in range of pH 6.0 - 13.0. The potential of this peak is around −1200 mV. Using cyclic voltammetry was determined that the process on the electrode surface is quasireversible, the reduction is controlled by diffusion and the anodic process is controlled by adsorption. Concentration dependence measured at HMDE by direct current voltammetry in 0.04 mol∙l-1 borat buffer (pH 9.1) is linear in two concentration intervals - 1∙10-3 - 2∙10-4 mol∙l-1 and 1∙10-4 - 8∙10-6 mol∙l-1 of TUDCA. There was no linear dependence between the increase of concentration of TUDCA and the height of the peak obtained on amalgam electrodes by methods DC, DP, cyclic and "square-wave" voltammetry. On HMDE was in several short concentration intervals measured by a CV method a linear dependence of cathodic and...
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The study of electrochemical reduction of chenodeoxycholic acid at stationary mercury-based electrodes
Patáková, Adéla ; Schwarzová, Karolina (advisor) ; Fischer, Jan (referee)
Chenodeoxycholic acid is the most common representative of bile acids in the human body. This work studies its electrochemical reduction at stationary mercury- based electrodes using the DC voltammetry and differential pulse voltammetry. These were performed on a silver solid amalgam electrode modified by a mercury meniscus (m-AgSAE) and a hanging mercury drop electrode (HMDE). On the scale of pH 4.0 - 12.0 offers CDCA one reduction signal in the area of highly negative potentials around −1400 mV. There is a distinctive change in the behavior of CDCA for buffers of pH lower than 6.0, compared to other pH values. This change is observable on both m-AgSAE and HMDE through the DC voltammetry and DPV methods. This happens due to protonization of carboxyl group on C24. This change is strongest with pH of 4.0. For that reason, CDCA was studied in two environments - a 0.04 mol.l−1 borat buffer (pH 9.1) - methanol (9:1) and in a BR buffer (pH 4.0) - methanol (9:1). In both environments, the lowest detection threshold has been reached through the DC voltammetry method on HMDE. The cyclic voltammetry method was used to study the electrode process. Again, measuring in pH 9.1 and pH 4.0 was done. For pH 9.1, this is a quasireversible process controlled by adsorption of both electrodes studied. For pH 4.0 is...
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The use of mercury electrodes to determine tauroursodeoxycholic acid
Pišnová, Kateřina ; Schwarzová, Karolina (advisor) ; Dejmková, Hana (referee)
This thesis is devoted to the study of reduction of Tauroursodeoxycholic acid (TUDCA) on mercury electrodes - on the hanging mercury drop electrode and a mercury electrode, using polarographic (difference pulse polarography (DPP), direct current tast polarography (DCTP)) and voltammetric (difference pulse voltammetry (DPV), adsorptive stripping differential pulse voltammetry (AdS-DPV)) techniques. TUDCA is a conjugate of ursodeoxycholic acid and taurine, which is used as medication. It was discovered that TUDCA gives a single peak (wave) and the potential of this peak (half-wave potential) is about -1200 mV. The most sensitive method used was DP voltammetry, which has limit od detection 3,17.10 6 mol.l 1 and limit of quantification 1,05.10 5 mol.l 1 , as it has a much lower limit of detection (2,96.10 7 mol.l 1 ) and limit of quantification (9,87.10 7 mol.l 1 ) than DP polarography. In applying AdS-DPV method the peak height was increased only by about 20 %, therefore this method was evaluated as analytically unbeneficial for this measurement. It was discovered that the methods used for the characterization of the electrode happening are controlled by adsorption and are quasi-reversible; probably is reduced proton of sulfonic group. Furthermore, it was discovered that TUDCA does not interfere with...
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Voltammetric Determination of the Explosive Penthrite
Vyvadil, Jan ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
This Bachelor Thesis is focused on the investigation of voltammetric behavior of the explosive penthrite (pentaerythritol tetranitrate) (PETN) and on searching for optimum conditions for its determination using differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE). Mixtures of Britton-Robinson buffer (BR-buffer) and methanol in a volume ratio of 9:1 were used as supporting electrolytes in the investigation of voltammetric behavior of PETN in aqueous-methanolic media, and methanolic solutions of tetramethylammonium bromide (TMAB) and tetrabutylammonium chloride (TBAC) were used for investigations in non-aqueous (methanolic) media. Initially, the study of the influence of pH on voltammetric behavior of PETN was performed. Three pH values of the BR-buffer were chosen as suitable: 2.0, 6.0, and 9.0. At these pH values, the influence of the content of methanol in a supporting electrolyte on the voltammetric response of PETN was measured. At all three pH values, the best responses were obtained at a volume ratio of the BR-buffer and methanol of 9:1 or at a 100% content of methanol (here, TMAB and TBAC methanolic supporting electrolytes were tested and TMAB was selected as the optimum one). Concentration dependences were measured in five different media (in the concentration...
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The Use of Chemically Modified Electrodes in Voltammetric Analysis of Nitroaromatic Compounds
Prchal, Vít ; Vyskočil, Vlastimil (advisor) ; Navrátil, Tomáš (referee)
The main objective of this Diploma Thesis is studying the possibility of detection of nitro derivatives of aromatic hydrocarbons by using chemically modified working electrodes in electrochemical analysis. Compounds analyzed in this work were 1-nitronaphthalene and 6- nitrochrysene - these compounds were chosen on previous experience with surface modified working electrodes (the chemical/physical properties of these substances). All the analyses were performed by using differential pulse voltammetry (DPV) on hanging mercury drop electrode (HMDE) in classic three-electrode system. The original premise of chemical modification of electrode surface is the change of its selectivity towards different compounds - meaning the change of the electrochemical response. The modification agent used in this thesis is 1-octanethiol. Its thiol group offers great potential of strong interaction with the metal surface of the mercury electrode. Voltammetric responses of both compounds were recorded in acidic, neutral and basic solutions (pH=2, pH=7, pH=12) including the responses when the electrode surface was modified. Next objective was the optimization of the modification procedure itself (transferring of the mercury drop from one media to another without damaging or tearing it off from the capillary orifice)....
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Voltammetric Determination of Herbicide Aclonifen Using Mercury Electrodes
Murcková, Klára ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
Presented Diploma Thesis is focused on electroanalytical determination of the herbicide Aclonifen, which belongs to a group of herbicides derived from diphenylether. These herbicides are used due to their effects - inhibition of protoporfyrinogen oxidase synthesis and also inhibition of biosynthesis of carotenoids. Due to its widespread use in agricultural, toxical effects on humans and because of its negative impacts particularly on aquatic ecosystems there is a need for methods capable of determining the presence of Aclonifen in the environment to monitor its ecological impacts. Optimal conditions for the determination of Aclonifen have been investigated in BR buffer - methanolic solution and in BR buffer. Electrochemical behavior of the substance has been studied using direct current voltammetry (DCV), differential pulse voltammetry (DPP) and adsorptive stripping voltammetry (AdSV) on the hanging mercury drop electrode (HMDE) and by using TAST polarography and differential pulse polarography (DPP) on the dropping mercury electrode (DME). UV/VIS spectrophotometric detection was used for comparison to electrochemical detection. Used wavelengths were 308 nm and 388 nm. For electrochemical determination of Aclonifen the above mentioned techniques were used and following results were obtained: DCV...
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