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Utilization of potential programs in flow electrochemical determination of biologically active organic compounds
Bavol, Dmytro ; Dejmková, Hana (advisor) ; Josypčuk, Bohdan (referee) ; Metelka, Radovan (referee)
9 Abstract In this Ph.D. thesis possibilities of using our proposed potential programs for a multiple-pulse amperometry and a fast scan differential pulse voltammetry in combination with flow systems are presented. The development of new sensitive amperometric and voltammetric methods for the determination of oxidisable biologically active organic compounds is another aim of this work. In the first part of the work, the flow injection system and multiple-pulse amperometric detection were employed to develop and optimize a simple, low-cost, and rapid method for the simultaneous determination of natural and synthetic antioxidants. This technique involves the application of an appropriate potential waveform consisting of a suitable sequence of pulses on a single working electrode, thus allowing distinguish the analytes in a mixture with no need of separation. Conditions for the determination of antioxidants and modelling of the potential program were tested and studied, respectively. Second part of the work describes and characterizes the application of the fast scan differential pulse voltammetry (FSDPV) in combination with the flow systems. FSDPV is the electroanalytical technique that use high scan rate to record voltammograms within several milliseconds and ensures high temporal resolution. This technique...
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Electrochemical oxidation of selected bile acids in acetonitrile
Habániková, Shannelle Diana ; Schwarzová, Karolina (advisor) ; Fischer, Jan (referee)
The concentration of bile acids is an important parameter in hepatobiliary tract diseases. This work deals with the electrochemical oxidation of the chenodeoxycholic (CDCA) and cholic acid (CA) at boron dopped diamond (BDD) electrode in comparison with the oxidation at glassy carbon (GCE) and platinum electrode (PtE), in a mixed environment of acetonitrile and water (0.26 % from 0.1 mol·l-1 HClO4, supporting electrolyte). The measurement was carried out in an electrochemical cell with salt bridge containing 0.5 mol·l-1 NaClO4 separating the working and the Pleskov's reference electrode (0.01 mol·l-1 AgNO3 and 1 mol·l-1 NaClO4 in acetonitrile). Cyclic voltammetry (CV) characterization of BDD electrode by a redox pair [Fe(CN)6]4-/3- (c = 0.1 mmol·l-1) in 1 mol·l-1 KCl was performed. Quasi-reversible behaviour was observed and the difference of the anodic and the cathodic peak potential ranged from 80 to 200 mV, depending on the scan rate. Alumina polishing (4 min) of the BDD electrode was identified as the most appropriate method of activating the surface and it was applied between consecutive voltammetric scans in the presence of CA and CDCA. Irreversible anodic peaks of CDCA and CA in acetonitrile-water (0.26 %) were observed at the relatively high potentials of about +1100 ± 100 mV, depending on...
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Novel Approaches in Electrochemical Determination of Xenobiotic Compounds and in Study of Their Interaction with DNA
Hájková, Andrea ; Vyskočil, Vlastimil (advisor) ; Trnková, Libuše (referee) ; Labuda, Ján (referee)
Presented Ph.D. Thesis is focused on the development of analytical methods applicable for determination of selected xenobiotic compounds and for monitoring DNA damage they can induce. The main attention has been paid to the development and testing of non-toxic electrode materials for preparation of miniaturized electrochemical devices and novel electrochemical DNA biosensors. 2-Aminofluoren-9-one (2-AFN) was selected as a model environmental pollutant, which belongs to the group of hazardous genotoxic substances. Its carcinogenic and mutagenic effects may represent a risk to living and working environment. 2-AFN has one oxo group, where the cathodic reduction occurs, and one amino group, where the anodic oxidation occurs. The voltammetric behavior of 2-AFN in the negative potential region was investigated at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) representing a non-toxic and more mechanically robust alternative to mercury electrodes. This working electrode was subsequently used for the development of a newly designed miniaturized electrode system (MES), which has many benefits as the possibility of simple field measurements, easy portability, and the measurement in sample volume 100 µL. Moreover, a glassy carbon electrode (GCE) was used for further investigation of...
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The Use of an Electrochemical DNA Biosensor in Detection of DNA Damage Caused by Genotoxic 2-Nitrofluorene
Stávková, Klára ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
2-Nitrofluorene is a model representative of nitrated polycyclic aromatic hydrocarbons (NPAH) which belongs to a group of mutagens and carcinogens. Interaction of DNA with genotoxic 2-nitrofluorene was monitored by an electrochemical DNA biosensor made of a glassy carbon electrode (GCE) and low molecular weight DNA from salmon sperm. Techniques used are electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and square-wave voltammetry (SWV). Using the EIS technique, no damage to DNA, which would cause strand breaks in DNA, was observed, whereas using the CV technique, the intercalation of NF to the structure of DNA was observed, leading to the formation of a NF-DNA complex. The intercalation results in a reduction of electroactive sites which can be oxidized. It was verified using the SWV technique, by which a decrease of the peak heights of adenosine and guanosine was observed. Because of the dangerous effect of NF on the structure of DNA, an electroanalytical method for its determination was developed. An applicability of the method was successfully tested on a model sample of sand. For the development of the technique, differential pulse voltammetry (DPV) was used in a mixture of the Britton-Robinson buffer of pH 7.0 and ethanol in a ratio of 7:3 (v/v) and with a periodic...
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Application of Antimony Film Electrodes for Determination of Pesticide Trifluralin
Gajdár, Július ; Fischer, Jan (advisor) ; Vyskočil, Vlastimil (referee)
Antimony film electrode was studied for the use in a voltammetric analysis of organic compounds. The substance chosen as an analyte was trifluralin, which is used as a pesticide. The comparison of different substrate electrodes was carried out between five electrodes, which were gold, silver, copper, polished amalgam and glassy carbon electrode (GCE). Best performance was observed on antimony film glassy carbon electrode (SbFGCE). It provided higher sensitivity and lower limit of quantification in comparison with bare GCE. The antimony film was stable and it provided good reproducibility (RSD = 5.2 %). Parameters of an electrochemical preparation of SbFGCE were optimized. Conditions for determination of concentration of trifluralin were optimized on newly prepared SbFGCE. The best conditions were in a solution of methanol and 0.1 M hydrochloric acid in 1:1 ratio measured by differential pulse voltammetry. The limit of quantification was determined as 1.2·10-6 mol·l-1 . A direct voltammetric measurement on SbFGCE was carried out in a model river sample. Lower limits of quantification were achieved with solid phase extraction (SPE). Recovery values were 86 ± 8 % in deionized water with a preconcentration factor of 125. The limit of quantification was lowered to value 1.1·10-8 mol·l-1 . The extraction...
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Utilization of carbon-based solid electrodes to electrochemical oxidation of acyclovir
Vaněčková, Eva ; Schwarzová, Karolina (advisor) ; Fischer, Jan (referee)
Electrochemical oxidation of acyclovir at glassy-carbone electrode and boron-doped diamond electrode gives one pH-dependent oxidation signal; the corresponding electrode reaction is controlled by diffusion. It is followed by a second indistinctive signal in the pH range 2,0 - 9,0. Further, optimization of conditions was carried out for determination of acyclovir using DC and DP voltammetry. The calibration dependence on GC electrode in B−R buffer (pH = 6,0) is linear only in the concentration range from 2 to 10 μmol∙l−1 for DCV with limit of detection 0,38 μmol∙l−1; for DPV it is not linear. BDD electrode has to be activated to prevent its passivation. Anodic activation at +2,4 V for 15 s with simultaneous stirring of solution results in relative standard deviation of 0,9% for acyclovir concentration of 1∙10−4 mol∙l−1. Using DCV and DPV methods linear concentration dependences were obtained in 0,1 mol∙l-1 nitric acid and in pH 6,0 B−R buffer. The lowest limit of detection and limit of quantification (LOD = 0,47 μmol∙l−1 a LOQ = 1,55 μmol∙l−1) and linear range from 0,6 to 100 μmol∙l−1 was reached in pH 6,0 B−R buffer. Further, standard addition method was used to quantify acyclovir in Zovirax tablets. Satisfactory recoveries of 101,1 ± 2,3 % using DCV and 98,8 ± 2,2 % using DPV at BDD (compared with the...
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The Use of a Simple Electrochemical DNA Biosensor for the Determination of Environmental Pollutants and Investigation of Their Interaction with DNA
Blašková, Marta ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
The interaction between three selected representatives of environmental pollutants - naphthalene, anthracene, and 2-aminoanthracene - and DNA was investigated using an electrochemical DNA biosensor based on a glassy carbon electrode (GCE) and low molecular weight DNA from salmon sperm (DNA/GCE). The interactions with DNA were monitored using square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). For naphthalene, there was no DNA damaging interaction observed. In the case of anthracene, the formation of an intercalation complex [DNA-anthracene] was observed. However, its formation does not cause DNA strand breaks. The formation of similar intercalation complex was observed for 2-aminoanthracene [DNA-2-aminoanthracene], where we suppose on the basis of the results obtained that the intercalation of 2-aminoanthracene into the DNA double helix induces a tension and subsequent formation of single-strand breaks, which cause that the fragments of DNA fall away from the electrode surface. The intercalative interaction of DNA with anthracene a 2-aminoanthracene was used in the development of electrochemical methods for determination of these compounds at the GCE and DNA/GCE. At the development of the methods, DC voltammetry (DCV) and differential pulse voltammetry (DPV) were used....
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Electrochemical Oxidation of Selected Bille Acids in Acetonitrile
Klouda, Jan ; Nesměrák, Karel (advisor) ; Rychlovský, Petr (referee)
The use of voltammetry for determining bile acids and similar compounds is described in literature, but in most cases separation precedes. The goal of this bachelor's thesis was to develop a method for direct determination and identification of seven selected bile acids. The experiments were carried out in non-aqueous medium of acetonitrile using DC voltammetry. As the working electrode a rotating disc platinum electrode and a rotating disc glassy carbon electrode were employed. Platinum electrode proved not to be suitable for this kind of use. The GCE on the other hand showed some potential, but the chemical properties of the bile acids exclude its use in terms of identification.
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Voltammetric Determination of 5-Nitrobenzimidazole Using Non-Traditional Electrode Materials
Chládková, Barbora ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
5 Abstract This Diploma Thesis is targeted on the determination of 5-nitrobenzimidazole (5-NBIA) using following techniques: DC voltammetry (DCV) and differential pulse voltammetry (DPV). As working electrodes, a silver amalgam paste electrode (AgA-PE), which was constructed for this determination in the form of a new prototype, a bismuth film electrode (BiFE), at which the optimum conditions for the deposition of the bismuth film at a suitable substrate (glassy carbon electrode and gold electrode were tested for this purpose) were initially optimized, and a glassy carbon electrode (GCE) were used. The optimum conditions for the voltammetric determination of 5-NBIA at the AgA-PE (in a medium of Britton-Robinson buffer (BR-buffer) of pH 7.0 for both DCV and DPV), at the BiFE with gold substrate (BR-buffer of pH 9.0 for both DCV and DPV; the film was deposited "ex situ" in a stirred plating solution (1000 mg L-1 Bi(III) solution in 0.1 mol L-1 acetate buffer of pH 4.5) for 300 s), and at the GCE (BR-buffer of pH 5,0 for both DCV and DPV). Under these conditions, calibration dependences were measured in the concentration ranges of 0.1 - 100 µmol L-1 (pro DCV a DPV na AgA-PE) and 1 - 100 µmol L-1 (pro DCV a DPV na BiFE a GCE), and the limits of quantification (LQs) were calculated for particular methods: LQ ≈...
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Novel Approaches in Electrochemical Determination of Xenobiotic Compounds and in Study of Their Interaction with DNA
Hájková, Andrea
Presented Ph.D. Thesis is focused on the development of analytical methods applicable for determination of selected xenobiotic compounds and for monitoring DNA damage they can induce. The main attention has been paid to the development and testing of non-toxic electrode materials for preparation of miniaturized electrochemical devices and novel electrochemical DNA biosensors. 2-Aminofluoren-9-one (2-AFN) was selected as a model environmental pollutant, which belongs to the group of hazardous genotoxic substances. Its carcinogenic and mutagenic effects may represent a risk to living and working environment. 2-AFN has one oxo group, where the cathodic reduction occurs, and one amino group, where the anodic oxidation occurs. The voltammetric behavior of 2-AFN in the negative potential region was investigated at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) representing a non-toxic and more mechanically robust alternative to mercury electrodes. This working electrode was subsequently used for the development of a newly designed miniaturized electrode system (MES), which has many benefits as the possibility of simple field measurements, easy portability, and the measurement in sample volume 100 µL. Moreover, a glassy carbon electrode (GCE) was used for further investigation of...
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