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Study of degradation behavior of abacavir using a diamond film electrode
Pražáková, Lucie ; Kubíčková, Anna (advisor) ; Kozlík, Petr (referee)
In this work the electrochemical degradation behavior of the drug abacavir is studied with the use of boron-doped diamond electrode. Oxidative degradation of the active substance abacavir, used to treat patients with HIV disease, was studied in a batch of three-electrode and two-electrode settings. In this work, the characteristics of five working boron-doped diamond electrodes, differing in a boron/carbon doping ratio of 500 ppm, 1000 ppm, 2000 ppm, 4000 ppm and 8000 ppm, were studied. The degradation in the three-electrode arrangement took place under potenciostatic electrolysis at potentials from 0,6 V to 2,0 V. The degradation in the two-electrode arrangement took place under conditions of potenciostatic electrolysis at higher potentials from 2,0 to 4,5 V. Optimal degradation, to the required values up to 25 %, was achieved at a potential of 3,5 V for an oxidation time of 10 minutes on a boron-doped diamond electrode with a boron/carbon doping ratio of 500 ppm and 1000 ppm. Separation and determination of abacavir and its degradation products were performed by ultra-high performance liquid chromatography with a mass detector. The degradation of abacavir produced two known degradation products, DP1 with relative retention times of 0,40 and DP2 with relative retention times of 0,45. The...
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Modification of boron doped diamond electrode by poly-L-lysine and its influence on electrochemical behaviour of dopamine and serotonin
Pejzlová, Michaela ; Fischer, Jan (advisor) ; Vyskočil, Vlastimil (referee)
This bachelor's thesis deals with the redox behavior of two neurotransmitters, dopamine and serotonin, at bare anodically activated (O-terminated) and poly-L-lysine-coated boron doped diamond electrode in two media, namely phosphate buffered saline and Neurobasal (medium commonly used for neuron cultivation experiments). Oxidation of dopamine in tested environments has a quasi-reversible character, while serotonin oxidizes irreversibly on boron doped diamond electrode, both O-terminated and poly-L-lysine-treated. Clearly, poly-L-lysine modification of boron doped diamond electrode leads to a decrease in peak currents and a positive shift in oxidation potentials compared to the O-terminated boron doped diamond electrode; interestingly, serotonin is much more sensitive to polymer coating than dopamine, particularly in Neurobasal medium. During successive measurements, a considerable decrease in recorded signals of both neurotransmitters can be observed. Hence, possibilities how to ensure stable current values were investigated: for dopamine, stirring the solution between the individual scans is sufficient method for obtaining repeatable signals (sr = 1.4-11.9 %, n = 5). However, in case of serotonin it is necessary to reactivate the electrode surface anodically in H2SO4 (Eact = +2400 mV) for 5...
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Degradation of the active pharmaceutical ingredient canagliflozin using electrochemical oxidation
Bolíková, Markéta ; Křížek, Tomáš (advisor) ; Kozlík, Petr (referee)
This bachelor thesis is aimed at degradation of the active pharmaceutical ingredient canagliflozin by the electrochemical oxidation. The aim is to explore the influence of given measurement conditions on the course and the results of the electrochemical oxidation and to find out, under which conditions the largest percentage of the degradation products is formed. These conditions are, for example, the concentrations and pH values of the buffers which are used to dissolve the samples of canagliflozin, the flow rate of the electrochemically stressed substance solution through the flow cell or the thickness of the gasket inserted in front of the working electrode. Canagliflozin is an orally administered blood glucose lowering antidiabetic and is used to treat diabetes mellitus 2. type. It is one of the inhibitors of the sodium-glucose transporter type 2. For the separation of the degradation products of this pharmaceutically active substance, a high performance liquid chromatography (HPLC) method with a UV/VIS diode array detector using an Agilent Poroshell 120 SB-Aq chromatographic column (2.1 × 100 mm; 2.7 µm) was chosen. The mobile phase contained an aqueous component, which was 10 mM formate buffer with pH 3.5 and the organic component, which was acetonitrile. The electrochemical oxidation of...
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The use of electrochemical oxidation in abacavir degradation studies
Pražáková, Lucie ; Kubíčková, Anna (advisor) ; Kozlík, Petr (referee)
The focus of this bachelor's thesis is the electrochemical degradation of abacavir. Abacavir is the active pharmaceutical ingredient of the medicine for human immunodeficiency virus (HIV). It was developed an electrochemical method for the oxidation of abacavir, including its excipients found in Ziagen tablets given to patients. Abacavir at a concentration of 0,15 mg·cm-3 was oxidized electrochemically at a constant potential (1,15V) on a specially assembled three-electrode apparatus. Subsequently, the quantity and type of the resulting products were analysed by a previously optimized chromatography method. The oxidation was relatively fast. After 7 minutes about 20 % of abacavir was oxidized. Two oxidation products were formed and their structures were confirmed by mass spectrometry.
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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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Electrochemical Oxidaction of Thioxoacetamides in Acetnonitrile Medium
Kudláček, Karel ; Nesměrák, Karel (advisor) ; Schwarzová, Karolina (referee)
Electrochemical oxidation of eight newly synthesized derivatives of 2-(fenylamino)-2-thioxoacetamidein 0,1 mol dm-3 sodium perchlorate - including effects of acid, base, and water - was studied. It was found that oxidation carried out in two subsequent steps, each of them is connected with exchanging of one electron. The oxidation is localised on sulphur atom, it is exchanged by oxygen atom in the final oxidation product. The effect of substituents on the course of electrochemical oxidation was also studied.
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QSPR and Electrochemical Oxidation of N-benzylsalicylthioamides
Kohoutová, Petra ; Nesměrák, Karel (advisor) ; Fischer, Jan (referee)
The study of the substituent effect on the voltammetric behaviour of newly synthesized N benzyl-salicylthioamides and the preparation and identification of products of their electrooxidation were the aims of this thesis. The voltametric characteristics were measured by DC voltammetry on a rotating disc electrode in a non-aqueous media. Using QSER, the effect of substituents on the anodic half wave potential was quantified, and statistically valid correlation equations were obtained. The influence of reaction media on the compounds electrooxidation was also studied. Using preparative electrolysis, the electrooxidation products of two selected N benzylsalicylthioamides were obtained. The one (structurally similar) product was identified in both cases. The following general scheme of electrochemical oxidation of N-benzylsalicylthioamides studied was proposed: the electrooxidation starts on sulphur atom by elimination of electrons, followed by translocation of charge on nitrogen atom, then hydrogen sulphite is eliminated, and a new ring is closed between two molecules of appropriate N-benzylsalicylthioamide.
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