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The influence of the surface pretreatment of boron doped diamond electrodes on electrochemical oxidation of phenol and its derivatives
Hnízdilová, Lucie ; Schwarzová, Karolina (advisor) ; Nesměrák, Karel (referee)
The aim of this thesis is the study of electrochemical oxidation of para-substituted phenol derivates using cyclic voltammetry (CV) and ,,direct current" voltammetry (DCV) on boron-doped diamond electrode (BDD) and comparison with some analogous meta-substituted compounds. Among the studied substances were p-cresol, 4-methoxyphenol, 4-hydroxybenzoic acid, 3-(4-hydroxyphenyl)propionic acid, 4-nitrophenol, 4-chlorophenol and 3-(trifluoromethyl)phenol. The oxidation of the analytes was performed in an acidic (pH 2,0) and basic (pH 11,0) Britton-Robinson buffer on mechanically polished, oxidated and hydrogenated surfaces. Another subject of the thesis is to analyze the influence of different substituents, characterized by the Hammett constant, on the oxidation potential of selected phenols. They are oxidized at more positive redox potentials in acidic media, than in basic media, where they are dissociated. The oxidation on the polished and hydrogenated surfaces were similar, whereas were shifted to higher values on the oxidated surface. Further, the signal intensity decreased on the oxidated one, and the oxidation of phenols was not recognizable in basic media. The passivation of the electrode was less significant in pH 2,0 buffer. The best result of Hammett correlation was achieved on a polished and...
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Analysis of the degradation products of the active substances in historical pharmaceutical relicts from 18th and 20th century.
Čambal, Peter ; Nesměrák, Karel (advisor) ; Kubíčková, Anna (referee)
Historical pharmaceutical preparations analyzed in this thesis were a senna extract more than 200 years old, an ointment "Naso-Merfen" 75 years old, and an ointment "Sulfathiazol" 42 years old. The active substances in the analyzed samples were sennosides A and B (senna extract), ephedrine and menthol (the ointment "Naso-Merfen"), and sulfathiazole (the ointment "Sulfathiazol"). The senna extract was analyzed by RP-HPLC and HPLC-MS. Separation conditions were optimized, especially for separation of the sennoside A and B enantiomers. The active substances were not detected in the sample. One degradation product and substances characteristic for senna were identified. Their presence in the historical and contemporary sample was compared. Detailed ESI− -MSn fragmentation mechanisms of sennoside A and B have been proposed. The sample of the ointment "Naso-Merfen" was analyzed by HILIC-UV, HPLC-MS, GC-MS, and AAS. Separation conditions were optimized. The active substances were quantified. Degradation products of the active substances were not detected in the sample. The sample of the ointment "Sulfathiazol" was analyzed by RP-HPLC and HPLC-MS. Separation conditions were optimized. The active substance was quantified. Degradation products of the active substance were not detected. The authenticity of...
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Analysis of the composition and degradation of pharmaceutical substances and pharmaceutical preparations from the 18th and 20th centuries
Kudláček, Karel ; Nesměrák, Karel (advisor) ; Bosáková, Zuzana (referee) ; Gabriel, Jiří (referee)
The dissertation focused on the analysis of twenty historical remains of pharmaceutical substances and pharmaceutical preparations dating to the 18th and 20th century by liquid and gas chromatography with UV-spectrometric or mass spectrometric detection. The analytical approach was chosen with regards to the age and pharmaceutical forms of the analyzed historical remain. The authenticity of the sample was verified by identifying the active ingredients, their possible degradation products and other excipients by tandem mass spectrometry. The fragmentation of some analytes was also studied by tandem mass spectrometry. The stability of historical pharmaceutical preparations from the 20th century was assessed on the basis of a decrease in the concentration of active substances compared to the content declared by the manufacturer or, in case of historical pharmaceutical remains from the 18th century, on the basis of active substance concentrations determined in the historical residue and current reference material. A multi-analytical approach combining five analytical methods, the results of which complement each other, was used to analyze the historical remains of ointments. While the active substances identified in ipecacuanha were found to be partially degraded, they were completely degraded in senna...
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Analysis of Nicotine or Opium Alkaloids in Historical Pharmaceutical Relics from 18th Century
Belianský, Michal ; Nesměrák, Karel (advisor) ; Kubíčková, Anna (referee)
Belianský M.: Analysis of Nicotine or Opium Alkaloids in Historical Pharmaceutical Relics from 18th Century. Bachelor Thesis. Prague, Charles University, Faculty of Science 2020. Abstract: Two samples of historical relics of pharmaceuticals dated to the 18th century were analyzed; the first sample contained tobacco, the second laudanum, i.e., a preparation containing opium. HPLC with UV or mass detection was used for analysis. Separation of the alkaloids was performed on X Bridge® BEH C18 column using binary gradient elution. By comparison with a modern tobacco sample and on the basis of data from the literature, the presence of nicotine degradation products, especially 6-hydroxy-N-methylmyosmine, was found in the historical sample. Because the nicotine content in the historical sample was very low, it was not possible to quantify it. The analysis of opium analytes in the second historical relics revealed the main opium alkaloids (cotarnine, morphine, meconin, papaverine, and noscapine) as well as their degradation products. Main alkaloids were also quantified. The ratio of noscapine to cotarnine was determined, which according to the literature is an indicator of the age of opium pharmaceuticals. Key words: degradation, HPLC, mass spectrometry, nicotine alkaloids, opium alkaloids
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Voltammetric Determination of 7-Dehydrocholesterol as a Biomarker of Smith-Lemli-Opitz Syndrom
Zárybnická, Adéla ; Schwarzová, Karolina (advisor) ; Nesměrák, Karel (referee)
The aim of this thesis was the development of a voltammetric method for the determination of 7-dehydrocholesterol as a biomarker of congenital disease Smith-Lemli-Opitz syndrome. The concentration of 7-dehydrocholesterol in plasma will increase hundred-fold to hundreds to thousands µmol L-1 in patients suffering from Smith-Lemli-Opitz syndrome. The determination of 7-dehydrocholesterol was carried out in artifical serum in this work, which was prepared to mimic the conditions of postnatal diagnosis of Smith-Lemli-Opitz syndrome. 7-dehydrocholestrol provides a well developed voltammetric signal at approximately +0.8 V vs. Ag/AgNO3 in acetonitrile. Differential pulse voltammetry with optimized parameters was used for the determination of 7-dehydrocholesterol. The presence of protein in artificial serum (human serum albumin) resulted in an unacceptably high detection limit of the method (178 µmol L-1 in artificial serum). Therefore, human serum albumin was eliminated from the artificial serum samples by precipitating it with acetonitrile and subsequently centrifuging the resulting suspension. At the same time, the ratio of aqueous and organic components in the studied medium was also adjusted with acetonitrile to achieve an optimal voltammetric response of 7-dehydrocholestrol. With regard to the...
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Sequential Injection Analysis for Spectrophotometric Determination of Biseptol Components
Kroiherová, Anna ; Nesměrák, Karel (advisor) ; Kozlík, Petr (referee)
A method using the sequential injection analysis technique for the spectrometric determination of two analytes, sulfamethoxazol and trimethoprim, in a mixture in the drug Biseptol® 480 without the need for their separation, was developed and optimized. Both analytes absorb in the UV spectrum, but only sulfamethoxazol, as primary amine, gives a colour product after derivatization reaction with sodium nitrite and N-(1-naphthyl)ethylenediamine, that can be detected in the VIS spectrum. The concentration of sulfamethoxazol is directly proportional to the absorbance of the colour product and by subtracting this concentration from the concentration of both analytes measured in the UV spectrum, the concentration of trimethoprim in the sample can be determined.
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Comparison of Calibration Methods for Determination of Quinine in Beverages
Handlová, Zuzana ; Nesměrák, Karel (advisor) ; Kozlík, Petr (referee)
The aim of this bachelor thesis is to compare three calibration methods used for determination of quinine in beverages performed by two instrumental methods. As the calibration methods, calibration curve method, standard addition method and spike were chosen. As the instrumental methods, UV spectrometry and RP-HPLC with UV and fluorescence detection were chosen. The calibration methods were compared in terms of accuracy, precision, and time consumption. The instrumental methods were compared in terms of accuracy. Five different tonic waters were chosen as authentic samples. The most precise results were provided by the calibration curve method. In terms of accuracy it was not possible to determine the most accurate calibration method. Spike was the least time-consuming calibration method. HPLC was more accurate compared to spectrometry. Key words: analytical calibration, spectrometry, high performance liquid chromatography, quinine
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Voltammetric behaviour of cholesterol on glassy carbon electrode
Bláhová, Eva ; Schwarzová, Karolina (advisor) ; Nesměrák, Karel (referee)
The aim of this Thesis is a study of voltammetric behaviour of cholesterol on glassy carbon electrode in the presence of acetonitrile and strong acid. The electrochemical oxidation occurs after dehydration of cholesterol induced by the acid. The study was performed using cyclic voltammetry, mostly in the presence of perchloric acid. Further, influence of other acids - sulphuric, nitric and phosphoric acid - was studied. Cholesterol provides in the presence of perchloric and sulphuric acid one anodic signal at the potential of +1400 mV vs. Ag/0,01 mol.l-1 AgNO3 in 1 mol.l-1 NaClO4 in acetonitrile. The influence of polarization rate, water content and concentration of perchloric acid in the supporting electrolyte on the oxidation signal of cholesterol was studied. Calibration dependence of cholesterol was measured using differential pulse voltammetry. The limit of detection was determined to be 4,83.10-6 mol.l-1 . Key words: Dehydration, glassy carbon electrode, cholesterol, oxidation, voltammetry
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Characterization and Analytical Application of Cobalt Pyridinoporfyrazinate as a Non-Platinum Mediator in Hydrogen Electrocatalysis
Klusáčková, Monika ; Nesměrák, Karel (advisor) ; Opekar, František (referee) ; Gál, Miroslav (referee)
This work reports on the cobalt pyridinoporphyrazinate (CoTmtppa) as a platinum-group metal-free catalyst for hydrogen evolution and oxidation reactions with the possibility of use in hydrogen energy and hydrogen potentiometric sensing. A different interaction of CoTmtppa with various electrode substrates, highly oriented pyrolytic graphite (HOPG) and annealed gold (Au(111)), affects its electrocatalytic behaviour in hydrogen reactions. The formation of a hydride-type complex with the bonding of hydrogen atoms to cobalt centre is supposed to be the rate-determining step. In the case of hydrogen evolution, the maximum catalytic activity of mediator was reached at pH = 11,0, when the HOPG/CoTmtppa showed overpotential decrease by 300 mV and an almost 60-fold increase of current densities compared to HOPG. The electrocatalytic activity of Au(111)/CoTmtppa resulted in a further decrease of overpotential by 175 mV in comparison with HOPG/Co(I)Tmtppa. The electrochemical oxidation of hydrogen was found to depend on hydrogen source which was electrochemically generated on-site or molecular hydrogen supplied from an external source. In the case of electrochemically generated hydrogen, the maximum activity of HOPG/CoTmtppa was reached at pH = 2.1 and an additional it was observed 50 % increase in current...
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