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Identification of polyphenolic compounds in plant extracts
Rýdlová, Iveta ; Rychlovský, Petr (advisor) ; Hraníček, Jakub (referee)
Thesis "Identification of selected polyphenols in extracts of medicinal plants" is divided into two parts. The first part is devoted to describing a general division polyphenolic compounds, their antioxidant activity and lists of the methods which are used for the analysis of these substances. The second part deals with the identification of these selected compounds using the RP - HPLC method with UV detection-DAD, and then with the tandem mass spectrometer with a triple quadrupole. The method was optimized, in this method was used gradient elution with 10-90% acetonitrile, 0,1% formic acid and deionized water. Analysis time was 38 minutes. Elution agents ran from polar to less polar substances. First of all eluted substances which contained the hydroxyl group directly on the benzene ring as e.g. phenolic acids, further eluted aglycones with bound sugar, which provides a higher polarity of the substance (flavanones glycosides), further followed the flavonols without attached saccharide units, at the latest the flavones eluted. This optimized method has proved to be reliable with good repeatability and accuracy for separation of polyphenols. Using the UV spectrometry the stability was measured. Due to the stability the substances proved to be stable compounds where their UV spectra don't change with...
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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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Sensitivity increasing of gold determination by electrochemical volatile species generation with AAS detection
Vacek, Tomáš ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
This thesis is focused on increasing the senstitivity of gold determination by electrochemical volatile species generation using two different types of electrolytic cells in continuous flow setting. Externally heated quartz tube atomizer was used as means of atomization and detection of gold with atomic absorption spectrometer. Generation parameters were optimized for electrolytic cell with an ion exchange (nafion) membrane. After selection of new cathode material (Cu) the carrier gas (Ar) flow rate was optimized, where an additional inlet of carrier gas was found to have possitive effect on increasing the sensitivity of determination of gold and efficiency of volatile specie transport to the atomizer. Experiments with Antifoam B showed possitive effect on generation, thus calibration was carried out for optimized experimetal conditions reaching detection limit of 0,53 mg.dm−3 . The efficiency of volatile specie transfer from liquid to gaseous phase was determined between 60 - 65 % by measuring the residual gold content in liquid waste by F-AAS method. Subsequently the effieciency of electrolytic generation of volatile gold specie with radioactive tracer isotopes and autoradigraphy was determined to 0,6 %. These methods confirmed adsorption of generated species on apparatus surface. Using ICP-MS as...
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Determination of vitamin B12 by flow analysis with chemiluminiscent detection
Svobodová, Kateřina ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
This thesis reports determination of vitamin B12 by flow techniques of analysis. This method is based on luminol-peroxide chemiluminiscence assay for the detection of cobalt (II) ions in vitamin B12 molecules. The method includes releasing of Co2+ from the vitamin B12 using different types of its decomposition; these are mentioned in this thesis. The efficiency of the decomposition of real samples of vitamin B12 in this study reached 74.43 %. The high efficiency was achieved with 1.5 mmol.l-1 K2S2O8 and irradiation time 1 minute. In the FIA mode, the linear range obtained was between 1.0 to 500 mg.l-1 with a relative standard deviation (RSD) 2.59% (n = 10), limit of detection (LOD) 55 µg.l-1 . The minimum sample volume required and the time of analysis were 60 µl and 140.2 s. In the SIA mode, the linear range obtained was between 0.01 to 50 mg.l-1 with an RSD = 4.5% (n = 10), LOD = 25 µg.l-1 . The minimum sample volume required and the time of analysis were 250 µl and 80.1 s. Interference study showed that from wide range of interfering ions were selected only Ni2+ , Zn2+ and NO2 - , that from concentration level 50 mg.l-1 they significantly affect the determination of the Co2+ in solution. The intensity of chemiluminiscence most suppress ion Zn2+ . The solution with the concentration ratio of Co2+...
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Dissociation Constants of Perfluorocarboxylic Acids
Vlasáková, Tereza ; Nesměrák, Karel (advisor) ; Rychlovský, Petr (referee)
Bachelor's thesis is concerned on dissociation exponents of perfluoroalkanoic acids. The published values of dissociation exponents have been reviewed. The dissociation exponents of six selected perfluoroalkanoic acids (from perfluoropentanoic to perfluorodecanoic acid) were determined using neutralization potentiometric titration method. The values of determined dissociation exponents ranges from pKa = 2,17 to 2,44, and they are in agreement with known data. The decrease of value of dissociation exponent with increasing number of carbon in alkyl chain has been observed. Also, the increase of values of dissociation exponents of perfluoroalkanoic acids in comparison with theirs nonfluorinated analogs has been confirmed.
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Influence of interfering elements on the electrochemical antimony hydride generation
Vacek, Tomáš ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
This thesis is focused on the study of different interfering elements during antimony electrochemical hydride generation. Interferences were studied for electrochemical hydride generation with electrolytic cell and also for chemical hydride generation using sodium tetrahydroborate as a reduction agent. The study included the comparison with oxygen influences. Hydride-forming elements (selenium and arsenic), transition metals (zinc, copper and nickel), different anions (chlorides, sulfates and nitrates) and sodium were tested as interferents. The most serious interferents were hydride-forming elements and nickel, where 100 % signal supression was observed in high interferent concentrations. As opposed to sodium and nickel, where almost none signal supression was observed at all concentrations. Keywords Interferences, electrochemical hydride generation, atomic absorption spectrometry, antimony, electrolytic cell, atomization, hydrides
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Antimony determination by electrochemical hydride generation
Suchá, Lenka ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
The aim of the presented bachelor thesis is to study the possibilities of the electrochemical hydride generation of volatile antimony hydride, using two newly constructed electrolytic cells. In this work, the properties of the cells were studied and consequently the basic characteristics of antimony determination obtained using new cells were compared with the chemical hydride generation method. At the beginning of the work, the relevant working parameters of both electrolytic cells were optimized. Under the optimal working conditions the calibration and other characteristics were carried out for antimony determination. Using the electrochemical hydride generation with thin-layer electrolytic cell and tubular cell and chemical hydride generation the sensitivity 3.40·10-3 l·μg-1 , 6.10·10-3 l·μg-1 and 2.10·10-3 l·μg-1 respectively were obtained. Finally, the influence of oxygen introduction in the different part of experimental setup was studied. This oxygen addition caused the characteristic and well-reproducible absorption peak. Key words Atomic absorption spectrometry, electrochemical generation of volatile compounds, quartz tube atomizer, thin-layer and tubular electrolytic cell, antimony
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Reducing of Transport Loses by the Determination of Cadmium Using Electrochemical Generation of Volatile Compounds
Kováčová, Darina ; Červený, Václav (advisor) ; Rychlovský, Petr (referee)
The aim of this work was to reduce transport loses during the determination of Cd by using electrochemical generation of volatile compounds connected to AAS. Firstly, optimum experimental conditions were found for analytical determination of Cd using electrochemical generation of its volatile form. The second part of this work was focused on avoiding of cadmium condensation on cold inner walls of inlet tube of the quartz atomizer. The two successful devices connecting directly the separator of gas from the liquid phase and the quartz atomizer were constructed. Thus, the transporting way for volatile form of Cd was made as short as possible. Better results were achieved using the device which contains sintered glass in the bottom part of the gas-liquid separator for further inlet of carrier gas (Ar). Further reducing of transport loses of the volatile form of Cd was achieved using a heating of the inlet tube of the atomizer on 310řC. Thanks to these two improvements of the apparatus ca three times higher sensitivity was reached using the technique of electrochemical generation of volatile form of Cd and AAS detection. Also corresponding depression of the limit of detection (0,064 µg·cm-3 ) was got. Keywords: Determination of Cd, atomic absorption spectrometry, elektrochemical generation of volatile...
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