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The utitilization of boron-doped diamond thin film electrode for the voltammetric and amperometric determination of amino derivatives of biphenyl
Maixnerová, Lucie ; Zima, Jiří (referee) ; Schwarzová, Karolina (advisor)
The aim to this work was to develop methods for the determination of 2 aminobiphenyl (2-AB), 3 aminobiphenyl (3-AB), and 4-aminobiphenyl (4-AB) in model mixtures. Concretely, the direct determination of the mixture of studied analytes has been tested using spectrophotometry and differential pulse voltammetry (DPV). Furthermore, separation and detection of 2-AB, 3-AB, and 4-AB have been performed using high performance liquid chromatography with electrochemical detection (HPLC-ED) with boron-doped diamond film thin electrode (BDDFE) in ,,wall-jet" configuration and using high performance liquid chromatography with UV detection (HPLC-UVD). It was found out that the spectrophotometric determination of 2-AB, 3-AB, and 4-AB is impossible in their mixture because of nearby values of local absorption maxima wavelengths of all three analytes studied. Upon the determination of 2-AB, 3-AB, and 4-AB in their mixture using DPV in BR buffer pH 2.0, the difference in peak potentials of 2-AB and 3-AB is too low for their determination in mixture. Upon the determination of mixture containing 2-AB and 4-AB in BR buffer pH 12.0, the limits of determination (LDs) were obtained in the concentration order of 10-6 mol.l-1 for 2-AB and 10-7 mol.l-1 for 4-AB. LDs for the mixture containing 3-AB and 4-AB were obtained in the...
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Redox and catalytic properties of modified papain
Lachmanová, Štěpánka ; Zima, Jiří (referee) ; Hudeček, Jiří (advisor)
Redox and Catalytic Properties of Modified Papain Endopeptidase papain could be modified by the organometallic complex [(η6 -C6H5(CH2)2NHCO(CH2)Cl)Ru(N^N)Cl]Cl, (N^N) = 1,10-phenanthroline (TB11), which binds to the free sulfhydryl group of cysteine in the active centre of protein. This modification influences the catalytic properties of papain. The redox properties of the TB11 complex in its free form and when it is bound to papain were studied by the polarographic and voltammetric methods. Modified endopeptidase is reduced in the adsorbed state. Therefore, a phase-sensitive AC voltammetry is used for studies of the electron transfer in the TB11 modified papain. This method gives suitable methodology for studying the electron transfer rates in the systems influenced by adsorption. Using this method the catalytic hydrogen evolution process was detected not only in the TB11, but also for TB11 covalently-attached to the papain molecule. The results help better understand the catalytic mechanism of the hydrogenation reactions in the presence of TB11 modified enzyme. Adsorption properties of papain at different substrates were studied by AFM measurement. The formation of a compact monolayer was proved for the gold substrate modified by a layer of 11-mercaptoundecanoic acid.
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Voltammetric Determination of Metronidazol at a Polished Silver Solid Amalgam Composite Electrode
Škvorová, Lucie ; Zima, Jiří (referee) ; Barek, Jiří (advisor)
The aim of this work was to find out the optimal conditions for voltammetric determination of metronidazole, which is used as an anti-tumor drug. The stability of stock solution of metronidazole in deionized water was monitored using UV-VIS absorption spectrophotometry. Optimum conditions for voltammetric determination of metronidazole at a polished silver solid amalgam composite electrode (p-AgSA-CE) have been investigated. The dependence of voltammetric behavior of metronidazole (1∙10-4 mol/L) on pH of analyzed solution has been investigated using DC voltammetry (DCV) and differential pulse voltammetry (DPV) in the pH range 2,1 - 12,1 in aqueous media of Britton- Robinson (BR) buffer. For electrochemically reducible nitro group of metronidazole, the mechanism of voltammetric reduction at p-AgSA-CE was proposed. The optimum medium of aqueous BR buffer pH 4.0 was chosen for measuring the concentration dependences for both voltammetric techniques. The concentration range 2∙10-6 - 1∙10-4 mol/L of metronidazole was measured using DCV and DPV at p-AgSA-CE with reached limits of quantification (LQs) 2∙10-6 mol/L and 4∙10-6 mol/L for DCV and DPV, respectively. For comparison of used voltammetric techniques with supplemental analytical method, the concentration range 2∙10-6 - 1∙10-4 mol/L of metronidazole...
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Determination of aminoglutethimide using HPLC-ED on carbon pastes
Vlachová, Karolína ; Šestáková, Ivana (referee) ; Zima, Jiří (advisor)
In this thesis, the determination of AGT, sooner used as anticancer drug, especially for the treatment of breast cancer in postmenopausal women or for the treatment of prostate cancer, by high performance liquid chromatogramy with UV spectrophotometric detection (HPLC-UV) and electrochemical detection (HPLC-ED) on carbon paste electrodes (CPEs) was studied. CPEs were prepared from glassy carbon microspheres and different pasting liquids - routinely used mineral oil (CPE-MO) and less commonly used tricresylphosphate (CPE-TCP) and silicone oil (CPE-SO). The concentration dependences of AGT were measured by HPLC-UV with detection wavelength 242 nm, by HPLC-ED with a working potencial of +1,3 V for CPE-MO and + 1,1 V for CPE-TCP in mobile phase containing phosphate buffer (pH 4) and methanol 50:50 (v/v). The following limits of detection were achieved - 3,6. 10-7 mol.l-1 for UV spectrophotometric detection, 2,5. 10-7 mol.l-1 for electrochemical detection with CPE-MO and 9,7. 10-7 mol.l-1 for electrochemical detection with CPE-TCP. AGT was also determined in model samples of urine. With HPLC-UV it was not possible to detect AGT, because of the interferences of other compounds. With HPLC-ED on CPE-MO the limit of detection 5,2. 10-7 mol.l-1 AGT was achieved. KEY WORDS Aminoglutethimide HPLC with UV...
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