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Study of tebuconazole complexes with metal ionts
Norková, Renáta ; Jaklová Dytrtová, Jana (advisor) ; Vyskočil, Vlastimil (referee)
Tebuconazole belongs to widely utilized plant fungicides, mostly in vineyards. Its traces are present in plant tissues, wine as well as in soil. The aim of the study was to determine stoichiometries and stabilities of metal (Cu, Zn, Cd, Ca and Ag) complexes with tebuconazole (1) by means of electrospray ionization mass spectrommetry (ESI-MS). It was found that the complexes of tebuconazole with copper ions are particularly stable ([Cu(1)]+ has appearance energy 224 kJ·mol-1 , corresponding with the dissociation of the water molecule from the tebuconazole molecule), while the stability of another tebuconazole complexes is lower, about 150 kJ·mol-1 . In real environmental samples, the detection of 1 itself is hampered by its spreading into various species. The method involved here is based upon a hyphenation of electrochemistry (amperometry) and electrospray-ionization mass spectrometry (ESI-MS). It uses the fact that Cu creates very stable complexes with 1. We demonstrate that at appropriate potentials (at higher than 500 mV) Cu cations can be generated in an electrochemical cell and subsequently form complexes with 1 present in the sample. The resulting complex [Cu(1)]+ is detected with ESI-MS. The intensity of detected complexes depends on the concentration of 1 and the oxidation level of the...
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Volumetric determination of weak and strong acid in the mixture.
Norková, Renáta ; Opekar, František (advisor) ; Jelínek, Ivan (referee)
The project is aimed to the study of the titration curves of the weak and strong acid mixtures. Purpose of the project is to compare titration curves computed on the basis of simple model, when neglecting influence of the solution's ionic strength , with experimental titration curve obtained through measuring under standard laboratory conditions. This comparison is carried out for one strong acid in the mixture with various weak acids, that differ in value of dissociation constant. How titration curves are influenced by the ratio of concentration of strong and weak acids is observed further.
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Optimization of a Flow Rate for a Hyphenation of Voltammetry with Electrospray Ionization Mass Spectrometry
Jaklová Dytrtová, Jana ; Jakl, M. ; Norková, Renáta ; Navrátil, Tomáš
The hyphenation of an electrochemical cell prior to mass spectrometer with electrospray ionization allows studying of products and/or of intermediates of electrode reactions. The measurement is realized in a flowing system. The flow rate of the sample markedly influences the MS signal intensity of the product. The calculated optimum value for the electrochemical cell with the sweep volume 0.72 μL is in the range from 0.4 to 0.5 mL h -1 . The experimental optimal value is 0.45 mL h -1 . The optimization of the flow rate has to be provided individually for each product, because the intensity also depends on the rate of the electrode reaction and product stability.
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Investigation of Complexes of Tebuconazole with Zinc
Jakl, M. ; Norková, Renáta ; Navrátil, Tomáš ; Jaklová Dytrtová, Jana ; Balík, J.
Tebuconazole is one of the most utilized triazole pesticides in agriculture. Its stability is highly affected by complexation with metals. Moreover, it creates more or less stable complexes with essential elements that become unavailable to plants. In the system with overbundant tebuconazole, an inert (very stable) complex with Zn was found. Elimination voltammetry wit linear scan was used for revealing of the electrode processes on the mercury surface. The relatively slow kinetically controlled step in tebuconazole/Zn complex formation indication indicates the great ability of Zn-tebuconazole system to react with more ligans. Therefore, multiligand Zn-tebuconazole complexes with other ligands are expected in the nature.
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