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Caffeine degradation by high frequency discharge in solutions
Korečková, Svatava ; Mravcová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The bachelor thesis deals with the degradation of caffeine in solutions by a high frequency discharge generated directly in the solution. The influence of experimental conditions such as the initial pH and conductivity of the solution, caffeine concentration or electrode geometry was studied. The prepared caffeine solutions had a concentration of 10–100 ppm and their initial pH was adjusted with electrolytes (NaCl, Na3PO4, Na2HPO4 and NaH2PO4). All experiments were performed in a batch plasma reactor consisting of a 400 ml beaker and two electrodes. UV-VIS spectrophotometry was used to determine the amount of degraded caffeine. It was found that the experimental conditions (electrical conductivity, power, type of electrode used, electrolyte used) have an effect on the degradation of caffeine. The most suitable electrolyte appears to be NaCl and the initial specific electrical conductivity set in the range of 400–500 S·cm–1.
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Study of plasma and plasma activated water effect for bacterial disease treatment
Korečková, Svatava ; Jirásek,, Vít (referee) ; Kozáková, Zdenka (advisor)
The aim of this master thesis was to prepare plasma-treated liquids (PTL), specifically plasma-treated saline solutions, using different plasma systems. Subsequently, PTL was applies onto selected microorganisms to determine its antimicrobial effect. Systems that use both direct and indirect plasma-liquid interactions were selected, and the plasma was generated at atmospheric pressure. The theoretical part is focused on the plasma treated water, the systems by which PTL can be produced, and a description of the characterization process, from the viewpoint of the amount of active particles or the physical-chemical properties. Here, the microbiological part of this work is also included, namely a description of the microorganisms used for the experimental part. The disease of otitis externa (inflammation of the external auditory canal) and the possibilities of its antibiotic treatment are also described here. In this work, PTL prepared by four different plasma systems were tested: the pinhole discharge with DC or AC high voltage source (PTLAC and PTLDC), the liquid electrode dielectric barrier discharge (PTLDBD), and the microwave surface wave discharge (PTLSW). Prepared PTLs were first characterized in terms of reactive particles (hydrogen peroxide, nitrates and nitrites) and changes in specific conductivity and pH. This was followed by microbiological testing of the antimicrobial efficiency of the prepared PTL. The bacteria Staphylococcus pseudintermedius, Pseudomonas aeruginosa and the yeast Malassezia pachydermatis were selected as test microorganisms. These microorganisms were exposed to PTL and the effects were studied for exposure times from 1 minute to 4 hours. After 24 hours of cultivation, the antimicrobial effects were evaluated by the standard plate count method and also by the image analysis method in the software Aurora. The next step was to compile antibiograms and compare the effect of the prepared PTL in different systems with the effect of antibiotics. In this master thesis, it was proven that the bacterium Pseudomonas aeruginosa is resistant to several antibiotics. Thus, the prepared PTLDC could represent the possibility of its inactivation without the use of antibiotics. Staphylococcus pseudintermedius and Malassezia pachydermatis do not have resistance to any antibiotic (antimycotic), but with incorrect use there is a risk of developing resistance, which is why PTL, with the highest antimicrobial effect, were also found for these microorganisms.
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Caffeine degradation by high frequency discharge in solutions
Korečková, Svatava ; Mravcová, Ludmila (referee) ; Kozáková, Zdenka (advisor)
The bachelor thesis deals with the degradation of caffeine in solutions by a high frequency discharge generated directly in the solution. The influence of experimental conditions such as the initial pH and conductivity of the solution, caffeine concentration or electrode geometry was studied. The prepared caffeine solutions had a concentration of 10–100 ppm and their initial pH was adjusted with electrolytes (NaCl, Na3PO4, Na2HPO4 and NaH2PO4). All experiments were performed in a batch plasma reactor consisting of a 400 ml beaker and two electrodes. UV-VIS spectrophotometry was used to determine the amount of degraded caffeine. It was found that the experimental conditions (electrical conductivity, power, type of electrode used, electrolyte used) have an effect on the degradation of caffeine. The most suitable electrolyte appears to be NaCl and the initial specific electrical conductivity set in the range of 400–500 S·cm–1.
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