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Dissociation behaviour of humic acids
Karbanová, Kateřina ; Kratochvílová, Romana (referee) ; Klučáková, Martina (advisor)
Humic acids are substances of natural origin and form the finest part of humic substances. They are formed by biochemical transformations of organic residues (mainly plants). They act as a weakly acidic polyelectrolytes with not exactly described structure. Their solubility is affected by pH value. The higher the pH value is the higher the solubility is. They are almost insoluble in acids. Bachelor thesis deals with the study of the dissociation behaviour of humic acids. Dissociation constant of humic acids is determined by three different methods – conductometric, spectrophotometric and combination of measurment pH and the content of acidic functional groups in Na2SO4. On the basis of results the methods are compared.
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Soil hydrogels based on the principle of controlled release
Macuráková, Viktória ; Smilková, Marcela (referee) ; Kratochvílová, Romana (advisor)
This bachelor thesis is focused on soil hydrogels, which operate on the principle of controlled release. The aim of the research was on the release of substances, and the practical use of hydrogels in agricultural practice. At work, we focused on the effect of humic substances and the quantities of the substances of the fertilizer NPK of hydrogel. Querying this data will use a variety of methods such as pH-metry, conductometry, spectrophotometry and chromatography and knowledge not only of the analysis but also the macromolecular chemistry. Experiment it was found that the content of sodium lignohumate does not affect the rate of release of potassium and phosphorus into the soil. Hydrogel which is located above the quantity of NPK fertilizer and a certain number of lignohumate released from its structures much larger amounts of ions such as Hydrogel without fertilizer NPK with approximately the same amount of lignohumate
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Development of New Application Forms of Humic Substances for Agricultural and Environmental application
Kratochvílová, Romana ; Kráčalík, Milan (referee) ; Salaš, Petr (referee) ; Klučáková, Martina (advisor)
The new forms of superabsorbent polymers (SAP) on the base of acrylic acid were developed and studied in this thesis. The SAP are focused on agricultural and environmental applications. While they are applied to the soil, SAP can prevent water losing and they become a reservoir of humidity in case of dry season, moreover in combination with fertiliser they play role of controlled release medium. Eight various samples of SAP were experimentally prepared by networking of partially neutralized acrylic acid. Potassium peroxydisulfate was used as the initiator and N,N–methylenebisacrylamide as the crossing agent. Some of samples contained addition of second monomer of acrylamide. All of them were enriched by fertilisers – natural lignohumate or synthetic NPK or combination of both. The swelling characteristics of prepared samples were investigated in conditions of various ionic strength. The influence of xerogels’ particles size on swelling properties was also observed. The viscoelastic characteristics of hydrogel form of all SAP were determined by using of rotation rheometer. The changing of viscoelastic properties were studied in dependence on time, on freezing and on repeating swelling cycles. On top of that the controlled releasing ability of SAP was tested due to three modelling experiments. The biological activity of all polymer products was tested at the end of the thesis. All samples of SAP were incorporated into the artificial soil and the ability of the water retention in the soil was observed. The growing experiments were running by using of corn plants. The size and the mass of each plant were measured and branching of the root was objectively evaluated by programme Harmonic and Fractal Image Analyzer.
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The behavior of superabsorbent polymers in artificial soils
Männlová, Adriana ; Smilek, Jiří (referee) ; Kratochvílová, Romana (advisor)
This bachelor thesis deals with the study of superabsorbent polymers for environmental and agricultural applications. Generally thessis preparations are to perform the funciton of irrigation ,so that thanks to its unique properties , can absorb water in tha rainy season and keep it arend the root system as long as possible. Superabsorbent polymers can also perform the fiction of fertilizer carries and thus ensure its gradual release. These gel structures were subjected to testing of their swelling in environments with different ionic strenght. Subsequently, in the long term monitored thein ability to trap water in the soil environment model.
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Determination of pKa of humic acids by means of UV/VIS spectrometry
Kratochvílová, Romana ; Maršálek,, Roman (referee) ; Klučáková, Martina (advisor)
The behaviour of humic acids in aqueous solutions is closely connected to the content of acid functional groups and their dissociation abilities. The titration methods are the most often used for the research of acid-base characteristics of humic acids, their results should lead to the determination of the content of functional groups and their pKa. However the determined values depend on many factors including the titration speed. The spectrophotometric determination of dissociation constant was used in this diploma thesis. Reliability of this method was confirmed in bachelor thesis where is mentioned that spectrophotometric determination of pKa corresponds with realistic dissociation behaviour of humic acids in the water much more better than values obtained from titration methods. The principle of newly used spectrophotometry method is the preparation of humic acids solutions in three different media with different pH values. Acid groups of humic acids are practically completely dissociated in intensely basic environment and the measured absorbance is caused by anion of „humate“. On the contrary their dissociation in acid environment is suppressed so much that we measure the absorbance of non-dissociated molecules of humic acids. Deionized water was used like neutral solvent. Water was replaced by acetic buffer in this thesis because of water’s properties which have significant influence on solutions' pH. Buffer was used for diluting or for solubilisation and in these both cases more stable pH values were occurred. The aim of this diploma thesis is investigate UV/VIS spectra of various solutions of humic acids with different values of pH and determinate mean value of pKa of humic acids which could be used like comparison of dissociation behaviours for vary samples. Values of acid dissociation constant were determined from measured dates and compared with values obtained by titration method. The UV/VIS spectra gained in combination with the results of pH measuring and the conductivity next showed the differences in the behaviour of differently prepared samples of humic acids.
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Characterization of hyaluronan interactions with albumin
Valentová, Kristýna ; Kratochvílová, Romana (referee) ; Chytil, Martin (advisor)
This bachelor thesis focuses on the research of physical interactions between hyaluronic acid and a protein albumin. In order to investigate these interactions following methods were used: pH and conductivity measurement, viscosimetry, turbidimetry and rheometry. The interactions were observed in solutions of fixed albumin concentration 1.0 gdm-3 and varying concentrations of hyaluronic acid from 0.1 to 2.0 gdm-3. Results were compared with a solution of hyaluronic acid without the addition of albumin. The results show that there are interactions between hyaluronic acid and albumin solutions, especially for those containing high molecular weight hyaluronic acid. The interactions exhibited a change in viscosity of solutions. We can see a reduction in viscosity after adding albumin to the reference solutions. The reduction is noticeable even in the low molecular weight HA solutions, but is not so significant.
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Superabsorbents with controlled release of nutrients
Závodská, Petra ; Kratochvílová, Romana (referee) ; Klučáková, Martina (advisor)
This thesis is focused on the study of superabsorbent polymers and their ability of control release of nutrients. These polymers can absorb huge amount of water, up to hundredth times more than the original weight is. In combination with nutrients, especially nitrogen, phosphorus, potassium and lignohumate, they make effective fertilizer. Due to this fact, the possibility of use in agriculture is increasing. Therefore, experiments that are researching the ability of containing the water were performed, the swelling capacity was measured. Experiments that are related to control release of nutrients were performed next. Therefore, this thesis is focused on the study of superabsorbent polymer characterisation, that can be used in agriculture.
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Solubility and dissociation of humic acids
Kratochvílová, Romana ; Jaroslav,, Záhora (referee) ; Klučáková, Martina (advisor)
The behaviour of humic acids in aqueous solutions is closely connected to the content of acid functional groups and their dissociation abilities. The titration methods are the most often used for the research of acid-basic characteristics of humic acids, their results should lead to the determination of the content of functional groups and their pKa. However the determined values depend on many factors including the titration speed. The aim of this bachelor’s thesis is to verify the possibility of UV/VIS spectrophotometry´s use as alternative method for the determination of pKa of humic acids and to compare the gained results with so far used method according to Henderson-Hasselbach. The principle of newly used spectrophotometry method is the preparation of humic acids solutions in three different media with different pH values. Acid groups of humic acids are practically completely dissociated in intensely basic environment and the measured absorbance is caused by anion of „humate“. On the contrary their dissociation in acid environment is suppressed so much that we measure the absorbance of non-dissociated molecules of humic acids. It was found out that after the modification it was possible to use the spectrophotometry method for the determination of pKa of these substances, while the use of method was verified within the three different samples of humic acids. The optimal ratio humic acids – water and the extent of wavelength for measuring UV/VIS spectra were determined. It was proved that the values of pKa determinated by these methods better describe the real dissociation behaviour of humic acids in water than traditional Henderson-Hasselbach method. The UV/VIS spectra gained in combination with the results of pH measuring and the conductivity next showed the differences in the behaviour of differently prepared samples of humic acids.
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Hyaluronan-albumin complexes behavior at physiological conditions.
Šuleková, Nikola ; Kratochvílová, Romana (referee) ; Chytil, Martin (advisor)
This thesis discusses the interactions of low molecular weight and high molecular weight hyaluronic acid (HA) with bovine serum albumin (BSA) in physiological environment. It is based on previous work dealing with HA and amphiphilic substances which are currently widely studied for its potential applications in medicine. Solutions of HA with fixed concentration and albumin of concentration in the range of 0,25 – 20 g/l were prepared at room temperature and at 37°C and examined by rheometry and turbidimetry. It was observed that the maximum absorbance increases with increasing concentration of BSA and does not show variations depending on the temperature of preparation. On the other hand, the turbidity occurs in significant differences between the samples prepared at ambient temperature and at 37°C. Overall, the turbidity increases with the concentration of BSA. Rasing the temperature caused the increase in viscosity of the samples, which was further varied with the concentration of BSA. Mixed solutions of high molecular weight HA and BSA showed the highest turbidity, maximum absorbance and viscosity, while the solutions of BSA showed the lowest values. The results indicate formation of complexes, of which properties are dependent on BSA concentration, the molecular weight of HA, and the temperature of preparation.
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Hydrodynamic properties of hyaluronan-lysin systems
Kunert, Vojtěch ; Kratochvílová, Romana (referee) ; Chytil, Martin (advisor)
This bachelor’s thesis studies the interactions of hyaluronan with partly protonized amino acids lysine and arginine. Rheology and viscosimetry were used to analyze the interactions. pH-metry and conductance measurements were used to check the interactions. Individual mixtures were measured and the data was compared to each other, but also in terms of partly and complete protonization. The interactions have been observed in all selected concentrations.
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