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Polarity-based sequential extraction method for the study of organic matter isolated from biochar
Vojáčková, Beáta ; Doskočil, Leoš (referee) ; Enev, Vojtěch (advisor)
This master’s thesis completely charakterizes the organic matter of biochar from a physicochemical point of view. The theoretical part is focused mainly on the use of biochar in technology industry, substance content, extraction and instrumental techniques used for its study. A Soxhlet apparatus and the method of sequential fractionation by a series of six organic solvents, which were ranked based on their increasing polarity, were used to extract the matter. The experimental part discusses the analysis of the obtained samples using thermal methods such as thermogravimetric (TGA) and elemental analysis (EA). In our case optical methods were used also; spectrometry with Fourier transform (FTIR-ATR), ultraviolet-visible (UV-VIS) and fluorescence spectrometry. Thanks to the scanning electron microscopy (SEM) were obtained images of the biochar surface. Continuous characterization including the results of the biogenic element content, individual functional groups and the values of established indices, allowed us to define the organic parts of biochar and contributed to the implementation of better methodology regarding the investigated issue.
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The width of potential window of boron doped diamond electrodes in dependence on their pretreatment and composition of the mixed electrolyte solution
Dvořáková, Klára ; Schwarzová, Karolina (advisor) ; Dejmková, Hana (referee)
The diploma thesis focuses on the range of the potential window of the BDD electrode in dependence on the composition of the mixed electrolyte solution and the treatment of the electrode surface. The measurements were performed on a polished (p-BDD) and O-terminated (O-BDD) electrode by the method of linear sweep voltammetry (LSV) in a three-electrode system. It was confirmed that in an environment with a suitable organic solvent, the range of the potential window widens. The measured solutions consisted of deionized water containing sodium perchlorate with a concentration of 1 mmol l−1 and one organic solvent in which sodium perchlorate with a concentration of 1 mmol l−1 was also dissolved. Acetonitrile, methanol, N,N-dimethylformamide and isopropanol were used in solutions (0 %, 1 %, 5 %, 10 %, 50 %, 70 %, 90 %, 95 %, 99 % or 100 % volume percent). Expansion, or the shortening of the potential window range was evaluated separately for each solvent in the anodic and cathodic regions. The expansion of the window on both sides was confirmed in acetonitrile as the concentration of the solvent increases, so it is based on this experiment as a universal solvent suitable for the determination of reducing and oxidizing analytes, from measurements on O-BDD and also on p-BDD. In the case of the remaining...
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Measurement of two-dimensional electronic spectroscopy response of solvents
Bouda, Karel ; Alster, Jan (advisor) ; Dostál, Jakub (referee)
Two-dimensional electronic spectroscopy is a technique used mainly for the study of energy transfer in organic systems. Nevertheless, it seems to be a good choice for studying plenty of other complexes, for example nanocrystals. However, these complexes require different solvents, not only water which is used for organic systems and has a known behaviour in this analysis. These solvents are mainly organic, such as benzene, toluene, xylene and others. The behaviour of these solvents during the 2DES measurements is unknown, therefore it is possible that the obtained data would be contaminated by signals from the solvent. This thesis provides a detailed description of the behaviour of 11 different solvents during the 2DES analysis. 1
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