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Study of Factors Influencing the Teduction of Rhenistane
Burešová, Helena ; Nesměrák, Karel (advisor) ; Rychlovský, Petr (referee)
The aim of the bachelor thesis was to study the influence of conditions on the reduction of ammonium perrhenate by selected reduction agents. The amount of reduced perrhenate was followed by differential pulse voltammetry (as the decrease of the height of DPV peak). The percentage of reduced perrhenate was expressed as a function of molar ratio of the reduction agent to perrhenate. The following four agents were employed: sodium borohydride, hydroxylamine hydrochloride, hydrazine hydrochloride, and ascorbic acid. An amount of 97.8% of rhenium reduced was achieved by 0.9-fold of molar excess of sodium borohydride in 2 mol dm-3 perchlorid acid. The threefold molar excess of hydroxylamine hydrochloride reduced rhenium by 85% (in medium with pH = 8.5). The threefold molar excess of hydazine hydrochloride reduced rhenium by 68% (in medium with pH = 5.0). Ascorbic acid was the last studied reduction agent; its threefold molar excess reduced rhenium by 98.7%.
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Cyclic Voltammetry as a Detection Technique in High Performance Liquid Chromatography
Burešová, Helena ; Nesměrák, Karel (advisor) ; Schwarzová, Karolina (referee)
The aim of the thesis was to study the possibility of employment of cyclic voltammetry as a detection technique in liquid chromatography. The phenothiazine derivatives (chlorpromazine hydrochloride, diethazine hydrochloride, and thioridazine hydrochloride) were used as model compounds. Firstly, the comparison of two potential detectors (tubular detector and bulk "wall-jet" detector) was accomplished. Only bulk "wal-jet" detector satisfied. Next, the conditions for the separation and detection of studied phenothiazines on RP-select B LiChrospher® 60 (250×4 mm) column with cyclic voltammetry as the detection techniques were optimized. The best separation is achieved in mobile phase consisted from the solution of 0.1 mol dm-3 sodium perchlorate in acetonitrile-water (80:20) mixture. The effect of flow rate of mobile phase and scan rate of polarization of the electrode on the symmetry of chromatographic peak was also followed, and optimal values of 0.5 ml min-1 for flow rate, and of 0.5 V s-1 for scan rate, were found. Under optimized conditions the calibration dependences of studied phenothiazines were measured in the range from 5×10-5 to 1×10-3 mol dm-3 for chlorpromazine, and in the range from 8×10-5 to 1×10-3 mol dm-3 for diethazine and thioridazine. The developed method was applied to...
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Study of Factors Influencing the Teduction of Rhenistane
Burešová, Helena ; Nesměrák, Karel (advisor) ; Rychlovský, Petr (referee)
The aim of the bachelor thesis was to study the influence of conditions on the reduction of ammonium perrhenate by selected reduction agents. The amount of reduced perrhenate was followed by differential pulse voltammetry (as the decrease of the height of DPV peak). The percentage of reduced perrhenate was expressed as a function of molar ratio of the reduction agent to perrhenate. The following four agents were employed: sodium borohydride, hydroxylamine hydrochloride, hydrazine hydrochloride, and ascorbic acid. An amount of 97.8% of rhenium reduced was achieved by 0.9-fold of molar excess of sodium borohydride in 2 mol dm-3 perchlorid acid. The threefold molar excess of hydroxylamine hydrochloride reduced rhenium by 85% (in medium with pH = 8.5). The threefold molar excess of hydazine hydrochloride reduced rhenium by 68% (in medium with pH = 5.0). Ascorbic acid was the last studied reduction agent; its threefold molar excess reduced rhenium by 98.7%.
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Ecotoxicity of mixed waste in Life Cycle Assessment
Lukáč, David ; Kočí, Vladimír (advisor) ; Burešová, Helena (referee)
Subject of the study is establishing ecotoxicity (in the form of EC50) and characterization factors (CF) of two real soil samples, contaminated by a mixture of heavy metals, by using terrestrial tests of ecotoxicity. The gained values are then compared to CF values nowadays used in life cycle assessment (LCA) studies and the differences are discussed. The heavy metals contents are assessed by sequential extraction with ICP-OES. To gain the EC50 values following organisms are used: enchytraeids Enchytraeus crypticus, collembolans Folsomia candida (determining inhibition of reproduction) and lettuce Lactuca sativa (determining inhibition of root growth). EC50 and CF values show higher ecotoxicity in the case of Vodárna sample than in the case of Rampa sample. A difference in CF assessment between the method of using terrestrial tests and mathematical method, which is used generally, is proved.
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