National Repository of Grey Literature 70 records found  beginprevious52 - 61next  jump to record: Search took 0.01 seconds. 
Determination of vitamin B12 by flow analysis with chemiluminiscent detection
Svobodová, Kateřina ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
This thesis reports determination of vitamin B12 by flow techniques of analysis. This method is based on luminol-peroxide chemiluminiscence assay for the detection of cobalt (II) ions in vitamin B12 molecules. The method includes releasing of Co2+ from the vitamin B12 using different types of its decomposition; these are mentioned in this thesis. The efficiency of the decomposition of real samples of vitamin B12 in this study reached 74.43 %. The high efficiency was achieved with 1.5 mmol.l-1 K2S2O8 and irradiation time 1 minute. In the FIA mode, the linear range obtained was between 1.0 to 500 mg.l-1 with a relative standard deviation (RSD) 2.59% (n = 10), limit of detection (LOD) 55 µg.l-1 . The minimum sample volume required and the time of analysis were 60 µl and 140.2 s. In the SIA mode, the linear range obtained was between 0.01 to 50 mg.l-1 with an RSD = 4.5% (n = 10), LOD = 25 µg.l-1 . The minimum sample volume required and the time of analysis were 250 µl and 80.1 s. Interference study showed that from wide range of interfering ions were selected only Ni2+ , Zn2+ and NO2 - , that from concentration level 50 mg.l-1 they significantly affect the determination of the Co2+ in solution. The intensity of chemiluminiscence most suppress ion Zn2+ . The solution with the concentration ratio of Co2+...
Determination of selective transition metals using electrochemical generation of volatile species with AAS detection
Mlejnek, Tomáš ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
The aim of this bachelor's thesis is to study the possibilities of electrochemical generation of volatile forms of copper, nickel and zinc with atomic absorption spectrometry detection. The electrochemical generation of volatile compounds were set in continuous flow analysis. A laboratory made on-membrane electrolytic cell with platinum electrodes was used for all experiments. Optimization of different conditions for electrochemical generation for specified analytes was determined via empiric methods. Optimized parameters were as follows: flow rate of carrier gas and electrolyte and generation current. The calibrations under the optimal values for both copper and zinc were measured. Other extended measurements were performed with zinc. For example, the optimization of electrolyte concentration, the influence of the atomization temperature, reversing polarity of the electrodes, the flow rate of electrolyte, the influence of salts as electrolytes, influence of DDTC, Antifoam B and oxygen addition. Possibilities of determination of zinc compounds by electrochemical generation were investigated at the end. Key words Electrochemical generation, volatile compounds, atomic absorption spectrometry, non- membrane flow-through electrolytic cell, quartz tube atomizer, copper, nickel, zinc
Possibilities of electrochemical generation of volatile compound of zinc
Kobrlová, Andrea ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
The aim of this work is to investigate the possibilities of electrochemical generation of volatile form of zinc. For the experiments a flow-through electrolytic cell was used. The system worked in continuous flow mode. At the first part of this work relevant working parameters, such as the generation current, the flow rate of the electrolytes and the carrier gas flow rate, were optimized. Under the optimal working parameters, the calibration and other characteristics of zinc determination by electrochemical generation were performed. Basic characteristics obtained for electrochemical generation were compared with chemical generation. The limit of detection for zinc determination by electrochemical generation was 2.65 mg dm-3 .
Influence of interfering elements on the electrochemical antimony hydride generation
Vacek, Tomáš ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
This thesis is focused on the study of different interfering elements during antimony electrochemical hydride generation. Interferences were studied for electrochemical hydride generation with electrolytic cell and also for chemical hydride generation using sodium tetrahydroborate as a reduction agent. The study included the comparison with oxygen influences. Hydride-forming elements (selenium and arsenic), transition metals (zinc, copper and nickel), different anions (chlorides, sulfates and nitrates) and sodium were tested as interferents. The most serious interferents were hydride-forming elements and nickel, where 100 % signal supression was observed in high interferent concentrations. As opposed to sodium and nickel, where almost none signal supression was observed at all concentrations. Keywords Interferences, electrochemical hydride generation, atomic absorption spectrometry, antimony, electrolytic cell, atomization, hydrides
Antimony determination by electrochemical hydride generation
Suchá, Lenka ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
The aim of the presented bachelor thesis is to study the possibilities of the electrochemical hydride generation of volatile antimony hydride, using two newly constructed electrolytic cells. In this work, the properties of the cells were studied and consequently the basic characteristics of antimony determination obtained using new cells were compared with the chemical hydride generation method. At the beginning of the work, the relevant working parameters of both electrolytic cells were optimized. Under the optimal working conditions the calibration and other characteristics were carried out for antimony determination. Using the electrochemical hydride generation with thin-layer electrolytic cell and tubular cell and chemical hydride generation the sensitivity 3.40·10-3 l·μg-1 , 6.10·10-3 l·μg-1 and 2.10·10-3 l·μg-1 respectively were obtained. Finally, the influence of oxygen introduction in the different part of experimental setup was studied. This oxygen addition caused the characteristic and well-reproducible absorption peak. Key words Atomic absorption spectrometry, electrochemical generation of volatile compounds, quartz tube atomizer, thin-layer and tubular electrolytic cell, antimony
Construction of miniature flow-through cells for electrochemical generation of volatile compounds
Hraníček, Jakub ; Rychlovský, Petr (advisor) ; Spěváčková, Věra (referee) ; Komárek, Josef (referee)
(EN) The presented dissertation thesis summarizes the new results of electrochemical generation of volatile compounds usable in atomic spectral methods. The main aim of this work is to develop and to characterize new types of electrolytic flow-through cells and to examine their possibilities of determination of arsenic, selenium and antimony by using the electrochemical hydride generation technique coupled with atomic absorption spectrometry with a quartz tube atomizer. Individual electrolytic cells were designed and constructed to comply with two important requirements. The cathode chamber of the electrolytic cell should have a minimal volume and a high efficiency of analyte conversion to the volatile hydride. Constructed electrolytic cells are divided into the construction groups and described in the experimental part. Selenium was chosen as the first analyte. The relevant working parameters (such as type, concentration and flow rate of electrolytes, generation current and carrier gas flow rate) were optimized for each newly constructed electrolytic cell. Under the optimal working parameters, the basic characteristics of selenium determination were found out by using electrochemical hydride generation. The electrolytic cells were compared to each other and with the classical electrolytic cell...
Electrochemical generation of tellurium hydride for AAS
Resslerová, Tina ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
Tellurium is non-biological element which is not common in the earth. It can be accumulated in a body and cause many health problems. In this work, tellurium is determined by the electrochemical hydride generation technique coupled with atomic absorption spectrometry with quartz tube atomizer. In the first part of this work, various relevant parameters of tellurium hydride generation were optimized to achieve high sensitivity. Under the optimal working parameters, calibration dependences and other basic characteristics were measured. Finally, the influence of oxygen added on the different places of set up was carried out. Optimized parameters were flow rate of the carrier gas, generation current, flow rate and concentration of electrolytes. Optimizations were measured for two different catholytes: hydrochloric and sulfuric acid, with similar results. In addition the calibration was measured with orthophosporic acid. Further experiments with oxygen were performed for sulfuric acid as the catholyte. Influence of oxygen on the baseline and the process of determination were performed, for both continuous and limited time addition.
Influence of interfering elements on the electrochemical selenium hydride generation
Vošmiková, Anna ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
This work is focused on the influence study of selected hydride forming elements (As, Sb), transition metals (Ni, Cu, Zn), anions (Cl- ,NO3 - ,SO4 - ) and cations (Ca2+ ,Na+ ), on the electrochemical hydride generation of selenium hydride. The analyte was converted to the volatile form and consequently atomized in a quartz tube atomizer. Atomic absorption spectrometer was used as a detection technique. For comparison, the same interference study was used to investigate for chemical hydride generation. The biggest influence on the analytical signal suppression was observed for other hydride forming elements at higher concentration (from 1mg/L of interfering elements the signal was suppressed by nearly 100 %). The transitions elements nickel and copper suppressed the analyte signal significantly. Neither selected anions nor cations suppress the signal significantly. No effect on the analytical signal was observed whet the sodium and calcium were tested at different concentration.
Determination of Se in selected food supplements using electrochemical generation of H2Se and AAS
Králová, Pavlína ; Červený, Václav (advisor) ; Hraníček, Jakub (referee)
The aim of this bachelor thesis was to verify the efficiency of electrochemical generation of H2Se in connection with atomic absorption spectrometry used to determination of selenium in real samples, specifically in selected food supplements with the declared content of selenium. Firstly, working conditions of apparatus for electrochemical generation of H2Se with atomic absorption spectrometry were optimized. Using these optimized conditions, calibration dependences for SeIV a SeVI were measured. It was found that for the quantitative determination of selenate, the prereduction step is needed. Therefore, prereduction of SeVI to SeIV was also optimized. After prereduction step, new calibrations were measured and figures of merit of determination of these selenium species were achieved from them. In conclusion, concentrations of Se in real samples of selected food supplements with the declared contents of SeIV and SeVI were determined and interference effects for such determination have been discussed.
Optimization of conditions for gold determination using electrochemical generation technique with spectrometric detection
Jareš, Radek ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
This presented work is focused on the verification of basic experimental parameters of the electrochemical generation. The gold was was used as the analyte. One aim was to verified the optimal values of selected parameters of electrochemical generation (these parameters were concentrations of catholyte and anolyte and its flow rate, flow rate of carrier gas, atomization temperature, …). The other aim was to study the influence of different experimental arrangement (especially in construction of electrolytic cell and the cathode material) on the optimal values of working parameters and the basic characteristics of the gold determination. The tested cathode materials were lead, platinum and copper. In all cases, platinum was used as an anode material. The highest sensitivity of the gold determination was observed in the case of an electrolytic cell with a cathode and an anode consisting of platinum.

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