National Repository of Grey Literature 75 records found  beginprevious60 - 69next  jump to record: Search took 0.01 seconds. 
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.
Determination of Total Antioxidant Capacity in Select Food products and Dietary Supplements by Flow Injection Analysis with Chemiluminiscent Detection
Průchová, Karolína ; Rychlovský, Petr (advisor) ; Hraníček, Jakub (referee)
In this diploma thesis, a functional method for the determination of total antioxidant capacity by flow injection analysis with the chemiluminiscent detection was successfully developed. Luminol in carbonate buffer (composed of Na2CO3, NaHCO3 and (NH4)2CO3), with Cu2+ ionts as a catalyst, was used as a chemiluminiscent reagent. Chemiluminiscent radiation was induced by a diluted solution of hydrogen peroxide, a long-lasting chemiluminiscence was observed. First part of this thesis is dedicated to the optimalisation of the experimantal conditions for antioxidant capacity measurements as well as to the construction of apparatus for flow measurings. L-ascorbic acid was used as a standard. In the second part of this thesis the freshly developed method was used to determinate total antioxidant capacity of real food product simples, namely tea and coffee simples, beers, wines, chocolates, fresh fruit juices and selected food supplements. Results of this analysis were expressed as a vitamin C equivalent antioxidant capacity (VCEAC) related to standard, in mg/ml for liquid simples and in g/mg for solid simples. Results obtained are: tea simples 53 - 347 mg/1g of dried product, coffee simples 399-449 mg/g of dried product, beers 1,1-1,4 mg/ml, wines 4,2 - 4,8 mg/ml, fresh lemon juice 4,7 mg/ml, fresh kiwi juice 2,1...
Tubular electrolytic cell for electrochemical generation of volatile compounds
Luštincová, Petra ; Hraníček, Jakub (advisor) ; Červený, Václav (referee)
The newly constructed tubular flow-through electrolytic cell useful for electrochemical generation of volatile compounds was used in this presented work. The general aim of this work was to test several cathode materials to obtain the best basic characteristics of selenium determination by electrochemical hydride generation using the tubular electrolytic cell. The tested cathode materials were lead wire, lead/tin alloy (75 % of Pb and 25 % of Sn) and granulated lead. At first the optimizations of relevant working parameters were carrier out for all of these cathode materials. Under the optimal working parameters, the basic characteristics of selenium determination were found. The highest sensitivity (7.6 · 103 dm3 µg-1 ) and the lowest limit of detection (0.42 µg.dm-3 ) were obtained for granulated lead as cathode material. Subject words: Analytical chemistry Key words: Atomic absorption spectrometry, electrochemical generation of volatile hydrides, tubular electrolytic cell
Possibilities of electrochemical generation of volatile compound of thallium
Marschner, Karel ; Hraníček, Jakub (advisor) ; Rychlovský, Petr (referee)
The possibilities of electrochemical generation of volatile thallium hydride have been studied in this work. A thin-layer electrolytic cell with minimal volume of cathode chamber has been employed. All experiments have been employed in electrochemical continuous flow generation. An electrochemical hydride generation technique was developed to improve the determination of analytes by atomic spectrometry. Effect of various experimental conditions such as kind of cathode material, type and concentration of electrolyte, amount of generation current and flow rate of carrier gas on the absorption signal was examined. Under the optimal values of previously mentioned parameters, the low sensitivity of thallium determination was achieved. So the experimental setup is not suitable for determination of low concentration of thallium in specimens. Keywords Atomic absorption spectrometry, electrochemical generation of volatile compounds, hydrides, thallium, electrolytic flow cell, optimization

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