National Repository of Grey Literature 36 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Optimization of chemical generation and subsequent atomization of volatile cadmium species for atomic absorption spectrometry
Sagapova, Linda ; Kratzer, Jan (advisor) ; Marschner, Karel (referee)
Generation and atomization of cadmium volatile compounds was optimized in this work in order to determine trace Cd concentration levels by volatile compound generation (VCG) with subsequent detection by atomic absorption spectrometry (AAS). Three designs of volatile compound generators have been tested including a conventional hydride generator in flow injection analysis (FIA) mode, a batch generator as well as a generator of volatile compounds of transition metals. The generation efficiency of Cd species was quantified as low as 4 % in the conventional hydride generator. Providing that dissolved oxygen was removed from the reaction solutions, the generation efficiency of Cd increased to 12 % in the same experimental arrangement. The highest Cd generation efficiency of 54 % was reached in the generator of volatile compounds of transition metals. In this set up a detection limit of 0.07 ng ml-1 Cd and a sensitivity of 3.2 s ng-1 Cd, respectively, were reached. Moreover, the structure of the volatile Cd species generated was identified as free atoms in all experimental arrangements of the generators investigated. Keywords atomic absorption spectrometry, cadmium, generation of volatile compounds, atomization of volatile compounds
Mechanism of atomization of selected hydride forming elements in an externally heated quartz tube atomizer and a dielectric barrier discharge atomizer
Juhászová, Lucie ; Kratzer, Jan (advisor) ; Hrdlička, Aleš (referee)
Atomization conditions for tin hydride in the planar dielectric barrier discharge (DBD) plasma atomizer were optimized with detection by atomic absorption spectrometry (AAS). The effects of apparatus arrangement such as the shape of a waveform function of the high voltage power supply source, DBD atomizer design as well as presence of a dryer tube filled with NaOH pellets to prevent residual aerosol and moisture transport into the DBD were investigated in detail. The optimal experimental setup consisted of a square wave high voltage power supply source coupled to a DBD with vapor-deposited electrodes in the presence of NaOH dryer upstream the DBD atomizer. Argon was found as the best discharge gas under a flow rate of 120 mL min-1 while the DBD optimum high voltage supply rate was 7 kV. A sensitivity of 0.05 s ng-1 Sn and a limit of detection of 1.1 ng mL-1 Sn were reached under optimized conditions. Optimization of the whole experimental setup resulted in 7-fold improvement of sensitivity compared to the original arrangement consisting of a sinusoidal source coupled to a DBD atomizer with glued electrodes in absence of the dryer. Keywords atomic absorption spectrometry, hydride generation, hydride atomization, quart tube atomizer, dielectric barrier discharge (DBD)
Speciation analysis of mercury in liquid and gaseous samples
Žídek, Radek ; Kratzer, Jan (advisor) ; Spěváčková, Věra (referee)
Generation efficiency of four mercury species, namely elemental mercury and hydrides of methyl-, ethyl- and phenylmercury from liquid samples was quantified. The species chemically generated were quantitatively trapped on a gold-coated amalgamator to be subsequently determined by AMA-254 technique. Three types of construction of volatile species generators were compared. Generation effciciency among the species was comparable, fluctuating around 60% in the conventional flow injection generator equipped with a gas liquid separator with forced outlet. Better results were reached for elemental mercury and methylmercury hydride in an automated batch generator system. Generation efficiency was higher than 90% for these two species and between 60 to 80% for ethyl- and phenylmercury hydrides, respectively. Speciation analysis of elemental mercury and sublimate in gaseous samples was optimized. These two species dominate in flue gases produced during coal combustion or waste incineration. Combination of two sorbent tubes packed with alumina and gold-coated alumina enables selective and quantitative retention of both species. Sublimate is trapped on a column packed with alumina while elemental mercury is retained on gold-coated alumina. The capacity of both sorbents was investigated as well as the effect of...
Miniature plasma DBD atomizer for AAS and AFS
Straka, Marek ; Kratzer, Jan (advisor) ; Hrdlička, Aleš (referee)
Five designs of dielectric barrier discharge (DBD) atomizers have been constructed and optimized employing arsane as a model analyte. The individual DBD designs differed from each other in the style of electrode attachment, electrode shape and area. An externally heated quartz tube atomizer and another DBD atomizer design that have been studied before were used as reference. All the atomizer designs studied including the reference atomizers were found compatible with detection by atomic absorption spectrometry (AAS) giving comparable sensitivity of 0.44 s ng-1 As and detection limit around 0.2 ng ml-1 As under optimum atomization conditions. However, significant differences in optimum operation conditions were found among the DBD designs in terms of the applied voltage depending strongly on the style of electrode attachment. The design with metal strip electrodes glued to a quartz body requires more than 14 kV to be operated. The design with sputtered electrodes of the same shape can reach the same sensitivity with 8.5 kV. Selected DBD designs have been proven to be compatible also with other spectrometric detectors such as atomic fluorescence spectrometry (AFS) reaching detection limit 0.05 ng ml-1 As or atomic emission spectrometry (AES) with detection limit of 30 ng ml-1 As showing the...
Speciation analysis of As and Hg in biological material
Petry-Podgórska, Inga ; Matoušek, Tomáš ; Migašová, M. ; Zemanová, Veronika ; Pavlík, Milan ; Pavlíková, D. ; Kratzer, Jan
This work was focused on an analysis of arsenic in selected plants and mercury in hair. A combination of HPLC and ICP-MS was used for analysis of biological tissues extracts. The\nspeciation analysis of low molecular arsenic and mercury species like inorganic iAs3+ and iAs5+, methylarsenic and dimethylarsenic forms was carried out with hydride generation (HG)\ntechnique, arsenic peptides and inorganic mercury (iHg2+) and its methylated form (MHg+) - with reverse phase (RP) chromatography and detected by ICP-MS.
Information System Assessment and Proposal of ICT Modification
Krätzer, Jan ; Novák, Lukáš (referee) ; Koch, Miloš (advisor)
This bachelor thesis deals with the assessment of the current situation of the information system of the company and it also focuses on the proposal of changes of this system in order to provide users more comfortable and faster work by its usage. The assessment of information system is based on the analysis and consultations with the firm's employees. The result of the solution was accepted by the CEO and the changes were valued as very beneficial.

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2 Kratzer, J.
5 Krätzer, Jan
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