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Modular design for in-atomizer preconcentration of hydride forming elements with AAS detection
Novák, Petr ; Kratzer, Jan (advisor) ; Korunová, Vlasta (referee)
Modular design of hydride trap-and-atomizer device for AAS is constructed and tested. Modular design enables to test different preconcentration surfaces easily. Efficient in- atomizer preconcentration allows to reach detection limits of hydride forming elements at ultratrace levels. Bismuth and arsenic were chosen as model analytes and their preconcentration efficiencies were quantified employing quartz and sapphire as preconcentration surfaces. The results reached in the modular design were compared to those found previously in the compact quartz trap-and-atomizer device. The performance of the modular design is fully comparable with that of compact trap-and-atomizer design. Modular design can thus be employed for testing of novel preconcentration surfaces.
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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
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A novel AAS atomizer based on a dielectric barrier plasma discharge
Novák, Petr ; Kratzer, Jan (advisor) ; Kanický, Viktor (referee)
Atomization of arsine in a novel hydride atomizer for atomic absorption spectrometry (HG-AAS) was thoroughly optimized. This plasma atomizer is based on a dielectric barrier discharge (DBD). Sensitivity and detection limit reached 0.48 s ng-1 As and 0.16 ng ml-1 As, respectively, under optimum atomization conditions (Ar discharge using a flow rate of 60 ml min-1 Ar, DBD power 17 W). Analytical figures of merit reached in DBD are comparable to those found in an externally heated quartz tube multiatomizer (MMQTA) that was chosen as a model of conventional approach to hydride atomization in HG-AAS. An extent of interferences (Se, Sb, Bi) during As determination was investigated comparing both MMQTA and DBD atomizers. The later one was found to be more resistant towards interferences. A simple preconcentration of As in a DBD atomizer was reached after oxygen introduction into the Ar plasma in the DBD resulting in analyte retention in the atomizer followed by its volatilization once the oxygen flow is switched off. Preconcentration efficiency of 100 % was reached and detection limit improvement by a factor of ten was achieved (0.01 ng ml-1 As, preconcentration period 300 s).
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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)
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Spectrometric determination of selected metals in the samples from old ecological burden area
Zurynková, Pavla ; Kratzer, Jan (advisor) ; Spěváčková, Věra (referee)
This bachelor thesis is focused on heavy metals pollution in the Králíky town and its vicinity, located in the Pardubice region. This region was selected because there had been a Tesla factory producing fluorescent lamps. Moreover, there is also a waste disposal of the fluorescent lamps wasters and other dangerous waste located about two kilometers far from the former factory. Soil samples from the waste disposal area as well as river sediment, samples taken in the Tichá Orlice river and the Králický brook have been analyzed Mercury, cadmium, lead, chromium, nickel, copper and arsenic levels in the samples were measured by inductively coupled plasma - mass spectrometry. The total mercury content has also been measured with single-purpose atomic absorption spectrometer AMA-254. An optimization of leaching conditions of the elements was performed prior the analysis of the samples employing certified reference material. High levels of mercury, cadmium, lead, chromium, nickel and copper have been found in the waste disposal area. Regarding the sediment samples the highest levels of pollution have been detected near outfall of the sewage water from the industrial area in the Králíky town (former Tesla factory and recent metal plating industry). The concentration of heavy metals in other sediment...
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Generation of zinc volatile species for determination by atomic spectrometry
Dlouhá, Kateřina ; Nováková, Eliška (advisor) ; Kratzer, Jan (referee)
This diploma thesis deals with the determination of zinc by volatile species generation with detection by atomic absorption or fluorescence spectrometry. Volatile zinc species are generated using hydrochloric acid and sodium borohydride stabilized with sodium hydroxide. Conditions influencing the generation and atomization of volatile species were optimized, namely hydrochloric acid concentration, sodium borohydride concentration, sodium hydroxide concentration, hydrochloric acid flow rate, sample loop volume, reaction coil volume, frit porosity in a gas-liquid separator, argon and hydrogen flow rates, and last, the temperature to which the quartz atomizer is heated. Under the optimal conditions, the detection limit of 33 μg·l−1 and the limit of determination of 110 μg·l−1 were reached. It was found that the addition of various reagents (especially 8-hydroxyquinoline) can increase the generation efficiency. With the addition of 1 % (m/V) 8-hydroxyquinoline to the standard/sample the limit of detection was 4 μg·l−1 and the limit of quantification was 12 μg·l−1 . Using an atomic fluorescence spectrophotometer as the detector, the standard reference material was analyzed and good match with the certified concentration value was found, the certified zinc concentration value in the reference material is...
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