National Repository of Grey Literature 73 records found  previous11 - 20nextend  jump to record: Search took 0.01 seconds. 
Evaluation of sequential extraction for speciation of arsenic in mining wastes
Grösslová, Zuzana ; Drahota, Petr (advisor) ; Vaněk, Aleš (referee)
ii SUMMARY This master thesis deals with selectivity assessment of an arsenic sequential extraction procedure for evaluating mobility in mine wastes. A modified sequential extraction procedure was designed on the basis of preliminary tests of extraction efficiency and selectivity for the synthetic As mineral phases (scorodite, amorphous iron arsenate, schwertmannite, goethite, jarosite) and five natural samples (Kaňk, Dlouhá Ves, Giftkies, Roudný) that were previously characterized for As concentration and speciation. The modified sequential extraction has five steps. The first leaching step was performed in nitrogen-purged deionized H2O for 10 hours; next step involved 0.01M NH4H2PO4 leaching for 16 hours. Phases in the third step were dissolved with 0.2M Tamm`s reagent in darkness for 2 hours. The fourth step was represented by 0.2M of Tamm`s reagent heated in water bath at 80řC for 4 hours. Strong acid solutions HCl/KClO3/HNO3 were used to leach sulphide phases in the last step. The testing of the sequential extraction procedure using model mixtures showed a good discrimination of several fractions: adsorbed arsenic, arsenic associated with poorly crystalline oxyhydroxide, hydroxosulfate and arsenate phases (amorphous iron arsenate, schwertmannite, ferrihydrite), arsenic associated with crystalline...
Anomalous occurences of arsenic in natural waters in the Czech Republic
Rodovská, Zuzana ; Drahota, Petr (advisor) ; Redlich, Aleš (referee)
This bachelor thesis reviews the data on the distribution of arsenic in surface and underground natural waters of the Czech Republic. In addition the thesis focuses on the occurrence of anomalous arsenic concentrations and tries to detect sources of arsenic contamination. Results of the thesis suggest high quality of the surface and groundwater in the Czech Republic with respect to arsenic. Its anomalous concentrations in the natural waters in Czech Republic have been rarely documented only in areas with strong anthropogenic impact and in areas affected by historical mining operations. Keywords: Arsenic, toxicity, contamination, surface water, groundwater, Czech Republic
Optimization of generation and atomization of arsines for speciation analysis by atomic fluorescence spectrometry
Marschner, Karel ; Dědina, Jiří (advisor) ; Komárek, Josef (referee)
Speciation analysis of arsenic based on selective hydride generation and detection by atomic fluorescence spectrometry have been studied in this work. It was found that under optimum conditions of atomization in the flame in gas shield atomizer, sensitivity was approximately twice higher and detection limit was about four times lower compared to miniature diffusion flame, which is a standard atomizer for atomic fluorescence spectrometry. The conditions to generate hydrides from both inorganic forms of the arsenic, i.e. from arsenite and arsenate, with the same efficiency have been found in the batch arrangement, by using 1 mol dm-3 hydrochlorid acid and 1% solution of tetrahydridoborate. To determine only trivalent form, TRIS buffer at pH 6.00 was used together with 1% sodium tetrahydridoborate. The detection limits found for inorganic arsenic, i.e. for arsenite and arsenate, respectively, were 15 ng dm-3 and 9 ng dm-3 . It was found that in the batch arrangement under these conditions it is possible to generate corresponding hydrides methylarsonate and dimethylarsonate with the same efficiency as from the inorganic form. Finally, it was found when slightly changing the gas-liquid separator design in order to introduce the mixture of tetrahydridoborate with hydrochloric acid to the bottom of the...
Speciation analysis of arsenic-glutathione complexes by ion-pairing HPLC-ICP-MS
Zušťáková, Veronika ; Matoušek, Tomáš (advisor) ; Červený, Václav (referee)
The thesis has focused on the separation of arsenic-glutathione species using ion-pairing high performance liquid chromatography with detection by inductively coupled plasma mass spectrometry. Species were separated on chromatographic column Prodigy ODS (3) using an aqueous mobile phase containing 4.7mM tetrabutylammonium hydroxide (TBAH), 2mM malonic acid and 4% methanol at pH 5.85 in the isocratic mode. Simple arsenic species - arsenite (iAsIII), arsenate (iAsV) monomethylarsenic acid (MAsIII), monomethylarsenous acid (MAsV), dimethylarsenic acid (DMAsIII) and dimethylarsenous acid (DMAsV), which served as arsenic standards to determine retention times, were successfully separated under these conditions. Arsenic-glutathione complexes As(GS)3, MAs(GS)2 and DMAs (GS) were not successfully separated. These complexes provided peaks of simple arsenic species. Peak broadening was observed in the first analysis of As(GS)3 and MAs(GS)2 complexes, which disappeared in subsequent analyses. This broadening probably represents a residual of glutathion complex which disintegrated to single species. Powered by TCPDF (www.tcpdf.org)
Arsenic determination in beer samples and raw materials for its preparation
Švadlenová, Veronika ; Hraníček, Jakub (advisor) ; Jelínek, Ivan (referee)
This thesis describes the optimization of the method for determination of arsenic by the chemical hydride generation coupled with AAS detection in beer samples and raw materials for its preparation. The beer usually contain arsenic at ultratrace level, however, it is necessary to monitor the concentration of this element in the beer. The routinely used method for determination of arsenic is determination by electrothermal atomization. This approach is time consuming, expensive and less sensitive. It has been developer suitable determination of arsenic as a faster and less expensive method. For this method there was optimized the flow rate of argon to 75 ml·min-1, the optimum flow rate for the reagents was 4.0 ml·min-1 and for the sample 5.0 ml·min-1 . 3 % NaBH4 in 0.5 % NaOH was used as the reducing agent for the determination of arsenic, and HCl diluted 1:1 with distilled water was used to acidify the sample. With this parameter LOD was 0.32 μg·l-1 and LOQ 1.05 μg·l-1 . It has been tested the arsenic determination in samples of barley, malt and potable water as beer raw materials. It has been found that the beer matrix is unsuitable for the hydride generation technique due to a stormy reaction in the gas/liquid phase separator. The effect of pretreatment, which is likely to enhance the effect of...
Microdomains in freshwater sediment as a driving factor in the biogeochemical processes
Duchoslav, Vojtěch ; Falteisek, Lukáš (advisor) ; Beranová, Jana (referee)
A natural arsenic anomaly at Mokrsko is a site of biogenic precipitation of realgar (As4S4) in stream sediment. The extent of the phenomenon in Mokrsko is globally unique. A previous study showed the ability of microorganisms to solubilize arsenic from its secondary minerals and to produce realgar precursors, i.e. sulfides and arsenites, by anaerobic respiration. The study also raised questions about the mechanism of realgar precipitation since physicochemical conditions favoring this reaction were never detected despite significant sampling efforts. We chemically and microbiologically analyzed sedimentary profiles to the depth of ca. 120 cm in order to understand the functioning of the biogeochemical system. The profiles comprised both the unsaturated and the saturated zone. We distinguished six different domains representing environments from the surface soil to anoxic sedimnent containing realgar-encrusted wood. An analysis of phylogenetic dissimilarity revealed that microbial communities from the various domains form distinct clusters. This suggests that different conditions prevail in the various domains, and that different biogeochemical processes take place there. Incubation (microcosm) experiments showed that bioprecipitation of realgar can be conducted in vitro. It requires a suppression...
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).
Trace and minor elements in coal and methods of their investigation
Páchová, Helena ; Opluštil, Stanislav (advisor) ; Sýkorová, Ivana (referee)
The aim of the bachelor thesis is to provide an overview of the minor and trace elements in coal matter and to characterize their origin, distribution and effect on quality of coal in term of its industrial utilization, including potential environmental impacts. The thesis describes main methods currently used when investigating coal geochemistry and mineralogy. The thesis includes overview of the distribution of these elements in the major coal deposits of the Czech Republic.
Arsenic in tree rings at As contaminated sites
Svoboda, Ondřej ; Mihaljevič, Martin (advisor) ; Vaněk, Aleš (referee)
Kutná Hora and its surrounding environment was affected by mining Ag, later Pb - Zn ore, lasting several centuries. As a result of mining, extreme concentrations of heavy metals and metalloids, especially As, in waters, soils and plants are. The aim of this work was to study the elemental composition of soils and tree rings, including processes between soil and plants on contaminated and uncontaminated area to describe biogeochemical processes between soil and plants. Elemental composition (V, Cr, Mn, Fe, Co, Cu, Zn, As, Cd, Sb, Tl, Pb) were determined in soils and tree rings of Scots pine (Pinus sylvestris) using ICP - MS. The measured concentrations of elements indicate contamination of soils and tree rings due to mining and metallurgical activities. The highest concentrations of As in soil (14 977 mg/kg) were found at contaminated site (Kaňk) at depth of 40 - 50 cm. This locality is situated on the heap, where waste from the mining and processing of ores are deposited, together with minerals and weathering products containing As. The uncontaminated area (Sukov) exhibited the maximum concentration of As in soils 124,38 mg/kg at a depth of 5 - 10 cm, due to the contamination by dust from the contamined sites. The highest concentrations of As in tree rings were determined in the contaminated area...
Determination of selected metals in tea samples and bag materials
Hlávka, Jan ; Nováková, Eliška (advisor) ; Hraníček, Jakub (referee)
This bachelor thesis is dealing with determination of antimony in materials modern pyramid-shape tea bags. Possible presence of antimony in these materials, e.g. polyethylene terephthalate (PET) or mixed materials, is caused by using it like catalyst in production of polyethylene terphthalete. The goal of this bachelor thesis is the verification of hypothesis, that antimony is present in materials of pyramide tea bags and that it is released to consumed drink, if higher concentration of antimony is present, and that it could pose a health risk to the consumer. At the same time, I studied if tea leaves are contaminated by other toxic elements, from which some can result from intesive agricultural production. They can be used as pesticides or be presnet in industrial fertilizers. In this thesis I examined the content of As, Cd, Cu, Sb and Zn in tea leaves sold in pyramide bags. These pyramide bags were purchased in local supermarkets and shops. The content of Sb in bags was determined too. The applied method included the decomposition of samples in a microwave decomposition device and analysis of the composition of the resulting solution by the ICP-MS method. Determined contents of the investigated elements were expressed like content of element in the sample in dry mass and the results were compared...

National Repository of Grey Literature : 73 records found   previous11 - 20nextend  jump to record:
Interested in being notified about new results for this query?
Subscribe to the RSS feed.