• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 68
  • 7
  • 3
  • Tagged with
  • 78
  • 70
  • 64
  • 64
  • 53
  • 52
  • 33
  • 27
  • 18
  • 16
  • 13
  • 11
  • 11
  • 11
  • 11
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Stanovení těžkých kovů v odpadních energetických materiálech s využitím sekvenční extrakce / Determination of heavy metals in waste energetic materials with using sequential extraction

Kořínková, Alena January 2011 (has links)
Tato diplomová práce pojednává o stanovení vybraných kovů v energetických odpadech, jako je úletový popílek, škvára, struska, ložový popel, produkt odsíření apod., které pocházejí ze čtyř moravských tepláren. Extrakce kovů z energetických materiálů byla provedena Tessierovou extrakcí. Za tímto účelem byla použita extrakční činidla chlorid hořečnatý (MgCl2), octan sodný (CH3COONa), hydroxylamin hydrochlorid v kyselině octové (NH2OH.HCl v CH3COOH), peroxid vodíku v kyselině dusičné (H2O2 v HNO3) a kyselina fluorovodíková (HF). Extrakce probíhala při teplotách 25°C a 40°C. Ve všech frakcích byly stanoveny olovo, měď a kadmium s využitím atomové absorpční spektrometrie (F AAS, ET AAS) a rtuť metodou AMA 254.
52

Výskyt těžkých kovů v blízkosti dopravních komunikací v Brně / Presence of heavy metals in vicinity of the roads in Brno

Brzobohatý, Jan January 2011 (has links)
Diploma thesis deals with the risk assessment of metals in soils near roads in the city of Brno. For samples collection has been chosen twenty-five localities which were divided into five groups depending on the traffic load, in order to compare the impact of transport on the risk of soil contamination with metals. In the soil samples were determined levels of six hazardous metals (Cd, Hg, Pb, Zn, Ni, Cu). Lead, zinc, nickel and copper were determined by the flame atomic absorption spectrometry (F-AAS), cadmium by the electrotermic atomic absorption spectrometry (ET-AAS) and mercury by the advanced mercury analyzer AMA 254.
53

Korozní degradace hořčíkových slitin v SBF roztocích / Corrosion degradation of magnesium alloys in SBF solutions

Ročňáková, Ivana January 2012 (has links)
Nowadays, magnesium alloys are used in many sectors of human activity, particularly in the aerospace and automotive industries, due to a combination of good mechanical properties and low density of magnesium. Recently, however, the attention is paid to the possibility of using magnesium alloys in the medical field, mainly due to the chemical properties of magnesium. The diploma thesis is focused on evaluating of the corrosion behavior of AZ31alloy and AZ61 alloys in SBF solutions that are solutions simulating body fluids. The alloys were subjected to immersion test in Hank’s solutions for time span from 24 to 1008 hours. The corrosion process was evaluated based on several factors: alloy composition, time and pH changes. The thesis also describes in detail the methodology for establishing magnesium and zinc by method of flame absorption spektrometry (F AAS). The determination of aluminum was carried out by atomic absorption spectrometry with electrothermal atomization (ET AAS).
54

Stanovení obsahu platiny na území města Brna / Determination of platinum in Brno's agglomeration

Dvořák, Rostislav January 2014 (has links)
This thesis is focused on the determination of platinum in samples of road dust and soil by atomic absorption spectrometry. The theoretical part describes the basic physical and chemical properties of platinum, platinum function in automotive converters and its behavior in the environment. In the experimental section summarizes the methods used to decompositions samples, concentration of the analyte and the main results of the measurements.
55

Stanovení platinových kovů ve velkých městských aglomeracích / Determination of platinum group metals in great urban agglomerations

Ježek, Stanislav January 2016 (has links)
The aim of this thesis is the actual elaboration literature search concerning the issue of platinum group metals in the environment, determination of platinum and palladium in great urban agglomerations. It includes chemical and physical properties, occurrence and platinum and palladium cycle in the environment. It also contains methods for extraction and determination of platinum and palladium.
56

Využití iontoměničů pro prekoncentraci platinových kovů / The use of ion exchanges for preconcentration of platinum group metals

Sýkora, Jiří January 2017 (has links)
The aim of this thesis is the elaboration of a detailed literature review on the use of ion exchangers for the preconcentration of platinum group metals. This work contains an actual literature review on this issue. In this work you will find information about the current occurrence of platinum metals in the environment, their impact on health, properties, resources and the use. There are also described ways of decomposition, extraction and use of ion exchangers. In the experimental part this thesis deals with optimization of ion exchangers and following application of real samples from the city of Brno.
57

Elektrochemické generování hydridů telluru a bismutu s detekcí AAS / Electrochemical generation of tellurium and bismuth hydrides for AAS

Resslerová, Tina January 2014 (has links)
Tellurium and bismuth are non-biogenous elements, which can be accumulated in human body. The aim of this work is focused on the determination of these elements by the electrochemical hydride generation with non-membrane electrolytic cell with quartz tube - atomic absorption spectrometry. The first step of the work was to optimize parameters for the continuous setup measurements and to obtain its figures of merit. After this, the arrangement with most suitable conditions for determination of these elements was converted to the flow injection setup (FIA) and all experimental parameters were again optimized and its figures of merit were obtained. The conditions of hydride generation were studied for platinum, lead and silver cathodes with hydrochloric and sulphuric acids and their sodium salts as electrolytes. The optimizations of the FIA setup were performed on platinum cathode in hydrochloric acid for bismuth and on lead cathode in sulphuric acid for tellurium. The limit of detection achieved for the generation of tellurium hydride was 1.1 ppm with a linear range up to 20 ppm; for the bismuth hydride the limit of detection was 9.5 ppm and limit of linearity 50 ppm. Keywords Bismuth, tellurium, electrochemical hydride generation, atomic absorption spectroscopy, flow injection analysis
58

Stanovení selenu metodou HG-AAS s prekoncentrací a atomizací v plazmovém výboji s dielektrickou bariérou / Selenium determination by HG-AAS with preconcentration and atomization in a dielectric barrier plasma discharge

Duben, Ondřej January 2015 (has links)
The aim of this thesis was to optimize atomization conditions for selenium hydride in a novel plasma atomizer based on dielectric barrier discharge (DBD) using atomic absorption spectrometry as a detector. Analytical characteristics have been subsequently determined and compared to those reached in a conventional externally heated quartz tube atomizer which was replaced by a sofisticated design of a multiatomizer (MMQTA) in this work. The limit of detection reached in DBD (0,24 ng ml−1 Se) is slightly worse to that observed in MMQTA (0,15 ng ml−1 Se). On the contrary, slightly better resistance towards interferences of Sb, Bi and As was observed in DBD atomizer in comparison with MMQTA. Possibility of selenium preconcentration in a DBD atomizer was studied reaching an overall preconcentration efficiency of 75 ± 5%. The detection limit in a preconcentration mode employing preconcentration period of 300 s has reached 0,012 ng ml−1 Se. Key words: hydride generation atomic absorption spectrometry, dielectric barrier discharge, hydride atomization, hydride trapping, selenium
59

HG-AAS s atomizací v plazmovém výboji s dielektrickou bariérou: optimalizace metody a analytické aplikace / HG-AAS with atomization in a dielectric barrier plasma discharge: method optimization and analytical applications

Zurynková, Pavla January 2016 (has links)
The aim of this diploma thesis was to optimize in detail atomization conditions for antimony hydride in a novel plasma atomizer based on a dielectric barrier discharge (DBD) with atomic absorption spetrometric detection. Argon was found as the best DBD discharge gas employing a flow rate of 50 ml min-1 Ar while the DBD power was optimized at 30 W. Analytical figures of merit including interference study of As, Se and Bi have been subsequently investigated and the results compared to those found in an externally heated quartz tube atomizer (QTA). The limit of detection reached in DBD (0.15 ng ml-1 Sb) is comparable to that observed in QTA (0.14 ng ml-1 Sb). Finally, possibility of stibane preconcentration in a DBD atomizer was studied. Preconcentration efficiency of 102 ± 6 % was found under optimized conditions.
60

Stanovení arsenu v pivu a surovinách pro jeho výrobu / Arsenic determination in beer samples and raw materials for its preparation

Švadlenová, Veronika January 2017 (has links)
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...

Page generated in 0.0241 seconds