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Fast separation of explosives by high performance liquid chromatography
Šesták, Jozef ; Vávrová, Milada (referee) ; Kahle,, Vladislav (advisor)
The topic of the diploma thesis is fast separation of explosives by HPLC and development of miniaturized liquid chromatograph for application in a handheld explosives detection device. In this work the retention of some nitrated explosives and selectivity in reversed phase system as a function of mobile phase composition is studied while methanol, acetonitrile and acetone as an organic solvent is used. Best selectivity and good retention can be observed in methanol mobile phase. Acetonitrile and acetone are not suitable for fast isocratic separation of mixture containing pentaerythritol tetranitrate because of its strong retention. Efficiency and permeability of monolithic column (Chromolith CapRod RP-18e) and columns filled with superficially porous particles are compared (Kinetex 2,6 µm C-18, Poroshell 120 SB-C18). Monolithic column with satisfying efficiency and high column permeability is the most suitable solution for fast separation of explosives. Assuming use of explosives detection device in different conditions the separation was optimized on temperature 50 °C. Under these conditions the 35% v/v methanol gives good retention and selectivity. For very fast scan analysis of pentaerythritol tetranitrate or other nitroaromatics use of 70% v/v acetone mobile phase is suitable. Construction of miniaturized liquid chromatograph that enables preconcentration of explosives from aqueous solutions and fast separation in less than 1 minute is described. This concept will be incorporated into the handheld explosives detection device where the explosives vapor will be absorbed into the water and after the separation detected by chemiluminescence.
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Modern detection methods of energetic materials
Šesták, Jozef ; Bednařík, Karel (referee) ; Friedl, Zdeněk (advisor)
The review of modern detection methods of explosives was composed. Firstly the thesis deals with the detection methods commonly used in forensics science such as gas chromatography, mass spectrometry, ion mobility spectrometry, Raman spectroscopy and mainly their innovations. Then the thesis is focused on simple but very sensitive methods using fluorescence and chemiluminescence. At the end a methods as the results of a latest research are mentioned. The main of them are micro cantilever sensors and differential reflectometry. Security and counterterrorist warfare is main point of thesis.
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High pressure modification of the simple automated liquid chromatographic system for splitless nano column gradient separations
Šesták, Jozef ; Kahle, Vladislav
Our simple liquid chromatographic system for splitless gradient nanocolumn separations at backpressure up to 50 bars was modified to run analysis under the pressure up to 300 bars. Programmable syringe pump was equipped with a 250-L high-pressure syringe and mobile phase gradients were created and stored in relatively long capillary. Available linear gradients of volumes from 5 to 50 L traced by uracil are presented. Sample introduction was performed as separate step and real large volume of sample (tens of microliters) could be injected and preconcentrated on-column. Relative standard deviation of retention times and peak areas were received (RSD < 0.3 % and RSD < 5 % respectively).
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China as a business partner for Czech companies
Šesták, Jan ; Němečková, Iveta (advisor) ; Hinčica, Vít (referee)
The thesis is divided into five main parts. In the introduction the author deals with fundamental analysis describing trade with China. The author describes strenghts and weaknesses of trading with China, choosing the right business partner and preparation of contracts. Furthermore, the author focuses on goods, which is on the Chinese market worth trading as well as on main projects, which are between the Czech Republic and China. In the thesis will be presented also important points of trading, such as mean of transport, market entry or basic iformation about chinese etiquette, which plays a major role. At the end of the thesis, there are two case studies that describe a specific example of trading.
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