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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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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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Multidimensional Liquid Phase Separations
Šesták, Jozef ; Čáslavský, Josef (referee) ; Pulkrabová, Jana (referee) ; Česla, Petr (referee) ; Kahle, Vladislav (advisor)
This dissertation is dedicated to the topic of multidimensional liquid phase separations. This separation techniques are developed for analysis of complex samples containing thermally labile, low volatile or high molecular weight components that can´t be analysed by two-dimensional (2D) gas chromatography. Concepts of peak capacity and orthogonality are explained and various methods of their determination are stated in theoretical part of dissertation. High performance column liquid chromatography (HPLC) and high performance capillary electrophoresis (HPCE) are suggested as the most suitable methods for automated multidimensional liquid phase separations on-line coupled to mass spectrometry. Configuration of simplified miniaturized liquid chromatograph is described in experimental part of this thesis. Original concept of the system has been extended by simple mobile phase gradient generation technique. Correct function was demonstrated on repeatable separation of alkylphenones, peptides, nitroaromatics, and nitroesters. This system has been utilized as a base for a couple of simple two-dimensional separation platforms for HILIC-MALDI-MS analysis of glycans, for separation of peptides based on off-line coupling of isoelectric focusing and capillary liquid chromatography, and finally for on-line IEC×RPLC, RPLC×RPLC, and HILIC×RPLC two-dimensional liquid chromatography. Correct operation of submitted platforms has been proved.
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Portable liquid chromatograph and analyses of hazardous substances
Šesták, Jozef ; Gogaľová, Zuzana ; Kahle, Vladislav ; Lunerová, K.
Progress in technology of microchips, batteries and LEDs in the last two decades enable development of portable instruments which can satisfy the requirements of modern liquid chromatography (LC). Application of portable LC is advantageous if simple and rapid sample treatment procedure followed by a short HPLC run can be executed in the point of sampling. Our research group have developed a concept of portable HPLC based on simple hydraulic scheme and a unique optical detector for simultaneous detection of absorbance and fluorescence of compounds eluted off microcolumn. Considering in-field analysis of hazardous substances, this instrument can be advantageous for analysis of compounds which are difficult to detect and quantify by other contemporary portable instruments utilizing different working principles due to incompatibility with their physico-chemical properties (e. g. microbial toxins).
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Detection and identification of aflatoxins by means of portable liquid chromatograph for purpose of control of biological weapons prohibition
Šesták, Jozef ; Lunerová, K.
Method describes screening detection and identification of selected mycotoxins aflatoxins (aflatoxins B1, B2, G1 and G2), ochratoxins A, B and zearalenon by means of portable miniaturzed capillary liquid chromatograph (miniLC) with UV/VIS and fluorescence detector (FLD). The aim of the method is to provide rapid screening method for finding/excluding the presence of given mycotoxins in unknown samples. In case of positive finding, it is necessary to perform confirmation analysis using other instrumental methods (e. g. LC-MS). The method is intended namely for the needs of technical support of the State Office for Nuclear Safety for control and supervising activities in field of execution of the Act No. 281/1997 Coll (Biological Act).
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