National Repository of Grey Literature 12 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Maximizing efficiency of field-amplified electrokinetic injection of weak bases for enantioselective capillary electrophoresis with sulfated cyclodextins
Šesták, Jozef ; Thormann, W.
The optimal conditions for field-amplified electrokinetic injection of cations followed by their separation based on the stereoselective interaction with sulfated cyclodextrins are discussed. Results show that addition of a short water plug together with a short plug free of cyclodextrins and with a buffer concentration similar to the BGE greatly increase the injection efficiency.
Chromatographic separation of aflatoxin analogues
Moravcová, Dana ; Planeta, Josef ; Lunerová, K. ; Duša, Filip ; Šesták, Jozef ; Kubíček, J. ; Horká, Marie
Three short particle-packed columns (50 x 2.1 mm) were compared for the rapid and efficient chromatographic separation of aflatoxin G1, G2, B1 and B2 analogues.
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.
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.
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.
System for fast analysis of explosives in the enviromnemt
Čapka, Lukáš ; Večeřa, Zbyněk ; Mikuška, Pavel ; Šesták, Jozef ; Kahle, Vladislav
Detection of explosives is the subject of many investigations by law enforcement agents and forensic scientist. The identification and discrimination of evidence taken from crime scenes is a common practice in forensic investigations. The higher demands on simple and fast determination of hazard materials or strange objects are required in connection with worldwide often repeated terrorist activities.
HILIC separation of AETMA-labeled glycans on a wide bore silica-based monolithic capillary column
Šesták, Jozef ; Křenková, Jana ; Moravcová, Dana ; Planeta, Josef ; Kahle, Vladislav
In this contribution, we report the separation of AETMA-labeled glycans on a wide bore (320-μm i. d.) silica-based monolithic capillary column modified by [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)-ammonium hydroxide.
ZIC-HILIC monolithic capillary column coupled with MALDI-MS: A tool for glycan analysis
Šesták, Jozef ; Křenková, Jana ; Moravcová, Dana ; Planeta, Josef ; Kahle, Vladislav
In this contribution, we report analysis of glycans enzymatically released from bovine ribonuclease B (RNase B) and human immunoglobulin G (hIgG) combining glycan separation using the synthesized zwitterionic silica-based monolithic capillary column and off-line MALDI-MS detection.
Simple liquid chromatography system for low flow rate gradient separations
Šesták, Jozef ; Kahle, Vladislav
Simple approach to the splitless micro-flow liquid chromatograph construction and functionality of the proposed system were presented.
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).

National Repository of Grey Literature : 12 records found   1 - 10next  jump to record:
See also: similar author names
7 Šesták, Jan
1 Šesták, Jindřich
1 Šesták, Jiří
1 Šesták, Josef
7 Šesták, Ján
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