National Repository of Grey Literature 114 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Development and testing of capillary columns based on ion exchanger
Vojta, Jiří ; Coufal, Pavel (advisor) ; Bosáková, Zuzana (referee)
In this work, capillary monolithic columns based on styrene, divinylbenzene and methacrylic acid were prepared by free radical polymerization inside fused sillica capillaries of 320 µm inner diameter. The columns were prepared by very simple process from polymerization mixtures with variable amount of methacrylic acid. Effect of electrostatic interactions between methacrylic acid, as weak cation-exchanger, and analytes on their retention was showed. Based on chromatographic measurements, effect of amount of methacrylic acid in polymerization mixtures on the morphological properties of monoliths and on the retention of small organic amines and benzene was discussed.
Development of Electrochemical Thin-layer Degradation Cell for Oxidation Stress Testing of Active Pharmaceutical Ingredients
Šefčík, Martin ; Kubíčková, Anna (advisor) ; Coufal, Pavel (referee)
In this thesis, the oxidation conditions in a new electrochemical "thin-layer" flow-through cell for the study of the oxidative degradation of active pharmaceutical ingredients were optimized. In this field, it is an innovative approach to studying the oxidation properties of substances. The cell was manufactured using 3D printing technology. Oxidation was carried out in a two-electrode arrangement with a working boron-doped diamond electrode (BDDE) and an auxiliary stainless steel electrode. Optimization of conditions was performed using salicylic acid as a model active pharmaceutical ingredient. The electrochemical approach was used to degrade this active pharmaceutical ingredient by the required approximately 20% of the original amount in only 2.3 min. Thus, the degradation time was significantly reduced compared to the oxidative stability stress tests of active pharmaceutical ingredients commonly used today. Two major degradation products were observed, namely gentisic acid and 2,3-dihydroxybenzoic acid. The degradation products obtained by electrochemical oxidation and chemical oxidation using hydrogen peroxide are identical.
On-line derivatization of saccharides in capillary electrophoresis
Mareš, Vít ; Křížek, Tomáš (advisor) ; Coufal, Pavel (referee)
Saccharides chains may suffer from various inaccuracies during their biosy- thesis, that effects their biologic functions. Therefore, they can be used for dia- gnosis of some diseases or quality control in biopharmaceutics. Capillary electro- phoresis has its place in diagnosing these occuring errors. In this thesis a method of on-line derivatization of saccharides in fused-silica capillary with 50 cm in lenght and 50 µm in inner diameter was developed. Gluco- se was used as a model molecule, which was labeled by a fluorescent derivatization reagent, 7-aminonaphthalene-1,3-disulfonic acid. Derivatization of glucose and its separation needed optimalization. First was determined an electrophoretic mo- bility of the derivatization reagent in 0.5; 1.0 and 2.5M acetic acid and 20mM phosphate buffer (pH = 3.5). Both, 2.5M acetic acid and 20mM phosphate buffer, were tested as solvents for 7-aminonaphthalene-1,3-disulfonic acid. The reaction with glucose was the best in acetic acid solution. On the contrary, phosphate buf- fer was found to be the best background electrolyte for the separation. Derivatized glucose was detected by UV detector at 229 nm. Henceforth, the reaction con- ditions were adjusted such as reaction time, voltage and time of its application. Input voltage was applied negative due to the...
The use of high-performance separation techniques for monitoring the bioaccumulation of selected micropollutants in plants of model root treatment plants
Modroczká, Karin ; Sobotníková, Jana (advisor) ; Coufal, Pavel (referee)
This bachelor's thesis deals with the determination of ibuprofen in model root refineries from Phalaris arundinacea extracts. The goal was to find out if the plant is able to accumulate ibuprofen from the aqueous solution which was added to the plant. A HPLC method with UV/VIS detection was also optimized to determine the ibuprofen content. A C18 column (4.6 mm × 150 mm × 3.5 µm) was used to analyse the samples. An isocratic program was used, in which the mobile phase consisted of methanol and an aqueous acetic acid solution of pH = 3,27. As part of the validation of the method, the repeatability, robustness, and yield (which was 99,04 %) of the method were verified. Furthermore, the linearity of the method, which was from 0,01 mg ml-1 to 2,0 mg ml-1 , the limit of detection (LOD = 0,049 mg ml-1 ) and the limit of quantification (LOQ = 0,16 mg ml-1 ) were determined. After the validation of the method, we can claim that the method is accurate, because the values of the relative standard deviations did not exceed 2 %. Infrared spectroscopy was used to verify the purity of ibuprofen batches. Last but not least, it was proven that Phalaris arundinacea has the ability to accumulate ibuprofen from an aqueous solution. Keywords: HPLC, ibuprofen, Phalaris arundinacea, root wastewater treatment plant,...
Optimization of electrodeposition of polyaniline on platinum electrode for propanol oxidation
Dobiášová, Klára ; Schwarzová, Karolina (advisor) ; Coufal, Pavel (referee)
Optimization of electrodeposition of polyaniline on platinum electrode for propanol oxidation Dobiášová Klára 2023 Abstract Composites of polyaniline (PANI) with rare metal nanoparticles (metal/PANI) are a promising material for the oxidation of aliphatic alcohols. In this work, the deposition of a polyaniline (PANI) film on a platinum electrode (Pt-PANI electrode) was performed potentiostatically and using cyclic voltammetry (CV). For both methods, the parameters influencing the deposition were optimized. For cyclic voltammetry, electrodeposition in aniline solution is significantly influenced by the final potential Efin of the scan. The PANI film with the highest current response during the deposition itself, which correlates with the thickness of the formed film, was created in the case of Efin + 1.1 V; i.e. the peak potential of the aniline oxidation peak. However, this method proved unreliable due to the poor reproducibility of the current response corresponding to PANI formation. For the PANI film formed by the CV method, its color change related to its oxidation state was investigated, with the color change being imperceptible to the naked eye in a basic environment and the most visible colour change occurring between + 0.05 V and + 0.2 V in an acidic environment. Potentiostatic deposition of...
Capillary monolithic columns based on copolymer of styrene, divinylbenzene and methacrylic acid and their application for separations of small molecules.
Musilová, Adéla ; Coufal, Pavel (advisor) ; Čabala, Radomír (referee) ; Sýkora, David (referee)
This work is focused on the preparation and characterization of capillary monolithic columns based on a copolymer of styrene, divinylbenzene and methacrylic acid for the chromatographic separation of small molecules. The capillary monolithic columns were prepared in the quartz capillaries by one-step radical copolymerization reaction of monomers of styrene, divinylbenzene and methacrylic acid in the presence of toluene and isooctane as porogenic solvents and azobisisobutyronitrile as an initiator. The effect of incorporation of methacrylic acid into the polymerization mixture on the separation behavior and efficiency in reversed phase capillary liquid chromatography (CLC) and capillary liquid electrochromatography (CEC) was studied using a test mixture of compounds containing thiourea, phenol, aniline, benzene, toluene, ethylbenzene, propylbenzene and butylbenzene. The Walters test for reversed stationary phases was employed to evaluate the hydrophobicity of the prepared columns. Based on the calculated value of hydrophobicity index of 10.76, the prepared monolithic columns can be classified as very hydrophobic. Excellent repeatability of measurements in CLC mode and very good repeatability of the monolithic column preparation were achieved. The effect of polymerization time on the chromatographic...
Analysis and characterization of liposomes using capillary electrophoresis
Orgoníková, Andrea ; Křížek, Tomáš (advisor) ; Coufal, Pavel (referee)
4 Abstract This diploma thesis deals with the analysis of three different types of liposomes using capillary electrophoresis with UV-VIS and laser induced fluorescence detection and the use of liposomes as a pseudostationary phase for analyte separations by liposome electrokinetic chromatography method. In experiments with DSPC-DSPG-PEG2000-DMPE liposomes encapsulating 5-fluoruracil, the peak of liposomes with encapsulated 5-fluoruracil and the peak of free 5-fluoruracil were successfully identified in the electropherograms. Both peaks showed the same absorption spectrum in the UV region, thus confirming their identity. It was proved that capillary electrophoresis with UV-VIS detection is useful for the separation and detection of free and encapsulated drug, which is necessary to determine the efficiency of encapsulation. By monitoring the change of effective analyte mobility after the addition of liposomes to the background electrolyte the applicability of the investigated liposomes in liposome electrokinetic chromatography was evaluated. A change in mobility was observed for negatively charged 5-fluoruracil and positively charged tryptamine and p-toluidine. The absolute value of the effective mobility of negatively charged 5-fluoruracil decreased by 18.2 % due to interactions with liposomes and effective...
Determination of estrogen pollutants in real water sample by HPLC-UV after solid phase extraction.
Kozlík, Petr ; Bosáková, Zuzana (advisor) ; Coufal, Pavel (referee)
4 Abstract Estrogens are considered to belong to chemicals that negatively affect the endocrine system, even if present at very low concentrations. They are discharged into environment as a result of an increasing application of drugs etc. This work is focused on the separation and quantification of five estrogens, namely estrone (E1), 17β-estradiol (βE2), 17α-estradiol (αE2), 17α-ethynylestradiol (EE2) and estriol (E3) in natural water samples by HPLC-UV method. The chromatographic system consisted of a C18 stationary phase (SunFire® C18, 150 x 4.6 mm, octadecyl bounded to silica gel, particle size 5 µm) and binary mobile phase of acetonitrile/water in various ratios in isocratic separation mode. The effect of acetonitrile content in the mobile phase and flow rate of the mobile phase on retention and separation parameters was tested. Under the optimized separation conditions (acetonitrile/water 40/60 (v/v), 1.3 ml/min), all the compounds were baseline resolved and eluted within 15 min. These experimental conditions were applied to the calibration measurements which were carried out within the concentration range from 0.001 to 1 mg/ml. Limits of detection (LOD) and limits of quantification (LOQ) for the individual estrogens and their mixture (standards dissolved in methanol) were determinated. The detection...
Analysis of adenosine triphosphate and adenosine diphosphate by HPLC-MS/MS
Černá, Martina ; Coufal, Pavel (advisor) ; Bosáková, Zuzana (referee)
In this bachelor thesis, ADP and ATP samples were analysed and detected with HPLC- MS/MS method. Approximate limit of detection (LOD) for these particular substances were found and their values were compared with the LOD values published in the literature obtained via the same methods and under very similar experimental conditions. Our limits of detection for nucleotides were comparable with the limits described in the literature. Mass spectrometry analysis was performed in the positive and the negative mode of multiple reaction monitoring analysis and electrospray was used for the analyte ionization. The optimal conditions for high performance liquid chromatography of ATP and ADP analysis were acquired on a ZIC - HILIC column with the mobile phase of 75:25 (v/v) acetonitrile / 10 mM ammonium acetate. Ammonium acetate buffer was adjusted to pH of 7.15 and the separation was done under the isocratic elution.

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3 COUFAL, Patrik
5 COUFAL, Petr
3 Coufal, Patrik
5 Coufal, Petr
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