|
|
Separation of liquid crystal forming substances using non-aqueous capillary electrokinetic chromatography
Čokrtová, Kateřina ; Křížek, Tomáš (advisor) ; Kubíčková, Anna (referee)
Liquid crystals are widely used in electronics, medicine and other fields. Analytical separations are important in the development of new liquid crystals to control the purity of synthesized substances. The sample analysis is important for detection of impurities formed during synthesis and for determination of chiral purity of the substance. Liquid crystal-forming substances cannot be separated by capillary zone electrophoresis due to the absence of readily ionizable groups. Electrokinetic chromatography is a method in which a suitable surfactant is added to the background electrolyte. The uncharged substances then interact with the electrically charged surfactant to obtain an effective charge. Separation can occur if they interact differently with the added surfactant. Another problem complicating the analysis is the very low solubility of analytes in water. Separations in this work were therefore carried out under non-aqueous conditions in acetonitrile. However, under these conditions a poor repeatability of the migration times of the substances was observed. Therefore, capillaries with differently coated inner walls were used in subsequent measurements. Surface modification should improve the repeatability of migration times. Several types of capillary coating have been tested. Dynamic coating...
|
|
|
Effect of separation electrolyte ions on baseline stability in capillary electrophoresis
Kolečkářová, Tereza ; Křížek, Tomáš (advisor) ; Kubíčková, Anna (referee)
Unstable electropherogram baseline of potassium buffer, found while studying electrophoretic mobilities of electroosmotic flow markers in different separation buffers [1], makes it harder for higher concentrations of buffers to evaluate the results. This work investigates, whether the above described phenomenon is confined to potassium ions, and if it is not, what conditions influence it. The measure of instability of signal baseline is taken as its standard deviation and it is compared for potassium, sodium, ammonium and lithium buffers. For potassium and sodium buffers influence of high voltage on the system is studied using pressure to mobilize solution inside the capillary. It is proven that the instability for potassium buffer is increased with high voltage. The instability of the signal is then compared for different voltage levels. The results show to the influence of Joule heating. The stability of signal baseline for all studied cations was found to be decreasing with increasing ionic strength and conductivity. This work concludes, that this phenomenon does not confine only to potassium ions. Even though the potassium buffer does not have the highest conductivity, signal instability was the highest however. The degree of instability of signal baseline for potassium buffer depends not only...
|
|
|
Characterization of protamine influence on indirect electrophoretic determination of heparin
Petrák, Ondřej ; Křížek, Tomáš (advisor) ; Kubíčková, Anna (referee)
Cílem této bakalářské práce bylo studium interakcí heparinu a protaminu v prostředí kapilární zónové elektroforézy pomocí jejich vlivu na velikost plochy píku tetraargininu. Byla použita křemenná kapilára o vnitřním průměru 50 µm a celkové délce 50 cm. Efektivní délka kapiláry byla 41,5 cm a vzorek byl dávkován na dlouhý konec kapiláry. Byl optimalizován způsob dávkování jednotlivých zón, vhodné složení základního elektrolytu bylo již známo z předešlých experimentů, na které tato práce navazovala. Základní elektrolyt byl složen z 0,1 M roztoku kyseliny trihydrogenfosforečné a 0,1% roztoku hydroxyethylcelulózy. Vzorek byl dávkován hydrodynamicky tlakem 5,0 kPa po dobu 120 s. Následně byla stejným tlakem po dobu 90 s dávkována zóna základního elektrolytu. Poslední dávkovanou zónou byla zóna tetraargininu o koncentraci 1 mg/ml, která byla dávkována hydrodynamicky tlakem 5,0 kPa po dobu 3 s. Posledním krokem bylo vložení separačního napětí 30 kV po dobu 30 s. Tetraarginin byl detegován při λ = 200 nm. Byly změřeny vlivy samotného heparinu/ protaminu a jejich směsí v různých vzájemných poměrech. Bylo ověřeno, že se zvyšující se koncentrací heparinu dochází k poklesu plochy píku tetraargininu. Nově bylo zjištěno, jaký vliv na velikost tohoto účinku má přítomnost protaminu. Zde došlo k překvapivému...
|
|
|
Enantioselective potential of sulfobutylether-β-cyclodextrin based chiral stationary phase
Folprechtová, Denisa ; Kalíková, Květa (advisor) ; Kubíčková, Anna (referee)
The aim of this diploma thesis was to prepare two new chiral stationary phases by dynamic coating of sulphobutylether-β-cyclodextrin (SBE-β-CD) with varying degrees of substitution onto strong anion-exchange stationary phases. The enantioselective potential and stability of the newly prepared chiral stationary phases were tested using a set of chiral analytes. The set contained structurally diverse analytes, i.e. benzodiazepines (oxazepam, lorazepam), phenothiazines (thioridazine, promethazine), β-blockers (labetalol, pindolol, propranolol, alprenolol), profens (carprofen, fenoprofen, flurbiprofen, indoprofen), flavanones (6-hydroxyflavanone, 7-hydroxyflavanone), DL-tryptophan and its derivatives (5-OH-DL-tryptophan, 5-F-DL-tryptophan, DL-tryptophan butylester and blocked aminoacid (t-Boc-DL-tryptophan)), dipeptides (glycyl-DL-phenylalanine, glycyl-DL-tryptophan) and Troger's base. Measurements were carried out in reversed-phase high-performance liquid chromatography. Mobile phases consisted of methanol/formic acid (pH 2.10) and methanol/10mmol l-1 ammonium acetate buffer (pH 4.00) in various volume ratios. The chiral stationary phase containing hexasubstituted SBE-β-CD was suitable for enantioseparation of eleven analytes. Four of them were baseline enantioresolved and seven partially. The chiral...
|
|
|
Indirect determination of heparin by capillary electrophoresis
Filounová, Barbora ; Křížek, Tomáš (advisor) ; Kubíčková, Anna (referee)
Heparin is a mixture of sulfonated polysaccharides which is negatively charged. Heparin is a substance which is important in organism and fundamentally affects its physiology. Main attribute of heparin is anticoagulation - it prevents the complete blood coagulation. This anticoagulant effect balances the hemocoagulation by influencing the coagulation pathway. In some cases a pharmacological application of heparin is needed so the heparin is administrated as a injection of physiological solution of sodium or calcium heparine salt. Monitoring of level of the heparin in blood is problematic - methods used today are based on the measurement of a time required for blood clot formation. The result evaluation is done by comparing a sample with reference solution. These methods are relatively imprecise, can not be used in "on-line" setting and are highly influenced by general health condition of patient. In this work some principles of affinity capillary electrophoresis were adapted from another work - heparin was determined indirectly by monitoring of decrease of the peak area of protamine. Protamine is medically used antidote of heparin because they create a stable complex together. In this work protamine was replaced by well defined tetraarginine because the most frequent amino acid in protamine is...
|
|
|
Validation of HPLC method for determination of purity of sofosbuvir and its transfer to UPLC system
Vymyslický, Filip ; Křížek, Tomáš (advisor) ; Kubíčková, Anna (referee)
The aim of this bachelor thesis was validation of HPLC method for determination of purity of sofosbuvir and its transfer to UPLC system. The parameters included in the validation plan were: the system suitability test, robustness, accuracy, linearity, recovery, limit of detection, and limit of quantification. Robustness was tested by the design of experiments approach. Method was transferred from the HPLC system to the UPLC system. The transfer was performed by randomization test, which was evaluated by statistical methods, namely by pairwise T-test and correlation analysis.
|
|
|
Approach to Diagnostics of School Readiness in the Three European Countries
Kubíčková, Anna ; Felcmanová, Lenka (advisor) ; Marádová, Eva (referee)
TITLE: Approach to Diagnostics of School Readiness in the Three European Countries AUTHOR: Anna Kubíčková DEPARTMENT: Department of Special Education SUPERVISOR: PhDr. Lenka Felcmanová, Ph.D. ABSTRACT: This thesis compares approaches to school readiness diagnostics in the Czech Republic, the United Kingdom of Great Britain and Northern Ireland and Austria. It explains the theoretical concept of school readiness, presents the possible consequences of inadequate readiness of a child enrolling in the first year of primary school, and gives examples of diagnostic materials used to evaluate school maturity and child readiness in the Czech Republic and abroad. This work describes the specifics of pre-school and early primary education, the processes of a child's entry into primary education and explains the involvement of educational authorities in the diagnostics of school readiness in the three studied countries. In practice, it compares the approaches to school readiness diagnostics and the entry of children into primary education through the testimonies of teachers and experts from these three countries. This thesis also deals with the different procedures for forwarding documents containing information on children's development from pre-school educational institutions to primary schools, the diversity of...
|
|
|
Effect of background electrolyte anions on markers of electroosmotic flow in capillary electrophoresis
Čokrtová, Kateřina ; Křížek, Tomáš (advisor) ; Kubíčková, Anna (referee)
Mobility of the electroosmotic flow is an important quantity in capillary electrophoresis because its value is needed to determine the effective electrophoretic mobility of analytes. The effective electrophoretic mobility is used for electrophoretic determination of physico-chemical constants, such as dissociation constants or stability constants, but it is also important in analytical chemistry because identification of analytes is based on the value of the effective mobility. The most common way to measure electroosmotic flow is to add a neutral substance to the sample. However, the neutral substance can gain electrophoretic mobility due to interactions with the components of the background electrolyte. This may cause an inaccurate determination of the velocity of the electroosmotic flow. The aim of this work was to measure the mobility of several common and less frequently used markers in the background electrolyte containing different anions and to find suitable marker - anion combinations in order to avoid major measurement errors. Relative mobility of eight markers in the pure background electrolyte and in the background electrolyte containing a salt of the studied anion - sodium chloride, sodium perchlorate or sodium sulphate - was measured and related mobility of thiourea. Acetate buffer...
|
|
|
Determination of Engine Coolants by UHPLC
Smrž, Dominik ; Kubíčková, Anna (advisor) ; Sobotníková, Jana (referee)
4 Abstract Nowadays, there is no standard method for determination of organic corrosion inhibitors in engine coolant. Due to that the aim of this bachelor thesis is to develop a rapid and effective method for their determination by UHPLC method in all commercially available engine coolants. The method was developed and optimized. The optimal separation conditions are: core-shell column Poroshell 120 SB-AQ, gradient elution programme of methanol and 0.05% (v/v) trifluoracetic acid solution mixture (concentration of methanol changes from 40 to 65 % (v/v)), dosed volume 1 µl, detection at wavelength 211 nm. All analyzes were performed at 25 řC. The analysis duration is 6.5 min. Calibration dependences were measured from 0.25 to 4.0 g l-1 for 2-ethylhexanoic, 3,5,5-trimethylhexanoic, nonanoic and decandioic acid, in range 0.025 - 0.400 g l-1 for imidazole, benzotriazole, methylbenzotriazole, benzothiazole-2-thiol and benzoic acid. The calibration curves are linear in whole range of detector for all chosen corrosion inhibitors. Key words engine coolants, organic acids, aryltrizoles, UHPLC, Core-Shell columns
|
|
|
Study of interaction between protamine and heparin and its applicability in capillary electrophoresis
Martínková, Eva ; Křížek, Tomáš (advisor) ; Kubíčková, Anna (referee)
Heparin is an acid mixture of glycosaminoglycans with high negative charge density which naturally occurs in human body. Due to its ability to bind antithrombin III and thus accelerate inhibition of thrombin it has anticoagulant effect. This is abundantly used in clinical practice for operations, in case of embolia or heart-attacks. Protamine is a mixture of small basic peptides, which is used in clinical practice as a heparin antidote. The interaction between heparin and protamine is electrostatic and is also used for determination of heparin in human plasma or blood using affinity methods. In my study it was found that if protamine and heparin are mixed in one vial, a complex is formed. Its resulting charge depends on concentration ratio of protamine and heparin. On the other hand, in case the protamine is injected as a sample and heparin is added to background electrolyte as a protein-binding ligand, it is possible to determine heparin from decreasing protamine peak area. Because of the complexity of protamine-heparin interaction, tetraarginine was used as structurally close model of protamine to increase repeatability of measurements. The method for determination of heparin was optimalised. It uses 20 mM or 60 mM ortho-phosphoric acid as background electrolyte, 1 mg/mL solution of tetraarginine...
|
guest ::
RSS feed.