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Study of retention and separation of pesticides in different modes of liquid chromatography
Dérerová, Tímea ; Kalíková, Květa (advisor) ; Riesová, Martina (referee)
4 Abstract This bachelor thesis is focused on a separation of six pesticides in reversed-phase and mixed-mode high performance liquid chromatography using Atlantis dC18, XSelect CSH C18, XSelect CSH Fluro-Phenyl and Atlantis Premier BEH C18 AX columns. The same manufacturing parameters - column and carrier particle dimensions opened up the possibility of their direct comparison in terms of retentivity and selectivity. The stationary phases were categorized using Walters test, in terms of hydrofobicity, silanol activity and efficiency. The analytes of interest were pesticides with a different mechanism of action in the environment. Two of them contained an acidic functional group that caused their elution at system void volume if pure water was used as aqueous part of mobile phase. For suppression of dissociation of acidic pesticides, the buffers, i.e., 10mM ammonium acetate, pH 4.7 and 10mM ammonium formate, pH 3.0 were used instead of pure water. Tested columns exhibited different retention and selectivity of analytes. For separation conditions optimization, an experimental approach, including changes in mobile phase composition and pH, and separation temperature, was used. Retention time, resolution and peak shape were all dependent on these chromatographic parameters. The retention of tested pesticides...
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Characterization and comparison of new reversed-phase HPLC columns
Putzová, Klára ; Kalíková, Květa (advisor) ; Kozlík, Petr (referee)
The aim of the bachelor thesis was to evaluate and compare interaction/separation properties of three chromatographic columns, namely XBridge C18, XSelect CSH C18 XSelect HSS C18, designed for reversed-phase high performance liquid chromatography. All the columns contain the same ligand, i.e. octadecyl but they differ in the stationary phase support. The columns were compared in terms of silanol activity, hydrophobicity, shape selectivity and efficiency. For this purpose, the simple chromatographic tests designed by Walters, Engelhardt and Galushko were used. Furthermore, the separation of five selected pesticides, namely acetochlor, fomesafen, isoproturon, metazachlor triflumuron, were optimized on tested columns in simple mobile phases composed of acetonitrile or methanol as organic modifiers and water. All the tested columns showed low silanol activity and medium to high hydrophobicity acording to the chromatographic tests used. The low silanol activity corelates with endcapping procedure used for all the columns. All pesticides were more retained in methanolic mobile phase due to the lower elution strength of methanol compared to acetonitrile in reversed-phase high performance liquid chromatography. The analysis time of separation varied for each column under the same chromatographic conditions. The...
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Optimization of HPLC separation of penicillin derivatives
Šímová, Veronika ; Kalíková, Květa (advisor) ; Tesařová, Eva (referee)
Penicillins are part of β-lactam antibiotics, which are wide spread in human and veterinary medicine. The aim of this bachelor work was to develop and to optimize HPLC method for separation of four derivatives of penicillin - amoxicillin, 4-hydroxyphenoxymethylpenicillin, benzylpenicillin and phenoxymethylpenicillin. The reserved phase HPLC with octodecyl stationary phase was used in this work. The baseline separation of all analytes was not obtained in isocratic elution. For this reason, the gradient elution was examined on the baseline resolution of all analytes was achieved and the analysis time did not exceed 22 minutes. The stability of methanolic solutions of penicillins was tested during eight days. Key words: HPLC, antibiotics, derivatives of penicillins, reverse mod, stability
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Characterization and comparison of new reversed-phase HPLC columns
Putzová, Klára ; Kalíková, Květa (advisor) ; Kozlík, Petr (referee)
The aim of the bachelor thesis was to evaluate and compare interaction/separation properties of three chromatographic columns, namely XBridge C18, XSelect CSH C18 XSelect HSS C18, designed for reversed-phase high performance liquid chromatography. All the columns contain the same ligand, i.e. octadecyl but they differ in the stationary phase support. The columns were compared in terms of silanol activity, hydrophobicity, shape selectivity and efficiency. For this purpose, the simple chromatographic tests designed by Walters, Engelhardt and Galushko were used. Furthermore, the separation of five selected pesticides, namely acetochlor, fomesafen, isoproturon, metazachlor triflumuron, were optimized on tested columns in simple mobile phases composed of acetonitrile or methanol as organic modifiers and water. All the tested columns showed low silanol activity and medium to high hydrophobicity acording to the chromatographic tests used. The low silanol activity corelates with endcapping procedure used for all the columns. All pesticides were more retained in methanolic mobile phase due to the lower elution strength of methanol compared to acetonitrile in reversed-phase high performance liquid chromatography. The analysis time of separation varied for each column under the same chromatographic conditions. The...
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Separation of chiral compounds
Šrolerová, Tereza ; Kubíčková, Anna (advisor) ; Křížek, Tomáš (referee)
This bachelor thesis deals with the chiral separation of newly synthesized orthoconic antiferroelectric liquid crystals using ultra-high performance liquid chromatography. These studied compounds differ in the alkyloxy-spacer length, in the presence and/or position of the fluorine atom on the phenyl ring and in the chiral center. The separation took place in a reverse separation mode using a chiral stationary phase based on derivatized amylose. First, the effect of mobile phase flow rate and column temperature on separation efficiency was exanimated. The effect of the composition of the mobile phase on the enantioseparation were studied at the optimum temperature and flow rate. The mobile phase was based on acetonitril, while deionized water was added gradually using isocratic elution. Furthermore, the effect of chromatographic conditions and the structure of the studied analytes on resolution and enantioselectivity was investigated, concretely the presence and position of fluorine atom on pfenyl ring, the length of alkyloxy-spacer and the effect of divergent chiral center. Under optimized chromatography conditions we succeeded to separate all examined substances on the base line. Key words: ultra-high performance chromatography, liquid crystals, enantioseparation, chiral stationary phase, reverse mode
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Optimization of HPLC separation of penicillin derivatives
Šímová, Veronika ; Kalíková, Květa (advisor) ; Tesařová, Eva (referee)
Penicillins are part of β-lactam antibiotics, which are wide spread in human and veterinary medicine. The aim of this bachelor work was to develop and to optimize HPLC method for separation of four derivatives of penicillin - amoxicillin, 4-hydroxyphenoxymethylpenicillin, benzylpenicillin and phenoxymethylpenicillin. The reserved phase HPLC with octodecyl stationary phase was used in this work. The baseline separation of all analytes was not obtained in isocratic elution. For this reason, the gradient elution was examined on the baseline resolution of all analytes was achieved and the analysis time did not exceed 22 minutes. The stability of methanolic solutions of penicillins was tested during eight days. Key words: HPLC, antibiotics, derivatives of penicillins, reverse mod, stability
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Optimization of HPLC method for separation of tetracyclines
Kučerová, Gabriela ; Kalíková, Květa (advisor) ; Janečková, Lucie (referee)
The aim of this work is to develop and to optimize HPLC method for separation of a set of four tetracycline antibiotics - tetracycline, chlortetracycline, oxytetracycline, and doxycycline. Four different reversed octadecyl-silica stationary phases in various mobile phase compositions were examined in isocratic elution. The baseline resolution of all the analytes was obtained by using two columns - Astec C18 and Atlantis C18 I. The optimized separation system consisted of Atlantis C18 I. column, ACN/0.1% formic acid 15/85 (v/v) as the mobile phase and flow rate of 2 ml/min. The baseline resolution was achieved and the analysis time did not exceed 27.5 minutes.
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