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System peaks in elektromigration systems with complexing agents
Dvořák, Martin ; Gaš, Bohuslav (advisor) ; Coufal, Pavel (referee)
Capillary zone electrophoresis (CZE) is a widely used analytical method. CZE is described theoretically very well and there are many simulation programs, which enable one to predict results of electrophoretic separations, and alternatively to study phenomena taking place during the electrophoretic separation in detail. The CZE method is not only an analytical method, but is often used for determination of many physical parameters of compounds, such as stability constants or complex mobilities. Among methods most often used for determination of complexation parameters belongs the affinity capillary electrophoresis (ACE). Its alternative is the vacancy affinity capillary electrophoresis (VACE). Whereas by the ACE method the stability constant is determined from the dependence of the analyte effiective electrophoretic mobility on the background electrolyte (BGE) composition, in the case of the VACE system peaks are used for this purpose. In this work the legitimacy of using system peaks in the VACE method for determination of stability constants was investigated. Several approaches dealing with the concentrating of complexing agent in the peak area were compared, both for the ACE and the VACE method. Two different kinds of electrophoretic systems were studied. In the first one, neutral cyclodextrin was used as...
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Influence of the interacting constituent of the background electrolyte on electrophoretic separation
Müllerová, Ludmila ; Dubský, Pavel (advisor) ; Kašička, Václav (referee) ; Petr, Jan (referee)
Capillary electrophoresis is a widely used separation method of analytical chemistry. Addition of a selector into the background electrolyte extends its applicability to separation of enantiomers or of compounds of similar physicochemical properties. In analytical practice, mixtures of selectors are also commonly used - either prepared intentionally to achieve better separation or because commercially available selectors may be mixtures of compounds differing in the degree of substitution and substituent positions. Mathematical description of these systems, which are highly relevant in analytical practice, can simplify search for optimal separation conditions. Also, it provides a useful insight into the separation mechanism. In this work, a model of electromigration of an analyte interacting with a mixture of two selectors is proposed and experimentally verified. This model results from a more general description of systems with an arbitrary number of selectors. The model shows that a selector mixture can be treated as a single selector if the ratio of the respective selector concentrations is kept constant. When the mixture is prepared intentionally, this description predicts, how separation potential of the mixture changes with its composition. Thus it allows the optimal composition and total...
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Determination of complexation constants of weak electrolyte analytes by Affinity capillary electrophroesis
Ansorge, Martin ; Šteflová, Jana (advisor) ; Ušelová, Kateřina (referee)
Capillary electrophoresis is not only excellent separation technique but it is often advantageously used for determination of physical-chemical parameters of compounds such as complexation constants of analyte and appropriate complexation agent. The most frequently used electrophoretic method for determination of complexation constants is affinity capillary electrophoresis. In the frame of this work the affinity capillary electrophoresis is used for determination of complexation constants of R and S enantiomers of flurbiprofen, particularly both its neutral and fully dissociated form with neutral β- cyclodextrin. For this purpose we utilized classical method introduced in literature, where complexation constants are determined at two pHs, where analyte is fully and partially dissociated, respectively. Simultaneously, the complexation constants were observed by the new method based on multidimensional nonlinear regression, where all data measured at different pHs and β-cyclodextrin concentrations were utilized for evaluation. Results show that classical method can be highly confusing, especially if unsuitable pH is chosen for determination of stability constants of neutral form of analyte. Multidimensional regression method provides substantially more reliable data but with higher error of estimate....
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Application of advanced models of electromigration by means of computer software
Malý, Michal ; Dubský, Pavel (advisor) ; Petr, Jan (referee) ; Thormann, Wolfgang (referee)
Motion of ions under the influence of electric field has been a subject of scientific interest for many decades. Capillary electrophoresis in particular benefited greatly from this research and mathematical models of electromigration applicable to capillary electrophoresis have been developed. As the sophistication of the models grew, so did the computational demands to evaluate them. In order to fully exploit the possibilities of advanced mathematical models a computer implementation capable of solving non-trivial problems at sufficient speed is necessary. This dissertation thesis explores applications of computer implementations of mathematical models re- lated to electromigration in two different areas. The main focus of this thesis is on the topic of linear theory of electromigration. We discuss the extension of the linear theory of electromigration beyond of just acid-base equilibria and computer implementation of this extented theory which is specialized to include complex-forming equilibria in order to be able to deal with affinity capillary electrophoresis prob- lems. Some technical aspects of the computer implementation are also discussed. This is followed upon by investigating certain selected affinity capillary electrophoresis systems. The purpose of this investi- gation is to re-derive...
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Mathematical modelling of linear and nonlinear phenomena in capillary electrophoresis
Dvořák, Martin ; Dubský, Pavel (advisor) ; Kašička, Václav (referee) ; Gebauer, Petr (referee)
Capillary electrophoresis is one of the prominent analytical separation methods. Currently, many computer programs exist which are able to predict the result of an electrophoretic experiment. Firstly, there are programs based on numerical solving of corresponding continuity equations and equations of chemical equilibria. Secondly, there are programs based on approximative models of capillary electrophoresis. Programs belonging to the first group are applicable to a wide range of modes of capillary electrophoresis and provide a precise solution. Their disadvantage is though a considerable time demand. On the other hand, the approximative models give the results almost immediately and, in addition, provide some theoretical relationships which are useful for optimization of the separation process. This dissertation thesis is focused on improvement and extension of validity of existing approximative models of capillary electrophoresis. As a part of this thesis, a model capable of a full-blown description of capillary electrokinetic chromatography is introduced. This model is implemented into program PeakMaster 6. The attention is also paid to a nonlinear model of electromigration without diffusion. This model enables a very good description of electromigration dispersion including effects related to...
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Influence of the interacting constituent of the background electrolyte on electrophoretic separation
Müllerová, Ludmila ; Dubský, Pavel (advisor) ; Kašička, Václav (referee) ; Petr, Jan (referee)
Capillary electrophoresis is a widely used separation method of analytical chemistry. Addition of a selector into the background electrolyte extends its applicability to separation of enantiomers or of compounds of similar physicochemical properties. In analytical practice, mixtures of selectors are also commonly used - either prepared intentionally to achieve better separation or because commercially available selectors may be mixtures of compounds differing in the degree of substitution and substituent positions. Mathematical description of these systems, which are highly relevant in analytical practice, can simplify search for optimal separation conditions. Also, it provides a useful insight into the separation mechanism. In this work, a model of electromigration of an analyte interacting with a mixture of two selectors is proposed and experimentally verified. This model results from a more general description of systems with an arbitrary number of selectors. The model shows that a selector mixture can be treated as a single selector if the ratio of the respective selector concentrations is kept constant. When the mixture is prepared intentionally, this description predicts, how separation potential of the mixture changes with its composition. Thus it allows the optimal composition and total...
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Determination of complexation constants of weak electrolyte analytes by Affinity capillary electrophroesis
Ansorge, Martin ; Šteflová, Jana (advisor) ; Ušelová, Kateřina (referee)
Capillary electrophoresis is not only excellent separation technique but it is often advantageously used for determination of physical-chemical parameters of compounds such as complexation constants of analyte and appropriate complexation agent. The most frequently used electrophoretic method for determination of complexation constants is affinity capillary electrophoresis. In the frame of this work the affinity capillary electrophoresis is used for determination of complexation constants of R and S enantiomers of flurbiprofen, particularly both its neutral and fully dissociated form with neutral β- cyclodextrin. For this purpose we utilized classical method introduced in literature, where complexation constants are determined at two pHs, where analyte is fully and partially dissociated, respectively. Simultaneously, the complexation constants were observed by the new method based on multidimensional nonlinear regression, where all data measured at different pHs and β-cyclodextrin concentrations were utilized for evaluation. Results show that classical method can be highly confusing, especially if unsuitable pH is chosen for determination of stability constants of neutral form of analyte. Multidimensional regression method provides substantially more reliable data but with higher error of estimate....
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System peaks in elektromigration systems with complexing agents
Dvořák, Martin ; Gaš, Bohuslav (advisor) ; Coufal, Pavel (referee)
Capillary zone electrophoresis (CZE) is a widely used analytical method. CZE is described theoretically very well and there are many simulation programs, which enable one to predict results of electrophoretic separations, and alternatively to study phenomena taking place during the electrophoretic separation in detail. The CZE method is not only an analytical method, but is often used for determination of many physical parameters of compounds, such as stability constants or complex mobilities. Among methods most often used for determination of complexation parameters belongs the affinity capillary electrophoresis (ACE). Its alternative is the vacancy affinity capillary electrophoresis (VACE). Whereas by the ACE method the stability constant is determined from the dependence of the analyte effiective electrophoretic mobility on the background electrolyte (BGE) composition, in the case of the VACE system peaks are used for this purpose. In this work the legitimacy of using system peaks in the VACE method for determination of stability constants was investigated. Several approaches dealing with the concentrating of complexing agent in the peak area were compared, both for the ACE and the VACE method. Two different kinds of electrophoretic systems were studied. In the first one, neutral cyclodextrin was used as...
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