|
|
Determination of stability constants of charged cyclodextrine complexes by capillary electrophoresis
Beneš, Martin ; Zusková, Iva (advisor) ; Dubský, Pavel (referee)
Martin Beneš Determination of stability constants of charged cyclodextrin comlexes by capillary electrophoresis Abstract Stability constant characterizes binding interaction between an analyte and complexation agent. These interactions play very important role in separation processes of, in other way undistinguishable, compounds, e.g. enantiomers. The most widely used complexation agents are cyclodextrins. Affinity capillary electrophoresis (ACE) belongs to methods suitable for the determination of stability constants. The stability constant is determined from the dependence of the effective mobility of analyte on the increasing concentration of complexation agent in background electrolyte (BGE). If charged CDs are used, the attention must be paid not only to viscosity of the BGE and to the influence of Joule heating on the temperature in the capillary but also to the increasing ionic strength. The thermodynamic stability constants of R,R- and S,S-hydrobenzoin and R- and S-(3-brom- 2-methyl-1-propanol) with cationic modified β-cyclodextrin: 6-monodeoxy-6-mono(3- hydroxy)propylamino-β-cyclodextrin hydrochlorid (PABCD) were determined by affinity capillary electrophoresis. The average temperature (25řC) of the BGE in the capillary was kept constant. This was achieved by decreasing of the cassette temperature...
|
|
|
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...
|
|
|
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...
|
|
|
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...
|
|
|
Nonlinear phenomena in electrokinetic chromatography
Dovhunová, Magda ; Dubský, Pavel (advisor) ; Koval, Dušan (referee) ; Ševčík, Juraj (referee)
Capillary electrophoresis often uses complexing agents since the interaction between the analyte and the complexing agent can result in achieving or improving the separation. Examples of such methods can be electrokinetic chromatography or affinity capillary electrophoresis (ACE). ACE is used to determine the complexing parameters. In case of chiral separation, this issue gets complicated, since the parameters of the two analytes (enantiomers) are not completely independent to one another. Therefore, a procedure has been proposed in this thesis, that should always be used to evaluate the complexing parameters of two enantiomers. Statistical evaluation of these parameters was assessed as well. This work also proposes a method that allows to determine the relative migration order of two enantiomers in two different complexing separation systems. The mathematical description of electrophoresis is based on continuity equations, that are inherently nonlinear. However, these equations can be linearized to obtain an approximate analytical solution. There was recently presented a generalized model, that enables inclusion of complete complexing equilibria in the theoretical description of electromigration. Thus, various phenomena, including nonlinear ones, associated with complexation can be predicted. This...
|
|
|
Dynamic Enantioseparation in Capillary Zone Electrophoresis
Dubský, Pavel ; Gaš, Bohuslav (advisor) ; Kašička, Václav (referee) ; Gebauer, Petr (referee)
12 4 CONCLUSION In the framework of my Ph.D. study, software EvalChir was developed for evaluation of elution profiles from dynamic enantioseparation. Further our previously developed simulation software SimulChir was extended by an iterative algorithm to be able to fit the experimental peak profiles by simulated ones and to find out the apparent rate constant of interconversion. Both the programs form complex solution for fast and easy evaluation of data obtained from dynamic enantioseparation techniques. A new method for determination of all four rate constants of interconversion involved in the true scheme (Figure 1A) was designed. In this way, the apparent thermodynamics is resolved back to the true one and an influence of a CS on the rate of interconversion can newly be studied. We verified this technique experimentally. A multi-CS enantioseparative system was described considering interaction of a chiral analyte with any arbitrary mixture of CSs. The model indicates that any multi-CS system may be formally treated as if only one CS was present there with some overall distribution constant, overall limit mobility and overall rate constant of interconversion of an enantiomer with respect to the mixture of CSs as a whole. The exact composition of the mixture even does not need to be known at all. On the...
|
|
|
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...
|
|
|
Automatic data analysis in capillary zone electrophoresis
Ördögová, Magda ; Dubský, Pavel (advisor) ; Heyda, Jan (referee)
Evaluating data in capillary zone electrophoresis usually involves many steps that require using several different programmes. Apart from evaluating the electrophoreogram itself, it is usual to process the obtained data in some other way. For example, a suitable model is fit to the data in order to obtain physical and chemical parameters of the separation (e.g. stability constant in case of complexation). It is also important to know the accuracy of the evaluation (the calculation error). In this work, new parts of the Eval programme, originally developed for electrophoreogram evaluation, were implemented. The programme now automatically estimates the Haarhoff-van der Linde function (solution of continuity equation in capillary) parameters for analyte peak. Complexing agents are often used to improve the separation in the capillary zone electrophoresis. Complexation in the capillary can be described by its physical and chemical parameters. A new part was added to the Eval programme that allows the user to fit a rectangular hyperbole function to the obtained data. Thus, the regression parameters of this dependence can be gained. The programme can also draw profile diagrams for these parameters, from which the confidence intervals can be read. An option that allows two dependencies to be fitted at...
|
|
|
Interaction of pesticides - 1-naphthylacetic acid and 1-naphthylacetamide - with cucurbit[7]uril and selected cyclodextrins
Ördögová, Magda ; Dubský, Pavel (advisor) ; Beneš, Martin (referee)
This work evaluates and compares interaction of 1-naphthylacetic acid and 1-naphthylacetamide with selected complexing agents. 1-naphthylacetic acid and 1-naphthylacetamide are used as pesticides. From the viewpoint of ecology, the possibility of regulation of the photodecomposition of these pesticides is interesting. Such regulation could be for example arranged by complexation. Cyclodextrins, known for its good capability of interaction with wide spectrum of substances, were chosen as the complexing agents. Next chosen complexing agent was cucurbit[7]uril that, according to literature, could be capable of even stronger interaction than cyclodextrins. Interactions were studied by methods of affinity capillary zone electrophoresis. The strenght of single interactions was compared and if it was possible, the stability constant of the complex was determined.
|
|
|
Electromigration behaviour of polyelectrolyte-ionic surfactant complexes and block copolymer vesicles
Černá, Karolina ; Zusková, Iva (advisor) ; Dubský, Pavel (referee)
Capillary zone electrophoresis (CZE) is not only a widely used analytical separation method, but it is also an important technique for determining physico-chemical parameters of materials. Significant use is also in the characterization of potentially interesting macromolecular substances. In this master's thesis, CZE was applied to the study of polyelectrolyte−oppositely charged ionic surfactant complexes. For the first studied complex formed by poly(ethylene oxide)-block-poly(sodium methacrylate) and surfactant N- dodecylpyridinium chloride, the electrophoretic mobility of surfactant depending on the ratio of surfactant concentration in the sample to the concentration of polyelectrolyte present in the background electrolyte was measured. However, we did not get the significant decrease in mobility as was predicted in the literature based on measuring the ζ-potential. This can be explained by the low stability of the complex in an electric field. The second system, the polyelectrolyte−surfactant complex of cationic−neutral hydrophilic block copolymer poly[3,5-bis(trimethylammoniummethyl)-4-hydroxystyrene iodide]-block-poly(ethylene oxide) and surfactant sodium dodecyl sulfate, could not be characterized using conventional CZE experiments described. The reason was probably due to a strong interaction of...
|
guest ::
RSS feed.