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2-D simulations of electromigration processes
Kolivoška, Viliam ; Gaš, Bohuslav (advisor) ; Koval, Dušan (referee)
6 Abstract In the presented thesis we introduce a computational model that can be used for 2-D and 3-D computer simulations of experiments in electrophoresis. The simulations are carried out by the aid of the finite element method (FEM). In particular, commercially available program Comsol Multiphysics 3.3 is employed. A general shape of continuity equation is chosen to express the mass, electric charge, momentum and energy conservation law. Diffusion, migration and convection terms are taken into account when formulating the mass conservation law. Both external (driving voltage) and internal (diffusion currents) terms are considered in the electric charge conservation law. Both constant voltage mode and constant current mode can be handled. A solvent is regarded as an incompressible Newtonian fluid. Both pressure-driven and electroosmotic flows can be taken into consideration. The heat convection as well as the heat diffusion is governed by the energy conservation law. Both strong and weak electrolytes (of any attainable valency) may be regarded as system constituents. Furthermore, the model can handle the ionic strength correction if desired. A task may be assigned either in Cartesian or cylindrical coordinates. The presented model was employed to solve four particular tasks. The first one inspects the...
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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...
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Enantioseparation and estimation of racemization barriers of selected helquats and their derivatives by capillary electrophoresis using sulfated cyclodextrins as chiral selectors
Sázelová, Petra ; Koval, Dušan ; Severa, Lukáš ; Reyes Gutierrez, Paul Eduardo ; Jirásek, Michael ; Teplý, Filip ; Kašička, Václav
Anionic highly sulfated β- and γ-cyclodextrins (S-CDs) and single-isomer heptakis-(2,3-diacetyl-6-sulfato)-β-CD (14Ac-7S-β-CD) were used for chiral separation of [5], [6] and [7]-ring helquats and helquat styryl dyes by capillary electrophoresis (CE) in the background electrolyte composed of 22 mM NaOH/35 mM H3PO4, pH 2.4. The CE method was applied for monitoring of racemization of eight helquats and helical dyes. Rate constant k of conversion, half-life T1/2 of racemization, and activation Gibbs free energy ΔGǂ of interconversion of one enantiomer into the other were calculated from the dependence of natural logarithm of enantiomeric excess (ee) on time using linear regression analysis.
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Affinity capillary electrophoresis applied to chiral separations of diquats and to determination of the stability constants of their complexes with sulfated cyclodextrins
Kašička, Václav ; Bílek, Jan ; Koval, Dušan ; Sázelová, Petra ; Talele, Harish Ramesh ; Severa, Lukáš ; Reyes Gutierrez, Paul Eduardo ; Teplý, Filip
Affinity capillary electrophoresis (ACE) using an aqueous 22/35 mM sodium/phosphate buffer, pH 2.5, as the background electrolyte (BGE), and 6 mM randomly highly sulfated alpha-, beta- and gamma-cyclodextrins (CDs) as chiral selectors has been successfully applied for separation of (P)- and (M)-enantiomers of a series of eleven new diquats (DQs) and for estimation of the strength of their complexes with the above CDs. The apparent stability constants of the DQs-CDs complexes were determined from the simultaneous ACE measurements of the dependence of effective electrophoretic mobilities of (P)- and (M)-enantiomers of DQs on the concentrations of CDs in the BGE by nonlinear regression analysis. The DQs enantiomers formed strong complexes with all three types of CDs with the apparent stability constants in the range (7.80 547.4) × 103 L/mol.
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Separation and characterizasion of stereoisomers of phosphinic pseudopeptides and serine by capillary electrophoresis
Koval, Dušan ; Jelínek, Ivan (advisor) ; Feltl, Ladislav (referee) ; Tesařová, Eva (referee) ; Stránský, Zdeněk (referee)
CoNcLUstoNs This work demonstrates that capillary electrophoresis is a suitable method for analysis and physico-chemical characterization of biomolecules. lt was exemplified by px" determination of a series of nove| phosphinic pseudopeptides and by separation oÍ stereoisomers of the phosphinic pseudopeptides and serine' A self-consistent procedure for pK" determination by CZE was carried out' ln particular' various background electro|ýes Were tested in the acidic region at pH < 2. A set of background eIectro|ýes Was eVa|uated for reIiab|e determination of eIectrophoretic mobiIities in the 1.S - 12pH interval. The temperature of the solution inside the separation capillary was measured by a simplified approach, thus enabling precise determination of the electrophoretic mobilities' Additionally, a throughput of the CZE method for the pK" determination was substantially improved, while high separation efficiency and precision of the electrophoretic mobilities was retained. The method benefits from adjustable velocity of e|ectroosmotic flow, achieved by modiÍication of the capi||ary inner surface, and efficient determination of electroosmotic mobility. Further, a study was performed which exp|ored the validity of onsager mode| for theoÍetica| description of concentration dependence of the e|ectÍophoretic...
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