Národní úložiště šedé literatury Nalezeno 22 záznamů.  1 - 10dalšíkonec  přejít na záznam: Hledání trvalo 0.00 vteřin. 
Determination of the Rate of Tetraethylammoniumion Transfer across the\nWater/1,2-DCE Interface with Steady-State Voltammetry at a Nano-ITIES
Silver, Barry Richard ; Holub, Karel ; Mareček, Vladimír
The rate of TEA+ ion transfer across the water/1,2-dichloroethane interface has been\nmeasured using steady-state cyclic voltammetry at a capillary with an orifice of nano-sized\ndimension. It was found that the average rate constant for TEA+ transfer from water to oil and\nfrom oil to water is 0.64 cm/s. The results are repeatable using the same capillary. This value\nis similar to that measured previously using electrochemical impedance spectroscopy and\nfluctuation analysis at the micro-interface.
Electrochemical Impedance Spectroscopy and Steady-State Voltammetry at the Micro-between Two Immiscible Electrolyte Solutions
Silver, Barry Richard ; Holub, Karel ; Mareček, Vladimír
The kinetic data of simple tetraethylammonium ion transfer across the water/1,2-DCE interface obtained by electrochemical impedance spectroscopy and steady-state voltammetry are compared. It is shown that the geometry of the microcapillary tip region is of critical importance to obtain reliable kinetic data. Quasi-reversible behavior of the ion transfer reaction, corresponding to an apparent standard rate constant of about 0.2 cm s-1, is observed with both experimental methods.\n
Noise Analysis of Ion Transfer Kinetics at the Micro Liquid/Liquid Interface
Josypčuk, Oksana ; Holub, Karel ; Mareček, Vladimír
Fluctuation analysis was utilized to determine the TEA ion transfer kinetics across the water/1,2-dichloroethane interface. The average value ks = 0.34 cm s-1 is comparable with the previously reported value ks = 0.2 cm s-1, derived from electrochemical impedance spectroscopy experiments. The experimental approach utilizing a thick wall glass microcapillary to fix the interface exhibits a very small stray capacitance value, proving this system to be suitable for determining the kinetics of the fast ion transfer across a liquid/ liquid interface. Application of a method employing a small perturbation signal prevents polarization of the inner capillary surface by current flowing through the cell. The induced polarization of the capillary can affect ion concentration at the interface due to electroosmosis and thus make the kinetics data evaluation difficult or erroneous.
Ion Current Enhancement at Glass Microcapillaries
Silver, Barry Richard ; Holub, Karel ; Mareček, Vladimír
Ion conductivity has been investigated at a reusable borosilicate glass microcapillary using DC and AC electrochemical techniques. The ion current enhancement at low frequencies is modeled using a simple serial resistance – inductor circuit. The enhancement effect is ascribed to an electrokinetic mass transport process at the capillary wall.
Characterization of Electrochemical Behavior of Lecithin-Cholesterol Mixture in Formation of Model Phospholipid Membranes
Nováková, Kateřina ; Navrátil, Tomáš ; Šestáková, Ivana ; Mareček, Vladimír ; Chýlková, J.
Electrochemical behavior of lecithin-cholesterol mixture in the form of phospholipid membranes (PLMs) was studied in this contribution. Lecithin (phosphatidylcholine) and cholesterol were chosen for this research, because they are essential for living cells. Electrochemical behavior of this system was studied using an electrochemical cell developed in our laboratory and with applying electrochemical impedance spectroscopy (EIS). Different ratios between lecithin and cholesterol placed on different polycarbonate substrates were tested. The influence of time and of temperature on formation of PLMs in presence of cholesterol was investigated.
(Strept)avidin-biotin interactions at amalgam electrodes covered by thiol monolayer
Josypčuk, Bohdan ; Mareček, Vladimír ; Yosypchuk, O.
Carboxylic group of 11-mercaptoundecanoic acid (MUA) can be used to creat a peptide bond with species containing amino group, e.g., peptides, and proteins. By the help of EDC-NHS technology, streptavidin or avidin was covalently bonded with MUA-monolayer at a silver solid amalgam electrode. Such prepared electrode was used for detecting biotin and biotinylated albumin in the supporting electrolyte (0.15 M NaCl, 0.05 M TRIS, pH 7.0). Electrochemical impendance spectroscopy was performed for the biosensor response monitored by impedance spectroscopy. Binding of biotin or biotinylated albumin with (strept)avidin a change in the resistance of the sensor in the concentration range of 0.5-20 μg mL-1. Electrochemical regeneration of the amalgam electrode permits simply to renew its surface and to create the new biosensor.
Transport of Copper Ions in the Presence and Absence of Ionosphere Calcimycin and the Influence of LMWOAs on this Transport
Parisová, Martina ; Navrátil, Tomáš ; Šestáková, Ivana ; Mareček, Vladimír
This work was focussed on preparation of model membranes formed on porous polycarbonate substrate. 1,2-dipalmytoil-sn-glycero-3-phosphocholine was used to form stable lipid bilayers in hydrophilic pores of polycarbonate membrane. For their characterization, electrochemical impendance spectroscopy (EIS) and voltammetry were applied. The transport of copper ions across these membranes in presence and absence of ionophore calcimysin has been studied. The effect of LMWOAs on transporting processes was investigated too.
Ion Current Rectification Behavior at Novel Borosilicate Glass Capillaries
Silver, Barry Richard ; Holub, Karel ; Mareček, Vladimír
We present an easy methodology to produce novel, robust and reusable borosilicate glass microcapillaries. Using these capillaries we investigate ion current rectification behavior using DC and AC electrochemical techniques. We find that two non-ohmic behaviors can manifest. The presence of low frequency inductive loops on the Nyquist plot tentatively suggests electrokinetic mass transport processes may be present at the capillary wall.
Utilization of electrochemical methods in studies of transporting processes across the phospholipid bilayers
Navrátil, Tomáš ; Šestáková, Ivana ; Mareček, Vladimír
This contribution deals with studying and characterization of transporting processes of heavy metals (lead and cadmium) in the form of their free ions and of their complexes with small organic ligands across biological membranes. These membranes are represented by model phospholipid bilayers, formed on the surface a suitable flat support material or in its pores. Phosphatidyl choline and phosphatidyl ethanolamine were used as the membrane building elements. Voltammetry and electrochemical impendance spectrometry (EIS) have been used for characterization of the transporting processes.
Transport of divalent cations across the gel supported phospholipid membranes
Navrátil, Tomáš ; Šestáková, Ivana ; Mareček, Vladimír
This contribution deals with elucidation of principles of transporting processes of heavy metals (mainly lead, cadmium) across the biological membranes. The real membranes were for purposes of described experiments, replaced by model membranes, which were composed of phospholipid bilayers. Two different phorpholipids (1,2-dipalmitoyl-sn-glycero-3-phosphocholine and the mixture of phospholipids obtained from soybeans (under commercial name Asolectin)) were used as the building elements for the formation of these membranes on the surface of the constructed gel electrode. The registered transporting processes have been characterized using voltammetry, and electrochemical impendance spectrometry (EIS). The impact of some parameters on these systems and processes was investigated.

Národní úložiště šedé literatury : Nalezeno 22 záznamů.   1 - 10dalšíkonec  přejít na záznam:
Viz též: podobná jména autorů
2 Mareček, Vojtěch
2 Mareček, Václav
2 Mareček, Vít
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