National Repository of Grey Literature 100 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Miniaturized boron doped diamond film electrode for neuroblastoma biomarkers determination
Hrdlička, Vojtěch ; Barek, J. ; Navrátil, Tomáš ; Taylor, Andrew
Cathodically pretreated miniaturized boron doped diamond film electrodewas successfully tested for the purposes of in-situ determination of neuroblastoma biomarkers after hollow-fibre based microextraction. Electrode was tested using K-3[Fe(CN)(6)] and vanillyl-mandelic acid as model substances. Limits of detection and determination are 2.2 and 6.6 mu mol L-1, respectively. Linear range was 2.2-100 mu molL(-1), repeatability 1.34% (n = 10).
Development of Novel Electrochemical Methods Using Various Membrane Materials for Monitoring of Selected Anticancer Drugs and Phytochelatins
Skalová, Štěpánka ; Barek, Jiří (advisor) ; Labuda, Ján (referee) ; Trnková, Libuše (referee)
Present Ph.D. Thesis is focused on the development of electrochemical methods for determination of anticancer drugs using various types of membranes for their preliminary separation. Furthermore, this Thesis reports the study of transport mechanisms of heavy metals in the presence of phytochelatins across biological membranes. Sodium anthraquinone-2-sulphonate (AQS) was used as a model compound for its similar structure with anthraquinone-based (AQ-based) anticancer drugs (doxo/daunorubicin) and also due to its better availability. All these compounds can be easily electrochemically oxidized and/or reduced. Redox behaviour of AQS was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in a cathodic region on mercury meniscus modified (m-AgSAE) and polished silver solid amalgam (p-AgSAE) electrodes, Obtained results were used for the development of a micro-volume voltammetric cell (MVVC). Its applicability for voltammetric determination of anticancer drugs was verified by using doxorubicin (DX) as a model substance. The second part of this Thesis deals with therapeutic monitoring of anticancer drugs in the blood circulation of the patients. For pilot experiments, a liquid-flow system with dialysis catheter and amperometric detection was used. The flow rate of carrier...
Voltammetric determination of 1-hydroxy-N-(4-nitrophenyl)naphthalene-2-carboxamide by voltammetry at a glassy carbon electrode in microvolumes of dimethyl sulfoxide
Gajdar, J. ; Goněc, T. ; Jampílek, J. ; Brázdová, Marie ; Bábková, Zuzana ; Fojta, Miroslav ; Barek, J. ; Fischer, J.
Voltammetric reduction and oxidation of 1-hydroxy-N-(4-nitrophenyl) naphthalene-2-carboxamide was investigated at glassy carbon electrode in dimethyl sulfoxide. Cyclic voltammetry was used to investigate the mechanism of reduction of nitro group and oxidation of hydroxyl group. The analyte was successfully determined in dimethyl sulfoxide by differential pulse voltammetry and the whole voltammetric procedure was miniaturised. Square wave voltammetry was employed to reduce the interference from dissolved oxygen. Determination in one drop (20 mu L) of 0.1 mol L-1 tetrabutyl-ammonium tetrafluoroborate in dimethyl sulfoxide provided very similar results compared to determination in the bulk solution. Limits of quantification were 5.0 mu mol L-1 for cathodic voltammetry and 5.3 mu mol L-1 for anodic voltammetry.
Voltammetry of 1-Hydroxy-N-(4-nitrophenyl)naphthalene-2-carboxamide at a Glassy Carbon Electrode
Gajdar, J. ; Goněc, T. ; Jampílek, J. ; Brázdová, Marie ; Bábková, Zuzana ; Fojta, Miroslav ; Barek, J. ; Fischer, J.
This electrochemical study is aimed at an investigation of a reaction mechanism and determination of 1-hydroxy-N-(4-nitrophenyl)naphthalene-2-carboxamide in media with various amount of an organic solvent (dimethyl sulfoxide or methanol). The studied analyte is a model substance from a group of recently prepared drugs with antibiotic characteriss Mechanism of reducible nitro group and oxidisable hydroxyl group is compared with studies of substructures and structurally similar compounds. Preliminary comparison of different media was carried out to find the best parameters for the determination.
Voltammetric Techniques for Analysis in a Single Drop of a Solution
Gajdar, J. ; Goněc, T. ; Jampílek, J. ; Brázdová, Marie ; Bábková, Zuzana ; Fojta, Miroslav ; Barek, J. ; Fischer, J.
This contribution describes miniaturization of voltammetric methods and some of the main problems caused by reducing the sample volume to 20 mu L. This study was carried out in dimethyl sulfoxide solutions and buffered aqueous solutions with 10% DMSO at a glassy carbon electrode. A novel antibiotic agent, 1-hydroxy-N-(4-nitrophenyl) naphthalene-2-carboxamide, was used as a model substance. This analyte was determined by cathodic and anodic voltammetry. Elimination of the negative influence of dissolved oxygen was performed in various manners. Two most effective methods were square wave voltammetry that can be used in the presence of dissolved oxygen and removal of oxygen in a microcell with nitrogen atmosphere inside.
Determination of a Novel Antimycobacterial Agent in a Single Drop of a Solution by Voltammetry at a Glassy Carbon Electrode
Gajdar, J. ; Goněc, T. ; Jampílek, J. ; Brázdová, Marie ; Bábková, Zuzana ; Fojta, Miroslav ; Barek, J. ; Fischer, J.
One of the novel antimycobacterial agents from the group of hydroxynaphthalene carboxamides (namely I-hydroxy-X-(4-nitrophenyl)naphthalene-2-carboxamide) was investigated using voltammetric methods for the first time. The study was carried out at a glassy carbon electrode by methods of cathodic and anodic differential pulse voltammetry in micro volumns (20 mu L) of an aqueous solution at pH 7 containing 10% dimethyl sulfoxide and in a real matrix of a bacterial growth medium. The miniaturized method was compared with the macro volume determination. The presence of oxygen in micro volumes presents the biggest obstacle for the miniaturized method.
Construction and Application of Flow Amperometric Biosensor Based on Enzymatic Reactor for Determination of Choline
Tvorynska, Sofiia ; Barek, J. ; Josypčuk, Bohdan
In this contribution, a novel fast, simple and stable biosensor with the enzymatic reactor based on choline oxidase (ChOx) was developed and applied for the determination of choline using flow injection analysis with amperometric detection. The preparation of the reactor is based on the covalent immobilization of ChOx with glutaraldehyde to mesoporous silica powder (SBA-15) previously covered by NH2-groups. The experimental parameters affecting the sensitivity and stability of the biosensor were optimized. The proposed biosensor with the newly developed ChOx-based reactor possesses good repeatability, reproducibility, long-term stability, and reusability. It was successfully applied for the determination of choline in commercial pharmaceuticals.
Electrochemical Enzymatic Biosensors for Determination of Catecholamines in Flow Systems\n
Josypčuk, Bohdan ; Barek, J. ; Josypčuk, Oksana
Several biosensors (BS) based on flow enzymatic mini-reactors containing a mesoporous silica powder covered by enzyme laccase or tyrosinase were used for determination of L-DOPA, dopamine, noradrenaline, and adrenaline. The silica powder of MCM-41 with covalently bonded laccase was found to be the best reactor filling for the detection of catecholamines. Relative current response of such BS was 100 % for dopamine, 32.1 % for L-DOPA, 26.2 % for noradrenaline, and 0.71 % for adrenaline. The practical applicability of Lac-MCM41 biosensor was successfully verified by the determination of dopamine and noradrenaline in medical solutions for infusions.
Voltammetric and Amperometric Determination of Nitrophenols Using Boron-Doped Diamond Film Electrode
Karaová, Jana ; Barek, Jiří (advisor) ; Šelešovská, Renáta (referee) ; Jaklová Dytrtová, Jana (referee)
Presented Ph.D. Thesis is focused on the use of the boron-doped diamond (BDD) electrodes for voltammetric and amperometric determination of selected nitrophenols: 2-nitrophenol (2NP), 4-nitrophenol (4NP), and 2,4-dinitrophenol (2,4DNP). These compounds are listed as "priority pollutants" by United States Environmental Protection Agency (US EPA) due to their negative impact on living organisms and are mainly used in agriculture as plant growth stimulators. BDD electrodes are used for determination of wide range of electrochemically both reducible and oxidisable organic compounds and have become a popular electrode material thanks to its commercial availability and excellent mechanical and electrochemical properties. A differential pulse voltammetric method was developed for the determination of 2NP, 4NP and 2,4DNP at a BDD film electrode using electrochemical reduction and of 4NP and 2,4DNP using electrochemical oxidation. The method was successfully applied for the direct determination of these compounds in drinking and river water in the concentration range from 4×10-7 to 2×10-5 mol.L-1 . To improve the limit of quantification, a preconcentration by solid phase extraction from 100 mL (drinking and river water) and 1000 mL (drinking water) of water samples was used with limit of determination...
Voltammetric Determination of Tumor Biomarkers using Flow Injection Analysis with Amperometric Detection
Němečková-Makrlíková, Anna ; Matysik, F.-M. ; Navrátil, Tomáš ; Barek, J. ; Vyskočil, V.
Three tumor biomarkers (homovanillic acid, vanillylmandelic acid, and 5-hydroxyindole-3-acetic acid) have been determined by flow injection analysis with amperometric detection at screen-printed carbon electrodes in optimum medium of Britton-Robinson buffer (0.04 mol l(-1), pH = 2.0). Dependences of the peaks current on the concentration of biomarkers were linear in the tested concentration region from 0.05 to 100 mu mol l(-1), with the limits of detection of 0.065 mu mol l(-1) for homovanillic acid, 0.053 mu mol l(-1) for vanillylmandelic acid, and 0.033 mu mol l(-1) for 5-hydroxyindole-3-acetic acid (calculated from heights), and 0.024 mu mol l(-1) for homovanillic acid, 0.020 mu mol l(-1) for vanillylmandelic acid, and 0.012 mu mol l(-1) for 5-hydroxyindole-3-acetic acid (calculated fromareas), respectively.

National Repository of Grey Literature : 100 records found   1 - 10nextend  jump to record:
See also: similar author names
6 Barek, J.
2 Barek, Jan
2 Barek, Jaroslav
1 Barek, Jiří
Interested in being notified about new results for this query?
Subscribe to the RSS feed.