Number of found documents: 226
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Supported Liquid Membranes for Hollow-Fibre Based Microextraction and Voltammetric Determination of Neuroblastoma Biomarkers
Josypčuk, Bohdan; Barek, J.; Josypčuk, Oksana
2018 - English
A new type of tubular detector (TD+AuxE) was proposed, fabricated, tested and compared\nwith a typical silver amalgam tubular detector developed earlier. Non-stop-flow differential\npulse voltammetric anodic stripping method (AS-DPV) and amperometric method in a\nglucose oxidase biosensor arrangement were tested. Both detectors were applied for AS-DPV\nmeasurements in flow systems for the first time. The proposed combination of tubular\ndetector with auxiliary electrode provides a much greater current response than the classic\narrangement with three individual electrodes. All relevant parameters (potentials of\naccumulation or detection, flow rate, analyte concentrations, shielding sleeve length, etc.)\nwere optimized for the developed TD+AuxE. Keywords: Flow analysis; Amperometry; Voltammetry Available at various institutes of the ASCR
Supported Liquid Membranes for Hollow-Fibre Based Microextraction and Voltammetric Determination of Neuroblastoma Biomarkers

A new type of tubular detector (TD+AuxE) was proposed, fabricated, tested and compared\nwith a typical silver amalgam tubular detector developed earlier. Non-stop-flow differential\npulse voltammetric ...

Josypčuk, Bohdan; Barek, J.; Josypčuk, Oksana
Ústav fyzikální chemie J. Heyrovského, 2018

Determination of Roughness Factor and Fractal Dimension of Zirconium in its Native and Surface Modified State using Atomic Force Microscopy. Effect of the Hydrogen\nEvolution Reaction on the Surface Structure
Novák, M.; Kocábová, Jana; Kolivoška, Viliam; Pospíšil, Lubomír; Macák, J.; Cichoň, Stanislav; Cháb, Vladimír; Hromadová, Magdaléna
2018 - English
Atomic force microscopy (AFM) was used to characterize surface morphology of pristine zirconium, Si modified and FeSi modified zirconium electrodes prior and after hydrogen evolution at potentials negative of the open circuit potential value. Two main characteristic parameters were obtained from the ex situ AFM height images, namely, the roughness factor and fractal dimension of the studied surface. The effect of hydrogen evolution reaction on the electrode surface morphology was discussed. Fractal dimension values were used successfully to explain the non ideality of the interfacial capacitance. Keywords: zirconium electrode; atomic force microscopy; fractal dimension Available at various institutes of the ASCR
Determination of Roughness Factor and Fractal Dimension of Zirconium in its Native and Surface Modified State using Atomic Force Microscopy. Effect of the Hydrogen\nEvolution Reaction on the Surface Structure

Atomic force microscopy (AFM) was used to characterize surface morphology of pristine zirconium, Si modified and FeSi modified zirconium electrodes prior and after hydrogen evolution at potentials ...

Novák, M.; Kocábová, Jana; Kolivoška, Viliam; Pospíšil, Lubomír; Macák, J.; Cichoň, Stanislav; Cháb, Vladimír; Hromadová, Magdaléna
Ústav fyzikální chemie J. Heyrovského, 2018

Differences in Oxidation Mechanism of Selected Bioflavonoids, UV-Vis and IR Spectroelectrochemical Study
Sokolová, Romana; Fiedler, Jan; Ramešová, Šárka; Kocábová, Jana; Degano, I.; Quinto, A.; Křen, Vladimír
2018 - English
The oxidation of selected bioflavonoids (quercetin, rhamnazin, fisetin, rhamnetin, taxifolin, luteolin, silybin and 2,3-dehydrosilybin) was studied by electrochemical and spectroscopic methods. The oxidation mechanism and formation of oxidation products depends on the chemical structure. Only small differences in the chemical structure of compounds with flavone, flavanone and flavonol motif result in extremely variable oxidation pathways and products. Products of oxidation and further decomposition were determined by HPLC-ESIMS/MS and HPLC-DAD. Keywords: oxidation; flavonoids; decomposition Available at various institutes of the ASCR
Differences in Oxidation Mechanism of Selected Bioflavonoids, UV-Vis and IR Spectroelectrochemical Study

The oxidation of selected bioflavonoids (quercetin, rhamnazin, fisetin, rhamnetin, taxifolin, luteolin, silybin and 2,3-dehydrosilybin) was studied by electrochemical and spectroscopic methods. The ...

Sokolová, Romana; Fiedler, Jan; Ramešová, Šárka; Kocábová, Jana; Degano, I.; Quinto, A.; Křen, Vladimír
Ústav fyzikální chemie J. Heyrovského, 2018

Redox Properties of Fluorinated Derivatives of 1,3-Diphenylisobenzofuran Chromophores for Singlet Fission
Šimková, Ludmila; Ludvík, Jiří
2018 - English
Derivatives of 1,3-diphenylisobenzofuran attract interest because they should be efficient as the molecules for singlet fission. The understanding of singlet fission in isolated molecules might be advantageous for use as solar cell sensitizers. This study is focused on fluorinated derivatives of 1,3-diphenylisobenzofuran and the effect of the position of fluorine atoms on their redox properties. For characterization of the redox properties standard electrochemical methods, and in situ UV-vis and EPR spectroscopy techniques were used. Keywords: 1,3-diphenylisobenzofuran; fluorinated derivatives; spectroelectrochemistry Available on request at various institutes of the ASCR
Redox Properties of Fluorinated Derivatives of 1,3-Diphenylisobenzofuran Chromophores for Singlet Fission

Derivatives of 1,3-diphenylisobenzofuran attract interest because they should be efficient as the molecules for singlet fission. The understanding of singlet fission in isolated molecules might be ...

Šimková, Ludmila; Ludvík, Jiří
Ústav fyzikální chemie J. Heyrovského, 2018

Electrochemical Monitoring of the Water Clusters Formation in an Organic Solvent in the Presence of Hydrated Ions
Mareček, Vladimír
2018 - English
An electrochemical method has been developed that makes it possible to monitor the\ndynamics of the co-extraction of water with hydrated chloride ions at the interface between\ntwo immiscible electrolyte solutions (ITIES). The interfacial potential was controlled by the\ndistribution of a common tetralkylammonium (TAA+) ion. Changes in the TAA+\nconcentration at the interface were monitored by measuring the open circuit potential (OCP).\nTransfer of hydrated chloride ions is accompanied by the transfer of TAA+, decreasing its\nconcentration on the aqueous side of the interface. This process involves the co-extraction of\nwater molecules with the hydrated chloride ions and the formation of water clusters in the\norganic solvent phase. The ability to monitor the process from the very beginning of interface\nformation allowed us to obtain important kinetic data. Keywords: Liquid/liquid interface; Water co-extraction dynamics; Emulsification Available on request at various institutes of the ASCR
Electrochemical Monitoring of the Water Clusters Formation in an Organic Solvent in the Presence of Hydrated Ions

An electrochemical method has been developed that makes it possible to monitor the\ndynamics of the co-extraction of water with hydrated chloride ions at the interface between\ntwo immiscible ...

Mareček, Vladimír
Ústav fyzikální chemie J. Heyrovského, 2018

Silver Solid Amalgam Electrodes as Perspective Tools for Sensitive Voltammetric Determinations of Food Azo Dyes Amaranth and Allura Red AC
Tvorynska, S.; Barek, J.; Josypčuk, Bohdan
2018 - English
In this paper, for the first time, the electrochemical behaviours of the food azo dyes Amaranth (E 123) and Allura Red AC (E 129) were investigated on two modifications of silver solid amalgam electrode, namely mercury meniscus modified, polished and compared with hanging mercury drop electrode using differential pulse voltammetry and direct current voltammetry. The effect of adsorption and the reduction mechanism on tested electrodes were described in detail. Measurements with amalgam electrodes showed good reproducibility, stability and high sensitivity. As a result, they were successfully applied for the determination of investigated azo dyes in different commercial drink samples. Keywords: voltammetry; azo dyes; amaranth Available at various institutes of the ASCR
Silver Solid Amalgam Electrodes as Perspective Tools for Sensitive Voltammetric Determinations of Food Azo Dyes Amaranth and Allura Red AC

In this paper, for the first time, the electrochemical behaviours of the food azo dyes Amaranth (E 123) and Allura Red AC (E 129) were investigated on two modifications of silver solid amalgam ...

Tvorynska, S.; Barek, J.; Josypčuk, Bohdan
Ústav fyzikální chemie J. Heyrovského, 2018

Electrochemical Study of Selected Pyrene Derivatives as Precursors to Organic Semiconductors
Koláčná, Lucie; Tobrman, T.; Ludvík, Jiří
2018 - English
A series of 9 precursors for pyrene based biodegradable organic (semi)conductors having tetrasubstituted double bond as a central organic core and photo- or redox active centers attached at this core were electrochemically investigated in order to determine the influence of individual parts of the molecule on the redox properties, to describe the location of the reduction center and to understand the structure - redox activity relationship of the mentioned compounds. Keywords: pyrene; cyclobutene; polarography Available at various institutes of the ASCR
Electrochemical Study of Selected Pyrene Derivatives as Precursors to Organic Semiconductors

A series of 9 precursors for pyrene based biodegradable organic (semi)conductors having tetrasubstituted double bond as a central organic core and photo- or redox active centers attached at this core ...

Koláčná, Lucie; Tobrman, T.; Ludvík, Jiří
Ústav fyzikální chemie J. Heyrovského, 2018

Supported Liquid Membranes for Hollow-Fibre Based Microextraction and Voltammetric Determination of Neuroblastoma Biomarkers
Hrdlička, Vojtěch; Barek, J.; Navrátil, Tomáš
2018 - English
Novel method of three phase hollow fibre based liquid/liquid/liquid microextraction coupled\nwith voltammetric determination of clinical biomarkers homovanillic and vanillylmandelic\nacid is being developed. Wide variety of water-immiscible supported liquid membranes\n(SLMs) were tested. Highest enrichment factors were obtained using butyl benzoate as SLM.\nEnrichment factors for 30 min HF-LPME were 3. 0.74 for HVA and 5. 0.45 for VMA,\nrespectively. Repeatability of HF-LPME of microM HVA or VMA was 19.0% for HVA and\n7.9 % for VMA (n=5), respectively. Keywords: Hollow-fibres; Liquid phase microextraction; Voltammetry Available at various institutes of the ASCR
Supported Liquid Membranes for Hollow-Fibre Based Microextraction and Voltammetric Determination of Neuroblastoma Biomarkers

Novel method of three phase hollow fibre based liquid/liquid/liquid microextraction coupled\nwith voltammetric determination of clinical biomarkers homovanillic and vanillylmandelic\nacid is being ...

Hrdlička, Vojtěch; Barek, J.; Navrátil, Tomáš
Ústav fyzikální chemie J. Heyrovského, 2018

Electrochemical Study of the Supported Iron Oxide Catalysts
Gál, M.; Horváth, B.; Navrátil, Tomáš
2018 - English
Propylene oxide (PO) belongs to the group of the most important chemical industrial\nintermediates. It is mainly used for polyurethanes, pharmaceuticals, textile, and detergent\nproduction. In this short contribution we tried to characterize supported iron(III) oxide\ncatalyst with different amount of Fe and to find an optimal iron(III) oxide content for the best\ncatalysts performance. The importance of phase quality on the selectivity of respective\ncatalysts samples is also discussed. Linear sweep voltammetry was chosen for this purpose.\nResults obtained by electrochemical methods are compared with efficiency (selectivity) of\nrespective catalysts. Keywords: Catalyst; Linear sweep voltammetry; Propylene oxide Available on request at various institutes of the ASCR
Electrochemical Study of the Supported Iron Oxide Catalysts

Propylene oxide (PO) belongs to the group of the most important chemical industrial\nintermediates. It is mainly used for polyurethanes, pharmaceuticals, textile, and detergent\nproduction. In this ...

Gál, M.; Horváth, B.; Navrátil, Tomáš
Ústav fyzikální chemie J. Heyrovského, 2018

HPLC-ED/UV with Solid Phase Extraction for the Determination of 5-Hydroxyindole-3-acetic Acid
Makrlíková, Anna; Dejmková, H.; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
2018 - English
Determination of 5-HIAA in human urine was successfully performed using HPLC-ED/UV with SPE. HPLC-ED is a very sensitive technique, presented method does not need any sample pre-treatment apart from SPE procedure, which replaced filtration of samples of human urine to avoid problems with clogging a HPLC column. The found native\nconcentrations of 5-HIAA in human urine using HPLC-ED with SPE fully corresponds with published normal concentrations in urine (17.8 - 58.3 micromol l-1). The found native concentrations of 5-HIAA were 18.4 micromol L-1 (calculated from peak height). The presented method is fast and could be used for simple\nscreening of human urine, because HPLC-ED/UV allows simultaneous determination of 5-HIAA, HVA, and VMA as important tumour biomarkers. Keywords: HPLC; electrochemical detection; spectrophotometric detection Available at various institutes of the ASCR
HPLC-ED/UV with Solid Phase Extraction for the Determination of 5-Hydroxyindole-3-acetic Acid

Determination of 5-HIAA in human urine was successfully performed using HPLC-ED/UV with SPE. HPLC-ED is a very sensitive technique, presented method does not need any sample pre-treatment apart from ...

Makrlíková, Anna; Dejmková, H.; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
Ústav fyzikální chemie J. Heyrovského, 2018

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