Number of found documents: 404
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HPLC-ED/UV with Solid Phase Extraction for the Determination of 5-Hydroxyindole-3-acetic Acid
Němečková-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 ...

Němečková-Makrlíková, Anna; Dejmková, H.; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
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

Investigation of Single Molecule Charge Transport Properties and Geometrical Arrangement in Terpyridine Architectures Supported by the Tetraphenylmethane Tripod
Kolivoška, Viliam; Sebechlebská, Táňa; Šebera, Jakub; Gasior, Jindřich; Lindner, M.; Lukášek, J.; Valášek, M.; Mayor, M.; Mészáros, G.; Hromadová, Magdaléna
2018 - English
Tripodal platforms were engineered recently to realize a well-defined directional contact between metallic electrodes and molecular architectures dedicated to serve as working elements for electronic applications. In this work we employ cyclic voltammetry, scanning tunneling microscopy break junction technique and theoretical approaches based on the combination of density functional theory and non-equilibrium Green´s function to investigate the geometrical arrangement and single molecule charge transport in terpyridine-based architectures supported by tetraphenylmethane tripod. We demonstrate that this architecture adopts a favorable geometrical arrangement capable of forming highly conductive molecular junctions and is thus suitable to serve as a basis for working molecular switches. Keywords: molecular electronics; Molecular conductors and switches; Tripodal platforms Available at various institutes of the ASCR
Investigation of Single Molecule Charge Transport Properties and Geometrical Arrangement in Terpyridine Architectures Supported by the Tetraphenylmethane Tripod

Tripodal platforms were engineered recently to realize a well-defined directional contact between metallic electrodes and molecular architectures dedicated to serve as working elements for electronic ...

Kolivoška, Viliam; Sebechlebská, Táňa; Šebera, Jakub; Gasior, Jindřich; Lindner, M.; Lukášek, J.; Valášek, M.; Mayor, M.; Mészáros, G.; Hromadová, Magdaléna
Ústav fyzikální chemie J. Heyrovského, 2018

Influence of Adsorption on Electrochemical Reduction of Pyridinium Derivatives
Nováková Lachmanová, Štěpánka; Dupeyre, G.; Lainé, P. P.; Hromadová, Magdaléna
2018 - English
Two expanded pyridinium-based compounds 1 and 2 were studied by cyclic voltammetry in two different environments. The nonaqueous solution suppresses the adsorption of the compounds on the electrode surface. Adsorption process in aqueous environment was confirmed by typical shape of the curve as well as by the linear dependence of peak current on the scan rate. The shift of standard redox potential in aqueous solution compared to nonaqueous environment toward more negative potential indicates the adsorption of reactant on the electrode surface. Larger shift observed for flat conjugated molecule 1 confirms its stronger adsorption than for the second molecule. Keywords: pyridinium derivatives; adsorption; cyclic voltammetry Available at various institutes of the ASCR
Influence of Adsorption on Electrochemical Reduction of Pyridinium Derivatives

Two expanded pyridinium-based compounds 1 and 2 were studied by cyclic voltammetry in two different environments. The nonaqueous solution suppresses the adsorption of the compounds on the electrode ...

Nováková Lachmanová, Štěpánka; Dupeyre, G.; Lainé, P. P.; Hromadová, Magdaléna
Ústav fyzikální chemie J. Heyrovského, 2018

Study of Metabolism of Synthetic Cannabinoids. Electrochemical Properties of JWH-018
Obluková, Michaela; Sokolová, Romana; Čabala, R.
2018 - English
In the recent years, many new substances have appeared in the drug market, which are abused for their psychoactive effect. They serve as alternative to classical drugs (heroin, cocaine, ecstasy) due to their legal status. The great concern is the ineffectiveness of the current methods of toxicological screening of biological samples to identify these new compounds. It is essential to know the metabolism pathway of these psychoactive substances for a development of a new efficient method for their detection. This report is devoted to understanding of oxidation and reduction mechanism of JWH-018 and JWH-250 by means of cyclic voltammetry and to identification of their redox products. Keywords: synthetic cannabinoids; metabolism; cyclic voltammetry Available at various institutes of the ASCR
Study of Metabolism of Synthetic Cannabinoids. Electrochemical Properties of JWH-018

In the recent years, many new substances have appeared in the drug market, which are abused for their psychoactive effect. They serve as alternative to classical drugs (heroin, cocaine, ecstasy) due ...

Obluková, Michaela; Sokolová, Romana; Čabala, R.
Ústav fyzikální chemie J. Heyrovského, 2018

HPLC-ED/UV for determination of vanillylmandelic acid in human urine after solid phase extraction
Němečková-Makrlíková, Anna; Dejmková, H.; Navrátil, Tomáš; Barek, J.; Vyskočil, V.
2018 - English
HPLC with electrochemical and spectrophotometric detection (ED/UV) after solid phase extraction (SPE) was used for determination of vanillylmandelic acid in human urine. HPLC-ED was performed at a glassy carbon electrode in a “wall-jet” arrangement in acetate-phosphate buffer at pH = 2.5 and gradient elution (increasing content of\nacetonitrile from 5 to 25% in 10 minutes) was used. Optimized parameters were following: flow rate of mobile phase 1 mL min−1, detection potential +1.1 V, detection wavelength 279 nm, injected volume 20 μL. Dependence of the peak current on the analyte concentration was linear in the concentration range from 10 to 150 μmol L−1, with obtained limits of detection 2.6 μmol L−1 (calculated from peak height) and 1.9 μmol L−1 (calculated from peak area) for HPLC-ED, and 11.0 μmol L−1 (calculated from peak height) and 9.8 μmol L−1 (calculated from peak area) for HPLC-UV. Keywords: HPLC; solid phase extraction; tumor biomarker Available on request at various institutes of the ASCR
HPLC-ED/UV for determination of vanillylmandelic acid in human urine after solid phase extraction

HPLC with electrochemical and spectrophotometric detection (ED/UV) after solid phase extraction (SPE) was used for determination of vanillylmandelic acid in human urine. HPLC-ED was performed at a ...

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

Charge Transport through Molecular Towers Based on Tetraphenylmethane Tripods
Kolivoška, Viliam; Šebera, Jakub; Lindner, M.; Valášek, M.; Mayor, M.; Mészáros, G.; Gasior, Jindřich; Hromadová, Magdaléna
2017 - English
Molecular platforms with multiple anchors were introduced recently to provide robust\ncoupling between molecular electronic components and metallic electrodes. In this work,\ncharge transport in tower-shaped single molecule conductors based on tetraphenylmethane\ntripod possessing three thiol anchors is investigated by scanning tunneling microscopy break\njunction technique. The effect of tripod substitution pattern and number of repeating units in\nmolecule is addressed. The substitution was found to influence conductance value in early\nstages of molecular junction evolution, where tower lays parallel to surface. In late stages, the\ncharge is transported through principal molecular axis and junction breaks thermally in tilted\nconfiguration. Keywords: Charge Transport Through Single Molecules; Break Junction Technique; Molecular Electronics Available on request at various institutes of the ASCR
Charge Transport through Molecular Towers Based on Tetraphenylmethane Tripods

Molecular platforms with multiple anchors were introduced recently to provide robust\ncoupling between molecular electronic components and metallic electrodes. In this work,\ncharge transport in ...

Kolivoška, Viliam; Šebera, Jakub; Lindner, M.; Valášek, M.; Mayor, M.; Mészáros, G.; Gasior, Jindřich; Hromadová, Magdaléna
Ústav fyzikální chemie J. Heyrovského, 2017

Miniaturized Boron Doped Diamond Film Electrode for Neuroblastoma Biomarkers Determination
Hrdlička, Vojtěch; Barek, J.; Navrátil, Tomáš; Taylor, Andrew
2017 - English
Cathodically pretreated miniaturized boron doped diamond film\nelectrode was successfully tested for the purposes of in-situ determination\nof neuroblastoma biomarkers after hollow-fibre based\nmicroextraction. Electrode was tested using K3[Fe(CN)6] and vanillylmandelic\nacid as model substances . Limits of detection and\ndetermination are 2.2 and 6.6 mu mol L-1, respectively. Linear range was\n2.2-100 mu mol L-1, repeatability 1.34% (n = 10). Keywords: biomarkers; boron doped diamond film; voltammetry Available on request at various institutes of the ASCR
Miniaturized Boron Doped Diamond Film Electrode for Neuroblastoma Biomarkers Determination

Cathodically pretreated miniaturized boron doped diamond film\nelectrode was successfully tested for the purposes of in-situ determination\nof neuroblastoma biomarkers after hollow-fibre ...

Hrdlička, Vojtěch; Barek, J.; Navrátil, Tomáš; Taylor, Andrew
Ústav fyzikální chemie J. Heyrovského, 2017

Determination of the Rate of Tetraethylammonium Ion Transfer across the\nWater/1,2-DCE Interface with Steady-State Voltammetry at a Nano-ITIES
Silver, Barry Richard; Holub, Karel; Mareček, Vladimír
2017 - English
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. Keywords: Ion transfer kinetics; Tetraethylammonium ion; Nanocapillary Available on request at various institutes of the ASCR
Determination of the Rate of Tetraethylammonium Ion Transfer across the\nWater/1,2-DCE Interface with Steady-State Voltammetry at a Nano-ITIES

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 ...

Silver, Barry Richard; Holub, Karel; Mareček, Vladimír
Ústav fyzikální chemie J. Heyrovského, 2017

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