Ústav fyzikální chemie J. Heyrovského

Nejnovější přírůstky:
2019-01-07
14:42
Voltammetric Determination of Tumor Biomarkers using Flow Injection Analysis with Amperometric Detection
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.

Úplný záznam
2019-01-07
14:42
HPLC-ED/UV for determination of vanillylmandelic acid in human urine after solid phase extraction
Makrlíková, Anna ; Dejmková, H. ; Navrátil, Tomáš ; Barek, J. ; Vyskočil, V.
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.

Úplný záznam
2018-07-09
13:44
Hollow-fibre Based Microextraction and Voltammetric Determination of Vanillylmandelic Acid
Hrdlička, Vojtěch ; Barek, J. ; Navrátil, Tomáš
New method of liquid/liquid/liquid hollow fibre based microextraction of vanillylmandelic acid coupled with voltammetric determination is being developed. Selected liquid membranes based on alcohols, aliphatic hydrocarbons and esters were tested. Highest enrichment factor of 2.52 after 30 minutes of extraction was obtained using propyl benzoate, RSD = 18.2 % (n=5). Mechanically and cathodically pretreated (-1000 mV vs. Ag/AgCl/3M KCl, 15 s) boron doped diamond electrode in a miniaturized arrangement was used for DPV determination. LOD = 1.2 micromol/l, RSD = 5.9% (n=10) for a 10 microl extract.

Úplný záznam
2018-07-09
13:44
Introducing Functionality by Graphene Covalent Grafting
Kovaříček, Petr ; Kalbáč, Martin
Graphene is a material of great potential in a broad range of applications, for each of which specific tuning of the material’s properties is required. This can be achieved, for example, by covalent functionalization. We have exploited protocols for surface grafting by diazonium salts, by nucleophilic and electrophilic substitution to perform graphene covalent modification of graphene on substrates. The painstaking analysis problem of monolayered materials was addressed using Raman spectroscopy, SERS, SEIRA, MS, AFM, XPS and SEM/EDX. The covalent grafting was shown to tolerate the transfer process, thus allowing ex post transfer from copper to other substrates. Functional devices often require combination of several materials with specific functions, such as graphene-polymer hybrid heterostructures. We have used the developed methodology of chemical functionalization for preparation of PEDOT:Graphene bilayers by selective in situ polymerization of EDOT on covalently functionalized graphene. The polymerization proceeds exclusively on the grafted graphene, and patterned structures with high spatial resolution down to 3 μm could have been prepared. The composite exhibits enhanced efficiency of electrochemical doping compared to pristine graphene, unsymmetrical transport characteristic with very good hole-transporting properties and efficient electronic communication between the two materials. The covalent functionalization of graphene thus introduces advanced functionality to the material, broadening its scope of applications.

Úplný záznam
2018-06-19
19:26
Electrochemical Study of Selected Pyrene Derivatives as Precursors to Organic Semiconductors
Koláčná, Lucie ; Tobrman, T. ; Ludvík, Jiří
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.

Úplný záznam
2018-06-19
19:26
Redox Properties of Fluorinated Derivatives of 1,3-Diphenylisobenzofuran Chromophores for Singlet Fission
Šimková, Ludmila ; Ludvík, Jiří
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.

Úplný záznam
2018-06-19
19:26
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
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.

Úplný záznam
2018-06-19
19:26
Study of Metabolism of Synthetic Cannabinoids. Electrochemical Properties of JWH-018
Obluková, Michaela ; Sokolová, Romana ; Čabala, R.
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.

Úplný záznam
2018-06-19
19:26
Influence of Adsorption on Electrochemical Reduction of Pyridinium Derivatives
Nováková Lachmanová, Štěpánka ; Dupeyre, G. ; Lainé, P. P. ; Hromadová, Magdaléna
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.

Úplný záznam
2018-06-19
19:26
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
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.

Úplný záznam