National Repository of Grey Literature 52 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
An Enzymatic Biosensor with Amperometric Detection in a Flow Injection Analysis for the Determination of L-lactic Acid: Development and Application
Tvorynska, Sofiia ; Barek, J. ; Josypčuk, Bohdan
An amperometric biosensor consisting of an enzymatic mini-reactor (lactate oxidase covalently\nattached to −NH2 functionalized mesoporous silica powder SBA−15 using glutaraldehyde) and\na silver amalgam-based screen-printed electrode acting as a transducer was developed for the\ndetermination of L-lactic acid (LA) in FIA. The detection potential of −0.9 V vs. Ag pseudoreference\nelectrode was applied for cathodic detection of enzymatically consumed oxygen.\nUnder the optimized conditions, the constructed biosensor enabled selective determination of\nLA with a micromolar limit of detection. Importantly, the proposed biosensor represented\nexcellent operational stability after ≥350 measurements. Finally, it was successfully applied to\nreal sample analysis.
A comparative study of covalent glucose oxidase and laccase immobilization techniques at powdered supports for biosensors fabrication
Tvorynska, Sofiia ; Barek, J. ; Josypčuk, Bohdan ; Nesměrák, K.
In order to develop the optimal strategy and to deepen the knowledge in the field of enzyme immobilization, three different techniques of covalent binding for two enzymes (glucose oxidase and laccase) at powdered surfaces were compared. Immobilization protocol was optimized by changing supports (two mesoporous silica powders (SBA−15, MCM−41) and a cellulose powder), the functionalized\ngroups introduced at support surfaces (−NH and −COOH), and the methods of activation (glutaraldehyde and carbodiimide). Amino and carboxyl functionalized mesoporous silica and cellulose powders\nwere prepared by silanization using (3-aminopropyl)triethoxysilane and carboxyethylsilanetriol, respectively. It was found that coupling of both enzymes by their –NH groups through glutaraldehyde to -NH functionalized supports, in particular SBA15−NH and cellulose−NH for glucose oxidase, MCM41−NH for laccase, showed the highest activity and the best stability.
Mercury Film Screen-Printed Electrodes
Josypčuk, Bohdan ; Šestáková, Ivana ; Tvorynska, Sofiia
Mercury film screen-printed electrodes (MF-SPEs) were designed, prepared and tested for the first time as perspective representatives among SPEs that allow measuring at high negative potentials. For this purpose, the precise electrochemical (coulometric) preparation procedure for mercury deposition at the working electrode surface of the commercial silver-SPE was developed and a universal method of preparing MF-electrodes from different metal-SPEs was described. An optimal electrolyzer construction for the mercury deposition, electrolyte composition, electrolysis potential, and an activation of electrode surfaces were proposed. Determination of the zinc content in food supplement tablets was used for the MF-SPEs practical testing.
Preparation, Testing and Application of Amalgam Screen-Printed Electrodes
Josypčuk, Bohdan ; Langmaier, Jan ; Tvorynska, Sofiia
Silver amalgam screen-printed electrodes (AgA-SPEs) were designed, prepared, and tested for\nthe first time as perspective representatives among SPEs for measuring at high negative\npotentials. The precise coulometric preparation procedure for mercury deposition at the\nworking electrode surface of the commercial silver-SPE was developed. An optimal\nelectrolyzer construction for the mercury deposition, electrolyte composition, and electrolysis\nconditions were proposed. The maximum value of hydrogen overvoltage (-1979 ± 4 mV) was\nfound on AgA-SPE with 50% (w/w) of Hg content in 0.1 mol L-1 NaOH, which is more negative\nthan with the original silver-SPE for 387 mV (-1592 ± 12 mV).
Comparison of the Covalent Laccase Immobilization at Amino- and Carboxylfunctionalized Mesoporous Silica, Glassy Carbon, and Graphite Powders using Different Coupling Agents for Optimal Biosensor Preparation
Tvorynska, Sofiia ; Barek, J. ; Josypčuk, Bohdan
In order to find the most suitable immobilization protocol, a comparison of three strategies\nbased on the application of –NH2 and –COOH functionalized supports with the different\nactivation agents (glutaraldehyde and carbodiimide) have been conducted for the covalent\nenzyme (laccase) attachment. Two kinds of the supports, namely mesoporous silica (SBA−15,\nMCM−41) and carbonaceous (glassy carbon, graphite) powders, have been used. It was found\nthat a biosensor consisted of tubular detector of silver solid amalgam as a working electrode\nand the enzymatic mini-reactor with laccase covalently attached to glutaraldehyde activated\n–NH2 functionalized MCM−41 shows the best results regarding sensitivity and stability for\ndopamine detection.
Construction and application of the amperometric uric acid biosensors based on the covalent immobilization of uricase by different strategies
Tvorynska, Sofiia ; Barek, J. ; Josypčuk, Bohdan
In this work, a promising combination of a biosensor based on the\nenzymatic mini-reactor with the detection principle of four-electron\nreduction of the consumed oxygen at highly negative potential has\nbeen developed for uric acid determination using flow injection\nanalysis. The construction of the biosensor provides a spatial\nsegregation of the biorecognition (uricase-based mini-reactor) and\ndetection (tubular detector of silver solid amalgam (TD-p-AgSA))\nparts. To find out the most appropriate enzyme immobilization\nprotocol, three different strategies of the covalent attachment for\nuricase from Bacillus fastidiosus have been compared. It was found\nthat the biosensor with the mini-reactor based on the covalent\nattachment of uricase via glutaraldehyde to -NH2 functionalized\nmesoporous silica powder MCM-41 showed extremely high stability\n(>1 year) and reusability (at least 600 measurements) The biosensor's\npractical applicability was confirmed by successful determination\nof uric acid in human urine.
Utilization of potential programs in flow electrochemical determination of biologically active organic compounds
Bavol, Dmytro ; Dejmková, Hana (advisor) ; Josypčuk, Bohdan (referee) ; Metelka, Radovan (referee)
9 Abstract In this Ph.D. thesis possibilities of using our proposed potential programs for a multiple-pulse amperometry and a fast scan differential pulse voltammetry in combination with flow systems are presented. The development of new sensitive amperometric and voltammetric methods for the determination of oxidisable biologically active organic compounds is another aim of this work. In the first part of the work, the flow injection system and multiple-pulse amperometric detection were employed to develop and optimize a simple, low-cost, and rapid method for the simultaneous determination of natural and synthetic antioxidants. This technique involves the application of an appropriate potential waveform consisting of a suitable sequence of pulses on a single working electrode, thus allowing distinguish the analytes in a mixture with no need of separation. Conditions for the determination of antioxidants and modelling of the potential program were tested and studied, respectively. Second part of the work describes and characterizes the application of the fast scan differential pulse voltammetry (FSDPV) in combination with the flow systems. FSDPV is the electroanalytical technique that use high scan rate to record voltammograms within several milliseconds and ensures high temporal resolution. This technique...
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
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.
Utilization of potential programs in flow electrochemical determination of biologically active organic compounds
Bavol, Dmytro ; Dejmková, Hana (advisor) ; Josypčuk, Bohdan (referee) ; Metelka, Radovan (referee)
9 Abstract In this Ph.D. thesis possibilities of using our proposed potential programs for a multiple-pulse amperometry and a fast scan differential pulse voltammetry in combination with flow systems are presented. The development of new sensitive amperometric and voltammetric methods for the determination of oxidisable biologically active organic compounds is another aim of this work. In the first part of the work, the flow injection system and multiple-pulse amperometric detection were employed to develop and optimize a simple, low-cost, and rapid method for the simultaneous determination of natural and synthetic antioxidants. This technique involves the application of an appropriate potential waveform consisting of a suitable sequence of pulses on a single working electrode, thus allowing distinguish the analytes in a mixture with no need of separation. Conditions for the determination of antioxidants and modelling of the potential program were tested and studied, respectively. Second part of the work describes and characterizes the application of the fast scan differential pulse voltammetry (FSDPV) in combination with the flow systems. FSDPV is the electroanalytical technique that use high scan rate to record voltammograms within several milliseconds and ensures high temporal resolution. This technique...

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