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Electrochemical Biosensors and Detectors Based on Silver Solid Amalgam for Analysis in Flow Systems
Josypčuk, Oksana ; Barek, Jiří (vedoucí práce) ; Vytřas, Karel (oponent) ; Ludvík, Jiří (oponent)
6 Abstrakt Tato disertační práce představuje nové možnosti využití amalgámových elektrod zejména při konstrukci elektrochemických biosenzorů. V první řadě byl navržen a zkonstruován tubulární detektor na bázi stříbrného pevného amalgámu pro stanovení redukujících se analytů v průtokových systémech. Nejdříve byl testován při ampérometrickém stanovení modelových roztoků Cd2+ , Zn2+ a 4-nitrophenolu pomocí injekční průtokové analýzy. Výsledky ukázaly, že navržený tubulární detektor představuje jednoduché a levné zařízení s dobrou opakovatelností, citlivostí a dlouhodobou stabilitou minimálně 2 roky. Jednou z hlavních jeho výhod je možnost měření při vysokých negativních potenciálech (~ 2 V ve vodném prostředí). Poté byl tubulární detektor úspěšně použit pro stanovení účinné látky lomustinu v chemoterapeutickém léčivu CeeNU® Lomustine metodou průtokové diferenční pulsní voltametrie. Pro stanovení v průtokových systémech byly taktéž navrženy a 14 měsíců testovány miniaturní referentní elektrody kalomelová (SCE-AgPA), merkurosulfátová a merkuroxidová na základě stříbrného pastového amalgámu. Všechny referentní elektrody se ukázaly být stabilní po celou dobu zkoumání. Největší odolnost proti polarizaci byla zaregistrována u SCE-AgPA, a proto právě tato referentní elektroda byla použita pro všechny experimenty...
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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.
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Electrochemical Measurements in Flow Systems on Silver Amalgam Tubular Detector Combined with Auxiliary Electrode
Josypčuk, Bohdan ; Barek, J. ; Josypčuk, Oksana
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.
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Electrochemical biosensors with flow-through enzymatic reactors
Josypčuk, Oksana ; Josypčuk, Bohdan
Twelve enzymatic biosensors with various silica powder reactors were fabricated and tested.\nExperiments with six silica materials showed that mesoporous silica SBA-15 was the best one\nin terms of covering by enzymes, sensitivity and lifetime of biosensors. The current response\nof the SBA15-glucose oxidase (GOx) sensor started to decrease only after 200-day testing.\nThe used amalgam tubular detector in a flow system allowed working at highly negative\npotentials. Statistical results of parallel measurements of model solutions with the fabricated\nbiosensors show their high accuracy and sensitivity. The proposed SBA15-GOx biosensor\nwas used for determination of glucose in commercial honey.
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Noise Analysis of Ion Transfer Kinetics at the Micro Liquid/Liquid Interface
Josypčuk, Oksana ; Holub, Karel ; Mareček, Vladimír
Fluctuation analysis was utilized to determine the TEA ion transfer kinetics across the water/1,2-dichloroethane interface. The average value ks = 0.34 cm s-1 is comparable with the previously reported value ks = 0.2 cm s-1, derived from electrochemical impedance spectroscopy experiments. The experimental approach utilizing a thick wall glass microcapillary to fix the interface exhibits a very small stray capacitance value, proving this system to be suitable for determining the kinetics of the fast ion transfer across a liquid/ liquid interface. Application of a method employing a small perturbation signal prevents polarization of the inner capillary surface by current flowing through the cell. The induced polarization of the capillary can affect ion concentration at the interface due to electroosmosis and thus make the kinetics data evaluation difficult or erroneous.
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Electrochemical Biosensors Based on Silver Solid Amalgam for Analysis in Flow Systems
Josypčuk, Oksana ; Barek, J. ; Josypčuk, Bohdan
In this contribution, the construction and preparation of 3 types of flow amperometric enzymatic biosensors based on silver solid amalgam (AgSA) were presented. Two of them consist of the tubular detector and enzymatic reactor of porous or powdered AgSA. The third biosensor was constructed using polished AgSA electrode. Reactors and polished AgSA electrodes were modified with thiols or chitosan and different enzymes were covalently immobilized by suitable techniques. Prepared biosensors were used for determination of ascorbic acid, glucose, hydrogen peroxide, catechol, pyrogallol, dopamine and sarcosine in model samples and in same cases in the real samples.
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Unique Properties of Amalgam Electrodes
Josypčuk, Bohdan ; Josypčuk, Oksana
Depending on metal-mercury ratio and on the method of preparation amalgam can be: 1) solid compact; 2) paste; 3) liquid; 4) monocrystalline; 5) porous; 6) powdered. High potential of hydrogen overvoltage is observed on amalgam electrodes and it is comparable with one on Hg-electrodes. Another important benefit is the possibility to prepare amalgam electrode, detector or reactor of required size and shape. From amalgams have been prepared and tested many types of electrodes for batch and flow-through systems. The diversity of amalgam materials provides some unique electrochemical properties of electrodes, the most important of which are described in this paper.
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Electrochemical Biosensors Based on Enzymatic Reactor with Amalgam Powder
Josypčuk, Bohdan ; Barek, J. ; Josypčuk, Oksana
Enzymatic reactor based on the powder of silver solid amalgam was suggested as the main part of biosensors in flow systems for the first time. 4-aminothiophenol, glutaraldehyde and enzyme were gradually bonded to the amalgam surface. Large surface of the fine amalgam particles maintains a big quantity of enzyme molecules. Biosensors were tested with enzymes ascorbate oxidase, glucose oxidase, catalase, tyrosinase and laccase. Electrochemical detection of the oxygen concentration change (for the first 3 enzymes) or the quinones concentration (tyrosinase and laccase) in the measured solution was done amperometrically by means of the tubular detector of silver solid amalgam. The current response of each biosensor was optimized with respect to the detection potential, the flow rate of the mobile phase, the injection volume and the enzymatic reactor volume. Under the found optimum conditions, concentration dependence and some statistical parameters of repeated measurements (relative standard deviation (RSD) for the studied enzymes was in the range 0.81 – 2.1 %) were measured. Biosensor with the ascorbate oxidase reactor was used for determination of ascorbic acid in the vitamin tablet Celaskon®. Results of the analysis were in good agreement with the contents of ascorbic acid declared by manufacturer and the RSD of these analyses was 2.0 %.
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