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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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Silver Amalgam Electrodes in Electroanalysis of Selected Agrochemicals
Daňhel, Aleš ; Barek, Jiří (advisor) ; Vytřas, Karel (referee) ; Ludvík, Jiří (referee)
4 ABSTRACT Development and testing of novel non-toxic electrode materials, detection arrangements and analytical methods applicable in determination of selected agrochemicals is the main aim of this Ph.D. Thesis. New working electrodes based on silver solid amalgam paste (AgSA-PE) with organic pasting liquid and other based on crystallic silver amalgam (CAgAE) were developed, their electrochemical behaviour investigated and further used in voltammetric determination of widespread and toxic environmental pollutant 4-nitrophenol (4-NP). This analyte could be determined by DPV at AgSA-PE with limit of detection (LD) 1×10í6 mol lí1 and using CAgAE with LD 4×10í7 mol lí1 , both in 0.2 mol lí1 acetate buffer pH 4.8. Attempts to decrease LDs by utilization of adsorptive stripping voltammetry were not successful in either case. Crystallic silver amalgam was also successfully used for construction of microcylindric flow-through cell and tested for amperometric determination of nitrophenol mixture in HPLC-ED system. Both novel electrodes were found to be suitable alternatives to toxic mercury electrodes and the CAgAE seems to be promising working electrode for flowing systems. Method for sample preparation and voltammetric determination of broad-spectrum herbicide Glyphosate in contaminated soil samples was also...
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Electrochemical sensor for ascorbic acid detection
Hlavička, Michal ; Kynclová, Hana (referee) ; Majzlíková, Petra (advisor)
This work deals with electrochemical detection of ascorbic acid using screen-printed three-electrode sensors. The work is divided into three parts, where the first describes the theory of thick-film technology, including the types and compositions of the pastes, fabrication and firing. The second part deals with the methods, measurement principles and the electrochemical detection of ascorbic acid. Experiments were done using screen-printed carbon electrodes in a solution of phosphate buffer and ascorbic acid. In conclusion the results are evaluated.
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Biosensors based on modified carbon nanotubes
Ferdusová, Helena ; Majzlík, Petr (referee) ; Hubálek, Jaromír (advisor)
The aim of this work is to describe biosensors for detection of substances in liquids using modified carbon nanotubes. This work reports on knowledge about nanotubes and electrochemical analysis methods which were used. The matter of direct electrochemical detection of insulin using CNTs modified thick layer planar carbon nanotubes is discussed. The elementary working electrodes were created by using of commercial carbon paste and were modified by thin film CNTs, CNTs/ruthenium oxide and CNTs/chitosan then. The best results of the insulin detection were achieved with the working electrodes modified by low concentration non-purified CNTs which had low elementary response in electrolyte and good response to increasing concentration of insulin in the concentration range from 0, 25 to 10 mol/L. The other modifications caused increasing of the electrode elementary response, but they did not significantly affect the detection.
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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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Optimization of a Flow Rate for a Hyphenation of Voltammetry with Electrospray Ionization Mass Spectrometry
Jaklová Dytrtová, Jana ; Jakl, M. ; Norková, Renáta ; Navrátil, Tomáš
The hyphenation of an electrochemical cell prior to mass spectrometer with electrospray ionization allows studying of products and/or of intermediates of electrode reactions. The measurement is realized in a flowing system. The flow rate of the sample markedly influences the MS signal intensity of the product. The calculated optimum value for the electrochemical cell with the sweep volume 0.72 μL is in the range from 0.4 to 0.5 mL h -1 . The experimental optimal value is 0.45 mL h -1 . The optimization of the flow rate has to be provided individually for each product, because the intensity also depends on the rate of the electrode reaction and product stability.
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