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Determination of metronidazole on modified carbon paste electrode
Axmannová, Hana ; Dejmková, Hana (advisor) ; Navrátil, Tomáš (referee)
This bachelor thesis examines the possibilities of suppression of the oxygen signal of carbon paste electrode by modification of the electrode with a reductant. Two modifiers were chosen: sodium sulphite and sodium hypophosphite. The unmodified carbon paste electrode was used for the comparison. The possibilities of using these developed electrodes were verified via determination of metronidazole by the differential pulse voltammetry. The conditions for the determination of metronidazole were optimized; for unmodified carbon paste electrode (CPE) buffer of pH 10 was selected as the optimum medium, for carbon paste electrode modified with sodium sulphite (S-CPE) buffer of pH 7 was selected, and finally for carbon paste electrode modified with sodium hypophosphite (F-CPE) buffer of pH 4 was selected as the optimum medium. In this media, concentration dependences were measured and detection and quantification limits were obtained. The possibility of increase of the sensitivity of determination by the accumulation step was studied, but the accumulation of metronidazole was not observed after 5 minutes. The detection and quantification limits for CPE were 1,7×10-5 mol/l and 5,6×10-5 mol/l, for S-CPE 6,8×10-5 mol/l and 2,3×10-4 mol/l and finally for F-CPE 1,3×10-5 mol/l and 4,3×10-5 mol/l. The developed...
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Chromatographic determination of nitrophenylhydrazines and their hydrazones using dual amperometric detection
Axmannová, Hana ; Dejmková, Hana (advisor) ; Fischer, Jan (referee)
This diploma thesis examines the optimization of the determination of nitrophenylhydrazines using high performance liquid chromatography with electrochemical detection on dual thin-layer electrode. The spectrophotometric detection was used for the comparison. The developed method was also tested for the determination of hydrazone produced by the reaction of 2,4-dinitrophenylhydrazine (DNPH) with benzaldehyde as a member of substances containing carbonyl group. The conditions for the determination of nitrophenylhydrazines were optimized; based on the hydrodynamic voltammograms, pH 3 of aqueous part of the mobile phase and potentials of +1,0 V and -1,0 V were chosen. Under these conditions, the repeatability was tested. The concentration dependences were also measured and detection limits were obtained. The detection limits were obtained from the peak heights both in anodic and cathodic potential range. For 2-nitrophenylhydrazine these limits were 9,5·10-8 mol/L for oxidation and 6,2·10-7 mol/L for reduction. For 2,4-dinitrophenylhydrazine the limits were 2,1·10-8 mol/L and 1,8·10-7 mol/L for oxidation and for reduction, respectively. For the preparation of hydrazone, DNPH was chosen due to its better cathodic response and it was mixed with benzaldehyde. The electrochemical behaviour of...
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Chromatographic determination of nitrophenylhydrazines and their hydrazones using dual amperometric detection
Axmannová, Hana ; Dejmková, Hana (advisor) ; Fischer, Jan (referee)
This diploma thesis examines the optimization of the determination of nitrophenylhydrazines using high performance liquid chromatography with electrochemical detection on dual thin-layer electrode. The spectrophotometric detection was used for the comparison. The developed method was also tested for the determination of hydrazone produced by the reaction of 2,4-dinitrophenylhydrazine (DNPH) with benzaldehyde as a member of substances containing carbonyl group. The conditions for the determination of nitrophenylhydrazines were optimized; based on the hydrodynamic voltammograms, pH 3 of aqueous part of the mobile phase and potentials of +1,0 V and -1,0 V were chosen. Under these conditions, the repeatability was tested. The concentration dependences were also measured and detection limits were obtained. The detection limits were obtained from the peak heights both in anodic and cathodic potential range. For 2-nitrophenylhydrazine these limits were 9,5·10-8 mol/L for oxidation and 6,2·10-7 mol/L for reduction. For 2,4-dinitrophenylhydrazine the limits were 2,1·10-8 mol/L and 1,8·10-7 mol/L for oxidation and for reduction, respectively. For the preparation of hydrazone, DNPH was chosen due to its better cathodic response and it was mixed with benzaldehyde. The electrochemical behaviour of...
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Determination of metronidazole on modified carbon paste electrode
Axmannová, Hana ; Dejmková, Hana (advisor) ; Navrátil, Tomáš (referee)
This bachelor thesis examines the possibilities of suppression of the oxygen signal of carbon paste electrode by modification of the electrode with a reductant. Two modifiers were chosen: sodium sulphite and sodium hypophosphite. The unmodified carbon paste electrode was used for the comparison. The possibilities of using these developed electrodes were verified via determination of metronidazole by the differential pulse voltammetry. The conditions for the determination of metronidazole were optimized; for unmodified carbon paste electrode (CPE) buffer of pH 10 was selected as the optimum medium, for carbon paste electrode modified with sodium sulphite (S-CPE) buffer of pH 7 was selected, and finally for carbon paste electrode modified with sodium hypophosphite (F-CPE) buffer of pH 4 was selected as the optimum medium. In this media, concentration dependences were measured and detection and quantification limits were obtained. The possibility of increase of the sensitivity of determination by the accumulation step was studied, but the accumulation of metronidazole was not observed after 5 minutes. The detection and quantification limits for CPE were 1,7×10-5 mol/l and 5,6×10-5 mol/l, for S-CPE 6,8×10-5 mol/l and 2,3×10-4 mol/l and finally for F-CPE 1,3×10-5 mol/l and 4,3×10-5 mol/l. The developed...
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