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Voltammetric Determination of Quinoxaline at a Mercury Meniscus Modified Silver Solid Amalgam Electrode
Kotasová, Marcela ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
The aim of this Bachelor Thesis was to develop sensitive, inexpensive, and less time-consuming voltammetric methods for the determination of quinoxaline. For this purpose, DC voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) were used. The optimization consisted of finding a suitable medium and a suitable regeneration of the electrode surface. The optimal medium for the determination of quinoxaline was a solution of the Britton-Robinson buffer of pH 13,0, and it was also found that for both techniques, it is advisable to use regeneration potentials Ein = -100 mV a Efin = -1800 mV for the cleaning of the electrode surface. Concentration dependences were measured in the concentration range of 1.10-7 - 1.10-4 mol.L-1 of quinoxaline. Over all concentration ranges, the dependences were non-linear, however, it was possible to fit them with a high correlation using a polynomial function of the second order. The limits of quantification (LQ) reached were 8.2×10-7 mol.L-1 (DCV - evaluated the peak height), 3.9×10-7 mol.L-1 (DPV - evaluated the peak height), and 2.8×10-7 mol.L-1 (DPV - evaluated the peak area). The spectrophotometric determination of quinoxaline, which was performed for a comparison, provided two peaks with the...
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Voltammetric Determination of Diacetyl and Pyruvate by Derivatization with o-Phenylenediamine
Kotasová, Marcela ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
The aim of this Diploma Thesis was to develop sensitive, inexpensive, and less time- consuming voltammetric methods for the determination of diacetyle and pyruvate, when both analytes are derivatized by ofenylendiamine (OPDA) and the resulting reaction products are determined. For this purpose, techniques DC voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m- AgSAE) were used. The optimization consisted of finding a suitable medium and regeneration of the electrode surface for the determination 2,3dimethylquinoxaline (2,3DMQ) and 2hydroxymethylquinoxaline (2OH3MQ), products of derivatization reactions. The optimal medium for the 2,3DMQ determination was a solution of the Britton-Robinson buffer (BRbuffer) of pH 6.0 for DCV (optimal regeneration potentials Ein = 400 mV and Efin = 900 mV, with limit of quantification LQ ≈ 1.2·10-6 mol·L-1 ) and pH 7.0 for DPV (Ein = 200 mV and Efin = -900 mV, LQ ≈ 1.1·10-7 mol·L-1 ). For 2OH3MQ, the optimal medium was BRbuffer of pH 4.0 and regeneration potentials Ein = 500 mV and Efin = 900 mV for both techniques (LQ ≈ 4.8·10-7 mol·L1 for DCV and 3,4·10-7 mol·L-1 for DPV). Optimization of derivatization reactions for the determination of diacetyle and pyruvate consisted of...
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Voltammetric Determination of Quinoxaline at a Mercury Meniscus Modified Silver Solid Amalgam Electrode
Kotasová, Marcela ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
The aim of this Bachelor Thesis was to develop sensitive, inexpensive, and less time-consuming voltammetric methods for the determination of quinoxaline. For this purpose, DC voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) were used. The optimization consisted of finding a suitable medium and a suitable regeneration of the electrode surface. The optimal medium for the determination of quinoxaline was a solution of the Britton-Robinson buffer of pH 13,0, and it was also found that for both techniques, it is advisable to use regeneration potentials Ein = -100 mV a Efin = -1800 mV for the cleaning of the electrode surface. Concentration dependences were measured in the concentration range of 1.10-7 - 1.10-4 mol.L-1 of quinoxaline. Over all concentration ranges, the dependences were non-linear, however, it was possible to fit them with a high correlation using a polynomial function of the second order. The limits of quantification (LQ) reached were 8.2×10-7 mol.L-1 (DCV - evaluated the peak height), 3.9×10-7 mol.L-1 (DPV - evaluated the peak height), and 2.8×10-7 mol.L-1 (DPV - evaluated the peak area). The spectrophotometric determination of quinoxaline, which was performed for a comparison, provided two peaks with the...
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