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Study of electrochemical behaviour of cinchona alkaloids at boron doped diamond electrode
Brunovská, Veronika ; Schwarzová, Karolina (advisor) ; Sokolová, Romana (referee)
The anodically oxidized boron doped diamond electrode was used in this study to investigate the electrochemical behaviour of quinoline and its derivative quinine in the anodic area in the aqueous medium, namely using methods of cyclic voltammetry (CV), square wave voltammetry (SWV) and square wave adsorptive stripping voltammetry (SWAdSV) and to adress their potential in voltammetric analysis. It was found by means of SWV that quinoline exhibits one anodic signal in BR buffer in the range of pH 3.0 - 12.0. Quinine shows one anodic signal in the range pH 2.0 - 5.0 later; at higher pH values other 2 to 4 less distinctive signals are formed, i.e, the mechanism is influenced by the presence of quinuclide ring and functional groups at the quinoline skeleton of quinine. It was proved by cyclic voltammetry that the anodic electrode reaction of quinoline is controlled by diffusion; for quinine the results are rather ambiguous. Using the optimized parameteres of SWV (Estep = 5 mV; f = 40 Hz and A = 50 mV) and media of BR buffer pH 5,0, linear dependence peaks height of quinoline on its concentration in the range of 1∙10-7 to 1∙10-4 mol.l-1 was obtained with limit of detection 3.53∙10-7 mol.l-1 . The concetration dependence of quinine under the same conditions is not linear in the range of 6∙10-7 to 1∙10-4...
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Study of electrochemical behaviour of quinine and cinchonidine at boron doped diamond electrode
Brunovská, Veronika ; Schwarzová, Karolina (advisor) ; Nesměrák, Karel (referee)
In this thesis, it was for the first time studied the electrochemical behaviour of cinchona alkaloids quinine and cinchonidine by cyclic voltammetry and differential pulse voltammetry using boron doped diamond (BDD) thin film as an electrode material. Cyclic voltammograms did not exhibit any significant anodic signals corresponding to a simple electrode reaction. However, current increase with indistinctive maxima compared to the basic electrolyte was recorded in Britton - Robinson buffers with pH 2,0 − 12,0 medium. Accordingly, insignificant signals observable in the cathodic area at far negative potential close to the potential of decomposition of the supporting electrolyte , presumably to the reduction of quinoline skeleton. It was found by means of differential pulse voltammetry that the number of those observable current maxima varies for quinine and cinchonidine in different supporting electrolytes. Quinine provided the best developed anodic peaks in the medium of BR buffer pH 5,0 and 6,0 and cinchonidine in pH 7,0, 9,0 and 12,0. The calibration dependence of anodic peak of quinine in BR buffer pH 5,0 is linear in the concentration range 6∙10−6 mol∙l−1 − 1∙10−4 mol∙l−1 with limit of quantitation 4,39∙10−6 mol∙l−1 . In the cathodic area the limit of quantitation is 4,33∙10−5 mol∙l-1 . The...
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