|
|
Electrochemical reduction of dehydrocholic and chenodeoxycholic acid at stationary mercury and amalgam electrodes
Patáková, Adéla ; Schwarzová, Karolina (advisor) ; Vyskočil, Vlastimil (referee)
This thesis deals with the study of electrochemical behaviour of dehydrocholic and chenodeoxycholic acid at stationary mercury-based electrodes - hanging mercury dropping electrode and silver solid amalgam electrode modified by a mercury meniscus. This is the first study of electrochemical behaviour of dehydrocholic acid which offers tree peaks with potentials around -1270 mV, -1450 mV and -1800 mV. The last one with the potential -1800 mV is probably the main peak given by reduction of carboxylic group of side chain of steroid skeleton. By cyclic voltammetry was determined that the process is quasireversible and is strongly influenced by adsorption of DHCA on the electrode surface and also by the pH which determines dissociation degree of carboxylic group. In the environment of BR buffer (pH 7.0) - methanol (9:1) was measured concentration dependence by DC, DP and "square-wave" voltammetry. By neither one of these methods have been reached satisfying limits of detection and wide linear dynamic ranges. However, the repeatable signals in wide range of pH can be used for electrochemical characterization of DHCA. CDCA offers in environment 0,04 mol·l-1 borat buffer (pH 9.1) - methanol (9:1) one signal with potential around -1350 mV. Position of this peak on the potential axe and also its height are...
|
|
|
Electrochemical reduction of dehydrocholic and chenodeoxycholic acid at stationary mercury and amalgam electrodes
Patáková, Adéla ; Schwarzová, Karolina (advisor) ; Vyskočil, Vlastimil (referee)
This thesis deals with the study of electrochemical behaviour of dehydrocholic and chenodeoxycholic acid at stationary mercury-based electrodes - hanging mercury dropping electrode and silver solid amalgam electrode modified by a mercury meniscus. This is the first study of electrochemical behaviour of dehydrocholic acid which offers tree peaks with potentials around -1270 mV, -1450 mV and -1800 mV. The last one with the potential -1800 mV is probably the main peak given by reduction of carboxylic group of side chain of steroid skeleton. By cyclic voltammetry was determined that the process is quasireversible and is strongly influenced by adsorption of DHCA on the electrode surface and also by the pH which determines dissociation degree of carboxylic group. In the environment of BR buffer (pH 7.0) - methanol (9:1) was measured concentration dependence by DC, DP and "square-wave" voltammetry. By neither one of these methods have been reached satisfying limits of detection and wide linear dynamic ranges. However, the repeatable signals in wide range of pH can be used for electrochemical characterization of DHCA. CDCA offers in environment 0,04 mol·l-1 borat buffer (pH 9.1) - methanol (9:1) one signal with potential around -1350 mV. Position of this peak on the potential axe and also its height are...
|
|
|
The study of electrochemical reduction of chenodeoxycholic acid at stationary mercury-based electrodes
Patáková, Adéla ; Schwarzová, Karolina (advisor) ; Fischer, Jan (referee)
Chenodeoxycholic acid is the most common representative of bile acids in the human body. This work studies its electrochemical reduction at stationary mercury- based electrodes using the DC voltammetry and differential pulse voltammetry. These were performed on a silver solid amalgam electrode modified by a mercury meniscus (m-AgSAE) and a hanging mercury drop electrode (HMDE). On the scale of pH 4.0 - 12.0 offers CDCA one reduction signal in the area of highly negative potentials around −1400 mV. There is a distinctive change in the behavior of CDCA for buffers of pH lower than 6.0, compared to other pH values. This change is observable on both m-AgSAE and HMDE through the DC voltammetry and DPV methods. This happens due to protonization of carboxyl group on C24. This change is strongest with pH of 4.0. For that reason, CDCA was studied in two environments - a 0.04 mol.l−1 borat buffer (pH 9.1) - methanol (9:1) and in a BR buffer (pH 4.0) - methanol (9:1). In both environments, the lowest detection threshold has been reached through the DC voltammetry method on HMDE. The cyclic voltammetry method was used to study the electrode process. Again, measuring in pH 9.1 and pH 4.0 was done. For pH 9.1, this is a quasireversible process controlled by adsorption of both electrodes studied. For pH 4.0 is...
|
guest ::
RSS feed.