A novel cyclically renewable liquid silver amalgam film electrode (R-AgLAFE) has been used for the first time in studies of electrode processes under “cap-pair” conditions. It has been presented detailed production process of prototype sensor R-AgLAFE with liquid amalgam film silver based electrode refreshed cyclically before each measurement, along with complete specifications of its metrologic and utility parameters. It has been shown that 2-thiocytosine is catalyzing the Bi(III) ions electroreduction. Studies clearly indicate the multi-phase mechanism of the electrode process, in which active complexes Bi—(RS—Hg) in the adsorption layer mediate in the transfer of electrons. Obtained results of measurements on mechanism and kinetics of “cap—pair” effect using novel R-AgLAFE sensor confirmed assumptions that it is an attractive alternative to HMDEs.
The results of kinetic measurements revealed an accelerating effect of acetazolamide (ACT) on the multistep In(III) ions electroreduction in chlorates(VII) on a novel, cyclically renewable liquid silver amalgam film electrode (R–AgLAFE). The kinetic and thermodynamic parameters were determined by applying the DC polarography, square-wave (SWV) and cyclic voltammetry (CV), as well as electrochemical impedance spectroscopy (EIS). It was shown that ACT catalyzed the electrode reaction (“cap-pair” effect) by adsorbing on the surface of the R–AgLAFE electrode. The catalytic activity of ACT was explained as related to its ability to form active In(III)- acetazolamide complexes on the electrode surface, facilitating the electron transfer process. The active complexes constitute a substrate in the electroreduction process and their different structures and properties are responsible for differences in the catalytic activity. The determined values of the activation energy ΔH≠ point to the catalytic activity of ACT in the In(III) ions electroreduction process in chlorates(VII). Analysis of the standard entropy values ΔS0 confirm changes in the dynamics of the electrode process.
Adsorption of acetazolamide (ACT) and the mixed adsorption layers of acetazolamide (ACT) - sodium 1-decanesulfonate (SDS) and acetazolamide - hexadecyltrimethylammonium bromide (CTAB) formed at the R-AgLAFe/ chlorates(VII) interface is described. The systems were characterized by the measurements of differential capacity, potential of zero charge, and surface tension at this potential. The adsorption parameters determined in the studied systems indicate the SDS domination in the adsorption equilibria formation and the competitive adsorption between the ACT - SDS or mixed micelles. However, acetazolamide dominates in the formation of adsorption equilibria of the ACT - CTAB mixture.
Bi(III) ions electroreduction in the presence of N-acetylcysteine (ACYS)at the nanostructured R-AgLAFE electrode has been studied by the voltammetric and impedance measurements. The experimental data indicates the multistage character of the electrode process and the catalytic influence of N-acetylcysteine on the Bi(III) ions electroreduction rate. It was found that this process is controlled by the chemical reaction of the Bi(III)–Hg(SR)2 activecomplexes formation on the electrode surface, which mediates electron transfer. Active complexes are a substrate in the process of electroreduction, and their different structure and properties are the reason for the diverse catalytic activity of N-acetylcysteine.
The catalytic influence of methionine (Mt) on the electroreduction of Bi(III) ions on the novel, cyclically renewable liquid silver amalgam film electrode (R–AgLAFE) in a non-complexing electrolyte solution was examined. The presence of methionine leads to a multistep reaction mechanism, where the transfer of the first electron is the rate limiting step, which is the subject of catalytic augmentation. The catalytic activity of methionine is a consequence of its ability to remove water molecules from the bismuth ion coordination sphere, as well as to form active complexes on the electrode surface, facilitating the electron transfer process.
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