Mariusz Grochowski

The Influence of Protonation on the Electroreduction of Bi (III) Ions in Chlorates (VII) Solutions of Different Water Activity

We examined the electroreduction of Bi (III) ions in chlorate (VII) solutions under varied protonation conditions of the depolariser using voltammetric and impedance methods. The results of the kinetic parameter correlation lead to the statement that the changes in the amount of chloric (VII) acid against the amount of its sodium salt in the supporting electrolytes of the low water activity have a significant influence on the rate of Bi (III) ion electroreduction. The increase of the concentration of chloric acid sodium salt, as well as the chloric (VII) acid alone within the particular concentration of the supporting electrolyte, inhibits the process of Bi (III) ion electroreduction. It should be associated with the reorganisation of the structure of the double layer connected with the slow dehydration inhibited by ClO 4− ions. The standard rate constants ks values with the increase of the chlorate (VII) concentrations for all the solutions examined of chlorates (VII) confirms the catalytic influence of the decrease of water activity on the process of Bi (III) ion electroreduction. The multistage process is confirmed by the non-rectilinear 1nkf = f(E) dependences.

Application of the catalytic properties of methionine to the determination of Bi(III) as well in the presence of Cu(II) ions at low levels by square wave voltammetry

ABSTRACT A simple and fast method for the determination of Bi(III) in the presence Cu(II) in non-complexing solution was proposed. The catalytic activity of L-methionine on Bi(III) ions electroreduction as well as lack of this amino acid influence on Cu(II) ions electroreduction process were utilised. The calibration graph of Bi(III) in 4 mol dm−3 chlorate (VII) in the presence of 5 × 10−2 mol dm−3 methionine is linear in the range of concentrations of Bi(III) from 3 × 10−7 to 1 × 10−4 mol dm−3. The detection and quantification limits were found to be 1.53 × 10−7 and 5.12 × 10−7 mol dm−3, respectively. Precision and recovery of the method were investigated by determination of Bi(III).

The effect of homocysteine and homocystine protonation on double-layer parameters at the electrode/chlorates(VII) interface:

In this study, a comparison of the properties of homocysteine and homocystine adsorption at mercury/chlorate(VII) interface was done. The adsorption of homocysteine and homocystine is in fact the adsorption of mercury(II) cysteine thiolate and mercury(I) cysteine thiolate. The differences in the capacity curves result probably from the formation of mercurous thiolate at the mercury surface. It seems that the changes in Ez and γ z values accompanying the change in the amino acid protonation in the basic electrolyte solution, confirm the altered arrangement of the cysteine mercury thiolates on the electrode surface.

The Effect of Protonated Ethionine Adsorption on Bi(III) Electroreduction in Chlorate(VII) Solutions with Varied Water Activity

AbstractThe Bi(III) electroreduction in the presence of the ethionine (Et) was studied under its different protonation and changes of water activity. In order to determine adsorption and kinetic parameters, the following were applied: DC polarography, square wave voltammetry (SWV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The influence of ethionine on the double-layer parameters at the electrode/chlorate (VII) interface and multistep Bi(III) ion electroreduction was found. The multistep Bi(III) electroreduction process is controlled by the kinetics of the formation of active Bi–Et complexes on the electrode surface. The size of the catalytic effect is connected with the equilibrium of the reaction creating active complexes before the successive transition of electrons. Graphical Abstractᅟ

Effects of Amino Acids Protonation on Double-Layer Parameters of the Electrode/Chlorates(VII) Interface, as well as Kinetics and Mechanism of Bi(III) Ion Electroreduction in the Aspect of the “Cap–Pair” Effect

It was found that both water activity and the presence of differently protonated homocysteine (HCE), homocystine (HCY) and ethionine (ET) affect on double layer parameters at the electrode/chlorates(VII) interface and multi-step Bi(III) ion electroreduction. The catalytic activity of amino acids increases in the order ET< HCY < HCE of large water activity (2 molndm-3 chlorate(VII)). For higher concentrations of chlorates(VII) (4 and 6 molndm-3 chlorate(VII)) there is observed a comparable effect of studied amino acids on the Bi(III) ions electroreduction rate particulary in the case of HCE and HCY. The mechanism of the catalytic effects of amino acids is associated with the formation of active complexes under specific conditions present on the electrode surface.