Electrolyte Dropping Electrode Research Articles

Mixed electrolyte effect on the stability of the interface between two immiscible electrolyte solutions

Polarization and interfacial tension measurements at an electrolyte dropping electrode or a sessile electrolyte drop are used to investigate the instability of the interface between the aqueous solution of LiCl and the organic solvent containing a mixture of the electrolytes composed of the non-adsorbing ions, here tetrabutylammonium tetraphenylborate (TBATPB) and bis(triphenylphosphoranylidene) ammonium tetrakis (pentafluorophenyl)borate (BATB). The instability is manifested by a substantial current enhancement and decrease of the interfacial tension accompanied by the vigorous mechanical oscillations of the drop. In contrast, no instability is observed when the organic solvent phase contains TBATPB or BATB alone. It is proposed that the hydrodynamic instability has the origin in the small faradaic current associated with the trace ion transfer, and that the initiating impulse is generated by the perturbation of the stratified distribution of the ions with the significantly different sizes (e.g., TBA+ and BA+) on the organic side of the interface. Effects of the potential and the electrolyte concentration on the current enhancement and the interfacial tension reduction are explained by the kinematic theory that has been established by Aogaki et al. (Electrochim. Acta 23 (1978) 867).

Interfacial instability associated with the transfer of non-adsorbing ions across the polarized water/1,2-dichloroethane interface

Polarography with the electrolyte dropping electrode is used to study the transfer of several non-adsorbing ions including Na+, H+, Cl−, tetrabutylammonium+ (TBA+) and tetraethylammonium+ (TEA+) across the water/1,2-dichloroethane interface. The transfer of Na+, H+, Cl− and TBA+ in the thermodynamically favored direction is accompanied by the interfacial instability, which is manifested by the substantial faradaic current amplification (polarographic current maximum). No such amplification is observed in case of the transfer of TEA+ in either direction. The potential range of the interfacial instability, as well as of its absence, is correctly predicted by the linear instability analysis developed by Aogaki et al. (Electrochim. Acta 23 (1978) 867). The analysis also provides an explanation for the experimentally observed decrease of the interfacial tension in the potential range of the instability. Two remarkable effects of the interfacial instability are demonstrated, specifically the irregularly repeated swapping of the faradaic current and the interfacial tension occurring close to the electrocapillary maximum between the amplified current/low interfacial tension and diffusion current/high interfacial tension levels, and the mechanical oscillation of the electrolyte drop in the former state.

Determination of lead(II) by online novel electrolyte dropping electrode using 1,10-phenanthroline in flow injection system

The transfer of Pb(II) facilitated by 1,10-phenanthroline (phen) presented in the methyl isobutyl ketone (MIBK) across the polarized water|MIBK interface was systematically investigated by novel electrolyte dropping electrode using cyclic voltammetry and square wave voltammetry. The protonation of 1,10-phenanthroline in polarized water|MIBK interface was explored. The dependence of the half-wave potential on PbCl2 and phen concentration was investigated and the stoichiometry of resulting metal ligand complex was formulated. Different concentrations of PbCl2 was determined online and the transfer peak current was proportional to the bulk concentration of the Pb2+ varied between 8 μM to 0.5 mM and 0.5 to 1 mM, and the linear regression coefficients were 0.9953 and 0.9995, respectively. The standard deviations (RSD) were 4.33, 5.80, 4.13, 3.88, 2.23, 3.39, 1.38, 2.42, 2.00, 2.73 and 2.37% for 8 times successive determinations of Pb2+ for the concentrations of 0.008, 0.05, 0.1, 0.2, 0.3, 0.35, 0.4, 0.5, 0.8, 0.9 and 1 mM, respectively. The long time stability of the electrolyte dropping electrode was tested and the result showed that this novel method was simple, rapid and efficient.

Electrochemical determination of cadmium(II) using dithizone assisted ion transfer and eletrolyte dropping electrode

The transfer of Cd(II) assisted by dithizone (DzH2) present in methyl isobutyl ketone (MIBK) at water–MIBK interface was systematically investigated by novel electrolyte dropping electrode (EDE) using cyclic voltammetry (CV) and square wave voltammetry (SWV). The protonation of DzH2 at polarized liquid–liquid interface was studied. The stoichiometry of resulting metal ligand complex was formulated. Transfer peak current was proportional to the bulk concentration of the Cd(II) varied between 1 μM to 0.1 mM and the maximum value of relative standard deviation was about 3.17%. The presented procedure was successfully applied for determination of Cd(II) in real samples.

On the facilitating effect of neutral macrocyclic ligands on the ion transfer across the interface between aqueous and organic solutions: Part III. Competitive facilitated ion-transfer

A theoretical equation of the reversible current–potential curves is derived for the competitive ion-transfer of two kinds of cations present in an aqueous (w) phase simultaneously facilitated by a macrocyclic ligand (L) present in an organic (o) phase. Especially, for the two limiting cases, i.e. case (A): c* M j ( j=1, 2)≫ c* L and case (B): c* L≫ c* M j (where c* M j and c* L denote the bulk concentrations of cation M j in the w-phase and of L in the o-phase, respectively), simple explicit expressions are derived and a method analyzing the facilitated waves is presented. Furthermore, the main part of the theoretical predictions obtained is verified experimentally at 25 °C by using the ion-transfer-polarographic method with the electrolyte dropping electrode, for the following four combinations: (i) competitive cations: protonated alanine and H +, L: benzo-18-crown-6 ether; (ii) Na + and Li +, benzo-15-crown-5 ether; (iii) K + and Na +, dibenzo-18-crown-6 ether; and (iv) Na + and Ba 2+, dibenzo-24-crown-8 ether.

Study of the Faradaic transfer of ions in a 1,2-dichloroethane extraction system. Similarities and differences in character between cobalt(II) and nickel(II) with 1,10-phenanthroline as the complexing agent

The character of the Faradaic transfer of Co2+ and Ni2+ ions across a dichloroethane (DCE)/aqueous interface in the presence of 1,10-phenanthroline (phen) as the complexing agent was observed by current scan polarography at an electrolyte dropping electrode (EDE) and by chronopotentiometry at a stationary water electrode (SWE). The observed behaviour was similar for both, when the complexing agent was originally added to the aqueous phase; however, very different behaviour was observed when the complexing agent was originally added to the organic phase (DCE). Thus, it follows from the difference in the behaviour, resulting from their different kinetic rates of association with phen, that Co2+ and Ni2+ can be easily separated from each other by ‘extraction’ using an electric field.

Ph effect of aqueous phase of a two immiscible liquid phases system on ion transfer across phase interface under conditions of electrolyte dropping electrode

The theoretical current-potential curves have been derived in the form Δ org aq ψ = f ( I) ( Δ org aq ψ is the Galvani potential difference between the aqueous and organic phase of a two-phase system; I is the mean current) describing the pH effect of the buffered aqueous phase on reversible transfer of ions, which are the products of dissociation equilibria in the aqueous phase, across the interface of two immiscible liquid phases under the condition of an electrolyte dropping electrode. On the basis of the derived current-potential dependences, the possibilities of the determination of the corresponding equilibrium constants are presented.

Electrolyte dropping electrode polarographic studies. Solvent effect on stability of crown ether complexes of alkali-metal cations

Electrolyte dropping electrode polarographic studies. Solvent effect on stability of crown ether complexes of alkali-metal cations

The electron transfer at a liquid / liquid interface studied by current-scan polarography at the electrolyte dropping electrode

Some novel systems are introduced as suitable for observing the electron transfer voltammograms and/or polarograms at the aqueous (W)/nitrobenzene (NB) interface. Among them, the polarographic processes with systems composed of hexacyanoferrate(II), hydroquinone or hydroxyl ion in W/7,7,8,8-tetracyanoquinodimethane (TCNQ) in NB, hexacyanoferrate(III) or Ce 4+ in W/ferrocene (FC) or tetrathiafulvalene (TTF) in NB and permanganate in W/tetraphenylborate ion in NB were found to be reversible under appropriate conditions. The relation between the limiting currents in polarograms and the concentration of reactants either in W or NB is presented. On the basis of analysis of reversible polarograms at the W/NB interface and a comparison with voltammograms at a platinum electrode in W or in NB, the half-wave potentials are connected to the oxidation-reduction potentials of the reactants in each individual solution, W or NB.

The role of non-ionic polyoxyethylene ether surfactants on ion transfer across aqueous/organic solution interfaces studied by polarography with the electrolyte dropping electrode

The transfer of Li +, Na +, K +, NH + 4, Mg 2+, Sr 2+, and Ba 2+ from aqueous solution to 1,2-dichloroethane or nitrobenzene facilitated by polyoxyethylene ethers, Triton X, was studied by current-scan polarography using the aqueous electrolyte dropping electrode. The facilitated ion transfer is attributable to the formation of a hydrophobic complex of metal ion with Triton X adsorbed at the aqueous/organic solution interface, followed by the transfer of the complex from the interface into the organic solution. The stability and the composition of the metal-Triton X complexes were investigated by changing the length of the oxyethylene chain of the Triton X, taking into account the iondipolar bond formation between metal ions and the oxyethylene chain. The adsorption-desorption behavior of the Triton X and metal-Triton X complex was elucidated by referring to drop time curves.

Electron Transfer Reaction across the Interface between two Immiscible Liquid Phases coupled with Preceding Homogeneous Chemical Reaction under the Conditions of the Electrolyte Dropping Electrode

Article Electron Transfer Reaction across the Interface between two Immiscible Liquid Phases coupled with Preceding Homogeneous Chemical Reaction under the Conditions of the Electrolyte Dropping Electrode was published on January 1, 1987 in the journal Zeitschrift für Physikalische Chemie (volume 268O, issue 1).

The transfer of anions at the aqueus/organic solutions interface studied by current-scan polarography with the electrolyte dropping electrode

Abstract The transfer of such anions as halides, their oxo-acid anions and other polyatomic anions was investigated at the aqueous/1,2-dichloroethane, nitrobenzene, or chloroform interface. The polarograms were reversible for most of the anions and therefore it was concluded that the transfer processes of these anions are controlled by the diffusion of anions in the aqueous and/or organic solutions. The half-wave potentials, ΔV 1 2 , of the polarograms, which can be related directly to the transfer energies, are discussed on the basis of the ionic radii, crystallographic forms, and charges of the anions. As for monovalent anions, linear relationships were obtained between ΔV 1 2 and the inverse of the thermochemical radii, irrespective of the kind of organic solvent. The analytical aspects of ion-transfer polarography in the determination of anions are also discussed.

Possibility of Application of the Electrolyte Dropping Electrode to the Study of Homogeneous Chemical Reactions

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Possibility of Application of the Electrolyte Dropping Electrode to the Study of Homogeneous Chemical Reactions

Possibility of Application of the Electrolyte Dropping Electrode to the Study of Homogeneous Chemical Reactions

Contribution to stationary curve of current vs potential of electron-transfer between two immiscible electrolyte solutions

Theoretical stationary curves of current vs potential that are mathematical expressions of an electron-transfer reaction, O1(w)+R2(non) ⇌ R1(w)+O2(non), proceeding at the interface of two immiscible phases between the redox couple O1/R1 in the aqueous phase (w) and the redox couple O2/R2 in the non-aqueous phase (non) has been derived. Procedures for the determination of the diffusion coefficients of the reactants in the corresponding phase and for the evaluation of thermodynamic and kinetic parameters of the electron-transfer reaction from the curve of mean current vs potential of this electron-transfer at the electrolyte dropping electrode have been suggested.

Effect of ion association and complex formation on Transfer of cation across the interface of two immiscible electrolyte solutions under polarographic conditions

Theoretical current-potential curves have been derived that are expressed by dependences Δαβφ=f(I) (Δαβφ is the Galvani potential difference between phases β and α, I is the mean current) describing the transfer of a cation across the interface of two immiscible electrolyte solutions affected by the formation of ion-pairs or complexes under the conditions of the electrolyte dropping electrode. Further, the effect of some components of the two-phase systems considered on the values of the half-wave potentials of the polarographic waves is discussed.

Effect of ion association and complex formation on transfer of cation across the interface of two immiscible electrolyte solutions under polarographic conditions

Theoretical current-potential curves have been derived that are expressed by dependences Δ α βφ=f( I) (Δ α βφ is the Galvani potential difference between phases β and α, I is the mean current) describing the transfer of a cation across the interface of two immiscible electrolyte solutions affected by the formation of ion-pairs or complexes under the conditions of the electrolyte dropping electrode. Further, the effect of some components of the two-phase systems considered on the values of the half-wave potentials of the polarographic waves is discussed.

Voltammetric interpretation of potential at ion-selective electrode using current-scan polarography at aqueous/organic solutions interface.

The behavior of solute ions at the interface between aqueous and organic phases is clearly demonstrated by the current-scan polarography at the electrolyte dropping electrode. The potential-generating process at the liquid membrane type ion-selective electrode is explained on the basis of the polarographic results.

Electrolysis with electrolyte dropping electrode Part III. Investigation of anions

Electrolysis with electrolyte dropping electrode Part III. Investigation of anions

Electrolysis with electrolyte dropping electrode: Part III. Investigation of anions

The application of the electrolyte dropping electrode (EDE) for investigation of transfer of anions across the water-nitrobenzene interface is described. For investigation of anion transfer tetraphenylborate salt of Crystal Violet was used as the base electrolyte for the nonaqueous phase. The cation of Crystal Violet is highly hydrophobic and widens the useful range toward the negative potentials. Its partition coefficient between water and nitrobenzene was determined colorimetrically. Transfer of five anions was investigated in this work: n-octoate, picrate, laurylsulphate, thiocyanate and perchlorate. The transfer was found to be reversible and the standard Gibbs energy of transfer for individual ions was determined. No effect of acetate and hydroxide ions was observed.