Electrode electrolyte dropping

The electrolyte dropping electrode [63] method, introduced in 1976, and subsequently used in conjunction with the four-electrode potentiostat [64], is a hydrodynamic technique, offering controlled convective transport. In essence, this approach is identical to the dropping mercury electrode [65] however, the drop consists of a flowing electrolyte liquid phase which forms a polarized ITIES with an immiscible continuous (receptor) phase. In... 

The electrolyte dropping electrode has found particular application in the study of ion transfer at the polarized ITIES, with an emphasis on analysis. A range of species have been detected amperometrically by measuring the transport-limited current ... 

In the majority of methods described thus far, the interfacial kinetics are deduced by measuring concentration changes in the bulk of the solution rather than at the interface, where the reaction occurs. This introduces a time lag, limiting the resolution of the measurement in the determination of interfacial kinetics. A more direct approach is to identify the interfacial flux. This can be achieved in the electrolyte dropping electrode, via the current flow, but this method is only applicable to net charge-transfer processes at externally polarized interfaces. 

Kakiuchi and Senda [36] measured the electrocapillary curves of the ideally polarized water nitrobenzene interface by the drop time method using the electrolyte dropping electrode [37] at various concentrations of the aqueous (LiCl) and the organic solvent (tetrabutylammonium tetraphenylborate) electrolytes. An example of the electrocapillary curve for this system is shown in Fig. 2. The surface excess charge density Q, and the relative surface excess concentrations T " and rppg of the Li cation and the tetraphenylborate anion respectively, were evaluated from the surface tension data by using Eq. (21). The relative surface excess concentrations and of the d anion and the... 

The facilitated transfers of Na+ and K+ into the NB phase were observed by the current-scan polarography at an electrolyte-dropping electrode [12]. In the case of ion transfers into the DCE phase, cyclic voltammetry was measured at an aqueous gel electrode [9]. Both measurements were carried out under two distinctive experimental conditions. One is a N15C5 diffusion-control system where the concentration of N15C5 in the organic phase is much smaller than that of a metal ion in the aqueous phase. The other is a metal ion diffusion-control system where, conversely, the concentration of metal ion is much smaller than that of N15C5. Typical polarograms measured in the both experimental systems are shown in Fig. 2. 

Fig. 9.3. The electrolyte dropping electrode REj, RE2 - reference electrodes CE2 - auxilliary electrode 1 - aqueous phase formed by dropping of the electrode 2 - nitrobenzene phase 3 - Teflon capillary 4 - sintered glass. The arrow denotes the connection to the reservoir with the aqueous electrolyte and the auxiliary electrode CEi. (After Samecefai. [20].)...

A hanging electrolyte drop electrode (fig. 9.4) was constructed for analytical purposes requiring electrolytic preconcentration of the test component [14, 15]. 

Fig. 9.4, The hanging electrolyte drop electrode. Symbols are the same as in fig. 9.2. (After Marebek and Samec [15].)...

Fig. 9.7. Determination of acetylcholine by differential pulse polarography with hanging electrolyte drop electrode. Acetylcholine concentrations 0-0, 1-0.5 ppm, 2-1 ppm, 3-2 ppm, 4-5 ppm.

A comprehensive and systematic investigation of the fundamental factors in ion transfer measurements in the electrolyte dropping electrode arrangement has been carried out in order to develop a quantitative method for analysis [68]. It was reported that the limiting currents were proportional to the concentration of monovalent ions such as Cs+, tetramethylammonium ion, CIO4, IO4, I-, Br, ReC)4, and BF4 in the concentration range between 10-5 and 10 3 M in aqueous solution, when 1,2-dichloroethane (DCE) was used as the organic phase. 

In this communication our attempts to exploit the electrolysis at ITIES for analytical purposes are described. As examples the determination of acetylcholine, tetraethylammonium, calcium, barium and strontium cations by differential pulse stripping voltammetry (DPSV) at the hanging electrolyte drop electrode (HEDE) will be presented. 

Currently a four-electrode system with automatic ohmic drop compensation[5] has been used for accurate polarization measurements at ITIES. However, this rather complicated experimental set-up and the large area of the water/nitrobenzene interface (about 100 mm )[5] have not permitted the use of the fast pulse technique Therefore, we have developed a simpler three-electrode system with the hanging electrolyte drop electrode.[1]... 

Fig. 1. Assembly for hanging electrolyte drop electrode. CE 1 and CE 2 are the counter electrodes, RE 1 is the reference electrode. Pot. is the conventional three-electrode potentiostat with the IR drop compensation, pC is the microcomputer.

Kihara, S., M. Suzuki, K. Maeda, K. Ogura, M. Matsui, and Z. Yoshida, The electron transfer at a liquid-liquid interface studied by current scann polarograph at the electrolyte dropping electrode, J Electroanal Chem, Vol. 271, (1989) p. 107. 

Koryta, J., Vanysek, P, Brezina, M. Electrolysis with an electrolyte dropping electrode. J. Electroanal. Chem. 1976, 67, 263-266. 

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