Supporting Electrolytes for Voltammetric Study of Ion Transfer at Nitrobenzene/Water Interface

Abstract

606The polarizable potential range was determined by cyclic voltammetry for the interface between an aqueous solution of lithium chloride or magnesium sulfate and a nitrobenzene solution of various electrolytes: tetrabutylammonium salts of tetraphenylborate, tetrakis(4-fluorophenyl)borate, tetrakis(4-chlorophenyl)borate, and tetrakis[3,5-bis(trifluoromethyl )phenyl]borate, and tetrapentyl-and tetrahexylammonium salts of tetraphenylborate.The anodic and cathodic limits of polarizable potential range were discussed with reference to the standard ion-transfer potentials of the supporting-electrolyte ions. where B1+ and Al are strongly hydrophobic ions (e.g. tetrabutylammonium ion, TBA+, and tetraphenylborate ion, TPB-), and B2+ and A2_ are strongly hydrophilic ions (e.g. Li+ and Cl-ions). Then the standard iontransfer potentials of A1_ and B2+ ions, Ao4 (j=A1~ and B2+), are extremely negative and those of B1+ and A2_ ions (j=B1+ and A2-) are extremely positive. As long as the Do 4 is not extremely positive (much less positive than A 4 i and A42) and is not extremely negative (much less negative than Do B, and Ao 4 A2), the transfer of the ions B1+ and A1_ from 0 to W and that of the ions B2+ and A2_ from W to 0 are negligibly small, so that the 0/ W interface behaves as an ideal-polarized interface. When the Do4 becomes so extremely positive as to be close to L1o 4 i and/or Ao 4 B2, or so extremely negative as to be close to L1o 4 and/ or L 4A2, the electric current across the 0 / W interface finally becomes observable. The anodic (positive-current) final rise of the current vs. potential (1 vs. Do4) curve corresponds to the transfer of A1_ ion from 0 to W and/or that of B2+ ion from W to 0, whereas the catholic (negative-current) final descent corresponds to the transfer of B1+ ion from 0 to W and/ or that of A2_ ion from W to 0. Such polarized 0 / W interfaces can work as the ion selective electrode surface for both voltammetric (or amperometric) and potentiometric determination of a specified ion or ions (in voltammetry) which are selectively transferable across the interface.4-6 Here it is essential that the ions other than the specified ion(s) must not be transferable across the interface. In other words, such ions as B1+, A1-, B2+, and A2_ serve as the supporting electrolytes. Thus, from an analytical point of view, it is highly desired that the polarizable potential range or what is called the potential window of the polarizable 0/W interface be as wide as possible. As a cation and an anion in W phase, Li+ and Mg2+ ions and Cl-and 5042 ions are usually employed. In most cases, the organic ions in 0 phase define the polarizable potential range. Thus TBA+ ion and TPB-ion are typically used as a cation and an anion in 0 phase. Crystal Violet'_9 and tetraphenylarsonium9"0 ions as cations and dicarbollylcobaltate(III)' and dipicrylaminate9 ions as anions have also been examined. In this study, we determined the polarizable potential range of the nitrobenzene (NB)/water(W) interface: a series of tetraalkylammonium...

Determination of the Electrostatic Potential of Oil-in-Water Emulsion Droplets by Combined Use of Two Membrane Potential-Sensitive Dyes

“…The Δ O W i of TClPB -was obtained by ion-transfer voltammetry with the polarized DCE | W interface. In a similar manner to that reported previously, 33 the value of Δ O W  TCIPB -(= +0.59 V) was estimated from the positive-current final rise of the cyclic voltammogram by referring to that of the tetraphenylborate ion (i.e., Δ O W  TPB -= +0.364 V). 34 It should be noted here that the influence of PSDs for estimating Δ O W eq should be negligibly small, because their initial concentration was very low, i.e., in the order of several tens of μM in DCE.…”

Separation and Purification of ε-Poly-l-lysine with Its Colorimetric Determination Using Dipicrylamine

“…These ΔG 0 tr,NB→W-values are much higher than those of picrate -, ClO4 -, Cl -, and SO4 2-anions (3, -10, -35, and < -51 kJ mol -1 , respectively), 15,16 which are hard to form a precipitate with polycationic εPL species.…”

A Liquid/Liquid-Type Heteropolyanion Reference Electrode for Ion-Transfer Voltammetry

“…Although the above cell system has been frequently utilized, its polarizable potential range (so-called "potential window") is not very wide (i.e., about 0.32 V), because the negative-current limit is determined by the transfer of TBA + that is not sufficiently hydrophobic. Thus far, some attempts have been made to broaden the potential window by replacing TBA + with more hydrophobic cations including Crystal Violet [8][9][10] , tetraphenylarsonium 10,11 , tetrapentylammonium (TPenA + ) 12 , and tetrahexylammonium (THexA + ) 12 ions. For example, the use of THexA + broadens the polarizable potential range in the negative direction by as much as ca.…”

“…For example, the use of THexA + broadens the polarizable potential range in the negative direction by as much as ca. 0.25 V. 12 In this case, however, such an L/L type reference electrode as shown in cell A is no longer available, because ∆ I II φ is not determined only by the distribution equilibrium of THexA + ; Cl -added initially to the aqueous phase (phase I) may be extracted to NB by THexA + of extreme hydrophobicity. The ∆ I II φ of the interface should be elucidated on the basis of the concept of the mixed ion-transfer potential [13][14][15][16] , and from a practical point of view, it seems inappropriate to use such an interface for a reference interface.…”

“…Figure 1 shows the scheme of the new reference electrode. In this reference electrode system, ∆ 12 O 40 ] (anhydrous) was dissolved in 44 ml of 1:1 (v/v) 1,4-dioxane-water containing 1.0 M sulfuric acid. After 15 h during which the β-isomer as an impurity was transformed into the α-isomer, 2 g of THexABr (Tokyo Kasei Kogyo Co. Ltd.) was added to the yellow heteropolyanion solution.…”