Ion pair extraction from water into oil in a (ferrocenylmethyl)trimethylammonium bromide (FcTMABr)sodium hexafluorophosphate (NaPF 6 ) system was studied kinetically by injection and manipulation of a single oil droplet of 10 À8 cm 3 and electrochemistry of the single droplet contacting a microelectrode. The FcTMA + concentration extracted into the oil phase at the distribution equilibrium was dependent on the FcTMABr, NaPF 6 , and NaCl concentrations in the water phase. The initial rate of the ion pair extraction was directly proportional to the FcTMABr concentration in water, while it was independent of the NaPF 6 and NaCl concentrations in water. These results indicate that the ion pair extraction rate is governed by the ion transfer of FcTMA + from water into the droplet, maintaining the electroneutrality in the droplet by the PF 6 À transfer.

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Mass transfer of an alkyl sulfate anion with a (ferrocenylmethyl)trimethylammonium cation from water into single oil microdroplets was kinetically studied by microcapillary injection, fluorescence microspectroscopy, and microelectrochemistry. The partitioning ratio and the extraction rate significantly depended on the alkyl chain length of the alkyl sulfate anion. The extraction rate for the n-dodecyl sulfate or n-tridecyl sulfate ion was proportional to both the alkyl sulfate ion and ferrocene derivative concentrations while that for the n-undecyl sulfate ion was proportional to the anion concentration alone. The results are discussed in terms of transfer of the individual ions across the microdroplet/water interface and adsorption/ion pair formation of the alkyl sulfate ion at the microdroplet/water interface.

A study of the mass transfer (MT) across an oil/water interface is important for the fundamental understanding of liquid/liquid extraction, biological membranes, and so on. The kinetic analysis of the fast MT of neutral species across an oil/water interface is difficult since the MT occurs during the construction of the oil/water interface. Several efforts have been devoted to the direct kinetic analyses of the fast MT of neutral species. [1][2][3][4][5][6] In mm-sized oil/water interface systems, however, the analysis of the overall extraction rate including a fast interfacial process is frequently complicated by nonsteady-state linear diffusion from the bulk solution phase to the interface. In µm-sized droplet/solution interface systems, on the other hand, the MT from the bulk solution phase to the microdroplet surface is steady-state spherical diffusion and is relatively fast. Therefore, the kinetic analysis of the fast interfacial MT can occur in single-microdroplet/solution systems. In this study, we propose single microdroplet injection and potential step electrolysis of the droplet to initiate the MT from the solution to the droplet. We applied the technique to the fast interfacial MT. Electrochemical measurements were performed without supporting electrolytes to demonstrate the interfacial MT as a model of actual liquid/liquid extraction systems. (7 cm 3 ) and put into contact with a gold disk microelectrode (25 µm in diameter), fabricated in a glass capillary (∼70 µm in diameter), using an injection-manipulation system (Narishige Co., Ltd., MN-151, MMW-200/IM-16) under an optical microscope (Nikon Co., Ltd., SMZ-U). As the counter and reference electrodes, Pt wire and Ag/AgCl/NaCl (sat.) electrodes were used. The electrochemical responses of the single droplet were measured by an electrochemical analyzer (BAS Inc., BAS100B/W). All measurements were performed at room temperature (20 -22˚C). Results and DiscussionA single TBP droplet was injected and covered on the microelectrode surface. The contact angle between the glass insulator and TBP in water was ∼90˚. A cyclic voltammogram (CV) of a single TBP droplet with dx = 20 µm and dy = 33 µm is shown in Fig. 1, where dx and dy are the distance from the electrode to the droplet surface normal to the electrode surface and the droplet diameter parallel to the electrode surface, respectively. A current(i)-potential(E) curve corresponding to the oxidation of FcN + to FcN 2+ was sigmoidal, analogous to that observed in a homogeneous solution using a microelectrode. 7No electrochemical response of FcN + without PF6 -was detected. A cathodic current for the reduction of FcN 2+ was not observed, since the dication would rapidly distribute into the water. When a neutral ferrocene derivative was extracted into a single droplet, the CV was a symmetrical peaked curve, as previously reported. 8,9 Since extraction of the solute from the water to the droplet was slow (> ∼10 s), the solute was completely electrolyzed during the forward potential sweep in the previous syst...

Over the last few decades, because of the significant development of anion exchange membranes, increasing efforts have been devoted the realization of anion exchange membrane fuel cells (AEMFCs) that operate with the supply of hydrogen generated on-site. In this paper, ammonia was selected as a hydrogen source, following which the effect of conceivable impurities, unreacted NH and atmospheric CO, on the performance of AEMFCs was established. As expected, we show that these impurities worsen the performance of AEMFCs significantly. Furthermore, with the help of in situ attenuated total reflection infrared (ATR-IR) spectroscopy, it was revealed that the degradation of the cell performance was primarily due to the inhibition of the hydrogen oxidation reaction (HOR). This is attributed to the active site occupation by CO-related adspecies derived from (bi)carbonate adspecies. Interestingly, this degradation in the HOR activity is suppressed in the presence of both NH and HCO because of the bicarbonate ion consumption reaction induced by the existence of NH. Further analysis using in situ ATR-IR and electrochemical methods revealed that the poisonous CO-related adspecies were completely removed under NH-HCO conditions, accompanied by the improvement in HOR activity. Finally, a fuel cell test was conducted by using the practical AEMFC with the supply of NH-contained H gas to the anode and ambient air to the cathode. The result confirmed the validity of this positive effect of NH-HCO coexistence on CO-tolerence of AEMFCs. The cell performance achieved nearly 95% of that without any impurity in the fuels. These results clearly show the impact of the chemically induced bicarbonate ion consumption reaction on the realization of highly CO-tolerent AEMFCs.

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A redox species was extracted from water (50 × 10 -6 dm 3 ) into a single micro-oil-droplet (30 × 10 -12 dm 3 ) in contact with a microelectrode using microcapillary injection and manipulation techniques. Further, an in situ microanalysis of the solute in a single oil droplet was demonstrated by differential pulse voltammetry. The redox species of 10 -16 mol concentrated in the droplet could be quantitatively analyzed independently of the distribution coefficient of the solute between the oil and water phases. The potential of this technique was considered in terms of the preconcentration and separation as well as a microanalysis and an ultratrace analysis.

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