www.elsevier.nl/locate/jelechem Journal of Electroanalytical Chemistry 496 (2001) 118 – 123 Membrane transport processes in the presence of an applied electrical potential gradient parallel to the aqueous  membrane interface Nobuhiro Kurauchi a , Yumi Yoshida a , Nobuyuki Ichieda a , Hiroyuki Ohde a , Osamu Shirai b , Kohji Maeda a , Sorin Kihara a, * a Department of Chemistry, Kyoto Institute of Technology, Matsugasaki, Sakyo, Kyoto 606 -8585, Japan b Japan Atomic Energy Research Institute, Oarai, Ibaraki 311 -1394, Japan Received 11 June 2000; received in revised form 11 September 2000; accepted 11 September 2000 Dedicated to Professor Mitsugi Senda on the occasion of his 70th birthday Abstract When a membrane system composed of two aqueous phases (W1 and W2) separated by a liquid membrane (M) was adopted and the potential difference E W1(A–B) , was applied between two sites (sites A and B) in W1 near to the W1  M interface, the ion transport reaction from W1 at site A to W1 at site B through M (W1 MW1 transport) was found to occur based on the voltammogram recorded by scanning E W1(A–B) and measuring the current between sites A and B. The efficiency of W1 MW1 transport was higher when the ratio of the concentration of electrolyte in W1 to that in M was lower. An ion or electron transfer reaction at the W1  M interface in a region between sites A and B (site C) could be realized under the application of E W1(A–B) . The ion transport from W2 to W1 through a domain formed in a part of M was also found to be possible under the applied E W1(A–B) . © 2001 Elsevier Science B.V. All rights reserved. Keywords: Domain; Electron transfer; Ion transfer; Membrane transport; Single interface; Voltammetry dation of the mechanism of W1 M W1 transport is expected to be very important for better understanding of biomembrane phenomena, as well as for the design of novel analytical methods mimicking the phenomena, though such investigations have been very few so far. In the present study, the fundamental feature of the W1 M W1 transport was elucidated with the aid of voltammetry for charge transfer at the interface of two immiscible electrolyte solutions (VITIES), and com- pared with that of the W1 M W2 transport [3–6]. 2. Experimental 2.1. Voltammetric measurements The electrolytic cell with an M used for the voltam- metric measurement of W1 M W2 transport was essentially identical to that in previous studies [3,4]. An example of the cell configuration is shown in Cell (1). 1. Introduction Generally speaking, the membrane transport of a charge (ion or electron) means the transfer of a charge from one aqueous solution (W1) to another (W2) across a membrane (M) as shown in Fig. 1(a). How- ever, the reaction that a charge is incorporated from W1 into M at one site (site A) of the W1  M interface and released from M to W1 at another site (site B) of the same interface after transfer in M can also be regarded as a variety of the membrane transport (see Fig. 1(b)). Hereafter, the former will be designated W1 M W2 transport and the latter W1 M W1 transport. The W1 M W1 transport is considered to occur often at the interface between an aqueous solution and a heterogeneous biomembrane with vari- ous domains [1,2]. Therefore, the electrochemical eluci- * Corresponding author. Tel./fax: +81-75-724 7518. E-mail address: kiharas@ipc.kit.ac.jp (S. Kihara). 0022-0728/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0022-0728(00)00385-5