Transmission mechanism of the change in membrane potential by use of organic liquid membrane system

Transmission of the change in potential difference across a liquid membrane was investigated based on the knowledge of voltammetry for the ion transfer at the interface of two immiscible electrolyte solutions by use of a U-shaped liquid membrane cell.Two aqueous phases (W1 and W1′) containing 0.1 M KCl were set on two 1,2-dichloroethane solution phases (M1 and M2) containing about 10−5 M potassium tetrakis(4-chlorophenyl)borate (K+ TCPB−) and 10−3 M tetrabutylammonium tetrakis(4-chlorophenyl)borate (TBA+ TCPB−), respectively. W1 and W1′ were connected via a salt bridge. Then, an aqueous phase (W2) containing 0.1 M KCl and 10−3 M tetrabutylammonium chloride (TBA+ Cl−) was put in the bottom of the cell, which was in contact with M1 and M2. Under the initial conditions, the potential difference (E) between W1 and W2 (EW1–W2) was identical with EW1′–W2 between W1′ and W2, and then EW1|M1 between W1 and M1 and EM1|W2 between M1 and W2 were also identical with EW1′|M2 between W1′ and M2 and EM2|W2 between M2 and W2, respectively. In this case, the W1|M1 and the W1′|M2 interfaces were depolarized by the distribution of K+, and the M1|W2 and the M2|W2 interfaces were depolarized by the distribution of TBA+. After addition of an adequate volume of 10−3 M TBA+ Cl− to W1, EW1–W2 and EW1′–W2 were shifted simultaneously. Since EM1|W2 and EM2|W2 remained unchanged on the addition of TBA+, the change of EW1′|M2 was induced by the change of EW1|M1. This situation can be considered to be a model of the signal transmission.

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► Transmission mechanism of the change in potential difference across a membrane was elucidated.
► The threshold of the concentration of transport ions can be explained in detail.
► The circular current flows during the excited condition.