CHARACTERISTICS OF POTENTIAL OSCILLATION ACROSS A WATER OCTANOL/WATERLIQUID MEMBRANE CONTAINING A SURFACE-ACTIVE SUBSTANCE/

Electrical potential oscillation across a water/octanol/water liquid m embrane containing a surface active substance was observed, Sodium dod ecyl sulfate (SDS), sodium oleate (SO). hexadecyltrimethylammonium bro mide (CTAB), oleic acid, dioctyl phosphate (DOPH). oleylamine, dioctan oylphosphatidylcholine (PC), decanol and cholesterol were used us the surface active substance in one of the aqueous phases. When SDS, CTAB and SO were used as. the surface active substance, spontaneous potenti al oscillation occurred. The direction of the pulse far CTAB was oppos ite to that for SDS and SO. The reproducibility of potential oscillati on depended on the concentration of the surface active substance. For oleic acid, DOPH and PC, only irregular pulses were observed. On using oleylamine, decanol and cholesterol. evident oscillation could not be detected at any concentration. The occurrence and reproducibility of the potential oscillation were explained by the mechanism that the pot ential oscillation across the liquid membrane is induced by the repeti tive formation and destruction of a surface active substance layer ads orbed at one of the octanol/water interfaces. In consideration uf the design of a surface active molecule for device applications, the molec ule must have a char-ge on the hydrophilic group which is sufficiently dissociated and have an appropriate stability oi. the surface active substance layer at the octanol/water interface.