Role of a surfactant in the electrical potential oscillation across a liquid membrane

✍ Scribed by Kensuke Arai; Satoshi Fukuyama; Fumiyo Kusu; Kiyoko Takamura

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 775 KB
• Volume: 40
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(95)00222-z

✦ Synopsis

Electrical potential oscillation across a liquid membrane of a water/octanol/water system, in which a surfactant and ethanol are present in one of the waters, and electrical potential between octanol and aqueous phases of the octanol/water system were measured. On using sodium dodecyl sulfate (SDS) as the surfactant, potential oscillation was initiated with a sudden potential change toward the more negative potential. The upper potential (E,.& and lower potential (E,,,,) of the first oscillation were affected by the electrolyte added to the aqueous phase containing no previous surfactant. With hexadecyltrimethylammonium bromide (CTAB) as the surfactant, dir* don of the pulse was opposite that when using SDS. The lower potential (E,,,,,) and upper potent, . (E,,,,,,) of the first oscillation were affected by the electrolyte. For instance, E . pnC and E. rTll were greatly affected by halide ion size. In contrast, EA,CTAB and E, SDS ..,"_" "'_"'I were only slightly affected by this para&eter.The effects of the electrolytes on E A.SDS and Gsm were essentially the same as those on potentials at the interface between the octanol and aqueous phases of the octanol/water system in the absence of SDS (E,,,,) and presence of SDS (ED.,,), respectively. The effects of electrolytes on EA.=** and E,.,,,,

were also basically the same as those on the potentials at the interface between the octanol and aqueous phases of the octanol/water system in the absence of CTAB (Ec,cTAB) and presence of CTAB (ED,cTAB ). respectively. Potential oscillation thus appears quite likely due to the repetitive formation and destruction of the surfactant layer adsorbed on the octanol/water interface.