Surface and electric properties of n-Octyl-ß-D-gluco-pyranoside (OGP) at the air / water interface

Surface pressure (TT - using De Nouy ring), and electric surface potential (AV - using vibrating plate method), were measured on free surface of "surface-chemically pure" solution of n-octyl-alfa-D-gluco-pyranoside (OGP) in pure water. The obtained surface excess (G") and surface potential (^V} vs. concentration (c) isotherms fall consistently in the concentration range of about 1 * 10(-5) to 2 * 10(-2) mol/dm OGP. The p vs. c data can be well described in terms of the Frumkin adsorption isotherm. The dependence of the AV on the surface excess (AFrumkin) is fairly linear in the entire adsorption range, implying a constant effective dipole moment of OGP molecule - the pi/e amounting to 0.32 š 0.04 D per molecule.