Kinetics of Adsorption of Protein at the Oil-Water Interface in the Presence of Cationic and Anionic Surfactants

Abstract

The interfacial tension (γ) of heptane-water system has been measured as functions of time (t) at a fixed concentration (C l p ) of protein bovine serum albumin at a given value of pH, ionic strength and temperature. The concentration C l s of anionic surfactant SDS and those of cationic surfactant cetyl trimethyl ammonium bromide cetyl pyridinium bromide, myristyl trimethyl ammonium bromide and dodecyl trimethyl ammonium bromide respectively have been kept constant during the measurement of interfacial tension lowering (Π). From the rate of change of Π with t, the first order rate constants k 1 and k 2 for the adsorption process have been evaluated for low and high ranges of time. Values of k 1 depend upon magnitude of C l s . pH and ionic strength of the medium. The effect of hydrocarbon chain length and the nature of hydrophillic group of the surfactant, on k 1 have been examined at different values of pH and ionic strength of the medium. The values of k 2 are found to be insensitive to the charge of all these parameters reason of which has been discussed. The data have been analysed by Ward-Tordai-McRitchi-Alexander equation for the estimation on area (ΔA) swept out by surfactant bound protein molecule during the protein adsorption at oil-water interface.