Adsorption and ion-pairing interactions of phospholipids in the system of two immiscible electrolyte solutions Part I. The behaviour of lecithin at the water/1,2-dichloroethane interface, compared with that of trimethyloctadecylammonium cation

The behaviour of l-α-lecithin (DPPC) at the interface of water and 1,2-dichloroethane electrolyte solutions was studied by cyclic voltammetry and surface tension measurements. Model calculations of the cyclic voltammograms were carried out for the conditions employed in the experiments and comparative voltammetric measurements were performed with the trimethyloctadecylammonium cation (TODA+). A five-step mechanism has been proposed and substantiated for the lecithin adsorption/desorption processes, involving sorption, acid–base and association/dissociation interactions. The TODA+ behaviour is simpler, independent of the pH and in principle it corresponds to a single adsorption/desorption step at the interface from the organic phase.