Enhanced ion transfer rate due to the presence of zwitterionic phospholipid monolayers at the ITIES

The transfer of cations across phospholipid monolayers at ITIES is studied both experimentally and theoretically. Further evidence of the enhanced rat e for cation transfer due to the presence of the monolayer is presented, an d a theoretical model that can explain these observations is worked out. Th e system considered experimentally is Li+ ion transfer across a hemispheric al water \ 1,2-dichloroethane interface covered by distearoyl phosphatidylc holine. The theoretical description is based on the electrical double layer correction to the Butler-Volmer equation, coupled with a solution of the P oisson-Boltzmann equation across the interfacial region. The phospholipid m onolayer is modelled as two parallel planes of charge, with the negative ch arge located at the ITIES and the positive charge located at a distance d i nto the aqueous phase. The enhancement factors predicted are found to be in agreement with our experimental results as well. as with those obtained by other authors. (C) 2000 Elsevier Science S.A. All rights reserved.