USE OF PENDENT DROP TECHNIQUE AS A FILM BALANCE AT LIQUID-LIQUID INTERFACES

The pendent drop technique has been extended to investigate insoluble monolayers of the phospholipid dipalmitoylphosphatidylcholine at the water/n-dodecane interface. The change of the drop size enables one to compress and expand the surfactant film. The dynamic interfacial tension of the film obtained by using axisymmetric drop shape analysis (ADSA) as a function of surface area provides thermodynamic data of the monolayer. The isotherm obtained with ADSA shows the same type of dynamic behaviour as measured with the classic Langmuir-Blodgett trough technique, Dynamic behaviour of insoluble monolayers, such as monofilm relaxation can be studied by ADSA more readily than by the common Langmuir film balances because of the uniform temperature of the entire system and uniform interfacial pressure and concentration along the drop surface.