In order to produce reference electrodes without liquid junction, it is necessary that such electrodes should have a membranerelectrolyte interface where electrolyte cannot cross by diffusion, then a stable potential drop is established and this potential drop is independent of the electrolyte composition. At first sight, it appears to be impossible to satisfy all these criteria; nevertheless, one of the tricks which has been proposed is to use a plasticized PVC membrane. Calculations of the interfacial potential difference at waterrhydrophobic phase interwx faces have been performed 16 and used in order to design reference electrodes In our work, the composition of the non-sensitive FET membrane was PVC and DNP in a ratio of 7:3 w diluted in THF. Such a composition was also used for the non sensitive FET membrane in pH measurements and satisfactory results were obtained in differential measurements.