A new type of ion-selective electrode based on the water membrane system is proposed. A NdCl3 water membrane electrode has been made to demonstrate its applicability to the determination of Nd(PMBP)3 in cyclohexanone. Conditions for stabilizing potential of ref. electrode in nonaq. system are optimized. It is observed that the potential response on the surface of two immiscible solution is bidirectional and the absolute values of slopes are identical. Nernstian response was exhibited for 3.2 ?10-4-1.0 ?10-2 mol cm-3 Nd(PMBP)3 at pH 5.0-5.7.

Key words: CHLORIDE, ION SELECTIVE ELECTRODE, MEMBRANE ELECTRODES, NEODYMIUM COMPOUNDS, PYRAZOLONE P, CYCLOHEXANONE, ION CONCENTRATION