Abstract: An amobarbital-selective electrode based on amobarbital-triheptyldodecylammonium ionpairs in nitrobenzene was prepared and studied. The electrode showed a linear response to amobarbital anion within 2 × 10^-2～5 × 10^-5M concentration range in 0.1M Na₂CO₃ medium. The slope of the electrode was 57 mV/ decade and the limit of detection was 2 × 10^-5M. The electrode can be used for the determination, of amobarbital in drug-substances by direct potentiometry or potentiometric titration with standard solution of sulfuric acid. Dissociation of electroactive material in liquid ion exchanger is also discussed in the paper.