SOME OBSERVATIONS ON A NEW ADIPHENINE-SELECTIVE PLASTIC MEMBRANE-ELECTRODE BASED ON ADIPHENINIUM TETRAPHENYLBORATE

A new adiphenine (Ad) ion-selective PVC membrane electrode based on the ion-pair complex of Ad with sodium tetraphenylborate was prepared and its performance characteristics were studied. The electrode exhibited a linear response with a good Nernstian slope over a relatively wide range of concentration. Up to 24 h continuous soaking, the calibration graph slope was constant at 53.0 mV/concentration decade, at 25 °C, then it decreased gradually as the time of soaking increases reaching 41 mV/decade after 11 days. The changes in pH did not affect the electrode performance within the range 2.2-7.5. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode. The electrode showed very good selectivity for Ad with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were used to determine Ad in pure solutions and in a pharmaceutical preparation. © 1990.