Ion-selective electrode for the determination of prazosin in tablets.

A poly (vinylchloride) (PVC) membrane electrode selective for prazosinium cation based on prazosinium-phosphotungstate (PZ)(3)PT ion-associate is prepared. The electrode exhibits a linear response with an approximate Nernstian slope over the range of 2.7 x 10(-6)-10(-2) M. Calibration graph slope of the electrode is 58 mV PZ(-1) concentration decade when preconditioned by soaking in distilled water for 1 h-20 days. The working pH of the electrode ranged from 1.5 to 6.4 and exhibits very good selectivity for the PZ with respect to a large number of inorganic cations and organic substances of biological importance. The standard additions method and potentiometric titration are used to determine the PZ in pure solution and in pharmaceutical preparations with satisfactory results.