Electrochemical response characteristics and analytical application of papaverine ion-selective membrane electrodes

The construction and electrochemical response characteristics of poly(vinyl chloride) matrix ion-selective electrodes (ISEs) for papaverine hydrochloride are described. The membranes incorporate ion association complexes of papaverine with tetraphenylborate {[B(C6H5)(4)](-)}, picrate {[C6H2(NO2)(3)O](-)}, tetraiodomercurate [(HgI4)](2-), tetraiodobismuthate [(BiI4)(-)], Reinecke salt {[Cr(NH3)(2)(SCN)(4)](-)} and heteropolycompounds of Keggin structure-molybdophosphoric acid [H-3(PMo12O40)], tungstophosphoric acid [H-3(PW12O40)], molybdosiliconic acid [H-4(SiMo12O40)], and tungstosiliconic acid [H-4(SiW12O40)] as electroactive materials for ionometric sensor controls. These ISEs show linear response for papaverine hydrochloride over the range from 1 x 10(-5) up to 5 x 10(-2) mol/l with cationic slopes from 42 up to 58 mV per concentration decade. These ISEs exhibit fast response time (up to 1 min), low determination limit (up to 1 x 10(-5) M), good stability (3-5 weeks) and reasonable selectivity. The ISEs were used for direct potentiometry and potentiometric titration {Na[B(C6H5)(4)]} of papaverine hydrochloride in pharmaceutical preparations. Results with mean accuracy of 98.6 +/- 0.9% of nominal were obtained, which correspond well to data obtained with the European Pharmacopoeial method.