ION-SELECTIVE ELECTRODES FOR PROMETHAZINE DETERMINATIONS IN PHARMACEUTICAL PREPARATIONS AND APPLICATION TO FLOW-INJECTION ANALYSIS

The construction and evaluation of PM-selective electrodes with a conv entional configuration and without internal reference solution are des cribed. Two different PVC membranes were prepared with PM tetraphenylb orate dissolved in 2-nitrophenyl octyl ether (type A) or bis(2-ethylhe xyl)sebacate (type B). When the electrodes were evaluated in 0.01 M io nic strength solutions, both presented linear responses from 5 x 10(-5 ) to 1 x 10(-2) Ni, slopes close to the theoretical value, practical d etection limits of -2 x 10(-5) M, reproducibilities of +/-0.2 mV/day, and a quick response (<20 s), Using phosphate buffer solutions (pH 6.0 ), type B electrodes presented a lower practical detection limit and a better reproducibility than type A. Selectivity against several catio ns was assessed by the separated solutions method, and the type B elec trodes were generally more selective. The type B membrane was also use d for the construction of tubular electrodes for the automatic analysi s of pharmaceutical products by flow injection analysis (FIA), These t ubular detectors, evaluated in a low dispersion FIA system, presented better selectivity and sensitivity than the corresponding conventional ones. Several pharmaceutical preparations were analyzed with both con ventional and tubular electrodes. The results obtained by FIA presente d relative deviations of <2% when compared with those obtained from th e United States Pharmacopoeia monographs.