CONSTRUCTION AND EVALUATION OF PVC CONVENTIONAL AND TUBULAR TRIPELENNAMINE-SELECTIVE ELECTRODES - THEIR APPLICATION IN PHARMACEUTICAL PREPARATIONS

The construction and evaluation of tripelennamine conventionally-shape d ion-selective electrodes and tubular detectors for the determination of this compound in pharmaceutical formulations are described. Electr odes with conventional configuration have been constructed without an internal reference solution, using several types of immobilized ionic sensors in PVC. The different electrode membranes were prepared by usi ng tripelennamine tetraphenylborate as ionic-exchanger, dissolved in 2 -nitrophenyl octyl ether (type A), dibutylphthalate (type B) and bis-( 2-ethylhexyl)sebacate (type C) as plasticizer solvents. The general wo rking characteristics of the different types of conventional electrode s were evaluated in tripelennamine solutions, with adjusted ionic stre ngth, showing a linear response in the concentration range of about 4 x 10(-5)-1 x 10(-1) M and a slope near the theoretical value. The elec trodes presented a fast response (>20 s) and a high reproducibility (/-0.2 mV per day). The electrode selectivity in the presence of some i nterferents, such as sodium, potassium, lithium, ammonium, chlorphenir amine, diphenydramine, promethazine, meclizine and pentazocine, was go od, particularly for those whose sensor membrane was prepared with tri pelennamine tetraphenylborate dissolved in 2-nitrophenyl octyl ether ( type A). Tubular detectors were also prepared using the same sensor me mbrane and were evaluated in a low-dispersion flow-injection manifold. Under these conditions the detectors presented response characteristi cs similar to those of the corresponding conventionally-shaped electro des. The analysis of different pharmaceutical forms (creams, syrups an d gels) gave good results with mean recoveries of 99.8-100.6% when the experiments were conducted by direct potentiometry and 99.9-100.4% wh ere the same determinations were conducted by flow-injection analysis with tubular detectors.