ION-SELECTIVE ELECTRODES FOR THE DETERMINATION OF THE ANTIARRHTHYMIC DRUG BRETYLIUM

Ion-selective poly(vinyl chloride) membrane electrodes and thick-film sensors for the determination of the antiarrhythmic drug bretylium in human serum are described. Ion-pair complexes of bretylium with the anionic counter ions tungstosilicate, reineckate [diamminetetracyanatochromate(III)], tetraphenylborate and dipicrylaminate were investigated as electroactive compounds for the electrode membranes. The membranes containing the bretylium-tungstosilicate complex showed the best properties with both types of transducers. The detection limits were determined to be 1 X 10(-7) mol dm-3 for the macroscopic electrodes and 8 x 10(-7) mol dm-3 for the thick-film sensors in 0.1 mol dm-3 Tris buffer at pH 7.4; slopes of 60.7 and 40.0 mV decade-1 respectively, were found. In pathological and non-pathological test sera, a detection limit of 5 x 10(-6) mol dm-3 was obtained with the thick-film transducers. The potentiometric selectivity coefficients towards structurally similar compounds such as ephedrine, dopamine and epinephrine (adrenaline) ranged from 10(-1.7) to 10(-3-4). Response times of 5-10 s were observed in buffered aqueous solutions as well as in human serum samples.