Spectroscopic and Conductometric Assay of Oxyphenonium Bromide in Pure Form and in Pharmaceuticals

The interactions between oxyphenonium bromide (OXBr) and two precipitating reagents, silver nitrate (AgNO3) and phosphomolybdic acid (PMA) have been studied by conductometric and spectroscopic techniques. The equilibrium constant, the solubility product constant and other functions related to the process of precipitating OXBr were calculated exploiting the conductometric procedure. Furthermore, new approaches towards equivalence point detection have been pursued. In this itinerary, differential conductivity methods and Boltzmann sigmoid fitting model were found to be more appropriate compared to the conventional routine. The described procedures allowed the determination of OXBr within the range of 1-20 mg using both reagents. The molar combining ratio reveals that (1:1) (drug: reagent) ion associates are formed for both reagents with OXBr. Moreover, the obtained precipitate has been spectroscopically characterized using IR and 1H-NMR. The proposed conductometric method was applied successively to pharmaceutical formulations containing OXBr and the results obtained were favorably compared with those obtained using the reference conductometric method.