Resolution of two-component mixtures in pharmaceutical formulations containing phenazopyridine hydrochloride by ratio spectra derivative spectrophotometry

The ratio spectra derivative spectrophotometry was applied for the simultaneous determination of phenazopyridine hydrochloride with sulfisoxazole or ampicillin trihydrate in binary mixtures. The procedures do not require any separation step. The analytical signals were measured at 252.3 and 276.6 nm in the phenazopyridine hydrochloride with sulfisoxazole in mixture, 324.9 and 283.6 nm in the phenazopyridine hydrochloride with ampicillin trihydrate in mixture for phenazopyridine hydrochloride and its co-existing compounds, respectively. in the first derivative of the ratio spectra of the mixture solutions in methanol. Calibration graphs were established for 2.0-18.0 mugml(-1) phenazopyridine hydrochloride and 2.0-32.0 mugml(-1) sulfisoxazole in phenazopyridine hydrochloride-sulfisoxazole mixture, and for 2.0-18.0 mugml(-1) phenazopyridine hydrochloride and 4.0-32.0 mugml(-1) ampicillin trihydrate in binary mixture. The method was successfully applied to the pharmaceutical formulations containing the above-mentioned drug combinations without any interference by the excipients. Vierordt's method was also developed for a comparison method.