Assay of ephedrine hydrochloride and theophylline in pharmaceutical formulations by differential-derivative spectroscopy

Rapid and accurate binary mixture resolution of ephedrine hydrochloride and theophylline was performed. Differential-derivative spectrophotometry with a zero-crossing measurement technique was used for the quantitative determination of ephedrine hydrochloride and theophylline in pharmaceuticals. Neither sample pretreatment nor separation were required. Linear calibration graphs of differential first derivative values (at 262.3 and 256.3 nm for theophylline and ephedrine hydrochloride, respectively) versus concentration (in the ranges 6.0-40.0 and 100.0-1000.0 mu g ml(-1) for theophylline and ephedrine hydrochloride, respectively) were obtained with negligible intercepts. Vierordt's method was also developed for a comparison method. Commercial tablet and laboratory-prepared mixtures containing both drugs were assayed using the developed methods. Both methods showed good linearity, precision and reproducibility. (C) 2000 Elsevier Science B.V. All rights reserved.