Abstract

The absorbance maxima of phenylpropanolamine hydrochloride, chlorpheniramine maleate and dextromethorphan hydrobromide in 0.1 N hydrochloric acid are 257, 265 and 278 nm, respectively. This paper presents two methods based on first derivative spectrophotometry for simultaneous estimations of these three drugs in combinations in pharmaceutical formulations. The first derivative amplitudes at 264.4, 278.5 and 288.9 nm are utilized for simultaneous estimations. The first method utilizes correlative regression equations and the second method utilizes simultaneous equations to avoid complex interferences at selected wavelengths in derivative spectra. All three drugs obey Beer's law in the concentration range employed for analysis. Linearity was validated by Least Squares Method. The results of analysis have been validated statistically and by recovery studies. Both methods are simple, economical, accurate, reproducible and rapid.