Spectrophotometric determination of phenylephrine HC1 and orphenadrine citrate in pure and in dosage forms

A simple and rapid spectrophotometric methods have been estimated for the microdetermination of phenylephrine HCl (I) and orphenadrine citrate (II). The proposed methods are based on the formation of ion-pair complexes between the examined drugs with alizarine (Aliz), alizarine red S (ARS), alizarine yellow G (AYG) or quinalizarine (Qaliz), which can be measured at the Optimum lambda(max). The optimization of the reaction conditions is investigated. Beer's law is obeyed in the concentration ranges 2-36 mug ml(-1), whereas optimum concentration as adopted from Ringbom plots was 3.5-33 mug ml(-1). The molar absorptivity, Sandell sensitivity, and detection limit are also calculated. The correlation coefficient was greater than or equal to0.9988 (n = 6) with a relative standard deviation of less than or equal to1.7, for six determinations of 20 mug ml(-1). The proposed methods are successfully applied to the determination of drugs I and II in their dosage forms using the standard addition technique. (C) 2002 Elsevier Science B.V. All rights reserved.