EXTRACTIVE SPECTROPHOTOMETRIC DETERMINATION OF SOME alpha-ADRENERGIC-ANTAGONISTS IN PURE FORMS AND IN PHARMACEUTICAL FORMULATIONS

A simple, rapid, and extractive spectrophotometric method was developed for the determination of some postsynaptic alpha-1 adrenoreceptor antagonists: doxazosin mesylate (DOX), terazosin (TRZ) and alfuzosine HCI (ALF) in pure forms and pharmaceutical formulations. The developed methods are based on the formation of yellow colored chloroform ion-pair complexes between the basic nitrogen of the drugs and dyes, namely: bromocresol green (BCG), bromothymol blue (B TB), methyl orange (MO) and alizarine red S (ARS), in acidic buffer of pH range 3.0-5.0. The formed complexes were extracted with chloroform or dichloromethane and measured at 418, 414, 425 and 426 nm for DOX, at 419, 415, 425 and 428 nm for TRZ and at 418, 412, 421 and 427 nm for ALF using BCG, BTB, MO and ARS, respectively. The analytical parameters and their effects on the reported systems are investigated Beer's law was obeyed in the range 1.0-130 mu g mL(-1) with correlation coefficient (n = 6) >= 0.9991. The molar absorpitivity, Sandell sensitivity, detection and quantification limits were also calculated. The composition of the ion associates was found 1:1 by Job's method. The proposed methods have been applied successfully for the analysis of the studied drugs in pure forms and in pharmaceutical formulations with percentage recoveries ranging from 99.18-100.61. The results of the analysis were validated statistically. The results were in good agreement and compared with those obtained with reported methods.