Extractive spectrophotometric determination of some α-adrenergic-antagonists in pure forms and in pharmaceutical formulations

A simple, rapid, and extractive spectrophotometric methods was developed for the determination of some postsynaptic α-1 adrenoreceptor antagonist; doxazosin mesylate (DOX), terazosin (TRZ) and alfuzosine HCl (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 (BTB), 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 and at 419, 415, 425 and 428 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 μg 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 ranges from 99.18-100.61. The results of analysis were validated statistically. The results were in good agreement and compared with those obtained with reported methods.