RESUMO
Three simple, sensitive and accurate spectrophotometric procedures have been established for the assay of Moexipril-HCI in bulk form, in pharmaceutical formulations, and in the presence of its degradation products. The procedures are based on the reaction between the examined drug and bromocresol purple [BCP], bromophenol blue [BPB], and bromothymol blue [BTB] in aqueous acidic medium producing an ion-pair complexes extracted in chloroform and measured at the optimum wavelengths. Reaction conditions were studied and optimized to obtain the maximum color intensity. The reactions were extremely rapid at room temperature and the absorbance values remains unchanged for 48 h. Beer's law was obeyed in the concentration ranges 4-32, 4-24, and 4-40 microg ml[-1] with molar absorptivities of 1.7x10[4], 2.1x10[4], and 1.5x10[4] mol[-1] cm[-1] and detection limit of 0.064, 0.065, and 0.077 microg ml[-1] for BCP, BPB, and BTB methods, respectively. The proposed methods have been applied successfully for the analysis of the drug in pure form and in its dosage forms with percentage recoveries range from 99.29 - 100.11. Statistical comparison of the results with those obtained by second derivatives spectrophotometric method shows excellent agreement and indicates no significant difference in accuracy and precision