Extractive Spectrophotometric Determination of Mirtazapine in Pure and Pharmaceutical Forms

Four simple and sensitive extractive spectrophotometric methods have been described for the assay of Mirtazapine either in pure form or in pharmaceutical formulations. The developed methods involve formation of coloured chloroform extractable ion-pair complexes of the drug with bromocresol green (BCG), bromophenol blue (BPB), bromothymol blue (BTB) and bromocresol purple (BCP) in acidic medium. The extracted complexes showed absorbance maxima at 417, 405, 412 and 405nm with use of the cited reagents, respectively. The stoichiometry of the complex is found to be 1:1 in each case. Beer’s law is obeyed in the concentration ranges 2.0-25, 2.0-25, 2.0-25, 2.5-25 μg/ml with BCG, BPB, BTB and BCP respectively. The effect of concentration of dye, pH, and interference of excipients have been studied and optimized. The limits of detection and quantification have been determined for four methods. All the four methods are validated as per the guidelines of ICH. The methods are applied to the determination of drug in commercial tablets and results of analysis are validated statistically through recovery studies.