Determination of binary mixture of raubasine and almitrine dismesylate by derivative spectrophotometry

A first derivative spectrophotometric [[1]D] and derivative ratio [1DD] methods were utilized to determine raubasine [I] and almitrine dismesylate respectively using methanol as a solvent. A linear relationship was obtained in the range from 6-20 microg ml[-1] raubasine for the [[1]D] method and 10- 24 microg ml[-1] almitrine dismesylate for the [[1]DD] method. By applying the proposed methods, it was possible to determine raubasine in its pure powdered from with accuracy 99.94 +/- 0.860 [n = 8] for the [[1]D] method and almitrine dismesylate with accuracy 100.07 +/- 0.784 [n = 8] for the [[1]DD] method. Laboratory prepared mixtures containing different ratios of [I], [II] were analyzed by the proposed methods. The proposed methods were validated and found to be suitable assay methods for raubasine [I] and almitrine dismesylate [II] in pharmaceutical formulations