Extractive spectrophotometric methods for the novel antidepressant drug in bulk and pharmaceutical dosage forms by using bromthymol blue and bromcresol green

Two sensitive and simple spectrophotometric methods for the estimation of reboxetine in pure form and in pharmaceutical formulations, are developed. The methods are based upon the interaction of the basic drugs in dry chloroform with bromthymol blue (BTB), and bromcresol green (BCG) in the same solvent to produce a stable yellow ion-association complexes. The colored products are quantified spectrophotometrically at their corresponding lambda(max). Beer's law is obeyed in case of BTB in the range 16.0-34.0 mug mL(-1) and 10.0-30.0 mug mL(-1) for BCG. The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations and percent recoveries are evaluated. Reboxetine was determined by measurement of its first derivative signals at 285.1 nm, respectively. Calibration graph was established for 8.0-40.0 mug mL(-1) of reboxetine for first derivative spectrophotometry. Application of the suggested methods to dosage forms is presented and compared with the first derivative spectrophotometric method. No interference was observed from common pharmaceutical adjuvants.