Spectrophotometric determination of tadalafil in pure and dosage forms

Two simple, rapid, and extractive spectrophotometric methods were developed for the determination of tadalafil (TDF) in both pure and tablet dosage form. These methods are based on the formation of ion-pair complexes between the basic nitrogen of the drug with bromocresol purple (BCP) and methyl orange (MO) in acidic buffer solution. The formed complexes were extracted with chloroform and measured at 410 and 425 nm using BCP and MO, respectively. Beer’s law was obeyed in the range 2.0-20 μg mL−1 with correlation coefficient (n = 6) ≥ 0.9996. The molar absorpitivity, Sandell sensitivity, detection and quantification limits were also calculated. The composition of the ion pairs was found 1:1 by Job’s method. The proposed methods have been applied successfully for the analysis of TDF in pure and in its dosage forms. These developed methods were validated for accuracy and precision.