Extractive spectrophotometric determination of ambrisentan.

PURPOSE Ambrisentan (ABS) is an antihypertensive drug used in the treatment of pulmonary atrial hypertension. The survey of literature for ABS revealed only two spectrophotometric methods for its quantification. The reported methods lack the sensitivity. This study is aimed at developing two sensitive extractive spectrophotometric methods for the determination of ABS in bulk and in tablets. METHODS The proposed methods are based on the formation of colored chloroform extractable ion-pair complexes of ABS with methylene blue (MB method) and safranine O (SO method) in buffered solution at pH 9.8. The extracted complexes showed maximum absorbance at 525 and 515 nm for methylene blue and safranine O, respectively. RESULTS In both the methods, the calibration curve was linear from 1-15 µg mL(-1) of drug. Apparent molar absorpitivities were 1.7911 x 10(5), 2.3272 x 10(5) L mol(-1) cm(-1); Sandell's sensitivities were 0.0215, 0.0162 µg cm(-2); LOD were 0.182, 0.175 µg mL(-1); LOQ were 0.551, 0.531 µg mL(-1) for methods MB and SO, respectively. The relative standard deviation and percent recovery ranged from 0.206-1.310% and 99.0-101.5%, respectively. CONCLUSION The results demonstrate that the proposed methods are sensitive, precise, accurate and inexpensive. These methods can easily be used for the assay of ABS in quality control laboratories.