Spectrophotometrc Methods for the Determination of Ambrisentan Using Charge Transfer Reagents

The color developing reaction between ambrisentan and 2,3-dichloro-5,6-dicyano-1,4- benzoquinone (DDQ) or 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (CLA) was successfully employed in the development of two simple and sensitive spectrophotometric methods (M1 and M2) for the determination of ambrisentan in its pharmaceutical dosage forms.The methods are based on the charge transfer reaction of ambrisentan with DDQ (M1) or CLA (M2), to give colored radical anions. The colored products are measured at 560 nmin methanol and at 520 nm in acetonitrile for the methods M1 and M2, respectively.Under the optimized reaction conditions, Beer’s law is obeyed in the range of 5–50 µg ml−1 for both the methods. The limit of detection, limit of quantification, molar absorptivity and Sandell’s sensitivity were also reported for both the methods. Intra- and inter-day precision and accuracy of the methods were satisfactory. The proposed method was successfully applied to the quantification of ambrisentan in its tablet dosage forms with good accuracy and precision.