Abstract
A rapid, simple and accurate spectrophotometric method has been developed and validated for the determination of aliskiren (ALS) in bulk and tablets. The method was based on the derivatization of ALS with ninhydrin (NIN). The reaction conditions were studied and optimized. ALS reacted with NIN efficiently in the presence of ascorbic acid (0.1%) as a reducing agent, in slightly acidic media (phosphate buffer 0.2 M, pH 6.0) at 90°C for 20 min. The λmax of the blue-violet derivative was found to be 569 nm. The stoichiometry of the reaction was studied. The molar ratio of ALS:NIN was 1:2. In addition, the reaction mechanism was postulated. ALS was linear in the range of 10-170 µg/ml. The regression equation was y = 0.008 X + 0.161 with a correlation coefficient (r = 0.9982). The developed method was accurate and specific. Recovery values were in the range of 99.63 – 101.2 with standard deviation (SD) not higher than 1.3%. Intra- and inter-assay precisions showed a relative standard deviation (RSD) less than 2%. The method was advantageous regarding sensitivity; the limit of detection (LOD) and quantification (LOQ) were found to be 1.27 and 3.85 µg/ml, respectively. The developed method was applied successfully for determination of ALS in tablets and compared statistically with a reference method (direct spectroscopy). Although the developed method has similar accuracy and precision to direct spectroscopy, sensitivity and range were greatly improved. In addition, it is easy to use and depends on inexpensive reagents and instruments which make it highly cost-effective. In addition, toxic and expensive organic solvents were avoided.
