Development and Validation of Kinetic Spectrophotometric Method for the Determination of Losartan Potassium in Pure and Commercial Tablets

Abstract

A validated kinetic spectrophotometric method has been developed for the determination of losartan potassium in pure and dosage forms. The method is based on oxidation of the losartan potassium with alkaline potassium permanganate at room temperature (25 ± 1 °C). The reaction is followed spectrophotometrically by measuring the increase in absorbance with time at 603 nm, and the initial rate, fixed time (at 12.0 min) and equilibrium time (at 90.0 min) methods are adopted for constructing the calibration graphs. All the calibration graphs are linear in the concentration range of 7.5–60.0 μg mL−1 and the calibration data resulted in the linear regression equations of n̈ = −6.422 × 10−7 + 1.173 × 10−5 C, A =3.30 × 10−4 + 5.28 × 10−3 C and A = −2.09 × 10−2 + 1.05 × 10−1 C for initial-rate, fixed time and equilibrium time methods, respectively. The limits of detection for initial rate, fixed time and equilibrium time methods are 0.71, 0.21 and 0.19 μg mL−1, respectively. The activation parameters such as Ea, ΔH‡, ΔS‡, and ΔG‡ are also determined for the reaction and found to be 87.34 KJ mol−1, 84.86 KJ mol−1, 50.96 JK−1 mol−1 and −15.10 KJ mol−1, respectively. The variables are optimized and the proposed methods are validated as per ICH guidelines. The method has been applied successfully to the estimation of losartan potassium in commercial tablets. The performance of the proposed methods was judged by calculating paired t- and F- values. The analytical results of the proposed methods when compared with those of the reference method show no significant difference in accuracy and precision and have acceptable bias.