Determination of Amlodipine Besilate and Azilsartan Medoxomil by UHPLC, HPTLC and Spectrophotometric Techniques

Abstract

Aims: To develop methods with complete validation according to ICH guidelines and to be applied for the determination of both drugs in laboratory prepared mixtures and in synthetic tablets.
 Study Design: Ultra high performance liquid chromatography (UHPLC), High performance thin layer chromatography (HPTLC) and visible spectrophotometric methods are developed for determination of amlodipine besilate and azilsartan medoxomil in laboratory-prepared mixtures and in synthetic tablets.
 Methodology: Two techniques have been developed for the simultaneous determination of amlodipine besilate and azilsartan medoxomil in pure form and synthetic tablets. The first was UHPLC in which separation was achieved on a C18 column using 0.1% o-phosphoric acid - acetonitrile - methanol (60:10:30, by volume) as mobile phase with detection at 243nm. The second was HPTLC where separation was performed on silica gel 60 F254 plates using chloroform- tolune-methanol-glacial acetic acid (7: 1.5: 1.5: 0.5 by volume) as a developing system and UV detection at 243nm. In addition, visible- spectrophotometric method was developed for determination of amlodipine besilate in presence of azilsartan medoxomil through formation of yellowish orange colored product after reaction of amlodipine besilate with anisaldehde in acid medium with λmax at 443 nm.
 Results: UHPLC method was linear over the concentration ranges of 2-20 μg/ mL and 4-40 μg/ mL while HPTLC method was linear over the concentration ranges of 0.2 -4.0 μg/ spot and 0.5-8.0 μg/ spot for amlodipine besilate and azilsartan medoxomil, respectively. The visible spectrophotometric method was found to be valid over the concentration range of 10–80 μg/mL for amlodipine besilate.
 Conclusion: The proposed three techniques are rapid, accurate and precise, thus can be effectively applied for the routine estimation of both drugs in bulk and in their combined formulations.