A Validated Enantioselective HPLC Method for Assay of S-Amlodipine Using Crown Ether as a Chiral Stationary Phase

Background: Hypertension represents a widespread cardiovascular condition although usually asymptomatic, is a major risk factor for myocardial ischemia, renal failure and stroke. Amlodipine is considered a powerful dihydropyridine calcium channel blocker used as antihypertensive agent. Its mechanism of action depend on relaxing the smooth muscle of the artery wall and decrease peripheral resistance. Methods: An accurate, sensitive and robust chiral HPLC method was developed for separation and quantitation of S(-)- amlodipine simultaneously in the presence of its R(+)- isomer. Chiral separation was applied using Daicel CROWNPAK CR(+) (5μm, 4.0x150 mm) column which contains (3,3'-diphenyl-1,1'- binaphthyl)-20-crown-6-ether coated into a 5μm reversed phase silica support. The mobile phase system was aqueous acidic 70% HClO4 (pH 2.0) and methanol in the proportion of (95:5 v/v), filtered through 0.45 μm membrane and degassed by before use, pumped at a flow rate was 0.8 mL min-1 with UV detector adjusted at 238 nm. Results: The chromatographic HPLC method was validated with respect to ICH guidelines. Linear concentration range was 5-60 μg mL-1 with correlation coefficient (r) about 0.9998, the detection and quantitation limits was found 1.66 and 5.05 μg m-1; respectively. Accuracy was evaluated using standard addition technique with mean recovery about 98.40 % while precision was assessed at intraday and interday level. It was found that all %RSD values below 2%. Conclusion: A simple, enantioselective, chiral HPLC method was developed and validated for the quantitation of amlodipine [S-(+)- isomer] in racemic tablets using CROWNPAK CR(+) chiral stationary phase. The proposed method is specific, precise, accurate, and robust which can be successfully applied for the routine analysis of S-AML in bulk and pharmaceutical dosage formulations.