STABILITY-INDICATING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ASSAY FOR ALPHA-METHYLDOPA IN SUSTAINED-RELEASE CAPSULES

A stability-indicating high-performance liquid chromatographic assay has been developed for the analysis of alpha-methyldopa (MD) in sustained-release capsules and in the presence of MD decomposition products and an MD industrial impurity, 3-O-methyl-methyldopa (MMD). The method utilizes reversed-phase chromatography (cyano-bonded column), an acidic mobile phase containing sodium heptanesulphonate as ion-pairing reagent and UV detection. Detector responses were linear in the ranges 0.5-200-mu-g/ml for MD and 0.2-100-mu-g/ml for MMD. The mean recoveries of MD from authentic sample and sustained-release capsules were 100.09 +/- 0.38 and 100.38 +/- 0.46%, respectively. The recovery of MD added to degraded MD were 99.69% by the proposed method and 153.13% by the US Pharmacopeial (USP) spectrophotometric method. The method is sensitive, accurate and rapid and can be used in routine analysis for MD.