Spectrophotometric Determination of Methyldopa and Dopamine Hydrochloride in Pharmaceutical Preparations Using Flow Injection Analysis


Abstract Methyldopa and dopamine hydrochloride were determined spectrophotometrically in the pure form and in the pharmaceutical preparations using flow-injection analysis (FIA). The method is based on oxidative coupling reaction of drug with 2-furoic acid hydrazide in the presence sodium nitroprusside in sodium hydroxide medium to form a reddish-orange soluble product that has a maximum absorption at 487 nm. The various chemical and physical variables were optimized. The calibration graphs are linear from 1 to 100 µg mL-1 for methyldopa and dopamine hydrochloride. The detection limit (S/N = 3) was 0.769 and 0.560 µg mL-1 for methyldopa and dopamine hydrochloride, respectively. The method was successfully applied to the analysis of methyldopa and dopamine hydrochloride in tablets and injections preparations, respectively. The results obtained by applying the proposed FIA method were in good agreement with those obtained by British Pharmacopoeia method.