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.