Spectrophotometric Determination of Methyldopa in Pure and Pharmaceutical Preparations by the Oxidative Coupling Reaction with 1, 5-Diaminonaphthalene in the Presence of Ammonium Ceric (IV) Nitrate

Oxidative coupling reactions are one of the significant methods used in the estimation of certain drugs in pharmaceutical formulations. this study describes the development of a fast and sensitive spectroscopic method considering the determination of trace amounts of methyldopa in an acidic aqueous solution.the adopted method centered on oxidative coupling due to the drug methyldopa with the reagent 1, 5-diaminonaphthalene in the presence of ceric (iv) ammonium nitrate as oxidizing agent to form a stable blue-colored product, giving the highest absorption at 730 nm. the product was appeared to agree beer's law within the limits of (5.4 - 39.6) μg /ml, and a value of molar absorptivity equal to 4.79471 ×104 l/ mol. cm. sandell’s index, 0.0044 μg/ cm2, relative standard deviation was in the range (0.5942 - 0.9687) %, whereas recovery average and determination factor were 99.908% and 0.9998. the proposed method has been successfully applied in the determination of methyldopa in its pharmaceutical preparations.