karbala journal of pharmaceutical sciences

A simple, accurate and sensitive spectrophotometric method for the determination of Methyldopa in pure and pharmaceutical preparations has been developed .The proposed method uses Thiamine Hydrochloride as anew chromogenic reagent . The method is based on the oxidative coupling reaction of Methyldopa with Thiamine Hydrochloride with potassium periodate in neutral media to form orange water soluble dye product , that has a maximum absorption at λmax 480 nm . Linear calibration graph was in the range of (1.00–25.00) µg.ml-1 with molar absorptivity of (0.53 ×104 L.mol-1.cm-1) ,a sandall sensitivity of (4.49 ×10-5 µg.cm-2) , correlation coefficient of (0.9997) , detection limit (0.38 µg.ml-1) and the relative standard deviation of RSD% (0.97) . The method was applied successfully for the determination of Methyldopa in pharmaceutical preparations and the value of recovery % was better than (102%)

A simple, accurate and sensitive colorimetric method for the determination of L-Dopa in pure and pharmaceutical preparations has been established .The proposed method uses 4–aminoantipayrine (4-AAP) as a chromogenic reagent . The method is based on the oxidative coupling reaction of L-Dopa with 4-AAP in the presence of sodium hydroxide as alkaline media to form a red water soluble dye product , that has a maximum absorption at 519 nm . Linearity was observed in the range of (0.20 – 30.00) µg.ml-1, with molar absorptivity of (0.58×104 L.mol-1.cm-1) ,a sandall sensitivity of (0.36×10-4µg.cm-2) , correlation coefficient of 0.9999 , detection limit (0.12 µg.ml-1) and the relative standard deviation is better than (1.013%) . The method was applied successfully for the determination of L-Dopa in pharmaceutical preparations and the value of recovery % was found ( 99.68 %).