INDIRECT SPECTROPHOTOMETRIC METHOD FOR MICRO DETERMINATION OF METHYLDOPA AND DOPAMINE HYDROCHLORIDE USING ORANGE G

An accurate and simple indirect spectrophotometric method has been created for the microdetermination of Methyldopa (MDP) and Dopamine hydrochloride (DA) in acidic media. The method was based on the catalytic oxidation reaction between Orang-G and N-bromosuccinimide in an acidic medium which could be used to create an indirect spectrophotometric method for the micro determination of dopamine hydrochloride and methyldopa in pure form and pharmaceutical formulations. The molar absorptivity and Sandell index of MDP and DA were (4.9×104 ,3.7×104 ) l.mol-1 .cm -1 and (0.0048,0.0051) ng/cm2 respectively. The correlation coefficient values were 0.9936,0.9966 with a recovery rate of 99.5% and 99.93%. In addition, the limit of detection (LOD) and limit of quantification (LOQ) were 0.24,0.1788, and 0.727,0.5418 µg\mL. The recommended method was effectively applied for the determination of Dopamine hydrochloride and methyldopa in commercial formulation. No interference was experimentally noticed from common pharmaceutical formulation adjuvants. Statistical evaluation of the results with the standard addition method showed an excellent agreement and showed no significant variance in terms of accuracy and precision