New Spectrophotometric Reduction–Oxidation System for Methyldopa Determination in Different Pharmaceutical Models

Abstract

Two spectrophotometric methods have been developed for the determination of methyldopa in the pure form and pharmaceutical formulations, both two methods based on the oxidation of the drug with an excess of N-Bromosuccinimide (NBS) and then reduction with 3,3-Diaminobenzidine (DAB), Absorbance of the resulting Magenta colored product is measured at 513 nm, the linearity ranged between (0.5 to 10) mg L−1 for the first spectroscopy method, and (0.5 to 15) mg L−1 for the second microfluid method. The detection limits (LOD) are 0.171, and 0.180 μg mL-1 for methyldopa in two methods spectroscopies, and microfluidic respectively. The limits of quantities (LOQ) are 0.571, and 0.600 μg mL-1 for methyldopa in two methods spectroscopies, and microfluidic respectively. The molar absorptivity (Ɛ) 2.58 ×104, 2.112×103 L mol-1 cm-1 for methyldopa in two methods spectroscopies, and microfluidic respectively. No interference was observed from common excipients in formulations. The results show a simple, accurate, fast, and readily applied method to the determination of methyldopa in pharmaceutical products. The proposed method was applied successfully for the determination of the drug in their pharmaceutical formulations.