Indirect Spectrophotometric Determination of Antidepressant Drugs by Oxidation Using Ponceau 4R Dye

Abstract

A simple and sensitive indirect spectrophotometric method has been developed for the assay of Adrenaline, Dopamine hydrochloride, and Methyldopa in their pure and pharmaceutical preparations. The method is based on the principle of oxidation of the above drugs with a known amount of the oxidizing agent, N-bromosuccinimide (NBS), in hydrochloric acid. The unreacted oxidant bleaches Ponceau 4R dye, then the absorbance of the remaining dye (ΔA) is measured at 507 nm. The method obeyed Beer’s law within the concentration range of 3.5-10, 4-15, and 5-20 μg/mL, with molar absorptivity values of 8.01×10⁴, 5.32×10⁴, and 4.93×10⁴ L. mol^-1cm^-1 for Adrenaline, Dopamine hydrochloride and Methyldopa, respectively. The recovery % ranged between 99.15% and 100.61 %, and the relative standard deviation (RSD) was less than 1.42 % for all drug compounds. The method was applied successfully to pharmaceutical preparations for the studied medicinal compounds from different origins, as its results were in good agreement with the original content of the drugs in their pharmaceutical formulations and with the standard addition procedure, which proved that there was no interference by the excipients