Batch and Flow-Injection Spectrophotometric Determination of Methyldopa Using Metochlopramide as diazotized Chromogenic Reagent

Abstract

New, simple and sensitive batch and Flow-injection spectrophotometric
methods for the determination of Methyldopa in pure form and in pharmaceutical
preparations were proposed. These methods were based on diazotization and coupling
reaction between methyldopa and diazotized metochlopramide in alkaline medium to
form an intense orange-red water-soluble dye that is stable and has a maximum
absorption at 470nm. A graphs of absorbance versus concentration show that Beer's
law is obeyed over the concentration range of 1-14 and 5-130 μg.mL-1 of Methyldopa,
with detection limits of 0.15 and 3.213 μg.mL-1 of Methyldopa for batch and FIA
methods, respectively. The FIA procedure sample throughput was 70h-1. All different
chemical and physical experimental parameters affecting on the development and
stability of the colored product were carefully studied and the proposed methods were
successfully applied to the determination of Methyldopa in pharmaceutical
preparations.