Spectrophotometric Methods for the Determination of Anti-Emetic Drugs in Bulk and in Pharmaceutical Preparations

Abstract

Four rapid, simple, reproducible and sensitive methods (A-D) for assaying domperidone (I) and metoclopramide (II) in a bulk sample and in dosage forms were investigated. The first and second methods, A and B, are based on the oxidation of I and/or II by Fe³⁺ in the presence of o-phenanthroline (o-phen) or bipyridyl (bipy). The formation of tris-complex upon reactions with Fe³⁺-o-phen and/or Fe³⁺-bipy mixture in an acetate buffer solution of the optimum pH-values was demonstrated. Methods C and D involve the addition of excess Ce⁴⁺ and the determination of unreacted oxidant by a decrease of the red color of chromotrope 2R (C2R) at a suitable λ_max of 528 nm for method C, or a decrease in the orange pink color of Rhodamine 6G (Rh6G) at a suitable λ_max value of 525 nm for method D. A regression analysis of Beer-Lambert plots showed a good correlation in the concentration range of 0.2 - 5.8 μg ml^-1. The apparent molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. For a more accurate analysis, the Ringbom optimum concentration ranges are 0.35 - 5.6 μg ml^-1. The developed methods were successfully applied to the determination of domperidone and metoclopramide in bulk and pharmaceutical preparations without any interference from common excipients.