Determination of some aminobenzoic acid derivatives: glafenine and metoclopramide

Simple, sensitive and accurate spectrophotometric methods for the determination of glafenine and metoclopramide hydrochloride are described. The first method is based on the oxidation of glafenine with iodic acid in strong acid medium to give a coloured diphenylbenzidine derivative and subsequent measurement of the coloured product at 509 nm. Beer's law is obeyed over the concentration range 2.5–20 μg ml⁻¹. The second method depends on the interaction of metoclopramide hydrochloride with p-dimethylaminocinnamaldehyde, to give a red coloured schiff's base with an absorbance maximum at 548 nm. Obedience to Beer's law is achieved over the concentration range 5–30 μg ml⁻¹. First-derivative method is used to overcome the slight interference of p-dimethylaminocinnamaldehyde reagent blank at the wavelength of measurement. Linearity between the peak heights at 576 nm versus concentration range 5–25 μg ml⁻¹ metoclopromide hydrochloride is obtained. The proposed methods have been successfully applied to the determination of these drugs in commercial products without interference. The validity of the methods is assessed by applying the standard addition technique, the relative standard deviation is less than 1%. The proposed methods are compared with reference methods with good agreement.