Spectrophotometric Determination of Catecholamines in Pharmaceutical Preparations Via Charge Transfer Complex Formation Using Bromanil Reagent

M.m Al-Sharook

doi:10.33899/edusj.2007.5781

Abstract

Spectrophotometric Determination of Catecholamines in Pharmaceutical Preparations Via Charge Transfer Complex Formation Using Bromanil Reagent

Highlights

Catecholamine drugs are aromatic vicinal-diols that consist of amines attached to a benzene ring bearing two hydroxyl groups
Several spectrophotometric methods have been applied to assay of catecholamines as cited in the literature including derivatization reaction with organic reagents such as o-phenanthroline[5], diazodized nitroaniline[6], ninhydrin[7], thiosemicarbazide[8,9] chloramine-T(10), phenylenediamine[11], and inorganic reagents like iodine[12], ammonium metavanadate[13] metaperiodate[14,15], cerium(VI) nitrate[16], neotetrazolium chloride[17]
The charge transfer complex reaction has been used for determination of catecholamine by using various organic reagents such as chloranil[27], DDQ[28] and fluoranil[29]

Summary

INTRODUCTION

Catecholamine drugs are aromatic vicinal-diols that consist of amines attached to a benzene ring bearing two hydroxyl groups (catechol). Determination of catecholamines in pharmaceutical: Aqueous formulation: Dopamine injection was diluted with distilled water in order to obtain a concentration range of the drug between 4-12 g.ml-1. When dilute aqueous solutions of catecholamine drugs were mixed with bromanil reagent in the presence of borate buffer solution of pH 9, a yellow coloured charge transfer complexes were observed with maximum absorption at 350, 366 and 368 nm for dopamine, methyldopa and levodopa respectively in contrast to reagent blank which shows a maximum absorption at 313 nm (Fig. 1). Quantification: Under the optimum conditions described above (Table 1) standard calibration curves of charge transfer complexes for catecholamine drugs and bromanil were constructed by plotting absorbance versus concentration (Fig. 2), and the good result of correlation coefficient indicating good linearity (Table 2). Beer’s law was obeyed over the concentration range as cited in (Table 2), and the resultant molar absorptivity indicates that the method is sensitive

Dopam ine

Sodium bicarbonate

Findings

Conclusions