N-Bromosuccinimide/fluorescein system for spectrophotometric determination of H2-receptor antagonists in their dosage forms

Abstract

A simple, accurate and sensitive spectrophotometric method for analysis of H₂-receptor antagonists has been developed and validated. The method was based on the reaction of these drugs with N-bromosuccinimide (NBS) and subsequent reaction of the remaining NBS with fluorescein (FLC) to give a pink colored product that was measured at 518 nm. Different variables affecting the reaction conditions were carefully studied and optimized. Under the optimum conditions, Beer’s law was obeyed in the drugs concentration range of 0.5-35 μg ml^-1. The assay limits of detection and quantitation were 0.13-1.32, and 0.44-4.42 μg ml^-1, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The reaction stoichiometry and mechanism were studied. The proposed method was successfully applied to the analysis of the investigated drugs in pure and pharmaceutical dosage forms (recovery was 98.3–102.1 ± 0.58–1.30%) without interference from the common excipients. Interference from ascorbic acid that is added as a stabilizer for the ampoule formulation was avoided by its oxidation with potassium bromate before applying the analytical procedure. The results obtained by the proposed method were comparable with those obtained by the official methods.