Abstract

Investigation and optimization of the use of spectrophotometry for the assay of rabeprazole sodiumwith in situ bromine and two dyes as reagents

Author(s): K.V.V.Satyanarayana, P.Nageswara Rao

Two simple and sensitive spectrophotometric methods are described for the assay of rabeprazole sodium (RPS) in pure and tablets using bromatebromide as the bromination reagent in acid medium, and two dyes as subsidiary reagents. The two methods are based on the bromination of RPS by a known excess of in situ generated bromine followed by determination of unreacted bromine by reactingwith a fixed amount ofmethyl orange (method A) or indigo carmine (method B) and measuring the absorbance at 508 or 610nm. In both methods, the amount of bromine reacted corresponds to the amount of RPS. The experimental conditions for the assay have been optimized. In twomethods, the absorbance is found to increase linearlywith the concentration of RPS at the respective wavelengths. Beer’s law is obeyed over the ranges 0.40-2.80 and 0.80-5.60gmL-1 formethodAand method B respectively and the respective molar absorptivity values are 1.29105 and 5.38104 lmol-1 cm-1. The limits of detection and quantification are reported for both methods. The statistical analysis of the methods was validated according to the present ICH guidelines. The proposed methods were applied to the analysis of tablet form of RPS and the results tallied well with the label claim. No interference was observed from the concomitant substances normally added to tablets.