Determination of ranitidine using potassium iodate and dichlorofluorescein

Abstract

Two methods for determining ranitidine hydrochloride (RNH) in pure drug and in formulations using potassium iodate and dichlorofuorescein are described. Titrimetry involves the oxidation of RNH by a known excess of potassium iodate in acidic conditions followed by iodometric determination of surplus iodate. In spectrophotometry also, the drug is oxidized by a large excess of iodate and the iodine released is oxidized to ICl₂^- in the presence of chloride ions, and is used to iodinate 2,7-dichlorofluorescein dye and the amount of iodinated dye is measured. Reaction conditions of both methods have been optimized. In titrimetry, the reaction stoichiometry has been established and the reaction scheme of the spectrophotometric method is given. Titrimetry is applicable over 1-16 mg range. In spectrophotometry, the system obeys Beer’s law for 5-50 <img src='/image/spc_char/micro.gif' border=0>g mL^-1. The molar absorptivity and Sandell sensitivity were calculated to be 3.88×10³ L Mol^-1 cm^-1 and 5.72 ng cm^-2, respectively. The calculated limits of detection and quantification were 2.14 and 7.15 <img src='/image/spc_char/micro.gif' border=0>g mL^-1, respectively. The proposed methods were applied successfully to the determination of RNH in pharmaceutical preparations with recoveries in the range of 98.28 ± 0.88 to 103 ± 1.96% (titrimetry) and 99.46 ± 1.88 to 102.58 ± 0.73% (spectrophotometry). The reliability of the assay was established by parallel determination by an established procedure and by recovery studies using standard–addition technique.