DEVELOPMENT OF NEW VISIBLE SPECTROPHOTOMETRIC METHODS FOR DETERMINATION OF BENIDIPINE HYDROCHLORIDE IN BULK AND FORMULATIONS BASED ON OXIDATIVE COUPLING AND DIAZO COUPLING REACTIONS

Three simple and sensitive visible spectrophotometric methods (A-C) have been developed for the estimation of Benidipine hydrochloride [BEN] from its bulk drug and dosage forms. The proposed methods are based on the reduction of the nitro group to amino group of the drug. This can be achieved by heating a mixture of an alcoholic solution of BEN, zinc powder and dilute hydrochloride in a water bath at 900c±5 for 15 minutes. The cold and clear filtrate reacts with 3-methyl-2-benzothiazolinonehydrazone hydrochloride in the presence of ferric chloride (Method A) or 4- amino phenazone –potassium ferri cyanide in the presence of weak base (Method B) or treated with nitrous acid for diazotization and then coupled with N-(1-Naphthyl) Ethylene Diamine dihydrochloride (NED) in acid medium (Method C) to form colored species with wavelength maximum at 620nm or 500nm or 525nm for methods A-C respectively. Beer’s law obeyed in the concentration range of 10-30μg/ml for both methods (A and B) and 8-40 μg/ml for method C. Commercial formulations were analysed, the results obtained by the proposed methods were in good agreement with the labeled amounts. Recovery in all the methods is found to be close to 99-100%.