Indirect Spectrophotometric Determination of Nitrazepam by Charge Transfer Complex Formation Reaction Using p-Bromanil as π-Acceptor

Abstract

A sensitive spectrophotometric method for the determination of nitrazepam in pure as well as in dosage form is described. The method is based on the reaction of reduced nitrazepam (RNZ) with p-bromanil in the presence of borate buffer solution of pH9 to form a pink color charge transfer(CT) complex of maximum absorption at 340 nm. Under the optimized reaction conditions, Beer’s law correlating the absorbance with nitrazepam concentration was obeyed in the range of 0.8-9.6 μg ml-1. The molar absorptivity was 1.977×104 L mol−1cm−1. The limits of detection was 0.093μg ml-1. The accuracy and precision of the method were satisfactory; the average recovery was 102% and values of relative standard deviations better than 1.5 %. The stoichiometry of the reaction was studied, and the reaction mechanism was postulated. The proposed CT complex formation method was successfully applied to the determination of nitrazepam in its pharmaceutical tablet with good accuracy and precision. The results obtained by the proposed method are compared with those obtained by the official method.

Keywords

• spectrophotometry
• charge transfer complex
• nitrazepam
• p-bromanil