Spectrophotometric Determination of Nitrazepam in Pharmaceutical Tablets by Oxidative Coupling Reaction with Pyrocatechol

A simple and sensitive spectrophotometric method was developed for the determination of nitrazepam (NZP) in pharmaceutical tablets. The method was based on oxidative coupling organic reaction of reduced NZP with pyrocatechol in the presence of ferric sulfate to form red water soluble product with maximum absorbance at 510 nm. The reaction conditions were studied and optimized. The linear range for the determination of NZP, and the detection limit were 1 – 24 μg mL-1 and 0.698 μg mL-1, respectively. The proposed method has been applied successfully for the determination of NZP in pharmaceutical tablets. A statistical comparison of these results with those obtained by the British pharmacopoeia procedure using the Student t-test and variance ratio F-test shows a good agreement and indicates no significant difference in accuracy and precision at the 95% confidence.