Colorimetric determination of diazepam in pharmaceutical preparations

A colorimetric method is presented for the estimation of diazepam as the pure drug and in formulations. Diazepam is hydrolyzed with 6N HCl to 2-methylamino-5-chlorobenzophenone, which is extracted with chloroform to give a yellow solution whose absorbance is measured at 410 nm against a solvent blank. The color obeys Beer's law in the concentration range of 0-30 mug/ml. In 5 determinations, recovery was 99.0 +/- 1.9%. The method is applicable to pure diazepam and its formulations for oral and parenteral use. No interferences were observed from pyridoxine hydrochloride and commonly used preservatives, vehicles, and colors.