High-performance liquid chromatography of benzodiazepines I: Stability-indicating assay of diazepam tablets.

A high-performance liquid chromatographic procedure was developed for diazepam tablet analysis. This procedure separates the manufacturing intermediate, 7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one, and the decomposition products, 3-amino-6-chloro-1-methyl-4-phenylcarbostyril and 2-methylamino-5-chlorobenzophenone, from diazepam. The liquid chromatographic procedure is superior to the USP UV assay because it is stability indicating. The method is simple, accurate, and fast, involving only one extraction step. A reversed-phase column and a methanol-water mobile phase were used. Under these conditions, 0.1% of the decomposition products was detectable. Typical samples of diazepam tablets showed no degradation.