High-performance liquid chromatographic determination of diethylpropion hydrochloride in tablets: isolation and identification of two decomposition products.

A rapid assay was developed for diethylpropion hydrochloride tablets using high-performance liquid chromatography (HPLC) with UV detection. This technique provided separation of the drug from other UV-absorbing components present as the result of decomposition. A major decomposition product detected by HPLC in extracts of tablets and of the cotton filler from a tablet bottle was collected from the column effluents. This product was subsequently identified as 1-phenyl-1,2-propanedione, a highly volatile compound. A second decomposition product, isolated from decomposed drug by distillation from alkaline solution, was identified as diethylamine, apparently present as the hydrochloride salt, GLC, UV, IR, NMR, and mass spectrometry were used to confirm the identity of the decomposition products. HPLC assay results compared favorably with results of the NF assay; the latter procedure separated the drug from 1-phenyl-1,2-propanedione via liquid-liquid extraction.