Second-order derivative spectrophotometric assay for imipramine hydrochloride and diazepam in pure admixtures and in dosage forms.

The determination of imipramine HCl and diazepam in tablets by derivative spectrophotometry is described. The drugs in combined preparations have been quantified using the second-order derivative spectra of their solutions in 0.1 M HCl. The method has been applied to pure drug mixtures as well as commercial preparations and was found to be precise and reproducible. Compliance of Beer's Law was observed in the concentration range of 10-70 micrograms ml-1 for imipramine HCl and 2-8 micrograms ml-1 for diazepam. Lower limits of detection at the 95% confidence level were 1.96 micrograms ml-1 for imipramine HCl and 0.21 microgram ml-1 for diazepam.