Spectrophotometric determination of isocarboxazid bulk drug and tablets by reaction with p-dimethylaminocinnamaldehyde.

A spectrophotometric method is described for the determination of isocarboxazid. The method is based on the reaction of the drug with p-dimethylaminocinnamaldehyde in the presence of trichloroacetic acid in a methanolic medium to produce a very intense red chromophore (lambda max = 500 nm, Emax = 1.05 x 10(5]. The reaction is proposed to proceed via electrophilic attack at the C-4 position of the isoxazole nucleus. Job's plot indicated a 1:1 drug-to-reagent ratio. Regression analysis of Beer's plot showed excellent correlation (r = 0.9996) in the concentration range 0.25-2.10 micrograms isocarboxazid/mL. The developed color is stable for at least 12 h. Results of analyses of bulk drug and tablets by the proposed method are comparable to those for USP XXI methods.