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Two simple and sensitive spectrophotometric methods are described for the assay of three MAO inhibitors: isocarboxazid, tranylcypromine sulphate and iproniazid phosphate. The first method is based on the formation of a highly coloured stable radical anion between the drug as an n-donor and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as a pi-electron acceptor. Beer's law is obeyed in the concentration range 0.2-3, 0.2-4 and 0.5-4 micrograms ml-1 for isocarboxazid, tranylcypromine sulphate and iproniazid phosphate, respectively. The second method involves the use of iodine monochloride (ICl) as an sigma-acceptor. It was found that ICl reacts quantitatively only with isocarboxazid and tranylcypromine sulphate; with iproniazid phosphate results were very poor. Beer's law is obeyed in the concentration range 2-20 micrograms ml-1 for both drugs. The optimum experimental parameters for colour production in each case were determined. The percentage recoveries obtained were in accordance with those obtained by the official methods. The proposed methods are characterized by high sensitivity.

Seven solvent systems for the thin-layer chromatographic separation of hydrazidic monoamine oxidase inhibitor drugs have been developed. Detection of compounds at the microgram level was performed with the aid of thirteen spray reagents.

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.

A GC procedure for the simultaneous determination of hydrazine and benzylhydrazine in isocarboxazid raw material and tablet formulations has been developed. The method is based on the reaction of benzoyltrifluoroacetone with hydrazine and benzylhydrazine to form the corresponding pyrazole derivatives. The minimum detectable amounts of hydrazine and benzylhydrazine in isocarboxazid are 0.002 and 0.02%, respectively.