Studies on the metabolism of procarbazine by mass spectrometry

The mass spectrometric properties of procarbazine and some of its breakdown products were examined using isotopic labeling and high resolution mass spectrometry. A specific intramolecular methyl group transfer, induced by electron impact, was used diagnostically to distinguish between two isomeric derivatives. The mass spectrometric information was used for identification of the in vivo metabolites of procarbazine in rat. Minimum sample manipulation was used due to the inherent instability of the suspected metabolites. The azo compound N-isopropyl- alpha -(2-methylazo)-p-toluamide was identified as the principal circulating metabolite of procarbazine.