Metabolism of 4-substituted-N-ethyl-N-methylanilines: chromatographic and mass spectrometric identification of N-oxidation metabolic products formed in vitro.

The electron impact and isobutane and ammonia chemical ionization mass spectral characteristics of the N-oxidation products of a series of 4-substituted-N-ethyl-N-methylanilines are described. The thermolability and the relative non-volatility of N-oxides of this type of tertiary aromatic amine makes their unequivocal identification by gas chromatography and electron impact mass spectrometry difficult. Mass spectral identification is facilitated by employing CI mass spectrometry where, under appropriate conditions, the N-oxides give intense protonated molecular ions. Chromatographic, electron impact and chemical ionization mass spectrometric evidence is presented which shows that these 4-substituted tertiary anilines undergo metabolic N-demethylation, N-de-ethylation and N-oxidation in vitro. The suitability of these tertiary aromatic amines as model substrates for mechanistic studies on C- and N-oxidation is discussed.