Positive and negative ion mass spectrometry of antiepileptic hydantoins and their analogs.

Positive ion electron impact (PIEI), positive ion chemical ionization (PICI), and negative ion chemical ionization (NICI) mass spectra of seven compounds of hydantoins and their analogs are presented; their probable fragmentation modes are also presented. In the PIEI mode, intensities of molecular ions differed according to different compounds. Cleavage at outsides of both carbonyl groups was commonly observed for all compounds. In the PICI mode, all compounds showed [M + 1]+ quasi-molecular ions constituting the base peaks. In the NICI mode, [M - 1]- quasi-molecular anions were the base peaks except for trimethadione and paramethadione. All negative spectra showed anions at m/z 42 due to [NCO]-; these peaks seem useful for screening of antiepileptics. An extraction procedure for the anti-epileptics from human urine or plasma, and their separation by gas chromatography (GC), are also presented to serve for their actual identification by GC/mass spectrometry.