Mass Spectrometric Research on Stable Radical of Piperidine N-oxides

In this paper, the fragmentation mechanism of 2, 2, 6, 6-tetramethyl-4-su- bstituted amino piperidine N-oxides are reported. From the data of exactmass measurements and metastable transition, three types of diagnostic ionproduced under EI condition have been proposed: (1) (M+H-CH_3)~+ ion,(2) (M-NO)~+ ion, (3) (M-CH_2O)~+ ion and its sequential fragment ion.In addition, the ions arisen from ring cleavage and elimination reaction arealso observed. On the basis of mass spectrometric behaviour for these com-pounds, some further instructive informations about labeled biological mole-cules can be obtained.