Abstract: The fragmentation mechanisrn of four isomers of pyridino and benzobenzanthrones was investigated by(EI)tandem mass spectrometry (MS/MS).The relationship between fragmentation pathways and structural characteristics was also discussed.Initial fragmentation pathways have been estimated by the intensities of fragmemt ions[M—H]⁺,[MHCN]⁺,[M—COH]⁺, [M—CO]ⁱ⁺, [M—(CO+2H)]ⁱ⁺and[M—(CO+HCN)]ⁱ⁺ produced from Mⁱ⁺ (i=1,2).They indicated remarkable differences and very interesting features depending upon the isomer' s component with or without nitrogen, and also the condensation positions of a pyridino or benzo ring to the benzanthrone skeleton.The collisioninduced dissociation(CID)spectra of M²⁺ ion showed more effectively specific differentiation for their fragmentation behaviors reflecting the structural characteristics of these isomers.

Key words: Polycyclic aromatic hydrocarbon, Pyridinobenzanthrone, MS/MS-CID spectra, Fragmentation mechanism