Characterization of 3-methoxyflavones using fast-atom bombardment and collision-induced dissociation tandem mass spectrometry.

A mass spectrometric method based on the combined use of fast-atom bombardment (FAB), collision-induced dissociation (CID) and linked scanning at constant B/E has been used for the analysis of the fragmentation behavior of protonated 3-methoxyflavones (3-MFs). It is shown that several diagnostic ions such as (1,3)A (+) and (0,2)B (+) ions allow for an unambiguous localization of functions in the A- and B-rings and that the position of an additional methoxy group in the B-ring could be determined by a detailed analysis of the spectral patterns. Isomeric 3-MFs can be differentiated using this methodology. General fragmentation patterns of 3-MFs are discussed and plausible formation mechanisms of relatively abundant fragment ions are proposed.