The Fragmentation Study Of Drug Reactive Molecules Under Differention Sources

The development of the ionization technology greatly expanded the role of mass spectrometry in many applications,especially in the field of drug analysis.The purpose of this dissertation is to address the fragmentation mechanisms of different drug active molecules,including cephalosporins,4(3H)-quinazolinones andα-hydroxy enones,under atmosphere pressure ionization and traditional electron ionization,and compare the fragmentation mechanism under these two ion sources.First,the effect of alkali metal cationization on the collision-induced dissociation(CID) of cephalosporins is discussed.The cleavage of C-X(X =O,N and S) in the site of C(3) and losses of CO₂ and CO both occur in these two situations.Their protonated molecular ions fragment mainly byβ-lactam cleavages between C(6)-C(7) and C(8)-N(1),while fragmentation of alkali metal cationized species include more complex multiple cleavage reactions.Ring cleavages become more facile in the sodiumed species. Moreover,rearrangement is favoured in sodiumed cationized species.Second,the fragmentation mechanisms of 4(3H)-quinazolinones andα-hydroxy enones are studied under APCI and EI,respectively.Also,the effect of the substituents on the fragmentation progress is discussed.It is concluded that although these compounds have similar framework,they presented different and characteristic fragmentation pathways.And the fragmentation patterns were obviously different when substituents were located in the ortho position to the neighbouring ring.