Identification of Coumarin Isomers by Mass Spectrometry Using Breakdown Curves

A mass spectrometry method was established to distinguish the position isomers of coumarin rapidly by using breakdown curves. The dynamic collision energies of 2-40 V were applied to the position isomers, and the breakdown curves were drawn by a pair of fragment ions with the same molecular weight and greatly difference abundance percentages in position isomers. Herein, the rapid distinction of monosubstituted linear furanocoumarins (LFCs), disubstituted LFCs, angular furanocoumarins (AFCs) and simple coumarins (SCs) was realized by this method. The possible fragmentation mechanisms of disubstituted LFCs, AFCs and SCs were deduced according to the abundance differences of fragment ions based on the high resolution and high sensitivity of mass spectrometry. The results indicated that the breakdown curves of 4 pairs of 5,8-monosubstituted LFCs, one pair of disubstituted LFCs, one pair of disubstituted LFCs and AFCs as well as one pair of SCs were obviously different. This is the first time to distinguish the position isomers of coumarin mentioned above by using breakdown curves. Moreover, the fragment ions with marked abundance differences of three pair position isomers of coumarin including 5,8-disubstituted LFCs, AFCs and LFCs, disubstituted SCs were reported by breakdown curves for the first time. This method is simple and can quickly distinguish these seven pair position isomers of coumarin without standards.