Differentiation of Furanocoumarin Isomers with Ratio of Relative Abundance of Characteristic Fragment Ions and Application in Angelicae dahuricae Radix

C-5-substituted and C-8-substituted furanocoumarin isomers, two important kinds of furanocoumarin, are widely documented as the main active constituents in Angelicae dahuricae radix. Due to the similar polarity and mass fragmentation pathways of such isomers, it is difficult to distinguish them using mass spectrometric methods. To address this issue, we developed a strategy employing combined full scan and product ion scan modes on an ultra high...