Probing reactive sites for ion‐molecule reactions of anthraquinones with dimethyl ether using an external source ion trap tandem mass spectrometer and computational chemistry

Abstract

Gas-phase ion-molecule reactions of anthraquinone derivatives with dimethyl ether (DME) were investigated using an external source ion trap mass spectrometer. Semi-empirical calculations were executed to determine possible reactive sites for the product ions. Collision activated dissociation (CAD) was successfully performed for very low abundance of ion-molecule products. Even for product ions with a relative intensity below 1%, CAD experiments can be successfully performed. Significantly more structural information could be elucidated based on this special feature. Importantly, the CAD spectra of very minor ions could be measured by this ion trap instrument, which significantly enhances the future role of the ion trap as a powerful analytical instrument. CAD of all product ions on anthraquinone compounds typically eliminates neutral molecules such as CO or H(2)O. A hydration phenomenon in the CAD processes resulting from the precursor ions incorporating one molecule of H(2)O and then eliminating one molecule of CO was observed in this study.

Characterization of the Principal Constituents of Danning Tablets, a Chinese Formula Consisting of Seven Herbs, by an UPLC-DAD-MS/MS Approach

“…Besides, these differences were also valuable for the identification of isomer pairs, such as emodin and aloe-emodin, physcion and rhein, as well as of their corresponding glycosides. Therefore, five free anthraquinones (peaks 25, 28, 30, 31 and 32) were identified as aloe-emodin, rhein, emodin, chrysophanol and physcion, respectively, by comparing their retention times, UV absorptions, and MS/MS fragmentation patterns with those of the standard references and literature data [16,17,18]. Besides, nine anthraquinone glycosides (peaks 2, 7, 10, 12, 17, 18, 19, 21 and 23) were identified (Figure S3).…”

9 Organic gas phase ion chemistry

“…The selectivity of dimethyl ether as a chemical ionization reagent towards anthraquinones has been evaluated in an ion trap mass spectrometer. 87 The two major reagent ions, CH 3 OCH 2 ϩ and (CH 3 ) 2 OH ϩ , react to give a series of ions including [MϩCH] ϩ , [MϩCH 3 ] ϩ , [MϩCH 3 OCH 2 ] ϩ and [Mϩ(CH 3 ) 2 OH] ϩ . The MS/MS behaviour of these ions was compared to the M ϩؒ ion.…”