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Differentiation of prototropic ions in regioisomeric caffeoyl quinic acids by electrospray ion mobility mass spectrometry
Author(s) -
Kuhnert Nikolai,
Yassin Ghada H.,
Jaiswal Rakesh,
Matei Marius F.,
Grün Christian H.
Publication year - 2015
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7151
Subject(s) - chemistry , electrospray , ion mobility spectrometry , mass spectrometry , ion , electrospray mass spectrometry , chromatography , electrospray ionization , quinic acid , organic chemistry
Rationale A series of dietary important regioisomeric chlorogenic acids were investigated by ion mobility mass spectrometry (IM‐MS). The existence of prototropic isomers separated in the drift dimension was observed and investigated further using tandem mass spectrometry (MS/MS) and compared with suitable synthetic analogues. Methods Using a quadrupole ion mobility time‐of‐flight mass spectrometer, the IM‐MS and IM‐MS/MS spectra of selected chlorogenic acids were recorded in the negative ion mode and compared with synthetic analogues. Results Regioisomeric di‐ and monocaffeoyl quinic acids can be readily separated and investigated using IM‐MS. Comparison of drift times allows assignment of the regiochemistry of precursor ions as well as for fragment ions. For 5‐caffeoyl quinic acid the existence of prototropic ions was suggested and probed using synthetic analogues, unable to show this type of isomerism. These investigations suggest the presence of prototropic isomers with carboxylate and phenolate sites, respectively. Conclusions We report on IM‐MS measurements on regioisomeric mono‐ and dicaffeoyl quinic acids, which are important dietary natural products. Both classes of compounds can be readily separated by IM‐MS in the drift time dimension and, following MS 2 experiments, fragment ion regiochemistry unambiguously determined. 5‐Caffeoyl quinic acid shows two IM‐MS signals, which we assign to prototropic isomers after comparison with suitable synthetic analogues, with a negative charge located at the carboxalate or phenolate functionality, respectively. Copyright © 2015 John Wiley & Sons, Ltd.