Abstract
Liquid chromatography-mass spectrometry- (LC-MS-) based multiple reaction monitoring (MRM) methods have been used to
detect and quantify metabolites for years. ,ese approaches rely on the monitoring of various fragmentation pathways of multiple
precursors and the subsequent corresponding product ions. However, MRM methods are incapable of confidently discriminating
between isomeric and isobaric molecules and, as such, the development of methods capable of overcoming this challenge has
become imperative. Due to increasing scanning rates of recent MS instruments, it is now possible to operate MS instruments both
in the static and dynamic modes. One such method is known as synchronized survey scan (SSS), which is capable of acquiring
a product ion scan (PIS) during MRM analysis. ,e current study shows, for the first time, the use of SSS-based PIS approach as
a feasible identification feature of MRM. To achieve the above, five positional isomers of dicaffeoylquinic acids (diCQAs) were
studied with the aid of SSS-based PIS method. Here, theMRMtransitions were automatically optimized using a 3,5-diCQA isomer
by monitoring fragmentation transitions common to all five isomers. Using the mixture of these isomers, fragmentation spectra of
the five isomers achieved with SSS-based PIS were used to identify each isomer based on previously published hierarchical
fragmentation keys. ,e optimized method was also used to detect and distinguish between diCQA components found in Bidens
pilosa and their isobaric counterparts found in Moringa oleifera plants. ,us, the method was shown to distinguish (by differences
in fragmentation patterns) between diCQA and their isobars, caffeoylquinic acid (CQA) glycosides. In conclusion, SSS allowed the
detection and discrimination of isomeric and isobaric compounds in a single chromatographic run by producing a PIS spectrum,
triggered in the automatic MS/MS synchronized survey scan mode.