Introduction: The structural annotation of target relies on high-resolution mass spectrometry (HRMS) information resulting in dubious identities in most cases. The accurate annotation of isomeric structures is still challenging to be confirmed with significant bottleneck.
Objective: This study focused on the improvement of structural annotation of candidate structures via four pairs of isomeric flavanone-7-O-diglucosides and their basic flavanone aglycones commonly detected in citrus products.
Method: An integrated liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) approach merging retention time, accurate mass, tandem mass spectrometry (MS/MS) information (diagnostic ions), ion ratio at selected collision energy was established successfully.
Results: Feasibility of this approach was validated confidently in biological samples with relative standard deviation (RSD) of ion ratio range from 3.91 to 12.28%. Differences of fragmentation patterns of citrus flavanones were illustrated reasonably. MS/MS fragments of (S)-hesperetin and (S)-isosakuranetin were complicated and showed typical radical ion [1,2 A - H]•- (m/z 164) in negative ESI mode due to the methoxyl group on B-ring, which showed huge difference with (R)-hesperetin and (R)-isosakuranetin.
Conclusion: This study integrated multiple levels to boost the confidence of structural annotation relied on LC-HRMS, and provided important values in practice for precise identification of citrus flavanones in biological matrices.
Keywords: citrus flavanones; collision energy; fragmentation pattern; high-resolution mass spectrometry; ion ratio.
© 2020 John Wiley & Sons, Ltd.