High-confidence structural identification of metabolites relying on tandem mass spectrometry through isomeric identification: A tutorial

MS/MS currently serves as the workhorse for metabolomics. Structural identification is extremely important to correlate statistical variables to biochemical functions and conventional strategies rely heavily on m/z values. Although addressing a large portion of structural characterization demands, it is still a significant distance towards unambiguous identification because isomers inherently generate quite similar MS/MS spectra. Except chromatographic separation, some emerging techniques have been developed for the stages of sample preparation, ionization, ion transport, ion dissociation and ion dissociation dynamics, to facilitate isomer identification using MS/MS, such as chemical derivatization, ion mobility spectrometry, ion dissociation techniques, and energy-resolved MS. In present tutorial, we summarize in depth and discuss the developments of cutting-edge techniques concerning differentiation and identification of isomers. Emphasis is given to fundamental concept clarification of each technique to benefit popularization. The tutorial is envisioned to offer meaningful information and helpful guidelines for analytical chemists concerning metabolomics through accentuating isomeric identification.