Hydrogen–Deuterium Scrambling Based on Chemical Isotope Labeling Coupled with LC–MS: Application to Amine Metabolite Identification in Untargeted Metabolomics

Identification of metabolites at trace level in complex samples is still one of major challenges in untargeted metabolomics. One formula in the metabolomic database is always corresponding for more than one candidate, which increases the difficulty and cost in the process of standard compound matching. Hydrogen-deuterium exchange combined with liquid chromatography-mass spectrometry (HDX-LC-MS) can decrease the number of candidates through reflecting the number of labile hydrogen atoms according to isotopic distribution. However, current methods of HDX-LC-MS are only suitable for the identification of metabolites with specific structures, which is insufficient for untargeted metabolomics. In this study, we developed an effective method for metabolite identification by H-D scrambling based on chemical isotope labeling coupled with LC-MS (HDS-CIL-LC-MS). HDS is sorted as the intramolecular HDX and occur with the addition of energy. After isotope labeling, the labile hydrogen atoms in analytes can produce HD...