An experimental approach to enhance parent ion fragmentation for metabolite identification studies: Application of dual collision cells in an orbital trap

Abstract

Recent mass spectrometry advancements including data-dependent scanning and high resolution mass spectrometry have aided metabolite profiling for non-radiolabeled xenobiotics. However, narrowing down a site of metabolism is often limited by the quality of collision induced dissociation (CID) based parent ion fragmentation. An alternative dissociation technique, higher energy collisional dissociation (HCD), enriches compound fragmentation and yields “triple quadrupole like fragmentation”. Applying HCD along with CID and data dependent scanning could enhance structural elucidation for small molecules. LC-MSn experiments with CID and HCD fragmentation were run for commercially available compounds on orbital trap, a hybrid linear ion trap-orbitrap mass spectrometer equipped with accurate mass measurement capability. The developed method included stepped normalized collision energy (SNCE) parameters to enhance MS fragmentation without tuning of compounds. All evaluated compounds demonstrated improved fragmentation under HCD as compared to CID. Results suggest that an LC-MSn method that incorporated both SNCE HCD and CID enabled parent ion fragmentations, afforded comprehensive structural information for the compounds under investigation. Such a method was remarkably better than one with only CID MSn in an ion trap. It is evident that such an acquisition method can augment identification of unknown metabolites in drug discovery by improving fragmentation efficiency of both the parent compound and putative metabolite(s)