Charge-Remote Fragmentation of Phospholipids in a Multi-Turn Tandem Time-of-Flight Mass Spectrometer"MULTUM-TOF/TOF"

High-energy collision-induced dissociation (CID) provides characteristic structural information about interested molecules, which cannot be obtained by low energy CID. High-energy CID is available using magnetic sector or time-of-flight (TOF) type mass spectrometers. In our laboratory, a multi-turn tandem TOF mass spectrometer (MULTUM-TOF/TOF) has been developed that has a multi-turn TOF mass spectrometer (MULTUM) as the first stage and a quadratic-field ion mirror as the second stage. MULTUM-TOF/TOF enables obtaining high-energy CID spectra with high resolving power for precursor ion selection. Furthermore, the signal-to-noise (S/N) ratio of the product ion mass spectrum is dramatically improved by increasing the number of cycles, because fragment ions caused by post-source decay are eliminated. The improved S/N ratio facilitates the recognition of signal peaks that have low intensity. In this paper, we performed the structural analysis of lysophosphatidylcholine (LPC) (18 : 1) using MULTUM-TOF/TOF. We obtained ions derived not only from a dissociation of the polar headgroup but also from charge-remote fragmentation generated by a high-energy CID process. Here, charge-remote fragmentation is the cleavage of a long-chain alkyl in a fatty acid moiety. Therefore, the position of the double bonds was successfully determined. The characteristics of product ion mass spectra obtained from sodiated and protonated LPC were also investigated.