Fig. 5.

MS/MS spectrum and structure of PC(16:0/18:1). The ion at m/z 86 is a characteristic fragment of the choline head group, which ionizes as an intact molecular ion at m/z 184.0. The fragment ion at m/z 478.3 is generated from loss of the 18:1 fatty acyl chain from the intact lipid molecule, whereas the m/z 504.3 fragment forms from loss of the 16:0 fatty acyl chain from the PC precursor. The protonated LPC(16:0/0:0) is formed as a fragment at m/z 496.3. Similarly, the fragment at m/z 522.3 corresponds to the protonated LPC(0:0/18:1). NL of the entire phosphocholine head group leads to the formation of the ion [M+H-183]⁺ at m/z 577.5, whereas the loss of trimethylamine from the phosphocholine head group generates the fragment ion [M+H-59]⁺ at m/z 701.5.