Figure 2.
A positive-ion mass spectrum of an equimolar mixture of phosphatidylcholine molecular species before and after corrections for 13C isotopologue distributions. A positive-ion ESI mass spectrum of an equimolar mixture (1 pmol/μL each) of di12:0, di14:1, di16:0, 16:0-18:1, di18:2, di18:1, 18:0-18:1, 18:0-20:4, di19:0, di20:4, and di22:6 PC in the presence of a small amount of LiOH shows eleven intense ion peaks corresponding to their lithiated adducts (as indicated). Essentially equal intensities of these ion peaks were obtained within experimental errors of 10% after correction for differential 13C isotopologue distributions relative to di12:0 PC as indicated with horizontal lines.