Focused lipidomics by tandem mass spectrometry

In this paper we performed focused analyses of phospholipids by using the data of precursor ion scanning and neutral loss scanning of their polar head groups and fatty acyl moieties for the specific search of categorical phospholipids. By using precursor ion scanning or neutral loss scanning of polar head groups in the positive ion mode, more sensitive identification were obtained than that in the negative ion mode. Precursor ion scanning of carbonic anions in the negative ion mode was also effective to identify molecular species of phospholipids having specified fatty acyl moieties. By using these analytical methods, the detection limits of individual metabolites are going up to 5–20-fold of former conventional methods. The important factor is that by focusing in some limited categories of molecules, detection limit is greatly enhanced, thus minor but important molecules can be detected. Moreover, combination of LC–MS/MS and focused scanning for head group was revealed to be useful to identify very minor molecular species in the focused class of phospholipids.