Location of unsaturated positions in phosphatidyl cholines by consecutive‐reaction monitoring

Consecutive‐reaction monitoring (MS 3 ) of negative ions has been shown to be useful in locating double bonds in the fatty acid ester groups of individual phosphatidyl cholines present in complex mixtures. This information is derived from charge‐remote fragmentations of carboxylate anions produced by collisional activation of the [MCH 3 ] − precursor ions from phosphatidyl cholines. The added selectivety of this technique increases the sensitivity, relative to that of tandem mass spectrometry (MS 2 ), such that only 3 pmol are needed to perform this analysis.