Tandem mass spectrometry of doubly charged poly(ethylene oxide) oligomers produced by electrospray ionization

Electrospray ionization combined with collision-induced dissociation has been applied to characterize fragmentation pathways of doubly charged poly(ethylene oxide) polymers. MS/MS spectra of doubly lithiated precursors were shown to provide the most informative data for this polymer structural analysis. Most fragment ions could be accounted for by applying the mechanisms proposed in the literature for singly charged oligomers. Although MS/MS experiments were conducted in a low collision energy regime, radical cationic fragments were also detected and were shown to further dissociate. This consecutive dissociation was explored performing hydrogen/deuterium exchange experiments and ab initio studies. Two different mechanisms had to be envisaged depending on the size of the fragmenting radical cationic species.