In-source collision induced dissociation study of polyethers cationized by alkali metal ions

In-source collision induced dissociation (ISCID) of polyethylene glycol (PEG) and polypropylene glycol (PPG) cationized by alkali metal ions was studied as a function of the chain length and collision energy using electrospray ionization mass spectrometry (ESI MS). The dissociation of the sodiated, potassiated and cesiated PEG and PPG yielded a neutral polyether and a cation without the formation of product ions resulting from the backbone cleavages. The survival yield (SY) method was applied to characterize the in-source fragmentation behavior of the cationized polyethers. The SY curves obtained by tandem MS/MS CID and in-source CID were compared. A remarkable difference was found, i.e. increasing the collision energy, the polyethers entirely dissociate in the collision cell, while the in-source SY plots level off at about 0.1–0.3. The finite SY values at large ISCID collision energies may suggest ion–molecule reactions in the ISCID region of the instrument. It was found that the characteristic ISCID50 collision energy corresponding to SY = 0.5 was dependent linearly on the number of the repeat units, i.e., on the size of the polyethers.

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► We report the ESI MS in-source collision induced dissociation of PEG and PPG.
► The survival yield method was applied to characterize the in-source fragmentation.
► The characteristic collision energy depends linearly on the size of the polyethers.
► The SY curves obtained by tandem MS/MS CID and in-source CID were compared.