Analysis of polypropyleneglycols using electrospray ionization mass spectrometry. Effects of cationizing agents on the mass spectra

In electrospray ionization mass spectrometry (ESI-MS) of polypropyleneglycol (PPG), effects of cationizing agents were examined. When NaI was used as a cationizing agent, the distribution of multiply-charged ions in the spectra was greatly affected by the ratio of cationizing agent and PPG. However, the distribution was not affected by the use of CH3COONH4. With an increase of cone voltage, fragmentation occurred by in-source collision-induced dissociation (CID) when CH3COONH4 was used. On the contrary, no decomposition of the PPG backbone was observed with NaI. Instead, the intensity of the lower-charged ions, whose mass-to-charge (m/z) ratios are larger, increased because of the elimination of Na+ with increase of cone voltage. Under optimum conditions for ESI-MS analysis, PPGs that have different molecular weights, different initiators or end groups were easily and accurately characterized. A tandem mass spectrometry (MS/MS) study of NH4+ adduct ions of PPG indicated that a vinyl-terminated linear structure is formed at the end group during the fragmentation.