Analysis of Polypropyleneglycols Using Electrospray Ionization Mass Spectrometry. Effects of Cationizing Agents on the Mass Spectra

Abstract

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.