Extended mass range by multiple charge: Sampling quadruply charged quasimolecular ions of poly(ethylene glycol) 4000

Mass spectrometric sampling of quasimolecular ions with charge as high as 4+ has been achieved by Electrohydrodynamic Ionization Mass Spectrometry (EHMS). Triply and quadruply charged sodium ion adducts of poly(ethylene glycol) 4000 oligomers with mass exceeding 3500 u were sampled from glycerol solution without fragmentation. Although the mass of these ions exceeded the nomical mass range of the spectrometer, they were detected because of multiple charge which lowered their mass‐to‐charge ratio. From the mass spectral intensities of these oligomer ions, the number average molecular weight of the polymer was caculated, and found to be in good agreement with results of an ASTM standard method.