Polyethylene glycol (PEG) oligomers, H(OC 2 H 4 O) n H, were analyzed by gas chromatography/mass spectrometry (GC/MS) for oligomers, n = 2-11, without indications of pyrolysis of the higher oligomers at oven temperatures of 330°C. The electron ionization (EI) mass spectra (70 eV and 12-14 eV) of these PEG oligomers contain only low molecular weight fragment ions and, essentially, no M + ions. The low-voltage EI spectra contain more abundant high mass ions and allow easier identification of the PEG oligomers. The major fragment ions in all EI spectra are (C 2 H 4 O) x H + at m/z 45, 89, 133 and 177. The base peak in the low-voltage spectra varies with molecular weight and suggests preferential cleavage at the second and third ether linkages. The relative molar sensitivities (70 eV EI) of PEG oligomers (n = 1-6) are linear functions of molecular weight or polarizability ratios. The CH 4 chemical ionization mass spectra of the PEG oligomers contain, predominantly, (C 2 H 4 O) x H + ions at m/z 45, 89, 133 and 177. The relative abundances of MH + ions vary markedly across the chromatographic peaks because these ions are formed predominantly by sample ion / sample molecule reactions. Proton transfer reactions from CH 5 + and C 2 H 5 + to the PEG oligomers are almost entirely dissociative. The i-C 4 H 10 CI mass spectra of PEG oligomers contain MH + as the base peaks. The relative abundances of MH + ions do not vary significantly across the chromatographic peaks but do increase with increasing pressure of i-C 4 H 10. The extent of decomposition of MH + ions in i-C 4 H 10 CI mass spectra increases with increasing molecular weight of the PEG oligomers. Relative molar sensitivities (CH 4 CI and i-C 4 H 10 CI) of PEG oligomers (n = 1-6) are essentially the same linear functions of molecular weight ratio.
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