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Gas Chromatography / Chemical Ionization Mass Spectrometry of Polyethylene Glycol Monoalkyl Ethers

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Author Affiliations

  • 1Basic Sciences Department, Chemistry Unit, Babcock University Ilishan Remo, Ogun State, NIGERIA
  • 2Department of Chemistry and Biochemistry, University of Delaware, Newark, DE.19716, USA
  • 3Department of Chemistry, Niger-Delta University, Bayelsa State, NIGERIA

Res.J.chem.sci., Volume 3, Issue (2), Pages 4-9, February,18 (2013)

Abstract

The CH4/CI mass spectra of polyethylene glycol monoalkyl ethers, CxH2x+1(C2H4O)nOH), contain MH+ and fragment ions that can be used to identify each oligomer. The relative abundances of the MH+ ions are low, variable, and increase with increasing sample size across the chromatographic peaks and not with increasing value of x or n; hence, a major portion of these ions is formed by sample ion/sample molecule reactions. The base peaks in CH4/CI are variable and are determined by the ethylene oxide moiety (x ≤3). Those of higher mass oligomers (x≥ 4, n≥ 3) are MH+ ions and ions formed by hydrogen rearrangement decompositions of the MH+ ions ((HOC2H4OH)nH+, n= 1,2.) Isobutane CI (i-C4H10/CI) spectra are pressure dependent. The pressure in the source of our mass spectrometer is not known but it is described by the ratio of ionic abundances of m/z 43 and 57: P(0.15) = I(43/57)= 0.15 (high pressure), and P(0.05) = I(43/57) = 0.05 (higher pressure). The spectra obtained at the lower pressure (P=0.15), show less fragmentation to that observed with CH4/CI. Those at higher pressure, P(0.05), contain essentially MH+ ion. The base peak at both pressures is the MH+ ions. Estimates of the heat of formation of some of the CH4 CI proton transfer reactions were made from the thermochemistry of some of the decomposition reactions using n-butyl ether oligomer as a model compound.

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