Journal of the American Society for Mass Spectrometry

, Volume 20, Issue 1, pp 1–9

The use of shift reagents in ion mobility-mass spectrometry: Studies on the complexation of an active pharmaceutical ingredient with polyethylene glycol excipients


  • Mark D. Howdle
    • Centre for Analytical Science, Department of ChemistryLoughborough University
  • Christine Eckers
    • GlaxoSmithKline
  • Alice M. -F. Laures
    • GlaxoSmithKline
    • Centre for Analytical Science, Department of ChemistryLoughborough University

DOI: 10.1016/j.jasms.2008.10.002

Cite this article as:
Howdle, M.D., Eckers, C., Laures, A.M.-. et al. J Am Soc Mass Spectrom (2009) 20: 1. doi:10.1016/j.jasms.2008.10.002


Gas-phase ion mobility studies of mixtures containing polyethylene glycols (PEG) and an active pharmaceutical ingredient (API), lamivudine, have been carried out using electrospray ionization-ion mobility spectrometry-quadrupole-time-of-flight mass spectrometry (ESI-IMS-Q-TOF). In addition to protonated and cationized PEG oligomers, a series of high molecular weight ions were observed and identified as noncovalent complexes formed between lamivudine and PEG oligomers. The noncovalent complex ions were dissociated using collision induced dissociation (CID) after separation in the ion mobility drift tube to recover the protonated lamivudine free from interfering matrix ions and with a drift time associated with the precursor complex. The potential of PEG excipients to act as “shift reagents,” which enhance selectivity by moving the mass/mobility locus to an area of the spectrum away from interferences, is demonstrated for the analysis of lamivudine in a Combivir formulation containing PEG and lamivudine.

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© American Society for Mass Spectrometry 2009