Analysis of Supramolecular Complexes of 3-Methylxanthine with Field Asymmetric Waveform Ion Mobility Spectrometry Combined with Mass Spectrometry

J Am Soc Mass Spectrom. 2016 May;27(5):800-9. doi: 10.1007/s13361-016-1351-y. Epub 2016 Feb 25.

Abstract

Miniaturised field asymmetric waveform ion mobility spectrometry (FAIMS), combined with mass spectrometry (MS), has been applied to the study of self-assembling, noncovalent supramolecular complexes of 3-methylxanthine (3-MX) in the gas phase. 3-MX forms stable tetrameric complexes around an alkali metal (Na(+), K(+)) or ammonium cation, to generate a diverse array of complexes with single and multiple charge states. Complexes of (3-MX)n observed include: singly charged complexes where n = 1-8 and 12 and doubly charged complexes where n = 12-24. The most intense ions are those associated with multiples of tetrameric units, where n = 4, 8, 12, 16, 20, 24. The effect of dispersion field on the ion intensities of the self-assembled complexes indicates some fragmentation of higher order complexes within the FAIMS electrodes (in-FAIMS dissociation), as well as in-source collision induced dissociation within the mass spectrometer. FAIMS-MS enables charge state separation of supramolecular complexes of 3-MX and is shown to be capable of separating species with overlapping mass-to-charge ratios. FAIMS selected transmission also results in an improvement in signal-to-noise ratio for low intensity complexes and enables the visualization of species undetectable without FAIMS.

Keywords: Charge state separation; Dissociation; FAIMS; Field asymmetric waveform ion mobility spectrometry; In-source CID; Mass spectrometry; Self-assembling complexes.

Publication types

  • Research Support, Non-U.S. Gov't