Ion mobility spectrometry – Mass spectrometry coupling for synthetic polymers

Abstract

This review covers applications of ion mobility spectrometry (IMS) hyphenated to mass spectrometry (MS) in the field of synthetic polymers. MS has become an essential technique in polymer science, but increasingly complex samples produced to provide desirable macroscopic properties of high‐performance materials often require separation of species prior to their mass analysis. Similar to liquid chromatography, the IMS dimension introduces shape selectivity but enables separation at a much faster rate (milliseconds vs minutes). As a post‐ionization technique, IMS can be hyphenated to MS to perform a double separation dimension of gas‐phase ions, first as a function on their mobility (determined by their charge state and collision cross section, CCS), then as a function of their m/z ratio. Implemented with a variety of ionization techniques, such coupling permits the spectral complexity to be reduced, to enhance the dynamic range of detection, or to achieve separation of isobaric ions prior to their activation in MS/MS experiments. Coupling IMS to MS also provides valuable information regarding the 3D structure of polymer ions in the gas phase and regarding how to address the question of how charges are distributed within the structure. Moreover, the ability of IMS to separate multiply charged species generated by electrospray ionization yields typical IMS‐MS 2D maps that permit the conformational dynamics of synthetic polymer chains to be described as a function of their length.

End group analysis of poly(methylmethacrylate)s using the most abundant peak in electrospray ionization‐ion mobility spectrometry‐tandem mass spectrometry and Fourier transform–based noise filtering

“…Indeed, IMS-MS has been extensively used for analyzing multiply charged polymers. [20][21][22][23][24][25][26][27] The molecular distribution of polymers represents another problem for mass spectra interpretation, but the use of MS/MS can limit the distribution to be analyzed. In this case, the first MS selects polymers of a certain m/z range, and the selected ions are analyzed in the second MS after CICS, in which ions attached to the polymers are partially reduced by a relatively soft collision without (or with slight) degradation.…”

“…Therefore, IMS can separate ions of the same m/z value but different z value generated from ESI. Indeed, IMS‐MS has been extensively used for analyzing multiply charged polymers 20–27 . The molecular distribution of polymers represents another problem for mass spectra interpretation, but the use of MS/MS can limit the distribution to be analyzed.…”

Using Ion Mobility–Mass Spectrometry to Extract Physicochemical Enthalpic and Entropic Contributions from Synthetic Polymers

“…Ion mobility–mass spectrometry (IM-MS) is a gas-phase technique, which separates different three-dimensional structures of ions such as peptides, proteins, − DNA, or other molecules according to their mass, charge, and collision cross-section (CCS). Synthetic polymers have as well been studied using IM-MS . These studies were mainly focused on analytical purposes in order to separate different polymer topologies − or different polymers in complex mixtures. , The two-dimensional IM-MS information (i.e., CCS values) is commonly matched with theoretical CCS computed from three-dimensional candidate structures ,− to obtain coordination numbers. ,− …”

Ion mobility mass spectrometry as a powerful tool to analyze complex macromolecular systems

“…It is thus a highly desirable quality of any method used for polymer analysis, to be able to distinguish between and identify different polymer topologies. 16 The ability to hyphenate MS with other techniques, such as column chromatography or a second MS-step offered to compensate for this drawback. In particular, the introduction of coupling MS with ion mobility spectrometry (IMS) by the Bowers-group in the mid to late 1990s resulted in a very powerful tool for the structural analysis of large molecular systems called ion mobility mass spectrometry (IMMS).…”

“…Optimizing the wave height and velocity as well as the gas pressure in the TWIMS cell can lead to better ion sensitivity than achievable with DTIMS. 16,68 A big disadvantage of TWIMS is that CCS is no longer directly correlated to t d under the effect of this nonlinear multidimensional dynamic electric field. Instead their relationship can be approximated by the power function…”