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RationaleNew ionization processes have been developed for biological mass spectrometry (MS) in which the matrix lifts the nonvolatile analyte into the gas phase as ions without any additional energy input. We rationalized that additional fundamental knowledge is needed to assess analytical utility for the field of synthetic polymers and additives. MethodsDifferent mass spectrometers (Thermo Orbitrap (Q‐)Exactive (Focus); Waters SYNAPT G2(S)) were employed. The formation of multiply charged polymer ions upon exposure of the matrix/analyte(/salt) sample to sub‐atmospheric pressure directly from the solid state and surfaces facilitates the use of advanced mass spectrometers for detection of polymeric materials including consumer products (e.g., gum). ResultsAstonishingly, using nothing more than a small molecule matrix compound (e.g., 2‐methyl‐2‐nitropropane‐1,3‐diol or 3‐nitrobenzonitrile) and a salt (e.g., mono‐ or divalent cation(s)), such samples upon exposure to sub‐atmospheric pressure transfer nonvolatile polymersandnonvolatile salts into the gas phase as multiply charged ions. These successes contradict the conventional understanding of ionization in MS, because can nonvolatile polymers be lifted in the gas phase as ions not only by as little as a volatile matrix but also by the salt required for ionizing the analyte through noncovalent metal cation adduction(s). Prototypevacuummatrix‐assisted ionization (vMAI) and automated sources using a contactless approach are demonstrated for direct analyses of synthetic polymers and plasticizers, minimizing the risk of contamination using direct sample introduction into the mass spectrometer vacuum. ConclusionsDirect ionization methods from surfaces without the need of high voltage, a laser, or even applied heat are demonstrated for characterization of detailed materials using (ultra)high‐resolution and accurate mass measurements enabled by the multiply charged ions extending the mass range of high‐performance mass spectrometers and use of a split probe sample introduction device. Our vision is that, with further development of fundamentals and dedicated sources, both spatial‐ and temporal‐resolution measurements are within reach if sensitivity is addressed for decreasing sample‐size measurements.
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Sublimation Driven Ionization for Use in Mass Spectrometry: Mechanistic Implications
Sublimation has been known at least since the middle ages. This process is frequently taught in schools through use of phase diagrams. Astonishingly, such a well-known process appears to still harbor secrets. Under conditions in which compound sublimation occurs, gas-phase ions are frequently detected using mass spectrometry. This was exploited in matrix-assisted ionization in vacuum vMAI) by adding analyte to subliming compounds used as matrices. Good vMAI matrices were those that ionize the added analyte with high sensitivity, but even matrices that fail this test often produce ions of likely matrix impurities suggesting that they may be good matrices for some compound types. We also show that binary matrices may be manipulated to provide desired properties such as fast analyses and improved sensitivity. These results imply that sublimation in some cases is more complicated than just molecules leaving a surface and that understanding the physical force responsible, and how the nonvolatile compound becomes charged, could lead to improved ionization efficiency for mass spectrometry. Here we provide insights into this process and an explanation of why this unexpected phenomenon has not previously been reported.
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- Award ID(s):
- 1913787
- PAR ID:
- 10202767
- Date Published:
- Journal Name:
- Journal of the American Society for Mass Spectrometry
- ISSN:
- 1044-0305
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/jasms.0c00297
