Sublimation Driven Ionization for Use in Mass Spectrometry: Mechanistic Implications

Abstract

Sublimation has been known at least since the middle ages. This process is frequently taught in schools through the 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 matrixassisted 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.

Triboionization in Discontinuous Atmospheric Pressure Inlet for a Miniature Ion Trap Mass Spectrometer

“…The analytes on the opposite side of the foil, which were adjacent to the inlet of the mass spectrometer, were pushed into the inlet, and they generated ions. The high-speed plume of particles generated by pulse valve matrix-assisted ionization can enhance the temporal and spatial sampling of MAI. , Research on triboelectrification (or contact electrification, which is more precise) also confirms that as static electricity accumulates, the discharge process between plates leads to ionization. , McEwen and Trimpin also reported some vMAI matrix generating triboluminescence during crystal cracking, which leads to charge seperation. , Therefore, we suspected that natural aging of the silicone tube would enhance contact electrification; hence, ionization without a VUV lamp could be observed more easily. We then explored the possible causes and influencing factors of this phenomenon.…”

“…43,44 McEwen and Trimpin also reported some vMAI matrix generating triboluminescence during crystal cracking, which leads to charge seperation. 45,46 Therefore, we suspected that natural aging of the silicone tube would enhance contact electrification; hence, ionization without a VUV lamp could be observed more easily. We then explored the possible causes and influencing factors of this phenomenon.…”

Unravel the Local Complexity of Biological Environments by MALDI Mass Spectrometry Imaging

“…For each point of the sample, mass spectra acquisition generates multiple heat maps. Although the precise mechanism of MALDI processes is still unknown, researchers have proposed several models such as the lucky survivors model [8], the coupled chemical and physical dynamics model [9], or the sublimation driven ionization model [10]. In MALDI MSI, the chemistry of the matrix plays an essential role in the desorption and ionization [11,12], and many improvements have been performed to increase the sensitivity and expand the chemical coverage [13][14][15].…”

A Combination MAI and MALDI Vacuum Source Operational from Atmospheric Pressure for Fast, Robust, and Sensitive Analyses

“…In vMAI, a specific matrix, or a matrix mixture, , is used which spontaneously converts compounds of the analyte associated with the matrix into gas-phase ions. This ionization process occurs during the sublimation of the matrix , and produces multiply charged ions, like ESI. In some cases, vMAI has produced higher sensitivity and selectivity compared to ESI or vacuum MALDI-TOF. , The ability to acquire 24 samples by vMAI in 4 min, disregarding the ca.…”