How Hot are Your Ions in TWAVE Ion Mobility Spectrometry?

Abstract

Effective temperatures of ions during traveling wave ion mobility spectrometry (TWIMS) analysis were measured using singly protonated leucine enkephalin dimer as a chemical thermometer by monitoring dissociation of the dimer into monomer, as well as the subsequent dissociation of monomer into a-, b-, and y-ions, as a function of instrumental parameters. At fixed helium cell and TWIMS cell gas flow rates, the extent of dissociation does not vary significantly with either the wave velocity or wave height, except at low (<500 m/s) wave velocities that are not commonly used. Increasing the flow rate of nitrogen gas into the TWIMS cell and decreasing the flow rate of helium gas into the helium cell resulted in greater dissociation. However, the mobility distributions of the fragment ions formed by dissociation of the dimer upon injection into the TWIMS cell are nearly indistinguishable from those of fragment ions formed in the collision cell prior to TWIMS analysis for all TWIMS experiments. These results indicate that heating and dissociation occur when ions are injected into the TWIMS cell, and that the effective temperature subsequently decreases to a point at which no further dissociation is observed during the TWIMS analysis. An upper limit to the effective ion temperature of 449 K during TWIMS analysis is obtained at a helium flow rate of 180 mL/min, TWIMS flow rate of 80 mL/min and traveling wave height of 40 V, which is well below previously reported values. Effects of ion heating in TWIMS on gas-phase protein conformation are presented.

Anomerization of Acrylated Glucose During Traveling Wave Ion Mobility Spectrometry

“…As a result, it can be concluded that most uncontrolled fragmentation giving rise to the ATDs shown in Figure 4 did not occur as ions traveled the TWIMS cell (which would have yielded a distribution of their drift time) but as they entered it. These findings are consistent with results previously reported using the same Synapt G2 instrument, which showed that ion injection in the mobility cell could raise the internal temperature to about 550-800 K, depending on the species [11,12]. Lowering voltages aimed at optimizing ion introduction in the mobility cell, as well as decreasing gas pressure in the He and in the mobility cells, allowed these fragmentations to be minimized to some extent but at the price of IMS separation of ammonium adducts of α-and β-Glu-5A (data not shown).…”

“…However, use of intense electric fields to achieve ion separation in traveling wave IMS (TWIMS) raises the issue of altering ion conformation during IMS analysis. Using a variety of thermometer ions for which dissociation energy was accurately characterized, the extent to which ions are heated along their pathway has been determined for different generations of TWIMS instruments [9][10][11][12]. These studies concluded that ion activation mostly occurred during their injection in the mobility Electronic supplementary material The online version of this article (doi:10.1007/s13361-015-1170-6) contains supplementary material, which is available to authorized users.…”

A Mechanism for Ionization of Nonvolatile Compounds in Mass Spectrometry: Considerations from MALDI and Inlet Ionization

“…With typical AP and IP MALDI instruments, desolvation of the matrix with release of bare analyte ions can occur anywhere before the mass analyzer without affecting the mass measurement accuracy. Thus, desolvation could be enhanced within rf fields or, for the SYNAPT G2, the traveling wave device within the instrument [42,82]. This is not the case for MALDI-TOF instruments where bare ion formation after acceleration will not be correctly mass analyzed.…”

Adduct-ion formation in trapped ion mobility spectrometry as a potential tool for studying molecular structures and conformations

“…g . pmethoxybenzylpyridinium (m/z 200) [19] and a leucine enkephalin dimer (m/z 1112) [20]. Ion heating may also cause disintegration of ion adducts and dimers in the mobility cell.…”