Ion Fragmentation and Filtering by Alpha Function in Ion Mobility Spectrometry for Improved Compound Differentiation

Abstract

Collision induced dissociation (CID) is a widely used technique in mass spectrometry to better understand the structural composition of ions and to improve the identification of compounds beyond the analysis of m/z. By increasing the kinetic energy of ions in an electric field, the collisions with neutral molecules may result in bond breakage, dissociation, or fragmentation of the molecular ion into smaller fragments if the necessary onset energy is exceeded. In this work and for the first time, we demonstrate CID in a field asymmetric time of flight ion mobility spectrometer (FAT-IMS). In contrast to the commonly used devices in mass spectrometry, the FAT-IMS operates at ambient pressure and temperature. Furthermore, the FAT-IMS allows separation of ions prior to dissociation, employing the shift occurring in the FAT region and, thus, an improved assignment of fragment ions to selected precursor ions. In this work, the effect of the operation parameters on the fragmentation efficiency of the FAT separator is analyzed. As proof of concept, eight saturated alcohols were investigated. The results show the expected substance-specific fragmentation behavior, which can be used to generate additional orthogonal information about certain analytes via their fragmentation pattern. Furthermore, a method for prefiltering analytes in FAT-IMS by the alpha function is introduced to remove spectral interferences.

IMS Instrumentation I: Isolated data acquisition for ion mobility spectrometers with grounded ion sources

“…Furthermore, the FPGA can also be used to provide additional timing functions, e.g. additional pulses for a FAT-IMS [22,23].…”

High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS) at 40 mbar

“…Another important benefit of HiKE-IMS is the possibility of changing the reduced electric field strength in the drift region independently of the reduced electric field in the reaction region in order to separate substances by their field-dependent ion mobility as known from FAIMS and DMS ,− allowing for improved substance identification. Furthermore, high reduced electric field strength can lead to fragmentation, ,, also improving substance identification.…”

Mechanism of atmospheric pressure chemical ionization of morphine, codeine, and thebaine in corona discharge–ion mobility spectrometry: Protonation, ammonium attachment, and carbocation formation

“…28,29 Furthermore, although ESI and CD are soft ionization methods, sometimes IMS peaks related to smaller fragments are also observed. [30][31][32][33] Hydration of ions and their fragmentation depend on the structure and basicity of the molecule M. 34 In addition, instrumental parameters and existence of modifier gases (dopants) influence the type of produced ions. [35][36][37] Because IMS is used for opiate alkaloids in both the solid and solution phase, hence, in this work, ionization of pure solids and aqueous solutions of morphine, codeine, and thebaine is studied by APCI-CD-IMS.…”

“… 27 However, other ions and larger clusters such as hydrated protonated molecules, MH + (H 2 O) n , and proton‐bound dimers, (M) 2 H + , are also formed 28,29 . Furthermore, although ESI and CD are soft ionization methods, sometimes IMS peaks related to smaller fragments are also observed 30–33 . Hydration of ions and their fragmentation depend on the structure and basicity of the molecule M 34 .…”