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

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.