Accepted Oral : Eleanor

Introduction

Ion mobility-mass spectrometry (IM-MS) is a powerful tool for analysing highly complex mixtures. IM-MS offers an additional, complementary dimension of separation that is orthogonal to typical liquid chromatography-mass spectrometry (LC-MS) techniques. Further sample characterisation is often carried out using MS/MS to investigate key structural features; however, when using a quadrupole for ion selection, the specificity of precursor ion selection is limited by instrument resolving power. In this work, we present a novel way of implementing cyclic ion mobility (cIM) to separate, trap, and re-inject precursor ions of interest in highly complex mixtures. This approach enables high resolution selection of precursor ions and the generation of high resolution fragment ion data in MS/MS experiments.

Methods

Complex materials, represented by one polymer sample and one crude oil sample, were dissolved in methanol and toluene respectively and infused directly into a Waters cyclic ion-mobility enabled quadrupole time-of-flight (Q-cIM-oaToF) mass spectrometer.

Ions of interest were initially selected in the quadrupole and passed into the cIM for separation where the multi-function array was used to selectively slice and store a particular mobility region and discard all other remaining ions. The stored ions were then re-injected into the cIM and subjected to further separation. This “ion enrichment” process was repeated to improve the selectivity of species of interest within each sample. The selected ions - either precursor ions or post-mobility fragment ions - were then analysed in the ToF.

Preliminary Data

The described process was employed to examine highly complex samples. Acquisition methods were created by web-based browser software that allowed the control of the multi-function array, which enables the user to develop experimental workflows and visualise the movement of ions within the cIM region over defined time periods. This approach greatly simplifies the method creation by allowing visualisation of the sequence steps in the method aligned with the arrival time distribution in real time. By implementing successive slicing steps, the desired species was “enriched” relative to its neighbours.

Employment of this procedure allowed high resolution isolation of precursor ions for activation and fragmentation in MS/MS studies. Both the precursor ion and the fragment ions are more highly resolved than typical MS/MS data produced by classical ion selection on a quadrupole followed by fragment ion analysis on a ToF. Resulting fragment ions were known to be uniquely associated with the precursor ion of interest, rather than being a mix of ions originating from various species within a nominal value m/z window. For example, in the crude oil sample, selection and enrichment of m/z 375.29 from the cluster of ions containing m/z 375.16, 375.20, 375.26, 375.29, 375.33, and 375.39 produced a different fragment ion distribution from that produced by m/z 389.31 from the cluster of ions containing m/z 389.19, 389.21, 389.27, 389.31, 389.36, and 389.40. The selected ions of interested differed by one CH2 structural unit and, while the overall appearance of the fragment ion spectra was broadly similar, the ion distribution within each nominal ion cluster exhibited significant differences in relative intensity. This provides valuable insight into key structural motifs. We have demonstrated the potential of cIM for ion slicing and enrichment to aid in detailed characterisation of complex samples.

Novel Aspect
The use of cyclic ion mobility mass spectrometry for a novel ion slicing and enrichment technique.

Options:

A post-doc is presenting author on this abstract? No
A graduate student is presenting author on this abstract? No
An undergraduate student is presenting author on this abstract? No

Oral Choice:

Ion Mobility: New Developments & Applications
Second Oral Choice:

Instrumentation: Innovative Separations Approaches Coupled to MS
Poster:

Ion Mobility: Applications

Submitting Author:

Eleanor Riches
Waters Corporation
Wilmslow,
eleanor_riches@waters.com