Oral: Development and Application of a Cyclic ion mobility mass spectrometer

Introduction

Over the past decade the use of ion-mobility mass-spectrometry (IM-MS) has rapidly expanded with the technique increasingly being used in more routine applications, including structural elucidation. Despite the increased adoption of the technique, until relatively recently improvements in IM resolution have been modest, limiting the separation of compounds with similar mobilities. We will discuss the development and application of a high-resolution cyclic ion mobility enabled mass spectrometer and the application to a variety of structural elucidation studies.

Methods and Results 

Studies were performed on a SELECT SERIES Cyclic IMS. The instrument is characterised by the ability to perform high resolution ion mobility separations using a 98cm circular TWAVE device with multi-pass capability. In addition, a multi-functional ion entry/exit array allows multiple rounds of mobility selection and separation (IMSn).

We present a variety of examples that demonstrate the benefits of this novel technology including; the use of high ion mobility resolution to characterise small molecule, oligosaccharide and peptide isomers and to perform high peak capacity separations of mixtures. We will specifically highlight the use of the flexible instrument geometry to perform multi-stage separations incorporating IMSn.

Sequencing of oligosaccharides is challenging because they are made up of isobaric units.  High resolution mobility separation of isomeric precursor ions followed by dissociation and further separation of products has allowed identification of anomeric and open ring forms of pentasaccharides. For crude oil analysis, we describe an ion ‘enrichment’ method in which mobility selection is performed on ions of interest and all others are discarded. Multiple rounds of this experiment are performed to increase selectivity and were coupled with collisional dissociation to provide insights into structural motifs. Finally, we demonstrate how Cyclic IMS enhances the analysis of native protein collision-induced unfolding pathways and ligand binding experiments.

Conclusions 

The Cyclic IMS mass spectrometer is a flexible research platform for the in-depth structural elucidation of a range of important samples from oils to biopharmaceuticals. The unique instrument geometry, and the capability to perform high resolution mobility separations and the unique IMSn functionality provide many possibilities for detailed studies.