14 February / March 2021
Delivering the Power of Ion Mobility Spectrometry - Mass Spectrometry to the Point of Analysis
by Ching Wu*, Greg Brabeck, Mark Osgood, Eugenie Hainsworth Excellims Corporation, 20 Main Street, Acton, MA 01720 Corresponding Author *
ching.wu@excellims.com
Abstract
With ion mobility (IM) built into many of the newer mass spectrometry (MS) systems, ion mobility spectrometry – mass spectrometry (IMS-MS) instrumentation has become the frontier of mass spectrometry development. The advantages of adding IM to MS include added isomer separation, structure based separation capability, and pre-separation of complex mixtures. Field portable MS is a fast growing area, offering high performance analysis of chemicals and biologics in-situ. Bringing the IMS-MS instrumentation to the point of analysis will provide rapid chemical detection in two dimensions (mobility and mass), delivering speed, performance, and robustness like that of an in-field IMS system. Key applications have been demonstrated in illicit drug detection, clinical diagnostics, and other specific on-site analysis needs.
Introduction
An ion mobility spectrometer can measure ion mobility of a gas phase molecule which is related to the molecular size and shape, indicating structure characteristics, while a mass spectrometer measures the mass (mass to charge ratio) of the molecule. Integrated ion mobility spectrometry - mass spectrometry offers more than one way to understand a gas phase molecule: now we not only know how heavy (mass) the molecule is, we also know how big (collision cross section) the molecule is. In the 1990s, further understanding of large biomolecules was one of the major motivations for the development of modern ion mobility mass spectrometry (IMMS) [1]. Historically, combining IMS with MS was demonstrated in the 70s, mainly for the purposes of understanding the ions formed in the IMS device, and further improving the performance of the IMS [2,3]. IMS and MS provide complementary information on the structure and composition of analytes. Increasingly, each technique is being taken into the field to quickly identify chemicals of interest such as explosives or narcotics. However, users have paid a price for the portability of previous fieldable instruments: poor performance and/or a single dimension of separation. In this work, a field portable IMS-MS system (MC3100, Excellims Corporation, Acton, Massachusetts, USA)
Figure 1. HPIMS ion mobility spectra of trisaccharide isomers, melezitose and raffinose; Red: melezitose and raffinose mixture, purple: raffinose only, and green: melezitose only.
with uncompromised IMS and MS system performance is presented. The desktop system integrates a high performance atmospheric pressure IMS with a linear ion trap MS, enabling chemical separation and identification based on both ion mobility and m/z. The IMS-MS system can detect chemicals based on their ion mobility and then introduce the same sample into the MS for m/z identification. Until now, ion mobility- mass two-dimensional (2D) chemical analysis could only be realised on laboratory scale models; now it has become a field portable compact instrument.
High performance ion mobility spectrometry
Recent advances in IMS have not only improved the resolving power of ion mobility separation, but also increased its compatibility with various mass analysers. Unfortunately, most of the systems are developed as integrated IMMS systems. To benefit from the ion mobility separation, researchers are required to obtain a complete bulky lab based IMMS system. Conventional IMS devices have been extensively developed to fit security and
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