Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Ion mobility spectrometry-mass spectrometry

Ion mobility spectrometry-mass spectrometry (IMS-MS) is a method that combines ion mobility spectrometry and mass spectrometry to identify different substances within a test sample.

History

On the one hand, ion mobility spectrometry was developed in the 60s and typically separates charged particles on a millisecond scale. On the other hand, time-of-flight mass spectrometry was developed in the 50s and typically separates charged particles on a microsecond scale. The combination of both instruments was pioneered in 1963 at the Bell Labs

• In 1963 McAfee and Edelson published an IMS-TOF combination. From their Letter to the Editor it is not conclusive whether they used an orthogonal extraction TOF. Most likely it was, because they seem to have used the TOF of the company Bendix, which was an orthogonal TOF.
• In 1967 McKnight, McAfee and Sipler published an IMS-TOF combination. Their instrument clearly included an orthogonal TOF..
• In 1969 Cohen et al. filed a patent on an IMS-QMS system. The QMS at that time was an improvement compared to the TOFMS, because the TOFMS lacked under the slowlyness of the electronic data acquisition systems at that time.
• In 1970, Young, Edelson and Falconer published an IMS-TOF with orthogonal extraction . They seem to have used the same system as McKnight et al. in 1967, incorporating slight modifications. Their work was later reproduced in the landmark book of Mason/McDaniel , which is regarded as the “bible of IMS” by those skilled in the art.
• In 1996 Guevremont et al. presented a poster at the ASMS conference about IMS-TOF.
• In 1997 Tanner patented a quadrupole with axial fields which can be used as a drift cell for IMS separation. He also mentions the combination of these quadrupoles with an orthogonal TOFMS .
• In 1998 Clemmer reinvented the IMS-TOF combination, using a co-axial IMS-TOF setup .
• In 1999 Clemmer reinvented the IMS-TOF with an orthogonal TOF system .

Instrumentation

Main articles: ion mobility spectrometer and mass spectrometer

The IMS-MS is a combination of an ion mobility spectrometer and a mass spectrometer. First the ion mobility spectrometer separates ions according to their mobilities. In a second step the mass spectrometer separates ions according to their mass-to-charge ratio. Such a combination is often referred to as a hyphenated separation or multi-dimensional separation.

There are different types of ion mobility spectrometers and there are different types of mass spectrometers. In principle it is possible to combine every type of the former with any type of the later.

Types of IMS

• TOFIMS (time-of-flight IMS) or the traditional ion mobility spectrometer
• DMS differential mobility spectrometer: a scannable filter, also called FAIMS
• DMA differential mobility analyzer: a scannable filter

Types of MS

• TOFMS (time-of-flight mass spectrometer)
• QMS (quadrupole mass spectrometer)
• ITMS (ion trap mass spectrometer)
• FTMS (Fourier transform mass spectrometer)
• SFMS (sector mass spectrometer)

Applications

The IMS-MS technique can be used for analyzing complex mixtures. It is used in:

• proteomics for the analysis of peptides
• detection of chemical warfare agents
• detection of explosives
• analysis of nano particles