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Thursday, November 07, 2013

The New Tandem MS: Ion Mobility Spectrometry/Mass Spectrometry

Analytical Analytical Seminar
1640 Chemistry
04:00 PM - 5:30 PM
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Speaker:   Gary Glish, University of North Carolina at Chapel Hill
Abstract:   Tandem mass spectrometry (MS/MS) is one of the most powerful methods available for chemical identification. However, as instruments become more and more sensitive there is an increasing challenge of isomeric and isobaric ions interfering with the analysis. The conventional approach to overcoming this problem is to use chromatography to separate analytes prior to ionization. While LC is a powerful analytical technique in its own right, it has some limitations when combined with mass spectrometry. A couple of important limitations are that the time frame of a chromatography separation is much slower than mass spectrometry (minutes to hours vs. seconds or less), and the order of analyte analysis cannot be adjusted in real-time. And for some real-time analyses, chromatography is not even an option. As an alternative to chromatographic separations, we are developing differential ion mobility spectrometry (DIMS) as a separation method prior to mass spectrometry. While mass spectrometry separates ions based on their mass-to-charge ratio, conventional drift tube ion mobility spectrometry (DTIMS) is based on the ions’ shape-to-charge ratio. For DIMS the separation mechanism is not totally understood and while shape-to-charge plays a role, other factors such as the ion interaction with the drift gas are important. This makes DIMS more orthogonal to MS than DTIMS. DIMS has other differences compared to DTIMS that make DIMS more useful as an alternative to chromatography when combined with MS. In this presentation the fundamentals of DIMS will be discussed. Examples will be shown using DIMS/MS for fundamental chemical studies, real-time aerosols analysis, and detection of targeted compounds in complex biological matrices.