High Resolution - Ion Mobility

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Pechar

In the case of TIMS (Trapped Ion Mobility Spectrometry), the ions are propelled through the tube with a gas flow, which is positioned orthogonally to the capillary. The electric field controls each ion to move beyond a position defined by the ion's mobility; where the thrust it experiences from the gas flow coincides with the strength of the electric field. A downward slope of the electric field allows the selective release of ions from the tube according to their mobility. 

Combined with a TOF (Time of Flight) analyser, this technique is useful for separating isomers that are indistinguishable by chromatography mass spectrometry, as they have the same m/z ratio. However, with ion mobility, they can be distinguished by their 1/K0 mobility value [V-s/cm2] or collision cross section (CCS), which are specific to each molecular structure. In addition, it allows cleaner spectra of each particular compound to be obtained, with its molecular peak and fragments if combined with MS/MS, from its mobilogram. 

It can also be combined with MS/MS Fragmentation with PASEF (Parallel Accumulation-Serial Fragmentation) technology. The equipment first performs ion mobility and, as the molecules jump the slope in isolation to follow the mass analyser, they are fragmented in the collision cell resulting in MS/MS spectra.