Figure 3. . Ion mobility spectrometry and its incorporation into LC-MS workflows.

(A) In ion mobility spectrometry (IMS), ions are separated based on their size and shape. In the example shown, the bile acids β-muricholic, urocholic and α-muricholic acids separate in order of fastest to slowest based on relative gas-phase ion shape. (B) The millisecond acquisitions of IMS are easily coupled between the minute and microsecond timescales of LC separations and TOF detection, since the time scale of each allows rapid sampling of the preceding separation. (C) Integration of IMS into LC-MS workflows provides an additional dimension of separation. Incorporating IMS provides greater coverage of the sample for the same LC separation length, or allows for decreasing the LC separation length while maintaining the same coverage. The example shows a human plasma total lipid extract analyzed by LC-IMS-MS. To indicate the increased separation capability obtained with the combination of LC and IMS, IMS-MS spectra were summed across three 10-s regions of the LC separation, creating three dimensional plots of m/z, drift time and intensity.

Figure 3C adapted with permission from [125] © Elsevier (2008).