Field Asymmetric Ion Mobility Spectrometry (ultraFAIMS) is a high speed, gas phase ion separation technique. When interfaced to a Mass Spectrometer, the ultraFAIMS device provides an additional separation stage.

The ultraFAIMS ion filter is orthogonal to both LC and MS, so has the potential to separate analytes that are difficult to distinguish using only LC-MS. In some cases, the ultraFAIMS stage can replace the LC and associated sample preparation steps.