Device for performing field asymmetric waveform ion mobility spectrometry

A device for performing field asymmetric waveform ion mobility spectrometry, “FAIMS”, the device comprising:

• a first segmented planar electrode including three or more segments, wherein the segments of the first segmented planar electrode are arranged in a first plane and extend in a direction parallel to an analytical axis of the device;
• a second segmented planar electrode including three or more segments, wherein the segments of the second segmented planar electrode are arranged in a second plane and extend in a direction parallel to the analytical axis of the device, wherein the first segmented planar electrode and the second segmented electrode are separated from each other to provide an analytical gap therebetween;
• propelling means for propelling ions through the analytical gap in a direction parallel to the analytical axis of the device;
• and
• a power supply;
• wherein the device is configured to operate in a FAIMS mode in which the power supply applies a set of voltage waveforms to the segments of the first and second segmented planar electrodes so as to produce an asymmetric time dependent electric field in the analytical gap for FAIMS analysis of ions propelled through the analytical gap by the propelling means;
• wherein the set of voltage waveforms are configured such that the asymmetric time dependent electric field has curved contours of equal field strength when viewed in a plane perpendicular to the analytical axis so as to focus ions having different differential mobilities towards different spatial domains, wherein each spatial domain extending along a respective curved contour of equal field strength when viewed in a plane perpendicular to the analytical axis;
• wherein the device has a focus controller configured to allow a user to change the curvature of the contours of equal field strength so as to change the strength of focussing provided by the asymmetric time dependent electric field.