Pushing the Resolving Power of Tyndall-Powell Gate Ion Mobility Spectrometry over 100 with No Sensitivity Loss for Multiple Ion Species.

Ion gate is a key buildup for drift tube ion mobility spectrometry (IMS) and its combination with mass spectrometry. Bradbury-Nielsen gate, as the most commonly used ion gate in IMS, possesses a distinct ion mobility discrimination effect due to its depletion features. This impedes the scaling of the ion gate opening time to improve the separation capability of IMS while keeping its sensitivity for multiple ion species. In this work, a Tyndall-Powell gate (TPG) simply composed of two identical wire grids was used to develop an ion gate with nearly no ion mobility discrimination for IMS. Experimental results showed that the TPG features a gate region where the electric field for opening the gate could be enhanced to effectively solve the ion mobility discrimination problem related to it. Meanwhile, enhancing that electric field enabled the TPG-IMS to keep a resolving power over 106 at 100 °C for ion peak with a signal-to-noise ratio up to 800. With that TPG-IMS, baseline separation of two ion peaks, the hydronium and the acetone monomer peaks with a reduced mobility difference of only 0.04 cm2 V-1 s-1, was achieved with no sensitivity loss for the least mobile acetone dimer ions.