Increased ion transmission in IMS: A high resolution, periodic-focusing DC ion guide ion mobility spectrometer

The resolution of ion mobility spectrometry (IMS) is of paramount importance for both post-ionization separations and structural characterization of ions that have similar ion-neutral collision cross sections; however, the instrumental features that lead to increased resolution also decrease ion transmission through the drift cell. The periodic-focusing DC ion guide (PDC IC) drift cell provides increased ion transmission with minimal loss in resolution. In earlier work we showed that the electrode geometry (inner diameter, thickness, and spacing) strongly affects ion focusing and ion transmission. Here, we critically evaluate the effect of the electrode geometry of a PDC IC drift cell on both ion transmission and resolution. In this study we examine two drift cells that differ in length (63 and 125 cm) and electrode configuration. We also examine the effects of applied voltage and pressure in an attempt to maximize both resolution and ion transmission. Experimental data obtained with fullerene and model peptide ions are compared with calculated ion trajectories using SIMION 8.0 simulations. Published by Elsevier B.V.