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 IG) 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 IG 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.

An investigation of increased length periodic-focusing DC ion guide (PDC IG) drift cells is presented. The PDC IG drift cell provides increased ion transmission with minimal loss in resolution compared with conventional uniform electric field designs.Figure optionsDownload high-quality image (90 K)Download as PowerPoint slideResearch highlights▶ Electrode geometry effects on ion transmission and mobility resolution for a periodic-focusing DC ion guide (PDC IG) drift cell. ▶ Increased ion transmission with a PDC IG drift cell with minimal degradation in mobility resolution. ▶ Ion mobility resolution increase on increased length PDC IG drift cell agrees with diffusion limited resolving power equation without a decrease in ion transmission.