Abstract View
Optimization of Multiplexed Orthogonal Injection of Ions from Electrospray Sources into a Low Pressure Ion Funnel as a Means to Improve Sensitivity
XI CHEN, Pei Su, Julia Laskin, Carlos Larriba-Andaluz, IUPUI
Abstract Number: 494
Working Group: Instrumentation and Methods
Abstract
The electrodynamic ion funnel has been widely used to efficiently focus and transmit ions in the expanding gas jet from electrospray ionization (ESI) sources at sub-ambient pressures (0.1–30 Torr). Multiplexing of the ESI emitters is one of the notable techniques used in RF funnels to increase ion current and sensitivity of the detector, in this case a Mass Spectrometer (MS). An experimental system consisting of four injection inlets orthogonal to the funnel axis was studied showing that the total ion current transmitted through to the mass spectrometer was almost proportional to the number of capillaries under some configurations and analyte sets. To optimize the design of the funnel, ion trajectory simulations were studied using SIMION software analyzing the ions movement at different pressures and ion inlets distribution (staggered or aligned, symmetric or otherwise). To aid with the simulation and to mimic the real environment harshness of pushing ions from atmospheric pressure into low pressure with as much realism as possible, the velocity profile inside capillaries and funnel chamber was simulated through the computational fluid dynamic (CFD) software SOLIDWORKS. The flow field was then added to the SIMION field simulations to track ion trajectories and optimize the geometry and orientation of the orthogonal inlets, and the pressure inside the system. Among the different cases studied, the one that performed the best was to split the four capillaries into two pairs on opposite sides of the funnel and aligned so that the flows from the capillaries countered each other. For this configuration, the optimized transmission pressure was found to be 7 Torr. The optimization steps laid out in this work provide a way to optimize the sensitivity of other ion sources in a controlled manner, making the study very useful in many disciplines.