PNNL

Abstract

Probing molecular properties in the gas phase require the integration of complementary ion manipulation approaches such as ion mobility spectrometry. Structures for lossless ion manipulations (SLIM) has recently been developed in our laboratory to perform ultra-high resolution ion mobility separations using traveling waves as well as provide other advanced capabilities. Despite its success, the design aspects of SLIM were not explored fully and remained largely unchanged. Here, we report on a computational evaluation using SIMION simulations of a number of traveling wave (TW) sequences that can be used in SLIM. The TW sequence used in the current SLIM device is a set of 8 electrodes where, at any time, 4 electrodes are held at high voltage (i.e. 1111) while the other 4 electrodes are held at low voltage (i.e. 0000) forming one micro-trapping region of 11110000 sequence. Ion trajectory simulations demonstrated the feasibility to simplify the 8-electrode set to a shorter sequence (e.g. 6-electrode or 4-electrode set) with maintained or improved performance via parameter optimization. The RF and TW amplitude, guard voltage, and TW speed were optimized subsequently on the symmetric sequences of the 4-, 6-, and 8-electrode sets to further improve the performance. The resolution, peak broadening, peak capacity, and peak generation rate of each sequence were evaluated, showing that the 111000 sequence of the 6electrode set has comparable performance as the current 11110000 sequence, and is always better than the 1100 sequence. This work provides insight and feasibility for simplification and modification of TW configuration in SLIM and other traveling wave devices.