Enhancing the Performance of Tyndall-Powell Gate Ion Mobility Spectrometry by Combining Ion Enrichment, Discrimination Reduction, and Temporal Compression into a Single Gating Process

The broad applications of ion mobility spectrometry (IMS) demand good sensitivity and resolving power for ion species with different reduced mobilities (K₀). In this work, a new Tyndall-Powell gate (TPG) gating method for combining ion enrichment, mobility discrimination reduction, and temporal compression into a single gating process is proposed to improve IMS analysis performance. The two-parallel-grid structure and well-confined gate region of the TPG make it convenient to spatiotemporally vary the electric fields within and around the gate region. Under the new gating method, a potential wave is applied on TPG grid 1 to enrich ions within the ionization region adjacent to the TPG during the gate-closed state; meanwhile, a potential wave is applied on TPG grid 2 to enhance mobility discrimination reduction and temporal compression simultaneously during the gate-open state. For triethyl phosphate (TEP) and dimethyl methylphosphonate mixtures, product ion peaks within K₀ of 1.9 to 1.1 cm²/V·s exhibit a 19-fold increase in ion current compared to the traditional TPG gating method, while maintaining a resolving power of 85. The estimated limit of detection for the TEP dimer is lowered from 8 ppb to 135 ppt. The new gating method can be applied to other TPG-based IMS systems to enhance their performance in analyzing complex samples.