A Replenishing Signal Hadamard Transform Ion Mobility Spectrometry with a Tri-State Ion Shutter

Ion mobility spectrometry (IMS) technology is advancing towards miniaturization and sensorization, which can limit performance. The Hadamard transform IMS (HT-IMS) improves ion utilization, leading to higher signal-to-noise ratios (SNR). In conventional HT-IMS, the Hadamard sequence runs in a continuous loop, discarding the first multiplexed signal, which may be critical in time-sensitive applications. This paper introduces a novel method, replenishing signal HT-IMS (RS-HT- IMS), which incorporates the first multiplexed signal to save acquisition time. However, the resulting spectra often contain false peaks, complicating sample identification and reducing SNR. This could be caused by ion discrimination in Tyndall-Powell gate (TPG), which leads to suboptimal ion signal modulation. In this study, we compare the performance of TPG and tri-state ion shutter in RS-HT-IMS using dimethyl methylphosphonate (DMMP), dipropylene glycol methyl ether (DPM), and methyl salicylate (MESA) as test substances. Compared to signal averaged IMS (SA-IMS), the SNR of RS-HT-IMS is improved by 5–6 times. The tri-state ion shutter significantly reduced false peaks, improved SNR by 1.8-2 times, and enhanced resolving power by over 20% compared to the TPG.