Achieving Improved Ion Swarm Shaping Based on Ion Leakage Control in Ion Mobility Spectrometry

In Ion Mobility Spectrometry (IMS), ion gates are essential for controlling ion flow, significantly impacting detection sensitivity and resolution. Despite various optimization methods, a clear approach is needed to define the performance limits of ion gates. This study proposes a linear relationship between peak intensity (Ip) and resolving power (Rp) at low ion quantities, introducing it as a reference for evaluating the optimization level. The Tri-State gate (TSG) enables the accurate study of this Ip–Rp relationship, but ion leakage of TSG disrupts control over narrow ion swarms, thereby limiting Rp. After the causes of ion leakage were examined, a preshaping method that removes the gate-opening phase was proposed to precisely control ion injection. This method leverages ion leakage to improve Rp while ensuring the linearity between Ip and Rp. The preserved linearity means avoiding excessive ion loss and shape distortion, ultimately leading to optimal resolving power. Simulations and experiments demonstrate that precise voltage adjustments effectively minimize ion leakage, enhancing resolving power by 50% (reaching a maximum of 106), while the corresponding decrease in signal intensity follows the Ip–Rp linear relationship. This approach expands the accessible range of Ip–Rp combinations without altering their fundamental relationship, reduces discrimination, and establishes a new evaluation method for optimizing ion gate performance in IMS.