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Ion gate is a key buildup for drift tube ion mobility spectrometry (IMS) and its combination with mass spectrometry. Bradbury-Nielsen gate, as the most commonly used ion gate in IMS, possesses a distinct ion mobility discrimination effect due to its depletion features. This impedes the scaling of the ion gate opening time to improve the separation capability of IMS while keeping its sensitivity for multiple ion species. In this work, a Tyndall-Powell gate (TPG) simply composed of two identical wire grids was used to develop an ion gate with nearly no ion mobility discrimination for IMS. Experimental results showed that the TPG features a gate region where the electric field for opening the gate could be enhanced to effectively solve the ion mobility discrimination problem related to it. Meanwhile, enhancing that electric field enabled the TPG-IMS to keep a resolving power over 106 at 100 °C for ion peak with a signal-to-noise ratio up to 800. With that TPG-IMS, baseline separation of two ion peaks, the hydronium and the acetone monomer peaks with a reduced mobility difference of only 0.04 cm2 V-1 s-1, was achieved with no sensitivity loss for the least mobile acetone dimer ions. [ABSTRACT FROM AUTHOR]

On-line monitoring of propofol in exhaled air is a potential way to evaluate the anaesthesia depth for patients during surgery. In this study, a negative Ni ionization high resolution ion mobility spectrometer with Bradbury-Nielsen-Gate-Grid structure was built to measure propofol with reactant ions Cl(HO) using dichloromethane as dopant. Instead of forming three propofol ions (M - H), M · O, and (M - H) with reactant ions O(HO), only product ion M · Cl was produced when introducing dichloromethane gas. The peak-to-peak resolution ( R) between reactant ions Cl(HO) and product ion M · Cl was 17.4, which was 1.6 times larger than that between O(HO) and product ion. Furthermore, the linear response range using reactant ions Cl(HO) was 3.5 times wider than that obtained with reactant ions O(HO). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]