Recently, a research team from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, developed a novel electric field correction technique that significantly enhances the sensitivity and resolving power of ion mobility spectrometry (IMS). By introducing an isolating grid (IG) near the ionization source, the team effectively eliminated electric field interference, resulting in greatly improved IMS performance.
The related findings have been published in Talanta.
Corona discharge represents one of the most widely used ionization sources in IMS, playing a critical role in detection. However, in such ionization sources, the distorted electric field generated by the discharge needle can penetrate the reaction region of the IMS tube, creating a highly inhomogeneous electric field. Such inhomogeneous electric field is easy to make ions shift to the wall of IMS tube during their traveling, which affects the trajectory and distribution of ions and reduces the detection performance of IMS.
In this study, the research team introduced a novel electric field correction method for IMS. By placing an IG just downstream of the discharge needle, they effectively shielded and corrected the inhomogeneous electric field generated by the needle. Both simulations and experimental results confirmed that the IG prevents ions from drifting toward the walls of the IMS tube and helps focus them along its central axis, thereby improving ion transport. Notably, when the IG was positioned 2 mm from the discharge needle, ion signal intensity increased by 9.3 times compared to configurations without the grid. At a distance of 6 mm, the intensity of reactant ions rose by 2.36 times, along with a 21% improvement in resolving power. These results demonstrate that the isolating grid can effectively eliminate electric field distortion in the ionization region, significantly enhancing the performance of IMS.
This design contributes to a marked enhancement in both the sensitivity and the resolving power of IMS.
This study received financial support from the National Natural Science Foundation of China, the HFIPS Director's Fund, the Anhui Provincial Key R&D Program and the Anhui Provincial Engineering Technology Research Center for Biomedical Optical Instrument.
The simulations of ion distribution along one of the radial directions: (a) in the absence of the IG; (b) in the presence of the IG (Image by LUO Yuanjiang)
(a): Ion mobility spectra measured without IG and with IG at different position, (b): The ratio of the RIP area, denoted as Si to the area S0 which corresponds to the condition in which the IG. (Image by LUO Yuanjiang)