Design of a New FAIMS Device With Replaceable Accessories and Analysis of the Impact of Spacing.

The plate spacing has a significant impact on the resolution and sensitivity of High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS). Theoretical and experimental analysis of this parameter is of great significance for improving the performance of FAIMS. A self-designed modular FAIMS device with replaceable upper and lower PCB plates was developed to provide a reliable experimental platform for investigating plate spacing as a single variable. In this device, the fixed mechanical positioning and conductive-contact connection help restore consistent electrode positioning. Theoretical analysis and SIMION simulations were first performed to predict the influence of plate spacing, followed by experimental validation. Plate spacings of 0.3, 0.4, 0.5, and 0.6 mm were set, and acetone samples were detected under the same electric field conditions. The simulation and experimental results show that with the increase of plate spacing, the FAIMS signal intensity (peak height) increases significantly: when the plate spacing increases from 0.3 to 0.6 mm, the signal intensity of the main peak increases by approximately 100%, and that of the secondary peak increases 4.6-fold. Moreover, the relative standard deviation (RSD) of all spacings is below 5%. Increasing the plate spacing significantly improves the sensitivity of the FAIMS system while the resolution does not change significantly, and the system maintains good separation capability. This study provides a theoretical basis and practical guidance for the optimal design of FAIMS instruments.