title: Resolution enhancement of field asymmetric waveform ion mobility spectrometry (FAIMS) by ion focusing.
abstract: BACKGROUND
  Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) is a material analysis technology which develops very fast in recent years. Resolution is an important factor used to estimate the performance of this technology. With greater resolution, it's always easier to separate complex mixtures.
  
  
  RESULTS
  A method to increase the resolution of FAIMS is put forward which focuses ions before they enter the drift tube. By adding several pairs of focus electrodes loaded with DC or RF voltage in front of the FAIMS drift tube, the height of the ion beam flowing into the drift tube is decreased, which improves the resolution of the FAIMS spectrum. The effectiveness of this method is verified through SIMION simulation and experiments. Both the DC focusing mode and the AC focusing mode can improve the resolution of the FAIMS system, with the biggest increase of 37%.
  
  
  CONCLUSIONS
  Compared with other methods of improving FAIMS resolution, this method needs neither additional special gases, nor additional auxiliary equipment. It is easy to miniaturize, and can work under atmospheric pressure.
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084, P,R, China. tangf@mail.tsinghua.edu.cn.
authors.forename: Fei
authors.initials: F
authors.lastname: Tang
authors.forename: Chulong
authors.initials: C
authors.lastname: Xu
authors.forename: Xiaohao
authors.initials: X
authors.lastname: Wang