Differential mobility spectrometer: Model of operation

Differential mobility spectrometry is a powerful tool used in a rapidly growing number and variety of applications for detection and characterization of gas-phase ions. In this paper a comprehensive mathematical model of the apparatus implementing the differential mobility spectrometry method is described. For completeness the mathematical theory of the method is provided. The model focuses on the analytical parameters of the differential mobility spectrometry instrument. The influence of instrumental parameters (carrier gas flow rate, separating field amplitude and waveform, filter gap size and geometry) and ion properties (diffusion, mobility and electric field mobility dependence) on the spectral peak characteristics (position, height and width) is examined. Both planar and coaxial instruments are covered in the same mathematical model. The model is extensively validated using published and our own experimental data. Proposed model is demonstrated to be in a good quantitative agreement with experimental data. This model explains all observed phenomena and predicts new ones such as high field focusing.