AN  ANALYTICAL  APPROACH  TO  ION  TRANSPORT 
IN  THE  INTERFACE  REGION  OF  THE  ERI AD  (ELECTROSPRAY)
ION  SOURCE

    There is still a need for improvements in interfacial systems of mass  spectrometers with atmospheric pressure ionization sources. The interface region is characterized by complicated gaseous and electrodynamic conditions that strongly influence the total ion transmission and ion beam characteristics at the entrance of the mass spectrometer. In our work, we present a simple analytical model for the estimation of ion beam characteristics at the exit of the interface region. The traditional "nozzle--skimmer" system is investigated by ion transport modeling using continuum-based approximation in the limit of low ion currents. The model quickly builds smoothed ion trajectories in a supersonic gas jet and electric field of the interface. It also builds the nozzle--skimmer ion current-voltage characteristics in paraxial approximation.