Atmospheric Pressure Chemical Ionization (APCI):

This interface uses nitrogen as a nebulizing gas and a heated nebulizer probe. The mobile droplets and the gas are heated to '120 ^oC in a desolvation chamber where a corona discharge generates electrons that ionize the mobile molecules to give reactant ions as shown in Figure. These ions then collide with analyte molecules to yield pseudomolecular ions by chemical ionization. The analyte ions are accelerated through skimmer-cones into the spectrometer whereas the uncharged solvent molecules are removed by differential pumping.

Schematic of atmospheric pressure chemical ionisation (APCI) source