Electrospray Ionization (ESI)

The spray of fine highly charged droplets is created at atmosphere pressure in the presence of an electric field. They are attracted to the capillary inlet of the mass spectrometer, which is hold at lower potential. Dry gas and/or heat applied to the droplets before they enter the vacuum of the mass spectrometer, causing the solvent to evaporate. Droplets decrease in size. Same charges give mutual repulses (exceeds the force of surface tension), ions leave the droplet through a "Taylor cone", they are induced into the orifice into the vacuum.