Electrostatic Spray Ionization Method

In an electrostatic spray ionization method for spraying a liquid layer from an insulating plate 2, the plate is arranged between two electrodes 1, 4. A constant high voltage power supply 3 is provided and an electric circuit is used to charge and discharge locally a surface of the liquid layer 7 on the insulating plate 2 by applying the power supply between the electrodes 1, 4.