An ion source and method for providing ionized particles to a
molecular/atomic analyser, such as a mass spectrometer, are disclosed.
The ion source includes a vessel defining a channel; a gas inlet
extending from the gas source into the channel, for introducing a gas
flow into the channel; a sample inlet extending into the channel for
introducing sample within the channel; and an ionizer to ionize the
sample in the channel. The vessel is sufficiently sealed to allow the
channel to be pressurized, at a pressure in excess of 100 Torr. At least
one gas source maintains the pressure of the channel at a pressure in
excess of 100 Torr and the pressure exterior to the channel at a pressure
in excess of 0.1 Torr and provides a gas flow that sweeps across the
ionizer to guide and entrain ions from the ionizer to the outlet.