Patent ID: 6914240

Claim:
An ion source for a mass spectrometer which operates at low pressure, the ion source comprising: a plurality of sample ionisers operative at atmospheric pressure to provide a plurality of streams of sample ions; an interface chamber, operable at a pressure lower than atmospheric pressure, having a plurality of entrance orifices located at a first position to collect sample ions into the interface chamber from said streams of sample ions and an exit orifice at a second position downstream of the said first position of the entrance orifices, for said sample ions to exit the interface chamber to the mass spectrometer, the interface chamber defining a plurality of separate ion paths for ions to travel between a respective one of the entrance orifices and the exit orifice, wherein each entrance orifice and the associated ion path are physically separated from the other entrance orifices and ion paths along at least a portion of each of the ion paths; and ion control means, located downstream of the said entrance orifices, and arranged selectively to prevent ions from passing along a chosen one or ones of the ion paths to the mass spectrometer.