Patent ID: 8592751

Claim:
A sample analysis system, operating at below atmospheric pressure, comprising: an ionization source for ionizing a sample into ions; an ion mobility filter that is either a differential mobility filter or a field asymmetric ion mobility filter including, at least two filter electrodes, the two filter electrodes being spaced apart from one another to form a constant sized gap between the two electrodes and an ion flow path that flows between the at least two filter electrodes through which the ions flow continuously; an inlet disposed upstream of said ion mobility filter for controlling pressure within the sample analysis system, said inlet having an orifice proximate the inlet; a controller operatively coupled to the ion filter for controlling operation thereto; a mass spectrometer for sensing ions not filtered by the ion filter, said mass spectrometer being sealingly connected to and disposed downstream from said ion mobility filter; and a pump disposed downstream from said mass spectrometer; wherein said pump reduces the pressure in the ion flow path to between about 0.2 to 0.9 atmospheres as a result of a pressure drop across said orifice.