Patent ID: 6635885
Filing Date: 2003-10-21
Classification: G01N,H01J

Abstract:
A gas delivery apparatus for delivering calibrant gas to the ionization chamber of a mass spectrometer which is evacuated by a vacuum pump comprising:a source of calibrant gas, a first valve for selectively connecting the source of calibrant gas to the ionization chamber of the mass spectrometer or to a vacuum pump, a first and second flow restrictor for selectively delivering calibrant gas from the source of calibrant gas at first and second flow rates, and a valve for selectively connecting the first or second flow restrictor to the first valve whereby gas is delivered to the ionization region or to the vacuum pump selectively at said first or second flow rate maintaining a constant flow of gas through the flow restrictor ensuring a continuously equilibrated system in order to provide a state of gas equilibrium with respect to surface absorption effects of the calibrant gas.