Efficient Atmospheric Pressure Interface for Mass Spectrometers and Method

Abstract

An interface for atmospheric pressure ionization sources has an ion transfer tube with a plurality of passageways through a sidewall such that background gas can be pumped away before it reaches an exit end of the ion transfer tube. A flow of the background gas out the exit end is reduced, and a proportion of laminar flow in the ion transfer tube may be increased. Pressure in the ion transfer tube is also reduced and desolvation is increased. In one embodiment, an enclosure surrounds an inner tube of the ion transfer tube within a first vacuum chamber such that the enclosure provides a reduced pressure region within the first vacuum chamber. Overall, transport efficiency is increased.

1 . An interface for a mass spectrometer, comprising:
 an ion transfer tube having an inlet end opening to an atmospheric pressure chamber, an outlet end opening to a low pressure chamber, and at least one sidewall surrounding an interior region through which is directed a flow of gas and ions, the sidewall extending along a central axis between the inlet end and the outlet end; at least a portion of the sidewall being fabricated from a porous material to permit the flow of gas from the interior region through the sidewall to a reduced-pressure region exterior to the sidewall.   
   
   
       2 . The interface of  claim 1 , wherein the atmospheric pressure chamber comprises an ion source chamber, and the low pressure chamber comprises a first vacuum chamber. 
   
   
       3 . The interface of  claim 2 , wherein the ion source chamber is configured as an electrospray ionization source. 
   
   
       4 . The interface of  claim 2 , wherein the ion source chamber is configured as a chemical ionization source. 
   
   
       5 . The interface of  claim 2 , wherein the reduced-pressure region is located within an enclosure extending around the sidewall, the enclosure being disposed within the first vacuum chamber and communicating with a pump. 
   
   
       6 . The interface of  claim 1 , further comprising a heater in thermal contact with the ion transfer tube. 
   
   
       7 . The interface of  claim 1 , wherein the porous material is at least one of a a permeable ceramic, or a permeable polymer. 
   
   
       8 . The interface of  claim 1 , wherein the porous material is a porous metal. 
   
   
       9 . The interface of  claim 1 , further comprising a skimmer lens having an aperture positioned proximate to the outlet end. 
   
   
       10 - 17 . (canceled)