Mass spectrometer and method of mass spectrometry

Abstract

A mass spectrometer is disclosed comprising an ion mobility spectrometer in combination with a quadrupole mass filter which is scanned in synchronisation with the pulsing of ions into the ion mobility spectrometer thereby enabling ions having a particular charge state to be preferentially transmitted. Another embodiment replaces the quadrupole mass filter with an axial time of flight mass filter and an injection electrode.

1 - 56 . (canceled)  
     
     
         57 . A mass spectrometer comprising: 
 a continuous ion source;    a first ion trap;    an ion mobility spectrometer downstream of said first ion trap, said ion mobility spectrometer comprising a plurality of electrodes having apertures therein through which ions may be transmitted, wherein in use a DC voltage gradient is maintained across at least a portion of said ion mobility spectrometer and at least some of said electrodes are supplied with an AC or RF voltage, and wherein at least some of said electrodes are housed in a vacuum chamber maintained in use at a pressure within the range 0.1-10 mbar;    a quadrupole mass filter downstream of said ion mobility spectrometer; and    an orthogonal time of flight mass analyser comprising a pusher and/or puller electrode, orthogonal drift region and detector, said orthogonal time of flight mass analyser being arranged downstream of said quadrupole mass filter.    
     
     
         58 . A mass spectrometer comprising: 
 a continuous ion source;    a first ion trap;    an ion mobility spectrometer downstream of said first ion trap, said ion mobility spectrometer comprising a plurality of electrodes having apertures therein through which ions may be transmitted, wherein in use a DC voltage gradient is maintained across at least a portion of said ion mobility spectrometer and at least some of said electrodes are supplied with an AC or RF voltage, and wherein at least some of said electrodes are housed in a vacuum chamber maintained in use at a pressure within the range 0.1-10 mbar;    a second ion trap downstream of said ion mobility spectrometer, said second ion trap comprising a plurality of electrodes having apertures through which ions may be transmitted, at least some of said electrodes being supplied in use with an AC or RF voltage;    an axial drift region downstream of said second ion trap; and    an orthogonal time of flight mass analyser comprising a pusher and/or puller electrode, orthogonal drift region and detector, said orthogonal time of flight mass analyser being arranged downstream of said axial drift region.    
     
     
         59 . An ion mobility spectrometer for separating ions according to their ion mobility, said ion mobility spectrometer comprising: 
 a plurality of electrodes having apertures wherein a DC voltage gradient is maintained across at least a portion of said ion mobility spectrometer and at least some of said electrodes are connected to an AC or RF voltage supply.    
     
     
         60 . An ion mobility spectrometer as claimed in  claim 59 , wherein said ion mobility spectrometer comprises: 
 an upstream section comprising a first plurality of electrodes having apertures arranged in a vacuum chamber; and    a downstream section comprising a second plurality of electrodes having apertures arranged in a further vacuum chamber, said vacuum chambers being separated by a differential pumping aperture.    
     
     
         61 . An ion mobility spectrometer as claimed in  claim 60 , wherein at least some of said electrodes in said upstream section are supplied with an AC or RF voltage having a frequency within the range 0.1-3.0 MHz.  
     
     
         62 . An ion mobility spectrometer as claimed in  claim 60 , wherein said upstream section is arranged to be maintained at a pressure within the range 0.1-10 mbar.  
     
     
         63 . An ion mobility spectrometer as claimed in  claim 60 , wherein at least some of said electrodes in said downstream section are supplied with an AC or RF voltage having a frequency within the range 0.1-3.0 MHz.  
     
     
         64 . An ion mobility spectrometer as claimed in  claim 60 , wherein said downstream section is arranged to be maintained at a pressure within the range 10 −3 -10 −2  mbar.  
     
     
         65 . An ion mobility spectrometer as claimed in  claim 60 , wherein a first DC voltage gradient is maintained in use across at least a portion of said upstream section and a second DC voltage gradient is maintained in use across at least a portion of said downstream section, said first DC voltage gradient being greater than said second DC voltage gradient.  
     
     
         66 . An ion mobility spectrometer as claimed in  claim 59 , wherein the ion mobility spectrometer comprises at least 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 electrodes.  
     
     
         67 . An ion mobility spectrometer as claimed in  claim 59 , wherein at least 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% of said electrodes have apertures which are of substantially the same size or area.  
     
     
         68 - 83 . (canceled)  
     
     
         84 . An ion mobility spectrometer as claimed in  claim 59 , further comprising, in combination: 
 a mass filter; and    a controller arranged to continuously vary a mass filtering characteristic of the mass filter so that multiply charged ions having a first charge state are onwardly transmitted in preference to singly charged ions.