Patent ID: 6794640
Filing Date: 2004-09-21
Classification: H01J

Abstract:
A mass spectrometer comprising:a mass selective ion trap; an orthogonal acceleration Time of Flight mass analyser arranged downstream of the ion trap, said orthogonal acceleration Time of Flight mass analyser comprising an electrode for orthogonally accelerating ions; and a control means for controlling said mass selective ion trap and said orthogonal acceleration Time of Flight mass analyser, wherein in a mode of operation said control means controls said ion trap and said orthogonal acceleration Time of Flight mass analyser so that: (i) at a first time t1 ions having mass to charge ratios within a first range are arranged to be substantially passed from said ion trap to said orthogonal acceleration Time of Flight mass analyser whilst ions having mass to charge ratios outside of said first range are not substantially passed to said orthogonal acceleration Time of Flight mass analyser and are substantially retained within said ion trap; (ii) at a later time t1+&Dgr;tt the electrode is arranged to orthogonally accelerate ions having mass to charge ratios within said first range; (iii) at a second later time t2 ions having mass to charge ratios within a second range are arranged to be substantially passed from said ion trap to said orthogonal acceleration Time of Flight mass analyser whilst ions having mass to charge ratios outside of said second range are not substantially passed to said orthogonal acceleration Time of Flight mass analyser and are substantially retained within said ion trap; and (iv) at a later time t2+&Dgr;t2 said electrode is arranged to orthogonally accelerate ions having mass to charge ratios within said second range, wherein &Dgr;t1â‰ &Dgr;t2.