GB2388955A - Controlled ion injection in an orthogonal TOF mass spectrometer - Google Patents

Controlled ion injection in an orthogonal TOF mass spectrometer Download PDF

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Publication number
GB2388955A
GB2388955A GB0224594A GB0224594A GB2388955A GB 2388955 A GB2388955 A GB 2388955A GB 0224594 A GB0224594 A GB 0224594A GB 0224594 A GB0224594 A GB 0224594A GB 2388955 A GB2388955 A GB 2388955A
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mode
mass
ions
ion
electrode
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GB2388955B (en
GB0224594D0 (en
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Robert Harold Bateman
Martin Green
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Micromass UK Ltd
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Micromass UK Ltd
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Priority claimed from GBGB0125241.0A external-priority patent/GB0125241D0/en
Priority claimed from GB0221502A external-priority patent/GB0221502D0/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/34—Dynamic spectrometers
    • H01J49/40—Time-of-flight spectrometers
    • H01J49/401—Time-of-flight spectrometers characterised by orthogonal acceleration, e.g. focusing or selecting the ions, pusher electrode

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

Abstract

The pusher electrode 4 of an orthogonal acceleration time-of-flight (oaTOF) mass analyser is operated in conjunction with an ion gate 2 to ensure that low mass background or matrix ions are not injected in to the drift region 5 of the mass analyser. The ion gate is switched between two modes of operation, it having a lower ion transmission efficiency in one mode than the other, ions being injected into the drift region a set time after the switch, so that only ions in a certain range of mass-to-charge ratios enter the drift tube. The ion gate may be an electrostatic device comprising at least one electrode used to alter, deflect, focus, defocus, attenuate or block an ion beam. Preferably, in a first mode the electrostatic device has no voltage applied to it, so that the ion beam passes unaffected, while in a second mode the device substantially prevents ions from being onwardly transmitted.

Description

76700004 v12 MASS SPECTROMETER
The present invention relates to a mass 5 spectrometer.
A common problem with known mass spectrometers is that the largest ions in a mass spectrum may originate from chemical species (i.e. background ions) which are
of no interest to the analysis. For example, the 10 background ions may comprise solvent ions, Gas
Chromatograph carrier gas ions, Chemical Ionisation reagent gas ions or air peaks from vacuum leaks. These background ions can give rise to large ion signals which
unless attenuated may saturate the ion detector thereby 15 affecting the integrity of the mass spectra produced and reducing the lifetime of the ion detector.
It is therefore desired to provide an improved mass spectrometer. According to a first aspect of the present 20 invention there is provided a mass spectrometer comprising: an ion source; an orthogonal acceleration Time of Flight mass analyses comprising an electrode for orthogonally 25 accelerating ions, an ion detector and a drift region therebetween; an ion gate upstream of the electrode; and control means for switching the ion gate between a first mode and a second mode, the second mode having a 30 lower ion transmission efficiency than the first mode, wherein in a mode of operation the control means: (i) switches the ion gate from the first mode to the second mode at a time T:; and (ii) causes the electrode to inject or orthogonally 35 accelerate ions into the drift region at a later time T1+AT:;
wherein AT is set such that ions having a mass to charge ratio < a value M1 are not substantially injected
-2 or orthogonally accelerated into the drift region by the electrode. An advantage of the preferred embodiment is that the ion signal from intense low mass to charge ratio 5 ions can be prevented from reaching the ion detector reducing the possibility of detector saturation and increasing the lifetime of the detector.
Preferably, ions having a mass to charge ratio 2 a value M1' are substantially injected or orthogonally 10 accelerated into said drift region by said electrode with a first transmission efficiency and ions having a mass to charge ratio in the range M1-M1' are substantially injected or orthogonally accelerated into said drift region by said electrode with a second 15 transmission efficiency lower than said first transmission efficiency, wherein M1 < M1'.
Preferably, M1' falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250i (vi) 250-300; (vii) 20 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500i (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950- 1000; (xxi) 1000-1500; (xxii) 1500-2000i (xxtii) 2000-2500; (xxiv) 2500- 3000; 25 and (xxv) > 3000.
After the ion gate has been switched from the first (ON) mode to the second (OFF) mode the pusher electrode is then energised after a delay time ATE, wherein ATl preferably falls within a range selected from the group 30 consisting of: (i) 0.1-1 psi (ii) 1-5 psi (iii) 5-10 psi (iv) 1015 psi (v) 15-20 psi (vi) 20-50 psi (vii) 50-100 psi (viii) 100-500 jUS; and (ix) 500-1000 As.
The low mass cut-off M1 preferably falls within a range selected from the group consisting of: (i) 1-5; 35 (ii) 5-10; (iii) 10-15; (iv) 15-20; (v) 20-25; (vi) 25 30; (vii) 30-35; (viii) 35-40; (ix) 40-45i (x) 45-50; (xi) 50-55; (xii) 55-60; (xiii) 60-65; (xiv) 65-70; (xv)
-3 70-75; (xvi) 75-100; (xvii) 100-150; (xviii) 150-200; (xix) 200-250; (xx) 250-300; (xxi) 300-350; (xxii) 350 400; (xxiii) 400-450; (xxiv) 450500; (xxv) 500-550; (xxvi) 550-600; (xxvii) 600-650; (xxviii) 650-700; 5 (xxix) 700-750; (xxx) 750-800; (xxx)) 800-850; (xxxii) 850-900; (xxxiii) 900-950; (xxxiv) 950-1000; and (xxxv) > 1000.
Further preferably M1 is selected from the group consisting of: (i) 4; (ii) 17; (iii) 18; (iv) 28; (v) 10 29; (vi) 40; (vii) 41; (viii) 93; (ix) 139; (x) 185; (xi) 37g; and (xii) 568.
Preferably, immediately after said control means has caused said electrode to inject or orthogonally accelerate ions into said drift region at time T,+GT 15 said control means switches said ion gate from said second mode to said first mode.
According to a second aspect of the present invention, there is provided a mass spectrometer comprising: 20 an ion source; an orthogonal acceleration Time of Flight mass analyses comprising an electrode for orthogonally accelerating ions, an ion detector and a drift region therebetween; 25 an ion gate upstream of the electrode) and control means for switching the ion gate between a first mode and a second mode, the second mode having a lower ion transmission efficiency than the first mode, wherein in a mode of operation the control means: 30 (i) switches the ion gate from the second mode to the first mode at a time T i and (ii) causes the electrode to inject or orthogonally accelerate ions into the drift region at a later time T TAT.;
35 wherein AT' is set such that ions having a mass to charge ratio > a value M3 are not substantially injected or orthogonally accelerated into the drift region by the
( -4 electrode. The embodiment enables high mass to charge ratio ions to be excluded from being orthogonally accelerated or otherwise injected into the drift region of the Time 5 of Flight mass analyses.
Preferably, ions having a mass to charge ratio < a value M3' are substantially injected or orthogonally accelerated into said drift region by said electrode with a first transmission efficiency and ions having a 10 mass to charge ratio in the range M3'-M3 are substantially injected or orthogonally accelerated into said drift region by said electrode with a second transmission efficiency lower than said first transmission efficiency, wherein M3' < M3.
15 Preferably, M3' falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-lOOi (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-3S0; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; 20 (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000- 2500; (xxiv) 2500-3000; and (xxv) > 3000.
The ion gate is switched from the second (OFF) mode 25 to the first (ON) mode and then after a delay time ATE the pusher electrode is energized. AT2 preferably falls within a range selected from the group consisting of: (i) 0.1-1 psi (ii) 1-5 psi (iii) 5-10 psi (iv) 10-15 psi (v) 15-20 psi (vi) 20-50 psi (vii) 50-100 psi (viii) 30 100-500 us; and (ix) 500- 1000 ps.
The high mass to charge ratio cut-off M3 preferably falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 100150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350 35 400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550 600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950 i
-5 (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
Preferably, immediately after said control means has caused said electrode to inject or orthogonally 5 accelerate ions into said drift region at time T;+AT said control means switches said ion gate from said first mode to said second mode.
According to a third aspect of the present invention, there is provided a mass spectrometer 10 comprising: an ion source; an orthogonal acceleration Time of Flight mass analyses comprising an electrode for orthogonally accelerating ions, an ion detector and a drift region 15 therebetween; an ion gate upstream of the electrode; and control means for switching the ion gate between a first mode and a second mode, the second mode having a lower ion transmission efficiency than the first mode, 20 wherein in a mode of operation the control means: (i) switches the ion gate from the second mode to the first mode at a time To; (ii) switches the ion gate from the first mode to the second mode at a later time T3+5T; and 25 (iii) causes the electrode to inject or orthogonally accelerate ions into the drift region at a yet later time T3+6T3+AT; wherein bT3 and AT3 are set such that ions having a mass to charge ratio < a value M1 are not substantially 30 injected or orthogonally accelerated into the drift region by the electrode and such that ions having a mass to charge ratio > a value M3 are not substantially injected or orthogonally accelerated into the drift region by the electrode, wherein M1 < M3.
35 According to this embodiment only ions within a certain bandpass are orthogonally accelerated or otherwise injected into the drift region of the Time of
-6- Flight mass analyses. This enables low mass to charge ratio background ions and high mass to charge ratio
background ions to be filtered out.
Preferably, ions having a mass to charge ratio M2 5 are substantially injected or orthogonally accelerated into said drift region by said electrode with a first transmission efficiency and other ions having a mass to charge ratio in the range M1-M3 are substantially injected or orthogonally accelerated into said drift 10 region by said electrode with a second transmission efficiency lower than said first transmission efficiency, wherein M1 < M2 < M3. M2 preferably falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 100150; (iv) 150-200; (v) 15 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750 800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; 20 (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
According to another form of the third embodiment, ions having a mass to charge ratio in a range M1'-M3' are substantially injected or orthogonally accelerated into said drift region by said electrode with a first 25 transmission efficiency and ions having a mass to charge ratio in the range M1-M1' and M3'-M3 are substantially injected or orthogonally accelerated into said drift region by said electrode with a second transmission efficiency lower than said first transmission 30 efficiency, wherein M1 < M1' < M3' < M3.
M1' preferably falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 35 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950i (xx) 950- 1000; (xxi) 1000-1500;
! (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
M3' preferably falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 5 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950- 1000; (xxi) 1000-1500; 10 (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
The length of time bT3 that the ion gate remains in the first (ON) mode preferably falls within a range selected from the group consisting of: (i) 0.1-1 psi 15 (ii) 1-5 psi (iii) 5-10 psi (iv) 10-15 psi (v) 15-20 psi (vi) 20-50 as; (vii) 50-100 psi (viii) 100-500 psi and (ix) 500-1000 us.
The delay time AT; preferably falls within a range selected from the group consisting of: (i) 0.1-1 psi 20 (ii) 1-5 psi (iii) 5-10 psi (iv) 10psi (v) 15-20 us; (vi) 20-50 Nisi (vii) 50-100 us; (viii) 100-500 psi and (ix) 500-1000 ps.
M1 preferably falls within a range selected from the group consisting of: (i) 1-5; (ii) 5-10; (iii) 10 25 15; (iv) 15-20; (v) 20-25; (vi) 25-30; (vii) 30-35; (viii) 35-40; (ix) 40-45; (x) 45-50; (xi) 50-55; (xii) 55-60; (xiii) 60-65; (xiv) 65-70; (xv) 70-75; (xvi) 75 100; (xvii) 100-150; (xviii) 150-200; (xix) 200-250i (xx) 250-300; (xxi) 300-350; (xxTi) 350400; (xxiii) 30 400-450; (xxiv) 450-500; (xxv) 500-550; (xxvi) 550-600; (xxvii) 600-650; (xxviii) 650-700; (xxix) 700-750; (xxx) 750-800; (xxx)) 800-850; (xxxii) 850-900; (xxxiii) 900 950; (xxxiv) 950-1000; and (xxxv) > 1000.
M3 preferably falls within a range selected from 35 the group consisting of: (i) 1-50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250i (vi) 250-300; (vii) 300350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi)
-8 - ! 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; 5 and (xxv) > 3000.
According to a fourth aspect of the present invention, there is provided a mass spectrometer comprising: an ion source; 10 an orthogonal acceleration Time of Flight mass analyses comprising an electrode for orthogonally accelerating ions, an ion detector and a drift region therebetween; an ion gate upstream of said electrode; and 15 control means for switching said ion gate between a first mode and a second mode, said second mode having a lower ion transmission efficiency than said first mode, wherein in a mode of operation said control means: (i) switches said ion gate from said first mode to 20 said second mode at a time To; (ii) switches said ion gate from said second mode to said first mode at a later time T4+6T4; and (iii) causes said electrode to inject or orthogonally accelerate ions into said drift region at a 25 yet later time T4+6T4+AT; wherein ST4 and AT4 are set such that ions having a mass to charge ratio equal to a value M2 are not substantially injected or orthogonally accelerated into said drift region by said electrode.
30 Preferably, M2 falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; 35 (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 9501000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 25003000;
( - 9-
and (xxv) > 3000.
Preferably, ions having a mass to charge ratio < a value M1 and ions having a mass to charge ratio 2 a value M3 are substantially injected or orthogonally 5 accelerated into said drift region by said electrode with a first transmission efficiency, and wherein ions having a mass to charge in the range M1-M3 are substantially injected or orthogonally accelerated into said drift region by said electrode with a second 10 transmission efficiency lower than said first transmission efficiency, wherein M1 < M2 < M3.
According to a fifth aspect of the present invention, there is provided a mass spectrometer comprising: 15 an ion source; an orthogonal acceleration Time of Flight mass analyser comprising an electrode for orthogonally accelerating ions, an ion detector and a drift region therebetween; 20 an ion gate upstream of said electrode; and control means for switching said ion gate between a first mode and a second mode, said second mode having a lower ion transmission efficiency than said first mode, wherein in a mode of operation said control means: 25 (i) switches said ion gate from said first mode to said second mode at a time T4; (ii) switches said ion gate from said second mode to said first mode at a later time T4+6T4; and (iii) causes said electrode to inject or 30 orthogonally accelerate ions into said drift region at a yet later time T+ 6T4+AT4; wherein bT4 and AT4 are set such that ions having a mass to charge ratio in a range M1'M3' are not substantially injected or orthogonally accelerated into 35 said drift region by said electrode, wherein M1' < M3'.
Preferably, M1' falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii)
( -10
100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 5 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) 3000.
Preferably, M3' falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 10 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450i (x) 450-500; (xi) 500-550i (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 9501000i (xxi) 1000-1500; 15 (xxii) 1500-2000i (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
Preferably, ions having a mass to charge ratio < a value Ml and ions having a mass to charge ratio > a value M3 are substantially injected or orthogonally 20 accelerated into said drift region by said electrode with a first transmission efficiency and ions having a mass to charge ratio in the range M1-M1' and ions having a mass to charge ratio in the range M3'M3 are substantially injected or orthogonally accelerated into 25 said drift region by said electrode with a second transmission efficiency lower than said first transmission efficiency, wherein M1 < M1' < M3' < M3.
Preferably, M1 falls within a range selected from the group consisting of: (i) 1-5; (ii) 5-lOi (iii) 10 30 15; (iv) 15-20; (v) 20-25; (vi) 25-30; (vii) 30-35; (viii) 35-40; (ix) 40-45; (x) 45-50; (xi) 50-55; (xii) 5560; (xiii) 60-65; (xiv) 65-70; (xv) 70-75; (xvi) 75 100; (xvii) 100-150; (xviii) 150-200; (xix) 200-250; (xx) 250-300i (xxi) 300-350; (xxii) 3S0400; (xxiii) 35 400-450i (xxiv) 450-500; (xxv) 500-550; (xxvi) 550-600; (xxvii) 600-650i (xxviii) 650-700i (xxix) 700-750; (xxx) 750-800; (xxx)) 800-850; (xxxTi) 850-900; (xxxTii) 900
- 1 1 950; (xxxiv) 950-1000; and (xxxv) > 1000.
Preferably, M3 falls within a range selected from the group consisting of (i) 1-50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250300; (vii) 5 300-350; (viii) 350-400; (lx) 400-450i (x) 450-500; (xi) 500550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; 10 and (xxv) > 3000 Preferably, the period of time bT4 that the ion gate is switched to the second (OFF) mode falls within a range selected from the group consisting of: (i) 0.1-1 psi (ii) 1-5 psi (iii) 5-10 psi (iv) 10-15 psi (v) 15-20 15 us; (vi) 20-50 psi (vii) 50-100 psi (viii) 100-500 psi and (ix) 500-1000 Us.
Preferably, the delay time ATE falls within a range selected from the group consisting of: (i) 0.1-1 use (ii) 1-5 psi (iii) 5-10 psi (iv) 10-15 psi (v) 15-20 psi 20 (vi) 20-50 psi (vii) 50-100 psi (viii) 100-500 psi and (ix) 500-1000 ps.
Common to all embodiments the electrode preferably comprises a pusher and/or puller electrode. The ion gate may comprise one or more electrodes for altering, 25 deflecting, reflecting, defocusing, attenuating or blocking a beam of ions. Preferably, in said second mode said ion transmission efficiency is substantially 0 but according to a less preferred embodiment in said second mode said ion transmission efficiency is < xt of 30 the ion transmission efficiency in said first mode, wherein x falls within a range selected from the group consisting of: (i) 0.001-0. 01; (ii) 0.01-0.1; (iii) 0.1-
1; (iv) l-10; and (v) 10-90.
Preferably, the electrode is repeatedly energised 35 with a frequency selected from the group consisting of: (i) 100-500 Hz; (ii) 0.5-1 kHz; (iii) 1-5 kHz; (iv) 5-10 kHz; (v) 10-20 kHz; (vi) 20-30 kHz; (vii) 30-40 kHz;
-12 (viii) 40-50 kHz; (ix) 50-60 kHz; (x) 60-70 kHz; (xi) 70-80 kHz; (xii) 80-90 kHz; (xiii) DO-100 kHz; (xiv) 100-500 kHz; (xv) 0.5-1 MHz; and (xvi) > 1 MHz.
The ion source preferably comprises a continuous 5 ion source. For example, the ion source may be selected from the group consisting of: (i) an Electron Impact ("EI") ion source; (ii) a Chemical Ionisation ("CI") ion source; (iii) a Field Ionisation ("FI") ion source; (iv)
an Electrospray ion source; (v) an Atmospheric Pressure 10 Chemical Ionisation ("APCI") ion source; (vi) an Inductively Coupled Plasma ("ICP") ion source) (vii) an Atmospheric Pressure Photo Ionisation ("APPI") ion source; (viii) a Fast Atom Bombardment ("FAB") ion source; and (ix) a Liquid Secondary Ions Mass 15 Spectrometry ("LSIMS") ion source.
According to a less preferred embodiment the ion source is a pseudocontinuous ion source. For example, the ion source may be selected from the group consisting of: (i) a Matrix Assisted Laser Desorption Ionisation 20 ("MALDI") ion source; and (ii) a Laser Desorption Ionisation ("LDI") ion source. Preferably, an RF ion guide comprising a collision gas for dispersing a packet of ions emitted by said ion source is provided.
The ion source may he coupled to a liquid or gas 25 chromatography source.
According to a sixth aspect of the present invention, there is provided a method of mass spectrometry, comprising: switching an ion gate from a first mode to a second 30 mode at a time To, said second mode having a lower ion transmission efficiency than said first mode; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of Flight mass analyser at a later time T+6Tli 35 wherein ATE is set such that ions having a mass to charge ratio < a value M1 are not substantially injected or orthogonally accelerated into said drift region.
-13 According to a seventh aspect of the present invention, there is provided a method of mass spectrometry, comprising: 5 switching an ion gate from a second mode to a first mode at a time T2, said second mode having a lower ion transmission efficiency than said first mode; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of 10 Flight mass analyses at a later time T2+6T2i wherein AT is set such that ions having a mass to charge ratio 2 a value M3 are not substantially injected or orthogonally accelerated into said drift region.
According to an eighth aspect of the present 15 invention, there is provided a method of mass spectrometry, comprising: switching an ion gate from a second mode to a first mode at a time T., said second mode having a lower ion transmission efficiency than said first mode; 20 switching said ion gate from said first mode to said second mode at a later time T:+ 5T3; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of Flight mass analyses at a yet later time T:+oT+AT3; 25 wherein GT3 and AT3 are set such that ions having a mass to charge ratio a value M1 are not substantially injected or orthogonally accelerated into said drift region and such that ions having a mass to charge ratio > a value M3 are not substantially injected or 30 orthogonally accelerated into said drift region, wherein M1 < M3.
According to a ninth aspect of the present invention, there is provided a method of mass spectrometry, comprising: 35 switching an ion gate from a first mode to a second mode at a time Tq, said second mode having a lower ion transmission efficiency than said first mode;
f -14 switching said ion gate from said second mode to said first mode at a later time T4+oT; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of 5 Flight mass analyser at a yet later time T4+5T4+AT4; wherein bT4 and AT4 are set such that ions having a mass to charge ratio equal to a value M2 are not substantially injected or orthogonally accelerated into said drift region.
10 According to a tenth aspect of the present invention, there is provided a method of mass spectrometry, comprising: switching an ion gate from a first mode to a second mode at a time T4, said second mode having a lower ion 15 transmission efficiency than said first mode; switching said ion gate from said second mode to said first mode at a later time T4+ oT; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of 20 Flight mass analyses at a yet later time T4+oT<+AT4; wherein BT4 and AT4 are set such that ions having a mass to charge ratio in a range M1'-M3' are not substantially injected or orthogonally accelerated into said drift region, wherein M1' < M3'.
25 In the present application where reference is made to ions having a mass to charge ratio this is intended to mean ions having a mass to charge ratio measured in units of daltons.
Various embodiments of the present invention will 30 now be described, by way of example only, and with reference to the accompanying drawings in which: Fig. 1 shows a preferred mass spectrometer; Fig. 2 illustrates a first embodiment wherein relatively low mass to charge ratio ions are prevented 35 from reaching the ion detector; Fig. 3 illustrates ions of different mass to charge ratios adjacent the pusher electrode according to the
-15 first embodiment; Fig. 4 shows the relative transmission of ions as a function of mass to charge ratio according to the first embodiment; 5 Fig. 5 illustrates a second embodiment wherein relatively high mass to charge ratio ions are prevented from reaching the ion detector, Fig. 6 shows the relative transmission of ions as a function of mass to charge ratio according to the second 10 embodiment; Fig. 7 illustrates a third embodiment wherein both relatively low mass to charge ratio ions and relatively high mass to charge ratio ions are prevented from reaching the ion detector; 15 Fig. 8 shows the relative transmission of ions as a function of mass to charge ratio according to the third embodiment; Fig. 9 shows the relative transmission of ions as a function of mass to charge ratio according to a 20 variation of the third embodiment) Fig. lo illustrates a fourth embodiment wherein only ions having a relatively narrow range of mass to charge ratios are prevented from reaching the ion detector; 25 Fig. 11 shows the relative transmission of ions as a function of mass to charge ratio according to the fourth embodiment) Fig. 12 shows the relative transmission of ions as a function of mass to charge ratio according to a 30 variation of the fourth embodiment; Fig. 13(a) shows a timing diagram for the first embodiment, Fig. 13(b) shows a timing diagram for the second embodiment, Fig. 13(c) shows a timing diagram for the third embodiment, and Fig. 13(d) shows a timing 35 diagram for the fourth embodiment) Fig. 14(a) shows a mass spectrum obtained according to the first embodiment and Fig. 14(b) shows a
-16 corresponding mass spectrum obtained conventionally; Figs. 15(a) shows the same mass spectrum shown in Fig. 14(a) but displayed over the reduced mass to charge ratio range 15-200 daltons, Fig. 15(b) shows the same 5 mass spectrum shown in Fig. 14(b) but displayed over the reduced mass to charge ratio range 15-200 daltons, and Fig. 15(c) shows the theoretically calculated relative transmission as a function of mass to charge ratio according to the first embodiment) and 10 Fig. 16(a) shows the same mass spectrum as shown in Fig. 14(a) and Fig. 15(a) but displayed over the yet further reduced mass to charge ratio range 15-66 daltons with the intensity magnified by a factor of 280, and Fig. 16(b) shows the same mass spectrum as shown in Fig. 15 14(b) and Fig. 15(b) but displayed over the yet further reduced mass to charge ratio range 15-66 daltons.
Various embodiments of the present invention will now be described in more detail with reference to Fig. 1. Ions emitted by an ion source 1 pass to an 20 electrostatic device 2 arranged upstream of an acceleration chamber 3 of an orthogonal acceleration Time of Flight mass analyses. The electrostatic device 2 may comprise a single deflection electrode or more preferably a pair of electrodes arranged preferably in 25 parallel andfurther preferably connected to a voltage supply. The electrostatic device 2 is preferably used to alter, deflect, reflect, defocus/ attenuate or block an ion beam incident upon the device 2.
In one embodiment the electrostatic device 2 does 30 not have any attenuating voltage applied to the device 2 when the device 2 is ON. When the device 2 is OFF a voltage is applied to device 2 in order to deflect ions.
The electrostatic device 2 acts as an ion gate 2 allowing ions to be transmitted in a first (ON) mode.
35 In a second (OFF) mode the ion gate 2 substantially reduces, preferably prevents, ions from being onwardly transmitted to the Time of Flight mass analyses.
( -17 The ion gate 2 is preferably positioned in a field
free region of ion transfer optics between the ion source 1 and the orthogonal acceleration pusher electrode 4 which forms part of an orthogonal 5 acceleration Time of Flight mass analyses. The orthogonal acceleration Time of Flight mass analyser comprises a pusher electrode 4, a drift region 5, an optional reflection 6 and an ion detector 7. The voltage supply to the ion gate 2 is preferably capable 10 of being switched ON/OFF in approximately 100 ns.
According to the first embodiment the ion gate 2 is set to be ON for the majority of a cycle Tc so as to transmit ions. In order to discriminate against ions with low mass to charge ratios the ion gate 2 is 15 switched to be OFF for preferably a relatively short period of time ATI. A short time AT' after the ion gate 2 has been switched OFF a pusher voltage is applied to the orthogonal acceleration pusher electrode 4. As soon as the pusher voltage is applied the ion gate 2 is 20 preferably switched back to ON. The ion gate 2 preferably remains ON until the beginning of the next cycle T. when it is again switched OFF. This cycle of switching the ion gate 2 ON/OFF may be repeated many times during one experimental run.
25 Fig. 2 shows a schematic representation of a mode of operation of the mass spectrometer according to the first embodiment. It is assumed that a continuous ion beam is arriving at the ion gate 2. The ions transmitted by the ion gate 2 continue to the region 30 adjacent the pusher electrode 4. The distance from the ion gate 2 to the pusher electrode 4 may be defined as L1, the length of the pusher electrode may be defined as L2 and the distance from the pusher electrode 4 to the ion detector 7 may be defined as L3. For ease of 35 illustration only, the ion detector 7 is shown as being the same length L2 as the pusher electrode 4 although this is not relevant to the principle of operation.
-18 Low mass to charge ratio ions having a mass to charge ratio < M1 have passed the pusher electrode 4 before it is energized whereas ions having a mass to charge ratio > M1 are disposed opposite the pusher 5 electrode 4 and hence are orthogonally accelerated by the pusher electrode 4 into the drift region 5 of the Time of Flight mass analyses. Ions having a mass to charge ratio > M1' are orthogonally accelerated with a relative transmission of 100S and ions having a mass to 10 charge ratio in the range M1-M1' are orthogonally accelerated with a relative transmission between 0'! and 100 -i. The relative transmission is shown and explained in more detail in relation to Fig. 4.
In an orthogonal acceleration Time of Flight mass 15 spectrometer the acceleration of ions into the drift region 5 of the Time of Flight mass analyses is orthogonal to the axial direction of the ion beam and hence the axial component of velocity of the ions remains unchanged. Therefore, the time taken for ions 20 to pass through the drift region 5 of the Time of Flight mass analyser to the ion detector 7 is the same as the time it would have taken for the ions to have travelled the axial distance L2+L3 from the end of the pusher electrode 4 closest to the ion gate 2 to the ion 25 detector 7 had they not been accelerated into the drift region 5.
If the maximum mass to charge ratio of ions arranged to be analyzed by the mass analyses is Mrr,TX then the cycle time T. between consecutive pulses of ions into 30 the drift region 5 is the time required for ions of mass to charge ratio MAX to travel the distance L2+L3 from the pusher electrode 4 to the ion detector 7. In addition to showing the positions of ions having mass to charge ratios equal to M1 and Ml' at the time the pusher 35 electrode 4 is about to be energized, Fig. 2 also shows the position of ions having a mass to charge ratio M[TI;X at the time the voltage is about to be applied to the
-19 pusher electrode 4. The ions are orthogonally accelerated in the drift region 5 after a delay time AT1 since the ion gate 2 was switched from ON to OFF.
Ions of mass to charge ratio equal to Ml have 5 travailed the distance Ll+ L2 since the ion gate 2 was switched OFF and therefore ions having a mass to charge ratio < Ml will not be transmitted into the drift region 5 of the Time of Flight mass analyses. Ions having a mass to charge ratio Ml' have travelled the distance Ll lo since the ion gate 2 was switched OFF and these ions will be transmitted into the Time of Flight mass analyses with a relative transmission of l00;,.
If the ions have an energy of zeV electron volts, distances are in metres, and ATE is in us, then the value 15 of Ml in daltons is given by: M1 VA71 2
20 5184(1,1+L2)2
and the value of Ml' in daltons is given by: M1' V.7,2
51841,12
30 hence: M1'= M1.(1+L2)
The relative transmission TO of ions into the drift region 5 is equal to the relative proportion of the 40 space opposite the pusher electrode occupied by ions of mass to charge ratio M. Accordingly: Ll +L2-L Tr = L2 or
-20 Tr = 1- L (1 -11) 5 where L is the distance travelled by ions with mass to charge M: 10 _ A7
L- - _
hence: Tr=l- -. -Ill [2 lo 72 M) Fig. 3 is similar to Fig. 2 and shows the disposition of ions having various different mass to charge ratios at the time T+AT, when the pusher electrode 4 is energized. Ions having a mass to charge 25 ratio < M1 are not orthogonally accelerated, ions having a mass to charge ratio in the range Ml-M1' are orthogonally accelerated with a relative transmission < 100; and ions having a mass to charge ratio 2 M1' are orthogonally accelerated with a relative transmission of 30 100':.
Fig. 4 shows the relative transmission as a function of mass to charge ratio according to the first embodiment for an ion energy of PO eV, delay time AT: of us and wherein L1 was 110 mm, L2 was 30 mm, L3 was 114 35 mm. Mm.X was set to 1500 daltons. For these values M1 equals 32 daltons and M1' equals 52 daltons.
Accordingly, ions having a mass to charge ratio < 32 daltons are not orthogonally accelerated whereas ions having a mass to charge ratio > 52 daltons are 40 orthogonally accelerated with 100;, relative transmission. Ions having a mass to charge ratio between 32 and 52 daltons are orthogonally accelerated with a relative transmission between 0' and look.
Any ions present with a mass to charge ratio value 45 equal to Mm'X will have a 100':, relative transmission provided that the distance L1 is not greater than the
-21 distance L3. Fig. 2 shows that ions with a mass to charge ratio equal to Mare from a first cycle A are separated from ions having the same mass to charge from a second subsequent cycle B by a small gap. This gap is 5 due to the effect of the ion gate 2 from the previous cycle A and corresponds with the period of time when no ions are transmitted by the ion gate 2. Fig. 2 shows where this gap will exist at the time the pusher voltage is about to be applied to the pusher electrode 4. As 10 can be seen, this gap starts a distance L1 before the ion detector 7 and accordingly if L1 is greater than L3 then the gap could appear in the region adjacent the pusher electrode 4. This would lead to a small reduction in transmission depending on the relative 15 values of the parameters L1, L2, L3, ATIand T. Any potential loss in transmission can be avoided if L1 is not greater than L3 and hence preferably the distance L1 is arranged to be less than L3.
According to the first embodiment ions having a 20 relatively low mass to charge ratio are substantially prevented from being orthogonally accelerated in the drift region 5 of the Time of Flight mass analyses.
This is particularly advantageous in a number of different situations. For example, with an Electron 25 Impact ("EI") ion source He. ions (m/z = 4) from the carrier gas for the Gas Chromatograph or N2+ ions (m/z = 28) from air may be particularly intense and can advantageously be excluded according to this embodiment.
With a Chemical Ionisation ("CI") ion source using 30 methane as the reagent gas C:H+ ions (m/z = 29), CH5+ ions (m/z = 17) and C3Hryt ions (m/z = 41) may be particularly intense and can advantageously be excluded according to this embodiment. Similarly, when using ammonia as the reagent gas NH4+ ions (m/z = 18) may be 35 particularly intense and can advantageously be excluded according to this embodiment.
The preferred embodiment is also suitable for use
! -22
with other types of ion source. For example, with an ICP ion source Are ions (m/z = 40) may be particularly intense and can be advantageously excluded according to this embodiment.
5 With a Matrix Assisted Laser Desorption Ionisation ("MALDI") ion source there are numerous different background ions which may be generated due to the
various matrices used. For examples, ions having a mass to charge ratio of 379 and 568 which correspond with the 10 dimer and trimer of the matrix alpha cyano-4-
hydroxycinnamic acid can be particularly intense.
Similarly, ions having a mass to charge ratio of 139 are observed when using 2,5, dibydroxybenzoic acid (DHB) as the MALDI matrix. These ions can be advantageously 15 excluded according to either the first embodiment or according to one of the further embodiments described in more detail below.
With a Liquid Secondary Ion Mass Spectrometry ("LSIMS") or Fast Atom Bombardment ("FAB") ion source 20 using glycerol as the matrix C3H90-+ ions (m/z = 93) and C,H170h ions (miz = 185) can be particularly intense and may be advantageously excluded according to the first embodiment or one of the further embodiments described in more detail below.
25 A second embodiment wherein relatively high mass to charge ratio ions may be excluded will now be described in relation to Fig. 5. Some ion sources have a continuum of background ions extending to quite high
mass to charge ratios and the background ions may in
30 some circumstances have higher mass to charge ratios than those of the analyte ions being analyzed. Such high mass to charge ratio ions may be of sufficient intensity to cause a problem with an orthogonal acceleration Time of Flight mass spectrometer. It is 35 normally necessary with an orthogonal acceleration Time of Flight mass analyser to wait until the ions having the highest mass to charge ratios arrive at the ion
-23 detector 7 before the pusher electrode 4 is energised again to orthogonally accelerate the next bunch of ions into the drift region 5. Otherwise, high mass to charge ratio ions from a first bunch of ions may arrive at the 5 ion detector 7 together with low mass to charge ratio ions from a subsequent second bunch of ions. These high mass to charge ratio ions would therefore contribute noise and would present artefact peaks within the resulting mass spectrum.
10 Also, where background ions extend to much higher
mass to charge ratios than the mass to charge ratio of the analyte ions this may make it necessary to wait for relatively long periods of time between pusher electrode pulses thereby reducing the duty cycle and hence 15 lowering the sensitivity of the mass spectrometer.
Accordingly, providing a high mass cut-off mode may be particularly advantageous in that this will eliminate noise and possible artefact peaks whilst maintaining the highest possible duty cycle and sensitivity.
20 According to the second embodiment the ion gate 2 is set to be OFF for the majority of a cycle so as to prevent ions being transmitted. In order to discriminate against ions with relatively high mass to charge ratios the ion gate 2 is switched to be ON for 25 preferably a relatively short period of time AT A short time LT2 after the ion gate 2 has been switched ON a pusher voltage is applied to the orthogonal acceleration pusher electrode 4. As soon as the pusher voltage is applied to the pusher electrode 4 the ion gate 2 is 30 preferably switched OFF. The ion gate 2 preferably remains OFF until the beginning of the next cycle T.: when it is again switched ON. This cycle of switching the ion gate 2 ON/OFF may be repeated many times during one experimental run.
35 Ions of mass to charge ratio M3' are those ions that have just travelled the axial distance L1+L2 since the ion gate 2 was switched ON. Accordingly, ions
-24 having a mass to charge ratio c M3' are orthogonally accelerated with a relative transmission of 100.
If the ions have an energy of zeV electron volts, distances are in metres, and AT2 is in us, then the value 5 of M3' in daltons is given by: M3' Y. AT2 2
10 5184 (LI+L2)2
and the value of M3 in daltons is given by: M3 V AT22
5184LI2
20 hence: M3 = M3' (1 + 1,2)
The relative transmission Tr of ions into the drift region 5 is equal to the relative proportion of the 30 space opposite the pusher electrode 4 occupied by ions of mass to charge ratio M, therefore: L-LI L2 7. or = or 40 7r=-(L-II) L2 where L is the distance travailed by ions with mass to charge M. Accordingly: Al', Iv L = I 50 72 \1 M
hence: Tr = _ 2 - LO 1,2 lo 72 M)
-25 Fig. 6 shows the relative transmission as a function of mass to charge ratio according to the second embodiment for an ion energy of 40 eV, delay time AT2 Of 15 ills and wherein L1 was 60 mm, L2 was 30 mm and L3 was 5 60 mm. MmaX was set to 800 daltons. For these values M3' equals 214 daltons and M3 equals 480 daltons.
Accordingly, ions having a mass to charge ratio < 214 daltons are orthogonally accelerated with a relative transmission of 100% whereas ions having a mass to 10 charge ratio > 480 daltons are not orthogonally accelerated. Ions having a mass to charge ratio between 214 and 480 daltons are orthogonally accelerated with a relative transmission between 0% and 100.
The ability to be able to filter out relatively 15 high mass to charge ratio ions is particularly advantageous with Gas Chromatograph ("GC") Mass Spectrometry where it is normally required to only analyze relatively low mass to charge ratio analyte ions, for example ions in the mass range 100-200 20 daltons. GC mass spectrometers can suffer from "bleed" peaks from the 5C column as high as 600-1000 daltons and it can therefore be necessary to have to wait until these ions arrive before firing the next pulse. Such an approach is obviously inefficient. This wait can be 25 eliminated by the use of the high mass cut-off method according to the second embodiment.
Fast Atom Bombardment ("FAB") and Liquid Secondary Ions Mass Spectrometry ("LSIMS") ion sources are notorious for giving a high level of background ions
30 having very high mass to charge ratios (e.g. 3000 daltons). The second embodiment is therefore particularly suitable for use with FAB and LSIMS ion sources. A third embodiment relating to bandpass 35 transmission mode of operation wherein both relatively high mass to charge ratio ions and relatively low mass to charge ratio ions are removed will now be described
-26 in relation to Fig. 7.
According to the third embodiment the ion gate 2 is set to be OFF for the majority of a cycle TO so as to prevent ions being transmitted. In order to 5 orthogonally accelerate only ions within a bandpass range of mass to charge ratios the ion gate 2 is switched to be ON for preferably a relatively short period of time GT3 A short time AT3 after the ion gate 2 has been switched back from ON to OFF a pusher voltage 10 is applied to the orthogonal acceleration pusher electrode 4. As soon as the pusher voltage is applied the ion gate 2 preferably remains switched OFF. The ion gate 2 preferably remains OFF until the beginning of the next cycle T. : when it is again switched ON for a 15 relatively short period of time. This cycle of switching the ion gate 2 ON/OFF may be repeated many times during one experimental run.
Ions of mass to charge ratio M1 are those ions that have just travelled the axial distance L1+L2 since the 20 ion gate 2 was switched from ON to OFF. Accordingly, ions having a mass to charge ratio < M1 are not orthogonally accelerated. Similarly, ions having a mass to charge ratio 2 M3 are not orthogonally accelerated.
Ions having a mass to charge ratio M2 are orthogonally 25 accelerated with a relative transmission of 100: and other ions having a mass to charge ratio within the range M1-M3 are orthogonally accelerated with a relative transmission between 0: and 100.
Fig. 8 shows the relative transmission as a 30 function of mass to charge ratio according to the third embodiment for an ion energy of 40 eV, oT3 of 3.25 As, delay time AT? of 6.5 ps and wherein L1 was 60 mm, L2 was 30 mm and L3 was 60 mm. MAX was set to 800 daltons. For these values M1 equals 40 daltons, M2 equals 90 daltons 35 and M3 equals 204 daltons. Accordingly, ions having a mass to charge ratio < 40 daltons are not orthogonally accelerated and similarly ions having a mass to charge
-27 ratio 2 204 daltons are not orthogonally accelerated.
Ions having a mass to charge ratio between 90 and 204 daltons are orthogonally accelerated with a relative transmission between 0% and 100%.
5 A variation of the third embodiment is contemplated wherein the range of ions orthogonally accelerated with 100 ; relative transmission is increased. This can be achieved by increasing the time oT 3 that the ion gate 2 is ON. This is illustrated further with reference to 10 Fig. 9 which shows the relative transmission as a function of mass to charge ratio according to the variation of the third embodiment for an ion energy of 40 eV, bT3 of 8.5 As, delay time ATE of 6.5 Us and wherein L1 was 60 mm, L2 was 30 mm and L3 was 60 mm.
15 MA was set to 800 daltons. For these values M1 equals 40 daltons, M1' equals 90 daltons, M3' equals 214 daltons and M3 equals 480 daltons. Accordingly, ions having a mass to charge ratio < 40 daltons are not; orthogonally accelerated and similarly ions having a 20 mass to charge ratio > 480 daltons are not orthogonally accelerated. Ions having a mass to charge ratio between 90 and 214 daltons are orthogonally accelerated with a relative transmission of 100% and ions having a mass to charge ratio between 40 and 90 daltons and between 214 25 and 480 daltons are orthogonally accelerated with a relative transmission between 0'c and 100.
A mass spectrometer according to the third embodiment may be used to filter out both relatively low mass to charge ratio ions and relatively high mass to 30 charge ratio ions as discussed above in relation to the first and second embodiments.
A fourth embodiment relating to bandpass filter mode of operation wherein only ions falling with a specific relatively narrow range of mass to charge 35 ratios are removed will now be described in relation to Fig. 10.
According to the fourth embodiment the ion gate 2
-28 is set to be ON for the majority of a cycle Tc so as to transmit ions. In order to orthogonally accelerate ions but not those falling within a specific range of mass to charge ratios the ion gate 2 is switched to be OFF for 5 preferably a relatively short period of time ETA A short time AT4 after the ion gate 2 has been switched back from OFF to ON a pusher voltage is applied to the orthogonal acceleration pusher electrode 4. As soon as the pusher voltage is applied the ion gate 2 preferably remains 10 switched ON. The ion gate preferably remains ON until the beginning of the next cycle T.: when it is again switched OFF. This cycle of switching the ion gate 2 ON/OFF may be repeated many times during one experimental run.
15 Ions of mass to charge ratio M1 are those ions that have just travelled the axial distance Ll+L2 since the ion gate 2 was switched from OFF to ON. Accordingly, ions having a mass to charge ratio < M1 are orthogonally accelerated with a relative transmission of 100Qj. Ions 20 having a mass to charge ratio 2 M3 are present from the previous cycle and are also orthogonally accelerated with a relative transmission of 100 6. Ions having a mass to charge ratio M2 are not orthogonally accelerated and other ions having a mass to charge ratio within the 25 range M1-M3 are orthogonally accelerated with a relative transmission between 0% and 100.
Fig. 11 shows the relative transmission as a function of mass to charge ratio according to the fourth embodiment for an ion energy of 40 eV, bT3 of 3.25 As, 30 delay time ATE of 6.5,us and wherein L1 was 60 mm, L2 was 30 mm and L3 was 60 mm. MA was set to 800 daltons.
For these values M1 equals 40 daltons, M2 equals 90 daltons and M3 equals 204 daltons. Accordingly, ions having a mass to charge ratio < 40 daltons are 35 orthogonally accelerated with 100'- relative transmission and similarly ions having a mass to charge ratio > 204 daltons are orthogonally accelerated with 100'' relative
-29 transmission. Ions having a mass to charge ratio between 90 and 204 daltons are orthogonally accelerated with a relative transmission between 0% and 100S, and ions having a mass to charge ratio of 90 daltons are not 5 orthogonally accelerated.
A variation of the fourth embodiment is contemplated wherein the range of ions not orthogonally accelerated is increased. This can be achieved by increasing the time that the ion gate 2 is closed. This 10 is illustrated further with reference to Fig. 12 which shows the relative transmission as a function of mass to charge ratio according to the variation of the fourth embodiment for an ion energy of 40 eV, ATE of 8.5 As, delay time AT: of 6.5 As and wherein L1 was 60 mm, L2 was 15 30 mm and L3 was 60 mm. Mrn.-,X was set to 800 daltons.
For these values M1 equals 40 daltons, M1' equals 90 daltons, M3' equals 214 daltons and M3 equals 480 daltons. Accordingly, ions having a mass to charge ratio < 40 daltons are orthogonally accelerated with 20 lOO'o relative transmission and similarly ions having a mass to charge ratio 2 480 daltons are orthogonally accelerated with loot relative transmission. Ions having a mass to charge ratio between 90 and 214 daltons are not orthogonally accelerated and ions having a mass 25 to charge ratio between 40 and 90 daltons and between 214 and 480 daltons are orthogonally accelerated with a relative transmission between Of and loot.
The mass spectrometer according to the fourth embodiment may be used, for example, with an ICP ion 30 source. An ICP ion source is used for analysis of elements but normally gives rise to a very intense peak at mass to charge ratio 40 due to Art ions from the argon plasma support gas. Therefore, since it may be desired to analyse both relatively low mass atomic ions such as 35 elements from lithium at mass to charge ratio to sulphur at mass to charge ratio 32 and relatively high mass atomic ions such as elements from scandium at mass
! -30 to charge ratio 45 to uranium and beyond on an orthogonal acceleration Time of Flight mass spectrometer then it would be highly beneficial to use the bandpass filtering mode of operation according to the fourth 5 embodiment wherein the intense argon ions at mass to charge ratio 40 can be effectively filtered out.
Fig. 13(a) shows a timing diagram for the first embodiment. The ion gate 2 is switched from ON to OFF at time To and then after a delay time ATl the pusher 10 electrode is energized (shown by an arrow) and immediately thereafter the ion gate 2 is switched back from OFF to ON, and remains ON for the rest of the cycle T (.. Fig. 13(b) shows a timing diagram for the second 15 embodiment. The ion gate 2 is switched from OFF to ON at time To and then after a delay time LT2 the pusher electrode is energised (shown by an arrow) and immediately thereafter the ion gate 2 is switched back from ON to OFF, and remains OFF for the rest of the 20 cycle Tc.
Fig. 13(c) shows a timing diagram for the third embodiment. The ion gate 2 is switched from OFF to ON at time To and remains ON for a time ATE. At time T3+ oT3 the ion gate 2 is switched back from ON to OFF and then 25 after a delay time AT: the pusher electrode is energized (shown by an arrow). The ion gate 2 remains OFF for the rest of the cycle T.:.
Fig. 13(d) shows a timing diagram for the fourth embodiment. The ion gate 2 is switched from ON to OFF 30 at time T4 and remains OFF for a time bT4. At time T4+ oT4 the ion gate 2 is switched back from OFF to ON and then after a delay time AT4 the pusher electrode is energized (shown by an arrow). The ion gate 2 remains ON for the rest of the cycle T.-.
35 Fig. 14 shows data obtained using an Electron Impact ("EI") ion source and the calibration compound Heptacosa (PFTBA) which was continuously introduced into
-31 an orthogonal acceleration Time of Flight mass spectrometer via a septum inlet. Fig. 14(a) shows a mass spectrum obtained when using low mass cut-off according to the first embodiment when L1 was 104 mm, L2 5 was 30 mm and L3 was 11 mm. The ion energy was 43 eV and the delay time AT1 was 9.0 As. An ion gate voltage of +9V was used. From these values M1 was calculated to be 37 daltons and M1' was calculated to be 62 daltons.
Fig. 14(b) shows a mass spectrum of Heptacosa (PFTBA) 10 obtained conventionally.
Fig. 15(a) shows the same mass spectrum shown in Fig. 14(a) but displayed over the reduced mass to charge range 15-200 daltons. Fig. 15(b) shows the same mass spectrum shown in Fig. 14(b) but displayed over the 15 reduced mass to charge range 15-200 daltons. Fig. 15(c) shows the theoretically calculated relative transmission as a function of mass to charge ratio according to the first embodiment. M1 and M1' are indicated by dotted lines on each diagram. It will be observed that there 20 is no loss of intensity for ions of mass to charge ratio > M1' (62 daltons) in the mass spectrum obtained according to the preferred embodiment compared with the mass spectrum obtained according to a conventional arrangement. 25 Fig. 16(a) shows the same mass spectrum as shown in Fig. 14(a) and Fig. 15(a) but displayed over the yet further reduced mass to charge range 15- 66 daltons with the intensity magnified by a factor of 280. Fig. 16(b) shows the same mass spectrum as shown in Fig. 14(b) and 30 Fig. 15(b) but displayed over the yet further reduced mass to charge range 15-66 daltons. These Figures illustrate the complete absence of ions having a mass to charge ratio < M1.
Although the present invention has been described 35 with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing
it -32 from the scope of the invention as set forth in the accompanying claims.

Claims (51)

  1. / -33
    76700004 v12 Claims
    5 1. A mass spectrometer comprising: an ion source; an orthogonal acceleration Time of Flight mass analyser comprising an electrode for orthogonally accelerating ions, an ion detector and a drift region 10 therebetween; an ion gate upstream of said electrode; and control means for switching said ion gate between a first mode and a second mode, said second mode having a lower ion transmission efficiency than said first mode, 15 wherein in a mode of operation said control means: (i) switches said ion gate from said first mode to said second mode at a time To; and (ii) causes said electrode to inject or orthogonally accelerate ions into said drift region at a 20 later time T1+AT1; wherein AT, is set such that ions having a mass to charge ratio < a value M1 are not substantially injected or orthogonally accelerated into said drift region by said electrode.
  2. 2. A mass spectrometer as claimed in claim 1, wherein ions having a mass to charge ratio > a value M1' are substantially injected or orthogonally accelerated into said drift region by said electrode with a first 30 transmission efficiency and ions having a mass to charge ratio in the range M1-M1' are substantially injected or orthogonally accelerated into said drift region by said electrode with a second transmission efficiency lower than said first transmission efficiency, wherein M1 < 35 M1'.
  3. 3. A mass spectrometer as claimed in claim 2, wherein
    -34 M1' falls within a range selected from the group consisting of: (i) 150; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; 5 (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700 750; (xvi) 750800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
  4. 4. A mass spectrometer as claimed in claim 1, 2 or 3, wherein ATl falls within a range selected from the group consisting of: (i) 0.1-1 psi (ii) 1-5 psi (iii) 5-10 psi (iv) 10-15 psi (v) 15-20 psi (vi) 20-50 us; (vii) 50-100 15 psi (viii) 100-500 psi and (ix) 500-1000 Us.
  5. 5. A mass spectrometer as claimed in any preceding claim, wherein M1 falls within a range selected from the group consisting of: (i) 1-5; (ii) 5-10; (iii) 10-15; 20 (iv) 15-20; (v) 20-25; (vi) 25-30; (vii) 30-35; (viii) 35-40; (ix) 40-45; (x) 45-50; (xi) 50-55; (xii) 55-60; (xiii) 60- 65; (xiv) 65-70; (xv) 70-75; (xvi) 75-100i (xvii) 100-150; (xviii) 150- 200; (xix) 200-250; (xx) 250-300; (xxi) 300-350; (xxii) 350-400; (xxiii) 400-450; 25 (xxiv) 450-500; (xxv) 500-550i (xxvi) 550-600; (xxvii) 600650; (xxviii) 650-700; (xxix) 700-750; (xxx) 750 800; (xxx)) 800-850; (xxxii) 850-900; (xxxTii) 900-950; (xxxiv) 950-1000; and (xxxv) > 1000.
    30
  6. 6. A mass spectrometer as claimed in any of claims 1-
    4, wherein M1 is selected from the group consisting of: (i) 4; (ii) 17; (iii) 18; (iv) 28; (v) 29; (vi) 40; (vii) 41; (viii) 93; (ix) 139; (x) 185; (xi) 379; and (xii) 568.
  7. 7. A mass spectrometer as claimed in any preceding claims, wherein immediately after said control means has
    -35 caused said electrode to inject or orthogonally accelerate ions into said drift region at time T1+AT, said control means switches said ion gate from said second mode to said first mode.
  8. 8. A mass spectrometer comprising: an ion source; an orthogonal acceleration Time of Flight mass analyses comprising an electrode for orthogonally 10 accelerating ions, an ion detector and a drift region therebetween; an ion gate upstream of said electrode; and control means for switching said ion gate between a first mode and a second mode, said second mode having a 15 lower ion transmission efficiency than said first mode, wherein in a mode of operation said control means: (i) switches said ion gate from said second mode to said first mode at a time T2; and (ii) causes said electrode to inject or 20 orthogonally accelerate ions into said drift region at a later time T2+AT; wherein AT2 is set such that ions having a mass to charge ratio > a value M3 are not substantially injected or orthogonally accelerated into said drift region by 25 said electrode.
  9. 9. A mass spectrometer as claimed in claim 8, wherein ions having a mass to charge ratio < a value M3' are substantially injected or orthogonally accelerated into 30 said drift region by said electrode with a first transmission efficiency and ions having a mass to charge ratio in the range M3'-M3 are substantially injected or orthogonally accelerated into said drift region by said electrode with a second transmission efficiency lower 35 than said first transmission efficiency, wherein M3' < M3.
    -36
  10. 10. A mass spectrometer as claimed in claim 9, wherein M3' falls within a range selected from the group consisting of: (i) 1-50; (ii) 50100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300350; 5 (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550600; (xiii) 600-650; (xiv) 650-700; (xv) 700-; 750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and 10 (xxv) > 3000.
  11. 11. A mass spectrometer as claimed in claim 8, 9 or 10, wherein AT2 falls within a range selected from the group consisting of: (i) 0.1-1 psi (ii) 1-5 psi (iii) 5-10 Us; 15 (iv) 10-15 psi (v) 15-20 psi (vi) 20-50 us; (vii) 50-100 psi (viii) 100-500 us; and (ix) 500-1000 us.
  12. 12. A mass spectrometer as claimed in any of claims 8 11, wherein M3 falls within a range selected from the 20 group consisting of: (i) 1-50; (ii) 50-100; (iii) 100 150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300 350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 25 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000. -
  13. 13. A mass spectrometer as claimed in any of claims 8 30 12, wherein immediately after said control means has caused said electrode to inject or orthogonally accelerate ions into said drift region at time T7+AT2 said control means switches said ion gate from said first mode to said second mode.
  14. 14. A mass spectrometer comprising: an ion source;
    -37 an orthogonal acceleration Time of Flight mass analyser comprising an electrode for orthogonally accelerating ions, an ion detector and a drift region therebetween; 5 an ion gate upstream of said electrode; and control means for switching said ion gate between a first mode and a second mode, said second mode having a lower ion transmission efficiency than said first mode, wherein in a mode of operation said control means: 10 (i) switches said ion gate from said second mode to said first mode at a time T?; (ii) switches said ion gate from said first mode to said second mode at a later time T-5T3; and (iii) causes said electrode to inject or
  15. 15 orthogonally accelerate ions into said drift region at a yet later time T3+ST3+ATl; wherein ST: and AT3 are set such that ions having a mass to charge ratio < a value M1 are not substantially injected or orthogonally accelerated into said drift 20 region by said electrode and such that ions having a mass to charge ratio > a value M3 are not substantially injected or orthogonally accelerated into said drift region by said electrode, wherein M1 < M3.
    25 15. A mass spectrometer as claimed in claim 14, wherein ions having a mass to charge ratio M2 are substantially injected or orthogonally accelerated into said drift region by said electrode with a first transmission efficiency and other ions having a mass to charge ratio 30 in the range M1-M3 are substantially injected or orthogonally accelerated into said drift region by said electrode with a second transmission efficiency lower than said first transmission efficiency, wherein Ml < M2 < M3.
  16. 16. A mass spectrometer as claimed in claim 15, wherein M2 falls within a range selected from the group
    -38 consisting of: (i) 1-50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700 5 750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
    10
  17. 17. A mass spectrometer as claimed in claim 14, wherein ions having a mass to charge ratio in a range M1'-M3' are substantially injected or orthogonally accelerated into said drift region by said electrode with a first transmission efficiency and ions having a mass to charge 15 ratio in the range Ml-M1' and M3'-M3 are substantially injected or orthogonally accelerated into said drift region by said electrode with a second transmission efficiency lower than said first transmission efficiency, wherein M1 < M1' < M3' < M3.
  18. 18. A mass spectrometer as claimed in claim 17, wherein M1' falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; 25 (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700 750; (xvi) 750-800; (xvii) 800- 850; (xviii) 850-900; (xix) 900-950; (xx) 9SO-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and 30 (xxv) > 3000.
  19. 19. A mass spectrometer as claimed in claim 17 or 18, wherein M3' falls within a range selected from the group consisting of: (i) 1-50; (ii) 50100; (iii) 100-150; 35 (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300350; (viii) 350-400; (ix) 400-450; (x) 450-500i (xi) 500-550; (xii) 550600; (xiii) 600-650; (xiv) 650-700; (xv) 700
    -39 750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900i (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500i (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
  20. 20. A mass spectrometer as claimed in any of claims 14 19, wherein ATfalls within a range selected from the group consisting of: (i) 0.1-1 psi (ii) 1-5 psi (iii) 5 10 Ids; (iv) 10-15 is; (v) 15-20 as; (vi) 20-50 psi (vii) 10 50-100 psi (viii) lOO-500 psi and (ix) SOO-1000 As.
  21. 21. A mass spectrometer as claimed in any of claims 14 20, wherein AT: falls within a range selected from the group consisting of: (i) 0.1-1 us; (ii) l-5 psi (iii) 5 15 10 psi (iv) 10-15 psi (v) 15-20 psi (vi) 20-50 psi (vii) 50-100 psi (viii) 100-500 psi and (ix) 500-1000 ps.
  22. 22. A mass spectrometer as claimed in any of claims 14 21, wherein M1 falls within a range selected from the 20 group consisting of: (i) 1-5i (ii) 5-10; (iii) 10-15; (iv) 15-20; (v) 20-25; (vi) 2530; (vii) 30-35; (viii) 35-40; (ix) 40-45; (x) 45-50; (xi) 50-55; (xTi) 55-60; (xiii) 6065; (xiv) 65-70; (xv) 70-75; (xvi) 75-100; (xvii) 100-150; (xviii) 150200; (xix) 200-250; (xx) 25 250-300; (xxi) 300-350; (xxTi) 350-400i (xxiii) 400-450; (xxiv) 450-500; (xxv) 500-550; (xxvi) 550-600; (xxvii) 600-650; (xxviii) 650-700; (xxix) 700-750; (xxx) 750 800; (xxx)) 800-850; (xxxii) 850-900; (xxxiii) 900-950; (xxxiv) 950-1000; and (xxxv) > 1000.
  23. 23. A mass spectrometer as claimed in any of claims 14 22, wherein M3 falls within a range selected from the group consisting of: (i) 1-50; (ii) 50-100; (iii) 100 150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300 35 350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii)
    -40 850-900; (xix) 900-950; (xx) g50-1000; (xxi) 1000-1500; (xxii) 15002000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
    5
  24. 24. A mass spectrometer comprising: an ion source; an orthogonal acceleration Time of Flight mass analyses comprising an electrode for orthogonally accelerating ions, an ion detector and a drift region 10 therebetween; an ion gate upstream of said electrode; and control means for switching said ion gate between a first mode and a second mode, said second mode having a lower ion transmission efficiency than said first mode, 15 wherein in a mode of operation said control means: (i) switches said ion gate from said first mode to said second mode at a time T4; (ii) switches said ion gate from said second mode to said first mode at a later time T4+6T4; and 20 (iii) causes said electrode to inject or orthogonally accelerate ions into said drift region at a yet later time T+ 6T4+AT; wherein bT4 and AT4 are set such that ions having a mass to charge ratio equal to a value M2 are not 25 substantially injected or orthogonally accelerated into said drift region by said electrode.
  25. 25. A mass spectrometer as claimed in claim 24, wherein M2 falls within a range selected from the group 30 consisting of: (i) 1-50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700 750; (xvi) 750-800; (xvii) 800850; (xviii) 850-900; 35 (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and (xxv) > 3000.
    ( -41
  26. 26 A mass spectrometer as claimed in claim 24 or 25, wherein ions having a mass to charge ratio < a value M1 and ions having a mass to charge ratio 2 a value M3 are 5 substantially injected or orthogonally accelerated into said drift region by said electrode with a first transmission efficiency, and wherein ions having a mass to charge in the range M1-M3 are substantially injected or orthogonally accelerated into said drift region by 10 said electrode with a second transmission efficiency lower than said first transmission efficiency, wherein M1 < M2 < M3.
  27. 27. A mass spectrometer comprising: 15 an ion source; an orthogonal acceleration Time of Flight mass analyses comprising an electrode for orthogonally accelerating ions, an ion detector and a drift region therebetween; 20 an ion gate upstream of said electrode; and control means for switching said ion gate between a first mode and a second mode, said second mode having a lower ion transmission efficiency than said first mode, wherein in a mode of operation said control means: 25 (i) switches said ion gate from said first mode to said second mode at a time T4; (ii) switches said ion gate from said second mode to said first mode at a later time T4+3T4; and (iii) causes said electrode to inject or 30 orthogonally accelerate ions into said drift region at a yet later time T4+6T4+AT4; wherein bT4 and AT4 are set such that ions having a mass to charge ratio in a range M1'-M3' are not substantially injected or orthogonally accelerated into 35 said drift region by said electrode, wherein M1' < M3'.
  28. 28. A mass spectrometer as claimed in claim 27, wherein
    -42 M1' falls within a range selected from the group consisting of: (i) 150; (ii) 50-100; (iii) 100-150; (iv) 150-200; tv) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; 5 (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700 750; (xvi) 750800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 1000-1500i (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000i and (xxv) > 3000.
  29. 29. A mass spectrometer as claimed in claim 27 or 28, wherein M3' falls within a range selected from the group consisting of: (i) 1-50; (ii) 50100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300350; 15 (viii) 350-400; (ix) 400-450; (x) 450-500i (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700i (xv) 700 750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 10001500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; and 20 (xxv) > 3000.
  30. 30. A mass spectrometer as claimed in claim 27, 28 or 29, wherein ions having a mass to charge ratio < a value Ml and ions having a mass to charge ratio > a value M3 25 are substantially injected or orthogonally accelerated into said drift region by said electrode with a first transmission efficiency and ions having a mass to charge ratio in the range M1-M1' and ions having a mass to charge ratio in the range M3'-M3 are substantially 30 injected or orthogonally accelerated into said drift region by said electrode with a second transmission efficiency lower than said first transmission efficiency, wherein M1 < M1' < M3' < M3.
    35
  31. 31. A mass spectrometer as claimed in claim 26 or 30, wherein M1 falls within a range selected from the group consisting of: (i) 1-5; (ii) 5-10; (iii) 10-15; (iv) 15
    ( -43
    20; (v) 20-25; (vi) 25-30; (vii) 30-35; (viii) 35-40; (ix) 90-45; (x) 4550; (xi) 50-55; (xii) 55-60; (xiii) 60-65; (xiv) 65-70; (xv) 70-75; (xvi) 75-100; (xvii) 100-150; (xviii) 150-200; (xix) 200-250; (xx) 250-300; 5 (xxi) 300-350; (xxii) 350-400; (xxiii) 400-450; (xxiv) 450-500; (xxv) 500-550i (xxvi) 550-600; (xxvii) 600-650; (xxviii) 650-700; (xxix) 700750; (xxx) 750-800; (xxx)) 800-850; (xxxii) 850-900; (xxxiii) 900-950; (xxxiv) 950 1000; and (xxxv) > 1000.
  32. 32. A mass spectrometer as claimed in claim 26, 30 or 31, wherein M3 falls within a range selected from the group consisting of (i) 1-50; (ii) 50-100; (iii) 100 150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300 15 350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; (xxi) 10001500; (xxii) 1500-2000; (xxiii) 2000-2500; (xxiv) 2500-3000; 20 and (xxv) > 3000.
  33. 33. A mass spectrometer as claimed in any of claims 24 32, wherein ST4 falls within a range selected from the group consisting of: (i) 0.1-1 us; (ii) 1-5 psi (iii) 5 25 10 psi (iv) 10-15 psi (v) 15-20 psi (vi) 20-50 psi (vii) 50-100 psi (viii) 100-500 as; and (lx) 500-1000 ps.
  34. 34. A mass spectrometer as claimed in any of claims 24 33, wherein AT4 falls within a range selected from the 30 group consisting of: (i) 0.1-1 psi (ii) 1-5 psi (iii) 5 10 as; (iv) 10-15 psi (v) 15-20 us; (vi) 20-50 Us; (vii) 50-100 us; (viii) 100-500 psi and (ix) 500-1000 As.
  35. 35. A mass spectrometer as claimed in any preceding 35 claim, wherein said electrode comprises a pusher and/or puller electrode.
    ( -44
  36. 36. A mass spectrometer as claimed in any preceding claim, wherein said ion gate comprises one or more electrodes for altering, deflecting, reflecting, defocusing, attenuating or blocking a beam of ions.
  37. 37. A mass spectrometer as claimed in any preceding claim, wherein in said second mode said ion transmission efficiency is substantially Off.
    10
  38. 38. A mass spectrometer as claimed in any of claims 1-
    36, wherein in said second mode said ion transmission efficiency is < xi of the ion transmission efficiency in said first mode, wherein x falls within a range selected from the group consisting of: (i) 0.001-0.01; (ii) 0.01 15 0.1; (iii) 0.1-l; (iv) 1-10; and (v) 10-90.
  39. 39. A mass spectrometer as claimed in any preceding claim, wherein said electrode is repeatedly energised with a frequency selected from the group consisting of: 20 (i) 100-500 Hz; (ii) 0.5-1 kHz; (iii) 1-5 kHz; (iv) 5-10 kHz; (v) 10-20 kHz; (vi) 20-30 kHz; (vii) 30-40 kHz; (viii) 40- 50 kHz; (ix) 50-60 kHzi (x) 60-70 kHz; (xi) 70-80 kHzi (xii) 80-90 kHz; (xiii) 90-100 kHz; (xiv) 100-500 kHz; (xv) 0.5-1 MHz; and (xvi) > 1 MHz.
  40. 40. A mass spectrometer as claimed in any preceding claim, wherein said ion source comprises a continuous ion source.
    30
  41. 41. A mass spectrometer as claimed in claim 40, wherein said ion source is selected from the group consisting of: (i) an Electron Impact ("EI") ion source; (ii) a Chemical Ionisation ("CI") ion source; (iii) a Field
    Ionisation ("FI") ion source; (iv) an Electrospray ion 35 source; (v) an Atmospheric Pressure Chemical Ionisation ("APCI") ion source; (vi) an Inductively Coupled Plasma ("ICP") ion source; (vii) an Atmospheric Pressure Photo
    -45 Ionisation ("APPI") ion source; (viii) a Fast Atom Bombardment ("FAB") ion source; and (ix) a Liquid Secondary Ions Mass Spectrometry ("LSIMS") ion source.
    5
  42. 42. A mass spectrometer as claimed in any of claims 1-
    39, wherein said ion source is a pseudo-continuous ion source.
  43. 43. A mass spectrometer as claimed in claim 42, 10 wherein said ion source is selected from the group consisting of: (i) a Matrix Assisted Laser Desorption Ionisation ("MALDI") ion source; and (ii) a Laser Desorption Ionisation ("LDI") ion source.
    15
  44. 44. A mass spectrometer as claimed in claim 43, further comprising an RF ion guide comprising a collision gas fox dispersing a packet of ions emitted by said ion source. 20
  45. 45. A mass spectrometer as claimed in any preceding claim, wherein said ion source is coupled to a liquid chromatography source.
  46. 46. A mass spectrometer as claimed in any of claims 1 25 44, wherein said ion source is coupled to a gas chromatography source.
  47. 47. A method of mass spectrometry, comprislug: switching an ion gate from a first mode to a second 30 mode at a time TZ, said second mode having a lower ion transmission efficiency than said first mode; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of Flight mass analyses at a later time Ti+AT,; 35 wherein ATl is set such that ions having a mass to charge ratio < a value M1 are not substantially injected or orthogonally accelerated into said drift region.
    -46
  48. 48. A method of mass spectrometry, comprising: switching an ion gate from a second mode to a first mode at a time T2, said second mode having a lower ion 5 transmission efficiency than said first mode; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of Flight mass analyser at a later time T2+AT2; wherein AT: is set such that ions having a mass to 10 charge ratio 2 a value M3 are not substantially injected or orthogonally accelerated into said drift region.
  49. 49. A method of mass spectrometry, comprising: switching an ion gate from a second mode to a first 15 mode at a time T3, said second mode having a lower ion transmission efficiency than said first mode; switching said ion gate from said first mode to said second mode at a later time T:+oT3; and injecting or orthogonally accelerating ions into a 20 drift region of an orthogonal acceleration Time of Flight mass analyser at a yet later time T+oT:+AT3; wherein OT3 and ATE are set such that ions having a mass to charge ratio < a value M1 are not substantially injected or orthogonally accelerated into said drift 25 region and such that ions having a mass to charge ratio > a value M3 are not substantially injected or orthogonally accelerated into said drift region, wherein M1 < M3.
    30
  50. 50. A method of mass spectrometry, comprising: switching an ion gate from a first mode to a second mode at a time T4, said second mode having a lower ion transmission efficiency than said first mode; switching said ion gate from said second mode to 35 said first mode at a later time T4+ 6T4; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of
    -47 Flight mass analyser at a yet later time T+5T4+AT4; wherein bT4 and AT4 are set such that ions having a mass to charge ratio equal to a value M2 are not substantially injected or orthogonally accelerated into 5 said drift region.
  51. 51. A method of mass spectrometry, comprising: switching an ion gate from a first mode to a second mode at a time T4, said second mode having a lower ion 10 transmission efficiency than said first mode; switching said ion gate from said second mode to said first mode at a later time T4+5T4; and injecting or orthogonally accelerating ions into a drift region of an orthogonal acceleration Time of 15 Flight mass analyses at a yet later time T4+oT4+AT4; wherein bT4 and AT4 are set such that ions having a mass to charge ratio in a range M1'-M3' are not substantially injected or orthogonally accelerated into said drift region, wherein M1' < M3'.
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EP1306881A3 (en) 2004-11-10
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EP1306881B1 (en) 2008-10-01
EP1306881A2 (en) 2003-05-02

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