METHOD AND APPARATUS FOR REDUCING SPACE CHARGE IN AN ION TRAP
First Claim
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1. A mass spectrometry apparatus, comprisinga first quadrupole;
- an exit lens; and
a linear ion trap disposed between the first quadrupole and the exit lens, the linear ion trap having a well-modulator quadrupole comprising at least two differently potentiated zones, defining at least two different sectors of the linear ion trap such that the linear ion trap is capable of being operated to form potential wells, alternately or simultaneously, in at least two different sectors of the linear ion trap, the sectors including a proximal sector nearer the first quadrupole and a distal sector nearer the exit lens,said linear ion trap being capable of operation whereby an ion population can be loaded from said first quadrupole into a well formed in said distal sector and, by manipulation of the potentials of differently potentiated zones of the well-modulator quadrupole, some of those ions can be transferred back to said first quadrupole by passage through a well formed in said proximal sector, the proximal sector well retaining a fraction of those ions,thereby preventing overfilling of the linear ion trap.
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Abstract
Ion trap apparatus and methods for efficiently addressing the effects of charge space caused by ion trap overfilling, useful in linear ion traps of mass spectrometers.
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Citations
25 Claims
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1. A mass spectrometry apparatus, comprising
a first quadrupole; -
an exit lens; and a linear ion trap disposed between the first quadrupole and the exit lens, the linear ion trap having a well-modulator quadrupole comprising at least two differently potentiated zones, defining at least two different sectors of the linear ion trap such that the linear ion trap is capable of being operated to form potential wells, alternately or simultaneously, in at least two different sectors of the linear ion trap, the sectors including a proximal sector nearer the first quadrupole and a distal sector nearer the exit lens, said linear ion trap being capable of operation whereby an ion population can be loaded from said first quadrupole into a well formed in said distal sector and, by manipulation of the potentials of differently potentiated zones of the well-modulator quadrupole, some of those ions can be transferred back to said first quadrupole by passage through a well formed in said proximal sector, the proximal sector well retaining a fraction of those ions, thereby preventing overfilling of the linear ion trap. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for mass spectrometry, comprising
(I) providing a mass spectrometry apparatus having a linear ion trap located between a first quadrupole of the device and the exit lens thereof, the linear ion trap comprising at least two sectors, including a proximal sector nearer said first quadrupole and a distal sector nearer said lens, each of the sectors being electrically potentiated differently from the other, (II) operating the mass spectrometer to transfer ions from the first quadrupole to the linear ion trap, (III) trapping transferred ions in a first sector of the linear ion trap that is maintained at a lower potential than that of the regions of the linear ion trap adjacent thereto, (IV) adjusting the potentials within the linear ion trap to transfer ions from the trapping sector to the adjacent first quadrupole and to retain a fraction of the ions in a second sector of said trap that is maintained at a lower potential than that of its adjacent regions in the linear ion trap, the second sector being the same or different from the first sector in step (III).
Specification