Radiant energy – Ionic separation or analysis
Reexamination Certificate
2003-05-30
2004-09-21
Wells, Nikita (Department: 2881)
Radiant energy
Ionic separation or analysis
C250S287000, C250S286000, C250S282000, C250S290000, C250S292000
Reexamination Certificate
active
06794641
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mass spectrometer and a method of mass spectrometry.
2. Discussion of the Prior Art
The present invention relates to a mass spectrometer and to a method of mass spectrometry.
Radio Frequency (RF) ion guides are commonly used for confining and transporting ions and comprise an arrangement of electrodes wherein an RF voltage is applied between neighbouring electrodes so that a pseudo-potential well or valley is provided. The pseudo-potential well can be arranged to confine ions and may be used to transport ions by acting as an ion guide. Its use as an ion guide is well known and can be very efficient.
Known RF ion guides can still function efficiently as an ion guide even at relatively high pressures where ions are likely to undergo frequent collisions with residual gas molecules. The collisions with gas molecules may cause ions to scatter and lose energy but the pseudo-potential well generated by the RF ion guide acts to radially confine the ions within the ion guide. In this respect the known RF ion guide has an advantage over guide wire types of ion guides where a DC voltage is applied to a central wire running down the centre of a conducting tube and wherein ions are held in orbit around the central guide wire. If ions undergo many collisions with gas molecules in a guide wire type of ion guide then they will lose energy and will eventually collapse into the central guide wire and be lost.
It is desired to provide an improved ion guide for a mass spectrometer and an improved method of mass spectrometry.
SUMMARY OF THE INVENTION
According to an aspect of the present invention there is provided a mass spectrometer comprising:
a device for temporally or spatially dispersing a group of ions according to a physico-chemical property;
an ion guide comprising a plurality of electrodes, the ion guide receiving in use at least some of the ions which have become dispersed according to the physico-chemical property;
wherein multiple trapping regions are generated or created along at least a portion of the length of the ion guide wherein at least a first group of ions having a physico-chemical property within a first range are trapped within a first trapping region and a second group of ions having a physico-chemical property within a second different range are trapped within a second different trapping region and wherein the multiple trapping regions are translated along at least a portion of the length of the ion guide.
According to the preferred embodiment at least a majority of ions trapped within the first trapping region and/or at least a majority of ions trapped within the second trapping region have substantially the same or similar the physico-chemical property. For example, at least 50%, 60%, 70%, 80%, 90% or 95% of ions in a particular trapping region may have substantially the same or similar physico-chemical property.
The physico-chemical property is preferably mass to charge ratio. Ions may be separated according to their mass to charge ratio by providing a field free region arranged upstream of the ion guide wherein ions which have been accelerated to have substantially the same kinetic energy become dispersed according to their mass to charge ratio. The field free region may be provided within an ion guide selected from the group consisting of: (i) a quadrupole rod set; (ii) a hexapole rod set; (iii) an octopole or higher order rod set; (iv) an ion tunnel ion guide comprising a plurality of electrodes having apertures through which ions are transmitted, the apertures being substantially the same size; (v) an ion funnel ion guide comprising a plurality of electrodes having apertures through which ions are transmitted, the apertures becoming progressively smaller or larger; and (vi) a segmented rod set.
According to the preferred embodiment a pulsed ion source is provided wherein in use a packet or ions emitted by the pulsed ion source enters the field free region. According to another embodiment an ion trap may be arranged upstream of the field free region wherein in use the ion trap releases a packet of ions which enters the field free region.
According to a less preferred embodiment the physico-chemical property may be ion mobility. According to this embodiment a drift region may be arranged upstream of the ion trap wherein ions become dispersed according to their ion mobility. In such an embodiment the drift region preferably has a constant axial electric field or a time varying axial electric field. The drift region may be provided within an ion guide selected from the group consisting of: (i) a quadrupole rod set; (ii) a hexapole rod set; (iii) an octopole or higher order rod set; (iv) an ion tunnel ion guide comprising a plurality of electrodes having apertures through which ions are transmitted, the apertures being substantially the same size; (v) an ion funnel ion guide comprising a plurality of electrodes having apertures through which ions are transmitted, the apertures becoming progressively smaller or larger; and (vi) a segmented rod set.
A pulsed ion source may be provided wherein in use a packet of ions emitted by the pulsed ion source enters the drift region. An ion trap may be arranged upstream of the drift region wherein in use the ion trap releases a packet of ions which enters the drift region.
According to another aspect of the present invention there is provided a mass spectrometer comprising:
a mass to charge ratio selective ion trap which releases in use at least a first group of ions having mass to charge ratios within a first range and then at least a second group of ions having mass to charge ratios within a second range;
an ion guide comprising a plurality of electrodes arranged to receive at least some of the first group of ions and at least some of the second group of ions;
wherein multiple trapping regions are generated or created along at least a portion of the length of the ion guide wherein at least some of the ions of the first group are trapped within a first trapping region and at least some of the ions of the second group are trapped within a second different trapping region; and
wherein the multiple trapping regions are translated along at least a portion of the length of the ion guide.
The mass to charge ratio selective ion trap may comprise a 2D (linear) quadrupole ion trap, a 3D (Paul) quadrupole ion trap or a Penning ion trap.
Preferably, at least a majority of the ions trapped within the first trapping region have substantially the same mass to charge ratio and/or at least a majority of the ions trapped within the second trapping region have substantially the same mass to charge ratio.
Preferably, at least a majority of the ions trapped within the first trapping region have mass to charge ratios which differ by less than x mass to charge ratio units and/or at least a majority of the ions trapped within the second trapping region have mass to charge ratios which differ by less than x mass to charge ratio units, wherein x is selected from the group consisting of: (i) 500; (ii) 450; (iii) 400; (iv) 350; (v) 300; (vi) 250; (vii) 200; (viii) 150; (ix) 100; (x) 90; (xi) 80; (xii) 70; (xiii) 60; (xiv) 50; (xv) 40; (xvi) 30; (xvii) 20; (xviii) 10; and (xix) 5.
At least a majority of the ions trapped within the first trapping region and/or at least a majority of the ions trapped within the second trapping region may have mass to charge ratios which differ by less than: (i) 30%; (ii) 25%; (iii) 20%; (iv) 15%; (v) 10%; (vi) 5%; (vii) 4%; (viii) 3%; (ix) 2%; or (x) 1%.
According to the preferred embodiment one or more transient DC voltages or one or more transient DC voltage waveforms are progressively applied to the electrodes so that ions are urged along the ion guide.
An axial voltage gradient may be maintained along at least a portion of the length of the ion guide and the axial voltage gradient preferably varies with time whilst ions are being transmitted through the ion guide.
The ion guide preferably comprises a first electrode held at a first ref
Bateman Robert Harold
Giles Kevin
Pringle Steve
Diederiks & Whitelaw PLC
Leybourne James J.
Micromass UK Limited
Wells Nikita
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