HK1145566B

HK1145566B - Mass spectrometer

Info

Publication number: HK1145566B
Application number: HK10112045.8A
Authority: HK
Inventors: 马丁‧格伦; 丹尼尔‧詹姆斯‧肯尼; 大卫‧兰格里奇; 詹森‧李‧维尔德古斯
Original assignee: 英国质谱公司
Priority date: 2007-07-12
Filing date: 2008-07-14
Publication date: 2013-11-15

Description

Mass spectrometer

Technical Field

The present invention relates to a mass spectrometer, a method of mass spectrometry, an ion trap and a method of trapping ions.

Background

3D or Paul ion traps comprising one central ring electrode and two end cap electrodes are well known and provide powerful and relatively inexpensive tools for many types of ion analysis.

2D or linear ion traps ("LITs") comprising two electrodes and a quadrupole rod set for axially confining ions within the ion trap are also well known. The sensitivity and dynamic range of commercial linear ion traps have improved significantly in recent years. Linear ion traps that eject ions axially (rather than radially) are particularly suitable for incorporation into hybrid mass spectrometers having linear ion path geometries. However, most commercial linear ion traps eject ions in a radial direction, which poses considerable design difficulties.

Disclosure of Invention

It is therefore desirable to provide an improved ion trap from which ions are ejected axially.

According to an aspect of the present invention, there is provided an ion trap comprising:

a first electrode set comprising a first plurality of electrodes;

a second electrode set comprising a second plurality of electrodes;

a first device arranged and adapted to apply one or more DC voltages to one or more electrodes of the first plurality of electrodes and/or to one or more electrodes of the second plurality of electrodes such that:

(a) ions having a radial displacement within a first range undergo a DC trapping field, DC potential barrier or barrier field in at least one axial direction serving to confine at least some of the ions within the ion trap; and is

(b) Ions having radial displacements within a second, different range experience (i) a substantially zero DC trapping field, a zero DC potential barrier, or a zero potential barrier field, such that at least some of the ions are not confined within the ion trap in at least one axial direction; and/or (ii) a DC extraction field, an accelerating DC potential difference or an extraction field to extract or accelerate at least some of the ions in at least one axial direction and/or to extract or accelerate at least some of the ions out of the ion trap; and

a second device arranged and adapted to vary, increase, decrease or alter the radial displacement of at least some of the ions within the ion trap.

The second device may be arranged to:

(i) causing at least some ions having a radial displacement falling within a first range at a first time to have a radial displacement falling within a second range at a second subsequent time; and/or

(ii) Causing at least some ions having a radial displacement falling within the second range at a first time to have a radial displacement falling within the first range at a second subsequent time.

According to a less preferred embodiment: (i) the first electrode set and the second electrode set comprise a plurality of electrically isolated portions of the same set of electrodes, and/or wherein the first electrode set and the second electrode set are mechanically formed from the same set of electrodes; and/or (ii) the first electrode set comprises regions of one set of electrodes having a dielectric coating and the second electrode set comprises different regions of the same set of electrodes; and/or (iii) the second electrode set comprises regions of one set of electrodes having a dielectric coating, while the first electrode set comprises different regions of the same set of electrodes.

The second electrode set is preferably arranged downstream of the first electrode set. The axial spacing between the downstream end of the first electrode set and the upstream end of the second electrode set is preferably selected from: (i) less than 1 mm; (ii)1-2 mm; (iii)2-3 mm; (iv)3-4 mm; (v)4-5 mm; (vi)5-6 mm; (vii)6-7 mm; (viii)7-8 mm; (ix)8-9 mm; (x)9-10 mm; (xi)10-15 mm; (xii)15-20 mm; (xiii)20-25 mm; (xiv)25-30 mm; (xv)30-35 mm; (xvi)35-40 mm; (xvii)40-45 mm; (xviii)45-50 mm; and (xix) > 50 mm.

The first electrode set is preferably arranged substantially adjacent and/or coaxially with the second electrode set.

The first plurality of electrodes preferably comprises a multipole rod set, a quadrupole rod set, a hexapole rod set, an octapole rod set, or a rod set having more than eight rods. The second plurality of electrodes preferably comprises a multipole rod set, a quadrupole rod set, a hexapole rod set, an octapole rod set, or a rod set having more than eight rods.

According to a less preferred embodiment, the first plurality of electrodes may comprise a plurality of electrodes or at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200 electrodes having apertures through which ions pass in use. According to a less preferred embodiment, the second plurality of electrodes may comprise a plurality of electrodes or at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200 electrodes having apertures through which ions pass in use.

According to this less preferred embodiment, the first electrode set has a first axial length and the second electrode set has a second axial length, and wherein the first axial length is substantially greater than the second axial length, and/or wherein the ratio of the first axial length to the second axial length is at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45 or 50.

The first device is preferably arranged and adapted to apply one or more DC voltages to one or more of the first plurality of electrodes and/or to one or more of the second plurality of electrodes so as to produce, in use, an electrical potential within the first electrode set and/or within the second electrode set that increases and/or decreases and/or varies with radial displacement in the first radial direction from a central longitudinal axis of the first electrode set and/or the second electrode set. The first device is preferably arranged and adapted to apply one or more DC voltages to one or more electrodes of the first plurality of electrodes and/or to one or more electrodes of the second plurality of electrodes so as to generate, in use, an electrical potential that increases and/or decreases and/or varies with radial displacement in the second radial direction from a central longitudinal axis of the first electrode set and/or the second electrode set. The second radial direction is preferably orthogonal to the first radial direction.

According to this preferred embodiment, the first device may be arranged and adapted to apply one or more DC voltages to one or more of the first plurality of electrodes and/or to one or more of the second plurality of electrodes so as to confine at least some positive and/or negative ions axially within the ion trap if said ions have a radial displacement from the central longitudinal axis of the first electrode set and/or the second electrode set greater than or less than a first value.

According to this preferred embodiment, the first device is preferably arranged and adapted to create, in use, one or more radially dependent axial DC potential barriers at one or more axial positions along the length of the ion trap. The one or more radially dependent axial DC barriers preferably substantially prevent at least some or at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% of positive and/or negative ions within the ion trap from axially crossing the one or more axial DC barriers and/or being axially extracted from the ion trap.

The first device is preferably arranged and adapted to apply one or more DC voltages to one or more of the first plurality of electrodes and/or to one or more of the second plurality of electrodes so as to generate, in use, an extraction field for extracting or accelerating at least some positive and/or ions out of the ion trap if said ions have a radial displacement from the central longitudinal axis of the first electrode and/or the second electrode greater or less than a first value.

The first device is preferably arranged and adapted to generate, in use, one or more axial DC extraction electric fields at one or more axial positions along the length of the ion trap. The one or more axial DC extraction electric fields preferably cause at least some, or at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% of the positive and/or negative ions within the ion trap to axially cross over and/or be axially extracted from the DC trapping field, DC potential barrier or barrier field.

According to this preferred embodiment, the first device is arranged and adapted to generate, in use, a DC trapping field, a DC potential barrier or a barrier field for confining at least some of the ions to at least one axial direction, and wherein the ions preferably have a radial displacement as measured from the central longitudinal axis of the first electrode set and/or the second electrode set in a range selected from: (i)0-0.5 mm; (ii)0.5-1.0 mm; (iii)1.0-1.5 mm; (iv)1.5-2.0 mm; (v)2.0-2.5 mm; (vi)2.5-3.0 mm; (vii)3.0-3.5 mm; (viii)3.5-4.0 mm; (ix)4.0-4.5 mm; (x)4.5-5.0 mm; (xi)5.0-5.5 mm; (xii)5.5-6.0 mm; (xiii)6.0-6.5 mm; (xiv)6.5-7.0 mm; (xv)7.0-7.5 mm; (xvi)7.5-8.0 mm; (xvii)8.0-8.5 mm; (xviii)8.5-9.0 mm; (xix)9.0-9.5 mm; (xx)9.5-10.0 mm; and (xxi) > 10.0 mm.

According to this preferred embodiment, the first device is arranged and adapted to provide a substantially zero DC trapping field, a zero DC potential barrier or a zero barrier field in at least one position such that at least some of these ions are not confined within the ion trap in at least one axial direction, and wherein the ions preferably have a radial displacement from the central longitudinal axis of the first electrode set and/or the second electrode set in a range selected from: (i)0-0.5 mm; (ii)0.5-1.0 mm; (iii)1.0-1.5 mm; (iv)1.5-2.0 mm; (v)2.0-2.5 mm; (vi)2.5-3.0 mm; (vii)3.0-3.5 mm; (viii)3.5-4.0 mm; (ix)4.0-4.5 mm; (x)4.5-5.0 mm; (xi)5.0-5.5 mm; (xii)5.5-6.0 mm; (xiii)6.0-6.5 mm; (xiv)6.5-7.0 mm; (xv)7.0-7.5 mm; (xvi)7.5-8.0 mm; (xvii)8.0-8.5 mm; (xviii)8.5-9.0 mm; (xix)9.0-9.5 mm; (xx)9.5-10.0 mm; and (xxi) > 10.0 mm.

The first apparatus is preferably arranged and adapted to generate, in use, a DC extraction field, an accelerating DC potential difference or an extraction field for extracting or accelerating at least some of the ions in at least one axial direction and/or extracting or accelerating at least some of the ions out of the ion trap, and wherein the ions have a radial displacement from the central longitudinal axis of the first electrode set and/or the second electrode set in a range selected from: (i)0-0.5 mm; (ii)0.5-1.0 mm; (iii)1.0-1.5 mm; (iv)1.5-2.0 mm; (v)2.0-2.5 mm; (vi)2.5-3.0 mm; (vii)3.0-3.5 mm; (viii)3.5-4.0 mm; (ix)4.0-4.5 mm; (x)4.5-5.0 mm; (xi)5.0-5.5 mm; (xii)5.5-6.0 mm; (xiii)6.0-6.5 mm; (xiv)6.5-7.0 mm; (xv)7.0-7.5 mm; (xvi)7.5-8.0 mm; (xvii)8.0-8.5 mm; (xviii)8.5-9.0 mm; (xix)9.0-9.5 mm; (xx)9.5-10.0 mm; and (xxi) > 10.0 mm.

The first plurality of electrodes preferably has an inscribed radius r1 and a first longitudinal axis, and/or wherein the second plurality of electrodes has an inscribed radius r2 and a second longitudinal axis.

The first device is preferably arranged and adapted to generate a DC trapping field, a DC potential barrier or a barrier field for confining at least some of these ions in at least one axial direction within the ion trap, and wherein the DC trapping field, DC potential barrier or barrier field increases and/or decreases and/or varies with increasing radius or displacement in a first radial direction from the first longitudinal axis and/or the second longitudinal axis up to at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the first inscribed radius r1 and/or the second inscribed radius r 2.

The first device is preferably arranged and adapted to generate a DC trapping field, a DC potential barrier or a barrier field for confining at least some of these ions in at least one axial direction within the ion trap, and wherein the DC trapping field, DC potential barrier or barrier field increases and/or decreases and/or varies with increasing radius or displacement in the second radial direction from the first longitudinal axis and/or the second longitudinal axis up to at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the first inscribed radius r1 and/or the second inscribed radius r 2. The second radial direction is preferably orthogonal to the first radial direction.

The first device is preferably arranged and adapted to provide a substantially zero DC trapping field, a zero DC potential barrier or a zero barrier field at the at least one location such that at least some of the ions are not confined within the ion trap in at least one axial direction, and wherein the substantially zero DC trapping field, zero DC potential barrier or zero barrier field extends with increasing radius or displacement in the first radial direction from the first longitudinal axis and/or the second longitudinal axis up to at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the first inscribed radius r1 and/or the second inscribed radius r 2. The first device is preferably arranged and adapted to provide a substantially zero DC trapping field, a zero DC potential barrier or a zero barrier field at the at least one location such that at least some of the ions are not confined within the ion trap in at least one axial direction, and wherein the substantially zero DC trapping field, zero DC potential barrier or zero barrier field extends with increasing radius or displacement from the first longitudinal axis and/or the second longitudinal axis in the second radial direction up to at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the first inscribed radius r1 and/or the second inscribed radius r 2. The second radial direction is preferably orthogonal to the first radial direction.

The first device is arranged and adapted to generate a DC extraction field, an accelerating DC potential difference or an extraction field for extracting or accelerating at least some of the ions in at least one axial direction and/or extracting or accelerating at least some of the ions out of the ion trap, and wherein the DC extraction field, accelerating DC potential difference or extraction field increases and/or decreases and/or varies with increasing radius or displacement in a first radial direction from the first longitudinal axis and/or the second longitudinal axis up to at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the first inscribed radius r1 and/or the second inscribed radius r 2. The first device is preferably arranged and adapted to generate a DC extraction field, an accelerating DC potential difference or an extraction field for extracting or accelerating at least some of the ions in at least one axial direction and/or extracting or accelerating at least some of the ions out of the ion trap, and wherein the DC extraction field, the accelerating DC potential difference or the extraction field increases and/or decreases and/or varies with increasing radius or displacement from the first longitudinal axis and/or the second longitudinal axis up to at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the first inscribed radius r1 and/or the second inscribed radius r2 in a second radial direction, wherein the second radial direction is orthogonal to the first radial direction.

According to this preferred embodiment, a DC trapping field, DC potential barrier or barrier field for confining at least some of the ions within the ion trap in at least one axial direction is generated at one or more axial positions along the length of the ion trap and located at least x mm upstream and/or downstream of the axial centre of the first electrode set and/or the second electrode set, where x is selected from: (i) less than 1; (ii) 1-2; (iii) 2-3; (iv) 3-4; (v) 4-5; (vi) 5-6; (vii) 6-7; (viii) 7-8; (ix) 8-9; (x) 9-10; (xi)10-15 parts of; (xii)15-20 parts of; (xiii) 20-25; (xiv) 25-30; (xv) 30-35; (xvi)35-40 parts of; (xvii) 40-45; (xviii)45-50 parts of; and (xix) > 50.

According to this preferred embodiment, a zero DC trapping field, a zero DC potential barrier or a zero potential barrier field is provided at one or more axial positions along the length of the ion trap and located at least y mm upstream and/or downstream of the axial centre of the first electrode set and/or the second electrode set, wherein y is selected from: (i) less than 1; (ii) 1-2; (iii) 2-3; (iv) 3-4; (v) 4-5; (vi) 5-6; (vii) 6-7; (viii) 7-8; (ix) 8-9; (x) 9-10; (xi)10-15 parts of; (xii)15-20 parts of; (xiii) 20-25; (xiv) 25-30; (xv) 30-35; (xvi)35-40 parts of; (xvii) 40-45; (xviii)45-50 parts of; and (xix) > 50.

According to this preferred embodiment, a DC extraction field, an accelerating DC potential difference or an extraction field for extracting or accelerating at least some of the ions in at least one axial direction and/or extracting or accelerating at least some of the ions out of the ion trap is generated at one or more axial positions along the length of the ion trap and located at least z mm upstream and/or downstream of the axial centre of the first and/or second electrode sets, wherein z is selected from: (i) less than 1; (ii) 1-2; (iii) 2-3; (iv) 3-4; (v) 4-5; (vi) 5-6; (vii) 6-7; (viii) 7-8; (ix) 8-9; (x) 9-10; (xi)10-15 parts of; (xii)15-20 parts of; (xiii) 20-25; (xiv) 25-30; (xv) 30-35; (xvi)35-40 parts of; (xvii) 40-45; (xviii)45-50 parts of; and (xix) > 50.

The first device is preferably arranged and adapted to apply one or more DC voltages to one or more electrodes of the first plurality of electrodes and/or to one or more electrodes of the second plurality of electrodes such that:

(i) in the operating mode, the radial and/or axial position of the DC trapping field, DC potential barrier or barrier field remains substantially constant as ions are ejected axially from the ion trap; and/or

(ii) In the operating mode, the radial and/or axial position of the substantially zero DC trapping field, zero DC potential barrier or zero potential barrier field remains substantially constant as ions are axially ejected from the ion trap; and/or

(iii) In the operating mode, the radial and/or axial position of the DC extraction field, the accelerating DC potential difference or the extraction field remains substantially constant as ions are ejected axially from the ion trap.

The first device is preferably arranged and adapted to apply one or more DC voltages to one or more electrodes of the first plurality of electrodes and/or to one or more electrodes of the second plurality of electrodes so as to:

(i) in an operational mode, varying, increasing, decreasing or scanning the radial and/or axial position of the DC trapping field, DC potential barrier or barrier field as ions are ejected axially from the ion trap; and/or

(ii) In an operational mode, varying, increasing, decreasing or scanning the radial and/or axial position of a substantially zero DC trapping field, zero DC potential barrier or zero potential barrier field as ions are ejected axially from the ion trap; and/or

(iii) In the operating mode, the radial and/or axial position of the DC extraction field, accelerating DC potential difference or extraction field is varied, increased, decreased or scanned as ions are ejected axially from the ion trap.

(i) in the operating mode, the amplitude of the DC trapping field, DC potential barrier or barrier field remains substantially constant as ions are axially ejected from the ion trap; and/or

(ii) In the operating mode, a substantially zero DC trapping field, a zero DC potential barrier or a zero potential barrier field remains substantially zero as ions are axially ejected from the ion trap; and/or

(iii) In the operating mode, the DC extraction field, the accelerating DC potential difference or the amplitude of the extraction field remains substantially constant as ions are ejected axially from the ion trap.

According to one embodiment, the first device is preferably arranged and adapted to apply one or more DC voltages to one or more electrodes of the first plurality of electrodes and/or to one or more electrodes of the second plurality of electrodes, in order to:

(i) in an operational mode, varying, increasing, decreasing or scanning the amplitude of the DC trapping field, DC potential barrier or barrier field as ions are ejected axially from the ion trap; and/or

(ii) In the operating mode, the DC extraction field, the accelerating DC potential difference or the amplitude of the extraction field is varied, increased, decreased or scanned as ions are ejected axially from the ion trap.

The second device is preferably arranged and adapted to apply a first and/or second phase opposition of one or more excitation voltages, AC voltages or deflection voltages to at least some of the first plurality of electrodes and/or to at least some of the second plurality of electrodes so as to excite at least some ions in at least one radial direction within the first electrode set and/or within the second electrode set and so that at least some ions are subsequently urged in at least one axial direction and/or axially ejected from the ion trap and/or moved through the DC trapping field, DC potential or barrier field. Ions that are pushed in at least one axial direction and/or ejected axially from the ion trap and/or moved through the DC trapping field, DC potential or barrier field preferably move along an ion path formed within the second electrode set.

The second device is preferably arranged and adapted to apply a first and/or second phase opposition of one or more excitation voltages, AC voltages or flexural voltages to at least some of the first plurality of electrodes and/or to at least some of the second plurality of electrodes so as to radially excite at least some ions in a mass or mass to charge ratio selective manner within the first electrode set and/or the second electrode set, thereby increasing radial movement of at least some ions in at least one radial direction within the first electrode set and/or the second electrode set in a mass or mass to charge ratio selective manner.

Preferably, the one or more excitation voltages, AC voltages or deflection voltages have an amplitude selected from the following: (i) peak to peak value of < 50 mV; (ii) peak-to-peak at 50-100 mV; (iii)100-150mV peak-to-peak; (iv)150-200mV peak-to-peak value; (v)200-250mV peak-to-peak value; (vi)250-300mV peak-to-peak value; (vii)300-350mV peak-to-peak; (viii)350-400mV peak-to-peak value; (ix)400-450mV peak-to-peak; (x)450-500mV peak-to-peak value; and (xi) > 500mV peak-to-peak. Preferably, the one or more excitation voltages, AC voltages or deflection voltages have a frequency selected from the following: (i) less than 10 kHz; (ii)10-20 kHz; (iii)20-30 kHz; (iv)30-40 kHz; (v)40-50 kHz; (vi)50-60 kHz; (vii)60-70 kHz; (viii)70-80 kHz; (ix)80-90 kHz; (x)90-100kHz (xi)100 and 110 kHz; (xii)110-120 kHz; (xiii)120-130 kHz; (xiv)130-140 kHz; (xv)140-150 kHz; (xvi)150 and 160 kHz; (xvii)160-170 kHz; (xviii)170 and 180 kHz; (xix)180-190 kHz; (xx)190 and 200 kHz; and (xxi)200-250 kHz; (xxii)250-300 kHz; (xxiii)300-350 kHz; (xxiv)350-400 kHz; (xxv)400-450 kHz; (xxvi)450-500 kHz; (xxvii)500-600 kHz; (xxviii)600-700 kHz; (xxix)700 and 800 kHz; (xxx)800-900 kHz; (xxxi)900-1000 kHz; and (xxxii) > 1 MHz.

According to this preferred embodiment, the second device is arranged and adapted to maintain the frequency and/or amplitude and/or phase of one or more excitation voltages, AC voltages or deflection voltages applied to at least some of the first plurality of electrodes and/or at least some of the second plurality of electrodes substantially constant.

According to this preferred embodiment, the second device is arranged and adapted to vary, increase, decrease or scan the frequency and/or amplitude and/or phase of one or more excitation voltages, AC voltages or deflection voltages applied to at least some of the first plurality of electrodes and/or at least some of the second plurality of electrodes.

The first electrode set preferably comprises a first central longitudinal axis, and wherein:

(i) a direct line of sight along the first central longitudinal axis; and/or

(ii) Substantially free of physical axial obstructions along the first central longitudinal axis; and/or

(iii) The ions transmitted along the first central longitudinal axis in use are transmitted with an ion transmission efficiency of substantially 100%.

The second electrode set preferably includes a second central longitudinal axis, and wherein:

(i) a direct line of sight along the second central longitudinal axis; and/or

(ii) Substantially free of physical axial obstruction along the second central longitudinal axis; and/or

(iii) The ions transmitted along the second central longitudinal axis in use are transmitted with an ion transmission efficiency of substantially 100%.

According to this preferred embodiment, the first plurality of electrodes individually and/or in combination have a first cross-sectional area and/or shape, and wherein the second plurality of electrodes individually and/or in combination have a second cross-sectional area and/or shape, wherein the first cross-sectional area and/or shape is substantially the same as the second cross-sectional area and/or shape at one or more points along the axial length of the first and second electrode sets, and/or wherein the first cross-sectional area and/or shape of the downstream end of the first plurality of electrodes is substantially the same as the second cross-sectional area and/or shape of the upstream end of the second plurality of electrodes.

According to a less preferred embodiment, the first plurality of electrodes individually and/or in combination have a first cross-sectional area and/or shape, and wherein the second plurality of electrodes individually and/or in combination have a second cross-sectional area and/or shape, wherein at one or more points along the axial length of the first and second electrode sets and/or at the downstream end of the first plurality of electrodes and the upstream end of the second plurality of electrodes, the ratio of the first cross-sectional area and/or shape to the second cross-sectional area and/or shape is selected from: (i) less than 0.50; (ii) 0.50-0.60; (iii) 0.60-0.70; (iv) 0.70-0.80; (v) 0.80-0.90; (vi) 0.90-1.00; (vii) 1.00-1.10; (viii) 1.10-1.20; (ix) 1.20-1.30; (x) 1.30-1.40; (xi) 1.40-1.50; and (xii) > 1.50.

According to this preferred embodiment, the ion trap preferably further comprises a first plurality of leaf or sub-electrodes arranged between the first electrodes and/or a second plurality of leaf or sub-electrodes arranged between the second set of electrodes.

The first plurality of vane electrodes or secondary electrodes and/or the second plurality of vane electrodes or secondary electrodes preferably each comprise a first set of vane electrodes or secondary electrodes arranged in a first plane and/or a second set of electrodes arranged in a second plane. The second plane is preferably orthogonal to the first plane.

The first set of blade or secondary electrodes preferably comprises a first set of blade or secondary electrodes arranged on one side of the first longitudinal axis of the first electrode set and/or the second longitudinal axis of the second electrode set and a second set of blade or secondary electrodes arranged on the opposite side of the first longitudinal axis and/or the second longitudinal axis. The first set of blade or secondary electrodes and/or the second set of blade or secondary electrodes preferably comprises at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 blade or secondary electrodes.

The second set of vane or secondary electrodes preferably comprises a third set of vane or secondary electrodes disposed on one side of the first and/or second longitudinal axis and a fourth set of vane or secondary electrodes disposed on an opposite side of the first and/or second longitudinal axis. The third set of blade or secondary electrodes and/or the fourth set of blade or secondary electrodes preferably comprises at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 blade or secondary electrodes.

Preferably, the first set of blade electrodes or secondary electrodes and/or the second set of blade electrodes or secondary electrodes and/or the third set of blade electrodes or secondary electrodes and/or the fourth set of blade electrodes or secondary electrodes are arranged between different pairs of electrodes constituting the first electrode set and/or the second electrode set.

The ion trap preferably further comprises a fourth device arranged and adapted to apply one or more first DC voltages and/or one or more second DC voltages to the following electrodes: (i) at least some of the vane electrodes or secondary electrodes; and/or (ii) a first set of blade electrodes or secondary electrodes; (ii) or (iii) a second set of blade or secondary electrodes; and/or (iv) a third set of blade or secondary electrodes; and/or (v) a fourth set of vane electrodes or secondary electrodes.

The one or more first DC voltages and/or the one or more second DC voltages preferably comprise one or more transient DC voltages or potentials and/or one or more transient DC voltage or potential waveforms.

The one or more first DC voltages and/or the one or more second DC voltages preferably cause:

(i) ions are pushed, driven, accelerated or propelled along at least a portion of the axial length of the ion trap towards the inlet or first region of the ion trap and/or in an axial direction; and/or

(ii) Ions that have been excited in at least one radial direction are pushed, driven, accelerated or propelled along at least a portion of the axial length of the ion trap towards the outlet or second region of the ion trap and/or in the opposite axial direction.

The one or more first DC voltages and/or the one or more second DC voltages preferably have substantially the same amplitude or different amplitudes. The magnitude of the one or more first DC voltages and/or the one or more second DC voltages is selected from: (i) less than 1V; (ii) 1-2V; (iii) 2-3V; (iv) 3-4V; (v) 4-5V; (vi) 5-6V; (vii) 6-7V; (viii) 7-8V; (ix) 8-9V; (x) 9-10V; (xi) 10-15V; (xii) 15-20V; (xiii) 20-25V; (xiv) 25-30V; (xv) 30-35V; (xvi) 35-40V; (xvii) 40-45V; (xviii) 45-50V; and (xix) > 50V.

The second device is preferably arranged and adapted to apply a first and/or second phase opposition of one or more of an excitation voltage, an AC voltage or a deflection voltage to the following electrodes: (i) at least some of the vane electrodes or secondary electrodes; and/or (ii) a first set of blade electrodes or secondary electrodes; and/or (iii) a second set of blade or secondary electrodes; and/or (iv) a third set of blade or secondary electrodes; and/or (v) a fourth set of vane electrodes or secondary electrodes; so as to excite at least some ions in at least one radial direction within the first electrode set and/or the second electrode set and such that at least some ions are subsequently urged in at least one axial direction and/or axially ejected from the ion trap and/or moved through the DC trapping field, DC potential or barrier field.

Ions that are pushed in at least one axial direction and/or ejected axially from the ion trap and/or moved through the DC trapping field, DC potential or barrier field preferably move along an ion path formed within the second electrode set.

According to this preferred embodiment, the second device is arranged and adapted to apply a first and/or second phase opposition of one or more excitation, AC or deflection voltages to the lower column electrodes: (i) at least some of the vane electrodes or secondary electrodes; and/or (ii) a first set of blade electrodes or secondary electrodes; and/or (iii) a second set of blade or secondary electrodes; and/or (iv) a third set of blade or secondary electrodes; and/or (v) a fourth set of vane electrodes or secondary electrodes; so as to radially excite at least some ions in a mass or mass to charge ratio selective manner within the first electrode set and/or the second electrode set, thereby increasing the radial movement of at least some ions in at least one radial direction in the mass or mass to charge ratio selective manner within the first electrode set and/or the second electrode set.

Preferably, the one or more excitation voltages, AC voltages or deflection voltages have an amplitude selected from the following: (i) peak to peak value of < 50 mV; (ii) peak-to-peak at 50-100 mV; (iii)100-150mV peak-to-peak; (iv)150-200mV peak-to-peak value; (v)200-250mV peak-to-peak value; (vi)250-300mV peak-to-peak value; (vii)300-350mV peak-to-peak; (viii)350-400mV peak-to-peak value; (ix)400-450mV peak-to-peak; (x)450-500mV peak-to-peak value; and (xi) > 500mV peak-to-peak.

Preferably, the one or more excitation voltages, AC voltages or deflection voltages have a frequency selected from the following: (i) less than 10 kHz; (ii)10-20 kHz; (iii)20-30 kHz; (iv)30-40 kHz; (v)40-50 kHz; (vi)50-60 kHz; (vii)60-70 kHz; (viii)70-80 kHz; (ix)80-90 kHz; (x)90-100kHz (xi)100 and 110 kHz; (xii)110-120 kHz; (xiii)120-130 kHz; (xiv)130-140 kHz; (xv)140-150 kHz; (xvi)150 and 160 kHz; (xvii)160-170 kHz; (xviii)170 and 180 kHz; (xix)180-190 kHz; (xx)190 and 200 kHz; and (xxi)200-250 kHz; (xxii)250-300 kHz; (xxiii)300-350 kHz; (xxiv)350-400 kHz; (xxv)400-450 kHz; (xxvi)450-500 kHz; (xxvii)500-600 kHz; (xxviii)600-700 kHz; (xxix)700 and 800 kHz; (xxx)800-900 kHz; (xxxi)900-1000 kHz; and (xxxii) > 1 MHz.

The second device may be arranged and adapted to maintain the frequency and/or amplitude and/or phase of one or more excitation voltages, AC voltages or deflection voltages applied to at least some of the plurality of blade or secondary electrodes substantially constant.

The second device may be arranged and adapted to vary, increase, decrease or scan the frequency and/or amplitude and/or phase of one or more excitation voltages, AC voltages or deflection voltages applied to at least some of the plurality of blade or secondary electrodes.

The first plurality of vane electrodes or secondary electrodes preferably individually and/or in combination have a first cross-sectional area and/or shape. The second plurality of vane electrodes or secondary electrodes preferably individually and/or in combination have a second cross-sectional area and/or shape. The first cross-sectional area and/or shape is preferably substantially the same as the second cross-sectional area and/or shape at one or more points along the length of the first and second pluralities of blade or secondary electrodes.

The first plurality of vane electrodes or secondary electrodes may individually and/or in combination have a first cross-sectional area and/or shape, and wherein the second plurality of vane electrodes or secondary electrodes individually and/or in combination have a second cross-sectional area and/or shape. At one or more points along the length of the first and second pluralities of blade or sub-electrodes, the ratio of the first cross-sectional area and/or shape to the second cross-sectional area and/or shape is selected from: (i) less than 0.50; (ii) 0.50-0.60; (iii) 0.60-0.70; (iv) 0.70-0.80; (v) 0.80-0.90; (vi) 0.90-1.00; (vii) 1.00-1.10; (viii) 1.10-1.20; (ix) 1.20-1.30; (x) 1.30-1.40; (xi) 1.40-1.50; and (xii) > 1.50.

The ion trap preferably further comprises a third device arranged and adapted to apply the first AC or RF voltage to the first set of electrodes and/or the second AC or RF voltage to the second set of electrodes. The first AC or RF voltage and/or the second AC or RF voltage preferably creates a pseudo-potential well within the first electrode set and/or the second electrode set for radially confining ions within the ion trap.

The first AC or RF voltage and/or the second AC or RF voltage preferably has an amplitude selected from the following: (i) peak to peak value < 50V; (ii) peak-to-peak at 50-100V; (iii)100-150V peak-to-peak; (iv) 150-; (v)200-250V peak-to-peak; (vi)250-300V peak-to-peak; (vii) 300-; (viii)350-400V peak-to-peak; (ix)400-450V peak-to-peak; (x)450-500V peak-to-peak; and (xi) > 500V peak-to-peak.

The first AC or RF voltage and/or the second AC or RF voltage preferably has a frequency selected from the following: (i) < 100 kHz; (ii) 100-; (iii)200-300 kHz; (iv)300-400 kHz; (v)400-500 kHz; (vi)0.5-1.0 MHz; (vii)1.0-1.5 MHz; (viii)1.5-2.0 MHz; (ix)2.0-2.5 MHz; (x)2.5-3.0 MHz; (xi)3.0-3.5 MHz; (xii)3.5-4.0 MHz; (xiii)4.0-4.5 MHz; (xiv)4.5-5.0 MHz; (xv)5.0-5.5 MHz; (xvi)5.5-6.0 MHz; (xvii)6.0-6.5 MHz; (xviii)6.5-7.0 MHz; (xix)7.0-7.5 MHz; (xx)7.5-8.0 MHz; (xxi)8.0-8.5 MHz; (xxii)8.5-9.0 MHz; (xxiii)9.0-9.5 MHz; (xxiv)9.5-10.0 MHz; and (xxv) > 10.0 MHz.

According to this preferred embodiment, the first AC or RF voltage and the second AC or RF voltage have substantially the same amplitude and/or the same frequency and/or the same phase.

According to a less preferred embodiment, the third device may be arranged and adapted to maintain the frequency and/or amplitude and/or phase of the first AC or RF voltage and/or the second AC or RF voltage substantially constant.

According to this preferred embodiment, the third device is arranged and adapted to vary, increase, decrease or scan the frequency and/or amplitude and/or phase of the first AC or RF voltage and/or the second AC or RF voltage.

According to one embodiment, the second device is arranged and adapted to excite ions by resonance ejection and/or mass selective instability and/or parametric excitation.

The second device is preferably arranged and adapted to increase the radial displacement of the ions by applying one or more DC potentials to at least some of the first plurality of electrodes and/or the second plurality of electrodes.

The ion trap preferably further comprises one or more electrodes arranged upstream and/or downstream of the first set of electrodes and/or the second set of electrodes, wherein in the operational mode one or more DC and/or AC or RF voltages are applied to the one or more electrodes so as to confine at least some ions axially within the ion trap.

In the operational mode, at least some ions are preferably arranged to be trapped or isolated in one or more upstream and/or intermediate and/or downstream regions of the ion trap.

In the operating mode, at least some of the ions are preferably arranged to be fragmented in one or more upstream and/or intermediate and/or downstream regions of the ion trap. The ions are preferably arranged to be fragmented by: (i) collision induced dissociation ("CID"); (ii) surface induced dissociation ("SID"); (iii) electron transfer dissociation; (iv) electron capture dissociation; (v) electron collision or impact dissociation; (vi) light induced dissociation ("PID"); (vii) laser induced dissociation; (viii) infrared radiation induced dissociation; (ix) ultraviolet radiation induced dissociation; (x) Thermal or temperature dissociation; (xi) Electric field induced dissociation; (xii) Magnetic field induced dissociation; (xiii) Enzymatic digestion or enzymatic degradation dissociation; (xiv) Dissociation of ion-ion reaction; (xv) Dissociation of ion-molecule reaction; (xvi) Dissociation of ion-atom reaction; (xvii) Ion-metastable ion reaction dissociation; (xviii) Dissociation of ion-metastable molecule reaction; (xix) Dissociation of ion-metastable atom reaction; and (xx) electron ionization dissociation ("EID").

According to one embodiment, the ion trap is maintained in the operating mode at a pressure selected from the group consisting of: (i) more than 100 mbar; (ii) more than 10 mbar; (iii) more than 1 mbar; (iv) greater than 0.1 mbar; (v) > 10^-2mbar；(vi)＞10^-3mbar；(vii)＞10^-4mbar；(viii)＞10^-5mbar；(ix)＞10^-6mbar；(x)＜100mbar；(xi)＜10mbar；(xii)＜1mbar；(xiii)＜0.1mbar；(xiv)＜10^-2mbar；(xv)＜10^-3mbar；(xvi)＜10^-4mbar；(xvii)＜10^-5mbar；(xviii)＜10^-6mbar；(xix)10-100mbar；(xx)1-10mbar；(xxi)0.1-1mbar；(xxii)10^-2To 10^-1mbar；(xxiii)10^-3To 10^-2mbar；(xxiv)10^-4To 10^-3mbar; and (xxv)10^-5To 10^-4mbar。

In the operating mode, at least some of the ions are preferably arranged to be separated in time as they pass at least part of the length of the ion trap according to their ion mobility or the rate of change of ion mobility with electric field strength.

According to one embodiment, the ion trap preferably further comprises a device or ion gate for pulsing ions into the ion trap and/or for converting a substantially continuous ion beam into a pulsed ion beam.

According to an embodiment, the first electrode set and/or the second electrode set are axially segmented into a plurality of axial segments or at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 axial segments. In the operational mode, at least some of the plurality of axial segments are preferably maintained at different DC potentials, and/or wherein one or more transient DC potentials or voltages or one or more transient DC potential or voltage waveforms are applied to at least some of the plurality of axial segments such that at least some ions are trapped in one or more axial DC potential wells, and/or wherein at least some ions are urged in a first axial direction and/or a second opposite axial direction.

In the working mode: (i) the ions are ejected from the ion trap substantially adiabatically without substantially transferring axial energy to the ions and/or in an axial direction; and/or (ii) ions are ejected axially from the ion trap in an axial direction with an average axial kinetic energy in a range selected from: (i) less than 1 eV; (ii)1-2 eV; (iii)2-3 eV; (iv)3-4 eV; (v)4-5 eV; (vi)5-6 eV; (vii)6-7 eV; (viii)7-8 eV; (ix)8-9 eV; (x)9-10 eV; (xi)10-15 eV; (xii)15-20 eV; (xiii)20-25 eV; (xiv)25-30 eV; (xv)30-35 eV; (xvi)35-40 eV; and (xvii)40-45 eV; and/or (iii) ions are ejected axially from the ion trap in an axial direction, and wherein the standard deviation of the axial kinetic energy is in a range selected from: (i) less than 1 eV; (ii)1-2 eV; (iii)2-3 eV; (iv)3-4 eV; (v)4-5 eV; (vi)5-6 eV; (vii)6-7 eV; (viii)7-8 eV; (ix)8-9 eV; (x)9-10 eV; (xi)10-15 eV; (xii)15-20 eV; (xiii)20-25 eV; (xiv)25-30 eV; (xv)30-35 eV; (xvi)35-40 eV; (xvii)40-45 eV; and (xviii)45-50 eV.

According to one embodiment, in the operational mode, a plurality of different species of ions having different mass to charge ratios are simultaneously axially ejected from the ion trap in substantially the same and/or substantially different axial directions.

In the operational mode, an additional AC voltage is applied to at least some of the first plurality of electrodes and/or at least some of the second plurality of electrodes. The one or more DC voltages are preferably modulated on the additional AC voltage such that at least some positive and negative ions are simultaneously confined within and/or simultaneously axially ejected from the ion trap. Preferably, the additional AC voltage has an amplitude selected from the following: (i) peak to peak value < 1V; (ii)1-2V peak-to-peak; (iii)2-3V peak-to-peak; (iv)3-4V peak-to-peak; (v)4-5V peak-to-peak; (vi)5-6V peak-to-peak; (vii)6-7V peak-to-peak; (viii)7-8V peak-to-peak; (ix)8-9V peak-to-peak; (x)9-10V peak-to-peak; and (xi) > 10V peak-to-peak. Preferably, the additional AC voltage has a frequency selected from the following frequencies: (i) less than 10 kHz; (ii)10-20 kHz; (iii)20-30 kHz; (iv)30-40 kHz; (v)40-50 kHz; (vi)50-60 kHz; (vii)60-70 kHz; (viii)70-80 kHz; (ix)80-90 kHz; (x)90-100 kHz; (xi) 100-; (xii)110-120 kHz; (xiii)120-130 kHz; (xiv)130-140 kHz; (xv)140-150 kHz; (xvi)150 and 160 kHz; (xvii)160-170 kHz; (xviii)170 and 180 kHz; (xix)180-190 kHz; (xx)190 and 200 kHz; and (xxi)200-250 kHz; (xxii)250-300 kHz; (xxiii)300-350 kHz; (xxiv)350-400 kHz; (xxv)400-450 kHz; (xxvi)450-500 kHz; (xxvii)500-600 kHz; (xxviii)600-700 kHz; (xxix)700 and 800 kHz; (xxx)800-900 kHz; (xxxi)900-1000 kHz; and (xxxii) > 1 MHz.

The ion trap is also preferably arranged and adapted to operate in at least one non-trapping mode of operation, wherein:

(i) applying DC and/or AC or RF voltages to the first electrode set and/or to the second electrode set such that the ion trap operates as a pure RF ion guide, or an ion guide that does not confine ions axially within it; and/or

(ii) DC and/or AC or RF voltages are applied to the first electrode set and/or to the second electrode set so that the ion trap operates as a mass filter or mass analyser so that some ions are mass selectively transmitted while other ions are significantly attenuated.

According to a less preferred embodiment, in the operating mode, ions which are not desired to be ejected axially instantaneously can be excited radially and/or ions which are desired to be ejected axially instantaneously can no longer be excited radially or to a lesser extent radially.

Ions that are desired to be momentarily ejected axially from the ion trap are preferably selectively ejected from the ion trap mass, and/or ions that are not desired to be momentarily ejected axially from the ion trap are preferably not selectively ejected from the ion trap mass.

According to this preferred embodiment, the first electrode set preferably comprises a first multipole set (e.g. a quadrupole set), and the second electrode set preferably comprises a second multipole set (e.g. a quadrupole set). Substantially the same amplitude and/or frequency and/or phase of the AC or RF voltage is preferably applied to the first multipole rod set and to the second multipole rod set in order to radially confine the ions within the first multipole rod set and/or the second multipole rod set.

a first device arranged and adapted to generate a first DC electric field to axially confine ions having a first radial displacement within the ion trap and a second DC electric field to extract or axially accelerate ions having a second radial displacement from the ion trap; and

a second device arranged and adapted to selectively mass vary, increase, decrease or scan the radial displacement of at least some of the ions such that those ions are axially ejected from the ion trap while other ions remain axially confined within the ion trap.

According to an aspect of the present invention there is provided a mass spectrometer comprising an ion trap as described above.

The mass spectrometer preferably further comprises:

(a) an ion source disposed upstream of the ion trap, wherein the ion source is selected from the group consisting of: (i) an electrospray ionization ("ESI") ion source; (ii) an atmospheric pressure photoionization ("APPI") ion source; (iii) an atmospheric pressure chemical ionization ("APCI") ion source; (iv) a matrix-assisted laser desorption ionization ("MALDI") ion source; (v) a laser desorption ionization ("LDI") ion source; (vi) an atmospheric pressure ionization ("API") ion source; (vii) a desorption ionization on silicon ("DIOS") ion source; (viii) an electron impact ("EI") ion source; (ix) a chemical ionization ("CI") ion source; (x) A field ionization ("FI") ion source; (xi) A field desorption ("FD") ion source; (xii) An inductively coupled plasma ("ICP") ion source; (xiii) A fast atom bombardment ("FAB") ion source; (xiv) A liquid secondary ion mass spectroscopy ("LSIMS") ion source; (xv) A desorption electrospray ionization ("DESI") ion source; (xvi) A source of nickel-63 radioactive ions; (xvii) An atmospheric pressure matrix-assisted laser desorption ionization ion source; and (xviii) a thermal spray ion source; and/or

(b) One or more ion guides disposed upstream and/or downstream of the ion trap; and/or

(c) One or more ion mobility separation devices and/or one or more field asymmetric ion mobility spectrometer devices arranged upstream and/or downstream of the ion trap; and/or

(d) One or more ion traps or one or more ion trapping regions arranged upstream and/or downstream of the ion traps; and/or

(e) One or more collision, fragmentation or reaction cells arranged upstream and/or downstream of the ion trap, wherein the one or more collision, fragmentation or reaction cells are selected from the group consisting of: (i) a collision induced dissociation ("CID") fragmentation device; (ii) a surface induced dissociation ("SID") cleavage apparatus; (iii) an electron transfer dissociation cleavage apparatus; (iv) an electron capture dissociation fragmentation device; (v) electron impact or impact dissociation fragmentation devices; (vi) a light induced dissociation ("PID") lysis device; (vii) a laser induced dissociation lysis device; (viii) an infrared radiation induced dissociation device; (ix) an ultraviolet radiation induced dissociation device; (x) A nozzle-dispenser interface cracking unit; (xi) An endogenous lysis device; (xii) An ion source collision induced dissociation fragmentation apparatus; (xiii) Thermal or temperature source cracking equipment; (xiv) An electric field induced cracking device; (xv) A magnetic field induced lysis device; (xvi) An enzymatic digestion or degradation cleavage apparatus; (xvii) An ion-ion reaction cracking device; (xviii) An ion-molecule reaction cracking device; (xix) An ion-atom reaction cracking device; (xx) An ion-metastable ion reaction cracking device; (xxi) An ion-metastable molecule reaction cracking device; (xxii) An ion-metastable atom reaction cracking device; (xxiii) An ion-ion reaction device for reacting ions to form adduct or product ions; (xxiv) An ion-molecule reaction device for reacting ions to form adduct or product ions; (xxv) An ion-atom reaction device for reacting ions to form adduct or product ions; (xxvi) Ion-metastable ion reaction equipment for reacting ions to form adduct or product ions; (xxvii) Ion-metastable molecule reaction equipment for reacting ions to form adduct or product ions; (xxviii) Ion-metastable atom reaction equipment for reacting ions to form adduct or product ions; and (xxix) electron ionization dissociation ("EID") lysis equipment; and/or

(f) A mass analyser selected from the following mass analysers: (i) a quadrupole mass analyzer; (ii) a 2D or linear quadrupole mass analyzer; (iii) paul or 3D quadrupole mass analyzers; (iv) penning (Penning) trap mass analyzer; (v) an ion trap mass analyser; (vi) a magnetic sector mass analyzer; (vii) an ion cyclotron resonance ("ICR") mass analyzer; (viii) a fast fourier transform ion cyclotron resonance ("FTICR") mass analyzer; (ix) an electrostatic or orbital trap mass analyzer; (x) A fourier transform electrostatic or orbital trap mass analyzer; (xi) A Fourier transform mass analyzer; (xii) A time-of-flight mass analyzer; (xiii) An orthogonal acceleration time-of-flight mass analyser; and (xiv) a linear acceleration time-of-flight mass aircraft; and/or

(g) One or more energy analyzers or electrostatic energy analyzers arranged upstream and/or downstream of the ion trap; and/or

(h) One or more ion detectors arranged upstream and/or downstream of the ion trap; and/or

(i) One or more mass filters disposed upstream and/or downstream of the ion trap, wherein the one or more mass filters are selected from the group consisting of: (i) a quadrupole mass filter; (ii)2D or linear quadrupole ion traps; (iii) paul or 3D quadrupole ion trap; (iv) a penning ion trap; (v) an ion trap; (vi) a magnetic sector mass filter; and (vii) a time-of-flight mass filter.

According to an aspect of the present invention, there is provided a dual mode device, including:

a first electrode set and a second electrode set;

a first device arranged and adapted to generate a DC potential field at a location along the ion trap to axially confine ions having a first radial displacement within the ion trap and to extract ions having a second radial displacement from the ion trap when the dual mode device is operating in a first mode of operation;

a second device arranged and adapted to selectively mass vary, increase, decrease or scan the radial displacement of at least some of the ions when the dual mode device is operating in the first mode of operation such that at least some of the ions are axially ejected from the ion trap while other ions remain axially confined within the ion trap; and

a third device arranged and adapted to apply DC and/or RF voltages to the first electrode set and/or to the second electrode set such that when the dual mode device is operating in the second mode of operation, the dual mode device operates as a mass filter or mass analyser or as an RF-only ion guide that forwards ions without axially confining them.

According to an aspect of the present invention, there is provided a method of trapping ions, the method comprising:

providing a first electrode set comprising a first plurality of electrodes and a second electrode set comprising a second plurality of electrodes;

applying one or more DC voltages to one or more electrodes of the first plurality of electrodes and/or to one or more electrodes of the second plurality of electrodes such that ions having a radial displacement within a first range experience a DC trapping field, DC potential barrier or barrier field in at least one axial direction serving to confine at least some of these ions within the ion trap, and wherein ions having a radial displacement within a second, different range experience:

(i) a substantially zero DC trapping field, zero DC potential barrier or zero potential barrier field such that at least some of the ions are not confined within the ion trap in at least one axial direction; and/or

(ii) A DC extraction field, an accelerating DC potential difference or an extraction field to extract or accelerate at least some of the ions in at least one axial direction and/or to extract or accelerate at least some of the ions out of the ion trap; and is

The radial displacement of at least some of the ions within the ion trap is varied, increased, decreased or altered.

According to an aspect of the present invention, there is provided a method of mass spectrometry comprising a method of trapping ions as described above.

According to an aspect of the invention, there is provided a computer program executable by a control system of a mass spectrometer comprising an ion trap, the computer program being arranged to cause the control system to:

(i) applying one or more DC voltages to one or more electrodes of the ion trap such that ions having a radial displacement within a first range within the ion trap experience a DC trapping field, DC potential barrier or barrier field in at least one axial direction serving to confine at least some of these ions within the ion trap, and wherein ions having a radial displacement within a second, different range experience: (a) a substantially zero DC trapping field, zero DC potential barrier or zero potential barrier field such that at least some of the ions are not confined within the ion trap in at least one axial direction; and/or (b) a DC extraction field, an accelerating DC potential difference or an extraction field to extract or accelerate at least some of the ions in at least one axial direction and/or to extract or accelerate at least some of the ions out of the ion trap; and is

(ii) The radial displacement of at least some of the ions within the ion trap is varied, increased, decreased or altered.

According to an aspect of the invention, there is provided a computer readable medium comprising computer executable instructions stored on the computer readable medium, the instructions being arranged to be executable by a control system of a mass spectrometer comprising an ion trap so as to cause the control system to:

The computer readable medium is preferably selected from: (i) a ROM; (ii) an EAROM; (iii) an EPROM; (iv) an EEPROM; (v) flashing; and (vi) optical discs.

a first electrode set comprising a first plurality of electrodes having a first longitudinal axis;

a second electrode set comprising a second plurality of electrodes having a second longitudinal axis, the second electrode set disposed downstream of the first electrode set;

a first device arranged and adapted to apply one or more DC voltages to one or more of the second plurality of electrodes so as to generate, in use, a barrier field having a potential that decreases with increasing radius or displacement from the second longitudinal axis in the first radial direction; and

a second device arranged and adapted to excite at least some ions in at least one radial direction within the first electrode set and/or to increase the radial displacement of at least some ions in at least one radial direction within the first electrode set.

a plurality of electrodes;

a first device arranged and adapted to apply one or more DC voltages to one or more of the plurality of electrodes to generate a DC field to axially confine at least some ions having a first radial displacement and to axially extract at least some ions having a second radial displacement.

The ion trap preferably further comprises: a second device arranged and adapted to excite at least some of the ions such that the radial displacement of at least some of the ions is varied, increased, decreased or altered such that at least some of the ions are extracted axially from the ion trap.

a plurality of electrodes;

a device arranged and adapted to maintain a positive DC electric field within a first region of the ion trap such that positive ions within the first region are prevented from exiting the ion trap in an axial direction, and wherein the device is arranged and adapted to maintain a zero or negative DC electric field within a second region of the ion trap such that positive ions within the second region are free to exit the ion trap in an axial direction or to be pushed, attracted or extracted in an axial direction so as to exit the ion trap.

a plurality of electrodes;

an apparatus arranged and adapted to maintain a negative DC electric field within a first region of the ion trap such that negative ions within the first region are prevented from exiting the ion trap in an axial direction, and wherein the apparatus is arranged and adapted to maintain a zero or positive DC electric field within a second region of the ion trap such that negative ions within the second region are free to exit the ion trap in an axial direction or to be pushed, attracted or extracted in an axial direction so as to exit the ion trap.

According to an aspect of the present invention there is provided an ion trap wherein in an operational mode ions are ejected from the ion trap substantially adiabatically in an axial direction.

According to this preferred embodiment, the ions within the ion trap have a first average energy E1 immediately prior to being axially ejected, and wherein the ions have a second average energy E2 immediately after being axially ejected from the ion trap, wherein E1 is substantially equal to E2. Preferably, the ions within the ion trap have a first energy range immediately prior to being axially ejected, and wherein the ions have a second energy range immediately after being axially ejected from the ion trap, wherein the first energy range is substantially equal to the second energy range. Preferably, the ions within the ion trap have a first energy spread Δ E1 immediately prior to being axially ejected, and wherein the ions have a second energy spread Δ E2 immediately after being axially ejected from the ion trap, wherein Δ E1 is substantially equal to Δ E2.

According to an aspect of the present invention there is provided an ion trap wherein in a mode of operation a radially dependent axial DC potential barrier is created at an exit region of the ion trap, wherein the DC potential barrier is non-zero, positive or negative at a first radial displacement and substantially zero, negative or positive at a second radial displacement.

a first device arranged and adapted to produce:

(i) a first axial DC electric field to axially confine ions having a first radial displacement within the ion trap; and

(ii) a second axial DC electric field to extract or axially accelerate ions having a second radial displacement from the ion trap; and

a second device arranged and adapted to selectively mass vary, increase, decrease or scan the radial displacement of at least some of the ions such that ions are axially ejected from the ion trap while other ions remain axially confined within the ion trap.

According to one aspect of the present invention there is provided a mass spectrometer comprising a device, wherein the device comprises an RF ion guide substantially free of physical axial obstruction and is configured such that, in use, an applied electric field is switched between at least two modes or states of operation, wherein in a first mode or state of operation the device forwards ions within a range of mass or mass to charge ratios, and wherein in a second mode or state of operation the device operates as a linear ion trap as follows: wherein ions are mass-selectively displaced in at least one radial direction and are ejected adiabatically in an axial direction by means of one or more radially dependent axial DC barriers.

According to one aspect of the present invention there is provided an ion trap wherein in an operating mode ions are ejected axially from the ion trap in an axial direction with an average axial kinetic energy in a range selected from: (i) less than 1 eV; (ii)1-2 eV; (iii)2-3 eV; (iv)3-4 eV; (v)4-5 eV; (vi)5-6 eV; (vii)6-7 eV; (viii)7-8 eV; (ix)8-9 eV; (x)9-10 eV; (xi)10-15 eV; (xii)15-20 eV; (xiii)20-25 eV; (xiv)25-30 eV; (xv)30-35 eV; (xvi)35-40 eV; and (xvii)40-45 eV.

According to one aspect of the present invention there is provided an ion trap wherein ions are ejected axially from the ion trap in an axial direction in an operational mode, and wherein the standard deviation of the axial kinetic energy is within a range selected from: (i) less than 1 eV; (ii)1-2 eV; (iii)2-3 eV; (iv)3-4 eV; (v)4-5 eV; (vi)5-6 eV; (vii)6-7 eV; (viii)7-8 eV; (ix)8-9 eV; (x)9-10 eV; (xi)10-15 eV; (xii)15-20 eV; (xiii)20-25 eV; (xiv)25-30 eV; (xv)30-35 eV; (xvi)35-40 eV; (xvii)40-45 eV; and (xviii)45-50 eV.

a first multipole rod set comprising a first plurality of rod electrodes;

a second multipole rod set comprising a second plurality of rod electrodes;

a first device arranged and adapted to apply one or more DC voltages to one or more rod electrodes of the first plurality of rod electrodes and/or to one or more rod electrodes of the second plurality of rod electrodes such that:

(b) Ions having a radial displacement in a second, different range experience: (i) a substantially zero DC trapping field, zero DC potential barrier or zero potential barrier field such that at least some of the ions are not confined within the ion trap in at least one axial direction; and/or (ii) a DC extraction field, an accelerating DC potential difference or an extraction field to extract or accelerate at least some of the ions in at least one axial direction and/or to extract or accelerate at least some of the ions out of the ion trap; and

The ion trap preferably further comprises:

a first plurality of blade electrodes or secondary electrodes arranged between the rods that make up the first multipole rod set; and/or

A second plurality of blade electrodes or secondary electrodes arranged between the rods that make up the second multipole rod set.

According to one embodiment of the invention, there is provided a mass spectrometer comprising a relatively high transmission RF ion guide or ion trap. The ion guide or ion trap is particularly advantageous in that: the central longitudinal axis of the ion trap is unobstructed by the electrodes. This is in contrast to known ion traps in which a cross-hair electrode is provided transverse to the central longitudinal axis of the ion trap, thus significantly reducing ion transport through the ion trap.

The preferred device can operate as a dual mode device and can be switched between at least two different modes or states of operation. For example, in a first mode or state of operation, the preferred apparatus may operate as a conventional mass filter or mass analyser such that only ions having a particular mass or mass to charge ratio or ions having a mass to charge ratio within a particular range are transmitted onwards. Preferably to significantly attenuate other ions. In a second mode or state of operation, the preferred apparatus can operate as a linear ion trap as follows: wherein ions are preferably mass-selectively displaced in at least one radial direction, and subsequently ions are preferably ejected, preferably axially adiabatically, mass-selectively, through a radially dependent axial DC potential barrier.

The preferred ion trap preferably comprises an RF ion guide or RF rod set. The ion trap preferably comprises two quadrupole rod sets arranged adjacent or in close proximity to each other and coaxially. The first quadrupole rod set is preferably arranged upstream of the second quadrupole rod set. The second quadrupole rod set is preferably significantly shorter than the first quadrupole rod set.

According to the preferred embodiment, one or more radially dependent axial DC barriers are preferably created at least one end of the preferred device. The one or more axial DC barriers are preferably created by applying one or more DC potentials to one or more of the rods comprising the second quadrupole rod set. The axial position of the one or more radially dependent DC barriers preferably remains substantially fixed as ions are ejected from the ion trap. However, other less preferred embodiments are also conceivable as follows: wherein the axial position of one or more radially dependent DC barriers may vary over time.

According to this preferred embodiment, the amplitude of the one or more axial DC barriers preferably remains substantially fixed. However, other less preferred embodiments are also conceivable as follows: wherein the magnitude of one or more axial DC barriers may vary over time.

The magnitude of the barrier field preferably varies in the first radial direction such that the magnitude of the axial DC barrier preferably decreases with increasing radius in the first radial direction. The magnitude of the axial DC barrier also preferably varies in a second different (orthogonal) radial direction, such that the magnitude of the axial DC barrier preferably increases with increasing radius in the second radial direction.

By applying or generating an auxiliary time-varying field within the ion guide or ion trap, ions within the ion trap are preferably mass selectively displaced. The auxiliary time-varying field preferably comprises an electric field preferably generated by applying an auxiliary AC voltage to one of the electrode pairs constituting the RF ion guide or the ion trap.

According to one embodiment, the one or more ions are preferably mass selectively radially displaced by selecting or arranging the frequency of the auxiliary time varying field to be close to or substantially corresponding to a mass-dependent characteristic frequency of oscillation of the one or more ions within the ion guide.

The mass-dependent characteristic frequency is preferably related to, corresponds to or substantially equal to the secular frequency of one or more ions within the ion trap. The secular frequency of ions in the preferred apparatus is a function of the mass-to-charge ratio of the ions. For a pure RF quadrupole, the long-term frequency can be approximated by the following equation:

where m/z is the mass-to-charge ratio of the ion, e is the electronic charge, V is the peak RF voltage, R₀Is the inscribed radius of the rod set and Ω is the angular frequency of the RF voltage.

Drawings

Various embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which:

figure 1 shows a schematic diagram of an ion trap in accordance with a preferred embodiment of the present invention;

figure 2 shows a potential energy plot between outlet electrodes arranged at the outlet of an ion trap according to an embodiment of the present invention, and shows an example of a radially dependent axial DC potential;

fig. 3 shows a section of the potential energy plot shown in fig. 2 along line y-0 and midway between the two y electrodes;

figure 4 shows a schematic diagram of an ion trap in which axially segmented vane electrodes are provided between adjacent rod electrodes, according to another embodiment;

fig. 5 shows the embodiment shown in fig. 4 in the (x ═ y) z plane, and shows how the blade electrode is preferably segmented in the axial direction;

fig. 6A shows a sequence of DC potentials preferably applied to individual blade electrodes arranged in the (x-y), z-plane, and fig. 6B shows further sequences of DC potentials also preferably applied to individual blade electrodes arranged in the (x-y), z-plane;

fig. 7A correspondingly shows a sequence of DC potentials preferably applied to individual blade electrodes arranged in the (x ═ y) z plane, and fig. 7B shows further sequences of DC potentials also preferably applied to individual blade electrodes arranged in the (x ═ y) z plane;

figure 8 shows a simion (rtm) simulation of the ion trap shown in the x, z plane in which an auxiliary AC voltage of frequency 69.936kHz is applied to one of the rod electrode pairs so as to excite ions of mass to charge ratio 300;

figure 9 shows a simion (rtm) simulation of the ion trap shown in the x, z plane in which an auxiliary AC voltage of frequency 70.170kHz is applied to one of the rod electrode pairs so as to excite ions of mass to charge ratio 299;

figure 10 shows a simion (rtm) simulation of an ion trap comprising blade electrodes shown in the x, z plane, in which an AC voltage is applied between the blade electrodes and two DC potential sequences of equal amplitude are applied to the blade electrodes;

figure 11 shows a simion (rtm) simulation of an ion trap comprising blade electrodes shown in the x, z plane, in which an AC voltage is applied between the blade electrodes and two DC potential sequences of different amplitude are applied to the blade electrodes;

figure 12 shows a mass spectrometer comprising a preferred ion trap and an ion detector according to one embodiment;

figure 13 shows a mass spectrometer comprising a mass filter or mass analyser arranged upstream of a preferred ion trap and ion detector according to one embodiment;

figure 14 shows a mass spectrometer comprising a preferred ion trap arranged upstream of a mass filter or mass analyser according to one embodiment; and is

Fig. 15 shows some experimental data.

Detailed Description

An embodiment of the present invention will now be described with reference to fig. 1. There is preferably provided an ion trap comprising: one or more inlet electrodes 1; a first main quadrupole rod set comprising two pairs of hyperbolic electrodes 2, 3; and a short second quadrupole rod set (or post-filter) arranged downstream of the main quadrupole rod set. The second, shorter quadrupole rod set preferably comprises two pairs of hyperbolic electrodes 4, 5 which can be considered to constitute two pairs of ejection electrodes 4, 5. A short second quadrupole rod set 4, 5 or post filter is preferably arranged to support axial ejection of ions from the ion trap.

In the operating mode, ions are preferably pulsed periodically into the ion trap by controlling the entrance electrode 1 or other ion optical components, such as an ion gate (not shown), which are preferably arranged upstream of the ion trap, in a pulsed manner. Ions pulsed into the ion trap are preferably radially confined within the ion trap as RF voltages are applied to the two pairs of electrodes 2, 3 which preferably constitute the first main quadrupole set. The ions are preferably radially confined within the pseudo-potential trap within the ion trap. One phase of the applied RF voltage is preferably applied to one pair of rod electrodes 2 constituting the first main quadrupole rod set, and the opposite phase of the applied RF voltage is preferably applied to the other pair of rod collectors 3 constituting the first main quadrupole rod set. Ions are preferably confined axially within the ion trap by applying a DC voltage to the entrance electrode 1 once the ions have entered the ion trap and also to at least one pair of ejection electrodes 4, 5 arranged at the exit of the ion trap. The two pairs of ejection electrodes 4, 5 are preferably maintained at the same RF voltage as the rod electrodes 2, 3 that make up the main quadrupole rod set. The amplitude and frequency of the RF voltage applied to the main rod electrodes 2, 3 and to the exit electrodes 4, 5 are preferably the same. The ions are therefore preferably confined both radially and axially within the ion trap.

Ions within the ion trap preferably lose kinetic energy due to collisions with background gas present within the ion trap, such that the ions within the ion trap may be considered to be in thermal energy after a period of time. As a result, the ions preferably form an ion cloud along the central axis of the ion trap.

The ion trap can be operated in a number of different modes of operation. The apparatus is preferably arranged to operate as a mass or mass to charge ratio selective ion trap. In this mode of operation, one or more DC voltages are preferably applied to at least one pair of exit or ejection electrodes 4, 5 arranged at the exit of the ion trap. Application of one or more DC voltages to at least one pair of ejection electrodes 4, 5 preferably results in a radially dependent axial DC potential barrier at the exit region of the ion trap. The shape of the radially dependent axial DC barrier is now described in more detail with reference to fig. 2.

Fig. 2 shows the potential surface generated between two pairs of outlet electrodes 4, 5, according to one embodiment, wherein a voltage of +4V relative to the DC bias applied to the main rod electrodes 2, 3 is applied to one pair of end electrodes 4. A voltage of-3V relative to the DC bias applied to the main rod electrodes 2, 3 is applied to the other pair of end electrodes 5.

The combination of two different DC voltages applied to the two pairs of end or exit electrodes 4, 5 preferably results in an on-axis potential barrier of +0.5V along the central longitudinal axis at the exit of the ion trap. The DC potential barrier is preferably sufficient to cause positively charged ions (i.e. cations) at thermal energy to be axially trapped within the ion guide. As shown in fig. 2, the axial trapping potential preferably increases with radius in the y-radial direction and decreases with radius in the x-radial direction.

Fig. 3 shows how the radially dependent DC potential varies with radius in the x-direction (i.e. along the halfway line of the two y-electrodes) when y is equal to zero in a standard coordinate system. The on-axis potential at x-0 and y-0 is +0.5V, and it is apparent that the potential decreases quadratically as the absolute value of x increases. This potential remains positive and therefore has the following effect: positively charged ions are axially confined within the ion trap as long as they do not move radially more than about 2mm in the x radial direction. At a radius of 2mm, the DC potential drops below the DC potential of the DC bias potential applied to the two pairs of hyperbolic rod electrodes 2, 3 constituting the main quadrupole rod set. As a result, ions moving radially more than 2mm in the x-direction will experience an extraction field when approaching an extraction or exit electrode 4, 5 arranged at the exit region of the ion trap. The extraction field is preferably used to accelerate ions moving radially more than 2mm axially out of the ion trap.

One way to increase the radial movement of ions in the x-direction within the ion trap (such that the ions subsequently experience an axial extraction field) is to: a small AC voltage (or deflection voltage) is applied between a pair of rod electrodes 3 constituting the main quadrupole rod set 2, 3. The AC voltage applied to the pair of electrodes 3 preferably generates an electric field in the x-direction between the two rod electrodes 3. This electric field preferably affects the movement of ions between the electrodes 3 and preferably causes the ions to oscillate in the x-direction at the frequency of the applied AC field. If the frequency of the applied AC field matches the secular frequency of the ions within the preferred apparatus (see equation 1 above), the ions will then preferably become resonant with the applied field. When the amplitude of ion movement in the x-direction becomes greater than the width of the axial potential barrier in the x-direction, the ions are no longer confined axially within the ion trap but instead experience the extraction field and are ejected axially from the ion trap.

The RF voltage is preferably applied to the end electrodes 4, 5 so that the ions remain radially confined when ejected axially from the ion trap.

The position of the radially dependent axial DC barrier preferably remains fixed. However, other less preferred embodiments are also conceivable as follows: wherein the position of the radially dependent axial potential barrier may be varied over time to achieve ejection or onward transmission of ions having a particular mass-to-charge ratio or mass-to-charge ratio within a particular range.

Figure 4 shows an ion trap according to another embodiment of the present invention. According to this embodiment, the ion trap preferably further comprises a plurality of axially segmented vane electrodes 6, 7. Figure 4 shows a cross-section of the ion trap in the x, y plane and shows how two pairs of blade electrodes 6, 7 may be provided between the main rod electrodes 2, 3 which make up the ion trap. The blade electrodes 6, 7 are preferably positioned in two different zero potential planes between the hyperbolic rod electrodes 2, 3. The vane electrodes 6, 7 preferably cause only minimal distortion of the field within the ion trap.

One pair of blade electrodes 6 is preferably arranged in the x-y plane, while the other pair of blade electrodes 7 is preferably arranged in the x-y plane. The two pairs of blade electrodes 6, 7 preferably terminate before the central axis of the ion trap, at an inscribed radius r. Thus, the axial ion guiding region along the central longitudinal axis of the ion trap preferably remains unrestricted or unobstructed (i.e. there is preferably a clear line of sight along the central axis of the ion trap). In contrast, known ion traps have a cross-wire electrode provided transverse to the central longitudinal axis of the ion trap, with the result that ion transport through the ion trap is reduced.

Figure 5 shows the ion trap shown in figure 4 in the (x ═ y) z plane. Ions entering the ion trap are preferably radially confined by a pseudo-potential field generated by the application of RF voltages to the main rod electrodes 2, 3. The ions are preferably confined in the axial direction by a DC potential, preferably applied to one or more of the entrance electrodes 8 and to the exit electrode 9. One or more inlet electrodes 8 are preferably arranged at the inlet of the ion trap and an outlet electrode 9 is preferably arranged at the outlet of the ion trap.

The blade electrodes 6 arranged in the x-y plane and the blade electrodes 7 arranged in the x-y plane are preferably segmented along the z-axis. According to the particular embodiment shown in fig. 5, the vane electrodes 6, 7 may be axially segmented to include twenty individual segmented electrodes arranged along the length of the preferred apparatus. However, other embodiments are also contemplated as follows: wherein the vane electrode may be axially segmented into a different number of electrodes.

The first vane electrode (#1) is preferably disposed at the entrance end of the ion trap, and the twentieth vane electrode (#20) is preferably disposed at the exit end of the ion trap.

According to one embodiment, the DC potentials are applied to the blade electrodes 6, 7, preferably according to a predetermined sequence. Fig. 6A and 6B illustrate a sequence of DC voltages that are preferably applied sequentially to the segmented vane electrodes 7 arranged in the x-y plane over a period of time from T-T0 to a subsequent time T-T21. At an initial time T-T0, all the segmented vane electrodes 9 are preferably maintained at a DC bias potential (e.g. zero) which is preferably the same as the DC bias applied to the primary shaft electrodes 2, 3. At subsequent time T1, a positive DC potential is preferably applied to the first blade electrode (#1) arranged in the x-y plane. At subsequent time T2, a positive DC potential is preferably applied to the first and second blade electrodes (#1, #2) arranged in the x ═ -y plane. The sequence is preferably formed and repeated such that a DC potential is preferably applied to the more leaf electrodes 7 progressively until at a subsequent time T20, the DC potential is preferably applied to all leaf electrodes 7 arranged in the x-y plane. Finally, at a subsequent time T21, the DC potential applied to the blade electrodes 7 arranged in the x-y plane is preferably removed substantially simultaneously from all the blade electrodes 7. For analysis of negatively charged ions (i.e. anions), a negative DC potential is preferably applied to the vane electrode 7 instead of a positive DC potential.

While a positive DC potential is preferably applied to the blade electrodes 7 arranged in the x-y plane, a positive DC potential is also preferably applied to the blade electrodes 6 arranged in the x-y plane. Fig. 7A and 7B illustrate a sequence of DC voltages that are preferably applied sequentially to the segmented vane electrodes 6 arranged in the x-y plane over a period of time from T-T0 to a subsequent time T-T21. At an initial time T-T0, all the segmented vane electrodes 6 are preferably maintained at a DC bias potential that is preferably the same as the DC bias applied to the primary shaft electrodes 2, 3 (i.e. zero). At subsequent time T1, a positive DC potential is preferably applied to the twentieth blade electrode (#20) arranged in the x-y plane. At subsequent time T2, a positive DC potential is preferably applied to the nineteenth and twentieth blade electrodes (#19, #20) arranged in the x ═ y plane. The sequence is preferably formed and repeated such that the DC potential is preferably applied to progressively more blade electrodes 6 until, at a subsequent time T20, the DC potential is preferably applied to all blade electrodes 6 arranged in the x-y plane. Finally, at a subsequent time T21, the DC potential applied to the blade electrodes 6 arranged in the x-y plane is preferably removed substantially simultaneously from all the blade electrodes 6. For analysis of negatively charged ions (i.e. anions), a negative DC potential is preferably applied to the vane electrode 6 instead of a positive DC potential.

For the positively charged ions captured, which are distributed randomly on average with respect to the central axis of the ion trap, the effect of applying a DC potential to the segmented leaf electrodes 7 arranged in the x-y plane and simultaneously applying a DC potential to the segmented leaf electrodes 6 arranged in the x-y plane, following the sequence described above with reference to fig. 6A-B and 7A-B, is: ions located on the central axis of the ion trap are pushed equally in a direction towards the inlet of the ion trap and in a direction towards the outlet of the preferred apparatus. As a result, ions located on the central axis of the ion trap will experience zero net force and will not gain energy in either direction on average.

However, ions radially displaced from the central axis towards the paddle electrodes 6 arranged in the x-y plane or towards the paddle electrodes 7 arranged in the x-y plane will preferably gain energy in one direction when these two series of DC potentials are applied to the paddle electrodes 6, 7 sequentially and simultaneously. The radially excited ions are thus preferably transported or pushed towards the outlet of the ion trap by the transient DC potential applied to the vane electrodes 6, 7.

According to one embodiment, it is also preferred to apply a small AC voltage or deflection voltage between all opposite segments of the blade electrode 7 arranged in the x-y plane. According to this embodiment, one phase of the AC voltage is preferably applied to all the blade electrodes arranged on one side of the central axis, while the opposite phase of the AC voltage is preferably applied to all the blade electrodes arranged on the other side of the central axis. The frequency of the AC or flex voltage applied to the blade electrode 7 preferably corresponds to the secular frequency of the ion or ions within the preferred apparatus that are desired to be ejected axially from the ion trap (see equation 1). Application of an AC voltage preferably causes the ions to increase their amplitude of oscillation in the x-y plane (i.e. in one radial direction). Thus, these ions will on average preferably experience a field accelerating towards the exit of the preferred device that is stronger than the corresponding field effecting acceleration towards the entrance of the preferred device. After the ions have acquired sufficient axial energy, the ions preferably overcome the radially dependent DC potential barrier provided by the exit electrode 9. The exit electrode 9 is preferably arranged to create a radially dependent DC potential barrier in the manner described above. Other embodiments are also contemplated as follows: wherein ions having a mass to charge ratio within a first range may be pushed, directed, accelerated or propelled in a first axial direction, while other ions having a mass to charge ratio within a second different range may be pushed, directed, accelerated or propelled simultaneously or otherwise in a second different axial direction. The second axial direction is preferably orthogonal to the first axial direction.

An ion trap comprising segmented vane electrodes 6, 7 (in which one or more DC voltage sequences are applied to the vane electrodes 6, 7 in sequence) preferably has the following advantages: the radially excited ions are then actively transported to the exit region of the ion trap by applying a transient DC voltage or potential to the blade electrodes 6, 7. The ions are then ejected axially from the ion trap, preferably without delay, regardless of their initial position along the z-axis of the ion trap.

The sequence of DC voltages or potentials preferably applied to the blade electrodes 6, 7 as described above with reference to fig. 6A-6B and 7A-7B illustrates only one specific combination of DC potential sequences that may be applied to the segmented blade electrodes 6, 7 in order to push or translate ions along the length of the ion trap after they have been excited in a radial direction. However, other embodiments are also contemplated as follows: wherein different sequences of DC potentials may be applied to one or more of the sets of blade electrodes 6, 7 with similar results.

The ion trap comprising segmented vane electrodes 6, 7 as described above may be operated in a variety of different modes of operation. For example, in one mode of operation, the magnitude of the transient DC voltage applied to the segmented vane electrodes 6 arranged in the x-y plane may be arranged such that it is greater than the magnitude of the transient DC voltage applied to the segmented vane electrodes 7 arranged in the x-y plane. As a result, ions will be pushed towards the entrance region of the ion trap, which are on average randomly distributed with respect to the central axis of the ion trap. Ions may be trapped within a localised region of the ion trap by appropriate application of a DC voltage, preferably applied to the entrance electrode 8. Ions sufficiently displaced in the x-y plane preferably cause acceleration of the ions towards the exit of the preferred device by applying an auxiliary AC or flexo voltage, preferably applied between the vane electrodes 7 arranged in the x-y plane. The ions are then ejected from the ion trap, preferably in an axial direction.

Other embodiments of the invention are also contemplated as follows: wherein ions of different mass to charge ratios may be sequentially released or ejected from the ion trap by varying or scanning one or more parameters related to the resonant mass to charge ratio of the ions over time. For example, referring to equation 1, the frequency of the auxiliary AC voltage or flex voltage applied to one of the rod electrode pairs 2, 3 and/or to one of the blade electrode sets 6, 7 may be varied over time, while the amplitude V of the main RF voltage applied to the rod electrodes 2, 3 and/or the frequency Ω of the main RF voltage may be maintained substantially constant (in order to radially confine ions within the ion trap).

According to another embodiment, the amplitude V of the primary RF voltage applied to the primary rod electrodes 2, 3 may be varied over time, while the frequency of the auxiliary AC voltage or flex voltage applied to the primary rod electrodes 2, 3 and/or the frequency Ω of the primary RF voltage may be maintained substantially constant.

According to another embodiment, the frequency Ω of the primary RF voltage applied to the primary rod electrodes 2, 3 may be varied over time, while the frequency of the auxiliary AC voltage or flex voltage applied to the primary rod electrodes 2, 3 and/or the amplitude V of the primary RF voltage may be maintained substantially constant.

According to another embodiment, the frequency Ω of the main RF voltage applied to the rod electrodes 2, 3 and/or the frequency of the auxiliary AC voltage or flex voltage and/or the amplitude V of the main RF voltage may be varied in any combination.

Figure 8 shows the results of SIMON 8(RTM) simulations of ion behaviour within a preferred ion trap arranged substantially as shown and described above with reference to figure 1. The inscribed radius R of the rod electrodes 2 and 3₀The modeling was 5 mm. The inlet electrode 1 is modeled as a voltage biased at +1V, while the rod collectors 2, 3 are modeled as voltages biased at 0V. The main RF voltage applied to the rod electrodes 2, 3 and to the exit electrodes 4, 5 was set at 150V (zero to peak amplitude) and a frequency of 1 MHz. In-phase RF voltages are applied to the pair of main rod collectors 3 and to the pair of terminal electrodes 5. The opposite phases of the RF voltage applied to the other pair of main rod collectors 2 and to the other pair of end electrodes 4. The pair of y-terminal electrodes 4A voltage biased at +4V, and the pair of x-terminal electrodes 5 are biased at-3V. Modeling background barometric pressure as 10^-4Bracket (1.3X 10)^-4Millibar) helium (resistance model with resistance linearly proportional to ion velocity). The initial ion axial energy was set at 0.1 eV.

At initial time zero, five ions were modeled as being provided within the ion trap. Ions were modeled as having mass-to-charge ratios of 298, 299, 300, 301, and 302. The ions were then immediately subjected to an auxiliary or excitation AC field generated by applying a sinusoidal AC potential difference of 30mV (peak to peak) between the pair of x-rod electrodes 3 at a frequency of 69.936 kHz. Under these simulation conditions, the radial movement of ions with a mass-to-charge ratio of 300 increased such that it was greater than the width of the axial DC potential barrier arranged at the exit of the ion trap. As a result, after 1.3ms, ions of mass to charge ratio 300 are extracted or ejected axially from the ion trap. The simulation is allowed to continue for around 10ms, during which time no other ions are extracted or ejected from the ion trap.

A second simulation was performed and the results are shown in fig. 9. Keeping all parameters the same as the previous simulation described above with reference to fig. 8, except that: the frequency of the applied auxiliary or excitation AC voltage or flex voltage applied to the pair of x-rod electrodes 3 increased from 69.936kHz to 70.170 kHz. In this simulation, this time an ion ejection with a mass-to-charge ratio 299, while all other ions remain confined within the ion trap. This result is in good agreement with equation 1.

Figure 10 shows the results of another SIMION 8(RTM) simulation in which the operation of an ion trap comprising segmented blade electrodes 6, 7 similar to that shown in figure 5 was modelled. The ion trap was modeled to operate in a mode in which a sequence of DC potentials were applied to the vane electrodes 6, 7 in a substantially similar manner as shown and described above with reference to figures 6A-B and 7A-B.

The blade electrodes 6, 7 are modeled as comprising two electrode sets. One blade electrode set 6 is arranged in the x-y plane, while the other blade electrode set 7 is arranged in the x-y planeArranged in the x-y plane. Each vane electrode set includes two electrodes, with a first one of the electrodes disposed on one side of the central ion guide region and a second one of the electrodes disposed on the other side of the central ion guide region. The first and second stripe electrodes are arranged to be coplanar. Each electrode comprised twenty individual blade electrodes. Each blade electrode extends 1mm along the z-axis (or axial direction). A 1mm spacing was maintained between adjacent blade electrodes. Inscribed radius R of quadrupole rod set₀Set at 5mm and the inscribed radius produced by the two pairs of vane electrodes 6, 7 is set at 2.83 mm.

A DC bias of +2V was modeled as applied to the inlet electrode 8 and a DC bias applied to the outlet electrode 9 was also modeled as + 2V. The DC bias applied to the main rod electrodes 2, 3 is set at 0V. The amplitude of the RF potential applied to the rod electrodes 2, 3 and to the exit electrode 9 was set at 450V (zero to peak), while the frequency of the RF potential was set at 1 MHz. The background air pressure was set to 10^-4Bracket (1.3X 10)^-4Millibar) helium (resistance model). The initial axial energy of the ions was set at 0.1 eV. Transient DC voltages are applied to the blade electrodes 6, 7, wherein the time step between each application of DC voltages to the segmented blade electrodes 6, 7 is set at 0.1 μ s. The magnitude of the DC voltage applied to the two sets of segmented blade electrodes 6, 7 is set at 4V.

At time zero, six positive ions are modeled as being provided within the ion trap. Ions were modeled as having mass-to-charge ratios of 327, 328, 329, 330, 331, and 332. The ions are then immediately subjected to an auxiliary or excitation AC field generated by applying a sinusoidal AC potential difference of 160mV (peak to peak) between the vane electrodes 7 arranged in the x-y plane. The frequency of the auxiliary or excitation AC voltage was set at 208.380 kHz. Under these simulation conditions, the radial movement of the ion of mass-to-charge ratio 329 increases in the x-y plane, with the result that the ion then acquires axial energy in the z-axis due to the transient DC voltage applied to the vane electrodes 6, 7. Ions of mass to charge ratio 329 are accelerated towards the exit electrode 9. The ions gain an axial energy sufficient to overcome the DC potential barrier applied by the exit electrode 9. As a result, ions of mass to charge ratio 329 are extracted or axially ejected from the ion trap after about 0.65 ms. Other ions remain trapped within the ion trap.

Figure 11 shows the results of a second SIMION 8(RTM) simulation of an ion trap with segmented vane electrodes 6, 7. The ion trap is arranged and operated in a similar mode to that described above with reference to figure 10. However, according to this simulation, the DC bias applied to the exit electrode 9 was reduced to 0V. The magnitude of the DC voltage gradually applied to the vane electrodes 7 arranged in the x-y plane was set to 3.5V, and the magnitude of the DC voltage gradually applied to the vane electrodes 6 arranged in the x-y plane was set to 4.0V. The amplitude of the auxiliary or excitation AC voltage applied between the foil electrodes 7 arranged in the x-y plane is set at 120mV (peak to peak) and has a frequency of 207.380 kHz.

Six ions of different mass to charge ratios are initially confined to the upstream end of the ion trap in proximity to the entrance electrode 8. The radial movement of an ion of mass to charge ratio 329 increases in the x-y plane until the average force to accelerate the ion towards the exit of the preferred device exceeds the average force to accelerate the ion towards the entrance of the preferred device. Ions with a mass to charge ratio 329 are shown to exit the preferred apparatus after about 0.9 ms.

According to one embodiment of the present invention, the preferred device can operate in a number of different modes. For example, in one mode of operation, the preferred apparatus may operate as a linear ion trap. In another mode of operation, the preferred apparatus can operate as a conventional quadrupole rod set mass filter or mass analyzer by applying appropriate RF and resolving DC voltages to the rod electrodes. A DC voltage may be applied to the exit electrode to provide a delayed DC ramp, also known as a Brubaker lens or a post filter.

According to another embodiment, the preferred apparatus may operate as an isolation unit and/or as a lysis unit. The ion packets may be arranged to enter the preferred apparatus. An auxiliary AC voltage or flex voltage may then be applied to isolate the ions. The auxiliary AC voltage or flex voltage preferably contains frequencies corresponding to secular frequencies of ions of various mass to charge ratios, but does not include secular frequencies corresponding to ions which are desired to be initially isolated and retained within the ion trap. The auxiliary AC voltage or flex voltage is preferably used to excite ions that are not desired or desired at resonance so that they are preferably decoupled from the rod or system. The remaining isolated ions are then preferably ejected axially and/or subjected to one or more fragmentation processes within the preferred apparatus.

According to one embodiment, the ions may be subjected to one or more fragmentation processes including collision induced dissociation ("CID"), electron transfer dissociation ("ETD"), or electron capture dissociation ("ECD") within the preferred apparatus. These processes can be repeated to facilitate MSn experiments. The generated fragment ions may be released in a mass-selective or non-mass-selective manner to a further preferred device arranged downstream.

Other embodiments are also contemplated as follows: wherein the preferred device may operate as a stand-alone device such as shown in figure 12. According to this embodiment, the ion source 11 may be arranged upstream of the preferred apparatus 10, while the ion detector 12 may be arranged downstream of the preferred apparatus 10. The ion source 11 preferably comprises a pulsed ion source, such as a laser desorption ionization ("LDI") ion source, a matrix-assisted laser desorption ionization ("MALDI") ion source, or a desorption ionization on silicon ("DIOS") ion source.

Alternatively, the ion source 11 may comprise a continuous ion source. If a continuous ion source is provided, an additional ion trap 13 may preferably be provided upstream of the preferred apparatus 10. The ion trap 13 is preferably used to store ions and then preferably periodically release the ions into the apparatus 10. The continuous ion source may include an electrospray ionization ("ESI") ion source, an atmospheric pressure chemical ionization ("APCI") ion source, an electron impact ("EI") ion source, an atmospheric pressure photoionization ("APPI") ion source, a chemical ionization ("CI") ion source, a desorption electrospray ionization ("DESI") ion source, an atmospheric pressure MALDI ("AP-MALDI") ion source, a fast atom bombardment ("FAB") ion source, a liquid secondary ion mass spectroscopy ("LSIMS") ion source, a field ionization ("FI") ion source, or a field desorption ("FD") ion source. Other continuous or pseudo-continuous ion sources may alternatively be used.

According to one embodiment, the preferred apparatus may be combined to form a hybrid mass spectrometer. For example, according to the embodiment shown in fig. 13, a mass analyzer or mass filter 14 in combination with a lysis device 13 may be provided upstream of the preferred device 10. An ion trap (not shown) may also be provided upstream of the preferred apparatus 10 to store ions which are then periodically released into the preferred apparatus 10. The lysis device 130 may be configured to operate as an ion trap or ion guide in certain modes of operation. According to the embodiment shown in fig. 13, ions that have first been mass selectively transported by the mass analyser or mass filter 14 may then be fragmented in the fragmentation device 13. The resulting fragment ions are then preferably mass analyzed by the preferred apparatus 10, while the axially ejected ions from the preferred apparatus 10 are then preferably detected by the downstream ion detector 12.

The mass analyser or mass filter 14 shown in figure 13 preferably comprises a quadrupole rod set mass filter or other ion trap. Alternatively, the mass analyser or mass filter 14 may comprise a magnetic sector mass filter or mass analyser or an axially accelerating time of flight mass analyser.

The fragmentation device 13 is preferably arranged to fragment ions by collision induced dissociation ("CID"), electron capture dissociation ("ECD"), electron transfer dissociation ("ETD"), or by surface induced dissociation ("SID").

FIG. 14 shows a mass spectrometer according to another embodiment. According to this embodiment, the preferred device 10 is preferably arranged upstream of the lysis device 13 and the mass analyser 15. The lysis device 13 is preferably arranged downstream of the preferred device 10 and upstream of the mass analyser 15. An ion trap (not shown) may be arranged upstream of the preferred device 10 to store and then periodically release ions towards the preferred device 10. The geometry shown in fig. 14 preferably allows ions to be ejected axially from the preferred apparatus 10 in a mass-dependent manner. The ions ejected axially from the preferred apparatus 10 are then preferably lysed in a lysis apparatus 13. The resulting fragment ions are then preferably analysed by a mass analyser 15.

The embodiment shown and described above with reference to fig. 14 preferably facilitates performing parallel MS/MS experiments, wherein ions exiting the preferred apparatus 10 in a mass-dependent manner are then preferably fragmented. This allows the distribution of fragment ions to parent ions to be achieved at a high duty cycle. The fragmentation device 13 may be arranged to fragment ions by collision induced dissociation ("CID"), electron capture dissociation ("ECD"), electron transfer dissociation ("ETD"), or surface induced dissociation ("SID"). The mass analyser 15 arranged downstream of the fragmentation device 13 preferably comprises a time-of-flight mass analyser or another ion trap. According to other embodiments, the mass analyzer 15 may comprise a magnetic sector mass analyzer, a quadrupole rod set mass analyzer, or a fourier transform based mass analyzer, such as an orbital capture mass spectrometer.

Other embodiments of the invention are also contemplated as follows: wherein ions can be radially displaced within the ion trap by means other than the application of a resonance-assisting AC voltage or a flexural voltage. For example, the ions may be radially displaced by mass selective instability and/or by parametric excitation and/or by applying a DC potential to one or more rod electrodes 2, 3 and/or to one or more blade electrodes 6, 7.

According to a less preferred embodiment, ions may be ejected axially from one or both ends of the ion trap in a sequential and/or simultaneous manner.

According to one embodiment, the preferred apparatus may be configured such that a plurality of different species of ions having different specific mass-to-charge ratios may be ejected axially from the ion trap substantially simultaneously and hence in a substantially parallel manner.

The preferred apparatus may be operated at elevated pressures so that ions may be separated in time in accordance with their ion mobility as they pass through or are ejected from the preferred apparatus in an operating mode.

Hybrid embodiments as described above with reference to fig. 13 and 14 may also include an ion mobility based separation stage. Ions may be separated according to their mobility within preferred apparatus 10 and/or within one or more separate ion mobility devices that may be located, for example, upstream and/or downstream of preferred apparatus 10.

According to one embodiment, one or more radially dependent DC barriers of position over time may be provided by segmenting the main quadrupole rod electrode rather than by providing additional blade electrodes. The DC potentials may be applied to the segments in a sequence substantially as described above. AC flexoelectric excitation between one or both pairs of quadrupole rods will result in selective axial ejection of mass.

According to one embodiment, the position of the different radially dependent barriers may vary over time.

According to one embodiment, different sequences describing the variation of the radially dependent barrier position over time may be implemented.

According to one embodiment, the axial position of the barrier field may vary along all or a portion of the length of the preferred device.

The time interval between application of DC potentials to different electrode segments within the preferred device may vary at any point during operation of the preferred device.

The magnitude of the DC voltage applied to different electrode segments at different times may vary at any point during operation of the preferred device.

According to this preferred embodiment, the same DC potential can be applied to opposing blade electrodes in the same plane at the same time. However, according to other embodiments, one or more DC voltages may be applied in other, more complex sequences without altering the operating principle.

For embodiments in which one or more radially dependent DC barriers are arranged to vary position over time, the preferred apparatus may be used in conjunction with an energy analyzer downstream of the preferred embodiment. The energy analyzer may for example comprise an electrostatic analyzer ("ESA") or a grid to which a suitable DC potential is applied.

For embodiments in which one or more radially dependent DC barriers are arranged to vary position over time, the preferred apparatus may also be used to substantially simultaneously confine and/or separate positive and negative ions.

According to one embodiment, the RF quadrupole may add an additional DC potential, resulting in a modification of equation 1.

One advantage of this preferred embodiment is that: the energy spread of ions exiting the device or ion trap is preferably relatively low and well defined. This is due to the fact that: according to the preferred embodiment, no axial energy is transferred to the ions from the main radially confining RF potential during ejection. This is in contrast to other known ion traps in which axial energy transfer from the confining RF potential to the confined ions is indispensable to the ejection process. This axial energy transfer may occur in the fringe field region at the exit of the device due to the interaction of the main RF potential and the DC barrier electrode.

This preferred embodiment is therefore particularly advantageous where ions are to be passed to a downstream device such as a downstream mass analyser or collision or reaction gas cell, the acceptance criteria of which may be such that the overall transmission and/or performance of the device is adversely affected by a large spread in input ion kinetic energy.

A SIMON 8(RTM) simulation similar to that described above with reference to figure 8 is used to record the kinetic energy of a group of ions exiting an ion trap arranged substantially as described above with reference to figure 1. The inscribed radius R of the rod electrodes 2 and 3₀The modeling was 4.16 mm. The inlet electrode 1 is modeled as a voltage biased at +1V, while the rod collectors 2, 3 are modeled as voltages biased at 0V. To be applied to the rod electrodes 2, 3 and the outlet electrodes 4, 5The main RF voltage is set at 800V (zero to peak amplitude) and a frequency of 1 MHz. In-phase RF voltages are applied to the pair of main rod collectors 3 and to the pair of terminal electrodes 5. The opposite phases of the RF voltage applied to the other pair of main rod collectors 2 and to the other pair of end electrodes 4. The pair of y-side electrodes 4 is biased at a voltage of +4V, and the pair of x-side electrodes 5 is biased at-2V. Modeling background barometric pressure as 10^-4Bracket (1.3X 10)^-4Millibar) helium (resistance model with resistance linearly proportional to ion velocity). The initial ion axial energy was set at 0.1 eV.

At initial time zero, 300 ions with a mass to charge ratio 609 were modeled as being provided within the ion trap. A sinusoidal AC potential difference of 200mV (peak to peak) was applied between the pair of x-rod electrodes 3 at a frequency of 240 kHz. The RF voltage applied to the rod electrode is then ramped up from its initial value to 1000V (zero to peak amplitude). Under these simulation conditions, the radial movement of the ions is increased such that it is larger than the width of the axial DC barrier arranged at the exit of the ion trap. As a result, the ions exit the ion trap axially. The kinetic energy of the ions was measured at a distance of 4mm from the end of the end electrode 5. The average dynamic of the ions is 2eV and the standard deviation of the kinetic energy is 2.7 eV.

For comparison, an alternative known axial ejection technique was modeled using SIMION 8 (RTM). The relevant parameters used were the same as above and the fringe field lens at the exit end of the device was set to a DC voltage of +2 volts. In this case, the average kinetic energy of the ions is 49.1eV, and the standard deviation of the kinetic energy is 56.7 eV.

Figure 15 shows data obtained from an experimental ion trap according to the preferred embodiment. The experimental ion trap was installed into a modified triple quadrupole mass spectrometer. Positive ion electrospray ionization was used to introduce bovine insulin samples, and a quadrupole mass filter upstream of the ion trap was used to select ions in a 4+ charge state. The ion trap was filled with ions for about two seconds before an analytical scan of the main limiting RF amplitude was performed at a scan rate of 2Da per second. One pair of exit electrodes was supplied with +20 volts DC and the other set of exit electrodes was supplied with-14 volts DC to create a radially dependent potential barrier. A mass spectrum of a narrow mass-to-charge ratio region encompassing the isotopic envelope of the 4+ charge state is shown. Under these conditions, a mass resolution of about 23,800 was achieved. According to one embodiment, a single multipole rod set may be used as a linear ion trap. Several specific mechanical configurations are contemplated.

According to one embodiment, a solid metal rod may be provided, wherein at least one or more regions of the rod comprise a dielectric coating covered by a conductive coating. The thickness of the coating is preferably such that the outer diameter of the rod does not increase significantly. A DC voltage may then be applied to the electrically conductive coating region to form one or more axial DC barriers, with the intention that the RF voltage applied to the primary rods form an RF quadrupole field through the coating with only a slight attenuation.

Another embodiment substantially identical to the above described embodiment is also envisaged, with the difference that: instead of a solid metal rod, a ceramic, quartz or similar rod with an electrically conductive coating may be used.

Finally, a further embodiment substantially identical to the two embodiments described above is also envisaged, with the difference that: instead of a dielectric and conductive coating, a thin, electrically insulating wire is wound onto the rod or in a groove formed in the surface of the rod.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as set forth in the following claims.

Claims

1. An ion trap comprising:

a first electrode set comprising a first plurality of electrodes;

a second electrode set comprising a second plurality of electrodes, wherein the second electrode set is disposed downstream of the first electrode set at an exit of the ion trap;

a first device arranged and adapted to apply two or more different DC voltages to the second plurality of electrodes such that: (a) ions having a radial displacement within a first range undergo a DC trapping field, DC potential barrier or barrier field in at least one axial direction to confine at least some of the ions within the ion trap; and (b) ions having a radial displacement within a second, different range are subjected to a DC extraction field, an accelerating DC potential difference or an extraction field used to extract or accelerate at least some of the ions in the at least one axial direction and/or to extract or accelerate at least some of the ions out of the ion trap;

wherein the first device is further arranged and adapted to apply the two or more different DC voltages to the second plurality of electrodes so as to confine at least some positive and/or negative ions axially within the ion trap if the ions have a radial displacement from a central longitudinal axis of the first electrode set and/or the second electrode set that is less than a first value; and wherein the first apparatus is arranged and adapted to apply the two or more different DC voltages to the second plurality of electrodes so as to produce, in use, an extraction field to extract or accelerate at least some positive and/or ions out of the ion trap if the ions have a radial displacement from the central longitudinal axis of the first and/or second electrode sets greater than the first value; and

a second device arranged and adapted to vary, increase, decrease or alter the radial displacement of at least some ions within the ion trap.

2. The ion trap of claim 1, wherein the first electrode set comprises a first central longitudinal axis, and wherein:

(i) a direct line of sight along the first central longitudinal axis; and/or

(ii) No physical axial obstruction along the first central longitudinal axis; and/or

(iii) The ions transmitted along the first central longitudinal axis in use are transmitted with an ion transmission efficiency of 100%.

3. The ion trap of claim 1, wherein the second electrode set comprises a second central longitudinal axis, and wherein:

(i) a direct line of sight along the second central longitudinal axis; and/or

(ii) No physical axial obstruction along the second central longitudinal axis; and/or

(iii) The ions transmitted along the second central longitudinal axis in use are transmitted with an ion transmission efficiency of 100%.

4. An ion trap as claimed in claim 1, wherein said second device is arranged to:

(i) causing at least some ions having a radial displacement falling within the first range at a first time to have a radial displacement falling within the second, different range at a second, subsequent time; and/or

(ii) Causing at least some ions having a radial displacement falling within the second different range at a first time to have a radial displacement falling within the first range at a second subsequent time.

5. An ion trap as defined in claim 1, wherein:

(a) the first plurality of electrodes comprises a multipole rod set, a quadrupole rod set, a hexapole rod set, an octapole rod set, or a rod set having more than eight rods; and/or

(b) The second plurality of electrodes includes a multipole rod set, a quadrupole rod set, a hexapole rod set, an octapole rod set, or a rod set having more than eight rods.

6. An ion trap as claimed in claim 1, wherein said first device is arranged and adapted to apply two or more different DC voltages to said second plurality of electrodes so as to produce, in use, an electrical potential within said first set of electrodes and/or within said second set of electrodes that increases and/or decreases and/or varies with radial displacement in a first radial direction from a central longitudinal axis of said first set of electrodes and/or said second set of electrodes; and is

Wherein the first device is arranged and adapted to apply two or more different DC voltages to the second plurality of electrodes so as to generate, in use, an electrical potential that increases and/or decreases and/or varies with radial displacement from a central longitudinal axis of the first electrode set and/or the second electrode set in a second radial direction, wherein the second radial direction is orthogonal to the first radial direction.

7. An ion trap as claimed in claim 1, wherein said second device is arranged and adapted to apply a first and/or second phase opposition of one or more excitation voltages, AC voltages or deflection voltages to at least some of said first plurality of electrodes and/or to at least some of said second plurality of electrodes so as to radially excite at least some ions in a mass or mass to charge ratio selective manner within said first electrode set and/or said second electrode set, thereby increasing radial movement of at least some ions in at least one radial direction within said first electrode set and/or said second electrode set in a mass or mass to charge ratio selective manner.

8. An ion trap as claimed in claim 1, further comprising a first plurality of vane or secondary electrodes arranged between said first electrodes and/or a second plurality of vane or secondary electrodes arranged between said second set of electrodes.

9. An ion trap as claimed in claim 1, wherein said second device is arranged and adapted to increase the radial displacement of ions by applying one or more DC potentials to at least some of said first and/or second plurality of electrodes.

10. An ion trap as claimed in claim 1, wherein in the operating mode:

(i) ions are ejected adiabatically from the ion trap without transferring axial energy to the ions and/or in an axial direction; and/or

(ii) Ions are ejected axially from the ion trap in an axial direction with an average axial kinetic energy in a range selected from: (i) less than 1 eV; (ii)1-2 eV; (iii)2-3 eV; (iv)3-4 eV; (v)4-5 eV; (vi)5-6 eV; (vii)6-7 eV; (viii)7-8 eV; (ix)8-9 eV; (x)9-10 eV; (xi)10-15 eV; (xii)15-20 eV; (xiii)20-25 eV; (xiv)25-30 eV; (xv)30-35 eV; (xvi)35-40 eV; and (xvii)40-45 eV; and/or

(iii) Ions are ejected axially from the ion trap in an axial direction, and wherein the standard deviation of the axial kinetic energy is in a range selected from the following ranges: (i) less than 1 eV; (ii)1-2 eV; (iii)2-3 eV; (iv)3-4 eV; (v)4-5 eV; (vi)5-6 eV; (vii)6-7 eV; (viii)7-8 eV; (ix)8-9 eV; (x)9-10 eV; (xi)10-15 eV; (xii)15-20 eV; (xiii)20-25 eV; (xiv)25-30 eV; (xv)30-35 eV; (xvi)35-40 eV; (xvii)40-45 eV; and (xviii)45-50 eV.

11. An ion trap as defined in claim 1, wherein the first set of electrodes comprises a first multipole set and the second set of electrodes comprises a second multipole set, and wherein the same amplitude and/or frequency and/or phase of AC or RF voltage is applied to the first multipole set and to the second multipole set so as to radially confine ions within the first and/or second multipole sets.

12. A mass spectrometer comprising an ion trap as claimed in any preceding claim.

13. A method of trapping ions, comprising:

providing a first electrode set comprising a first plurality of electrodes and a second electrode set comprising a second plurality of electrodes, the second electrode set being disposed downstream of the first electrode set at an exit of an ion trap;

applying two or more different DC voltages to the second plurality of electrodes such that ions having a radial displacement within a first range experience a DC trapping field, DC potential barrier or barrier field that serves to confine at least some of the ions within the ion trap in at least one axial direction, and wherein ions having a radial displacement within a second different range experience a DC extraction field, accelerating DC potential difference or extraction field that serves to extract or accelerate at least some of the ions in the at least one axial direction and/or to extract or accelerate at least some of the ions out of the ion trap;

wherein the two or more different DC voltages are applied to the second plurality of electrodes so as to confine at least some positive and/or negative ions axially within the ion trap if the ions have a radial displacement from a central longitudinal axis of the first electrode set and/or the second electrode set that is less than a first value; and wherein the two or more different DC voltages are applied to the second plurality of electrodes so as to generate, in use, an extraction field that acts to extract or accelerate at least some positive and/or ions out of the ion trap if the ions have a radial displacement from the central longitudinal axis of the first electrode set and/or the second electrode set that is greater than the first value; and

varying, increasing, decreasing or altering the radial displacement of at least some ions within the ion trap.

14. A method of mass spectrometry comprising the method of capturing ions of claim 13.