WO2004109741A2 - Extraction d'ions - Google Patents

Extraction d'ions Download PDF

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Publication number
WO2004109741A2
WO2004109741A2 PCT/GB2004/002455 GB2004002455W WO2004109741A2 WO 2004109741 A2 WO2004109741 A2 WO 2004109741A2 GB 2004002455 W GB2004002455 W GB 2004002455W WO 2004109741 A2 WO2004109741 A2 WO 2004109741A2
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WO
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Prior art keywords
ions
electrical field
ion
field
gas
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WO2004109741A3 (fr
Inventor
John Hoyes
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MS HORIZONS Ltd
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MS HORIZONS Ltd
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Priority to GB0600268A priority Critical patent/GB2419462B/en
Publication of WO2004109741A2 publication Critical patent/WO2004109741A2/fr
Publication of WO2004109741A3 publication Critical patent/WO2004109741A3/fr
Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/622—Ion mobility spectrometry
    • G01N27/623—Ion mobility spectrometry combined with mass spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/622—Ion mobility spectrometry
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/04—Arrangements for introducing or extracting samples to be analysed, e.g. vacuum locks; Arrangements for external adjustment of electron- or ion-optical components

Definitions

  • This invention relates to ion extraction devices, analytical devices incorporating same, methods of extracting ions and methods of analysing ions or physical phenomena associated with ions, with particular, but by no means exclusive, reference to mass spectrometry.
  • US 4,283,626 describes the use of a "leaky dielectric" inserted inside the multiple to allow for the provision of a drift field to speed the ions through a collision cell.
  • This leaky dielectric is transparent to the RF field (thus maintaining a potential well) but has enough resistivity to allow a potential gradient to be applied axially along its length.
  • US 4,283,626 recognises that such a drift field in the presence of gas may be used to separate ions for analytical purposes.
  • US 5,847,386 describes a number of different methods to induce a smooth axial field along the length of the linear guides to speed the transmission of ions through them.
  • Such methods include segmenting of the rods themselves, or using external ring electrodes, or tapering the rods themselves or using different pitch circle diameters for oppositely phased rod sets at either end of the guide.
  • US patent publication 2002/0070338 describes the use of segmented rods to provide an axial D.C. field and to give separation of the ion species according to their Ion mobility. Again, RF confinement is combined with a drift field in the presence of gas. This combination is versatile since ions may be manipulated in a wide variety of ways using D.C travelling waves in the axial direction to create moving potential wells while maintaining radial confinement with the ponderomotive force from the RF supply.
  • Related techniques are described in US 5,206,506 and US 6483109. The contents of US 4,283,626; US 5,847,386; US 2002/0070338; US 5,206,506 and US 6,483,109 are hereby incorporated by reference.
  • the present invention addresses this desire and, furthermore, provides numerous non- limiting advantages which are set forth below.
  • the electrical field is applied axially across the laminar flow.
  • the method may further comprise the step of confining the entrained ions radially with respect to the axis of flow of the laminar flow of carrier gas.
  • the step of confining the entrained ions may comprise radially confining the ions by a ponderomotive force. It is preferred to radially confine the ions, since this prevents diffusion losses of ions.
  • the ponderomotive force may be supplied by suitable means such as an RF multipole or ring set.
  • the step of varying the electrical field may comprise reducing the magnitude of the electrical field to a level that permits ions of a first range of ion mobilities to pass through the electrical field by preventing ions of a second range of ion mobilities from passing through the electrical field.
  • the electrical field may be reduced in a stepwise manner or a continuous manner.
  • an isolating electrical field may be applied so as to prevent ions upstream of the isolating electrical field from being carried to the barrier region.
  • the isolating electrical field may be reduced so as to permit ions upstream of the isolating electrical field to be carried to the barrier region.
  • the step of varying the electrical field may be performed so as to extract ions from the barrier region in a pulsed manner.
  • the electrical field may be varied between at least a first state and a second state, with the peak magnitude of the electrical field in the second state being less than the peak magnitude of the electrical field in the first state, so that ions of a defined range of mobilities can be extracted from the barrier region when the electrical field is in the second state and prevented from passing out of the barrier region when the electrical field is in the fust state.
  • the location of the peak magnitude of the electrical field in the second state may be upstream of the location of the peak magnitude of the electrical field in the first state so that only ions of a desired range of mobilities which are situated in a predetermined range of locations are extracted.
  • a scheme may be employed in which the magnitude of the electrical field is first reduced, and then pulsed extraction of ions is performed.
  • the electrical field in the barrier region may be selected so as to produce a spatial separation of ions of different ion mobilities in the barrier region.
  • the method may further comprise the step of applying a drift field to at least a portion of the laminar flow of carrier gas.
  • An arrangement comprising a leaky dielectric shield may be used to provide the drift field.
  • the arrangement may be a multipole arrangement.
  • the velocity distribution of the carrier gas as a function of radial position of the laminar flow in the barrier region may be substantially parabolic.
  • a method of analysing ions or phenomena associated with ions comprising the steps of:
  • the analysis means may comprise mass spectrometry means such as a time of flight (TOF) mass spectrometer, or a multipole, Fourier transform or ion trap mass spectrometer. Other forms of analysis means, such as a spectroscopic technique, may be employed instead. Phenomena associated with ions, such as ion-molecule, ion-radical or ion-ion reactions, might be analysed using techniques to analyse reaction products, measure reaction rates and study reaction dynamics.
  • TOF time of flight
  • ion trap mass spectrometer e.g., a multipole, Fourier transform or ion trap mass spectrometer.
  • Other forms of analysis means such as a spectroscopic technique, may be employed instead.
  • Phenomena associated with ions such as ion-molecule, ion-radical or ion-ion reactions, might be analysed using techniques to analyse reaction products, measure reaction rates and study reaction dynamics.
  • the analysis means may comprise a collision cell. Ions may be extracted from the collision cell using a method according to the first aspect of the invention. According to a third aspect of the invention there is provided an ion extraction device comprising:
  • gas flow means including a gas flow conduit suitable for generating a laminar flow of carrier gas therethrough;
  • ion entrance means through which ions can be introduced into the gas flow conduit so that said ions become entrained in said laminar flow
  • electrical field producing means for applying an electrical field to a barrier region of the gas flow conduit, the electrical field producing means being operable to apply the electrical field across the direction of laminar flow in said gas flow conduit so as to prevent at least some ions entrained in a laminar flow in the gas flow conduit from passing through the electrical field;
  • the electrical field producing means is variable so as to allow ions of chosen characteristics to pass through the electrical field.
  • the ion extraction device may further comprise ion radial confinement means for confining entrained ions radially with respect to the axis of flow of the laminar flow of carrier gas through the gas flow means.
  • the ion radial confinement means may comprise means for generating a ponderomotive force in the gas flow means.
  • the ion radial confinement means may comprise an RF electrode set.
  • the ion extraction device may further comprise drift field applying means for applying a drift field along at least a portion of the gas flow conduit.
  • the gas flow conduit may comprise a duct.
  • the electrical field producing means may be variable so as to reduce the magnitude of the electrical field to a level that permits ions of a first range of ion mobilities to pass through the electrical field but prevents ions of a second range of ion mobilities from passing through the electrical field.
  • the ion extraction device may further comprise ion isolation means operable to apply an isolating electrical field upstream of the barrier region so as to prevent ions upstream of the isolating electrical field from being carried to the barrier region.
  • the electrical field producing means may be operable to extract ions from the field in a pulsed manner.
  • the ion extraction device may further comprise an ion source.
  • an analytical device comprising:
  • analysis means for analysing ions or phenomena associated with ions
  • analysis means is coupled to the ion extraction device so that ions extracted from the ion extraction device are introduced to the analysis means.
  • the analysis means may comprise mass spectrometry means, such as a time of flight (TOF) mass spectrometer, or a multipole, Fourier transformation or ion trap mass spectrometer.
  • mass spectrometry means such as a time of flight (TOF) mass spectrometer, or a multipole, Fourier transformation or ion trap mass spectrometer.
  • the analytical device may further comprise a collision cell.
  • the collision cell may comprise:
  • a collision cell gas flow conduit through which the laminar flow of the carrier gas generated in the ion extraction device can be introduced and sustained;
  • collision gas inlet means for introducing a gas to the gas flow conduit
  • collision cell electrical field producing means for applying an electrical field to a barrier region of the collision cell gas flow conduit, the collision cell electrical field producing means being operable to apply the electrical field across the direction of laminar flow in said collision cell gas flow conduit so as to prevent at least some ions entrained in the laminar flow in the collision cell gas flow conduit from passing through the electrical field;
  • collision cell electrical field producing means is variable so as to allow ions of chosen characteristics to pass through the electrical field.
  • the collision cell may further comprise collision cell drift field applying means for applying a drift field along at least a portion of the collision cell gas flow conduit of sufficient magnitude to overcome the force provided by a gas entering the collision cell through the collision gas inlet means.
  • the collision cell drift field applying means may comprise a leaky dielectric shield.
  • the collision cell drift field applying means may comprise a multipole electrode set.
  • the number of electrodes in the multipole electrode set may be greater than four, eg, an octapole or hexapole arrangement might be used. Alternatively, a quadrupole might be used.
  • This multipole electrode set can also provide radial confinement of the ions.
  • Ions that are present in, for example, a tube will be swept along with the same velocity as the carrier gas flowing through it.
  • the kinetic energy of any ion in the tube depends only on its mass and its position in the duct.
  • the ponderomotive force from the effective potential well squeezes the ions radially to the centre of the device where the gas velocity is at its maximum.
  • the gas velocity around the centre varies only slightly from this value as one moves radially outwards over short distances due to the nature of the parabaloid profile of the gas flow. If the tube is long enough to give rise to laminar flow conditions then over a short axial distance the velocity can be considered independent of axial position .
  • the ions can be considered to be of a single defined velocity.
  • a potential barrier field may impede the motion of the ions according to their ion mobility. For a certain field strength the impeding force due to the barrier field equals the driving force from the carrier gas and then the ion comes to a standstill in the tube, diffusion losses being prevented by the ponderomotive radial confinement. If the barrier field is then reduced the ion continues on it way into subsequent stages of the spectrometer. By sweeping the barrier potential sequentially from high to low values ions of lower to higher mobilities are able to escape the device.
  • This device therefore creates a new type of axial well somewhat analogous to the electrostatic axial potential wells used in trapping linear multipoles.
  • This new well is a hybrid type which is gas driven on one side and electrostatically driven on the other side.
  • the trapping characteristic of this well depends upon an ion's mobility as well as the applied potential.
  • This new "Barrier Spectrometer" provided by the present invention is advantageous over prior art in that it allows a flexible time scale of ejection of ions of chosen mobility that is not limited to the millisecond timescale of separation common to drift tube based devices. Furthermore, knowledge of gas pressures and velocities along the duct and the application of an axial field of desired profile can lead to ions of differing mobilities occupying different static positions along the length of the device.
  • This spatial dispersion offers advantages in terms of a reduction in space charge effects, the space charge capacity of a line being greater than that of a point. A further advantage of the spatial dispersion is the possibility of selectively fragmenting or reacting ions at specific locations in the device either by optical, resonance or other means.
  • ions at the end of the device may be pulsed out by well defined short duration extraction pulses for purposes of efficient interfacing to subsequent spectrometer stages e.g. quadrupole, TOF, FTMS, or other MS devices.
  • spectrometer stages e.g. quadrupole, TOF, FTMS, or other MS devices.
  • optimise the collision energy of a fragmentation stage downstream from the device Ion of a certain mobility may have a well characterised optimum collision energy for efficient fragmentation, and therefore the output of the barrier spectrometer can be controlled to provide the optimum collision energy for an ion so all ions of preselected type exiting the device undergo optimum fragmentation.
  • the spatial separation between ions can be varied for a given set of ions by varying the length of the barrier region and, in particular, by varying the profile of the electrical field within the barrier region.
  • Non-limiting examples of separations between ions are in the range 10 to 300 mm. It should be noted that this spatial separation between ions is a static separation, since the spacial positioning of the ions and their spatial separations are maintained as long as the electrical field is maintained constant. Furthermore, the spatial separation can be varied as desired by appropriate variations of the electrical field. This static spatial separation can be contrasted with the temporal separation between ions which is provided by the prior ait techniques discussed above which rely on differing times of flight of differing ions.
  • the spatial separation is not a constant one (but rather increases as a function the flight time).
  • the ions are of course in motion, in contrast to the present invention in which the electrical field in the barrier region (in combination with the force provided by the laminar flow) can hold ions in a spatially distinct, static position.
  • Figure 1 shows the effective ponderomotive potential acting on a gas flow containing ions
  • Figure 2 shows the velocity of an ion and electric fields acting on the ion in the barrier region of the device shown in Figure 1;
  • Figure 3 shows a number of ions of differing mobilities in the barrier region of an ion extraction device and the associated electric potential
  • Figure 4 shows the variation of isolation and barrier potentials in order to perform fill, isolate and scan steps
  • Figure 5 shows a scheme for extracting ions through use of a pulsed extraction field
  • Figure 6 shows (a) an embodiment of an analytical device of the invention and (b) a tandem mobility instrument of the invention
  • Figure 7 is a potential energy diagram for the passage of an ion through the instrument of Figure 6 (b);
  • Figure 8 shows an embodiment of an intermediate stage for use in the tandem mobility instrument of Figure 6 (b).
  • Figure 9 shows a further embodiment of an ion extraction device of the invention.
  • the first force is the ponderomotive force in the radial direction caused by an inhomogeneous oscillatory field wliich has its direction towards the weaker field.
  • the ponderomotive force provides radial confinement and prevents diffusion losses of the ions.
  • the second force is of the flowing carrier gas which sweeps the ions along at the same velocity as the gas.
  • the third force is created by the field supplied by a potential barrier which may impede or extract ions as desired according to their size and polarity.
  • this "barrier" field is oriented axially with respect to the direction of flow of the carrier gas.
  • the ponderomotive force can be generated by an effective potential well created by an oscillating (RF) electric field.
  • the ponderomotive force allows trapping in three dimension as in the case of the Paul trap, which trapping is impossible to achieve by purely electrostatic means because Laplace's equation dictates that stationary points are always saddle points i.e. there are no real potential minima.
  • the RF field is typically applied to a multiple rod set or ring set. The size and nature of the effective potential of a multiple has been derived using the adiabatic approximation of Gerlich et al, ibid, and is shown to be:
  • the impetus to the ions that is provided by the flowing gas depends on the nature of the duct through which it is flowing.
  • the ion extraction device is placed between two vacuum chamber of differing pressures, and the natural gas flow between these chambers provides the driving force necessary for the operation of the device. Steady laminar flow is desirable for operation of the device.
  • the special case of such flow in a circular pipe is described by the Hagen-Poiseuille law, see for example "Mechanisms of fluids" by Bernard Massey and John Ward Smith - Nelson Thornes Press (reprinted 2001), ISBN 0-7487-4043-0. This law shows that the velocity of the gas v g as it flows in the x direction is given by:
  • the present invention may operate in a choked flow manner.
  • the Hagen-Poiseuille equation allows us to determine the velocity of the gas and therefore the velocity of the swept ion at any point in the duct given knowledge of upstream and downstream pressure and duct geometry. Laminar flow is ensured by consideration of pressure differential and duct geometry.
  • a useful parameter is the Reynolds number which for a circular duct is given by:
  • the third force experienced by ions flowing through the duct is from the potential barrier.
  • This electric field can accelerate or retard ions depending on is size and direction.
  • the motion of an ion at these elevated pressures depends on an ion's mobility rather than its mass to charge ratio as would be the case of a collision less medium.
  • a comprehensive review by E A Mason and E W McDaniel “The mobility and diffusion of ions in gases” Wiley series in plasma physics, John Wiley & Sons 1973 ISBN 0-471-58387-1 sets out the framework of the concept of ion mobility.
  • K is a constant of proportionality and is known as the scalai- of mobility
  • E b is the barrier potential field.
  • the relationship is valid if ions acquire velocities that are below or of the order of thermal velocities otherwise K becomes a tensor.
  • a scalar value for the ion mobility the ion mobility does ho ever decrease with increasing pressure.
  • the pressure in the duct or other conduit changes along its length as the pressure in the duct changes. Knowledge of this pressure variation and the application of the desired axial field profile can lead to the spatial separation of the ions as previously described.
  • Figure 1 shows a first chamber 10 at a relatively high pressure Pu, a guide duct 12 in which laminar gas flow is developed, and a second chamber 14 at a relatively low pressure Po.
  • the effective (ponderomotive) potential confines ions radially as they progress down the guide in the presence of a gas (for presentational memeposes, electrodes which are used to generate the potential are not shown in Figure 1). Note that, if the upstream pressure Pu is high, then the effective potential field may be reduced at the upstream end of the guide.
  • the value of the effective potential field increases to a constant value where by the reduction due to high pressure collisions is minimal (the effective potential field is reduced when the number of collisions an ion undergoes during an RF period is high - for a comprehensive explanation see A V Tolmachev, Nuclear instruments and method in physics research B, 124 (1997) 112- 119).
  • the effective potential field is of a constant form E3(r), the effective potential field being some function of radius dependant on multipole geometry and laminar flow, laminar flow having been established and having a characteristic maximum velocity v 3 at guide pressure P3. Ions are also subjected to a barrier potential field E b .
  • Figure 2 shows the case where the guide duct is long compared to the extent of the potential banier so the velocity of the gas flow v g can be considered constant over the length
  • FIG. 3 shows a potential banier where the field reduces linearly, that is to say the voltage reduces parabolically from its maximum value. Ions of higher mobility are shown in Figure 3 as small spheres compared to the large spheres representing ion of lower mobility. This illustrates the spatial spread of ions of differing mobilities.
  • the spectrometer is preferably operated in a fill-isolate-scan operation cycle. In such a scheme there is a fill cycle in which ions are allowed to accumulate behind the potential banier, and an isolate cycle in which no more ions are admitted to the device. This prevents ions of low mobility entering the device after the barrier is lowered to eject the initial population, that is to say aliasing in the resultant spectrum is avoided.
  • the device is then scanned to eject ions of higher and higher mobilities.
  • the isolation stage is preferably fitted upstream of the banier stage, and advantageously this isolation stage may itself accumulate ions for subsequent release to the banier thus retaining a 100% duty cycle (complete utilisation of ions from the source).
  • Figure 4 shows the electric field generated in the spectrometer during these different stages. Note that for simplicity the isolation stage is always shown having steep sides to the potential gradient - it should be understood that the size of the electric field of the isolation stage should be simply high enough to prevent any ions being transmitted to the barrier stage.
  • Figure 4d-4f shows how the barrier stage is scanned from high to low field allowing ions of progressively higher mobility to traverse the barrier to subsequent stages of the spectrometer.
  • the barrier field may be decreased stepwise down to the minimum value or it may be scanned continuously.
  • the ions of differing mobilities may be ejected when desired. This is in contrast to the drift tube experiments whereby ions exit at ever decreasing mobilities on the timescale of the drift tube separation itself, this timescale is commonly milliseconds.
  • This flexibility of temporal ejection means that the banier spectrometer may be optimally interface to the subsequent stages of the spectrometer; be they detector, quadrupole, TOF, FTMS, ion trap, or a combination of any of these components.
  • the spatial separation of ions shown in Figure 3 may be exploited by using a pulsed extraction field at the end of the banier.
  • This pulsed extraction field may be adjusted to penetrate only the veiy end of the ion extraction device so that ions of a desired mobility or range of mobilities may be extracted in pulses of any desired duration.
  • Figure 5 shows how such a scheme may be employed.
  • the scheme depicted in Figure 5 can be an adjunct to the scheme shown in Figure 4, in which the alternation between states land 2 is taking place on a faster time scale than the variation in barrier height.
  • the pulsed extracting field can be considered to be an auxiliary field wliich is imposed upon the variation in banier field in the scan mode shown in Figure 4. Again the banier may be scanned continuously or in a stepwise fashion.
  • One method of operation would be to set up a particular maximum banier field E max , and then alternate between state 1 and 2 until no more ions are extracted, then to reduce the barrier height to a new lower value of E max and repeat the stepping between states 1 and 2.
  • Other schemes would suggest themselves to the skilled reader.
  • analytical devices of the present invention comprise an ion source, a barrier stage and a detector.
  • the spectrometer When using electrospray ionisation the spectrometer may be constructed using only a single rotary pump. Typically pressure would be in the millibar region but pressures as high as 20 mbar and as low as 10 "3 millibar may be employed.
  • Figure 6a is a schematic diagram of this embodiment, wliich may be portable and so suitable for field use, comprising an ion source 60, an ion extraction device 62 and a detector 64. In the ion extraction device 62 ions from the ion source 60 are entrained in a laminar flow of a earner gas and the banier potential is developed using the principles set forth herein.
  • the detector 64 can be any detector suitable for analysing the ions extracted from the ion extraction device 62 or for analysing physical phenomena associated in some way with ions extracted from the ion extraction device 62.
  • the detector 64 might comprise a spectroscopic technique or a mass spectrometric technique.
  • mass spectrometric techniques comprise quadruple, TOF, and FTMS techniques. It is possible to utilise a plurality of detection techniques in the detector 64 stage.
  • the invention is not limited to the use of electrospray ionisation as the source of ions.
  • ions sources might be used, such as, for example, MALDI (Matrix Assisted Laser Desorption Ionisation), electron impact, chemical ionisation, fast atom bombardment, field ionisation, field desorption, and soft ionisation techniques employing vacuum ultraviolet or soft X-ray radiation produced by a convenient light source such as a laser.
  • MALDI and other laser based ionisation techniques
  • MALDI is pulsed in nature, and thus it is not necessary in such instances to employ an ionisation stage to prevent build-up of ions.
  • Figure 6b shows a tandem mobility instrument which can be - but is not limited to - a tandem mobility TOF instrument.
  • the instrument comprises in common with the embodiment shown in Figure 6 (a) an ion source 60, and an ion extraction device 62. Additionally, the instrument comprises a MS detector 66 and a further stage 68 at intermediate pressure situated between the ion extraction device 62 and the MS detector 66.
  • the stage 68 may itself take the form of a further ion extraction device having a barrier potential which can be selectively varied to allow chosen ions entrained in a common flow of a carrier gas to exit the stage 68. Alternatively, the stage 68 may act as a collision cell to fragment ions of a known mobility emerging from ion extraction device 62.
  • FIG. 7 shows the potential energy diagram an ion sees in such a spectrometer, i.e. a spectrometer in which the stage 68 is also an ion extraction device of the present invention.
  • Ion extraction device 62 may be of the scanning type as shown in Figure 4 or of the pulsed extraction type as shown in Figure 5.
  • Stage 68 is preferably of the pulsed extraction type in the instance in which the detector 66 is an orthogonal TOF as this configuration allows a 100% duty cycle for the fragment ions generated upstream of a stage 68.
  • FIG 8 shows a possible construction method for stage 68 shown in Figure 7.
  • This spectrometer may double as a collision cell with gas being introduced pail way down the cell through gas inlet 70.
  • the stage 68 comprises a central duct 72 which may be formed of a leaky dielectric material of internal diameter D of constant resistivity, with a multiple rod set 74 providing the ponderomotive radial confinement force.
  • the spectrometer further comprises electrodes 76, 78, 80.
  • the gas is introduced a distance LI from the input end of the duct 72 and laminar flow conditions can be established in opposing directions towards each of the ends of the tube. This is because the outside chamber pressure is lower than in the duct 72.
  • the potential field of the type shown previously in Figure 3 can be created by application of potentials 2 and 3 to the electrodes 78, 80.
  • the diameter of the duct 72 varies in the region of between electrodes 78 and 80 .
  • the constant resistivity of the leaky dielectric means that most of the potential drop and therefore higher electric field takes place at the exit end of the duct 72.
  • An auxiliary pulsed output field may now be derived from a pulsed voltage 4 applied to an end plate 82 at the output end of the device.
  • Figure 9 shows another method of construction of an ion extraction device whereby a duct 90 is positioned between an upstream chamber 92 and a downstream chamber 94.
  • the duct 90 comprises a ring set 96 spaced by insulators 98 which are pushed or bonded together to create a gas tight constmction.
  • the duct need not be long enough to establish a full parabolic laminar flow profile at the region in which the banier potential is established as the gas proceeds down the duct it changes velocity profile from flat to parabolic as shown with profiles A,B &C.

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Abstract

L'invention concerne un procédé permettant d'extraire des ions, consistant : à préparer une source d'ions ; à entraîner ces ions dans un flux laminaire d'un gaz vecteur ; à préparer une région barrière dans laquelle un champ électrique est appliqué sur le flux laminaire de gaz vecteur, la magnitude et la direction du champ électrique étant choisies de manière à empêcher au moins certains des ions entraînés dans le flux laminaire de traverser le champ électrique ; et à modifier le champ électrique de façon à permettre à des ions qui présentent des caractéristiques choisies de traverser le champ électrique
PCT/GB2004/002455 2003-06-06 2004-06-07 Extraction d'ions Ceased WO2004109741A2 (fr)

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GB0600268A GB2419462B (en) 2003-06-06 2004-06-07 Ion extraction

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GBGB0313016.8A GB0313016D0 (en) 2003-06-06 2003-06-06 Ion extraction
GB0313016.8 2003-06-06

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Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007148115A3 (fr) * 2006-06-23 2008-10-02 Micromass Ltd Spectromètre de masse
WO2009068887A2 (fr) 2007-11-30 2009-06-04 Micromass Uk Limited Détecteur de gaz à multiplicateur d'électrons
JP2009532681A (ja) * 2006-04-03 2009-09-10 エムディーエス アナリティカル テクノロジーズ， ア ビジネス ユニット オブ エムディーエス インコーポレイテッド， ドゥーイング ビジネス スルー イッツ サイエックス ディビジョン 質量分析計の入口端および出口端にてイオンバリアを提供するための方法と装置
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GB2487326A (en) * 2007-04-11 2012-07-18 Bruker Daltonik Gmbh Measurement of the mobility of mass-selected ions
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EP3783638A1 (fr) * 2015-02-05 2021-02-24 Bruker Daltonik GmbH Spectromètre de mobilité à piège ionique avec accumulation parallèle
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US8253095B2 (en) 2009-09-17 2012-08-28 Bruker Daltonik Gmbh High-resolution ion mobility spectrometry
EP2685487A4 (fr) * 2011-03-11 2015-03-18 Shimadzu Corp Spectromètre de masse
DE102012004398B4 (de) 2011-04-26 2020-07-30 Bruker Daltonik Gmbh Spektrenaufnahmearten für Ionenfallen-Mobilitätsspektrometer
GB2534943A (en) * 2014-04-30 2016-08-10 Micromass Ltd Mass spectrometer with reduced potential drop
US9978572B2 (en) 2014-04-30 2018-05-22 Micromass Uk Limited Mass spectrometer with reduced potential drop
GB2534943B (en) * 2014-04-30 2019-01-09 Micromass Ltd Mass spectrometer with reduced potential drop
DE102014110334A1 (de) * 2014-07-22 2016-01-28 Krohne Messtechnik Gmbh Verfahren zur Trennung von elektrisch geladenen Teilchen bezüglich ihrer Energie und Energiefilter
EP3783638A1 (fr) * 2015-02-05 2021-02-24 Bruker Daltonik GmbH Spectromètre de mobilité à piège ionique avec accumulation parallèle
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GB2419462B (en) 2007-02-28

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