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WO1993018540A1 - Spectrometre de masse - Google Patents

Spectrometre de masse Download PDF

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Publication number
WO1993018540A1
WO1993018540A1 PCT/GB1993/000434 GB9300434W WO9318540A1 WO 1993018540 A1 WO1993018540 A1 WO 1993018540A1 GB 9300434 W GB9300434 W GB 9300434W WO 9318540 A1 WO9318540 A1 WO 9318540A1
Authority
WO
WIPO (PCT)
Prior art keywords
ions
line
mass spectrometer
field generating
generating means
Prior art date
Application number
PCT/GB1993/000434
Other languages
English (en)
Inventor
Thomas Oliver Merren
Original Assignee
Fisons Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fisons Plc filed Critical Fisons Plc
Publication of WO1993018540A1 publication Critical patent/WO1993018540A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/06—Electron- or ion-optical arrangements
    • H01J49/067—Ion lenses, apertures, skimmers
    • 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
    • H01J49/0431—Arrangements for introducing or extracting samples to be analysed, e.g. vacuum locks; Arrangements for external adjustment of electron- or ion-optical components for liquid samples
    • H01J49/044—Arrangements for introducing or extracting samples to be analysed, e.g. vacuum locks; Arrangements for external adjustment of electron- or ion-optical components for liquid samples with means for preventing droplets from entering the analyzer; Desolvation of droplets

Definitions

  • This invention relates to mass spectrometers and in particular to mass spectrometers wherein mass analysis is accomplished by means of a quadrupole mass analyzer or mass filter.
  • an ion beam from an ion source passes to a detector via an intermediately positioned mass selector.
  • the mass selector, filter or analyzer selects the ions permitted to impinge on the detector on the basis of their mass to charge ratio by means of superimposed radio frequency and dc electric fields.
  • a magnetic analyzer selects ions on the basis of their momentum and charge. This involves the application of a magnetic field perpendicular to the ion beam causing it to be deflected by an amount dependent on the mass to charge ratio of the ions.
  • ions of a particular mass to charge ratio can be detected by selecting the strength of the magnetic field or the energy with which the ions enter the magnetic field.
  • a quadrupole mass analyzer consists of four electrically conductive electrodes arranged symmetrically about and very accurately parallel to the line joining the ion source and detector. Opposite pairs of electrodes are coupled together and an electrostatic potential oscillating at a radio frequency is applied between the pairs. Opposite pairs are biased with dc potentials - positive in the x direction, negative in the y direction with respect to the potential on the axis defined by the electrodes. Ions are injected along the axis defined by the electrodes towards the detector and as a result of subjection to a combination of electrical forces, a complex trajectory is described.
  • the trajectory is determined by the dc potential (U) , the radiofrequency zero-to-peak voltage (V) and the angular frequency of the oscillating potential ( ⁇ ) .
  • these values may be set to permit only ions having a specific m/e ratio to reach the detector, ions having different m/e ratios being lost by collision with the device itself.
  • the device may be used as a mass analyzer, in which U and V may be varied whilst maintaining their ratio constant so that ions of differing mass may be collected in turn on the detector.
  • Quadrupole analyzers are advantageous in that they are generally smaller and comparatively cheaper than analyzers based on magnetic sectors. Furthermore, since U and V may be electronically swept, high scan speeds are possible. However, a disadvantage of such quadrupole analyzers is that the signal to noise ratio can be poor.
  • Displacement or inclination of the source axis relative to the quadrupole axis introduces mechanical complications, however, and precludes the fitting of an ion source to a multi-purpose quadrupole analyzer in the conventional line-of-sight configuration.
  • the present invention provides a mass spectrometer comprising a quadrupole mass analyzer having an entrance aperture, an ion source disposed on the axis of said analyzer, particle intercepting means blocking the line-of-sight path between said ion source and said entrance aperture, and field generating means for directing ions from said ion source into said entrance aperture, said field generating means comprising first field generating means for deflecting ions from said source away from said axis to avoid said particle intercepting means and second field generating means for directing into said entrance aperture ions so deflected by said first means.
  • the deflecting and intercepting means can be made sufficiently compact that their incorporation into a spectrometer having ion source and mass analyzer in the conventional line-of-sight configuration is generally relatively facile.
  • the field for directing the ion beam towards the quadrupole entrance may be generated in a variety of ways and may, for example, comprise magnetic or electrostatic fields disposed so as to prevent an ion beam from travelling along a trajectory defined by the direct line-of-sight path from the ion source to the quadrupole analyzer entrance in such a way that charged particles are caused to travel in trajectories which avoid collision with the means provided to block the said line-of-sight path but which preferably do not prevent subsequent mass:charge separation of particles in the analyzer itself.
  • the field generating means operate to impose at least one pair, e.g. a matched pair, of opposing deflecting electrostatic fields on the ion beam such that it is deflected by the field of the first field generating means off the axis defined by the ion source and the entrance to the quadrupole analyzer, and is subsequently returned to the axis by means of the field of the second field generating means.
  • the second field generating means comprises means for directing ions into the entrance aperture of the analyzer along trajectories substantially aligned or parallel to the analyzer axis.
  • the field generating means conveniently comprise a plurality of conducting plates disposed about the ion path and defining apertures through which the ion path passes.
  • the first field generating means comprises at least one such plate which tapers in thickness towards the ion path.
  • the second field generating means comprises a pair of plates on opposite sides of the ion path defining between them an aperture angled to the line-of-sight path from ion source to mass analyzer and with its mid point displaced from the line-of-sight path.
  • the line-of-sight path between the ion source and the entrance to the quadrupole analyzer may be blocked by any suitable physical means arranged so that at least one barrier completely blocks the path defined by a straight line joining the ion source and quadrupole entrance, although barriers provided by planar or curved plates are preferred. These may be formed of any suitable material, however, conducting materials such as metals are preferred. Conveniently this particle intercepting means is provided by one of the conducting plates of the field generating means which extends into the line-of-sight path between the ion source and the mass analyzer.
  • deflecting electrostatic fields may be applied to the ion beam by means of the barriers themselves.
  • Suitable potentials may be in the range of -20 to +350v, for negative ion separation.
  • the barriers may be disposed relative to the deflecting means such that the action of the deflecting field causes selected charged particles within the ion beam to travel in trajectories which avoid collision with the physical barriers.
  • the actual number of barriers disposed between the ion source and quadrupole is not critical provided that the line-of- sight path is effectively blocked.
  • the conducting plates of the field generating means conveniently have apertures therein through which the ion path passes.
  • the invention provides a mass spectrometer having an ion source, a quadrupo.le mass analyzer, field generating means for directing ions from said source into the entrance of said analyzer along a non-linear ion path, and particle intercepting means blocking the line-of-sight path from said source to said entrance, said field generating and particle intercepting means comprising a plurality of conducting plates disposed to the sides of said non ⁇ linear path substantially perpendicular to said line-of- sight path, at least one of said plates being arranged to direct said ions away from said line-of-sight path, at least one of said plates being arranged to direct said ions towards said line-of-sight path and at least one of said plates tapering in thickness towards said non-linear path.
  • the present invention provides a method of enhancing the sensitivity of mass analysis of a sample comprising the steps of: a) creating an ionised, vaporised sample in an ion source lying on the axis of a quadrupole mass analyzer, preferably by ion or neutral particle beam bombardment of a solid surface, e.g.
  • the sample may be ionised by any means appropriate for mass spectrometry, for example photoionisation, electron impact, fast ion bombardment, fast atom bombardment, etc. , but as indicated above ion beam or neutral particle beam bombardment are preferred.
  • photoionisation electron impact, fast ion bombardment, fast atom bombardment, etc.
  • ion beam or neutral particle beam bombardment are preferred.
  • Figure 1 is a schematic drawing of a mass spectrometer according to the invention.
  • Figure 2 is a schematic drawing of the mass spectrometer of Figure 1 in greater detail
  • Figure 3 is a drawing of a conductive plate assembly suitable for use in the spectrometer of Figure 2;
  • Figure 4 is a drawing of another conductive plate assembly suitable for use in the spectrometer of Figure 2;
  • Figure 5 is a schematic drawing of a further alternative version of a spectrometer according to the invnetion.
  • Figure 6 is a schematic drawing of another alternative version of a spectrometer according to the invention.
  • Figure 1 shows a mass spectrometer of the present invention arranged for separation of negatively charged ions. Plates (2, 3, 4 and 5) are held at approximately zero potential. Ions emerging from the ion source (l) travel towards the quadrupole analyzer and are influenced by a series of electrostatic fields created by positively charged plates (6, 7, 8, 9, 10, 11), where plate 8 blocks the line-of-sight path from the ion source to the quadrupole. A potential approximately of +180V is applied to plates 6 and 8, +60V to plates 7 and 9 and +160V to plates 10 and 11. The resulting fields cause the charged particles in the ion beam to be deflected from their original trajectory and ultimately be refocused at the entrance to the quadrupole analyzer (12) . After mass analysis, the beam of ions pass to a detector (13) which may, for example, be a Faraday plate or an electron multiplier.
  • a detector (13) which may, for example, be a Faraday plate or an electron multiplier.
  • an ion source generally indicated by 1 comprises a solid surface 14 on the end of an insertion probe 15 on which a sample to be analyzed may be deposited.
  • a beam of neutral particles 16 or ions is directed at the surface 14 and bombards the sample deposited on it to release ions for analysis.
  • Ion source 1 further comprises a source chamber 17 and a repeller block 18 which are mounted on a flange 19.
  • the path of the ions leaving the surface -14 is schematically represented by the trajectory 20 and is determined by the electrostatic fields generated by suitable potentials applied to the conductive plates 2- 11 which are disposed as shown in Figure 2.
  • the ions emerge from the last of these to pass through an entrance aperture 21 into a quadrupole mass analyzer 12 wherein they undergo mass analysis.
  • the conducting plates 2-11 and the plate 22 in which the aperture 21 is formed are mounted on four insulating rod assemblies from a flange 19 and are spaced apart by insulating spacers (some of which are shown at 23 in Figure 2) , or on the insulated spacers 24 from the source chamber 17.
  • the ion source 1, surface 14 and the entrance aperture 21 of the quadrupole analyzer 12 are disposed on the axis of the analyzer as in most conventional quadrupole mass spectrometers. However, the line-of- sight path 25 between the ion source 1 and the analyzer 12 which would otherwise exist is blocked by one of the conductive plates (8 in Figures 1 and 2) .
  • the first field generating means for changing the direction of at least some of the ions leaving the source 1 comprises the conductive plates 2 , 3, 4 and 5.
  • plates 2 and 4 may be separate plates they preferably comprise a single plate comprising a large aperture 26, asymmetrically disposed about the line-of-sight path 25, through which both the primary particle or ion beam 16 and the ions to be analyzed may pass.
  • the conductive plates 3 and 5 may be separate plates, they preferably comprise the single assembly shown in Figure 3.
  • the plate 3 which forms the lower part of the assembly extends to support the tapered upper portion 5 which comprises a machined block through which a hole 28 is bored to allow the passage of the primary beam 16.
  • the tapered portion 5 is attached to the plate 3 by screws.
  • Plate 3 also comprises an aperture 27 through which the ions to be analyzed may pass. Aperture 27 is displaced from the line-of-sight path 25 which falls on the centre-line 29 of the plate 3.
  • the first field generating means produces an electrostatic field in the space between the plates 3,5 and 6,8 which can be represented by curved lines of force which cross the line-of-sight path 25 at an acute angle rather than perpendicularly, as they would if the tapered conductive plate 5 was omitted. As a consequence, the direction of travel of the ions passing through the apertures 26 and 27 is changed to that indicated by the trajectory 20 ( Figure 2) .
  • Particle intercepting means for blocking the line- of-sight path 25 are provided by the conducting plates 6, 8. These may comprise separate plates but preferably are a single plate comprising an aperture 30 which is positioned so that the line-of-sight path 25 does not pass through it.
  • the ions whose direction has been changed by the first field generating means pass through the aperture 30 to the second field generating means which comprises the conductive plates 7, 9, 10 and 11 and which is . arranged to change the direction of the ions so that they pass through the entrance aperture 21 on trajectories substantially aligned with the axis of the quadrupole analyzer 12, thereby ensuring that maximum performance is obtained from the analyzer.
  • the conductive plates 7 and 9 are displaced from one another along the axis of the quadrupole as shown in Figure 2. They are joined by two bent conductive strips 31, 32 ( Figure 4) and define an aperture 33 whose centre is displaced from the line-of-sight path 25 which is located on the centre-line 34 of Figure 3 assembly.
  • the conductive plates 10 and 11 are conveniently a single plate comprising an aperture 35 which is located on the line-of-sight path 25.
  • all the conductive plates in the apparatus above described may be made of stainless steel.
  • the potentials applied to the various plates may be as below:
  • Plates 2, 3, 4 and 5 0 volts Plates 6 and 8: +180 volts Plates 7 and 9: + 60 volts Plates 10 and 11: +160 volts.
  • FIG. 5 illustrates an alternative method of constructing the first field generating means.
  • the tapered conductive plate 5 may be replaced by a series of flat plate electrodes 35-40 which are mounted on two mounting pillars 41 secured to the plate 3.
  • Each of electrodes 35-40 comprises a hole through which the primary beam 16 may pass.
  • the electrodes 35-40 may conveniently be maintained at the same potential and are arranged so that their edges define a surface similar ' to that defined by the tapered plate 4 in the embodiment of Figures l and 2, so that a similar electrostatic field is generated.
  • FIG. 6 A similar, but less preferred, embodiment is shown in Figure 6.
  • the conductive plates 3 and 5 are replaced by a pair of plate electrodes 42 and 43 which define an aperture 44 displaced from the line-of- sight path 25.
  • a potential difference is maintained between electrodes 42 and 43, thereby causing the ion beam passing through the aperture 44 to be deflected away from the line-of-sight path 25.
  • a hole 45 is provided in the electrode 42 to allow the passage of the primary beam 16.
  • the electrodes 42 and 43 may also comprise portions which extend substantially parallel to the line-of-sight path 25 in the manner of . conventional beam deflector plates.

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

Abstract

Un spectromètre de masse comprend un analyseur de masse quadripolaire ayant une ouverture d'entrée, une source d'ions située sur l'axe dudit analyseur, un organe d'interception de particules qui bloque la voie en visibilité directe entre ladite source d'ions et ladite ouverture d'entrée, et un générateur de champ qui dirige les ions de la source vers l'ouverture d'entrée. Le générateur de champ comprend un premier organe générateur de champ qui dévie de l'axe les ions émis par la source de manière à éviter l'organe d'interception de particules et un deuxième organe générateur de champ qui dirige vers l'entrée les ions déviés par le premier organe. L'utilisation de cet agencement permet d'améliorer considérablement le rapport signal:bruit, équivalent en certain cas à une réduction du bruit par un facteur supérieur à 100.
PCT/GB1993/000434 1992-03-03 1993-03-03 Spectrometre de masse WO1993018540A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB929204524A GB9204524D0 (en) 1992-03-03 1992-03-03 Mass spectrometer
GB9204524.4 1992-03-03

Publications (1)

Publication Number Publication Date
WO1993018540A1 true WO1993018540A1 (fr) 1993-09-16

Family

ID=10711367

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1993/000434 WO1993018540A1 (fr) 1992-03-03 1993-03-03 Spectrometre de masse

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GB (1) GB9204524D0 (fr)
WO (1) WO1993018540A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8450681B2 (en) 2011-06-08 2013-05-28 Mks Instruments, Inc. Mass spectrometry for gas analysis in which both a charged particle source and a charged particle analyzer are offset from an axis of a deflector lens, resulting in reduced baseline signal offsets
US8796620B2 (en) 2011-06-08 2014-08-05 Mks Instruments, Inc. Mass spectrometry for gas analysis with a one-stage charged particle deflector lens between a charged particle source and a charged particle analyzer both offset from a central axis of the deflector lens
US8796638B2 (en) 2011-06-08 2014-08-05 Mks Instruments, Inc. Mass spectrometry for a gas analysis with a two-stage charged particle deflector lens between a charged particle source and a charged particle analyzer both offset from a central axis of the deflector lens
CN116783481A (zh) * 2021-01-29 2023-09-19 Atonarp株式会社 气体分析装置和控制方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3859226A (en) * 1972-11-11 1975-01-07 Leybold Heraeus Verwaltung Secondary ion mass spectroscopy
FR2295562A1 (fr) * 1974-12-20 1976-07-16 Leybold Heraeus Gmbh & Co Kg Optique pour particules chargees
DE4041871A1 (de) * 1989-12-25 1991-06-27 Hitachi Ltd Massenspektrometer mit plasmaionenquelle

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3859226A (en) * 1972-11-11 1975-01-07 Leybold Heraeus Verwaltung Secondary ion mass spectroscopy
FR2295562A1 (fr) * 1974-12-20 1976-07-16 Leybold Heraeus Gmbh & Co Kg Optique pour particules chargees
DE4041871A1 (de) * 1989-12-25 1991-06-27 Hitachi Ltd Massenspektrometer mit plasmaionenquelle

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8450681B2 (en) 2011-06-08 2013-05-28 Mks Instruments, Inc. Mass spectrometry for gas analysis in which both a charged particle source and a charged particle analyzer are offset from an axis of a deflector lens, resulting in reduced baseline signal offsets
US8796620B2 (en) 2011-06-08 2014-08-05 Mks Instruments, Inc. Mass spectrometry for gas analysis with a one-stage charged particle deflector lens between a charged particle source and a charged particle analyzer both offset from a central axis of the deflector lens
US8796638B2 (en) 2011-06-08 2014-08-05 Mks Instruments, Inc. Mass spectrometry for a gas analysis with a two-stage charged particle deflector lens between a charged particle source and a charged particle analyzer both offset from a central axis of the deflector lens
CN116783481A (zh) * 2021-01-29 2023-09-19 Atonarp株式会社 气体分析装置和控制方法

Also Published As

Publication number Publication date
GB9204524D0 (en) 1992-04-15

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