EP0960431B1 - A method for element-selective detection, a micro plasma mass spectrometer for use in the method and a micro plasma ion source, together with applications thereof - Google Patents

A method for element-selective detection, a micro plasma mass spectrometer for use in the method and a micro plasma ion source, together with applications thereof Download PDF

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Publication number
EP0960431B1
EP0960431B1 EP98904444A EP98904444A EP0960431B1 EP 0960431 B1 EP0960431 B1 EP 0960431B1 EP 98904444 A EP98904444 A EP 98904444A EP 98904444 A EP98904444 A EP 98904444A EP 0960431 B1 EP0960431 B1 EP 0960431B1
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EP
European Patent Office
Prior art keywords
ion source
plasma
plasma ion
mass spectrometer
micro
Prior art date
Legal status (The legal status 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 status listed.)
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EP98904444A
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German (de)
English (en)
French (fr)
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EP0960431A1 (en
Inventor
Cato Brede
Stig Pedersen-Bjergaard
Tyge Greibrokk
Elsa Lundanes
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PEDERSEN BJERGAARD STIG
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PEDERSEN BJERGAARD STIG
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/105—Ion sources; Ion guns using high-frequency excitation, e.g. microwave excitation, Inductively Coupled Plasma [ICP]

Definitions

  • the invention concerns a method for element-selective detection of chromatographically or electrophoretically separated compounds, wherein for the detection there is employed a plasma mass spectrometer with a radio-frequency generator, a mass analyser and an ion detector.
  • the invention also concerns a plasma mass spectrometer, especially for element-selective detection of chromatographically or electrophoretically separated compounds, wherein the plasma mass spectrometer comprises a radio-frequency generator, a mass analyser and an ion detector.
  • ICP-MS Inductively coupled plasma mass spectrometry
  • RF-GD-MS radio-frequency glow discharge mass spectrometry
  • Detection methods based on ICP-MS, RE-GD-MS and MIP-MS respectively employ the same method for transferring the ions from the plasma to the mass analyser which works in a high vacuum.
  • the ions are transferred via a so-called “sampler” and a “skimmer". In this process the ions are transferred from atmospheric pressure or low pressure to high vacuum, but the drawback is that as much as 99% of the ions are lost.
  • an object of the invention is therefore to provide a new element-selective detector based on micro plasma ionization and mass spectrometric detection of the ions.
  • a further object of the invention is that the detector should be able to be used for detection of all elements in the periodic table. Yet another object of the invention is that it should be possible to directly transfer ions from the plasma to the mass analyser under vacuum conditions in the mass spectrometer. Yet a further object of the invention is to be able to use low gas flow rates, typically less than 25 ml/min, preferably less than 10 ml/min and most preferably from 1-4 ml/min, and is able to employ all gases suitable as plasma forming gases, such as helium, neon, argon, hydrogen, nitrogen etc. Finally, it is also an object of the invention to provide a simple micro plasma probe which can be used in existing commercial mass spectrometers, e.g. as an option in addition to commonly used ion sources.
  • a method which is characterized by providing a micro plasma ion source in the mass spectrometer's high vacuum chamber, connecting a radio-frequency electrode in the micro plasma ion source with the radio-frequency generator, introducing into the micro plasma ion source plasma gas which carries one or more separated compounds which are to be detected in the mass spectrometer, and creating a radio-frequency potential on the radio-frequency electrode, thus creating micro plasma in the micro plasma ion source by discharges between the radio-frequency electrode and an earth connection provided at the micro plasma ion source, whereby the separated compound(s) which are to be analysed are atomized with the creation of atomic ions which are subsequently expelled from the micro plasma ion source into the mass spectrometer's high vacuum chamber for separation in the mass analyser and detection in an ion detector provided near the mass analyser; a plasma mass spectrometer which is characterized in that the plasma ion source is a micro plasma ion source provided in
  • a radio-frequency electrode which is arranged to be connected to the radio-frequency generator for the creation of a radio-frequency potential on the radio-frequency electrode, and that around or adjacent to the capillary channel there are provided one or more earth electrodes, with the result that when plasma gas which carries one or more of the compounds which have to be detected is introduced at the inlet of the channel, and when the radio-frequency potential is impressed on the radio-frequency electrode, a plasma is capacitively created in the channel by discharges between the radio-frequency electrode and the earth electrode or electrodes, whereby the compound or compounds are atomized into atomic ions.
  • micro plasma ion source is employed according to the invention for installation in existing, commercial mass spectrometers.
  • a transition piece 8 leads from the atmospheric pressure outside the mass spectrometer into the mass spectrometer's high vacuum chamber 1.
  • the micro plasma ion source 10 is attached to the supply line 17 inside the high- vacuum chamber 1, with the result that the micro plasma ion source projects into the high vacuum chamber.
  • the supply line 17 passes through the transition piece 8.
  • a radio-frequency generator 2 which generates a radio-frequency potential is connected to the micro plasma ion source 10 via the transition piece 8.
  • a not shown lead 21 from the plasma ion source 10 to earth is also passed through the transition piece 8.
  • the micro plasma ion source 10 is located as mentioned inside the mass spectrometer's high vacuum chamber.
  • the atomic ions which are created flow out of the micro plasma ion source's outlet 15, are deflected electrostatically by the repeller 6 and focused by the electrostatic lenses 7, whereupon the ions are separated in the mass analyser 3 and detected in the ion detector 4.
  • a suitable plasma gas for example helium or argon, mixed with the sample which is to be analysed, is introduced into the micro plasma ion source 10.
  • the supply line 17 is passed into the micro plasma ion source 10 via the transition piece 8 which forms a seal between the atmospheric pressure and the vacuum in the mass spectrometer's high vacuum chamber 1.
  • the micro plasma ion source 10 comprises a radio- frequency electrode 11 and one or more earth electrodes 12, as will be discussed later.
  • the radio-frequency generator 2 is connected to the radio- frequency electrode 11, and plasma is generated by the radio-frequency generator impressing on the radio-frequency electrode a radio-frequency electrical potential.
  • the frequency may, for example, be between 100 kHz and 100 MHz. In a preferred embodiment 350 kHz is used.
  • the plasma gas is now mainly capacitively converted to a plasma, and in this plasma the inserted sample is atomized, with creation of atomic ions, which as mentioned flow out of the micro plasma ion source's 10 outlet 15 and are analysed in the mass spectrometer for determination of the elements.
  • the radio-frequency generator 2 impresses a radio-frequency potential on the radio-frequency electrode 11, discharges are obtained between the radio-frequency electrode and the earth electrode or earth electrodes 12, the plasma gas introduced into the channel 13 is converted into a plasma and the accompanying sample is atomized with subsequent creation of atomic ions, as discussed above in connection with the description of the micro plasma mass spectrometer in Fig. 1.
  • Fig. 3 illustrates a second preferred embodiment of the micro plasma ion source 10 according to the invention. It differs from the embodiment in Fig. 2 in that the radio-frequency electrode 11 is mounted around the micro plasma ion source's outlet 15, i.e. the outlet of the capillary channel or the capillary tube 13. In this case the earthed metal tube 16 constitutes the earth electrode 12. Otherwise the mode of operation of the micro plasma ion source 10 is as mentioned above in connection with Fig. 2.
  • Fig. 4 illustrates a third preferred embodiment of the micro plasma ion source 10 according to the invention. It corresponds mainly to the embodiment in Fig. 2, but in this case the capillary channel or capillary tube 15 at the outlet 15 is provided with a narrowing 18.
  • the narrowing 18 at the outlet 13 causes the pressure in the plasma gas or the plasma in the channel or the tube 13 to become higher, thus influencing the properties of the micro plasma ion source, for example by increasing the energy density in the plasma. Otherwise the mode of operation of the micro plasma ion source 10 is as mentioned above in connection with the embodiment in Fig. 2.
  • the micro plasma probe as illustrated in Fig. 6 is easily attached to the mass spectrometer and is secured by means of vacuum. Between the micro plasma probe and the opening in the mass spectrometer there is provided a not shown rubber O-ring to ensure a good seal.
  • the illustrated micro plasma probe is very simple to install and dismantle, thus making it easy to equip existing commercial mass spectrometers, so that they can be employed as a micro plasma mass spectrometer according to the invention.
  • the supply line 17 for plasma gas and the sample included therein is a capillary quartz tube with an internal diameter of 0.32 mm and external diameter of 0.45 mm.
  • the channel or tube 13 in the micro plasma ion source 10 may also be a capillary quartz tube, formed in one piece with the supply line 17.
  • the capillary tube of quartz is then passed through the radio-frequency electrode 11 and the earth electrode 12 at the outlet.
  • These electrodes 11, 12 may, for example, be in the form of metal tubes with an internal diameter of 0.5 mm and external diameter of
  • Fig. 7 illustrates a second embodiment of the micro plasma ion source 10 implemented as a micro plasma probe.
  • This embodiment is similar to the one given in Fig. 6, except that the part of the capillary tube 13 which protrudes out of the earthed metal tube 16, is encapsuled by an outer fused silica tube 25.
  • the fused silica tube 25 is provided with a strong narrowing 18 at the outlet 15 and is tightly attached to the earthed metal tube 16 by a TeflonTM tubing 26.
  • TeflonTM tubing 26 TeflonTM tubing
  • the gas consumption may be as low as 1 ml/min, but it is preferred to employ a consumption of 2.25 ml/min, which is the output of the gas chromatograph.
  • the radio-frequency electrode 11 and the outer earth eletrode 12 are made of steel wire which is twisted around the fused silica tube 25.
  • FIG. 8 illustrates an apparatus set-up for element-selective detection in micro plasma mass spectrometry and the use of gas chromatographic separation.
  • the actual micro plasma mass spectrometer is designed as illustrated in Fig. 1, and reference is therefore made to the above discussion of this figure.
  • a gas chromatograph has an open tubular column 37 which ends in a T-connection 38 in order to mix the sample with oxygen-doped helium which is used as plasma gas and supplied from a helium gas supply 30 with pressure regulator and gauge, while the oxygen, which in this case is used as scavenger gas, comes from the oxygen gas supply 31 which is similarly equipped with pressure regulator and gauge.
  • a T-connection 32 divides the helium gas flow into a carrier gas flow and an external helium flow.
  • An external helium flow gauge 33 and an external helium flow regulator 34 are provided between the T-connection 32 and the T-connection 35, the T-connection 35 being used to introduce oxygen to the external helium flow through, for example, a 20 ⁇ m microcapillary column of fused silica.
  • the helium carrier gas line is conveyed to a "split-splitless" injector 36.
  • the plasma gas doped with oxygen is transported from the T-connection 38 at the end of the tubular column 37 and the separated sample is added through a heated feed line 9 with a temperature control unit 39 to the supply line 17 and the inlet 14 of the plasma ion source 10. It should not be necessary to provide a detailed description of this apparatus set-up, since the technique will be well known to those skilled in the art.
  • helium was employed as plasma gas in the micro plasma ion source.
  • Helium has a high ionization potential, providing a plasma with high energy, thus enabling the method and the micro plasma mass spectrometer according to the invention to be successfully employed for the detection of elements with a high ionization potential.
  • the flow rate of helium influences the plasma energy, the plasma pressure and the extension of plasma from the foremost electrode in the micro plasma ion source's channel. Since collisions in the plasma create the atomic ions, the amount of colliding species and their energy will, for example, be important factors.
  • a scavenger gas was added to the plasma gas in order to remove carbon deposits which were formed on the quartz wall in the capillary tube 13.
  • oxygen was employed as scavenger gas, since oxygen is considered to be effective with respect to chlorine-selective detection.
  • a detection limit of 3.3 gs -1 was achieved.
  • hydrogen instead of oxygen as scavenger gas a somewhat higher detection limit for chlorine was achieved.
  • Gas flow rates of less than 25 ml/s were employed, but higher flow rates were also possible.
  • a radio-frequency potential of 350 kHz was used, but the frequency can be higher or lower, for example in the range 100 kHz to 100 MHz.
  • An internal diameter of the tube or channel of only 320 ⁇ m gave a narrow ion beam from the outlet of the micro plasma ion source.
  • the small volume of the channel resulted in a power output of only 2.0 watt being employed for the discharge.
  • micro plasma ion source as specified above and employed in a mass spectrometer effectively realizes a micro plasma mass spectrometer according to the invention.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Electron Tubes For Measurement (AREA)
EP98904444A 1997-02-14 1998-02-12 A method for element-selective detection, a micro plasma mass spectrometer for use in the method and a micro plasma ion source, together with applications thereof Expired - Lifetime EP0960431B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NO970707A NO304861B1 (no) 1997-02-14 1997-02-14 FremgangsmÕte ved elementselektiv deteksjon, mikroplasmamassespektrometer til bruk ved fremgangsmÕten og plasmaionekilde, samt anvendelser av disse
NO970707 1997-02-14
PCT/NO1998/000048 WO1998036440A1 (en) 1997-02-14 1998-02-12 A method for element-selective detection, a micro plasma mass spectrometer for use in the method and a plasma ion source, together with applications thereof

Publications (2)

Publication Number Publication Date
EP0960431A1 EP0960431A1 (en) 1999-12-01
EP0960431B1 true EP0960431B1 (en) 2002-04-10

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EP98904444A Expired - Lifetime EP0960431B1 (en) 1997-02-14 1998-02-12 A method for element-selective detection, a micro plasma mass spectrometer for use in the method and a micro plasma ion source, together with applications thereof

Country Status (7)

Country Link
EP (1) EP0960431B1 (no)
JP (1) JP2001512617A (no)
AU (1) AU719247B2 (no)
CA (1) CA2278807A1 (no)
DE (1) DE69804772T2 (no)
NO (1) NO304861B1 (no)
WO (1) WO1998036440A1 (no)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007042746A2 (en) * 2005-10-11 2007-04-19 Gv Instruments Ion source preparation system

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7274015B2 (en) * 2001-08-08 2007-09-25 Sionex Corporation Capacitive discharge plasma ion source
DE10248055B4 (de) * 2002-10-11 2012-02-23 Spectro Analytical Instruments Gmbh & Co. Kg Methode zur Anregung optischer Atom-Emission und apparative Vorrichtung für die spektrochemische Analyse
US7460225B2 (en) 2004-03-05 2008-12-02 Vassili Karanassios Miniaturized source devices for optical and mass spectrometry
DE102009046504B4 (de) * 2009-11-06 2016-06-09 Westfälische Wilhelms-Universität Münster Verfahren und Vorrichtung zum Analysieren eines Stoffgemisches
JP5784825B2 (ja) * 2011-05-20 2015-09-24 パーデュー・リサーチ・ファウンデーションＰｕｒｄｕｅ Ｒｅｓｅａｒｃｈ Ｆｏｕｎｄａｔｉｏｎ 試料を分析するためのシステムおよび方法

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* Cited by examiner, † Cited by third party
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JP3215487B2 (ja) * 1992-04-13 2001-10-09 セイコーインスツルメンツ株式会社 誘導結合プラズマ質量分析装置
CA2116821C (en) * 1993-03-05 2003-12-23 Stephen Esler Anderson Improvements in plasma mass spectrometry
JPH07272671A (ja) * 1994-03-29 1995-10-20 Ulvac Japan Ltd ガス分析装置及びガス分析方法
WO1997020620A1 (en) * 1995-12-07 1997-06-12 The Regents Of The University Of California Improvements in method and apparatus for isotope enhancement in a plasma apparatus
EP0792091B1 (en) * 1995-12-27 2002-03-13 Nippon Telegraph And Telephone Corporation Elemental analysis method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007042746A2 (en) * 2005-10-11 2007-04-19 Gv Instruments Ion source preparation system
WO2007042746A3 (en) * 2005-10-11 2007-12-21 Gv Instr Ion source preparation system

Also Published As

Publication number Publication date
NO970707L (no) 1998-08-17
NO304861B1 (no) 1999-02-22
AU719247B2 (en) 2000-05-04
AU6231498A (en) 1998-09-08
NO970707D0 (no) 1997-02-14
DE69804772T2 (de) 2002-11-28
JP2001512617A (ja) 2001-08-21
DE69804772D1 (de) 2002-05-16
WO1998036440A1 (en) 1998-08-20
CA2278807A1 (en) 1998-08-20
EP0960431A1 (en) 1999-12-01

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