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 PDFInfo
- 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
- Authority
- 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.)
- Expired - Lifetime
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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)
Description
Claims (26)
- A method for element-selective detection of chromato graphically or electrophoretically separated compounds, wherein for the detection there is employed a plasma mass spectrometer with a plasma ion source (10), a mass analyser (3) and an ion detector (4),
characterized in that the plasma ion source is a micro plasma ion source (10) located in the mass spectrometer's high vacuum chamber (1), and in that a plasma gas carrying one or more of the separated compounds, which are to be detected in the mass spectrometer, is introduced into the micro plasma ion source (10), whereby the separated compound(s) are atomized with the creation of atomic ions which are subsequently expelled from the micro plasma ion source (10) into the mass spectrometer's high vacuum chamber (1) for separation in the mass analyser (3) and detection in the ion detector (4). - A method according to claim 1,
characterized in that the plasma in the micro plasma ion source (10) is formed capacitively by discharges between one or more radio-frequency electrodes (11) connected to a radio-frequency generator (2) and one or more earth connections (12). - A method according to claims 1-2,
characterized in that the radio-frequency potential has any frequency between 100 kHz and 100 MHz, and in that the frequency is preferably 350 kHz. - A method according to claims 1-3,
characterized in that helium, neon, argon, hydrogen,or nitrogen are employed as plasma gas. - A method according to claims 1-4,
characterized in that in the micro plasma ion source, any gas flow rate between 1 and 50 ml/min is employed. - A plasma mass spectrometer, especially for element-selective detection of chromatographically or electrophoretically separated compounds, wherein the plasma mass spectrometer comprises a plasma ion source (10), a mass analyser (3) and an ion detector (4),
characterized in that the plasma ion source is a micro plasma ion source (10) located in the mass spectrometer's high vacuum chamber (1), and in that a plasma gas carrying one or more of the separated compounds, which are to be detected in the mass spectrometer, is introduced into the micro plasma ion source (10), whereby the separated compound(s) are atomized with the creation of atomic ions which are subsequently expelled from the micro plasma ion source (10) into the mass spectrometer's high vacuum chamber (1) for separation in the mass analyser (3) and detection in the ion detector (4). - A plasma mass spectrometer according to claim 6,
characterized in that the plasma in the micro plasma ion source (10) is formed capacitively by discharges between one or more radio-frequency electrodes (11) connected to a radio-frequency generator (2) and one or more earth connections (12). - A plasma mass spectrometer according to claims 6-7,
characterized in that the radio-frequency potential has any frequency between 100 kHz and 100 MHz, and in that the frequency is preferably 350 kHz. - A plasma mass spectrometer according to claims 6-8,
characterized in that helium or argon are employed as plasma gas. - A plasma mass spectrometer according to claims 6-9,
characterized in that in the micro plasma ion source, any gas flow rate between 1 and 50 ml/min is employed. - A plasma ion source (10) for use in a plasma mass spectrometer, especially for element-selective detection of chromatographically or electrophoretically separated compounds, wherein the mass spectrometer comprises the plasma ion source (10), a mass analyser (3) and an ion detector (4), wherein the plasma ion source (10) has an inlet (14) at one end and an outlet (15) at the opposite end, and wherein the plasma ion source is arranged in the mass spectrometer in such a manner that the inlet (14) and the outlet (15) are located in the mass spectrometer's high vacuum chamber (1), characterized in that the plasma ion source is a micro plasma ion source (10), in that between inlet (14) and outlet (15) the micro plasma ion source (10) is equipped with a capillary channel (13), in that a plasma gas which carries one or more of the compounds which are to be detected is introduced at the inlet (14) of the channel (13), and in that the micro plasma ion source (10) is provided with means for employing the plasma gas in the channel (13) to create and maintain a plasma inside the capillary channel (13), with the result that the compound or compounds are atomized into atomic ions.
- A plasma ion source according to claim 11,
characterized in that the means for forming the plasma in the capillary channel (13) comprises one or more radio-frequency electrodes (11) connected to a radio-frequency generator (2) and one or more earth connections (12), and in that the electrodes are located outside of the capillary tube (13), around its circumference. - A plasma ion source according to claim 11-12,
characterized in that the radio-frequency potential imposed on the one or more radio-frequency electrodes (12) has any frequency between 100 kHz and 100 MHz, and in that the frequency is preferably 350 kHz. - A plasma ion source according to claims 11-13,
characterized in that the capillary channel (13) is designed in the form of a tube with an internal diameter of less than 2 mm, thus permitting a gas flow rate of 25 ml/min or less to be employed. - A plasma ion source according to claims 11-14,
characterized in that the tube (13) is a fused silica capillary tube. - A plasma ion source according to claims 11-14,
characterized in that the inlet (14) is connected to an earthed metal tube (16) which contains a supply line (17) for the plasma gas, and in that the earthed metal tube (16) constitutes the earth electrode or one of the earth electrodes (12). - A plasma ion source according to claims 11-14,
characterized in that the radio-frequency electrode (11) is provided at the outlet (15). - A plasma ion source according to claims 11-14,
characterized in that the earth electrode or earth electrodes (12) are provided between the radio-frequency electrode (11) and the inlet (14). - A plasma ion source according to claims 11-14,
characterized in that the earth electrode or earth electrodes (12) are provided at the outlet (15). - A plasma ion source according to claims 11-19,
characterized in that the capillary channel (13) at the outlet (15) is provided with a narrowing (18). - A plasma ion source according to claim 11-20,
characterized in that the supply line (17) is formed in one piece with the plasma ion source (10), with the result that the capillary channel (13) also acts as a supply pipe. - A plasma ion source according to claim 21,
characterized in that the capillary tube (13) is encapsulated by an outer tube (25), in that the outer tube (25) is provided with a narrowing (18) at the outlet 15, and in that it is tightly attached to the earthed metal tube (16) in the other end, and thus the outer tube (25) provides a satisfactory tight encapsulation of the capillary tube (13) such that the micro plasma ion source (10) can maintain the plasma with a plasma gas flow rate of less than 4 ml/min. - A plasma ion source according to claim 22,
characterized in that in the micro plasma ion source, any gas flow rate between 1 and 4 ml/min is employed, preferably the gas flow rate is 2.25 ml/min. - A plasma ion source according to claim 22 or 23,
characterized in that in the micro plasma ion source, the gas flow rate equals the rate of the effluent from any conventional gas chromatograph. - Application of the method according to claims 1-6,
a plasma mass spectrometer according to claims 7-10 and a plasma ion source according to claims 11-24 for selective detection of all elements in the periodic table, especially the halogens and non-metals. - Application of a plasma ion source according to claims 11-22 for installation in existing, commercial mass spectrometers.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NO970707A NO304861B1 (en) | 1997-02-14 | 1997-02-14 | Method of Element Selective Detection, Microplasma Mass Spectrometer for Use in the Method and Plasma Ion Source, and Applications of These |
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 |
Family
ID=19900391
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
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 (en) |
JP (1) | JP2001512617A (en) |
AU (1) | AU719247B2 (en) |
CA (1) | CA2278807A1 (en) |
DE (1) | DE69804772T2 (en) |
NO (1) | NO304861B1 (en) |
WO (1) | WO1998036440A1 (en) |
Cited By (1)
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)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7274015B2 (en) * | 2001-08-08 | 2007-09-25 | Sionex Corporation | Capacitive discharge plasma ion source |
DE10248055B4 (en) * | 2002-10-11 | 2012-02-23 | Spectro Analytical Instruments Gmbh & Co. Kg | Method for excitation of optical atomic emission and apparatus for spectrochemical analysis |
US7460225B2 (en) | 2004-03-05 | 2008-12-02 | Vassili Karanassios | Miniaturized source devices for optical and mass spectrometry |
DE102009046504B4 (en) * | 2009-11-06 | 2016-06-09 | Westfälische Wilhelms-Universität Münster | Method and device for analyzing a substance mixture |
EP2710623B1 (en) | 2011-05-20 | 2019-10-23 | Purdue Research Foundation (PRF) | System for analyzing a sample |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3215487B2 (en) * | 1992-04-13 | 2001-10-09 | セイコーインスツルメンツ株式会社 | Inductively coupled plasma mass spectrometer |
CA2116821C (en) * | 1993-03-05 | 2003-12-23 | Stephen Esler Anderson | Improvements in plasma mass spectrometry |
JPH07272671A (en) * | 1994-03-29 | 1995-10-20 | Ulvac Japan Ltd | Method and device for gas analysis |
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 |
-
1997
- 1997-02-14 NO NO970707A patent/NO304861B1/en not_active IP Right Cessation
-
1998
- 1998-02-12 DE DE69804772T patent/DE69804772T2/en not_active Expired - Fee Related
- 1998-02-12 EP EP98904444A patent/EP0960431B1/en not_active Expired - Lifetime
- 1998-02-12 JP JP53562498A patent/JP2001512617A/en active Pending
- 1998-02-12 AU AU62314/98A patent/AU719247B2/en not_active Ceased
- 1998-02-12 WO PCT/NO1998/000048 patent/WO1998036440A1/en active IP Right Grant
- 1998-02-12 CA CA002278807A patent/CA2278807A1/en not_active Abandoned
Cited By (2)
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 (en) | 1998-08-17 |
AU6231498A (en) | 1998-09-08 |
CA2278807A1 (en) | 1998-08-20 |
NO970707D0 (en) | 1997-02-14 |
NO304861B1 (en) | 1999-02-22 |
DE69804772T2 (en) | 2002-11-28 |
EP0960431A1 (en) | 1999-12-01 |
WO1998036440A1 (en) | 1998-08-20 |
JP2001512617A (en) | 2001-08-21 |
DE69804772D1 (en) | 2002-05-16 |
AU719247B2 (en) | 2000-05-04 |
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