ION INLET ASSEMBLY

Abstract

An ion inlet assembly for connecting to a mass spectrometer housing is disclosed comprising a sampling limiting body (325) having a sampling orifice (329). The sampling limiting body (325) comprises a nickel disk wherein the disk and sampling orifice (329) are made or formed by an electroforming process.

Claims

1. An ion inlet assembly for connecting to a mass spectrometer housing comprising: a gas cone assembly having a gas cone orifice; and a sampling limiting body having a sampling orifice; wherein said sampling limiting body is removably attached beneath the gas cone assembly to the mass spectrometer housing.

2. An ion inlet assembly as claimed in claim 1 wherein said sampling limiting body comprises a disk.

3. An ion inlet assembly as claimed in claim 1, wherein said gas cone assembly is connectable to a gas supply such that gas is arranged to flow, in use, towards said gas cone orifice.

4. An ion inlet assembly as claimed in claim 2, wherein said disk is flat.

5. (canceled)

6. An ion inlet assembly as claimed in claim 2, wherein said disk is substantially round or circular.

7. (canceled)

8. (canceled)

9. (canceled)

10. An ion inlet assembly as claimed in claim 1, wherein said sampling limiting body is arranged to be supplied with a voltage in use.

11. An ion inlet assembly as claimed in claim 1, wherein said sampling orifice is substantially round or circular.

12. An ion inlet assembly as claimed in claim 1, wherein said sampling limiting body comprises a plurality of sampling orifices.

13. An ion inlet assembly as claimed in claim 1, further comprising a vacuum holding member having an orifice to allow the flow of ions into a mass spectrometer.

14. An ion inlet assembly for connecting to a mass spectrometer housing comprising: a gas cone assembly having a gas cone orifice; a sampling limiting body having an orifice, wherein said sampling limiting body is removably attached beneath the gas cone assembly to the mass spectrometer housing; and a vacuum holding member having an orifice to allow the flow of ions into the mass spectrometer, wherein said vacuum holding member is arranged underneath the sampling limiting body; wherein upon attachment to a mass spectrometer housing said vacuum holding member provides at least a partial vacuum seal upon removal of the sampling limiting body.

15. An ion inlet assembly as claimed in claim 14, wherein said sampling limiting body comprises a disk.

16. An ion inlet assembly as claimed in claim 14, wherein said gas cone assembly being arranged to connected to a gas supply so that gas is arranged to flow towards said orifice in use.

17. An ion inlet assembly as claimed in claim 14, wherein said ion inlet assembly is attached, in use, to a mass spectrometer housing by a mounting device.

18. An ion inlet assembly as claimed in claim 17, wherein said mounting device is attached, in use, to a mass spectrometer housing without mechanical fasteners.

19. A mass spectrometer comprising an ion inlet assembly as claimed in claim 1.

20. (canceled)

21. (canceled)

22. A method of connecting an ion inlet assembly to a mass spectrometer housing, said ion inlet assembly comprising a gas cone assembly having a gas cone orifice, and a sampling limiting body, said method comprising: removably attaching said sampling limiting body to said mass spectrometer housing by resting said gas cone assembly upon said sampling limiting body.

23. An ion inlet assembly as claimed in claim 2, wherein said disk is a nickel disk.

24. An ion inlet assembly as claimed in claim 23, wherein said disk and said sampling orifice are made or formed by an electroforming process.

25. An ion inlet assembly as claimed in claim 1, wherein said sampling limiting body has a polished surface that is arranged to face towards said gas cone assembly.

26. An ion inlet assembly as claimed in claim 1, wherein said sampling limiting body is removably attached to the mass spectrometer housing by the gas cone assembly resting upon the sampling limiting body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Various embodiments of the present invention will now be described, by way of example, together with other arrangements given for illustrative purposes only and with reference to the accompanying drawings in which:

[0096] FIG. 1 shows a conventional ion inlet assembly;

[0097] FIG. 2 shows an alternative conventional ion inlet assembly having a reverse cone geometry;

[0098] FIG. 3 shows an ion inlet assembly in accordance with a preferred embodiment of the present invention;

[0099] FIG. 4 shows an exploded view of an ion inlet assembly according to a preferred embodiment of the present invention;

[0100] FIG. 5 shows a sampling limiting body housed within a sampling limiting body housing in accordance with an embodiment of the present invention;

[0101] FIG. 6 shows a cross-sectional view of a sampling limiting body in accordance with an embodiment of the present invention; and

[0102] FIG. 7 shows a vacuum holding member in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0103] A conventional ion inlet assembly will now be described.

[0104] FIG. 1 shows a conventional ion inlet assembly 110. The conventional arrangement comprises an outer gas cone 114 and an inner gas cone 112 of similar form which are nested together so that the angles and hole diameters may be varied to fit machine performance. The outer gas cone 114 comprises a high precision machined component with stringent cleaning requirements. The outer gas cone 114 is followed by an inner gas cone 112. These parts are high cost and the orifice 116 in the inner gas cone 112 is prone to being damaged and/or at least partially blocked. In particular, the orifice 116 in the inner gas cone 112 may become partially blocked during cleaning and it can be difficult for a user to determine whether or not the orifice 116 is partially blocked.

[0105] The intersecting angles of the inner and outer gas cones 112,114 results in the formation of an entrance aperture 116. An isolation valve 118 is located downstream of the inner and outer gas cones 112,144. The isolation valve 118 is arranged to prevent a downstream vacuum chamber 120 from venting when the inlet assembly is removed. The isolation valve 118 is expensive to manufacture and requires the user to close it before the ion inlet assembly is removed in order to maintain analyser vacuum.

[0106] FIG. 2 shows an alternative conventional ion inlet assembly having a reverse cone geometry. In this assembly the entrance aperture 216 is formed behind the gas cone 212. An aperture 222 through the gas cone 212 is provided.

[0107] An opening 224 about the centre of the cone can be obtained via a sharp intersection of two differing cone angles controlled to a height. The reverse cones require the drilling of a very small precise hole into the cone, part of which is then joined to the main body.

[0108] It will be understood by those skilled in the art that the arrangements shown in FIGS. 1 and 2 require precision turning and drilling processes which are highly expensive leading to a high cost component. Furthermore, the inner gas cone 112 as shown in FIG. 1 is particularly prone to being damaged and/or partially blocked.

[0109] The cones are required to be chemically robust and to withstand exposure to solvents during normal operation. In order to maintain this level of performance the cones must be regularly removed from the assembly and cleaned.

[0110] The removal of the cones will mean total loss of vacuum unless an isolation valve is provided. Furthermore, regularly cleaning exposes the cones to the risk of damage and it is not always easy to determine whether or not an orifice in one of the cones is partially blocked.

[0111] A preferred embodiment of the present invention will now be described.

[0112] FIG. 3 shows a schematic of an ion inlet assembly for a mass spectrometer in accordance with an embodiment of the present invention. An ion source (not shown) is located in an external ionisation chamber 303 and analyte ions are directed to a vacuum chamber 305 of a mass spectrometer 301.

[0113] The ionisation chamber 303 is separated from the vacuum chamber 305 by a vacuum chamber wall 307. Ions from the ion source are directed towards the ion inlet assembly 309 which covers an aperture 311 in the vacuum chamber wall 307.

[0114] A gas cone structure comprises an inner gas cone body 313 with a central aperture 315 through the cone (at the point of the cone) and an outer gas cone 317. The outer gas cone 317 is arranged to provide a hollow area or annulus 319 between the inner gas cone 313 and the outer gas cone 317.

[0115] An outer gas cone aperture 321 is arranged in the outer gas cone 317 at the point of the cone.

[0116] The gas cone structure is arranged to allow for the gas cone to be connected to a gas port (not shown) which directs a flow of gas through the hollow area or annulus 319 between the inner gas cone 313 and the outer gas cone 317 and towards the outer gas cone aperture 321.

[0117] The outer gas cone 317 is preferably attached to the housing 323 of the instrument by means of a retaining device (not shown). The retaining device (not shown) is preferably arranged to hold the outer gas cone 317 in place and by holding the outer gas cone 317 in place, the inner gas cone 313 is preferably also held in place by the outer gas cone 317 resting upon it.

[0118] The retaining device is preferably designed to hold the sample cone arrangement in place without the need to use mechanical fasteners.

[0119] A sampling limiting body 325 in the form of a nickel electroformed disk is preferably arranged or otherwise secured within a sampling limiting body mounting 327. The sampling limiting body 325 is preferably attached beneath the inner gas cone 313 to the housing 323 such that the sampling limiting body mounting 327 and the sampling limiting body 325 cover the aperture 311 of the vacuum chamber 305.

[0120] The sampling limiting body 325 has an aperture or sampling orifice 329 through which ions can pass. The sampling limiting body mounting 327 and sampling limited body in the form of a disk 325 are arranged to sit upon the housing 323 and are removably held in position by the inner gas cone 313 resting upon the sampling limiting body mounting 327.

[0121] A vacuum holding member 331 is preferably arranged underneath the sampling limiting body 325 and the sampling limiting body mounting 327. The vacuum holding member 331 is preferably arranged to cover the aperture 311 of the vacuum chamber 305 and is attached to the housing 323 by the sampling limiting body mounting 327 resting upon the vacuum holding member 331. Upon removal of the sampling limiting body 325 and the sampling limiting body mounting 327, the vacuum holding member 331 will preferably remain being held in place without the sampling limiting body 325 and the sampling limiting body mounting 327 resting upon the vacuum holding member 331 when the instrument remains at sufficient vacuum level which will prevent complete loss of internal vacuum pressure. This reduces the time taken for the instrument to return to an operational state after the sample limiting body 325 has been replaced.

[0122] The gas cone structure preferably comprises an outer gas cone 317 and an inner gas cone 313 which are two separate structures. The manufacture of the gas cone structure as two separate structures is relatively easy to manufacture and clean. However, according to a less preferred embodiment the gas cone structure may comprise a single structure.

[0123] The gas cone structure is preferably held in place by a retaining device which is designed to hold the sample cone arrangement in place without the need to use mechanical fasteners such as screws or Allen bolts. This removes the possibility of the failure of such fasteners or of a user applying insufficient or incorrect tension to such fasteners. Advantageously, no tools are preferably required by a user in order to attach and secure the gas cone assembly to an ion block of the mass spectrometer.

[0124] Less preferred embodiments are nonetheless contemplated wherein the gas cone is still be held in place with the use of mechanical fasteners, screws or Allen bolts.

[0125] According to the preferred embodiment the central aperture in the outer gas cone 317 is preferably in the range 2-4 mm. According to less preferred embodiments the central aperture in the outer gas cone 317 may be in the range 0.5 to 10 mm. The central aperture in the inner gas cone 313 is preferably in the range 0.5 to 1.5 mm. According to less preferred embodiments the central aperture in the inner gas cone 313 may be in the range 0.1 to 5 mm.

[0126] FIG. 4 shows an exploded view of an ion inlet assembly according to a preferred embodiment of the present invention. The gas cone structure comprises an inner gas cone body 413 with a central aperture 415 through the cone at the point of the cone. An outer gas cone 417 is provided and provides a hollow area or annulus (not shown) between the inner gas cone 413 and the outer gas cone 417.

[0127] An outer gas cone aperture 421 is arranged in the outer gas cone 417 at the point of the cone. The gas cone structure is arranged to allow the attachment to a gas port 433. The gas port 433 directs a gas flow through the hollow area or annulus (not shown) between the inner gas cone 413 and the outer gas cone 417 and towards the aperture of the outer gas cone 421.

[0128] The outer gas cone 417 is preferably arranged to be attached to the housing 423 of the instrument by means of a retaining device 435. The retaining device 435 is preferably arranged to hold the outer gas cone 417 in place and by holding the outer gas cone 417 in place, the inner gas cone 413 is preferably also held in place by the outer gas cone 417 resting upon it.

[0129] The retaining device 435 is preferably arranged to hold the sample cone arrangement in place without the need to use mechanical fasteners.

[0130] The sampling limiting body 425 preferably comprises an electroformed nickel disk and is preferably arranged or otherwise mounted in a sampling limiting body mounting 427. The sampling limiting body mounting 427 is preferably arranged to be attached beneath the inner gas cone 413 to the housing 423, such that the sampling limiting body mounting 427 and the sampling limiting body 425 cover the aperture 411 of the vacuum chamber.

[0131] The sampling limiting body comprising a disk has an aperture 429 through which ions can pass. The sampling limiting body mounting 427 and the sampling limiting body 425 are preferably arranged to sit upon the housing 423 and can be removably held in place by the inner gas cone 413 resting upon the sampling limiting body mounting 427.

[0132] A vacuum holding member 431 is preferably arranged underneath the sampling limiting body 425 and the sampling limiting body mounting 427. The vacuum holding member 431 is preferably arranged to cover the aperture 411 of the vacuum chamber and is capable of attachment to the housing 423 by the sampling limiting body mounting 427 resting upon the vacuum holding member 431. Upon removal of the sampling limiting body 425 and the sampling limiting body mounting 427, the vacuum holding member 431 will preferably remain in place without the sampling limiting body 427 resting upon the vacuum holding member 431 when the instrument is held at vacuum by the pressure differential created by the vacuum chamber (not visible) being at lower pressure than the ionisation chamber.

[0133] A washer 437 is preferably arranged to form a seal between the vacuum holding member 431 and the housing 423.

[0134] FIG. 5 shows a sampling limiting body in accordance with an embodiment of the present invention. The sampling limiting body comprises a nickel electroformed disk which is mounted within a sampling limiting body housing 525 so that the sampling limiting body can be secured relative to the vacuum housing (not shown).

[0135] The sampling limiting body may have stepped geometry 539 through the thickness of the aperture orifice 529.

[0136] The sampling limiting body is preferably substantially flat in form and is produced or otherwise formed by using an additive electroforming manufacturing processes rather than being machined from solid stock material. The disk forms a gas limiting orifice and is made from nickel by an electroforming processes which is particularly advantageous relative to conventional arrangements.

[0137] According to an embodiment the sampling limiting body comprising a disk may be grown complete in a single process and preferably requires no further finishing. The disk may be manufactured with an internal aperture having various different forms or profiles. The internal aperture preferably comprises a round or circular aperture although other embodiments are contemplated wherein the aperture may have other different geometries. According to an embodiment the internal aperture may be formed so as to have rifling i.e. helical grooves.

[0138] Embodiments are contemplated wherein more than one aperture may be provided in the sampling limiting body or disk in order to allow greater throughput of sample into the mass spectrometer. The one or more apertures are preferably arranged on or around the central axis.

[0139] According to other less preferred embodiments the one or more apertures may be arranged off the central axis.

[0140] A particularly advantageous aspect of the present invention is that by electroforming the sampling limiting body from nickel, the aperture size in the nickel disk can be precisely and consistently manufactured. The manufacturing process is, advantageously, highly repeatable.

[0141] One of the main advantages of the electroforming process which is utilised according to the present invention is that the low cost of fabricating the sampling limiting body allows the sampling limiting body to become essentially a disposable item. The disposable nature of the sampling limiting body according to the preferred embodiment essentially negates the need to clean or service the part.

[0142] According to the preferred embodiment the sampling limiting body and the corresponding sampling limiting body housing 525 may be easily removed. Easy removal of the sampling limiting body and the corresponding sampling limiting body housing 525 is achieved by the pinching removal of the housing. The two parts can then be discarded and replaced at low cost as a complete unit. According to an alternative embodiment only the sampling limiting body need be discarded or otherwise replaced.

[0143] The sampling limiting body housing 525 is preferably made of synthetic rubber such as VITON although other embodiments are contemplated wherein the sampling limiting body housing 525 may be made from a polymeric material.

[0144] The sampling limiting body housing 525 is preferably pliable so that the sampling limiting body can be manipulated to sit on top of the housing of the mass spectrometer and create a seal against it.

[0145] The sampling limiting body housing 525 is preferably made of an electrically conductive material so that, when in use, an electric current may be applied through the housing to the sampling limiting body from connections on the vacuum housing.

[0146] The sampling limiting body housing 525 is preferably arranged to form an interference fit with the sampling limiting body or disk. In particular, the outer diameter of the sampling limiting body or disk is preferably arranged to be slightly larger than the inner diameter of the sampling limiting body housing 525. The conductive flexible sampling limiting body housing 525 preferably ensures that a gas tight seal is formed with the sampling limiting body or disk. Furthermore, since the sampling limiting body housing 525 is preferably conductive, then electrical contact can be readily established between the nickel sampling limiting body and an ion block of a mass spectrometer via the sampling limiting body housing 525. The tight interference fit between the sampling limiting body and the sampling limiting body housing 525 has also been found to provide improved electrical conductivity.

[0147] FIG. 6 shows a sampling limiting body 625 in accordance with a preferred embodiment of the invention. The sampling limiting body 625 is preferably in the form of a disk. According to an embodiment the disk may have a polished front (outer) surface 641 and a second rear (inner) matt surface 643. The polished surface 641 is preferably arranged to sit against the sampling limiting body housing (not shown) and preferably faces towards the gas cone structure. The second matt face 643 preferably has a stepped surface 639. The aperture for the transmittal of ions is preferably arranged to be inside the stepped surface so that the aperture 629 is at the point where the sampling limiting body 625 is of least diameter. This reduces the likelihood of blockages.

[0148] Other embodiments are contemplated wherein the outer surface 641 may comprise a matt surface and/or the inner surface 643 may comprise a polished surface. According to other embodiments both surfaces may comprise matt surfaces or polished surfaces. The outer surface 641 may be stepped and/or the inner surface 643 may be flat. In some embodiments both surfaces may be stepped or flat.

[0149] The sampling limiting body is preferably nickel grown. According to less preferred embodiments the sampling limiting body may be made from stainless steel or aluminium.

[0150] The sampling limiting body may be coated with, for example, gold or another electrically conductive material. In other embodiments the sampling limiting body may be made using a laser machining processes.

[0151] In some embodiments information relating to the sampling limiting body may be added to one or both surfaces. According to the preferred embodiment visual information is preferably displayed on the outer shiny surface.

[0152] The sampling limiting body preferably comprises a flat disk, further preferably a stepped disk. According to other less preferred embodiments the sampling limiting body may be concave or convex in form.

[0153] The stepped disk may include one or more stepped levels on either or both sides of the sampling limiting body. The stepped levels may have rounded or pointed corners.

[0154] The flat disk is preferably substantially round or circular but according to less preferred embodiments the flat disk may have a different geometry.

[0155] The flat disk may be shaped so that it is keyed to ensure that the disk is used for the appropriate instrument thereby avoiding accidental installation or insertion within a wrong or unsuitable instrument.

[0156] Embodiments of the present invention are contemplated wherein multiple orifices are provided in the sampling limiting body.

[0157] Embodiments are contemplated wherein the area of one or more orifices is preferably in the range of 2000 m.sup.2 to 13 mm.sup.2. The area of the orifice preferably depends upon the requirements for the vacuum system of the mass spectrometer in question. According to a particularly preferred embodiment the area of the orifice is preferably in the range of 30000 to 125000 m.sup.2.

[0158] According to an embodiment multiple holes may be provided in the sampling limiting body. For example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or more than 15 holes or orifices may be provided in the sampling limiting body. Preferably, the combined area of all the holes or apertures is in the range of 2000 m.sup.2 to 13 mm.sup.2.

[0159] According to other embodiments the area of the orifice(s) is preferably in the range of 30000 to 125000 m.sup.2.

[0160] The sampling limiting body aperture preferably has a diameter in the range of 100-200 m. According to other embodiments the sampling limiting body aperture may have a diameter in the range of 50-2000 m.

[0161] Preferably, the sampling limiting body has a diameter in the range of 3-15 mm. According to other further embodiments the sampling limiting body may have a diameter in the range of 1-25 mm.

[0162] The sampling limiting body preferably has a thickness in the range of 0.2-1 mm. In further embodiments the sampling limiting body preferably has a thickness in the range of 0.1-3 mm.

[0163] The vacuum holding member is preferably arranged to hold a vacuum when the sampling limiting body and gas cone assembly has been removed. This advantageously removes the need for an isolation valve to be provided and thereby reduces the manufacturing cost of the mass spectrometer.

[0164] According to a particularly preferred embodiment the disk has a diameter of 7 mm and a thickness of 0.5 mm. According to an embodiment the sampling limiting body aperture or orifice 629 may have a diameter in the range 90-200 m. For example, disks having an orifice 629 diameter of 90 m and 200 m may be used.

[0165] Although not shown in FIG. 6, the disk may be electroformed so that the aperture or orifice 629 is provided in a single build layer of the electroforming process. According to an embodiment, the single build layer may have a thickness of 25 m. Accordingly, a disk 625 may be provided which is 5 mm thick and wherein a rear bore 639 having a diameter of 1 mm extends for 4.975 mm so that the aperture or orifice 629 is formed in a single build layer having a thickness of 0.025 mm. Although the aperture or orifice 629 can be formed in a thin single build layer, the disk 625 has been found to be robust and to possess an exceptional degree of consistency during the manufacturing process.

[0166] FIG. 7 shows in greater detail the vacuum holding member 731. The vacuum holding member 731 preferably has an aperture 745 in the surface facing towards the sampling limiting body (not shown) for the ions to pass through. The vacuum holding member 731 preferably has a ridge 747 which holds a washer 737 in place. When attached to the ion inlet system (not shown), the washer 737 preferably sits against the entrance of the ion inlet system (not shown) creating a seal with the housing (not shown). When in place, the vacuum holding member 731 preferably provides a vacuum seal with the ion inlet entrance (not shown) to prevent the ion inlet system (not shown) from being open to the atmosphere and resulting in the whole instrument venting.

[0167] The vacuum holding member aperture preferably has a diameter in the range of 0.3 to 5 mm. In further embodiments the vacuum holding member aperture may have a diameter in the range of 0.1-10 mm.

[0168] In addition to holding a vacuum upon the removal of the sampling limiting body, an additional benefit of the vacuum holding member 731 is that it also helps to keep the main ion inlet in the ion block clean.

[0169] Although the present invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as set forth in the accompanying claims.