GB2402545A

GB2402545A - Reflectron for a mass spectrometer

Info

Publication number: GB2402545A
Application number: GB0410363A
Authority: GB
Inventors: Steve Curbishley; John Brian Hoyes; Jeff Locket; Richard Tydesley
Original assignee: Micromass UK Ltd
Current assignee: Micromass UK Ltd
Priority date: 2003-05-16
Filing date: 2004-05-10
Publication date: 2004-12-08
Anticipated expiration: 2024-05-10
Also published as: GB0311567D0; GB0410363D0; GB2402545B

Abstract

A reflectron comprises a tubular body 6 having four or more electrodes 7 deposited onto an inner surface. The body 6 is preferably of a single piece of ceramic material, machined, moulded, cast or sintered in one piece, and may be of circular, square, rectangular or elliptical cross-section. The electrodes may comprise conductive or metallic paint. Resistors 8 may be connected between the electrodes 7.

Description

81070001d21

MASS SPECTROMETER

The present invention relates to a reflectron for a mass spectrometer and in particular to a reflectron of a Time of Flight mass spectrometer.

Reflectrons are electrostatic ion mirrors which are used in Time of Flight mass analysers to reflect ions which have travelled the length of a drift or flight region back through the drift or flight region to an ion detector. The reflectron therefore extends the flight path (and hence the flight time) of a Time of Flight mass analyser without increasing the overall size of the mass spectrometer.

Known reflections generate an electric field within the reflectron which causes ions which enter the reflectron to be decelerated, reflected and then accelerated back out of the reflectron. Known reflections comprise a plurality of electrodes maintained at different electrical potentials. The resulting electric field generated within the reflectron may be either substantially linear or non-linear.

It is known to use reflections in conjunction with other ion optical components to correct for the spatial and velocity spread of ions emitted from an ion source.

Reflectrons therefore can be used to help improve the mass resolution of a mass spectrometer. However, in order not to adversely affect the mass resolution of a mass spectrometer conventional reflections have to be manufactured and assembled to a particularly high mechanical tolerance.

A particular known reflectron comprises nine individual metal ring electrodes supported on a frame.

The ring electrodes have lips and eight insulating - 2 - spacers arranged between the lips of the ring electrodes. Each element of the known reflection must be manufactured and assembled very precisely if the reflection is not to adversely affect the mass resolution of the mass spectrometer.

It is therefore desired to provide a reflection which is less complex to manufacture and assemble.

According to an aspect of the present invention there is provided a reflection for a mass spectrometer, the reflection comprising: a ceramic tubular body; and at least n conductive strips, rings, films or electrodes arranged on an inner surface of the ceramic tubular body, wherein n 2 4.

According to different embodiments at least 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more than 20 strips, rings, films or electrodes may be arranged on an inner surface of the tubular body.

Preferably, at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or > 20 of the conductive strips, rings, films or electrodes have substantially the same width and/or thickness and/or surface area.

The conductive strips, rings, films or electrodes preferably comprise conductive or metallic paint.

At least some of the conductive strips, rings, films or electrodes are preferably deposited on, painted or otherwise applied to the inner surface of the tubular body.

According to a preferred embodiment the tubular body is substantially cylindrical. However, according to other less preferred embodiments at least a portion of the tubular body may be non-cylindrical. For - 3 example, at least a portion of the tubular body may have a substantially square, rectangular or elliptical cross section.

Preferably, one or more contact pins extend through a wall of the tubular body. One or more resistors may be deposited or otherwise arranged on an inner or outer surface of the tubular body and may be arranged to connect with the contact pins. One or more of the conductive strips, rings, films or electrodes may therefore be effectively connected to one or more of the resistors.

According to a less preferred embodiment the reflection may comprise at least one further tubular body. The further tubular body is preferably coaxial with the ceramic tubular body. The further tubular body preferably comprises a ceramic tubular body preferably comprising at least four conductive strips, rings, films or electrodes arranged on an inner surface of the further tubular body.

According to another aspect of the present invention there is provided a reflectron for a mass spectrometer, wherein the reflection comprises a hollow body comprising at least n conductive strips, rings, films or electrodes deposited or painted on to an inner surface of the hollow body, wherein n 2 4.

According to another aspect of the present invention there is provided a mass spectrometer comprising a reflection as described above.

The reflection preferably forms part of a Time of Flight mass analyses.

According to another aspect of the present invention there is provided a method of mass spectrometry comprising: - 4 - providing a reflectron comprising a ceramic tubular body wherein at least n conductive strips, rings, films or electrodes are arranged on an inner surface of the ceramic tubular body, wherein n 2 4; and reflecting ions using the reflectron.

According to another aspect of the present invention there is provided a method of mass spectrometry comprising: providing a reflectron comprising a hollow body comprising at least n conductive strips, rings, films or electrodes deposited or painted on to an inner surface of the hollow body, wherein n 2 4; and reflecting ions using the reflectron.

According to another aspect of the present invention there is provided a method of making a reflectron for a mass spectrometer comprising: providing a tubular ceramic body; and arranging, applying or depositing four or more conductive strips, rings, films or electrodes on to an inner surface of the tubular body.

According to another aspect of the present invention there is provided a method of making a reflectron for a mass spectrometer comprising: providing a hollow body; and depositing or painting four or more conductive strips, rings, films or electrodes on to an inner surface of the hollow body.

A reflectron according to the preferred embodiment is constructed from a ceramic carcass or tubular body.

A plurality of conductive strips, rings, films or electrodes are preferably deposited on or painted on to an inner surface of the ceramic carcass or tubular body. - 5

The preferred reflectron is particularly advantageous in that the mechanical tolerances of the preferred reflectron do not need to be as high as known reflections in order to achieve comparable results.

Known reflections are also relatively complex to manufacture and assemble. In contrast the preferred reflectron is significantly simpler and less expensive to manufacture and assemble and yet achieves at least the same if not better mass resolution. In particular, the preferred reflectron can, for example, be made to tolerances which are at least ten times less demanding than the required tolerances of the known reflectron.

Another advantage of the preferred reflectron is that the electrodes provided along the length of the reflectron can be made much smaller (i.e. thinner) than the ring electrodes of a conventional reflectron.

Therefore, the preferred reflectron may comprise a greater number of electrodes per unit length along the length of the reflectron compared with a conventional reflectron. This enables the homogeneity of the electric field generated within the preferred reflectron to be substantially improved compared with a conventional reflectron.

Alternatively, increasing the number of the electrodes per unit length along the length of the reflectron allows the diameter of the reflectron to be reduced without reducing the performance of the reflectron. Therefore, a smaller and more compact mass analyzer can be implemented using the preferred reflectron.

The tubular body or ceramic carcass is preferably cylindrical. However, according to other embodiments at least a portion preferably the whole of the tubular or - 6 - hollow body or ceramic carcass may be non-cylindrical.

It is contemplated, for example, that the reflectron may have a square, rectangular or elliptical cross-section if it is desired to minimise to the maximum extent possible the volume of the reflectron when an ion beam having a non-cylindrical cross-section is received within the mass analyses.

In one embodiment at least some of the conductive strips, rings, films or electrodes arranged on the inner surface of the tubular or hollow body may be connected by resistors deposited on or otherwise arranged on the inner and/or outer surface of the tubular or hollow body. The resistors may be used to establish a linear or non-linear voltage gradient along the length of the reflectron.

According to an embodiment multiple carcasses or tubular bodies may be stacked together or otherwise co axially aligned thereby providing a longer overall reflectron.

Various embodiments of the present invention together with other arrangements given for illustrative purposes only will now be described, by way of example only, and with reference to the accompanying drawings in which: Fig. 1 shows a conventional reflectron comprising nine metal ring electrodes assembled on a support; Fig. 2 shows a preferred reflectron comprising a ceramic tubular body with a plurality of electrodes arranged on an inner surface of the ceramic body; Fig. 3 shows a mass spectrum of Leucine Enkephalin recorded using a mass spectrometer incorporating a reflectron according to the preferred embodiment and which demonstrates that the preferred reflectron does - 7 - not adversely affect the mass resolution of the mass spectrometer; and Fig. 4 shows a portion of the mass spectrum shown in Fig. 3 in greater detail.

A known reflectron is shown in Fig. 1. The reflectron 1 comprises nine separate conductive metal ring electrodes 2 having a diameter of 170 mm and separated by eight insulating spacers (not shown). The ring electrodes 2 and insulating spacers are assembled together and are supported externally by a frame. The ring electrodes 2 are interconnected by a series of resistors. Each component of the conventional reflectron 1 must be very precisely manufactured and assembled in order not to adversely affect the overall mass resolution of the mass spectrometer. Furthermore, since there are so many components in the conventional reflectron the tolerances build up and this places significantly constaints on the manufacture and assembly of the reflectron.

A reflectron according to a preferred embodiment is shown in Fig. 2. The preferred reflectron comprises a ceramic tubular or hollow body 6 or carcass which may be of similar diameter to that of a conventional reflectron (i.e. 170 mm). A plurality of conductive metal strips, rings, films or electrodes 7 are preferably deposited, painted or otherwise applied on or adhered to the inner surface of the tubular body 6. Accordingly, a plurality of electrodes are provided on an inner surface of the tubular or hollow body 6. Each strip, ring, film or electrode 7 is preferably longitudinally spaced from a neighbouring strip, ring, film or electrode 7. The spacing of the strips, rings, films or electrodes 7 - 8 avoids forming a conductive path between neighbouring strips, rings, films or electrodes 7.

The ceramic tubular or hollow body 6 is particularly advantageous in that some ceramics have a relatively low coefficient of thermal expansion.

Accordingly, the spacing between adjacent strips, rings, films or electrodes 7 and also the diameter of the conductive strips, rings, films or electrodes 7 remains substantially constant over a wide range of operating temperatures.

According to the preferred embodiment the tubular or hollow body 6 is preferably machined from a solid piece of material but according to less preferred embodiments the tubular body 6 may be manufactured by molding, casting or wintering. The surfaces of a molded, cast or wintered body may be machined to achieve the required component tolerances.

The mechanical construction of the tubular body or carcass 6 of the preferred embodiment as shown in Fig. 2 is such that the end faces of the reflection are preferably ground flat and are substantially orthogonal to the longitudinal axis of the reflection to within a defined tolerance.

Contact pins for the strips, rings, films or electrodes 7 disposed on the inner surface of the tubular or hollow body 6 may be provided which preferably pass or project through the wall of the carcass or tubular body 6. The contact pins are preferably inter-connected by resistors 8 as shown in Fig. 2 such that each electrode of the reflection can be maintained, in use, at different desired potentials.

Therefore, the conductive strips, rings, films or electrodes 7 of the reflection according to the - 9 preferred embodiment are preferably effectively inter- connected by resistors 8. In this way a linear or nonlinear voltage gradient may be maintained along the length of the reflectron by applying a voltage across both ends of the chain of resistors 8.

According to the preferred embodiment the inner surface of the reflectron preferably carries or is provided with a plurality of circular strips, rings, films or other electrodes 7. According to an embodiment the strips, rings, films or electrodes 7 may be formed or deposited on the inner surface of the tubular body 6 by using a metal loaded or other electrically conductive paint.

According to an embodiment the number of circular strips, rings, films or electrodes 7 provided on the inner surface of the tubular body 6 may be substantially the same as the number of ring electrodes provided in a conventional reflectron. However, according to other embodiments a greater or lesser number of electrodes may be provided.

The preferred reflectron as shown in Fig. 2 has been demonstrated to be stable in use when high voltages (e.g. up to 13,000 V) were applied to the reflectron.

Conventional reflections are typically operated at relatively lower voltages (e.g. 9,800 V) and hence the preferred reflectron is capable of being used in comparable circumstances to that of a conventional reflectron.

Fig. 3 shows a mass spectrum of Leucine Enkephalin acquired using a preferred reflectron as shown in Fig. 2. The mass spectrum shown in Fig. 3 illustrates that the mass resolution of an orthogonal acceleration Time of Flight mass spectrometer fitted with the single - 10 component reflection according to the preferred embodiment is at least comparable with the mass resolution of a Time of Flight mass spectrometer fitted with a conventional reflection as shown in Fig. 1.

Fig. 4 shows a portion of the mass spectrum shown in Fig. 3 in greater detail and shows that the resulting mass peaks have a width at half height of 0.085 Da.

This corresponds to a mass resolution of 6540 (FWHM) at a mass to charge ratio of 555.9224. For a similar Time of Flight mass spectrometer using a conventional reflection the mass resolution at such a mass to charge ratio is typically between 5000 and 6000. Therefore, it is apparent that the preferred reflectron enables a high resolution Time of Flight mass spectrometer to be provided.

Although the carcass or tubular body 6 is preferably made of a ceramic material, it is also contemplated that according to other less preferred embodiments the tubular body or carcass 6 may be made at least partially from materials including plastic, sintered materials, resinous materials, or materials comprising glass, fused silica or quartz.

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. À 11

Claims

81070001c14 Claims 1. A reflection for a mass spectrometer, said

reflection comprising: a ceramic tubular body; and at least n conductive strips, rings, films or electrodes arranged on an inner surface of said ceramic tubular body, wherein n 2 4.
2. A reflection as claimed in claim 1, wherein n is selected from the group consisting of: (i) 4; (ii) 5; (iii) 6; (iv) 7; (v) 8; (vi) 9; (vii) 10; (viii) 11; (ix) 12; (x) 13; (xi) 14; (xii) 15; (xiii) 16; (xiv) 17; (xv) 18; (xvi) 19; (xvii) 20; and (xviii) > 20.
3. A reflection as claimed in claim 1 or 2, wherein at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or > 20 of said conductive strips, rings, films or electrodes have substantially the same width and/or thickness and/or surface area.
4. A reflection as claimed in claim 1, 2 or 3, wherein said conductive strips, rings, films or electrodes comprise conductive or metallic paint.
5. A reflection as claimed in any preceding claim, wherein at least some of said conductive strips, rings, films or electrodes are deposited on to said inner surface of said tubular body.
6. A reflectron as claimed in any preceding claim, wherein said tubular body is substantially cylindrical.
7. A reflectron as claimed in any of claims 1-5, wherein at least a portion of said tubular body is non- cylindrical.
8. A reflectron as claimed in claim 7, wherein at least a portion of said tubular body has a substantially square, rectangular or elliptical crosssection.
9. A reflectron as claimed in any preceding claim, wherein one or more contact pins extend through a wall of said tubular body.
10. A reflectron as claimed in any preceding claim, further comprising one or more resistors deposited or otherwise arranged on an inner or outer surface of said tubular body.
11. A reflectron as claimed in claim 10, wherein one or more of said conductive strips, rings, films or electrodes are connected to one or more of said resistors.
12. A reflectron as claimed in any preceding claim, wherein said reflectron further comprises a further tubular body.
13. A reflectron as claimed in claim 12, wherein said further tubular body is co-axial with said ceramic tubular body.
14. A reflectron as claimed in claim 12 or 13, wherein said further tubular body comprises a ceramic tubular body comprising at least four conductive strips, rings, films or electrodes arranged on an inner surface of said further tubular body.
15. A reflectron for a mass spectrometer, wherein said reflectron comprises a hollow body comprising at least n conductive strips, rings, films or electrodes deposited or painted on to an inner surface of said hollow body, wherein n 2 4.
16. A mass spectrometer comprising a reflectron as claimed in any preceding claim.
17. A mass spectrometer as claimed in claim 16, wherein said reflectron forms part of a Time of Flight mass analyses.
18. A method of mass spectrometry comprising: providing a reflectron comprising a ceramic tubular body wherein at least n conductive strips, rings, films or electrodes are arranged on an inner surface of said ceramic tubular body, wherein n 2 4; and reflecting ions using said reflectron.
19. A method of mass spectrometry comprising: providing a reflectron comprising a hollow body comprising at least n conductive strips, rings, films or electrodes deposited or painted on to an inner surface of said hollow body, wherein n 2 4; and reflecting ions using said reflectron. 14
20. A method of making a reflection for a mass spectrometer comprising: providing a tubular ceramic body; and arranging, applying or depositing four or more conductive strips, rings, films or electrodes on to an inner surface of said tubular body.
21. A method of making a reflection for a mass spectrometer comprising: providing a hollow body; and depositing or painting four or more conductive strips, rings, films or electrodes on to an inner surface of said hollow body.