Patent Application
20100133431
This invention relates to apparatus for use with ion sources commonly associated with mass spectrometers and ion mobility spectrometers.
No Federal or State money was used to develop the present invention.
Mass spectrometers are used to identify and quantitate compounds. Mass spectrometers analyse compounds by the mass to charge ratio of ions formed of the molecules of such compounds or the fragments of such molecules. Mass spectrometers generally have ion sources, which provide ions of the compounds for analysis. One form of ion source is an atmospheric pressure ionization (API) sources. An API source is, as its name suggests, an ion source that creates ions at approximately atmospheric pressure. These ions are directed to substantially closed sections of the mass spectrometer operating at low pressure or vacuum.
API sources suitable for generating ions from solutions include electrospray, atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) sources, all of which involve the formation of an aerosol from the solution. Electrospray sources form the aerosol by means of an electrical field created between an inlet capillary through which the solution is introduced and a counter electrode disposed downstream of the exit of the capillary. This electrical field also results in the ionization of at least some of a sample dissolved in the solution. APCI and APPI ion sources form the aerosol by means of a nebulizer, usually a concentric flow pneumatic nebulizer, and further comprise additional means for ionizing sample molecules comprised in the aerosol. These additional means may comprise a corona discharge (APCI sources) or a beam of photons (APPI sources). A nebulizer may also be used in electrospray sources to increase the maximum solution flow rate that the source can accept. Ionization may also be effected by a combination of some or all of the methods described.
API sources, which produce an aerosol comprising electrically charged droplets of the solution, are produced in a region containing gas at approximately atmospheric pressure. The charged droplets may comprise solvated ions characteristic of the sample dissolved in the solution. Droplets and solvated ions are sampled from the aerosol into a region of lower pressure through a small orifice or capillary tube, usually along a sampling axis inclined to the central axis of the aerosol. At least some of the ions entering the region of lower pressure are subsequently transmitted to a mass analyser through a sequence of vacuum chambers of progressively reducing pressure. These vacuum chambers usually comprise ion guides of various types. Mass analysers used in conjunction with these ion sources include linear quadrupoles, quadrupole, cylindrical and “Kingdon” ion trap analysers, magnetic sector analysers, ion cyclotron resonance analysers (ICR or FTMS analysers), time-of-flight analysers, or combinations of these analysers for use in tandem (MS/MS) apparatus. API ion sources are also used in ion mobility spectrometers, including field asymmetric ion mobility spectrometers (FAIMS) and in mass spectrometers comprising an ion mobility stage as well as more conventional mass filters or analysers. The charged droplets present in the aerosol may be at least partly desolvated through contact with gas molecules present in the atmospheric pressure region of the source. Desolvation may also be assisted by suitably directing (relative to the aerosol axis) gas flows into that region, and/or by heating the capillary, nebulizer and gas flows. Improved desolvation may also be obtained by heating the wall enclosing the atmospheric pressure region, particularly in the vicinity of the orifice through which ions may pass leave the source and pass into the mass analyser. Some prior sources also comprise means for flowing heated gas counter to the direction of travel of ions and droplets through the orifice.
Often, the solution admitted into API ionization sources is the eluent from a liquid chromatograph. Commonly used chromatographic flow rates are between 0.1 and 1.0 ml/min, but only a small fraction of the aerosol generated from the solution passes through the orifice into the region of lower pressure. The remainder of the aerosol is waste. Because the solvents (and samples) used for liquid chromatography may be poisonous, the atmospheric pressure region of an API source is usually enclosed. The chamber also serves to reduce contamination from material that may be present in the laboratory air causing interference to an analysis. As one or more flows of desolvation gas are introduced into the chamber, it must be fitted with an exhaust port through which gas and waste solvent can leave and be conducted to a safe discharge point.
Unfortunately, the majority of samples typically analysed with liquid chromatography are non-volatile, and the solvents employed often comprise non-volatile buffer salts. Because the majority of the spray does not enter the orifice, these non-volatile constituents tend to accumulate on surfaces within the atmospheric pressure enclosures, from which they may subsequently be released by contact with the aerosol to interfere with a subsequent analysis. They may also form insulating layers on electrically conducting surfaces within the chamber, which may become electrically charged and adversely affect the transport of ions into the orifice. In order to maintain performance, therefore, the atmospheric pressure chamber of prior API sources requires regular cleaning.
It is an object of the invention to provide API ionization sources and spectrometers, and apparatus for use in such ionization sources and spectrometers, in which the deposition of material on critical surfaces inside the sources is less than in prior sources. It is another object of the invention to provide API ionization sources, spectrometers and apparatus for use in such ionization sources and spectrometers that are more easily cleaned than are prior equipment. A further object of the invention is to provide apparatus for exhausting API ionization sources and spectrometers.
As used herein, “atmospheric pressure” includes the operation of an ion source in the presence of significant quantities of gas, perhaps with pressures several hundred torr either side of atmospheric pressure itself. The term is generally used in the art to distinguish this type of ionization source from those that operate under high or medium vacuum, for example, electron impact or chemical ionization sources. Further, the term “charged particles” is meant to include singly- and multiply-charged ions, solvated ions, adduct ions, and cluster ions, etc, all formed from a sample in an ionization source operating at atmospheric pressure (as defined above), and also charged droplets of solvent comprising molecules or ions characteristic of a sample.
Embodiments of the present invention are directed to apparatus, device and methods of performing mass spectrometry in which the deposition of material on critical surfaces inside the sources is readily removed. One embodiment is directed to a device for placement in a chamber of an interface housing. The interface housing has at least one wall defining the chamber and has at least one exit port and at least one working port in the wall. The chamber is for receiving an aerosol, having at least a working portion, an exiting portion and a falling or fallen portion. The working portion of the aerosol is received by the working port. The exiting portion of the aerosol flows past the working port and is received by the exit port. The fallen or falling portion of the aerosol refers to that portion not received by the exit port or the working port and falls out of suspension.
The device comprises a deflector and a support member. The deflector has aerosol deflecting surfaces and a first position in which the deflector is positioned for directing an aerosol flowing past the working port to the exit port and a second position in which the deflector is removed from the chamber. The support member is affixed to the deflector and has mounting means for removably mounting the deflector in the first position. In the second position the support member and the deflector are removed from the chamber to allow removal of the fallen portion of aerosol deposited on the device or disposal of the device.
Thus, the user's contact with substances, solvents and materials, that can be harmful, and potentially toxic, is minimized. The device can be discarded as a disposable item or more readily cleaned of the falling portion of the aerosol by immersion in cleaning solutions rather than manual wiping and blotting of the chamber wall.
Preferably, the support member has at least one planar section having a top surface, a bottom surface and at least one edge surface. At least one of the edge surface and bottom surface is removably mounted to the at least one wall with the deflector in the first position. In the first position, the top surface collects fallen aerosol, and, in said second position, the support member is removed from the chamber to allow removal of fallen aerosol deposited on the top surface.
The deflector is a foil positioned to deflect gas and aerosol in a predetermined direction. A preferred foil is a tubular member having a passage. The passage has a passage inlet and a passage outlet. The passage outlet is in fluid communication with the exit port and the passage inlet receives the exiting portion of the aerosol as the deflector assumes the first position. The tubular member may have any number of cross sectional shapes or forms such as a circle, ellipse, oval, and multisided forms.
One preferred embodiment features a deflector movably affixed to the support member to allow the deflector to be assume at least two orientations within the chamber. Thus, the deflector can be optimized for particular applications or chambers.
A preferred chamber has a bottom and the planar section of the support member, in said first position, is adjacent the bottom to collect fallen aerosol. Preferably, at least one edge of the device has a containment ridge to collect fallen aerosol.
One preferred device further comprises handle means affixed to at least one of said deflector and support member to facilitate manually grasping the device for removal or positioning in the chamber. The handle may take several forms including by way of example without limitation, tabs or knobs projecting from the top surface of the support member, tethers, and other means for gripping the device.
Preferably, the device acts as a manifold, directing the flow of gases circulating in the chamber. For example, one embodiment of the present invention features a tubular member having an opening or projections to allow working aerosol to enter the working port.
The device is preferably retained in the first position by gravity or the support member engages the wall of the chamber when the device is in the first position. One embodiment of the present invention features a bottom surface of the planar member having a adhesive for sticking to the wall of the chamber or the chamber is equipped with clips or slots for receiving the support member.
Embodiments of the present invention further comprise an apparatus in which the device, as a manifold, is part of the larger surrounding structure of the interface housing, in which it is received. The interface housing has at least one wall defining a chamber and having at least one exit port and at least one working port in the wall. The chamber receives an aerosol having at least a working portion, an exiting portion and a falling portion. The working portion is received by the working ports. The exiting portion flows past at least one working port and is received by at least one exit port. The falling portion comprises the part of the aerosol that falls out of suspension.
The device further comprises at least one manifold. The at least one manifold has a deflector and a support member, as previously described. The support member is affixed to the deflector and has mounting means for removably mounting the deflector in the first position and in the second position said support member and said deflector removed from the chamber to allow removal of the falling portion of aerosol deposited on the manifold and cleaning of the manifold or disposal of the manifold.
One embodiment of the invention features an interface housing constructed and arranged to receive sequentially a plurality of manifold devices. The plurality of manifolds may address special operating needs or be of a disposable nature to avoid the step of cleaning. Disposable manifolds are preferably made of inexpensive plastic or fiber board or a combination thereof.
Preferably, the apparatus further comprises an ionization source selected from
the group consisting of photoionization means, chemical ionization means and electrospray ionization means. Embodiments of the present invention allow the chamber to receive a manifold device for each of the selected group or combinations.
The apparatus of the present invention further comprises at least one of
the components of a mass spectrometer in communication with the working port. These components are selected from the group consisting of linear quadrupole mass filters, quadrupole, cylindrical or linear ion traps, magnetic sector mass analysers, “Kingdon” trap mass analysers, ICR or Fourier Transform mass analysers, and time of flight mass analysers. The invention may also comprise an ion mobility spectrometer or field-asymmetric ion mobility spectrometer (FAIMS), having an ionization source as described, or a mass spectrometer comprising both an ion mobility spectrometer and at least one mass analyser as listed above.
A further embodiment of the present invention features a method of servicing an interface housing. The interface housing has at least one wall defining a chamber and having at least one exit port and at least one working port in the wall. The chamber receives an aerosol having at least a working portion, an exiting portion and a falling portion. The working portion is received by the working port. The exiting portion flows past the working port and is received by the exit port. And, the falling portion comprises a part of said aerosol that falls out of suspension. The interface housing further has a door means, for accessing the chamber, having an open position and a closed position. The method comprising the step of placing the door means in an open position and removing, if present a manifold, and inserting a manifold having a deflector and a support member. The deflector has aerosol deflecting surfaces and, in a first position, the deflector is positioned for directing an aerosol flowing past the working port to the exit port. In a second position, the deflector is removed from the chamber. The support member is affixed to the deflector and has mounting means for removably mounting the deflector in the first position. In the second position, the support member and the deflector are removed from the chamber to allow removal of said fallen portion of aerosol deposited on the manifold or discarded. And, the method comprises the step of removably mounting the now cleaned support member with the deflector or a new support member and deflector in the first position.
These and other features and advantages will be apparent to those skilled in the art upon viewing the Figures and reading the detailed description that follows.
Embodiments of the invention will now be described in greater detail with reference to the figures, in which:
The present invention will be described in detail with respect to preferred embodiments directed to a device in the form of a manifold for removing the falling portion of a aerosol in an interface housing for a mass spectrometer. Those skilled in the art will recognize that the present invention is capable of being modified and altered and has utility in other applications as well.
Referring first to
The deflector 2 is an air foil for directing at least some of an aerosol circulating in a interface housing towards an exit port as will be described later. The deflector 2 may comprise one or more surfaces, curved or planar, for directing the flow of gases. As depicted, deflector 2 is cylindrical in shape defining a passage 53 having an entrance 3 and an exit 4, as best seen in
Returning now to
Support member 5 is generally planar and has a bottom surface 50, a top surface 52 and a first edges 7a and 7b and second edges 8a and 8b. Second edges 8a and 8b of the plate member 5 are curved as shown to facilitate positioning of support member 5 in an ionization source (as described below) and collecting falling aerosol. A lug or tab 6 projects upward from the top surface 52 to provide a gripping surface or handle for the device 1. In addition or in the alternative, lug or tab 6 may comprise a tether or knob [not shown] to facilitate handling or removal of the device 2 from an interface housing.
The aerosol 12 is generated inside interface housing 10 having a chamber 23 bounded by a wall 24. Chamber 23 typically contains an inert gas (eg, nitrogen) at atmospheric pressure (as defined above), which may be introduced though a gas inlet 25. In the case of an electrospray ionization source, sample solution introduced into a capillary tube 15 may be sprayed into the chamber 23 by maintaining an electrical potential difference between the capillary 15 and the sampling housing 16 an/or a counter electrode (not shown), thereby generating the aerosol 12. This well-known electrospray process produces charged particles and/or droplets in the aerosol that may comprise ions characteristic of the sample. At least some of these charged particles then pass along the sampling axis 18 and are mass analysed, as described.
In the case of an atmospheric pressure chemical ionization (APCI) source, charged particles may be produced from the aerosol by a corona discharge generated by application of a suitable potential difference between the wall 24 and a corona electrode 26 supported in an insulator 27 in the wall 24. In such a source the aerosol 12 is generated by a nebulizer 14 that may be a concentric flow pneumatic nebulizer in which a nebulizing gas (e.g., nitrogen) is introduced through a tube 28 surrounding and concentric with the capillary 15. Such a nebulizer also may be advantageously employed in electrospray ion sources to increase the maximum solution flow rate that the source can accept. Preferably the nebulizing gas and the components of the nebulizer 14 are heated.
Atmospheric pressure photoionization (APPI) sources and spectrometers according to the invention may comprise apparatus as shown in
In order to assist desolvation of the charged particles entering the sampling housing 16, both the sampling housing and the inlet housing 17 may be heated. A heated desolvation gas (sometimes known as a “cone gas”) may also be introduced from the gas inlet 29 into the space between the housings so that it flows out of the orifice in the apex of the sampling housing 16 into the enclosure 23. As in conventional ionization sources, both housings 16 and 17 may comprise hollow cones with the orifices formed in their apices. Desolvation of the aerosol may be assisted by a flow of gas introduced through one or more inlets 25 and 29 (inlet 29 surrounds the capillary tube 15 and nebulizing gas inlet 28).
Referring next to
Wall 24 comprises an aperture 34 that receives the sampling housing 16 and inlet housing 17. When assembled in a mass spectrometer the housing of the evacuated chamber 19 abuts the face 35 of the wall 24. Face 36 of wall 24 comprises another aperture 37 to which an assembly comprising the nebulizer 14 and inlet capillary 15 are fitted.
In use, in order to receive at least some of the aerosol 12, the device 1 of
The upwardly projecting edges 8a and 8b further serve to collect falling aerosol.
When in position in the chamber 23, support member 5 is oriented so that the lug 6 is adjacent to the door 30, thereby providing a handle to assist its removal when door 30 is opened.
Returning to
In the embodiment illustrated in
Charged particles travelling along the sampling axis 18 must pass unobstructed to the sampling housing 16 and inlet housing 17. To facilitate this, the entrance 3 of the deflector 2 comprises a cut-away portion 9 that is aligned with the sampling axis 18 when the device 1 is in its first position in the chamber 23. This allows unobstructed passage of the charged particles while maintaining the maximum reception of the aerosol in the entrance 3.
In another embodiment, illustrated in
It will be appreciated that although the embodiments shown in
In the mass spectrometer and ionization source of
Other means for removably locating the deflector 2 in the chamber 23 may be used. For example, the means for removably locating may comprise a support member that engages in slots 43 (
A further embodiment of the present invention directed to a method of servicing an interface housing 23. Referring now to
Thus, embodiments of the present invention have been described with respect to the preferred embodiments with the understanding that the invention is capable of modification and alteration. Therefore, the invention should not be limited to the precise details set forth herein but should comprise such subject matter set forth in the claims that follow and their equivalents.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US08/57505 | 3/19/2008 | WO | 00 | 2/11/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 60910490 | Apr 2007 | US |
