Method and ion optical system for reducing charge

Abstract

According to a first aspect, this disclosure provides a method for reducing charge on a contaminated surface of an ion optical system, the contaminated surface having a layer of charged contaminants. The method includes: generating charged particles by exciting a radiation source different from the contaminated surface of the ion optical system; and neutralizing at least a portion of the charged contaminant layer by causing the charged particles to interact with the charged contaminant layer, wherein (i) the radiation source includes an electromagnetic radiation source, wherein exciting the radiation source includes causing the electromagnetic radiation source to emit electromagnetic radiation, and wherein generating charged particles includes causing the electromagnetic radiation to interact with the charged contaminant layer and / or the ion optical system to generate charged particles; and / or (ii) the radiation source includes an electron source, wherein exciting the radiation source includes causing the electron source to emit free electrons. In a second aspect, an ion optical system is provided, the ion optical system being configured to reduce charge on a contaminated surface of the ion optical system.

Description

Technical Field

[0001] This disclosure relates to ion optical systems and methods for reducing the charge on contaminated surfaces of ion optical systems. Background Technology

[0002] Ion optics are used in a variety of analytical instruments to manipulate and transport ions. For example, ion optics systems are widely used in mass spectrometers to focus, transport, and eject ions from different regions. Examples of ion optics elements in a typical ion optics system include ion guides, lenses, ion carpets, and ion funnels. In these elements, an appropriate field for manipulating ions is applied via electrodes. Ion optics systems typically apply electric and / or magnetic fields within the system to manipulate charged ions, which experience electric and / or magnetic forces as they travel through such fields. Some ion optics systems perform a single function of transporting ions from one region to another, while others can capture, transport, and / or eject ions at different times.

[0003] Ion optics devices in various systems, including mass spectrometers (e.g., vacuum systems), can suffer from contamination caused by ion deposition on their surfaces. When ions are deposited, these contaminants can become highly charged. This contamination negatively impacts the performance of the ion optics system by affecting the field established within it. For example, the accumulation of charge on the electrodes in an ion optics system can reduce the transmitted ion current or broaden the isolation characteristic curve (e.g., in a quadrupole).

[0004] Attempts to address these issues typically involve ventilating the system and mechanically cleaning contaminated areas. Other methods for keeping ion optics relatively uncontaminated include reducing exposure time (e.g., as described in US-9,543,131) or deflecting ions to areas where charge accumulation is less severe. For example, slits can be incorporated into the quadrupole to keep most of the relevant pole surfaces clean, as described in GB-2,555,032. However, a drawback of this technique is that variations in the quadrupole surface geometry can affect (e.g., reduce to some extent) the quadrupole's quality resolution.

[0005] Another approach is to add an additional filter or electrode to the quadrupole, which filters out unwanted material and reduces contamination of the main quadrupole. Examples of this approach can be found in US-7,211,788 and US-9,929,003. While these solutions are known to be feasible, they still require cleaning the additional rod, albeit at longer intervals.

[0006] This disclosure aims to address these and other problems present in existing ion optical systems. Summary of the Invention

[0007] In this context, and according to the first aspect, a method is provided. Additionally, an ion optical system is provided.

[0008] This invention aims to improve the performance of ion optics systems by partially or completely neutralizing charged contaminated areas. Reducing the charge on the surface of the ion optics system decreases the interference potential caused by charged contaminants. Since the interference potential degrades the performance of the ion optics system, neutralizing the charge is highly advantageous.

[0009] Embodiments of this disclosure use charged particles (e.g., protons, electrons, ions, and / or anions) to perform this neutralization. When electrons are used, these electrons may be photoelectrons (i.e., electrons emitted from the material via the photoelectric effect) or other types of electrons, such as thermionic electrons (i.e., electrons emitted from the material via thermionic emission).

[0010] The embodiments of this disclosure are particularly useful in ion optics systems of high-throughput mass spectrometry systems. The embodiments of this disclosure are also useful under vacuum conditions and during operation of the ion optics system. For example, this disclosure provides methods and systems that allow for the periodic removal (or at least reduction) of charged contaminants in the ion optics system.

[0011] According to a first aspect, this disclosure provides a method for reducing the charge on a contaminated surface of an ion optical system having a layer of charged contaminants. The method includes: generating charged particles by exciting a radiation source different from the contaminated surface of the ion optical system; and neutralizing at least a portion of the charged contaminant layer by causing the charged particles to interact with the charged contaminant layer, wherein (i) the radiation source includes an electromagnetic radiation source, wherein exciting the radiation source includes causing the electromagnetic radiation source to emit electromagnetic radiation, and wherein generating charged particles includes causing the electromagnetic radiation to interact with the charged contaminant layer and / or the ion optical system to generate charged particles; and / or (ii) the radiation source includes an electron source, wherein exciting the radiation source includes causing the electron source to emit free electrons. "Excited radiation source" means that a radiation source (i.e., an electromagnetic radiation source and / or an electron source) is activated (i.e., turned on) such that it causes the emission of electromagnetic radiation (in the case of an electromagnetic radiation source) and / or free electrons (in the case of an electron source).

[0012] According to the first aspect, electromagnetic radiation can interact with the contaminated surface of an ion optical system to generate charged particles.

[0013] In a second aspect, the present invention provides an ion optical system configured to reduce the charge on a contaminated surface of the ion optical system. The ion optical system includes: a surface; and a radiation source configured to generate charged particles, wherein the radiation source is different from the contaminated surface. The ion optical system is configured to neutralize at least a portion of the charged contaminant layer on the surface by causing the charged particles to interact with the charged contaminant layer. The radiation source includes: (i) an electromagnetic radiation source configured to emit electromagnetic radiation that interacts with the charged contaminant layer and / or the ion optical system to generate charged particles; and / or (ii) an electron source configured to emit free electrons.

[0014] According to the second aspect, electromagnetic radiation can interact with the surface of an ion optical system to generate charged particles.

[0015] In a third aspect, an analytical instrument is provided that includes the aforementioned ion optical system, wherein the ion optical system includes an ion source configured to provide ions to the ion optical system. The radiation source may be different from the contaminated surface and from the ion source.

[0016] These systems and methods advantageously allow charged contaminants (e.g., accumulated ions) on critical surfaces (e.g., electrodes) of ion optics systems to be at least partially neutralized by charged particles. By neutralizing this charge, performance degradation of the ion optics system that occurs during normal use can be suppressed. These methods can be repeated frequently, thereby increasing throughput (due to the need for longer intervals between manual maintenance events). These methods and systems provide a relatively low-cost way to reduce charge and can be easily retrofitted into existing systems by adding one or more radiation sources.

[0017] The present invention also provides a method for reducing contamination in an ion optical system, the ion optical system comprising a contaminated surface having a layer of charged contaminants thereon, the method comprising: exciting a charged particle source to generate charged particles having a kinetic energy greater than 0 eV; and neutralizing at least a portion of the charged contaminant layer by allowing the charged particles to enter the charged contaminant layer. This provides charged particles for at least partially neutralizing contaminants in a manner similar to the method described above.

[0018] The aforementioned advantages, and various other advantages, will become apparent from this disclosure. Attached Figure Description

[0019] The present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0020] Figure 1 An ion optical system according to the first embodiment is shown;

[0021] Figure 2An ion optical system according to the second embodiment is shown;

[0022] Figure 3 The quadrupole ion optical system in the third embodiment is shown;

[0023] Figure 4 The quadrupole ion optical system in the fourth embodiment is shown;

[0024] Figure 5 The effect of pollution on the isolation characteristic curve is shown;

[0025] Figure 6 The effect of the embodiments of this disclosure on the isolation characteristic curve is shown;

[0026] Figure 7 The continuous transport of ions is illustrated when an embodiment of this disclosure is implemented;

[0027] Figure 8 The arrangement of the radiation source and quadrupole electrodes in the fifth embodiment is shown;

[0028] Figure 9 The advantages of the fourth implementation plan were demonstrated;

[0029] Figure 10 An analytical instrument according to an embodiment of this disclosure is shown. Detailed Implementation

[0030] exist Figure 1 The diagram shows a schematic representation of a first embodiment of an ion optical system 100. The ion optical system 100 includes a contaminated surface 101 having a charged contaminant layer 102 thereon. The charged contaminant layer 102 is depicted as having a positive charge (+) along the contaminated surface 101. The ion optical system 100 also includes a radiation source 103 configured to generate charged particles. In this embodiment, the charged particles are electrons (depicted as e-), but other types of charged particles may also be used. The radiation source 103 is different from the contaminated surface 101.

[0031] exist Figure 1 In this implementation scheme, radiation source 103 emits electromagnetic radiation, as indicated by the dashed arrow. This electromagnetic radiation induces the emission of electrons, which are another form of radiation, namely beta radiation. The paths of these electrons are shown by solid arrows.

[0032] In use, the ion optical system 100 performs a method for reducing the charge on the contaminated surface 101 of the ion optical system 100. Electrons are generated via the photoelectric effect after being excited by the radiation source 103. The ion optical system 100 neutralizes at least a portion of the charged contaminant layer 102 by causing the electrons to interact with it. This results in the electrons neutralizing the charge on the charged contaminant layer 102, thereby partially neutralizing the charged contaminant layer 102.

[0033] Figure 1 The radiation source 103 generates electrons through the photoelectric effect, and the radiation source 103 is an electromagnetic radiation source. Exciting the radiation source 103 involves causing the electromagnetic radiation source 103 to emit electromagnetic radiation to generate electrons (i.e., indirectly generating free electrons by causing photons to generate photoelectrons). The ion optical system 100 includes a photoemitting material, and generating electrons (or other charged particles, if other charged particles are used) involves interacting the electromagnetic radiation with the photoemitting material to generate electrons. The electromagnetic radiation source may be directed toward the photoemitting material and / or a suitable optical system may guide the electromagnetic radiation toward the photoemitting material.

[0034] exist Figure 1 In one embodiment, the photoemitting material is present in two different elements of the ion optical system 100. The first portion of the photoemitting material 104 is different from the contaminated surface 101. Furthermore, the contaminated surface 101 itself serves as the second portion of the photoemitting material.

[0035] In use, radiation source 103 generates electrons for discharge and cleaning of contaminated surface 101. This is achieved by emitting electromagnetic radiation (e.g., UV light radiation) that travels toward and interacts with portions of the photoemitting material. This radiation causes the contaminated surface 101 to emit electrons itself (described herein as an "internal photoelectric effect") and causes the first portion of the photoemitting material 104 to emit free electrons (described herein as an "external photoelectric effect"). Therefore, in Figure 1 In the first embodiment, the radiation source 103 is configured to generate photoelectrons in two different ways. These photoelectrons then at least partially neutralize the charged contaminant 102, thereby reducing the charge on the contaminated surface 101.

[0036] Under the external photoelectric effect, electrons typically leave the metal surface (or other photoelectric emitting surface) surrounding the contaminated area with relatively low energy and will fly towards the charged contaminated area that is only attracted by charge, such as... Figure 1 As shown. Figure 1 The curved path of electrons in the diagram illustrates how free electrons can be guided toward charged contaminant 102.

[0037] In some cases, relatively high voltages may be present on the electrodes, and photoelectrons may be accelerated, also generating secondary electrons, desorbed neutral particles, vacuum ultraviolet (VUV) radiation, and X-ray bremsstrahlung. Therefore, this disclosure also provides a method for cleaning contaminated surface 101 using rapid electron bombardment. Thus, in general, the ion optics system of this disclosure may include one or more electrodes, and the methods described herein may include applying a voltage to at least one electrode of the ion optics system to accelerate charged particles (e.g., free electrons) and thereby generate additional radiation for neutralizing at least a portion of the charged contaminant layer. This can enhance the neutralization of charged contaminants. In some cases, the method may involve applying a magnetic field to the ion optics system to guide electrons or other charged particles toward the charged contaminant layer. This can also improve charge neutralization.

[0038] In the case of an internal photoelectric effect, mobile electrons from the photoemitting material (e.g., a metal) beneath the contaminant layer 102 are transferred to the contaminated surface 101. Some photons may reach the contaminated area after reflection from surrounding surfaces (e.g., surrounding metal surfaces). The layer is preferably thin enough to be transparent to electromagnetic radiation (e.g., to UV photons). Typical thicknesses can be greater than 5 nm, down to a few micrometers (e.g., 1 µm to 2 µm). Such a layer can be completely or at least partially neutralized using this disclosure. In some cases, when the contaminant layer has a thickness of 1 µm to 2 µm, the layer can be almost completely neutralized.

[0039] In a preferred embodiment, the photoemitting material is a metallic material. Metallic materials can have a suitable work function, allowing for the generation of a sufficiently large number of electrons to perform neutralization. Therefore, metals can be a good source of electrons. However, other materials can also be used.

[0040] In some embodiments, the photoemitting material includes a contaminated surface of an ion optics system. A contaminated surface may, for example, be the surface of an electrode in the ion optics system. Electrodes in an ion optics system may become contaminated during normal operation. Some embodiments of this disclosure utilize the fact that electrodes can also serve as a good source of electrons or other charged particles that can be used to neutralize charged contaminants.

[0041] exist Figure 1In the diagram, the first portion of the photoemitting material 104 is shown as a typical photoemitting material. It should be understood that the first portion of the photoemitting material 104 may be an electrode of an ion optics system, or the first portion of the photoemitting material 104 may be another emitting surface adjacent to the contaminated surface 101. In some cases, the ion optics system may include multiple electrodes, and the contaminated surface may be one of the multiple electrodes, and the photoemitting material may be another electrode (or some other photoemitting surface in the ion optics system). Each of the multiple electrodes may be contaminated, and each of the multiple electrodes may be configured to provide electrons for cleaning another electrode among the multiple electrodes. Therefore, the ion optics system may include: one or more electrodes different from at least a portion of the photoemitting material; and / or one or more electrodes that are at least a portion of the photoemitting material.

[0042] The electromagnetic radiation sources described herein may include ultraviolet (UV) radiation sources. UV light can provide photons with appropriate energy to induce the emission of electrons from common photoelectroluminescent materials. The wavelength of the light used may vary depending on the work function of the photoelectroluminescent material. The electromagnetic radiation sources described herein may include one or more light-emitting diodes (LEDs). LEDs are widely available and can provide photons with appropriate energy for generating electrons. However, other photon sources may also be provided.

[0043] exist Figure 1 In the first embodiment shown, the radiation source 103 is configured to generate photoelectrons in two different ways. However, other ways of providing electrons are also possible.

[0044] exist Figure 2 The diagram shows a second embodiment of the ion optical system 200. This embodiment is similar to... Figure 1 An ion optical system 100, wherein a charged contaminant layer 102 is present on a contaminated surface 101. The contaminated surface 101 and the charged contaminant 102 are as described above regarding... Figure 1 As described.

[0045] Figure 2 The radiation source 203 of the ion optical system 200 and Figure 1 The difference lies in the ion optical system 100. In this second embodiment, the radiation source 203 emits free electrons (i.e., directly generates free electrons), and is therefore a β radiation source, rather than... Figure 1The electromagnetic radiation source in the ion optical system 200. When the radiation source 203 of the ion optical system 200 is excited, the ion optical system 200 neutralizes at least a portion of the charged contaminant layer 102 by causing free electrons emitted by the radiation source 203 to interact with the charged contaminant layer 102. Therefore, the charge on the contaminated surface 101 is reduced. The accelerated free electrons can also evaporate the contaminant 102, which can be beneficial in cases where the evaporated material will not coat other substances essential for proper operation of the surface.

[0046] Radiation source 203 can be of various types. For example, free electrons can be generated by the thermal emission of electrons from a heated filament. Various materials can be used, such as tungsten and rhenium. In some embodiments, a field emission source can be used.

[0047] Figure 1 and Figure 2 The system can be combined. For example, at least one electromagnetic radiation source (e.g., 103) and at least one beta radiation source (e.g., 203) can be provided in a single system. Other radiation sources may also be present.

[0048] Returning to the general terminology used previously, in some embodiments, the radiation source includes an electron source (i.e., the charged particles may be electrons), and exciting the radiation source includes causing the electron source to emit free electrons. In this case, the radiation source is therefore a beta radiation source. The electron source is preferably different from the contaminated surface of the ion optics system, and the electron source may include a filament. Exciting the radiation source may include heating the filament to emit free electrons. Various materials may be selected for the filament depending on the nature of the contaminant and the required electron energy.

[0049] Although electrons are used as charged particles for reducing charge in the above embodiments, other charged particles may also be used. For example, while some embodiments are described in terms of free electrons performing the discharge, discharge can actually be performed by any type of charge carrier, such as protons, electrons, ions, and / or anions. Therefore, some embodiments may include generating charged particles using a source of protons, ions, and / or anions and having these charged particles interact with the contaminant layer.

[0050] In some implementations, charged particles can be activated by electromagnetic radiation. This activation can cause the charged particles to move and be attracted to charged molecules, thereby neutralizing those molecules. For example, moving protons can perform charging, or moving electrons or ions / anions within the deposit can themselves perform discharging. These mechanisms can serve as the basis for the above-mentioned... Figure 1 and Figure 2 The mechanism described is used to supplement or replace the existing mechanism for execution.

[0051] Next turn Figure 3 and Figure 4The third and fourth embodiments of this disclosure have been applied to a quadrupole mass filter (which can be described as a quadrupole ion optics system) within a ThermoScientific™ Orbitrap Exploris™ 480 mass spectrometer. Six UV LEDs emitting wavelengths of 265 nm (4.68 eV) are positioned on opposite sides of the quadrupole, such that the emitted UV light passes through an opening (slit) in the quadrupole housing and partially falls onto the inner surface of the quadrupole rod. The slit in the quadrupole housing is a structural feature of many known quadrupoles, and therefore the slit already exists in existing ion optics systems without any modification. This allows for easy modification of the embodiments of this disclosure.

[0052] In a general sense, the ion optical system described herein may include a housing having one or more openings (e.g., slits, which are elongated openings with a length greater than their width). The method described herein may also include radiating (e.g., Figure 1 as well as Figure 3 and Figure 4 Electromagnetic radiation in, or Figure 2 Free electrons in the material pass through one or more openings. When the radiation is electromagnetic, this can cause the electromagnetic radiation to interact with the photoelectroluminescent material to generate electrons. It can also allow electrons or other charged particles to pass through such openings (slits) in the shell.

[0053] exist Figure 3 and Figure 4 In this process, the UV LED is slightly shifted upwards or downwards relative to the ion axis plane to improve the irradiation efficiency of the rod, as shown in the following example. Figure 8 and Figure 9 To explain in more detail. The quadrupole was previously contaminated with ubiquitine. Without using the embodiments of this disclosure, further ubiquitine deposition would cause rapid charging of the contaminated area, resulting in a broadening of the isolation characteristic curve. For example... Figure 5 As shown, this broadening can be observed using a FlexMix calibration solution with a low m / z of 69. Different curves correspond to different exposure times of the quadrupole to ubiquitin ions. These datasets were generated using direct infusion of concentrated ubiquitin solution, corresponding to ubiquitin flow rates of 10 µl / min or 250 ng / min. Figure 5 In the first two hours of operation, a widening of the m / z 69 isolation characteristic curve was observed.

[0054] like Figure 6 As shown, if ubiquitin deposition is repeated with the UV LED on, no broadening of the isolation characteristic curve is observed even after 57 hours. It is worth noting that, as... Figure 7As shown, despite the presence of photoelectrons, the quadrupole continues to operate and transport ions as usual. Ions and electrons do not interfere with each other because their extremely low concentrations make the probability of interaction infinitesimal within the residence time of ions in the quadrupole (which is typically on the order of microseconds). Quadrupole neutralization and operating cycles can be varied if desired. Therefore, it can be seen that embodiments of this disclosure can allow for a significant increase in the interval between maintenance or cleaning.

[0055] Next, turn to Figure 8 The fifth embodiment shows the arrangement of the radiation source and the quadrupole electrode. Figure 8 The arrangement can be implemented in any of the previously described embodiments, including embodiments using internal and / or external photoelectric effects. Figure 8 a) is a side view, and Figure 8 b) is the front view. Figure 8 In the diagram, multiple radiation sources 1 are shown facing and positioned close to the quadrupole 2. Figure 8 As can be seen, the radiation sources are spaced apart along the length of the rod. That is, each radiation source is located at a different distance along the length of the rod. Furthermore, the LEDs are offset relative to the axis of the rod. Radiation source 1 is preferably an LED, such as a UV LED, but other radiation sources can be provided in a similar arrangement.

[0056] Figure 9 It shows Figure 8 The advantages of this arrangement. Figure 9 a) shows the horizontal arrangement of the radiation sources, while Figure 9 b) illustrates the repositioned arrangement of the radiation source. Here is a schematic diagram showing the penetration of light within the quadrupole. Figure 9 a) and Figure 9 In (b), radiation source 1 faces the quadrupole 2 (shown as a small rectangle) with contaminant 3 on it. Figure 9 As can be seen in b), the use Figure 9 The shifted arrangement in b) irradiates a larger surface area of ​​the contaminated area.

[0057] In ion optics systems that include a pair of electrodes (or any other paired contaminated surfaces), there will be a plane that bisects the pair of electrodes. For example... Figure 9 As shown, it may be advantageous to displace one or more (i.e., multiple) radiation sources relative to the plane bisecting a pair of electrodes (i.e., not to position them on that plane). This increases the area of ​​the electrodes that are irradiated and thus neutralized. In some embodiments, the ion optics system may include multiple pairs of electrodes and multiple radiation sources, wherein each radiation source is displaced relative to the plane bisecting the corresponding pair of electrodes. It may be advantageous to have no radiation source located on the plane bisecting any pair of electrodes.

[0058] The implementation schemes described herein can be applied to components within analytical instruments. In fact, the ion optics system described herein can be part of an analytical instrument that includes an ion source configured to supply ions to the ion optics system. The methods described herein for reducing charge contamination on contaminated surfaces can be applied to any component of an analytical instrument (except for the ion source).

[0059] Figure 10 A schematic diagram of an exemplary analytical instrument is shown. (e.g.) Figure 10 As schematically shown, the exemplary analytical instrument includes an ion source 10, a mass filter 20, a fragmentation device 30, and a mass analyzer 40. It should be noted that... Figure 10 This is merely illustrative, and the instrument may, and indeed in implementation, include any number of one or more additional components, such as ion optics. For example, the analytical instrument may include one or more ion transfer stages arranged between any of the components shown, including, for example, an atmospheric pressure interface configured to allow some or all of the ions to be suitably transferred through the instrument. The ion transfer stage may include any suitable number and configuration of ion optics, such as optionally including one or more ion guides, lenses, and / or other ion optics.

[0060] The ion optical system described herein may include any of the described components of the analytical instrument (other than ion source 10), and similarly, the contaminated surface may be the surface of any of the described components of the analytical instrument (other than ion source 10). Similarly, the methods described herein for reducing charge on the contaminated surface of the optical system may be applied to the surface of any component of the analytical instrument (other than ion source 10). Specifically, the ion optical system may include at least a portion of the mass filter 20 and / or the fragmentation device 30 and / or the mass analyzer 40 and / or other optical devices of the analytical instrument. The contaminated surface of the ion optical system may be the surface of the mass filter 20 and / or the surface of the fragmentation device 30 and / or the surface of the mass analyzer 40 and / or the surface of other optical devices of the analytical instrument. For example, the contaminated surface may be the surface of an electrode of a component of the analytical instrument. The methods described herein for reducing charge on the contaminated surface are most effectively applied to the mass filter 20 of the analytical instrument because the mass filter 20 is particularly prone to contamination. Similarly, in a preferred embodiment, the ion optical system includes the mass filter 20 of the analytical instrument, and the contaminated surface is the surface of the mass filter 20.

[0061] Ion source 10 is configured to generate ions from a sample. Ion source 10 may be coupled to a separation device (not shown), such as a liquid chromatography (LC) separation device, a gas chromatography (GC) separation device, or a capillary electrophoresis separation device, etc., such that the sample ionized in ion source 10 originates from the separation device. Ion source 10 can be any suitable ion source, such as an electrospray ionization (ESI) ion source, an atmospheric pressure ionization (API) ion source, a chemical ionization ion source, an electron collision (EI) ion source, or the like. Many other types of ionization are also possible.

[0062] As described above, the method and ion optical system of this disclosure employ a radiation source ( Figure 10 (Not shown in the image). Radiation sources may include, for example, Figure 1 , Figure 3 and Figure 4 The electromagnetic radiation sources exemplified and / or such as Figure 2 The example illustrates a free electron source. This radiation source differs from the ion source 10 of the analytical instrument. The radiation source also differs from the contaminated surface of the components forming part of the ion optics system. Because the radiation source of the ion optics system differs from the ion source 10 of the analytical instrument, neutralizing at least a portion of the charged contaminant layer does not require interrupting the ion flow from the ion source 10. In fact, the ion source 10 can operate during the excitation of the radiation source and the neutralization of a portion of the charged contaminant layer through interaction with the charged particles generated by the excitation. In other words, neutralizing at least a portion of the charged contaminant layer can be performed during the ion flow from the ion source 10.

[0063] As in Figure 3 and Figure 4 As discussed in the context of the implementation scheme, the radiation source may optionally be arranged outside the housing surrounding the components of the analytical instrument, wherein radiation, free electrons, or other charged particles pass through openings in the housing to neutralize contaminated surfaces of the components within the housing. Alternatively, as in Figure 8 and Figure 9 As described in the context of the implementation scheme, the radiation source can be positioned close to a component of the analytical instrument. Optionally, multiple radiation sources can be used, such as... Figure 8 and Figure 9 As shown.

[0064] The analytical instrument may additionally or alternatively include an ion separation device (not shown) arranged downstream of the ion source and configured to separate sample ions based on physicochemical properties. For example, the instrument may include an ion mobility (IM) separator, a micro-ion mobility separator, or a device configured to separate ions based on their mass-to-charge ratio (m / z). The ion optics system described herein may include such an ion separation device, and the contaminated surface may be the surface of the ion separation device.

[0065] A mass filter 20 is disposed downstream of an ion source 10 and is configured to receive ions from the ion source 10 (optionally via an ion separation device). The mass filter 20 is configured to filter the received ions according to their mass-to-charge ratio (m / z). The mass filter 20 can be configured such that received ions with a m / z within the mass filter's m / z transmission window (or "isolation window") are forward-transmitted by the mass filter, while received ions with a m / z outside the m / z transmission window are attenuated by the mass filter, i.e., not forward-transmitted by the mass filter. The width and / or center m / z of the transmission window are controllable (variable), for example, by suitably controlling the RF voltage and DC voltage applied to the electrodes of the mass filter 20. Thus, for example, the mass filter 20 can operate in a transmission mode, whereby most or all of the ions within a relatively wide m / z window are forward-transmitted by the mass filter 20, and can also operate in a filtering mode, whereby only ions within a relatively narrow m / z window (centered on a desired m / z) are forward-transmitted by the mass filter 20. The filter 20 can be any suitable type of filter, such as a quadrupole filter. Figure 3 and Figure 4 This is an example of applying an embodiment of the present invention to a four-stage mass filter.

[0066] The fragmentation device 30 is arranged downstream of the mass filter 20 and is configured to receive most or all of the ions transmitted by the mass filter 20. The fragmentation device 30 can be configured to selectively fragment some or all of the received ions, i.e., to generate fragment ions. The fragmentation device 30 can operate in a fragmentation mode, where most or all of the received ions are fragmented to generate fragment ions (which can then be forwarded from the fragmentation device 30), and can operate in a non-fragmentation mode, where most or all of the received ions are forwarded without (intentionally) fragmentation. A non-fragmentation mode can also be achieved by allowing ions to bypass the fragmentation device 30. The fragmentation device 30 can also operate in one or more intermediate operating modes, whereby the degree of fragmentation is controllable (variable). The fragmentation device 30 can also operate at higher orders (MS). N The fragmentation operation mode is used, for example, the fragment ions are further fragmented once or multiple times by the fragmentation device 30.

[0067] The fragmentation device 30 can be any suitable type of fragmentation device, such as, for example, collision-induced dissociation (CID) fragmentation device, electron-induced dissociation (EID) fragmentation device, photodissociation fragmentation device, etc. Many other types of fragmentation are possible.

[0068] Mass analyzer 40 is positioned downstream of fragmentation device 30 and configured to receive ions from fragmentation device 30. Therefore, depending on the operating mode of fragmentation device 30, mass analyzer 40 can receive undisturbed precursor ions and / or fragment ions. Mass analyzer 40 is configured to analyze the received ions to determine their mass-to-charge ratio (m / z) and / or mass, i.e., the mass spectrum of the generated ions. Mass analyzer 40 can be any suitable type of mass analyzer, such as an ion trap mass analyzer, an electrostatic orbit trap mass analyzer (such as the Orbitrap™ FT mass analyzer manufactured by Thermo Fisher Scientific), a time-of-flight (ToF) mass analyzer such as a multiple reflection time-of-flight (MR-ToF) mass analyzer, or a quadrupole mass analyzer. Many other types of mass analyzers are also possible.

[0069] In some implementations, the instrument may include more than one mass analyzer. For example, the instrument may be a dual mass analyzer mixed mass spectrometer of the type described in EP 3,410,463, the contents of which are incorporated herein by reference.

[0070] Similarly, Figure 10 As shown, the instrument is under the control of a control unit 50, such as a suitably programmed computer, which controls the operation of various components of the instrument and, for example, sets the voltages to be applied to these components. The control unit 50 can also receive and process data from various components, including the analyzer. The control unit 50 can be configured to independently control the operation of the ion source 10 and the radiation source.

[0071] The instrument can operate in various operating modes. Specifically, the instrument can be a tandem mass spectrometer capable of operating in both MS1 and MS2 operating modes.

[0072] In MS1 ​​(or “full mass scan”) operating mode, mass filter 20 operates in its transport operating mode, and fragmentation device 30 operates in its non-fragmentation operating mode, for example, such that a wide range of m / z (e.g., full mass range) of undfragmented (“precursor” or “parent”) ions is analyzed by analyzer 40 to generate MS1 spectra.

[0073] In MS2 operating mode, mass filter 20 operates in its filtration operating mode, and fragmentation device 30 operates in its fragmentation operating mode, for example, causing precursor ions in a selected narrow m / z range to be fragmented, and the resulting fragment ("product" or "daughter") ions are analyzed by analyzer 40 to generate MS2 spectra.

[0074] The instrument can also operate in one or more higher-order fragmentation modes (such as, for example, MS3 mode), where the primary ion is fragmented, at least some of the resulting fragment ions are themselves fragmented, and second-generation fragment ions (“grandchild ions”) are analyzed by analyzer 40 to produce an MS3 spectrum. Typically, the instrument can operate in any order of fragmentation modes, i.e., at MS... N Operation mode operation, where N≥2.

[0075] It will be understood that many changes can be made to the above systems and methods while retaining the advantages mentioned above. For example, where a particular component has been described, an alternative component that provides the same or similar functionality can be provided.

[0076] While this disclosure primarily discusses positively charged contaminants, negatively charged contaminants can also be neutralized by electron bombardment and / or directly by electromagnetic radiation (e.g., UV light). Therefore, in the methods and systems described herein, the charged contaminant layer can be either a positively charged or a negatively charged contaminant layer.

[0077] By simply adding a radiation source (e.g., an electromagnetic radiation source, such as a UV source or a filament) in appropriate locations, the embodiments of this disclosure can be used in a variety of ion optics systems without altering the geometry of the ion optics device. Therefore, this disclosure provides a more versatile solution compared to existing solutions. Furthermore, the embodiments of this disclosure are relatively low-cost, and the LEDs can operate at far below their nominal power to extend their lifespan.

[0078] The embodiments disclosed herein can be used in various ion optical systems, such as ion directors and ion traps (e.g., quadrupoles). In some cases, a magnetic field can be used to guide electrons. Different sources of electromagnetic radiation (e.g., UV light) can be placed outside the vacuum region, with the radiation entering via optical fibers or windows.

[0079] The embodiments disclosed herein may use a variety of numbers of radiation sources. Some embodiments use six LEDs, but it should be understood that the number, type, and arrangement of radiation sources can vary.

[0080] Any contaminated surfaces of RF and / or DC ion optics (such as in quadrupoles) can be treated using embodiments of this disclosure, including when such systems are filled with gas. In some embodiments, the gas pressure can be reached (e.g., adjusted to reach) a level where the mean free path of electrons becomes significantly less than the minimum gap between the nearest electrodes at different potentials. Therefore, in general, embodiments of this disclosure may include controlling the gas pressure within an ion optics system (e.g., within the housing of a trap, such as a quadrupole) such that the mean free path of electrons is less than the spacing between electrodes in the ion optics system (e.g., the closest distance between adjacent electrodes). The gas pressure used is more relevant to external photoelectric effects because gas pressure does not play a significant role in internal photoelectric effects. Even at higher gas pressures, electrons with certain energies can reach contaminants after multiple scatterings from charged regions.

[0081] As previously mentioned, the energy of electrons can vary depending on the specific contaminant and the specific contaminated surface. When using the photoelectric effect, the energy of the electromagnetic radiation can be selected such that electrons have at least the minimum energy (e.g., work function) required to leave the photoemitting material (e.g., a solid metal). Electrons can be accelerated by the RF and / or DC voltage of the electrodes and / or also influenced by the potential due to impurities. Electron energy may vary from 0 eV to 3 keV (or at most 2 keV or 1 keV, etc.). Other values ​​may be used depending on the specific circumstances. The photon energy can be set as the work function of the photoemitting material plus or minus at most 2 eV, or at most 1 eV, to account for the electron distribution at the Fermi energy and the possible effects of adsorbates.

[0082] Depending on surface purity and measurement techniques, the work function of stainless steel ranges from 4.4 eV to 4.5 eV, while that of Invar alloy (Fe-36Ni) ranges from 4.5 eV to 5 eV. Photoelectrons from gold-plated Invar alloy can also be used, and various work functions ranging from 4.8 eV to 5.4 eV have been reported. Therefore, in some embodiments, electrons can have energies greater than the work function of the material forming the photoemitting surface.

[0083] In some implementations, electrodes (e.g., rods) may be coated with a metal having a low work function to facilitate the generation of photoelectrons. For example, generally, at least one electrode (and optionally the contaminated surface) of an ion optics system may be a coated electrode that is at least partially (or completely) coated with a material having a lower work function than the material of the coated electrode. While tunneling currents may function over distances below 5 nm in proteins, substantial neutralization via tunneling is unlikely for contamination thicknesses >5 nm due to the work function of Invar alloys (a common material) being approximately 4.5 eV to 5 eV. In any case, at least some electrons may transfer from the contaminated surface to the contaminant layer, rather than being strictly free electrons; these are mobile electrons.

[0084] It should be recognized that the methods and systems described herein are reusable. For example, an ion optical system can be repeatedly and at least partially neutralized. Therefore, in general, the present invention also provides a method of operating an ion optical system, comprising: introducing a sample into the ion optical system; manipulating and ejecting the sample using the ion optical system; and performing any of the methods described herein for reducing charge on the ion optical system. These steps can be repeated once or multiple times. For example, these steps can be repeated at regular intervals or between each loading of the sample. In some cases, the method can be performed continuously while the sample is captured, transported, or otherwise manipulated. By using these methods, the performance of the ion optical system can be reliably maintained.

[0085] Unless otherwise stated, each feature disclosed in this specification may be replaced by an alternative feature for the same, equivalent, or similar purpose. Therefore, unless otherwise stated, each disclosed feature is merely one example of a series of equivalent or similar attribute features.

[0086] As used herein (including in the claims), unless the context otherwise indicates, the singular form of a term herein should be understood to include the plural form, and vice versa, where the context permits. For example, unless the context otherwise indicates, the singular form included herein in the claims, such as “a / an” (e.g., an electrode or a surface), means “one or more” (e.g., one or more electrodes, or one or more surfaces). In the description and claims of this disclosure, the words “comprising,” “including,” “having,” and “containing,” as well as variations of the words such as “constituting” and “composed of” or similar, indicate that the described feature includes the following additional feature and is not intended to exclude the presence of other components.

[0087] The use of any and all examples or exemplary language (“e.g.,” “such as,” and similar languages) provided herein is intended only to better illustrate this disclosure and, unless otherwise required, does not indicate any limitation on the scope of this disclosure. No language in this specification should be construed as indicating any unrequired element necessary for the practice of this disclosure.

[0088] Unless otherwise stated or required by context, any steps described in this specification may be performed in any order or simultaneously. Furthermore, the fact that a step is described as being performed after another step does not preclude intermediate steps being performed.

[0089] All aspects and / or features disclosed in this specification can be combined in any combination, except for at least some mutually exclusive combinations of such features and / or steps. Specifically, preferred features of this disclosure apply to all aspects and embodiments of this disclosure and can be used in any combination. Similarly, features described in non-essential combinations can be used individually (not in combination).

[0090] Furthermore, this disclosure also provides methods for manufacturing and using the systems described herein. For example, methods for manufacturing any of the systems described herein, and methods for using the systems described herein, are provided.

Claims

1. A method for reducing the charge on a contaminated surface of an ion optical system, the contaminated surface having a layer of charged contaminants, the method comprising: Charged particles are generated by exciting a radiation source that is different from the contaminated surface of the ion optical system. as well as At least a portion of the charged contaminant layer is neutralized by causing the charged particles to interact with the charged contaminant layer; Wherein: (i) the radiation source includes an electromagnetic radiation source, wherein exciting the radiation source includes causing the electromagnetic radiation source to emit electromagnetic radiation, and wherein generating the charged particles includes causing the electromagnetic radiation to interact with the charged contaminant layer and / or the ion optical system to generate the charged particles; and / or (ii) The radiation source includes an electron source, wherein exciting the radiation source includes causing the electron source to emit free electrons.

2. The method of claim 1, wherein the ion optical system comprises a photoemitting material, and wherein generating the charged particles comprises interacting the electromagnetic radiation with the photoemitting material to generate the charged particles.

3. The method according to claim 2, wherein the photoelectric emitting material is a metallic material.

4. The method of claim 2, wherein the photoelectroluminescent material comprises the contaminated surface of the ion optical system.

5. The method of claim 4, wherein the contaminated surface is the electrode surface of the ion optical system.

6. The method according to any one of claims 2 to 5, wherein at least a portion of the photoemitting material is different from the contaminated surface.

7. The method according to any one of claims 2 to 5, wherein when photons from the electromagnetic radiation source interact with the photoelectric emitting material, the photoelectric emitting material generates electrons and / or protons.

8. The method according to any one of claims 2 to 5, wherein the ion optical system comprises a housing having one or more openings, and the method further comprises passing the electromagnetic radiation through the one or more openings to interact with the photoemitting material to generate the charged particles.

9. The method according to any one of claims 2 to 5, wherein the electromagnetic radiation source comprises an ultraviolet (UV) radiation source; and / or wherein the electromagnetic radiation source comprises one or more light-emitting diodes (LEDs).

10. The method according to any one of claims 2 to 5, wherein the electron source is different from the contaminated surface of the ion optical system; and / or wherein the electron source comprises a filament, wherein exciting the radiation source comprises heating the filament to emit the free electrons.

11. The method according to any one of claims 2 to 5, wherein the ion optical system comprises one or more electrodes, and wherein the contaminated surface is the surface of the one or more electrodes.

12. The method of claim 11, wherein the method further comprises controlling the gas pressure within the ion optical system such that the mean free path of electrons is less than the spacing between electrodes in the ion optical system.

13. The method according to any one of claims 2 to 5, wherein the ion optical system comprises a pair of electrodes, and the radiation source is displaced relative to a plane bisecting the pair of electrodes.

14. The method of claim 13, wherein the ion optical system comprises a plurality of pairs of electrodes and a plurality of radiation sources, wherein each radiation source is displaced relative to a plane bisecting the corresponding pair of electrodes.

15. The method of any one of claims 2 to 5, wherein the ion optical system comprises one or more electrodes, and the method further comprises applying a voltage to at least one electrode of the ion optical system to accelerate the charged particles and thereby generate additional radiation for neutralizing the at least portion of the charged contaminant layer.

16. The method according to any one of claims 2 to 5, further comprising applying a magnetic field in the ion optical system to guide the charged particles toward the charged contaminant layer.

17. The method according to any one of claims 2 to 5, wherein the ion optical system is a quadrupole electrode system; and / or wherein the charged particles include any one or more of the following: protons; electrons; and / or ions.

18. The method according to any one of claims 2 to 5, wherein the charged contaminant layer is a positively charged contaminant layer.

19. The method according to any one of claims 2 to 5, wherein the ion optical system is part of an analytical instrument comprising an ion source configured to provide ions to the ion optical system, wherein the radiation source is different from the contaminated surface and from the ion source.

20. The method according to any one of claims 2 to 5, wherein the ion optical system is part of an analytical instrument comprising an ion source configured to supply ions to the ion optical system, wherein the step of neutralizing at least a portion of the charged contaminant layer by causing the charged particles to interact with the charged contaminant layer is performed without interrupting the ion flow from the ion source.

21. A method for operating an ion optical system, the method comprising: (i) Introducing the sample into the ion optical system; (ii) Manipulating and ejecting the sample using the ion optical system; as well as (iii) The ion optical system is subjected to the method according to any of the preceding claims.

22. The method of claim 21, further comprising: Repeat steps (i), (ii) and (iii) once or more.

23. An ion optical system configured to reduce the charge on a contaminated surface of the ion optical system, the ion optical system comprising: surface; and A radiation source configured to generate charged particles, wherein the radiation source is different from the surface; and The ion optical system is configured to neutralize at least a portion of the charged contaminant layer on the surface by causing the charged particles to interact with the charged contaminant layer. Wherein (i): the radiation source includes an electromagnetic radiation source configured to emit electromagnetic radiation that interacts with the charged contaminant layer and / or the ion optical system to generate the charged particles; and / or (ii) The radiation source includes an electron source configured to emit free electrons.

24. The ion optical system of claim 23, wherein the ion optical system comprises a photoemitting material, and wherein the electromagnetic radiation source is configured to emit electromagnetic radiation that interacts with the photoemitting material to generate the charged particles.

25. The ion optical system according to claim 23 or claim 24, wherein the ion optical system is configured to perform the method according to any one of claims 1 to 22.

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