Patent Application
20210134583
The present invention relates to the ion guide technology, and in particular to an ion guide device and method as well as mass spectrometer.
It is well-known that quadrupole device is the ion optics most widely used in the various current commercial mass spectrometers. The quadrupole device has a very simple electrode structure. Generally, an ion transmission passageway is formed by arranging only two pairs of parallel rod-shaped electrodes at intervals, and a RF voltage Vrf and a DC voltage Udc with opposite polarities are applied to the two pairs of rod-shaped electrodes to generate a quadrupole field therein for transmitting and screening ions. In practical applications, by adjusting the amplitude, frequency and the like of the RF voltage Vrf and the DC voltage Udc, quadrupole rods can be used as various ion optics such as mass analyzers, ion guide devices, and ion collision and reaction devices. Mass analyzers are the earliest and also most important application of the quadrupole device. In 1953, Professor Wolfgang Paul et al. from the University of Bonne in Germany proposed the use of electric-field-based quadrupole mass analyzer to separate ions with different mass-to-charge ratios. The related devices and methods may refer to U.S. Pat. No. 2,939,952. Since then, the quadrupole mass analyzer gradually becomes the most common ion separation mean used in the mass spectrometer. So far, in the mainstream mass spectrometers including single-quadrupole mass spectrometer, triple-quadrupole mass spectrometer, and quadrupole time-of-flight mass spectrometer, as the core components, the quadrupole devices still play a very important role and have a huge application market.
As described above, in addition to the mass analyzers, the quadrupole devices are widely used as ion guide devices for the mass spectrometers to realize efficient ion transmission over different pressure intervals and extremely excellent ion beam compression effects. Generally, when the quadrupole device is used as ion guide device, RF voltages with opposite polarities are applied to only two pairs of rod-shaped electrodes in order to confine ions in the radial direction; meanwhile, to be convenient for ions to enter and leave the quadrupole rods in an axial direction, an identical bias voltage Ubias is often applied to all electrodes, so as to establish an axial potential gradient at the entrance and the exit. Under normal circumstances, ions pass through the quadrupole rods mainly by means of the initial kinetic energy obtained during entering the quadrupole rods. When the pressure is low, there are few times for ions to collide with neutral gas molecules, and the loss of kinetic energy of ions is also low, so that the ions can quickly pass through the quadrupole rods. However, when the gas pressure rises, since the loss of kinetic energy resulted from frequent collision of ions with molecules is very high, it takes a very long period of time or even impossible for the ions to pass through the quadrupole rods by only the initial kinetic energy of the ions. Thus, the sensitivity of instruments will be reduced, and the analysis speed will also be influenced greatly. For example, in an operating mode of alternately switching between positive and negative polarities, a mass spectrometer needs to periodically empty and fill ions, but the flight time of ions limits the minimal time for the instruments to obtain stable output.
In addition to the mass analyzer and ion guide device, ion collision/reaction cell is also a very important application of the quadrupole device. The ion collision/reaction cell is mainly the device for colliding the precursor ions with molecules for dissociation reaction, and then analyzing the resulting product ions to obtain the structural information of precursor ions or to improve the detection selectivity and sensitivity.
By taking the collision induced dissociation as an example, generally, ions accelerated by an electric field are fed into an collision cell which is filled with a collision gas (argon, nitrogen or helium) and maintained at a certain pressure (1 to 2 Pa); and then, the ions are collided with gas molecules so that part of kinetic energy is converted into internal energy, so that some chemical bonds are broken and a plurality of fragment ions are generated. Due to the excellent ion focusing capability, the quadrupole device is often used as collision cell. Like common ion guide devices, in order to facilitate ions to pass through the collision cell and improve the analysis speed, it is required to establish an axial electric field for driving ion transmission. In U.S. Pat. No. 7,675,031, Michael Knoicek et el. have proposed a structure having a plurality of auxiliary electrodes interposed between adjacent electrodes of quadrupole device, wherein an axial DC potential gradient is applied to the auxiliary electrodes to generate an axial electric field for driving ion transmission. Meanwhile, this patent has further disclosed a curved structure based on this technique. It is well-known that using a curved ion guide device as well as a curved collision cell, are not only beneficial for reducing the interference from the neutral noise but also convenient for the overall design of the instrument to reduce the area occupancy of the instrument. Therefore, many commercial instruments use various curved ion guide devices.
However, in order to improve the dissociation efficiency of ions, the incident kinetic energy of ions is very high, generally dozens or hundreds of volts. If a collision cell is of a curved structure, high-speed incident ions are often too fast to be deflected by the RF voltage, and instead, they directly collide onto the electrodes to cause ion loss. However, if the RF voltage is increased, the mass range of ions that can pass through will be narrowed, and as a result, the generated fragment ions are difficult to pass through.
In order to solve this problem, in U.S. Pat. No. 8,084,750, Felician Muntean has proposed a method of applying a radial DC electric field in a curved quadrupole ion guide, for providing a centrifugal force for the deflection of ions. Meanwhile, this radial deflection electric field is gradually reduced from the entrance to the exit, so that the ion transmission efficiency and the mass window width can be optimized globally. This method can provide both an axial driving electric field and a radial deflection electric field, and is very suitable for curved collision cell. Two typical structures of this method are as follows: all electrodes of a quadrupole ion guide based on square rods are divided into a plurality of segments, and two adjacent electrodes in the quadrupole ion guide are divided into a plurality of segments. The former structure is relatively complicated and also difficult to assemble. However, it is relatively convenient to apply a voltage, so that a proportion of the axial driving electric field and the radial deflection electric field may be controlled conveniently. The latter structure is relatively simple. However, the size of components of the two electric fields cannot be separately controlled, and the overall performance of the device is difficult to optimize.
In view of the deficiencies in the prior arts, an objective of the present invention is to provide an ion guide device and associated method as well as a mass spectrometer in order to solve the problems in the prior arts.
To achieve this objective and other objectives, the present invention provides an ion guide device, including: a first electrode assembly, including at least one pair of first electrode units parallelly arranged along a spatial axis; a second electrode assembly, including at least one pair of second electrode units parallelly arranged along the said spatial axis, wherein each of the second electrode units includes a plurality of segmented electrodes arranged in the axial direction, and an ion transmission channel in the axial direction is formed within a space surrounded by the first electrode assembly and the second electrode assembly; and, a power supply device configured to apply a RF voltage to one of the first electrode assembly and the second electrode assembly or separately apply RF voltages with different polarities to the first electrode assembly and the second electrode assembly so that a RF field is formed in a direction perpendicular to the said spatial axis to confine ions, and apply a DC voltage to at least part of the said segmented electrodes of the second electrode assembly so that a DC potential gradient is formed inside the ion transmission channel.
In an embodiment of the present invention, the spatial axis is a straight axis, a curve axis or a combination of the both.
In an embodiment of the present invention, each of the first electrode units at least includes one electrode or a plurality of electrodes.
In an embodiment of the present invention, surfaces of the first electrode assembly and the second electrode assembly facing the spatial axis are parallel or perpendicular.
In an embodiment of the present invention, at least part of electrodes in the first electrode assembly and the second electrode assembly are one or more of plate-shaped electrodes, rod-shaped electrodes, and thin-layer electrodes attached to a PCB or a ceramic substrate.
In an embodiment of the present invention, the included angle between a distribution direction of the plurality of segmented electrodes and the axial direction remains unchanged or changes gradually.
In an embodiment of the present invention, at least two of the plurality of segmented electrodes are identical in at least one of size or shape.
In an embodiment of the present invention, the waveform of the RF voltage is at least one of sine wave, square wave, sawtooth wave and triangular wave.
In an embodiment of the present invention, the RF voltages with different polarities are RF voltages which are opposite in polarity and identical in amplitude and frequency, or RF voltages which are different in at least one of phase, amplitude and frequency.
In an embodiment of the present invention, the RF field is a quadrupole field or a multipole field.
In an embodiment of the present invention, a pressure value of the gas is within one of the following ranges: a) 2×105 Pa to 2×103 Pa; b) 2×103 Pa to 20 Pa; c) 1 Pa to 2 Pa; d) 2 Pa to 2×10−1 Pa; e) 2×10−1 Pa to 2×10−3 Pa; and, f)<2×10−3 Pa.
To achieve this objective and other objectives, the present invention provides an ion guide device, including: a first electrode assembly, including at least one pair of first electrode units parallelly arranged along a spatial axis; a second electrode assembly, including at least one pair of second electrode units parallelly arranged along the said spatial axis, wherein a high-resistance material layer is coated on a surface of each of the second electrode units facing the spatial axis, and an ion transmission channel in the axial direction is formed within a space surrounded by the first electrode assembly and the second electrode assembly; and, a power supply device configured to apply a RF voltage to one of the first electrode assembly and the second electrode assembly or separately apply RF voltages with different polarities to the first electrode assembly and the second electrode assembly so that a RF field is formed in a direction perpendicular to the spatial axis to confine ions, and apply a DC voltage to the second electrode assembly so that a DC potential gradient in the axial direction is formed inside the ion transmission channel.
In an embodiment of the present invention, the spatial axis is a straight axis, a curve axis or a combination of the both.
In an embodiment of the present invention, each of the first electrode units at least includes one electrode or a plurality of electrodes.
In an embodiment of the present invention, surfaces of the first electrode assembly and the second electrode assembly facing the spatial axis are parallel or perpendicular.
In an embodiment of the present invention, at least part of electrodes in the first electrode assembly and the second electrode assembly are one or more of plate-shaped electrodes, rod-shaped electrodes, and thin-layer electrodes attached to a PCB or a ceramic substrate.
In an embodiment of the present invention, the included angle between an extension direction of the second electrode units and the axial direction remains unchanged or changes gradually.
In an embodiment of the present invention, the waveform of the RF voltage is at least one of sine wave, square wave, sawtooth wave and triangular wave.
In an embodiment of the present invention, the RF voltages with different polarities are RF voltages which are opposite in polarity and identical in amplitude and frequency, or RF voltages which are different in at least one of phase, amplitude and frequency.
In an embodiment of the present invention, the RF field is a quadrupole field or a multipole field.
In an embodiment of the present invention, the pressure value of the gas is within one of the following ranges: a) 2×105 Pa to 2×103 Pa; b) 2×103 Pa to 20 Pa; c) 1 Pa to 2 Pa; d) 2 Pa to 2×10−1 Pa; e) 2×10−1 Pa to 2×10−3 Pa; and, f)<2×10−3 Pa.
To achieve this objective and other objectives, the present invention provides a mass spectrometer, including: one or more ion guide devices described above, and the ion guide device is used as any one of the following devices: a) a preceding-stage ion guide device; b) an ion compression device; c) an ion storage device; d) a collision cell device; and, e) an ion buncher device.
To achieve this objective and other objectives, the present invention provides an ion guide method, including the steps of: providing a first electrode assembly and a second electrode assembly, the first electrode assembly including at least one pair of first electrode units parallelly arranged along a spatial axis, the second electrode assembly including at least one pair of second electrode units parallelly arranged along the said spatial axis, wherein each of the second electrode units includes a plurality of segmented electrodes arranged in the axial direction, and an ion transmission channel in the axial direction is formed within a space surrounded by the first electrode assembly and the second electrode assembly; and, applying a RF voltage to one of the first electrode assembly and the second electrode assembly or separately applying RF voltages with different polarities to the first electrode assembly and the second electrode assembly so that a RF field is formed in a direction perpendicular to the spatial axis to confine ions, and applying a DC voltage to at least part of segmented electrodes of the second electrode assembly so that a DC potential gradient is formed inside the ion transmission channel.
To achieve this objective and other objectives, the present invention provides an ion guide method, including the steps of: providing a first electrode assembly and a second electrode assembly, the first electrode assembly including at least one pair of first electrode units parallelly arranged along a spatial axis, the second electrode assembly including at least one pair of second electrode units parallelly arranged along the said spatial axis, wherein a high-resistance material layer is coated on a surface of each of the second electrode units facing the spatial axis, and an ion transmission channel in the axial direction is formed within a space surrounded by the first electrode assembly and the second electrode assembly; and, applying a RF voltage to one of the first electrode assembly and the second electrode assembly or separately applying RF voltages with different polarities to the first electrode assembly and the second electrode assembly so that a RF field is formed in a direction perpendicular to the spatial axis to confine ions, and applying a DC voltage to the second electrode assembly so that a DC potential gradient is formed inside the ion transmission channel.
In conclusion, in the ion guide device and method and the mass spectrometer provided by the present invention, a pair of parallel electrode assemblies, among the electrode assemblies surrounded a spatial axis to form an ion transmission channel, is segmented in a certain direction, so that a DC voltage can be separately applied to the segmented electrodes to form a DC potential gradient. In this way, not only an electric field driving component in an axial direction but also an electric field component perpendicular to the axial direction can be provided to control the motion of ions in the ion transmission channel. As a result, the problems of low analysis speed, limited ion incident energy, difficulty to balance the device structure simplification and the performance optimization and the like are solved.
Implementations of the present invention will be described below by specific embodiments, and other advantages and effects of the present invention may be easily obtained by those skilled in the art from the contents disclosed in the description.
It is to be noted that, the structure, scale, size and the like shown in the accompanying drawings of the description are merely used for allowing those skilled in the art to understand and read the contents disclosed in the description and not intended to limit the implementable conditions of the present invention, and thus have no any technically substantive meaning. Without influencing the effects and objectives which may be achieved by the present invention, any structural modification, changes in scale, or size adjustments shall fall into the scope defined by the technical contents of the present invention. Meanwhile, terms such as “upper”, “lower”, “left”, “right”, “middle” and “one” used in the description are merely used for clear statement and not intended to limit the implementable scope of the present invention, and any changes or adjustments in relative relations shall be regarded as falling to the implementable scope of the present invention without substantively changing the technical contents.
As shown in
In this embodiment, the first electrode assembly includes at least one pair of first electrode units 101 parallelly arranged along a spatial axis. The first electrode units 101 may be one-piece to which an identical voltage is applied.
In this embodiment, the second electrode assembly includes at least one pair of second electrode units 102 parallelly arranged in parallel in the axial direction, wherein each of the second electrode units 102 includes a plurality of segmented electrodes 103 arranged in the axial direction.
An ion transmission channel in the axial direction is formed within a space surrounded by the first electrode assembly and the second electrode assembly. In this embodiment, the surfaces of the first electrode assembly and the second electrode assembly facing the spatial axis are perpendicular, so as to enclose the ion transmission channel. It is to be particularly noted that, in other embodiments, the ion transmission channel is not necessarily enclosed by the first electrode assembly and the second electrode assembly, for example, as shown in Embodiment 2, and is not limited to the structure in Embodiment 1.
The power supply device may provide a RF voltage output to apply a RF voltage to either of the first electrode assembly and the second electrode assembly or separately apply RF voltages with different polarities to the first electrode assembly and the second electrode assembly, so that a RF field is formed in a direction (e.g., a radial direction) perpendicular to the said spatial axis to confine ions.
For example, in an embodiment, the power supply device may apply a RF voltage with a first polarity to two first electrode units 101 and apply a RF voltage with a second polarity to two second electrode units 102 (i.e., the segmented electrodes 103), so that a quadrupole RF field is formed for confining ions within the ion transmission channel, wherein the RF voltages with different polarities are RF voltages which are opposite in polarity and identical in amplitude and frequency, or RF voltages which are different in at least one of phase, amplitude and frequency. In addition, the waveform of the RF voltages is at least one of sine wave, square wave, sawtooth wave and triangular wave.
Of course, the above description is illustrative. The RF field may change according to different structures of the first electrode assembly and the second electrode assembly. Other multipole fields may be formed. It is not limited to this embodiment.
Moreover, the power supply device may further provide a DC voltage output to apply a DC voltage to at least part of segmented electrodes 103 of the second electrode assembly so that a DC potential gradient is formed inside the ion transmission channel (e.g., a direction indicated by an arrow A).
It is to be noted that the power supply device does not consist of a single power supply component, and instead, it may contain a plurality of power supply components, part of which outputs a RF voltage while the other part of which outputs a DC voltage.
Principally, the ion guide device provided by the present invention may change the value of the stable parameter a of each position within the ion transmission channel while generating an axial driving electric field. According to the Mathieu equation:
where u denotes x and y coordinates of a plane of the quadrupole field,
ξ=Ωt/2
is a dimensionless parameter,
Ω=2πf
is a RF circular frequency, t denotes the time, and a and q are stable parameters in the quadrupole mass analyzer theory and correspond to a RF voltage Vrf and a DC voltage Udc, respectively, with reference to the following formulae:
It can be seen that, when the DC voltage Udc is different, the value of the stable parameter a changes correspondingly. Therefore, when a gradually reduced DC voltage is applied to the segmented electrodes 103, the value of a, which is gradually reduced in the axial direction, may be obtained for ions with a fixed mass-to-charge ratio. In accordance with a stabilization diagram of the quadrupole mass analyzer, when proper values of a and q are used, ions with different mass-to-charge ratios may be screened. That is, particular ions are allowed to stably pass through the quadrupole rod, while some ions are not allowed to pass through the quadrupole rod due to the loss of stability of motion in the radial direction. Therefore, the ion guide device provided by the present invention may provide an axial driving electric field, and may also specifically remove ions with a certain particular mass-to-charge ratio from a particular region of the ion transmission channel so as to reduce chemical noise. Meanwhile, with the decrease of the value of a, survival ions are more and more stable, so that very excellent ion focusing effect may be achieved.
Optionally, at least two of the plurality of segmented electrodes 103 are identical in at least one of size or shape. Although the segmented electrodes 103 shown in
Optionally, the ion guide device may operate at a particular pressure, and effectively improve the transmission speed of ions. The pressure value may be within one of the following ranges: a) 2×105 Pa to 2×103 Pa; b) 2×103 Pa to 20 Pa; c) 1 Pa to 2 Pa; d) 2 Pa to 2×10−1 Pa; e) 2×10−1 Pa to 2×10−3 Pa; and, f)<2×10−3 Pa, wherein particularly when the ion guide device operates at a pressure over 1 Pa, the transmission time of ions can be effectively reduced to below 1 ms or even less.
In an embodiment, comprehensively considering the processing difficulty level, performance requirement and other practical factors, the first and second electrode assemblies may be in various forms such as plate-shaped electrodes, rod-shaped electrodes, or thin-layer electrodes attached to a PCB or a ceramic substrate.
The spatial axis is not limited to a straight axis, and it can be a form of a curve axis or a combination of the straight axis and the curve axis. This will be described in Embodiment 3 and Embodiment 4.
As shown in
The advantage of the curve axis lies in that an included angle between a segmentation direction of the segmented electrodes 301 of the second electrode units 302 and the direction of the spatial axis always changes. As shown in
When the ion guide device in this embodiment is used as a collision cell, since the initial incident kinetic energy of ions is very high, almost no axial driving force is required. Instead, a radial acting force is highly required to assist ion deflection and prevent ions from colliding onto the electrodes because they are too fast to be deflected. When ions move forward for a certain distance, due to the collision of ions with neutral gas molecules, the kinetic energy of ions is lost gradually, and a certain axial driving force (for example, generated by an axial DC electric field component in a direction indicated by an arrow C) is highly required in this case. Almost no radial acting force (for example, generated by a radial DC electric field component in a direction indicated by an arrow D) is required. Apparently, the device in this embodiment exactly meets such a requirement of the collision cell.
In addition, the ion guide device with the curve axis may reduce the neutral noise and decrease the area occupancy of the instrument.
As shown in
The ion guide device in this embodiment has a smaller size than that in Embodiment 3, and may adopt any combination of a plurality of ion guide devices, which is flexible. For example, the ion guide devices in two embodiments may be combined to form the ion guide device in
The first electrode units may be one-piece, or may consist of segmented electrodes to which different DC voltages are applied. Embodiments 5 and 6 will be described hereinafter.
As shown in
As shown in
As shown in
Meanwhile, the ion guide device in this embodiment includes multiple pairs of first electrode units 701, and RF voltages with opposite polarities are applied to adjacent first electrode units.
In this case, the segmentation direction of the second electrode assembly is neither perpendicular nor parallel to the spatial axis. Thus, both an axial driving electric field component (indicated by an arrow F) and a lateral DC electric field component (indicated by an arrow G) may be generated within the ion transmission channel to push ions to one side. Specifically,
The segmented electrode structure of the second electrode units is not necessary, and the second electrode units may be implemented by some alternative schemes in other embodiments, for example, by coating high-resistance material.
As shown in
As shown in
The preceding Embodiments 2 to 7 may be applied to Embodiments 8 and 9. By designing a corresponding pattern for the high-resistance material layer and rationally selecting a voltage application position, it is possible to achieve the DC potential gradient effects similar to those that can be achieved by a segmented electrode structure without using the segmented electrode structure. Compared with the structure in Embodiment 1, this embodiment is more convenient to apply a DC voltage.
In combination with the above embodiments, the present invention further provides a mass spectrometer, including: one or more ion guide devices, and the ion guide device is used as any one of the following devices: a) a preceding-stage ion guide device; b) an ion compression device; c) an ion storage device; d) a collision cell device; and, e) an ion buncher device.
In conclusion, in the ion guide device and associated method as well as the mass spectrometer provided by the present invention, a pair of parallel electrode assemblies, among electrode assemblies surrounding a spatial axis to form an ion transmission channel, is segmented in a certain direction, so that a DC voltage can be separately applied to the segmented electrodes to form a DC potential gradient. In this way, not only an electric field driving component in an axial direction but also an electric field component perpendicular to the axial direction can be provided to control the motion of ions in the ion transmission channel. As a result, the problems of low analysis speed, limited ion incident energy, difficulty to balance the device structure simplification and the performance optimization and the like are solved.
The embodiments are merely for illustratively describing the principle and effects of the present invention, and not intended to limit the present invention. Those skilled in the art may make modifications or alterations to the embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical idea of the present invention shall be embraced by the claims of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201710256210.0 | Apr 2017 | CN | national |
This application is a U.S. national stage entry of PCT Application Serial No. PCT/JP2017/018712, filed May 18, 2017, which claims priority to and the benefit of, Chinese Patent Application Serial No. 201710256210.0, filed Apr. 19, 2017, which are incorporated herein by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/018712 | 5/18/2017 | WO | 00 |
