CN220895454U

CN220895454U - Differential quadrupole rod array and mass spectrometer having the same

Info

Publication number: CN220895454U
Application number: CN202322493457.8U
Authority: CN
Inventors: 王志明
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-09-13
Filing date: 2023-09-13
Publication date: 2024-05-03
Anticipated expiration: 2033-09-13

Abstract

The utility model relates to a differential quadrupole array and a mass spectrometer with the differential quadrupole array. The differential quadrupole rod array comprises a plurality of groups of differential quadrupole rods, each group of differential quadrupole rods comprises four metal plates which extend on a radial plane of the differential quadrupole rod array and have identical contour lines, the four metal plates are rotationally symmetrically arranged in the radial plane, the plurality of groups of differential quadrupole rods are arranged in a sequential and aligned manner along an axial direction and form ion transmission channels extending along the axial direction, wherein each group of differential quadrupole rods is individually controlled by a digital driving circuit. The differential quadrupole array and the mass spectrometer with the differential quadrupole array of the utility model are easy to manufacture and can realize multiple functions in the same mass spectrometer, including ion acceleration/deceleration, ion convergence/divergence, ion selection, ion collision, linear ion trap and ion mobility separation, and the order of the functions can be defined as required.

Description

Differential quadrupole rod array and mass spectrometer having the same

Technical Field

The utility model relates to the technical field of mass spectrometers, in particular to a differential quadrupole rod array and a mass spectrometer with the differential quadrupole rod array.

Background

Mass spectrometers are widely used for detection analysis of substances, for example for determining their atomic mass or relative abundance. In the detection process, firstly, substances to be analyzed are ionized to form an ion source, and the formed ions have a specific mass-to-charge ratio; the ions are then passed into a mass analyser capable of forming a specific electric field to separate the ions according to their mass to charge ratio; the separated ions sequentially enter an ion detector, and the amplified ion signals are collected to form a mass spectrogram.

Mass spectrometers include quadrupole mass spectrometers, ion trap mass spectrometers, and the like, which are capable of performing a variety of functions including ion convergence, ion steering, mass selection, ion collisions, ion traps, ion mobility separation, and the like. Various mass spectrometers have different configurations depending on the functions they can perform. Different kinds of mass spectrometers are selected for different mass spectrometry applications. Thus, in order to perform different mass spectrometry, different mass spectrometers need to be prepared, and the instrument cost is high.

Quadrupole mass selectors (quadrupoles for short) are core elements in quadrupole mass spectrometers, in which four electrode rods are placed in parallel on two planes perpendicular to each other, two electrode rods on the same plane are applied with the same radio frequency alternating voltage, and the voltages applied by two groups of electrode rods on the two planes are opposite to each other. The radially inner profile of the ideal four electrode rods is hyperbolic, and the electric field thus formed is capable of maximizing ion transport and ion selection. However, the hyperbolic profile has considerable difficulty in processing, resulting in problems of low yield and high cost of the quadrupole rods having the hyperbolic profile.

The quadrupoles may be configured as single quadrupoles or as series quadrupoles. By applying the appropriate voltages, the quadrupole can operate in three modes, namely True Total Ion (TTI), scanning, and selective Ion monitoring (Selected Ion Monitoring, SIM). In the ion full-pass TTI mode, no dc voltage is applied to the quadrupole rods, but only a radio frequency voltage is applied, so that ions are not filtered, and charged ions pass through the quadrupole rods. In the scanning mode, signals of each mass number are acquired in turn within a given mass-to-charge ratio range. In the selected ion monitoring SIM mode, only ion signals of a specified mass to charge ratio or ratios are acquired. Single quadrupole operation in the modes described above can achieve primary mass spectrometry (MS ¹).

The series quadrupole rods are formed by connecting a plurality of groups of quadrupole rods in series. Typical tandem quadrupoles include three sets of tandem quadrupoles (QQQ), with spacers disposed between the first and third sets of quadrupoles at both ends and the second set of quadrupoles in the middle, the spacers separating the three sets of quadrupoles in three different isolation chambers, each of which is provided with a suction port to ensure the respective vacuum levels within the isolation chambers. The spacer is provided with a through hole for the passage of ions at a position where the ion optical axis passes, the through hole being small enough not to affect the respective vacuum degree of each isolation chamber. And an air inlet is arranged in the isolation cavity where the second group of quadrupole rods are positioned, and can release inert gas into the isolation cavity where the second group of quadrupole rods are positioned, so that a collision pool is formed under the isolation of the spacers. By applying appropriate voltages across the sets of quadrupole rods, various applications can be realized, including full scan, selective ion monitoring, ion scan, parent ion scan, neutral loss scan, neutral acquisition scan, multiple reaction monitoring (Multiple Reaction Monitoring, MRM), and so forth. For example, to enable application of MRM, a first set of quadrupoles may be operated in SIM mode to select precursor ions, a second set of quadrupoles may be operated in TTI mode to form a collision cell, and a third set of quadrupoles may be operated in SIM mode to select fragment ions. Thereby, a mass-or ion-selective function is achieved in the first and third sets of quadrupoles, while an ion-collision function is achieved in the collision cell. In the ion collision process, precursor ions selected by the first group of quadrupole rods collide with rare gas molecules in a collision cell to be dissociated (the process is also called collision induced dissociation, collision Induced Dissociation and CID), and then generated fragment ions enter an ion detector through the selection of the third group of quadrupole rods to form a mass spectrogram, and the structure of the precursor ions can be reversely pushed through the mass spectrogram. Thus, a secondary mass spectrum (MS ²) is achieved.

However, to achieve higher order mass spectrometry (MS ⁿ, n > 2), more quadrupole rods need to be connected in series, which increases the space occupied by the instrument. Thus, generally higher order mass spectrometry will be achieved by means of ion trap mass spectrometers.

The linear ion trap has a structure similar to that of a quadrupole rod, and the difference is that two polar plates are arranged at two ends of the quadrupole rod, and voltage with the polarity opposite to that of ions is applied to the polar plates, so that the ions can shuttle back and forth between the polar plates, thereby realizing the function of the linear ion trap. Meanwhile, in the four-pole rods of every two groups, at least one group of four-pole rods is provided with a narrow slit. In an initial state, reverse-phase radio-frequency alternating voltages are applied to quadrupole rods of different groups, so that all ions can be reserved in the ion trap; then another set of alternating voltages is applied to the slotted set of quadrupole rods to cause ions to enter an unstable state and then to be ejected from the slots. Meanwhile, the ion trap can be filled with inert gas with a certain concentration, so that ions collide with the inert gas in the ion trap for multiple times to generate multiple times of dissociation. By adjusting the voltage, the dissociated fragment ions can be sequentially ejected from the narrow slits, enter the ion detector to form a mass spectrum, and the precursor ion structure can be reversely pushed through the mass spectrum. Thus, multi-stage mass spectrometry (MS ⁿ) is achieved.

Ion Mobility mass spectrometry is a mass spectrometry method for separating ions by depending on their Ion Mobility (IM), i.e., a function of realizing Ion Mobility separation. The main difference between the mass spectrometer and the conventional mass spectrometer is that the former comprises an ion drift tube, and electric fields for driving ions to advance are applied to two ends of the ion drift tube, and buffer gas with a certain concentration, such as nitrogen, helium, carbon dioxide, sulfur hexafluoride, ammonia, carbon tetrafluoride and the like, is filled in the ion drift tube.

Because of the different structures of single quadrupole mass spectrometers, tandem quadrupole mass spectrometers, ion trap mass spectrometers, ion mobility mass spectrometers, each having unique elements such as spacers forming collision cells, slots on quadrupole rods forming linear ion traps and plates at both ends, ion drift tubes, etc., the functions of these mass spectrometers cannot be realized on the same device.

Disclosure of utility model

The object of the present utility model is to provide a differential quadrupole array which is easy to manufacture and can realize various functions, and a mass spectrometer having the differential quadrupole array, so that various functions such as ion acceleration/deceleration, ion convergence/divergence, ion selection, ion collision, linear ion trap, ion mobility separation and the like can be realized in any section in the same mass spectrometer.

According to one aspect of the present utility model there is provided a differential quadrupole rod array comprising a plurality of sets of differential quadrupole rods, each set of differential quadrupole rods comprising four metal plates extending in a radial plane of the differential quadrupole rod array and having identical contour lines, the four metal plates being rotationally symmetrically arranged in the radial plane, the plurality of sets of differential quadrupole rods being arranged in a sequential and aligned manner along an axial direction and forming ion transport channels extending along the axial direction, wherein each set of differential quadrupole rods is individually controlled by a digitizing drive circuit.

The fabrication of the differential quadrupole rod array of the present utility model is easier than a rod quadrupole rod formed by turning or grinding. For example, a metal plate having a desired profile, such as a hyperbolic profile, may be precision stamped or laser cut in batches on a large metal plate or printed circuit board, and then combined by precision positioning and/or calibration to form the differential quadrupole rod array of the present utility model. The manufacturing mode has high precision, high yield and low cost.

Each group of differential quadrupoles can form a sub-electric field through the radially inner edge thereof, and the superposition of the sub-electric fields formed by the groups of differential quadrupoles can form a combined electric field which is similar to the electric field formed by the common quadrupoles. For example, a first radio-frequency alternating voltage having a certain direct voltage component is applied to one pair of opposite metal plates of each set of differential quadrupoles, a second radio-frequency alternating voltage having a certain direct voltage component is applied to the other pair of opposite metal plates of each set of differential quadrupoles, and the first radio-frequency alternating voltage is the same as the second radio-frequency alternating voltage in coefficient and opposite in phase, the differential quadrupoles are capable of forming an electric field approximating quadrupoles operating in SIM mode, such that the differential quadrupoles also operate in SIM mode, selecting ions passing through the differential quadrupoles.

Each set of differential quadrupoles is individually controlled by a digital drive circuit, meaning that the voltages applied across each set of differential quadrupoles can be controlled independently of each other. In this way, it is possible to form different functional areas on different axial sections, depending on the voltage applied to them, by groups of differential quadrupoles. These functional areas may perform functions including ion acceleration/deceleration, ion convergence/divergence, ion selection, ion collisions, linear ion traps, and ion mobility separation.

Preferably, the differential quadrupole array can be configured as pre-quadrupoles, single quadrupoles, tandem quadrupoles, linear ion traps, ion drift tubes, and combinations thereof by controlling the digitizing drive circuit to perform functions of ion convergence/divergence, ion selection, ion collisions, linear ion traps, and/or ion mobility separation in any order across the differential quadrupole array.

Preferably, at least one modulatable electric field distributed along the axial direction is formed on the differential quadrupole rod array by controlling the digitizing drive circuit. For example, by applying a direct voltage across two sets of differential quadrupoles, a modulated electric field in the axial direction can be created between the two sets of differential quadrupoles. The axially-directed, modulated electric field is capable of performing functions such as ion acceleration/deceleration. Further, the direction and/or intensity and/or axial length of the modulatable electric field can be varied by the digital drive circuit.

In particular, the modulatable electric field is a plurality of electric fields differing in direction and/or intensity and/or axial length.

Preferably, one or more sets of differential quadrupoles at any position of the array of differential quadrupoles are configured as ion gates by controlling the digitizing drive circuit. For example, a pulsed voltage may be applied across a set of differential quadrupoles to configure the set of differential quadrupoles as an ion gate, wherein ions cannot pass through the set of differential quadrupoles when the pulsed voltage is the same polarity as the ions, such that the ion gate is in a closed state; when the pulse voltage is, for example, zero or opposite to the polarity of the ions, the ions can pass through the set of differential quadrupoles, leaving the ion gate in an open state.

Preferably, the radially inner profile of the metal plate is hyperbolic, whereby the resulting electric field is capable of maximizing ion transport and ion selection.

Preferably, the metal plate is formed by precision stamping or laser cutting on a metal plate or printed circuit board.

Preferably, the thickness of the metal plate is 0.1-2mm. A metal plate having a certain thickness can form a desired electric field at the radially inner edge, however, a too thick metal plate is disadvantageous for shaping by means of stamping or laser cutting. The metal plate should preferably be designed to have a thickness of 0.1-2mm, as studied by the applicant.

Preferably, the axial spacing between the metal plates in the axial direction is 0.1-2mm. The spacing between the metal plates is too narrow, so that the risk of voltage breakdown is high; too wide a spacing between the metal plates can result in a combined electric field that differs too much from the electric field created by conventional quadrupoles, affecting the functioning of the functional regions of the differential quadrupoles array, for example, degrading the accuracy of ion selection. The metal plates should preferably be designed with an axial spacing of 0.1-2mm, as studied by the applicant.

Preferably, an insulating structure is arranged between the metal plates, and the insulating structure is an insulating coating coated on the axial end face of the metal plate or an insulating sheet arranged between the adjacent metal plates. The insulating structure can prevent the metal plates from being broken down by voltage, so that the axial distance between the metal plates in the axial direction is smaller than 2mm, in particular smaller than 0.1mm, thereby improving the performance of the combined electric field, namely enhancing the function realization of each functional area of the differential quadrupole rod array, such as improving the precision of ion selection.

Preferably, the metal plate is kept at a constant temperature, for example 100 degrees celsius, in an operating state by a heating device and a temperature sensor, so that ions or neutral molecules cannot accumulate on the metal plate, preventing the metal plate from being contaminated.

According to another aspect of the present utility model there is provided a mass spectrometer comprising a housing and an ion source and an ion detector mounted within the housing, wherein the mass spectrometer is provided with the differential quadrupole array described above between the ion source and the ion detector. Based on the differential quadrupole array, multiple functions including ion acceleration/deceleration, ion convergence/divergence, ion selection, ion collision, linear ion trap and ion mobility separation can be achieved in any order in the same mass spectrometer by individually controlled digital drive circuits.

Preferably, one or more gas inlets are provided on an inner wall of the mass spectrometer on one or more radial planes within the range of the differential quadrupole array, the gas inlets being configured to release gas into the differential quadrupole array to form a gas space corresponding to the position of the gas inlets so as to cooperate with an electric field formed by a voltage applied across the differential quadrupole array to enable ions to perform ion collisions, ion mobility separations and the like in the gas space.

In one embodiment, a radio frequency alternating voltage is applied by the digitizing drive circuit to differential quadrupoles within the gas space to achieve ion acceleration and ion collision functions within the gas space. Preferably, the radio frequency alternating voltage applied across the differential quadrupoles within the gas space is increasing. The increasing radio frequency alternating voltage can realize the ion acceleration function, and precursor ions with a certain speed collide with gas in a gas space, particularly inert gas to be dissociated into ion fragments, so that the ion collision function is realized.

In another embodiment, a direct voltage and/or a radio frequency alternating voltage is applied across differential quadrupoles of the gas space by the digitizing drive circuit to perform the function of a linear ion trap within the gas space. By applying a direct voltage and/or a radio frequency alternating voltage across the gas space, an axial confinement field can be formed and eventually the function of an ion trap is achieved within the gas space. Preferably, after a predetermined time, the application of the direct current voltage and/or the radio frequency alternating voltage to the differential quadrupole at the end of the gas space is stopped by the digitizing drive circuit so as to allow ion fragments, which are formed by multiple collisions and dissociation, to reach the ion detector.

In yet another embodiment, the digital driving circuit applies a direct current voltage to differential quadrupoles at two ends of the gas space or a direct current increasing voltage to differential quadrupoles in the gas space to achieve the functions of ion acceleration and ion mobility separation in the gas space. By applying a direct current voltage to the differential quadrupoles at both ends of the gas space or by applying a direct current increasing voltage to the differential quadrupoles within the gas space, the differential quadrupoles in the gas can be configured as ion drift tubes, so that ions in the gas space can be accelerated, and ions with a suitable velocity can be separated in the gas space at different speeds according to the ion mobility of the ions.

Preferably, there are no radially extending spacers between the sets of differential quadrupoles to form the isolation chamber. The spacers typically extend in a radial direction from the inner wall of the chamber in which the differential quadrupole array is located, towards the ion optical axis, i.e. the central axis of the ion transport channel, and form through holes for the passage of ions only at the locations where the ion optical axis passes. The through holes are typically small enough not to affect the respective vacuum levels of the isolation chambers on either side of the spacer. The spacer is not arranged between the differential quadrupoles, so that the functions can be realized flexibly at any position of the differential quadrupoles array.

Drawings

For a better understanding of the above and other objects, features, advantages and functions of the present utility model, reference should be made to the preferred embodiments illustrated in the accompanying drawings. Like reference numerals refer to like parts throughout the drawings. It will be appreciated by persons skilled in the art that the drawings are intended to schematically illustrate preferred embodiments of the utility model, and that the scope of the utility model is not limited in any way by the drawings, and that the various components are not drawn to scale.

FIG. 1 shows a schematic diagram of a first embodiment of a mass spectrometer of the present utility model;

FIG. 2 shows a side view of a first set of differential quadrupoles in a differential quadrupole rod array of the present utility model;

FIG. 3 shows a schematic diagram of a second embodiment of a mass spectrometer of the present utility model;

FIG. 4 shows a schematic diagram of a third embodiment of a mass spectrometer of the present utility model;

FIG. 5 shows a schematic diagram of a fourth embodiment of a mass spectrometer of the present utility model;

FIG. 6 shows a schematic diagram of a fifth embodiment of a mass spectrometer of the present utility model;

FIG. 7 shows a schematic diagram of a sixth embodiment of a mass spectrometer of the present utility model; and

Fig. 8 shows a schematic diagram of another embodiment of the differential quadrupole array of the utility model.

Detailed Description

Specific embodiments of the present utility model will now be described in detail with reference to the accompanying drawings. What has been described herein is merely a preferred embodiment according to the present utility model, and other ways of implementing the utility model will occur to those skilled in the art on the basis of the preferred embodiment, and are intended to fall within the scope of the utility model as well.

Fig. 1 and 3-7, respectively, schematically illustrate various embodiments of a mass spectrometer 1 of the present utility model, each of which is implemented based on the same mass spectrometer to achieve different functions including ion acceleration/deceleration, ion convergence/divergence, ion selection, ion collision, linear ion trap, and ion mobility separation. In these embodiments, the main difference is the voltage applied by the digitizing drive circuit across each set of differential quadrupoles. The structure of the mass spectrometer 1, and in particular the differential quadrupole array 10, is described in detail below.

Referring to fig. 1, a mass spectrometer 1 of the present utility model comprises a housing 40, and an ion source 20 and an ion detector 30 located inside the housing 40, wherein a differential quadrupole rod array 10 of the present utility model is located between the ion source 20 and the ion detector 30 and comprises eight sets of differential quadrupole rods 101 to 108. Each set of differential quadrupoles comprises four metal plates (see fig. 2) extending in a radial plane of the array of differential quadrupoles 10 and having identical contour lines, the four metal plates being rotationally symmetrically arranged in the radial plane, eight sets of differential quadrupoles 101 to 108 being arranged in a sequential and aligned manner along an axial direction of the axis L and forming an ion transport channel 110 extending along said axial direction, wherein each set of differential quadrupoles is individually controlled by a digitizing drive circuit, being applied with independent voltages U1 to U8, i.e. the voltages applied thereto are independently controllable between the sets of differential quadrupoles. The independently applied voltages U1 to U8 cause each set of differential quadrupoles to form a sub-field on their radially inner edges, which in turn further superimpose to form a combined field that controls the ion motion path 200 of ions in the ion transport channel 110. By controlling the digital driving circuit, the voltages applied to each set of differential quadrupoles can be controlled individually to control the sub-fields and the combined fields formed by superposition of the sub-fields, thereby achieving control of the ion motion path 200.

One or more air inlets may be provided on the inner wall of the mass spectrometer 1, in particular on the housing 40, which air inlets lie on one or more radial planes within the range of the differential quadrupole array 10. For example, referring to fig. 1, a first gas inlet 120 is provided on a first radial plane S1 between the two sets of differential quadrupoles 103 and 104, and a second gas inlet 122 is provided on a second radial plane S2 between the two sets of differential quadrupoles 105 and 106 closer to the ion detector 30. The first gas inlet 120 and the second gas inlet 122 are configured to release gas into the interior of the differential quadrupole separately or cooperatively to form a gas space corresponding to the position of the first gas inlet 120 and/or the second gas inlet 122. The gas space is used to perform specific functions such as ion collisions, ion mobility separation. Preferably, the suction port 130 is disposed on opposite sides of the first gas inlet 120 and the second gas inlet 122 and closer to the ion source 20. The suction port 130 is used to suck gas, particularly gas released from the gas inlet, to maintain the vacuum in the chamber. By selecting the gas inlets at different positions and adjusting the gas release rate of the gas inlets, the positions and concentrations of the gas molecules distributed in the axial direction can be controlled. In this way, the position and concentration of the gas space, such as the collision cell, can be adjusted.

Spacers 50 and 60 are respectively provided between the ion source 20 and the differential quadrupole array 10 and between the differential quadrupole array 10 and the ion detector 30, and the spacers 50 and 60 are perforated at positions where the axis L passes through so as to allow ions to pass through. At the same time, a vacuum pressure differential can be established in the space separated by spacers 50 and 60, which is advantageous in the operation of the mass spectrometer.

The above-described spacers are not provided between the respective sets of differential quadrupole rods 101 to 108, so that the differential quadrupole rod array 10 can be used more flexibly. However, in other embodiments, spacers may be provided between groups of differential quadrupoles to limit the vacuum level within a particular space, to create a particular gas space, and/or to reduce the effects of an electric field between adjacent differential quadrupoles.

Fig. 2 shows the first set of differential quadrupole rods 101 of fig. 1 and its four metal plates 101A, 101B, 101C, 101D from the side, the radially inner profile of which is hyperbolic, so that the resulting electric field is able to maximize ion transport and ion selection. The metal plate may also have a radially inner contour of other shapes, such as a pointed tip, a circular arc or a straight line.

As shown in fig. 2, in the four metal plates 101A to 101D of the first group of differential quadrupole rods 101, two oppositely disposed metal plates are applied with the same voltage, i.e., the voltage U1 applied to the first group of differential quadrupole rods 101 includes U1 ⁺ and U1 ^-, simply U1 ^+/-.

In one embodiment, the voltage U1 ⁺＝U₁+V₁ cos ωt may be applied across the metal plates 101A and 101C, while the opposite voltage U1 ^-＝-U₁-V₁ cos ωt is applied across the other two oppositely disposed metal plates 101B and 101D. The voltage U1 ^+/- includes a dc voltage component and a radio frequency voltage component, where U ₁ is a dc voltage coefficient and V ₁ is a radio frequency voltage coefficient, and the phases of the two sets of voltages are opposite. The values of U ₁ and V ₁ can be arbitrarily set under the separate control of the digitizing drive circuit.

In another embodiment, the same voltage, U1 ⁺＝U1^-, may be applied across both pairs of metal plates. For example, by applying the same first dc voltage to one set of differential quadrupoles near the front end and the same second dc voltage to the other set of differential quadrupoles near the end, a modulated electric field can be formed between the two sets of differential quadrupoles distributed in the axial direction. When the first direct-current voltage is larger than the second direct-current voltage, a decelerating electric field is formed, and ions are decelerated when passing through; conversely, when the second direct current voltage is larger than the first direct current voltage, an accelerating electric field is formed, and ions are accelerated when passing through. This is advantageous for forming an ion drift tube and further achieving the function of ion mobility separation. The direction and/or intensity and/or axial length of the modulatable electric field can be varied by means of an independently controlled digital drive circuit. A plurality of modulated electric fields distributed along the axial direction can also be formed on the differential quadrupole rod array, and the directions and/or the intensities and/or the axial lengths of the modulated electric fields can be independently set through the digital driving circuit, and can be set to be the same or different.

The above-described voltage application method is also applicable to the other differential quadrupoles 102 to 108.

For example, a direct current increasing voltage or a direct current decreasing voltage is applied to two pairs of metal plates of the plurality of groups of differential quadrupole rods, and an accelerating electric field or a decelerating electric field can be formed between the plurality of groups of differential quadrupole rods, so as to realize the function of accelerating/decelerating ions.

Alternatively, the one or more sets of differential quadrupoles can be configured as ion gates by controlling the digital drive circuit to apply, for example, pulsed voltages across two pairs of metal plates of the one or more sets of differential quadrupoles. When the pulse voltage is the same as the polarity of the ions, the ions cannot pass through the one or more groups of differential quadrupole rods, so that the ion gate is in a closed state; when the pulsed voltage is, for example, zero or opposite to the polarity of the ions, the ions can pass through the one or more sets of differential quadrupoles, leaving the ion gate in an open state.

The voltages applied to the individual metal plates are different, so that the electric fields formed by the metal plates, and in particular the radially inner edges thereof, are different, enabling the differential quadrupole array to perform its respective functions, including ion acceleration/deceleration, ion convergence/divergence, ion selection, ion collision, linear ion trap and ion mobility separation, in any axial section. The following description is made in connection with specific examples.

In the first embodiment of fig. 1, a direct current voltage and a radio frequency voltage DC/RF are applied across the differential quadrupoles 101 to 108 such that the differential quadrupole array 10 as a whole operates in a Selective Ion Monitoring (SIM) mode. In this mode, ions of a desired mass to charge ratio move in the ion transport channel 110 along the ion motion path 200 about the axis L and eventually pass through the differential quadrupole rod array 10 to the ion detector 30; ions with undesirable mass-to-charge ratios move along the ion path 210, collide with the differential quadrupoles, and eventually fail to reach the ion detector 30. Thus, the differential quadrupole array 10 can be configured as a single quadrupole by the individually controlled digital driving circuit, thereby realizing the function of ion selection.

Alternatively, the differential quadrupole array 10 as a whole can be operated in either an ion full pass (TTI) mode or a scanning mode by adjusting the voltage applied across each of the differential quadrupoles 101 to 108 by a digital drive circuit.

In the second embodiment of fig. 3, unlike the first embodiment, only the radio frequency voltage RF is applied to the differential quadrupole rods 101 to 104 without applying the direct current voltage, and the radio frequency voltage coefficient is gradually increased. In this case, the movement radius of the ions in the radial direction gradually decreases due to the influence of the gradually increasing electric field when the ions pass through the axial section, and the path 200 having a larger movement radius gradually becomes the path 220 having a smaller movement radius. In this way, by the individually controlled digital driving circuit, the differential quadrupole rod array 10 is used as a pre-quadrupole rod in the axial sections of the differential quadrupole rods 101 to 104, achieving the effect of ion convergence. In contrast, if the radio frequency voltage coefficient is adjusted to be gradually reduced by the digital driving circuit, the effect of ion divergence can be achieved.

In this embodiment, a direct voltage and a radio frequency voltage DC/RF are applied across the differential quadrupoles 105 to 108 such that the differential quadrupole array 10 as a whole operates in SIM mode. As such, the differential quadrupole array 10 is configured as a combination of pre-quadrupoles and single quadrupoles by a separately controlled digital drive circuit.

In the third embodiment of fig. 4, unlike the first embodiment, a first direct voltage and a first radio frequency voltage DC/RF are applied across the differential quadrupoles 101 and 102 such that the differential quadrupoles array 10 operates in SIM mode over the axial section in which the differential quadrupoles 101 to 102 are located and precursor ions having a first mass to charge ratio are selected to pass through; no dc voltage is applied to the differential quadrupoles 103 and 104 but only a radio frequency voltage RF is applied so that the differential quadrupoles array 10 operates in TTI mode over the axial section in which the differential quadrupoles 103 to 104 are located. Preferably, the radio frequency alternating voltage RF applied across the differential quadrupoles 103 and 104 is increasing, i.e. its radio frequency voltage component V ₃<V₄, such that ions are accelerated as they pass through the differential quadrupoles 103 and 104. On the one hand, the ion acceleration can compensate the kinetic energy loss caused by ion collision, and on the other hand, the smooth proceeding of the ion collision requires a certain initial velocity of the ions. At the same time, the first gas inlet 120 releases inert gas, maintaining the distribution of inert gas within the axial section where, for example, the differential quadrupoles 103 to 104 are located to form a gas space with the inert gas. In this way, a collision cell is formed in the axial section in which the differential quadrupole rods 103 to 104 are located. Precursor ions enter the collision cell at an initial velocity and collide with inert gas molecules in the collision cell, thereby dissociating into a plurality of fragment ions. Thereafter, a second direct current voltage and a second radio frequency voltage DC/RF are applied across the differential quadrupoles 105 to 108 such that the differential quadrupoles array 10 operates in SIM mode over the axial section in which the differential quadrupoles 105 to 108 are located and fragment ions of a second mass to charge ratio are selected to pass through to the ion detector 30; ions/fragment ions of non-conforming mass-to-charge ratio impinge on the metal plate along ion travel path 230 and do not reach ion detector 30. Thus, the differential quadrupole array 10 is configured as a triple tandem quadrupole by the digital driving circuit, and the functions of ion collision and ion selection are realized.

Alternatively, the differential quadrupole array 10 can also be operated in TTI mode or scanning mode over the axial sections of the differential quadrupoles 105 to 108 by adjusting the voltages applied across the differential quadrupoles 105 to 108 by a digital drive circuit.

In the fourth embodiment of fig. 5, unlike the third embodiment, the axial sections in which the differential quadrupoles 101 to 104 are arranged as the first quadrupoles of the triple tandem quadrupoles, the axial sections in which the differential quadrupoles 105 to 106 are arranged as the second quadrupoles of the triple tandem quadrupoles, and the axial sections in which the differential quadrupoles 107 to 108 are arranged as the third quadrupoles of the triple tandem quadrupoles, while the second gas inlets 122 on the second radial plane S2 are enabled and the first gas inlets 120 on the first radial plane S1 are disabled to form the gas space or collision cell described above on the axial sections including the second radial plane S2. In this way, the number of differential quadrupoles used to select precursor ions having a first mass to charge ratio can be increased, and thus the path that precursor ions pass through when selected in the first quadrupoles is prolonged, which in some cases can increase the accuracy of ion selection of precursor ions. Accordingly, in this embodiment, the path travelled by the fragment ions in the differential quadrupole is shortened, and when the TTI mode is operated on the axial section in which the differential quadrupoles 107 to 108 are located, appropriate shortening of the path travelled by the fragment ions in the differential quadrupoles does not have an adverse effect.

This means that by individually controlling the voltages applied to the differential quadrupoles, the length of the individual functional areas formed by the differential quadrupoles array 10, which are of limited length, can be reasonably distributed. Furthermore, the absence of radially extending spacers between the differential quadrupoles 101 to 108 also facilitates the length distribution of the respective functional regions.

In the fifth embodiment of fig. 6, unlike the first embodiment, differential quadrupoles 103 and 106 are applied with a dc voltage of opposite polarity to the ions to form an axial confinement field in which the ions are confined, thereby configuring differential quadrupoles array 10 as a linear ion trap to perform the function of a linear ion trap or ion confinement. Furthermore, the axial binding field may also be formed in other ways, including by an rf alternating voltage or a combination of an rf alternating voltage and a dc voltage.

Furthermore, no direct voltage is applied to the differential quadrupoles 104 and 105, but only a radio frequency voltage RF is applied, so that the differential quadrupoles array 10 operates in TTI mode over the axial section in which the differential quadrupoles 104 to 105 are located. At the same time, gas may be released through the first gas inlet 120 and/or the second gas inlet 122, forming the gas space or collision cell described above within the axial section of the differential quadrupoles 103-106. The ions to be bound collide with gas molecules in the collision cell and dissociate when they reciprocate along the ion movement path 250 between the differential quadrupoles 103 and 106, thereby realizing the ion collision function.

After a predetermined time, the bound ions shuttle several back and forth within the axial sections of the differential quadrupoles 103-106 and undergo multiple collisions and dissociation. At this point, the application of a dc voltage and/or rf alternating voltage to the end differential quadrupole 106 may be stopped by the digitizing drive circuit to cause the fragment ions to reach the ion detector 30 along the ion path 260. In this case, the voltage applied across the differential quadrupoles 106 to 108 can also be adjusted by the digital drive circuit to operate the differential quadrupoles array 10 in TTI mode (as shown in fig. 6), scan mode or SIM mode over the axial sections of the differential quadrupoles 106 to 108.

In the sixth embodiment of fig. 7, unlike the first embodiment, a first direct voltage and a first radio frequency voltage DC/RF are applied across the differential quadrupoles 101 and 102 such that the differential quadrupoles array 10 operates in SIM mode over the axial section in which the differential quadrupoles 101 to 102 are located and precursor ions having a first mass to charge ratio are selected to pass through; a first direct-current voltage DC is applied to the differential quadrupole 103 and a second direct-current voltage DC, which is greater than the first direct-current voltage, is applied to the differential quadrupole 106, so that an accelerating electric field (similar to an ion drift tube) in the axial direction is formed between the differential quadrupoles 103 and 106; no direct voltage but only a radio frequency voltage RF is applied across the differential quadrupoles 104 and 105, so that the differential quadrupoles array 10 operates in TTI mode over the axial section in which the differential quadrupoles 104 to 105 are located. At the same time, the second gas inlet 122 releases a buffer gas that forms a gas space in the axial section where the differential quadrupoles 103 to 106 are located and a counter flow opposite to the axial movement direction of the ions in the central region. The precursor ions have the same mass-to-charge ratio, but the structures of the precursor ions may be different, so that the ion mobility of the precursor ions is different, and the relative positions among the ions are changed according to the ion mobility of the precursor ions in the process of interaction with the buffer gas, so that the ions with different structures are separated, and the ion mobility separation function is realized. For example, in fig. 7, more compact ions move along an ion motion path 270 and more relaxed ions move along an ion motion path 280.

Alternatively, a direct increasing voltage may be applied across differential quadrupoles 103 to 106 within the gas space to achieve ion acceleration and ion mobility separation functions in the gas space.

Additionally, a differential quadrupole, for example differential quadrupole 103, at the front end of the gas space can also be configured as the aforementioned ion gate in order to introduce ions into the gas space in batches.

Furthermore, the differential quadrupoles 107 to 108 may be suitably energized as needed to operate their axial sections in, for example, TTI mode. In this way, a part of the differential quadrupole array 10 is configured as an ion drift tube by controlling the digital driving circuit, and the ion mobility separation function is realized therein.

Based on the above embodiments, appropriate voltages can be applied to the differential quadrupoles in any axial section as desired to achieve the above functions and combinations thereof in any order, including ion acceleration/deceleration, ion convergence/divergence, ion selection, ion collision, linear ion trap, and ion mobility separation.

In the above embodiment, only a differential quadrupole array 10 consisting of eight sets of differential quadrupoles 101-108 is shown. However, the differential quadrupole array 10 can include more sets of differential quadrupoles. Furthermore, the thickness of the metal plates of each set of differential quadrupoles is preferably the same and in the range of 0.1-2mm, and the axial spacing between adjacent differential quadrupoles is preferably the same and in the range of 0.1-2 mm. A metal plate having a certain thickness can form a desired electric field at the radially inner edge, however, a too thick metal plate is disadvantageous for shaping by means of stamping or laser cutting. The spacing between the metal plates is too narrow, so that the risk of voltage breakdown is high; too wide a spacing between the metal plates can result in a combined electric field that differs too much from the electric field created by conventional quadrupoles, affecting the functioning of the functional regions of the differential quadrupoles array, for example, degrading the accuracy of ion selection.

In one embodiment, the array of differential quadrupoles comprises 1024 sets of differential quadrupoles, each set of differential quadrupoles comprising four metal plates of 0.1mm thickness with a hyperbolic radially inward profile, the 1024 sets of differential quadrupoles being disposed at 0.1mm intervals along the axial direction, all of the differential quadrupoles being individually controlled by a digitizing drive circuit.

In another embodiment, the array of differential quadrupoles comprises 256 sets of differential quadrupoles, each set comprising four metal plates of thickness 2mm, the radially inner profile of the metal plates being hyperbolic, the 256 sets of differential quadrupoles being arranged at intervals of 2mm in the axial direction, all of the differential quadrupoles being individually controlled by a digitizing drive circuit.

Fig. 8 shows another embodiment of the differential quadrupole rod array of the present utility model, which differs from the above embodiment in that an insulating structure 109 is provided between the metal plates of adjacent differential quadrupole rods. For example, the insulating structure 109 may be an insulating coating applied on the axial end face of the metal plate, or an insulating sheet provided between adjacent metal plates. Such an insulating structure 109 is effective in preventing voltage breakdown between metal plates, so that the axial spacing between adjacent differential quadrupoles may be less than 2mm, and in particular may be less than 0.1mm. The smaller the spacing between adjacent differential quadrupoles, the more closely the combined electric field created by superposition of the sub-fields of each set of differential quadrupoles approximates the electric field created by a conventional differential quadrupole, thus improving, for example, the accuracy of ion selection.

In addition, as described above, ions with a satisfactory mass-to-charge ratio pass through the differential quadrupole rods, while ions with an unsatisfactory mass-to-charge ratio strike the metal plates of the differential quadrupole rods. In order to prevent the accumulation of these ions of undesirable mass to charge ratio and possibly neutral molecules doped in between on the metal plate of the differential quadrupole, a heating device and a temperature sensor may be provided in the mass spectrometer, the metal plate of the differential quadrupole being heated by the heating device and the temperature being controlled at, for example, 100 degrees celsius by the temperature sensor. The thermal motion of the metal atoms on the surface of the heated metal plate is more intense so that ions and neutral molecules cannot adhere to and accumulate thereon.

The foregoing description of various embodiments of the utility model has been presented for the purpose of illustration to one of ordinary skill in the relevant art. It is not intended that the utility model be limited to the exact embodiment disclosed or as illustrated. As above, many alternatives and variations of the present utility model will be apparent to those of ordinary skill in the art. Thus, while some alternative embodiments have been specifically described, those of ordinary skill in the art will understand or relatively easily develop other embodiments. The present utility model is intended to embrace all alternatives, modifications and variations of the present utility model described herein and other embodiments that fall within the spirit and scope of the utility model described above.

Reference numerals illustrate:

1. Mass spectrometer

10. Differential quadrupole rod array

20. Ion source

30. Ion detector

40. Shell body

50. 60 Spacer

101-108 Differential quadrupole rod

101A-101D metal plate

109 Insulating structure

110 Ion transmission channel

120 First air inlet

122 Second air inlet

130 Air extraction opening

200 Ion motion path

210 Ion motion path

220 Ion motion path

230 Ion motion path

240 Ion motion path

250 Ion motion path

260 Ion motion path

270 Ion motion path

280 Ion motion path

L axis

S1 first radial plane

S2 second radial plane

DC voltage

RF radio frequency voltage

DC/RF DC voltage superimposed radio frequency voltage

Voltages applied to differential quadrupoles of each set U1-U8

A pair of voltages applied to a first set of differential quadrupoles of U1 ⁺

Another pair of voltages applied to the first set of differential quadrupoles of U1 ^-

Claims

1. A differential quadrupole rod array comprising a plurality of sets of differential quadrupole rods, each set of differential quadrupole rods comprising four metal plates extending in a radial plane of the differential quadrupole rod array and having identical contour lines, the four metal plates being rotationally symmetrically arranged in the radial plane, the plurality of sets of differential quadrupole rods being arranged in a sequential and aligned manner along an axial direction and forming ion transport channels extending along the axial direction, characterized in that each set of differential quadrupole rods is individually controlled by a digitizing drive circuit.

2. The differential quadrupole rod array of claim 1, wherein the differential quadrupole rod array is configured as pre-quadrupoles, single quadrupoles, tandem quadrupoles, linear ion traps, ion drift tubes, and combinations thereof by controlling the digitizing drive circuit so as to achieve ion convergence/divergence, ion selection, ion collision, linear ion trap, and/or ion mobility separation functions, and the order of the aforementioned functions can be defined as desired.

3. A differential quadrupole rod array according to claim 1, characterized in that at least one modulatable electric field distributed along the axial direction is formed on the differential quadrupole rod array by controlling the digitizing drive circuit, the direction and/or intensity and/or axial length of the modulatable electric field being changeable by the digitizing drive circuit.

4. A differential quadrupole rod array according to claim 3, wherein the modulatable electric field is a plurality of electric fields differing in direction and/or intensity and/or axial length.

5. The differential quadrupole rod array of claim 1, wherein one or more sets of differential quadrupole rods at any location of the differential quadrupole rod array are configured as ion gate by controlling the digitizing drive circuit.

6. A differential quadrupole rod array according to claim 1, wherein the radially inner profile of the metal plate is hyperbolic.

7. A differential quadrupole rod array according to claim 1, wherein the metal plate is formed by precision stamping or laser cutting on a metal sheet or printed circuit board.

8. A differential quadrupole rod array according to claim 1, wherein the thickness of the metal plates is 0.1-2mm and the axial spacing between the metal plates in the axial direction is 0.1-2mm.

9. A differential quadrupole rod array according to claim 1, characterized in that an insulating structure is arranged between the metal plates, the insulating structure being an insulating coating applied on the axial end faces of the metal plates or an insulating sheet arranged between adjacent metal plates.

10. A differential quadrupole rod array according to claim 9, wherein the axial spacing between the metal plates in the axial direction is less than 2mm.

11. A differential quadrupole rod array according to claim 10, wherein the axial spacing between the metal plates in the axial direction is less than 0.1mm.

12. A differential quadrupole rod array according to claim 1, wherein the metal plate is kept at a constant temperature in an operating state by a heating means and a temperature sensor.

13. A mass spectrometer comprising a housing and an ion source and an ion detector mounted within the housing, wherein the mass spectrometer is provided with a differential quadrupole array according to any one of claims 1-12 between the ion source and the ion detector.

14. The mass spectrometer of claim 13, in which one or more gas inlets are provided on an inner wall of the mass spectrometer, the gas inlets being configured to release gas into the array of differential quadrupoles to form a gas space corresponding to the location of the gas inlets.

15. The mass spectrometer of claim 14, in which a radio frequency alternating voltage is applied by the digitizing drive circuit across differential quadrupoles within the gas space to achieve ion acceleration and ion collisions functions within the gas space.

16. The mass spectrometer of claim 15, in which the rf alternating voltage applied across the differential quadrupoles in the gas space is increasing.

17. The mass spectrometer of claim 14, wherein a direct voltage and/or a radio frequency alternating voltage is applied across differential quadrupoles of the gas space by the digitizing drive circuit to perform the function of a linear ion trap within the gas space.

18. The mass spectrometer of claim 17, wherein the application of the dc voltage and/or rf alternating voltage to the differential quadrupole at the end of the gas space is stopped by the digitizing drive circuit after a predetermined time has elapsed.

19. The mass spectrometer of claim 14, wherein a direct current voltage is applied across differential quadrupoles across the gas space or a direct current increasing voltage is applied across differential quadrupoles within the gas space by the digitizing drive circuit to achieve ion acceleration and ion mobility separation functions within the gas space.

20. The mass spectrometer of claim 13, in which there are no radially extending spacers between the sets of differential quadrupoles to form an isolation chamber.