Device and method for rapid detection of ion signals in mass spectrometer using graphene electrode

Abstract

The present invention relates to the technical field of mass spectrometry instruments, and in particular to a device and method for rapid detection of ion signals in a mass spectrometer using a graphene electrode. The device comprises a mass spectrometer mass analyzer, a graphene electrode, a graphene electrode group, and a current or voltage measuring device; the graphene electrode is installed on one side of the ion extraction end of the mass spectrometer mass analyzer, and a plurality of small holes for ions to pass through are provided on the graphene electrode, which is used for the passage of ions separated from the mass spectrometer mass analyzer; wherein: when the graphene electrode group is 2 electrodes, the current and voltage detection device is directly connected to the 2 electrodes; when the graphene electrode group is 3 or more electrodes, the current signal of ions passing through each graphene electrode can be measured separately, and the current signal generated when ions pass through two adjacent electrodes can also be measured. The graphene material of the present invention has excellent conductivity, high strength, stability, and reduces the replacement of electrode materials.

Description

Technical Field

[0001] The present invention relates to the technical field of mass spectrometry instruments, and in particular to a device and method for quickly detecting ion signals in a mass spectrometer using a graphene electrode. Background Art

[0002] Mass spectrometer is one of the high-end scientific instruments in the current analytical instruments. It can analyze various chemical components in samples quickly, accurately and with high sensitivity. It is widely used in various fields such as scientific research, environmental protection, medicine and health, food safety, etc. When mass spectrometer analyzes chemical components, its basic working principle is to place the generated sample ions, that is, various molecular ions, in an electric field or magnetic field, and then analyze them according to the movement process of the ions in the electric field or magnetic field and the mass-to-charge ratio of the ions, and their differences in space or time. The mass spectrometry analysis results can be obtained by measuring the ion signals of different mass-to-charge ratios that are distinguished in space or time. According to the different principles on which the mass analyzer relies, such as which electric field or magnetic field is used to distinguish ions, mass spectrometers are divided into several categories, such as magnetic mass spectrometer, time-of-flight mass spectrometer, quadrupole mass spectrometer, quadrupole ion trap mass spectrometer, orbital ion trap mass spectrometer, and ion cyclotron resonance mass spectrometer. Although the principles and types of mass spectrometers vary, they are all composed of the following main parts, namely, an ion source that produces sample molecular ions, an ion mass analyzer that distinguishes the mass-to-charge ratio of ions, and an ion signal detection device. The ion signal detection device in the mass spectrometer is one of the core components of the mass spectrometer. Its function is to obtain mass spectrometry signals corresponding to ions and ion quantities. There are several methods commonly used to detect ions, one of which is an ion detector, or electron multiplier, including a channel electron multiplier and a microchannel plate electron multiplier. They are widely used in almost all current magnetic mass spectrometers, quadrupole mass spectrometers, ion trap mass spectrometers, and time-of-flight mass spectrometers. Its working principle is as follows: Figure 1 As shown, its basic working process is that when ions with a certain energy hit the surface of the ion detector, more than one secondary electron will be generated. Under the action of the working voltage of the ion detector, the secondary electron will continue to hit the surface of the ion detector, generating more and more electrons, and so on, until finally an electron flow related to the incident ion is output from the tail end of the ion detector. By recording this electron flow signal, a mass spectrum signal corresponding to a certain mass-to-charge ratio is obtained.

[0003] Ion detectors are consumables in mass spectrometers, that is, the electron multipliers currently used have a certain service life. The main reasons are: (1) All electron multipliers will age due to the aging of their manufacturing materials, resulting in lower and lower electron multiplication efficiency, that is, for the same incident ions, the mass spectrometry signal obtained will become weaker and weaker; therefore, all electron multipliers have a certain service life; (2) Electron multipliers produced by different electron multiplier manufacturers and different batches may have different final electron multiplication efficiencies due to differences in the materials or processes used, which may cause the mass spectrometry signals generated by equal numbers of incident ions to be unequal in size; (3) In theory, the total amount of secondary electrons generated in the ion detector by the N ions output by the mass analyzer should be equal to N times that of one ion. However, since the secondary electron emission capacity of the material is limited, if a large number of ions or electrons collide with the very small surface area of ​​the electron multiplier in a very short time, the number of secondary electrons generated often has an upper limit, resulting in the so-called signal "saturation" phenomenon, resulting in inaccurate quantitative analysis results. (4) Experiments have shown that electron multipliers often have a mass discrimination effect, that is, an ion with a large mass-to-charge ratio and a large volume produces different numbers of secondary electrons than an ion with a small mass-to-charge ratio and a small volume. This ultimately results in different mass spectrometry signal intensities for the same number of "large ions" and "small ions", resulting in inaccurate analysis results. Electron multipliers, as consumables, are not only expensive, but also inconvenient to replace.

[0004] In view of the importance of ion detectors, i.e., electron multipliers, to mass spectrometers and the defects of electron multipliers themselves, the present invention provides a brand-new ion signal detection device and method for mass spectrometers. In this device and method, a graphene electrode and a current and voltage measuring device connected to the graphene electrode are used. The graphene electrode is processed with numerous small holes through which ions can pass. This electrode is installed at the ion extraction end of any mass analyzer; according to the electromagnetic principle, when ions pass through the graphene electrode, a current signal will be generated. The current signal generated by the ions passing through the graphene electrode is measured, and the mass spectrum signal for these ions is obtained. And the traditional device and method for measuring ion mass spectrum signals using electron multipliers. The present invention has a simple device structure, low cost, is difficult to be damaged, does not cause saturation and mass discrimination effects, and can achieve high-sensitivity testing of ion mass spectrum signals. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a graphene electrode for a rapid detection device and method of ion signals in a mass spectrometer. It can replace the existing ion detector or electron multiplier and be used in magnetic mass spectrometer, time-of-flight mass spectrometer, quadrupole mass spectrometer and quadrupole ion trap mass spectrometer to detect ion signals analyzed by various mass analyzers. The ion rapid detection device and method provided by the present invention include a graphene electrode and a current or voltage signal measuring device connected to the graphene electrode. The graphene electrode is installed on one side of the ion extraction end of the mass analyzer of the mass spectrometer, and a plurality of small holes for ions to pass through are provided on the graphene electrode for the passage of ions separated from the mass analyzer of the mass spectrometer. The graphene electrode used can be a single layer of graphene or a multilayer of graphene. The graphene electrode is processed with small holes for ions to pass through, and the size and number of the small holes are not limited.

[0006] The technical solution for achieving the purpose of the present invention is:

[0007] A device for quickly detecting ion signals in a mass spectrometer using a graphene electrode comprises a mass spectrometer mass analyzer, a graphene electrode, a graphene electrode group, and a current or voltage measuring device; the graphene electrode is installed on one side of the ion extraction end of the mass spectrometer mass analyzer, and a plurality of small holes for ions to pass through are arranged on the graphene electrode, so as to allow the ions separated from the mass spectrometer mass analyzer to pass through; wherein: when the graphene electrode group is composed of two electrodes, the current and voltage detecting device is directly connected to the two electrodes; when the graphene electrode group is composed of three or more electrodes, the current signal of the ions passing through each graphene electrode can be measured respectively, and the current signal generated when the ions pass through two adjacent electrodes can also be measured.

[0008] Furthermore, the mass spectrometer mass analyzer is any one of a time-of-flight mass analyzer, a quadrupole mass analyzer, an ion trap mass analyzer, a single focusing sector magnetic field mass analyzer, a double focusing sector magnetic field mass analyzer, other types of magnetic mass analyzers, or a combination of any of the above mass analyzers.

[0009] Furthermore, the graphene electrode is a single-layer graphene or a multi-layer graphene, and a plurality of small holes through which ions can pass are processed on the graphene electrode.

[0010] A method for using a graphene electrode in a rapid detection device for ion signals in a mass spectrometer, the detection method is as follows: According to the electromagnetic principle, when a charged particle passes through a plane in space, the current I generated is:

[0011]

[0012] In the above formula, ΔQ is the amount of charge that passes within ΔT time. For a single charge, its charge is 1.6*10-19 Cullen;

[0013] Generally speaking, the thickness of a single-layer graphene sheet is about 0.334nm, or 3.34*10 -10 In time-of-flight mass spectrometry, the velocity of ions leaving the ion extraction end of the time-of-flight mass analyzer is about 105 m / s. Therefore, the time taken for ions to pass through the single-layer graphene electrode is:

[0014]

[0015] Therefore, the current generated by a singly charged ion passing through a single-layer graphene electrode is:

[0016]

[0017] If the final measurement is a voltage signal and the sampling resistor is 1000 ohms, the measured voltage signal is:

[0018] V = 5E-5*1000 = 50mV

[0019] If 10 singly charged ions pass through a single-layer graphene electrode at the same time, the measured voltage signal is:

[0020] V 10 =50mV*10=500mV

[0021] If an ion with 10 charges, such as a biomacromolecule ion produced by electrospray ionization, passes through a single-layer graphene electrode, the voltage generated by it can also be calculated using the above principle.

[0022] Furthermore, when measuring the current generated by the movement of ions between two adjacent graphene electrodes, the ion current measurement method is as follows:

[0023] According to the principles of electromagnetism, when a charged particle passes through two adjacent electrodes, the current I generated between the two electrodes is:

[0024]

[0025] In the above formula, ΔQ is the amount of charge that passes through in ΔT time. For a single charge, its charge is 1.6*10-19 coulombs, and ΔT is the time it takes for the ion to pass through the distance between the two electrodes;

[0026] If two graphene electrodes are placed 1 mm apart in the experiment, the speed of ions leaving the ion extraction end of the time-of-flight mass analyzer is about 105 m / s. Therefore, the time taken for ions to pass through the single-layer graphene electrode is:

[0027]

[0028] Therefore, the current generated by a singly charged ion passing through a single-layer graphene electrode is:

[0029]

[0030] If the final measurement is a voltage signal and the sampling resistor is 1000 ohms, the measured voltage signal is:

[0031] V = 1.6E-11*1000 = 1.6E-8V

[0032] If 10 singly charged ions pass through a single-layer graphene electrode at the same time, the measured voltage signal is:

[0033] V 10 =1.6E-8V*10=1.6E-7V

[0034] If an ion with 10 charges, such as a biomacromolecule ion produced by electrospray ionization, passes through a single-layer graphene electrode, the voltage generated by it can also be calculated using the above principle.

[0035] The graphene electrode for measuring the ion signal of the mass analyzer of the present invention can be graphene composed of pure carbon or a graphene derivative containing other elements, and its preparation method and composition are not limited. It can be a single-layer graphene or a multi-layer graphene. In short, its preparation method and composition are not limited.

[0036] After adopting the technical solution, the present invention has the following positive effects:

[0037] (1) The present invention does not use a traditional ion detector, so there is no problem of detector aging, damage, and replacement, thus saving costs.

[0038] (2) The present invention measures the current signal generated by the movement of ions, the magnitude of which is only related to the number of ions and the number of charges carried by the ions. Therefore, there is no so-called signal saturation, mass discrimination, etc.

[0039] (3) The graphene material of the present invention has excellent conductivity, high strength and stability, and reduces the replacement of electrode materials.

[0040] (4) Theoretically, the current generated by N charges will be strictly equal to N times the current generated by one charge, that is, the mass spectrometry signal intensity generated by the same number of "large ions" and "small ions" (assuming that the "large ions" and "small ions" have the same number of charges) will be exactly the same, and the quantitative analysis results will be accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments and in conjunction with the accompanying drawings, wherein

[0042] Figure 1 This is a common schematic diagram of the time-of-flight mass spectrometry structure;

[0043] Figure 2 This is a schematic diagram of the operation of a traditional electron multiplier;

[0044] Figure 3 This is a working principle diagram of a single-layer graphene electrode of the present invention;

[0045] Figure 4 This is a working principle diagram of the multilayer graphene electrode of the present invention;

[0046] Figure 5 is a three-dimensional schematic diagram of a multilayer graphene electrode of the present invention;

[0047] Figure 6 It is a schematic diagram of the structure of an electrospray ionization-time-of-flight mass spectrometry-graphene electrode detection system constructed according to the technology provided by the present invention. DETAILED DESCRIPTION

[0048] (Example 1)

[0049] The present invention comprises a mass spectrometer mass analyzer, a graphene electrode, a graphene electrode group, and a current or voltage measuring device; the graphene electrode is installed on one side of the ion extraction end of the mass spectrometer mass analyzer, and a plurality of small holes for ions to pass through are arranged on the graphene electrode, which are used for the passage of ions separated from the mass spectrometer mass analyzer; wherein: when the graphene electrode group is two electrodes, the current and voltage detection device is directly connected to the two electrodes; when the graphene electrode group is three or more electrodes, the current signal of ions passing through each graphene electrode can be measured respectively, and the current signal generated when ions pass through two adjacent electrodes can also be measured.

[0050] The mass analyzer of the mass spectrometer is any one of a time-of-flight mass analyzer, a quadrupole mass analyzer, an ion trap mass analyzer, a single focusing sector magnetic field mass analyzer, a double focusing sector magnetic field mass analyzer, other types of magnetic mass analyzers, or a combination of any of several mass analyzers.

[0051] The graphene electrode is a single layer of graphene or a multilayer of graphene, and a number of small holes are processed on the graphene electrode to allow ions to pass through.

[0052] (Example 2)

[0053] Figure 1This is a complete schematic diagram of the time-of-flight mass spectrometer structure. After the substance is ionized by the ion source 1, it becomes a charged particle and enters the mass analyzer time-of-flight tube through the metal capillary 2. 3 is the high-voltage electrode plate of one section of the time-of-flight tube, and 4 is the other part of the low-voltage electrode plate (which can be grounded). Between 3 and 4 is the acceleration zone of the time-of-flight tube. After acceleration, the particles enter the free flight zone between 4 and 5 for free flight. Assuming that the mass of the sample ion is m and the charge it carries is e, the ion is accelerated in the accelerating electrode and the voltage it receives is V. The energy obtained by the ion after being accelerated is: E=eV. At this time, all the energy is converted into the kinetic energy of the ion, that is:

[0054]

[0055] The speed mentioned here refers to the speed at which the ions reach after being accelerated in the acceleration zone, so

[0056]

[0057] Assuming that the free flight distance of the ion is L, the time required for the ion to fly distance L is:

[0058]

[0059] For ions with different mass-to-charge ratios, their flight times are different. After passing through the mass analyzer, the ions reach the detector 6 where they continuously collide.

[0060] Figure 2 This is the working principle diagram of the detector. Ions enter the electron multiplier tube through the incident port. The number of ions doubles with each collision. After N consecutive collisions, the number of single ions becomes 2. n The electrons are collected by the electrodes behind the electron multiplier to obtain the current or voltage signals of the incident ions, which eventually become mass spectrometry signals.

[0061] Figure 4 It is a schematic diagram of the working principle of a single graphene electrode 10 of the present invention. When ions pass through the graphene electrode, an image current is generated. By measuring the current or voltage signal, the mass spectrum signal of the incident ion can be obtained.

[0062] A method for detecting a graphene electrode in a rapid detection device for ion signals in a mass spectrometer, the detection method being as follows:

[0063] According to the principles of electromagnetism, when a charged particle passes through a plane in space, the current I generated is:

[0064]

[0065] In the above formula, ΔQ is the amount of charge that passes through in ΔT time. For a single charge, its charge is 1.6*10 -19 Cullen;

[0066] Generally speaking, the thickness of a single-layer graphene sheet is about 0.334nm, or 3.34*10 -10 In time-of-flight mass spectrometry, the velocity of ions leaving the ion extraction end of the time-of-flight mass analyzer is about 105 m / s. Therefore, the time taken for ions to pass through the single-layer graphene electrode is:

[0067]

[0068] Therefore, the current generated by a singly charged ion passing through a single-layer graphene electrode is:

[0069]

[0070] If the final measurement is a voltage signal and the sampling resistor is 1000 ohms, the measured voltage signal is:

[0071] V = 5E-5*1000 = 50mV

[0072] If 10 singly charged ions pass through a single-layer graphene electrode at the same time, the measured voltage signal is:

[0073] V 10 =50mV*10=500mV

[0074] If an ion with 10 charges, such as a biomacromolecule ion produced by electrospray ionization, passes through a single-layer graphene electrode, the voltage generated by it can also be calculated using the above principle.

[0075] (Example 3)

[0076] Figure 3 It is a schematic diagram of the working principle of multiple groups of graphene electrodes 7 of the present invention. When ions pass through two adjacent electrode plates, the image current signal or voltage signal generated by detection is converted into the required mass spectrometry signal.

[0077] Figure 5 It is a three-dimensional structural diagram of multiple groups of graphene electrodes. Multiple groups of graphene electrodes are placed in parallel with small holes in the middle. Current or voltage detection devices are placed at both ends of the graphene electrodes.

[0078] Figure 6 The figure is a schematic diagram of the structure of the electrospray ionization-time of flight mass analyzer-graphene detection system constructed according to the technology provided by the present invention. Figure 6In the graphene electrode, the charged particles separated by the mass analyzer are emitted from the emission port 5, pass through the deflection electrode, and enter the graphene electrode. The size of the particles can be obtained from the previous analysis.

[0079] When measuring the current generated by the movement of ions between two adjacent graphene electrodes, the ion current measurement method is as follows:

[0080] According to the principles of electromagnetism, when a charged particle passes through two adjacent electrodes, the current I generated between the two electrodes is:

[0081]

[0082] In the above formula, ΔQ is the amount of charge that passes through in ΔT time. For a single charge, its charge is 1.6*10-19 coulombs, and ΔT is the time it takes for the ion to pass through the distance between the two electrodes;

[0083] If two graphene electrodes are placed 1 mm apart in the experiment, the speed of ions leaving the ion extraction end of the time-of-flight mass analyzer is about 105 m / s. Therefore, the time taken for ions to pass through the single-layer graphene electrode is:

[0084]

[0085] Therefore, the current generated by a singly charged ion passing through a single-layer graphene electrode is:

[0086]

[0087] If the final measurement is a voltage signal and the sampling resistor is 1000 ohms, the measured voltage signal is:

[0088] V = 1.6E-11*1000 = 1.6E-8V

[0089] If 10 singly charged ions pass through a single-layer graphene electrode at the same time, the measured voltage signal is:

[0090] V 10 =1.6E-8V*10=1.6E-7V

[0091] If an ion with 10 charges, such as a biomacromolecule ion produced by electrospray ionization, passes through a single-layer graphene electrode, the voltage generated by it can also be calculated using the above principle.

[0092] Obviously, in the device and method for rapid detection of ion signals in a mass spectrometer using a graphene electrode provided in the present invention, there is no need to use an electron multiplier for ion signal detection.

[0093] It is worth noting that the above is only a preferred embodiment of the present invention, and does not limit the patent protection scope of the present invention. The present invention can be used not only for time-of-flight mass spectrometry but also for any other mass spectrometers such as quadrupole mass spectrometry, quadrupole ion trap mass spectrometry, and sector magnetic mass spectrometry. The present invention can also improve the materials and structures of the above-mentioned various components, or replace them with technical equivalents. Therefore, all equivalent structural changes made using the description and illustrations of the present invention, or directly or indirectly applied to other related technical fields are also included in the scope of the present invention.

Claims

1. A graphene electrode is used in a rapid detection device of ion signals in a mass spectrometer, characterized in that: The invention comprises a mass spectrometer mass analyzer, a graphene electrode, a graphene electrode group, and a current or voltage measuring device; the graphene electrode is installed on one side of the ion extraction end of the mass spectrometer mass analyzer, and a plurality of small holes for ions to pass through are arranged on the graphene electrode, so as to allow the ions separated from the mass spectrometer mass analyzer to pass through; the graphene electrode is a single-layer graphene or a multi-layer graphene; wherein: when the graphene electrode group is two electrodes, the current and voltage detecting device is directly connected to the two electrodes; when the graphene electrode group is three or more electrodes, the current signal of the ions passing through each graphene electrode can be measured respectively, and the current signal generated when the ions pass through two adjacent electrodes can also be measured.

2. The graphene electrode according to claim 1 is used for a rapid detection device of ion signals in a mass spectrometer, characterized in that: The mass analyzer of the mass spectrometer is any one of a time-of-flight mass analyzer, a quadrupole mass analyzer, an ion trap mass analyzer, a single focusing sector magnetic field mass analyzer, a double focusing sector magnetic field mass analyzer, other types of magnetic mass analyzers, or a combination of any of the above mass analyzers.

3. A detection method for a rapid detection device of ion signals in a mass spectrometer using the graphene electrode according to claim 1, characterized in that: The detection method is as follows: According to the principles of electromagnetism, when a charged particle passes through a plane in space, the current I generated is: In the above formula, ΔQ is the amount of charge that passes within ΔT time. For a single charge, its charge is 1.6*10 -19 Cullen; Generally speaking, the thickness of a single-layer graphene sheet is about 0.334nm, or 3.34*10 -10 In a time-of-flight mass spectrometer, the speed at which ions leave the ion extraction port of a time-of-flight mass analyzer is about 10 5 m / s, so the time taken for the ions to pass through the single-layer graphene electrode is: Therefore, the current generated by a singly charged ion passing through a single-layer graphene electrode is: If the final measurement is a voltage signal and the sampling resistor is 1000 ohms, the measured voltage signal is: V = (5E-5) * 1000 = 50mV If 10 singly charged ions pass through a single-layer graphene electrode at the same time, the measured voltage signal is: V 10 =50mV*10=500mV If an ion with 10 charges passes through a single-layer graphene electrode, the voltage generated can also be calculated using the above principle.

4. The method for detecting a graphene electrode used in a rapid detection device for ion signals in a mass spectrometer according to claim 3, characterized in that: When measuring the current generated by the movement of ions between two adjacent graphene electrodes, the ion current measurement method is as follows: According to the principles of electromagnetism, when a charged particle passes through two adjacent electrodes, the current I generated between the two electrodes is: In the above formula, ΔQ is the amount of charge that passes within ΔT time. For a single charge, its charge is 1.6*10 -19 Coulomb, ΔT is the time taken for an ion to pass through the distance between two electrodes; If two graphene electrodes are placed 1 mm apart in the experiment, the ions will move at a speed of about 10 5 m / s, so the time taken for the ions to pass through the single-layer graphene electrode is: Therefore, the current generated by a singly charged ion passing through a single-layer graphene electrode is: If the final measurement is a voltage signal and the sampling resistor is 1000 ohms, the measured voltage signal is: V=(1.6E-11)*1000=1.6E-8V If 10 singly charged ions pass through a single-layer graphene electrode at the same time, the measured voltage signal is: V 10 =(1.6E-8V)*10=1.6E-7V If an ion with 10 charges passes through a single-layer graphene electrode, the voltage generated can also be calculated using the above principle.

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