Microwave induced plasma ion source coupled to a multi-cup mass spectrometer

Abstract

The application discloses a microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device, which comprises a gas sampling system, a plasma ion source, an interface, an ion lens system, a mass analyzer and a multi-receiving detector which are sequentially connected; wherein the plasma ion source is a microwave-induced plasma ion source, and the interface is connected with a vacuum pump. The microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device can realize high-precision and accurate determination of oxygen isotopes in oxygen.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical analysis, in particular to a microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device. BACKGROUND

[0002] Plasma is formed by the energy induced transfer of standing wave in the resonant cavity, and is maintained in the quartz tube or ceramic tube located in the resonant cavity. This electrodeless system is called microwave-induced plasma. One of the great advantages of microwave-induced plasma is that Ar and He plasma can be easily realized. Since He plasma has a higher ionization energy, it is widely used in the determination of non-metal elements. Currently, microwave-induced plasma is usually connected with atomic emission spectrometry, quadrupole mass spectrometry and time-of-flight mass spectrometry. Due to the limitation of the selected mass spectrometer being a single-receiving cup mass spectrometer, the above devices can usually achieve accurate determination of element content, but their precision and accuracy are poor when determining isotopic composition.

[0003] Oxygen is the main component of crust and mantle rocks and fluids, and is the most abundant element in silicate earth. Oxygen isotope is considered to be an effective means to study many geological processes, and has been widely used in many frontier scientific research fields such as continental formation and evolution, early history of the earth, magmatic-hydrothermal process and mineralization, crust-mantle material composition and interaction, ancient ocean and ancient climate change, and planetary geology and celestial evolution.

[0004] At present, the most commonly used method for determining isotopic composition is a multi-receiving inductively coupled plasma mass spectrometer. However, the ion source of the mass spectrometer is an argon ion source. The first ionization energy of argon (15.8 eV) is slightly higher than that of oxygen (13.6 eV). When the argon ion source is used, the ionization rate of oxygen is low, which will cause the problems of low signal intensity and large mass fractionation. Although the predecessors have also used helium inductively coupled plasma, there are difficulties in modifying a large number of hardware such as coils, torch tubes and radio frequency power sources, and the disadvantages of accelerating torch tube corrosion, serious interface discharge and difficulty in forming and maintaining. In addition, the inductively coupled plasma under normal pressure is also easily affected by N2, O2, H2O and CO2 in the air, and cannot fundamentally eliminate the interference of air. SUMMARY

[0005] The main purpose of the present application is to provide a microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device, which aims to realize high-precision and accurate determination of oxygen isotopes in oxygen.

[0006] In order to achieve the above purpose, the microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device provided by the present application comprises a gas sampling system, a plasma ion source, an interface, an ion lens system, a mass analyzer and a multi-receiving detector connected in sequence.

[0007] The plasma ion source is a microwave-induced plasma ion source, and the interface is connected with a vacuum pump.

[0008] Optionally, the gas sampling system comprises a working gas supply device connected with the microwave-induced plasma ion source through a conduit, and a gas terminal purification device is arranged on the conduit.

[0009] The application further provides a method for determining oxygen isotopes in oxygen gas, comprising the following steps:

[0010] S10. Providing a combination device of a microwave-induced plasma ion source and a multi-receiving cup mass spectrometer as described above;

[0011] S20. Vacuumizing the interface by the vacuum pump;

[0012] S30. Passing standard oxygen gas into the microwave-induced plasma ion source by the gas sampling system to ionize, and then sequentially entering the interface, the ion lens system, the mass analyzer and the multi-receiving detector to perform mass spectrum detection, so as to obtain sample mass spectrum data of the standard oxygen gas;

[0013] S40. Passing sample oxygen gas into the microwave-induced plasma ion source by the gas sampling system to ionize, and then sequentially entering the interface, the ion lens system, the mass analyzer and the multi-receiving detector to perform mass spectrum detection, so as to obtain sample mass spectrum data of the sample oxygen gas;

[0014] S50. Calibrating the sample mass spectrum data by the sample mass spectrum data to obtain oxygen isotope composition of the sample oxygen gas.

[0015] Optionally, in S20, the vacuum pump is used to vacuumize so that the air pressure in the interface is 0.2-0.3 mbar; and / or,

[0016] In S20, the pumping speed of the vacuum pump is set to 3 m 3 / h.

[0017] Optionally, in S30 and S40, the working gas of the microwave-induced plasma ion source is helium, and the flow rate of the helium is set to 100-700 ml / min.

[0018] Optionally, the purity of the sample oxygen gas and the standard oxygen gas is not less than 99.999%.

[0019] Optionally, in step S30, the injection flow rate of the standard oxygen is controlled by a gas mass flow meter with a range of 2 ml / min; and / or,

[0020] In step S40, the injection flow rate of the sample oxygen is controlled by a gas mass flow meter with a range of 2 ml / min.

[0021] Optionally, in step S30, the injection flow rate of the standard oxygen is set to ≤0.4 ml / min; and / or,

[0022] In step S40, the injection flow rate of the sample oxygen is set to ≤0.4 ml / min.

[0023] Optionally, in step S30 and step S40, the resolution of the mass analyzer is set to 3000-4000.

[0024] Optionally, the standard mass spectrum data and the sample mass spectrum data are ( 16 O 18 O) + / ( 16 O 16 O) + and / or,

[0025] In step S50, the oxygen isotope composition is δ 18 O.

[0026] In this technical solution, a microwave-induced plasma ion source is combined with a multi-collector mass spectrometer. First, oxygen is introduced into the microwave-induced plasma ion source using a gas injection system, where it is ionized. The ionized oxygen enters the ion lens system through the interface to be focused into an ion beam. The ion beam is then separated according to its mass-to-charge ratio in the mass analyzer. Finally, multi-collector detection is performed in a multi-collector detector to obtain mass spectrum data of oxygen. In this device, since the interface is connected to a vacuum pump, the interface can be evacuated to achieve a low pressure. This not only reduces the interference of atmospheric oxygen on the determination of oxygen isotopes in the measured oxygen, but also achieves low-pressure plasma conditions that further help to improve the ionization degree of oxygen, thereby increasing the signal strength of oxygen and greatly improving the precision and accuracy of oxygen isotope determination. In addition, the multi-collector mass spectrometer has the advantage of simultaneously receiving different isotopes, reducing the impact of plasma instability on the accuracy of oxygen isotope determination. Therefore, this technical solution combines the advantages of simultaneous isotope detection of multiple-collector mass spectrometers with the advantages of plasma high ionization energy to achieve high-precision and accurate determination of oxygen isotopes in oxygen. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a schematic structural diagram of a device combining a microwave-induced plasma ion source and a multi-collecting cup mass spectrometer proposed in the present invention;

[0029] Figure 2 Schematic diagram of the process for determining oxygen isotopes in oxygen proposed by the present invention;

[0030] Figure 3 This is a diagram showing the spectral peaks when measuring the oxygen isotope composition in Example 2 of the present invention;

[0031] Figure 4 In Example 3 of the present invention ( 16 O 16 O) + The signal intensity, background signal intensity and signal-to-noise ratio change with the helium flow rate;

[0032] Figure 5 For Example 4 of the present invention ( 16 O 16 O) + How the signal intensity, background signal intensity and signal-to-noise ratio change with power;

[0033] Figure 6 In Example 5 of the present invention ( 16 O 16 O) + How the signal intensity changes with oxygen flow rate;

[0034] Figure 7 The oxygen isotope determination accuracy in Example 6 of the present invention is as follows ( 16 O 16 O) + The signal intensity changes and the long-term accuracy of oxygen isotope determination are also analyzed.

[0035] Description of Figure Numbers:

[0036]

[0037] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0038] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments.

[0039] It should be noted that, in the embodiments, the specific conditions not mentioned are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not marked with the manufacturer, and are all conventional products that can be purchased on the market.

[0040] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. For example, "A and / or B" includes A scheme, or B scheme, or A and B scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it. When the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection claimed by the present application. Based on the embodiments in the present application, all other embodiments obtained by a person skilled in the art without creative labor are within the scope of protection of the present application.

[0041] In the prior art, a gas mass spectrometer is used to determine the oxygen isotopes in oxygen, and high-precision oxygen isotope composition can be determined. The present application aims to provide a new determination device different from the current gas mass spectrometer, so as to achieve high-precision and accurate determination of oxygen isotopes in oxygen.

[0042] In view of this, the present application provides a microwave-induced plasma ion source and a multi-receiving cup mass spectrometer combined device, please refer to Figure 1 The microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device 100 includes a gas sampling system 1, a plasma ion source, an interface 3, an ion lens system (not shown in the figure), a mass analyzer and a multi-receiving detector connected in sequence. Wherein, the plasma ion source is a microwave-induced plasma ion source 2, and the interface 3 is connected with a vacuum pump 31.

[0043] In the technical solution, the microwave-induced plasma ion source is combined with the multi-receiving cup mass spectrometer, oxygen is introduced into the microwave-induced plasma ion source 2 by the gas sampling system 1, ionization is realized in the microwave-induced plasma ion source 2, the ionized oxygen enters the ion lens system through the interface 3 to be focused into an ion beam, the ion beam is separated according to the mass-to-charge ratio in the mass analyzer, and finally multi-receiving detection is performed in the multi-receiving detector, so that the mass spectrum data of oxygen are obtained. In the device, the interface 3 is connected with the vacuum pump 31, so that the interface 3 can be vacuumized to realize low pressure, which not only reduces the interference of atmospheric oxygen on the determination of oxygen isotopes in the measured oxygen, but also realizes the low pressure plasma condition, which is more helpful to improve the ionization degree of oxygen, thereby improving the signal strength of oxygen and greatly improving the precision and accuracy of the determination of oxygen isotopes. In addition, the multi-receiving mass spectrometer has the advantage of simultaneous receiving of different isotopes, which reduces the influence of plasma instability on the precision of the determination of oxygen isotopes. Therefore, on the basis of the higher ionization energy of the plasma, the multi-receiving cup mass spectrometer is combined with the advantage of simultaneous receiving of isotopes to realize high-precision and accurate determination of oxygen isotopes in oxygen.

[0044] Further, the gas sampling system 1 comprises a working gas supply device 11 connected with the microwave-induced plasma ion source 2 through a conduit, and a gas terminal purification device 12 is arranged on the conduit. The working gas supply device 11 is used to inject working gas into the microwave-induced plasma ion source 2, and the working gas is purified once before being injected into the ion source through the arrangement of the gas terminal purification device 12, which helps to reduce the influence of oxygen and oxygen-containing compounds on the determination of oxygen isotopes. Of course, the working gas supply device 11 can be a gas tank or the like for storing working gas, and the specific structure of the working gas supply device 11 is not limited in the application; the gas terminal purification device 12 is a commonly used gas purification device in the art, and will not be described in detail herein.

[0045] Of course, the gas sampling system 1 further comprises a standard oxygen supply device 13 and a sample oxygen supply device 14, the standard oxygen supply device 13 is connected with the microwave-induced plasma ion source 2 through a conduit, and a flow meter 15 is arranged on the conduit, and the sample oxygen supply device 14 is connected with the microwave-induced plasma ion source 2 through a conduit, and a flow meter 15 is arranged on the conduit. Specifically, in the embodiment of the application, the standard oxygen supply device 13 and the sample oxygen supply device 14 are both gas tanks.

[0046] In addition, in order to further reduce the influence of air oxygen on the determination precision of oxygen isotopes, the plasma ion source 2 and the interface 3 are in sealed connection.

[0047] Specifically, in the embodiment of the present application, the vacuum pump 31 is a mechanical pump.

[0048] The present application also provides a method for determining oxygen isotopes in oxygen gas, which utilizes the mass spectrometer as described above to determine oxygen isotopes in sample oxygen gas, such as Figure 2 as shown, the method for determining oxygen isotopes in oxygen gas comprises the following steps:

[0049] Step S10, providing a combination device of a microwave-induced plasma ion source and a multi-receiving cup mass spectrometer as described above.

[0050] Step S20, vacuumizing the interface by the vacuum pump.

[0051] Specifically, in step S20, a vacuum pump is used to vacuumize so that the air pressure in the interface is 0.2-0.3 mbar, realizing better low pressure conditions. In step S20, the pumping speed of the vacuum pump is set to 3 m 3 / h, under the above pumping speed, the influence of oxygen in air can be further avoided.

[0052] Step S30, using the gas sampling system to pass standard oxygen gas into the microwave-induced plasma ion source for ionization, and then sequentially into the interface, the ion lens system, the mass analyzer and the multi-receiving detector for mass spectrometry detection, to obtain the standard sample mass spectrum data of the standard oxygen gas.

[0053] A great advantage of the microwave-induced plasma ion source is that it is easy to use helium or argon as working gas to realize helium plasma or argon plasma, and in the embodiment of the present application, helium is preferably used as working gas. Specifically, in step S30, the working gas of the microwave-induced plasma ion source is helium, and the flow rate of the helium is set to 100-700 ml / min, preferably, the flow rate of the helium is set to 100 ml / min. The microwave-induced plasma ion source uses helium as working gas to realize helium plasma, and helium plasma has higher ionization energy than argon plasma, because the first ionization energy of helium is 24.5 eV, which is much higher than the first ionization energy of argon (15.8 eV), and the higher first ionization energy of helium also ensures the ionization of oxygen in oxygen gas (the first ionization energy of oxygen is 13.6 eV), which can realize higher ionization degree of oxygen, ensuring the accuracy of the standard sample mass spectrum data, thereby improving the precision and accuracy of the determination of oxygen isotopes in standard oxygen gas.

[0054] In step S30, the sampling flow rate of the standard oxygen gas is controlled by a gas mass flow meter with a range of 2 ml / min, to better control the sampling flow rate of the standard oxygen gas.

[0055] In step S30, the sample flow rate of the standard oxygen is set to be ≤0.4 ml / min, preferably, the sample flow rate of the standard oxygen is 0.4 ml / min, so as to obtain the highest signal intensity while the dynamic linear relationship between the sample flow rate of the standard oxygen and the signal intensity is achieved, and the accurate determination of the oxygen isotopes is ensured.

[0056] In step S40, the sample oxygen is introduced into the microwave-induced plasma ion source by the gas sampling system for ionization, and then sequentially enters the interface, the ion lens system, the mass analyzer and the multi-receiving detector for mass spectrum detection, so as to obtain the sample mass spectrum data of the sample oxygen.

[0057] In step S40, the working gas of the microwave-induced plasma ion source is helium, and the flow rate of the helium is set to be 100-700 ml / min, preferably, the flow rate of the helium is set to be 100 ml / min. This also helps to achieve higher ionization degree of oxygen, ensure the accuracy of the sample mass spectrum data, and thus improve the precision and accuracy of the determination of the oxygen isotopes in the sample oxygen.

[0058] In step S40, the sample flow rate of the sample oxygen is controlled by the gas mass flow meter with a range of 2 ml / min, so as to better control the sample flow rate of the sample oxygen.

[0059] In step S40, the sample flow rate of the sample oxygen is set to be ≤0.4 ml / min, preferably, the sample flow rate of the sample oxygen is 0.4 ml / min, so as to obtain the highest signal intensity while the dynamic linear relationship between the sample flow rate of the sample oxygen and the signal intensity is achieved, and at the same time, the signal intensity of the sample oxygen is ensured to be consistent with the signal intensity of the standard oxygen, and the accurate determination of the oxygen isotopes is ensured.

[0060] In step S50, the sample mass spectrum data is externally corrected by the standard mass spectrum data, so as to obtain the oxygen isotope composition of the sample oxygen.

[0061] The standard mass spectrum data and the sample mass spectrum data are both the ratio of ( 16 O 18 O) + / ( 16 O 16 O) + In step S50, the oxygen isotope composition is δ 18 O , and thus the specific calculation formula of the oxygen isotope composition of the sample oxygen is as follows:

[0062] R= ( 16 O 18 O) + / ( 16 O16 O) + ;

[0063] r= 18 O / 16 O=R / (2+R);

[0064]

[0065] wherein, R is ( 16 O 16 O) + and ( 16 O 18 O) + the ratio of signal intensity, r is 18 O / 16 O the ratio of, r sample for the sample oxygen 18 O / 16 O the ratio of, r std for the standard oxygen 18 O / 16 O the ratio of.

[0066] It should be noted that the purity of the sample oxygen and the standard oxygen is not less than 99.999%, so that the sample oxygen and the standard oxygen are not affected by other impurities in the oxygen during the oxygen isotope determination process, and the accuracy of the oxygen isotope determination is improved.

[0067] And in steps S30 and S40, the resolution of the mass analyzer is set to 3000-4000, that is, the mass resolution of the mass analyzer m / Δm=3000-4000, the range of 3000-4000 is high mass resolution, which is beneficial to avoid the interference of ( 14 N 18 O) + and ( 16 O 16 O 1 H 1 H) + to ( 16 O 16 O) + and ( 16 O 18 O) + .

[0068] The determination method of the oxygen isotope in the oxygen provided by the application is simple and effective, and can be widely promoted. In addition, since the determination method uses the above-mentioned microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device for oxygen isotope determination, it has all the beneficial effects of the microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device, which will not be repeated here.

[0069] The technical solutions of the present application are further described in detail below in combination with specific examples and experimental data. It should be understood that the following examples are only used to explain the present application and do not limit the present application.

[0070] Example 1

[0071] (1) A microwave-induced plasma ion source and multi-receiving cup mass spectrometer combined device is provided, which comprises a gas sampling system, a plasma ion source, an interface, an ion lens system, a mass analyzer and a multi-receiving detector connected in sequence; wherein the plasma ion source is a microwave-induced plasma ion source, and the interface is connected with a vacuum pump.

[0072] (2) The interface is vacuumized by the vacuum pump, so that the air pressure in the interface is 0.2 mbar, and the pumping speed of the vacuum pump is set to 3 m 3 / h;

[0073] (3) The standard oxygen gas (purity 99.999%, sampling flow rate set to 0.4 ml / min) is introduced into the microwave-induced plasma ion source (working gas is helium, helium flow rate set to 100 ml / min) for ionization by using the gas sampling system, and then sequentially enters the interface, the ion lens system, the mass analyzer (resolution set to high mass resolution = 3800) and the multi-receiving detector for mass spectrometry to obtain the standard sample mass spectrum data of the standard oxygen gas;

[0074] (4) The sample oxygen gas (purity 99.999%, sampling flow rate set to 0.4 ml / min) is introduced into the microwave-induced plasma ion source (working gas is helium, helium flow rate set to 100 ml / min) for ionization by using the gas sampling system, and then sequentially enters the interface, the ion lens system, the mass analyzer (resolution set to high mass resolution = 3800) and the multi-receiving detector for mass spectrometry to obtain the sample mass spectrum data of the sample oxygen gas;

[0075] (5) The sample mass spectrum data is calibrated by using the standard sample mass spectrum data to obtain the oxygen isotope composition δ 18 O of the sample oxygen gas.

[0076] Steps (1)-(5) are performed on one standard oxygen gas and one sample oxygen gas (O2 samp ), and the oxygen isotope composition δ samp O of O2 18 is obtained, and the comparison results with the recommended values of the gas mass spectrometer (MAT 253) are shown in the following Table 1.

[0077] Table 1 delta 18 Measured value and MAT 253 recommended value of O

[0078]

[0079] As can be seen from Table 1, compared with the MAT 253 recommended value, the accurate oxygen isotope composition can be obtained by Example 1, and the determination precision is higher, about 0.14‰, which indicates that the combined equipment of the microwave-induced plasma ion source and the multi-receiving cup mass spectrometer provided by the application, and the oxygen isotope determination method for oxygen gas by using the combined equipment can realize high-precision and accurate determination of oxygen isotope in oxygen gas.

[0080] Example 2

[0081] The combined equipment provided by the application is used for oxygen isotope determination of oxygen gas with high mass resolution, and a spectrum peak condition diagram used for determination of oxygen isotope composition is obtained (see Figure 3 ). The mass spectrum detection is measured by 16 O 16 O + and 16 O 18 O + signal intensity, wherein the signal intensity of 17 O 16 O 17 O + cannot be determined due to too small abundance and too narrow platform. As can be seen from Figure 3 , under high mass resolution, the peak center is placed at the low mass end, and there is a very obvious interference peak at the high mass end, wherein the interference peaks at the high mass end of mass numbers 32 and 34 are peaks of 14 N 18 O + and 16 O 16 O 1 H 1 H + .

[0082] Example 3

[0083] The oxygen isotope determination of oxygen gas is carried out by using the combined equipment provided by the application, wherein the power of the microwave-induced plasma is 160W, the flow rate of oxygen gas introduced into the microwave-induced plasma ion source by the gas sampling system is 0.4ml / min, the pumping speed of the vacuum pump is 3m 3 / h, the flow rate of helium working gas introduced into the microwave-induced plasma ion source by the gas sampling system is 100-700ml / min, and 16 O 16 O+ The signal intensity, background signal intensity and sensitivity of Figure 4 .Depend on Figure 4 It can be seen that when the flow rate of helium increases from 100ml / min to 700ml / min, ( 16 O 16 O) + The signal intensity, background signal intensity and sensitivity all showed a decreasing trend. 16 O 16 O) + The sensitivity reaches its highest value when the helium flow rate is 100 ml / min.

[0084] Example 4

[0085] The oxygen isotope of oxygen was determined by the combined equipment provided by the present invention, and the power of microwave induced plasma was increased from 60W to 160W, and the result was ( 16 O 16 O) + The signal intensity, background signal intensity and signal-to-noise ratio are shown in Figure 5 .Depend on Figure 5 As can be seen, as the power increases from 60W to 160W, both the signal intensity and background signal gradually increase, but the sensitivity also increases linearly. This shows that in order to achieve higher sensitivity and high-precision and accurate determination of oxygen isotopes at low oxygen content, higher power is required.

[0086] Example 5

[0087] The oxygen isotope of oxygen is determined by the combined device provided by the present invention. The power of the microwave-induced plasma is 160W, the flow rate of the helium working gas introduced into the microwave-induced plasma ion source by the gas injection system is 100ml / min, and the flow rate of the oxygen introduced into the microwave-induced plasma ion source by the gas injection system is 0.04-0.52ml / min, wherein ( 16 O 16 O) + The signal intensity was measured to obtain the relationship between the signal intensity and the oxygen flow rate. The results are shown in Figure 6 .Depend on Figure 6 As can be seen, signal intensity is directly proportional to oxygen flow rate. However, when the oxygen flow rate is greater than 0.4 ml / min, the relationship between oxygen flow rate and signal intensity deviates from the dynamic linear relationship. This indicates that under experimental conditions, an oxygen flow rate of 0.04 to 0.4 ml / min is required to achieve an accurate dynamic linear range for the precise determination of oxygen isotopes in oxygen. To achieve a higher signal intensity, the present invention recommends using an oxygen flow rate of 0.4 ml / min.

[0088] Example 6

[0089] The oxygen isotope of oxygen was determined by the combination device provided by the application. The relationship between signal intensity and accuracy of oxygen isotope composition of oxygen and long-term determination accuracy was monitored. The data results show that 18 O / 16 O has an exponential relationship with the accuracy (1SE) of 16 O 16 O) + . The results are shown in Figure 7 . When the signal intensity of 16 O 16 O) + is lower than 5V, 18 O / 16 O has poor determination accuracy. However, as the signal intensity of 16 O 16 O) + increases from 5V to 15V, 18 O / 16 O determination accuracy is greatly improved. When the signal intensity of 16 O 16 O) + is higher than 15V, 18 O / 16 O determination accuracy gradually slows down. Considering that the maximum range of the Faraday cup is 50V, long-term determination of high signal will affect the service life of the Faraday cup. The application suggests that the signal intensity of 16 O 16 O) + is 10-12V.

[0090] After one year of long-term determination, the obtained δ 18 O value is 0.01±0.12‰ (2SD, n=186), and the results are shown in Figure 7 . Therefore, the long-term determination accuracy of δ 18 O obtained by the test method provided by the application is 0.12‰.

[0091] The above is only a preferred embodiment of the application, and does not limit the patent scope of the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the application shall be included in the patent protection scope of the application.

Claims

1. A device combining a microwave induced plasma ion source and a multi-collection cup mass spectrometer, characterized in that: It includes a gas injection system, a plasma ion source, an interface, an ion lens system, a mass analyzer, and a multi-receiver detector that are connected in sequence; The plasma ion source is a low-pressure microwave-induced helium plasma ion source, and the interface is connected to a vacuum pump, which is used to induce the gas pressure of the plasma ion source to be 0.2-0.3 mbar.

2. The combined device of microwave induced plasma ion source and multi-collection cup mass spectrometer according to claim 1, characterized in that: The gas sampling system comprises a working gas supply device, which is connected to the low-pressure microwave-induced helium plasma ion source via a conduit, and a gas terminal purification device is provided on the conduit.

3. A method for determining oxygen isotopes in oxygen, characterized in that: The method for determining oxygen isotopes in oxygen comprises the following steps: Step S10, providing a device combining the microwave induced plasma ion source and the multi-collecting cup mass spectrometer as claimed in claim 1 or 2; Step S20: vacuuming the interface by the vacuum pump; Step S30, using the gas injection system to pass standard oxygen gas into the low-pressure microwave-induced helium plasma ion source for ionization, and then sequentially passing the standard oxygen gas into the interface, the ion lens system, the mass analyzer, and the multi-collector detector for mass spectrometry detection, thereby obtaining standard sample mass spectrum data of the standard oxygen gas; Step S40: using the gas sampling system to pass the sample oxygen into the low-pressure microwave-induced helium plasma ion source for ionization, and then sequentially passing the sample oxygen into the interface, the ion lens system, the mass analyzer, and the multi-collector detector for mass spectrometry detection, thereby obtaining sample mass spectrum data of the sample oxygen; Step S50: calibrate the sample mass spectrum data using the standard mass spectrum data to obtain the oxygen isotope composition of the sample oxygen.

4. The method for determining oxygen isotopes in oxygen according to claim 3, wherein: In step S20, a vacuum pump is used to evacuate the interface so that the pressure inside the interface is 0.2-0.3 mbar; and / or, In step S20, the vacuum pump speed is set to 3 m 3 / h.

5. The method for determining oxygen isotopes in oxygen according to claim 3, wherein: In step S30 and step S40, the working gas of the low-pressure microwave-induced helium plasma ion source is helium, and the flow rate of the helium is set to 100-700 ml / min.

6. The method for determining oxygen isotopes in oxygen according to claim 3, wherein: The purity of the sample oxygen and the standard oxygen is not less than 99.999%.

7. The method for determining oxygen isotopes in oxygen according to claim 3, wherein: In step S30, the injection flow rate of the standard oxygen is controlled by a gas mass flow meter with a range of 2 ml / min; and / or, In step S40, the injection flow rate of the sample oxygen is controlled by a gas mass flow meter with a range of 2 ml / min.

8. The method for determining oxygen isotopes in oxygen according to claim 3, wherein: In step S30, the injection flow rate of the standard oxygen is set to ≤0.4 ml / min; and / or, In step S40, the injection flow rate of the sample oxygen is set to ≤0.4 ml / min.

9. The method for determining oxygen isotopes in oxygen according to claim 3, wherein: In step S30 and step S40, the resolution of the mass analyzer is set to 3000-4000.

10. The method for determining oxygen isotopes in oxygen according to claim 3, wherein: The standard mass spectrum data and the sample mass spectrum data are ( 16 O 18 O) + / ( 16 O 16 O) + and / or, In step S50, the oxygen isotope composition is δ 18 O.

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