A method for mass spectrometric determination of stable isotope abundances

Abstract

The present invention discloses a method for mass spectrometry determination of stable isotope abundances, comprising the following steps: Step 1, performing a magnetic field scan on stable isotopes using a mass spectrometer. After the magnetic field scan, select the spectrum obtained by a Faraday cup with appropriate signals, and use the valence state with obvious isotope signals in this spectrum as the ions to be measured; Step 2, preliminarily and roughly determine the abundance ratio from the isotope ion signals obtained in Step 1, and then select a Faraday cup for each isotope ion; Step 3, determine the magnetic field position of each isotope ion in the corresponding Faraday cup; Step 4, measure each isotope ion signal respectively at the corresponding magnetic field position to obtain each isotope ion signal value; Step 5, perform abundance calculation using each isotope ion signal value obtained in Step 4 to obtain the abundance of each stable isotope. The method of the present invention is simple to operate, has high efficiency, accurate measurement, and a wide application range.

Description

Technical Field

[0001] The present invention relates to the technical field of determining the abundance of stable isotopes by a gas mass spectrometer, and particularly to a method for mass spectrometric determination of the abundance of stable isotopes. Background Art

[0002] Different nuclides of the same element with the same number of protons but different numbers of neutrons are called isotopes of the element. According to whether they are radioactive, isotopes can be divided into two categories: radioactive isotopes and stable isotopes.

[0003] A stable isotope mass spectrometer is an instrument for quickly and accurately analyzing stable isotopes. Usually, a mass spectrometer is set according to the determination of certain specific stable isotopes. Especially for the Faraday cup that receives signals, once the position is fixed, it cannot be changed by the experimenter, which brings great limitations to the measurement personnel. Mass spectrometers are very expensive. If a mass spectrometer that meets the requirements needs to be purchased when measuring other stable isotopes, the cost is too high and the purchase cycle is long.

[0004] When it is necessary to measure other stable isotope substances, in many cases, the mass spectrometer cannot meet the measurement requirements and cannot automatically measure under the condition of fixed hardware. A stable isotope substance contains one isotope or multiple stable isotopes, and some even have up to more than a dozen isotopes, which is very difficult to measure.

[0005] Moreover, when the abundance of a certain isotope in the stable isotope is much higher than that of other isotopes, even close to 100%, and the abundances of other isotopes are so small that they are close to 0, it is very difficult to measure, and the usual measurement methods can no longer meet the requirements. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for mass spectrometric determination of the abundance of stable isotopes in view of the technical defects existing in the prior art.

[0007] Another purpose of the present invention is to provide an application of a mass spectrometry test method in the analysis of isotope abundance

[0008] The technical solution adopted to achieve the purpose of the present invention is as follows:

[0009] A method for mass spectrometric determination of the abundance of stable isotopes includes the following steps:

[0010] Step 1, using a mass spectrometer to perform a magnetic field scan on stable isotopes. After the magnetic field scan, each Faraday cup will obtain the signal values of each isotope. Observe the signal values of each isotope ion in each Faraday cup respectively, select the spectrum obtained by the Faraday cup with appropriate signals, and use the valence state with obvious isotope signals in this spectrum as the ion to be measured;

[0011] Step 2: Based on the isotope ion signals obtained in Step 1, roughly determine the abundance ratio initially. Then, select a Faraday cup for each isotope ion.

[0012] Step 3: Determine the magnetic field position of each isotope ion in the corresponding Faraday cup.

[0013] Step 4: Measure the signal of each isotope ion at the corresponding magnetic field position respectively to obtain the signal value of each isotope ion.

[0014] Step 5: Calculate the abundance using the signal value of each isotope ion obtained in Step 4 to obtain the abundance of each stable isotope.

[0015] In the above technical solution, the appropriate Faraday cup in Step 1 means that the ion signal in this Faraday cup is strong, within the range of the measuring range, without interference signals or the interference signals can be ignored.

[0016] In the above technical solution, the magnetic field scanning range in Step 1 is 1 - 14000.

[0017] The mass spectrometer is a MAT253 type gas isotope mass spectrometer, and the mass spectrometry determination method uses eight Faraday cups from cup1 to cup8.

[0018] In the above technical solution, the Faraday cup in Step 2 is selected by the following method:

[0019] If the signal value of an isotope ion in a certain Faraday cup is within the range of the measuring range and the magnitude is within the range of 10% - 70% of the upper limit of the measuring range, and compared with the background signal, the background signal can be ignored, then it can be used as a measurement scheme.

[0020] If the signal value of an isotope ion in a certain Faraday cup is within the range of the measuring range, but less than 10% of the upper limit of the measuring range, and the order of magnitude is close to the order of magnitude of the background, and the background signal cannot be ignored, then select the one with the largest magnification among multiple other Faraday cups as the measurement scheme.

[0021] If the signal value of an isotope ion in a certain Faraday cup is within the range of the measuring range, but the signal is too large, exceeding the measuring range, and the top of the peak shape is flat-top, then select the ones with smaller magnification among multiple other Faraday cups to make the signal value within the range of 10% - 70% of the upper limit of the measuring range, and compared with the background signal, the background signal can be ignored, as the measurement scheme.

[0022] In the above technical solution, the magnetic field position in Step 3 is determined by the following method: Set the initially determined magnetic field value, conduct a high-voltage scan, and observe whether the peak center of this isotope is at the set voltage position. If it is, determine this position. If not, continue to adjust the magnetic field position until the peak center is at the set voltage position.

[0023] In the above technical solution, when measuring the isotope ion signal in step 4, first perform background measurement at the corresponding magnetic field position to obtain the background measurement value, then introduce the sample, and then perform signal measurement at the corresponding magnetic field position to obtain the signal measurement value. The isotope ion signal value = signal measurement value - background measurement value.

[0024] In the above technical solution, the isotope includes one or more isotopes.

[0025] In the above technical solution, the isotope substance measured by the mass spectrometry test method is natural abundance or enriched and separated abundance.

[0026] On the other hand, the present invention provides an application of a mass spectrometry test method in isotope abundance analysis, where the isotope is one or more of Xe element, Ge element, C element, B element, and Si element.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. The method of the present invention realizes the determination of the abundance of general natural abundance stable isotopes, the determination of the abundance of target isotopes with high abundance in stable isotopes, the determination of the abundance of various types of stable isotopes, the rapid determination of stable isotope abundance, and the determination of stable isotopes with different types and different abundance gradients. At the same time, it enables the rapid determination of stable isotope substances with one or more isotopes.

[0029] 2. Compared with the single Faraday cup abundance measurement method, the method of the present invention has higher measurement efficiency and flexibility, can measure more types of stable isotopes, has a wider abundance range for measuring the same stable isotope, has a higher degree of automation combined with the instrument, does not require manual parameter switching and other operations during the measurement process, the measurement process is more concise, the program is complete, and it is easy to operate.

[0030] 3. The method of the present invention is simple to operate, has high efficiency, accurate measurement, and a wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the magnetic field scanning spectrum diagram of the stable isotope ion signal in Example 1.

[0032] Figure 2 It is the enlarged view of the isotope ion signal to be measured in Example 1.

[0033] Figure 3 It is the high-voltage scanning diagram in each Faraday cup in Example 1.

[0034] Figure 4 For Example 1 136 The high-voltage scanning diagram of Xe in cup8.

[0035] Figure 5 It is the flow chart of Xe isotope measurement in Example 1.

[0036] Figure 6 It is the flow chart of Xe isotope abundance measurement procedure.

[0037] Figure 7 It is the magnetic field scanning spectrum of Xe isotope in each Faraday cup after enrichment and separation.

[0038] Figure 8 It is the flow chart of high-abundance Xe abundance measurement in Example 2.

[0039] Figure 9 It is the magnetic field scanning spectrum of GeF4 sample in Example 3.

[0040] Figure 10 It is the enlarged view of the spectrum of signal ions in cup5 in Example 3.

[0041] Figure 11 It is the peak shape diagram of Ge isotope signal ions in the Faraday cup in Example 3.

[0042] Figure 12 For Example 3 70 It is the peak shape diagram of Ge isotope signal ions in the Faraday cup.

[0043] Figure 13 It is the flow chart of Ge isotope abundance determination in Example 3.

[0044] Figure 14 It is the magnetic field scanning spectrum of CF4 in cup5 in Example 4.

[0045] Figure 15 It is the enlarged view of the signal ion spectrum in cup5 in Example 4.

[0046] Figure 16 In Example 4 12 It is the peak shape diagram of C isotope in cup4.

[0047] Figure 17 In Example 4 13 It is the peak shape diagram of C isotope in cup5.

[0048] Figure 18 It is the flow chart of C stable isotope abundance measurement procedure in Example 4. Specific implementation manners

[0049] The present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] The specific implementation manners of the present invention are described by taking the MAT253 type gas isotope mass spectrometer as an example. The mass number range of the MAT253 mass spectrometer is 1 to 150, and it has 9 Faraday cups. The switching of the Faraday cups can be achieved by switching the signal channels, which are represented by cup1 to cup9 in this text. Cup8 and cup9 share one signal channel, so at most 8 Faraday cups can be used simultaneously. In the present invention, cup1 to cup8 are used.

[0051] The instrument parameters of each embodiment of the present invention are all these parameters, as shown in Table 1:

[0052] Table 1 Basic measurement parameters of MAT253 mass spectrometer Parameter setting

[0053]

[0054] Example 1

[0055] Determination of the abundance of natural Xe stable isotopes

[0056] Step 1: Use the mass spectrometer to perform a magnetic field scan on the stable isotopes. After the magnetic field scan, each Faraday cup will obtain the signal values of each isotope. Observe the signal values of each isotope ion in each Faraday cup respectively, and select the spectrum obtained by the Faraday cup with appropriate signals. Use the valence state with obvious isotope signals in this spectrum as the ion to be measured.

[0057] The mass spectrometer performs a magnetic field scan on Xe, and each Faraday cup will obtain a set of spectra. Among them, the spectrum of cup4 is as Figure 1 shown. There are many isotopes of Xe, 9 kinds. In Figure 1 two obvious Xe isotope signals can be seen, which are Xe 2+ and Xe + ion signals respectively. Among them, the Xe + signal is larger. Therefore, determine the Xe + ion as the ion to be measured. The magnified spectrum is as Figure 2 shown.

[0058] Step 2: Roughly determine the abundance ratio initially from the signals obtained in Step 1, and then select Faraday cups for each isotope ion.

[0059] After analyzing according to the Faraday cup selection method, determine 124 Xe, 126 Xe, 128 Xe, 129 Xe, 130 Xe, 131 Xe, 132 Xe, 134 Xe, 136Xe sequentially selects cup1, cup2, cup3, cup4, cup5, cup6, cup7, cup8, cup8. Since the Faraday cup positions of the MAT253 mass spectrometer used in the experiment are set for the Xe isotope abundances, only one peak jump is required during the measurement process.

[0060] Step 3: Determine the magnetic field positions of each isotope ion in the corresponding Faraday cup.

[0061] By observing Figure 2 each isotope peak, the magnetic field positions of the isotopes in the Faraday cup can be initially determined. To further accurately determine the magnetic field positions, ensure that the peak shape is normal, set the initially determined magnetic field value, perform a high-voltage scan, and observe whether the peak center of the isotope is at the 9.5 kV position. If it is, determine this position; if not, continue to adjust the magnetic field position until the peak center is at the 9.5 kV position, as Figure 3 shown. As shown by the instrument measurement, the magnetic field values of 9 isotopes are sequentially set for the corresponding Faraday cups, as shown in Table 2:

[0062] Table 2 Faraday cups and corresponding magnetic field positions of Xe isotopes

[0063]

[0064] As can be seen from Table 2, at a magnetic field of 12544, cup1 to cup8 can respectively receive 124 Xe, 126 Xe, 128 Xe, 129 Xe, 130 Xe, 131 Xe, 132 Xe, 134 Xe. Subsequently, jump to a magnetic field of 12579, and cup8 receives 136 Xe. One peak jump can complete the measurement.

[0065] Step 4: Measure the signal of each isotope ion at the corresponding magnetic field position to obtain the signal value of each isotope ion. Set the data in Table 2 into the control program so that the measurement program can call this data and control it according to the process as Figure 6 shown to obtain the corresponding isotope ion signal value.

[0066] Step 5: Use the measurement results obtained in Step 4 to calculate the abundances to obtain the abundances of each stable isotope.

[0067] Taking 124 the abundance calculation of Xe as an example:

[0068]

[0069] Unify the magnification factor. The magnification factors of the 8 Faraday cups are successively 1×10 10 ,, 3×10 11 , 1×10 10 , 3×10 8 , 3×10 9 , 3×10 8 , 3×10 8 , 3×10 9 , taking one of the Faraday cups as a reference, each Faraday cup needs to be multiplied by the corresponding coefficient: Therefore:

[0070]

[0071] Successively, we can obtain:

[0072]

[0073] Finally, we can obtain 124 The Xe abundance is

[0074]

[0075] Successively, we can obtain the abundance values of other isotopes.

[0076] Repeat step 4 for full-automatic measurement. Each measurement has 6 groups of data. The abundance values of the 6 groups of isotopes are shown in Table 3:

[0077] Table 3 Abundance measurement values of Xe isotopes

[0078]

[0079] The measurement result analysis is shown in Table 4:

[0080] Table 4 Analysis of measurement results of Xe isotopes (%)

[0081]

[0082] From the data in Table 4, it can be seen that the relative standard deviations of the 9 isotopes of Xe are all ≤0.131%, and the absolute value of the relative error from the reference value is ≤2.08%. In addition to the errors caused during the measurement process in the error sources, there are also differences between the experimental samples themselves and the samples used for the reference value. The measurement results have good repeatability, accuracy, and reliability.

[0083] Example 2

[0084] Determination of the abundance of highly enriched Xe stable isotopes after concentration and separation

[0085] After highly enriched separation of stable isotopes, the abundance of the target isotope will reach more than 90%, and the other isotopes except the target isotope will be very small, with a difference of up to six orders of magnitude. Usually, the conventional sample measurement methods can no longer meet the requirements, and the measurement methods are as follows.

[0086] Step 1: Use a mass spectrometer to perform a magnetic field scan on the stable isotopes. After the magnetic field scan, each Faraday cup will obtain the signal values of each isotope. Observe the signal values of each isotope ion in each Faraday cup separately, and select the spectrum obtained from the Faraday cup with appropriate signals. Use the valence state with obvious isotope signals in this spectrum as the ion to be measured.

[0087] In Example 1, it has been determined that the signal ion of Xe isotope is Xe + ions, which will not be repeated here.

[0088] Step 2: Roughly determine the abundance ratio preliminarily from the signals obtained in Step 1. Then, select Faraday cups for each isotope ion.

[0089] The isotope spectrum obtained by scanning is as Figure 7 shown. It can be seen from Figure 7 that for some ions, the signals exceed the range in multiple Faraday cups. Because the abundance ratios of the isotopes after enrichment vary greatly, the abundance of the high-abundance ones can reach more than 99%, while the abundance of the low-abundance ones can be less than 0.0001%, with a gap of up to six orders of magnitude. Therefore, the scheme of Example 1 is no longer applicable, and the measurement scheme must be improved. Since cup2 has the largest amplification factor, all those with very low abundance should be measured using cup2, while the high-abundance isotope ions should use Faraday cups with low amplification factors to prevent signal distortion beyond the measurement range. The Faraday cups determined for each isotope ion are shown in Table 5.

[0090] Table 5 Faraday cups and corresponding magnetic field positions for high-abundance Xe isotopes

[0091]

[0092] It can be seen from Table 5 that during the measurement of the abundance of high-abundance Xe, multiple peak-jump measurements with switched magnetic field values are required.

[0093] Step 3: Determine the magnetic field positions of each isotope ion in the corresponding Faraday cups.

[0094] The magnetic field positions corresponding to the Faraday cups are shown in Table 5.

[0095] Step 4: Measure the signal of each isotope ion separately at the corresponding magnetic field positions to obtain the signal values of each isotope ion. Set the data in Table 5 into the control program so that the measurement program can call this data. According toFigure 8 Control is performed according to the process shown below.

[0096] Step 5: Use the measurement results obtained in Step 4 to calculate the abundances, and obtain the abundances of each stable isotope.

[0097] The measurement results after the program runs are shown in Table 6.

[0098] Table 6 Measurement Results of High-Abundance Xe Isotope Abundances (%)

[0099]

[0100] As shown in Table 6, for the stable isotope 136 Xe, the abundance is as high as 95.7195%, the standard deviation is only 0.0090%, and the relative standard deviation is 0.009%. The measurement repeatability is good, the results are stable and reliable, and meet the measurement requirements. Among them, 126 Xe and 128 Xe have relatively large relative standard deviations because their abundances are extremely low, at the order of 10 -6 magnitude. The standard deviation also retains more digits than others. Otherwise, they are all 0. Although the range is only 0.0001%, it also causes a relatively large relative standard deviation. However, the influence on the high-abundance 136 Xe can be ignored.

[0101] Example 3

[0102] Determination of the Abundance of Ge Stable Isotopes in GeF4

[0103] Step 1: Use a mass spectrometer to perform a magnetic field scan on the stable isotopes. After the magnetic field scan, each Faraday cup will obtain the signal values of each isotope. Observe the signal values of each isotope ion in each Faraday cup respectively, and select the spectrum obtained from the Faraday cup with appropriate signals. Use the valence state with obvious isotope signals in this spectrum as the ion to be measured.

[0104] The isotope spectrum obtained by scanning the GeF4 sample is as shown in Figure 9 . The signal ions determined by spectrum analysis are the signal ions shown in the circle. From left to right, they are 70 GeF3 + , 72 GeF3 + , 73 GeF3 + , 74 GeF3 + and 76 GeF3 + .

[0105] Step 2: Roughly determine the abundance ratio initially from the signals obtained in Step 1, and then select Faraday cups for each isotope ion.

[0106] As shown in Table 7, after analysis and verification, it is determined that 70 For Ge, cup5 is selected, and the corresponding magnetic field number is 12334. 72 Ge, 73 Ge, 74 Ge, and 76 Ge are respectively selected as cup5, cup6, cup7, and cup8, and the magnetic field is 12472 in all cases, with one peak jump. Figure 9 The enlarged view of the signal to be measured is as shown in Figure 10 the figure.

[0107] Table 7 Faraday cups and corresponding magnetic field positions of each isotope in GeF4

[0108]

[0109] Step 3: Determine the magnetic field position of each isotope ion in the corresponding Faraday cup.

[0110] The corresponding magnetic field positions of the Faraday cups are shown in Table 7, and the peak shape diagrams of each ion in the corresponding Faraday cups are as shown in Figure 11 and 12 the figures. It can be seen that the peak shape diagrams of each ion signal in the Faraday cup are good, and the peak centers are all at the working voltage of 9.5 kV.

[0111] Step 4: Measure the signal of each isotope ion at the corresponding magnetic field position respectively to obtain the signal value of each isotope ion. Set the data in Table 7 into the control program so that the measurement program can call this data and control it according to the process as shown in Figure 13 the figure to obtain the corresponding isotope ion signal value.

[0112] Step 5: Use the measurement results obtained in Step 4 to calculate the abundances to obtain the abundances of each stable isotope.

[0113] From the data in Table 8, it can be seen that the relative standard deviations of the 5 stable isotopes of Ge are all less than 0.309%, and the absolute values of the relative errors compared with the reference values are ≤ 1.48% except for 76 Ge. 73 The data of Ge has more reserved digits to avoid the situation where the absolute error is 0 while the relative error is not 0. After analysis, the main source of the error is the difference between the experimental sample and the reference value sample.

[0114] Table 8 Measurement results of natural GeF4 isotope abundances

[0115]

[0116] Example 4

[0117] Abundance determination of C stable isotopes in CF4

[0118] Step 1: Use a mass spectrometer to perform a magnetic field scan on the stable isotopes. After the magnetic field scan, each Faraday cup will obtain the signal value of each isotope. Observe the signal value of each isotope ion in each Faraday cup respectively, select the spectrum obtained by the Faraday cup with a suitable signal, and use the valence state of the isotope signal with obvious signal in the spectrum as the ion to be measured.

[0119] The isotope spectrum obtained by scanning the CF4 sample is as follows: Figure 14 As shown: The signal ion determined by spectrum analysis is, 12 CF3 + and 13 CF3 + Ions. Figure 14 The ion signal to be measured is amplified, such as Figure 15 shown.

[0120] Step 2: Preliminarily and roughly determine the abundance ratio based on the signal obtained in step 1, and then select a Faraday cup for each isotope ion.

[0121] Step 3, determining the magnetic field position of each isotope ion in the corresponding Faraday cup.

[0122] After spectrum analysis and verification, the ion Faraday cup and the corresponding magnetic field number are determined as shown in Table 9.

[0123] Table 9 Natural CF4 isotope ion Faraday cup and corresponding magnetic field position

[0124]

[0125] The peak shape of each ion in the corresponding Faraday cup is shown in the figure below: Figure 16 and 17 As shown. Figure 16 and Figure 17 It can be seen that the isotope peak shape is good, and the peak center is at the working voltage position of 9.5kV.

[0126] Step 4, measure each isotope ion signal at the corresponding magnetic field position to obtain each isotope ion signal value. Set the data in Table 9 into the control program so that the measurement program can call the data. Figure 18 The process shown is controlled to obtain the corresponding isotope ion signal value.

[0127] Step 5, using the measurement results obtained in step 4 to perform abundance calculation to obtain the abundance of each stable isotope.

[0128] Table 10 Natural CF4 isotope abundance measurement results (%)

[0129]

[0130] From the data in Table 10, it can be seen that the relative standard deviations of the C abundance measurements in CF4 are all ≤0.0278%, and the relative errors from the reference values are all ≤0.0555%.

[0131] Example 5

[0132] In addition to the above stable isotopes, the abundance determinations of the Si stable isotope in SiF4 and the B stable isotope in BF3 were also verified, and the measurement methods and procedures were the same. They will not be elaborated here. The measurement results are shown in Table 11 and Table 12.

[0133] Table 11 Measurement Results of the Abundance of the Si Stable Isotope in SiF4 (%)

[0134]

[0135] As can be seen from Table 11, the standard deviations of the measurement results of the abundance of the Si stable isotope in SiF4 are all ≤0.0040%, the relative standard deviations are all ≤0.127%, and the absolute values of the relative errors from the reference values are ≤0.79%.

[0136] Table 12 Measurement Results of the Abundance of the B Stable Isotope in BF3 (%)

[0137]

[0138]

[0139] As can be seen from Table 12, the standard deviations of the measurement results of the abundance of the B stable isotope are all ≤0.0057%, the relative standard deviations are all ≤0.030%, and the absolute values of the relative errors from the reference values are ≤2.84%.

[0140] In summary, this measurement method measures the abundances of multiple stable isotopes and the abundances of stable isotopes after enrichment, and the measurement results all have good repeatability and accuracy.

[0141] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for mass spectrometric determination of stable isotope abundances, characterized in that, The following steps are involved: Step 1, use a mass spectrometer to perform magnetic field scanning on the stable isotope. After the magnetic field scanning, each Faraday cup will obtain the signal value of each isotope, observe the signal value of each isotope ion in each Faraday cup respectively, select the spectrum obtained by the Faraday cup with suitable signal, and use the valence state of the isotope signal in the spectrum as the ion to be measured. The magnetic field scanning range is 1 to 14000; the mass spectrometer is a MAT253 gas isotope mass spectrometer, and the mass spectrometry method uses eight Faraday cups from cup1 to cup8; Step 2: The abundance ratio is roughly determined based on the isotope ion signals obtained in step 1. Then, a Faraday cup is selected for each isotope ion. The Faraday cup is selected by the following method: If the signal value of an isotope ion in a Faraday cup is within the range and the size is within the range of 10% to 70% of the upper limit of the range, it is used as the measurement scheme; If the signal value of an isotope ion in a Faraday cup is within the range, but less than 10% of the upper limit of the range, and the order of magnitude is close to the background order of magnitude, then the one with the largest amplification factor among the other multiple Faraday cups is selected as the measurement scheme; If the signal value of an isotope ion in a certain Faraday cup is within the range, but the signal is too large, exceeds the range, and the peak is flat, then select multiple other Faraday cups with smaller magnification factors to make their signal values ​​within the range of 10% to 70% of the upper limit of the range as the measurement plan; Step 3, determining the magnetic field position of each isotope ion in the corresponding Faraday cup; Step 4, measuring each isotope ion signal at a corresponding magnetic field position to obtain each isotope ion signal value; Step 5, using each isotope ion signal value obtained in step 4 to perform abundance calculation to obtain the abundance of each stable isotope.

2. The mass spectrometry method according to claim 1, characterized in that The Faraday cup with suitable signal in step 1 means that the ion signal in the Faraday cup is strong and within the measuring range, and there is no interference signal or the interference signal can be ignored.

3. The mass spectrometry method according to claim 1, wherein The magnetic field position in step 3 is determined by the following method: setting a preliminarily determined magnetic field value, performing a high voltage scan, and observing whether the peak center of the isotope is at the set voltage position. If so, the position is determined; if not, the magnetic field position is continuously adjusted until the peak center is at the set voltage position.

4. The mass spectrometry method according to claim 1, characterized in that, When measuring the isotope ion signal in step 4, first perform background measurement at the corresponding magnetic field position to obtain a background measurement value, then add the sample, and then perform signal measurement at the corresponding magnetic field position to obtain a signal measurement value, where the isotope ion signal value = signal measurement value - background measurement value.

5. The mass spectrometry method according to claim 1, wherein The isotope comprises one or more isotopes.

6. The mass spectrometry method according to claim 5, wherein The isotopic substance measured by the mass spectrometry method is the natural abundance or the concentrated separation abundance.

7. Use of a mass spectrometry method according to any one of claims 1-6 in isotope abundance analysis, characterized in that, The isotope is one or more of Xe, Ge, C, B and Si.

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