Method for measuring magnesium isotope by using Na-Al double-element dilution

Abstract

The invention belongs to the technical field of isotope analysis, and discloses a method for measuring magnesium isotope by using Na-Al double element dilution, which comprises the following steps: carrying out chemical digestion, isotope separation and concentration matching on a sample to be measured to obtain an Mg sample solution; diluting the Mg sample solution and the Mg standard solution with a nitric acid solution, and adding Na-Al double-element mixed standard solutions with different volumes to obtain a plurality of standard solutions to be detected and a plurality of sample solutions to be detected; testing the plurality of standard solutions to be tested and the plurality of sample solutions to be tested by using MC-ICPMS by using a sample-standard sample interpolation method, and collecting data; and calculating the isotope composition of Mg in the Mg sample solution according to the collected data. According to the method, the Na-Al double-element dilution method and the sample-standard sample interpolation method are combined, so that outliers of individual data points are effectively avoided, and accurate measurement of Mg isotopes is realized on MC-ICPMS (Monte Carlo-Inductively Coupled Plasma Mass Spectrometry).

Description

Technical Field

[0001] The present invention relates to the technical field of isotope analysis, in particular to a method for determining magnesium isotopes by using Na-Al dual-element dilution, and in particular to a method for determining magnesium isotopes by using Na-Al dual-element dilution based on a multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS). Background Art

[0002] Magnesium isotopes have important applications and scientific significance in the fields of earth science, environmental science, and biogeochemistry. By studying the composition of magnesium isotopes, we can reveal the physical and chemical processes of mantle melting, magma evolution, and carbonate diagenesis, providing key evidence for understanding paleoclimate changes and sediment formation. In marine chemistry, magnesium isotopes reflect changes in the chemical composition of seawater and its relationship to the global carbon cycle, which helps to study ocean acidification and mineral precipitation processes. In biogeochemistry, magnesium isotopes are used to study the absorption and utilization mechanisms of magnesium by plants and marine organisms, revealing the circulation patterns of magnesium in ecosystems. In addition, magnesium isotopes also have potential applications in industrial mineral mining, salt lake resource assessment, and hydrogeochemistry, providing an important tool for revealing geochemical processes and environmental evolution.

[0003] Precise magnesium isotope determination, a technique developed primarily in this century, relies on high-precision mass spectrometers and rigorous chemical separation procedures. Currently, magnesium isotope analysis primarily relies on high-precision mass spectrometry techniques, such as multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). MC-ICPMS, with its advantages of high sensitivity and simultaneous detection of multiple isotopes, is the mainstream technique for magnesium isotope analysis. However, isotope fractionation is unavoidable during MC-ICPMS determination of magnesium isotopes.

[0004] In the prior art, the main correction methods used to correct for instrumental mass fractionation are sample-standard interpolation, double isotope dilution, and element dilution. However, since Mg lacks a diluent element with similar mass but different isotopes, element dilution cannot be used for correction. The double dilution method is only applicable to systems with four stable isotopes, and Mg has three stable isotopes, so the double dilution method cannot be used to correct for instrumental fractionation. Therefore, the sample-standard interpolation method is currently the method used to correct for instrumental isotope mass fractionation when analyzing Mg isotope composition using MC-ICPMS.

[0005] However, the sample-standard interpolation method requires the instrument to remain stable. Even small fluctuations in laboratory temperature, humidity, and pressure can lead to unstable analytical results. Furthermore, the sample-standard interpolation method requires that the sample and interpolated standard have identical elemental and acid concentrations, resulting in matrix effects. Therefore, the matching between the sample and standard is highly demanding. These factors often lead to individual outliers in the sample-standard interpolation analysis of Mg isotopes, affecting the precision and accuracy of the isotope analysis. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a method for determining magnesium isotopes using Na-Al double element dilution. 23 Na and 27 Al is used as the diluting element in the dual-element dilution method. The Na-Al dual-element dilution method combined with the sample-standard interpolation method is used to measure Mg isotopes. This helps to correct the isotope fractionation effect during instrumental analysis and accurately analyze the Mg isotope composition of the sample to be tested.

[0007] The method of determining magnesium isotopes by using Na-Al double element dilution of the present invention is achieved by the following technical solution:

[0008] The present invention takes into account that the ionization efficiency of Na and Al is close to that of Mg, and has good adaptability under the same analysis conditions of MC-ICPMS, which helps to achieve accurate fractionation correction. 23 Stable isotopes of Na and Al 27 Stable isotopes of Al and Mg ( 24 Mg, 25 Mg and 26 Mg) are close in mass and complementary, so the present invention is based on 23 Na and 27 Al is used as the diluting element in the dual-element dilution method. Measuring Mg isotopes using the Na-Al dual-element dilution method helps correct the isotope fractionation effect during instrumental analysis, thereby accurately analyzing the Mg isotope composition of the sample to be tested. The present invention provides a method for determining Mg isotopes using the Na-Al dual-element dilution method, comprising the following steps:

[0009] Step 1, preparation of Mg dual element diluent:

[0010] Will 23 Na element single standard solution and 27 The Al element single standard solution is mixed to obtain a Na-Al dual element mixed standard solution, and the Na-Al dual element mixed standard solution is used as a Mg dual element diluent; wherein the Na element concentration of the Na-Al dual element mixed standard solution is the same as the Al element concentration.

[0011] It should be noted that the present invention is relatively low-cost and readily available. 23 Na element single standard solution and 27 The Al element single standard solution is used as the raw material for the preparation of the Mg double element diluent, which reduces the experimental cost and makes this method extremely easy to promote and apply.

[0012] In some preferred embodiments of the present invention, the 23 The single standard solution of Na element is GSB-Na with a concentration of 1000ppm. 27 The single standard solution of Al element is GSB-Al with a concentration of 1000ppm, and the 23 Na element single standard solution and 27 Mix equal volumes of Al element single standard solution to form 23 Na and 27 The concentration of Al element is 500ppm of Na-Al dual element mixed standard solution.

[0013] In some preferred embodiments of the present invention, the mass concentration of the nitric acid solution is 1% to 3%, preferably 2%.

[0014] Step 2, preparation of Mg sample solution:

[0015] The sample to be tested is subjected to chemical digestion, isotope separation and concentration matching in sequence to obtain a Mg sample solution.

[0016] It should be noted that the chemical digestion, isotope separation and concentration matching of the sample to be tested in the present invention are all carried out by conventional technical means in the art, which should be known to those skilled in the art, and therefore the present invention will not be described in detail here.

[0017] Step 3, preparation of the standard solution and sample solution to be tested:

[0018] The Mg standard solution is used as an external calibration standard. After the Mg sample solution and the Mg standard solution are diluted with a nitric acid solution, different volumes of the Mg dual-element diluent are added respectively to obtain multiple standard solutions to be tested and multiple sample solutions to be tested.

[0019] It should be noted that, in some preferred embodiments of the present invention, the Mg standard solution used is a pure Mg solution with a concentration of 1000 ppm.

[0020] Step 4, instrument testing:

[0021] The sample-standard interpolation method is adopted, and a multi-collector inductively coupled plasma mass spectrometer is used to test a plurality of the standard solutions to be tested and a plurality of the sample solutions to be tested, and the 27 Al, 23 Na,24 Mg, 25 Mg and 26 Signal data of Mg.

[0022] It should be noted that the sample-standard interpolation method of the present invention adopts the order of "standard-sample-standard" so that the standard solution to be tested and the sample solution to be tested are tested alternately to correct the isotope fractionation coefficient β during the instrument analysis process.

[0023] In some preferred embodiments of the present invention, the present invention realizes simultaneous determination on a multi-collector inductively coupled plasma mass spectrometer by increasing the deflection voltage (Dispersion Quad). 23 Na, 24 Mg, 25 Mg, 26 Mg and 27 Al's signal.

[0024] Among them, in some more preferred embodiments of the present invention, when the multi-collector inductively coupled plasma mass spectrometer is tested, wet sampling is adopted, and the nebulizer used is a PFA nebulizer.

[0025] In some more preferred embodiments of the present invention, when testing with a multi-collector inductively coupled plasma mass spectrometer, the focus voltage and deflection voltage at which the centers of the Mg isotope peaks coincide are selected as test parameters. For example, in some more preferred embodiments, when testing with a Neptune Plus multi-collector inductively coupled plasma mass spectrometer, when the focus voltage (Focus Quad) is set to -3.3V to -3.5V and the deflection voltage (Dispersion Quad) is set to 41.8V to 42.0V, the centers of the Mg isotope peaks coincide, thereby achieving accurate isotope ratio measurement. When using a Neptune Plus multi-collector inductively coupled plasma mass spectrometer for testing, other test parameters are as follows: the integration time (Integration Time) is set to 2.095s~2.100s; the number of blocks (Number of Blocks) is set to ≥1; and the number of cycles per block (Cycles / Block) is set to 25~35. This ensures that the isotope composition can be accurately measured without wasting too much time and causing a large isotope fractionation effect on the instrument.

[0026] Step 5, data analysis:

[0027] According to the collected data, the signal data is obtained and calculated. 27 Al / 23 Na, 25 Mg / 24 Mg, 26 Mg / 24 Mg and isotope fractionation coefficient β; using 27 Al / 23 The isotopic composition of Mg in the Mg sample solution is calculated using Na and the isotope fractionation coefficient β.

[0028] It should be noted that the present invention is based on the measured 23 Na, 24 Mg, 25 Mg, 26 Mg and 27 Al's data is calculated 27 Al / 23 Na, 25 Mg / 24 Mg and 26 Mg / 24 Mg ratio; and using the obtained 27 Al / 23 Na is used to calibrate the sample solution and the standard solution to be tested. 25 Mg / 24 Mg and 26 Mg / 24 The isotopic composition of Mg in the Mg test solution is calculated specifically by the following steps:

[0029] 1) Obtained through testing 23 Na, 24 Mg, 25 Mg, 26 Mg and 27 The signal data of Al is calculated as ( 27 Al / 23 Na) Measured 、( 25 Mg / 24 Mg) Measured and( 26 Mg / 24 Mg) Measured Three isotope ratios.

[0030] 2) Based on the calculated ( 27 Al / 23 Na) Measured As input, the isotope fractionation coefficient β is calculated using the formula shown in Equation 1:

[0031]

[0032] In formula 1, ( 27 Al / 23 Na) Measured Calculated from the test data in step 1) above 27 Al / 23 Na value; ( 27 Al / 23 Na) True is 1, for 27 The relative atomic mass of Al is 26.9815384; for 23 The relative atomic mass of Na is 22.9897693.

[0033] 3) Using the isotope fractionation coefficient β and ( 25 Mg / 24 Mg) Measured As input, the formula shown in formula 2 is used to calculate ( 25 Mg / 24 Mg) True :

[0034]

[0035] In formula 2, for 25 The relative atomic mass of Mg is 25.9825930; for 24 The relative atomic mass of Mg is 23.9850417.

[0036] 4) Using the isotope fractionation coefficient β and ( 26 Mg / 24 Mg) Measured As input, the formula shown in formula 3 is used to calculate ( 26 Mg / 24 Mg) True :

[0037]

[0038] In formula 3, for 26 The relative atomic mass of Mg is 24.9858370.

[0039] 5) According to the method of steps 1) to 4) above, calculate each standard solution to be tested and each sample solution to be tested to obtain the ( 25 Mg / 24 Mg) True and( 26 Mg / 24 Mg) True Value. The obtained standard solution to be tested ( 25 Mg / 24 Mg) True and( 26Mg / 24 Mg) True Value as ( 25 Mg / 24 Mg) Standard and( 26 Mg / 24 Mg) Standard , the obtained sample solution ( 25 Mg / 24 Mg) True and( 26 Mg / 24 Mg) True Value as ( 25 Mg / 24 Mg) Sample and( 26 Mg / 24 Mg) Sample .

[0040] 6) The isotope ratio of the standard solution to be tested obtained in step 5) is ( 26 Mg / 24 Mg) Standard and the isotope ratio of the sample solution to be tested ( 26 Mg / 24 Mg) Sample As input, the Mg isotope δ in the Mg sample solution is calculated by the formula shown in Formula 4. 26 Mg content:

[0041]

[0042] 7) The isotope ratio of the standard solution to be tested is obtained ( 25 Mg / 24 Mg) Standard and the isotope ratio of the sample solution to be tested ( 25 Mg / 24 Mg) Sample As input, the Mg isotope δ in the Mg sample solution is calculated by the formula shown in Formula 5. 25 Mg content:

[0043]

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention is 23 Na and 27Al is used as the dilution element in the double element dilution method. Since the ionization efficiency of Na and Al is relatively close to that of Mg, it has good adaptability under the same analysis conditions of MC-ICPMS, which helps to achieve accurate fractionation correction. Furthermore, the Na-Al double dilution method does not require complex calculations when correcting the fractionation error in the instrument analysis process. The corrected Mg isotope ratio can be obtained by using only the function provided by the instrument. Moreover, when the Na-Al double dilution method and the sample-standard interpolation method are used in combination, the advantages of the sample-standard interpolation method can be obtained, while making up for the shortcomings of the sample-standard interpolation method that has strict requirements on the adaptation of the sample and the standard matrix. Moreover, the double element dilution method provides higher correction redundancy, and the robustness of the correction model can be improved by combining the isotope ratios of the two elements and the isotope ratio of the sample. In addition, the present invention is relatively low-cost and easy to obtain. 23 Na element single standard solution and 27 Using a single-standard Al solution as the raw material for preparing the dual-element Mg diluent reduces experimental costs and makes the invented determination method highly accessible and applicable. By combining the Na-Al dual-element dilution method with sample-standard interpolation, the present invention effectively avoids outliers in individual data points, enabling precise Mg isotope measurement using MC-ICPMS. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a diagram of the Faraday cup structure.

[0047] Figure 2 This is the peak shape diagram of each isotope during the determination process of Example 1.

[0048] Figure 3 The main parameter settings of the instrument during the measurement process of Example 1.

[0049] Figure 4 This is the test result of Example 1. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0051] Example 1

[0052] This embodiment provides a method for determining magnesium isotopes using Na-Al dual element dilution, comprising the following steps:

[0053] Step 1, preparation of Mg dual element diluent:

[0054] GSB-Na with a concentration of 1000ppm was used as 23 The Na element single standard solution is GSB-Al with a concentration of 1000ppm. 27Al element single standard solution, GSB-Na with a concentration of 1000ppm and GSB-Al with a concentration of 1000ppm are mixed in equal volumes to obtain a Na-Al dual element mixed standard solution, and the obtained Na-Al dual element mixed standard solution is used as a Mg dual element diluent, that is, the Mg dual element diluent used in this embodiment, 23 Na and 27 The concentration of Al element was 500 ppm.

[0055] Step 2, preparation of Mg sample solution:

[0056] The sample to be tested is subjected to chemical digestion, isotope separation and concentration matching in sequence using conventional technical means in the art to obtain a Mg sample solution.

[0057] Step 3, preparation of the standard solution and sample solution to be tested:

[0058] A pure Mg solution MsMg with a concentration of 1000 ppm was used as a Mg standard solution and an external calibration standard. The Mg sample solution and the Mg standard solution were diluted with a nitric acid solution with a mass concentration of 2%, and then different volumes of the Mg dual-element diluent were added until the Mg concentration reached 1000 ppb, the Na concentration reached 700 ppb, and the Al concentration reached 700 ppb, respectively. This yielded multiple standard solutions and multiple sample solutions to be tested.

[0059] Step 4, instrument testing:

[0060] The sample-standard interpolation method is adopted, and multiple standard solutions to be tested and multiple sample solutions to be tested are tested alternately in the order of "standard-sample-standard", and the concentrations of each standard solution to be tested and each standard solution to be tested and the sample solution to be tested are collected. 27 Al, 23 Na, 24 Mg, 25 Mg and 26 Mg signal.

[0061] Step 5, data analysis:

[0062] According to the collected data, the signal data is obtained and calculated. 27 Al / 23 Na, 25 Mg / 24 Mg, 26 Mg / 24 Mg and isotope fractionation coefficient β; using 27 Al / 23The isotopic composition of Mg in the Mg sample solution is calculated using Na and the isotope fractionation coefficient β. The specific calculation formula is as follows:

[0063] 5.1) Obtained through testing 23 Na, 24 Mg, 25 Mg, 26 Mg and 27 The signal data of Al is calculated as ( 27 Al / 23 Na) Measured 、( 25 Mg / 24 Mg) Measured and( 26 Mg / 24 Mg) Measured Three isotope ratios.

[0064] 5.2) is calculated based on ( 27 Al / 23 Na) Measured As input, the isotope fractionation coefficient β is calculated using the formula shown in Equation 1:

[0065]

[0066] In formula 1, ( 27 Al / 23 Na) Measured Calculated from the test data in step 5.1) above 27 Al / 23 Na value; ( 27 Al / 23 Na) True is 1, for 27 The relative atomic mass of Al is 26.9815384; for 23 The relative atomic mass of Na is 22.9897693.

[0067] 5.3) Using the isotope fractionation coefficient β and ( 25 Mg / 24 Mg) Measured As input, the formula shown in formula 2 is used to calculate ( 25 Mg / 24 Mg) True :

[0068]

[0069] In formula 2, for 25The relative atomic mass of Mg is 25.9825930; for 24 The relative atomic mass of Mg is 23.9850417.

[0070] 5.4) Using the isotope fractionation coefficient β and ( 26 Mg / 24 Mg) Measured As input, the formula shown in formula 3 is used to calculate ( 26 Mg / 24 Mg) True :

[0071]

[0072] In formula 3, for 26 The relative atomic mass of Mg is 24.9858370.

[0073] 5.5) According to the method of steps 5.1) to 5.4) above, calculate each standard solution and sample solution to be tested to obtain the ( 25 Mg / 24 Mg) True and( 26 Mg / 24 Mg) True Value. The obtained standard solution to be tested ( 25 Mg / 24 Mg) True and( 26 Mg / 24 Mg) True Value as ( 25 Mg / 24 Mg) Standard and( 26 Mg / 24 Mg) Standard , the obtained sample solution ( 25 Mg / 24 Mg) True and( 26 Mg / 24 Mg) True Value as ( 25 Mg / 24 Mg) Sample and( 26 Mg / 24 Mg) Sample .

[0074] 5.6) The isotope ratio of the standard solution to be tested obtained in step 5.5) above ( 26Mg / 24 Mg) Standard and the isotope ratio of the sample solution to be tested ( 26 Mg / 24 Mg) Sample As input, the Mg isotope δ in the Mg sample solution is calculated by the formula shown in Formula 4. 26 Mg content:

[0075]

[0076] 5.7) The isotope ratio of the standard solution to be tested is obtained ( 25 Mg / 24 Mg) Standard and the isotope ratio of the sample solution to be tested ( 25 Mg / 24 Mg) Sample As input, the Mg isotope δ in the Mg sample solution is calculated by the formula shown in Formula 5. 25 Mg content:

[0077]

[0078] It should be noted that all the above-mentioned Mg isotope analysis tests in this example were performed on a multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS, model Neptune Plus), and during the experiment, wet injection was adopted, the nebulizer used was a PFA nebulizer, the injection rate was 100 μL / min, and the analysis mode was low-resolution mode.

[0079] During the experiment of this embodiment, the corresponding relationship between each Faraday cup and isotope is: L5- 23 Na; L3- 24 Mg; C- 25 Mg; H2- 26 Mg; H4- 27 Al, and each Faraday cup has a structure such as Figure 1 shown.

[0080] Set the Focus Quad to -3.4V and the Dispersion Quad to 41.9V to achieve the coincidence of the centers of the Mg isotope peaks. The coincident isotope peak diagram is as follows: Figure 2 As shown, in order to achieve accurate measurement of isotope ratios. It should be noted that Figure 2 The horizontal axis in the middle is Mass[u], which represents the relative atomic mass of the isotope, and the vertical axis on the left is Intensity[V].

[0081] In this example, the Neptune Plus multi-collector inductively coupled plasma mass spectrometer was used to analyze Mg isotopes. Some of the main instrument parameters are as follows: Figure 3 As shown. During analysis, this example set the Integration Time to 2.097s, the Number of Blocks to 1, and the Cycles / Block to 30. This ensures accurate isotopic composition measurement without wasting too much time, which could lead to significant isotope fractionation. Furthermore, during analysis, the standard solution and the sample solution were interleaved to correct for isotope fractionation during the instrumental analysis.

[0082] This embodiment combines the Na-Al dual element dilution method and the sample-standard sample interpolation method. The test results after the above test analysis are as follows Figure 4 As shown, it can be seen that δ 25 Mg = -2.53‰ ± 0.04‰ (2SD) and δ 26 Mg=-4.89‰±0.04‰(2SD), which shows that the determination method of the present invention can achieve δ 25 Mg and δ 26 The long-term accuracy for Mg was 0.04‰ (2SD), which is significantly lower than the long-term accuracy of the widely used sample-standard interpolation method (generally ~0.08‰, 2SD). Furthermore, the assay method of the present invention is less sensitive to matrix effects in the sample and standard solution, making sample preparation more convenient before analysis and testing.

[0083] Based on the above, the present invention combines the Na-Al double dilution method with the sample-standard interpolation method, which not only obtains the advantages of the sample-standard interpolation method, but also makes up for the disadvantage of the sample-standard interpolation method that has strict requirements on the compatibility of the sample and standard matrix. Moreover, the double element dilution method provides higher calibration redundancy, and the combination of the two element isotope ratios and the sample isotope ratio can improve the robustness of the calibration model. In addition, the present invention is relatively low-cost and readily available. 23 Na element single standard solution and 27 Using a single-standard Al solution as the raw material for preparing the dual-element Mg diluent reduces experimental costs and makes the invented determination method highly accessible and applicable. By combining the Na-Al dual-element dilution method with sample-standard interpolation, the present invention effectively avoids outliers in individual data points, enabling precise Mg isotope measurement using MC-ICPMS.

[0084] Obviously, the above embodiment only lists a Na / Al ratio and a Na / Mg ratio for accurately determining Mg isotopes. On the basis of the above embodiment, a person skilled in the art can replace the Na / Al ratio and the Na / Mg ratio to achieve the same effect of the present invention, or make equivalent replacements for some of the technical features therein. All other embodiments obtained within the spirit and principles of the present invention without making creative work shall fall within the scope of protection of the present invention.

Claims

1. A method for determining magnesium isotopes using Na-Al double element dilution, characterized in that: The following steps are involved: Will 23 Na element single standard solution and 27 The Al element single standard solution is mixed to obtain a Na-Al dual element mixed standard solution, and the Na-Al dual element mixed standard solution is used as a Mg dual element diluent; wherein the Na element concentration of the Na-Al dual element mixed standard solution is the same as the Al element concentration; The sample to be tested is subjected to chemical digestion, isotope separation and concentration matching in sequence to obtain a Mg sample solution; Using a Mg standard solution as an external calibration standard, diluting the Mg sample solution and the Mg standard solution with a nitric acid solution, and then adding different volumes of the Mg dual-element diluent to obtain a plurality of standard solutions to be tested and a plurality of sample solutions to be tested; The sample-standard interpolation method is adopted, and a multi-collector inductively coupled plasma mass spectrometer is used to test a plurality of the standard solutions to be tested and a plurality of the sample solutions to be tested, and the 27 Al, 23 Na, 24 Mg, 25 Mg and 26 Signal data of Mg; According to the collected signal data, we can calculate 27 Al / 23 Na, 25 Mg / 24 Mg, 26 Mg / 24 Mg and isotope fractionation coefficient β; using 27 Al / 23 The isotopic composition of Mg in the Mg sample solution is calculated using Na and the isotope fractionation coefficient β.

2. The method for determining magnesium isotopes by Na-Al double element dilution according to claim 1, wherein: Specifically, use the following steps to 27 Al / 23 The isotopic composition of Mg in the Mg sample solution is calculated using Na and the isotope fractionation coefficient β: 1) Obtained through testing 23 Na, 24 Mg, 25 Mg, 26 Mg and 27 The signal data of Al is calculated as ( 27 Al / 23 Na) Measured 、( 25 Mg / 24 Mg) Measured and( 26 Mg / 24 Mg) Measured Three isotope ratios; 2) Based on the calculated ( 27 Al / 23 Na) Measured As input, the isotope fractionation coefficient β is calculated by the formula shown in formula 1: In formula 1, ( 27 Al / 23 Na) Measured Calculated from the test data in step 1) above 27 Al / 23 Na value; ( 27 Al / 23 Na) True is 1; for 27 The relative atomic mass of Al is 26.9815384; for 23 The relative atomic mass of Na is 22.9897693; 3) Using the isotope fractionation coefficient β and ( 25 Mg / 24 Mg) Measured As input, the formula shown in formula 2 is used to calculate ( 25 Mg / 24 Mg) True : In formula 2, for 25 The relative atomic mass of Mg is 25.9825930; for 24 The relative atomic mass of Mg is 23.9850417; 4) Using the isotope fractionation coefficient β and ( 26 Mg / 24 Mg) Measured As input, the formula shown in formula 3 is used to calculate ( 26 Mg / 24 Mg) True : In formula 3, for 26 The relative atomic mass of Mg is 24.9858370; 5) According to the method of steps 1) to 4) above, calculate each standard solution to be tested and each sample solution to be tested to obtain the ( 25 Mg / 24 Mg) True and( 26 Mg / 24 Mg) True Value; the obtained standard solution to be tested ( 25 Mg / 24 Mg) True and( 26 Mg / 24 Mg) True Value as ( 25 Mg / 24 Mg) Standard and( 26 Mg / 24 Mg) Standard , the obtained sample solution ( 25 Mg / 24 Mg) True and( 26 Mg / 24 Mg) True Value as ( 25 Mg / 24 Mg) Sample and( 26 Mg / 24 Mg) Sample ; 6) The isotope ratio of the standard solution to be tested obtained in step 5) is ( 26 Mg / 24 Mg) Standard and the isotope ratio of the sample solution to be tested ( 26 Mg / 24 Mg) Sample As input, the Mg isotope δ in the Mg sample solution is calculated by the formula shown in Formula 4. 26 Mg content: 7) The isotope ratio of the standard solution to be tested is obtained ( 25 Mg / 24 Mg) Standard and the isotope ratio of the sample solution to be tested ( 25 Mg / 24 Mg) Sample As input, the Mg isotope δ in the Mg sample solution is calculated by the formula shown in Formula 5. 25 Mg content:

3. The method for determining magnesium isotopes by Na-Al double element dilution according to claim 1, wherein: During the multi-collector inductively coupled plasma mass spectrometer test, wet sampling was adopted, and the nebulizer used was a PFA nebulizer.

4. The method for determining magnesium isotopes by Na-Al double element dilution according to claim 1, wherein: During the multi-collector inductively coupled plasma mass spectrometer test, the focusing voltage and the deflection voltage when the centers of the isotope peaks of Mg coincide are selected as test parameters.

5. The method for determining magnesium isotopes by Na-Al double element dilution according to claim 1, wherein: described 23 The single standard solution of Na element is GSB-Na with a concentration of 1000ppm.

6. The method for determining magnesium isotopes using Na-Al double element dilution according to claim 1, wherein: described 27 The single standard solution of Al element is GSB-Al with a concentration of 1000ppm.

7. The method for determining magnesium isotopes using Na-Al double element dilution according to claim 1, wherein: The Mg standard solution is a pure Mg solution with a concentration of 1000 ppm.

8. The method for determining magnesium isotopes using Na-Al double element dilution according to claim 1, wherein: The mass concentration of the nitric acid solution is 1% to 3%.

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