A method for determining magnesium isotopes using Na-Al dual-element dilution

Abstract

This invention belongs to the field of isotope analysis technology and discloses a method for determining magnesium isotopes using Na-Al dual-element dilution. The method includes the following steps: chemically digesting the sample to be tested, separating and matching the isotopes to obtain a Mg sample solution; diluting the Mg sample solution and a Mg standard solution with nitric acid solution, and then adding different volumes of Na-Al dual-element mixed standard solution to obtain multiple standard solutions and multiple sample solutions to be tested; using the sample-standard interpolation method, testing and collecting data from the multiple standard solutions and multiple sample solutions to be tested using MC-ICPMS; and calculating the isotopic composition of Mg in the Mg sample solution based on the collected data. This invention, by combining the Na-Al dual-element dilution method and the sample-standard interpolation method, effectively avoids outliers in individual data points and achieves accurate measurement of Mg isotopes on MC-ICPMS.

Description

Technical Field

[0001] This invention relates to the field of isotope analysis technology, and to a method for determining magnesium isotopes using Na-Al dual-element dilution. In particular, it designs a method for determining magnesium isotopes using Na-Al dual-element dilution based on a multi-receiver inductively coupled plasma mass spectrometer (MC-ICPMS). Background Technology

[0002] Magnesium isotopes have significant applications and scientific importance in Earth sciences, environmental sciences, and biogeochemistry. Studying magnesium isotopic composition can reveal the physicochemical processes of mantle melting, magma evolution, and carbonate rock formation, providing crucial evidence for understanding paleoclimate change and sedimentary genesis. In marine chemistry, magnesium isotopes reflect changes in seawater chemical composition and their relationship to the global carbon cycle, aiding in the study of ocean acidification and mineral precipitation processes. In biogeochemistry, magnesium isotopes are used to study the mechanisms of magnesium uptake and utilization by plants and marine organisms, revealing the cycling patterns of magnesium in ecosystems. Furthermore, magnesium isotopes have potential applications in industrial mineral mining, salt lake resource assessment, and hydrogeochemistry, providing important tools for revealing geochemical processes and environmental evolution.

[0003] The precise determination of magnesium isotopes has primarily developed in this century, relying on high-precision mass spectrometers and rigorous chemical separation procedures. Currently, magnesium isotope analysis mainly depends on high-precision mass spectrometry techniques, such as multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). MC-ICPMS has the advantages of high sensitivity and simultaneous detection of multiple isotopes, making it the mainstream technique for magnesium isotope analysis. However, isotopic fractionation inevitably occurs during MC-ICPMS determination of Mg isotopes.

[0004] In existing technologies, the main correction methods used to correct instrument mass fractionation effects include sample-standard interpolation, dual isotope dilution, and elemental dilution. However, since Mg lacks diluents with similar masses but different isotopes, elemental dilution cannot be used for correction. Dual diluent dilution is only suitable for systems with four stable isotopes; Mg has three stable isotopes, therefore, dual diluent dilution cannot be used to correct instrument fractionation. Therefore, sample-standard interpolation is currently the method used to correct instrument isotope mass fractionation when analyzing Mg isotopic composition using MC-ICPMS.

[0005] However, the sample-standard interpolation method requires the instrument to remain stable; even small changes in laboratory temperature, humidity, and pressure can lead to unstable analytical results. Furthermore, this method demands that the analyte and the interpolated standard have the same elemental concentration, acid concentration, and other matrix effects, thus requiring a high degree of matching between the sample and the standard. These factors often result in outliers in individual data points when analyzing Mg isotopes using the sample-standard interpolation method, affecting the precision and accuracy of isotope analysis. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for determining magnesium isotopes using Na-Al dual-element dilution. This invention uses... 23 Na and 27 Al is used as a diluent element in the two-element dilution method. By combining the Na-Al two-element dilution method with the sample-standard interpolation method to measure Mg isotopes, it helps to correct the isotope fractionation effect in the instrument analysis process, so as to accurately analyze the Mg isotope composition of the sample to be tested.

[0007] The present invention provides a method for determining magnesium isotopes using Na-Al dual-element dilution, which is achieved through the following technical solution:

[0008] This invention takes into account that the ionization efficiencies of Na and Al are relatively close to those of Mg, exhibiting good compatibility under the same analytical conditions in MC-ICPMS, which facilitates accurate fractionation correction. Furthermore, the stable isotopes of Na... 23 Stable isotopes of Na and Al 27 Stable isotopes of Al and Mg ( 24 Mg 25 Mg and 26 Mg) have similar and complementary masses, therefore this invention uses 23 Na and 27 Al, as a diluent element in the Na-Al dual-element dilution method, helps to correct for isotope fractionation effects during instrument analysis when measuring Mg isotopes, thus enabling accurate analysis of the Mg isotope composition of the sample. Furthermore, this invention provides a method for determining magnesium isotopes using Na-Al dual-element dilution, 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 single-element standard solution was mixed to obtain a Na-Al dual-element standard solution, which was used as a Mg dual-element diluent; wherein the Na element concentration and Al element concentration of the Na-Al dual-element standard solution were the same.

[0011] It should be noted that this invention is made at a relatively low cost and is readily available. 23 Na element single standard solution and 27 Using Al elemental single-standard solution as a raw material for preparing Mg dual-element diluent reduces experimental costs and makes this method easy to promote and apply.

[0012] In some preferred embodiments of the present invention, the following are employed: 23 The sodium element single standard solution was GSB-Na with a concentration of 1000 ppm. 27 The Al element single standard solution is GSB-Al with a concentration of 1000 ppm, and the... 23 Na element single standard solution and 27 Equal volumes of Al element single-standard solution were mixed to form 23 Na element and 27 A Na-Al bi-element mixed standard solution with an Al concentration of 500 ppm.

[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 was subjected to chemical digestion, isotope separation and concentration matching in sequence to obtain Mg sample solution.

[0016] It should be noted that the chemical digestion, isotope separation and concentration matching of the test samples in this invention are all performed using conventional techniques in the field, which should be known to those skilled in the art, and therefore will not be described in detail here.

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

[0018] Using a Mg standard solution as an external calibration standard, the Mg sample solution and the Mg standard solution were diluted with nitric acid solution, and then different volumes of the Mg dual-element diluent were added to obtain multiple standard solutions 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 was employed, and a multi-receiver inductively coupled plasma mass spectrometer was used to test multiple standard solutions and multiple sample solutions, respectively. Samples were collected from each standard solution and each sample solution. 27 Al、 23 Na、24 Mg 25 Mg and 26 Mg signal data.

[0022] It should be noted that the sample-standard interpolation method described in this invention uses a "standard-sample-standard" sequence to alternately test the standard solution to be tested and the sample solution to be tested, in order to correct the isotope fractionation coefficient β during the instrument analysis process.

[0023] In some preferred embodiments of the present invention, the present invention achieves simultaneous determination on a multi-receiver 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] In some preferred embodiments of the present invention, the multi-receiver inductively coupled plasma mass spectrometer is used for testing with wet sample introduction and a PFA nebulizer is used.

[0025] In some preferred embodiments of the present invention, when the multi-receiver inductively coupled plasma mass spectrometer is used for testing, the focusing voltage and deflection voltage at which the peak centers of each isotope of Mg coincide are selected as the test parameters. For example, in some preferred embodiments, when the Neptune Plus multi-receiver inductively coupled plasma mass spectrometer is used for testing, 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, at which point the peak centers of each isotope of Mg coincide, so as to achieve accurate measurement of isotope ratios. Furthermore, when using the Neptune Plus multi-receiver inductively coupled plasma mass spectrometer for testing, other testing parameters were set as follows: integration time was set to 2.095s to 2.100s; number of blocks was set to ≥1; and cycle number per block was set to 25 to 35. This ensured that while achieving accurate measurement of isotopic composition, too much time was wasted, which could lead to a large isotopic fractionation effect on the instrument.

[0026] Step 5, Data Analysis:

[0027] Based on the collected data, signal data is obtained, and calculations are performed. 27 Al / 23 Na、 25 Mg / 24 Mg 26 Mg / 24 Mg and isotopic fractionation coefficient β; utilizing 27 Al / 23 The isotopic composition of Mg in the Mg sample solution was calculated using Na and the isotopic fractionation coefficient β.

[0028] It should be noted that this invention is based on the measured... 23 Na、 24 Mg 25 Mg 26 Mg and 27 The data of Al were calculated to obtain 27 Al / 23 Na、 25 Mg / 24 Mg and 26 Mg / 24 The ratio of Mg; 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 ratio of Mg is calculated, and the isotopic composition of Mg in the Mg test solution is obtained through the following steps:

[0029] 1) Obtained through testing 23 Na、 24 Mg 25 Mg 26 Mg and 27 The signal data of Al was used to calculate ( 27 Al / 23 Na) Measured 、( 25 Mg / 24 Mg) Measured and( 26 Mg / 24 Mg) Measured The ratio of the three isotopes.

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

[0031]

[0032] In Equation 1, ( 27 Al / 23 Na) Measured The result calculated based on the test data in step 1) above. 27 Al / 23 Na value; ( 27 Al / 23 Na) True =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 isotopic fractionation coefficient β and ( 25 Mg / 24 Mg) Measured As input, the formula shown in Equation 2 is used to calculate ( 25 Mg / 24 Mg) True :

[0034]

[0035] In Equation 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 isotopic fractionation coefficient β and ( 26 Mg / 24 Mg) Measured As input, the formula shown in Equation 3 is used to calculate ( 26 Mg / 24 Mg) True :

[0037]

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

[0039] 5) Following the methods in steps 1) to 4) above, calculate the values ​​of each standard solution and sample solution to be tested, and obtain the values ​​of each standard solution and sample solution measured. 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 to be tested ( 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) above ( 26 Mg / 24 Mg) Standard 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 using the formula shown in Equation 4. 26 Mg content:

[0041]

[0042] 7) The isotope ratio of the obtained standard solution to be tested ( 25 Mg / 24 Mg) Standard 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 using the formula shown in Equation 5. 25 Mg content:

[0043]

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

[0045] This invention is based on 23 Na and 27Al, as a dilution element in the two-element dilution method, exhibits good compatibility under the same analytical conditions of MC-ICPMS due to the similar ionization efficiencies of Na and Al to Mg, thus facilitating accurate fractionation correction. Furthermore, the Na-Al two-dilution method does not require complex calculations when correcting fractionation errors in instrumental analysis; the corrected Mg isotope ratio can be obtained using only the instrument's built-in functions. Moreover, combining the Na-Al two-dilution method with the sample-standard interpolation method yields the advantages of the latter while mitigating its stringent requirements for sample and standard matrix compatibility. Additionally, the two-element dilution method provides higher correction redundancy; combining the isotope ratios of the two elements with the sample isotope ratio improves the robustness of the correction model. Furthermore, this invention offers advantages in terms of relatively low cost and easy availability. 23 Na element single standard solution and 27 Using Al single-element standard solution as a raw material for preparing Mg dual-element diluent reduces experimental costs and makes the invented determination method easy to promote and apply. This invention, by combining the Na-Al dual-element dilution method and the sample-standard interpolation method, effectively avoids outliers in individual data points, achieving accurate measurement of Mg isotopes on MC-ICPMS. Attached Figure Description

[0046] Figure 1 This is a structural diagram of the Faraday Cup.

[0047] Figure 2 The image shows the peak shapes of each isotope during the measurement process in Example 1.

[0048] Figure 3 The main instrument parameters were set during the measurement process in Example 1.

[0049] Figure 4 The results are from Example 1. Detailed Implementation

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

[0051] Example 1

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

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

[0054] Using GSB-Na at a concentration of 1000 ppm as 23 A single-standard Na solution, using GSB-Al with a concentration of 1000 ppm as... 27To obtain a Na-Al dual-element standard solution, equal volumes of 1000 ppm GSB-Na and 1000 ppm GSB-Al were mixed. This Na-Al dual-element standard solution was then used as the Mg dual-element diluent, which is the Mg dual-element diluent used in this embodiment. 23 Na element and 27 The concentration of Al was 500 ppm.

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

[0056] Using conventional techniques in this field, the sample to be tested was subjected to chemical digestion, isotope separation and concentration matching in sequence to obtain a Mg sample solution.

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

[0058] A pure Mg solution, MsMg, with a concentration of 1000 ppm, was used as the Mg standard solution and as an external calibration standard. The Mg sample solution and the Mg standard solution were diluted with a 2% nitric acid solution, 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, resulting in multiple standard solutions and multiple sample solutions to be tested.

[0059] Step 4, Instrument Testing:

[0060] Using a sample-standard interleaving method, following a "standard-sample-standard" sequence, a multi-receiver inductively coupled plasma mass spectrometer was employed to alternately test multiple standard solutions and multiple sample solutions, collecting data on the concentrations of each standard solution and each sample solution. 27 Al、 23 Na、 24 Mg 25 Mg and 26 The signal of Mg.

[0061] Step 5, Data Analysis:

[0062] Based on the collected data, signal data is obtained, and calculations are performed. 27 Al / 23 Na、 25 Mg / 24 Mg 26 Mg / 24 Mg and isotopic fractionation coefficient β; utilizing 27 Al / 23The isotopic composition of Mg in the Mg sample solution was calculated using Na and the isotopic fractionation coefficient β, and 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 was used to calculate ( 27 Al / 23 Na) Measured 、( 25 Mg / 24 Mg) Measured and( 26 Mg / 24 Mg) Measured The ratio of the three isotopes.

[0064] 5.2) The calculated ( 27 Al / 23 Na) Measured Using the input as an example, the isotopic fractionation coefficient β is calculated using the formula shown in Equation 1:

[0065]

[0066] In Equation 1, ( 27 Al / 23 Na) Measured This is the result calculated based on the test data in step 5.1) above. 27 Al / 23 Na value; ( 27 Al / 23 Na) True =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) with isotopic fractionation coefficient β and ( 25 Mg / 24 Mg) Measured As input, the formula shown in Equation 2 is used to calculate ( 25 Mg / 24 Mg) True :

[0068]

[0069] In Equation 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) with isotopic fractionation coefficient β and ( 26 Mg / 24 Mg) Measured As input, the formula shown in Equation 3 is used to calculate ( 26 Mg / 24 Mg) True :

[0071]

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

[0073] 5.5) Following the methods described in steps 5.1) to 5.4), calculate the values ​​of each standard solution and sample solution to be tested, obtaining the ( ) of each standard solution and sample solution measured. 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 to be tested ( 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 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 using the formula shown in Equation 4. 26 Mg content:

[0075]

[0076] 5.7) The isotope ratio of the obtained standard solution to be tested ( 25 Mg / 24 Mg) Standard 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 using the formula shown in Equation 5. 25 Mg content:

[0077]

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

[0079] In the experiment of this embodiment, the correspondence between each Faraday cup and isotope is as follows: L5- 23 Na; L3- 24 Mg; C- 25 Mg;H2- 26 Mg;H4- 27 Al, and the structure of each Faraday cup is as follows Figure 1 As shown.

[0080] The Focus Quad was set to -3.4V and the Dispersion Quad to 41.9V to achieve the overlap of the peak centers of each isotope of Mg, and the peak shape of the overlapped isotopes is shown in the figure below. Figure 2 As shown, this is to achieve accurate measurement of isotope ratios. It should be noted that... Figure 2 The horizontal axis 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 embodiment, when analyzing Mg isotopes using the Neptune Plus multi-receiver inductively coupled plasma mass spectrometer, some key instrument parameters are as follows: Figure 3 As shown in the figure. In this embodiment, during analysis, the Integration Time is set to 2.097s; the Number of Blocks is set to 1; and the Cycles / Block is set to 30. This is to achieve accurate measurement of isotopic composition without wasting too much time and causing a large isotopic fractionation effect in the instrument. Furthermore, in this embodiment, the analysis of the standard solution and the sample solution is interleaved to correct for isotopic fractionation during the instrument's analysis process.

[0082] This embodiment combines the Na-Al dual-element dilution method and the sample-standard interpolation method, and the test results after the above test analysis are as follows: Figure 4 As shown, δ 25 Mg = -2.53‰ ± 0.04‰ (2SD) and δ 26 Mg = -4.89‰ ± 0.04‰ (2SD), indicating that the δ value can be determined using the method of this invention. 25 Mg and δ 26 The long-term accuracy for Mg is 0.04‰ (2SD), which is much lower than the long-term accuracy of the widely used sample-standard interpolation method (typically ~0.08‰, 2SD). Furthermore, the method of this invention is less sensitive to matrix effects in the test sample and standard solution, and facilitates sample preparation before analysis.

[0083] As described above, this invention, by combining the Na-Al double dilution method and the sample-standard interpolation method, not only achieves the advantages of the sample-standard interpolation method but also overcomes its drawback of stringent requirements for sample and standard matrix compatibility. Furthermore, the dual-element dilution method provides higher calibration redundancy, and by combining the isotope ratios of the two elements and the sample isotope ratio, the robustness of the calibration model can be improved. In addition, this invention offers advantages such as relatively low cost and easy availability. 23 Na element single standard solution and 27 Using Al single-element standard solution as a raw material for preparing Mg dual-element diluent reduces experimental costs and makes the invented determination method easy to promote and apply. This invention, by combining the Na-Al dual-element dilution method and the sample-standard interpolation method, effectively avoids outliers in individual data points, achieving accurate measurement of Mg isotopes on MC-ICPMS.

[0084] Obviously, the above embodiments only illustrate one method for accurately determining the Na / Al ratio and Na / Mg ratio of Mg isotopes. Those skilled in the art can replace the Na / Al ratio and Na / Mg ratio to achieve the same effect as the present invention based on the above embodiments, or make equivalent substitutions for some of the technical features. All other embodiments obtained within the spirit and principles of the present invention without creative effort are within the scope of protection of the present invention.

Claims

1. A method for determining magnesium isotopes using Na-Al dual-element dilution, characterized in that, Includes the following steps: Will 23 Na element single standard solution and 27 The Al element single standard solution was mixed to obtain the Na-Al dual element mixed standard solution, and the Na-Al dual element mixed standard solution was used as the Mg dual element diluent; wherein, the Na element concentration and Al element concentration of the Na-Al dual element mixed standard solution were the same. The sample to be tested was subjected to chemical digestion, isotope separation and concentration matching in sequence to obtain Mg sample solution; Using Mg standard solution as an external calibration standard, the Mg sample solution and the Mg standard solution were diluted with nitric acid solution, and then different volumes of the Mg dual-element diluent were added to obtain multiple standard solutions and multiple sample solutions to be tested. The sample-standard interpolation method was employed, and a multi-receiver inductively coupled plasma mass spectrometer was used to test multiple standard solutions and multiple sample solutions, respectively. Samples were collected from each standard solution and each sample solution. 27 Al、 23 Na、 24 Mg 25 Mg and 26 Mg signal data; Based on the collected signal data, the following calculations were performed. 27 Al / 23 Na、 25 Mg / 24 Mg 26 Mg / 24 Mg and isotopic fractionation coefficient β; utilizing 27 Al / 23 The isotopic composition of Mg in the Mg sample solution was calculated using Na and the isotopic fractionation coefficient β.

2. The method for determining magnesium isotopes using Na-Al dual-element dilution as described in claim 1, characterized in that, Specifically, through the following steps, using 27 Al / 23 The isotopic composition of Mg in the Mg sample solution was calculated using Na and the isotopic fractionation coefficient β: 1) Obtained through testing 23 Na、 24 Mg 25 Mg 26 Mg and 27 The signal data of Al was used to calculate ( 27 Al / 23 Na) Measured 、( 25 Mg / 24 Mg) Measured and( 26 Mg / 24 Mg) Measured Ratios of the three isotopes; 2) Based on the calculated ( 27 Al / 23 Na) Measured Using the input as an example, the isotopic fractionation coefficient β is calculated using the formula shown in Equation 1: In Equation 1, ( 27 Al / 23 Na) Measured The result calculated based on the test data in step 1) above. 27 Al / 23 Na value;( 27 Al / 23 Na) True =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 isotopic fractionation coefficient β and ( 25 Mg / 24 Mg) Measured As input, the formula shown in Equation 2 is used to calculate ( 25 Mg / 24 Mg) True : In Equation 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 isotopic fractionation coefficient β and ( 26 Mg / 24 Mg) Measured As input, the formula shown in Equation 3 is used to calculate ( 26 Mg / 24 Mg) True : In Equation 3, for 26 The relative atomic mass of Mg is 24.9858370; 5) Following the methods in steps 1) to 4) above, calculate the values ​​of each standard solution and sample solution to be tested, and obtain the values ​​of each standard solution and sample solution measured. 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 to be tested ( 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) above ( 26 Mg / 24 Mg) Standard 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 using the formula shown in Equation 4. 26 Mg content: 7) The isotope ratio of the obtained standard solution to be tested ( 25 Mg / 24 Mg) Standard 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 using the formula shown in Equation 5. 25 Mg content:

3. The method for determining magnesium isotopes using Na-Al dual-element dilution as described in claim 1, characterized in that, When testing with the multi-receiver inductively coupled plasma mass spectrometer, wet sample introduction is used, and the nebulizer used is a PFA nebulizer.

4. The method for determining magnesium isotopes using Na-Al dual-element dilution as described in claim 1, characterized in that, When testing with the multi-receiver inductively coupled plasma mass spectrometer, the focusing voltage and deflection voltage at which the peak centers of each isotope of Mg coincide are selected as the test parameters.

5. The method for determining magnesium isotopes using Na-Al dual-element dilution as described in claim 1, characterized in that, The 23 The Na element single standard solution is GSB-Na with a concentration of 1000 ppm.

6. The method for determining magnesium isotopes using Na-Al dual-element dilution as described in claim 1, characterized in that, The 27 The Al element single standard solution is GSB-Al with a concentration of 1000 ppm.

7. The method for determining magnesium isotopes using Na-Al dual-element dilution as described in claim 1, characterized in that, 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 dual-element dilution as described in claim 1, characterized in that, The mass concentration of the nitric acid solution is 1% to 3%.

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