Method for separating, purifying and determining Cu isotope in basalt or peridotite sample

Abstract

The invention relates to a method for separating, purifying and determining Cu isotope in a basalt or peridotite sample, and belongs to the technical field of Cu isotope separation. A method for separating and purifying Cu isotope in a basalt or peridotite sample comprises the following steps: digesting the basalt or peridotite sample to obtain a digestion solution; adding an ammonia water solution into the digestion solution to obtain a precipitate, centrifuging to obtain a supernatant, and adding hydrochloric acid to obtain a basic treatment solution; and the basic treatment liquid is separated and purified through anion exchange resin, and the Cu isotope solution is obtained. According to the purification method, the pH values of different ions precipitated in ammonia water are different, the precipitation is formed by adding the ammonia water solution, Cu mainly exists in the solution in the form of ammonia complex ions [Cu (NH3) 4] < 2 + > and then is separated from most matrix elements, and the process is simple and efficient.

Description

Technical Field

[0001] The invention relates to the technical field of Cu isotope separation, and in particular to a method for separating, purifying and determining Cu isotopes in basalt or peridotite samples. Background Art

[0002] Copper (Cu) is a transition metal with two stable isotopes: 63 Cu (69.17%) and 65 Cu (30.83%). Cu is moderately volatile, siderophilic, and highly sulfur-philic, so the Cu isotope ratio can be used to trace geological processes such as partial melting or crystallization differentiation. Peridotite and basalt are the products of partial melting and crystallization differentiation, respectively. Accurately measuring the Cu isotope ratio in these rock samples is of great significance in revealing these geological processes.

[0003] Sample preparation is the key to high-precision Cu isotope determination. Sample preparation mainly includes two parts: sample digestion and separation and purification of target elements. Conventional chemical reagents (HNO3, HF, HCl, etc.) are usually used to completely dissolve the sample, and then solid phase extraction is used to separate the matrix elements while ensuring that the elements to be measured have a high recovery rate. This process needs to follow two principles: 1) Try not to introduce other interfering elements and reduce the background of the entire process to the lowest level; 2) The target element is not lost and the recovery rate is close to 100%.

[0004] At present, the separation and purification of Cu in basalt or peridotite samples mainly adopts solid phase extraction, that is, separation is carried out according to the difference in the binding force between different ions in the solution and the active groups of the resin in the resin column. Anion resins such as AG MP-1M and AG1-X8 are usually used to separate the target element Cu through 2-4 column passes, where the number of column passes mainly depends on the Cu content and Fe / Cu ratio in the sample. The lower the Cu content or the higher the Fe / Cu ratio, the more column passes. This leads to the following problems in the actual test process: 1) The Cu content is low (< 10 ppm) and the Fe / Cu ratio is high (> 3000). The Cu isotope test requires a large sample weight, which will make the chemical treatment procedure complicated and time-consuming; 2) The higher the sample weight, the higher the content of matrix elements such as Mg, Al, Ca, Ti, Cr, and Fe in the sample, which will make the separation and purification complicated; 3) The more separation and purification times, the higher the background of the whole process, and the recovery rate may also be reduced. 4) In addition, if the content of matrix elements is too high, it will seriously interfere with the sensitivity of the elements to be tested and will also affect the accuracy of the test. Summary of the invention

[0005] In view of the above analysis, the present invention aims to provide a method for separation, purification and determination of Cu isotopes in basalt or peridotite samples, so as to solve at least one of the problems of the existing Cu isotope separation and purification process, the large number of column passes, the large amount of acid and resin used, the high cost, the low efficiency, the low Fe ion removal rate, and the impact on the test accuracy.

[0006] A method for separating and purifying Cu isotopes in basalt or peridotite samples, comprising: Digesting the basalt or peridotite sample to obtain a digestion solution; Adding an ammonia solution to the digestion solution to obtain a precipitate, centrifuging to obtain a supernatant, and adding hydrochloric acid to obtain a basic treatment solution; The basic treatment solution is separated and purified by anion exchange resin to obtain a Cu isotope solution.

[0007] Further, an aqueous ammonia solution is added until the solution pH is ≥ 12 to obtain a precipitate.

[0008] Furthermore, the mass fraction of ammonia water in the ammonia solution is 25-28%.

[0009] Further, the digestion specifically comprises the following steps: (1a) Add concentrated HNO3 and concentrated HF to a basalt or peridotite sample and heat in a sealed container until the sample is completely dissolved or a small amount of white flocculent precipitate is present to obtain a solution; (1b) evaporating the solution to dryness and cooling to room temperature, adding concentrated HCl and concentrated HNO3, and heating in a sealed container to obtain a clear solution; (1c) The clear solution is evaporated to dryness and cooled to room temperature, a dilute HNO3 solution is added, and the mixture is heated in a sealed container until a clear solution is obtained, i.e., the digestion solution.

[0010] Furthermore, in step (1a), the mass ratio of the basalt or peridotite sample to the total volume of concentrated HNO3 and concentrated HF is 100 mg: 3 mL, and the volume ratio of concentrated HNO3 and concentrated HF is 2:1.

[0011] Furthermore, in step (1b), the volume ratio of concentrated HCl to concentrated HNO3 is 3:1.

[0012] Furthermore, in step (1c), the mass fraction of HNO3 in the dilute HNO3 solution is 0.5 mol / L.

[0013] Furthermore, the preparation of the basic treatment solution specifically includes the following steps: (2a) adding the digestion solution to an aqueous ammonia solution until the pH of the solution becomes alkaline; (2b) standing the mixture until a precipitate is formed, centrifuging the mixture to separate the solid precipitate from the supernatant, and retaining the supernatant; (2c) evaporating the supernatant to dryness and cooling to room temperature, adding concentrated HCl, and heating in a sealed container until the hot solution becomes clear; (2d) The clear solution was evaporated to dryness and cooled to room temperature, and 8 mol / L HCl was added to obtain the basic treatment solution.

[0014] Furthermore, the method for preparing the Cu isotope solution comprises the following steps: (3a) filling the ion exchange column with anion exchange resin to obtain an anion resin exchange column; (3b) adding the basic treatment solution to the anion resin exchange column, eluting with 8 mol / L HCl to elute the matrix elements, so that the Cu ions are retained on the anion resin exchange column; (3c) The anion resin exchange column adsorbed with Cu ions is further eluted with 8 mol / L HCl solution to elute the Cu ions and collect the Cu isotope solution.

[0015] In a second aspect, the present invention provides a method for determining Cu isotopes in basalt or peridotite samples, which specifically includes the following steps: The Cu isotope solution prepared by the above method is made into a Cu isotope on-machine solution; The Cu isotope composition was obtained by using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS).

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) The purification method of the present invention utilizes the different pH values ​​of precipitation of different ions in ammonia water, and forms a precipitate by adding an ammonia solution, wherein Cu is mainly in the form of an ammonia complex ion [Cu(NH3)4] 2+ exists in the solution in the form of, and is then separated from most matrix elements. The process is simple and efficient.

[0017] (2) The purification method of the present invention is used to pre-enrich and purify Cu, which effectively solves the problem of excessive Fe ion content in the chemical pretreatment process. The Fe ion removal rate is as high as 95%, and there are significant reductions in the number of column passes, acid usage, resin usage and the cost of the entire process.

[0018] (3) The Cu isotope determination method of the present invention has good reproducibility. High-precision Cu isotope data can be obtained by the method of the present invention, which can be used to determine the Cu isotope ratio of basalt or peridotite samples.

[0019] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents particularly pointed out in the description. DETAILED DESCRIPTION

[0020] The following embodiments of the present invention illustrate the principles of the present invention and are not intended to limit the scope of the present invention.

[0021] Rocks are usually composed of a variety of minerals with different properties. For example, common minerals in basalt and peridotite include olivine, pyroxene, spinel, etc. The chemical composition of these minerals is complex and contains a large number of matrix elements, such as silicon, aluminum, iron, magnesium, calcium, etc. These matrix elements will interfere with the separation and analysis of Cu isotopes, increasing the difficulty of analysis. Low-content Cu isotopes are easily lost during the separation process, resulting in low recovery, which affects the accuracy and reliability of the final isotope analysis results. To accurately determine the isotope composition, the target isotope needs to be completely separated from other matrix elements and interfering elements. However, due to the complex sample matrix and diverse mineral composition, the separation process is easily affected by many factors, such as the type of acid, the amount of acid used, the concentration of the acid, etc., which makes separation and purification difficult. At the same time, the recovery rate of the target isotope needs to be close to 100% during the separation process, which is very challenging in actual operation.

[0022] In the prior art, it is first necessary to use a special resin to separate Cu from other matrix elements, and then further purified by a cation exchange resin. The whole separation process requires accurate control of the concentration and dosage of various chemical reagents, as well as the conditions such as the temperature and time of separation, which may cause the loss or pollution of Cu isotopes if not carefully. In the separation process, Cu isotopes are easily lost, and it is difficult to ensure that their recovery rate is close to 100%. For example, when using a special resin and a cation exchange resin to separate, a part of Cu isotopes may remain on the resin, or be contaminated by other elements during elution, thereby causing a reduction in the recovery rate.

[0023] The mineral composition of basalt and peridotite is complex, and it is difficult to effectively separate the minerals in them using common mineral separation methods. For example, simple physical separation methods such as gravity separation and magnetic separation are difficult to separate Cu from complex mineral combinations in minerals such as olivine and pyroxene. The content of Cu in basalt and peridotite is very low, and it needs to be completely separated from other matrix elements and interfering elements to ensure its high purity. Ordinary mineral separation methods are difficult to meet this requirement, which easily leads to the loss and contamination of Cu isotopes, affecting the accuracy of its analysis results.

[0024] A specific embodiment of the present invention discloses a method for separating and purifying Cu isotopes in basalt or peridotite samples, comprising: Digesting the basalt or peridotite sample to obtain a digestion solution; Adding an ammonia solution to the digestion solution to obtain a precipitate, centrifuging to obtain a supernatant, and adding hydrochloric acid to obtain a basic treatment solution; The basic treatment solution is separated and purified by anion exchange resin to obtain a Cu isotope solution.

[0025] Compared with the prior art, the method of the present invention utilizes the different pH values ​​of precipitation of different ions in ammonia water, and forms Mg(OH)2, Al(OH)3, Ca(OH)2, TiO2·xH2O, Cr(OH)3, Fe(OH)3 and other precipitates by adding ammonia solution, among which Cu is mainly in the form of ammonia complex ion [Cu(NH3)4] 2+ It exists in the solution in the form of, and is then separated from most matrix elements (Mg, Al, Ca, Ti, Cr, Fe, etc.). The process is simple and efficient.

[0026] The method of the present invention is used to pre-enrich and purify Cu, which effectively solves the problem of excessively high Fe ion content in the chemical pretreatment process, and the Fe ion removal rate is as high as 95%. Whether it is the number of column passes, the amount of acid used, the amount of resin used or the cost of the entire process, there are significant reductions.

[0027] The method of the present invention has good reproducibility. High-precision Cu isotope data can be obtained by the method of the present invention, and is used for determining the Cu isotope ratio of basalt or peridotite samples.

[0028] Specifically, the basalt or peridotite sample is digested in a polytetrafluoroethylene sample dissolution tank.

[0029] Specifically, ammonia water is added until the solution pH value is ≥ 12. Since Cu is first precipitated and then dissolved in ammonia water, the pH value is very important. Different pH values ​​result in different Cu recovery rates, which will lead to large differences in results. Therefore, the present invention controls the pH value to be ≥ 12.

[0030] It should be noted that the basalt or peridotite samples in the present invention are international standard samples, and the amount required for Cu isotope determination is mainly determined by the Cu content in the sample and the instrument testing technology.

[0031] Typically, high-precision Cu isotope determination requires 1 ppm of Cu, so the weighed mass is 5 to 200 mg, depending on the Cu content in the sample.

[0032] Specifically, the digestion specifically includes: (1a) Add concentrated HNO3 and concentrated HF to a basalt or peridotite sample and heat in a sealed container until the sample is completely dissolved or a small amount of white flocculent precipitate is present to obtain a solution; (1b) evaporating the solution to dryness and cooling to room temperature, adding concentrated HCl and concentrated HNO3, and heating in a sealed container to obtain a clear solution; (1c) The clear solution is evaporated to dryness and cooled to room temperature, a dilute HNO3 solution is added, and the mixture is heated in a sealed container until a clear solution is obtained, i.e., the digestion solution.

[0033] Specifically, in step (1a), the mass ratio of the basalt or peridotite sample to the total volume of concentrated HNO3 and concentrated HF is 100 mg: 3 mL, and the volume ratio of concentrated HNO3 to concentrated HF is 2: 1. HF acid is added to remove Si, and concentrated HNO3 is added to dissolve.

[0034] Specifically, in step (1b), the volume ratio of concentrated HCl to concentrated HNO3 is 3:1. The acidity of aqua regia composed of concentrated HCl and concentrated HNO3 is strong, which can dissolve the sample better. Specifically, in step (1c), the mass fraction of HNO3 in the dilute HNO3 solution is 0.5 mol / L. Dilute HNO3 plays a role in dissolving the sample and reacts better with ammonia water.

[0035] Specifically, the mass fraction of ammonia water in the ammonia solution is 25-28%.

[0036] Specifically, the preparation of the basic treatment solution comprises the following steps: (2a) adding the digestion solution to an aqueous ammonia solution until the pH of the solution becomes alkaline; (2b) Let the mixture stand for 10 min until a precipitate is formed, centrifuge to separate the solid precipitate from the supernatant, and retain the supernatant; (2c) evaporating the supernatant to dryness and cooling to room temperature, adding concentrated HCl, and heating in a sealed container until the hot solution becomes clear; (2d) The clear solution was evaporated to dryness and cooled to room temperature, and 8 mol / L HCl was added to obtain the basic treatment solution.

[0037] Specifically, in step (2a), the pH value is adjusted to be ≥12.

[0038] It should be noted that when the pH value is 12, the matrix elements in the sample can basically exist in the form of precipitates such as Mg(OH)2, Al(OH)3, Ca(OH)2, TiO2·xH2O, Cr(OH)3, and Fe(OH)3.

[0039] In step (2c), concentrated HCl is added as a transfer medium to convert the ammonia water added in the previous step into a hydrochloric acid medium to ensure that there is no residue. In step (2d), 8 mol / L hydrochloric acid is used as the concentration for column flow in preparation for the next step.

[0040] Specifically, the method for preparing the Cu isotope solution comprises the following steps: (3a) filling the ion exchange column with anion exchange resin to obtain an anion resin exchange column; (3b) adding the basic treatment solution to the anion resin exchange column, eluting with 8 mol / L HCl to elute the matrix elements, so that the Cu ions are retained on the anion resin exchange column; (3c) The anion resin exchange column adsorbed with Cu ions is further eluted with 8 mol / L HCl solution to elute the Cu ions and collect the Cu isotope solution.

[0041] Specifically, in step (3a), the anion exchange resin is washed three times with ultrapure water (MQ water) and 0.5 mol / L HNO3 alternately, and then 8 mol / L HCl solution is added to balance the anion exchange resin to obtain an anion resin exchange column.

[0042] Specifically, the anion exchange resin is AG MP-1M anion exchange resin, which is a large-pore strong alkaline anion exchange resin.

[0043] Another specific embodiment of the present invention discloses a method for determining Cu isotopes in basalt or peridotite samples, which specifically includes the following steps: The Cu isotope solution prepared by the above method is made into a Cu isotope on-machine solution; The Cu isotope composition was obtained by using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS).

[0044] Specifically, the Cu isotope solution is evaporated to dryness, added into a concentrated nitric acid medium, evaporated to dryness, and then added with a 2% by mass HNO3 solution to dissolve, thereby obtaining an on-machine solution.

[0045] Specifically, the Cu stable isotope ratio is determined by the sample-standard interpolation method.

[0046] Specifically, the test of Cu isotope composition is carried out in low resolution mode, and the corresponding MC-ICP-MS working parameter settings are shown in Table 1: Table 1 MC-ICP-MS operating parameters

[0047] In order to correct the mass discrimination effect of the instrument, the external standard solution of Cu (NIST SRM 3114) needs to be measured before and after the determination of the Cu isotope composition of the sample. The injection system needs to be cleaned with 2 wt% HNO3 before each test. The determination sequence is as follows: 2 wt% HNO3 cleaning-NIST SRM 3114-2 wt% HNO3 cleaning-test sample- 2 wt% HNO3 cleaning-NIST SRM 3114-2 wt% HNO3 cleaning-test sample- 2 wt% HNO3 cleaning-NIST SRM 3114-2 wt% HNO3 cleaning-test sample- 2 wt% HNO3 cleaning-NIST SRM 3114-2 wt% HNO3 cleaning… To ensure the reliability of the data, each sample was measured at least three times.

[0048] The mass discrimination of Cu isotope data is corrected using the sample-standard interpolation method, that is, the average fractionation coefficient of the external standard solution NIST SRM 3114 with known isotope ratios before and after the sample is measured is calculated, and it is approximately considered to be consistent with the fractionation coefficient of the sample, and then the true isotope ratio of the sample is calculated: R sam = r samp / Ave.(r std ) Where R sam is the true isotope ratio after correction, r samp is the isotope ratio measured in the sample or standard, Ave.(r std ) is the average of the isotope ratios of the two standard samples before and after the sample.

[0049] The result is then converted to NIST SRM 976 to obtain the δ 65 Cu NIST SRM 976 The value is taken as the final Cu isotope detection result. The specific conversion formula is as follows: δ 65 Cu NIST SRM 976 = δ 65 Cu NIST SRM 3114 - 0.06.

[0050] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0051] Example 1 This embodiment takes the basalt standard samples BIR-1, BHVO-2, BCR-2 developed by the United States Geological Survey, the basalt standard sample JB-1b developed by the Geological Survey of Japan, and the peridotite standard sample JP-1 as examples to illustrate the specific implementation methods of the technical solution of the present invention.

[0052] The reagents and materials used in this example are further described: CMOS grade hydrochloric acid, nitric acid, hydrofluoric acid, and ammonia water: produced by Sinopharm Chemical Reagent Co., Ltd.

[0053] AG MP-1M resin: produced by Bio-Rad, USA, particle size 75-150 μm.

[0054] MQ water: prepared by Millipore-Q Element system of Millipore Corporation, USA, with water resistivity of 18.2 MΩ / cm.

[0055] MC-ICP MS: Sapphire collision reaction cell multi-collector inductively coupled plasma mass spectrometer produced by Nu Company; equipped with a nebulizer with a flow rate of 100 μl / min produced by ESI Company, USA.

[0056] NIST SRM 3114 Standard Sample: Published by the National Institute of Standards and Technology.

[0057] Polytetrafluoroethylene (PFA) beaker: Produced by Savillex, USA. It was cleaned with 50 wt% CMOS-grade hydrochloric acid, 50 wt% CMOS-grade nitric acid and MQ water in sequence before use.

[0058] A method for determining Cu isotopes in a basalt or peridotite sample in this embodiment specifically includes the following steps: (1) Accurately weigh 8 mg BIR-1, 7.7 mg BHVO-2, 19 mg JB-1b, 53 mg BCR-2, and 170 mg JP-1 and place them in polytetrafluoroethylene sample dissolving containers respectively; (2a) Add 1-3 mL 15.5 mol / L HNO3 and 0.5-0.15 mL 23.1 mol / L HF to the sample dissolving tank and heat at 150°C in a sealed container until the geological sample is completely dissolved or a small amount of white flocculent precipitate is present; (2b) The solution obtained in step (2a) was evaporated to dryness at 120°C and cooled to room temperature, 1.5 mL 11.3 mol / L HCl and 0.5 mL 15.5 mol / L HNO3 were added, and the mixture was heated in a sealed container at 120°C until a clear solution was obtained; (2c) The clear solution obtained in step (2b) was evaporated to dryness at 120°C and cooled to room temperature, 1 mL of 0.5 mol / L HNO3 solution was added, and the mixture was heated in a sealed container at 150°C until a clear solution was obtained, i.e., the digestion solution.

[0059] (3a) Add 4-5 ml of 25-28% ammonia solution to the digestion solution and adjust the pH value of the solution to 12. (3b) Allow to stand for 10 min until Fe(OH)3 and other precipitates are formed, and centrifuge at a speed of 5000 r / min for 10 min to separate the solid precipitate and the supernatant. Discard the precipitate and retain the supernatant. (3c) The supernatant obtained in step (3b) was evaporated to dryness at 120°C and cooled to room temperature, 1 mL of 11.3 mol / L HCl was added, and the mixture was heated in a sealed container at 150°C until a clear solution was obtained; (3d) The clear solution obtained in step (3c) was evaporated to dryness at 120° C. and cooled to room temperature, and 1 mL of 8 mol / L HCl was added to obtain the basic treatment solution.

[0060] (4a) The ion exchange column is filled with anion exchange resin, and the anion exchange resin is washed three times with 5 mL ultrapure water (MQ water) and 7 mL 0.5 M HNO3 alternately, and then 10 mL 8 mol / L HCl is added to balance the anion exchange resin to obtain an anion resin exchange column; (4b) Add the basic treatment solution to the anion resin exchange column described in (4a), elute with 9 mL 8 mol / L HCl to elute the matrix elements Mg, Al, K, Na, Ni, etc., so that the Cu ions are retained on the anion resin exchange column; (4c) The anion resin exchange column adsorbed with Cu ions is further eluted with 28 mL of 8M HCl solution to elute the Cu ions and collect the Cu isotope solution; (4d) Evaporate the collected Cu isotope solution, add 1 mL 15.5 mol / L HNO3, evaporate to dryness at 120℃ and cool to room temperature, add 1 ml 2 wt% HNO3 solution to dissolve, and obtain the upper solution.

[0061] (5) A multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) was used to test the Cu isotope solution. The sample-standard interpolation method was used for mass fractionation correction to obtain the Cu stable isotope composition.

[0062] Comparative Example 1 The method for determining Cu isotopes in basalt or peridotite samples in this comparative example is the same as that in Example 1, except that steps (2c) to (3b) are omitted and the clarified solution of (2b) is directly subjected to steps (3c) to (5).

[0063] Comparative Example 2 The method for determining Cu isotopes in the basalt or peridotite sample of this comparative example is the same as that of Example 1, except that in step (3a), the pH value is adjusted to 10.5.

[0064] Test Example 1 Calculate the δ of 5 international standards in Example 1, Comparative Example 1 and Comparative Example 2 65 Cu NIST SRM 976 The results and column times are shown in Table 2.

[0065] Table 2

[0066] From the results in Table 2, it can be seen that the method of the present invention can achieve high-precision measurement of Cu isotopes in basalt and peridotite samples (2SD ~ 0.02‰) by using one column separation and purification, which is within the error range of δ 65 Cu NIST SRM 976 The ratios are consistent, but the accuracy is significantly improved. The method of the present invention reduces the number of column passes and saves costs.

[0067] Test Example 2 The matrix elements of the solution before passing through the column of Example 1 and Comparative Example 2, i.e., the basic treatment solution in step (3d), were tested respectively; the matrix elements of the basic treatment solution in the clarified solution of step (2b) was tested before passing through the column of Comparative Example 1. The test was performed using the BCR-2 sample as an example, and the results are shown in Table 3.

[0068] Table 3

[0069] It can be seen from Table 3 that the matrix elements in the solution before passing through the column are significantly reduced by the method of the present invention.

[0070] The inventors also conducted the above test on other samples, and the results were basically the same. Due to limited space, they are not listed one by one.

[0071] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for separating and purifying Cu isotopes in basalt or peridotite samples, characterized in that: include: Digesting the basalt or peridotite sample to obtain a digestion solution; Adding an ammonia solution to the digestion solution to obtain a precipitate, centrifuging to obtain a supernatant, and adding hydrochloric acid to obtain a basic treatment solution; The basic treatment solution is separated and purified by anion exchange resin to obtain a Cu isotope solution.

2. The method for separating and purifying Cu isotopes in basalt or peridotite samples according to claim 1, characterized in that: Ammonia solution was added until the solution pH was ≥ 12 to obtain a precipitate.

3. The method for separating and purifying Cu isotopes in basalt or peridotite samples according to claim 1 or 2, characterized in that: The mass fraction of ammonia water in the ammonia water solution is 25-28%.

4. The method for separating and purifying Cu isotopes in basalt or peridotite samples according to claim 1, characterized in that: The digestion specifically comprises the following steps: (1a) Add concentrated HNO3 and concentrated HF to a basalt or peridotite sample and heat in a sealed container until the sample is completely dissolved or a small amount of white flocculent precipitate is present to obtain a solution; (1b) evaporating the solution to dryness and cooling to room temperature, adding concentrated HCl and concentrated HNO3, and heating in a sealed container to obtain a clear solution; (1c) The clear solution is evaporated to dryness and cooled to room temperature, a dilute HNO3 solution is added, and the mixture is heated in a sealed container until a clear solution is obtained, i.e., the digestion solution.

5. The method for separating and purifying Cu isotopes in basalt or peridotite samples according to claim 4, characterized in that: In step (1a), the mass ratio of the basalt or peridotite sample to the total volume of concentrated HNO3 and concentrated HF is 100 mg: 3 mL, and the volume ratio of concentrated HNO3 and concentrated HF is 2:

1.

6. The method for separating and purifying Cu isotopes in basalt or peridotite samples according to claim 4, characterized in that: In step (1b), the volume ratio of concentrated HCl to concentrated HNO3 is 3:

1.

7. The method for separating and purifying Cu isotopes in basalt or peridotite samples according to claim 4, characterized in that: In step (1c), the mass fraction of HNO3 in the dilute HNO3 solution is 0.5 mol / L.

8. The method for separating and purifying Cu isotopes in basalt or peridotite samples according to claim 1, characterized in that: The preparation of the basic treatment solution specifically includes the following steps: (2a) adding the digestion solution to an aqueous ammonia solution until the pH of the solution becomes alkaline; (2b) standing the mixture until a precipitate is formed, centrifuging the mixture to separate the solid precipitate from the supernatant, and retaining the supernatant; (2c) evaporating the supernatant to dryness and cooling to room temperature, adding concentrated HCl, and heating in a sealed container until the hot solution becomes clear; (2d) The clear solution was evaporated to dryness and cooled to room temperature, and 8 mol / L HCl was added to obtain the basic treatment solution.

9. The method for separating and purifying Cu isotopes in basalt or peridotite samples according to claim 1, characterized in that: The method for preparing the Cu isotope solution comprises the following steps: (3a) filling the ion exchange column with anion exchange resin to obtain an anion resin exchange column; (3b) adding the basic treatment solution to the anion resin exchange column, eluting with 8 mol / L HCl to elute the matrix elements, so that the Cu ions are retained on the anion resin exchange column; (3c) The anion resin exchange column adsorbed with Cu ions is further eluted with 8 mol / L HCl solution to elute the Cu ions and collect the Cu isotope solution.

10. A method for determining Cu isotopes in basalt or peridotite samples, characterized in that: The details include: Prepare a Cu isotope on-machine solution by using the Cu isotope solution prepared by the method according to any one of claims 1 to 9; The Cu isotope composition was obtained by using a multi-collector inductively coupled plasma mass spectrometer to test the Cu isotope solution.

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