A method for analyzing hafnium isotope in a geological sample

Abstract

This invention discloses a method for Hf isotope analysis in geological samples, belonging to the field of chemical analysis technology. The method includes the following steps: dissolving the geological sample to obtain a sample solution; chemical separation and enrichment, loading the sample solution into an ion exchange column loaded with UTEVA extraction resin to separate and enrich hafnium from the sample solution; and mass spectrometry analysis, where the Hf element obtained from the 0.3 mol / L nitric acid solution can be directly analyzed using a multi-collector inductively coupled plasma mass spectrometer combined with membrane desolvation injection to obtain high-precision Hf isotope mass spectrometry results. This method can separate and enrich Hf element in geological samples, is simple and fast to operate, highly efficient, low in cost, and has a low background and high recovery rate, making it particularly suitable for Hf isotope analysis in geological samples with low Hf content.

Description

Technical Field

[0001] This invention belongs to the field of chemical analysis technology, specifically relating to a method for Hf isotope analysis in geological samples. Background Technology

[0002] Depend on 176 Lu is generated through β decay. 176 The Lu-Hf isotope system, established based on Hf (with a half-life of 35.9 billion years), possesses strong stability and resistance to thermal disturbances, making it a very useful and important tool for isotope dating and tracing in geosciences. Because the variation range of Hf isotope ratios in different geochemical reservoirs is very small, the analytical and testing precision required for Hf isotope ratios is also extremely high.

[0003] Therefore, the development of Hf isotope analysis techniques directly impacts the widespread application of the Lu-Hf isotope system in Earth sciences. Traditional methods for analyzing Hf isotopes in geological samples are complex, cumbersome, costly, and generate large amounts of waste liquid. Furthermore, sample preparation involves multiple evaporations and transfers of the sample solution, posing a significant risk of cross-contamination. In particular, mafic and ultramafic geological samples are rich in insoluble minerals that are difficult to decompose, and the abundance of Hf in these samples is as low as ppb. Obtaining high-precision Hf isotope analysis results requires large sample volumes, which increases the difficulty of sample decomposition, related chemical separation pretreatment, and instrumental testing. To date, there are few reports on Hf isotope analysis methods for geological samples with low Hf content, which severely restricts our research on the genesis of these geological samples. Summary of the Invention

[0004] In view of the above, the purpose of this invention is to establish a simple, rapid, efficient, and low-cost method for separating and enriching Hf elements from geological samples. This method will be applied to the analysis and research of geological samples, such as ferromagnesian and ultraferromagnesian samples with low Hf content, thus realizing the goal of using experimental techniques to serve scientific research.

[0005] A method for Hf isotope analysis in geological samples includes the following steps:

[0006] (1) Sample decomposition: Add the geological sample to the sample dissolving apparatus, wet it with ultrapure water, add concentrated hydrochloric acid and concentrated hydrofluoric acid, and then keep it at 185~195℃ for 45~50h for digestion; after natural cooling, add concentrated perchloric acid, evaporate it at 145~155℃, add concentrated hydrochloric acid, evaporate it at 145~155℃, raise the temperature to 165~175℃, wait until no more white smoke is emitted, add concentrated hydrochloric acid until no more white smoke is emitted, add boric acid solution at 145~155℃, evaporate it at 145~155℃ to wet salt state, add 10±0.5 mol / L nitric acid to extract it into a centrifuge tube, centrifuge, and the clear liquid is the sample dissolution;

[0007] (2) Chemical separation and enrichment: The sample solution is loaded into an ion exchange column loaded with UTEVA extraction resin. The matrix elements and interfering elements are first eluted with 10±0.5mol / L nitric acid, and then the Hf element in the sample solution is eluted with 0.3±0.03mol / L nitric acid. The Hf element elution solution is collected.

[0008] (3) Mass spectrometry test: The Hf element eluent obtained in step (2) was analyzed by mass spectrometry using a multi-receiver inductively coupled plasma mass spectrometer combined with membrane desolvation injection to obtain the Hf isotope ratio mass spectrometry test results.

[0009] Further, in step (1), 2±0.1 mL of concentrated hydrochloric acid and 1±0.1 mL of concentrated hydrofluoric acid are added for digestion for every 200±1 mg of geological sample. The concentrated hydrochloric acid is added in two parts, first 0.5±0.1 mL and then 1.5±0.1 mL. When evaporating at 145~155℃, 0.5±0.1 mL of concentrated perchloric acid and 0.5±0.1 mL of concentrated hydrochloric acid are added for every 200±1 mg of geological sample. When evaporating at 165~175℃, 0.5±0.1 mL of concentrated hydrochloric acid is added for every 200±1 mg of geological sample. 3±0.2 mL of 0.24±0.02 mol / L boric acid solution is added for every 200±1 mg of rock sample. During extraction, 4±0.2 mL of 10±0.5 mol / L nitric acid is added for extraction for every 200±1 mg of geological sample. Extraction is performed twice while hot, 2±0.1 mL each time.

[0010] Further, in step (1), the concentration of concentrated hydrochloric acid is 12±0.5 mol / L, the concentration of concentrated hydrofluoric acid is 27.6±0.5 mol / L, and the concentration of concentrated perchloric acid is 70% (v / v).

[0011] Furthermore, the particle size of the UTEVA extraction resin is 50~100um; the UTEVA extraction resin exchange column is made by filling a PP material chromatography column with a porous polyethylene gasket into a UTEVA resin slurry soaked in dilute nitric acid (2mol / L). The column inner diameter is 0.7±0.1 cm and the resin volume is 1.5±0.1 ml.

[0012] Furthermore, before loading the sample solution onto the ion exchange column containing the extraction resin, the resin column needs to be pre-cleaned with 10±1 mL of ultrapure water and 30±0.5 mL of 0.05±0.01 mol / L hydrochloric acid, and then the resin column is equilibrated with 5±0.1 mL of 10±0.5 mol / L nitric acid.

[0013] Furthermore, when passing the sample solution through an ion exchange column loaded with extraction resin: for every 200 mg of geological sample, the matrix elements and interfering elements should first be eluted with 6 ± 0.1 mL of 10 ± 0.5 mol / L nitric acid, and then the Hf element should be eluted with 8.0 ± 0.5 mL of 0.3 ± 0.03 mol / L nitric acid. The Hf element eluent should be collected and then used for mass spectrometry analysis.

[0014] Furthermore, the multi-receiver inductively coupled plasma mass spectrometer is a Nu Plasma II multi-receiver inductively coupled plasma mass spectrometer, which includes an Aridus II membrane desolvation sample introduction system. The Aridus II membrane desolvation sample introduction system is configured such that the separated Hf is atomized into an aerosol by an atomizer and then enters a nebulization chamber at 110°C to maintain it in a vapor state, so that the aerosol directly enters the inductively coupled plasma, thereby obtaining the Hf isotope ratio mass spectrometry test results.

[0015] Preferably, the detection conditions of the multi-receiver inductively coupled plasma mass spectrometer are as follows: argon is used as the carrier gas, the argon gas flow rate is 4.5 L / min, the nebulization chamber temperature is 110℃, the membrane temperature is 160℃, the sample injection rate is 100 μL / min, the cooling gas (argon) flow rate is 13.0 L / min, and the auxiliary gas (argon) flow rate is 0.9 L / min.

[0016] During mass spectrometry detection, ten Faraday cups were used to receive Hf isotopes. Specifically, Faraday cups H5, H4, H3, H2, H1, L1, L2, L3, and L4 were used for receiving Hf isotopes. 180 Hf, 179 Hf, 178 Hf, 177 Hf, 176 Hf, 174 Hf, 173 Yb、 172 Yb and 171 Yb, center cup (Ax) reception 175 Lu + .

[0017] Hf isotope ratio refers to 176 Hf / 177 Hf.

[0018] Furthermore, the UTEVA extraction resin needs to be pretreated before being packed into the column. The pretreatment involves soaking in 1.5~2.5 mol / L nitric acid and shaking and ultrasonically vibrating for 20~40 minutes to remove floating matter, and then soaking in 1.5~2.5 mol / L nitric acid for more than one week before use.

[0019] Furthermore, after use, the UTEVA resin exchange column is first rinsed with a mixed acid of hydrochloric acid, nitric acid, and hydrofluoric acid with a total volume of 10±0.5mL and a concentration of 0.3±0.1mol / L, then rinsed with a mixed acid of hydrochloric acid, nitric acid, and hydrofluoric acid with a total volume of 10±0.5mL and a concentration of 0.03±0.01mol / L, and finally rinsed with 10±0.5mL of ultrapure water.

[0020] This method can achieve one-step column separation and enrichment of hafnium in geological samples. It is simple, fast, efficient, and low-cost, with good separation effect of matrix elements, high recovery rate, and low background. Attached Figure Description

[0021] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0022] Figure 1 This is a flowchart illustrating the high-precision Hf isotope analysis method according to an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and thoroughly described below with reference to specific examples.

[0024] This invention discloses a method for Hf isotope analysis in geological samples. See also... Figure 1 A preferred embodiment of the present invention uses an exchange column of UTEVA extraction resin to separate matrix elements and interfering elements from geological samples, and to separate and enrich the target element Hf, mainly including the following steps:

[0025] (1) Decomposition of rock samples

[0026] A certain weight of geological sample is weighed and dissolved in various inorganic solvents to obtain a rock sample solution. The specific procedure for sample decomposition is as follows: A certain weight of geological sample powder is placed into the inner cup of a double-layered digestion vessel containing a PTFE (polytetrafluoroethylene) sample dissolver. Appropriate amounts of purified concentrated hydrochloric acid (HCl) and concentrated hydrofluoric acid (HF) are added sequentially. After capping, the inner cup is placed inside the outer steel sleeve of the digestion vessel, and the vessel is placed in an oven at 190°C for at least 48 hours under sealed conditions. After natural cooling, the steel sleeve is removed, and the PTFE sample dissolver is taken out. Add an appropriate amount of purified concentrated perchloric acid (HClO4) to the sample solution, place it on a hot plate, and heat to 150°C to evaporate the sample to near dryness; then add an appropriate amount of high-purity concentrated hydrochloric acid and evaporate the sample to near dryness; raise the temperature to 170°C, wait for the perchloric acid to stop emitting white fumes, and then add an appropriate amount of high-purity concentrated hydrochloric acid to ensure that the white fumes stop emitting; adjust the hot plate to 150°C, add an appropriate amount of 0.24±0.02mol / L boric acid (H3BO3), and evaporate to a wet salt state; then add 4 mL of 10mol / L nitric acid (HNO3) to extract into a clean centrifuge tube. Centrifuge the extracted sample to obtain a clear solution ready for column loading.

[0027] During the sample decomposition process, concentrated hydrochloric acid and concentrated hydrofluoric acid were used for prolonged high-temperature dissolution (not lower than 190℃) to decompose the sample and avoid sample heterogeneity. Hydrofluoric acid can effectively destroy silicates in rock samples; however, during the decomposition process, a large amount of Ca and Mg (major elements) and rare earth elements in the sample will form a large amount of fluoride precipitates such as CaF2 and MgF2, which will cause Hf loss after adsorption, affecting Hf recovery. At the same time, multiple condition experiments showed that the presence of hydrofluoric acid in the completely dissolved sample solution will affect the adsorption efficiency of UTEVA resin for hafnium. Therefore, perchloric acid was subsequently added, and evaporation by heating was used to volatilize the fluoride in the sparingly soluble magnesium fluoride and calcium fluoride produced after dissolution as HF; boric acid was added to form volatile BF3, and major elements such as Ca and Mg and rare earth elements exist in the form of cations, thereby achieving the decomposition of fluorides, avoiding Hf loss, and ensuring high recovery rate and analytical quality.

[0028] (2) Separation and enrichment of Hf element by UTEVA resin column

[0029] The sample solution was loaded into an exchange column containing UTEVA extraction resin to separate and enrich the Hf element in the sample solution. The UTEVA resin column had an inner diameter of approximately 0.7 cm and a resin volume of 1.5 mL; the UTEVA resin particle size was 50–100 μm.

[0030] The specific procedure is as follows: The UTEVA extraction resin exchange column is pre-cleaned with ultrapure water until the effluent is neutral, then washed with 30 mL of 0.05 mol / L HCl. Subsequently, the exchange column is equilibrated with 5 mL of 10 mol / L HNO3. Then, a 10 mol / L HNO3 solution of the sample to be separated is loaded onto the UTEVA resin exchange column, and eluted with 6 mL of 10 mol / L HNO3 to elute elements such as iron (Fe), Ca, Mg, Al, K, Na, Ti, Cr, Ni, and Ba. At this point, Hf is strongly adsorbed by the UTEVA resin. Subsequently, 8 mL of 0.3 mol / L HNO3 is added to the UTEVA resin column to elute Hf, ready for mass spectrometry analysis.

[0031] The UTEVA leaching resin needs to be pretreated before use. The pretreatment involves soaking in dilute nitric acid (approximately 2 mol / L) and thoroughly shaking and ultrasonically vibrating for 30 minutes to remove floating matter, followed by soaking in 2 mol / L HNO3 for at least one week before use.

[0032] After use, the UTEVA resin exchange column is eluted sequentially with 10 mL of a mixed acid solution of HCl-HNO3-HF (each acid concentration is 0.3 mol / L), 10 mL of a HCl-HNO3-HF solution (each acid concentration is 0.03 mol / L), and 10 mL of H2O.

[0033] The principle of the chemical separation and enrichment process is as follows: On a UTEVA resin column, under 10 mol / L HNO3 medium conditions, matrix elements such as Fe, Ca, Mg, Al, K, Na, Ti, Cr, Ni, and Ba, as well as interfering elements, are weakly retained, while Hf is strongly retained. Therefore, during the loading of the 10 mol / L HNO3 sample solution and the elution with 6 mL of 10 mol / L HNO3, matrix elements such as Fe, Ca, Mg, Al, K, Na, Ti, Cr, Ni, and Ba, as well as interfering elements, rapidly pass through the resin column. At this point, Hf is strongly adsorbed by the UTEVA resin. Subsequently, since the retention of Hf is very weak on the UTEVA resin column under 0.3 mol / L HNO3 medium conditions, 8 mL of 0.3 mol / L HNO3 can be used for desorption.

[0034] It is worth noting that nitric acid and hydrochloric acid are the main eluting reagents in the above chemical separation process, and the separation of extraction resin columns is highly sensitive to the acidity of hydrochloric acid and nitric acid. Therefore, the acidity of the eluent should be strictly calibrated. At the same time, extraction resin columns are highly sensitive to the amount of resin loaded; the amount of resin loaded should be accurately controlled when packing the resin column.

[0035] The specific chemical separation and enrichment process is listed in Table 1.

[0036] Table 1: Chemical process for the chemical separation and enrichment of Hf using UTEVA resin exchange column

[0037]

[0038] (3) Mass spectrometry test

[0039] High-precision Hf isotope ratios can be obtained by mass spectrometry analysis of Hf element solutions after separation and enrichment using multi-receiver inductively coupled plasma mass spectrometry (MC-ICP-MS). This invention employs a membrane desolvation method for sample introduction and utilizes a Nu Plasma II MC-ICP-MS instrument in static multi-receiver mode.

[0040] When using the membrane desolvation injection system (Aridus II, CETAC, USA), the temperatures of the nebulization chamber and the membrane are set to 110°C and 160°C, respectively, so that the Hf element is atomized into an aerosol by the nebulizer and then enters the 110°C nebulization chamber, where it is kept in a vapor state.

[0041] Compared with traditional methods for analyzing Hf isotopes in geological samples, the method for analyzing Hf isotopes in geological samples provided by this invention has the following advantages: 1) It can achieve one-step column separation and enrichment of hafnium in geological samples, which is simple, fast, efficient, low-cost, and produces little waste liquid. In particular, the common reagent hydrofluoric acid is not used in the chemical separation and enrichment process, and the obtained sample solution does not need to be evaporated and reconstituted, and can be directly tested by mass spectrometry, avoiding cross-contamination; 2) It has good matrix element separation effect, high recovery rate, and low process background, and is particularly suitable for high-precision analysis of Hf elements in geological samples with low Hf content; 3) The sample dissolution method has a relatively short time and can decompose up to 200 mg of sample, which is particularly suitable for trace element analysis and Sr-Nd-Pb isotope analysis of ferromagnesian and ultraferromagnesian samples; 4) In the chemical separation process, UTEVA resin columns can be combined with other resin columns to form a nested column for the separation and enrichment of Sr-Nd-Pb isotopes from the same dissolved geological sample, so as to ensure the homology of multiple isotope systems.

[0042] The following examples, Examples 1 to 3, provide specific embodiments of the Hf isotope analysis method of the present invention. The sources of the raw materials and equipment used in the examples are described below:

[0043] 1) Superior grade (GR grade) hydrochloric acid, nitric acid, and hydrofluoric acid: produced by China National Pharmaceutical Group Chemical Reagent Co., Ltd., all certified by Savillex. TM The DST-1000 sub-boiling still (manufactured by Minnetonka, USA, which purifies by distillation without reaching the boiling point) is used for sub-boiling distillation purification.

[0044] 2) Perchloric acid: 70% v / v, produced by Aldrich, USA.

[0045] 3) Boric acid: concentration is 0.24 mol / L.

[0046] 4) Ultrapure water: prepared using the Thermo GenPure_UV_xCAD_Plus system from the United States, with an output water resistivity of 18.2 MΩ / cm (25℃).

[0047] 5) Double-walled digestion vessel: manufactured by Nanjing Zhenghong Company. The outer vessel is made of national standard non-magnetic stainless steel and has a circular tenon and groove sealing design. It is manually tightened with a screw and has a vent hole. The inner cup is a 15 ml Teflon dissolving vessel. Before use, the dissolving vessel is rinsed with high-purity nitric acid, high-purity hydrochloric acid and ultrapure water at 120°C.

[0048] 6) UTEVA resin: Produced by TrisKem International, France (Part No. ., UT-B25-S), resin particle size 50-100μm;

[0049] 7) UTEVA resin columns: Poly-Prep columns (Bio-Rad Laboratories Inc., USA) are 6cm long with an inner diameter of about 0.7cm. The lower end is equipped with a porous polyethylene gasket and filled with about 1.5 ml of UTEVA extraction resin (particle size 50-100μm).

[0050] 8) Multiple collector inductively coupled plasma-mass spectrometry (ICP-MS): Manufactured by Nu Instruments, UK, model Nu PlasmaII.

[0051] 9) Membrane desolvation injection system: manufactured by CETAC, USA, model Aridus II.

[0052] 10) JMC 475 Hf standard solution: National Institute of Standards and Technology (NIST) standard sample, diluted to 30 ppm, used to monitor the instrument status of Nu Plasma II multi-collector inductively coupled plasma mass spectrometry when determining Hf isotopes.

[0053] 11) Rock standard samples: BCR-2 (basalt), BHVO-2 (basalt), and AGV-2 (andesite) from the United States Geological Survey (USGS).

[0054] 12) All sample dissolution and chemical separation experiments of this invention were carried out in a Class 100 fume hood and a Class 100 clean bench in a Class 1000 cleanroom to obtain low elemental process blank background values. Example 1

[0055] The high-precision Hf isotope analysis method provided in Example 1 of this invention includes the following process:

[0056] (1) Sample dissolution: Weigh approximately 200 mg of powdered international rock standard AGV-2 (andesite) and place it in the polytetrafluoroethylene (PTFE) sample dissolution vessel of the double-layer digestion vessel. Add approximately 0.2 mL of ultrapure water to moisten the sample. Then, add 0.5 mL of 12 mol / L hydrochloric acid dropwise. After the sample shows no reaction, add 1.5 mL of 12 mol / L hydrochloric acid and 1 mL of 27.6 mol / L hydrofluoric acid. After capping the PTFE sample dissolution vessel, place it in the outer steel sleeve of the digestion vessel. Tighten the steel sleeve cap and place it in an oven at 190°C for 48 hours. After natural cooling, remove the PTFE sample dissolution vessel. Then, add 0.5 mL of 70% (v / v) concentrated perchloric acid to the sample solution in the PTFE sample dissolution vessel and place it on a hot plate. Evaporate to near dryness at 150°C, then add 0.5 mL of 12 mol / L hydrochloric acid and evaporate to near dryness. Heat to 170℃ until all white fumes are emitted, then add 0.5 mL of 12 mol / L hydrochloric acid to ensure all white fumes are eliminated. Next, add 3 mL of 0.24 mol / L boric acid solution and evaporate on a 150℃ hot plate until a wet salt solution is formed. Finally, add 4 mL of 10 mol / L nitric acid to extract into a centrifuge tube (while hot, 2 mL × 2 extractions). Centrifuge the extracted sample (3500 rpm, 5 minutes), and load the supernatant onto a column.

[0057] (2) Chemical separation and enrichment: The dissolved sample solution was transferred to a pretreated UTEVA resin exchange column to separate Hf from the matrix solution. The chemical separation and enrichment procedure is shown in Table 1. First, the UTEVA resin column was pre-washed with 10 mL of ultrapure water and 30 mL of 0.05 mol / L HCl, and then equilibrated with 5 mL of 10 mol / L HNO3. Then, the 10 mol / L HNO3 solution of the sample to be separated was loaded onto the UTEVA resin column (load volume: approximately 4 mL), and 1 mL (0.5 mL each time, in two doses) of 10 mol / L HNO3 was carefully added dropwise along the inner wall of the column, followed by rinsing with 5 mL of 10 mol / L HNO3. Next, 8 mL (2 mL each time, in four doses) of 0.3 mol / L HNO3 was added to the UTEVA resin column to elute Hf, and the solution was collected in a clean centrifuge tube for mass spectrometry analysis. After use, the UTEVA resin exchange column is rinsed sequentially with 10 mL of a mixed acid solution of HCl-HNO3-HF (each acid concentration is 0.3 mol / L), 10 mL of a HCl-HNO3-HF solution (each acid concentration is 0.03 mol / L), and 10 mL of ultrapure water until neutral.

[0058] (3) Perform high-precision testing of isotope ratios on the obtained Hf samples.

[0059] High-precision measurement of Hf isotope ratios was performed using a membrane desolvation injection method and a static multi-collector configuration on a Nu PlasmaII multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). This mass spectrometer is equipped with 16 Faraday cups and 5 ion counters. This invention utilizes Faraday cups H5, H4, H3, H2, H1, L1, L2, L3, and L4 for collecting the ions. 180 Hf, 179 Hf, 178 Hf, 177 Hf, 176 Hf, 174 Hf, 173 Yb、 172 Yb and 171 Yb, center cup (Ax) reception 175 Lu + The specific Nu PlasmaII MC-ICPMS test parameters are shown in Table 2.

[0060] Table 2. Hf isotope Nu Plasma II MC-ICPMS test parameters

[0061]

[0062] The instrument was optimized using the international standard solution JMC 475 for Hf. The Hf test concentration was 30 ng / mL. 180 Hf + The signal is approximately 5V. The mass spectrometer typically acquires at least two data blocks, with 20 data points per block (cycles), and an integration time of 15 seconds per data point. Between each sample analysis, the injection system is cleaned with 0.3 mol / L HNO3. Under optimized instrument conditions, the standard solution JMC 475... 176 Hf / 177 The Hf value obtained from multiple tests was 0.282166 ± 0.000006 (2SD, n=15), which is consistent with its recommended value (0.282160) within the range of analytical error.

[0063] In order to deduct 176 Yb、 176 Lu 176 Interference with the Hf signal necessitates processing of Hf isotope measurement data (see reference (1): by monitoring...). 175 Lu + and 173 Yb + and based on 176 Lu = 0.02655× 175 Lu and 176 Yb = 0.79323 × 173 Yb proceeds 176 Hf correction. Then, based on the exponential law, using... 179 Hf / 177 Mass fractionation correction was performed using Hf = 0.7325.

[0064] The results of Hf isotope ratio determination of andesite international rock standard AGV-2 are shown in Table 3.

[0065] Table 3. Results of Hf isotope ratio analysis in international rock standard sample AGV-2

[0066]

[0067] Example 2

[0068] Example 2 is largely the same as Example 1, except that the geological sample used in this example is the international basalt rock standard BCR-2, and the Hf isotope analysis results are shown in Table 4.

[0069] Table 4. Results of Hf isotope ratio analysis in international rock standard sample BCR-2

[0070]

[0071] Example 3

[0072] Example 3 is largely the same as Example 1, except that the geological sample used in this example is the international basalt rock standard BHVO-2, which has a lower Hf content than BCR-2. The Hf isotope analysis results are shown in Table 5.

[0073] Table 5. Results of Hf isotope ratio analysis in international rock standard sample BHVO-2

[0074]

[0075] The numerical values ​​following the data in Tables 3 to 5 represent the serial numbers of the cited references.

[0076] Reference 1: Yang, Y., Zhang, H., Chu, Z., Xie, L., Wu, F., 2010.Combined chemical separation of Lu, Hf, Rb, Sr, Sm and Nd from a single rockdigest and precise and accurate isotope determinations of Lu-Hf, Rb-Sr andSm-Nd isotope systems using Multi-Collector ICP-MS and TIMS. International Journal of Mass. Spectrometry, 290(2-3): 120-126.

[0077] Reference 2: Li, C. et al., 2015. A rapid single column separationscheme for high-precision Sr-Nd-Pb isotopic analysis in geological samples using thermal ionization mass spectrometry. Analytical Methods, 7(11): 4793-4802.

[0078] Reference 3: Guan, Q., Sun, Y., Yue, Y., Liu, X., Zhao, S., 2019. ASimplified Method Using a Single TODGA Resin Column for the Purification ofSr, Nd and Hf in Geological Materials and the Determination of their IsotopicRatios by Multi-collector Inductively Coupled Plasma-mass Spectrometry. Analytical Sciences, 35: 323.

[0079] Reference 4: Li, C., Wang,

[0080] The following content from Examples 1 to 3 above is described below:

[0081] Sample purity, recovery rate and blank background value

[0082] In the embodiments of this disclosure, during the experimental setup, elution curve experiments were conducted using a mixed standard solution of trace elements and the international rock standard sample BCR-2. Major elements in the elution curves were determined using inductively coupled plasma optical emission spectrometry (ICP-OES) (IRIS Advantage ICPOES manufactured by Thermo-Fisher Scientific, USA), and trace elements were determined using inductively coupled plasma mass spectrometry (ICP-MS). All matrix elements, such as Fe, Ca, Mg, Al, K, Na, Ti, Cr, Ni, and Ba, were completely eluted. Hf was completely resolved using 8 mL of 0.3 mol / L nitric acid, with a recovery rate >96% and high purity. Lu was not detected in the tests.

[0083] In the embodiments of this disclosure, the analytical process is simple, fast, and uses few reagents and instruments. 180 When Hf diluent is used to detect the blank background value of Hf, the blank value for the entire process is less than 10 pg. When the sample size of rock sample is 200 mg, for geological samples with Hf content as low as 0.01 ug / g, the ratio of Hf content in the sample to the blank background value is greater than 200, and the blank background value can be ignored.

[0084] It is worth noting that since the extraction resin is made by coating the extractant onto an inert support material, long-term use of the exchange column may cause the extractant to be lost from the resin, leading to changes in the elution curve. The resin may also exhibit a memory effect, and repeated use may cause cross-contamination between samples. Therefore, it is recommended to periodically review the elution curve and recovery rate.

[0085] Repeatability test results of Hf isotope ratios in rock standards

[0086] The reliability and reproducibility of Hf isotope determination results were tested using rock standards with different matrix compositions and Hf contents, as shown in Table 3-5. The results indicate that BCR-2, BHVO-2, and AGV-2... 176 Hf / 177 The Hf measurement results were in high agreement with the test data reported in the literature, and the accuracy of the repeated measurements was better than 0.01%, which fully demonstrates that the method of the present invention is accurate and reliable. Therefore, the single-column UTEVA resin of the present invention can perform efficient Hf chemical separation on geological samples with complex matrices, and the separated Hf has high purity. The separated Hf solution can be directly subjected to high-precision Hf isotope analysis using MC-ICP-MS mass spectrometry.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make improvements or modifications based on the above description, and all easily conceivable improvements and modifications should be covered within the patent protection scope of the present invention.

Claims

1. A method for Hf isotope analysis in geological samples, characterized in that, Includes the following steps: (1) Sample decomposition: Add the geological sample to the sample dissolving apparatus, wet it with ultrapure water, add concentrated hydrochloric acid and concentrated hydrofluoric acid, and then keep it at 185~195℃ for 45~50h for digestion; after natural cooling, add concentrated perchloric acid, evaporate it at 145~155℃, add concentrated hydrochloric acid, evaporate it at 145~155℃, raise the temperature to 165~175℃, wait until no more white smoke is emitted, add concentrated hydrochloric acid until no more white smoke is emitted, add boric acid solution at 145~155℃, evaporate it at 145~155℃ to wet salt state, add 10±0.5 mol / L nitric acid to extract it into a centrifuge tube, centrifuge, and the clear liquid is the sample dissolution; (2) Chemical separation and enrichment: The sample solution is loaded into an ion exchange column loaded with UTEVA extraction resin. The matrix elements and interfering elements are first eluted with 10±0.5mol / L nitric acid, and then the Hf element in the sample solution is eluted with 0.3±0.03mol / L nitric acid. The Hf element elution solution is collected. (3) Mass spectrometry test: The Hf element eluent obtained in step (2) was analyzed by mass spectrometry using a multi-receiver inductively coupled plasma mass spectrometer combined with membrane desolution injection, and the Hf isotope ratio mass spectrometry test results were obtained. In step (1), for every 200±1 mg of geological sample, 2±0.1 mL of concentrated hydrochloric acid and 1±0.1 mL of concentrated hydrofluoric acid need to be added for digestion. The concentrated hydrochloric acid is added in two parts: first 0.5±0.1 mL, then 1.5±0.1 mL. When evaporating at 145~155℃, 0.5±0.1 mL of concentrated perchloric acid and 0.5±0.1 mL of concentrated hydrofluoric acid need to be added for every 200±1 mg of geological sample. When evaporating at 165~175℃, for every 200±1 mg of geological sample, 2±0.1 mL of concentrated hydrochloric acid and 1.5±0.1 mL of concentrated hydrofluoric acid need to be added. For every 200±1 mg of geological sample, 0.5±0.1 mL of concentrated hydrochloric acid needs to be added; for every 200±1 mg of rock sample, 3±0.2 mL of 0.24±0.02 mol / L boric acid solution needs to be added; during extraction, for every 200±1 mg of geological sample, 4±0.2 mL of 10±0.5 mol / L nitric acid needs to be added; the concentration of concentrated hydrochloric acid is 12±0.5 mol / L, the concentration of concentrated hydrofluoric acid is 27.6±0.5 mol / L, and the concentration of concentrated perchloric acid is 70%.

2. The method for Hf isotope analysis in geological samples according to claim 1, characterized in that, The UTEVA extraction resin has a particle size of 50~100μm; the UTEVA extraction resin exchange column is made by filling a PP material chromatography column with a porous polyethylene gasket with a UTEVA resin slurry soaked in 2mol / L nitric acid. The column inner diameter is 0.7±0.1 cm and the resin volume is 1.5±0.1 ml.

3. The method for Hf isotope analysis in geological samples according to claim 1, characterized in that, Before loading the sample solution onto an ion exchange column containing extraction resin, the resin column needs to be pre-cleaned with 10±1 mL of ultrapure water and 30±0.5 mL of 0.05±0.01 mol / L hydrochloric acid, and then equilibrated with 5±0.1 mL of 10±0.5 mol / L nitric acid.

4. The method for Hf isotope analysis in geological samples according to claim 1, characterized in that, When passing the sample solution through an ion exchange column loaded with extraction resin: for every 200 mg of geological sample, the matrix elements and interfering elements should first be eluted with 6 ± 0.1 mL of 10 ± 0.5 mol / L nitric acid, and then the Hf element should be eluted with 8.0 ± 0.5 mL of 0.3 ± 0.03 mol / L nitric acid. The Hf element eluent should be collected and then used for mass spectrometry analysis.

5. The method for Hf isotope analysis in geological samples according to claim 1, characterized in that, The multi-receiver inductively coupled plasma mass spectrometer is a Nu Plasma II multi-receiver inductively coupled plasma mass spectrometer, which includes an Aridus II membrane desolvation sample introduction system. The Aridus II membrane desolvation sample introduction system is configured such that the separated Hf is atomized into an aerosol by an atomizer and then enters a 110°C atomization chamber to maintain it in a vapor state. The aerosol directly enters the inductively coupled plasma, and multiple Faraday cups are used to simultaneously receive Hf isotope ions, thereby obtaining Hf isotope ratio mass spectrometry test results.

6. The method for Hf isotope analysis in geological samples according to claim 1, characterized in that, The detection conditions of the multi-receiver inductively coupled plasma mass spectrometer are as follows: argon is used as the carrier gas, the argon gas flow rate is 4.5 L / min, the nebulizer temperature is 110℃, the membrane temperature is 160℃, the injection rate is 100 μL / min, the cooling gas is argon, the cooling gas flow rate is 13.0 L / min, the auxiliary gas is argon, and the auxiliary gas flow rate is 0.9 L / min.

7. The method for Hf isotope analysis in geological samples according to claim 5, characterized in that, Ten Faraday cups were used to receive Hf isotopes. Specifically, Faraday cups H5, H4, H3, H2, H1, L1, L2, L3, and L4 were used to receive Hf isotopes. 180 Hf, 179 Hf, 178 Hf, 177 Hf, 176 Hf, 174 Hf, 173 Yb、 172 Yb and 171 Yb, center cup reception 175 Lu + .

8. The method for Hf isotope analysis in geological samples according to claim 1, characterized in that, The UTEVA extraction resin needs to be pretreated before being packed into the column. The pretreatment involves soaking in 1.5~2.5 mol / L nitric acid and shaking and ultrasonically vibrating for 20~40 minutes to remove floating matter, and then soaking in 1.5~2.5 mol / L nitric acid for more than one week before use.

9. The method for Hf isotope analysis in geological samples according to claim 1, characterized in that, After use, the ion exchange column loaded with UTEVA extraction resin is first rinsed with a mixed acid of hydrochloric acid, nitric acid, and hydrofluoric acid with a total volume of 10±0.5 mL and a concentration of 0.3±0.1 mol / L, then rinsed with a mixed acid of hydrochloric acid, nitric acid, and hydrofluoric acid with a total volume of 10±0.5 mL and a concentration of 0.03±0.01 mol / L, and finally rinsed with 10±0.5 mL of ultrapure water.

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