Rapid extraction method of Ba isotope in barite
By adding ultrapure water dropwise to the surface of barite sample and using laser erosion to form nanoparticles, and using double diluent method to correct, the problem of long time and low accuracy of Ba isotope analysis in barite is solved, and fast and efficient high-space resolution testing is achieved.
Patent Information
- Application Number
- CN202510675810.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-23
- Publication Date
- 2025-07-18
AI Technical Summary
In the prior art, the analysis method of Ba isotopes in barite is long and has low accuracy, making it difficult to achieve fast and high spatial resolution testing. Especially in the analysis of laser erosion multi-received inductively coupled plasma mass spectrometer (LA-MC-ICP-MS), there is a lack of effective sample pretreatment separation and purification process, resulting in serious impact of matrix elements.
A laser erosion system was used to add a small amount of ultrapure water extract to the surface of the barite sample to form nanoparticles through laser erosion, and the mass fractionation correction was performed in combination with the double diluent method to simplify the pre-treatment process and directly obtain a testable solution.
The sample pretreatment time was shortened from 5 days to 1 hour, which improved the efficiency and accuracy of Ba isotope analysis, achieved high spatial resolution testing, and achieved the accuracy of whole karst solution analysis level.
Smart Images
Figure CN120333953A_ABST
Abstract
Description
Technical Field
[0001] This specification relates to the field of laser ablation inductively coupled plasma mass spectrometers, and particularly relates to a rapid extraction method for Ba isotopes in barite. Background Art
[0002] The use of laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has become the most conventional isotope detection method in the field of earth sciences. Appropriate pretreatment techniques are necessary for accurate analysis of element content and isotope composition of refractory geological samples. When performing whole-rock solution analysis of isotope composition in geological minerals, it is usually necessary to completely dissolve the sample using chemical methods, and the digested solution also needs to be purified by a chromatographic column to avoid the influence of interfering ions.
[0003] Barium (Ba) is an alkaline earth metal element in the second main group of the sixth period and is a geochemical indicator applied in low-temperature and high-temperature environments in geological research. Barite is a refractory geological mineral that is insoluble in water and common acids (such as nitric acid, hydrochloric acid, and hydrofluoric acid). The digestion process using the alkali fusion method is complex and introduces a high process background. The difficulty in performing whole-rock solution analysis of Ba isotopes in barite lies in how to quickly process barite into a testable solution.
[0004] For the whole-rock solution analysis of Ba isotopes in barite, the barite digestion methods used in previous studies include the following 4 types: Na2CO3 solution exchange method (von Allmen et al., 2010), ion complex method (Griffith et al., 2008), HI acid digestion method (Takano and Watanuki, 1972), and H2O extraction method (Tian et al., 2020). When performing whole-rock solution analysis of Ba isotopes in barite, the Na2CO3 solution exchange method is generally used to digest barite, and the sample matrix is removed by chromatographic column separation and purification to avoid the influence of interfering ions. The entire pretreatment process takes about 5 - 7 days. Zhang et al. (2022) used LA-MC-ICP-MS to perform in-situ micro-area analysis of Ba isotopes in barite, and used a laser ablation system to sample and obtain aerosol particles representing the Ba isotope composition of the sample for analysis. Although a high spatial resolution (about 24 μm size) can be obtained, this method requires the use of matrix-matched standard substances to correct the instrumental mass fractionation during the analysis process, and the precision of measuring Ba isotopes (δ 137 Ba: 0.09‰, 2SD) is significantly lower than the precision of whole-rock solution analysis (δ 137Ba: 0.05‰, 2SD), and during the analysis process, matrix-matched reference materials are relied on to correct the instrumental mass fractionation. Therefore, in the prior art, laser is still used as the ablation sampling method for the analysis of Ba isotopes in barite.
[0005] When in-situ micro-area analysis of Ba isotopes in barite is carried out by using a laser ablation multi-collector inductively coupled plasma mass spectrometer (LA-MC-ICP-MS), due to the lack of a sample pretreatment separation and purification process, it will be affected by the generated matrix elements. Therefore, how to better separate and purify Ba isotopes in barite belongs to a difficult problem to overcome in this field. Based on this, for those skilled in the art, it is necessary to study a method with less sample usage and shorter sample treatment time to achieve better detection. Summary of the Invention
[0006] The present invention provides a rapid extraction method for Ba isotopes in barite, specifically as follows: Place the barite sample target on the laser ablation system tabletop, drop a small amount of extraction solution on the surface of the sample target, use a laser to pass through the extraction solution and focus on the sample surface for laser ablation, use the laser to perform in-situ sampling and digestion on the barite sample, transfer the sample extraction solution after sampling to a centrifuge tube, and the droplet recovery is also carefully aspirated and transferred to a 5 mL centrifuge tube using a pipette. Then, 5 - 10 μL of extraction solution can be added dropwise to the sampling area to rinse the sample surface, and then the rinsing solution is also transferred to the same centrifuge tube to ensure the recovery rate of the ablation products. Add a double diluent to the centrifuge tube and make up the volume with an acidic medium to obtain a sample test solution. Finally, by the method of adding a double diluent, it is made up to 1.5 mL with 2% (v / v) HNO3, and accurate correction is carried out using the mass fractionation in MC-ICP-MS testing.
[0007] Further, the extraction solution is ultrapure water with a resistivity of 18.2 MΩ·cm.
[0008] Further, the laser beam spot diameter is 16 - 90 μm.
[0009] Further, the laser energy density is 2.5 - 4.5 J·cm -2 。
[0010] Further, the laser ablation frequency is 1 - 6 Hz.
[0011] Further, the volume of the extraction solution is 5 - 12 μL.
[0012] Further, the number of ablation times is 200 - 400 times Further, making up the volume with an acidic medium specifically is: 2% (v / v) HNO3.
[0013] Beneficial Effects:
[0014] 1) Add a small amount of extraction solution onto the surface of the sample target. The extraction solution only needs to form a hemispherical droplet under the action of gravity and surface tension using ultrapure water extraction solution. The extraction droplet serves as a laser ablation chamber. BaSO4 in barite decomposes into soluble BaO under the action of laser energy. Meanwhile, a double diluent is added to accurately correct the mass fractionation in MC-ICP-MS testing. The pretreatment time for Ba isotope analysis of the refractory mineral barite is shortened from 5 days to 1 hour, and a large amount of acids, bases, and toxic reagents are not required, realizing green and rapid pretreatment of geological samples.
[0015] 2) Compared with in-situ laser ablation sampling combined with MC-ICP-MS analysis, this method combines the double diluent method to correct the instrument mass fractionation during testing, and can obtain the Ba isotope composition of barite samples at the scale of dozens of micrometers, realizing high spatial resolution, rapid, and accurate Ba isotope testing. Brief Description of the Drawings
[0016] The embodiments of this specification will be further described in the manner of exemplary embodiments, and these exemplary embodiments will be described in detail through the drawings. These embodiments are not restrictive. In these embodiments, the same numbers represent the same structures, where: Figure 1 is a schematic diagram of the basic principle of the in-situ laser rapid digestion technology in the embodiments of this specification.
[0017] Figure 2 is a scanning electron microscope photograph of the ablation pit for in-situ laser rapid digestion sampling in the embodiments of this specification.
[0018] Figure 3 is a white light interferometer photograph of the cross-sectional profile of the ablation pit for in-situ laser rapid digestion sampling in the embodiments of this specification.
[0019] Figure 4 is the influence of different extraction solution volumes on the Ba sampling mass of the test sample Ba-FJ in the embodiments of this specification.
[0020] Figure 5 is the influence of different extraction solution volumes on the δ 137 / 134 Ba composition in the test sample Ba-FJ in the embodiments of this specification.
[0021] Figure 6 is a compilation of the actual test results of four natural barite Ba isotope reference materials in the embodiments of this specification. Detailed Embodiments
[0022] To more clearly illustrate the technical solutions of the embodiments of this specification, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some examples or embodiments of this specification. For those of ordinary skill in the art, without creative efforts, this specification can also be applied to other similar scenarios based on these drawings. It should be understood that these exemplary embodiments are only provided to enable those skilled in the relevant art to better understand and then implement this specification, rather than limiting the scope of this specification in any way. Unless obvious from the context or otherwise stated, the same reference numerals in the figures represent the same structure or operation.
[0023] Conventional digestion techniques for geological samples can be divided into alkali fusion method and acid digestion method. Due to the addition of a large amount of fluxes such as sodium hydroxide, sodium peroxide, sodium carbonate, or lithium metaborate during the pretreatment process in the alkali fusion method, the sample solution obtained after treatment has problems such as complex matrix composition and potential interference in mass spectrometry testing. Acid digestion method can be divided into open digestion method, microwave digestion method, and closed high-pressure digestion method, using inorganic acid reagents including nitric acid, hydrochloric acid, hydrofluoric acid, sulfuric acid, and perchloric acid, etc., which is a commonly used pretreatment method in the field of geological analysis. However, these conventional pretreatment methods have the disadvantages of cumbersome and time-consuming processes, low efficiency, the use of a large amount of acids, alkalis, and toxic chemical reagents, being not green and environmentally friendly, and high process background (alkali fusion method). How to achieve rapid and green digestion pretreatment of refractory geological minerals is of great significance.
[0024] In the prior art, laser is still used as the ablation sampling method for in-situ analysis of Ba isotopes in barite. As mentioned above, Zhang et al. (2022) used LA-MC-ICP-MS for in-situ micro-area analysis of Ba isotopes in barite, using a laser ablation system to sample and obtain aerosol particles representing the Ba isotope composition of the sample for analysis. Although high spatial resolution can be obtained, the precision of the measured Ba isotopes (δ 137 Ba: 0.09‰, 2SD) is significantly lower than the analysis precision of whole-rock solution (δ 137Ba: 0.05‰, 2SD). During the analysis process, it relies on matrix-matched reference materials to correct the instrumental mass fractionation. The matrix-matched reference material correction method is to use reference materials that are the same as or similar to the sample matrix to correct the mass fractionation generated by the instrument during the measurement process. Its accuracy is also relatively high, but relatively speaking, it may be affected by some factors. For example, in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) Rb-Sr isochron dating, when analyzing natural biotite GA-1550 with a known Rb-Sr isochron age, the accuracy of the one-step correction method relying only on NIST SRM 610 glass is only 2% (RSD); while using ZBH-25 biotite as the second matrix-matched reference material for a two-step correction method, the accuracy reaches 0.3% (RSD).
[0025] The accuracy of the matrix-matched reference material correction method is generally between % level and ‰ level. However, the accuracy of the double spike method can usually reach the ‰ level or even higher. By adding two spikes of the same element with known element content and isotope ratio to the sample, the isotope composition of the mixture is determined by mass spectrometry analysis, and the measured values are iteratively calculated according to specific mass fractionation laws to finally obtain the true isotope composition of the sample. The double spike method has very high accuracy and excellent performance in multiple isotope systems. For example, in molybdenum isotope determination, using a multi-collector inductively coupled plasma mass spectrometer combined with the double spike method to correct the instrumental mass fractionation, within a 95% confidence range, the long-term external precision can reach 0.035‰ / amu. The accuracy of the double spike method is relatively higher because in essence it is an internal standard method. The added double spikes are consistent with the target element, which can more accurately correct the isotope fractionation that may occur during the sample treatment process and is not affected by the matrix matching effect between the sample and the standard sample.
[0026] Currently, for the measurement of Ba isotopes, due to the limitation of the solid sampling method, the double spike method cannot be used to accurately correct the instrumental mass fractionation, resulting in the accuracy of Ba isotope determination being lower than that of whole-rock solution analysis and unable to better meet the need for analyzing small Ba isotope fractionation in complex genetic geological samples (such as during the ore-forming process of ore deposits, the samples have multiple stages, different provenances and components, etc.).
[0027] The technical solution is specifically as follows: Place the spar sample target on the tabletop of the laser ablation system. Use a laser to focus through the extraction solution onto the sample surface for laser ablation. The barite in the ablation area is heated by the laser with an extremely high power density to form a plasma, the atomic lattice is damaged to form nanoparticles, and BaSO4 in the barite is thermally decomposed to form BaO that is soluble in the extraction solution. Based on this, rapid extraction of Ba isotopes from the insoluble mineral barite is achieved. Drop a small amount of extraction solution on the surface of the sample target. Only ultrapure water is required as the extraction solution. The extraction solution forms a hemispherical droplet under the action of gravity and surface tension. The extraction solution droplet serves as a laser ablation chamber. This effectively solves the problems of long pre-treatment time and difficult treatment of Ba isotope samples. The difference from general laser sampling is that this sampling does not require a closed ablation cell and protective gas, reducing the consumption of working gases such as argon or helium and lowering the laboratory operation cost. The specific amount of ultrapure water used is 5 - 12 μL, which can be directly dropped onto the sample target surface with a pipette (one-time drop, no need for multiple drops) to form a hemispherical droplet. The droplet is also recovered by carefully sucking with a pipette and transferring it to a 5 mL centrifuge tube. Then, 5 - 10 μL of extraction solution can be dropped onto the sampling area to rinse the sample surface, and then the rinsing solution is also transferred to the same centrifuge tube to ensure the recovery rate of the ablation products. Add about 5 μL of double diluent to the recovered sample, and dilute it to 1.5 mL with 2% (v / v) HNO3 and wait for on-machine testing.
[0028] As Figure 1 shown, the specific embodiments of this specification provide a rapid extraction method for Ba isotopes in barite, which directly ablates and samples the insoluble mineral barite using a laser without the need for acids or alkalis as extraction substances. The specific method is as follows: BaSO4 in barite is thermally decomposed into soluble BaO under the action of laser energy with an energy density of 2.5 - 4.5 J·cm -2 At the same time, a double diluent is added to accurately correct the mass fractionation in the MC-ICP-MS test. The advantage of this is that the pre-treatment time for Ba isotope analysis of the insoluble mineral barite is shortened from 5 days to 1 hour. Use a laser to perform in-situ sampling and digestion on the barite sample, transfer the extraction solution of the sampled sample to a centrifuge tube, add an appropriate amount of double diluent to the centrifuge tube and dilute it with an acidic medium to obtain a sample test solution; then introduce the sample test solution into MC-ICP-MS for detection to obtain the Ba isotope value of the sample.
[0029] Experiments were carried out in this laboratory using a Neptune Plus multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS, ThermoFisher Scientific, Bremen, Germany) in combination with a nanosecond laser system (ns-LA, GeoLas Pro, Coherent, Germany). A Jet sampling cone and an X skimmer cone were used for the analysis. The GeoLas Pro laser ablation system (Coherent, Germany) uses a 193 nm nanosecond laser with ArF gas as the laser working gas. The optimal double spike composition and double spike ratio in the mixture were calculated by Monte Carlo simulation, and 66.53% of the 135 Ba single-diluent solution was mixed with 33.47% of the 137 Ba single-diluent solution, and diluted to a mass concentration of about 20 μg -1 (total Ba) with 5% (v / v) HNO3 to prepare the 135 Ba- 137 Ba double-diluent solution.
[0030] In the parameter optimization, we tried different laser ablation frequencies and energy densities. The finally determined laser ablation parameters were: spot diameter of 60 μm, frequency range of 4 Hz, energy ~3.0 J·cm -2 , ablation times of 300 times, and the best parameter for the extraction solution was an extraction solution volume of 10 μL.
[0031] Figure 2 Shown is a scanning electron microscope photograph of the ablation pit for in-situ laser rapid digestion sampling. The BaO nanoparticles obtained by laser rapid digestion sampling have dissolved in the surface extraction solution. The shape of the ablation pit for laser sampling is relatively regular, without the formation of a molten edge or sample fragmentation.
[0032] Figure 3 Shown is a white light interferometer photograph of the cross-sectional profile of the ablation pit for in-situ laser rapid digestion sampling. The cross-section of the ablation pit is relatively regular and flat. The theoretical sampling amount can be obtained by calculating the volume of the ablation pit. The ablation pit has a diameter of only 60 μm, a sampling volume of about 4.7×10 -8 cm 3 , and a sampling mass of about 2.1×10 -7 g, achieving unexpected results for samples with a very scarce sample amount in the study of ore deposit genesis, saving the use of the sample amount. The in-situ laser rapid digestion sampling behavior is controllable, which helps to obtain high-spatial-resolution and high-precision (δ 137 Ba: 0.05‰, 2SD, consistent with the currently highest-precision whole-rock solution analysis method) Ba isotope data.
[0033] Using different extraction solution volumes for in-situ laser rapid digestion strongly affects the Ba sampling mass and δ in the test samples137 / 134 Composed of Ba. Figure 4 Data shows that when using an extraction solution with a volume of 7 - 12 μL, relatively consistent Ba sampling quality can be obtained.
[0034] Figure 5 The data shows that when using an extraction solution with a volume of 6 - 12 μL, the δ in the test sample 137 / 134 Ba composition is consistent with the recommended value within the test uncertainty range.
[0035] From the above data, it can be seen that it is better to use an extraction solution with a volume between 7 - 12 μL for in - situ laser rapid digestion. Secondly, the volume of the extraction solution should be fixed during the sampling operation to ensure the consistency of sampling conditions when analyzing reference materials and actual samples.
[0036] The Ba isotope composition analysis of barite can be carried out using the technology of the present invention. Figure 6 It shows the δ of 4 natural barites obtained using this technology 137 / 134 Ba composition. The parameters for in - situ laser rapid digestion sampling are specifically: 10 μL volume of ultrapure water extraction solution, 60 - micron laser ablation beam spot, and 4 Hz laser ablation frequency.
[0037] The δ of Ba - FJ, Ba - FRA, Ba - HN, and Ba - YN 137 / 134 Ba compositions are 0.21 ± 0.05‰ (2SD, n = 3), 0.66 ± 0.02‰ (2SD, n = 3), 0.16 ± 0.03‰ (2SD, n = 3), and 0.25 ± 0.05‰ (2SD, n = 3), which are consistent within the error range with the reference values of 0.21 ± 0.03‰ (2SD, n = 2), 0.67 ± 0.03‰ (2SD, n = 2), 0.15 ± 0.01‰ (2SD, n = 2), and 0.29 ± 0.03‰ (2SD, n = 2) measured by the whole - rock solution method, and are better than 0.23 ± 0.09‰ (2SD, n = 46), 0.67 ± 0.10‰ (2SD, n = 53), 0.18 ± 0.10‰ (2SD, n = 69), and 0.33 ± 0.09‰ (2SD, n = 35) in fs - LA - MC - ICP - MS analysis. The test uncertainty of the isotope composition of the four barites is about 0.05‰. The data obtained represent high - spatial - resolution data at the scale of dozens of microns in the sample, which can meet the needs of applied research on the Ba isotope composition in natural barite samples.
[0038] The technical solution of this application does not require a complex chemical digestion process for the refractory geological mineral barite. During the pretreatment process, no chemical reagents such as concentrated acids and alkalis need to be added, which not only avoids the matrix background interference in Ba isotope determination brought by the reagents, but also avoids environmental pollution during the sample pretreatment process. It can solve the problem that it is difficult to quickly obtain a testable solution due to difficult digestion in the analysis of Ba isotopes in refractory geological mineral barite. Compared with the methods used in traditional barite digestion, the sample pretreatment efficiency of this method is increased by about 1000 times, greatly improving the work efficiency. Compared with in-situ laser ablation sampling combined with MC-ICP-MS analysis, this method combines the double-diluent method to correct the instrument mass fractionation during the test, and can obtain the Ba isotope composition of barite samples at the scale of dozens of micrometers, realizing high-spatial-resolution rapid and accurate Ba isotope testing.
[0039] The present invention is a breakthrough in the pretreatment method for Ba isotope analysis in barite, which is simple and efficient and can be quickly popularized in geological analysis laboratories.
[0040] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only an example and does not constitute a limitation to this specification. Although not explicitly stated here, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are proposed in this specification, so such modifications, improvements, and corrections still belong to the spirit and scope of the exemplary embodiments of this specification.
[0041] Similarly, it should be noted that in order to simplify the expression of this specification disclosure and thus help the understanding of one or more embodiments of the invention, in the description of the embodiments of this specification above, sometimes multiple features are merged into one embodiment, drawing, or description thereof. However, this disclosure method does not mean that the features required by the object of this specification are more than those mentioned in the claims. In fact, the features of the embodiment are less than all the features of the above-disclosed single embodiment.
[0042] For each patent, patent application, patent application publication, and other materials cited in this specification, such as articles, books, specifications, publications, documents, etc., their entire contents are hereby incorporated into this specification as references. Except for the application history documents that are inconsistent with or conflict with the content of this specification, and except for the documents that limit the broadest scope of the claims of this specification (currently or subsequently appended to this specification). It should be noted that if there are inconsistencies or conflicts between the descriptions, definitions, and / or uses of terms in the supplementary materials of this specification and the content described in this specification, the descriptions, definitions, and / or uses of terms in this specification shall prevail.
[0043] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, by way of example and not limitation, alternative configurations of the embodiments of this specification may be regarded as consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly presented and described in this specification.
Claims
1. A rapid extraction method for Ba isotopes in barite, characterized in that: Place the spar sample target on the laser ablation system tabletop, drop the extraction solution on the surface of the sample target, use the laser to pass through the extraction solution and focus it on the sample surface for laser ablation, use the laser to perform in-situ sampling and digestion on the barite sample, transfer the sample extraction solution after sampling to a centrifuge tube, add a double diluent to the centrifuge tube and make up the volume with an acidic medium to obtain a sample test solution, and finally accurately correct the mass fractionation in the MC-ICP-MS test by the double diluent method.
2. The extraction method according to claim 1, wherein The extraction solution is ultrapure water with a resistivity of 18.2 MΩ·cm.
3. The extraction method according to claim 1, characterized in that, The laser beam spot diameter is 16 - 90 μm.
4. The extraction method according to claim 1, characterized in that, The laser energy density is 2.5 - 4.5 J·cm -2 .
5. The extraction method according to claim 1, wherein The laser ablation frequency is 1 - 6 Hz.
6. The extraction method according to claim 1, characterized in that, The volume of the extraction solution is 5 - 12 μL.