A pretreatment method for determination of antimony isotopes in water with low antimony content

Abstract

The present invention relates to the field of analysis and detection technology, and provides a pretreatment method for the determination of antimony isotopes in water bodies with low antimony content. The present invention uses BrCl to digest organic matter in water samples with low antimony content, and then uses a solid phase extraction device to enrich and purify the antimony in the digestion solution to obtain an enriched purified solution. The method provided by the present invention has a good digestion effect on organic matter and a good enrichment effect on antimony in large-volume sample solutions, and will not cause fractionation of antimony isotopes, and can achieve accurate detection of antimony isotopes in low-content water samples. The method provided by the present invention performs pretreatment and antimony isotope detection on natural water bodies with an antimony content of less than 0.1 μg / L, filling the current gap in the determination of antimony isotopes in freshwater water bodies with low antimony content.

Description

Technical Field

[0001] The invention relates to the technical field of analysis and detection, and in particular to a pretreatment method for determining antimony isotopes in water with low antimony content. Background Art

[0002] Antimony (Sb) is a toxic and carcinogenic metalloid element. Human industrial activities such as antimony mining, smelting, coal combustion and brake pad wear will lead to large amounts of antimony being discharged into the environment, and antimony pollution has gradually attracted widespread attention. Antimony has been listed as a global priority pollutant by the U.S. Environmental Protection Agency (EPA) and the European Union's Basel Convention. High concentrations of antimony in the environment pose a significant risk to human health, and it is necessary to develop effective methods to control antimony pollution. Aquatic ecosystems are the most active interface in the biogeochemical cycle of Sb and play an important role in the global Sb cycle. Antimony emitted by human activities is an important cause of environmental antimony pollution. For example, antimony mining not only causes pollution of surrounding water bodies, but also causes pollution of aquatic ecological environments in remote areas. Studies have shown that antimony in ice cores of the Himalayas increased significantly in the industrial era, which means that antimony can be transported long distances around the world through the atmosphere. In order to study the biogeochemical cycle of antimony and control antimony pollution in aquatic environments, research on waters with low antimony content in remote areas is also very necessary. Recent studies have shown that biological processes, reduction, adsorption, evaporation, and precipitation in environmental systems can all lead to significant antimony isotope fractionation. These observations suggest that antimony isotopes may be a useful environmental tracer to reveal the source, transformation, migration, and biogeochemical processes of antimony in the environment.

[0003] As far as we know, there are few reports on the isotopic composition of antimony in aquatic environments in the literature. The relevant reports are mainly focused on mining wastewater and seawater. There is no isotopic study on low-content antimony (<1μg / L) in freshwater water. Resongles et al. (Resongles, Eléonore, et al. "Antimony isotopic composition in river waters affected by ancient mining activity." Talanta 144 (2015): 851-861.) established the thiol-cellulose powder (TCP) method based on the TCF method and applied it to the isotopic analysis of river water samples. However, the river involved was polluted by the mining area and had a high Sb content (32μg / L). Li et al. (Li, Shuyang, et al. "A new purification method based on a thiol silica column for high precision antimony isotope measurements." Journal of Analytical Atomic Spectrometry 36.1(2021):157-164.) developed a new purification procedure for high-precision Sb isotope analysis using a thiol silica gel column and used it to determine the Sb isotope composition in river water samples, but only involved polluted rivers. Farlii et al. (Colin, Ferrari, et al. "A single-step purification method for the precise determination of the antimony isotopic composition of environmental, geological and biological samples by HG-MC-ICP-MS." Journal of Analytical Atomic Spectrometry 36.4(2021):776-785.) established a single-step purification method based on the TCP method to analyze the Sb content in human blood and urine. However, the concentrations of Sb were relatively high, 26 g / L and 51 g / L, respectively, and no detailed digestion process was given in this method.

[0004] It can be seen that there is currently no systematic method for determining low-level antimony isotopes in aquatic ecosystems. Since the current method uses nitric acid and hydrogen peroxide to digest the sample, 2mL of nitric acid and 0.4mL of hydrogen peroxide need to be added to 2mL of sample. This method can effectively digest small-volume water samples, but for large-volume water samples, if you want to achieve complete digestion of organic matter, you must increase the amount of nitric acid and hydrogen peroxide in proportion. Excessive amounts of nitric acid and hydrogen peroxide will increase the blank value, resulting in reduced accuracy of the test results, and this operation is unreasonable. Therefore, the current method cannot effectively digest water samples with a volume of more than 20mL, and it is difficult to measure antimony isotopes in low-level freshwater in nature. In order to further understand the research on the biogeochemical cycle of antimony in natural water bodies (such as lakes and rivers), it is necessary to solve the problem of determining antimony isotopes in low-level water bodies. Summary of the invention

[0005] In view of this, the present invention provides a pretreatment method for the determination of antimony isotopes in water with low antimony content. The pretreatment method provided by the present invention can effectively digest a large volume of water sample with low antimony content and effectively enrich antimony without causing isotopic fractionation of antimony, thus filling the gap in the determination of antimony isotopes in water with low antimony content at home and abroad.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A pretreatment method for determining antimony isotopes in water with low antimony content comprises the following steps:

[0008] Mixing a low antimony content water sample and a BrCl solution for digestion treatment to obtain a digestion solution; the volume of the BrCl solution is 1% to 10% of the volume of the low antimony content water sample;

[0009] The digestion solution is enriched and purified by a solid phase extraction device to obtain an enriched and purified solution; the resin used for the enrichment and purification is a mercapto resin, and the eluent is a hydrochloric acid solution;

[0010] The antimony content in the low antimony content water sample is less than 0.1 μg / L.

[0011] Preferably, the volume of the low antimony content water sample is 20 mL to 1 L; the concentration of the BrCl solution is 0.25 g / mL.

[0012] Preferably, the digestion temperature is 130-140° C. and the time is 72-96 hours.

[0013] Preferably, after the digestion treatment is completed, the method further comprises using NH 2 OH·HCl solution neutralizes the remaining BrCl, the NH 2The concentration of OH·HCl solution is 0.25 g / mL.

[0014] Preferably, before the enrichment and purification, the neutralized digestion solution is mixed with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution for a reduction reaction, and the reduction reaction time is more than 4 hours; the concentration of hydrochloric acid in the system obtained by mixing the neutralized digestion solution with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution is 0.5 mol / L, and the concentrations of potassium iodide and ascorbic acid are both 5 mg / mL.

[0015] Preferably, the solid phase extraction device is a CNW 12-position solid phase extraction vacuum device.

[0016] Preferably, the sample loading flow rate of the solid phase extraction device is 1-2 mL / min; and the concentration of the hydrochloric acid solution for elution is 6 mol / L.

[0017] Preferably, before the elution, the resin column is cleaned using 6 mol / L, 0.5 mol / L and 2.5 mol / L hydrochloric acid solutions.

[0018] Preferably, after the enrichment and purification, the method further comprises mixing the obtained enriched and purified liquid with hydrogen peroxide for secondary digestion, and then evaporating the obtained sample liquid to near dryness, and then mixing the obtained sample with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution to obtain a test liquid; the concentration of hydrochloric acid in the test liquid is 3 mol / L, and the concentrations of potassium iodide and ascorbic acid are both 5 mg / mL.

[0019] The present invention also provides a method for determining antimony isotopes in water with low antimony content, comprising the following steps:

[0020] The low antimony content water body is pretreated according to the pretreatment method described in the above scheme, and then the antimony content and antimony isotope are detected respectively by HG-AFS method or HG-MC-ICP-MS method.

[0021] The present invention provides a pretreatment method for determining antimony isotopes in water with low antimony content, comprising the following steps: mixing a water sample with low antimony content and a BrCl solution for digestion treatment to obtain a digestion solution; the volume of the BrCl solution is 1% to 10% of the volume of the water sample with low antimony content; using a solid phase extraction device to enrich and purify the digestion solution to obtain an enriched purified solution; the resin used for the enrichment and purification is a mercapto resin, and the eluent is a hydrochloric acid solution; the antimony content in the water sample with low antimony content is less than 0.1 μg / L. The present invention uses BrCl to digest organic matter in the water sample with low antimony content, has a good digestion effect, uses a small amount of BrCl solution, can achieve effective digestion of a large volume of water samples, and will not affect the accuracy of subsequent detection results; at the same time, the present invention uses a solid phase extraction device to enrich and purify the antimony in the digestion solution, has a good enrichment effect, and will not cause antimony fractionation. At present, the pretreatment methods for the determination of antimony isotopes in water bodies in the art only involve polluted water bodies with high antimony content (>1 mg / L). The method provided by the present invention is for water bodies with antimony content <0.1 μg / L, specifically natural water bodies (including lake water, paddy field water and rainwater, etc.), filling the gap in the determination of antimony isotopes in water bodies in low-content freshwater areas. Furthermore, the present invention uses BrCl for digestion, with less reagent usage and low cost.

[0022] The present invention also provides a method for determining antimony isotopes in water with low antimony content, comprising the following steps: pre-treating the water with low antimony content according to the pre-treatment method described in the above scheme, and then detecting the antimony content and antimony isotopes respectively by HG-AFS method or HG-MC-ICP-MS method. After pre-treating the water with low antimony content by the method of the present invention, accurate detection of antimony content and antimony isotopes can be achieved. The present invention conducted experiments on antimony standard solutions and natural water samples to verify the feasibility of the method of the present invention. The experimental results show that the antimony recovery rate is 100±5% (n=44, 2SD) when the method of the present invention is used to determine the antimony isotopes in ultrapure water spiked samples, and it will not cause antimony isotope fractionation. 123 Sb / 121 The accuracy of the Sb isotope ratio is less than 0.4ε(2σ); at the same time, the antimony content in natural water bodies such as lake water, rice field water and rainwater was tested. The results showed that the antimony recovery rate was high and no antimony loss was caused in the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the present invention when a solid phase extraction device is used for enrichment and purification;

[0024] Figure 2 The recovery test results of different digestion methods and different neutralizing agents when ultrapure water is used as the sample in Example 1;

[0025] Figure 3 The antimony concentration test results of different digestion methods when lake water, rain water and paddy field water are used as samples in Example 1;

[0026] Figure 4 The antimony recovery test results when using ultrapure water samples in Example 2;

[0027] Figure 5 The antimony isotope test results when using ultrapure water samples in Example 2;

[0028] Figure 6 This is a graph showing the relationship between the antimony recovery rate and the antimony isotope value in Example 4. DETAILED DESCRIPTION

[0029] The present invention provides a pretreatment method for determining antimony isotopes in water with low antimony content, comprising the following steps:

[0030] Mixing a low antimony content water sample and a BrCl solution for digestion treatment to obtain a digestion solution; the volume of the BrCl solution is 1% to 10% of the volume of the low antimony content water sample;

[0031] The digestion solution is enriched and purified by a solid phase extraction device to obtain an enriched and purified solution; the resin used for the enrichment and purification is a thiol resin, and the eluent is a hydrochloric acid solution;

[0032] The antimony content in the low antimony content water sample is less than 0.1 μg / L.

[0033] The present invention mixes a low antimony content water sample and a BrCl solution for digestion treatment to obtain a digestion solution. In the present invention, the antimony content in the low antimony content water sample is less than 0.1 μg / L; the low antimony content water sample is preferably a natural water body, specifically lake water, paddy field water and rainwater; the volume of the low antimony content water sample is preferably 20mL to 1L, and in a specific embodiment of the present invention, the volume of the low antimony content water sample can be 20mL, 100mL, 200mL, 500mL or 1L; the volume of the BrCl solution is preferably 1% to 10% of the volume of the low antimony content water sample, preferably 1% to 5%; the concentration of the BrCl solution is preferably 0.25g / mL. The present invention preferably adjusts the amount of BrCl solution added according to the content of organic matter in the water sample. The higher the organic matter content, the more BrCl solution is added, so as to completely decompose the organic matter in the water sample. In a specific embodiment of the present invention, when the content of organic matter in the water sample with low antimony content is 0-30 mg / L, the amount of BrCl solution added is preferably 1-10% of the volume of the water sample. The present invention has no special requirements for the preparation method of the BrCl solution, and a method well known to those skilled in the art can be used.

[0034] In the present invention, the temperature of the digestion treatment is preferably 130-140°C, more preferably 130-135°C, the time of the digestion treatment is preferably 72-96h, more preferably 72-86h; the digestion treatment is carried out under closed conditions. BrCl has strong oxidizing properties and can digest organic matter in water samples, thereby separating antimony combined with organic matter and other substances, turning complexed antimony into free antimony. At the same time, because BrCl has strong oxidizing properties, the obtained free antimony is pentavalent antimony.

[0035] In the present invention, after the digestion treatment is completed, it is preferred to further include using NH 2 OH·HCl solution neutralizes the remaining BrCl in the digestion solution, and the NH 2 The concentration of OH·HCl solution is preferably 0.25 g / mL, and the solvent is ultrapure water; in the present invention, the BrCl solution is yellow, and NH 2 The OH·HCl solution becomes colorless after neutralization. In a specific embodiment of the present invention, NH 2 OH·HCl solution, the neutralization is considered complete when the solution becomes colorless and does not turn yellow after standing for 5 to 10 minutes.

[0036] After obtaining the digestion solution, the present invention also preferably mixes the obtained digestion solution with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution for reduction reaction, and the time of the reduction reaction is preferably more than 4 hours, more preferably 4 to 6 hours; the concentration of hydrochloric acid in the system obtained by mixing the oxidation treatment solution with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution is preferably 0.5 mol / L, and the concentrations of potassium iodide and ascorbic acid are preferably 5 mg / mL (recorded as 0.5M HCl+0.5% (w / v) KI-AA system). The present invention preferably adds 3 mol / L hydrochloric acid and 10% (w / v) KI-AA solution to the digestion solution, adjusts the amount of the two solutions and ultrapure water added according to the volume of the sample, and prepares a 0.5M HCl+0.5% (w / v) KI-AA solution system, wherein the 10% (w / v) KI-AA solution is prepared from 1g KI, 1g AA and 10mL ultrapure water. The present invention adds hydrochloric acid and KI-AA solution to prepare a reducing agent, so that all antimony in the sample is reduced to a trivalent state, and the concentrations of hydrochloric acid and KI-AA in the reduction system are controlled within the above range to meet the sample loading requirements of the subsequent enrichment and purification steps, so that the antimony in the sample is combined with the mercapto resin to avoid the loss of antimony.

[0037] After the reduction reaction is completed, the present invention uses a solid phase extraction device to enrich and purify the reduced digestion solution to obtain an enriched and purified solution. In the present invention, the resin used for enrichment and purification using the solid phase extraction device is a thiol resin. In a specific embodiment of the present invention, the model of the thiol resin is Cleanert SH, and the pore size is The particle size is 40 μm, purchased from Tianjin Bona Aiger Technology Co., Ltd. (China); the solid phase extraction device is preferably a CNW 12-position solid phase extraction vacuum device. In the present invention, the sample loading flow rate of the solid phase extraction device is preferably 1-2 mL / min; the concentration of the hydrochloric acid solution for elution is preferably 6 mol / L; before the elution, it is preferably also included to wash the resin column with 6 mol / L, 0.5 mol / L and 2.5 mol / L hydrochloric acid solutions in sequence, wherein the 6 mol / L and 0.5 mol / L hydrochloric acid solutions are used to wash the resin column before loading, and the 2.5 mol / L hydrochloric acid solution is used to wash the resin column after loading, which is described in detail below.

[0038] The present invention preferably first adds a mercapto resin into the resin column above the CNW 12-position solid phase extraction vacuum device, and then uses 6mol / L and 0.5mol / L hydrochloric acid solutions to clean the resin column; the usage ratio of the 6mol / L hydrochloric acid solution and the mercapto resin for cleaning is preferably 4mL:1-2g, and the usage ratio of the 0.5mol / L hydrochloric acid solution and the mercapto resin for cleaning is preferably 8mL:1-2g; during cleaning, the present invention preferably adds the hydrochloric acid solution in batches, and the usage amount each time is preferably 1mL.

[0039] After the resin column is cleaned with a 0.5 mol / L hydrochloric acid solution, the upper end of the resin column is connected to a Teflon bottle filled with a sample solution by a tube, and the flow rate is adjusted to 1-2 mL / min for loading; then the resin column is cleaned with a 2.5 mol / L hydrochloric acid solution, and the amount ratio of the 2.5 mol / L hydrochloric acid solution to the mercapto resin for cleaning is preferably 6 mL:1-2 g, and the hydrochloric acid solution is preferably added in batches during cleaning, and the amount of each addition is preferably 1 mL; the present invention uses a 2.5 mol / L hydrochloric acid solution to clean the resin column after loading and before elution, so as to remove interfering elements such as Sn.

[0040] After the resin column is cleaned, 6 mol / L hydrochloric acid solution is used for elution; in the present invention, the ratio of the hydrochloric acid solution for elution to the mercapto resin is preferably 8 mL:1-2 g, and during elution, 1 mL of hydrochloric acid solution is preferably added each time. The eluate is collected to obtain an enriched purified solution. Figure 1 It is a schematic diagram of the solid phase extraction device used for enrichment and purification in the present invention.

[0041] After the enrichment and purification is completed, the present invention preferably mixes the obtained enriched and purified liquid with hydrogen peroxide for secondary digestion, and then evaporates the obtained sample liquid to near dryness, and then mixes the obtained sample with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution to obtain a test solution; the concentration of hydrochloric acid in the test solution is 3 mol / L, and the concentrations of potassium iodide and ascorbic acid are both 5 mg / mL (recorded as 3MHCl+0.5% (w / v) KI-AA system); in the present invention, the temperature of the secondary digestion is preferably 100°C, the time is preferably 4h, and the secondary digestion is preferably carried out under closed conditions; the volume ratio of the enriched and purified liquid to hydrogen peroxide is preferably 4:1; the concentration of the hydrogen peroxide is preferably 35wt%. When passing through the column, trace organic matter will enter the enriched and purified liquid. The present invention uses hydrogen peroxide to digest the sample after passing through the column again to avoid the influence of organic matter on the experimental data. After the hydrogen peroxide digestion is completed, the sample solution is evaporated to near dryness, specifically to a wet salt state, and then mixed with hydrochloric acid, ultrapure water and potassium iodide-ascorbic acid solution. The present invention preferably adds 6 mol / L hydrochloric acid, ultrapure water and 10% (w / v) KI-AA solution to the sample after the solvent is evaporated, and the concentration of the components in the obtained test solution is adjusted to meet the above requirements.

[0042] The present invention also provides a method for determining antimony isotopes in water with low antimony content, comprising the following steps:

[0043] The low antimony content water body is pretreated according to the pretreatment method described in the above scheme, and then detected by HG-AFS method (atomic spectroscopy) or HG-MC-ICP-MS method (multi-receiver plasma mass spectrometry), wherein the HG-AFS method is used to determine the antimony content, and the HG-MC-ICP-MS method is used to determine the antimony isotope.

[0044] In the present invention, the HG-AFS method preferably tests the antimony content by a standard curve method, that is, testing antimony standard solutions of different concentrations, plotting a standard curve with antimony concentration as the horizontal coordinate and peak surface as the vertical coordinate, and determining the antimony content in the sample to be tested based on the peak area of ​​the sample to be tested and the standard curve.

[0045] In the present invention, the test conditions of the HG-AFS method are preferably as shown in Table 1:

[0046] Table 1 Test conditions of HG-AFS method

[0047] Acidic medium 3 mol / L HCl solution reducing agent <![CDATA[2wt%NaBH 4 -0.5wt%NaOH]]> Acidity of sample or standard 3 mol / L HCl solution Lamp current 60~70mA Photomultiplier tube negative high voltage 280～300V Carrier gas flow rate 400mL / min Protective gas flow rate 900~1000mL / min Atomizer preheat temperature 200℃

[0048] In the present invention, the mass spectrometer used in the HG-MC-ICP-MS method is specifically Nu Plasma II MC-ICP-MS. The present invention has no special requirements for the hydride generator used in the HG-MC-ICP-MS method and the HG-AFS method, and any hydride generator familiar to those skilled in the art may be used.

[0049] In the present invention, the test conditions of the HG-MC-ICP-MS method are preferably as shown in Table 2:

[0050] Table 2 Test conditions of HG-MC-ICP-MS method

[0051]

[0052] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] The conditions of the HG-AFS test in the embodiment are shown in Table 1, and the conditions of the HG-MC-ICP-MS test are shown in Table 2, which will not be described in detail below.

[0054] The solutions used in the following examples are:

[0055] Preparation of BrCl solution (0.25 g / mL): weigh 15.2 g pure KBrO 3 and 10.8 g KBr, heated at 250 °C for 12 h, added with 200 mL ultrapure water, and after the raw materials were dissolved, added with 800 mL of distilled concentrated hydrochloric acid to obtain a BrCl solution.

[0056] Preparation of 10% (w / v) KI-AA solution: Dissolve 1 g KI and 1 g AA in 10 mL ultrapure water to obtain a 10% (w / v) KI-AA solution.

[0057] The Sb standard solution used was NIST 3102a standard Sb solution.

[0058] Example 1 Digestion of water samples

[0059] 1. By verifying different reducing agents (SnCl 2 NH 2 OH·HCl and ascorbic acid (AA)) to determine the best neutralizer for neutralizing BrCl in the sample

[0060] Add 20 mL of ultrapure water, 200 μL of BrCl and 50 ng of Sb standard solution to the PFA cup and heat it on a 130°C hot plate for 72 h. After the sample cools down, add SnCl 2 Solution (0.2 g / mL), NH 2 OH·HCl (0.25 g / mL), and AA (0.1 g / mL) are used to neutralize the BrCl in the sample (neutralized until the liquid is colorless and transparent, and does not turn yellow after standing for 5 to 10 minutes). Hydrochloric acid and 10% (w / v) KI-AA are added to the obtained sample, and a 3M HCl+0.5% (w / v) KI-AA solution system is prepared according to the volume of the sample, and the reduction is carried out for more than 4 hours; then the obtained sample is subjected to HG-AFS test, and the recovery rate of antimony is calculated according to the test results, thereby determining the best neutralizing agent.

[0061] 2. Comparison between BrCl digestion and aqua regia digestion

[0062] Ultrapure water, lake water, rainwater and paddy water samples were added with known antimony standard solution, then sealed and left to stand at room temperature for at least 24 hours, and then digested with aqua regia and BrCl, respectively.

[0063] Aqua regia digestion: Add 2 mL of aqua regia to 20 mL of sample, heat on a 100 °C hot plate for at least 4 h, wait for the sample to cool, and steam on a 90 °C hot plate until almost dry, then add 0.5 mL of HNO 3 (distilled once through a DST-1000 acid purification system before use) and 1.5 mL H 2 O 2 (35wt%), heated in a sealed container on a 100℃ hot plate for at least 4h for secondary digestion. After the sample cooled, evaporated on a 90℃ hot plate until nearly dry. Then add 6mol / L HCl solution and 10% (w / v) KI-AA solution to convert the sample into a 3M HCl+0.5% (w / v) KI-AA system, reduce for at least 4h, and then measure the antimony concentration of the sample by HG-AFS.

[0064] BrCl digestion: Add 0.2 mL of BrCl solution to 20 mL of sample and place on a 130°C hot plate for 72 h. After the sample cools, add 50 μL of NH 2 OH·HCl (0.25 g / mL) was used to neutralize the BrCl in the sample. Then 6 mol / L HCl solution and 10% (w / v) KI-AA solution were added to convert the sample solution into a 3 M HCl + 0.5% (w / v) KI-AA system and reduced for at least 4 h before the antimony concentration of the sample was determined by HG-AFS.

[0065] Figure 2The recovery test results of different digestion methods and different neutralizers when ultrapure water was used as the sample; Figure 3 The antimony concentration test results of different digestion methods when using lake water, rain water and paddy field water as samples.

[0066] Figures 2-3 The test results show that NH 2 OH·HCl as a neutralizer for BrCl has a higher sample recovery rate and a smaller relative error than the other two reagents, with a recovery rate of 99.2±8% (2σ, n=16). When using BrCl digestion and aqua regia digestion, the antimony recovery rate of ultrapure water plus antimony standard samples is about 100%, indicating that these two methods will not cause antimony loss and pollution. However, the antimony concentration of natural samples digested by BrCl is significantly higher than that of natural samples digested by aqua regia. The concentration of lake water digested by BrCl is 0.25±0.03μg / L (2σ, n=7), and the concentration of paddy water is 0.24±0.026μg L -1 (2σ, n=3), rainwater concentration is 0.11±0.054μg / L -1 (2σ, n = 9); the lake water concentration of aqua regia digestion was 0.2 ± 0.032 μg / L (2σ, n = 10), the paddy water concentration was 0.17 ± 0.032 μg / L (2σ, n = 5), and the rainwater concentration was 0.07 ± 0.024 μg / L (2σ, n = 8). The above results show that the use of BrCl digestion and the use of NH 2 When OH·HCl was used as the neutralizer, the test results of antimony were more accurate and the recovery rate was higher.

[0067] Example 2 Enrichment and purification of large volume low-content water samples

[0068] Add NIST 3102a standard antimony solution to 200 mL of ultrapure water to make the antimony concentration reach 0.1 μg / L, thereby simulating the low antimony concentration in natural freshwater areas. Add 2 mL of BrCl solution (0.25 g / mL) and place it on a 130°C hot plate for 72 hours. After the sample cools down, add 0.5 mL of NH 2 OH·HCl (0.25 g / mL) was used to neutralize the BrCl in the sample. Hydrochloric acid and 10% (w / v) KI-AA solution were added to the neutralized sample solution to convert the sample solution into a 0.5 M HCl+0.5% (w / v) KI-AA system and the reduction was performed for more than 4 h.

[0069] Add 1g of mercapto resin to the resin column above the CNW 12-position solid phase extraction vacuum device, then wash with 4mL of 6mol / L HCl solution, and balance the resin column with 8mL of 0.5mol / L HCl solution (add 1mL each time, 4 times and 8 times respectively). The upper end of the resin column is connected to the Teflon bottle containing the sample with a tube, and the flow rate is adjusted to 1-2mL / min for sample loading. After 200mL of sample is loaded, wash the resin column with 6mL of 2.5mol / L HCl solution (only 1mL is added each time) to remove interfering elements such as Sn. Finally, elute the antimony in the resin column with 8mL of 6mol / L HCl solution (add 1mL each time), and collect the eluted solution in a PFA cup. Add 2mL of 35wt% HCl 2 O 2 Seal it on a 100℃ hot plate for 4 hours, and after cooling, steam it on a 90℃ hot plate until it is wet salt. Finally, add 6mol / L HCl solution, ultrapure water, and 10% (w / v) KI-AA solution to the sample to make the sample reach 3M HCl+0.5% (w / v) KI-AA system. One part is used for HG-AFS to determine the antimony concentration and calculate the recovery rate, and the other part is used for HG-MC-ICP-MS to determine the antimony isotope.

[0070] The ultrapure water samples in the above method were replaced by lake water, paddy field water and rain water samples respectively to verify whether this method is also applicable to natural water samples.

[0071] Figure 4 This is the antimony recovery test result when using ultrapure water sample. Figure 5 This is the antimony isotope test result when using ultrapure water samples.

[0072] according to Figures 4-5 It can be seen that when the method of the present invention is used to test the ultrapure water spiked sample, the recovery rate is 100.2±5% (2σ, n=9), and the isotope value of antimony is 0.00±0.40ε (2σ, n=9), which is within the isotope value range of the NIST3102a antimony standard solution, indicating that the method of the present invention is used to purify and enrich a 200 mL volume sample without causing isotope fractionation of antimony.

[0073] Table 3 shows the test results of natural water samples.

[0074] Table 3 Test results of natural water spike experiment

[0075]

[0076] The test results in Table 3 show that the recovery rate of antimony in paddy water sample is 100±0.05% (2σ, n=3) for the purification and enrichment of 200mL natural sample by the method of the present invention, the recovery rate of antimony in lake water sample is 95.4±0.00% (2σ, n=3), and the recovery rate of antimony in rainwater sample is 100.4±0.03% (2σ, n=2), which shows that the method of the present invention is feasible and will not cause antimony loss in the sample.

[0077] Example 3 Antimony isotope determination of water samples with different organic matter contents

[0078] Artificial humus and natural humus of different concentrations were used as samples, and BrCl was digested after adding antimony standard to judge the digestion ability of BrCl. The humus samples of different concentrations used in this embodiment were prepared by humus and ultrapure water; the specific steps are as follows:

[0079] 20 ng of antimony standard solution was added to 20 mL of artificial humus samples (5, 10, 15, 20, 30 and 40 mg / L) and natural humus samples (5, 10, 20 and 30 mg / L) with different concentration gradients to obtain spiked sample solutions. Then BrCl solution was added for digestion. During the digestion process, the amount of BrCl added increased with the increase of organic matter concentration. The specific amount added is shown in Table 4. Other operating conditions were consistent with Example 2. The recovery rate was calculated by measuring the antimony concentration using HG-AFS. The results are shown in Tables 4 and 5.

[0080] Table 4 Digestion recovery of artificial humic acid added to Sb standard solution (NIST3102a)

[0081]

[0082] Table 5 Recovery rate of natural humic acid digestion by adding Sb standard solution (NIST3102a)

[0083]

[0084] The experimental results in Tables 4 and 5 show that for 5-40 mg / L artificial humus, the recovery rate of antimony is 95-105%; for 5-30 mg / L natural humus, the recovery rate of antimony is 94-105%, indicating that the BrCl digestion method of the present invention is feasible.

[0085] Example 4 Effect of high content organic matter digestion on antimony isotope fractionation

[0086] In order to explore whether incomplete digestion of high-content organic matter will cause antimony isotope fractionation, the present invention determined the antimony isotopes after adding 20 ng NIST3102a antimony standard solution to 30 mg / L artificial humus samples at different recovery rates.

[0087] Add 20 ng of NIST3102a antimony standard solution to a 30 mg / L artificial humus sample (20 mL), let it stand at room temperature for more than 72 hours, then add 20 μL to 2 mL of BrCl solution, heat it on a 130 °C hot plate for 1 to 24 hours, and obtain different degrees of incomplete digestion samples by reducing the amount of BrCl solution added and the heating time. Then add an appropriate amount of NH 2 OH·HCl (0.25 g / mL) was used to neutralize the BrCl in the sample, and the subsequent operation method was consistent with Example 2.

[0088] A portion of the obtained test solution was used to determine the antimony concentration and calculate the recovery rate by HG-AFS, and the other portion was used to determine the antimony isotope by HG-MC-ICP-MS. According to the experimental results obtained, the recovery rate was plotted as the horizontal axis and the antimony isotope value as the vertical axis. The results obtained are as follows Figure 6 shown.

[0089] Figure 6 The results in show that when the recovery is greater than 80%, isotopic fractionation of antimony does not occur.

[0090] Example 5 Comparison of using CNW 12-position solid phase extraction vacuum device and not using the device

[0091] Without using the device: Add 20 ng of NIST 3102a antimony standard solution into 20 mL of ultrapure water and load the sample manually.

[0092] Using a CNW 12-position solid phase extraction vacuum device: Add 20 ng of NIST3102a antimony standard solution to 200 mL of ultrapure water and load the sample using a CNW 12-position solid phase extraction vacuum device.

[0093] The remaining operations are the same as those in Example 2.

[0094] The samples collected by purification and enrichment were respectively subjected to antimony isotope determination. The results showed that the isotope value of antimony sampled manually was -0.01±0.48ε(2σ, n=18), and the isotope value of antimony sampled by CNW 12-position solid phase extraction vacuum device was 0.00±0.40ε(2σ, n=9), both of which were within the standard range (-0.4ε~0.4ε). The above results show that manual sampling and solid phase extraction device sampling will not cause antimony isotope fractionation, but manual sampling cannot be performed on water samples with a volume of more than 100mL, while the solid phase extraction device is more conducive to processing large-volume and low-concentration samples without causing antimony loss, and is conducive to the realization of automated operation.

[0095] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A pretreatment method for determining antimony isotopes in water with low antimony content, characterized in that: The following steps are involved: The low antimony content water sample and the BrCl solution are mixed for digestion treatment to obtain a digestion solution; the volume of the BrCl solution is 1% to 10% of the volume of the low antimony content water sample; the volume of the low antimony content water sample is 20mL to 1L; after the digestion treatment is completed, the BrCl in the digestion solution is neutralized with an NH2OH·HCl solution, and the concentration of the NH2OH·HCl solution is 0.25g / mL; The digestion solution is enriched and purified by a solid phase extraction device to obtain an enriched and purified solution; the resin used for the enrichment and purification is a thiol resin, and the eluent is a hydrochloric acid solution; before the enrichment and purification, the neutralized digestion solution is mixed with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution for a reduction reaction, and the reduction reaction time is more than 4 hours; the concentration of hydrochloric acid in the system obtained by mixing the neutralized digestion solution with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution is 0.5 mol / L, and the concentrations of potassium iodide and ascorbic acid are both 5 mg / mL; The antimony content in the low antimony content water sample is less than 0.1 μg / L.

2. The pre-treatment method according to claim 1, characterized in that: The concentration of the BrCl solution is 0.25 g / mL.

3. The pre-treatment method according to claim 1, characterized in that: The digestion temperature is 130-140° C. and the digestion time is 72-96 hours.

4. The pre-treatment method according to claim 1, characterized in that: The solid phase extraction device is a CNW 12-position solid phase extraction vacuum device.

5. The pre-treatment method according to claim 1 or 4, characterized in that: The sample loading flow rate of the solid phase extraction device is 1-2 mL / min; the concentration of the eluent is 6 mol / L.

6. The pre-treatment method according to claim 1, characterized in that: Before the elution, the resin column is cleaned with 6 mol / L, 0.5 mol / L and 2.5 mol / L hydrochloric acid solutions.

7. The pre-treatment method according to claim 1, characterized in that: After the enrichment and purification, the method further includes mixing the obtained enriched and purified liquid with hydrogen peroxide for secondary digestion, and then evaporating the obtained sample liquid to near dryness, and then mixing the obtained sample with hydrochloric acid, ultrapure water, and potassium iodide-ascorbic acid solution to obtain a test liquid; the concentration of hydrochloric acid in the test liquid is 3 mol / L, and the concentrations of potassium iodide and ascorbic acid are both 5 mg / mL.

8. A method for determining antimony isotopes in water with low antimony content, characterized in that: The following steps are involved: The low antimony content water body is pretreated according to the pretreatment method according to any one of claims 1 to 7, and then the antimony content and antimony isotope are detected by HG-AFS and HG-MC-ICP-MS respectively.

Images