In-situ enrichment method and analysis method of water phase Hg(II) isotope

Abstract

The present application relates to the field of water phase Hg (II) isotope determination, and provides a water phase Hg (II) isotope in-situ enrichment method and analysis method.The present application uses a DGT device to adsorb the water body to be measured, and obtains a DGT device adsorbed with Hg (II); the adsorption film of the DGT device is an NSBA adsorption film; the NSBA adsorption film in the DGT device adsorbed with Hg (II) is eluted, and Hg (II) eluent is obtained, wherein the mercury concentration in the Hg (II) eluent needs to be greater than or equal to 0.5 ng / mL; and the eluent for the elution is reverse aqua regia.The method of the present application only needs to place the NSBA-DGT device in the water body to be measured to adsorb Hg (II) in the water body to be measured in-situ, without directly grabbing sampling, thereby reducing the pollution possibility in the sample transfer process of the water body to be measured, and when used for subsequent water phase Hg (II) isotope detection, the accuracy is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-phase Hg(II) isotope determination, and particularly provides an in-situ enrichment method and an analysis method for water-phase Hg(II) isotope. BACKGROUND

[0002] Mercury is a global pollutant that has received much attention due to its accumulation and persistence. It can be transported globally through the atmosphere and subsequently deposited in terrestrial and aquatic ecosystems. Once deposited in terrestrial and aquatic systems, mercury is converted to more toxic methylmercury (MeHg) by certain anaerobic microorganisms and subsequently accumulates in the food chain, posing a threat to human and environmental health. Free water-phase Hg 2+ and its unstable state Hg(II) (collectively referred to as Hg(II)) are the main species of methylation, which play a crucial role in aquatic ecosystems due to their high activity and bioavailability. Mercury isotope is a powerful tracing tool that helps better understand the biogeochemical cycling processes that occur between mercury species in aquatic ecosystems.

[0003] There are still great challenges in using mercury isotope technology to accurately trace the sources and migration processes of mercury in aquatic ecosystems. The main challenges are: the traditional sampling method is complex and tedious, and the sampling and storage requirements are harsh. In addition, during the collection, storage and transportation of samples, the samples may be contaminated, and the physical and chemical properties of the samples (such as pH value, redox conditions) are prone to change, which also causes great uncertainty in the determination of the concentration and isotope composition of the samples, resulting in a large error in the detection results. SUMMARY

[0004] Therefore, the present application aims to provide an in-situ enrichment method and an analysis method for water-phase Hg(II) isotope. The in-situ enrichment method provided by the present application reduces the possibility of contamination during the transfer of the water sample to be tested, and is used for the subsequent detection of Hg(II) isotope in water, which has high accuracy.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides an in-situ enrichment method for Hg(II) isotope in water, comprising the following steps:

[0007] (1) using a DGT device to adsorb the water to be tested to obtain a DGT device adsorbed with Hg(II); the adsorption film of the DGT device is an NSBA adsorption film;

[0008] (2) eluting the NSBA adsorption film in the DGT device adsorbed with Hg(II) in step (1) to obtain an Hg(II) eluent, wherein the concentration of mercury in the Hg(II) eluent is greater than or equal to 0.5 ng / mL;

[0009] The eluent used in the elution is reverse aqua regia.

[0010] The NSBA adsorption film is a polyacrylamide hydrogel film, and the polyacrylamide hydrogel film is distributed with SBA-15 type mesoporous silica material modified with thiol and amino groups, wherein the molar ratio of the thiol and the amino group is (4-6):1.

[0011] Preferably, the adsorption time is greater than or equal to 24 hours.

[0012] Preferably, when the concentration of mercury in the solution obtained by the elution is less than 0.5 ng / mL, the method further comprises enrichment, wherein the enrichment comprises a first enrichment method or a second enrichment method; the first enrichment method comprises: adding a reducing agent to the solution obtained by the elution to reduce Hg(II) to obtain a reduction system; and blowing nitrogen into the reduction system to re-enrich the reduced Hg(0) into dilute reverse aqua regia with a volume percentage of 40% to obtain an Hg(II) eluent meeting the requirements for instrument analysis; the reducing agent is SnCl2 aqueous solution with a concentration of 0.2 g / mL; the blowing flow rate of the nitrogen is less than or equal to 200 mL / min, and the blowing time of the nitrogen is 2 hours.

[0013] Preferably, the second enrichment method comprises: the second enrichment method comprises: eluting the NSBA adsorption film in a plurality of DGT devices adsorbed with Hg(II), and combining the solutions obtained by the elution to obtain an Hg(II) eluent meeting the requirements for instrument analysis.

[0014] Preferably, the acidity of the Hg(II) eluent is greater than or equal to 40%.

[0015] The application provides a method for analyzing Hg(II) isotope in an aqueous phase, comprising the following steps:

[0016] The method according to the above technical solution is used to enrich a water body to be measured in situ to obtain an Hg(II) eluent;

[0017] The Hg(II) eluent is detected by MC-ICP-MS to obtain the measured value of δ 202 Hg, Δ 199 Hg and Δ 201 Hg;

[0018] The measured value of δ 202 Hg is corrected to obtain the actual value of δ 202 Hg of the water body to be measured;

[0019] The correction value of the correction is -0.18 ‰.

[0020] Preferably, the MC-ICP-MS uses GBW07405, BCR-482 solid standard material, NIST SRM 3133 mercury isotope standard solution and NIST SRM 8610 mercury isotope standard solution as external standards, and NIST 997 Tl standard solution as internal standard to perform quality control on the sample.

[0021] The application provides an in-situ enrichment method of Hg(II) isotope in an aqueous phase, comprising the following steps: (1) using a DGT device to adsorb a water body to be measured, so as to obtain a DGT device adsorbing Hg(II); the adsorption film of the DGT device is an NSBA adsorption film; (2) eluting the NSBA adsorption film in the DGT device adsorbing Hg(II) in step (1), so as to obtain an Hg(II) eluent, the mercury concentration in the Hg(II) eluent is greater than or equal to 0.5 ng / mL; the eluent of the elution is reverse aqua regia; the NSBA adsorption film is a polyacrylamide hydrogel film, the polyacrylamide hydrogel film is distributed with SBA-15 type mesoporous silica material modified by thiol and amino groups; the molar ratio of the thiol and the amino group is (4-6):1. The in-situ enrichment method provided by the application only needs to place the DGT device provided with the NSBA adsorption film in the water body to be measured to adsorb Hg(II) in the water body to be measured in-situ, without direct grabbing sampling, so that the pollution possibility in the sample transfer process of the water body to be measured is reduced, and the detection accuracy is improved when the water phase Hg(II) isotope is detected subsequently.

[0022] The application further provides an analysis method of water phase Hg(II) isotope, comprising the following steps: in-situ enrichment of a water body to be measured according to the in-situ enrichment method in the above technical solution, so as to obtain an Hg(II) eluent; detection of the Hg(II) eluent by MC-ICP-MS, so as to obtain the measured value of δ 202 Hg, Δ 199 Hg and Δ 201 Hg; correction of the measured value of δ 202 Hg, so as to obtain the actual value of δ 202 Hg of the water body to be measured; the correction value of the correction is -0.18 ‰. Since the analysis method of the application places the DGT device provided with the NSBA adsorption film in the water phase to be measured to enrich Hg(II) in the water body to be measured in-situ, compared with the traditional method, the pollution possibility in the sample transfer process of the water body to be measured is reduced, and the detection accuracy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1Effect diagram of elution of NSBA adsorption film by aqua regia and reverse aqua regia. DETAILED DESCRIPTION

[0024] The application provides an in-situ enrichment method of Hg (II) isotopes in an aqueous phase, comprising the following steps:

[0025] (1) adsorbing a water body to be measured by using a DGT device to obtain a DGT device adsorbed with Hg (II); the adsorption film of the DGT device is an NSBA adsorption film;

[0026] (2) eluting the NSBA adsorption film in the DGT device adsorbed with Hg (II) in step (1) to obtain an Hg (II) eluent, and the mercury concentration in the Hg (II) eluent is greater than or equal to 0.5 ng / mL;

[0027] The eluent for elution is reverse aqua regia.

[0028] The NSBA adsorption film is a polyacrylamide hydrogel film, the polyacrylamide hydrogel film is distributed with SBA-15 type mesoporous silica material which is double-modified by sulfydryl and amino groups, and the molar ratio of the sulfydryl and the amino group is (4-6):1.

[0029] In the application, the raw materials used in the application are preferably commercially available products, unless otherwise specified.

[0030] The DGT device is used to adsorb the water body to be measured, and the DGT device adsorbed with Hg (II) is obtained; the adsorption film of the DGT device is an NSBA adsorption film.

[0031] In the application, the NSBA adsorption film is a polyacrylamide hydrogel film, the polyacrylamide hydrogel film is distributed with SBA-15 type mesoporous silica material which is double-modified by sulfydryl and amino groups, and the molar ratio of the sulfydryl and the amino group is (4-6):1.

[0032] In the application, the preparation method of the NSBA adsorption film preferably comprises the following steps:

[0033] Step one, preparing SBA-15 mesoporous silica material double-modified by sulfydryl and amino groups:

[0034] (1) In a conical flask, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) was dissolved with 1.9 mol / L hydrochloric acid. After P123 was fully dissolved, the reaction temperature was raised to 40°C, and tetraethyl orthosilicate (TEOS) was added dropwise, with the amount of silicon contained being 5% of the molar number of P123. After stirring for 60 min, mercaptopropyl trimethoxysilane (MPTMS) was added dropwise, with the molar ratio of the two being x = MPTMS / ((TEOS + MPTMS), x = 0.2. After stirring for 20 h, the mixed solution was transferred to a high-pressure reaction kettle, and aged at 100°C for 24 h. The obtained product was cooled, filtered, washed, and dried;

[0035] (2) After the material obtained in step (1) was vacuum dehydrated, it was moved into a round-bottom flask, and toluene and 3-aminopropyltrimethoxysilane (APTMS) were added. Stirring was performed at 110°C for 24 h. The obtained product was sequentially washed with toluene, anhydrous ethanol, and deionized water for 2-3 times, and vacuum dried.

[0036] (3) The material obtained in step (2) was added to a round-bottom flask with 95% ethanol, heated, stirred, and refluxed for 24 h. After cooling, filtration, washing, and vacuum drying, a thiol amino double-modified SBA-15 mesoporous silica heavy metal adsorbent was prepared.

[0037] Step two, a cross-linking agent DGTgel cross-linker with a concentration of 2% purchased from DGT Research Limited in the United Kingdom, MQ water, and an acrylamide solution produced by GE Healthcare were mixed in a ratio of 15:47.5:37.5 by volume to obtain a glue-making solution, wherein the mass percentage concentration of the acrylamide solution was 40%, and the solution was stored in a 4°C refrigerator for standby use.

[0038] Step three, after the thiol amino double-modified SBA-15 mesoporous silica material prepared in step one was fully ground, it was mixed with the glue-making solution prepared in step two in a mass-volume ratio of 1:30 to obtain a glue-making solution, and a mixed solution was prepared by ultrasonic treatment for 3 min.

[0039] Step four, to the mixed solution prepared in step three, 10% ammonium persulfate solution was added in an amount of 1 / 150 of the volume of the polyacrylamide solution, and tetramethyl diethylamine solution was added in an amount of 1 / 800 of the volume of the polyacrylamide solution, and a mixed solution was obtained by mixing uniformly.

[0040] Step five, the mixed solution prepared in step four is injected into the gap between two glass plates clamped with 0.25 mm thick U-shaped Teflon sheet at a rate of 5 mL / min, air bubbles are removed, and then the solution is horizontally transferred to an oven at 42℃ and placed for 40 min, until the solution in the glass plate is gelled into a film, and then the film is soaked in pure water for 24 h, during which the film is washed with pure water for 4 times, thereby obtaining the NSBA adsorption film.

[0041] In the present application, the adsorption time is preferably ≥24 h.

[0042] In the present application, the shell, filter membrane and diffusion layer of the DGT device are purchased from Nanjing Weishen Environmental Protection Technology Co., Ltd. In the present application, the material of the filter membrane of the DGT device is preferably polyether sulfone (PES); the pore size of the filter membrane is preferably 0.45 μm, and the thickness of the filter membrane is preferably 0.14 mm. In the present application, the material of the diffusion layer of the DGT device is preferably agarose gel; the thickness of the diffusion layer is preferably 0.8 mm. In the present application, the other structures of the DGT device are consistent with the prior art.

[0043] After obtaining the DGT device adsorbed with Hg(II), the NSBA adsorption film in the DGT device adsorbed with Hg(II) is eluted in the present application to obtain a Hg(II) eluent, and the mercury concentration in the Hg(II) eluent is ≥0.5 ng / mL.

[0044] Before the elution, the present application preferably further comprises rinsing the NSBA adsorption film in the DGT device adsorbed with Hg(II). In the present application, the rinsing reagent preferably comprises deionized water. The present application does not make specific limitations on the time and number of rinsing, as long as the impurities on the NSBA adsorption film in the DGT device adsorbed with Hg(II) can be completely removed.

[0045] In the present application, the eluent for elution is reverse aqua regia. In the present application, the ratio of the volume of the eluent for elution to the area of the NSBA adsorption film is preferably 5 mL:3.14 cm 2 In the present application, the elution mode is preferably oscillation elution; and the oscillation elution time is preferably 8-12 h.

[0046] In the present application, the acidity of the Hg(II) eluent is preferably ≥40%, and further preferably 40%.

[0047] In the present application, the mercury concentration in the Hg(II) eluent is ≥0.5 ng / mL. In the present application, when the mercury concentration in the solution obtained by elution is <0.5 ng / mL, the present application preferably further comprises enrichment; and the enrichment preferably comprises a first enrichment method or a second enrichment method.

[0048] In the present application, the first enrichment method preferably comprises: adding a reducing agent to the eluted solution to reduce Hg(II) to obtain a reduction system; blowing nitrogen into the reduction system to re-enrich the reduced Hg(0) into dilute reverse aqua regia with a volume percentage of 40% to obtain Hg(II) eluent meeting the requirements of on-machine.In the present application, the dilute reverse aqua regia with a volume percentage of 40% is a solution obtained by mixing reverse aqua regia and water in a volume ratio of 4:6.In the present application, the reducing agent is preferably a SnCl2 aqueous solution with a concentration of 0.2 g / mL; the present application does not specifically limit the amount of the reducing agent, as long as it can completely convert Hg(II) into Hg(0).In the present application, the blowing flow rate of nitrogen is preferably ≤200 mL / min, and further preferably 100-200 mL / min; the blowing time of nitrogen is preferably 2 h.

[0049] In the present application, the second enrichment method preferably comprises: eluting the NSBA adsorption membranes of the plurality of DGT devices adsorbed with Hg(II), and combining the eluted solutions to obtain Hg(II) eluent meeting the requirements of on-machine.

[0050] The present application also provides a method for analyzing Hg(II) isotope in water phase, comprising the following steps:

[0051] The in-situ enrichment method according to the above technical solution is used to enrich the water body to be measured in-situ to obtain Hg(II) eluent;

[0052] The Hg(II) eluent is detected by MC-ICP-MS to obtain the measured values of δ 202 Hg, Δ 199 Hg and Δ 201 Hg;

[0053] The measured value of δ 202 Hg is corrected to obtain the actual value of δ 202 Hg of the water body to be measured;

[0054] The correction value of the correction is-0.18 ‰.

[0055] The in-situ enrichment method according to the above technical solution is used to enrich the water body to be measured in-situ to obtain Hg(II) eluent. In the present application, the parameters of in-situ enrichment are preferably consistent with the above technical solution, which will not be described here.

[0056] After obtaining the Hg(II) eluent, the Hg(II) eluent is detected by MC-ICP-MS to obtain the measured values of δ 202 Hg, Δ 199 Hg and Δ 201 Hg.

[0057] In the present application, the MC-ICP-MS preferably uses GBW07405, BCR-482 solid standard substance, NIST SRM3133 mercury isotope standard solution and NIST SRM 8610 mercury isotope standard solution as external standard, and NIST 997 Tl standard solution as internal standard to perform quality control on the sample.

[0058] The present application does not make specific limitation to the detection parameters of the MC-ICP-MS, and the detection parameters well known to those skilled in the art can be adopted.

[0059] After obtaining the measured value of δ 202 The present application corrects the measured value of δ 202 Hg to obtain the actual value of δ 202 Hg of the water body to be measured.

[0060] In the present application, the correction value of the correction is preferably -0.18‰.

[0061] In the present application, the correction value is preferably obtained by the following steps:

[0062] (a) Put the DGT device (the adsorption film is NSBA adsorption film) into 100 mL of NIST SRM 3133 isotope mercury standard solution containing 0.01 mol / L NaCl and ~ 60 ng / mL at different temperatures (15 ℃, 25 ℃ and 35 ℃), and the oscillation speed of the constant temperature oscillator is 120 rpm. At different time points from 0 to 24 h, take out the DGT device from the solution, take out the adsorption film of the DGT device, elute the adsorption film with 5 mL of reverse aqua regia for 8-12 h to obtain the eluate at different time points. In addition, add 1% BrCl to the residual liquid (the remaining solution after the DGT device is taken out at different time points) to convert other forms of mercury into Hg(II), and then store it in a 4 ℃ refrigerator for cold preservation, so as to facilitate subsequent Hg(II) concentration and isotope analysis.

[0063] If the mercury concentration in the eluate at different time points does not meet the standard for on-machine isotope determination (≥0.5 ng / mL), the mercury enrichment system of CVAFS can be used for counter-enrichment of the eluate at different time points; specifically: 10-12 mL of eluate to be enriched is loaded into a bubble bottle, 5 mL of SnCl2 aqueous solution with a concentration of 0.2 g / mL is added to the bubble bottle to reduce Hg(II), so that Hg(II) in the eluate to be enriched is converted into Hg(0), and then nitrogen gas with a flow rate of 100-200 mL / min is introduced into the bubble bottle, and the blowing is continued for 2 h, so that the reduced Hg(0) is counter-enriched in 5 mL of dilute reverse aqua regia with a volume percentage of 40%.

[0064] (b) Prepare the GBW07405 and BCR-482 solid standard solution, accurately configure 0.5 ng / mL of NIST SRM 3133 mercury isotope standard solution and NIST SRM 8610 mercury isotope standard solution, 20 ng / mL Tl (NIST 997) standard solution to control the sample quality standard.

[0065] (c) The eluent at different time points is detected by an online mercury generation system and a multi-receiving inductively coupled plasma mass spectrometer (MC-ICP-MS), and the δ 202 Hg, Δ 199 Hg and Δ 201 Hg values of the sample can be obtained.

[0066] The proportion of mercury adsorbed by the DGT device at different temperatures and the isotope values thereof are shown in Table 1.

[0067] Table 1 Proportion of mercury adsorbed by DGT at different temperatures and isotope values thereof

[0068]

[0069] As can be seen from Table 1, under the conditions of 15, 25 and 35℃, compared with the δ 202 Hg and Δ 199 Hg reference value (~0‰), the Hg-MDF produced by the DGT in the process of adsorbing mercury molecules has a deviation of about 0.1-0.2‰, and the deviation values at the three temperatures have no significant difference (p>0.05), so the average value of δ 202 Hg at the three different temperatures (-0.18‰) is taken as the correction value; in addition, no obvious isotope non-mass fractionation (Hg-MIF ~0‰) is detected in the whole experiment. Therefore, the Hg-MDF deviation value (-0.18‰) can be used to correct the field samples, and the MIF does not need to be corrected.

[0070] The in-situ enrichment method and analysis method of Hg(II) isotope in an aqueous phase provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the present application.

[0071] Example 1

[0072] Selection of eluent

[0073] (I) The NSBA adsorption membrane (area 3.14 cm 2(The NSBA adsorption membrane was prepared according to the method described in the specific implementation section) The membrane was immersed in 30 mL of the test solution containing 0.01 mol / L NaCl and 1 ng / mL Hg(II) for 24 h to adsorb Hg(II) and obtain the NSBA adsorption membrane adsorbed with Hg(II).

[0074] (II) Rinse the surface impurities of the NSBA adsorption membrane that has adsorbed Hg(II) obtained in step (I) with ultrapure water. Use lens paper to dry the water on the surface of the NSBA adsorption membrane that has adsorbed Hg(II). Then, place the rinsed NSBA adsorption membrane that has adsorbed Hg(II) into Teflon bottles containing 5 mL of aqua regia and 5 mL of anti-aqua regia and continuously shake and elute. There are two elution methods for aqua regia: water bath heating for 3 h and room temperature for 8 h. Anti-aqua regia is eluted at room temperature for 8-12 h. Three eluents are obtained.

[0075] (III) Add 5 mL of ultrapure water to each of the three eluents obtained in step (II) to dilute them and obtain three Hg(II) eluents.

[0076] (IV) The concentrations of the three Hg(II) eluents obtained in step (III) and the concentrations of the test solutions before and after adsorption by the NSBA adsorption membrane were determined using CVAFS (Tekran 2500).

[0077] (V) The adsorption efficiency of the NSBA adsorption membrane for Hg(II) and the elution efficiency of aqua regia and its anti-aqua regia for Hg(II) were calculated from the data in step (IV). The results are as follows: Figure 1 As shown.

[0078] from Figure 1 It can be seen that the elution efficiency of 5 mL of reverse aqua regia for Hg(II) is 100.75±8.91%, while the elution efficiency of 5 mL of aqua regia (both water bath and room temperature methods) for Hg(II) is 76.36-79.87%. Therefore, reverse aqua regia was finally determined to be the elution reagent for NSBA adsorption membrane.

[0079] Example 2

[0080] Indoor experimental verification

[0081] (1) Put the DGT device (the adsorption membrane is NSBA adsorption membrane; the filter membrane is polyether sulfone membrane (PES) with a pore size of 0.45 μm and a thickness of 0.14 mm; the diffusion layer is agarose gel membrane with a thickness of 0.8 mm) into 100 mL of a solution containing 0.01 mol / L NaCl and ~ 60 ng / mL of NIST SRM 3133 isotope mercury standard solution at different temperatures (15°C, 25°C and 35°C), and the oscillation speed of the constant temperature oscillator is 120 rpm. At different time points from 0 to 24 h, the DGT device is taken out of the solution, the adsorption membrane of the DGT device is taken out, and the adsorption membrane is eluted with 5 mL of reverse aqua regia for 12 h to obtain the eluate at different time points. In addition, 1% BrCl is added to the residual liquid (the remaining solution after the DGT device is taken out at different time points) to convert other forms of mercury into Hg(II), and then it is stored in a 4°C refrigerator. The steps (III) and (IV) of Example 1 are repeated.

[0082] If the mercury concentration in the eluate at different time points does not meet the standard for isotope determination on the instrument (≥ 0.5 ng / mL), the eluate at different time points can be counter-enriched using the mercury enrichment system of CVAFS; specifically: 10 mL of the eluate to be enriched is placed in a bubble bottle, 5 mL of SnCl2 aqueous solution with a concentration of 0.2 g / mL is added to the bubble bottle to reduce Hg(II) in the eluate to be enriched, and then nitrogen gas with a flow rate of 100-200 mL / min is introduced into the bubble bottle to blow for 2 h, so that the reduced Hg(0) is counter-enriched in 5 mL of dilute reverse aqua regia with a volume percentage of 40%.

[0083] (2) Prepare the GBW07405 and BCR-482 solid standard substance to be tested, accurately configure 0.5 ng / mL of NIST SRM 3133 mercury isotope standard solution and NIST SRM 8610 mercury isotope standard solution, and 20 ng / mL Tl (NIST 997) standard solution to control the sample quality standard.

[0084] (3) The eluate at different time points is detected by the online mercury generation system and the multi-receiving inductively coupled plasma mass spectrometer (MC-ICP-MS), and the δ 202 Hg, Δ 199 Hg and Δ 201 Hg values in the sample can be obtained.

[0085] Firstly, the stability of the MC-ICP-MS instrument is determined by NIST SRM 3133 and three standard substances (internal and external standards), and the specific results are shown in Table 2.

[0086] Table 2 Experimental data of the stability of the MC-ICP-MS instrument

[0087]

[0088]

[0089] From Table 2, it can be seen that the determination results are consistent with the reference values, indicating that the MC-ICP-MS instrument is relatively stable during the determination of all samples.

[0090] The proportion of mercury adsorbed by the DGT device at different temperatures and the isotope values thereof are shown in Table 1. From Table 1, it can be seen that the Hg-MDF produced by the DGT in the process of adsorbing mercury molecules is 0.18‰, based on which, for subsequent field research, the field DGT samples can be corrected by using this value as a correction value; and no obvious isotope mass fractionation (Hg-MIF ~ 0‰) is detected in the entire experimental process, indicating that the MIF value detected by the DGT in the subsequent detection can reflect the true MIF signal of the natural sample, further confirming the reliability of the method.

[0091] Example 3

[0092] Field application

[0093] The NSBA-DGT device was placed in the paddy soil solution, taken out after 14 days, and the impurities on the surface were washed clean with ultrapure water, and then taken back to the laboratory for elution and detection. The elution and detection were the same as in Examples 1 and 2, and the results are shown in Table 3.

[0094] Table 3 Isotopic composition of DGT in environmental samples (corrected values)

[0095]

[0096] As can be seen from Table 3, the combination of DGT and MC-ICP-MS can be used to capture the mercury isotope composition of Hg(II) in the water phase of the paddy soil solution. As shown in Table 3, the measured δ 202 Hg values are -2.10 to -1.99‰, and a small non-mass fractionation (MIF) is monitored, with a Δ 199 Hg value of 0.11 to 0.22‰.

[0097] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for in-situ enrichment of aqueous Hg(II) isotopes, characterized in that, The method comprises the following steps: (1) using a DGT device to adsorb a water body to be measured to obtain a DGT device adsorbed with Hg(II); the adsorption film of the DGT device is an NSBA adsorption film; (2) eluting the NSBA adsorption film in the DGT device adsorbed with Hg(II) in step (1) to obtain an Hg(II) eluent, and the concentration of mercury in the Hg(II) eluent is greater than or equal to 0.5 ng / mL; The eluent for the elution is reverse aqua regia; The NSBA adsorption film is a polyacrylamide hydrogel film, and the polyacrylamide hydrogel film is distributed with SBA-15 type mesoporous silica material modified with thiol and amino groups; the molar ratio of the thiol and the amino group is (4-6):

1.

2. The in situ enrichment method of claim 1, wherein, The adsorption time is greater than or equal to 24 hours.

3. The in situ enrichment method of claim 1, wherein, When the concentration of mercury in the solution obtained by the elution is less than 0.5 ng / mL, the method further comprises enrichment; the enrichment comprises a first enrichment method or a second enrichment method; The first enrichment method comprises: adding a reducing agent to the solution obtained by the elution to reduce Hg(II) to obtain a reduction system; Nitrogen gas is blown into the reduction system, and the reduced Hg(0) is re-enriched into dilute reverse aqua regia with a volume percentage of 40% to obtain an Hg(II) eluent meeting the requirements for instrument operation; the reducing agent is SnCl2 aqueous solution with a concentration of 0.2 g / mL; the blowing flow rate of the nitrogen gas is less than or equal to 200 mL / min, and the blowing time of the nitrogen gas is 2 hours.

4. The in situ enrichment method of claim 3, wherein, The second enrichment method comprises: eluting the NSBA adsorption films in a plurality of DGT devices adsorbed with Hg(II), and combining the solutions obtained by the elution to obtain an Hg(II) eluent meeting the requirements for instrument operation.

5. The in situ enrichment method of claim 1, wherein, The acidity of the Hg(II) eluent is greater than or equal to 40%.

6. A method for the analysis of aqueous Hg(II) isotopes, characterized in that, The method comprises the following steps: The in-situ enrichment method according to any one of claims 1-5 is used to enrich a water body to be measured in-situ to obtain an Hg(II) eluent; The Hg(II) eluate was detected by MC-ICP-MS, and δ 202 Hg, Δ 199 Hg and Δ 201 Hg measured values; The δ 202 The measured value of Hg is corrected to obtain the actual value of δ 202 Hg of the water body to be measured. The corrected correction value is -0.18 ‰.

7. The analysis method according to claim 6, characterized in that, The MC-ICP-MS uses GBW07405 and BCR-482 solid standard substances, NIST SRM 3133 mercury isotope standard solution and NIST SRM 8610 mercury isotope standard solution as external standards, and NIST 997 Tl standard solution as an internal standard to perform quality control on the sample.

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